Showing papers by "General Dynamics published in 2010"

Radio Frequency Tomography for Tunnel Detection

Abstract: Radio frequency (RF) tomography is proposed to detect underground voids, such as tunnels or caches, over relatively wide areas of regard. The RF tomography approach requires a set of low-cost transmitters and receivers arbitrarily deployed on the surface of the ground or slightly buried. Using the principles of inverse scattering and diffraction tomography, a simplified theory for below-ground imaging is developed. In this paper, the principles and motivations in support of RF tomography are introduced. Furthermore, several inversion schemes based on arbitrarily deployed sensors are devised. Then, limitations to performance and system considerations are discussed. Finally, the effectiveness of RF tomography is demonstrated by presenting images reconstructed via the processing of synthetic data.

Visual classification of coarse vehicle orientation using Histogram of Oriented Gradients features

Abstract: For an autonomous vehicle, detecting and tracking other vehicles is a critical task. Determining the orientation of a detected vehicle is necessary for assessing whether the vehicle is a potential hazard. If a detected vehicle is moving, the orientation can be inferred from its trajectory, but if the vehicle is stationary, the orientation must be determined directly. In this paper, we focus on vision-based algorithms for determining vehicle orientation of vehicles in images. We train a set of Histogram of Oriented Gradients (HOG) classifiers to recognize different orientations of vehicles detected in imagery. We find that these orientation-specific classifiers perform well, achieving a 88% classification accuracy on a test database of 284 images. We also investigate how combinations of orientation-specific classifiers can be employed to distinguish subsets of orientations, such as driver's side versus passenger's side views. Finally, we compare a vehicle detector formed from orientation-specific classifiers to an orientation-independent classifier and find that, counter-intuitively, the orientation-independent classifier outperforms the set of orientation-specific classifiers.

The role of cognitive systems engineering in the systems engineering design process

Abstract: The article is intended to aid students and consumers of Cognitive Systems Engineering (CSE) in learning about CSE. A proliferation of terms describing CSE and related constructs makes it difficult to sort out differences and similarities across approaches. To aid the reader in exploring CSE, we examine areas of confusion surrounding CSE, define CSE, and discuss the role of CSE in the systems engineering design process. We advocate the use of CSE principles and methods as a means to incorporate worker needs, expertise, cognitive demands, constraints, and goals throughout the design process. Articulation of the value case for CSE is offered as a vehicle to foster collaboration across disciplines. © 2009 Wiley Periodicals, Inc. Syst Eng

Identification of microRNAs associated with hyperthermia-induced cellular stress response

Abstract: MicroRNAs (miRNAs) are a class of small RNAs that play a critical role in the coordination of fundamental cellular processes. Recent studies suggest that miRNAs participate in the cellular stress response (CSR), but their specific involvement remains unclear. In this study, we identify a group of thermally regulated miRNAs (TRMs) that are associated with the CSR. Using miRNA microarrays, we show that dermal fibroblasts differentially express 123 miRNAs when exposed to hyperthermia. Interestingly, only 27 of these miRNAs are annotated in the current Sanger registry. We validated the expression of the annotated miRNAs using qPCR techniques, and we found that the qPCR and microarray data was in well agreement. Computational target-prediction studies revealed that putative targets for the TRMs are heat shock proteins and Argonaute-2—the core functional unit of RNA silencing. These results indicate that cells express a specific group of miRNAs when exposed to hyperthermia, and these miRNAs may function in the regulation of the CSR. Future studies will be conducted to determine if other cells lines differentially express these miRNAs when exposed to hyperthermia.

Dynamic Modeling of a Two-Axis, Parallel, H-Frame-Type XY Positioning System

Abstract: XY positioning is an important task in industrial applications. This paper addresses the dynamic modeling of a belt-driven, parallel-type XY positioning system constructed in the form of a capitalized H. The system uses one long timing belt to transmit the rotation of two stationary motors to end-effector motion. Due to less moved masses, the studied H-frame system is potentially capable of fast acceleration, and therefore, faster positioning than traditional stacked systems. The use of an elastic transmission element also causes the biggest disadvantage of the system, which is an uncertainty of end-effector position due to stretching in the belt. Thus, the objective of this paper is to develop a dynamic model that can capture the response of this system. Using Lagrange's method, an eighth-order lumped parameter dynamic model of the stage motion is derived. The effect of nonlinear friction in the pulleys and cart motion is added to the model. The response of the model was simulated in MATLAB Simulink, and the model prediction is compared with real data obtained from the developed system. The results show that the model can accurately predict the dynamics of the developed H-frame positioning system.

Harvesting Single Ferroelectric Domain Stressed Nanoparticles for Optical and Ferroic Applications

Abstract: We describe techniques to selectively harvest single ferroelectric domain nanoparticles of BaTiO3 as small as 9 nm from a plethora of nanoparticles produced by mechanical grinding. High resolution transmission electron microscopy imaging shows the unidomain atomic structure of the nanoparticles and reveals compressive and tensile surface strains which are attributed to the preservation of ferroelectric behavior in these particles. We demonstrate the positive benefits of using harvested nanoparticles in disparate liquid crystal systems.

Predicted radar/optical feature fusion gains for target identification

Abstract: Airborne tracking and identification (ID) of high value ground targets is a difficult task impacted by sensor, target, and environmental conditions. Layered sensing, using a combination of standoff and short-range sensors, maintains target track and identification in cluttered environments such as cities or densely vegetated areas through sensor diversity. Data, feature, decision, or information fusion is necessary for high confidence target classification to be achieved using multiple sensors and sensor modalities. Target identification performance is improved by exploiting the extra information gained from independent sensing modalities through information fusion for automatic target recognition (ATR). Increased target ID has been demonstrated using spatial-temporal multi-look sensor fusion and decision level fusion. To further enhance target ID performance and increase decision confidence, feature level fusion techniques are being investigated. A fusion performance model for feature level fusion was applied to a combination of sensor types and features to provide estimates of a fusion gain. This paper presents a fusion performance gain for Synthetic Aperture Radar (SAR), electro-optical (EO), and infrared (IR) video stationary target identification.

Quantitative investigation of the bioeffects associated with terahertz radiation

Abstract: The biological effects associated with Terahertz (THz) radiation are not well characterized. In this study, we investigated the cellular response of human dermal fibroblasts exposed to an optically-pumped molecular gas THz laser (υ = 2.52 THz, irradiance = 84.8 mW/cm 2 , exposure duration = 5 to 80 minutes). Computational dosimetry was conducted using finite-difference time-domain (FDTD) modeling techniques. Empirical dosimetry was conducted using infrared cameras and thermocouples. Cellular viability was assessed 24 h post-exposure using MTT calorimetric assays. Quantitative PCR was performed 4 h post-exposure to evaluate the transcriptional activation of genes involved in protein and DNA damage pathways. Comparable analyses were also performed for hyperthermic and genotoxic positive control samples. For all of the exposure durations tested, we found that greater than 95% of the cells were viable post-exposure. In addition, the exposed cells showed only minor increases (~3.5-fold) in heat shock protein expression. The empirical dosimetric data showed that the temperature of the cells increased by ~3 °C during exposure. This value was consistent with that predicted by the computational models. Interestingly, although the THz-exposed cells exhibited increases in heat shock protein expression, the magnitude of these increases was comparable to those observed in hyperthermic controls. In addition, none of the DNA repair genes tested were up-regulated in the THz-exposed cells, whereas 40-fold increases were observed in the genotoxic control cells. These results suggest that the biological effects imposed by THz radiation appear to be primarily photothermal in nature.

Determination of death thresholds and identification of terahertz (THz)-specific gene expression signatures

Abstract: In recent years, numerous security, military, and medical applications have been developed which use Terahertz (THz) radiation. These developments have heightened concerns in regards to the potential health risks that are associated with this type of radiation. To determine the cellular and molecular effects caused by THz radiation, we exposed several human cell lines to high-power THz radiation, and then we determined death thresholds and gene expression profiles. Necrotic and apoptotic death thresholds were determined for Jurkat cells using an optically-pumped molecular gas THz source (υ = 2.52 THz, H = 227 mW/cm 2 ), MTT viability assays, and flow cytometric techniques. In addition, we used confocal microscopic techniques to demarcate lethal spatial regions in a monolayer of dermal fibroblasts exposed to THz radiation. Then, to determine if cells exhibit a THz-specific gene expression signature, we exposed dermal fibroblasts to THz radiation and analyzed their transcriptional response using microarray gene chips. We found that 60% of the Jurkat cells survived the 30-minute THz exposure, whereas only 20% survived the 40-minute exposure. The flow data confirmed these results and provided evidence that THz-induced cell death was mediated using both nectrotic and apoptotic processes. The preliminary microscopy studies provided convincing evidence warranting future efforts using these techniques. Lastly, we found that dermal fibroblasts up-regulated several genes when exposed to THz radiation. Overall, these results provide evidence for the cellular and molecular effects associated with THz radiation, and we speculate that the identified up-regulated genes may serve as excellent candidate biomarkers for THz exposures.

RF Tomography for Below-Ground Imaging of Extended Areas and Close-in Sensing

Abstract: Three extensions to radio-frequency (RF) tomography for imaging of voids under wide areas of regard are presented. These extensions are motivated by three challenges. One challenge is the lateral wave, which propagates in proximity of the air-earth interface and represents the predominant radiation mechanism for wide-area surveillance, sensing of denied terrain, or close-in sensing. A second challenge is the direct-path coupling between transmitters (Txs) and receivers (Rxs), that affects the measurements. A third challenge is the generation of clutter by the unknown distribution of anomalies embedded in the ground. These challenges are addressed and solved using the following strategies: 1) A forward model for RF tomography that accounts for lateral waves expressed in closed form (for fast computation); 2) a strategy that reduces the direct-path coupling between any Tx-Rx pair; and 3) an improved inversion scheme that is robust with respect to noise, clutter, and high attenuation. A finite-difference time domain simulation of a scenario representing close-in sensing of a denied area is performed, and reconstructed images obtained using the improved and the classical models of RF tomography are compared.

Error analysis of a two-layer method for the electromagnetic characterization of conductor-backed absorbing material using an open-ended waveguide probe

Abstract: A two-layer nondestructive method for characterizing the electric and magnetic properties of lossy conductor-backed magnetic materials using a ∞anged rectangular-waveguide probe is examined. The two re∞ection measurements necessary to determine both permittivity and permeability are made by flrst applying the probe to the material under test and then applying the probe to a known-material layer placed on top of the material under test. The theoretical re∞ection coe-cient is obtained using a rigorous full-wave solution, and an extrapolation scheme is used to minimize the error due to truncating the modal expansion of the waveguide flelds. An error analysis is performed to compare the performance of the technique to the two-thickness method, which utilizes two difierent thicknesses of the material under test. The properties of the known material layer that result in the least error due to network analyzer uncertainty are determined. The sensitivity of the two-layer method is also explored and discussed.

Methods and apparatus for multiple-antenna communication of wireless signals with embedded synchronization/pilot sequences

Abstract: Embodiments include methods for determining synchronization/pilot sequences (SPS) to be utilized in conjunction with transmissions by antennas of a multiple-antenna transmitter. The SPS include pilot signals that are positioned at subcarriers that are orthogonal in frequency with subcarriers at which pilot signals of other antennas are positioned. The pilot signals may be unevenly spaced across the in-band subcarriers. The multiple-antenna transmit system generates a plurality of wireless signals, each of which may include an SPS having synchronization information in a first plurality of in-band subcarriers and the pilot signals in a second plurality of in-band subcarriers. The wireless signals are simultaneously radiated over a wireless communication channel using a different antenna. A receiver receives channel-affected versions of the wireless signals, and produces a corrected signal by applying corrections to the received signal based on estimated channel perturbations within the received signal.

Analytical energy gradients of Coulomb‐attenuated time‐dependent density functional methods for excited states

Abstract: We present an implementation and validation of the analytical energy gradient of time-dependent density functional theory (TDDFT) using Coulomb-attenuated (CA) functionals for excited state energies, dipole moments, geometries, and vibrational frequencies. The CA-TDDFT gradient is based on the previous long-range corrected TDDFT of (Chiba et al. J Chem Phys 2006, 124, 144106) and the Z-vector formalism of (Furche and Ahlrichs J Chem Phys 2002, 117, 7433). Geometry optimization using CA-TDDFT was carried out for molecules (substituted stilbenes and coumarins) having intramolecular charge-transfer excited states and for a series of small molecules (CO, HCN, CH2O, CH2S, CCl2, C2H2, trans-(CHO)2). We assess the results of the CA functionals, the long-range corrected LC-BLYP functional, and the B3LYP hybrid functional, by comparing to accurate experimental data. The results highlight the applicabilty of different functionals for excited state properties. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010

Flapping Wing Micro-Air-Vehicle Control Employing Triangular Wave Strokes and Cycle-Averaging

Abstract: The recent development of the world’s rst robotic insect capable of vertical takeo at the Harvard Microrobotics Lab has sparked research e orts into devising similar vehicles capable of untethered ight. The vehicle design has been extended in simulation to use one actuator per wing to produce sinusoidal apping motion in a plane. This work proposes employing a generic triangular wave to generate the apping wing stroke angle. The resulting expressions for the wing beat cycle-averaged aerodynamic forces and moment are signi cantly simpler than those computed using sinusoidal waveforms, thus easing algebraic manipulation and analytical analysis. Wing beat parameters are employed as control inputs, a ecting the cycle-averaged aerodynamic forces and moments. The resulting control authority is assessed analytically. A ve degree-of-freedom control design is devised and used to control a six degree-of-freedom simulation of the vehicle. The simulation model is driven by the instantaneous aerodynamic forces and moments; and the cycle-averaged expressions are only used for control design. Three sets of wing beat parameters are used as control inputs to illustrate the freedom in control design and implementation. One mimics the sinusoidal waveform studies cases. The others illustrate how amplitude modulation can replace frequency modulation to achieve comparable performance results.

Automated Multiple Target Detection and Tracking in UAV Videos

Abstract: In this paper, a novel system is presented to detect and track multiple targets in Unmanned Air Vehicles (UAV) video sequences. Since the output of the system is based on target motion, we first segment foreground moving areas from the background in each video frame using background subtraction. To stabilize the video, a multi-point-descriptor-based image registration method is performed where a projective model is employed to describe the global transformation between frames. For each detected foreground blob, an object model is used to describe its appearance and motion information. Rather than immediately classifying the detected objects as targets, we track them for a certain period of time and only those with qualified motion patterns are labeled as targets. In the subsequent tracking process, a Kalman filter is assigned to each tracked target to dynamically estimate its position in each frame. Blobs detected at a later time are used as observations to update the state of the tracked targets to which they are associated. The proposed overlap-rate-based data association method considers the splitting and merging of the observations, and therefore is able to maintain tracks more consistently. Experimental results demonstrate that the system performs well on real-world UAV video sequences. Moreover, careful consideration given to each component in the system has made the proposed system feasible for real-time applications.

A comparative approach for the investigation of biological information processing: an examination of the structure and function of computer hard drives and DNA.

Abstract: Background: The robust storage, updating and utilization of information are necessary for the maintenance and perpetuation of dynamic systems. These systems can exist as constructs of metal-oxide semiconductors and silicon, as in a digital computer, or in the “wetware” of organic compounds, proteins and nucleic acids that make up biological organisms. We propose that there are essential functional properties of centralized information-processing systems; for digital computers these properties reside in the computer’s hard drive, and for eukaryotic cells they are manifest in the DNA and associated structures. Methods: Presented herein is a descriptive framework that compares DNA and its associated proteins and sub-nuclear structure with the structure and function of the computer hard drive. We identify four essential properties of information for a centralized storage and processing system: (1) orthogonal uniqueness, (2) low level formatting, (3) high level formatting and (4) translation of stored to usable form. The corresponding aspects of the DNA complex and a computer hard drive are categorized using this classification. This is intended to demonstrate a functional equivalence between the components of the two systems, and thus the systems themselves. Results: Both the DNA complex and the computer hard drive contain components that fulfill the essential properties of a centralized information storage and processing system. The functional equivalence of these components provides insight into both the design process of engineered systems and the evolved solutions addressing similar system requirements. However, there are points where the comparison breaks down, particularly when there are externally imposed information-organizing structures on the computer hard drive. A specific example of this is the imposition of the File Allocation Table (FAT) during high level formatting of the computer hard drive and the subsequent loading of an operating system (OS). Biological systems do not have an external source for a map of their stored information or for an operational instruction set; rather, they must contain an organizational template conserved within their intra-nuclear architecture that “manipulates” the laws of chemistry and physics into a highly robust instruction set. We propose that the epigenetic structure of the intra-nuclear environment and the non-coding RNA may play the roles of a Biological File Allocation Table (BFAT) and biological operating system (Bio-OS) in eukaryotic cells.

Sparse reconstruction methods in RF Tomography for underground imaging

Abstract: Underground imaging involving RF Tomography is generally severely ill-posed posed. Tikhonov Regularization is perhaps the most common method to address this ill-posedness. The proposed methods are based upon the realistic assumptions that targets (e.g. tunnels) are sparse and clustered in the scene, and have known electrical properties. Therefore, we explore the use of alternative regularization strategies leveraging sparsity of the signal and its spatial gradient, while also imposing physically-derived amplitude constraints. By leveraging this prior knowledge, cleaner scene reconstructions are obtained.

Protein Changes in Macrophages Induced by Plasma from Rats Exposed to 35-GHz Millimeter Waves

Abstract: A macrophage assay and proteomic screening were used to investigate the biological activity of soluble factors in the plasma of millimeter wave-exposed rats. NR8383 rat macrophages were incubated for 24 h with 10% plasma from male Sprague-Dawley rats that had been exposed to sham conditions, or exposed to 42 °C environmental heat or 35 GHz millimeter waves at 75 mW/cm² until core temperature reached 41.0 °C. Two-dimensional polyacrylamide gel electrophoresis, image analysis, and Western blotting were used to analyze approximately 600 protein spots in the cell lysates for changes in protein abundance and levels of 3-nitrotyrosine, a marker of macrophage stimulation. Proteins of interest were identified using peptide mass fingerprinting. Compared to plasma from sham-exposed rats, plasma from environmental heat- or millimeter wave-exposed rats increased the expression of 11 proteins, and levels of 3-nitrotyrosine in seven proteins, in the NR8383 cells. These altered proteins are associated with inflammation, oxidative stress, and energy metabolism. Findings of this study indicate both environmental heat and 35 GHz millimeter wave exposure elicit the release of macrophage-activating mediators into the plasma of rats.

Multi-scale characterization of inhomogeneous morphologically textured microstructures

Abstract: A computationally efficient microstructure characterization technique is presented that separately identifies morphological texture and any orientation dependence of second-phase clustering via a concise visual representation. This technique, the Vector Multi-Scale Analysis of Area Fractions (VMSAAF), is then applied to computer-generated microstructures to understand the effects of second-phase area fraction, aspect ratio, alignment propensity, variant orientation, and degree of microstructure banding on the homogenous length scale—a metric used to quantify clustering—as well as the extent of representative volume elements for a microstructure.

Prototype Implementation and Concept Validation of a 4-D Trajectory Fuel Burn Model Application

Abstract: As new technologies are implemented to enhance the National Airspace System it is important to consider their impact on the environment and on the cost of operations. One of the major considerations for both is the amount of fuel consumed by aircraft. This paper describes a unique methodology that can be used to estimate the total fuel consumed by aircraft based on their 4-D trajectories and the weather through which they flew. This methodology is based on the European Organisation for the Safety of Air Navigation (EUROCONTROL) BADA (Base of Aircraft Data) fuel burn model. The paper then describes how the BADA fuel burn model and weather data provided by the National Weather Service were implemented in a prototype application and how this prototype was validated using actual data recorded during a flight for a specific aircraft. The paper concludes with a summary that includes suggestions for improvements that should be incorporated when implementing the production version of the application.

Separation kernel with memory allocation, remote procedure call and exception handling mechanisms

Abstract: A computer-implemented system (90) is provided that supports a high degree of separation between processing elements. The computer-implemented system (90) comprises a plurality of cells (92) residing on the computer-implemented system, where each cell (92) includes a domain of execution (94) and at least one processing element (96); a separation specification (99) that governs communication between the processing elements (96); and a kernel (98) of an operating system that facilitates execution of the processing elements (96) and administers the communication between the processing elements (96) in accordance with the separation specification (99), such that one processing element (96) can influence the operation of another processing element (96) only as set forth by the separation specification (99). In particular, the separation specification provides memory allocation, remote procedure calls and exception handling mechanisms.

Damage thresholds for terahertz radiation

Abstract: Several international organizations establish minimum safety standards to ensure that workers and the general population are protected against adverse health effects associated with electromagnetic radiation. Suitable standards are typically defined using published experimental data. To date, few experimental studies have been conducted at Terahertz (THz) frequencies, and as a result, current THz standards have been defined using extrapolated estimates from neighboring spectral regions. In this study, we used computational modeling and experimental approaches to determine tissue-damage thresholds at THz frequencies. For the computational modeling efforts, we used the Arrhenius damage integral to predict damage-thresholds. We determined thresholds experimentally for both long (minutes) and short (seconds) THz exposures. For the long exposure studies, we used an in-house molecular gas THz laser (υ= 1.89 THz, 189.92 mW/cm2, 10 minutes) and excised porcine skin. For the short exposure studies, we used the Free Electron Laser (FEL) at Jefferson Laboratory (υ= 0.1-1.0 THz, 2.0-14.0 mW/cm2, 2 seconds) and wet chamois cloths. Thresholds were determined using conventional damage score determination and probit analysis techniques, and tissue temperatures were measured using infrared thermographic techniques. We found that the FEL was ideal for tissue damage studies, while our in-house THz source was not suitable to determine tissue damage thresholds. Using experimental data, the tissue damage threshold (ED50) was determined to be 7.16 W/cm2. This value was in well agreement with that predicted using our computational models. We hope that knowledge of tissue-damage thresholds at THz frequencies helps to ensure the safe use of THz radiation.

Mitigation of coupling in RF Tomography with applications to belowground sensing

Abstract: In imaging applications based on RF Tomography, coupling between transmitters and receivers is a principal technical challenge to be overcome. To mitigate the coupling, we propose to activate different transmitters simultaneously, and determine their respective current source distribution in order to create electric field nulls at desired points (e.g., the receivers). The current design problem must take into consideration physical and system constraints of the radiators. As such, the current design must be formulated as a nonlinear programming problem. These constraints are discussed in details, and our method is validated using FDTD simulations.

Reconfigurable vehicle power and signal distribution system

Abstract: A reconfigurable vehicle power and signal distribution system (10) is disclosed. The system comprises at least one conduit section (11) for housing a first and second power rail (22), and a communication line (20) for communicating signals along the conduit. The system further comprises a transfer hub (27) which enables the transfer of power and signals to a distribution hub that comprises a plurality of terminals for separately providing conditioned power to various system modules of the vehicle. The distribution of power from the distribution hub is dependent on signals received from a control unit via the communication line, which controls the power usage within the vehicle. The system enables the at least one conduit section, transfer hub and distribution hub to be reconfigured according to the topography of the vehicle.

Flapping Wing Micro-Air-Vehicle 4-DOF Controller Applied to a 6-DOF Model

Abstract: apping motion. It is shown that by modulating the frequency and bias of the wing strokes, the cycle-average moments and the cycle-averaged lift can be manipulated. A controller is devised which utilizes the resulting four degree-of-freedom control authority to maneuver the vehicle. In particular, simulation results are provided showing how the vehicle can be made to traverse a trajectory generated from waypoints. The design provides advantages over previous similar control strategies which used ve degrees-offreedom control. There are fewer wing beat parameters to manipulate and the formulation of the commanded forces and moments is dierent, facilitating alternative future system and control analysis approaches.

Symbol timing synchronization methods and apparatus

Abstract: Embodiments include methods and apparatus for performing symbol timing synchronization for a symbol-bearing signal. The symbol-bearing signal is sampled to produce a plurality of symbol samples. First-direction interpolation processes are performed on the plurality of symbol samples in a first temporal direction, where the first temporal direction is a direction from a first sampling time towards a second sampling time. In addition, second-direction interpolation processes are performed on the symbol samples in a second temporal direction, where the second temporal direction is a direction from the second sampling time towards the first sampling time, resulting in a set of interpolated symbol samples.

Ocean deployable biodegradable optical fiber cable

Abstract: An optical fiber cable has a transparent core for transmitting optical data and a biodegradable protective covering. When placed in water, the protective covering dissolves in water after a few days. The raw remaining optical fiber cover is very thin, approximately 0.003 inches in diameter and very fragile. The optical core is easily broken into fine particles which becomes sand on the sea floor.