Showing papers by "General Dynamics published in 2012"

A robotic fish caudal fin: effects of stiffness and motor program on locomotor performance

Abstract: We designed a robotic fish caudal fin with six individually moveable fin rays based on the tail of the bluegill sunfish, Lepomis macrochirus Previous fish robotic tail designs have loosely resembled the caudal fin of fishes, but have not incorporated key biomechanical components such as fin rays that can be controlled to generate complex tail conformations and motion programs similar to those seen in the locomotor repertoire of live fishes We used this robotic caudal fin to test for the effects of fin ray stiffness, frequency and motion program on the generation of thrust and lift forces Five different sets of fin rays were constructed to be from 150 to 2000 times the stiffness of biological fin rays, appropriately scaled for the robotic caudal fin, which had linear dimensions approximately four times larger than those of adult bluegill sunfish Five caudal fin motion programs were identified as kinematic features of swimming behaviors in live bluegill sunfish, and were used to program the kinematic repertoire: flat movement of the entire fin, cupping of the fin, W-shaped fin motion, fin undulation and rolling movements The robotic fin was flapped at frequencies ranging from 05 to 24 Hz All fin motions produced force in the thrust direction, and the cupping motion produced the most thrust in almost all cases Only the undulatory motion produced lift force of similar magnitude to the thrust force More compliant fin rays produced lower peak magnitude forces than the stiffer fin rays at the same frequency Thrust and lift forces increased with increasing flapping frequency; thrust was maximized by the 500× stiffness fin rays and lift was maximized by the 1000× stiffness fin rays

Pronounced effects of anisotropy on plasmonic properties of nanorings fabricated by electron beam lithography.

Abstract: Gold nanoring dimers were fabricated via EBL with dimensions of 127.6 ± 2.5 and 57.8 ± 2.3 nm for the outer and inner diameters, respectively, with interparticle separations ranging from 17.8 ± 3.4 to 239.2 ± 3.7 nm. The coupling between the inner and outer surfaces of a single nanoring renders it very sensitive to any anisotropy. We found that anisotropy in the particle geometry and anisotropy introduced by the substrate combine to create very unique spectral features in this system.

The GOES-R Proving Ground: Accelerating User Readiness for the Next-Generation Geostationary Environmental Satellite System

Abstract: The Geostationary Operational Environmental Satellite R series (GOES-R) Proving Ground engages the National Weather Service (NWS) forecast, watch, and warning community and other agency users in preoperational demonstrations of the new and advanced capabilities to be available from GOES-R compared to the current GOES constellation. GOES-R will provide significant advances in observing capabilities but will also offer a significant challenge to ensure that users are ready to exploit the new 16-channel imager that will provide 3 times more spectral information, 4 times the spatial coverage, and 5 times the temporal resolution compared to the current imager. In addition, a geostationary lightning mapper will provide continuous and near-uniform real-time surveillance of total lightning activity throughout the Americas and adjacent oceans encompassing much of the Western Hemisphere. To ensure user readiness, forecasters and other users must have access to prototype advanced products within their operational en...

An Optimization-Based Parallel Particle Filter for Multitarget Tracking

Abstract: Particle filters are used in state estimation applications because of their capability to solve nonlinear and non-Gaussian problems effectively. However, they have high computational requirements, especially in the case of multitarget tracking, where data association is the bottleneck. In order to perform data association and estimation together, an augmented state vector, whose dimensions depend on the number of targets, is typically used in particle filters. With data association, the computational load increases exponentially as the number of targets increases. In this case, parallelization is a possibility for achieving real-time feasibility in large-scale multitarget tracking applications. In the work presented here, an optimization-based scheduling algorithm, that is suitable for parallel implementation of particle filter, is presented. This proposed scheduling algorithm minimizes the total computation time for the bus-connected heterogeneous primary-secondary architecture. Further, this scheduler is capable of selecting the optimal number of processors from a large pool of secondary processors and mapping the particles among the selected ones. A new distributed resampling algorithm suitable for parallel computing is also proposed. Furthermore, a less communication-intensive parallel implementation of the particle filter without compromising tracking accuracy using an efficient load balancing technique, in which optimal particle migration among secondary processors is ensured, is presented. Simulation results demonstrate the tracking effectiveness of the new parallel particle filter and the speedup achieved using parallelization.

Spectral LADAR: active range-resolved three-dimensional imaging spectroscopy

Abstract: We present the concept and experimental results for Spectral LADAR, an augmented LADAR imager combining three-dimensional (3D) time-of-flight ranging with active multispectral sensing in the shortwave infrared (1080–1620 nm). The demonstrated technique is based on a nanosecond regime pulsed supercontinuum transmitter and spectrally multiplexed receiver that computes a high-resolution range value for each of 25 spectral bands. A low frame-rate prototype unit is described. Results demonstrating 3D imaging and material type classification of objects, especially those obscured by camouflage, are shown at effective stand-off ranges exceeding 40 m. These capabilities and the highly eye safe wavelengths at which the system operates make it suitable for applications in military imaging and robotic perception.

Parameters for Pyrethroid Insecticide QSAR and PBPK/PD Models for Human Risk Assessment

Abstract: In this review we have examined the status of parameters required by pyrethroid QSAR-PBPK/PD models for assessing health risks. In lieu of the chemical,biological, biochemical, and toxicological information developed on the pyrethroids since 1968, the finding of suitable parameters for QSAR and PBPK/PD model development was a monumental task. The most useful information obtained came from rat toxicokinetic studies (i.e., absorption, distribution, and excretion), metabolism studies with 14C-cyclopropane- and alcohol-labeled pyrethroids, the use of known chiral isomers in the metabolism studies and their relation to commercial products. In this review we identify the individual chiralisomers that have been used in published studies and the chiral HPLC columns available for separating them. Chiral HPLC columns are necessary for isomer identification and for developing kinetic values (Vm,, and Kin) for pyrethroid hydroxylation. Early investigators synthesized analytical standards for key pyrethroid metabolites, and these were used to confirm the identity of urinary etabolites, by using TLC. These analytical standards no longer exist, and muste resynthesized if further studies on the kinetics of the metabolism of pyrethroids are to be undertaken.In an attempt to circumvent the availability of analytical standards, several CYP450 studies were carried out using the substrate depletion method. This approach does not provide information on the products formed downstream, and may be of limited use in developing human environmental exposure PBPK/PD models that require extensive urinary metabolite data. Hydrolytic standards (i.e., alcohols and acids) were available to investigators who studied the carboxylesterase-catalyzed hydrolysis of several pyrethroid insecticides. The data generated in these studies are suitable for use in developing human exposure PBPK/PD models.Tissue:blood partition coefficients were developed for the parent pyrethroids and their metabolites, by using a published mechanistic model introduced by Poulin and Thiele (2002a; b) and log DpH 7.4 values. The estimated coefficients, especially those of adipose tissue, were too high and had to be corrected by using a procedure in which the proportion of parent or metabolite residues that are unbound to plasma albumin is considered, as described in the GastroPlus model (Simulations Plus, Inc.,Lancaster, CA). The literature suggested that Km values be adjusted by multiplying Km by the substrate (decimal amount) that is unbound to microsomal or CYPprotein. Mirfazaelian et al. (2006) used flow- and diffusion-limited compartments in their deltamethrin model. The addition of permeability areas (PA) having diffusion limits, such as the fat and slowly perfused compartments, enabled the investigators to bring model predictions in line with in vivo data.There appears to be large differences in the manner and rate of absorption of the pyrethroids from the gastrointestinal tract, implying that GI advanced compartmental transit models (ACAT) need to be included in PBPK models. This is especially true of the absorption of an oral dose of tefluthrin in male rats, in which 3.0-6.9%,41.3-46.3%, and 5.2-15.5% of the dose is eliminated in urine, feces, and bile,respectively (0-48 h after administration). Several percutaneous studies with the pyrethroids strongly support the belief that these insecticides are not readily absorbed, but remain on the surface of the skin until they are washed off. In one articular study (Sidon et al. 1988) the high levels of permethrin absorption through the forehead skin (24-28%) of the monkey was reported over a 7- to 14-days period.Wester et al. (1994) reported an absorption of 1.9% of pyrethrin that had been applied to the forearm of human volunteers over a 7-days period.SAR models capable of predicting the binding of the pyrethroids to plasma and hepatic proteins were developed by Yamazaki and Kanaoka (2004), Saiakhov et al. (2000), Colmenarejo et al. (2001), and Colmenarejo (2003). QikProp(Schrodinger, LLC) was used to obtain Fu values for calculating partition coefficients and for calculating permeation constants (Caco-2, MDCK, and logBBB). ADMET Predictor (Simulations Plus Inc.) provided Vm~,x and Km values for the hydroxylation of drugs/pyrethroids by human liver recombinant cytochrome P450 enzymes making the values available for possible use in PBPK/PD models.The Caco-2 permeability constants and CYP3A4 Vmax and Km values are needed in PBPK/PD models with GI ACAT sub models. Modeling work by Chang et al.(2009) produced rate constants (kcat) for the hydrolysis of pyrethroids by rat serumcarboxylesterases. The skin permeation model of Potts and Guy (1992) was used topredict K, values for the dermal absorption of the 15 pyrethroids.The electrophysiological studies by Narahashi (1971) and others (Breckenridgeet al. 2009; Shafer et al. 2005; Soderlund et al. 2002; Wolansky and Harrill 2008)demonstrated that the mode of action of pyrethroids on nerves is to interfere with the changes in sodium and potassium ion currents. The pyrethroids, being highly lipid soluble, are bound or distributed in lipid bilayers of the nerve cell membrane and exert their action on sodium channel proteins. The rising phase of the action potential is caused by sodium influx (sodium activation), while the falling phase is caused by sodium activation being turned off, and an increase in potassium efflux(potassium activation). The action of allethrin and other pyrethroids is caused by an inhibition or block of the normal currents. An equation by Tatebayashi and Narahashi (1994) that describes the action of pyrethroids on sodium channels was found in the literature. This equation, or some variation of it, may be suitable for use in the PD portion of pyrethroid PBPK models.

On modeling biomolecular–surface nonbonded interactions: application to nucleobase adsorption on single-wall carbon nanotube surfaces

Abstract: In this work we explored the selectivity of single nucleobases towards adsorption on chiral single-wall carbon nanotubes (SWCNTs) by density functional theory calculations. Specifically, the adsorption of molecular models of guanine (G), adenine (A), thymine (T), and cytosine (C), as well as of AT and GC Watson?Crick (WC) base pairs on chiral SWCNT C(6, 5), C(9, 1) and C(8, 3) model structures, was analyzed in detail. The importance of correcting the exchange?correlation functional for London dispersion was clearly demonstrated, yet limitations in modeling such interactions by considering the SWCNT as a molecular model may mask subtle effects in a molecular?macroscopic material system. The trend in the calculated adsorption energies of the nucleobases on same diameter C(6, 5) and C(9, 1) SWCNT surfaces, i.e.?G?>?A?>?T?>?C, was consistent with related computations and experimental work on graphitic surfaces, however contradicting experimental data on the adsorption of single-strand short homo-oligonucleotides on SWCNTs that demonstrated a trend of G?>?C?>?A?>?T (Albertorio et?al 2009 Nanotechnology 20 395101). A possible role of electrostatic interactions in this case was partially captured by applying the effective fragment potential method, emphasizing that the interplay of the various contributions in modeling nonbonded interactions is complicated by theoretical limitations. Finally, because the calculated adsorption energies for Watson?Crick base pairs have shown little effect upon adsorption of the base pair farther from the surface, the results on SWCNT sorting by salmon genomic DNA could be indicative of partial unfolding of the double helix upon adsorption on the SWCNT surface.

Method and Apparatus for Communicating in an Increased Coverage Area to a Wireless Communication Unit

Abstract: A method for increasing coverage in a wireless communication system is described. The method comprises, at the network element: transmitting a first portion of subframes comprising a number of resource blocks to a first wireless communication unit in a first mode of operation, wherein the number of resource blocks are transmitted at a first power level per resource block; and transmitting, a second portion of subframes to a second wireless communication unit in a second mode of operation at a second power level, wherein the second portion of subframes comprise a lower number of resource blocks than the first portion of subframes and the lower number of resource blocks is transmitted at a second power level per resource block that is higher than the first power level per resource block.

Using state dominance for path planning in dynamic environments with moving obstacles

Abstract: Path planning in dynamic environments with moving obstacles is computationally complex since it requires modeling time as an additional dimension. While in other domains there are state dominance relationships that can significantly reduce the complexity of the search, in dynamic environments such relationships do not exist. This paper presents a novel state dominance relationship tailored specifically for dynamic environments, and presents a planner that uses that property to plan paths over ten times faster than without using state dominance.

Immobilization of the Laccases from Trametes versicolor and Streptomyces coelicolor on Single‐wall Carbon Nanotube Electrodes: A Molecular Dynamics Study

Abstract: In this work, we investigate the immobilization of laccases from Trametes versicolor (TvL) and the small laccase (SLAC) from Streptomyces coelicolor on single-wall carbon nanotube (SWCNT) surfaces. SLAC may potentially offer improved adsorption on the electrode, thus improving bioelectrocatalytic activity via direct electron transfer (DET). Laccase immobilization on SWCNTs is achieved non-covalently with a molecular tether (1-pyrene butanoic acid, succinimidyl ester) that forms an amide bond with an amine group on the laccase surface while the pyrene coordinates to the SWCNT by π–π stacking. In our approach, density functional theory calculations were first used to model the interaction energies between SWCNTs and pyrene to validate an empirical force field, thereafter applied in molecular dynamics (MD) simulations. In the simulated models, the SWCNT was placed near the region of the (type 1) Cu(T1) atom in the laccases, and in proximity to other regions where adsorption seems likely. Calculated interaction energies between the SWCNTs and laccases and distances between the SWCNT surface and the Cu(T1) atom have shown that SWCNTs adsorb more strongly to SLAC than to TvL, and that the separation between the SWCNTs and Cu(T1) atoms is smaller for SLAC than for TvL, having implications for improved DET.

Geohazards assessment and mapping of some Balkan countries

Abstract: The assessment of geological hazard is a topic with significant interest for the Balkans. During the last decade of twentieth century, most of the countries in the region have embarked on the road of a hasty transitory period from totalitarian regimes to democracy. Development of free market economy has given rise to uncontrolled movement of people, fast construction of housing and facilities and unproportioned accumulation of population around and in big cities. Besides Greece, an old member of European Union, and two newcomers in the organization, Romania and Bulgaria, the other countries are all hoping to enter the Union as faster as they can. Many different candidate or full-fledged member country programs of European Community offer a lot of joint and cross-border projects for constructing road infrastructure and facilities. As development accelerates in the Balkans and given the intensive geohazard elements that this territory exhibits, it becomes increasingly important to understand, study, and map these elements for being aware of the damage to the total environment these hazards might cause. The geohazard map and assessment of some Balkan countries has been carried out through two scientific meetings in Ohrid, Macedonia, and Tirana, Albania during 2007. The map is compiled in the Albanian Geological Survey, Tirana, Albania in the scale 1:1,000,000. As a base map, we used the topographic map produced by VGI, formerly Yugoslavia mapping authorities. As a seismic layer in our map, we used the values of peak ground acceleration obtained from Global Seismic Hazard Assessment Program. Two catalogs were constructed: The first one that contains the crustal earthquakes (hypocentral depth within first 70 km) and the second one that contains intermediate earthquakes (hypocentral depth below 70 km). This work is largely based on previous studies and investigations by earth scientists and specialists of each country comprised in this territory. In this respect, the map we constructed should be considered as a preliminary composite geohazard map with the possibility to be enriched and added with other new elements and data in the future.

Method and apparatus for a wireless communication unit operating on a virtual carrier

Abstract: A method for a low bandwidth wireless communication unit to re-synchronize to a wireless communication system employing one or more virtual carrier(s) after the wireless communication unit has lost synchronization is described. The method comprises, at the wireless communication unit: entering a sleep mode of operation following communication on a first virtual carrier; waking up from the sleep mode of operation on a default virtual carrier that is not the first virtual carrier; and acquiring synchronization information using synchronization signals that occupy subcarrier resources that overlap with the subcarrier resources occupied by the default virtual carrier to re-synchronize with the wireless communication system.

Polymer projectile having an integrated driving band

Abstract: A lightweight projectile having an integrated driving band positioned around the exterior of the polymer base of the projectile for engaging the rifling of a barrel to impart spin stabilization to the projectile. The driving band protrudes from the polymer base to minimize the contact between the polymer base and the rifling to reduce friction between the barrel and the projectile as the projectile is fired. The reduced friction allows the lightweight projectile to be propelled with minimal propellant force while still retaining the ballistic advantages of a spin stabilized projectile.

Nanoplasmonic Array Enhancement of Two-Photon Absorption in a Dye Film

Abstract: We investigate the enhancement of the effective two-photon absorption cross section of a film of an organic dye by a plasmonic triangular prism array through finite element calculations and experim...

Gun sight for use with superelevating weapon

Abstract: A gun sight is disclosed herein for use with a weapon configured for superelevation. The gun sight includes, but is not limited to, an imaging system configured to capture an image of an area down range of the imaging system, to display the image on a display unit having a display, and further configured to rotate in elevation. The gun sight further includes, but is not limited to, a drive mechanism configured to rotate the imaging system. The gun sight still further includes, but is not limited to, a processor communicatively coupled with the drive mechanism and with the imaging system, the processor configured to receive information from the imaging system relating to the image and to control the drive mechanism based on the information to rotate the imaging system in a manner that causes the image to remain on the display when the weapon is superelevated.

Combination of resonance Raman spectroscopy and docking simulations to study the nonspecific binding of a free-base porphyrin to a globular protein.

Abstract: Understanding the conformational changes induced by small ligands noncovalently bound to proteins is a central problem in biophysics. We focus on the binding location of the water-soluble porphyrin, meso-tetrakis (p-sulfonatophenyl) porphyrin, to a globular protein, β-lactoglobulin, which has been observed to partially unfold when irradiated by laser light. Identifying the binding location is necessary to determine the mechanism of action as well as the atoms and residues involved in the photoinduced partial unfolding. Such atomic details are typically investigated by nuclear magnetic resonance or X-ray crystallography. However, for biomolecules in solution at the low concentrations (μM) required to deliver uniform laser irradiation, these traditional techniques do not currently provide sufficient information, and one must rely upon less direct spectroscopic methods. We describe a method that uses resonance Raman spectroscopy and density functional theory (DFT) to select the most likely binding configuration among a set of solutions yielded by computational docking algorithms. This methodology may be generalized to use with other ligand-protein complexes where the ligand structure is amenable to DFT simulations.

Alternative Mechanisms in Hydrogen Production by Aluminum Anion Clusters

Abstract: Possible mechanisms for the reaction of aluminum anion clusters with water have been studied theoretically using density functional theory for four different size clusters. Our results confirm the previously found (Reber et al. J. Phys. Chem. A2010, 114, 6071) importance of Lewis-acid and Lewis-base sites on the cluster in the size specificity of the reactivity. However, alternative viable mechanisms have been found using both Langmuir–Hinshelwood and Eley–Rideal kinetics. Grotthuss-like mechanisms appear to be the most energetically favorable. We show that while the superatom theory successfully predicts reactivity of smaller clusters, it is less useful for the larger clusters.

Effect of β-bromo substitution on the photophysical properties of meso-phenyl, meso-carbazole, and meso-triphenylamine porphyrins

Abstract: We present results of an experimental photophysical study of a series of novel brominated and non-brominated porphyrins that contain phenyl, carbazole, or triphenylamine in the meso-position. In addition we have looked at the effects of incorporating a zinc metal into the porphyrin system relative to the free base. Structure-property relationships are established using various absorption and emission techniques including femtosecond pump probe transient absorption and nanosecond laser flash photolysis. With slightly increasing electron donating strength (phenyl < carbazole < triphenylamine) red shifts were observed in all data. The same effect was observed upon the addition of bromine in the beta position. Due to the heavy atom affect of the bromines both the singlet and triplet excited state lifetimes were significantly shorter in the brominated porphyrins. For the T1–Tn absorption data we observe a large absorption in the near infrared region with the brominated carbazole and triphenylamine. The largest effect of the addition of zinc was in the ground state absorption and emission where a blue shift in the data was observed. Some effects were also observed in the kinetic decays with zinc as the metal compared to the free base porphyrins.

Cognitive wireless local area network over fibers: Architecture, research issues and testbed implementation

Abstract: We introduce a novel architecture incorporating broadband radio over optical fiber and cognitive radio technologies into a unified network platform named Cognitive Wireless Local Area Network over Fibers (CWLANoF). We first elaborate on the system architecture and more specifically on various topologies to integrate optical fibers and wireless devices in CWLANoF. The mixture of centralized processing capability as well as distributed sets of antennas in this system leads to a rich set of research issues that are presented in this article. Finally, we present a testbed architecture built on a software defined radio platform, along with its implementation and test plans.

Communication units, integrated circuits and methods for supporting a virtual carrier

Abstract: A network element for controlling a usage of at least one resource is described. The network element comprises: a transmitter for transmitting a signal identifying at least one uplink resource to at least one wireless communication unit; a signal processor operably coupled to the transmitter for generating the signal; and a receiver for receiving a transmission from the at least one wireless communication unit on the identified at least one uplink resource. The signal processor is arranged to allocate the uplink resource for the at least one wireless communication unit in a first portion of a first sub-frame on a first frequency and a first portion of a second sub-frame on a second frequency wherein a time gap is allocated between an end of the first portion of the first sub-frame and a beginning of the first portion of a second sub-frame.

The effect of simulated field storage conditions on the accuracy of rapid user-friendly blood pathogen detection kits.

Abstract: Being able to test for the presence of blood pathogens at forward locations could reduce morbidity and mortality in the field. Rapid, user-friendly blood typing kits for detecting Human Immunodeficiency Virus (HIV), Hepatitis C Virus (HCV), and Hepatitis B Virus (HBV) were evaluated to determine their accuracy after storage at various temperatures/humidities. Rates of positive tests of control groups, experimental groups, and industry standards were compared (Fisher's exact χ2, p ≤ 0.05). Compared to the control group, 2 of 10 HIV detection devices were adversely affected by exposure to high temperature/high humidity or high temperature/low humidity. With one exception, none of the environmentally exposed HCV or HBV detection devices exhibited significant differences compared to those stored under control conditions. For HIV, HCV, and HBV devices, there were differences compared to the industry standard. Collectively, this evaluation of pathogen detection kits revealed that diagnostic performance ...

Analysis of link performance for the FOENEX laser communications system

Abstract: A series of experiments were conducted to validate the performance of the free-space optical communications (FSOC) subsystem under DARPA's FOENEX program. Over six days, bidirectional links at ranges of 10 and 17 km were characterized during different periods of the day to evaluate link performance. This paper will present the test configuration, evaluate performance of the FSOC subsystem against a variety of characterization approaches, and discuss the impact of the results, particularly with regards to the optical terminals. Finally, this paper will summarize the impact of turbulence conditions on the FSOC subsystem and present methods for estimating performance under different link distances and turbulence conditions.

Polymeric waveguide electro-optic beam-steering device with DNA biopolymer conductive cladding layers

Abstract: A polymer electro-optic (EO) waveguide beam-steering device with deoxyribonucleic acid (DNA) biopolymer conductive cladding layers and a core layer of the commercially available EO polymer SEO100 is demonstrated with 100% relative poling efficiency. This demonstration device exhibits a deflection efficiency of 99 mrad/kV with a corresponding in-device EO coefficient r33 of 124 pm/V at 1550 nm. When the DNA biopolymer bottom cladding layer is replaced by the commonly used cladding polymer UV15, the deflection efficiency and in-device r33 drop to 34 mrad/kV and 43 pm/V, respectively.

Short recoil impulse averaging weapon system

Abstract: A weapon system is provided. The weapon system includes a receiver and an operating group. The operating group includes a barrel extension at least partially housed within the receiver and arranged to axially translate relative to the receiver; an operating rod (op-rod) assembly arranged to axially translate within the barrel extension; and a bolt assembly arranged to axially translate within the barrel extension. The system further includes a gas accelerator coupled to the barrel and the op-rod assembly; a buffer assembly including a self-centering spring and a hydraulic piston assembly having a first end coupled to the receiver and a second end coupled to the barrel extension; and a feeder coupled to the receiver and configured to provide the round to the operating group.

Spectroscopic structure-property relationships of a series of polyaromatic platinum acetylides.

Abstract: To develop a structure–spectroscopic property relationship in platinum acetylides having poly(aromatic hydrocarbon) ligands, we synthesized a series of chromophores with systematic variation in the...