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Sample records for pointer driven microheater

  1. A laser pointer driven microheater for precise local heating and conditional gene regulation in vivo. Microheater driven gene regulation in zebrafish

    PubMed Central

    2009-01-01

    Background Tissue heating has been employed to study a variety of biological processes, including the study of genes that control embryonic development. Conditional regulation of gene expression is a particularly powerful approach for understanding gene function. One popular method for mis-expressing a gene of interest employs heat-inducible heat shock protein (hsp) promoters. Global heat shock of hsp-promoter-containing transgenic animals induces gene expression throughout all tissues, but does not allow for spatial control. Local heating allows for spatial control of hsp-promoter-driven transgenes, but methods for local heating are cumbersome and variably effective. Results We describe a simple, highly controllable, and versatile apparatus for heating biological tissue and other materials on the micron-scale. This microheater employs micron-scale fiber optics and uses an inexpensive laser-pointer as a power source. Optical fibers can be pulled on a standard electrode puller to produce tips of varying sizes that can then be used to reliably heat 20-100 μm targets. We demonstrate precise spatiotemporal control of hsp70l:GFP transgene expression in a variety of tissue types in zebrafish embryos and larvae. We also show how this system can be employed as part of a new method for lineage tracing that would greatly facilitate the study of organogenesis and tissue regulation at any time in the life cycle. Conclusion This versatile and simple local heater has broad utility for the study of gene function and for lineage tracing. This system could be used to control hsp-driven gene expression in any organism simply by bringing the fiber optic tip in contact with the tissue of interest. Beyond these uses for the study of gene function, this device has wide-ranging utility in materials science and could easily be adapted for therapeutic purposes in humans. PMID:20042114

  2. Microheater Array Boiling Experiment

    NASA Technical Reports Server (NTRS)

    Kim, Jungho; McQuillen, John; Balombin, Joe

    2002-01-01

    By conducting pool boiling tests in microgravity, the effect of buoyancy on the overall boiling process and the relative magnitude of other phenomena can be assessed. Data from KC-135 and sounding rocket experiments indicate little effect of gravity on boiling heat transfer at wall superheats below 25 C, despite vast differences in bubble behavior between gravity levels. In microgravity, a large primary bubble, surrounded by smaller satellite bubbles, moved over the surface, occasionally causing nucleation. Once formed, the primary bubble size remained constant for a given superheat, indicating evaporation at the bubble base is balanced with condensation on the bubble cap. The primary bubble's size increased with wall superheat. Most heaters under the primary bubble had low heat transfer rates, suggesting liquid dryout. Strong Marangoni convection developed in microgravity, forming a 'jet' into the bulk liquid that forced the bubble onto the heater. An experiment is being designed for the. Microgravity Science Glovebox. This experiment uses two 96 element microheater arrays, 2.7 and 7.0 mm in size. These heaters are individually controlled to operate at a constant temperature, measuring local heat fluxes as a function of time and space. Most boiling experiments operate at constant wall heat flux with larger heaters, allowing only time and space-averaged measurements. Each heater is about the bubble departure size in normal gravity, but significantly smaller than the bubble departure size in reduced gravity.

  3. Fortran 90 pointers vs ``Cray`` pointers

    SciTech Connect

    Martin, J.

    1991-10-23

    The Fortran 77 standard does not contain pointer facilities, but because of heavy user demand, many Fortran 77 compilers have been extended with ``Cray`` pointers. The demand for pointers in Fortran was heard by the standards committee, X3J3, and a pointer facility was added to the follow-on Fortran standard, Fortran 90. X3J3, for reasons that may soon become apparent, chose not to follow existing practice and specify ``Cray`` pointers, but to standardize a somewhat different pointer facility. Fortran 90 pointers complement the Fortran 90 language; they fit will with the new Fortran 90 array processing and data facilities. The popularity of ``Cray`` pointers indicates that they fit well with Fortran 77, and since Fortran 90 contains all of Fortran 77, it would be possible to extend Fortran 90 processors to accept ``Cray`` pointers as well. This would make it easier for existing codes that use pointers to migrate to new Fortran 90 processors. But is it a good idea for a processor to provide two pointer facilities? How difficult is it to convert from ``Cray`` pointers to Fortran 90 pointers? This paper provides some information that may be helpful in answering these questions.

  4. Fortran 90 pointers vs Cray'' pointers

    SciTech Connect

    Martin, J.

    1991-10-23

    The Fortran 77 standard does not contain pointer facilities, but because of heavy user demand, many Fortran 77 compilers have been extended with Cray'' pointers. The demand for pointers in Fortran was heard by the standards committee, X3J3, and a pointer facility was added to the follow-on Fortran standard, Fortran 90. X3J3, for reasons that may soon become apparent, chose not to follow existing practice and specify Cray'' pointers, but to standardize a somewhat different pointer facility. Fortran 90 pointers complement the Fortran 90 language; they fit will with the new Fortran 90 array processing and data facilities. The popularity of Cray'' pointers indicates that they fit well with Fortran 77, and since Fortran 90 contains all of Fortran 77, it would be possible to extend Fortran 90 processors to accept Cray'' pointers as well. This would make it easier for existing codes that use pointers to migrate to new Fortran 90 processors. But is it a good idea for a processor to provide two pointer facilities How difficult is it to convert from Cray'' pointers to Fortran 90 pointers This paper provides some information that may be helpful in answering these questions.

  5. Tin Oxide Microheater for Chemical Sensors

    NASA Astrophysics Data System (ADS)

    Gharesi, Mohsen; Ansari, Mohammad

    2016-03-01

    Tin oxide is the main material utilized for the fabrication of chemical sensing pellets which operate at elevated temperatures. The heating is commonly carried out with ruthenium dioxide resistors. Here, a tin oxide-based microheater is developed for microsensor applications. These microheaters are fabricated on 0.5 mm thick alumina substrates using spray pyrolysis technique. The optimum SnO2 heaters have a sheet resistivity in the 40-70 Ω/a range. Ohmic Ag/SnO2 contacts are formed by silver paste printing followed by an appropriate thermal annealing, which provide connections to the external circuitry. Durability tests are carried out on several samples; the long-term performance of the fabricated devices is satisfactory. The method allows the elimination of the expensive ruthenium dioxide from the structure of generic gas sensors.

  6. An Acoustothermal Microheater with Omni-temperature Controllability

    NASA Astrophysics Data System (ADS)

    Ha, Byung Hang; Lee, Kang Soo; Destgeer, Ghulam; Park, Jinsoo; Jung, Jin Ho; Sung, Hyung Jin

    Here we report the first observation of rapid volumetric heating of polydimethylsiloxane (PDMS) under cyclic loadings at a range of high (∼MHz) frequencies. Based on the finding, we developed a microheater which utilizes the vibration damping of PDMS, the most commonly used material in microfluidics, induced by sound waves generated and precisely controlled by a surface acoustic wave (SAW) microfluidic system. An omni-temperature controllability of the microheater enabled us to perform two-step continuous flow polymerase chain reaction for a billion-fold amplification of 134 bp DNA amplicon in less than 45 sec.

  7. X-ray beam pointer

    NASA Technical Reports Server (NTRS)

    Nelson, C. W.

    1980-01-01

    Inexpensive, readily assembled pointer aims X-ray machine for welded assembly radiographs. Plumb bob used for vertical alinement and yardstick used to visualize X-ray paths were inconvenient and inaccurate. Pointer cuts alinement time by one-half and eliminates necessity of retakes. For 3,000 weld radiographs, pointer will save 300 worker-hours and significant materials costs.

  8. GNU Fortran Cray Pointer Extension

    Energy Science and Technology Software Center (ESTSC)

    2005-07-27

    The gfortran compiler is a Fortran front end to the GNU Compiler Collection. The Cray Pointer extension adds to this existing compiler support for Cray-style integer pointers. This non-standard but widely used extension adds the functionality of C-like pointers to the Fortran language.

  9. Photothermal lesions in soft tissue induced by optical fiber microheaters.

    PubMed

    Pimentel-Domínguez, Reinher; Moreno-Álvarez, Paola; Hautefeuille, Mathieu; Chavarría, Anahí; Hernández-Cordero, Juan

    2016-04-01

    Photothermal therapy has shown to be a promising technique for local treatment of tumors. However, the main challenge for this technique is the availability of localized heat sources to minimize thermal damage in the surrounding healthy tissue. In this work, we demonstrate the use of optical fiber microheaters for inducing thermal lesions in soft tissue. The proposed devices incorporate carbon nanotubes or gold nanolayers on the tips of optical fibers for enhanced photothermal effects and heating of ex vivo biological tissues. We report preliminary results of small size photothermal lesions induced on mice liver tissues. The morphology of the resulting lesions shows that optical fiber microheaters may render useful for delivering highly localized heat for photothermal therapy. PMID:27446642

  10. Photothermal lesions in soft tissue induced by optical fiber microheaters

    PubMed Central

    Pimentel-Domínguez, Reinher; Moreno-Álvarez, Paola; Hautefeuille, Mathieu; Chavarría, Anahí; Hernández-Cordero, Juan

    2016-01-01

    Photothermal therapy has shown to be a promising technique for local treatment of tumors. However, the main challenge for this technique is the availability of localized heat sources to minimize thermal damage in the surrounding healthy tissue. In this work, we demonstrate the use of optical fiber microheaters for inducing thermal lesions in soft tissue. The proposed devices incorporate carbon nanotubes or gold nanolayers on the tips of optical fibers for enhanced photothermal effects and heating of ex vivo biological tissues. We report preliminary results of small size photothermal lesions induced on mice liver tissues. The morphology of the resulting lesions shows that optical fiber microheaters may render useful for delivering highly localized heat for photothermal therapy. PMID:27446642

  11. Infrared Risley beam pointer

    NASA Astrophysics Data System (ADS)

    Harford, Steven T.; Gutierrez, Homero; Newman, Michael; Pierce, Robert; Quakenbush, Tim; Wallace, John; Bornstein, Michael

    2014-03-01

    Ball Aerospace & Technologies Corp. (BATC) has developed a Risley Beam Pointer (RBP) mechanism capable of agile slewing, accurate pointing and high bandwidth. The RBP is comprised of two wedged prisms that offer a wide Field of Regard (FOR) and may be manufactured and operated with diffraction limited optical quality. The tightly packaged mechanism is capable of steering a 4 inch beam over a 60° half angle cone with better than 60 μrad precision. Absolute accuracy of the beam steering is better than 1 mrad. The conformal nature of the RBP makes it an ideal mechanism for use on low altitude aircraft and unmanned aerial vehicles. Unique aspects of the opto-mechanical design include i) thermal compliance to maintain bearing preload and optical figure over a wide temperature range; and ii) packaging of a remote infrared sensor that periodically reports the temperature of both prisms for accurate determination of the index of refraction. The pointing control system operates each prism independently and employs an inner rate loop nested within an outer position loop. Mathematics for the transformation between line-of-sight coordinates and prism rotation are hosted on a 200 MHz microcontroller with just 516 KB of RAM.

  12. Safety recommendations for laser pointers.

    PubMed

    Rockwell, R J; Ertle, W J; Moss, C E

    1998-08-01

    The use of laser diode pointers that operate in the visible radiation region (400-760 nm) is becoming widespread. These pointers are intended for use by educators while presenting talks in the classroom or at conventions and meetings. They are also useful in any situation where one needs to point out special items during any instructive situation. The pointers can be purchased in novelty stores, mail-order magazines, office supply stores, common electronic stores, and over the internet. The power omitted by these laser pointers ranges from 1 to 5 mW. The potential for hazard with laser pointers is generally considered to be limited to the unprotected eyes of individuals who might be exposed by a direct beam (intrabeam viewing). No skin hazard usually exists. There are, however, even more powerful laser pointers now appearing. The units are imported into the U.S. often without proper manufacturer certification or labeling. The potential for hazards with these devices is not well understood by the general public and workers, and numerous exposure incidents have been recorded by the authors. Users of these products need to be alerted to the potential hazards and be encouraged to follow appropriate safety recommendations. These factors are discussed and safety recommendations for laser pointers are presented. PMID:10182367

  13. Reduction of thermal emission background in high temperature microheaters

    NASA Astrophysics Data System (ADS)

    Armstrong, Philip R.; Mah, Merlin L.; Olson, Kyle D.; Taylor, Lucas N.; Talghader, Joseph J.

    2016-05-01

    High temperature microheaters have been designed and constructed to reduce the background thermal emission radiation produced by the heater. Such heaters allow one to probe luminescence with very low numbers of photons where the background emission would overwhelm the desired signal. Two methods to reduce background emission are described: one with low emission materials and the other with interference coating design. The first uses platforms composed of material that is transparent to mid-infrared light and therefore of low emissivity. Heating elements are embedded in the periphery of the heater. The transparent platform is composed of aluminum oxide, which is largely transparent for wavelengths less than about 8 μm. In the luminescent microscopy used to test the heater, an optical aperture blocks emission from the heating coils while passing light from the heated objects on the transparent center of the microheater. The amount of infrared light transmitted through the aperture was reduced by 90% as the aperture was moved from the highly emissive heater coils at 450 °C to the largely transparent center at the same temperature. The second method uses microheaters with integrated multilayer interference structures designed to limit background emission in the spectral range of the low-light luminescence object being measured. These heaters were composed of aluminum oxide, titanium dioxide, and platinum and were operated over a large range of temperatures, from 50 °C to 600 °C. At 600 °C, they showed a background photon emission only 1/800 that of a comparison heater without the multilayer interference structure. In this structure, the radiation background was sufficiently reduced to easily monitor weak thermoluminescent emission from CaSO4:Ce,Tb microparticles.

  14. Virus based Full Colour Pixels using a Microheater

    NASA Astrophysics Data System (ADS)

    Kim, Won-Geun; Kim, Kyujung; Ha, Sung-Hun; Song, Hyerin; Yu, Hyun-Woo; Kim, Chuntae; Kim, Jong-Man; Oh, Jin-Woo

    2015-09-01

    Mimicking natural structures has been received considerable attentions, and there have been a few practical advances. Tremendous efforts based on a self-assembly technique have been contributed to the development of the novel photonic structures which are mimicking nature’s inventions. We emulate the photonic structures from an origin of colour generation of mammalian skins and avian skin/feathers using M13 phage. The structures can be generated a full range of RGB colours that can be sensitively switched by temperature and substrate materials. Consequently, we developed an M13 phage-based temperature-dependent actively controllable colour pixels platform on a microheater chip. Given the simplicity of the fabrication process, the low voltage requirements and cycling stability, the virus colour pixels enable us to substitute for conventional colour pixels for the development of various implantable, wearable and flexible devices in future.

  15. Virus based Full Colour Pixels using a Microheater.

    PubMed

    Kim, Won-Geun; Kim, Kyujung; Ha, Sung-Hun; Song, Hyerin; Yu, Hyun-Woo; Kim, Chuntae; Kim, Jong-Man; Oh, Jin-Woo

    2015-01-01

    Mimicking natural structures has been received considerable attentions, and there have been a few practical advances. Tremendous efforts based on a self-assembly technique have been contributed to the development of the novel photonic structures which are mimicking nature's inventions. We emulate the photonic structures from an origin of colour generation of mammalian skins and avian skin/feathers using M13 phage. The structures can be generated a full range of RGB colours that can be sensitively switched by temperature and substrate materials. Consequently, we developed an M13 phage-based temperature-dependent actively controllable colour pixels platform on a microheater chip. Given the simplicity of the fabrication process, the low voltage requirements and cycling stability, the virus colour pixels enable us to substitute for conventional colour pixels for the development of various implantable, wearable and flexible devices in future. PMID:26334322

  16. Virus based Full Colour Pixels using a Microheater

    PubMed Central

    Kim, Won-Geun; Kim, Kyujung; Ha, Sung-Hun; Song, Hyerin; Yu, Hyun-Woo; Kim, Chuntae; Kim, Jong-Man; Oh, Jin-Woo

    2015-01-01

    Mimicking natural structures has been received considerable attentions, and there have been a few practical advances. Tremendous efforts based on a self-assembly technique have been contributed to the development of the novel photonic structures which are mimicking nature’s inventions. We emulate the photonic structures from an origin of colour generation of mammalian skins and avian skin/feathers using M13 phage. The structures can be generated a full range of RGB colours that can be sensitively switched by temperature and substrate materials. Consequently, we developed an M13 phage-based temperature-dependent actively controllable colour pixels platform on a microheater chip. Given the simplicity of the fabrication process, the low voltage requirements and cycling stability, the virus colour pixels enable us to substitute for conventional colour pixels for the development of various implantable, wearable and flexible devices in future. PMID:26334322

  17. Thread Migration in the Presence of Pointers

    NASA Technical Reports Server (NTRS)

    Cronk, David; Haines, Matthew; Mehrotra, Piyush

    1996-01-01

    Dynamic migration of lightweight threads supports both data locality and load balancing. However, migrating threads that contain pointers referencing data in both the stack and heap remains an open problem. In this paper we describe a technique by which threads with pointers referencing both stack and non-shared heap data can be migrated such that the pointers remain valid after migration. As a result, threads containing pointers can now be migrated between processors in a homogeneous distributed memory environment.

  18. The design, fabrication and characterization of a silicon microheater for an integrated MEMS gas preconcentrator

    NASA Astrophysics Data System (ADS)

    Yeom, Junghoon; Field, Christopher R.; Bae, Byunghoon; Masel, Richard I.; Shannon, Mark A.

    2008-12-01

    We report the design and fabrication of a microheater unit as a key component of an integrated micro gas preconcentrator that has an ultra-small preconcentrator volume (<0.25 µL) and microvalves for fast injection speeds (<1 ms). Monolithic integration of the microvalves into the microheater of the preconcentrator gives rise to challenges in designing the microheater and implementing thermal isolation for low power and energy consumption. A preconcentrator chamber, 3.5 × 1.5 mm2 in planform area and 40 µm deep, was built in the device layer of a silicon-on-insulator wafer and filled with an array of microposts with a preconcentrator volume of 0.2-0.25 µL. Different generations of the microheaters and their mating dies were fabricated to show the effects of thermal isolation and thermal mass of the system on the performance of the heater. The microheater assembly with the least thermal mass and most thermal isolation can reach 300 °C in 100 ms with 12.3 W of power and is expected to consume less than 2 J during the operation of each preconcentration cycle.

  19. A Light-Activated Microheater for the Remote Control of Enzymatic Catalysis.

    PubMed

    Cao, Yuanyuan; Wang, Zhen; Liao, Shenglong; Wang, Jian; Wang, Yapei

    2016-01-18

    The remote control of enzymatic catalysis is of significant importance in disease treatment and industrial applications. Herein, we designed a microheater composed of a porous polylactic acid (PLA) matrix and polydopamine (PDA) with notable photothermal conversion capability. Starch hydrolysis, catalyzed by using α-amylase, was accelerated in the presence of the microheater under illumination with near-infrared light or natural sunlight at room temperature. Additionally, the methodology was extended to the preparation of microwave-absorbing materials with the deposition of polyaniline on porous PLA matrix. The porous morphology improves the energy-conversion efficiency. PMID:26603499

  20. Dynamic behaviors of approximately ellipsoidal microbubbles photothermally generated by a graphene oxide-microheater

    PubMed Central

    Xing, Xiaobo; Zheng, Jiapeng; Li, Fengjia; Sun, Chao; Cai, Xiang; Zhu, Debin; Lei, Liang; Wu, Ting; Zhou, Bin; Evans, Julian; Chen, Ziyi

    2014-01-01

    Thermal microbubbles generally grow directly from the heater and are spherical to minimize surface tension. We demonstrate a novel type of microbubble indirectly generated from a graphene oxide-microheater. Graphene oxide's photothermal properties allowed for efficient generation of a thermal gradient field on the microscale. A series of approximately ellipsoidal microbubbles were generated on the smooth microwire based on heterogeneous nucleation. Other dynamic behaviors induced by the microheater such as constant growth, directional transport and coalescence were also investigated experimentally and theoretically. The results are not only helpful for understanding the bubble dynamics but also useful for developing novel photothermal bubble-based devices. PMID:25124694

  1. Development of microheaters for gas sensor with an AT-Mega 8535 temperature controller using a PWM (pulse width modulation) method

    NASA Astrophysics Data System (ADS)

    Megayanti, Meti; Panatarani, Camellia; Joni, I. Made

    2016-03-01

    Microheater is the main component in gas sensor characterized by their sensitivity, selectivity, and time response of gas sensor which is depend on the microheater temperature stability. A Cu microheater was developed and utilized AT-Mega 8535 controller using a PWM (pulse width modulation) method. This control system is interfaced to the PC to observe the real time temperature response of the microheater. Three initial resistance (R0) variations of microheater were developed in an open loop control system. The power characteristic of designed microheater depends on the specified microheater initial resistance. The smaller R0, the less power required to reach a temperature setting value. The developed microheater was designed to reach a temperature setting value of 250°C having resistance 0.531 Ω for 1.979 Watt and 0.265 Ω for 1.072 Watt respectively. The results of the investigation on the control performances shows microheater-control system achieved operating temperature up to 250°C. The response of the temperature control shows smallest R0 resulted in a high stability with short settling time, short delay time and small ripple for temperature setting values higher than 150°C. The obtained error of microheater temperature with R0 = 0.265 is 8.596 %. It is concluded that the developed microheater can be utilized as a component of a gas sensor.

  2. Development and characterization of a microheater array device for real-time DNA mutation detection

    NASA Astrophysics Data System (ADS)

    Williams, Layne; Okandan, Murat; Chagovetz, Alex; Blair, Steve

    2008-04-01

    DNA analysis, specifically single nucleotide polymorphism (SNP) detection, is becoming increasingly important in rapid diagnostics and disease detection. Temperature is often controlled to help speed reaction rates and perform melting of hybridized oligonucleotides. The difference in melting temperatures, Tm, between wild-type and SNP sequences, respectively, to a given probe oligonucleotide, is indicative of the specificity of the reaction. We have characterized Tm's in solution and on a solid substrate of three sequences from known mutations associated with Cystic Fibrosis. Taking advantage of Tm differences, a microheater array device was designed to enable individual temperature control of up to 18 specific hybridization events. The device was fabricated at Sandia National Laboratories using surface micromachining techniques. The microheaters have been characterized using an IR camera at Sandia and show individual temperature control with minimal thermal cross talk. Development of the device as a real-time DNA detection platform, including surface chemistry and associated microfluidics, is described.

  3. Development and characterization of a microheater array device for real-time DNA mutation detection

    NASA Astrophysics Data System (ADS)

    Williams, Layne; Okandan, Murat; Chagovetz, Alex; Blair, Steve

    2008-02-01

    DNA analysis, specifically single nucleotide polymorphism (SNP) detection, is becoming increasingly important in rapid diagnostics and disease detection. Temperature is often controlled to help speed reaction rates and perform melting of hybridized oligonucleotides. The difference in melting temperatures, Tm, between wild-type and SNP sequences, respectively, to a given probe oligonucleotide, is indicative of the specificity of the reaction. We have characterized Tm's in solution and on a solid substrate of three sequences from known mutations associated with Cystic Fibrosis. Taking advantage of Tm differences, a microheater array device was designed to enable individual temperature control of up to 18 specific hybridization events. The device was fabricated at Sandia National Laboratories using surface micromachining techniques. The microheaters have been characterized using an IR camera at Sandia and show individual temperature control with minimal thermal cross talk. Development of the device as a real-time DNA detection platform, including surface chemistry and associated microfluidics, is described.

  4. Modeling and experimental investigation of an integrated optical microheater in silicon-on-insulator.

    PubMed

    Kaushal, Saket; Das, Bijoy Krishna

    2016-04-10

    A linear piecewise model has been formulated to analyze the performance of a metallic microheater integrated with single-mode waveguides (λ∼1550  nm) in silicon-on-insulator (SOI). The model has been used to evaluate integrated optical microheaters fabricated in a SOI substrate with 2 µm device layer thickness. The Fabry-Perot modulation technique has been used to extract the effective thermo-optic phase shift and response time. The effective thermal power budget of Peff,π∼500  µW (out of actually consumed power Pπ=1.1  mW) for a π phase shift and a switching time of τ∼9  µs, have been recorded for a typical Ti heater stripe of length LH=50  µm, width WH=2  µm, and thickness tH∼150  nm, integrated with a Fabry-Perot waveguide cavity of length ∼20  mm. It has been shown that the performance of a heater improves (in terms of power budget) as the length of a microheater decreases. However, smaller heater size requires higher joule heating to obtain a desired phase shift, which is again found to be dependent on polarization of the guided mode because of thermal stress. PMID:27139842

  5. Adaptive Optics Imaging in Laser Pointer Maculopathy.

    PubMed

    Sheyman, Alan T; Nesper, Peter L; Fawzi, Amani A; Jampol, Lee M

    2016-08-01

    The authors report multimodal imaging including adaptive optics scanning laser ophthalmoscopy (AOSLO) (Apaeros retinal image system AOSLO prototype; Boston Micromachines Corporation, Boston, MA) in a case of previously diagnosed unilateral acute idiopathic maculopathy (UAIM) that demonstrated features of laser pointer maculopathy. The authors also show the adaptive optics images of a laser pointer maculopathy case previously reported. A 15-year-old girl was referred for the evaluation of a maculopathy suspected to be UAIM. The authors reviewed the patient's history and obtained fluorescein angiography, autofluorescence, optical coherence tomography, infrared reflectance, and AOSLO. The time course of disease and clinical examination did not fit with UAIM, but the linear pattern of lesions was suspicious for self-inflicted laser pointer injury. This was confirmed on subsequent questioning of the patient. The presence of linear lesions in the macula that are best highlighted with multimodal imaging techniques should alert the physician to the possibility of laser pointer injury. AOSLO further characterizes photoreceptor damage in this condition. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:782-785.]. PMID:27548458

  6. Three-Dimensional Pointers for Stereoscopic Projection.

    ERIC Educational Resources Information Center

    Hayman, H. J. G.

    1984-01-01

    Because class size often limits student opportunity to handle individual models, teachers use stereoscopic projections to demonstrate structural features. Describes three-dimensional pointers for use with different projection systems so teachers can indicate a particular atom or bond to entire classes, avoiding the perspective problems inherent in…

  7. Microheater as an alternative to lasers for in-vitro fertilization applications

    NASA Astrophysics Data System (ADS)

    Palanker, Daniel V.; Turovets, Igor; Glazer, Rima; Reubinoff, Benjamin E.; Hilman, Dalia; Lewis, Aaron

    1999-06-01

    During the last decade various lasers have been applied to drilling of the micrometer-sized holes in the zona pellucida of oocytes for in-vitro fertilization applications. In this paper we describe an alternative approach to laser instrumentation based on microfabricated device capable of precise drilling of uniform holes in the zona pellucida of oocytes. This device consists of a thin (1 micrometer) film microheater built on the tip of glass capillary with a diameter varying between a few to a few tens of micrometers. Duration of the pulse of heat produced by this microheater determines the spatial confinement of the heat wave in the surrounding liquid medium. We have demonstrated that gradual microdrilling of the zona pellucida can be accomplished using a series of pulses with duration of about 300 microseconds when the microheater was held in contact with the zona pellucida. Pulse energy applied to 20 micrometer tip was about 4 (mu) J. In vitro development and hatching of 127 micromanipulated embryos was compared to 103 non-drilled control embryos. The technique was found to be highly efficient in creating round, uniform, well defined holes with a smooth wall surface, matching the size of the heating source. The architecture of the surrounding zona pellucida was unaffected by the drilling, as demonstrated by scanning electron microscopy. Micromanipulated embryos presented no signs of thermal damage under light microscopy. The rate of blastocyst formation and hatching was similar in the micromanipulated and control groups. Following further testing in animal models, this methodology may be used as a cost- effective alternative to laser-based instrumentation in clinical applications such as assisted hatching and embryo biopsy.

  8. Assessment of the risk from laser pointers

    NASA Astrophysics Data System (ADS)

    Moseley, Harry; Tulley, F. M.

    2001-01-01

    We have examined a number of laser pointers that have been removed form the possession of accused persons by police in Scotland. An analysis of the first 30 consecutive items has shown that 28 were Class 3B, with radiated power up to 9.3 mW. These are potentially hazardous if viewed directly. Transient exposure is unlikely to cause long-term damage but prolonged exposure may cause permanent retinal injury.

  9. Optofluidic microvalve-on-a-chip with a surface plasmon-enhanced fiber optic microheater.

    PubMed

    Kim, Hyun-Tae; Bae, Hyungdae; Zhang, Zhijian; Kusimo, Abisola; Yu, Miao

    2014-09-01

    We present an optofluidic microvalve utilizing an embedded, surface plasmon-enhanced fiber optic microheater. The fiber optic microheater is formed by depositing a titanium thin film on the roughened end-face of a silica optical fiber that serves as a waveguide to deliver laser light to the titanium film. The nanoscale roughness at the titanium-silica interface enables strong light absorption enhancement in the titanium film through excitation of localized surface plasmons as well as facilitates bubble nucleation. Our experimental results show that due to the unique design of the fiber optic heater, the threshold laser power required to generate a bubble is greatly reduced and the bubble growth rate is significantly increased. By using the microvalve, stable vapor bubble generation in the microchannel is demonstrated, which does not require complex optical focusing and alignment. The generated vapor bubble is shown to successfully block a liquid flow channel with a size of 125 μm × 125 μm and a flow rate of ∼10 μl/min at ∼120 mW laser power. PMID:25538813

  10. Optofluidic microvalve-on-a-chip with a surface plasmon-enhanced fiber optic microheater

    PubMed Central

    Zhang, Zhijian; Kusimo, Abisola; Yu, Miao

    2014-01-01

    We present an optofluidic microvalve utilizing an embedded, surface plasmon-enhanced fiber optic microheater. The fiber optic microheater is formed by depositing a titanium thin film on the roughened end-face of a silica optical fiber that serves as a waveguide to deliver laser light to the titanium film. The nanoscale roughness at the titanium-silica interface enables strong light absorption enhancement in the titanium film through excitation of localized surface plasmons as well as facilitates bubble nucleation. Our experimental results show that due to the unique design of the fiber optic heater, the threshold laser power required to generate a bubble is greatly reduced and the bubble growth rate is significantly increased. By using the microvalve, stable vapor bubble generation in the microchannel is demonstrated, which does not require complex optical focusing and alignment. The generated vapor bubble is shown to successfully block a liquid flow channel with a size of 125 μm × 125 μm and a flow rate of ∼10 μl/min at ∼120 mW laser power. PMID:25538813

  11. Permanent retinal injury from recreational laser pointer.

    PubMed

    Noble, Carl; Blice, Jeffrey

    2015-03-01

    This case report was performed to display the visually significant damage to the retina that can occur with brief exposure to a handheld laser pointer. Laser use in the military is ever increasing in form of target designators, rangefinders, or radar warning systems with powers far greater than used in this case. There is great potential for future cases of retinal damage among active duty members, and the importance of prevention through laser safety programs and recognition through trained medical personnel is paramount. PMID:25735035

  12. POINTER: Portable Intelligent Trainer for External Robotics

    NASA Technical Reports Server (NTRS)

    Kuiper, Hilbert; Rikken, Patrick J.

    1994-01-01

    Intelligent tutoring systems (ITS's) play an increasing role in training and education of people with different levels of skill and knowledge. As compared to conventional computer based training (CBT) an ITS provides more tailored instruction by trying to mimic the teaching behavior of a human instructor as much as possible and is therefore much more flexible. This paper starts with an introduction to ITS's, followed by the description of an ITS for training of an (astronaut) operator in monitoring and controlling robotic arm procedures. The robotic arm will be used for exchange of equipment between a space station and a space plane involving critical and accurate movements of the robotic arm. The ITS for this application, called Pointer, is developed by TNO Physics and Electronics Laboratory and is based upon an existing ITS that includes procedural training. Pointer has been developed on a workstation whereas the target platform was a portable computer. Therefore, a lot of attention had to be paid to scaling effects and keeping up with user friendliness of the much smaller user interface. Although the learning domain was the control of a robotic arm, it is clear that use of intelligent training technologies on a portable computer has many other applications (payload operations, operation control rooms, etc.). Training can occur at any time and place in an attractive and cost effective way.

  13. Advanced Reference Counting Pointers for Better Performance

    NASA Technical Reports Server (NTRS)

    Reinholtz, William

    2007-01-01

    A computer program implements reference counting pointers (RCPs) that are lock-free, thread-safe, async-safe, and operational on a multiprocessor computer. RCPs are powerful and convenient means of managing heap memory in C++ software. Most prior RCP programs use locks to ensure thread safety and manage concurrency. The present program was developed in a continuing effort to explore ways of using the C++ programming language to develop safety-critical and mission- critical software. This effort includes exploration of lock-free algorithms because they offer potential to avoid some costly and difficult verification problems. Unlike previously published RCP software, the present program does not use locks (meaning that no thread can block progress on another thread): Instead, this program implements algorithms that exploit capabilities of central-processing- unit hardware so as to avoid locks. Once locks are eliminated, it becomes possible to realize the other attributes mentioned in the first sentence. In addition to the abovementioned attributes, this program offers several advantages over other RCP programs that use locks: It is smaller (and, hence, is faster and uses less memory), it is immune to priority inversion, and there is no way for it to cause a C++ exception.

  14. X-Ray Diffraction Simulation Using Laser Pointers and Printers.

    ERIC Educational Resources Information Center

    Johnson, Neil E.

    2001-01-01

    Uses a laser pointer to demonstrate the analogy between optical and X-ray diffraction and a laser printer with 600 or 1200 dot resolution to create and modify arrays, print them on transparencies, and illuminate them with laser pointers. Includes 14 references. (Author/YDS)

  15. 49 CFR 384.220 - Problem Driver Pointer System information.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 5 2013-10-01 2013-10-01 false Problem Driver Pointer System information. 384.220... COMPLIANCE WITH COMMERCIAL DRIVER'S LICENSE PROGRAM Minimum Standards for Substantial Compliance by States § 384.220 Problem Driver Pointer System information. Before issuing a CLP or CDL to any person,...

  16. 49 CFR 384.220 - Problem Driver Pointer System information.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 5 2014-10-01 2014-10-01 false Problem Driver Pointer System information. 384.220... COMPLIANCE WITH COMMERCIAL DRIVER'S LICENSE PROGRAM Minimum Standards for Substantial Compliance by States § 384.220 Problem Driver Pointer System information. Before issuing a CLP or CDL to any person,...

  17. 49 CFR 384.220 - Problem Driver Pointer System information.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 5 2012-10-01 2012-10-01 false Problem Driver Pointer System information. 384.220... COMPLIANCE WITH COMMERCIAL DRIVER'S LICENSE PROGRAM Minimum Standards for Substantial Compliance by States § 384.220 Problem Driver Pointer System information. Before issuing a CLP or CDL to any person,...

  18. Thermopower measurements of atomic and molecular junctions using microheater-embedded mechanically-controllable break junctions

    NASA Astrophysics Data System (ADS)

    Tsutsui, Makusu; Morikawa, Takanori; Arima, Akihide; Taniguchi, Masateru

    2015-03-01

    There has been growing interest in developing high-performance thermoelectric materials for realizing thermoelectric power generation. Quantum confinement effects in low-dimensional structures are expected to provide high electronic density of states for enhanced thermopower, and thus considered as a promising approach for achieving a high figure of merit (M. S. Dresselhaus et al., Adv. Mat. 19 (2007) 1043-1053). From this respect, it is interesting to study thermoelectric properties of atomic and molecular junctions and evaluate their potential as a thermoelectric material. Recently, we have developed a heater-embedded micro-fabricated mechanically-controllable break junction (MCBJ) for investigating the thermoelectric transport in single-atom and -molecule junctions. Using the MCBJ devices, we could repeatedly form stable junctions at room temperatures via a self-breaking mechanism with one side being heated by the adjacent microheater. In my presentation, I will show the results of simultaneous measurements of the thermoelectric voltage and the electrical conductance of atom-sized Au junctions and Au-benzenedithiol-Au junctions and discuss on the geometrical dependence of thermoelectric transport.

  19. Bilateral macular injury from a green laser pointer.

    PubMed

    Dirani, Ali; Chelala, Elias; Fadlallah, Ali; Antonios, Rafic; Cherfan, George

    2013-01-01

    We report the case of a 13-year-old boy who had a bilateral macular injury after playing with a green laser pointer for a duration of 1 minute. Clinical examination revealed a decrease in visual acuity and macular injury in both eyes, and imaging investigations revealed a bilateral macular lesion due to exposure to the laser pointer. At 3 months' follow up, visual function had improved but remained partially impaired. This case emphasizes the importance of cautious and appropriate use of laser pointer devices because of the potential vision-threatening hazards induced by mishandling of these devices. PMID:24204114

  20. Laser pointer induced macular damage: case report and mini review.

    PubMed

    Turaka, Kiran; Bryan, J Shepard; Gordon, Alan J; Reddy, Rahul; Kwong, Henry M; Sell, Clive H

    2012-06-01

    To report laser pointer induced damage to retina and choroid and briefly review literature. A case report of a 13-year old Caucasian boy developed blurry central vision and central scotoma in right eye (OD). He was exposed for one minute to class IIIA green laser pointer of 650 nm wavelength and 5 mW power. Clinical examination showed a grayish lesion in foveal region. Ancillary testing revealed disruption of the retinal pigment epithelial (RPE) layer in foveal region and indocyanine green angiography demonstrated evidence of choroidal hypofluorescence suggestive of choroidal infarction in OD. Visual acuity improved from 20/100 to 20/60 in one day and he was treated with tapering doses of oral prednisolone (40 mg) for 3 weeks. Laser pointer with a power of >5 mW caused damage to RPE in the macula. Children should not be given laser pointers as toys especially those with label of danger instructions. PMID:22466425

  1. Laser Pointers Can Cause Serious Eye Damage in Kids

    MedlinePlus

    ... that needs to be considered," Almeida said. "Legislation [regulating the pointers] is probably overkill, given the numbers ... the journal Pediatrics . SOURCES: David Almeida, M.D., Ph.D., ophthalmologist, Minneapolis; Charles Wykoff, M.D., Ph. ...

  2. Thermoelectric voltage measurements of atomic and molecular wires using microheater-embedded mechanically-controllable break junctions

    NASA Astrophysics Data System (ADS)

    Morikawa, Takanori; Arima, Akihide; Tsutsui, Makusu; Taniguchi, Masateru

    2014-06-01

    We developed a method for simultaneous measurements of conductance and thermopower of atomic and molecular junctions by using a microheater-embedded mechanically-controllable break junction. We find linear increase in the thermoelectric voltage of Au atomic junctions with the voltage added to the heater. We also detect thermopower oscillations at several conductance quanta reflecting the quantum confinement effects in the atomic wire. Under high heater voltage conditions, on the other hand, we observed a peculiar behaviour in the conductance dependent thermopower, which was ascribed to a disordered contact structure under elevated temperatures.

  3. Weak measurements with orbital-angular-momentum pointer states.

    PubMed

    Puentes, G; Hermosa, N; Torres, J P

    2012-07-27

    Weak measurements are a unique tool for accessing information about weakly interacting quantum systems with minimal back action. Joint weak measurements of single-particle operators with pointer states characterized by a two-dimensional Gaussian distribution can provide, in turn, key information about quantum correlations that can be relevant for quantum information applications. Here we demonstrate that by employing two-dimensional pointer states endowed with orbital angular momentum (OAM), it is possible to extract weak values of the higher order moments of single-particle operators, an inaccessible quantity with Gaussian pointer states only. We provide a specific example that illustrates the advantages of our method both in terms of signal enhancement and information retrieval. PMID:23006067

  4. Eosinophilic cystitis in a female German wire-haired pointer

    PubMed Central

    Evason, Michelle D.; Carr, Anthony P.

    2007-01-01

    A 7-month-old, intact female, German wire-haired pointer presented with a 3-week history of stranguria, pollakiuria, and dysuria that was nonresponsive to antibiotics. Two prior episodes of dysuria-stranguria appeared to respond to antibiotic therapy. Bladder wall biopsies revealed eosinophilic cystitis and the dog responded well to medical management. PMID:17542370

  5. Activities Using Headsticks and Optical Pointers: A Description of Methods.

    ERIC Educational Resources Information Center

    Eriksson, Britt-Marie; And Others

    A variety of head-mounted aids have been developed in the past decade to fill in the functional gaps of children and adults unable to use their hands at standard capacity. For those with speech difficulties, the optical pointer, headstick and mouthstick also provide communication alternatives. This handbook discusses the characteristics of several…

  6. 49 CFR 384.220 - Problem Driver Pointer System information.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 5 2011-10-01 2011-10-01 false Problem Driver Pointer System information. 384.220 Section 384.220 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION FEDERAL MOTOR CARRIER SAFETY REGULATIONS STATE COMPLIANCE WITH COMMERCIAL...

  7. Evaluation of a green laser pointer for flow cytometry.

    PubMed

    Habbersett, Robert C; Naivar, Mark A; Woods, Travis A; Goddard, Gregory R; Graves, Steven W

    2007-10-01

    Flow cytometers typically incorporate expensive lasers with high-quality (TEM00) output beam structure and very stable output power, significantly increasing system cost and power requirements. Red diode lasers minimize power consumption and cost, but limit fluorophore selection. Low-cost DPSS laser pointer modules could possibly offer increased wavelength selection but presumed emission instability has limited their use. A $160 DPSS 532 nm laser pointer module was first evaluated for noise characteristics and then used as the excitation light source in a custom-built flow cytometer for the analysis of fluorescent calibration and alignment microspheres. Eight of ten modules tested were very quiet (RMS noise < or = 0.6% between 0 and 5 MHz). With a quiet laser pointer module as the light source in a slow-flow system, fluorescence measurements from alignment microspheres produced CVs of about 3.3%. Furthermore, the use of extended transit times and < or =1 mW of laser power produced both baseline resolution of all 8 peaks in a set of Rainbow microspheres, and a detection limit of <20 phycoerythrin molecules per particle. Data collected with the transit time reduced to 25 micros (in the same instrument but at 2.4 mW laser output) demonstrated a detection limit of approximately 75 phycoerythrin molecules and CVs of about 2.7%. The performance, cost, size, and power consumption of the tested laser pointer module suggests that it may be suitable for use in conventional flow cytometry, particularly if it were coupled with cytometers that support extended transit times. PMID:17712796

  8. Coupling-deformed pointer observables and weak values

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Xiang; Wu, Shengjun; Chen, Zeng-Bing

    2016-03-01

    While the novel applications of weak values have recently attracted wide attention, weak measurement, the usual way to extract weak values, suffers from risky approximations and severe quantum noises. In this paper, we show that the weak-value information can be obtained exactly in strong measurement with postselections, via measuring the coupling-deformed pointer observables, i.e., the observables selected according to the coupling strength. With this approach, we keep all the advantages claimed by weak-measurement schemes and at the same time solve some widely criticized problems thereof, such as the questionable universality, systematical bias, and drastic inefficiency.

  9. Light polarization experiments with a diode laser pointer

    NASA Astrophysics Data System (ADS)

    Benenson, Raymond E.

    2000-01-01

    Polarized light has many uses: glare reduction, stress analysis, microscope image enhancement, thin-film characterization, astronomy, saccharimetry, and atomic spectroscopy. Here we discuss introductory polarized light measurements in which a diode laser pointer replaces the more frequently used polarized He-Ne laser. A diode laser has been used in introductory optics experiments, and in a more advanced polarization-reflection experiment. Its strong collimated beam is completely polarized and, being free of infrared radiation, it permits Polaroid sheets to be used successfully with semiconductor detectors.

  10. Predictability sieve, pointer states, and the classicality of quantum trajectories

    SciTech Connect

    Dalvit, D. A. R.; Zurek, W. H.; Dziarmaga, J.

    2005-12-15

    We study various measures of classicality of the states of open quantum systems subject to decoherence. Classical states are expected to be stable in spite of decoherence, and are thought to leave conspicuous imprints on the environment. Here these expected features of environment-induced superselection are quantified using four different criteria: predictability sieve (which selects states that produce least entropy), purification time (which looks for states that are the easiest to find out from the imprint they leave on the environment), efficiency threshold (which finds states that can be deduced from measurements on a smallest fraction of the environment), and purity loss time (that looks for states for which it takes the longest to lose a set fraction of their initial purity). We show that when pointer states--the most predictable states of an open quantum system selected by the predictability sieve--are well defined, all four criteria agree that they are indeed the most classical states. We illustrate this with two examples: an underdamped harmonic oscillator, for which coherent states are unanimously chosen by all criteria, and a free particle undergoing quantum Brownian motion, for which most criteria select almost identical Gaussian states (although, in this case, the predictability sieve does not select well defined pointer states)

  11. Fast-Response, Sensitivitive and Low-Powered Chemosensors by Fusing Nanostructured Porous Thin Film and IDEs-Microheater Chip

    PubMed Central

    Dai, Zhengfei; Xu, Lei; Duan, Guotao; Li, Tie; Zhang, Hongwen; Li, Yue; Wang, Yi; Wang, Yuelin; Cai, Weiping

    2013-01-01

    The chemiresistive thin film gas sensors with fast response, high sensitivity, low power consumption and mass-produced potency, have been expected for practical application. It requires both sensitive materials, especially exquisite nanomaterials, and efficient substrate chip for heating and electrical addressing. However, it is challenging to achieve repeatable microstructures across the films and low power consumption of substrate chip. Here we presented a new sensor structure via the fusion of metal-oxide nanoporous films and micro-electro-mechanical systems (MEMS)-based sensing chip. An interdigital-electrodes (IDEs) and microheater integrated MEMS structure is designed and employed as substrate chip to in-situ fabricate colloidal monolayer template-induced metal-oxide (egg. SnO2) nanoporous sensing films. This fused sensor demonstrates mW-level low power, ultrafast response (~1 s), and parts-per-billion lever detection for ethanol gas. Due to the controllable template strategy and mass-production potential, such micro/nano fused high-performance gas sensors will be next-generation key miniaturized/integrated devices for advanced practical applications. PMID:23591580

  12. Fast-Response, Sensitivitive and Low-Powered Chemosensors by Fusing Nanostructured Porous Thin Film and IDEs-Microheater Chip

    NASA Astrophysics Data System (ADS)

    Dai, Zhengfei; Xu, Lei; Duan, Guotao; Li, Tie; Zhang, Hongwen; Li, Yue; Wang, Yi; Wang, Yuelin; Cai, Weiping

    2013-04-01

    The chemiresistive thin film gas sensors with fast response, high sensitivity, low power consumption and mass-produced potency, have been expected for practical application. It requires both sensitive materials, especially exquisite nanomaterials, and efficient substrate chip for heating and electrical addressing. However, it is challenging to achieve repeatable microstructures across the films and low power consumption of substrate chip. Here we presented a new sensor structure via the fusion of metal-oxide nanoporous films and micro-electro-mechanical systems (MEMS)-based sensing chip. An interdigital-electrodes (IDEs) and microheater integrated MEMS structure is designed and employed as substrate chip to in-situ fabricate colloidal monolayer template-induced metal-oxide (egg. SnO2) nanoporous sensing films. This fused sensor demonstrates mW-level low power, ultrafast response (~1 s), and parts-per-billion lever detection for ethanol gas. Due to the controllable template strategy and mass-production potential, such micro/nano fused high-performance gas sensors will be next-generation key miniaturized/integrated devices for advanced practical applications.

  13. Direct state reconstruction with coupling-deformed pointer observables

    NASA Astrophysics Data System (ADS)

    Zhu, Xuanmin; Zhang, Yu-Xiang; Wu, Shengjun

    2016-06-01

    Direct state tomography (DST) using weak measurements has received wide attention. Based on the concept of coupling-deformed pointer observables presented by Zhang et al. [Y.-X. Zhang, S. Wu, and Z.-B. Chen, Phys. Rev. A 93, 032128 (2016), 10.1103/PhysRevA.93.032128], a modified direct state tomography (MDST) is proposed, examined, and compared with other typical state tomography schemes. MDST has exact validity for measurements of any strength. We identify the strength needed to attain the highest efficiency level of MDST by using statistical theory. MDST is much more efficient than DST in the sense that far fewer samples are needed to reach DST's level of reconstruction accuracy. Moreover, MDST has no inherent bias when compared to DST.

  14. A Scalable Nonuniform Pointer Analysis for Embedded Program

    NASA Technical Reports Server (NTRS)

    Venet, Arnaud

    2004-01-01

    In this paper we present a scalable pointer analysis for embedded applications that is able to distinguish between instances of recursively defined data structures and elements of arrays. The main contribution consists of an efficient yet precise algorithm that can handle multithreaded programs. We first perform an inexpensive flow-sensitive analysis of each function in the program that generates semantic equations describing the effect of the function on the memory graph. These equations bear numerical constraints that describe nonuniform points-to relationships. We then iteratively solve these equations in order to obtain an abstract storage graph that describes the shape of data structures at every point of the program for all possible thread interleavings. We bring experimental evidence that this approach is tractable and precise for real-size embedded applications.

  15. [Laser pointers are not toys; eye injury with permanent loss of visual acuity].

    PubMed

    Keunen, Jan E E; Delbecq, Ann-Laure M H; Cruysberg, J R M Hans; van Meurs, Jan C; Gan, Ivan M; Berendschot, Tos T J M

    2014-01-01

    In the nineteen-nineties, there was much hype in the European media about presumed laser pointer maculopathy. However, the recent introduction of more powerful and therefore more dangerous laser pointers and their easy availability on the internet necessitates vigilance on the issue. This is an urgent matter, as here we report three cases of proven maculopathy due to an unsafe laser pointer. Three boys aged 13, 9 and 12 years used an unsafe laser pointer as a toy and looked repeatedly into the pointer, resulting in a permanent reduction in visual acuity due to macular damage. Laser pointers are not designed to be children's toys or instruments to annoy people in a crowd. Health authorities and the ophthalmic community should be aware of the potential danger of improper use of high-output laser pointers and warn the general public before the widespread availability of unsafe laser pointers and consequently laser pointer-induced macular damage becomes a true social problem. PMID:25308223

  16. Heat transfer and bubble detachment in subcooled pool boiling from a downward-facing microheater array in a nonuniform electric field.

    PubMed

    Liu, Zan; Herman, Cila; Kim, Jungho

    2009-04-01

    The effects of a nonuniform electric field on vapor bubble detachment and heat transfer in subcooled pool boiling from a microheater array are investigated. The heater array faced downward to simulate a -1 g gravity condition and to eliminate the dominant masking effect of the buoyancy force. Experiments were conducted at different subcooling levels for various wall temperatures and electric field magnitudes. A dielectric fluid, FC-72, was used as the working fluid at ambient pressure. The array of 3 x 3 independently controlled microheaters was maintained at constant temperature and the rate of heat transfer from each heater was measured. Bubble images were recorded using a high-speed camera. The electric field was applied between the horizontal downward-facing microheater array, which was grounded, and a spherical, off-axis electrode beneath it. Boiling heat transfer results with and without the electric field are presented in this study. In the absence of the nonuniform electric field, compared to the same bulk fluid temperature and wall superheat settings in the +1 g situation, a much larger primary bubble was formed on the heater array, due to the coalescence of the secondary bubbles that nucleated on the heater array. The vapor bubble remained on the heater array surface and no bubble detachment was observed. With the nonuniform electric field applied, bubbles were lifted and sheared off from the heater array surface. The electric field was able to break up the primary bubble into several smaller bubbles--considerably greater heat transfer enhancement was measured than under similar conditions in +1 g. PMID:19426316

  17. Pointer states for primordial fluctuations in inflationary cosmology

    NASA Astrophysics Data System (ADS)

    Kiefer, Claus; Lohmar, Ingo; Polarski, David; Starobinsky, Alexei A.

    2007-04-01

    Primordial fluctuations in inflationary cosmology acquire classical properties through decoherence when their wavelengths become larger than the Hubble scale. Although decoherence is effective, it is not complete, so a significant part of primordial correlations remains up to the present moment. We address the issue of the pointer states which provide a classical basis for the fluctuations with respect to the influence by an environment (other fields). Applying methods from the quantum theory of open systems (the Lindblad equation), we show that this basis is given by narrow Gaussians that approximate eigenstates of field amplitudes. We calculate both the von Neumann and linear entropy of the fluctuations. Their ratio to the maximal entropy per field mode defines a degree of partial decoherence in the entropy sense. We also determine the time of partial decoherence making the Wigner function positive everywhere which, for super-Hubble modes during inflation, is virtually independent of coupling to the environment and is only slightly larger than the Hubble time. On the other hand, assuming a representative environment (a photon bath), the decoherence time for sub-Hubble modes is finite only if some real dissipation exists.

  18. SSRPT (SSR Pointer Trackeer) for Cassini Mission Operations - A Ground Data Analysis Tool

    NASA Technical Reports Server (NTRS)

    Kan, E.

    1998-01-01

    Tracking the resources of the two redundant Solid State Recorders (SSR) is a necessary routine for Cassini spacecraft mission operations. Instead of relying on a full-fledged spacecraft hardware/software simulator to track and predict the SSR recording and playback pointer positions, a stand-alone SSR Pointer Tracker tool was developed as part of JPL's Multimission Spacecraft Analysis system.

  19. Retinal damage induced by mirror-reflected light from a laser pointer.

    PubMed

    Thanos, Solon; Böhm, Michael R R; Meyer zu Hörste, Melissa; Schmidt, Peter-Fritz

    2015-01-01

    The safety of laser pointers is a major public health issue since class I and II laser pointers are available worldwide and used as toys by children despite several reports cautioning such use. Here we present the first case of retinal injury caused by the laser beam of a toy laser pointer operated by a school boy and directed via the rear-view mirror of a bus into the eye of the driver. This case emphasises the great importance of cautious and appropriate use of low-energy laser pointers. Laser pointers of any class should not be made available to children because they are unlikely to understand the risks of such lasers when using them in play. PMID:26438673

  20. An automatic recognition method of pointer instrument based on improved Hough transform

    NASA Astrophysics Data System (ADS)

    Xu, Li; Fang, Tian; Gao, Xiaoyu

    2015-10-01

    For the automatic recognition of pointer instrument, the method for the automatic recognition of pointer instrument based on improved Hough Transform was proposed in this paper. The automatic recognition of pointer instrument is applied to all kinds of lighting conditions, but the accuracy of it binaryzation will be influenced when the light is too strong or too dark. Therefore, the improved Ostu method was suggested to realize recognition for adaptive thresholding of pointer instrument under all kinds of lighting conditions. On the basis of dial image characteristics, Otsu method is used to get the value of maximum between-cluster variance and initial threshold than analyze its maximum between-cluster variance value to determine the light and shade of the image. When the images are too bright or too dark, the smaller pixels should be given up and then calculate the initial threshold by Otsu method again and again until the best binaryzation image was obtained. Hence, transform the pointer straight line of the binaryzation image to Hough parameter space through improved Hough Transform to determine the position of the pointer straight line by searching the maximum value of arrays of the same angle. Finally, according to angle method, the pointer reading was obtained by the linear relationship for the initial scale and angle of the pointer instrument. Results show that the improved Otsu method make pointer instrument possible to obtained the accuracy binaryzation image even though the light is too bright or too dark , which improves the adaptability of pointer instrument to automatic recognize the light under different conditions. For the pressure gauges with range of 60MPa, the relative error identification reached to 0.005 when use the improved Hough Transform Algorithm.

  1. Demonstration of a Balloon Borne Arc-Second Pointer Design

    NASA Technical Reports Server (NTRS)

    DeWeese, Keith D.; Ward, Philip R.

    2006-01-01

    Many designs for utilizing stratospheric balloons as low-cost platforms on which to conduct space science experiments have been proposed throughout the years. A major hurdle in extending the range of experiments for which these vehicles are useful has been the imposition of the gondola dynamics on the accuracy with which an instrument can be kept pointed at a celestial target. A significant number of scientists have sought the ability to point their instruments with jitter in the arc-second range. This paper presents the design and analysis of a stratospheric balloon borne pointing system that is able to meet this requirement. The test results of a demonstration prototype of the design with similar ability are also presented. Discussion of a high fidelity controller simulation for design analysis is presented. The flexibility of the flight train is represented through generalized modal analysis. A multiple controller scheme is utilized for coarse and fine pointing. Coarse azimuth pointing is accomplished by an established pointing system, with extensive flight history, residing above the gondola structure. A pitch-yaw gimbal mount is used for fine pointing, providing orthogonal axes when nominally on target. Fine pointing actuation is from direct drive dc motors, eliminating backlash problems. An analysis of friction nonlinearities and a demonstration of the necessity in eliminating static friction are provided. A unique bearing hub design is introduced that eliminates static friction from the system dynamics. A control scheme involving linear accelerometers for enhanced disturbance rejection is also presented. Results from a linear analysis of the total system and the high fidelity simulation are given. Results from a generalized demonstration prototype are presented. Commercial off-the-shelf (COTS) hardware was used to demonstrate the efficacy and performance of the pointer design for a mock instrument. Sub-arcsecond pointing ability from a ground hang test setup

  2. Thermal macular injury from a 154 mW green laser pointer.

    PubMed

    Lim, Maria E; Suelzer, Joseph; Moorthy, Ramana S; Vemuri, Gautam

    2014-12-01

    We report a case of accidental thermal injury due to improper use of a laser pointer obtained outside of the United States. A 13-year-old received a laser pointer as a gift and looked at a reflection of the beam. The patient underwent full ophthalmologic examination with fundus photography, spectral domain optical coherence tomography, and fluorescein angiography. Visual acuity in the left eye was 20/100 at presentation. Fundus examination and ancillary tests were consistent with thermal macular injury. The laser pointer was analyzed and found to be a green diode laser with average power output of 154 mW. PMID:25448152

  3. ADIFOR working note No. 11: ADIFOR strategies related to POINTER usage in MM5

    SciTech Connect

    Bischof, C.; Khademi, P.; Knauff, T.

    1994-03-01

    POINTERs are nonstandard Fortran statements which cannot be processed by ADIFOR. We are interested in generating derivative code for MM5, a mesoscale model code which uses POINTERs extensively and in a particular structured manner. We briefly report on POINTERs and their role in MM5 and, for their particular usage in MM5, describe the three-step code transformation scheme consisting of pre-ADIFOR, ADIFOR, and post-ADIFOR transformations that result in the generation of correct derivative code for MM5.

  4. Pointers, Lessons Learned, and Rules of Thumb for Successful Vibro-Acoustic Data Acquisition

    NASA Technical Reports Server (NTRS)

    Rossoni, Peter

    1998-01-01

    This presentation contains helpful pointers for successful vibroacoustic data acquisition in the following three areas: Instrumentation, Vibration Control and Pyro-shock data acquisition and analysis. A helpful bibliography is provided.

  5. The Measurement of the Speed of Light Using a Laser Pointer.

    ERIC Educational Resources Information Center

    Mak, Se-yuen; Yip, Din-yan

    2000-01-01

    Presents a method for measuring the speed of light using a laser pointer with adjustable focus as the signal carrier, a signal generator to modulate the light beam, and a student oscilloscope to detect the phase shift. (Author/CCM)

  6. Retinal Damage from Laser Pointer Misuse - Case Series from the Military Sector in Oman.

    PubMed

    Shenoy, Radha; Bialasiewicz, Alexander A; Bandara, Asoka; Isaac, Roshini

    2015-01-01

    Laser pointers are practical and safe training tools when used properly. If used incorrectly they can cause ocular damage, potentially resulting in devastating vision loss. The ocular and visual morbidity can result in significant expenses for medical care and inability to work (temporarily or permanently) for civilians and military personnel. We present three cases of soldiers who experienced vision loss following exposure to laser pointers, while celebrating successful football game. PMID:26180486

  7. Retinal Damage from Laser Pointer Misuse – Case Series from the Military Sector in Oman

    PubMed Central

    Shenoy, Radha; Bialasiewicz, Alexander A; Bandara, Asoka; Isaac, Roshini

    2015-01-01

    Laser pointers are practical and safe training tools when used properly. If used incorrectly they can cause ocular damage, potentially resulting in devastating vision loss. The ocular and visual morbidity can result in significant expenses for medical care and inability to work (temporarily or permanently) for civilians and military personnel. We present three cases of soldiers who experienced vision loss following exposure to laser pointers, while celebrating successfull football game. PMID:26180486

  8. Arc-Second Pointer for Balloon-Borne Astronomical Instrument

    NASA Technical Reports Server (NTRS)

    Ward, Philip R.; DeWeese, Keith

    2004-01-01

    A control system has been designed to keep a balloon-borne scientific instrument pointed toward a celestial object within an angular error of the order of an arc second. The design is intended to be adaptable to a large range of instrument payloads. The initial payload to which the design nominally applies is considered to be a telescope, modeled as a simple thin-walled cylinder 24 ft (approx.= 7.3 m) long, 3 ft (approx.= 0.91 m) in diameter, weighing 1,500 lb (having a mass of .680 kg). The instrument would be mounted on a set of motor-driven gimbals in pitch-yaw configuration. The motors on the gimbals would apply the control torques needed for fine adjustments of the instrument in pitch and yaw. The pitch-yaw mount would, in turn, be suspended from a motor mount at the lower end of a pair of cables hanging down from the balloon (see figure). The motor in this mount would be used to effect coarse azimuth control of the pitch-yaw mount. A notable innovation incorporated in the design is a provision for keeping the gimbal bearings in constant motion. This innovation would eliminate the deleterious effects of static friction . something that must be done in order to achieve the desired arc-second precision. Another notable innovation is the use of linear accelerometers to provide feedback that would facilitate the early detection and counteraction of disturbance torques before they could integrate into significant angular-velocity and angular-position errors. The control software processing the sensor data would be capable of distinguishing between translational and rotational accelerations. The output of the accelerometers is combined with that of angular position and angular-velocity sensors into a proportional + integral + derivative + acceleration control law for the pitch and yaw torque motors. Preliminary calculations have shown that with appropriate gains, the power demand of the control system would be low enough to be satisfiable by means of storage

  9. SD-OCT features of laser pointer maculopathy before and after systemic corticosteroid therapy.

    PubMed

    Hossein, Mohammad; Bonyadi, Jabbarpour; Soheilian, Roham; Soheilian, Masoud; Peyman, Gholam A

    2011-01-01

    The authors report spectral-domain optical coherence tomography findings of laser pointer-induced maculopathy in a 25-year-old man after accidental laser pointer exposure of less than 1 second. The Class 3R laser pointer (output wavelength 532 nm and output power 3.5 to 4.5 mW [continuous wave]) had U.S. Food and Drug Administration certification. One day after exposure, he had visual blurring and metamorphopsia of his right eye. He was treated with a systemic high-dose corticosteroid. Spectral-domain optical coherence tomography disclosed a hyperreflective band in the foveal region. After 1 week of treatment, disappearance of hyperreflectivity was observed on spectral-domain optical coherence tomography. At 6 months, residual disruption of the outer retinal layer at the fovea remained unchanged. Spectral-domain optical coherence tomography was a useful and sensitive tool for evaluating retinal damage and subsequent resolution after treatment. PMID:22165950

  10. Photoblepharokeratoconjunctivitis caused by invisible infrared radiation emitted from a green laser pointer.

    PubMed

    Khedr, Yahya A H; Khedr, Abdulla H

    2014-01-01

    There are a wide variety of laser pointers sold to the general public. Among those are the high-powered diode-pumped solid-state lasers (>5 mW), which do not follow the laser safety regulations for packing, and are sold as regular lasers without the infrared (IR) filters. In this case report, we encountered a patient with photoblepharokeratoconjunctivitis caused by the invisible IR radiations emitted from a green laser pointer. Owing to the thermal effect of the invisible IR rays led to the disease. PMID:24618868

  11. Pointer Animation Implementation at Development of Multimedia Learning of Java Programming

    ERIC Educational Resources Information Center

    Rusli, Muhammad; Atmojo, Yohanes Priyo

    2015-01-01

    This research represents the development research using the references of previous research results related to the development of interactive multimedia learning (learner controlled), specially about the effectiveness and efficiency of multimedia learning of a content that developed by pointer animation implementation showing the content in…

  12. A Laser-Pointer-Based Spectrometer for Endpoint Detection of EDTA Titrations

    ERIC Educational Resources Information Center

    Dahm, Christopher E.; Hall, James W.; Mattioni, Brian E.

    2004-01-01

    A laser spectrometer for the ethylenediaminetetra-acetic acid (EDTA) titration of magnesium or calcium ions that is designed around a handheld laser pointer as the source and a photoresistor as the detector is developed. Findings show that the use of the spectrometer reduces the degree of uncertainty and error in one part of the EDTA titrations,…

  13. Sport Instruction for Individuals with Disabilities. The Best of Practical Pointers.

    ERIC Educational Resources Information Center

    American Alliance for Health, Physical Education, Recreation and Dance, Reston, VA.

    This book, written for teachers by teachers, includes articles by 14 contributing authors and is divided into three sections. Section 1 is entitled "Practical Pointers for Team Sports" and contains the following chapters: "Mainstreaming the Physically Handicapped for Team Sports" (S. J. Grosse); "Program Guide to Team Soccer for the Mentally…

  14. The Trainee Teacher and His Practice Class. Fifty Pointers for the Student-Teacher.

    ERIC Educational Resources Information Center

    Rees, Alun L. W.

    1969-01-01

    This handbook, based on the author's experience of supervising the English practice-classes of trainee teachers, was originally compiled for the specific use of students at the National University of Trujillo, Peru, and consists of a list of pointers embracing the most prevalent of trainees' shortcomings observed over a period of years at all…

  15. Performance of Rank-2 Fortran 90 Pointer Arrays vs. Allocatable Arrays

    SciTech Connect

    Zywicz, E

    2005-10-13

    The computational performance of two-dimensional Fortran 90 arrays defined with the pointer attribute were compared to identically sized arrays defined with the allocatable attribute. The goal of this work was to quantify the computational cost of using each array type within a high-performance finite element setting.

  16. Laser Pointers: Low-Cost, Low-Tech Innovative, Interactive Instruction Tool

    ERIC Educational Resources Information Center

    Zdravkovska, Nevenka; Cech, Maureen; Beygo, Pinar; Kackley, Bob

    2010-01-01

    This paper discusses the use of laser pointers at the Engineering and Physical Sciences Library, University of Maryland, College Park, as a personal response system (PRS) tool to encourage student engagement in and interactivity with one-shot, lecture-based information literacy sessions. Unlike more sophisticated personal response systems like…

  17. Laser-Induced Fluorescence in Gaseous [I[subscript]2] Excited with a Green Laser Pointer

    ERIC Educational Resources Information Center

    Tellinghuisen, Joel

    2007-01-01

    A green laser pointer could be used in a flashy demonstration of laser-induced fluorescence in the gas phase by directing the beam of the laser through a cell containing [I[subscript]2] at its room temperature vapor pressure. The experiment could be used to provide valuable insight into the requirements for laser-induced fluorescence (LIF) and the…

  18. VIEWCACHE: An incremental pointer-based access method for autonomous interoperable databases

    NASA Technical Reports Server (NTRS)

    Roussopoulos, N.; Sellis, Timos

    1993-01-01

    One of the biggest problems facing NASA today is to provide scientists efficient access to a large number of distributed databases. Our pointer-based incremental data base access method, VIEWCACHE, provides such an interface for accessing distributed datasets and directories. VIEWCACHE allows database browsing and search performing inter-database cross-referencing with no actual data movement between database sites. This organization and processing is especially suitable for managing Astrophysics databases which are physically distributed all over the world. Once the search is complete, the set of collected pointers pointing to the desired data are cached. VIEWCACHE includes spatial access methods for accessing image datasets, which provide much easier query formulation by referring directly to the image and very efficient search for objects contained within a two-dimensional window. We will develop and optimize a VIEWCACHE External Gateway Access to database management systems to facilitate database search.

  19. VIEWCACHE: An incremental pointer-based access method for autonomous interoperable databases

    NASA Technical Reports Server (NTRS)

    Roussopoulos, N.; Sellis, Timos

    1992-01-01

    One of biggest problems facing NASA today is to provide scientists efficient access to a large number of distributed databases. Our pointer-based incremental database access method, VIEWCACHE, provides such an interface for accessing distributed data sets and directories. VIEWCACHE allows database browsing and search performing inter-database cross-referencing with no actual data movement between database sites. This organization and processing is especially suitable for managing Astrophysics databases which are physically distributed all over the world. Once the search is complete, the set of collected pointers pointing to the desired data are cached. VIEWCACHE includes spatial access methods for accessing image data sets, which provide much easier query formulation by referring directly to the image and very efficient search for objects contained within a two-dimensional window. We will develop and optimize a VIEWCACHE External Gateway Access to database management systems to facilitate distributed database search.

  20. Certified Absence of Dangling Pointers in a Language with Explicit Deallocation

    NASA Astrophysics Data System (ADS)

    de Dios, Javier; Montenegro, Manuel; Peña, Ricardo

    Safe is a first-order eager functional language with facilities for programmer controlled destruction of data structures. It provides also regions, i.e. disjoint parts of the heap, where the program allocates data structures, so that the runtime system does not need a garbage collector. A region is a collection of cells, each one big enough to allocate a data constructor. Deallocating cells or regions may create dangling pointers. The language is aimed at inferring and certifying memory safety properties in a Proof Carrying Code like environment. Some of its analyses have been presented elsewhere. The one relevant to this paper is a type system and a type inference algorithm guaranteeing that well-typed programs will be free of dangling pointers at runtime.

  1. Implementing MPI-IO atomic mode and shared file pointers using MPI one-sided communication.

    SciTech Connect

    Latham, R.; Ross, R.; Thakur, R.; Mathematics and Computer Science

    2007-07-01

    The ROMIO implementation of the MPI-IO standard provides a portable infrastructure for use on top of a variety of underlying storage targets. These targets vary widely in their capabilities, and in some cases additional effort is needed within ROMIO to support all MPI-IO semantics. Two aspects of the interface that can be problematic to implement are MPI-IO atomic mode and the shared file pointer access routines. Atomic mode requires enforcing strict consistency semantics, and shared file pointer routines require communication and coordination in order to atomically update a shared resource. For some file systems, native locks may be used to implement these features, but not all file systems have lock support. In this work, we describe algorithms for implementing efficient mutex locks using MPI-1 and the one-sided capabilities from MPI-2. We then show how these algorithms may be used to implement both MPI-IO atomic mode and shared file pointer methods for ROMIO without requiring any features from the underlying file system. We show that these algorithms can outperform traditional file system lock approaches. Because of the portable nature of these algorithms, they are likely useful in a variety of situations where distributed locking or coordination is needed in the MPI-2 environment.

  2. Student Perceptions of the Use of a Laser Pointer for Intra-Operative Guidance in Feline Castration.

    PubMed

    Badman, Märit; Höglund, Katja; Höglund, Odd V

    2016-01-01

    In veterinary clinical education, students perform surgery under guided supervision. This study aimed to determine if students' perception of how well they understood verbal guidance could be improved by using a laser pointer during feline castration. It was assumed that a teacher's use of a laser pointer could help students identify structures of importance during surgery. The hypothesis was that use of a laser pointer would improve student understanding of verbal guidance during surgery. Eighteen privately owned male cats were electively neutered by fourth- and fifth-year veterinary students at the Swedish University of Agricultural Sciences, Uppsala, Sweden. Each student performed orchiectomy on one cat. One testis was removed while the student received verbal guidance combined with a laser pointer, and the other testis was removed while the student received only verbal guidance. The use of a laser pointer alternated between first and second testis. After surgery, students rated how well they understood verbal guidance on a visual-analog scale (100 mm) for each instructional method. The two ratings were compared in a student's two-sided t-test. The median score with or without guidance with a laser pointer was 81 (59-96) and 54 (25-86), respectively (p<.001). This study showed that laser pointers enhanced verbal guidance given to students during surgery. The suggested mechanism of explanation is that the technology enabled a more precise guidance of location and identification of anatomic structures. PMID:27128854

  3. Gyroscope-driven mouse pointer with an EMOTIV® EEG headset and data analysis based on Empirical Mode Decomposition.

    PubMed

    Rosas-Cholula, Gerardo; Ramirez-Cortes, Juan Manuel; Alarcon-Aquino, Vicente; Gomez-Gil, Pilar; Rangel-Magdaleno, Jose de Jesus; Reyes-Garcia, Carlos

    2013-01-01

    This paper presents a project on the development of a cursor control emulating the typical operations of a computer-mouse, using gyroscope and eye-blinking electromyographic signals which are obtained through a commercial 16-electrode wireless headset, recently released by Emotiv. The cursor position is controlled using information from a gyroscope included in the headset. The clicks are generated through the user's blinking with an adequate detection procedure based on the spectral-like technique called Empirical Mode Decomposition (EMD). EMD is proposed as a simple and quick computational tool, yet effective, aimed to artifact reduction from head movements as well as a method to detect blinking signals for mouse control. Kalman filter is used as state estimator for mouse position control and jitter removal. The detection rate obtained in average was 94.9%. Experimental setup and some obtained results are presented. PMID:23948873

  4. Gyroscope-Driven Mouse Pointer with an EMOTIV® EEG Headset and Data Analysis Based on Empirical Mode Decomposition

    PubMed Central

    Rosas-Cholula, Gerardo; Ramirez-Cortes, Juan Manuel; Alarcon-Aquino, Vicente; Gomez-Gil, Pilar; Rangel-Magdaleno, Jose de Jesus; Reyes-Garcia, Carlos

    2013-01-01

    This paper presents a project on the development of a cursor control emulating the typical operations of a computer-mouse, using gyroscope and eye-blinking electromyographic signals which are obtained through a commercial 16-electrode wireless headset, recently released by Emotiv. The cursor position is controlled using information from a gyroscope included in the headset. The clicks are generated through the user's blinking with an adequate detection procedure based on the spectral-like technique called Empirical Mode Decomposition (EMD). EMD is proposed as a simple and quick computational tool, yet effective, aimed to artifact reduction from head movements as well as a method to detect blinking signals for mouse control. Kalman filter is used as state estimator for mouse position control and jitter removal. The detection rate obtained in average was 94.9%. Experimental setup and some obtained results are presented. PMID:23948873

  5. SEQ-POINTER: Next generation, planetary spacecraft remote sensing science observation design tool

    NASA Technical Reports Server (NTRS)

    Boyer, Jeffrey S.

    1994-01-01

    Since Mariner, NASA-JPL planetary missions have been supported by ground software to plan and design remote sensing science observations. The software used by the science and sequence designers to plan and design observations has evolved with mission and technological advances. The original program, PEGASIS (Mariners 4, 6, and 7), was re-engineered as POGASIS (Mariner 9, Viking, and Mariner 10), and again later as POINTER (Voyager and Galileo). Each of these programs were developed under technological, political, and fiscal constraints which limited their adaptability to other missions and spacecraft designs. Implementation of a multi-mission tool, SEQ POINTER, under the auspices of the JPL Multimission Operations Systems Office (MOSO) is in progress. This version has been designed to address the limitations experienced on previous versions as they were being adapted to a new mission and spacecraft. The tool has been modularly designed with subroutine interface structures to support interchangeable celestial body and spacecraft definition models. The computational and graphics modules have also been designed to interface with data collected from previous spacecraft, or on-going observations, which describe the surface of each target body. These enhancements make SEQ POINTER a candidate for low-cost mission usage, when a remote sensing science observation design capability is required. The current and planned capabilities of the tool will be discussed. The presentation will also include a 5-10 minute video presentation demonstrating the capabilities of a proto-Cassini Project version that was adapted to test the tool. The work described in this abstract was performed by the Jet Propulsion Laboratory, California Institute of Technology, under contract to the National Aeronautics and Space Administration.

  6. Controlling mouse pointer position using an infrared head-operated joystick.

    PubMed

    Evans, D G; Drew, R; Blenkhorn, P

    2000-03-01

    This paper describes the motivation for and the design considerations of a low-cost head-operated joystick. The paper briefly summarizes the requirements of head-operated mouse pointer control for people with disabilities before discussing a set of technological approaches that can be used to satisfy these requirements. The paper focuses on the design of a head-operated joystick that uses infrared light emitting diodes (LED's) and photodetectors to determine head position, which is subsequently converted into signals that emulate a Microsoft mouse. There are two significant findings. The first is that, while nonideal device characteristics might appear to make the joystick difficult to use, users naturally compensate for nonlinearities, in a transparent manner, because of visual feedback of mouse pointer position. The second finding, from relatively informal, independent trials, indicates that disabled users prefer a head-operated device that has the characteristics of a joystick (a relative pointing device) to those of a mouse (an absolute pointing device). PMID:10779114

  7. Structural features of a potential gas hydrate area in the Pointer Ridge off southwest Taiwan

    NASA Astrophysics Data System (ADS)

    Wang, Hsueh-Fen; Hsu, Shu-Kun; Tsai, Ching-Hui; Chen, Song-Chuen; Liu, Char-Shine; Lin, Hsiao-Shan

    2015-04-01

    The offshore area of the southwest Taiwan is located in the oblique convergence zone between the northern continental margin of South China Sea and the Manila accretionary wedge. To the west of the deformation front offshore southwestern Taiwan, the Pointer Ridge is located in the passive South China Sea continental margin. The continental margin is compose of extensional horst-and-graben structures. There are numerous submarine channels and linear ridge, formed due to the submarine erosion across the continental slope region. According to geophysical research off SW Taiwan, abundant gas hydrate may exist. In this study, our purpose is to understand the relationship between the near-seafloor structures of the Pointer Ridge and the gas hydrate formation off SW Taiwan. The data we used include multi-beam echo sounder (MBES), side-scan sonar (SSS), sub-bottom profiler (SBP) and the multi-channel reflection seismic (MCS) data. Our results show the pockmark and gas seepage structures mainly appear in the place where the gradient of the BSR thickness is maximum. Those sites contain authigenic carbonate signature shown in the sub-bottom profiler. We also observe several folds and faults structures in this extensional background; however, these compressional features need further studies.

  8. Optimizing Semantic Pointer Representations for Symbol-Like Processing in Spiking Neural Networks.

    PubMed

    Gosmann, Jan; Eliasmith, Chris

    2016-01-01

    The Semantic Pointer Architecture (SPA) is a proposal of specifying the computations and architectural elements needed to account for cognitive functions. By means of the Neural Engineering Framework (NEF) this proposal can be realized in a spiking neural network. However, in any such network each SPA transformation will accumulate noise. By increasing the accuracy of common SPA operations, the overall network performance can be increased considerably. As well, the representations in such networks present a trade-off between being able to represent all possible values and being only able to represent the most likely values, but with high accuracy. We derive a heuristic to find the near-optimal point in this trade-off. This allows us to improve the accuracy of common SPA operations by up to 25 times. Ultimately, it allows for a reduction of neuron number and a more efficient use of both traditional and neuromorphic hardware, which we demonstrate here. PMID:26900931

  9. Detection of explosives and latent fingerprint residues utilizing laser pointer-based Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Malka, Itamar; Petrushansky, Alona; Rosenwaks, Salman; Bar, Ilana

    2013-12-01

    A modular, compact Raman spectrometer, based on a green laser pointer, an air cooled intensified charged coupled device and a x, y motorized translation stage was developed and applied for point detection. Its performance was tested for measurements of Raman spectra of liquids, trace amounts of explosives and individual particles, as well as for locating individual particles of interest and for chemical imaging of residues of latent human fingerprints. This system was found to be highly sensitive, identifying masses as low as ~1 ng in short times. The point and real-time detection capabilities of the spectrometer, together with the portability that it offers, make it a potential candidate for replacing existing Raman microscopes and for field applications.

  10. Optimizing Semantic Pointer Representations for Symbol-Like Processing in Spiking Neural Networks

    PubMed Central

    Gosmann, Jan; Eliasmith, Chris

    2016-01-01

    The Semantic Pointer Architecture (SPA) is a proposal of specifying the computations and architectural elements needed to account for cognitive functions. By means of the Neural Engineering Framework (NEF) this proposal can be realized in a spiking neural network. However, in any such network each SPA transformation will accumulate noise. By increasing the accuracy of common SPA operations, the overall network performance can be increased considerably. As well, the representations in such networks present a trade-off between being able to represent all possible values and being only able to represent the most likely values, but with high accuracy. We derive a heuristic to find the near-optimal point in this trade-off. This allows us to improve the accuracy of common SPA operations by up to 25 times. Ultimately, it allows for a reduction of neuron number and a more efficient use of both traditional and neuromorphic hardware, which we demonstrate here. PMID:26900931

  11. Pretty Lights and Glowing Rocks: Using Lasers Pointers to Demonstrate Optical Phenomena

    NASA Astrophysics Data System (ADS)

    Huang, A.; Bodner, G.; Zheng, C.

    2011-12-01

    Green and violet lasers have recently become both inexpensive and portable, more than 70 years after the first laser was built. Despite the technology's age, the general public is still fascinated by the exotic nature of laser light. This activity uses green and violet laser pointers to produce a veritable rainbow of colors from household items and common minerals. Our objective is to create an educational experience which uses vivid colors and appealing effects to engage the audience, while teaching basic optical concepts such as scattering, fluorescence, Snell's law, and the quantum nature of light. The activity can be adapted to a lecture demonstration or to a laboratory exercise in which students handle the lasers and test samples. Learning outcomes have not been formally measured, but this demonstration will still captivate audiences in museum settings, community outreach programs, and introductory science courses.

  12. Analogue mouse pointer control via an online steady state visual evoked potential (SSVEP) brain-computer interface

    NASA Astrophysics Data System (ADS)

    Wilson, John J.; Palaniappan, Ramaswamy

    2011-04-01

    The steady state visual evoked protocol has recently become a popular paradigm in brain-computer interface (BCI) applications. Typically (regardless of function) these applications offer the user a binary selection of targets that perform correspondingly discrete actions. Such discrete control systems are appropriate for applications that are inherently isolated in nature, such as selecting numbers from a keypad to be dialled or letters from an alphabet to be spelled. However motivation exists for users to employ proportional control methods in intrinsically analogue tasks such as the movement of a mouse pointer. This paper introduces an online BCI in which control of a mouse pointer is directly proportional to a user's intent. Performance is measured over a series of pointer movement tasks and compared to the traditional discrete output approach. Analogue control allowed subjects to move the pointer faster to the cued target location compared to discrete output but suffers more undesired movements overall. Best performance is achieved when combining the threshold to movement of traditional discrete techniques with the range of movement offered by proportional control.

  13. Peace and Conflict Research in the Age of the Cholera: Ten Pointers to the Future of Peace Studies.

    ERIC Educational Resources Information Center

    Galtung, Johan

    1996-01-01

    Presents 10 pointers that can lead to constructive peace making. Covers issues such as a definition of peace; the training of peace workers; the role of the state system in creating conflict; legitimizing peace actions; and suggestions for future peace creation. Discusses the links between direct, structural, and cultural violence. (DSK)

  14. A Mobile Robot Operation with Instruction of Neck Movement using Laser Pointer

    NASA Astrophysics Data System (ADS)

    Shibata, Satoru; Yamamoto, Tomonori; Jindai, Mitsuru

    A human-robot system in which a mobile robot follows the movement of the laser spot projected on the floor by the laser pointer attached at the human head is considered. Human gives instruction of desired movement to the omni-directional mobile robot by rotating his or her head. The mobile robot can realize intended movement by following the movement of the laser spot on the floor. By projecting an instructive point to be followed by the mobile robot, the user can clearly recognize the relation between the direction being faced and the desired position of the mobile robot. In addition, the user can convey a motion trajectory to the mobile robot continuously. Kansei transfer function is introduced between the instruction movement of the laser spot and following motion of the robot to realize psychologically acceptable motion of the robot. In addition, three modes, stopping mode, following mode, and autonomous motion mode to the target, are considered. The effectiveness of the proposed system was discussed experimentally, and confirmed by the smooth trajectory of the following motion of the mobile robot and good psychological evaluations.

  15. Human sound localization: measurements in untrained, head-unrestrained subjects using gaze as a pointer.

    PubMed

    Populin, Luis C

    2008-09-01

    Studies of sound localization in humans have used various behavioral measures to quantify the observers' perceptions; a non-comprehensive list includes verbal reports, head pointing, gun pointing, stylus pointing, and laser aiming. Comparison of localization performance reveals that in humans, just as in animals, different results are obtained with different experimental tasks. Accordingly, to circumvent problems associated with task selection and training, this study used gaze, an ethologically valid behavior for spatial pointing in species with a specialized area of the fovea, to measure sound localization perception of human subjects. Orienting using gaze as a pointer does not require training, preserves the natural link between perception and action, and allows for direct behavioral comparisons across species. The results revealed, unexpectedly, a large degree of variability across subjects in both accuracy and precision. The magnitude of the average angular localization errors for the most eccentric horizontal targets, however, were very similar to those documented in studies that used head pointing, whereas the magnitude of the localization errors for the frontal targets were considerably larger. In addition, an overall improvement in sound localization in the context of the memory-saccade task, as well as a lack of effect of initial eye and head position on perceived sound location were documented. PMID:18575853

  16. Exact time-dependent pointer state in a Jaynes-Cummings model with intensity-dependent level shift

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Xu, Chang; Ren, Zhongzhou

    2015-06-01

    We show that in the Jaynes-Cummings model with an intensity-dependent level shift whose magnitude is tuned to give rise to periodic collapse and revival, there exists a kind of time evolution where the two-level system and a coherent boson field stay absolutely disentangled throughout the evolution, in spite of the nonzero interaction between them. This constitutes an explicit example for an exact time-dependent pointer state of the two-level system, which perhaps distinguishes this evolution from all known disentangled evolutions in JC-related models. The construction of such an evolution is made possible by a vast level degeneracy in the energy level structure. Two possible ways to observe this phenomenon are also discussed. We believe that the present work could contribute to the understanding of pointer states.

  17. Improving interaction in navigated surgery by combining a pan-tilt mounted laser and a pointer with triggering

    NASA Astrophysics Data System (ADS)

    Ojdanic, D.; Chen, L.; Peitgen, H.-O.

    2012-02-01

    User interaction during navigated surgery is often a critical issue in the overall procedure, as several complex aspects must be considered, such as sterility, workflow, field of view, and cognitive load. This work introduces a new approach for intraoperative interaction that seamlessly fits the high surgical requirements. A navigation system, typically consisting of a tracking system and a monitor for 3D virtual models, is augmented with a tracked pointer with triggering functionality and a pan-tilt mounted laser. The pointer, which is sterile and can be applied for landmark-based organ registration, is used for wireless interaction with the monitor scene. The laser system enables the calibration of the monitor, which is out of the tracking system's range. Moreover, the laser beam can focus on any organ point defined on the virtual model, which improves targeting or visual feedback during intervention. The calibration of the laser system, monitor, and triggered pointer is achieved by an effective procedure, which can be easily repeated in operating room. The mathematical background of the calibration is based on the Levenberg-Marquardt and Umeyama's algorithms.

  18. Cost-effective handoff scheme based on mobility-aware dual pointer forwarding in proxy mobile IPv6 networks.

    PubMed

    Son, Seungsik; Jeong, Jongpil

    2014-01-01

    In this paper, a mobility-aware Dual Pointer Forwarding scheme (mDPF) is applied in Proxy Mobile IPv6 (PMIPv6) networks. The movement of a Mobile Node (MN) is classified as intra-domain and inter-domain handoff. When the MN moves, this scheme can reduce the high signaling overhead for intra-handoff/inter-handoff, because the Local Mobility Anchor (LMA) and Mobile Access Gateway (MAG) are connected by pointer chains. In other words, a handoff is aware of low mobility between the previously attached MAG (pMAG) and newly attached MAG (nMAG), and another handoff between the previously attached LMA (pLMA) and newly attached LMA (nLMA) is aware of high mobility. Based on these mobility-aware binding updates, the overhead of the packet delivery can be reduced. Also, we analyse the binding update cost and packet delivery cost for route optimization, based on the mathematical analytic model. Analytical results show that our mDPF outperforms the PMIPv6 and the other pointer forwarding schemes, in terms of reducing the total cost of signaling. PMID:24555172

  19. Seismic Investigation of the Pointer Ridge offshore southwestern Taiwan: Detection of fluid migration pathways and fault seal analysis

    NASA Astrophysics Data System (ADS)

    Han, W. C.; Liu, C. S.; Lin, C. C.; Wang, Y.

    2014-12-01

    This study analyzes both 2D and 3D seismic images in the Pointer Ridge area for gas hydrate investigation. Pointer Ridge is a ridge situated on the passive China continental margin formed by down slope erosion of the continental slope material on either side of the ridge. High methane flux rate and several seismic chimneys were observed in this area from previous studies, which may imply active ongoing fluid migration processes. To find the possible fluid migration pathways and understand the fluid migration processes, we firstly use both 2D and 3D seismic images to map the spatial distribution of the BSRs, and to identify the structural and sedimentary features in our study area. Secondly, seismic attribute analyses are carried out for fluid migration pathways detection and fault seal analysis. Finally, we propose a conceptual model to illustrate how fluids migrate along those pathways to the seafloor. The results show that the fluid migration pathways obtained from seismic attribute analysis results correlate well with the chimney and fault structures recognized from conventional seismic amplitude sections. We suggest that high angle normal faults may play an important role for fluid migrating upward, and the ongoing fluid migration processes will increase the seafloor instabilities. Since the Pointer Ridge is a gas hydrate leaking site, our results could provide useful information for further risk evaluation.

  20. Effects of trajectory exercise using a laser pointer on electromyographic activities of the gluteus maximus and erector spinae during bridging exercises.

    PubMed

    Kim, Yu-Ri; Yoo, Won-Gyu

    2016-01-01

    [Purpose] The purpose of this study was to investigate activities of the hip extensors and erector spinae during bridging exercise by using instruments with a laser pointer on the pelvic belt. [Subjects] Twelve subjects (age, 23 to 33 years) with non-specific low back pain volunteered for this study. [Methods] Subjects performed bridging exercises with and without trajectory exercises by using a laser pointer fixed to a pelvic strap. The erector spinae, gluteus maximus and hamstring activities with and without trajectory exercises using a laser pointer were recorded on using electromyography. [Results] Compared to the without laser pointer group, the group that underwent bridging with trajectory exercises using a laser pointer had significantly higher gluteus maximus activity and significantly lower erector spinae activity. Significantly higher gluteus maximus/erector spinae activity ratios were observed when performing trajectory exercises using a laser pointer during bridging exercises. [Conclusion] This result suggests that trajectory exercises using a laser pointer during a bridging exercise would be effective for improving gluteus maximus activity. PMID:27065555

  1. Effects of trajectory exercise using a laser pointer on electromyographic activities of the gluteus maximus and erector spinae during bridging exercises

    PubMed Central

    Kim, Yu-Ri; Yoo, Won-Gyu

    2016-01-01

    [Purpose] The purpose of this study was to investigate activities of the hip extensors and erector spinae during bridging exercise by using instruments with a laser pointer on the pelvic belt. [Subjects] Twelve subjects (age, 23 to 33 years) with non-specific low back pain volunteered for this study. [Methods] Subjects performed bridging exercises with and without trajectory exercises by using a laser pointer fixed to a pelvic strap. The erector spinae, gluteus maximus and hamstring activities with and without trajectory exercises using a laser pointer were recorded on using electromyography. [Results] Compared to the without laser pointer group, the group that underwent bridging with trajectory exercises using a laser pointer had significantly higher gluteus maximus activity and significantly lower erector spinae activity. Significantly higher gluteus maximus/erector spinae activity ratios were observed when performing trajectory exercises using a laser pointer during bridging exercises. [Conclusion] This result suggests that trajectory exercises using a laser pointer during a bridging exercise would be effective for improving gluteus maximus activity. PMID:27065555

  2. Observation of the two-dimensional reciprocal lattice by use of lattice grating sheets and a laser pointer

    NASA Astrophysics Data System (ADS)

    Tsutaoka, Takanori; Tokunaga, Tomohito; Umeda, Takashi; Maehara, Toshinobu

    2014-09-01

    Demonstration of the diffraction patterns from the two-dimensional Bravais lattice has been studied by use of the two single line lattice grating sheets and a laser pointer. A variable two-dimensional lattice grating was prepared using two grating sheets which are closely attached to each other. The five types of two-dimensional Bravais lattices can be produced by adjusting the relative angle between two single line lattices. The light diffraction patterns from the two-dimensional Bravais lattices indicate the reciprocal lattices of these basic two-dimensional lattice structures.

  3. Laser-pointer-induced self-focusing effect in hybrid-aligned dye-doped liquid crystals

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Aihara, Yosuke; Kinoshita, Motoi; Mamiya, Jun-Ichi; Priimagi, Arri; Shishido, Atsushi

    2015-05-01

    Nonlinear optics deals with phenomena where “light controls light” e.g., there is mediation by an intensity-dependent medium through which light propagates. This field has attracted much attention for its immense potential in applications dependent on nonlinear processes, such as frequency conversion, multiple-photon absorption, self-phase modulation, and so on. However, such nonlinearities are typically only observed at very high light intensities and thus they require costly lasers. Here, we report on a self-focusing effect induced with a 1 mW handheld laser pointer. We prepared polymer-stabilized dye-doped liquid crystals, in which the molecular director orientation gradually changes from homeotropic at one surface to homogeneous at the other. This is referred to as hybrid alignment. In such films, the threshold intensity needed to form diffraction rings was reduced by a factor of 8.5 compared to that in conventional homeotropic cells, which enabled the induction of the self-focusing effect with a laser pointer.

  4. Laser-pointer-induced self-focusing effect in hybrid-aligned dye-doped liquid crystals.

    PubMed

    Wang, Jing; Aihara, Yosuke; Kinoshita, Motoi; Mamiya, Jun-Ichi; Priimagi, Arri; Shishido, Atsushi

    2015-01-01

    Nonlinear optics deals with phenomena where "light controls light"; e.g., there is mediation by an intensity-dependent medium through which light propagates. This field has attracted much attention for its immense potential in applications dependent on nonlinear processes, such as frequency conversion, multiple-photon absorption, self-phase modulation, and so on. However, such nonlinearities are typically only observed at very high light intensities and thus they require costly lasers. Here, we report on a self-focusing effect induced with a 1 mW handheld laser pointer. We prepared polymer-stabilized dye-doped liquid crystals, in which the molecular director orientation gradually changes from homeotropic at one surface to homogeneous at the other. This is referred to as hybrid alignment. In such films, the threshold intensity needed to form diffraction rings was reduced by a factor of 8.5 compared to that in conventional homeotropic cells, which enabled the induction of the self-focusing effect with a laser pointer. PMID:25944052

  5. Laser-pointer-induced self-focusing effect in hybrid-aligned dye-doped liquid crystals

    PubMed Central

    Wang, Jing; Aihara, Yosuke; Kinoshita, Motoi; Mamiya, Jun-ichi; Priimagi, Arri; Shishido, Atsushi

    2015-01-01

    Nonlinear optics deals with phenomena where “light controls light”; e.g., there is mediation by an intensity-dependent medium through which light propagates. This field has attracted much attention for its immense potential in applications dependent on nonlinear processes, such as frequency conversion, multiple-photon absorption, self-phase modulation, and so on. However, such nonlinearities are typically only observed at very high light intensities and thus they require costly lasers. Here, we report on a self-focusing effect induced with a 1 mW handheld laser pointer. We prepared polymer-stabilized dye-doped liquid crystals, in which the molecular director orientation gradually changes from homeotropic at one surface to homogeneous at the other. This is referred to as hybrid alignment. In such films, the threshold intensity needed to form diffraction rings was reduced by a factor of 8.5 compared to that in conventional homeotropic cells, which enabled the induction of the self-focusing effect with a laser pointer. PMID:25944052

  6. Investigative Studies of Refractive Indices of Liquids and a Demonstration of Refraction by the Use of a Laser Pointer and a Lazy Susan

    ERIC Educational Resources Information Center

    Wong, Siu Ling; Mak, Se-yuen

    2008-01-01

    We describe the design of a simple homemade apparatus for the measurement of the refractive indices of liquids and demonstration of refraction. A circular transparent plastic tank and a lazy Susan are held concentrically. A laser pointer is mounted on the lazy Susan with its laser beam pointing radially through the centre of the plastic tank.…

  7. Pointers from the Americas.

    PubMed

    Aragon-choudhury, P

    1992-01-01

    During a sharing session which took place at a conference sponsored by the Philippine Institute for Social Studies and Action in 1991, Peruvian Victoria Villanueva and US citizen Margaret Ann Schuller discussed their work. Schuller reported on her upcoming book entitled "Freedom from Violence: Women's Strategies Around the World." In addition to proposing a definition of violence against women, the book will include 12 case studies from Malaysia, Bolivia, Mexico, India, Pakistan, Thailand, Sri Lanka, Brazil, Zimbabwe, Chile, Africa, and Alaska describing how national organizations of women are dealing with the problem. An important advance is the development of a framework to look at the connection which exists between violence and health issues. Villanueva described the work of the Movimiento Manuela Ramos, which was organized informally to deal with reproductive rights and abortion and has since expanded to parent groups of women who defend legal and medical cases as paid paralegals. Manuela Ramos uses popular media, traditional drama, and even state television to publicize its issues. Manuela Ramos has accomplished important work on rape, unsafe abortion, and maternal mortality, but most importantly, the women involved with the organization have had the opportunity to develop their self-esteem. PMID:12288567

  8. Pointers for Parenting.

    ERIC Educational Resources Information Center

    Bessant, Helen P., Ed.

    Presented are 11 brief articles designed to help parents enhance their children's school performance and generally improve the home environment. Included is information on the following topics: the role of the social worker in parent education, home activities to improve a child's reading skills, developing listening skill through instructional…

  9. Teuchos::RefCountPtr beginner's guide : an introduction to the Trilinos smart reference-counted pointer class for (almost) automatic dynamic memory management in C++.

    SciTech Connect

    Bartlett, Roscoe A

    2004-06-01

    Dynamic memory management in C++ is one of the most common areas of difficulty and errors for amateur and expert C++ developers alike. The improper use of operator new and operator delete is arguably the most common cause of incorrect program behavior and segmentation faults in C++ programs. Here we introduce a templated concrete C++ class Teuchos::RefCountPtr<>, which is part of the Trilinos tools package Teuchos, that combines the concepts of smart pointers and reference counting to build a low-overhead but effective tool for simplifying dynamic memory management in C++. We discuss why the use of raw pointers for memory management, managed through explicit calls to operator new and operator delete, is so difficult to accomplish without making mistakes and how programs that use raw pointers for memory management can easily be modified to use RefCountPtr<>. In addition, explicit calls to operator delete is fragile and results in memory leaks in the presents of C++ exceptions. In its most basic usage, RefCountPtr<> automatically determines when operator delete should be called to free an object allocated with operator new and is not fragile in the presents of exceptions. The class also supports more sophisticated use cases as well. This document describes just the most basic usage of RefCountPtr<> to allow developers to get started using it right away. However, more detailed information on the design and advanced features of RefCountPtr<> is provided by the companion document 'Teuchos::RefCountPtr : The Trilinos Smart Reference-Counted Pointer Class for (Almost) Automatic Dynamic Memory Management in C++'.

  10. Comparative efficacy of new interfaces for intra-procedural imaging review: the Microsoft Kinect, Hillcrest Labs Loop Pointer, and the Apple iPad.

    PubMed

    Chao, Cherng; Tan, Justin; Castillo, Edward M; Zawaideh, Mazen; Roberts, Anne C; Kinney, Thomas B

    2014-08-01

    We adapted and evaluated the Microsoft Kinect (touchless interface), Hillcrest Labs Loop Pointer (gyroscopic mouse), and the Apple iPad (multi-touch tablet) for intra-procedural imaging review efficacy in a simulation using MIM Software DICOM viewers. Using each device, 29 radiologists executed five basic interactions to complete the overall task of measuring an 8.1-cm hepatic lesion: scroll, window, zoom, pan, and measure. For each interaction, participants assessed the devices on a 3-point subjective scale (3 = highest usability score). The five individual scores were summed to calculate a subjective composite usability score (max 15 points). Overall task time to completion was recorded. Each user also assessed each device for its potential to jeopardize a sterile field. The composite usability scores were as follows: Kinect 9.9 (out of 15.0; SD = 2.8), Loop Pointer 12.9 (SD = 13.5), and iPad 13.5 (SD = 1.8). Mean task completion times were as follows: Kinect 156.7 s (SD = 86.5), Loop Pointer 51.5 s (SD = 30.6), and iPad 41.1 s (SD = 25.3). The mean hepatic lesion measurements were as follows: Kinect was 7.3 cm (SD = 0.9), Loop Pointer 7.8 cm (SD = 1.1), and iPad 8.2 cm (SD = 1.2). The mean deviations from true hepatic lesion measurement were as follows: Kinect 1.0 cm and for both the Loop Pointer and iPad, 0.9 cm (SD = 0.7). The Kinect had the least and iPad had the most subjective concern for compromising the sterile field. A new intra-operative imaging review interface may be near. Most surveyed foresee these devices as useful in procedures, and most do not anticipate problems with a sterile field. An ideal device would combine iPad's usability and accuracy with the Kinect's touchless aspect. PMID:24706159

  11. Measuring solid-state quantum yields: The conversion of a frequency-doubled Nd:YAG diode laser pointer module into a viable light source.

    PubMed

    Daglen, Bevin C; Harris, John D; Dax, Clifford D; Tyler, David R

    2007-07-01

    This article outlines the difficulties associated with measuring quantum yields for solid-state samples using a high-pressure mercury arc lamp as the irradiation source. Details are given for the conversion of an inexpensive frequency-doubled neodymium-doped yttrium aluminum garnet (Nd:YAG) diode laser pointer module into a viable irradiation source. The modified Nd:YAG laser was incorporated into a computer-controlled system, which allowed for the simultaneous irradiation and spectroscopic monitoring of the sample. The data obtained with the Nd:YAG diode laser system show far less scatter than data obtained with a high-pressure Hg arc lamp, and consequently the degradation rates obtained with the laser system could be calculated with far greater accuracy. PMID:17672778

  12. Design, development, and in-flight testing of a pointer/tracker for in-flight experiments to measure aero-optical effects over a scaled turret

    NASA Astrophysics Data System (ADS)

    Krizo, Matthew J.; Cusumano, Salvatore J.; Fiorino, Steven T.; Heap, Ryan; Velten, Victor; Brown, Joshua; Bartell, Richard J.

    2013-07-01

    We address the design, development, and testing of a pointer/tracker as a probe beam for the purpose of making high-speed, aero-optical measurements of the flow over a scaled beam director turret. The tracker uses retro-reflection of the probe beam off of a Reflexite annulus surrounding the turret. The constraints of the design required a near-total-commercial off the shelf system that could be quickly installed and removed in a rented aircraft. Baseline measurements of environmental vibrations are used to predict pointing performance; mitigation of line-of-sight jitter on the probe beam is achieved through passive isolation and the design of relay optics. Accommodation of ambient light is made with the use of wavelength filters and track algorithms. Postanalysis of measured data is compared to design estimates.

  13. US Coast Guard/US Maritime Administration Cooperative Research on marine engine exhaust emissions. Marine exhaust emissions measurement of the M/V Kings Pointer. Final report

    SciTech Connect

    Allen, S.J.; Bentz, A.P.

    1996-07-01

    This report presents the results of emissions testing conducted on board the M/V KINGS POINTER in May 1995. The objective of this testing was to conduct baseline instrumentation, monitoring, and evaluation of the engine exhaust emissions as part of joint U.S. Coast Guard/Maritime Administration cooperative research on controlling air pollution from ships. The U.S. Coast Guard`s interest in emissions testing arises from both its desire to meet all federal and state air quality regulations and the fact that in the future it may be called upon to enforce regulations in the marine environment. The U.S. Maritime Administration`s interest in this and related research is based on its efforts to assure that its vessels and those of the privately-owned U.S. Flag Merchant Marine can comply with future air pollution control requirements. Underway tests were conducted of the 224-foot M/V KINGS POINTER in which two of its four diesel-electric generators were sampled for NO, NO2, CO, and SO2 in the exhaust. Additional data on fuel flow and power output were collected at five speeds over the full range of vessel operating ranges. NOx values were calculated and compared with standards proposed by the Environmental Protection Agency (EPA) and the International Maritime Organization (IMO). Results showed that average NOx values were 9.4 g/kWh which is slightly below the 10.9 g/kWh upper limit or cap that is being proposed by the IMO for a diesel engine with a rated speed of 1200 RPM. Additional conclusions and recommendations on the technique of portable emissions monitoring instrumentation are made.

  14. Model Driven Engineering

    NASA Astrophysics Data System (ADS)

    Gaševic, Dragan; Djuric, Dragan; Devedžic, Vladan

    A relevant initiative from the software engineering community called Model Driven Engineering (MDE) is being developed in parallel with the Semantic Web (Mellor et al. 2003a). The MDE approach to software development suggests that one should first develop a model of the system under study, which is then transformed into the real thing (i.e., an executable software entity). The most important research initiative in this area is the Model Driven Architecture (MDA), which is Model Driven Architecture being developed under the umbrella of the Object Management Group (OMG). This chapter describes the basic concepts of this software engineering effort.

  15. Laser-Driven Fusion.

    ERIC Educational Resources Information Center

    Gibson, A. F.

    1980-01-01

    Discusses the present status and future prospects of laser-driven fusion. Current research (which is classified under three main headings: laser-matter interaction processes, compression, and laser development) is also presented. (HM)

  16. Computer Workstation: Pointer/Mouse

    MedlinePlus

    ... and long term use. Potential Hazards: When the sensitivity for the input device is not appropriately set, ... provide adequate control. A mouse that has insufficient sensitivity may require large deviation of the wrist to ...

  17. Driven Markovian Quantum Criticality.

    PubMed

    Marino, Jamir; Diehl, Sebastian

    2016-02-19

    We identify a new universality class in one-dimensional driven open quantum systems with a dark state. Salient features are the persistence of both the microscopic nonequilibrium conditions as well as the quantum coherence of dynamics close to criticality. This provides a nonequilibrium analogue of quantum criticality, and is sharply distinct from more generic driven systems, where both effective thermalization as well as asymptotic decoherence ensue, paralleling classical dynamical criticality. We quantify universality by computing the full set of independent critical exponents within a functional renormalization group approach. PMID:26943517

  18. The driven spinning top

    NASA Astrophysics Data System (ADS)

    Grosu, Ioan; Featonby, David

    2016-05-01

    This driven top is quite a novelty and can, with some trials, be made using the principles outlined here. This new top has many applications in developing both understanding and skills and these are detailed in the article. Depending on reader’s available time and motivation they may feel an urge to make one themselves, or simply invest a few pounds in the one that has been designed, tested and manufactured to a high standard. Either way the unique design of the driven top can provide several hours of interesting experimentation. Our aim here is simply to inform and inspire readers to further investigation and experimentation.

  19. Transport in driven plasmas

    SciTech Connect

    Fisch, N.J.

    1985-03-01

    A plasma in contact with an external source of power, especially a source that interacts specifically with high-velocity electrons, exhibits transport properties, such as conductivity, different from those of an isolated plasma near thermal equilibrium. This is true even when the bulk of the particles in the driven plasma are near thermal equilibrium. To describe the driven plasma we derive an adjoint equation to the inhomogeneous, linearized, dynamic Boltzmann equation. The Green's functions for a variety of plasma responses can then be generated. It is possible to modify the Chapman-Enskog expansion in order to incorporate the response functions derived here.

  20. Exfoliative cutaneous lupus erythematosus in German shorthaired pointer dogs: disease development, progression and evaluation of three immunomodulatory drugs (ciclosporin, hydroxychloroquine, and adalimumab) in a controlled environment

    PubMed Central

    Mauldin, Elizabeth A.; Morris, Daniel O.; Brown, Dorothy C.; Casal, Margret L.

    2011-01-01

    Six German shorthaired pointer dogs (two females, four males) with exfoliative cutaneous lupus erythematosus (ECLE) were studied in a controlled setting until disease progression necessitated euthanasia. During investigations into the heredity of disease, five dogs received immunomodulatory drugs to alleviate clinical signs (lameness, erythema, scaling, erosions/ulcers). One dog served as a control and received only baths and oral fatty acids. Four dogs received ciclosporin (5–10 mg/kg once daily) for 4.5 months to 2 years. Ciclosporin decreased erythema and arthralgia, but did not halt worsening of lesions. Three dogs received hydroxychloroquine (5–10 mg/kg once daily) for 8 weeks, 7 months, and 9 months, respectively, with no side effects. Hydroxychloroquine appeared to slow clinical progression in two dogs on extended treatment and normalized globulin levels in all three dogs while receiving the drug. Four dogs, including the control dog, were euthanized between 1 and 4.5 years of age. Two remaining male dogs received a tumour necrosis factor (TNF)-α antagonist, adalimumab, at 0.5 mg/kg every 2 weeks for 8 weeks then weekly for 8 weeks. Serum TNF-α levels were not significantly altered nor were quantifiable changes seen in skin lesions or lameness. Subsequently, the dogs were maintained on hydroxychloroquine for another year. This is the first study to evaluate the use of a TNF-α inhibitor for canine lupus and the first to address the safety of long-term administration of hydroxychloroquine, albeit in a small number of dogs. The study documents the progression of ECLE and generally poor response to therapy. PMID:20374572

  1. Plasma sheath driven targets

    NASA Astrophysics Data System (ADS)

    Brownell, J. H.; Freeman, B. L.

    1980-02-01

    Plasma focus driven target implosions are simulated using hydrodynamic-burn codes. Support is given to the idea that the use of a target in a plasma focus should allow 'impedance matching' between the fuel and gun, permitting larger fusion yields from a focus-target geometry than the scaling laws for a conventional plasma focus would predict.

  2. Data Driven Teachers

    ERIC Educational Resources Information Center

    Tech & Learning, 2009

    2009-01-01

    Data-driven decision-making (DDDM) is a system of teaching and management practices that gets better information about students into the hands of classroom teachers. This article discusses the five major elements: (1) good baseline data; (2) measurable instructional goals; (3) frequent formative assessment; (4) professional learning communities;…

  3. The Driven Spinning Top

    ERIC Educational Resources Information Center

    Grosu, Ioan; Featonby, David

    2016-01-01

    This driven top is quite a novelty and can, with some trials, be made using the principles outlined here. This new top has many applications in developing both understanding and skills and these are detailed in the article. Depending on reader's available time and motivation they may feel an urge to make one themselves, or simply invest a few…

  4. Argument-Driven Inquiry

    ERIC Educational Resources Information Center

    Sampson, Victor; Grooms, Jonathon; Walker, Joi

    2009-01-01

    Argument-Driven Inquiry (ADI) is an instructional model that enables science teachers to transform a traditional laboratory activity into a short integrated instructional unit. To illustrate how the ADI instructional model works, this article describes an ADI lesson developed for a 10th-grade chemistry class. This example lesson was designed to…

  5. Electrically driven optical antennas

    NASA Astrophysics Data System (ADS)

    Kern, Johannes; Kullock, René; Prangsma, Jord; Emmerling, Monika; Kamp, Martin; Hecht, Bert

    2015-09-01

    Unlike radiowave antennas, so far optical nanoantennas cannot be fed by electrical generators. Instead, they are driven by light or indirectly via excited discrete states in active materials in their vicinity. Here we demonstrate the direct electrical driving of an in-plane optical antenna by the broadband quantum-shot noise of electrons tunnelling across its feed gap. The spectrum of the emitted photons is determined by the antenna geometry and can be tuned via the applied voltage. Moreover, the direction and polarization of the light emission are controlled by the antenna resonance, which also improves the external quantum efficiency by up to two orders of magnitude. The one-material planar design offers facile integration of electrical and optical circuits and thus represents a new paradigm for interfacing electrons and photons at the nanometre scale, for example for on-chip wireless communication and highly configurable electrically driven subwavelength photon sources.

  6. Laser driven radiography

    SciTech Connect

    Perry, M.D.; Sefcik, J.; Cowan, T.

    1997-12-20

    Intense laser (> 1021 W/cm{sup 3}) driven hard x-ray sources offer a new alternative to conventional electron accelerator Bremsstrahlung sources. These laser driven sources offer considerable simplicity in design and potential cost advantage for multiple axis views. High spatial and temporal resolution is achievable as a result of the very small source size (<100 um) and short-duration of the laser pulse. We have begun a series of experiments with the Petawatt laser at LLNL to determine the photon flux achievable with these sources and assess their potential for Stewardship applications. Additionally, we are developing a conceptual design and cost estimate of a multi-pulse, multi-axis (up to five) radiographic facility utilizing the Contained Firing Facility at site 300 and existing laser hardware.

  7. Test-driven programming

    NASA Astrophysics Data System (ADS)

    Georgiev, Bozhidar; Georgieva, Adriana

    2013-12-01

    In this paper, are presented some possibilities concerning the implementation of a test-driven development as a programming method. Here is offered a different point of view for creation of advanced programming techniques (build tests before programming source with all necessary software tools and modules respectively). Therefore, this nontraditional approach for easier programmer's work through building tests at first is preferable way of software development. This approach allows comparatively simple programming (applied with different object-oriented programming languages as for example JAVA, XML, PYTHON etc.). It is predictable way to develop software tools and to provide help about creating better software that is also easier to maintain. Test-driven programming is able to replace more complicated casual paradigms, used by many programmers.

  8. Adiabatically driven Brownian pumps.

    PubMed

    Rozenbaum, Viktor M; Makhnovskii, Yurii A; Shapochkina, Irina V; Sheu, Sheh-Yi; Yang, Dah-Yen; Lin, Sheng Hsien

    2013-07-01

    We investigate a Brownian pump which, being powered by a flashing ratchet mechanism, produces net particle transport through a membrane. The extension of the Parrondo's approach developed for reversible Brownian motors [Parrondo, Phys. Rev. E 57, 7297 (1998)] to adiabatically driven pumps is given. We demonstrate that the pumping mechanism becomes especially efficient when the time variation of the potential occurs adiabatically fast or adiabatically slow, in perfect analogy with adiabatically driven Brownian motors which exhibit high efficiency [Rozenbaum et al., Phys. Rev. E 85, 041116 (2012)]. At the same time, the efficiency of the pumping mechanism is shown to be less than that of Brownian motors due to fluctuations of the number of particles in the membrane. PMID:23944411

  9. Gas-driven microturbine

    SciTech Connect

    Sniegowski, J.J.; Rodgers, M.S.; McWhorter, P.J.; Aeschliman, D.P.; Miller, W.M.

    1996-06-27

    This paper describes an invention which relates to microtechnology and the fabrication process for developing microelectrical systems. It describes a means for fabricating a gas-driven microturbine capable of providing autonomous propulsion in which the rapidly moving gases are directed through a micromachined turbine to power devices by direct linkage or turbo-electric generators components in a domain ranging from tenths of micrometers to thousands of micrometers.

  10. Data-Driven Objectness.

    PubMed

    Hongwen Kang; Hebert, Martial; Efros, Alexei A; Kanade, Takeo

    2015-01-01

    We propose a data-driven approach to estimate the likelihood that an image segment corresponds to a scene object (its "objectness") by comparing it to a large collection of example object regions. We demonstrate that when the application domain is known, for example, in our case activity of daily living (ADL), we can capture the regularity of the domain specific objects using millions of exemplar object regions. Our approach to estimating the objectness of an image region proceeds in two steps: 1) finding the exemplar regions that are the most similar to the input image segment; 2) calculating the objectness of the image segment by combining segment properties, mutual consistency across the nearest exemplar regions, and the prior probability of each exemplar region. In previous work, parametric objectness models were built from a small number of manually annotated objects regions, instead, our data-driven approach uses 5 million object regions along with their metadata information. Results on multiple data sets demonstrates our data-driven approach compared to the existing model based techniques. We also show the application of our approach in improving the performance of object discovery algorithms. PMID:26353218

  11. Trace anomaly driven inflation

    NASA Astrophysics Data System (ADS)

    Hawking, S. W.; Hertog, T.; Reall, H. S.

    2001-04-01

    This paper investigates Starobinsky's model of inflation driven by the trace anomaly of conformally coupled matter fields. This model does not suffer from the problem of contrived initial conditions that occurs in most models of inflation driven by a scalar field. The universe can be nucleated semiclassically by a cosmological instanton that is much larger than the Planck scale provided there are sufficiently many matter fields. There are two cosmological instantons: the four sphere and a new ``double bubble'' solution. This paper considers a universe nucleated by the four sphere. The AdS/CFT correspondence is used to calculate the correlation function for scalar and tensor metric perturbations during the ensuing de Sitter phase. The analytic structure of the scalar and tensor propagators is discussed in detail. Observational constraints on the model are discussed. Quantum loops of matter fields are shown to strongly suppress short scale metric perturbations, which implies that short distance modifications of gravity would probably not be observable in the cosmic microwave background. This is probably true for any model of inflation provided there are sufficiently many matter fields. This point is illustrated by a comparison of anomaly driven inflation in four dimensions and in a Randall-Sundrum brane-world model.

  12. Driven superconducting quantum circuits

    NASA Astrophysics Data System (ADS)

    Nakamura, Yasunobu

    2014-03-01

    Driven nonlinear quantum systems show rich phenomena in various fields of physics. Among them, superconducting quantum circuits have very attractive features such as well-controlled quantum states with design flexibility, strong nonlinearity of Josephson junctions, strong coupling to electromagnetic driving fields, little internal dissipation, and tailored coupling to the electromagnetic environment. We have investigated properties and functionalities of driven superconducting quantum circuits. A transmon qubit coupled to a transmission line shows nearly perfect spatial mode matching between the incident and scattered microwave field in the 1D mode. Dressed states under a driving field are studied there and also in a semi-infinite 1D mode terminated by a resonator containing a flux qubit. An effective Λ-type three-level system is realized under an appropriate driving condition. It allows ``impedance-matched'' perfect absorption of incident probe photons and down conversion into another frequency mode. Finally, the weak signal from the qubit is read out using a Josephson parametric amplifier/oscillator which is another nonlinear circuit driven by a strong pump field. This work was partly supported by the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST), Project for Developing Innovation Systems of MEXT, MEXT KAKENHI ``Quantum Cybernetics,'' and the NICT Commissioned Research.

  13. Water-driven micromotors.

    PubMed

    Gao, Wei; Pei, Allen; Wang, Joseph

    2012-09-25

    We demonstrate the first example of a water-driven bubble-propelled micromotor that eliminates the requirement for the common hydrogen peroxide fuel. The new water-driven Janus micromotor is composed of a partially coated Al-Ga binary alloy microsphere prepared via microcontact mixing of aluminum microparticles and liquid gallium. The ejection of hydrogen bubbles from the exposed Al-Ga alloy hemisphere side, upon its contact with water, provides a powerful directional propulsion thrust. Such spontaneous generation of hydrogen bubbles reflects the rapid reaction between the aluminum alloy and water. The resulting water-driven spherical motors can move at remarkable speeds of 3 mm s(-1) (i.e., 150 body length s(-1)), while exerting large forces exceeding 500 pN. Factors influencing the efficiency of the aluminum-water reaction and the resulting propulsion behavior and motor lifetime, including the ionic strength and environmental pH, are investigated. The resulting water-propelled Al-Ga/Ti motors move efficiently in different biological media (e.g., human serum) and hold considerable promise for diverse biomedical or industrial applications. PMID:22891973

  14. System Driven Workarounds

    NASA Technical Reports Server (NTRS)

    Connell, Linda; Wichner, David; Jakey, Abegael Marie

    2013-01-01

    The Aviation Safety Reporting System (ASRS) in a partnership between the National Aeronautics and Space Administration (NASA), the Federal Aviation Administration (FAA), participating carriers, and labor organizations. It is designed to improve the National Airspace System by collecting and studying reports detailing unsafe conditions and events in the aviation industry. Employees are able to report safety issues or concerns with confidentiality and without fear of discipline. Safety reports highlighting system driven workarounds for the aviation community highlight the human workaround for the complex aviation system.

  15. THERMALLY DRIVEN ATMOSPHERIC ESCAPE

    SciTech Connect

    Johnson, Robert E.

    2010-06-20

    Accurately determining the escape rate from a planet's atmosphere is critical for determining its evolution. A large amount of Cassini data is now available for Titan's upper atmosphere and a wealth of data is expected within the next decade on escape from Pluto, Mars, and extra-solar planets. Escape can be driven by upward thermal conduction of energy deposited well below the exobase, as well as by nonthermal processes produced by energy deposited in the exobase region. Recent applications of a model for escape driven by upward thermal conduction, called the slow hydrodynamic escape model, have resulted in surprisingly large loss rates for the atmosphere of Titan, Saturn's largest moon. Based on a molecular kinetic simulation of the exobase region, these rates appear to be orders of magnitude too large. Therefore, the slow hydrodynamic model is evaluated here. It is shown that such a model cannot give a reliable description of the atmospheric temperature profile unless it is coupled to a molecular kinetic description of the exobase region. Therefore, the present escape rates for Titan and Pluto must be re-evaluated using the atmospheric model described here.

  16. Heat driven pulse pump

    NASA Technical Reports Server (NTRS)

    Benner, Steve M (Inventor); Martins, Mario S. (Inventor)

    2000-01-01

    A heat driven pulse pump includes a chamber having an inlet port, an outlet port, two check valves, a wick, and a heater. The chamber may include a plurality of grooves inside wall of the chamber. When heated within the chamber, a liquid to be pumped vaporizes and creates pressure head that expels the liquid through the outlet port. As liquid separating means, the wick, disposed within the chamber, is to allow, when saturated with the liquid, the passage of only liquid being forced by the pressure head in the chamber, preventing the vapor from exiting from the chamber through the outlet port. A plurality of grooves along the inside surface wall of the chamber can sustain the liquid, which is amount enough to produce vapor for the pressure head in the chamber. With only two simple moving parts, two check valves, the heat driven pulse pump can effectively function over the long lifetimes without maintenance or replacement. For continuous flow of the liquid to be pumped a plurality of pumps may be connected in parallel.

  17. Qplus AFM driven nanostencil.

    PubMed

    Grévin, B; Fakir, M; Hayton, J; Brun, M; Demadrille, R; Faure-Vincent, J

    2011-06-01

    We describe the development of a novel setup, in which large stencils with suspended silicon nitride membranes are combined with atomic force microscopy (AFM) regulation by using tuning forks. This system offers the possibility to perform separate AFM and nanostencil operations, as well as combined modes when using stencil chips with integrated tips. The flexibility and performances are demonstrated through a series of examples, including wide AFM scans in closed loop mode, probe positioning repeatability of a few tens of nanometer, simultaneous evaporation of large (several hundred of micron square) and nanoscopic metals and fullerene patterns in static, multistep, and dynamic modes. This approach paves the way for further developments, as it fully combines the advantages of conventional stenciling with the ones of an AFM driven shadow mask. PMID:21721701

  18. Muscle-driven nanogenerators

    DOEpatents

    Wang, Zhong L.; Yang, Rusen

    2011-03-01

    In a method of generating electricity, a plurality of living cells are grown on an array of piezoelectric nanowires so that the cells engage the piezoelectric nanowires. Induced static potentials are extracted from at least one of the piezoelectric nanowires when at least one of the cells deforms the at least one of the piezoelectric nanowires. A cell-driven electrical generator that includes a substrate and a plurality of spaced-apart piezoelectric nanowires disposed on the substrate. A plurality of spaced-apart conductive electrodes interact with the plurality of piezoelectric nanowires. A biological buffer layer that is configured to promote growth of cells is disposed on the substrate so that cells placed on the substrate will grow and engage the piezoelectric nanowires.

  19. Soliton driven angiogenesis

    PubMed Central

    Bonilla, L. L.; Carretero, M.; Terragni, F.; Birnir, B.

    2016-01-01

    Angiogenesis is a multiscale process by which blood vessels grow from existing ones and carry oxygen to distant organs. Angiogenesis is essential for normal organ growth and wounded tissue repair but it may also be induced by tumours to amplify their own growth. Mathematical and computational models contribute to understanding angiogenesis and developing anti-angiogenic drugs, but most work only involves numerical simulations and analysis has lagged. A recent stochastic model of tumour-induced angiogenesis including blood vessel branching, elongation, and anastomosis captures some of its intrinsic multiscale structures, yet allows one to extract a deterministic integropartial differential description of the vessel tip density. Here we find that the latter advances chemotactically towards the tumour driven by a soliton (similar to the famous Korteweg-de Vries soliton) whose shape and velocity change slowly. Analysing these collective coordinates paves the way for controlling angiogenesis through the soliton, the engine that drives this process. PMID:27503562

  20. Steady Capillary Driven Flow

    NASA Technical Reports Server (NTRS)

    Weislogel, Mark M.

    1996-01-01

    A steady capillary driven flow is developed for a liquid index in a circular tube which is partially coated with a surface modifier to produce a discontinuous wetting condition from one side of the tube to the other. The bulk flow is novel in that it is truly steady, and controlled solely by the physics associated with dynamic wetting. The influence of gravity on the flow is minimized through the use of small diameter tubes approximately O(1 mm) tested horizontally in a laboratory and larger tubes approximately O(10 mm) tested in the low gravity environment of a drop tower. Average steady velocities are predicted and compared against a large experimental data set which includes the effects of tube dimensions and fluid properties. The sensitivity of the velocity to surface cleanliness is dramatic and the advantages of experimentation in a microgravity environment are discussed.

  1. Consistent model driven architecture

    NASA Astrophysics Data System (ADS)

    Niepostyn, Stanisław J.

    2015-09-01

    The goal of the MDA is to produce software systems from abstract models in a way where human interaction is restricted to a minimum. These abstract models are based on the UML language. However, the semantics of UML models is defined in a natural language. Subsequently the verification of consistency of these diagrams is needed in order to identify errors in requirements at the early stage of the development process. The verification of consistency is difficult due to a semi-formal nature of UML diagrams. We propose automatic verification of consistency of the series of UML diagrams originating from abstract models implemented with our consistency rules. This Consistent Model Driven Architecture approach enables us to generate automatically complete workflow applications from consistent and complete models developed from abstract models (e.g. Business Context Diagram). Therefore, our method can be used to check practicability (feasibility) of software architecture models.

  2. Multilane driven diffusive systems

    NASA Astrophysics Data System (ADS)

    Curatolo, A. I.; Evans, M. R.; Kafri, Y.; Tailleur, J.

    2016-03-01

    We consider networks made of parallel lanes along which particles hop according to driven diffusive dynamics. The particles also hop transversely from lane to lane, hence indirectly coupling their longitudinal dynamics. We present a general method for constructing the phase diagram of these systems which reveals that in many cases their physics reduce to that of single-lane systems. The reduction to an effective single-lane description legitimizes, for instance, the use of a single TASEP to model the hopping of molecular motors along the many tracks of a single microtubule. Then, we show how, in quasi-2D settings, new phenomena emerge due to the presence of non-zero transverse currents, leading, for instance, to strong ‘shear localization’ along the network.

  3. Soliton driven angiogenesis

    NASA Astrophysics Data System (ADS)

    Bonilla, L. L.; Carretero, M.; Terragni, F.; Birnir, B.

    2016-08-01

    Angiogenesis is a multiscale process by which blood vessels grow from existing ones and carry oxygen to distant organs. Angiogenesis is essential for normal organ growth and wounded tissue repair but it may also be induced by tumours to amplify their own growth. Mathematical and computational models contribute to understanding angiogenesis and developing anti-angiogenic drugs, but most work only involves numerical simulations and analysis has lagged. A recent stochastic model of tumour-induced angiogenesis including blood vessel branching, elongation, and anastomosis captures some of its intrinsic multiscale structures, yet allows one to extract a deterministic integropartial differential description of the vessel tip density. Here we find that the latter advances chemotactically towards the tumour driven by a soliton (similar to the famous Korteweg-de Vries soliton) whose shape and velocity change slowly. Analysing these collective coordinates paves the way for controlling angiogenesis through the soliton, the engine that drives this process.

  4. Soliton driven angiogenesis.

    PubMed

    Bonilla, L L; Carretero, M; Terragni, F; Birnir, B

    2016-01-01

    Angiogenesis is a multiscale process by which blood vessels grow from existing ones and carry oxygen to distant organs. Angiogenesis is essential for normal organ growth and wounded tissue repair but it may also be induced by tumours to amplify their own growth. Mathematical and computational models contribute to understanding angiogenesis and developing anti-angiogenic drugs, but most work only involves numerical simulations and analysis has lagged. A recent stochastic model of tumour-induced angiogenesis including blood vessel branching, elongation, and anastomosis captures some of its intrinsic multiscale structures, yet allows one to extract a deterministic integropartial differential description of the vessel tip density. Here we find that the latter advances chemotactically towards the tumour driven by a soliton (similar to the famous Korteweg-de Vries soliton) whose shape and velocity change slowly. Analysing these collective coordinates paves the way for controlling angiogenesis through the soliton, the engine that drives this process. PMID:27503562

  5. Fluid-driven metamorphism

    NASA Astrophysics Data System (ADS)

    Jamtveit, B.; Ulven, O. I.; Malthe-Sorenssen, A.

    2014-12-01

    Metamorphic processes in the Earth crust are almost invariably associated with fluid migration. Many lines of evidence suggest that fluid migration is intimately coupled both to the metamorphic reactions, and to associated deformation processes. Petrologic arguments suggest that all granulite facies and most amphibolite facies rocks are essentially dry (no free fluid phase) at normal geothermal gradients outside periods of heating-produced fluid generation. In addition, except at high pressure - low temperature condition, fluid-consuming reactions leads to an increase in solid volume and a potential clogging of any initial pore space. Hence, fluid migration in medium and high-grade metamorphic rocks is in general associated with some porosity producing process. Porosity generation may occur by either chemical or mechanical processes. In systems with high fluid fluxes, porosity may be produced by dissolution and transport of mass out of the system. Such fluxes can normally only be sustained over short length scales and limited time scales. In systems where the infiltrating fluid is far from equilibrium with the rock matrix, mechanical porosity generation can arise from local stresses generated by the volume change of volatilization reactions. Furthermore, it has become increasingly clear that crustal rocks may be under significant tectonic stress, even far from plate tectonic boundaries. In situations where the rocks are close to critically stressed, any stress perturbations caused by reaction driven changes in solid volume or fluid pressure gradients may lead to dilatant deformation and porosity production on a scale much larger than the characteristic length scales of the reacting rock units. Field observations, experimental studies and modeling results will be presented that focus on reaction driven porosity generation in systems subject to variable initial differential stresses.

  6. MRI driven magnetic microswimmers.

    PubMed

    Kósa, Gábor; Jakab, Péter; Székely, Gábor; Hata, Nobuhiko

    2012-02-01

    Capsule endoscopy is a promising technique for diagnosing diseases in the digestive system. Here we design and characterize a miniature swimming mechanism that uses the magnetic fields of the MRI for both propulsion and wireless powering of the capsule. Our method uses both the static and the radio frequency (RF) magnetic fields inherently available in MRI to generate a propulsive force. Our study focuses on the evaluation of the propulsive force for different swimming tails and experimental estimation of the parameters that influence its magnitude. We have found that an approximately 20 mm long, 5 mm wide swimming tail is capable of producing 0.21 mN propulsive force in water when driven by a 20 Hz signal providing 0.85 mW power and the tail located within the homogeneous field of a 3 T MRI scanner. We also analyze the parallel operation of the swimming mechanism and the scanner imaging. We characterize the size of artifacts caused by the propulsion system. We show that while the magnetic micro swimmer is propelling the capsule endoscope, the operator can locate the capsule on the image of an interventional scene without being obscured by significant artifacts. Although this swimming method does not scale down favorably, the high magnetic field of the MRI allows self propulsion speed on the order of several millimeter per second and can propel an endoscopic capsule in the stomach. PMID:22037673

  7. Gradient Driven Fluctuations

    NASA Technical Reports Server (NTRS)

    Cannell, David

    2005-01-01

    We have worked with our collaborators at the University of Milan (Professor Marzio Giglio and his group-supported by ASI) to define the science required to measure gradient driven fluctuations in the microgravity environment. Such a study would provide an accurate test of the extent to which the theory of fluctuating hydrodynamics can be used to predict the properties of fluids maintained in a stressed, non-equilibrium state. As mentioned above, the results should also provide direct visual insight into the behavior of a variety of fluid systems containing gradients or interfaces, when placed in the microgravity environment. With support from the current grant, we have identified three key systems for detailed investigation. These three systems are: 1) A single-component fluid to be studied in the presence of a temperature gradient; 2) A mixture of two organic liquids to be studied both in the presence of a temperature gradient, which induces a steady-state concentration gradient, and with the temperature gradient removed, but while the concentration gradient is dying by means of diffusion; 3) Various pairs of liquids undergoing free diffusion, including a proteidbuffer solution and pairs of mixtures having different concentrations, to allow us to vary the differences in fluid properties in a controlled manner.

  8. Compositionally Driven Dynamos

    NASA Astrophysics Data System (ADS)

    Soderlund, K. M.; Schubert, G.

    2014-12-01

    It is generally believed that compositional convection driven by inner core solidification is the main driver of the geodynamo. Thermal evolution considerations make it likely that compositional convection is also behind the present dynamos of Mercury and Ganymede as well as the early dynamos in the Moon, Mars and smaller solar system bodies. Compositional buoyancy can arise in several different ways, for example, through inner core solidification and FeS flotation with upward mixing and through freezing out and sinking of iron snow near the core-mantle boundary or deeper within the core. The mode of core cooling and freezing depends on conditions of temperature and pressure in the core and the concentration of light elements such as sulfur. Different distributions of compositional buoyancy will give rise to different patterns of core convection and dynamo magnetic fields. We report here the first results of a systematic study of the distribution of compositional buoyancy on the dynamo-generated magnetic fields, with an emphasis on Mars' core evolution due to iron rain.

  9. Beam Driven Stratospheric Airship

    NASA Astrophysics Data System (ADS)

    Onda, Masahiko

    2003-05-01

    Even though satellite, balloons and aircraft have served admirably as aerospace platforms for remote sensing and telecommunication, requirements for a new kind of platforms - an easily modifiable, sub-orbital platform - have been widely identified. The High-Altitude Long-Range Observational Platform(HALROP) was at first conceptualized as a solar power driven unmanned LTA (Lighter-Than-Air) vehicle or an airship to maintain a station-keeping position in the lower stratosphere for long-durations and to carry out missions such as high-resolution monitoring and high-speed informational relays. Nevertheless solar power is not available in winter seasons in the high-latitudinal regions. Therefore, alternative power sources are necessary and the candidates are surface-to-air transmission of microwave energy and high-power laser beams. The author introduces a wireless power transmission test by microwave carried in 1995 in Kobe, Japan, and then, discusses possibilities of using laser beam for powering such LTA platforms.

  10. Invention-driven marketing

    NASA Technical Reports Server (NTRS)

    Carlson, William E.

    1994-01-01

    Suppose you have just created a revolutionary bicycle suspension which allows a bike to be ridden over rough terrain at 60 miles per hour. In addition, suppose that you are deeply concerned about the plight of hungry children. Which should you do: be sure all hungry children have bicycles; transfer the technology for your new suspension to bicycle manufacturers worldwide; or start a company to supply premium sports bicycle based on your patented technology, and donate the profits to a charity which feeds hungry children? Woven through this somewhat trivial example is the paradox of technology transfer - the supplier (owner) may want to transfer technology; but to succeed, he or she must reformulate the problem as a user need for which there is a new and better solution. Successful technology transfer is little more than good marketing applied to an existing invention, process, or capability. You must identify who needs the technology, why they need it, why the new technology is better than alternatives, how much the customers are willing and able to pay for these benefits, and how to distribute products based on the technology tc the target customers. In market-driven development, the term 'technology transfer' is rarely used. The developers focus on studying user needs and designing solution They may have technology needs, but they don't have technology in search of a use.

  11. Fluid driven recipricating apparatus

    DOEpatents

    Whitehead, John C.

    1997-01-01

    An apparatus comprising a pair of fluid driven pump assemblies in a back-to-back configuration to yield a bi-directional pump. Each of the pump assemblies includes a piston or diaphragm which divides a chamber therein to define a power section and a pumping section. An intake-exhaust valve is connected to each of the power sections of the pump chambers, and function to direct fluid, such as compressed air, into the power section and exhaust fluid therefrom. At least one of the pistons or diaphragms is connected by a rod assembly which is constructed to define a signal valve, whereby the intake-exhaust valve of one pump assembly is controlled by the position or location of the piston or diaphragm in the other pump assembly through the operation of the rod assembly signal valve. Each of the pumping sections of the pump assemblies are provided with intake and exhaust valves to enable filling of the pumping section with fluid and discharging fluid therefrom when a desired pressure has been reached.

  12. Fluid driven reciprocating apparatus

    DOEpatents

    Whitehead, J.C.

    1997-04-01

    An apparatus is described comprising a pair of fluid driven pump assemblies in a back-to-back configuration to yield a bi-directional pump. Each of the pump assemblies includes a piston or diaphragm which divides a chamber therein to define a power section and a pumping section. An intake-exhaust valve is connected to each of the power sections of the pump chambers, and function to direct fluid, such as compressed air, into the power section and exhaust fluid therefrom. At least one of the pistons or diaphragms is connected by a rod assembly which is constructed to define a signal valve, whereby the intake-exhaust valve of one pump assembly is controlled by the position or location of the piston or diaphragm in the other pump assembly through the operation of the rod assembly signal valve. Each of the pumping sections of the pump assemblies are provided with intake and exhaust valves to enable filling of the pumping section with fluid and discharging fluid therefrom when a desired pressure has been reached. 13 figs.

  13. Salinity driven oceanographic upwelling

    DOEpatents

    Johnson, David H.

    1986-01-01

    The salinity driven oceanographic upwelling is maintained in a mariculture device that includes a long main duct in the general shape of a cylinder having perforated cover plates at each end. The mariculture device is suspended vertically in the ocean such that one end of the main duct is in surface water and the other end in relatively deep water that is cold, nutrient rich and relatively fresh in comparison to the surface water which is relatively warm, relatively nutrient deficient and relatively saline. A plurality of elongated flow segregating tubes are disposed in the main duct and extend from the upper cover plate beyond the lower cover plate into a lower manifold plate. The lower manifold plate is spaced from the lower cover plate to define a deep water fluid flow path to the interior space of the main duct. Spacer tubes extend from the upper cover plate and communicate with the interior space of the main duct. The spacer tubes are received in an upper manifold plate spaced from the upper cover plate to define a surface water fluid flow path into the flow segregating tubes. A surface water-deep water counterflow is thus established with deep water flowing upwardly through the main duct interior for discharge beyond the upper manifold plate while surface water flows downwardly through the flow segregating tubes for discharge below the lower manifold plate. During such counterflow heat is transferred from the downflowing warm water to the upflowing cold water. The flow is maintained by the difference in density between the deep water and the surface water due to their differences in salinity. The upwelling of nutrient rich deep water is used for marifarming by fertilizing the nutrient deficient surface water.

  14. Salinity driven oceanographic upwelling

    DOEpatents

    Johnson, D.H.

    1984-08-30

    The salinity driven oceanographic upwelling is maintained in a mariculture device that includes a long main duct in the general shape of a cylinder having perforated cover plates at each end. The mariculture device is suspended vertically in the ocean such that one end of the main duct is in surface water and the other end in relatively deep water that is cold, nutrient rich and relatively fresh in comparison to the surface water which is relatively warm, relatively nutrient deficient and relatively saline. A plurality of elongated flow segregating tubes are disposed in the main duct and extend from the upper cover plate beyond the lower cover plate into a lower manifold plate. The lower manifold plate is spaced from the lower cover plate to define a deep water fluid flow path to the interior space of the main duct. Spacer tubes extend from the upper cover plate and communicate with the interior space of the main duct. The spacer tubes are received in an upper manifold plate spaced from the upper cover plate to define a surface water fluid flow path into the flow segregating tubes. A surface water-deep water counterflow is thus established with deep water flowing upwardly through the main duct interior for discharge beyond the upper manifold plate while surface water flows downwardly through the flow segregating tubes for discharge below the lower manifold plate. During such counterflow heat is transferred from the downflowing warm water to the upflowing cold water. The flow is maintained by the difference in density between the deep water and the surface water due to their differences in salinity. The upwelling of nutrient rich deep water is used for marifarming by fertilizing the nutrient deficient surface water. 1 fig.

  15. Smart friction driven systems

    NASA Astrophysics Data System (ADS)

    Nitsche, Rainer; Gaul, Lothar

    2005-02-01

    Vibration properties of most assembled mechanical systems depend on frictional damping in joints. The nonlinear transfer behavior of the frictional interfaces often provides the dominant damping mechanism in a built-up structure and plays an important role in the vibratory response of the structure (Gaul and Nitsche 2001 Appl. Mech. Rev. 54 93-105). For improving the performance of systems, many studies have been carried out to predict, measure and/or enhance the energy dissipation of friction. To enhance the friction damping in joint connections a semi-active joint is investigated. A rotational joint connection is designed and manufactured such that the normal force in the friction interface can be influenced with a piezoelectric stack disc. With the piezoelectric device the normal force and thus the friction damping in the joint connection can be controlled. A control design method, namely semi-active control, is investigated. The recently developed LuGre friction model is used to describe the nonlinear transfer behavior of joints. This model is based on a bristle model and turns out to be highly suitable for systems assembled by such smart joints. Those systems can also be regarded as friction driven systems, since the energy flow is controlled by smart joints. The semi-active method is well suited for large space structures since the friction damping in joints turned out to be a major source of damping. To show the applicability of the proposed concept to large space structures a two-beam system representing a part of a large space structure is considered. Two flexible beams are connected with a semi-active joint connection. It can be shown that the damping of the system can be improved significantly by controlling the normal force in the semi-active joint connection. Experimental results validate the damping improvement due to the semi-active friction damping.

  16. Data-driven batch schuduling

    SciTech Connect

    Bent, John; Denehy, Tim; Arpaci - Dusseau, Remzi; Livny, Miron; Arpaci - Dusseau, Andrea C

    2009-01-01

    In this paper, we develop data-driven strategies for batch computing schedulers. Current CPU-centric batch schedulers ignore the data needs within workloads and execute them by linking them transparently and directly to their needed data. When scheduled on remote computational resources, this elegant solution of direct data access can incur an order of magnitude performance penalty for data-intensive workloads. Adding data-awareness to batch schedulers allows a careful coordination of data and CPU allocation thereby reducing the cost of remote execution. We offer here new techniques by which batch schedulers can become data-driven. Such systems can use our analytical predictive models to select one of the four data-driven scheduling policies that we have created. Through simulation, we demonstrate the accuracy of our predictive models and show how they can reduce time to completion for some workloads by as much as 80%.

  17. Surface tension driven convection experiment

    NASA Technical Reports Server (NTRS)

    Ostrach, Simon; Kamotani, Yasuhiro

    1988-01-01

    Thermocapillary flow is driven by a thermally induced surface tension variation along a liquid free surface. In the Earth-gravity environment such flows are usually overshadowed by buoyancy driven flows, but at reduced gravity conditions their influence could be significant. A comprehensive theoretical and experimental research program was stated 12 years ago and is still being continued. Past work done at Case Western Reserve University as well as work done by others is reviewed. The justification for low-gravity experiments is presented.

  18. Patron-Driven Ebook Acquisition

    ERIC Educational Resources Information Center

    Breitbach, William; Lambert, Joy E.

    2011-01-01

    Selecting the most appropriate content for a community is a challenge librarians have faced since the dawn of libraries. Formal patron-driven acquisition (PDA) models have been around for at least a decade. These models attempt to collect materials based on known patron demand. Some libraries simply use a suggestion form, while others use…

  19. Acuity-driven gigapixel visualization.

    PubMed

    Papadopoulos, Charilaos; Kaufman, Arie E

    2013-12-01

    We present a framework for acuity-driven visualization of super-high resolution image data on gigapixel displays. Tiled display walls offer a large workspace that can be navigated physically by the user. Based on head tracking information, the physical characteristics of the tiled display and the formulation of visual acuity, we guide an out-of-core gigapixel rendering scheme by delivering high levels of detail only in places where it is perceivable to the user. We apply this principle to gigapixel image rendering through adaptive level of detail selection. Additionally, we have developed an acuity-driven tessellation scheme for high-quality Focus-and-Context (F+C) lenses that significantly reduces visual artifacts while accurately capturing the underlying lens function. We demonstrate this framework on the Reality Deck, an immersive gigapixel display. We present the results of a user study designed to quantify the impact of our acuity-driven rendering optimizations in the visual exploration process. We discovered no evidence suggesting a difference in search task performance between our framework and naive rendering of gigapixel resolution data, while realizing significant benefits in terms of data transfer overhead. Additionally, we show that our acuity-driven tessellation scheme offers substantially increased frame rates when compared to naive pre-tessellation, while providing indistinguishable image quality. PMID:24051856

  20. Driven shielding capacitive proximity sensor

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor); McConnell, Robert L. (Inventor)

    2000-01-01

    A capacitive proximity sensing element, backed by a reflector driven at the same voltage as and in phase with the sensor, is used to reflect the field lines away from a grounded robot arm towards an intruding object, thus dramatically increasing the sensor's range and sensitivity.

  1. Data-Driven Proficiency Profiling

    ERIC Educational Resources Information Center

    Mostafavi, Behrooz; Liu, Zhongxiu; Barnes, Tiffany

    2015-01-01

    Deep Thought is a logic tutor where students practice constructing deductive logic proofs. Within Deep Thought is a data-driven mastery learning system (DDML), which calculates student proficiency based on rule scores weighted by expert-decided weights in order to assign problem sets of appropriate difficulty. In this study, we designed and tested…

  2. Pattern Formation in Driven Systems

    NASA Astrophysics Data System (ADS)

    Klymko, Katherine

    Model colloidal particles of two types, driven in opposite directions, will in two dimensions segregate into lanes, a phenomenon studied extensively by Lowen and co-workers [Dzubiella et al. Phys. Rev. E 65, 021402 (2002)]. We have simulated mixtures of oppositely-driven particles using three numerical protocols. We find that laning results from enhanced diffusion, in the direction perpendicular to the drive, of particles surrounded by particles of the opposite type, consistent with the observation of Vissers et al. [Soft Matter 7, 6, 2352 (2011)]. By comparing protocols we find that enhanced diffusion follows from a simple geometrical constraint: oppositely-driven particles must, in the time taken to encounter each other in the direction of the drive, diffuse in the perpendicular direction by about one particle diameter. This constraint implies that the effective lateral diffusion constant grows linearly with drive speed and as the square root of the packing fraction, a prediction supported by our numerics. By invoking an analogy between hard particles with environment-dependent mobilities and mutually attractive particles we argue that there exists an equilibrium system whose pattern-forming properties are similar to those of the driven system. Katherine Klymko acknowledges support from the NSF Graduate Research Fellowship.

  3. Capillary-driven microfluidic chips with evaporation-induced flow control and dielectrophoretic microbead trapping

    NASA Astrophysics Data System (ADS)

    Temiz, Yuksel; Skorucak, Jelena; Delamarche, Emmanuel

    2014-07-01

    This work reports our efforts on developing simple-to-use microfluidic devices for point-of-care diagnostic applications with recent extensions that include the trapping of microbeads using dielectrophoresis (DEP) and the modulation of the liquid flow using integrated microheaters. DEP serves the purpose of trapping microbeads coated with receptors and analytes for detection of a fluorescent signal. The microheater is actuated once the chip is filled by capillarity, creating an evaporation-induced flow tuned according to assay conditions. The chips are composed of a glass substrate patterned with 50-nm-thick Pd electrodes and microfluidic structures made using a 20-μm-thick dry-film resist (DFR). Chips are covered/sealed by low temperature (50°C) lamination of a 50-μm-thick DFR layer having excellent optical and mechanical properties. To separate cleaned and sealed chips from the wafer, we used an effective chip singulation technique which we informally call the "chip-olate" process. In the experimental section, we first studied dielectrophoretic trapping of 10-μm beads for flow rates ranging from 80 pL s-1 to 2.5 nL s-1 that are generated by an external syringe pump. Then, we characterized the embedded microheater in DFR-covered chips. Flow rates as high as 8 nL s-1 were generated by evaporation-induced flow when the heater was biased by 10 V, corresponding to 270-mW power. Finally, DEP-based trapping and fluorescent detection of functionalized beads were demonstrated as the flow was generated by evaporation-induced flow after the microfluidic structures were filled by capillarity.

  4. Pulsed Power Driven Fusion Energy

    SciTech Connect

    SLUTZ,STEPHEN A.

    1999-11-22

    Pulsed power is a robust and inexpensive technology for obtaining high powers. Considerable progress has been made on developing light ion beams as a means of transporting this power to inertial fusion capsules. However, further progress is hampered by the lack of an adequate ion source. Alternatively, z-pinches can efficiently convert pulsed power into thermal radiation, which can be used to drive an inertial fusion capsule. However, a z-pinch driven fusion explosion will destroy a portion of the transmission line that delivers the electrical power to the z-pinch. They investigate several options for providing standoff for z-pinch driven fusion. Recyclable Transmission Lines (RTLs) appear to be the most promising approach.

  5. Schematic driven silicon photonics design

    NASA Astrophysics Data System (ADS)

    Chrostowski, Lukas; Lu, Zeqin; Flückiger, Jonas; Pond, James; Klein, Jackson; Wang, Xu; Li, Sarah; Tai, Wei; Hsu, En Yao; Kim, Chan; Ferguson, John; Cone, Chris

    2016-03-01

    Electronic circuit designers commonly start their design process with a schematic, namely an abstract representation of the physical circuit. In integrated photonics on the other hand, it is very common for the design to begin at the physical component level. In order to build large integrated photonic systems, it is crucial to design using a schematic-driven approach. This includes simulations based on schematics, schematic-driven layout, layout versus schematic verification, and post-layout simulations. This paper describes such a design framework implemented using Mentor Graphics and Lumerical Solutions design tools. In addition, we describe challenges in silicon photonics related to manufacturing, and how these can be taken into account in simulations and how these impact circuit performance.

  6. Magnetically driven quantum heat engine.

    PubMed

    Muñoz, Enrique; Peña, Francisco J

    2014-05-01

    We studied the efficiency of two different schemes for a magnetically driven quantum heat engine, by considering as the "working substance" a single nonrelativistic particle trapped in a cylindrical potential well, in the presence of an external magnetic field. The first scheme is a cycle, composed of two adiabatic and two isoenergetic reversible trajectories in configuration space. The trajectories are driven by a quasistatic modulation of the external magnetic-field intensity. The second scheme is a variant of the former, where the isoenergetic trajectories are replaced by isothermal ones, along which the system is in contact with macroscopic thermostats. This second scheme constitutes a quantum analog of the classical Carnot cycle. PMID:25353739

  7. Kaehler-driven tribrid inflation

    SciTech Connect

    Antusch, Stefan; Nolde, David E-mail: david.nolde@unibas.ch

    2012-11-01

    We discuss a new class of tribrid inflation models in supergravity, where the shape of the inflaton potential is dominated by effects from the Kaehler potential. Tribrid inflation is a variant of hybrid inflation which is particularly suited for connecting inflation with particle physics, since the inflaton can be a D-flat combination of charged fields from the matter sector. In models of tribrid inflation studied so far, the inflaton potential was dominated by either loop corrections or by mixing effects with the waterfall field (as in 'pseudosmooth' tribrid inflation). Here we investigate the third possibility, namely that tribrid inflation is dominantly driven by effects from higher-dimensional operators of the Kaehler potential. We specify for which superpotential parameters the new regime is realized and show how it can be experimentally distinguished from the other two (loop-driven and {sup p}seudosmooth{sup )} regimes.

  8. Heterogeneity in motor driven transport

    NASA Astrophysics Data System (ADS)

    Tabei, Ali

    2015-03-01

    I will discuss quantitative analysis of particle tracking data for motor driven vesicles inside an insulin secreting cell. We use this method to study the dynamical and structural heterogeneity inside the cell. I will discuss our effort to explain the origin of observed heterogeneity in intracellular transport. Finally, I will explain how analyzing directional correlations in transport trajectories reveals self-similarity in the diffusion media.

  9. Thermocapillary driven turbulent heat transfer

    SciTech Connect

    Arpaci, V.S.; Kao, S.H.

    1996-12-31

    For thermocapillary driven flows, the authors explain the foundations of the flow regimes described by Ma{sup 1/2} and Ma{sup 1/3} in the recent dimensional, computational and experimental study of Kamotani, Chang and Ostrach who follow different arguments than those presented here. Also, the authors introduce another regime described by Ma{sup 1/4} for laminar flow. Fig. 1 borrowed from Kamotani et al. (1996) illustrates the three flow regimes.

  10. Kinetics of accelerator driven devices

    SciTech Connect

    Perry, R.T.; Buksa, J.; Houts, M.

    1994-09-01

    Kinetic calculations were made to show that subcritical accelerator driven devices are robust and stable. The calculations show that large changes in reactivity that would lead to an uncontrollable excursion in a reactor would lead only to a new power level in subcritical device. Calculations were also made to show the rate of power changes resulting from startup and shutdown, and that methods also exist for continuously monitoring the reactivity of a subcritical system.

  11. Kinetics of accelerator driven devices

    SciTech Connect

    Perry, R. T.; Buksa, John; Houts, Michael

    1995-09-15

    Kinetic calculations were made to show that subcritical accelerator driven devices are robust and stable. The calculations show that large changes in reactivity that would lead to an uncontrollable excursion in a reactor would lead only to a new power level in a subcritical device. Calculations were also made to show the rate of power changes resulting from startup and shutdown, and that methods also exist for continuously monitoring the reactivity of a subcritical system.

  12. Mission Driven Science at Argonne

    SciTech Connect

    Thackery, Michael; Wang, Michael; Young, Linda

    2012-01-01

    Mission driven science at Argonne means applying science and scientific knowledge to a physical and "real world" environment. Examples include testing a theoretical model through the use of formal science or solving a practical problem through the use of natural science. At the laboratory, our materials scientists are leading the way in producing energy solutions today that could help reduce and remove the energy crisis of tomorrow.

  13. Driven one-component plasmas

    SciTech Connect

    Rizzato, Felipe B.; Pakter, Renato; Levin, Yan

    2009-08-15

    A statistical theory is presented that allows the calculation of the stationary state achieved by a driven one-component plasma after a process of collisionless relaxation. The stationary Vlasov equation with appropriate boundary conditions is reduced to an ordinary differential equation, which is then solved numerically. The solution is then compared with the molecular-dynamics simulation. A perfect agreement is found between the theory and the simulations. The full current-voltage phase diagram is constructed.

  14. Active and driven hydrodynamic crystals.

    PubMed

    Desreumaux, N; Florent, N; Lauga, E; Bartolo, D

    2012-08-01

    Motivated by the experimental ability to produce monodisperse particles in microfluidic devices, we study theoretically the hydrodynamic stability of driven and active crystals. We first recall the theoretical tools allowing to quantify the dynamics of elongated particles in a confined fluid. In this regime hydrodynamic interactions between particles arise from a superposition of potential dipolar singularities. We exploit this feature to derive the equations of motion for the particle positions and orientations. After showing that all five planar Bravais lattices are stationary solutions of the equations of motion, we consider separately the case where the particles are passively driven by an external force, and the situation where they are self-propelling. We first demonstrate that phonon modes propagate in driven crystals, which are always marginally stable. The spatial structures of the eigenmodes depend solely on the symmetries of the lattices, and on the orientation of the driving force. For active crystals, the stability of the particle positions and orientations depends not only on the symmetry of the crystals but also on the perturbation wavelengths and on the crystal density. Unlike unconfined fluids, the stability of active crystals is independent of the nature of the propulsion mechanism at the single-particle level. The square and rectangular lattices are found to be linearly unstable at short wavelengths provided the volume fraction of the crystals is high enough. Differently, hexagonal, oblique, and face-centered crystals are always unstable. Our work provides a theoretical basis for future experimental work on flowing microfluidic crystals. PMID:22864543

  15. Edge-driven microplate kinematics

    USGS Publications Warehouse

    Schouten, Hans; Klitgord, Kim D.; Gallo, David G.

    1993-01-01

    It is known from plate tectonic reconstructions that oceanic microplates undergo rapid rotation about a vertical axis and that the instantaneous rotation axes describing the microplate's motion relative to the bounding major plates are frequently located close to its margins with those plates, close to the tips of propagating rifts. We propose a class of edge-driven block models to illustrate how slip across the microplate margins, block rotation, and propagation of rifting may be related to the relative motion of the plates on either side. An important feature of these edge-driven models is that the instantaneous rotation axes are always located on the margins between block and two bounding plates. According to those models the pseudofaults or traces of disrupted seafloor resulting from the propagation of rifting between microplate and major plates may be used independently to approximately trace the continuous kinematic evolution of the microplate back in time. Pseudofault geometries and matching rotations of the Easter microplate show that for most of its 5 m.y. history, block rotation could be driven by the drag of the Nazca and Pacific plates on the microplate's edges rather than by a shear flow of mantle underneath.

  16. Is "Market-Driven" Good Enough?

    ERIC Educational Resources Information Center

    Kaufman, Roger

    1995-01-01

    Discusses marketing and management strategies and evaluates the path most traveled; going beyond market-driven; proactive and reactive organizational positioning; ways to manage human and physical resources to make both market-driven and market-making contributions; and values necessary for an organization to move from market-driven to…

  17. Capacitive Proximity Sensors With Additional Driven Shields

    NASA Technical Reports Server (NTRS)

    Mcconnell, Robert L.

    1993-01-01

    Improved capacitive proximity sensors constructed by incorporating one or more additional driven shield(s). Sensitivity and range of sensor altered by adjusting driving signal(s) applied to shield(s). Includes sensing electrode and driven isolating shield that correspond to sensing electrode and driven shield.

  18. Remapping Attention Pointers: Linking Physiology and Behavior.

    PubMed

    Rolfs, Martin; Szinte, Martin

    2016-06-01

    Our eyes rapidly scan visual scenes, displacing the projection on the retina with every move. Yet these frequent retinal image shifts do not appear to hamper vision. Two recent physiological studies shed new light on the role of attention in visual processing across saccadic eye movements. PMID:27118641

  19. Preferential enhancement of laser-driven carbon ion acceleration from optimized nanostructured surfaces

    NASA Astrophysics Data System (ADS)

    Dalui, Malay; Wang, W.-M.; Trivikram, T. Madhu; Sarkar, Subhrangshu; Tata, Sheroy; Jha, J.; Ayyub, P.; Sheng, Z. M.; Krishnamurthy, M.

    2015-07-01

    High-intensity ultrashort laser pulses focused on metal targets readily generate hot dense plasmas which accelerate ions efficiently and can pave way to compact table-top accelerators. Laser-driven ion acceleration studies predominantly focus on protons, which experience the maximum acceleration owing to their highest charge-to-mass ratio. The possibility of tailoring such schemes for the preferential acceleration of a particular ion species is very much desired but has hardly been explored. Here, we present an experimental demonstration of how the nanostructuring of a copper target can be optimized for enhanced carbon ion acceleration over protons or Cu-ions. Specifically, a thin (≈0.25 μm) layer of 25-30 nm diameter Cu nanoparticles, sputter-deposited on a polished Cu-substrate, enhances the carbon ion energy by about 10-fold at a laser intensity of 1.2×1018  W/cm2. However, particles smaller than 20 nm have an adverse effect on the ion acceleration. Particle-in-cell simulations provide definite pointers regarding the size of nanoparticles necessary for maximizing the ion acceleration. The inherent contrast of the laser pulse is found to play an important role in the species selective ion acceleration.

  20. Preferential enhancement of laser-driven carbon ion acceleration from optimized nanostructured surfaces.

    PubMed

    Dalui, Malay; Wang, W-M; Trivikram, T Madhu; Sarkar, Subhrangsu; Sarkar, Subhrangshu; Tata, Sheroy; Jha, J; Ayyub, P; Sheng, Z M; Krishnamurthy, M

    2015-01-01

    High-intensity ultrashort laser pulses focused on metal targets readily generate hot dense plasmas which accelerate ions efficiently and can pave way to compact table-top accelerators. Laser-driven ion acceleration studies predominantly focus on protons, which experience the maximum acceleration owing to their highest charge-to-mass ratio. The possibility of tailoring such schemes for the preferential acceleration of a particular ion species is very much desired but has hardly been explored. Here, we present an experimental demonstration of how the nanostructuring of a copper target can be optimized for enhanced carbon ion acceleration over protons or Cu-ions. Specifically, a thin (≈ 0.25 μm) layer of 25-30 nm diameter Cu nanoparticles, sputter-deposited on a polished Cu-substrate, enhances the carbon ion energy by about 10-fold at a laser intensity of 1.2 × 10(18)  W/cm(2). However, particles smaller than 20 nm have an adverse effect on the ion acceleration. Particle-in-cell simulations provide definite pointers regarding the size of nanoparticles necessary for maximizing the ion acceleration. The inherent contrast of the laser pulse is found to play an important role in the species selective ion acceleration. PMID:26153048

  1. Preferential enhancement of laser-driven carbon ion acceleration from optimized nanostructured surfaces

    PubMed Central

    Dalui, Malay; Wang, W.-M.; Trivikram, T. Madhu; Sarkar, Subhrangshu; Tata, Sheroy; Jha, J.; Ayyub, P.; Sheng, Z. M.; Krishnamurthy, M.

    2015-01-01

    High-intensity ultrashort laser pulses focused on metal targets readily generate hot dense plasmas which accelerate ions efficiently and can pave way to compact table-top accelerators. Laser-driven ion acceleration studies predominantly focus on protons, which experience the maximum acceleration owing to their highest charge-to-mass ratio. The possibility of tailoring such schemes for the preferential acceleration of a particular ion species is very much desired but has hardly been explored. Here, we present an experimental demonstration of how the nanostructuring of a copper target can be optimized for enhanced carbon ion acceleration over protons or Cu-ions. Specifically, a thin (≈0.25 μm) layer of 25–30 nm diameter Cu nanoparticles, sputter-deposited on a polished Cu-substrate, enhances the carbon ion energy by about 10-fold at a laser intensity of 1.2×1018  W/cm2. However, particles smaller than 20 nm have an adverse effect on the ion acceleration. Particle-in-cell simulations provide definite pointers regarding the size of nanoparticles necessary for maximizing the ion acceleration. The inherent contrast of the laser pulse is found to play an important role in the species selective ion acceleration. PMID:26153048

  2. Catastrophe-driven vs what?

    SciTech Connect

    Stever, H.G.

    1995-12-31

    The author notes that much has been accomplished by catastrophe-driven scientific effort. Examples include World War II and the social wars against crime, poverty and hunger and famine. A positive approach is suggested to be more appropriate as the drivers of science. Three tables are presented and outline a positive base for justifying scientific endeavor: (1) Examples of Major Societal Goals to Which Science and Technology Contribute. (2) Policy Areas That Would Benefit from the Articulation of Long-Term S&T Goals; and (3) Major Components of the Science and Technology Base.

  3. Casimir-force-driven ratchets.

    PubMed

    Emig, T

    2007-04-20

    We explore the nonlinear dynamics of two parallel periodically patterned metal surfaces that are coupled by the zero-point fluctuations of the electromagnetic field between them. The resulting Casimir force generates for asymmetric patterns with a time periodically driven surface-to-surface distance a ratchet effect, allowing for directed lateral motion of the surfaces in sizable parameter ranges. It is crucial to take into account inertia effects and hence chaotic dynamics which are described by Langevin dynamics. Multiple velocity reversals occur as a function of driving, mean surface distance, and effective damping. These transport properties are shown to be stable against weak ambient noise. PMID:17501407

  4. Driven discrete time quantum walks

    NASA Astrophysics Data System (ADS)

    Hamilton, Craig S.; Barkhofen, Sonja; Sansoni, Linda; Jex, Igor; Silberhorn, Christine

    2016-07-01

    We introduce the driven discrete time quantum walk (QW), where walkers are added during the walk instead of only at the beginning. This leads to interference in walker number and very different dynamics when compared to the original QW. These dynamics have two regimes, which we illustrate using the one-dimensional line. Then, we explore a search application which has certain advantages over current search protocols, namely that it does not require a complicated initial state nor a specific measurement time to observe the marked state. Finally, we describe a potential experimental implementation using existing technology.

  5. Photocell System Driven by Mechanoluminescence

    NASA Astrophysics Data System (ADS)

    Terasaki, Nao; Xu, Chao-Nan; Imai, Yusuke; Yamada, Hiroshi

    2007-04-01

    A mechanoluminescence driven photocell system consisting of a mechanoluminescent (ML) material and a photocell was prepared. The ML material developed in our laboratory is the world’s first material developed for a practical use in the elastic deformation region. In this system, the ML composite (an epoxy pellet including europium-doped strontium aluminate (SAO:E), one of the most efficient ML materials) was used as a light source, and a silicon solar cell was used as the photoelectric converter. With the application of compressive stress to the ML composite pellet in the system, the photocurrent corresponding to the mechanoluminescence was successfully observed.

  6. Actively driven thermal radiation shield

    DOEpatents

    Madden, Norman W.; Cork, Christopher P.; Becker, John A.; Knapp, David A.

    2002-01-01

    A thermal radiation shield for cooled portable gamma-ray spectrometers. The thermal radiation shield is located intermediate the vacuum enclosure and detector enclosure, is actively driven, and is useful in reducing the heat load to mechanical cooler and additionally extends the lifetime of the mechanical cooler. The thermal shield is electrically-powered and is particularly useful for portable solid-state gamma-ray detectors or spectrometers that dramatically reduces the cooling power requirements. For example, the operating shield at 260K (40K below room temperature) will decrease the thermal radiation load to the detector by 50%, which makes possible portable battery operation for a mechanically cooled Ge spectrometer.

  7. Ontology-Driven Information Integration

    NASA Technical Reports Server (NTRS)

    Tissot, Florence; Menzel, Chris

    2005-01-01

    Ontology-driven information integration (ODII) is a method of computerized, automated sharing of information among specialists who have expertise in different domains and who are members of subdivisions of a large, complex enterprise (e.g., an engineering project, a government agency, or a business). In ODII, one uses rigorous mathematical techniques to develop computational models of engineering and/or business information and processes. These models are then used to develop software tools that support the reliable processing and exchange of information among the subdivisions of this enterprise or between this enterprise and other enterprises.

  8. Magnetically driven quantum heat engine

    NASA Astrophysics Data System (ADS)

    Munoz, Enrique; Pena, Francisco

    2015-03-01

    In analogy with classical thermodynamics, a quantum heat engine generates useful mechanical work from heat, by means of a reversible sequence of transformations (trajectories), where the ``working substance'' is of quantum mechanical nature. Several theoretical implementations for a quantum heat engine have been discussed in the literature, such as entangled states in a qubit, quantum mechanical versions of the Otto cycle, and photocells. In this work, we propose yet a different alternative by introducing the concept of a magnetically driven quantum heat engine. We studied the efficiency of such system, by considering as the ``working substance'' a single nonrelativistic particle trapped in a cylindrical potential well, as a model for a semiconductor quantum dot, in the presence of an external magnetic field. The trajectories are driven by a quasistatic modulation of the external magnetic-field intensity, while the system is in contact with macroscopic thermostats. The external magnetic field modulation allows to modify the effective geometric confinement, in analogy with a piston in a classical gas. E. Munoz acknowledges financial support from Fondecyt under Contract 1141146.

  9. Assessing respondent-driven sampling.

    PubMed

    Goel, Sharad; Salganik, Matthew J

    2010-04-13

    Respondent-driven sampling (RDS) is a network-based technique for estimating traits in hard-to-reach populations, for example, the prevalence of HIV among drug injectors. In recent years RDS has been used in more than 120 studies in more than 20 countries and by leading public health organizations, including the Centers for Disease Control and Prevention in the United States. Despite the widespread use and growing popularity of RDS, there has been little empirical validation of the methodology. Here we investigate the performance of RDS by simulating sampling from 85 known, network populations. Across a variety of traits we find that RDS is substantially less accurate than generally acknowledged and that reported RDS confidence intervals are misleadingly narrow. Moreover, because we model a best-case scenario in which the theoretical RDS sampling assumptions hold exactly, it is unlikely that RDS performs any better in practice than in our simulations. Notably, the poor performance of RDS is driven not by the bias but by the high variance of estimates, a possibility that had been largely overlooked in the RDS literature. Given the consistency of our results across networks and our generous sampling conditions, we conclude that RDS as currently practiced may not be suitable for key aspects of public health surveillance where it is now extensively applied. PMID:20351258

  10. On Rank Driven Dynamical Systems

    NASA Astrophysics Data System (ADS)

    Veerman, J. J. P.; Prieto, F. J.

    2014-08-01

    We investigate a class of models related to the Bak-Sneppen (BS) model, initially proposed to study evolution. The BS model is extremely simple and yet captures some forms of "complex behavior" such as self-organized criticality that is often observed in physical and biological systems. In this model, random fitnesses in are associated to agents located at the vertices of a graph . Their fitnesses are ranked from worst (0) to best (1). At every time-step the agent with the worst fitness and some others with a priori given rank probabilities are replaced by new agents with random fitnesses. We consider two cases: The exogenous case where the new fitnesses are taken from an a priori fixed distribution, and the endogenous case where the new fitnesses are taken from the current distribution as it evolves. We approximate the dynamics by making a simplifying independence assumption. We use Order Statistics and Dynamical Systems to define a rank-driven dynamical system that approximates the evolution of the distribution of the fitnesses in these rank-driven models, as well as in the BS model. For this simplified model we can find the limiting marginal distribution as a function of the initial conditions. Agreement with experimental results of the BS model is excellent.

  11. Assessing respondent-driven sampling

    PubMed Central

    Goel, Sharad; Salganik, Matthew J.

    2010-01-01

    Respondent-driven sampling (RDS) is a network-based technique for estimating traits in hard-to-reach populations, for example, the prevalence of HIV among drug injectors. In recent years RDS has been used in more than 120 studies in more than 20 countries and by leading public health organizations, including the Centers for Disease Control and Prevention in the United States. Despite the widespread use and growing popularity of RDS, there has been little empirical validation of the methodology. Here we investigate the performance of RDS by simulating sampling from 85 known, network populations. Across a variety of traits we find that RDS is substantially less accurate than generally acknowledged and that reported RDS confidence intervals are misleadingly narrow. Moreover, because we model a best-case scenario in which the theoretical RDS sampling assumptions hold exactly, it is unlikely that RDS performs any better in practice than in our simulations. Notably, the poor performance of RDS is driven not by the bias but by the high variance of estimates, a possibility that had been largely overlooked in the RDS literature. Given the consistency of our results across networks and our generous sampling conditions, we conclude that RDS as currently practiced may not be suitable for key aspects of public health surveillance where it is now extensively applied. PMID:20351258

  12. Piezoelectrically-driven Thermoacoustic Refrigerator

    NASA Astrophysics Data System (ADS)

    Chinn, Daniel George

    Thermoacoustic refrigeration is an emerging refrigeration technology which does not require any moving parts or harmful refrigerants in its operation. This technology uses acoustic waves to pump heat across a temperature gradient. The vast majority of thermoacoustic refrigerators to date have used electromagnetic loudspeakers to generate the acoustic input. In this thesis, the design, construction, operation, and modeling of a piezoelectrically-driven thermoacoustic refrigerator are detailed. This refrigerator demonstrates the effectiveness of piezoelectric actuation in moving 0.3 W of heat across an 18 degree C temperature difference with an input power of 7.6 W. The performance characteristics of this class of thermoacoustic-piezoelectric refrigerators are modeled by using DeltaEC software and the predictions are experimentally validated. The obtained results confirm the validity of the developed model. Furthermore, the potential of piezoelectric actuation as effective means for driving thermoacoustic refrigerators is demonstrated as compared to the conventional electromagnetic loudspeakers which are heavy and require high actuation energy. The developed theoretical and experimental tools can serve as invaluable means for the design and testing of other piezoelectrically-driven thermoacoustic refrigerator configurations.

  13. Investigating Reaction-Driven Cracking

    NASA Astrophysics Data System (ADS)

    Kelemen, P. B.; Hirth, G.; Savage, H. M.

    2013-12-01

    Many metamorphic reactions lead to large volume changes, and potentially to reaction-driven cracking [1,2]. Large-scale hydration of mantle peridotite to produce serpentine or talc is invoked to explain the rheology of plate boundaries, the nature of earthquakes, and the seismic properties of slow-spread ocean crust and the 'mantle wedge' above subduction zones. Carbonation of peridotite may be an important sink in the global carbon cycle. Zones of 100% magnesite + quartz replacing peridotite, up to 200 m thick, formed where oceanic mantle was thrust over carbonate-bearing metasediments in Oman. Talc + carbonate is an important component of the matrix in subduction mélanges at Santa Catalina Island , California, and the Sanbagawa metamorphic belt, Japan. Engineered systems to emulate natural mineral carbonation could provide relatively inexpensive CO2 capture and storage [3]. More generally, engineered reaction-driven cracking could supplement or replace hydraulic fracture in geothermal systems, solution mining, and extraction of tight oil and gas. The controls on reaction-driven cracking are poorly understood. Hydration and carbonation reactions can be self-limiting, since they potentially reduce permeability and armor reactive surfaces [4]. Also, in some cases, hydration or carbonation may take place at constant volume. Small changes in volume due to precipitation of solid products increases stress, destabilizing solid reactants, until precipitation and dissolution rates become equal at a steady state stress [5]. In a third case, volume change due to precipitation of solid products causes brittle failure. This has been invoked on qualitative grounds to explain, e.g., complete serpentinization of mantle peridotite [6]. Below ~ 300°C, the available potential energy for hydration and carbonation of olivine could produce stresses of 100's of MPa [2], sufficient to fracture rocks to 10 km depth or more, causing brittle failure below the steady state stress required

  14. Asynchronous Event-Driven Particle Algorithms

    SciTech Connect

    Donev, A

    2007-08-30

    We present, in a unifying way, the main components of three asynchronous event-driven algorithms for simulating physical systems of interacting particles. The first example, hard-particle molecular dynamics (MD), is well-known. We also present a recently-developed diffusion kinetic Monte Carlo (DKMC) algorithm, as well as a novel stochastic molecular-dynamics algorithm that builds on the Direct Simulation Monte Carlo (DSMC). We explain how to effectively combine event-driven and classical time-driven handling, and discuss some promises and challenges for event-driven simulation of realistic physical systems.

  15. Asynchronous Event-Driven Particle Algorithms

    SciTech Connect

    Donev, A

    2007-02-28

    We present in a unifying way the main components of three examples of asynchronous event-driven algorithms for simulating physical systems of interacting particles. The first example, hard-particle molecular dynamics (MD), is well-known. We also present a recently-developed diffusion kinetic Monte Carlo (DKMC) algorithm, as well as a novel event-driven algorithm for Direct Simulation Monte Carlo (DSMC). Finally, we describe how to combine MD with DSMC in an event-driven framework, and discuss some promises and challenges for event-driven simulation of realistic physical systems.

  16. Acoustically driven arrayed waveguide grating.

    PubMed

    Crespo-Poveda, A; Hernández-Mínguez, A; Gargallo, B; Biermann, K; Tahraoui, A; Santos, P V; Muñoz, P; Cantarero, A; de Lima, M M

    2015-08-10

    We demonstrate compact tunable phased-array wavelength-division multiplexers driven by surface acoustic waves (SAWs) in the low GHz range. The devices comprise two couplers, which respectively split and combine the optical signal, linked by an array of single-mode waveguides (WGs). Two different layouts are presented, in which multi-mode interference couplers or free propagating regions were separately employed as couplers. The multiplexers operate on five equally distributed wavelength channels, with a spectral separation of 2 nm. A standing SAW modulates the refractive index of the arrayed WGs. Each wavelength component periodically switches paths between the output channel previously asigned by the design and the adjacent channels, at a fixed applied acoustic power. The devices were monolithically fabricated on (Al,Ga)As. A good agreement between theory and experiment is achieved. PMID:26367971

  17. Photogated humidity-driven motility

    NASA Astrophysics Data System (ADS)

    Zhang, Lidong; Liang, Haoran; Jacob, Jolly; Naumov, Panče

    2015-06-01

    Hygroinduced motion is a fundamental process of energy conversion that is essential for applications that require contactless actuation in response to the day-night rhythm of atmospheric humidity. Here we demonstrate that mechanical bistability caused by rapid and anisotropic adsorption and desorption of water vapour by a flexible dynamic element that harnesses the chemical potential across very small humidity gradients for perpetual motion can be effectively modulated with light. A mechanically robust material capable of rapid exchange of water with the surroundings is prepared that undergoes swift locomotion in effect to periodic shape reconfiguration with turnover frequency of <150 min-1. The element can lift objects ~85 times heavier and can transport cargos ~20 times heavier than itself. Having an azobenzene-containing conjugate as a photoactive dopant, this entirely humidity-driven self-actuation can be controlled remotely with ultraviolet light, thus setting a platform for next-generation smart biomimetic hybrids.

  18. Multifunctionalities driven by ferroic domains

    SciTech Connect

    Yang, J. C.; Huang, Y. L.; Chu, Y. H.; He, Q.

    2014-08-14

    Considerable attention has been paid to ferroic systems in pursuit of advanced applications in past decades. Most recently, the emergence and development of multiferroics, which exhibit the coexistence of different ferroic natures, has offered a new route to create functionalities in the system. In this manuscript, we step from domain engineering to explore a roadmap for discovering intriguing phenomena and multifunctionalities driven by periodic domain patters. As-grown periodic domains, offering exotic order parameters, periodic local perturbations and the capability of tailoring local spin, charge, orbital and lattice degrees of freedom, are introduced as modeling templates for fundamental studies and novel applications. We discuss related significant findings on ferroic domain, nanoscopic domain walls, and conjunct heterostructures based on the well-organized domain patterns, and end with future prospects and challenges in the field.

  19. Light-driven phase shifter

    DOEpatents

    Early, James W.

    1990-01-01

    A light-driven phase shifter is provided for modulating a transmission light beam. A gaseous medium such as argon is provided with electron energy states excited to populate a metastable state. A tunable dye laser is selected with a wavelength effective to deplete the metastable electron state and may be intensity modulated. The dye laser is directed through the gaseous medium to define a first optical path having an index of refraction determined by the gaseous medium having a depleted metastable electron state. A transmission laser beam is also directed through the gaseous medium to define a second optical path at least partially coincident with the first optical path. The intensity of the dye laser beam may then be varied to phase modulate the transmission laser beam.

  20. Impulse-driven Micromechanism Capsule

    NASA Astrophysics Data System (ADS)

    Ito, Takahiro; Ishimori, Shohei; Hayashi, Teru

    We have developed a traveling small capsule, which has a smooth outer surface and is driven by inertia force and friction force. Measuring only 7 mm in diameter and 12 mm in length, it is sufficiently small to be placed in the human gullet or intestines. The capsule contains a small magnet and a coil, and an electric pulse drives the magnet to move the capsule. We performed an experimental investigation on making our capsule travel on a plastic material, which has similar elasticity characteristics to the living body. We also showed that it can travel on the surface of a pig's intestine. Our capsule may be useful for medical treatments such as inspection, drug delivery and operation.

  1. Laser-driven fusion reactor

    DOEpatents

    Hedstrom, J.C.

    1973-10-01

    A laser-driven fusion reactor consisting of concentric spherical vessels in which the thermonuclear energy is derived from a deuterium-tritium (D + T) burn within a pellet'', located at the center of the vessels and initiated by a laser pulse. The resulting alpha -particle energy and a small fraction of the neutron energy are deposited within the pellet; this pellet energy is eventually transformed into sensible heat of lithium in a condenser outside the vessels. The remaining neutron energy is dissipated in a lithium blanket, located within the concentric vessels, where the fuel ingredient, tritium, is also produced. The heat content of the blanket and of the condenser lithium is eventually transferred to a conventional thermodynamic plant where the thermal energy is converted to electrical energy in a steam Rankine cycle. (Official Gazette)

  2. Photogated humidity-driven motility

    PubMed Central

    Zhang, Lidong; Liang, Haoran; Jacob, Jolly; Naumov, Panče

    2015-01-01

    Hygroinduced motion is a fundamental process of energy conversion that is essential for applications that require contactless actuation in response to the day–night rhythm of atmospheric humidity. Here we demonstrate that mechanical bistability caused by rapid and anisotropic adsorption and desorption of water vapour by a flexible dynamic element that harnesses the chemical potential across very small humidity gradients for perpetual motion can be effectively modulated with light. A mechanically robust material capable of rapid exchange of water with the surroundings is prepared that undergoes swift locomotion in effect to periodic shape reconfiguration with turnover frequency of <150 min−1. The element can lift objects ∼85 times heavier and can transport cargos ∼20 times heavier than itself. Having an azobenzene-containing conjugate as a photoactive dopant, this entirely humidity-driven self-actuation can be controlled remotely with ultraviolet light, thus setting a platform for next-generation smart biomimetic hybrids. PMID:26067649

  3. Current-driven atomic waterwheels

    NASA Astrophysics Data System (ADS)

    Dundas, Daniel; McEniry, Eunan J.; Todorov, Tchavdar N.

    2009-02-01

    A current induces forces on atoms inside the conductor that carries it. It is now possible to compute these forces from scratch, and to perform dynamical simulations of the atomic motion under current. One reason for this interest is that current can be a destructive force-it can cause atoms to migrate, resulting in damage and in the eventual failure of the conductor. But one can also ask, can current be made to do useful work on atoms? In particular, can an atomic-scale motor be driven by electrical current, as it can be by other mechanisms? For this to be possible, the current-induced forces on a suitable rotor must be non-conservative, so that net work can be done per revolution. Here we show that current-induced forces in atomic wires are not conservative and that they can be used, in principle, to drive an atomic-scale waterwheel.

  4. Current-driven atomic waterwheels.

    PubMed

    Dundas, Daniel; McEniry, Eunan J; Todorov, Tchavdar N

    2009-02-01

    A current induces forces on atoms inside the conductor that carries it. It is now possible to compute these forces from scratch, and to perform dynamical simulations of the atomic motion under current. One reason for this interest is that current can be a destructive force--it can cause atoms to migrate, resulting in damage and in the eventual failure of the conductor. But one can also ask, can current be made to do useful work on atoms? In particular, can an atomic-scale motor be driven by electrical current, as it can be by other mechanisms? For this to be possible, the current-induced forces on a suitable rotor must be non-conservative, so that net work can be done per revolution. Here we show that current-induced forces in atomic wires are not conservative and that they can be used, in principle, to drive an atomic-scale waterwheel. PMID:19197311

  5. Schematic driven layout of Reed Solomon encoders

    NASA Technical Reports Server (NTRS)

    Arave, Kari; Canaris, John; Miles, Lowell; Whitaker, Sterling

    1992-01-01

    Two Reed Solomon error correcting encoders are presented. Schematic driven layout tools were used to create the encoder layouts. Special consideration had to be given to the architecture and logic to provide scalability of the encoder designs. Knowledge gained from these projects was used to create a more flexible schematic driven layout system.

  6. Gravity-Driven Hydraulic Fractures

    NASA Astrophysics Data System (ADS)

    Germanovich, L. N.; Garagash, D.; Murdoch, L. C.; Robinowitz, M.

    2014-12-01

    This study is motived by a new method for disposing of nuclear waste by injecting it as a dense slurry into a hydraulic fracture that grows downward to great enough depth to permanently isolate the waste. Disposing of nuclear waste using gravity-driven hydraulic fractures is mechanically similar to the upward growth of dikes filled with low density magma. A fundamental question in both applications is how the injected fluid controls the propagation dynamics and fracture geometry (depth and breadth) in three dimensions. Analog experiments in gelatin [e.g., Heimpel and Olson, 1994; Taisne and Tait, 2009] show that fracture breadth (the short horizontal dimension) remains nearly stationary when the process in the fracture "head" (where breadth is controlled) is dominated by solid toughness, whereas viscous fluid dissipation is dominant in the fracture tail. We model propagation of the resulting gravity-driven (buoyant or sinking), finger-like fracture of stationary breadth with slowly varying opening along the crack length. The elastic response to fluid loading in a horizontal cross-section is local and can be treated similar to the classical Perkins-Kern-Nordgren (PKN) model of hydraulic fracturing. The propagation condition for a finger-like crack is based on balancing the global energy release rate due to a unit crack extension with the rock fracture toughness. It allows us to relate the net fluid pressure at the tip to the fracture breadth and rock toughness. Unlike the PKN fracture, where breadth is known a priori, the final breadth of a finger-like fracture is a result of processes in the fracture head. Because the head is much more open than the tail, viscous pressure drop in the head can be neglected leading to a 3D analog of Weertman's hydrostatic pulse. This requires relaxing the local elasticity assumption of the PKN model in the fracture head. As a result, we resolve the breadth, and then match the viscosity-dominated tail with the 3-D, toughness

  7. Evaluation of Respondent-Driven Sampling

    PubMed Central

    McCreesh, Nicky; Frost, Simon; Seeley, Janet; Katongole, Joseph; Tarsh, Matilda Ndagire; Ndunguse, Richard; Jichi, Fatima; Lunel, Natasha L; Maher, Dermot; Johnston, Lisa G; Sonnenberg, Pam; Copas, Andrew J; Hayes, Richard J; White, Richard G

    2012-01-01

    Background Respondent-driven sampling is a novel variant of link-tracing sampling for estimating the characteristics of hard-to-reach groups, such as HIV prevalence in sex-workers. Despite its use by leading health organizations, the performance of this method in realistic situations is still largely unknown. We evaluated respondent-driven sampling by comparing estimates from a respondent-driven sampling survey with total-population data. Methods Total-population data on age, tribe, religion, socioeconomic status, sexual activity and HIV status were available on a population of 2402 male household-heads from an open cohort in rural Uganda. A respondent-driven sampling (RDS) survey was carried out in this population, employing current methods of sampling (RDS sample) and statistical inference (RDS estimates). Analyses were carried out for the full RDS sample and then repeated for the first 250 recruits (small sample). Results We recruited 927 household-heads. Full and small RDS samples were largely representative of the total population, but both samples under-represented men who were younger, of higher socioeconomic status, and with unknown sexual activity and HIV status. Respondent-driven-sampling statistical-inference methods failed to reduce these biases. Only 31%-37% (depending on method and sample size) of RDS estimates were closer to the true population proportions than the RDS sample proportions. Only 50%-74% of respondent-driven-sampling bootstrap 95% confidence intervals included the population proportion. Conclusions Respondent-driven sampling produced a generally representative sample of this well-connected non-hidden population. However, current respondent-driven-sampling inference methods failed to reduce bias when it occurred. Whether the data required to remove bias and measure precision can be collected in a respondent-driven sampling survey is unresolved. Respondent-driven sampling should be regarded as a (potentially superior) form of convenience

  8. Osteocyte-Driven Bone Remodeling

    PubMed Central

    Bellido, Teresita

    2013-01-01

    Osteocytes, the most abundant cells in bone, have been long postulated to detect and respond to mechanical and hormonal stimuli and to coordinate the function of osteoblasts and osteoclasts. The discovery that the inhibitor of bone formation sclerostin is primarily expressed in osteocytes in bone and it is downregulated by anabolic stimuli provided a mechanism by which osteocytes influence the activity of osteoblasts. Advances of the last few years provided experimental evidence demonstrating that osteocytes also participate in the recruitment of osteoclasts and the initiation of bone remodeling. Apoptotic osteocytes trigger yet to be identified signals that attract osteoclast precursors to specific areas of bone, which in turn differentiate to mature, bone resorbing osteoclasts. Osteocytes are also the source of molecules that regulate generation and activity of osteoclasts, such as OPG and RANKL; and genetic manipulations of the mouse genome leading to loss or gain of function, or to altered expression of either molecule in osteocytes, markedly affect bone resorption. This review highlights these investigations and discusses how the novel concept of osteocyte-driven bone resorption and formation impacts our understanding of the mechanisms by which current therapies control bone remodeling. PMID:24002178

  9. Cosmic ray driven Galactic winds

    NASA Astrophysics Data System (ADS)

    Recchia, S.; Blasi, P.; Morlino, G.

    2016-08-01

    The escape of cosmic rays from the Galaxy leads to a gradient in the cosmic ray pressure that acts as a force on the background plasma, in the direction opposite to the gravitational pull. If this force is large enough to win against gravity, a wind can be launched that removes gas from the Galaxy, thereby regulating several physical processes, including star formation. The dynamics of these cosmic ray driven winds is intrinsically non-linear in that the spectrum of cosmic rays determines the characteristics of the wind (velocity, pressure, magnetic field) and in turn the wind dynamics affects the cosmic ray spectrum. Moreover, the gradient of the cosmic ray distribution function causes excitation of Alfvén waves, that in turn determine the scattering properties of cosmic rays, namely their diffusive transport. These effects all feed into each other so that what we see at the Earth is the result of these non-linear effects. Here we investigate the launch and evolution of such winds, and we determine the implications for the spectrum of cosmic rays by solving together the hydrodynamical equations for the wind and the transport equation for cosmic rays under the action of self-generated diffusion and advection with the wind and the self-excited Alfvén waves.

  10. Adaptation Driven by Spatial Heterogeneities

    NASA Astrophysics Data System (ADS)

    Hermsen, Rutger

    2011-03-01

    Biological evolution and ecology are intimately linked, because the reproductive success or ``fitness'' of an organism depends crucially on its ecosystem. Yet, most models of evolution (or population genetics) consider homogeneous, fixed-size populations subjected to a constant selection pressure. To move one step beyond such ``mean field'' descriptions, we discuss stochastic models of evolution driven by spatial heterogeneity. We imagine a population whose range is limited by a spatially varying environmental parameter, such as a temperature or the concentration of an antibiotic drug. Individuals in the population replicate, die and migrate stochastically. Also, by mutation, they can adapt to the environmental stress and expand their range. This way, adaptation and niche expansion go hand in hand. This mode of evolution is qualitatively different from the usual notion of a population climbing a fitness gradient. We analytically calculate the rate of adaptation by solving a first passage time problem. Interestingly, the joint effects of reproduction, death, mutation and migration result in two distinct parameter regimes depending on the relative time scales of mutation and migration. We argue that the proposed scenario may be relevant for the rapid evolution of antibiotic resistance. This work was supported by the Center for Theoretical Biological Physics sponsored by the National Science Foundation (NSF) (Grant PHY-0822283).

  11. Bubble-driven inertial micropump

    NASA Astrophysics Data System (ADS)

    Torniainen, Erik D.; Govyadinov, Alexander N.; Markel, David P.; Kornilovitch, Pavel E.

    2012-12-01

    The fundamental action of the bubble-driven inertial micropump is investigated. The pump has no moving parts and consists of a thermal resistor placed asymmetrically within a straight channel connecting two reservoirs. Using numerical simulations, the net flow is studied as a function of channel geometry, resistor location, vapor bubble strength, fluid viscosity, and surface tension. Two major regimes of behavior are identified: axial and non-axial. In the axial regime, the drive bubble either remains inside the channel, or continues to grow axially when it reaches the reservoir. In the non-axial regime, the bubble grows out of the channel and in all three dimensions while inside the reservoir. The net flow in the axial regime is parabolic with respect to the hydraulic diameter of the channel cross-section, but in the non-axial regime it is not. From numerical modeling, it is determined that the net flow is maximal when the axial regime crosses over to the non-axial regime. To elucidate the basic physical principles of the pump, a phenomenological one-dimensional model is developed and solved. A linear array of micropumps has been built using silicon-SU8 fabrication technology that is used to manufacture thermal inkjet printheads. Semi-continuous pumping across a 2 mm-wide channel has been demonstrated experimentally. Measured net flow with respect to viscosity variation is in excellent agreement with simulation results.

  12. Parkfield seismicity: Fluid-driven?

    SciTech Connect

    Johnson, P.A.; McEvilly, T.V.

    1995-07-10

    Characteristics of microearthquake occurrence along the locked-to-creeping transition of the San Andreas fault at Parkfield in central California are reviewed for evidence that fault zone fluids play a critical role in slip dynamics there. Previous studies at Parkfield have defined a low-velocity, anisotropic, attenuating fault zone and a high V{sub P}/V{sub S} ratio in the nucleation zone of the repeating M 6 earthquakes. Most of the ongoing seismicity is organized into a temporally-evolving checkerboard pattern of alternating high and low seismic slip regions divided on the fault zone at 3-6 km spacings. Much of the seismicity is further confined to a few hundred small (20-30 m radius) cells of densely clustered microearthquakes that exhibit periodic recurrence. Space-time development of small (tens to hundreds of meters), transient (minutes to days) earthquake sequences reveals diffusivelike outward spreading along the fault zone. There is some evidence for anomalous source mechanisms in sequence-initiating events, possibly indicative of hydraulic fracturing. The data are consistent with a model in which some microearthquake clusters and confined sequences occur by the cyclic pressurization of fluid within localized patches of the fault zone. The consequent modulation of the effective normal stress leads to fluid-driven slip manifested both as the highly periodic earthquake clusters and as localized earthquake sequences observed at Parkfield. 53 refs., 8 figs., 1 tab.

  13. Rank-Driven Markov Processes

    NASA Astrophysics Data System (ADS)

    Grinfeld, Michael; Knight, Philip A.; Wade, Andrew R.

    2012-01-01

    We study a class of Markovian systems of N elements taking values in [0,1] that evolve in discrete time t via randomized replacement rules based on the ranks of the elements. These rank-driven processes are inspired by variants of the Bak-Sneppen model of evolution, in which the system represents an evolutionary `fitness landscape' and which is famous as a simple model displaying self-organized criticality. Our main results are concerned with long-time large- N asymptotics for the general model in which, at each time step, K randomly chosen elements are discarded and replaced by independent U[0,1] variables, where the ranks of the elements to be replaced are chosen, independently at each time step, according to a distribution κ N on {1,2,…, N} K . Our main results are that, under appropriate conditions on κ N , the system exhibits threshold behavior at s ∗∈[0,1], where s ∗ is a function of κ N , and the marginal distribution of a randomly selected element converges to U[ s ∗,1] as t→∞ and N→∞. Of this class of models, results in the literature have previously been given for special cases only, namely the `mean-field' or `random neighbor' Bak-Sneppen model. Our proofs avoid the heuristic arguments of some of the previous work and use Foster-Lyapunov ideas. Our results extend existing results and establish their natural, more general context. We derive some more specialized results for the particular case where K=2. One of our technical tools is a result on convergence of stationary distributions for families of uniformly ergodic Markov chains on increasing state-spaces, which may be of independent interest.

  14. Optimal protocols for slowly driven quantum systems.

    PubMed

    Zulkowski, Patrick R; DeWeese, Michael R

    2015-09-01

    The design of efficient quantum information processing will rely on optimal nonequilibrium transitions of driven quantum systems. Building on a recently developed geometric framework for computing optimal protocols for classical systems driven in finite time, we construct a general framework for optimizing the average information entropy for driven quantum systems. Geodesics on the parameter manifold endowed with a positive semidefinite metric correspond to protocols that minimize the average information entropy production in finite time. We use this framework to explicitly compute the optimal entropy production for a simple two-state quantum system coupled to a heat bath of bosonic oscillators, which has applications to quantum annealing. PMID:26465432

  15. KRAS-driven ROS promote malignant transformation

    PubMed Central

    Suh, Yongjoon; Lee, Su-Jae

    2015-01-01

    The mechanism underlying KRAS (Kirsten rat sarcoma viral oncogene homolog)-driven cellular transformation remains unclear because of the complexity of its downstream effectors. Park et al. recently reported that levels of reactive oxygen species (ROS) are increased by KRAS and are responsible for KRAS-driven malignant transformation, and further identified the signaling cascade involved as KRAS/p38/PDPK1/PKCδ/p47phox/NOX1. These findings provide new insight into the molecular mechanisms governing KRAS-driven malignant transformation. PMID:27308397

  16. Mission-driven market strategies: lessons from the field. A study of six successful Catholic systems finds mission and values clarity more relevant than ever.

    PubMed

    1998-01-01

    Convinced that Catholic organizations might have special strengths for succeeding in price-competitive markets, the Catholic Health Association, with the assistance of a national membership advisory committee and The Lewin Group, Fairfax, VA, studied six healthcare organizations that are successfully meeting the challenges of difficult environments. Based on more than 100 interviews and assessments of the environments in which these progressive mission-driven organizations operate, the researchers identified strategies that can assist other faith-based health organizations. The Lewin Group's Kevin J. Sexton, who led the research team, explained that "the study examined how the organizations embraced their mission and used their values in three areas: linkages with other organizations, linkages with physicians, and strategies for balancing delivery and insurance." CHA's executive vice president William J. Cox said the study sites were selected to obtain a range of marketplace, sponsorship, and structural experiences. "We wanted to learn how Catholic organizations responded to environmental forces with strategies that were grounded in mission," Cox said. CHA has published the study in a resource packet that describes the five major findings, profiles the cases, and provides Best Practices Checklists--specific pointers to guide organizations in their efforts. The following study excerpts provide a brief overview of the findings and a sample of the Best Practices Checklists. To obtain the complete resource, Mission-Driven Market Strategies: Lessons from the Field, call the Catholic Health Association at 314-253-3458 (for more information see the advertisement on p. 62). PMID:10181593

  17. Stem clutch for motor driven valve

    NASA Technical Reports Server (NTRS)

    Blum, D. E.; Wiltens, J. F.

    1972-01-01

    Development of mechanical device to reduce possibility of damage to motor driven needle valve is discussed. Mechanical clutch is employed to allow slippage when needle valve reaches limit of travel. Operation of system for various conditions is described.

  18. Gas-driven filter pressing in magmas

    USGS Publications Warehouse

    Sisson, T.W.; Bacon, C.R.

    1999-01-01

    Most silicic and some mafic magmas expand via second boiling if they crystallize at depths of about 10 km or less. The buildup of gas pressure due to second boiling can be relieved by expulsion of melt out of the region of crystallization, and this process of gas-driven filter pressing assists the crystallization differentiation of magmas. For gas-driven filter pressing to be effective, the region of crystallization must inflate slowly relative to buildup of pressure and expulsion of melt These conditions are satisfied in undercooled magmatic inclusions and in thin sheets of primitive magma underplating cooler magma reservoirs. Gas-driven filter pressing thereby adds fractionated melt to magma bodies. Gas-driven filter pressing is probably the dominant process by which highly evolved melts segregate from crystal mush to form aplitic dikes in granitic plutons; this process could also account for the production of voluminous, crystal-poor rhyolites.

  19. Laboratory blast wave driven instabilities

    NASA Astrophysics Data System (ADS)

    Kuranz, Carolyn

    2008-04-01

    This presentation discusses experiments well-scaled to the blast wave driven instabilities during the explosion phase of SN1987A. Blast waves occur following a sudden, finite release of energy, and consist of a shock front followed by a rarefaction wave. When a blast wave crosses an interface with a decrease in density, hydrodynamic instabilities will develop. These experiments include target materials scaled in density to the He/H layer in SN1987A. About 5 kJ of laser energy from the Omega Laser facility irradiates a 150 μm plastic layer that is followed by a low density foam layer. A blast wave structure similar to those in supernovae, is created in the plastic layer. The blast wave crosses a perturbed interface, which produces nonlinear, unstable growth dominated by the Rayleigh-Taylor (RT) instability. Recent experiments have been performed using complex initial conditions featuring a three-dimensional interface structure with a wavelength of 71 μm in two orthogonal directions, at times supplemented by an additional sinusoidal mode of 212 μm or 424 μm. We have detected the interface structure under these conditions, using dual orthogonal radiographs on some shots, and will show some of the resulting data. Recent advancements in our x-ray backlighting techniques have greatly improved the resolution of our x-ray radiographic images. Under certain conditions, the improved images show some mass extending beyond the RT spike and penetrating further than previously observed. Current simulations do not show this phenomenon. This presentation will discuss the amount of mass in these spike extensions as well as the error analysis of this calculation. Future experiments will also be discussed. They will be focusing on realistic initial conditions based on 3D stellar evolution models. This research was sponsored by the Stewardship Science Academic Alliances Program through DOE Research Grants DE-FG52-07NA28058, DE-FG52-04NA00064, and other grants and contracts.

  20. Immunization of traffic-driven epidemic spreading

    NASA Astrophysics Data System (ADS)

    Yang, Han-Xin; Wang, Bing-Hong

    2016-02-01

    In this paper, we study the control of the traffic-driven epidemic spreading by immunization strategy. We consider the random, degree-based and betweenness-based immunization strategies, respectively. It is found that the betweenness-based immunization strategy can most effectively prevent the outbreak of traffic-driven epidemic. Besides, we find that the critical number of immune nodes above which epidemic dies out is increased with the enhancement of the spreading rate and the packet-generation rate.

  1. A Micropump Driven by Marangoni Effect

    NASA Astrophysics Data System (ADS)

    Sugimoto, Kenji; Iwamoto, Kaoru; Kawamura, Hiroshi

    A micropump driven by the thermocapillary convection is proposed. The purpose of this study is to examine the flow structure in liquid region and the effect of the geometry on the performance of the present micropump. There are two significant advantages in the thermocapillary-driven system. First, the surface forces become more dominant than the volume forces with decreasing scale. The present micropump driven by the surface forces shows an advantage in the micro scale over a diaphragm pump driven by the volume forces. Secondary, the thermocapillary driven system contains no movable parts; thus, it allows a very simple structure compared to the diaphragm one. In the present micropump system, a number of ribs are distributed along the flow circuit between a heater and a cooler. Since heat transfer from these ribs to the working liquid imposes temperature gradients along the gas-liquid interfaces, the flow from the hot to the cold side is induced by the Marangoni effect. Fundamental characteristics of the present micropump are studied on the basis of three-dimensional simulation conducted taking the gas, liquid and ribs into account. In this study, the flow structure corresponding to the temperature field was observed. The present calculation has revealed that the flow field exhibits a transition from steady flow to oscillatory flow when the Marangoni number exceeds a critical value of about 2,000-2,500. An experiment was also performed. The liquid flow driven by the present micropump system was confirmed through the experiment.

  2. Radiative Interaction Between Driver and Driven Gases in an Arc-Driven Shock Tube

    NASA Technical Reports Server (NTRS)

    Bogdanoff, David W.; Park, Chul

    2001-01-01

    An electric-arc driven shock tube was operated with hydrogen as the driven gas and either hydrogen or helium as the driver gas. Electron density was measured behind the primary shock wave spectroscopically from the width of the Beta line of hydrogen. The measured electron density values were many times greater than the values calculated by the Rankine - Hugoniot relations. By accounting for the radiative transfer from the driver gas to the driven gas, the measured electron density values were numerically recreated.

  3. Supernova-driven interstellar turbulence

    NASA Astrophysics Data System (ADS)

    Joung, M. K. Ryan

    To study how supernova feedback structures the turbulent interstellar medium, we construct 3D models of vertically stratified gas stirred by discrete supernova explosions, including vertical gravitational field and parametrized heating and cooling. The models reproduce many observed characteristics of the Galaxy such as global circulation of gas (i.e., galactic fountain) and the existence of cold dense clouds in the galactic disk. Global quantities of the model such as warm and hot gas filling factors in the midplane, mass fraction of thermally unstable gas, and the averaged vertical density profile are compared directly with existing observations, and shown to be broadly consistent. We find that energy injection occurs over a broad range of scales. There is no single effective driving scale, unlike the usual assumption for idealized models of incompressible turbulence. However, >90% of the total kinetic energy is contained in wavelengths shortward of 200 pc. The shape of the kinetic energy spectrum differs substantially from that of the velocity power spectrum, which implies that the velocity structure varies with the gas density. Velocity structure functions demonstrate that the phenomenological theory proposed by Boldyrev is applicable to the medium. We show that it can be misleading to predict physical properties such as the stellar initial mass junction based on numerical simulations that do not include self-gravity of the gas. Even if all the gas in turbulently Jeans unstable regions in our simulation is assumed to collapse and form stars in local freefall times, the resulting total collapse rate is significantly lower than the value consistent with the input supernova rate. Supernova-driven turbulence inhibits star formation globally rather than triggering it. Feedback from massive stars is perhaps the least understood aspect of the current scenario of large-scale structure formation. Many recent observations on both galactic and cosmological scales require

  4. Towards Redox-Driven Unidirectional Molecular Motion.

    PubMed

    Logtenberg, Hella; Areephong, Jetsuda; Bauer, Jurica; Meetsma, Auke; Feringa, Ben L; Browne, Wesley R

    2016-06-17

    Redox-driven molecular motion is an attractive alternative to light-driven processes. Here, the ability of an overcrowded alkene-based unimolecular light-driven rotary motor (A) to be driven by oxidation/reduction cycles is explored. We show that two-electron oxidation of A is followed by irreversible deprotonation and reduction to form a monocationic species D(+) , in which the stereogenic center is lost. This latter species was isolated through preparative electrolysis and its structure was confirmed by using single-crystal X-ray analysis. However, at short timescales and in the absence of Brønsted acids, these processes can be outrun and the oxidation of A to a dicationic species B(2+) occurs, in which the central double bond (the axle of the molecular motor) becomes a single bond; when followed by rapid reduction, it results in the reformation of A, potentially in both its stable and unstable conformations. The latter conformation, if formed, undergoes thermal helix inversion, completing a rotary cycle. The data obtained regarding these reactions provide a window of opportunity for the motor to be driven electrochemically, without degradation from chemical reactions of the oxidized motor. PMID:26853700

  5. Attributing Study Effort to Data-Driven and Goal-Driven Effects: Implications for Metacognitive Judgments

    ERIC Educational Resources Information Center

    Koriat, Asher; Nussinson, Ravit

    2009-01-01

    In self-paced learning, when the regulation of effort is goal driven (e.g., allocated to different items according to their relative importance), judgments of learning (JOLs) increase with study time. When it is data driven (i.e., determined by the ease of committing the item to memory), JOLs decrease with study time (Koriat, Ma'ayan, & Nussinson,…

  6. 14 CFR 36.9 - Acoustical change: Propeller-driven small airplanes and propeller-driven commuter category...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... airplanes and propeller-driven commuter category airplanes. 36.9 Section 36.9 Aeronautics and Space FEDERAL... AIRWORTHINESS CERTIFICATION General § 36.9 Acoustical change: Propeller-driven small airplanes and propeller-driven commuter category airplanes. For propeller-driven small airplanes in the primary, normal,...

  7. 14 CFR 36.9 - Acoustical change: Propeller-driven small airplanes and propeller-driven commuter category...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... airplanes and propeller-driven commuter category airplanes. 36.9 Section 36.9 Aeronautics and Space FEDERAL... AIRWORTHINESS CERTIFICATION General § 36.9 Acoustical change: Propeller-driven small airplanes and propeller-driven commuter category airplanes. For propeller-driven small airplanes in the primary, normal,...

  8. 14 CFR 36.9 - Acoustical change: Propeller-driven small airplanes and propeller-driven commuter category...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... airplanes and propeller-driven commuter category airplanes. 36.9 Section 36.9 Aeronautics and Space FEDERAL... AIRWORTHINESS CERTIFICATION General § 36.9 Acoustical change: Propeller-driven small airplanes and propeller-driven commuter category airplanes. For propeller-driven small airplanes in the primary, normal,...

  9. 14 CFR 36.9 - Acoustical change: Propeller-driven small airplanes and propeller-driven commuter category...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... airplanes and propeller-driven commuter category airplanes. 36.9 Section 36.9 Aeronautics and Space FEDERAL... AIRWORTHINESS CERTIFICATION General § 36.9 Acoustical change: Propeller-driven small airplanes and propeller-driven commuter category airplanes. For propeller-driven small airplanes in the primary, normal,...

  10. 14 CFR 36.9 - Acoustical change: Propeller-driven small airplanes and propeller-driven commuter category...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... airplanes and propeller-driven commuter category airplanes. 36.9 Section 36.9 Aeronautics and Space FEDERAL... AIRWORTHINESS CERTIFICATION General § 36.9 Acoustical change: Propeller-driven small airplanes and propeller-driven commuter category airplanes. For propeller-driven small airplanes in the primary, normal,...

  11. Gas engine driven chiller development and economics

    SciTech Connect

    Koplow, M.D.; Searight, E.F.; Panora, R.

    1986-03-01

    The TECOGEN Division of Thermo Electron Corporation has developed a nominal 150 ton engine driven chiller system under the sponsorship of the Gas Research Institute. The system incorporates an engine directly driving a screw compressor to produce about 130 tons of cooling capacity and a single effect absorption chiller driven by hot water recovered from engine heat to produce another 30 tons of cooling capacity. An economic analysis shows that it will be possible to recover the cost premium of engine driven chiller systems in most US cities in 3 years or less with the O and M savings of these systems when this cost premium is $30 per ton. 4 references, 13 figures, 5 tables.

  12. Three levels of data-driven science

    NASA Astrophysics Data System (ADS)

    Igarashi, Yasuhiko; Nagata, Kenji; Kuwatani, Tatsu; Omori, Toshiaki; Nakanishi-Ohno, Yoshinori; Okada, Masato

    2016-03-01

    A research project, called “the Initiative for High-dimensional Data-Driven Science through Deepening of Sparse Modeling” is introduced. A concept, called the three levels of data-driven science, is proposed to untie the complicated relation between many fields and many methods. This concept claims that any problem of data analysis should be discussed at different three levels: computational theory, modeling, and representation/algorithm. Based on the concept, how to choose a suitable method among several candidates is discussed through our study on spectral deconvolution. In addition, how to find a universal problem across the disciplines is presented by explaining our proposed ES-SVM method. Moreover, it is illustrated that the hierarchical structure of data analysis should be visualized and shared. From these discussions, we believe that data-driven science is mother of science, namely, a scientific framework that drives many fields of science.

  13. Metamodel-Driven Evolution with Grammar Inference

    NASA Astrophysics Data System (ADS)

    Bryant, Barrett R.; Liu, Qichao; Mernik, Marjan

    2010-10-01

    Domain-specific modeling (DSM) has become one of the most popular techniques for incorporating model-driven engineering (MDE) into software engineering. In DSM, domain experts define metamodels to describe the essential problems in a domain. A model conforms to a schema definition represented by a metamodel in a similar manner to a programming language conforms to a grammar. Metamodel-driven evolution is when a metamodel undergoes evolutions to incorporate new concerns in the domain. However, this results in losing the ability to use existing model instances. Grammar inference is the problem of inferring a grammar from sample strings which the grammar should generate. This paper describes our work in solving the problem of metamodel-driven evolution with grammar inference, by inferring the metamodel from model instances.

  14. Topological characterization of periodically driven quantum systems

    NASA Astrophysics Data System (ADS)

    Kitagawa, Takuya; Berg, Erez; Rudner, Mark; Demler, Eugene

    2010-12-01

    Topological properties of physical systems can lead to robust behaviors that are insensitive to microscopic details. Such topologically robust phenomena are not limited to static systems but can also appear in driven quantum systems. In this paper, we show that the Floquet operators of periodically driven systems can be divided into topologically distinct (homotopy) classes and give a simple physical interpretation of this classification in terms of the spectra of Floquet operators. Using this picture, we provide an intuitive understanding of the well-known phenomenon of quantized adiabatic pumping. Systems whose Floquet operators belong to the trivial class simulate the dynamics generated by time-independent Hamiltonians, which can be topologically classified according to the schemes developed for static systems. We demonstrate these principles through an example of a periodically driven two-dimensional hexagonal lattice tight-binding model which exhibits several topological phases. Remarkably, one of these phases supports chiral edge modes even though the bulk is topologically trivial.

  15. Glassy dynamics of driven elastic manifolds

    SciTech Connect

    Vinokur, V.M.

    1996-12-31

    We study the low-temperature dynamics of an elastic manifold driven through a random medium. For driving forces well below the zero- temperature depinning force, the manifold advances via thermally activated hops over the energy barriers separating favorable metastable states. We develop a scaling theory of the thermally activated dynamics (creep) and find a nonlinear glassy response for the driven manifold, {upsilon}{approximately}exp(-const{times}F{sup - {mu}}). We consider an exactly solvable 1-D model for random driven dynamics which exhibits a creep-like velocity-force characteristic. We discuss a microscopic mechanism for the creep motion and show that the distribution of waiting times for the hopping processes scales as a power law. This power-law distribution naturally yields an exponential response for the creep of the manifold.

  16. Microphysics of Cosmic Ray Driven Plasma Instabilities

    NASA Astrophysics Data System (ADS)

    Bykov, A. M.; Brandenburg, A.; Malkov, M. A.; Osipov, S. M.

    2013-10-01

    Energetic nonthermal particles (cosmic rays, CRs) are accelerated in supernova remnants, relativistic jets and other astrophysical objects. The CR energy density is typically comparable with that of the thermal components and magnetic fields. In this review we discuss mechanisms of magnetic field amplification due to instabilities induced by CRs. We derive CR kinetic and magnetohydrodynamic equations that govern cosmic plasma systems comprising the thermal background plasma, comic rays and fluctuating magnetic fields to study CR-driven instabilities. Both resonant and non-resonant instabilities are reviewed, including the Bell short-wavelength instability, and the firehose instability. Special attention is paid to the longwavelength instabilities driven by the CR current and pressure gradient. The helicity production by the CR current-driven instabilities is discussed in connection with the dynamo mechanisms of cosmic magnetic field amplification.

  17. Microphysics of Cosmic Ray Driven Plasma Instabilities

    NASA Astrophysics Data System (ADS)

    Bykov, A. M.; Brandenburg, A.; Malkov, M. A.; Osipov, S. M.

    Energetic nonthermal particles (cosmic rays, CRs) are accelerated in supernova remnants, relativistic jets and other astrophysical objects. The CR energy density is typically comparable with that of the thermal components and magnetic fields. In this review we discuss mechanisms of magnetic field amplification due to instabilities induced by CRs. We derive CR kinetic and magnetohydrodynamic equations that govern cosmic plasma systems comprising the thermal background plasma, comic rays and fluctuating magnetic fields to study CR-driven instabilities. Both resonant and non-resonant instabilities are reviewed, including the Bell short-wavelength instability, and the firehose instability. Special attention is paid to the longwavelength instabilities driven by the CR current and pressure gradient. The helicity production by the CR current-driven instabilities is discussed in connection with the dynamo mechanisms of cosmic magnetic field amplification.

  18. Light-Driven Polymeric Bimorph Actuators

    NASA Technical Reports Server (NTRS)

    Adamovsky, Gregory; Sarkisov, Sergey S.; Curley, Michael J.

    2009-01-01

    Light-driven polymeric bimorph actuators are being developed as alternatives to prior electrically and optically driven actuators in advanced, highly miniaturized devices and systems exemplified by microelectromechanical systems (MEMS), micro-electro-optical-mechanical systems (MEOMS), and sensor and actuator arrays in smart structures. These light-driven polymeric bimorph actuators are intended to satisfy a need for actuators that (1) in comparison with the prior actuators, are simpler and less power-hungry; (2) can be driven by low-power visible or mid-infrared light delivered through conventional optic fibers; and (3) are suitable for integration with optical sensors and multiple actuators of the same or different type. The immediate predecessors of the present light-driven polymeric bimorph actuators are bimorph actuators that exploit a photorestrictive effect in lead lanthanum zirconate titanate (PLZT) ceramics. The disadvantages of the PLZT-based actuators are that (1) it is difficult to shape the PLZT ceramics, which are hard and brittle; (2) for actuation, it is necessary to use ultraviolet light (wavelengths < 380 nm), which must be generated by use of high-power, high-pressure arc lamps or lasers; (3) it is difficult to deliver sufficient ultraviolet light through conventional optical fibers because of significant losses in the fibers; (4) the response times of the PLZT actuators are of the order of several seconds unacceptably long for typical applications; and (5) the maximum mechanical displacements of the PLZT-based actuators are limited to those characterized by low strains beyond which PLZT ceramics disintegrate because of their brittleness. The basic element of a light-driven bimorph actuator of the present developmental type is a cantilever beam comprising two layers, at least one of which is a polymer that exhibits a photomechanical effect (see figure). The dominant mechanism of the photomechanical effect is a photothermal one: absorption of

  19. New Instabilities in Line Driven Winds

    NASA Technical Reports Server (NTRS)

    Martens, P. C. H.

    1985-01-01

    The physical mechanisms which potentially lead to instabilities in line driven winds, the drift instability and the line shape instability, are discussed. A general three dimensional treatment of the stability problem of line driven winds which leads to the general dispersion equation is proposed. From this dispersion equation automatically a third physical mechanism driving instability in stellar winds is deduced; the thermal drift instability which is related to changes in absorption of radiation caused by temperature perturbations. This mechanism results in growing inwardly propagating sound waves.

  20. Statistical Transmutation in Floquet Driven Optical Lattices

    NASA Astrophysics Data System (ADS)

    Sedrakyan, Tigran A.; Galitski, Victor M.; Kamenev, Alex

    2015-11-01

    We show that interacting bosons in a periodically driven two dimensional (2D) optical lattice may effectively exhibit fermionic statistics. The phenomenon is similar to the celebrated Tonks-Girardeau regime in 1D. The Floquet band of a driven lattice develops the moat shape, i.e., a minimum along a closed contour in the Brillouin zone. Such degeneracy of the kinetic energy favors fermionic quasiparticles. The statistical transmutation is achieved by the Chern-Simons flux attachment similar to the fractional quantum Hall case. We show that the velocity distribution of the released bosons is a sensitive probe of the fermionic nature of their stationary Floquet state.

  1. Statistical Transmutation in Floquet Driven Optical Lattices.

    PubMed

    Sedrakyan, Tigran A; Galitski, Victor M; Kamenev, Alex

    2015-11-01

    We show that interacting bosons in a periodically driven two dimensional (2D) optical lattice may effectively exhibit fermionic statistics. The phenomenon is similar to the celebrated Tonks-Girardeau regime in 1D. The Floquet band of a driven lattice develops the moat shape, i.e., a minimum along a closed contour in the Brillouin zone. Such degeneracy of the kinetic energy favors fermionic quasiparticles. The statistical transmutation is achieved by the Chern-Simons flux attachment similar to the fractional quantum Hall case. We show that the velocity distribution of the released bosons is a sensitive probe of the fermionic nature of their stationary Floquet state. PMID:26588392

  2. Light modulated electron beam driven radiofrequency emitter

    DOEpatents

    Wilson, M.T.; Tallerico, P.J.

    1979-10-10

    The disclosure relates to a light modulated electron beam-driven radiofrequency emitter. Pulses of light impinge on a photoemissive device which generates an electron beam having the pulse characteristics of the light. The electron beam is accelerated through a radiofrequency resonator which produces radiofrequency emission in accordance with the electron, hence, the light pulses.

  3. Layzer type models for pressure driven shells

    SciTech Connect

    Hurricane, O A

    2004-09-16

    Models for the nonlinear instability of finite thickness shells driven by pressure are constructed in the style of Layzer. Equations for both Cartesian and cylindrically convergent/divergent geometries are derived. The resulting equations are appropriate for incompressible shells with unity Atwood number. Predictions from the equations compare well with two-dimensional simulations.

  4. Terahertz-driven linear electron acceleration.

    PubMed

    Nanni, Emilio A; Huang, Wenqian R; Hong, Kyung-Han; Ravi, Koustuban; Fallahi, Arya; Moriena, Gustavo; Miller, R J Dwayne; Kärtner, Franz X

    2015-01-01

    The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30-50 MeV m(-1) gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/proton accelerators with simple accelerating structures, high repetition rates and significant charge per bunch. These ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams. PMID:26439410

  5. ISKME Special Series Part I: Data Driven

    ERIC Educational Resources Information Center

    Panettieri, Joseph C.

    2006-01-01

    In early December 2005, the School District of Philadelphia announced that, for the fourth consecutive year, students showed measurable improvement on standardized, nationally normed TerraNova tests. The school's good performance was induced by a well managed instructional program that includes data-driven instruction and decision-making…

  6. High-explosive driven crowbar switch

    DOEpatents

    Dike, Robert S.; Kewish, Jr., Ralph W.

    1976-01-13

    The disclosure relates to a compact explosive driven switch for use as a low resistance, low inductance crowbar switch. A high-explosive charge extrudes a deformable conductive metallic plate through a polyethylene insulating layer to achieve a hard current contact with a supportive annular conductor.

  7. Persistence of Value-Driven Attentional Capture

    ERIC Educational Resources Information Center

    Anderson, Brian A.; Yantis, Steven

    2013-01-01

    Stimuli that have previously been associated with the delivery of reward involuntarily capture attention when presented as unrewarded and task-irrelevant distractors in a subsequent visual search task. It is unknown how long such effects of reward learning on attention persist. One possibility is that value-driven attentional biases are plastic…

  8. Terahertz-driven linear electron acceleration

    DOE PAGESBeta

    Nanni, Emilio A.; Huang, Wenqian R.; Hong, Kyung-Han; Ravi, Koustuban; Fallahi, Arya; Moriena, Gustavo; Dwayne Miller, R. J.; Kärtner, Franz X.

    2015-10-06

    The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30–50 MeVm-1 gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/proton acceleratorsmore » with simple accelerating structures, high repetition rates and significant charge per bunch. As a result, these ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams.« less

  9. Terahertz-driven linear electron acceleration

    SciTech Connect

    Nanni, Emilio A.; Huang, Wenqian R.; Hong, Kyung-Han; Ravi, Koustuban; Fallahi, Arya; Moriena, Gustavo; Dwayne Miller, R. J.; Kärtner, Franz X.

    2015-10-06

    The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30–50 MeVm-1 gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/proton accelerators with simple accelerating structures, high repetition rates and significant charge per bunch. As a result, these ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams.

  10. Terahertz-driven linear electron acceleration

    PubMed Central

    Nanni, Emilio A.; Huang, Wenqian R.; Hong, Kyung-Han; Ravi, Koustuban; Fallahi, Arya; Moriena, Gustavo; Dwayne Miller, R. J.; Kärtner, Franz X.

    2015-01-01

    The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30–50 MeV m−1 gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/proton accelerators with simple accelerating structures, high repetition rates and significant charge per bunch. These ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams. PMID:26439410

  11. Mission Driven and Data Informed Leadership

    ERIC Educational Resources Information Center

    Holter, Anthony C.; Frabutt, James M.

    2012-01-01

    The contemporary challenges facing Catholic schools and Catholic school leaders are widely known. Effective and systemic solutions to these mounting challenges are less widely known or discussed. This article highlights the skills, knowledge, and dispositions associated with mission driven and data informed leadership--an orientation to school…

  12. The evolution to market-driven quality.

    PubMed

    Bruno, R J

    1992-01-01

    Quality experts and Baldrige Award recipients agree that whether or not a company wins the coveted award, it gains countless benefits from going through the application process. In 1989, one unit at GTE applied for the Baldrige. This article details the results of that process, as well as the company's ongoing pursuit of market-driven quality. PMID:10121457

  13. Terahertz-driven linear electron acceleration

    NASA Astrophysics Data System (ADS)

    Nanni, Emilio A.; Huang, Wenqian R.; Hong, Kyung-Han; Ravi, Koustuban; Fallahi, Arya; Moriena, Gustavo; Dwayne Miller, R. J.; Kärtner, Franz X.

    2015-10-01

    The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30-50 MeV m-1 gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/proton accelerators with simple accelerating structures, high repetition rates and significant charge per bunch. These ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams.

  14. What Data for Data-Driven Learning?

    ERIC Educational Resources Information Center

    Boulton, Alex

    2012-01-01

    Corpora have multiple affordances, not least for use by teachers and learners of a foreign language (L2) in what has come to be known as "data-driven learning" or DDL. The corpus and concordance interface were originally conceived by and for linguists, so other users need to adopt the role of "language researcher" to make the most of them. Despite…

  15. Microwave-driven ultraviolet light sources

    DOEpatents

    Manos, Dennis M.; Diggs, Jessie; Ametepe, Joseph D.

    2002-01-29

    A microwave-driven ultraviolet (UV) light source is provided. The light source comprises an over-moded microwave cavity having at least one discharge bulb disposed within the microwave cavity. At least one magnetron probe is coupled directly to the microwave cavity.

  16. Viscous Driven-Cavity Solver: User's Manual

    NASA Technical Reports Server (NTRS)

    Wood, William A.

    1997-01-01

    The viscous driven-cavity problem is solved using a stream-function and vorticity formulation for the incompressible Navier-Stokes equations. This report provides the user's manual and FORTRAN code for the set of governing equations presented in NASA TM-110262.

  17. Triggering of high-speed neurite outgrowth using an optical microheater

    PubMed Central

    Oyama, Kotaro; Zeeb, Vadim; Kawamura, Yuki; Arai, Tomomi; Gotoh, Mizuho; Itoh, Hideki; Itabashi, Takeshi; Suzuki, Madoka; Ishiwata, Shin’ichi

    2015-01-01

    Optical microheating is a powerful non-invasive method for manipulating biological functions such as gene expression, muscle contraction, and cell excitation. Here, we demonstrate its potential usage for regulating neurite outgrowth. We found that optical microheating with a water-absorbable 1,455-nm laser beam triggers directional and explosive neurite outgrowth and branching in rat hippocampal neurons. The focused laser beam under a microscope rapidly increases the local temperature from 36 °C to 41 °C (stabilized within 2 s), resulting in the elongation of neurites by more than 10 μm within 1 min. This high-speed, persistent elongation of neurites was suppressed by inhibitors of both microtubule and actin polymerization, indicating that the thermosensitive dynamics of these cytoskeletons play crucial roles in this heat-induced neurite outgrowth. Furthermore, we showed that microheating induced the regrowth of injured neurites and the interconnection of neurites. These results demonstrate the efficacy of optical microheating methods for the construction of arbitrary neural networks. PMID:26568288

  18. Locomotion response of airborne, ambulatory and aquatic insects to thermal stimulation using piezoceramic microheaters

    NASA Astrophysics Data System (ADS)

    Visvanathan, Karthik; Gianchandani, Yogesh B.

    2011-12-01

    This paper reports the locomotion response of airborne, ambulatory and aquatic insects to thermal stimulation. A finite element model has been developed to predict the variation of insect-stimulator interface temperature with input power. Piezothermal stimulators have been fabricated from lead zirconate titanate (PZT) using a batch mode micro ultrasonic machining process. Typical sizes range from 200 µm to 3.2 mm. For PZT stimulators, the temperature and thermal efficiency reach the maximum value around the resonance frequency which is typically in the range of 650 kHz to 47 MHz. Experiments have been conducted on green June beetles (GJBs), Madagascar hissing roaches and green diving beetles (GDBs) in order to show the versatility of the proposed technique. The stimulators have been implanted near the antennae of the GJBs and on either side of the thorax of the Madagascar hissing roaches and GDBs, respectively. In all cases, the insects move away from the direction of the actuated stimulator. The left and right turns are statistically similar. Thermal stimulation achieves an overall success rate of 78.7%, 92.8% and 61.6% in GJBs, roaches and GDBs, respectively. On average, thermal stimulation results in an angle turn of about 13.7°-16.2° on GJBs, 30°-45° on the roaches and 30°-50° on GDBs. The corresponding average input power is 360, 330 and 100 mW for GJBs, roach and GDBs, respectively. Scaling limits of the PZT stimulators for operating these stimulators are also discussed.

  19. Physical Science Informatics: Providing Open Science Access to Microheater Array Boiling Experiment Data

    NASA Technical Reports Server (NTRS)

    McQuillen, John; Green, Robert D.; Henrie, Ben; Miller, Teresa; Chiaramonte, Fran

    2014-01-01

    The Physical Science Informatics (PSI) system is the next step in this an effort to make NASA sponsored flight data available to the scientific and engineering community, along with the general public. The experimental data, from six overall disciplines, Combustion Science, Fluid Physics, Complex Fluids, Fundamental Physics, and Materials Science, will present some unique challenges. Besides data in textual or numerical format, large portions of both the raw and analyzed data for many of these experiments are digital images and video, requiring large data storage requirements. In addition, the accessible data will include experiment design and engineering data (including applicable drawings), any analytical or numerical models, publications, reports, and patents, and any commercial products developed as a result of the research. This objective of paper includes the following: Present the preliminary layout (Figure 2) of MABE data within the PSI database. Obtain feedback on the layout. Present the procedure to obtain access to this database.

  20. Outflow Driven Turbulence in Star Forming Clouds

    NASA Astrophysics Data System (ADS)

    Frank, Adam

    Setting young stellar object jets and outflows in their broadest context requires an understanding of outflows as “feedback” in the development of molecular cloud turbulence and the determination of star formation efficiencies. In this contribution I review our group’s recent studies exploring relationships between protostellar outflows and turbulence in molecular clouds. We first present studies of turbulence and fossil cavities driven by YSO outflows using numerical simulations which track the evolution of single transient jets driven into a turbulent medium. Our simulations show both the effect of turbulence on outflow structures and, conversely, the effect of outflows on the ambient turbulence. These studies demonstrate that individual transient outflows have the capacity to re-energize decaying turbulence. Next we present simulations of multiple interacting jets. We show that turbulence can readily be sustained by these interactions and show that it is possible to broadly characterize an effective driving scale of the outflows. Comparing the velocity spectrum obtained in our studies to that of an isotropically forced control we show that in outflow driven turbulence a power law of the form E(k) ∝ k - β is indeed achieved. However we find a steeper spectrum β ˜ 3 is obtained in outflow driven turbulence models than in isotropically forced simulations β ˜ 2. 0. Taken together both studies provide broad support for the conclusion that fossil cavities driven by decaying jets can provide a source of turbulence and feedback which mediate star formation processes in molecular clouds. Whether this does obtain in real clouds remains a point which must be demonstrated

  1. Coherent states of the driven Rydberg atom: Quantum-classical correspondence of periodically driven systems

    SciTech Connect

    Vela-Arevalo, Luz V.; Fox, Ronald F.

    2005-06-15

    A methodology to calculate generalized coherent states for a periodically driven system is presented. We study wave packets constructed as a linear combination of suitable Floquet states of the three-dimensional Rydberg atom in a microwave field. The driven coherent states show classical space localization, spreading, and revivals and remain localized along the classical trajectory. The microwave strength and frequency have a great effect in the localization of Floquet states, since quasienergy avoided crossings produce delocalization of the Floquet states, showing that tuning of the parameters is very important. Using wavelet-based time-frequency analysis, the classical phase-space structure is determined, which allows us to show that the driven coherent state is located in a large regular region in which the z coordinate is in resonance with the external field. The expectation values of the wave packet show that the driven coherent state evolves along the classical trajectory.

  2. The interplay of goal-driven and stimulus-driven influences on spatial orienting.

    PubMed

    Otten, Mara; Schreij, Daniel; Los, Sander A

    2016-08-01

    Search for a target stimulus among distractors is subject to both goal-driven and stimulus-driven influences. Variables that selectively modify these influences have shown strong interaction effects on saccade trajectories toward the target, suggesting the involvement of a shared spatial orienting mechanism. However, subsequent manual response times (RTs) have revealed additive effects, suggesting that different mechanisms are involved. In the present study, we tested the hypothesis that an interaction for RTs is obscured by preceding multisaccade trajectories, promoted by the continuous presence of distractors in the display. In two experiments, we compared a condition in which distractors were removed soon after the presentation of the search display to a standard condition in which distractors were not removed. The results showed additive goal-driven and stimulus-driven effects on RTs in the standard condition, but an interaction when distractors were removed. These findings support the view that both variables influence a shared spatial orienting mechanism. PMID:27259486

  3. Coherent states of the driven Rydberg atom: Quantum-classical correspondence of periodically driven systems

    NASA Astrophysics Data System (ADS)

    Vela-Arevalo, Luz V.; Fox, Ronald F.

    2005-06-01

    A methodology to calculate generalized coherent states for a periodically driven system is presented. We study wave packets constructed as a linear combination of suitable Floquet states of the three-dimensional Rydberg atom in a microwave field. The driven coherent states show classical space localization, spreading, and revivals and remain localized along the classical trajectory. The microwave strength and frequency have a great effect in the localization of Floquet states, since quasienergy avoided crossings produce delocalization of the Floquet states, showing that tuning of the parameters is very important. Using wavelet-based time-frequency analysis, the classical phase-space structure is determined, which allows us to show that the driven coherent state is located in a large regular region in which the z coordinate is in resonance with the external field. The expectation values of the wave packet show that the driven coherent state evolves along the classical trajectory.

  4. Dust-driven and plasma-driven currents in the inner magnetosphere of Saturn

    NASA Astrophysics Data System (ADS)

    Olson, J.; Brenning, N.

    2012-04-01

    General equations for dust-driven currents and current systems JD in magnetized plasmas are derived and, as a concrete example, applied to the E ring of Saturn at radial distances 3RSdriven current systems down to the ionosphere of Saturn, both rotating with the magnetospheric plasma. One of these closes across the polar cap, and the other over a limited range in latitude. These dust-driven current systems are embedded in three systems of plasma-driven currents Jp: a ring current, a cross-polar-cap current system, and an ion pickup current system. Both the JD and the Jp current systems have been quantitatively assessed from a data set for the E ring of Saturn in which the unknown distribution of small dust is treated by a power law extrapolation from the known distribution of larger dust. From data on the magnetic perturbations during a crossing of the equatorial plane, an approximate constraint on the fraction of the electrons that can be trapped on the dust is derived. For this amount of electron capture, it is demonstrated that all three types of dust-driven currents are, within somewhat more than an order of magnitude, of the same strength as the corresponding types of plasma-driven currents. Considering also that both plasma and dust densities vary with the geyser activity at the south pole of Enceladus, it is concluded that both the dust-driven and the plasma-driven contributions to the current system associated with the E ring need to be retained for a complete description.

  5. Control apparatus for hydraulically driven generator

    SciTech Connect

    Beckwith, S.

    1985-08-06

    Apparatus for controlling a hydraulically driven generator for supplying electrical power to power mains. The generator is coupled to a turbine driven by a fluid flow through a duct. The duct has a one-fourth turn butterfly valve controlled by a fluid-actuated operator and the operator receives fluid from the duct by way of a normally closed valve which, when energized, creates water pressure on the operator for opening the butterfly valve. A second, normally open solenoid provides an emergency exit for the water from the operator to relieve the water pressure thereon and thereby close the butterfly valve when certain conditions exist, such as sudden loss of line voltage, overvoltage or deviation in frequency of the line voltage. A differential pressure switch across the turbine rotor also controls the starting of the system to assure proper flow of fluid through the duct before commencing operation of the generator itself.

  6. A signature for turbulence driven magnetic islands

    SciTech Connect

    Agullo, O.; Muraglia, M.; Benkadda, S.; Poyé, A.; Yagi, M.; Garbet, X.; Sen, A.

    2014-09-15

    We investigate the properties of magnetic islands arising from tearing instabilities that are driven by an interchange turbulence. We find that such islands possess a specific signature that permits an identification of their origin. We demonstrate that the persistence of a small scale turbulence maintains a mean pressure profile, whose characteristics makes it possible to discriminate between turbulence driven islands from those arising due to an unfavourable plasma current density gradient. We also find that the island poloidal turnover time, in the steady state, is independent of the levels of the interchange and tearing energy sources. Finally, we show that a mixing length approach is adequate to make theoretical predictions concerning island flattening in the island rotation frame.

  7. Odd-frequency Superconductivity in Driven Systems

    NASA Astrophysics Data System (ADS)

    Triola, Christopher; Balatsky, Alexander

    We show that Berezinskii's classification of the symmetries of Cooper pair amplitudes in terms of parity under transformations that invert spin, space, time, and orbital degrees of freedom holds for driven systems even in the absence of translation invariance. We then discuss the conditions under which pair amplitudes which are odd in frequency can emerge in driven systems. Considering a model Hamiltonian for a superconductor coupled to an external driving potential, we investigate the influence of the drive on the anomalous Green's function, density of states, and spectral function. We find that the anomalous Green's function develops odd in frequency component in the presence of an external drive. Furthermore we investigate how these odd-frequency terms are related to satellite features in the density of states and spectral function. Supported by US DOE BES E 304.

  8. Electrically Driven Spin Dynamics of Paramagnetic Impurities

    NASA Astrophysics Data System (ADS)

    Saha, D.; Siddiqui, L.; Bhattacharya, P.; Datta, S.; Basu, D.; Holub, M.

    2008-05-01

    The spin dynamics of dilute paramagnetic impurities embedded in a semiconductor GaAs channel of a conventional lateral spin valve has been investigated. It is observed that the electron spin of paramagnetic Mn atoms can be polarized electrically when driven by a spin valve in the antiparallel configuration. The transient current through the MnAs/GaAs/MnAs spin valve bears the signature of the underlying spin dynamics driven by the exchange interaction between the conduction band electrons in GaAs and the localized Mn electron spins. The time constant for this interaction is observed to be dependent on temperature and is estimated to be 80 ns at 15 K.

  9. Electrically driven spin dynamics of paramagnetic impurities.

    PubMed

    Saha, D; Siddiqui, L; Bhattacharya, P; Datta, S; Basu, D; Holub, M

    2008-05-16

    The spin dynamics of dilute paramagnetic impurities embedded in a semiconductor GaAs channel of a conventional lateral spin valve has been investigated. It is observed that the electron spin of paramagnetic Mn atoms can be polarized electrically when driven by a spin valve in the antiparallel configuration. The transient current through the MnAs/GaAs/MnAs spin valve bears the signature of the underlying spin dynamics driven by the exchange interaction between the conduction band electrons in GaAs and the localized Mn electron spins. The time constant for this interaction is observed to be dependent on temperature and is estimated to be 80 ns at 15 K. PMID:18518470

  10. Light-driven artificial molecular machines

    NASA Astrophysics Data System (ADS)

    Zheng, Yue Bing; Hao, Qingzhen; Yang, Ying-Wei; Kiraly, Brian; Chiang, I.-Kao; Huang, Tony Jun

    2010-08-01

    Artificial molecular machines represent a growing field of nanoscience and nanotechnology. Stimulated by chemical reagents, electricity, or light, artificial molecular machines exhibit precisely controlled motion at the molecular level; with this ability molecular machines have the potential to make significant impacts in numerous engineering applications. Compared with molecular machines powered by chemical or electrical energy, light-driven molecular machines have several advantages: light can be switched much faster, work without producing chemical waste, and be used for dual purposes-inducing (writing) as well as detecting (reading) molecular motions. The following issues are significant for light-driven artificial molecular machines in the following aspects: their chemical structures, motion mechanisms, assembly and characterization on solid-state surfaces. Applications in different fields of nanotechnology such as molecular electronics, nano-electro-mechanical systems (NEMS), nanophotonics, and nanomedicine are envisaged.

  11. Laser-driven fusion etching process

    DOEpatents

    Ashby, C.I.H.; Brannon, P.J.; Gerardo, J.B.

    1987-08-25

    The surfaces of solids are etched by a radiation-driven chemical reaction. The process involves exposing a substrate coated with a layer of a reactant material on its surface to radiation, e.g., a laser, to induce localized melting of the substrate which results in the occurrence of a fusion reaction between the substrate and coating material. The resultant reaction product and excess reactant salt are then removed from the surface of the substrate with a solvent which is relatively inert towards the substrate. The laser-driven chemical etching process is especially suitable for etching ionic substrates, e.g., LiNbO/sub 3/, such as used in electro-optical/acousto-optic devices. It is also suitable for applications wherein the etching process is required to produce an etched ionic substrate having a smooth surface morphology or when a very rapid etching rate is desired.

  12. Laser-driven fusion etching process

    DOEpatents

    Ashby, Carol I. H.; Brannon, Paul J.; Gerardo, James B.

    1989-01-01

    The surfaces of solid ionic substrates are etched by a radiation-driven chemical reaction. The process involves exposing an ionic substrate coated with a layer of a reactant material on its surface to radiation, e.g. a laser, to induce localized melting of the substrate which results in the occurrance of a fusion reaction between the substrate and coating material. The resultant reaction product and excess reactant salt are then removed from the surface of the substrate with a solvent which is relatively inert towards the substrate. The laser-driven chemical etching process is especially suitable for etching ionic salt substrates, e.g., a solid inorganic salt such as LiNbO.sub.3, such as used in electro-optical/acousto-optic devices. It is also suitable for applications wherein the etching process is required to produce an etched ionic substrate having a smooth surface morphology or when a very rapid etching rate is desired.

  13. Surface chemistry driven actuation in nanoporous gold

    SciTech Connect

    Biener, J; Wittstock, A; Zepeda-Ruiz, L; Biener, M M; Zielasek, V; Kramer, D; Viswanath, R N; Weissmuller, J; Baumer, M; Hamza, A V

    2008-04-14

    Although actuation in biological systems is exclusively powered by chemical energy, this concept has not been realized in man-made actuator technologies, as these rely on generating heat or electricity first. Here, we demonstrate that surface-chemistry driven actuation can be realized in high surface area materials such as nanoporous gold. For example, we achieve reversible strain amplitudes in the order of a few tenths of a percent by alternating exposure of nanoporous Au to ozone and carbon monoxide. The effect can be explained by adsorbate-induced changes of the surface stress, and can be used to convert chemical energy directly into a mechanical response thus opening the door to surface-chemistry driven actuator and sensor technologies.

  14. Position Control of Tendon-Driven Fingers

    NASA Technical Reports Server (NTRS)

    Abdallah, Muhammad E.; Platt, Robert, Jr.; Hargrave, B.; Pementer, Frank

    2011-01-01

    Conventionally, tendon-driven manipulators implement some force control scheme based on tension feedback. This feedback allows the system to ensure that the tendons are maintained taut with proper levels of tensioning at all times. Occasionally, whether it is due to the lack of tension feedback or the inability to implement sufficiently high stiffnesses, a position control scheme is needed. This work compares three position controllers for tendon-driven manipulators. A new controller is introduced that achieves the best overall performance with regards to speed, accuracy, and transient behavior. To compensate for the lack of tension feedback, the controller nominally maintains the internal tension on the tendons by implementing a two-tier architecture with a range-space constraint. These control laws are validated experimentally on the Robonaut-2 humanoid hand. I

  15. Model-Driven Theme/UML

    NASA Astrophysics Data System (ADS)

    Carton, Andrew; Driver, Cormac; Jackson, Andrew; Clarke, Siobhán

    Theme/UML is an existing approach to aspect-oriented modelling that supports the modularisation and composition of concerns, including crosscutting ones, in design. To date, its lack of integration with model-driven engineering (MDE) techniques has limited its benefits across the development lifecycle. Here, we describe our work on facilitating the use of Theme/UML as part of an MDE process. We have developed a transformation tool that adopts model-driven architecture (MDA) standards. It defines a concern composition mechanism, implemented as a model transformation, to support the enhanced modularisation features of Theme/UML. We evaluate our approach by applying it to the development of mobile, context-aware applications-an application area characterised by many non-functional requirements that manifest themselves as crosscutting concerns.

  16. Building Test Cases through Model Driven Engineering

    NASA Astrophysics Data System (ADS)

    Sousa, Helaine; Lopes, Denivaldo; Abdelouahab, Zair; Hammoudi, Slimane; Claro, Daniela Barreiro

    Recently, Model Driven Engineering (MDE) has been proposed to face the complexity in the development, maintenance and evolution of large and distributed software systems. Model Driven Architecture (MDA) is an example of MDE. In this context, model transformations enable a large reuse of software systems through the transformation of a Platform Independent Model into a Platform Specific Model. Although source code can be generated from models, defects can be injected during the modeling or transformation process. In order to delivery software systems without defects that cause errors and fails, the source code must be submitted to test. In this paper, we present an approach that takes care of test in the whole software life cycle, i.e. it starts in the modeling level and finishes in the test of source code of software systems. We provide an example to illustrate our approach.

  17. Hydrodynamic synchronisation of optically driven rotors

    NASA Astrophysics Data System (ADS)

    Debono, Luke J.; Box, Stuart; Phillips, David B.; Simpson, Stephen H.; Hanna, Simon

    2015-08-01

    Hydrodynamic coupling is thought to play a role in the coordinated beating of cilia and flagella, and may inform the future design of artificial swimmers and pumps. In this study, optical tweezers are used to investigate the hydrodynamic coupling between a pair of driven oscillators. The theoretical model of Lenz and Ryskin [P. Lenz and A. Ryskin, Phys. Biol. 3, 285{294 (2006)] is experimentally recreated, in which each oscillator consists of a sphere driven in a circular trajectory. The optical trap position is maintained ahead of the sphere to provide a tangential driving force. The trap is also moved radially to harmonically constrain the sphere to the circular trajectory. Analytically, it has been shown that two oscillators of this type are able to synchronise or phase-lock under certain conditions. We explore the interplay between synchronisation mechanisms and find good agreement between experiment, theory and Brownian dynamics simulations.

  18. Stellar winds driven by Alfven waves

    NASA Technical Reports Server (NTRS)

    Belcher, J. W.; Olbert, S.

    1973-01-01

    Models of stellar winds were considered in which the dynamic expansion of a corona is driven by Alfven waves propagating outward along radial magnetic field lines. In the presence of Alfven waves, a coronal expansion can exist for a broad range of reference conditions which would, in the absence of waves, lead to static configurations. Wind models in which the acceleration mechanism is due to Alfven waves alone and exhibit lower mass fluxes and higher energies per particle are compared to wind models in which the acceleration is due to thermal processes. For example, winds driven by Alfven waves exhibit streaming velocities at infinity which may vary between the escape velocity at the coronal base and the geometrical mean of the escape velocity and the speed of light. Upper and lower limits were derived for the allowed energy fluxes and mass fluxes associated with these winds.

  19. Solvable model of a strongly driven micromaser

    SciTech Connect

    Lougovski, P.; Walther, H.; Casagrande, F.; Lulli, A.; Englert, B.-G.; Solano, E.

    2004-02-01

    We study the dynamics of a micromaser where the pumping atoms are strongly driven by a resonant classical field during their transit through the cavity mode. We derive a master equation for this strongly driven micromaser, involving the contributions of the unitary atom-field interactions and the dissipative effects of a thermal bath. We find analytical solutions for the temporal evolution and the steady state of this system by means of phase-space techniques, providing an unusual solvable model of an open quantum system, including pumping and decoherence. We derive closed expressions for all relevant expectation values, describing the statistics of the cavity field and the detected atomic levels. The transient regime shows the buildup of mixtures of mesoscopic fields evolving towards a super-Poissonian steady-state field that, nevertheless, yields atomic correlations that exhibit stronger nonclassical features than the conventional micromaser.

  20. A charge-driven molecular water pump.

    PubMed

    Gong, Xiaojing; Li, Jingyuan; Lu, Hangjun; Wan, Rongzheng; Li, Jichen; Hu, Jun; Fang, Haiping

    2007-11-01

    Understanding and controlling the transport of water across nanochannels is of great importance for designing novel molecular devices, machines and sensors and has wide applications, including the desalination of seawater. Nanopumps driven by electric or magnetic fields can transport ions and magnetic quanta, but water is charge-neutral and has no magnetic moment. On the basis of molecular dynamics simulations, we propose a design for a molecular water pump. The design uses a combination of charges positioned adjacent to a nanopore and is inspired by the structure of channels in the cellular membrane that conduct water in and out of the cell (aquaporins). The remarkable pumping ability is attributed to the charge dipole-induced ordering of water confined in the nanochannels, where water can be easily driven by external fields in a concerted fashion. These findings may provide possibilities for developing water transport devices that function without osmotic pressure or a hydrostatic pressure gradient. PMID:18654410

  1. Actomyosin ring driven cytokinesis in budding yeast.

    PubMed

    Meitinger, Franz; Palani, Saravanan

    2016-05-01

    Cytokinesis is the final process in the cell cycle that physically divides one cell into two. In budding yeast, cytokinesis is driven by a contractile actomyosin ring (AMR) and the simultaneous formation of a primary septum, which serves as template for cell wall deposition. AMR assembly, constriction, primary septum formation and cell wall deposition are successive processes and tightly coupled to cell cycle progression to ensure the correct distribution of genetic material and cell organelles among the two rising cells prior to cell division. The role of the AMR in cytokinesis and the molecular mechanisms that drive AMR constriction and septation are the focus of current research. This review summarizes the recent progresses in our understanding of how budding yeast cells orchestrate the multitude of molecular mechanisms that control AMR driven cytokinesis in a spatio-temporal manner to achieve an error free cell division. PMID:26845196

  2. Statistical Transmutation in Periodically Driven Optical Lattices

    NASA Astrophysics Data System (ADS)

    Sedrakyan, Tigran; Galitski, Victor; Kamenev, Alex

    We show that interacting bosons in a periodically driven two dimensional (2D) optical lattice may effectively exhibit fermionic statistics. The phenomenon is similar to the celebrated Tonks-Girardeau regime in 1D. The Floquet band of a driven lattice develops the moat shape, i.e., a minimum along a closed contour in the Brillouin zone. Such degeneracy of the kinetic energy favors fermionic quasiparticles. The statistical transmutation is achieved by the Chern-Simons flux attachment similar to the fractional quantum Hall case. We show that the velocity distribution of the released bosons is a sensitive probe of the fermionic nature of their stationary Floquet state. This work was supported by the PFC-JQI (T.S.), USARO and Simons Foundation (V.G.), and DOE Contract DE-FG02-08ER46482 (A.K.).

  3. Active microrheology of driven granular particles.

    PubMed

    Wang, Ting; Grob, Matthias; Zippelius, Annette; Sperl, Matthias

    2014-04-01

    When pulling a particle in a driven granular fluid with constant force Fex, the probe particle approaches a steady-state average velocity v. This velocity and the corresponding friction coefficient of the probe ζ=Fex/v are obtained within a schematic model of mode-coupling theory and compared to results from event-driven simulations. For small and moderate drag forces, the model describes the simulation results successfully for both the linear as well as the nonlinear region: The linear response regime (constant friction) for small drag forces is followed by shear thinning (decreasing friction) for moderate forces. For large forces, the model demonstrates a subsequent increasing friction in qualitative agreement with the data. The square-root increase of the friction with force found in [Fiege et al., Granul. Matter 14, 247 (2012)] is explained by a simple kinetic theory. PMID:24827243

  4. Dynamic signatures of driven vortex motion.

    SciTech Connect

    Crabtree, G. W.; Kwok, W. K.; Lopez, D.; Olsson, R. J.; Paulius, L. M.; Petrean, A. M.; Safar, H.

    1999-09-16

    We probe the dynamic nature of driven vortex motion in superconductors with a new type of transport experiment. An inhomogeneous Lorentz driving force is applied to the sample, inducing vortex velocity gradients that distinguish the hydrodynamic motion of the vortex liquid from the elastic and-plastic motion of the vortex solid. We observe elastic depinning of the vortex lattice at the critical current, and shear induced plastic slip of the lattice at high Lorentz force gradients.

  5. Wave-driven Countercurrent Plasma Centrifuge

    SciTech Connect

    A.J. Fetterman and N.J. Fisch

    2009-03-20

    A method for driving rotation and a countercurrent flow in a fully ionized plasma centrifuge is described. The rotation is produced by radiofrequency waves near the cyclotron resonance. The wave energy is transferred into potential energy in a manner similar to the α channeling effect. The countercurrent flow may also be driven by radiofrequency waves. By driving both the rotation and the flow pattern using waves instead of electrodes, physical and engineering issues may be avoided.

  6. Photonic Crystal Laser-Driven Accelerator Structures

    SciTech Connect

    Cowan, B.; /SLAC

    2005-09-19

    We discuss simulated photonic crystal structure designs for laser-driven particle acceleration, focusing on three-dimensional planar structures based on the so-called ''woodpile'' lattice. We demonstrate guiding of a speed-of-light accelerating mode by a defect in the photonic crystal lattice and discuss the properties of this mode. We also discuss particle beam dynamics in the structure, presenting a novel method for focusing the beam. In addition we describe some potential coupling methods for the structure.

  7. Renormalization in Periodically Driven Quantum Dots.

    PubMed

    Eissing, A K; Meden, V; Kennes, D M

    2016-01-15

    We report on strong renormalization encountered in periodically driven interacting quantum dots in the nonadiabatic regime. Correlations between lead and dot electrons enhance or suppress the amplitude of driving depending on the sign of the interaction. Employing a newly developed flexible renormalization-group-based approach for periodic driving to an interacting resonant level we show analytically that the magnitude of this effect follows a power law. Our setup can act as a non-Markovian, single-parameter quantum pump. PMID:26824557

  8. Electrically Driven Technologies for Radioactive Aerosol Abatement

    SciTech Connect

    David W. DePaoli; Ofodike A. Ezekoye; Costas Tsouris; Valmor F. de Almeida

    2003-01-28

    The purpose of this research project was to develop an improved understanding of how electriexecy driven processes, including electrocoalescence, acoustic agglomeration, and electric filtration, may be employed to efficiently treat problems caused by the formation of aerosols during DOE waste treatment operations. The production of aerosols during treatment and retrieval operations in radioactive waste tanks and during thermal treatment operations such as calcination presents a significant problem of cost, worker exposure, potential for release, and increased waste volume.

  9. Scaling the electromagnetically driven explosive shock simulator

    NASA Technical Reports Server (NTRS)

    Persh, Robert I.

    1987-01-01

    A heavy payload electromagnetically driven explosive shock simulator, referred to as EDESS-3, has been assembled and characterized at the Navel research Weapons Center. EDESS-3 is the logical outgrowth of the earlier EDESS 1 and 2 simulator work which explored the use of electrical pulse power technology for the generation of explosive like shocks. The features of the EDESS-3 are presented, and designs for the next generation of EDESS machines are introduced.

  10. A User Driven Dynamic Circuit Network Implementation

    SciTech Connect

    Guok, Chin; Robertson, David; Chaniotakis, Evangelos; Thompson, Mary; Johnston, William; Tierney, Brian

    2008-10-01

    The requirements for network predictability are becoming increasingly critical to the DoE science community where resources are widely distributed and collaborations are world-wide. To accommodate these emerging requirements, the Energy Sciences Network has established a Science Data Network to provide user driven guaranteed bandwidth allocations. In this paper we outline the design, implementation, and secure coordinated use of such a network, as well as some lessons learned.

  11. Tuned, driven, and active soft matter

    NASA Astrophysics Data System (ADS)

    Menzel, Andreas M.

    2015-02-01

    One characteristic feature of soft matter systems is their strong response to external stimuli. As a consequence they are comparatively easily driven out of their ground state and out of equilibrium, which leads to many of their fascinating properties. Here, we review illustrative examples. This review is structured by an increasing distance from the equilibrium ground state. On each level, examples of increasing degree of complexity are considered. In detail, we first consider systems that are quasi-statically tuned or switched to a new state by applying external fields. These are common liquid crystals, liquid crystalline elastomers, or ferrogels and magnetic elastomers. Next, we concentrate on systems steadily driven from outside e.g. by an imposed flow field. In our case, we review the reaction of nematic liquid crystals, of bulk-filling periodically modulated structures such as block copolymers, and of localized vesicular objects to an imposed shear flow. Finally, we focus on systems that are "active" and "self-driven". Here our range spans from idealized self-propelled point particles, via sterically interacting particles like granular hoppers, via microswimmers such as self-phoretically driven artificial Janus particles or biological microorganisms, via deformable self-propelled particles like droplets, up to the collective behavior of insects, fish, and birds. As we emphasize, similarities emerge in the features and behavior of systems that at first glance may not necessarily appear related. We thus hope that our overview will further stimulate the search for basic unifying principles underlying the physics of these soft materials out of their equilibrium ground state.

  12. Chaos control of parametric driven Duffing oscillators

    SciTech Connect

    Jin, Leisheng; Mei, Jie; Li, Lijie

    2014-03-31

    Duffing resonators are typical dynamic systems, which can exhibit chaotic oscillations, subject to certain driving conditions. Chaotic oscillations of resonating systems with negative and positive spring constants are identified to investigate in this paper. Parametric driver imposed on these two systems affects nonlinear behaviours, which has been theoretically analyzed with regard to variation of driving parameters (frequency, amplitude). Systematic calculations have been performed for these two systems driven by parametric pumps to unveil the controllability of chaos.

  13. Driven drops with contact line damping

    NASA Astrophysics Data System (ADS)

    Xia, Yi; Chang, Chun-Ti; Steen, Paul

    2015-11-01

    A water droplet placed on a hydrophobic plate is driven by plate-normal oscillations. Resulting droplet motions are largely inviscid, having Reynolds number >100 (Ohnesorge 0.002). We are interested in isolating the effective damping, sometimes called Davis dissipation, owing to a moving contact line that is not completely mobile. In this talk, we report energy budgets as influenced by contact angle - contact line speed relationships for variously prepared surfaces.

  14. Dissipative adaptation in driven self-assembly.

    PubMed

    England, Jeremy L

    2015-11-01

    In a collection of assembling particles that is allowed to reach thermal equilibrium, the energy of a given microscopic arrangement and the probability of observing the system in that arrangement obey a simple exponential relationship known as the Boltzmann distribution. Once the same thermally fluctuating particles are driven away from equilibrium by forces that do work on the system over time, however, it becomes significantly more challenging to relate the likelihood of a given outcome to familiar thermodynamic quantities. Nonetheless, it has long been appreciated that developing a sound and general understanding of the thermodynamics of such non-equilibrium scenarios could ultimately enable us to control and imitate the marvellous successes that living things achieve in driven self-assembly. Here, I suggest that such a theoretical understanding may at last be emerging, and trace its development from historic first steps to more recent discoveries. Focusing on these newer results, I propose that they imply a general thermodynamic mechanism for self-organization via dissipation of absorbed work that may be applicable in a broad class of driven many-body systems. PMID:26530021

  15. A gasdynamic gun driven by gaseous detonation

    NASA Astrophysics Data System (ADS)

    Li, Jinping; Chen, Hong; Zhang, Shizhong; Zhang, Xiaoyuan; Yu, Hongru

    2016-01-01

    A gasdynamic gun driven by gaseous detonation was developed to address the disadvantages of the insufficient driving capability of high-pressure gas and the constraints of gunpowder. The performance of this gasdynamic gun was investigated through experiments and numerical simulations. Much more powerful launching capability was achieved by this gun relative to a conventional high-pressure gas gun, owing to the use of the chemical energy of the driver gas. To achieve the same launching condition, the initial pressure required for this gun was an order of magnitude lower than that for a gun driven by high-pressure H2. Because of the presence of the detonation, however, a more complex internal ballistic process of this gun was observed. Acceleration of projectiles for this gun was accompanied by a series of impulse loads, in contrast with the smooth acceleration for a conventional one, which indicates that this gun should be used conditionally. The practical feasibility of this gun was verified by experiments. The experiments demonstrated the convenience of taking advantage of the techniques developed for detonation-driven shock tubes and tunnels.

  16. A gasdynamic gun driven by gaseous detonation.

    PubMed

    Li, Jinping; Chen, Hong; Zhang, Shizhong; Zhang, Xiaoyuan; Yu, Hongru

    2016-01-01

    A gasdynamic gun driven by gaseous detonation was developed to address the disadvantages of the insufficient driving capability of high-pressure gas and the constraints of gunpowder. The performance of this gasdynamic gun was investigated through experiments and numerical simulations. Much more powerful launching capability was achieved by this gun relative to a conventional high-pressure gas gun, owing to the use of the chemical energy of the driver gas. To achieve the same launching condition, the initial pressure required for this gun was an order of magnitude lower than that for a gun driven by high-pressure H2. Because of the presence of the detonation, however, a more complex internal ballistic process of this gun was observed. Acceleration of projectiles for this gun was accompanied by a series of impulse loads, in contrast with the smooth acceleration for a conventional one, which indicates that this gun should be used conditionally. The practical feasibility of this gun was verified by experiments. The experiments demonstrated the convenience of taking advantage of the techniques developed for detonation-driven shock tubes and tunnels. PMID:26827358

  17. A Precession-Driven Lunar Dynamo

    NASA Astrophysics Data System (ADS)

    Tian, B. Y.; Stanley, S.; Tikoo, S. M.; Weiss, B. P.

    2014-12-01

    Paleomagnetic studies of Apollo samples suggest that the Moon generated a magnetic field with surface field intensities of several tens of microteslas until at least 3.56 billion years ago (Ga). The field then declined by an order of magnitude from 3.56 - 3.19 Ga. Because of difficulties in reproducing such a long-lived and intense field with convection-driven dynamos, a dynamo driven by precession of the mantle relative to the core was proposed as an alternative. However, there have not been any detailed numerical models demonstrating the feasibility, lifetime, and intensity of such a lunar dynamo. Using fully 3D magnetohydrodynamic simulations, we determined the strength and duration of a mechanically-driven dynamo powered by mantle precession. We found that this mechanism was capable of not only generating the 10-100μT paleomagnetic intensities observed in Apollo samples aged between 4.25 and 3.56 Ga, but also reproducing the precipitous decline in paleointensity beyond 3.56 Ga as the obliquity of the Moon decreased below 15°.

  18. Magnetic Control of Solutal Buoyancy Driven Convection

    NASA Technical Reports Server (NTRS)

    Ramachandran, N.; Leslie, F. W.

    2003-01-01

    Volumetric forces resulting from local density variations and gravitational acceleration cause buoyancy induced convective motion in melts and solutions. Solutal buoyancy is a result of concentration differences in an otherwise isothermal fluid. If the fluid also exhibits variations in magnetic susceptibility with concentration then convection control by external magnetic fields can be hypothesized. Magnetic control of thermal buoyancy induced convection in ferrofluids (dispersions of ferromagnetic particles in a carrier fluid) and paramagnetic fluids have been demonstrated. Here we show the nature of magnetic control of solutal buoyancy driven convection of a paramagnetic fluid, an aqueous solution of Manganese Chloride hydrate. We predict the critical magnetic field required for balancing gravitational solutal buoyancy driven convection and validate it through a simple experiment. We demonstrate that gravity driven flow can be completely reversed by a magnetic field but the exact cancellation of the flow is not possible. This is because the phenomenon is unstable. The technique can be applied to crystal growth processes in order to reduce convection and to heat exchanger devices for enhancing convection. The method can also be applied to impose a desired g-level in reduced gravity applications.

  19. Exploring Titan with Autonomous, Buoyancy Driven Gliders

    NASA Astrophysics Data System (ADS)

    Morrow, M. T.; Woolsey, C. A.; Hagerman, G. M.

    Buoyancy driven underwater gliders are highly efficient winged underwater vehicles which locomote by modifying their internal shape. The concept, which is already well-proven in Earth's oceans, is also an appealing technology for remote terrain exploration and environmental sampling on worlds with dense atmospheres. Because of their high efficiency and their gentle, vertical take-off and landing capability, buoyancy driven gliders might perform long duration, global mapping tasks as well as light-duty, local sampling tasks. Moreover, a sufficiently strong gradient in the planetary boundary layer may enable the vehicles to perform dynamic soaring, achieving even greater locomotive efficiency. Shape Change Actuated, Low Altitude Robotic Soarers (SCALARS) are an appealing alternative to more conventional vehicle technology for exploring planets with dense atmospheres. SCALARS are buoyancy driven atmospheric gliders with a twin-hulled, inboard wing configuration. The inboard wing generates lift, which propels the vehicle forward. Symmetric changes in mass distribution induce gravitational pitch moments that provide longitudinal control. Asymmetric changes in mass distribution induce twist in the inboard wing that provides directional control. The vehicle is actuated solely by internal shape change; there are no external seals and no exposed moving parts, save for the inflatable buoyancy ballonets. Preliminary sizing analysis and dynamic modeling indicate the viability of using SCALARS to map the surface of Titan and to investigate features of interest.

  20. Epidemic cycles driven by host behaviour

    PubMed Central

    Althouse, Benjamin M.; Hébert-Dufresne, Laurent

    2014-01-01

    Host immunity and demographics (the recruitment of susceptibles via birthrate) have been demonstrated to be a key determinant of the periodicity of measles, pertussis and dengue epidemics. However, not all epidemic cycles are from pathogens inducing sterilizing immunity or are driven by demographics. Many sexually transmitted infections are driven by sexual behaviour. We present a mathematical model of disease transmission where individuals can disconnect and reconnect depending on the infectious status of their contacts. We fit the model to historic syphilis (Treponema pallidum) and gonorrhea (Neisseria gonorrhoeae) incidence in the USA and explore potential intervention strategies against syphilis. We find that cycles in syphilis incidence can be driven solely by changing sexual behaviour in structured populations. Our model also explains the lack of similar cycles in gonorrhea incidence even if the two infections share the same propagation pathways. Our model similarly illustrates how sudden epidemic outbreaks can occur on time scales smaller than the characteristic demographic time scale of the population and that weaker infections can lead to more violent outbreaks. Behaviour also appears to be critical for control strategies as we found a bigger sensitivity to behavioural interventions than antibiotic treatment. Thus, behavioural interventions may play a larger role than previously thought, especially in the face of antibiotic resistance and low intervention efficacies. PMID:25100316

  1. Dissipative adaptation in driven self-assembly

    NASA Astrophysics Data System (ADS)

    England, Jeremy L.

    2015-11-01

    In a collection of assembling particles that is allowed to reach thermal equilibrium, the energy of a given microscopic arrangement and the probability of observing the system in that arrangement obey a simple exponential relationship known as the Boltzmann distribution. Once the same thermally fluctuating particles are driven away from equilibrium by forces that do work on the system over time, however, it becomes significantly more challenging to relate the likelihood of a given outcome to familiar thermodynamic quantities. Nonetheless, it has long been appreciated that developing a sound and general understanding of the thermodynamics of such non-equilibrium scenarios could ultimately enable us to control and imitate the marvellous successes that living things achieve in driven self-assembly. Here, I suggest that such a theoretical understanding may at last be emerging, and trace its development from historic first steps to more recent discoveries. Focusing on these newer results, I propose that they imply a general thermodynamic mechanism for self-organization via dissipation of absorbed work that may be applicable in a broad class of driven many-body systems.

  2. Epidemic cycles driven by host behaviour.

    PubMed

    Althouse, Benjamin M; Hébert-Dufresne, Laurent

    2014-10-01

    Host immunity and demographics (the recruitment of susceptibles via birthrate) have been demonstrated to be a key determinant of the periodicity of measles, pertussis and dengue epidemics. However, not all epidemic cycles are from pathogens inducing sterilizing immunity or are driven by demographics. Many sexually transmitted infections are driven by sexual behaviour. We present a mathematical model of disease transmission where individuals can disconnect and reconnect depending on the infectious status of their contacts. We fit the model to historic syphilis (Treponema pallidum) and gonorrhea (Neisseria gonorrhoeae) incidence in the USA and explore potential intervention strategies against syphilis. We find that cycles in syphilis incidence can be driven solely by changing sexual behaviour in structured populations. Our model also explains the lack of similar cycles in gonorrhea incidence even if the two infections share the same propagation pathways. Our model similarly illustrates how sudden epidemic outbreaks can occur on time scales smaller than the characteristic demographic time scale of the population and that weaker infections can lead to more violent outbreaks. Behaviour also appears to be critical for control strategies as we found a bigger sensitivity to behavioural interventions than antibiotic treatment. Thus, behavioural interventions may play a larger role than previously thought, especially in the face of antibiotic resistance and low intervention efficacies. PMID:25100316

  3. Current-Driven Filament Instabilities in Relativistic Plasmas. Final report

    SciTech Connect

    Ren, Chuang

    2013-02-13

    This grant has supported a study of some fundamental problems in current- and flow-driven instabilities in plasmas and their applications in inertial confinement fusion (ICF) and astrophysics. It addressed current-driven instabilities and their roles in fast ignition, and flow-driven instabilities and their applications in astrophysics.

  4. 14 CFR 25.1127 - Exhaust driven turbo-superchargers.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Exhaust driven turbo-superchargers. 25.1127... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Powerplant Exhaust System § 25.1127 Exhaust driven turbo-superchargers. (a) Each exhaust driven turbo-supercharger must be approved or shown to...

  5. 30 CFR 75.1728 - Power-driven pulleys.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Power-driven pulleys. 75.1728 Section 75.1728... MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Miscellaneous § 75.1728 Power-driven pulleys. (a) Belts, chains, and ropes shall not be guided onto power-driven moving pulleys, sprockets, or drums with...

  6. 30 CFR 77.407 - Power-driven pulleys.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Power-driven pulleys. 77.407 Section 77.407... for Mechanical Equipment § 77.407 Power-driven pulleys. (a) Belts, chains, and ropes shall not be guided onto power-driven moving pulleys, sprockets, or drums with the hands except on slow...

  7. 14 CFR 25.1127 - Exhaust driven turbo-superchargers.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Exhaust driven turbo-superchargers. 25.1127... driven turbo-superchargers. (a) Each exhaust driven turbo-supercharger must be approved or shown to be... and for cooling turbine parts where temperatures are critical. (c) If the normal...

  8. 14 CFR 25.1127 - Exhaust driven turbo-superchargers.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Exhaust driven turbo-superchargers. 25.1127... driven turbo-superchargers. (a) Each exhaust driven turbo-supercharger must be approved or shown to be... and for cooling turbine parts where temperatures are critical. (c) If the normal...

  9. 14 CFR 25.1127 - Exhaust driven turbo-superchargers.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Exhaust driven turbo-superchargers. 25.1127... driven turbo-superchargers. (a) Each exhaust driven turbo-supercharger must be approved or shown to be... and for cooling turbine parts where temperatures are critical. (c) If the normal...

  10. 14 CFR 25.1127 - Exhaust driven turbo-superchargers.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Exhaust driven turbo-superchargers. 25.1127... driven turbo-superchargers. (a) Each exhaust driven turbo-supercharger must be approved or shown to be... and for cooling turbine parts where temperatures are critical. (c) If the normal...

  11. 46 CFR 169.623 - Power-driven steering systems.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Power-driven steering systems. 169.623 Section 169.623... Machinery and Electrical Steering Systems § 169.623 Power-driven steering systems. (a) Power-driven steering... system must automatically resume operation after an electric power outage. (b) Control of...

  12. 46 CFR 169.623 - Power-driven steering systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Power-driven steering systems. 169.623 Section 169.623... Machinery and Electrical Steering Systems § 169.623 Power-driven steering systems. (a) Power-driven steering... system must automatically resume operation after an electric power outage. (b) Control of...

  13. 46 CFR 169.623 - Power-driven steering systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Power-driven steering systems. 169.623 Section 169.623 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Machinery and Electrical Steering Systems § 169.623 Power-driven steering systems. (a) Power-driven...

  14. 46 CFR 169.623 - Power-driven steering systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Power-driven steering systems. 169.623 Section 169.623 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Machinery and Electrical Steering Systems § 169.623 Power-driven steering systems. (a) Power-driven...

  15. 46 CFR 169.623 - Power-driven steering systems.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Power-driven steering systems. 169.623 Section 169.623 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Machinery and Electrical Steering Systems § 169.623 Power-driven steering systems. (a) Power-driven...

  16. What we learn from surveillance testing of standby turbine driven and motor driven pumps

    SciTech Connect

    Christie, B.

    1996-12-01

    This paper describes a comparison of the performance information collected by the author and the respective system engineers from five standby turbine driven pumps at four commercial nuclear electric generating units in the United States and from two standby motor driven pumps at two of these generating units. Information was collected from surveillance testing and from Non-Test actuations. Most of the performance information (97%) came from surveillance testing. {open_quotes}Conditional Probabilities{close_quotes} of the pumps ability to respond to a random demand were calculated for each of the seven standby pumps and compared to the historical record of the Non-Test actuations. It appears that the Conditional Probabilities are comparable to the rate of success for Non-Test actuations. The Conditional Probabilities of the standby motor driven pumps (approximately 99%) are better than the Conditional Probabilities of the standby turbine driven pumps (82%-96% range). Recommendations were made to improve the Conditional Probabilities of the standby turbine driven pumps.

  17. Legitimising data-driven models: exemplification of a new data-driven mechanistic modelling framework

    NASA Astrophysics Data System (ADS)

    Mount, N. J.; Dawson, C. W.; Abrahart, R. J.

    2013-07-01

    In this paper the difficult problem of how to legitimise data-driven hydrological models is addressed using an example of a simple artificial neural network modelling problem. Many data-driven models in hydrology have been criticised for their black-box characteristics, which prohibit adequate understanding of their mechanistic behaviour and restrict their wider heuristic value. In response, presented here is a new generic data-driven mechanistic modelling framework. The framework is significant because it incorporates an evaluation of the legitimacy of a data-driven model's internal modelling mechanism as a core element in the modelling process. The framework's value is demonstrated by two simple artificial neural network river forecasting scenarios. We develop a novel adaptation of first-order partial derivative, relative sensitivity analysis to enable each model's mechanistic legitimacy to be evaluated within the framework. The results demonstrate the limitations of standard, goodness-of-fit validation procedures by highlighting how the internal mechanisms of complex models that produce the best fit scores can have lower mechanistic legitimacy than simpler counterparts whose scores are only slightly inferior. Thus, our study directly tackles one of the key debates in data-driven, hydrological modelling: is it acceptable for our ends (i.e. model fit) to justify our means (i.e. the numerical basis by which that fit is achieved)?

  18. Modeling beam-driven and laser-driven plasma Wakefield accelerators with XOOPIC

    SciTech Connect

    Bruhwiler, David L.; Giacone, Rodolfo; Cary, John R.; Verboncoeur, John P.; Mardahl, Peter; Esarey, Eric; Leemans, Wim

    2000-06-01

    We present 2-D particle-in-cell simulations of both beam-driven and laser-driven plasma wakefield accelerators, using the object-oriented code XOOPIC, which is time explicit, fully electromagnetic, and capable of running on massively parallel supercomputers. Simulations of laser-driven wakefields with low ({approximately} 10{sup 16} W/cm{sup 2}) and high ({approximately} 10{sup 18} W/cm{sup 2}) peak intensity laser pulses are conducted in slab geometry, showing agreement with theory. Simulations of the E-157 beam wakefield experiment at the Stanford Linear Accelerator Center, in which a 30 GeV electron beam passes through 1 m of preionized lithium plasma, are conducted in cylindrical geometry, obtaining good agreement with previous work. We briefly describe some of the more significant modifications to XOOPIC required by this work, and summarize the issues relevant to modeling electron-neutral collisions in a particle-in-cell code.

  19. Metabolic Dependencies in RAS-Driven Cancers.

    PubMed

    Kimmelman, Alec C

    2015-04-15

    The ability to inhibit the RAS oncogene has been the holy grail of oncology because of the critical role of this gene in a multitude of tumor types. In addition, RAS-mutant tumors are among the most aggressive and refractory to treatment. Although directly targeting the RAS oncogene has proven challenging, an alternative approach for treating RAS-driven cancers is to inhibit critical downstream events that are required for tumor maintenance. Indeed, much focus has been put on inhibiting signaling cascades downstream of RAS. Recent studies have shown that oncogenic RAS promotes a metabolic reprogramming of tumor cells, shifting them toward an anabolic metabolism necessary to produce biomass to support unconstrained proliferation. These cancers also use a diverse set of fuel sources to meet their metabolic needs and have even developed a variety of mechanisms to act as metabolic scavengers to obtain necessary metabolic substrates from both extracellular and intracellular sources. Collectively, these adaptations can create "metabolic bottlenecks" whereby tumor cells rely on particular pathways or rate-limiting metabolites. In this regard, inhibiting individual or combinations of these metabolic pathways can attenuate growth in preclinical models. Because these dependencies are tumor selective and downstream of oncogenic RAS, there is the opportunity for therapeutic intervention. Although targeting tumor metabolism is still in the early days of translation to patients, our continued advances in understanding critical metabolic adaptations in RAS-driven cancers, as well as the ability to study this altered metabolism in relevant tumor models, will accelerate the development of new therapeutic approaches. Clin Cancer Res; 21(8); 1828-34. ©2015 AACR. See all articles in this CCR Focus section, "Targeting RAS-Driven Cancers." PMID:25878364

  20. Hysteresis in Pressure-Driven DNA Denaturation

    PubMed Central

    Hernández-Lemus, Enrique; Nicasio-Collazo, Luz Adriana; Castañeda-Priego, Ramón

    2012-01-01

    In the past, a great deal of attention has been drawn to thermal driven denaturation processes. In recent years, however, the discovery of stress-induced denaturation, observed at the one-molecule level, has revealed new insights into the complex phenomena involved in the thermo-mechanics of DNA function. Understanding the effect of local pressure variations in DNA stability is thus an appealing topic. Such processes as cellular stress, dehydration, and changes in the ionic strength of the medium could explain local pressure changes that will affect the molecular mechanics of DNA and hence its stability. In this work, a theory that accounts for hysteresis in pressure-driven DNA denaturation is proposed. We here combine an irreversible thermodynamic approach with an equation of state based on the Poisson-Boltzmann cell model. The latter one provides a good description of the osmotic pressure over a wide range of DNA concentrations. The resulting theoretical framework predicts, in general, the process of denaturation and, in particular, hysteresis curves for a DNA sequence in terms of system parameters such as salt concentration, density of DNA molecules and temperature in addition to structural and configurational states of DNA. Furthermore, this formalism can be naturally extended to more complex situations, for example, in cases where the host medium is made up of asymmetric salts or in the description of the (helical-like) charge distribution along the DNA molecule. Moreover, since this study incorporates the effect of pressure through a thermodynamic analysis, much of what is known from temperature-driven experiments will shed light on the pressure-induced melting issue. PMID:22496765

  1. Magnon-driven quantum dot refrigerators

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Huang, Chuankun; Liao, Tianjun; Chen, Jincan

    2015-12-01

    A new model of refrigerator consisting of a spin-splitting quantum dot coupled with two ferromagnetic reservoirs and a ferromagnetic insulator is proposed. The rate equation is used to calculate the occupation probabilities of the quantum dot. The expressions of the electron and magnon currents are obtained. The region that the system can work in as a refrigerator is determined. The cooling power and coefficient of performance (COP) of the refrigerator are derived. The influences of the magnetic field, applied voltage, and polarization of two leads on the performance are discussed. The performances of two different magnon-driven quantum dot refrigerators are compared.

  2. Surface Tension Driven Convection Experiment Completed

    NASA Technical Reports Server (NTRS)

    Jacobson, Thomas P.; Sedlak, Deborah A.

    1997-01-01

    The Surface Tension Driven Convection Experiment (STDCE) was designed to study basic fluid mechanics and heat transfer on thermocapillary flows generated by temperature variations along the free surfaces of liquids in microgravity. STDCE first flew on the USML-1 mission in July 1992 and was rebuilt for the USML-2 mission that was launched in October 1995. This was a collaborative project with principal investigators from Case Western Reserve University (CWRU), Professors Simon Ostrach and Yasuhiro Kamotani, along with a team from the NASA Lewis Research Center composed of civil servants and contractors from Aerospace Design & Fabrication, Inc. (ADF), Analex, and NYMA, Inc.

  3. Eye-gaze driven surgical workflow segmentation.

    PubMed

    James, A; Vieira, D; Lo, B; Darzi, A; Yang, G Z

    2007-01-01

    In today's climate of clinical governance there is growing pressure on surgeons to demonstrate their competence, improve standards and reduce surgical errors. This paper presents a study on developing a novel eye-gaze driven technique for surgical assessment and workflow recovery. The proposed technique investigates the use of a Parallel Layer Perceptor (PLP) to automate the recognition of a key surgical step in a porcine laparoscopic cholecystectomy model. The classifier is eye-gaze contingent but combined with image based visual feature detection for improved system performance. Experimental results show that by fusing image instrument likelihood measures, an overall classification accuracy of 75% is achieved. PMID:18044559

  4. RF Driven Multicusp H- Ion Source

    SciTech Connect

    Leung, K.N.; DeVries, G.J.; DiVergilio, W.F.; Hamm, R.W.; Hauck, C.A.; Kunkel, W.B.; McDonald, D.S.; Williams, M.D.

    1990-06-01

    An rf driven multicusp source capable of generating 1-ms H{sup -} beam pulses with a repetition rate as high as 150 Hz has been developed. This source can be operated with a filament or other types of starter. There is almost no lifetime limitation and a clean plasma can be maintained for a long period of operation. It is demonstrated that rf power as high as 25 kW could be coupled inductively to the plasma via a glass-coated copper-coil antenna. The extracted H{sup -} current density achieved is about 200 mA/cm{sup 2}.

  5. Arc-driven rail accelerator research

    NASA Technical Reports Server (NTRS)

    Ray, Pradosh K.

    1987-01-01

    Arc-driven rail accelerator research is analyzed by considering wall ablation and viscous drag in the plasma. Plasma characteristics are evaluated through a simple fluid-mechanical analysis considering only wall ablation. By equating the energy dissipated in the plasma with the radiation heat loss, the average properties of the plasma are determined as a function of time and rate of ablation. Locations of two simultaneously accelerating arcs were determined by optical and magnetic probes and fron streak camera photographs. All three measurements provide consistent results.

  6. Neutrino physics with accelerator driven subcritical reactors

    NASA Astrophysics Data System (ADS)

    Ciuffoli, Emilio; Evslin, Jarah; Zhao, Fengyi

    2016-01-01

    Accelerator driven system (ADS) subcritical nuclear reactors are under development around the world. They will be intense sources of free, 30-55 MeV μ + decay at rest {overline{ν}}_{μ } . These ADS reactor neutrinos can provide a robust test of the LSND anomaly and a precise measurement of the leptonic CP-violating phase δ, including sign(cos(δ)). The first phase of many ADS programs includes the construction of a low energy, high intensity proton or deuteron accelerator, which can yield competitive bounds on sterile neutrinos.

  7. Dynamical plasma response during driven magnetic reconnection.

    PubMed

    Egedal, J; Fasoli, A; Nazemi, J

    2003-04-01

    Direct measurements of a collisionless current channel during driven magnetic reconnection are obtained for the first time on the Versatile Toroidal Facility. The size of the diffusion region is found to scale with the electron drift orbit width, independent of the ion mass and plasma density. Based on experimental observations, analytic expressions governing the dynamical evolution of the current profile and the formation of the electrostatic potential that develops in response to the externally imposed reconnection drive are established. This time response is closely linked to the presence of ion polarization currents. PMID:12689297

  8. Four-level refrigerator driven by photons

    NASA Astrophysics Data System (ADS)

    Wang, Jianhui; Lai, Yiming; Ye, Zhuolin; He, Jizhou; Ma, Yongli; Liao, Qinghong

    2015-05-01

    We propose a quantum absorption refrigerator driven by photons. The model uses a four-level system as its working substance and couples simultaneously to hot, cold, and solar heat reservoirs. Explicit expressions for the cooling power Q˙c and coefficient of performance (COP) ηCOP are derived, with the purpose of revealing and optimizing the performance of the device. Our model runs most efficiently under the tight coupling condition, and it is consistent with the third law of thermodynamics in the limit T →0 .

  9. Four-level refrigerator driven by photons.

    PubMed

    Wang, Jianhui; Lai, Yiming; Ye, Zhuolin; He, Jizhou; Ma, Yongli; Liao, Qinghong

    2015-05-01

    We propose a quantum absorption refrigerator driven by photons. The model uses a four-level system as its working substance and couples simultaneously to hot, cold, and solar heat reservoirs. Explicit expressions for the cooling power Q̇(c) and coefficient of performance (COP) η(COP) are derived, with the purpose of revealing and optimizing the performance of the device. Our model runs most efficiently under the tight coupling condition, and it is consistent with the third law of thermodynamics in the limit T→0. PMID:26066099

  10. Fluctuation-driven topological Hund insulators

    NASA Astrophysics Data System (ADS)

    Budich, Jan Carl; Trauzettel, Björn; Sangiovanni, Giorgio

    2013-06-01

    We investigate the role of electron-electron interaction in a two-band Hubbard model based on the Bernevig-Hughes-Zhang Hamiltonian exhibiting the quantum spin Hall (QSH) effect. By means of dynamical mean-field theory, we find that a system with topologically trivial noninteracting parameters can be driven into a QSH phase at finite interaction strength by virtue of local dynamical fluctuations. For very strong interaction, the system reenters a trivial insulating phase by going through a Mott transition. We obtain the phase diagram of our model by direct calculation of the bulk topological invariant of the interacting system in terms of its single-particle Green's function.

  11. Light-driven robotics for nanoscopy

    NASA Astrophysics Data System (ADS)

    Glückstad, Jesper; Palima, Darwin

    2013-03-01

    The science fiction inspired shrinking of macro-scale robotic manipulation and handling down to the micro- and nanoscale regime opens new doors for exploiting the forces and torques of light for micro- and nanoscopic probing, actuation and control. Advancing light-driven micro-robotics requires the optimization of optical forces and torques that, in turn, requires optimization of the underlying light-matter interaction. This report is two-fold desribing the new use of proprietary strongholds we currently are harnessing in the Programmable Phase Optics in Denmark on new means of sculpting of both light and matter for robotically probing at the smallest biological length scales.

  12. Optimality of Contraction-Driven Crawling

    NASA Astrophysics Data System (ADS)

    Recho, P.; Joanny, J.-F.; Truskinovsky, L.

    2014-05-01

    We study a particular mechanism of cell motility allowing a precise formulation of the condition of optimal trade-off between performance and metabolic cost. In the model, a steadily crawling fragment is represented by a layer of active gel placed on a frictional surface and driven by contraction only. We find analytically the distribution of contractile elements (pullers) ensuring that the efficiency of self-propulsion is maximal. We then show that natural assumptions about advection and diffusion of pullers produce a distribution that is remarkably close to the optimal one and is qualitatively similar to the one observed in experiments on fish keratocytes.

  13. Plasma-driven ultrashort bunch diagnostics

    NASA Astrophysics Data System (ADS)

    Dornmair, I.; Schroeder, C. B.; Floettmann, K.; Marchetti, B.; Maier, A. R.

    2016-06-01

    Ultrashort electron bunches are crucial for an increasing number of applications, however, diagnosing their longitudinal phase space remains a challenge. We propose a new method that harnesses the strong electric fields present in a laser driven plasma wakefield. By transversely displacing driver laser and witness bunch, a streaking field is applied to the bunch. This field maps the time information to a transverse momentum change and, consequently, to a change of transverse position. We illustrate our method with simulations where we achieve a time resolution in the attosecond range.

  14. Diffusion Driven Combustion Waves in Porous Media

    NASA Technical Reports Server (NTRS)

    Aldushin, A. P.; Matkowsky, B. J.

    2000-01-01

    Filtration of gas containing oxidizer, to the reaction zone in a porous medium, due, e.g., to a buoyancy force or to an external pressure gradient, leads to the propagation of Filtration combustion (FC) waves. The exothermic reaction occurs between the fuel component of the solid matrix and the oxidizer. In this paper, we analyze the ability of a reaction wave to propagate in a porous medium without the aid of filtration. We find that one possible mechanism of propagation is that the wave is driven by diffusion of oxidizer from the environment. The solution of the combustion problem describing diffusion driven waves is similar to the solution of the Stefan problem describing the propagation of phase transition waves, in that the temperature on the interface between the burned and unburned regions is constant, the combustion wave is described by a similarity solution which is a function of the similarity variable x/square root of(t) and the wave velocity decays as 1/square root of(t). The difference between the two problems is that in the combustion problem the temperature is not prescribed, but rather, is determined as part of the solution. We will show that the length of samples in which such self-sustained combustion waves can occur, must exceed a critical value which strongly depends on the combustion temperature T(sub b). Smaller values of T(sub b) require longer sample lengths for diffusion driven combustion waves to exist. Because of their relatively small velocity, diffusion driven waves are considered to be relevant for the case of low heat losses, which occur for large diameter samples or in microgravity conditions, Another possible mechanism of porous medium combustion describes waves which propagate by consuming the oxidizer initially stored in the pores of the sample. This occurs for abnormally high pressure and gas density. In this case, uniformly propagating planar waves, which are kinetically controlled, can propagate, Diffusion of oxidizer decreases

  15. Advanced motor driven clamped borehole seismic receiver

    DOEpatents

    Engler, Bruce P.; Sleefe, Gerard E.; Striker, Richard P.

    1993-01-01

    A borehole seismic tool including a borehole clamp which only moves perpendicular to the borehole. The clamp is driven by an electric motor, via a right angle drive. When used as a seismic receiver, the tool has a three part housing, two of which are hermetically sealed. Accelerometers or geophones are mounted in one hermetically sealed part, the electric meter in the other hermetically sealed part, and the clamp and right angle drive in the third part. Preferably the tool includes cable connectors at both ends. Optionally a shear plate can be added to the clamp to extend the range of the tool.

  16. Advanced motor driven clamped borehole seismic receiver

    DOEpatents

    Engler, B.P.; Sleefe, G.E.; Striker, R.P.

    1993-02-23

    A borehole seismic tool is described including a borehole clamp which only moves perpendicular to the borehole. The clamp is driven by an electric motor, via a right angle drive. When used as a seismic receiver, the tool has a three part housing, two of which are hermetically sealed. Accelerometers or geophones are mounted in one hermetically sealed part, the electric motor in the other hermetically sealed part, and the clamp and right angle drive in the third part. Preferably the tool includes cable connectors at both ends. Optionally a shear plate can be added to the clamp to extend the range of the tool.

  17. A goal-driven neural propositional interpreter.

    PubMed

    Lima, P M

    2001-06-01

    This work presents ARQ-PROP-II, the propositional version of a neural engine for finding proofs by refutation using the Resolution Principle. This neural architecture does not require special arrangements or modules to do forward or backward reasoning, being driven by the goal posed to it. ARQ-PROP-II is capable of integrated monotonic reasoning with complete and incomplete knowledge. The neural mechanism presented herein is the first to our knowledge that does not require that the knowledge base be either pre-encoded or learnt. PMID:11574968

  18. Accelerator driven sub-critical core

    DOEpatents

    McIntyre, Peter M; Sattarov, Akhdiyor

    2015-03-17

    Systems and methods for operating an accelerator driven sub-critical core. In one embodiment, a fission power generator includes a sub-critical core and a plurality of proton beam generators. Each of the proton beam generators is configured to concurrently provide a proton beam into a different area of the sub-critical core. Each proton beam scatters neutrons within the sub-critical core. The plurality of proton beam generators provides aggregate power to the sub-critical core, via the proton beams, to scatter neutrons sufficient to initiate fission in the sub-critical core.

  19. Driven reconnection in the earth's magnetotail

    NASA Technical Reports Server (NTRS)

    Forbes, T. G.

    1991-01-01

    In the standard reconnection model, a low flow speed leads to steady reconnection at a distant-tail x-line, but a high flow speed leads to the formation of a near-earth x-line and the onset of an auroral substorm. This paper discusses recent work which suggests that a pile-up of magnetic flux in the earth's magnetotail will occur whenever reconnection is strongly driven by the solar wind and that the near-earth x-line might result from a flux pile-up at the distant-tail x-line.

  20. Diagnostics for Respondent-driven Sampling

    PubMed Central

    2016-01-01

    Summary Respondent-driven sampling (RDS) is a widely used method for sampling from hard-to-reach human populations, especially populations at higher risk for HIV. Data are collected through peer-referral over social networks. RDS has proven practical for data collection in many difficult settings and is widely used. Inference from RDS data requires many strong assumptions because the sampling design is partially beyond the control of the researcher and partially unobserved. We introduce diagnostic tools for most of these assumptions and apply them in 12 high risk populations. These diagnostics empower researchers to better understand their data and encourage future statistical research on RDS. PMID:27226702

  1. Parametrically driven surface waves on viscous ferrofluids

    NASA Astrophysics Data System (ADS)

    Müller, Hanns Walter

    1998-11-01

    Standing waves on the surface of a ferrofluid in a normal magnetic field can be excited by a vertical vibration of the container. A stability theory for the onset of these parametrically driven waves is developed, taking viscous dissipation and finite depth effects into account. It will be shown that a careful choice of the filling level permits the normal and anomalous dispersion branches to be measured. Furthermore it will be demonstrated that the parametric driving mechanism may lead to a delay of the Rosensweig instability. A bicritical situation can be achieved when Rosensweig and Faraday waves interact.

  2. Fiber optic mounted laser driven flyer plates

    SciTech Connect

    Paisley, D.L.

    1990-12-31

    This invention is comprised of a laser driven flyer plate where the flyer plate is deposited directly onto the squared end of an optical fiber. The plasma generated by a laser pulse drives the flyer plate toward a target. In another embodiment, a first metal layer is deposited onto the squared end of an optical fiber, followed by a layer of a dielectric material and a second metal layer. The laser pulse generates a plasma in the first metal layer, but the plasma is kept away from the second metal layer by the dielectric layer until the pressure reaches the point where shearing occurs. 2 figs.

  3. Fundamental studies on a heat driven lamp

    NASA Technical Reports Server (NTRS)

    Lawless, J. L.

    1985-01-01

    A detailed theoretical study of a heat-driven lamp has been performed. This lamp uses a plasma produced in a thermionic diode. The light is produced by the resonance transition of cesium. An important result of this study is that up to 30% of the input heat is predicted to be converted to light in this device. This is a major improvement over ordinary thermionic energy converters in which only approx. 1% is converted to resonance radiation. Efficiencies and optimum inter-electrode spacings have been found as a function of cathode temperature and the radiative escape factor. The theory developed explains the operating limits of the device.

  4. Energy-beam-driven rapid fabrication system

    DOEpatents

    Keicher, David M.; Atwood, Clinton L.; Greene, Donald L.; Griffith, Michelle L.; Harwell, Lane D.; Jeantette, Francisco P.; Romero, Joseph A.; Schanwald, Lee P.; Schmale, David T.

    2002-01-01

    An energy beam driven rapid fabrication system, in which an energy beam strikes a growth surface to form a molten puddle thereon. Feed powder is then injected into the molten puddle from a converging flow of feed powder. A portion of the feed powder becomes incorporated into the molten puddle, forcing some of the puddle contents to freeze on the growth surface, thereby adding an additional layer of material. By scanning the energy beam and the converging flow of feed powder across the growth surface, complex three-dimensional shapes can be formed, ready or nearly ready for use. Nearly any class of material can be fabricated using this system.

  5. Accelerator-driven X-ray Sources

    SciTech Connect

    Nguyen, Dinh Cong

    2015-11-09

    After an introduction which mentions x-ray tubes and storage rings and gives a brief review of special relativity, the subject is treated under the following topics and subtopics: synchrotron radiation (bending magnet radiation, wiggler radiation, undulator radiation, brightness and brilliance definition, synchrotron radiation facilities), x-ray free-electron lasers (linac-driven X-ray FEL, FEL interactions, self-amplified spontaneous emission (SASE), SASE self-seeding, fourth-generation light source facilities), and other X-ray sources (energy recovery linacs, Inverse Compton scattering, laser wakefield accelerator driven X-ray sources. In summary, accelerator-based light sources cover the entire electromagnetic spectrum. Synchrotron radiation (bending magnet, wiggler and undulator radiation) has unique properties that can be tailored to the users’ needs: bending magnet and wiggler radiation is broadband, undulator radiation has narrow spectral lines. X-ray FELs are the brightest coherent X-ray sources with high photon flux, femtosecond pulses, full transverse coherence, partial temporal coherence (SASE), and narrow spectral lines with seeding techniques. New developments in electron accelerators and radiation production can potentially lead to more compact sources of coherent X-rays.

  6. Skyrmion motion driven by oscillating magnetic field

    PubMed Central

    Moon, Kyoung-Woong; Kim, Duck-Ho; Je, Soong-Geun; Chun, Byong Sun; Kim, Wondong; Qiu, Z.Q.; Choe, Sug-Bong; Hwang, Chanyong

    2016-01-01

    The one-dimensional magnetic skyrmion motion induced by an electric current has attracted much interest because of its application potential in next-generation magnetic memory devices. Recently, the unidirectional motion of large (20 μm in diameter) magnetic bubbles with two-dimensional skyrmion topology, driven by an oscillating magnetic field, has also been demonstrated. For application in high-density memory devices, it is preferable to reduce the size of skyrmion. Here we show by numerical simulation that a skyrmion of a few tens of nanometres can also be driven by high-frequency field oscillations, but with a different direction of motion from the in-plane component of the tilted oscillating field. We found that a high-frequency field for small skyrmions can excite skyrmion resonant modes and that a combination of different modes results in a final skyrmion motion with a helical trajectory. Because this helical motion depends on the frequency of the field, we can control both the speed and the direction of the skyrmion motion, which is a distinguishable characteristic compared with other methods. PMID:26847334

  7. Flux-driven simulations of turbulence collapse

    SciTech Connect

    Park, G. Y.; Kim, S. S.; Jhang, Hogun; Rhee, T.; Diamond, P. H.; Xu, X. Q.

    2015-03-15

    Using three-dimensional nonlinear simulations of tokamak turbulence, we show that an edge transport barrier (ETB) forms naturally once input power exceeds a threshold value. Profiles, turbulence-driven flows, and neoclassical coefficients are evolved self-consistently. A slow power ramp-up simulation shows that ETB transition is triggered by the turbulence-driven flows via an intermediate phase which involves coherent oscillation of turbulence intensity and E×B flow shear. A novel observation of the evolution is that the turbulence collapses and the ETB transition begins when R{sub T} > 1 at t = t{sub R} (R{sub T}: normalized Reynolds power), while the conventional transition criterion (ω{sub E×B}>γ{sub lin} where ω{sub E×B} denotes mean flow shear) is satisfied only after t = t{sub C} ( >t{sub R}), when the mean flow shear grows due to positive feedback.

  8. Skyrmion motion driven by oscillating magnetic field

    NASA Astrophysics Data System (ADS)

    Moon, Kyoung-Woong; Kim, Duck-Ho; Je, Soong-Geun; Chun, Byong Sun; Kim, Wondong; Qiu, Z. Q.; Choe, Sug-Bong; Hwang, Chanyong

    2016-02-01

    The one-dimensional magnetic skyrmion motion induced by an electric current has attracted much interest because of its application potential in next-generation magnetic memory devices. Recently, the unidirectional motion of large (20 μm in diameter) magnetic bubbles with two-dimensional skyrmion topology, driven by an oscillating magnetic field, has also been demonstrated. For application in high-density memory devices, it is preferable to reduce the size of skyrmion. Here we show by numerical simulation that a skyrmion of a few tens of nanometres can also be driven by high-frequency field oscillations, but with a different direction of motion from the in-plane component of the tilted oscillating field. We found that a high-frequency field for small skyrmions can excite skyrmion resonant modes and that a combination of different modes results in a final skyrmion motion with a helical trajectory. Because this helical motion depends on the frequency of the field, we can control both the speed and the direction of the skyrmion motion, which is a distinguishable characteristic compared with other methods.

  9. Progress of Laser-Driven Plasma Accelerators

    NASA Astrophysics Data System (ADS)

    Nakajima, Kazuhisa

    2007-07-01

    There is a great interest worldwide in plasma accelerators driven by ultra-intense lasers which make it possible to generate ultra-high gradient acceleration and high quality particle beams in a much more compact size compared with conventional accelerators. A frontier research on laser and plasma accelerators is focused on high energy electron acceleration and ultra-short X-ray and Tera Hertz radiations as their applications. These achievements will provide not only a wide range of sciences with benefits of a table-top accelerator but also a basic science with a tool of ultrahigh energy accelerators probing an unknown extremely microscopic world. Harnessing the recent advance of ultra-intense ultra-short pulse lasers, the worldwide research has made a tremendous breakthrough in demonstrating high-energy high-quality particle beams in a compact scale, so called "dream beams on a table top", which represents monoenergetic electron beams from laser wakefield accelerators and GeV acceleration by capillary plasma-channel laser wakefield accelerators. This lecture reviews recent progress of results on laser-driven plasma based accelerator experiments to quest for particle acceleration physics in intense laser-plasma interactions and to present new outlook for the GeV-range high-energy laser plasma accelerators.

  10. Test Driven Development of Scientific Models

    NASA Technical Reports Server (NTRS)

    Clune, Thomas L.

    2012-01-01

    Test-Driven Development (TDD) is a software development process that promises many advantages for developer productivity and has become widely accepted among professional software engineers. As the name suggests, TDD practitioners alternate between writing short automated tests and producing code that passes those tests. Although this overly simplified description will undoubtedly sound prohibitively burdensome to many uninitiated developers, the advent of powerful unit-testing frameworks greatly reduces the effort required to produce and routinely execute suites of tests. By testimony, many developers find TDD to be addicting after only a few days of exposure, and find it unthinkable to return to previous practices. Of course, scientific/technical software differs from other software categories in a number of important respects, but I nonetheless believe that TDD is quite applicable to the development of such software and has the potential to significantly improve programmer productivity and code quality within the scientific community. After a detailed introduction to TDD, I will present the experience within the Software Systems Support Office (SSSO) in applying the technique to various scientific applications. This discussion will emphasize the various direct and indirect benefits as well as some of the difficulties and limitations of the methodology. I will conclude with a brief description of pFUnit, a unit testing framework I co-developed to support test-driven development of parallel Fortran applications.

  11. Current driven instability in collisional dusty plasmas

    NASA Astrophysics Data System (ADS)

    Pandey, B. P.; Vladimirov, S. V.; Samarian, A.

    2009-11-01

    The current driven electromagnetic instability in a collisional, magnetized, dusty medium is considered in the present work. It is shown that in the presence of the magnetic field aligned current, the low-frequency waves in the medium can become unstable if the ratio of the current to the ambient field is larger than the light speed times the wave number. The growth rate of the instability depends upon the ratio of the Alfvén to the dust cyclotron frequency as well as on the ratio of the current density J to the dust charge density Zend, where Z is the number of electronic charge on the grain, e is the electron charge, and nd is the dust number density. The typical growth rate of this instability is on the order of Alfvén frequency which compares favorably with the electrostatic, cross-field current driven, Farley-Buneman instability and thus could play an important role in the Earth's ionosphere.

  12. Bleb-driven chemotaxis of Dictyostelium cells.

    PubMed

    Zatulovskiy, Evgeny; Tyson, Richard; Bretschneider, Till; Kay, Robert R

    2014-03-17

    Blebs and F-actin-driven pseudopods are alternative ways of extending the leading edge of migrating cells. We show that Dictyostelium cells switch from using predominantly pseudopods to blebs when migrating under agarose overlays of increasing stiffness. Blebs expand faster than pseudopods leaving behind F-actin scars, but are less persistent. Blebbing cells are strongly chemotactic to cyclic-AMP, producing nearly all of their blebs up-gradient. When cells re-orientate to a needle releasing cyclic-AMP, they stereotypically produce first microspikes, then blebs and pseudopods only later. Genetically, blebbing requires myosin-II and increases when actin polymerization or cortical function is impaired. Cyclic-AMP induces transient blebbing independently of much of the known chemotactic signal transduction machinery, but involving PI3-kinase and downstream PH domain proteins, CRAC and PhdA. Impairment of this PI3-kinase pathway results in slow movement under agarose and cells that produce few blebs, though actin polymerization appears unaffected. We propose that mechanical resistance induces bleb-driven movement in Dictyostelium, which is chemotactic and controlled through PI3-kinase. PMID:24616222

  13. Graphene-contact electrically driven microdisk lasers

    PubMed Central

    Kim, Yoon-Ho; Kwon, Soon-Hong; Lee, Jung Min; Hwang, Min-Soo; Kang, Ju-Hyung; Park, Won Il; Park, Hong-Gyu

    2012-01-01

    Active nanophotonic devices are attractive due to their low-power consumption, ultrafast modulation speed and high-density integration. Although electrical operation is required for practical implementation of these devices, it is not straightforward to introduce a proper current path into such a wavelength-scale nanostructure without affecting the optical properties. For example, to demonstrate electrically driven nanolasers, complicated fabrication techniques have been used thus far. Here we report an electrically driven microdisk laser using a transparent graphene electrode. Current is injected efficiently through the graphene sheet covering the top surface of the microdisk cavity, and, for the first time, lasing operation was achieved with a low-threshold current of ~300 μA at room temperature. In addition, we measured significant electroluminescence from a graphene-contact subwavelength-scale single nanopillar structure. This work represents a new paradigm for the practical applications of integrated photonic systems, by conformally mounting graphene on the complex surfaces of non-planar three-dimensional nanostructures. PMID:23047681

  14. Axially Loaded Behavior of Driven PC Piles

    NASA Astrophysics Data System (ADS)

    Hsu, Shih-Tsung

    2010-05-01

    To obtain a fair load-settlement curve of a driven pile, and to evaluate the ultimate pile capacity more accurately, a numerical model was created to simulate the ground movements during a pile being driven. After the procedure, the axially loaded behaviors of the piles in silty sand were analyzed. The numerical results are compared with those results by full scale pile load tests. It was found, although the loads added on the tested piles are different from those by the numerical analyses which applied displacement increments on piles, the load-settlement behaviors of piles calculated from the numerical model were close to those measured from field tests before the piles stressed to peak. Total load, shaft friction, and point bearing do not reach peak values at the same pile settlement; furthermore, the point bearing slowly increases all the while, with no peak. However, the point bearing only contributes 10˜20% of ultimate pile capacity. No matter which relative density of silty sand, pile diameter, and pile length increased, ultimate pile capacity increased as well.

  15. Accelerating Science Driven System Design With RAMP

    SciTech Connect

    Wawrzynek, John

    2015-05-01

    Researchers from UC Berkeley, in collaboration with the Lawrence Berkeley National Lab, are engaged in developing an Infrastructure for Synthesis with Integrated Simulation (ISIS). The ISIS Project was a cooperative effort for “application-driven hardware design” that engages application scientists in the early parts of the hardware design process for future generation supercomputing systems. This project served to foster development of computing systems that are better tuned to the application requirements of demanding scientific applications and result in more cost-effective and efficient HPC system designs. In order to overcome long conventional design-cycle times, we leveraged reconfigurable devices to aid in the design of high-efficiency systems, including conventional multi- and many-core systems. The resulting system emulation/prototyping environment, in conjunction with the appropriate intermediate abstractions, provided both a convenient user programming experience and retained flexibility, and thus efficiency, of a reconfigurable platform. We initially targeted the Berkeley RAMP system (Research Accelerator for Multiple Processors) as that hardware emulation environment to facilitate and ultimately accelerate the iterative process of science-driven system design. Our goal was to develop and demonstrate a design methodology for domain-optimized computer system architectures. The tangible outcome is a methodology and tools for rapid prototyping and design-space exploration, leading to highly optimized and efficient HPC systems.

  16. Inertial effects in adiabatically driven flashing ratchets

    NASA Astrophysics Data System (ADS)

    Rozenbaum, Viktor M.; Makhnovskii, Yurii A.; Shapochkina, Irina V.; Sheu, Sheh-Yi; Yang, Dah-Yen; Lin, Sheng Hsien

    2014-05-01

    We study analytically the effect of a small inertial correction on the properties of adiabatically driven flashing ratchets. Parrondo's lemma [J. M. R. Parrondo, Phys. Rev. E 57, 7297 (1998), 10.1103/PhysRevE.57.7297] is generalized to include the inertial term so as to establish the symmetry conditions allowing directed motion (other than in the overdamped massless case) and to obtain a high-temperature expansion of the motion velocity for arbitrary potential profiles. The inertial correction is thus shown to enhance the ratchet effect at all temperatures for sawtooth potentials and at high temperatures for simple potentials described by the first two harmonics. With the special choice of potentials represented by at least the first three harmonics, the correction gives rise to the motion reversal in the high-temperature region. In the low-temperature region, inertia weakens the ratchet effect, with the exception of the on-off model, where diffusion is important. The directed motion adiabatically driven by potential sign fluctuations, though forbidden in the overdamped limit, becomes possible due to purely inertial effects in neither symmetric nor antisymmetric potentials, i.e., not for commonly used sawtooth and two-sinusoid profiles.

  17. Radiatively Driven Turbulence at the Cloud Top

    NASA Astrophysics Data System (ADS)

    de Lozar, Alberto; Mellado, Juan Pedro

    2012-11-01

    We use Direct Numerical Simulations to investigate a radiatively-driven smoke cloud-top mixing layer. This configuration mimics relevant aspects of stratocumuls clouds, in particular the mixing across an inversion that bounds a radiatively driven turbulent flow. A 1D formulation is employed for the radiation calculations. Below the inversion a convective boundary layer propagates downwards into the cloud-bulk. The convective boundary layer decouples from the inversion properties other than the injected buoyancy flux. This buoyancy flux is equal to the total radiative cooling minus the cooling of the inversion layer where the cloud mixes with the free atmosphere. An exact equation at a properly defined inversion point divides the inversion cooling into three components: a molecular flux, a turbulent flux and the direct radiative cooling by the smoke inside the inversion layer. The normalized turbulent flux levels to a constant value (0 . 175 +/- 0 . 05), which is independent of the stratification. As suggested by earlies studies, we observe that the turbulent entrainment only occurs at the small scales and that eddies larger than four optical lengths (50 m in a typical DYCOMS-II cloud) perform little or no entrainment.

  18. Stochastic Event-Driven Molecular Dynamics

    SciTech Connect

    Donev, Aleksandar Garcia, Alejandro L.; Alder, Berni J.

    2008-02-01

    A novel Stochastic Event-Driven Molecular Dynamics (SEDMD) algorithm is developed for the simulation of polymer chains suspended in a solvent. SEDMD combines event-driven molecular dynamics (EDMD) with the Direct Simulation Monte Carlo (DSMC) method. The polymers are represented as chains of hard-spheres tethered by square wells and interact with the solvent particles with hard-core potentials. The algorithm uses EDMD for the simulation of the polymer chain and the interactions between the chain beads and the surrounding solvent particles. The interactions between the solvent particles themselves are not treated deterministically as in EDMD, rather, the momentum and energy exchange in the solvent is determined stochastically using DSMC. The coupling between the solvent and the solute is consistently represented at the particle level retaining hydrodynamic interactions and thermodynamic fluctuations. However, unlike full MD simulations of both the solvent and the solute, in SEDMD the spatial structure of the solvent is ignored. The SEDMD algorithm is described in detail and applied to the study of the dynamics of a polymer chain tethered to a hard-wall subjected to uniform shear. SEDMD closely reproduces results obtained using traditional EDMD simulations with two orders of magnitude greater efficiency. Results question the existence of periodic (cycling) motion of the polymer chain.

  19. Science Goal Driven Observing and Spacecraft Autonomy

    NASA Technical Reports Server (NTRS)

    Koratkar, Amuradha; Grosvenor, Sandy; Jones, Jeremy; Wolf, Karl

    2002-01-01

    Spacecraft autonomy will be an integral part of mission operations in the coming decade. While recent missions have made great strides in the ability to autonomously monitor and react to changing health and physical status of spacecraft, little progress has been made in responding quickly to science driven events. For observations of inherently variable targets and targets of opportunity, the ability to recognize early if an observation will meet the science goals of a program, and react accordingly, can have a major positive impact on the overall scientific returns of an observatory and on its operational costs. If the onboard software can reprioritize the schedule to focus on alternate targets, discard uninteresting observations prior to downloading, or download a subset of observations at a reduced resolution, the spacecraft's overall efficiency will be dramatically increased. The science goal monitoring (SGM) system is a proof-of-concept effort to address the above challenge. The SGM will have an interface to help capture higher level science goals from the scientists and translate them into a flexible observing strategy that SGM can execute and monitor. We are developing an interactive distributed system that will use on-board processing and storage combined with event-driven interfaces with ground-based processing and operations, to enable fast re-prioritization of observing schedules, and to minimize time spent on non-optimized observations.

  20. Bleb-driven chemotaxis of Dictyostelium cells

    PubMed Central

    Zatulovskiy, Evgeny; Tyson, Richard; Bretschneider, Till

    2014-01-01

    Blebs and F-actin–driven pseudopods are alternative ways of extending the leading edge of migrating cells. We show that Dictyostelium cells switch from using predominantly pseudopods to blebs when migrating under agarose overlays of increasing stiffness. Blebs expand faster than pseudopods leaving behind F-actin scars, but are less persistent. Blebbing cells are strongly chemotactic to cyclic-AMP, producing nearly all of their blebs up-gradient. When cells re-orientate to a needle releasing cyclic-AMP, they stereotypically produce first microspikes, then blebs and pseudopods only later. Genetically, blebbing requires myosin-II and increases when actin polymerization or cortical function is impaired. Cyclic-AMP induces transient blebbing independently of much of the known chemotactic signal transduction machinery, but involving PI3-kinase and downstream PH domain proteins, CRAC and PhdA. Impairment of this PI3-kinase pathway results in slow movement under agarose and cells that produce few blebs, though actin polymerization appears unaffected. We propose that mechanical resistance induces bleb-driven movement in Dictyostelium, which is chemotactic and controlled through PI3-kinase. PMID:24616222

  1. Microwave Driven Actuators Power Allocation and Distribution

    NASA Technical Reports Server (NTRS)

    Forbes, Timothy; Song, Kyo D.

    2000-01-01

    Design, fabrication and test of a power allocation and distribution (PAD) network for microwave driven actuators is presented in this paper. Development of a circuit that would collect power from a rectenna array amplify and distribute the power to actuators was designed and fabricated for space application in an actuator array driven by a microwave. A P-SPICE model was constructed initially for data reduction purposes, and was followed by a working real-world model. A voltage up - converter (VUC) is used to amplify the voltage from the individual rectenna. The testing yielded a 26:1 voltage amplification ratio with input voltage at 9 volts and a measured output voltage 230VDC. Future work includes the miniaturization of the circuitry, the use of microwave remote control, and voltage amplification technology for each voltage source. The objective of this work is to develop a model system that will collect DC voltage from an array of rectenna and propagate the voltage to an array of actuators.

  2. Temporal percolation in activity-driven networks

    NASA Astrophysics Data System (ADS)

    Starnini, Michele; Pastor-Satorras, Romualdo

    2014-03-01

    We study the temporal percolation properties of temporal networks by taking as a representative example the recently proposed activity-driven-network model [N. Perra et al., Sci. Rep. 2, 469 (2012), 10.1038/srep00469]. Building upon an analytical framework based on a mapping to hidden variables networks, we provide expressions for the percolation time Tp marking the onset of a giant connected component in the integrated network. In particular, we consider both the generating function formalism, valid for degree-uncorrelated networks, and the general case of networks with degree correlations. We discuss the different limits of the two approaches, indicating the parameter regions where the correlated threshold collapses onto the uncorrelated case. Our analytical predictions are confirmed by numerical simulations of the model. The temporal percolation concept can be fruitfully applied to study epidemic spreading on temporal networks. We show in particular how the susceptible-infected-removed model on an activity-driven network can be mapped to the percolation problem up to a time given by the spreading rate of the epidemic process. This mapping allows us to obtain additional information on this process, not available for previous approaches.

  3. Piezoelectric driven thermo-acoustic refrigerator

    NASA Astrophysics Data System (ADS)

    Chinn, D. G.; Nouh, M.; Aldraihem, O.; Baz, A.

    2011-03-01

    Thermoacoustic refrigeration is an emerging refrigeration technology which does not rely for in its operation on the use of any moving parts or harmful refrigerants. This technology uses acoustic waves to pump heat across a temperature gradient. The vast majority of thermoacoustic refrigerators to date have used electromagnetic loudspeakers to generate the acoustic input. In this paper, the design, construction, operation, and modeling of a piezoelectric-driven thermoacoustic refrigerator are detailed. This refrigerator demonstrates the effectiveness of piezoelectric actuation in moving 0.3 W of heat across an 18 degree C temperature difference with an input power of 7.6 W. The performance characteristics of this class of thermoacoustic-piezoelectric refrigerator are modeled using DeltaEC software and the predictions are validated experimentally. The obtained results confirm the validity of the developed model. Furthermore, the potential of piezoelectric actuation as effective means for driving thermoacoustic refrigerators is demonstrated as compared to the conventional electromagnetic loudspeakers which are heavy and require high actuation energy. The developed theoretical and experimental tools can serve as invaluable means for the design and testing of other piezoelectric driven thermoacoustic refrigerator configurations.

  4. Progress of Laser-Driven Plasma Accelerators

    SciTech Connect

    Nakajima, Kazuhisa

    2007-07-11

    There is a great interest worldwide in plasma accelerators driven by ultra-intense lasers which make it possible to generate ultra-high gradient acceleration and high quality particle beams in a much more compact size compared with conventional accelerators. A frontier research on laser and plasma accelerators is focused on high energy electron acceleration and ultra-short X-ray and Tera Hertz radiations as their applications. These achievements will provide not only a wide range of sciences with benefits of a table-top accelerator but also a basic science with a tool of ultrahigh energy accelerators probing an unknown extremely microscopic world.Harnessing the recent advance of ultra-intense ultra-short pulse lasers, the worldwide research has made a tremendous breakthrough in demonstrating high-energy high-quality particle beams in a compact scale, so called ''dream beams on a table top'', which represents monoenergetic electron beams from laser wakefield accelerators and GeV acceleration by capillary plasma-channel laser wakefield accelerators. This lecture reviews recent progress of results on laser-driven plasma based accelerator experiments to quest for particle acceleration physics in intense laser-plasma interactions and to present new outlook for the GeV-range high-energy laser plasma accelerators.

  5. ISOTROPICALLY DRIVEN VERSUS OUTFLOW DRIVEN TURBULENCE: OBSERVATIONAL CONSEQUENCES FOR MOLECULAR CLOUDS

    SciTech Connect

    Carroll, Jonathan J.; Frank, Adam; Blackman, Eric G.

    2010-10-10

    Feedback from protostellar outflows can influence the nature of turbulence in star-forming regions even if they are not the primary source of velocity dispersion for all scales of molecular clouds. For the rate and power expected in star-forming regions, we previously (Carroll et al.) demonstrated that outflows could drive supersonic turbulence at levels consistent with the scaling relations from Matzner although with a steeper velocity power spectrum than expected for an isotropically driven supersonic turbulent cascade. Here, we perform higher resolution simulations and combine simulations of outflow driven turbulence with those of isotropically forced turbulence. We find that the presence of outflows within an ambient isotropically driven turbulent environment produces a knee in the velocity power spectrum at the outflow scale and a steeper slope at sub-outflow scales than for a purely isotropically forced case. We also find that the presence of outflows flattens the density spectrum at large scales effectively reducing the formation of large-scale turbulent density structures. These effects are qualitatively independent of resolution. We have also carried out Principal Component Analysis (PCA) for synthetic data from our simulations. We find that PCA as a tool for identifying the driving scale of turbulence has a misleading bias toward low amplitude large-scale velocity structures even when they are not necessarily the dominant energy containing scales. This bias is absent for isotropically forced turbulence but manifests strongly for collimated outflow driven turbulence.

  6. Stimulus-driven and knowledge-driven processes in attention to warbles

    NASA Astrophysics Data System (ADS)

    Dowling, W. Jay; Tillmann, Barbara

    2003-10-01

    Listeners identified warbles differing in amplitude-modulation rate (3-10 Hz). And measured RT while listeners maintained above 90% correct responses. After a practice session listeners identified target warbles following stimulus-driven or knowledge-driven cues. The stimulus-driven cue was a 250-ms ``beep'' at the target pitch (valid) or another pitch (invalid); the knowledge-driven cue was a midrange ``melody'' pointing to the target pitch (always valid). A 500-ms target warble followed the cue after delays of 0-500 ms (250-750 ms SOA). The listener pressed a key to indicate ``slow'' or ``fast.'' RTs were shortest at the briefest delay. In contrast to results from a memory task, RTs here were much shorter, and we found no evidence for IOR or attentional blink. Listeners began generating responses while the target was still sounding. Invalid ``beeps'' slowed responses at the briefest (but not the longer) delays; adding a valid ``beep'' to the valid ``melody'' did not speed responses.

  7. The effects of goal-driven and data-driven regulation on metacognitive monitoring during learning: a developmental perspective.

    PubMed

    Koriat, Asher; Ackerman, Rakefet; Adiv, Shiri; Lockl, Kathrin; Schneider, Wolfgang

    2014-02-01

    Research in metacognition (Koriat, Ma'ayan, & Nussinson, 2006) suggests bidirectional links between monitoring and control during learning: When self-regulation is goal-driven, monitoring affects control so that increased study time (ST) enhances judgments of learning (JOLs). However, when self-regulation is data-driven, JOLs are based on the feedback from control, and therefore JOLs decrease with ST under the heuristic that ease of encoding is diagnostic of successful recall. Evidence for both types of relationships occurring within the same situation was found for adults. We examined the development of the ability to respond differentially to data-driven and goal-driven variation in ST within the same task. Children in Grades 5 and 6 exhibited a positive ST-JOL relationship for goal-driven regulation and a negative relationship for data-driven regulation but never in the same task. In contrast, the JOLs and recall of 9th graders and college students yielded differential cosensitivity to data-driven and goal-driven variation. The 5th and 6th graders also evidenced an adult-like pattern of JOLs and recall under a partitioning procedure that helped them in factoring the variation in ST due to data-driven and goal-driven variation in ST. The results are discussed in terms of the metacognitive sophistication needed for considering both types of variation simultaneously in making metacognitive judgments. PMID:23421442

  8. Influence of driven current on resistive tearing mode in Tokamaks

    NASA Astrophysics Data System (ADS)

    Wang, S.; Ma, Z. W.; Zhang, W.

    2016-05-01

    The influence of driven current on the m /n =2 /1 resistive tearing mode is studied systematically using a three-dimensional toroidal magnetohydrodynamic code. A uniform driven current with Gaussian distribution in the radial direction is imposed around the unperturbed rational surface. It is found that the driven current can locally modify the profiles of the current and safety factor, such that the tearing mode becomes linearly stable. The stabilizing effect increases with the increase of the driven current Icd or the decrease of its width δcd , unless an excessively large driven current reverses the magnetic shear near the rational surface and drives other instabilities such as double or triple tearing modes. The stabilizing effect can be negligible or becomes reversed if the maximum driven current density is not at the unperturbed rational surface.

  9. Planetary dynamos driven by helical waves - II

    NASA Astrophysics Data System (ADS)

    Davidson, P. A.; Ranjan, A.

    2015-09-01

    In most numerical simulations of the Earth's core the dynamo resides outside the tangent cylinder and may be crudely classified as being of the α2 type. In this region the flow comprises a sea of thin columnar vortices aligned with the rotation axis, taking the form of alternating cyclones and anticyclones. The dynamo is thought to be driven by these columnar vortices within which the flow is observed to be highly helical, helicity being a crucial ingredient of planetary dynamos. As noted in Davidson, one of the mysteries of this dynamo cartoon is the origin of the helicity, which is observed to be positive in the south and negative in the north. While Ekman pumping at the mantle can induce helicity in some of the overly viscous numerical simulations, it is extremely unlikely to be a significant source within planets. In this paper we return to the suggestion of Davidson that the helicity observed in the less viscous simulations owes its existence to helical wave packets, launched in and around the equatorial plane where the buoyancy flux is observed to be strong. Here we show that such wave packets act as a potent source of planetary helicity, constituting a simple, robust mechanism that yields the correct sign for h north and south of the equator. Since such a mechanism does not rely on the presence of a mantle, it can operate within both the Earth and the gas giants. Moreover, our numerical simulations show that helical wave packets dispersing from the equator produce a random sea of thin, columnar cyclone/anticyclone pairs, very like those observed in the more strongly forced dynamo simulations. We examine the local dynamics of helical wave packets dispersing from the equatorial regions, as well as the overall nature of an α2-dynamo driven by such wave packets. Our local analysis predicts the mean emf induced by helical waves, an analysis that rests on a number of simple approximations which are consistent with our numerical experiments, while our global

  10. Solar Dynamo Driven by Periodic Flow Oscillation

    NASA Technical Reports Server (NTRS)

    Mayr, Hans G.; Hartle, Richard E.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    We have proposed that the periodicity of the solar magnetic cycle is determined by wave mean flow interactions analogous to those driving the Quasi Biennial Oscillation in the Earth's atmosphere. Upward propagating gravity waves would produce oscillating flows near the top of the radiation zone that in turn would drive a kinematic dynamo to generate the 22-year solar magnetic cycle. The dynamo we propose is built on a given time independent magnetic field B, which allows us to estimate the time dependent, oscillating components of the magnetic field, (Delta)B. The toroidal magnetic field (Delta)B(sub phi) is directly driven by zonal flow and is relatively large in the source region, (Delta)(sub phi)/B(sub Theta) much greater than 1. Consistent with observations, this field peaks at low latitudes and has opposite polarities in both hemispheres. The oscillating poloidal magnetic field component, (Delta)B(sub Theta), is driven by the meridional circulation, which is difficult to assess without a numerical model that properly accounts for the solar atmosphere dynamics. Scale-analysis suggests that (Delta)B(sub Theta) is small compared to B(sub Theta) in the dynamo region. Relative to B(sub Theta), however, the oscillating magnetic field perturbations are expected to be transported more rapidly upwards in the convection zone to the solar surface. As a result, (Delta)B(sub Theta) (and (Delta)B(sub phi)) should grow relative to B(sub Theta), so that the magnetic fields reverse at the surface as observed. Since the meridional and zonai flow oscillations are out of phase, the poloidal magnetic field peaks during times when the toroidal field reverses direction, which is observed. With the proposed wave driven flow oscillation, the magnitude of the oscillating poloidal magnetic field increases with the mean rotation rate of the fluid. This is consistent with the Bode-Blackett empirical scaling law, which reveals that in massive astrophysical bodies the magnetic moment tends

  11. Driving Ms. Data: Creating Data-Driven Possibilities

    ERIC Educational Resources Information Center

    Hoffman, Richard

    2005-01-01

    This article describes how driven Web sites help schools and districts maximize their IT resources by making online content more "self-service" for users. It shows how to set up the capacity to create data-driven sites. By definition, a data-driven Web site is one in which the content comes from some back-end data source, such as a database, and…

  12. Foam-Driven Fractures of an Elastic Matrix

    NASA Astrophysics Data System (ADS)

    Lai, Ching-Yao; Smiddy, Sam; Stone, Howard

    2015-11-01

    We report an experimental study of foam-driven fractures in an elastic matrix. When a pressurized foam is constantly injected into a gelatin matrix with a constant flow rate, the foam generates a disc-like fracture which is commonly observed in liquid-driven fractures. Compare to liquid-driven fractures, foam-driven fractures grow faster with time. We investigate how the rheological behaviour of foams affects the fracture characteristics by varying the air volume fraction of the foam, the types and concentration of surfactants in the foam. Foam-fracturing reduces the environmental costs of hydraulic fracturing, which inspires this laboratory study.

  13. Epidemic spreading driven by biased random walks

    NASA Astrophysics Data System (ADS)

    Pu, Cunlai; Li, Siyuan; Yang, Jian

    2015-08-01

    Random walk is one of the basic mechanisms of many network-related applications. In this paper, we study the dynamics of epidemic spreading driven by biased random walks in complex networks. In our epidemic model, infected nodes send out infection packets by biased random walks to their neighbor nodes, and this causes the infection of susceptible nodes that receive the packets. Infected nodes recover from the infection at a constant rate λ, and will not be infected again after recovery. We obtain the largest instantaneous number of infected nodes and the largest number of ever-infected nodes respectively, by tuning the parameter α of the biased random walks. Simulation results on model and real-world networks show that spread of the epidemic becomes intense and widespread with increase of either delivery capacity of infected nodes, average node degree, or homogeneity of node degree distribution.

  14. Ion beam driven warm dense matter experiments

    NASA Astrophysics Data System (ADS)

    Bieniosek, F. M.; Ni, P. A.; Leitner, M.; Roy, P. K.; More, R.; Barnard, J. J.; Kireeff Covo, M.; Molvik, A. W.; Yoneda, H.

    2007-11-01

    We report plans and experimental results in ion beam-driven warm dense matter (WDM) experiments. Initial experiments at LBNL are at 0.3-1 MeV K+ beam (below the Bragg peak), increasing toward the Bragg peak in future versions of the accelerator. The WDM conditions are envisioned to be achieved by combined longitudinal and transverse neutralized drift compression to provide a hot spot on the target with a beam spot size of about 1 mm, and pulse length about 1-2 ns. The range of the beams in solid matter targets is about 1 micron, which can be lengthened by using porous targets at reduced density. Initial experiments include an experiment to study transient darkening at LBNL; and a porous target experiment at GSI heated by intense heavy-ion beams from the SIS 18 storage ring. Further experiments will explore target temperature and other properties such as electrical conductivity to investigate phase transitions and the critical point.

  15. Controlling Contagion Processes in Activity Driven Networks

    NASA Astrophysics Data System (ADS)

    Liu, Suyu; Perra, Nicola; Karsai, Márton; Vespignani, Alessandro

    2014-03-01

    The vast majority of strategies aimed at controlling contagion processes on networks consider the connectivity pattern of the system either quenched or annealed. However, in the real world, many networks are highly dynamical and evolve, in time, concurrently with the contagion process. Here, we derive an analytical framework for the study of control strategies specifically devised for a class of time-varying networks, namely activity-driven networks. We develop a block variable mean-field approach that allows the derivation of the equations describing the coevolution of the contagion process and the network dynamic. We derive the critical immunization threshold and assess the effectiveness of three different control strategies. Finally, we validate the theoretical picture by simulating numerically the spreading process and control strategies in both synthetic networks and a large-scale, real-world, mobile telephone call data set.

  16. Bistability in a Driven-Dissipative Superfluid

    NASA Astrophysics Data System (ADS)

    Labouvie, Ralf; Santra, Bodhaditya; Heun, Simon; Ott, Herwig

    2016-06-01

    We experimentally study a driven-dissipative Josephson junction array, realized with a weakly interacting Bose-Einstein condensate residing in a one-dimensional optical lattice. Engineered losses on one site act as a local dissipative process, while tunneling from the neighboring sites constitutes the driving force. We characterize the emerging steady states of this atomtronic device. With increasing dissipation strength γ the system crosses from a superfluid state, characterized by a coherent Josephson current into the lossy site, to a resistive state, characterized by an incoherent hopping transport. For intermediate values of γ , the system exhibits bistability, where a superfluid and an incoherent branch coexist. We also study the relaxation dynamics towards the steady state, where we find a critical slowing down, indicating the presence of a nonequilibrium phase transition.

  17. Bistability in a Driven-Dissipative Superfluid.

    PubMed

    Labouvie, Ralf; Santra, Bodhaditya; Heun, Simon; Ott, Herwig

    2016-06-10

    We experimentally study a driven-dissipative Josephson junction array, realized with a weakly interacting Bose-Einstein condensate residing in a one-dimensional optical lattice. Engineered losses on one site act as a local dissipative process, while tunneling from the neighboring sites constitutes the driving force. We characterize the emerging steady states of this atomtronic device. With increasing dissipation strength γ the system crosses from a superfluid state, characterized by a coherent Josephson current into the lossy site, to a resistive state, characterized by an incoherent hopping transport. For intermediate values of γ, the system exhibits bistability, where a superfluid and an incoherent branch coexist. We also study the relaxation dynamics towards the steady state, where we find a critical slowing down, indicating the presence of a nonequilibrium phase transition. PMID:27341243

  18. Turbulence driven particle transport in Texas Helimak

    SciTech Connect

    Toufen, D. L.; Guimaraes-Filho, Z. O.; Marcus, F. A.; Caldas, I. L.; Gentle, K. W.

    2012-01-15

    We analyze the turbulence driven particle transport in Texas Helimak [K. W. Gentle and H. He, Plasma Sci. Technol. 10, 284 (2008)], a toroidal plasma device with a one-dimensional equilibrium with magnetic curvature and shear. Alterations on the radial electric field, through an external voltage bias, change the spectral plasma characteristics inducing a dominant frequency for negative bias values and a broad band frequency spectrum for positive bias values. When applying a negative bias, the transport is high where the waves propagate with phase velocities near the plasma flow velocity, an indication that the transport is strongly affected by a wave particle resonant interaction. On the other hand, for positive bias values, the plasma has a reversed shear flow, and we observe that the transport is almost zero in the shearless radial region, an evidence of a transport barrier in this region.

  19. Microscopic dynamics of synchronization in driven colloids

    PubMed Central

    Juniper, Michael P.N.; Straube, Arthur V.; Besseling, Rut; Aarts, Dirk G.A.L.; Dullens, Roel P.A.

    2015-01-01

    Synchronization of coupled oscillators has been scrutinized for over three centuries, from Huygens' pendulum clocks to physiological rhythms. One such synchronization phenomenon, dynamic mode locking, occurs when naturally oscillating processes are driven by an externally imposed modulation. Typically only averaged or integrated properties are accessible, leaving underlying mechanisms unseen. Here, we visualize the microscopic dynamics underlying mode locking in a colloidal model system, by using particle trajectories to produce phase portraits. Furthermore, we use this approach to examine the enhancement of mode locking in a flexible chain of magnetically coupled particles, which we ascribe to breathing modes caused by mode-locked density waves. Finally, we demonstrate that an emergent density wave in a static colloidal chain mode locks as a quasi-particle, with microscopic dynamics analogous to those seen for a single particle. Our results indicate that understanding the intricate link between emergent behaviour and microscopic dynamics is key to controlling synchronization. PMID:25994921

  20. Thermalization of field driven quantum systems

    PubMed Central

    Fotso, H.; Mikelsons, K.; Freericks, J. K.

    2014-01-01

    There is much interest in how quantum systems thermalize after a sudden change, because unitary evolution should preclude thermalization. The eigenstate thermalization hypothesis resolves this because all observables for quantum states in a small energy window have essentially the same value; it is violated for integrable systems due to the infinite number of conserved quantities. Here, we show that when a system is driven by a DC electric field there are five generic behaviors: (i) monotonic or (ii) oscillatory approach to an infinite-temperature steady state; (iii) monotonic or (iv) oscillatory approach to a nonthermal steady state; or (v) evolution to an oscillatory state. Examining the Hubbard model (which thermalizes under a quench) and the Falicov-Kimball model (which does not), we find both exhibit scenarios (i–iv), while only Hubbard shows scenario (v). This shows richer behavior than in interaction quenches and integrability in the absence of a field plays no role. PMID:24736404

  1. Datasheet Driven Silicon Carbide Power MOSFET Model

    SciTech Connect

    Mudholkar, M; Ahmed, S; Ericson, MN; Frank, SS; Britton, CL; Mantooth, HA

    2014-05-01

    A compact model for SiC Power MOSFETs is presented. The model features a physical description of the channel current and internal capacitances and has been validated for dc, CV, and switching characteristics with measured data from a 1200-V, 20-A SiC power MOSFET in a temperature range of 25 degrees C to 225 degrees C. The peculiar variation of on-state resistance with temperature for SiC power MOSFETs has also been demonstrated through measurements and accounted for in the developed model. In order to improve the user experience with the model, a new datasheet driven parameter extraction strategy has been presented which requires only data available in device datasheets, to enable quick parameter extraction for off-the-shelf devices. Excellent agreement is shown between measurement and simulation using the presented model over the entire temperature range.

  2. Test Driven Development of Scientific Models

    NASA Technical Reports Server (NTRS)

    Clune, Thomas L.

    2014-01-01

    Test-Driven Development (TDD), a software development process that promises many advantages for developer productivity and software reliability, has become widely accepted among professional software engineers. As the name suggests, TDD practitioners alternate between writing short automated tests and producing code that passes those tests. Although this overly simplified description will undoubtedly sound prohibitively burdensome to many uninitiated developers, the advent of powerful unit-testing frameworks greatly reduces the effort required to produce and routinely execute suites of tests. By testimony, many developers find TDD to be addicting after only a few days of exposure, and find it unthinkable to return to previous practices.After a brief overview of the TDD process and my experience in applying the methodology for development activities at Goddard, I will delve more deeply into some of the challenges that are posed by numerical and scientific software as well as tools and implementation approaches that should address those challenges.

  3. Laser-Driven Mini-Thrusters

    NASA Astrophysics Data System (ADS)

    Sterling, Enrique; Lin, Jun; Sinko, John; Kodgis, Lisa; Porter, Simon; Pakhomov, Andrew V.; Larson, C. William; Mead, Franklin B.

    2006-05-01

    Laser-driven mini-thrusters were studied using Delrin® and PVC (Delrin® is a registered trademark of DuPont) as propellants. TEA CO2 laser (λ = 10.6 μm) was used as a driving laser. Coupling coefficients were deduced from two independent techniques: force-time curves measured with a piezoelectric sensor and ballistic pendulum. Time-resolved ICCD images of the expanding plasma and combustion products were analyzed in order to determine the main process that generates the thrust. The measurements were also performed in a nitrogen atmosphere in order to test the combustion effects on thrust. A pinhole transmission experiment was performed for the study of the cut-off time when the ablation/air breakdown plasma becomes opaque to the incoming laser pulse.

  4. Instability in electromagnetically driven flows. II

    NASA Astrophysics Data System (ADS)

    Rodriguez Imazio, Paola; Gissinger, Christophe

    2016-03-01

    In a previous paper, we have reported numerical simulations of the magnetohydrodynamic flow driven by a travelling magnetic field in an annular channel, at low Reynolds number. It was shown that the stalling of such induction pump is strongly related to magnetic flux expulsion. In the present article, we show that for larger hydrodynamic Reynolds number, and with more realistic boundary conditions, this instability takes the form of a large axisymmetric vortex flow in the (r, z)-plane, in which the fluid is locally pumped in the direction opposite to the one of the magnetic field. Close to the marginal stability of this vortex flow, a low-frequency pulsation is generated. Finally, these results are compared to theoretical predictions and are discussed within the framework of experimental annular linear induction electromagnetic pumps.

  5. Arnold diffusion in a driven optical lattice

    NASA Astrophysics Data System (ADS)

    Boretz, Yingyue; Reichl, L. E.

    2016-03-01

    The effect of time-periodic forces on matter has been a topic of growing interest since the advent of lasers. It is known that dynamical systems with 2.5 or more degrees of freedom are intrinsically unstable. As a consequence, time-periodic driven systems can experience large excursions in energy. We analyze the classical and quantum dynamics of rubidium atoms confined to a time-periodic optical lattice with 2.5 degrees of freedom. When the laser polarizations are orthogonal, the system consists of two 1.5 uncoupled dynamical systems. When laser polarizations are turned away from orthogonal, an Arnold web forms and the dynamics undergoes a fundamental change. For parallel polarizations, we find huge random excursions in the rubidium atom energies and significant entanglement of energies in the quantum dynamics.

  6. Mission Success Driven Space System Sparing Analysis

    NASA Technical Reports Server (NTRS)

    Knezevic, J.

    1995-01-01

    Among the maintenance resources, the spare parts are the most difficult to predict. Items in the space systems are very different from the point of view of reliability, cost, weight, volume, etc. The different combinations of spares make different contribution to the: mission success, spare investment, volume occupied and weight. Hence, the selection of spares for a mission planned must take into account all of these features. This paper presents the generic mission success driven sparing model developed, for the complex space systems. The mathematical analysis used in the model enables the user to select the most suitable selection of the spare package for the mission planned. The illustrative examples presented clearly demonstrate the applicability and usefulness of the model introduced.

  7. Instability in electromagnetically driven flows. I

    NASA Astrophysics Data System (ADS)

    Gissinger, Christophe; Rodriguez Imazio, Paola; Fauve, Stephan

    2016-03-01

    The magnetohydrodynamic flow driven by a travelling magnetic field in an annular channel is investigated numerically. For sufficiently large magnetic Reynolds number Rm, or if a large enough pressure gradient is externally applied, the system undergoes an instability in which the flow rate in the channel dramatically drops from synchronism with the wave to much smaller velocities. This transition takes the form of a saddle-node bifurcation for the time-averaged quantities. In this first paper, we characterize the bifurcation and study the stability of the flow as a function of several parameters. We show that the bifurcation of the flow involves a bistability between Poiseuille-like and Hartman-like regimes and relies on magnetic flux expulsion. Based on this observation, new predictions are made for the occurrence of this stalling instability.

  8. Stop motion microphotography of laser driven plates

    SciTech Connect

    Frank, A.M.; Trott, W.M.

    1994-09-01

    Laser driven plates have been used for several years for high velocity shock wave and impact studies. Recent questions about the integrity and ablation rates of these plates coupled with an improved capability for microscopic stop motion photography led to this study. For these experiments, the plates were aluminum, coated on the ends of optical fibers. A high power laser pulse in the fiber ionizes the aluminum at the fiber/coating interface. The plasma thus created accelerates the remaining aluminum to high velocities, several kilometers per second. We defined {open_quotes}thick{close_quotes} or {open_quotes}thin{close_quotes} coatings as those where a flying plate (flyer) was launched vs. the material being completely ionized. Here we were specifically interested in the thick/thin boundary to develop data for the numerical models attempting to predict flyer behavior.

  9. Mechanically driven interface propagation in biological tissues

    NASA Astrophysics Data System (ADS)

    Ranft, Jonas; Aliee, Maryam; Prost, Jacques; Jülicher, Frank; Joanny, Jean-François

    2014-03-01

    Many biological tissues consist of more than one cell type. We study the dynamics of an interface between two different cell populations as it occurs during the growth of a tumor in a healthy host tissue. Recent work suggests that the rates of cell division and cell death are under mechanical control, characterized by a homeostatic pressure. The difference in the homeostatic pressures of two cell types drives the propagation of the interface, corresponding to the invasion of one cell type into the other. We derive a front propagation equation that takes into account the coupling between cell number balance and tissue mechanics. We show that in addition to pulled fronts, pushed-front solutions occur as a result of convection driven by mechanics.

  10. Power-stroke-driven actomyosin contractility

    NASA Astrophysics Data System (ADS)

    Sheshka, R.; Truskinovsky, L.

    2014-01-01

    In ratchet-based models describing actomyosin contraction the activity is usually associated with actin binding potential while the power-stroke mechanism, residing inside myosin heads, is viewed as passive. To show that contraction can be propelled directly through a conformational change, we propose an alternative model where the power stroke is the only active mechanism. The asymmetry, ensuring directional motion, resides in steric interaction between the externally driven power-stroke element and the passive nonpolar actin filament. The proposed model can reproduce all four discrete states of the minimal actomyosin catalytic cycle even though it is formulated in terms of continuous Langevin dynamics. We build a conceptual bridge between processive and nonprocessive molecular motors by demonstrating that not only the former but also the latter can use structural transformation as the main driving force.

  11. Correlations and thermalization in driven cavity arrays

    SciTech Connect

    Dai Li; Angelakis, Dimitris G.; Kwek, Leong Chuan; Mancini, S.

    2011-09-23

    We show that long-distance steady-state quantum correlations (entanglement) between pairs of cavity-atom systems in an array of lossy and driven coupled resonators can be established and controlled. The maximal of entanglement for any pair is achieved when their corresponding direct coupling is much smaller than their individual couplings to the third party. This effect is reminiscent of the coherent trapping of the three-level atoms using two classical coherent fields. Different geometries for coherent control are considered. For finite temperature, the steady state of the coupled lossy atomcavity arrays with driving fields is in general not a thermal state. Using an appropriate distance measure for quantum states, we find that the change rate of the degree of thermalization with respect to the driving strength is consistent with the entanglement of the system.

  12. Laser-Driven Mini-Thrusters

    SciTech Connect

    Sterling, Enrique; Lin Jun; Sinko, John; Kodgis, Lisa; Porter, Simon; Pakhomov, Andrew V.; Larson, C. William; Mead, Franklin B. Jr.

    2006-05-02

    Laser-driven mini-thrusters were studied using Delrin registered and PVC (Delrin registered is a registered trademark of DuPont) as propellants. TEA CO2 laser ({lambda} = 10.6 {mu}m) was used as a driving laser. Coupling coefficients were deduced from two independent techniques: force-time curves measured with a piezoelectric sensor and ballistic pendulum. Time-resolved ICCD images of the expanding plasma and combustion products were analyzed in order to determine the main process that generates the thrust. The measurements were also performed in a nitrogen atmosphere in order to test the combustion effects on thrust. A pinhole transmission experiment was performed for the study of the cut-off time when the ablation/air breakdown plasma becomes opaque to the incoming laser pulse.

  13. Circuit Model for Gun Driven Spheromaks

    SciTech Connect

    Thomassen, K I

    2000-07-14

    In this note we derive circuit equations for sustained spheromaks, in the phase after a spheromak is detached from the gun and sustained in a flux conserver. The impedance of the spheromak during the formation and ''bubble burst'' phase has been discussed by Barnes et. al. We assume here that the spheromak is formed and helicity is being delivered to it from the gun, currents are above the threshold current, and the {lambda}-gradients are outward ({lambda} decreasing inward). We follow an open field line that begins and ends at the gun electrodes, encircling the closed flux surfaces of the spheromak, and apply power and helicity balance equations for this gun-driven system. In addition to these equations one will need to know the initial conditions (currents, stored energies) after the ''bubble burst'' in order to project forward in time.

  14. Wind-driven circulation in Titan's seas

    NASA Astrophysics Data System (ADS)

    Tokano, Tetsuya; Lorenz, Ralph D.

    2015-01-01

    Circulation in Titan's seas forced by wind is simulated by an ocean circulation model using surface wind data predicted by a global circulation model. Wind-driven circulation is insignificant throughout much of the annual cycle but becomes significant from late spring to late summer, when the wind stress becomes strong. The large-scale circulation in summer is predominantly southward near the sea surface and northward near the sea bottom. The sea surface current can get as fast as 5 cms-1 in some areas. Titan's rotation affects the vertical structure of sea currents in the form of an Ekman spiral if the wind is strong. The maximum wind setup at the shores is of the same order of magnitude as the tidal range. Wind stirring may reduce thermal stratification in summer but may be unable to destroy stratification of methane-rich liquids on top of ethane-rich liquids that can result from imbalances between evaporation and precipitation.

  15. Wind-driven circulation in Titan's seas

    NASA Astrophysics Data System (ADS)

    Tokano, Tetsuya; Lorenz, Ralph D.

    2015-04-01

    Circulation in Titan's seas forced by wind is simulated by an ocean circulation model using surface wind data predicted by a global circulation model. Wind-driven circulation is insignificant throughout much of the annual cycle, but becomes significant from late spring to late summer, when the wind stress becomes strong. The large-scale circulation in summer is predominantly southward near the sea surface and northward near the sea bottom. The sea surface current can get as fast as 5 cms-1 in some areas. Titan's rotation affects the vertical structure of sea currents in the form of an Ekman spiral if the wind is strong. The maximum wind set-up at the shores is of the same order of magnitude as the tidal range. Wind stirring may reduce thermal stratification in summer, but may be unable to destroy stratification of methane-rich liquids on top of ethane-rich liquids that can result from imbalances between evaporation and precipitation.

  16. Photon scattering from strongly driven atomic ensembles

    SciTech Connect

    Jin Luling; Evers, Joerg; Macovei, Mihai

    2011-10-15

    The second-order correlation function for light emitted from a strongly and near-resonantly driven dilute cloud of atoms is discussed. Because of the strong driving, the fluorescence spectrum separates into distinct peaks, for which the spectral properties can be defined individually. It is shown that the second-order correlations for various combinations of photons from different spectral lines exhibit bunching together with super-Poissonian or sub-Poissonian photon statistics, tunable by the choice of the detector positions. Additionally, a Cauchy-Schwarz inequality is violated for photons emitted from particular spectral bands. The emitted light intensity is proportional to the square of the number of particles, and thus can potentially be intense. Three different averaging procedures to model ensemble disorder are compared.

  17. Dynamics of antiferromagnets driven by spin current

    NASA Astrophysics Data System (ADS)

    Cheng, Ran; Niu, Qian

    2014-02-01

    When a spin-polarized current flows through a ferromagnetic (FM) metal, angular momentum is transferred to the background magnetization via spin-transfer torques. In antiferromagnetic (AFM) materials, however, the corresponding problem is unsolved. We derive microscopically the dynamics of an AFM system driven by spin current generated by an attached FM polarizer, and find that the spin current exerts a driving force on the local staggered order parameter. The mechanism does not rely on the conservation of spin angular momentum, nor does it depend on the induced FM moments on top the AFM background. Two examples are studied: (i) A domain wall is accelerated to a terminal velocity by purely adiabatic effect where the Walker's breakdown is avoided. (ii) Spin injection modifies the AFM resonance frequency, and spin current injection triggers spin wave instability of local moments above a threshold.

  18. Arc-driven rail gun research

    NASA Technical Reports Server (NTRS)

    Ray, P. K.

    1984-01-01

    The equations describing the performance of an inductively-driven rail gun are analyzed numerically. Friction between the projectile and rails is included through an empirical formulation. The equations are applied to the experiment of Rashleigh and Marshall to obtain an estimate of energy distribution in rail guns as a function of time. The effect of frictional heat dissipation on the bore of the gun is calculated. The mechanism of plasma and projectile acceleration in a dc rail gun is described from a microscopic point of view through the establishment of the Hall field. The plasma conductivity is shown to be a tensor indicating that there is a small component of current parallel to the direction of acceleration. The plasma characteristics are evaluated as a function of plasma mass through a simple fluid mechanical analysis of the plasma. By equating the energy dissipated in the plasma with the radiation heat loss, the properties of the plasma are determined.

  19. OMOGENIA: A Semantically Driven Collaborative Environment

    NASA Astrophysics Data System (ADS)

    Liapis, Aggelos

    Ontology creation can be thought of as a social procedure. Indeed the concepts involved in general need to be elicited from communities of domain experts and end-users by teams of knowledge engineers. Many problems in ontology creation appear to resemble certain problems in software design, particularly with respect to the setup of collaborative systems. For instance, the resolution of conceptual conflicts between formalized ontologies is a major engineering problem as ontologies move into widespread use on the semantic web. Such conflict resolution often requires human collaboration and cannot be achieved by automated methods with the exception of simple cases. In this chapter we discuss research in the field of computer-supported cooperative work (CSCW) that focuses on classification and which throws light on ontology building. Furthermore, we present a semantically driven collaborative environment called OMOGENIA as a natural way to display and examine the structure of an evolving ontology in a collaborative setting.

  20. Power absorption in acoustically driven ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Labanowski, D.; Jung, A.; Salahuddin, S.

    2016-01-01

    Surface acoustic waves (SAWs) have recently been used to drive ferromagnetic resonance by exploiting the coupling between strain and magnetization in magnetostrictive materials in a technique called acoustically driven ferromagnetic resonance (ADFMR). In this work, we quantitatively examine the power absorbed by the magnetic elements in such systems. We find that power absorption scales exponentially with the length of the magnetic element in the direction of SAW propagation, with the rate of scaling set by the thickness of magnetic material. In addition, we find that ADFMR behaves consistently across a wide range of input power values (>65 dB). Our results indicate that devices such as filters, oscillators, and sensors can be designed that operate with very low power, yet provide high tunability.

  1. Edge convection driven by externally applied potentials

    SciTech Connect

    D'Ippolito, D. A.; Myra, J. R.

    2000-08-01

    A theoretical model of convection in collisional tokamak edge and scrape-off-layer plasmas is described. In the linear theory, any mechanism for poloidal and toroidal symmetry breaking of the equilibrium will drive ExB flows; this result stems from the parallel thermal and pressure forces in Ohm's law. In the nonlinear theory, the quadratic coupling of the perturbations leads to quasilinear-type fluxes in the vorticity, density, and temperature equations. If the convection is strong enough, these fluxes lead to an ambipolarity constraint on the equilibrium electric field and to increased transport of particles and energy. The theory shows qualitative agreement with some tokamak experiments in which potential perturbations are externally driven by radio frequency antennas. (c) 2000 American Institute of Physics.

  2. Measures of intermittency in driven supersonic flows

    NASA Astrophysics Data System (ADS)

    Porter, D.; Pouquet, A.; Woodward, P.

    2002-08-01

    Scaling exponents for structure functions of the velocity, density, and entropy are computed for driven supersonic flows for rms Mach numbers of order unity, with numerical simulations using the piecewise parabolic method algorithm on grids of up to 5123 points. The driving is made up of either one or three orthogonal shear waves. In all cases studied, the compressible component of the velocity in the statistically steady regime is weaker than its solenoidal counterpart by roughly a factor of 6. Exponents for the longitudinal component of the velocity are comparable to what is found in the incompressible case and appear insensitive to the presence of numerous shocks. Scaling exponents of the transverse components of the velocity are comparable to those for the longitudinal component. Density and entropy structure functions display strong departures from linear scaling. Finally, the scaling of structure functions of the energy transfer is also given and compared with the Kolmogorov refined similarity hypothesis.

  3. Arnold diffusion in a driven optical lattice.

    PubMed

    Boretz, Yingyue; Reichl, L E

    2016-03-01

    The effect of time-periodic forces on matter has been a topic of growing interest since the advent of lasers. It is known that dynamical systems with 2.5 or more degrees of freedom are intrinsically unstable. As a consequence, time-periodic driven systems can experience large excursions in energy. We analyze the classical and quantum dynamics of rubidium atoms confined to a time-periodic optical lattice with 2.5 degrees of freedom. When the laser polarizations are orthogonal, the system consists of two 1.5 uncoupled dynamical systems. When laser polarizations are turned away from orthogonal, an Arnold web forms and the dynamics undergoes a fundamental change. For parallel polarizations, we find huge random excursions in the rubidium atom energies and significant entanglement of energies in the quantum dynamics. PMID:27078351

  4. Query driven visualization of astronomical catalogs

    NASA Astrophysics Data System (ADS)

    Buddelmeijer, Hugo; Valentijn, Edwin A.

    2013-01-01

    Interactive visualization of astronomical catalogs requires novel techniques due to the huge volumes and complex structure of the data produced by existing and upcoming astronomical surveys. The creation as well as the disclosure of the catalogs can be handled by data pulling mechanisms (Buddelmeijer et al. 2011). These prevent unnecessary processing and facilitate data sharing by having users request the desired end products. In this work we present query driven visualization as a logical continuation of data pulling. Scientists can request catalogs in a declarative way and set process parameters directly from within the visualization. This results in profound interoperation between software with a high level of abstraction. New messages for the Simple Application Messaging Protocol are proposed to achieve this abstraction. Support for these messages are implemented in the Astro-WISE information system and in a set of demonstrational applications.

  5. Modeling of an Implosion Driven Hypervelocity Launcher

    NASA Astrophysics Data System (ADS)

    Loiseau, Jason; Higgins, Andrew; Szirti, Daniel; Batchelor, Patrick; Zhang, Fan; Tanguay, Vincent

    2007-06-01

    Modelling work carried out on the implosion driven launcher under concurrent development is presented. The launcher consists of a thin walled metal tube surrounded by explosive which when detonated pinches the tube shut and drives a strong shock into the projectile. The commercial hydrocode LS-DYNA was used to quantitatively and qualitatively evaluate the design parameters of the launcher and their effect on implosion dynamics and performance. These parameters include fill pressure, tube diameter, explosive layer thickness, and explosives tampering. The launcher is primarily modeled using a quasi 2D Arbitrary Langrage Euler formulation. A full 3-D axisymmetric model is also employed. The model is evaluated against experimental data previously collected. Additional developmental work on a second stage launcher taking advantage of a phase velocity between the imploding tube and explosives via the use of angled flyer plates and cones is also carried out.

  6. Microscopic dynamics of synchronization in driven colloids.

    PubMed

    Juniper, Michael P N; Straube, Arthur V; Besseling, Rut; Aarts, Dirk G A L; Dullens, Roel P A

    2015-01-01

    Synchronization of coupled oscillators has been scrutinized for over three centuries, from Huygens' pendulum clocks to physiological rhythms. One such synchronization phenomenon, dynamic mode locking, occurs when naturally oscillating processes are driven by an externally imposed modulation. Typically only averaged or integrated properties are accessible, leaving underlying mechanisms unseen. Here, we visualize the microscopic dynamics underlying mode locking in a colloidal model system, by using particle trajectories to produce phase portraits. Furthermore, we use this approach to examine the enhancement of mode locking in a flexible chain of magnetically coupled particles, which we ascribe to breathing modes caused by mode-locked density waves. Finally, we demonstrate that an emergent density wave in a static colloidal chain mode locks as a quasi-particle, with microscopic dynamics analogous to those seen for a single particle. Our results indicate that understanding the intricate link between emergent behaviour and microscopic dynamics is key to controlling synchronization. PMID:25994921

  7. Science Goal Driven Observing and Spacecraft Autonomy

    NASA Technical Reports Server (NTRS)

    Jones, Jeremy; Grosvenor, Sandy; Korathkar, Anuradha; Memarsadeghi, Nargess; Wolf, Karl; Obenschain, Arthur F. (Technical Monitor)

    2002-01-01

    Spacecraft autonomy will be an integral part of mission operations in the coming decade. While recent missions have made great strides in the ability to autonomously monitor and react to changing health and physical status of spacecraft, little progress has been made in responding quickly to science driven events. For observations of inherently variable targets and targets of opportunity, the ability to recognize early if an observation will meet the science goals of a program, and react accordingly, can have a major positive impact on the overall scientific returns of an observatory and on its operational costs. If the onboard software can reprioritize the schedule to focus on alternate targets, discard uninteresting observations prior to downloading, or download a subset of observations at a reduced resolution, the spacecraft's overall efficiency will be dramatically increased. The science goal monitoring (SGM) system is a proof- of-concept effort to address the above challenge. The SGM will have an interface to help capture higher-level science goals from the scientists and translate them into a flexible observing strategy that SGM can execute and monitor. We are developing an interactive distributed system that will use on-board processing and storage combined with event-driven interfaces with ground-based processing and operations, to enable fast re-prioritization of observing schedules, and to minimize time spent on non-optimized observations. This paper will focus on our strategy for developing SGM and the technical challenges that we have encountered. We will discuss the SGM architecture as it applies to the proposed MIDEX-class mission Kronos. However, the architecture and interfaces will also be designed for easy adaptability to other observing platforms, including ground-based systems and to work with different scheduling and pipeline processing systems.

  8. Magnetically driven accretion in protoplanetary discs

    NASA Astrophysics Data System (ADS)

    Simon, Jacob B.; Lesur, Geoffroy; Kunz, Matthew W.; Armitage, Philip J.

    2015-11-01

    We characterize magnetically driven accretion at radii between 1 and 100 au in protoplanetary discs, using a series of local non-ideal magnetohydrodynamic (MHD) simulations. The simulations assume a minimum mass solar nebula (MMSN) disc that is threaded by a net vertical magnetic field of specified strength. Confirming previous results, we find that the Hall effect has only a modest impact on accretion at 30 au, and essentially none at 100 au. At 1-10 au the Hall effect introduces a pronounced bimodality in the accretion process, with vertical magnetic fields aligned to the disc rotation supporting a strong laminar Maxwell stress that is absent if the field is anti-aligned. In the anti-aligned case, we instead find evidence for bursts of turbulent stress at 5-10 au, which we tentatively identify with the non-axisymmetric Hall-shear instability. The presence or absence of these bursts depends upon the details of the adopted chemical model, which suggests that appreciable regions of actual protoplanetary discs might lie close to the borderline between laminar and turbulent behaviour. Given the number of important control parameters that have already been identified in MHD models, quantitative predictions for disc structure in terms of only radius and accretion rate appear to be difficult. Instead, we identify robust qualitative tests of magnetically driven accretion. These include the presence of turbulence in the outer disc, independent of the orientation of the vertical magnetic fields, and a Hall-mediated bimodality in turbulent properties extending from the region of thermal ionization to 10 au.

  9. Integrated Nucleosynthesis in Neutrino Driven Winds

    SciTech Connect

    Roberts, L F; Woosley, S E; Hoffman, R D

    2010-03-26

    Although they are but a small fraction of the mass ejected in core-collapse supernovae, neutrino-driven winds (NDWs) from nascent proto-neutron stars (PNSs) have the potential to contribute significantly to supernova nucleosynthesis. In previous works, the NDW has been implicated as a possible source of r-process and light p-process isotopes. In this paper we present time-dependent hydrodynamic calculations of nucleosynthesis in the NDW which include accurate weak interaction physics coupled to a full nuclear reaction network. Using two published models of PNS neutrino luminosities, we predict the contribution of the NDW to the integrated nucleosynthetic yield of the entire supernova. For the neutrino luminosity histories considered, no true r-process occurs in the most basic scenario. The wind driven from an older 1.4M{sub {circle_dot}} model for a PNS is moderately neutron-rich at late times however, and produces {sup 87}Rb, {sup 88}Sr, {sup 89}Y, and {sup 90}Zr in near solar proportions relative to oxygen. The wind from a more recently studied 1.27M{sub {circle_dot}} PNS is proton-rich throughout its entire evolution and does not contribute significantly to the abundance of any element. It thus seems very unlikely that the simplest model of the NDW can produce the r-process. At most, it contributes to the production of the N = 50 closed shell elements and some light p-nuclei. In doing so, it may have left a distinctive signature on the abundances in metal poor stars, but the results are sensitive to both uncertain models for the explosion and the masses of the neutron stars involved.

  10. Failure-probability driven dose painting

    SciTech Connect

    Vogelius, Ivan R.; Håkansson, Katrin; Due, Anne K.; Aznar, Marianne C.; Kristensen, Claus A.; Rasmussen, Jacob; Specht, Lena; Berthelsen, Anne K.; Bentzen, Søren M.

    2013-08-15

    Purpose: To demonstrate a data-driven dose-painting strategy based on the spatial distribution of recurrences in previously treated patients. The result is a quantitative way to define a dose prescription function, optimizing the predicted local control at constant treatment intensity. A dose planning study using the optimized dose prescription in 20 patients is performed.Methods: Patients treated at our center have five tumor subvolumes from the center of the tumor (PET positive volume) and out delineated. The spatial distribution of 48 failures in patients with complete clinical response after (chemo)radiation is used to derive a model for tumor control probability (TCP). The total TCP is fixed to the clinically observed 70% actuarial TCP at five years. Additionally, the authors match the distribution of failures between the five subvolumes to the observed distribution. The steepness of the dose–response is extracted from the literature and the authors assume 30% and 20% risk of subclinical involvement in the elective volumes. The result is a five-compartment dose response model matching the observed distribution of failures. The model is used to optimize the distribution of dose in individual patients, while keeping the treatment intensity constant and the maximum prescribed dose below 85 Gy.Results: The vast majority of failures occur centrally despite the small volumes of the central regions. Thus, optimizing the dose prescription yields higher doses to the central target volumes and lower doses to the elective volumes. The dose planning study shows that the modified prescription is clinically feasible. The optimized TCP is 89% (range: 82%–91%) as compared to the observed TCP of 70%.Conclusions: The observed distribution of locoregional failures was used to derive an objective, data-driven dose prescription function. The optimized dose is predicted to result in a substantial increase in local control without increasing the predicted risk of toxicity.

  11. Integrated Nucleosynthesis in Neutrino-driven Winds

    NASA Astrophysics Data System (ADS)

    Roberts, L. F.; Woosley, S. E.; Hoffman, R. D.

    2010-10-01

    Although they are but a small fraction of the mass ejected in core-collapse supernovae, neutrino-driven winds (NDWs) from nascent proto-neutron stars (PNSs) have the potential to contribute significantly to supernova nucleosynthesis. In previous works, the NDW has been implicated as a possible source of r-process and light p-process isotopes. In this paper, we present time-dependent hydrodynamic calculations of nucleosynthesis in the NDW which include accurate weak interaction physics coupled to a full nuclear reaction network. Using two published models of PNS neutrino luminosities, we predict the contribution of the NDW to the integrated nucleosynthetic yield of the entire supernova. For the neutrino luminosity histories considered, no true r-process occurs in the most basic scenario. The wind driven from an older 1.4 M sun model for a PNS is moderately neutron-rich at late times however, and produces 87Rb, 88Sr, 89Y, and 90Zr in near solar proportions relative to oxygen. The wind from a more recently studied 1.27 M sun PNS is proton-rich throughout its entire evolution and does not contribute significantly to the abundance of any element. It thus seems very unlikely that the simplest model of the NDW can produce the r-process. At most, it contributes to the production of the N = 50 closed shell elements and some light p-nuclei. In doing so, it may have left a distinctive signature on the abundances in metal-poor stars, but the results are sensitive to both uncertain models for the explosion and the masses of the neutron stars involved.

  12. Gyrokinetic simulation of current-driven instabilities

    NASA Astrophysics Data System (ADS)

    McClenaghan, Joseph

    The gyrokinetic toroidal code(GTC) capability has been extended for simulating current-driven instabilities in magnetized plasmas such as kink and resistive tearing modes with kinetic effects. This new gyrokinetic capability enables first-principles, integrated simulations of macroscopic magnetohydrodynamic(MHD) modes, which limit the performance of burning plasmas and threaten the integrity of fusion devices. The excitation and evolution of macroscopic MHD modes often depend on the kinetic effects at microscopic scales and the nonlinear coupling of multiple physical processes. GTC simulation in the fluid limit of the internal kink modes in cylindrical geometry has been verified by benchmarking with an MHD eigenvalue code. The global simulation domain covers the magnetic axis which is necessary for simulating the macroscopic MHD modes. Gyrokinetic simulations of the internal kink modes in the toroidal geometry find that ion kinetic effects significantly reduce the growth rate even when the banana orbit width is much smaller than the radial width of the perturbed current layer at the mode rational surface. This new GTC capability for current-driven instability has now been extended to simulate fishbone instabilities excited by energetic particles and resistive tearing modes. GTC has also been applied to study the internal kink modes in astrophysical jets that are formed around supermassive black holes. Linear simulations find that the internal kink modes in astrophysical jets are unstable with a broad eigenmode. Nonlinear saturation amplitude of these kink modes is observed to be small, suggesting that the jets can remain collimated even in the presence of the internal kink modes. Generation of a mean parallel electric field by the nonlinear dynamics of internal kink modes and the potential implication of this field on particle acceleration in jets has been examined.

  13. Scaling up nanoscale water-driven energy conversion into evaporation-driven engines and generators

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Goodnight, Davis; Gao, Zhenghan; Cavusoglu, Ahmet H.; Sabharwal, Nina; Delay, Michael; Driks, Adam; Sahin, Ozgur

    2015-06-01

    Evaporation is a ubiquitous phenomenon in the natural environment and a dominant form of energy transfer in the Earth's climate. Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world. Here, we report evaporation-driven engines that can power common tasks like locomotion and electricity generation. These engines start and run autonomously when placed at air-water interfaces. They generate rotary and piston-like linear motion using specially designed, biologically based artificial muscles responsive to moisture fluctuations. Using these engines, we demonstrate an electricity generator that rests on water while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1 kg) that moves forward as the water in the car evaporates. Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment.

  14. Current-driven plasma acceleration versus current-driven energy dissipation. I - Wave stability theory

    NASA Technical Reports Server (NTRS)

    Kelly, A. J.; Jahn, R. G.; Choueiri, E. Y.

    1990-01-01

    The dominant unstable electrostatic wave modes of an electromagnetically accelerated plasma are investigated. The study is the first part of a three-phase program aimed at characterizing the current-driven turbulent dissipation degrading the efficiency of Lorentz force plasma accelerators such as the MPD thruster. The analysis uses a kinetic theory that includes magnetic and thermal effects as well as those of an electron current transverse to the magnetic field and collisions, thus combining all the features of previous models. Analytical and numerical solutions allow a detailed description of threshold criteria, finite growth behavior, destabilization mechanisms and maximized-growth characteristics of the dominant unstable modes. The lower hybrid current-driven instability is implicated as dominant and was found to preserve its character in the collisional plasma regime.

  15. Scaling up nanoscale water-driven energy conversion into evaporation-driven engines and generators.

    PubMed

    Chen, Xi; Goodnight, Davis; Gao, Zhenghan; Cavusoglu, Ahmet H; Sabharwal, Nina; DeLay, Michael; Driks, Adam; Sahin, Ozgur

    2015-01-01

    Evaporation is a ubiquitous phenomenon in the natural environment and a dominant form of energy transfer in the Earth's climate. Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world. Here, we report evaporation-driven engines that can power common tasks like locomotion and electricity generation. These engines start and run autonomously when placed at air-water interfaces. They generate rotary and piston-like linear motion using specially designed, biologically based artificial muscles responsive to moisture fluctuations. Using these engines, we demonstrate an electricity generator that rests on water while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1 kg) that moves forward as the water in the car evaporates. Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment. PMID:26079632

  16. Scaling up nanoscale water-driven energy conversion into evaporation-driven engines and generators

    PubMed Central

    Chen, Xi; Goodnight, Davis; Gao, Zhenghan; Cavusoglu, Ahmet H.; Sabharwal, Nina; DeLay, Michael; Driks, Adam; Sahin, Ozgur

    2015-01-01

    Evaporation is a ubiquitous phenomenon in the natural environment and a dominant form of energy transfer in the Earth's climate. Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world. Here, we report evaporation-driven engines that can power common tasks like locomotion and electricity generation. These engines start and run autonomously when placed at air–water interfaces. They generate rotary and piston-like linear motion using specially designed, biologically based artificial muscles responsive to moisture fluctuations. Using these engines, we demonstrate an electricity generator that rests on water while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1 kg) that moves forward as the water in the car evaporates. Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment. PMID:26079632

  17. Family Ethnic Socialization and Ethnic Identity: A Family-Driven, Youth-Driven, or Reciprocal Process?

    PubMed Central

    Umaña-Taylor, Adriana J.; Zeiders, Katharine H.; Updegraff, Kimberly A.

    2013-01-01

    The current study examined the longitudinal associations between family ethnic socialization and youths’ ethnic identity among a sample of Mexican-origin youth (N = 178, Mage = 18.17, SD = .46). Findings from multiple-group cross lagged panel models over a two year period indicated that for U.S.-born youth with immigrant parents, the process appeared to be family-driven: Youths’ perceptions of family ethnic socialization in late adolescence were associated with significantly greater ethnic identity exploration and resolution in emerging adulthood, while youths’ ethnic identity during late adolescence did not significantly predict youths’ future perceptions of family ethnic socialization. Conversely, for U.S.-born youth with U.S. born parents, youths’ ethnic identity significantly predicted their future perceptions of family ethnic socialization but perceptions of family ethnic socialization did not predict future levels of youths’ ethnic identity, suggesting a youth-driven process. Findings were consistent for males and females. PMID:23421841

  18. Differentiating between marketing-driven and technology-driven vendors of medical information systems.

    PubMed

    Friedman, B A; Mitchell, W; Singh, K

    1994-08-01

    Buyers of medical information systems such as laboratory information systems need to recognize that the vendors of such systems may pursue corporate strategies emphasizing expenditures on marketing and client services, expenditures on technology and research and development (R&D), or a more balanced approach. The strategic goals and objectives of a vendor of an information system should align closely with those of a potential hospital client. A restless hospital client seeking cutting-edge technology will probably be dissatisfied with a system vendor who emphasizes slow ongoing incremental system development. Objective criteria for distinguishing between a marketing-driven vendor and a technology-driven vendor of medical information systems, and their variants, are presented based on the ratio of marketing expenditures to sales revenue compared with the ratio of research and development expenditures to sales revenue of the company. More subjective narrative criteria are also offered for making such distinctions. PMID:8060224

  19. Respondent-Driven Sampling in Participatory Research Contexts: Participant-Driven Recruitment

    PubMed Central

    2006-01-01

    This article reports on the use of respondent-driven sampling (RDS) in participatory and community-based research. Participant-driven recruitment (PDR) retains all of the analytic capabilities of RDS while enhancing the role of respondents in framing research questions, instrument development, data interpretation, and other aspects of the research process. Merging the capabilities of RDS with participatory research methods, PDR creates new opportunities for engaging community members in research addressing social issues and in utilizing research findings within community contexts. This article outlines PDR’s synthesis of RDS and participatory research approaches, describes how PDR is implemented in community contexts, and provides two examples of the use of PDR, illustrating its process, potentials, and challenges. PMID:16933100

  20. A comparison of wake measurements in motor-driven and flow-driven turbine experiments

    NASA Astrophysics Data System (ADS)

    Araya, Daniel B.; Dabiri, John O.

    2015-07-01

    We present experimental data to compare and contrast the wake characteristics of a turbine whose rotation is either driven by the oncoming flow or prescribed by a motor. Velocity measurements are collected using two-dimensional particle image velocimetry in the near-wake region of a lift-based, vertical-axis turbine. The wake of this turbine is characterized by a spanwise asymmetric velocity profile which is found to be strongly dependent on the turbine tip speed ratio (TSR), while only weakly dependent on Reynolds number ( Re). For a given Re, the TSR is controlled either passively by a mechanical brake or actively by a DC motor. We find that there exists a finite region in TSR versus Re space where the wakes of the motor-driven turbine and flow-driven turbine are indistinguishable to within experimental precision. Outside of this region, the sign of the net circulation in the wake changes as TSR is increased by the motor. Shaft torque measurements show a corresponding sign change above this TSR threshold set by circulation, indicating a transition from net torque due to lift to net torque due to drag produced by the turbine blades, the latter of which can give wake measurements that are inconsistent with a flow-driven turbine. The results support the claim that the turbine kinematics and aerodynamic properties are the sole factors that govern the dynamics of its wake, irrespective of the means to move the turbine blades. This has significance for both experimental and computational studies where it may be necessary, or perhaps more economical, to prescribe the turbine kinematics in order to analyze its aerodynamic characteristics.

  1. The differences between storms driven by helmet streamer CIRs and storms driven by pseudostreamer CIRs

    NASA Astrophysics Data System (ADS)

    Borovsky, Joseph E.; Denton, Michael H.

    2013-09-01

    A corotating interaction region (CIR) is formed when fast coronal hole origin solar wind overtakes slow solar wind and forms a region of compressed plasma and magnetic field. The slow wind upstream of the coronal hole fast wind can be either of helmet streamer origin or pseudostreamer origin. For a collection of 125 CIR-driven geomagnetic storms, the slow wind ahead of each CIR is examined; for those storm not containing ejecta, each CIR is categorized as a helmet streamer CIR (74 of the 125 storms) or a pseudostreamer CIR (11 of the 125 storms). Separate superposed epoch studies are performed on the two groups to discern the differences between storms driven by pseudostreamer CIRs and those driven by helmet streamer CIRs. A major difference is that pseudostreamer CIR storms tend not to have a calm before the storm, so the outer plasmasphere does not refill before storm onset, and the outer electron radiation belt does not exhibit a pre-storm decay. The superdense plasma sheet is weaker for pseudostreamer CIR storms, and the dropout of the electron radiation belt is weaker. Pseudostreamer CIR storms and helmet streamer CIR storms tend to be of the same strength as measured by the magnitude of Kp, MBI (midnight boundary index), or Dst.

  2. Demonstration of a Balloon Borne Arc-second Pointer Design

    NASA Astrophysics Data System (ADS)

    Deweese, K.; Ward, P.

    Many designs for utilizing stratospheric balloons as low-cost platforms on which to conduct space science experiments have been proposed throughout the years A major hurdle in extending the range of experiments for which these vehicles are useful has been the imposition of the gondola dynamics on the accuracy with which an instrument can be kept pointed at a celestial target A significant number of scientists have sought the ability to point their instruments with jitter in the arc-second range This paper presents the design and analysis of a stratospheric balloon borne pointing system that is able to meet this requirement The test results of a demonstration prototype of the design with similar ability are also presented Discussion of a high fidelity controller simulation for design analysis is presented The flexibility of the flight train is represented through generalized modal analysis A multiple controller scheme is utilized for coarse and fine pointing Coarse azimuth pointing is accomplished by an established pointing system with extensive flight history residing above the gondola structure A pitch-yaw gimbal mount is used for fine pointing providing orthogonal axes when nominally on target Fine pointing actuation is from direct drive dc motors eliminating backlash problems An analysis of friction nonlinearities and a demonstration of the necessity in eliminating static friction are provided A unique bearing hub design is introduced that eliminates static friction from the system dynamics A control scheme involving linear

  3. Why Am I Learning Evolution? Pointers towards Enacted Scientific Literacy

    ERIC Educational Resources Information Center

    Olander, Clas

    2013-01-01

    This paper explores affordances in teaching evolution, especially those in which evolution is made relevant to and argued for in a grade 9 biology classroom, thus giving potential answers to the pupils' legitimate question,"'why am I learning evolution?" The aim of the paper is methodological in the sense that it explores…

  4. Automatic Tie Pointer for In-Situ Pointing Correction

    NASA Technical Reports Server (NTRS)

    Deen, Robert G/

    2011-01-01

    The MARSAUTOTIE program generates tie points for use with the Mars pointing correction software "In-Situ Pointing Correction and Rover Microlocalization," (NPO-46696) Soft ware Tech Briefs, Vol. 34, No. 9 (September 2010), page 18, in a completely automated manner, with no operator intervention. It takes the place of MARSTIE, although MARSTIE can be used to interactively edit the tie points afterwards. These tie points are used to create a mosaic whose seams (boundaries of input images) have been geometrically corrected to reduce or eliminate errors and mis-registrations. The methods used to find appropriate tie points for use in creating a mosaic are unique, having been designed to work in concert with the "MARSNAV" program to be most effective in reducing or eliminating geometric seams in a mosaic. The program takes the input images and finds overlaps according to the nominal pointing. It then finds the most interesting areas using a scene activity metric. Points with higher scene activity are more likely to correlate successfully in the next step. It then uses correlation techniques to find matching points in the overlapped image. Finally, it performs a series of steps to reduce the number of tie points to a manageable level. These steps incorporate a number of heuristics that have been devised using experience gathered by tie pointing mosaics manually during MER operations. The software makes use of the PIG library as described in "Planetary Image Geometry Library" (NPO-46658), NASA Tech Briefs, Vol. 34, No. 12 (December 2010), page 30, so it is multi-mission, applicable without change to any in-situ mission supported by PIG. The MARSAUTOTIE algorithm is automated, so it requires no user intervention. Although at the time of this reporting it has not been done, this program should be suitable for integration into a fully automated mosaic production pipeline.

  5. Balloon Borne Arc-Second Pointer Feasibility Study

    NASA Technical Reports Server (NTRS)

    Ward, Philip R.; DeWeese, Keith D.

    2003-01-01

    For many years scientists have been utilizing stratospheric balloons as low-cost platforms on which to conduct space science experiments. A major hurdle in extending the range of experiments for which these vehicles are useful has been the imposition of the gondola dynamics on the accuracy with which an instrument can be kept pointed at a celestial target. A significant number of scientists have sought the ability to point their instruments with jitter in the arc-second range. This paper presents the design and analysis of a stratospheric balloon borne pointing system that is able to meet this requirement. The foundation for a high fidelity controller simulation is presented. The flexibility of the flight train is represented through generalized modal analysis. A multiple controller scheme is introduced for coarse and fine pointing. Coarse azimuth pointing is accomplished by an established pointing system, with extensive flight history, residing above the gondola structure. A pitch-yaw gimbal mount is used for fine pointing, providing orthogonal axes when nominally on target. Fine pointing actuation is from direct drive dc motors, eliminating backlash problems. An analysis of friction nonlinearities and a demonstration of the necessity in eliminating static fiction are provided. A unique bearing hub design is introduced that eliminates static fiction from the system dynamics. A control scheme involving linear accelerometers for enhanced disturbance rejection is also presented. Results from a linear analysis of the total system and the high fidelity simulation are given. This paper establishes that the proposed control strategy can be made robustly stable with significant design margins. Also demonstrated is the efficacy of the proposed system in rejecting disturbances larger than those considered realistic. Finally, we see that sub arc-second pointing stability can be achieved for a large instrument pointing at an inertial target.

  6. Design of a terminal pointer hand controller for teleoperator applications

    NASA Technical Reports Server (NTRS)

    Saenger, E. L.; Woltosz, W. S.

    1973-01-01

    The design is described of a hand controller intended to achieve the highest possible compatibility with the hand of the human operator in a teleoperator system. Concepts drawings and model development are discussed along with the development of a prototype, and the mathematical control laws.

  7. School Construction and Technology...A Few Important Pointers.

    ERIC Educational Resources Information Center

    Griffin, Richard A.; Fowler, Laura S.

    2001-01-01

    The most overlooked facet of school construction is the dovetailing of permanent construction insurance and technology construction insurance. Advice is provided about technology and technology purchases, highlighting problems associated with costs, copyright infringements, delivery delays, electrical wiring, hardware, student records, vendors,…

  8. Concepts as Semantic Pointers: A Framework and Computational Model

    ERIC Educational Resources Information Center

    Blouw, Peter; Solodkin, Eugene; Thagard, Paul; Eliasmith, Chris

    2016-01-01

    The reconciliation of theories of concepts based on prototypes, exemplars, and theory-like structures is a longstanding problem in cognitive science. In response to this problem, researchers have recently tended to adopt either hybrid theories that combine various kinds of representational structure, or eliminative theories that replace concepts…

  9. Living Conditions of Some Basic School Children: Pointers to Disadvantage.

    ERIC Educational Resources Information Center

    Grant, D. R. B.

    This study, conducted by the Bernard Van Leer Foundation Project for Early Childhood Education (PECE), presents the results of a survey which was carried out to identify home deficits in socioeconomically disadvantaged children's preparation for schooling. The study was conducted in Jamaica during July, August, and September, 1970, and was…

  10. Play and Recreation for Individuals with Disabilities: Practical Pointers.

    ERIC Educational Resources Information Center

    Grosse, Susan J., Ed.; Thompson, Donna, Ed.

    This book contains practical information that reflects new developments in sports participation for individuals with disabilities. The focus is on meeting the challenges of the outdoor environment, learning through appropriate and safe play, and keeping fit through active leisure. Specifics include practical aspects of camping and outdoor…

  11. The Dynamics of a Parametrically Driven Damped Pendulum

    NASA Astrophysics Data System (ADS)

    Das, A.; Kumar, K.

    2015-05-01

    Ordered and chaotic states of a parametrically driven planar pendulum with viscous damping are numerically investigated. The damping makes the number of chaotic windows fewer but with larger width. Stroboscopic maps of the chaotic motion of the pendulum, driven either subharmonically or harmonically, show strange attractors with inversion symmetry in the phase plane.

  12. A value-driven mechanism of attentional selection

    PubMed Central

    Anderson, Brian A.

    2013-01-01

    Attention selects stimuli for cognitive processing, and the mechanisms that underlie the process of attentional selection have been a major topic of psychological research for over 30 years. From this research, it has been well documented that attentional selection can proceed both voluntarily, driven by visual search goals, and involuntarily, driven by the physical salience of stimuli. In this review, I provide a conceptual framework for attentional control that emphasizes the need for stimulus selection to promote the survival and wellbeing of an organism. I argue that although goal-driven and salience-driven mechanisms of attentional selection fit within this framework, a central component that is missing is a mechanism of attentional selection that is uniquely driven by learned associations between stimuli and rewards. I go on to review recent evidence for such a value-driven mechanism of attentional selection, and describe how this mechanism functions independently of the well-documented salience-driven and goal-driven mechanisms. I conclude by arguing that reward learning modifies the attentional priority of stimuli, allowing them to compete more effectively for selection even when nonsalient and task-irrelevant. PMID:23589803

  13. Data-Driven Hint Generation from Peer Debugging Solutions

    ERIC Educational Resources Information Center

    Liu, Zhongxiu

    2015-01-01

    Data-driven methods have been a successful approach to generating hints for programming problems. However, the majority of previous studies are focused on procedural hints that aim at moving students to the next closest state to the solution. In this paper, I propose a data-driven method to generate remedy hints for BOTS, a game that teaches…

  14. Instrumentation: Software-Driven Instrumentation: The New Wave.

    ERIC Educational Resources Information Center

    Salit, M. L.; Parsons, M. L.

    1985-01-01

    Software-driven instrumentation makes measurements that demand a computer as an integral part of either control, data acquisition, or data reduction. The structure of such instrumentation, hardware requirements, and software requirements are discussed. Examples of software-driven instrumentation (such as wavelength-modulated continuum source…

  15. Overview of nonlinear theory of kinetically driven instabilities

    SciTech Connect

    Berk, H.L.; Breizman, B.N.

    1998-09-01

    An overview is presented of the theory for the nonlinear behavior of instabilities driven by the resonant wave particle interaction. The approach should be applicable to a wide variety of kinetic systems in magnetic fusion devices and accelerators. Here the authors emphasize application to Alfven were driven instability, and the principles of the theory are used to interpret experimental data.

  16. Fokker-Planck/Transport model for neutral beam driven tokamaks

    SciTech Connect

    Killeen, J.; Mirin, A.A.; McCoy, M.G.

    1980-01-01

    The application of nonlinear Fokker-Planck models to the study of beam-driven plasmas is briefly reviewed. This evolution of models has led to a Fokker-Planck/Transport (FPT) model for neutral-beam-driven Tokamaks, which is described in detail. The FPT code has been applied to the PLT, PDX, and TFTR Tokamaks, and some representative results are presented.

  17. Pulsed power driven hohlraum research at Sandia National Laboratories

    SciTech Connect

    Leeper, R.J.; Alberts, T.E.; Allshouse, G.A.

    1996-06-01

    Three pulsed power driven hohlraum concepts are being investigated at Sandia for application to inertial fusion research. These hohlraums are driven by intense proton and Li ion beams as well as by two different types of z-pinch x-ray sources. Research on these hohlraum systems will continue on Sandia`s PBFA II-Z facility.

  18. Data Driven Math Intervention: What the Numbers Say

    ERIC Educational Resources Information Center

    Martin, Anthony W.

    2013-01-01

    This study was designed to determine whether or not data driven math skills groups would be effective in increasing student academic achievement. From this topic three key questions arose: "Would the implementation of data driven math skills groups improve student academic achievement more than standard instruction as measured by the…

  19. A Framework for Goal-Driven Pair Drills

    ERIC Educational Resources Information Center

    Saito, Hidetoshi

    2008-01-01

    This paper proposes a framework for goal-driven pair drills. What distinguishes these drills from ordinary controlled drills lies in the motivating characteristics such as clear goals, outcomes, and communicativeness. With these features present, goal-driven pair drills encourage learners to process multiple layers of language skill aspects. A…

  20. Observation of the coupling of the driven dust acoustic wave

    SciTech Connect

    Williams, Jeremiah D.; Duff, James

    2010-03-15

    In this study, the coupling between the naturally occurring dust acoustic wave (DAW) and the discharge current modulation is examined. It is confirmed that, when the wave is driven by modulating the discharge current, the DAW is driven at the same frequency as the current modulation.

  1. Using Database-Driven Web Pages for Your Courses.

    ERIC Educational Resources Information Center

    Sullivan, Peter

    1999-01-01

    Describes database-driven Web pages that dynamically display different information each time the page is accessed in response to the user's needs. Highlights include information management; online assignments; grade tracking; updating Web pages; creating database-driven Web pages; and examples of how they have been used for a high school physics…

  2. A Consumer-Driven Approach To Increase Suggestive Selling.

    ERIC Educational Resources Information Center

    Rohn, Don; Austin, John; Sanford, Alison

    2003-01-01

    Discussion of the effectiveness of behavioral interventions in improving suggestive selling behavior of sales staff focuses on a study that examined the efficacy of a consumer-driven approach to improve suggestive selling behavior of three employees of a fast food franchise. Reports that consumer-driven intervention increased suggestive selling…

  3. Radiation-Driven Warping. 2; Nonisothermal Disks

    NASA Technical Reports Server (NTRS)

    Maloney, Philip R.; Begelman, Mitchell C.; Nowak, Michael A.

    1998-01-01

    Recent work by Pringle and by Maloney, Begelman, & Pringle has shown that geometrically thin, optically thick, accretion disks are unstable to warping driven by radiation torque from the central source. This work was confined to isothermal (i.e., surface density Sigma varies as R(sup -3/2) disks. In this paper we generalize the study of radiation-driven warping to include general power-law surface density distributions, Sigma varies as R(sup -delta).We consider the range from Delta = 3/2 (the isothermal case) to Delta = -3/2, which corresponds to a radiation-pressure-supported disk; this spans the range of surface density distributions likely to be found in real astrophysical disks. In all cases there are an infinite number of zero-crossing solutions (i.e., solutions that cross the equator), which are the physically relevant modes if the outer boundary of the disk is required to lie in a specified plane. However, unlike the isothermal disk, which is the degenerate case, the frequency eigenvalues for Delta does not equal 3/2 are all distinct. In all cases the location of the zero moves outward from the steady state (pure precession) value with increasing growth rate; thus, there is a critical minimum size for unstable disks. Modes with zeros at smaller radii are damped. The critical radius and the steady state precession rate depend only weakly on Delta. An additional analytic solution has been found for Delta = 1. The case Delta = 1 divides the solutions into two qualitatively different regimes. For Delta greater than or equal to 1, the fastest growing modes have maximum warp amplitude, close to the disk outer edge, and the ratio of Beta(sub max) to the warp amplitude at the disk inner edge, Beta(sub o), is much greater than 1. For Delta less than 1, Beta(sub max/Beta(sub o) approximately equals 1, and the warp maximum steadily approaches the origin as Delta decreases. This implies that nonlinear effects must be important if the warp extends to the disk inner edge

  4. Gravity-driven intrusions in stratified fluids

    NASA Astrophysics Data System (ADS)

    Maurer, Benjamin Dudley

    All natural fluids stratify. Stable stratifications, in which isobars and isopycnals are parallel, are capable of supporting internal wave motion. Unstable stratification, in which density and pressure gradients are not aligned, results in gravity-driven flow. Gravity currents are a subset of these flows in which horizontal density gradients sharpen and propagate horizontally, transporting mass, momentum, and energy. If the density of the gravity current is within the density extrema of the stably stratified ambient fluid, it propagates as an intrusion at an intermediate height. Through laboratory experiments and numerical simulations, this dissertation explores the influence of stratification on the dynamics of gravity-driven intrusions. Intrusions require stable stratification in the ambient fluid, which is capable of transporting momentum and energy away from the current in the form of internal waves. We investigate the constant velocity propagation of well-mixed intrusions propagating into a linearly stratified ambient fluid. Varying the level of neutral buoyancy, we quantify the corresponding variation in structure, momentum, and energy of the upstream wave field. Adjacent stable stratifications of differing vertical density structure necessarily entail horizontal density gradients. These gradients determine the hydrostatic pressure differences driving the ensuing gravity current. We examine the mid-depth, constant velocity propagation of one linearly stratified fluid into another more strongly linearly stratified fluid. Working from the available potential energy of the system and measurements of the intrusion thickness, we develop an energy model to describe the speed of the intrusion in terms of the ratio of the two buoyancy frequencies. Distinct from adjacent linear stratifications, adjacent discrete stratifications may create flow consisting of interleaving intrusions. Single intrusions into a two-layer ambient fluid are well understood. Limiting our

  5. Impact Forces from Tsunami-Driven Debris

    NASA Astrophysics Data System (ADS)

    Ko, H.; Cox, D. T.; Riggs, H.; Naito, C. J.; Kobayashi, M. H.; Piran Aghl, P.

    2012-12-01

    Debris driven by tsunami inundation flow has been known to be a significant threat to structures, yet we lack the constitutive equations necessary to predict debris impact force. The objective of this research project is to improve our understanding of, and predictive capabilities for, tsunami-driven debris impact forces on structures. Of special interest are shipping containers, which are virtually everywhere and which will float even when fully loaded. The forces from such debris hitting structures, for example evacuation shelters and critical port facilities such as fuel storage tanks, are currently not known. This research project focuses on the impact by flexible shipping containers on rigid columns and investigated using large-scale laboratory testing. Full-scale in-air collision experiments were conducted at Lehigh University with 20 ft shipping containers to experimentally quantify the nonlinear behavior of full scale shipping containers as they collide into structural elements. The results from the full scale experiments were used to calibrate computer models and used to design a series of simpler, 1:5 scale wave flume experiments at Oregon State University. Scaled in-air collision tests were conducted using 1:5 scale idealized containers to mimic the container behavior observed in the full scale tests and to provide a direct comparison to the hydraulic model tests. Two specimens were constructed using different materials (aluminum, acrylic) to vary the stiffness. The collision tests showed that at higher speeds, the collision became inelastic as the slope of maximum impact force/velocity decreased with increasing velocity. Hydraulic model tests were conducted using the 1:5 scaled shipping containers to measure the impact load by the containers on a rigid column. The column was instrumented with a load cell to measure impact forces, strain gages to measure the column deflection, and a video camera was used to provide the debris orientation and speed. The

  6. Accelerator-driven Transmutation of Waste

    NASA Astrophysics Data System (ADS)

    Venneri, Francesco

    1998-04-01

    Nuclear waste from commercial power plants contains large quantities of plutonium, other fissionable actinides, and long-lived fission products that are potential proliferation concerns and create challenges for the long-term storage. Different strategies for dealing with nuclear waste are being followed by various countries because of their geologic situations and their views on nuclear energy, reprocessing and non-proliferation. The current United States policy is to store unprocessed spent reactor fuel in a geologic repository. Other countries are opting for treatment of nuclear waste, including partial utilization of the fissile material contained in the spent fuel, prior to geologic storage. Long-term uncertainties are hampering the acceptability and eventual licensing of a geologic repository for nuclear spent fuel in the US, and driving up its cost. The greatest concerns are with the potential for radiation release and exposure from the spent fuel for tens of thousands of years and the possible diversion and use of the actinides contained in the waste for weapons construction. Taking advantage of the recent breakthroughs in accelerator technology and of the natural flexibility of subcritical systems, the Accelerator-driven Transmutation of Waste (ATW) concept offers the United States and other countries the possibility to greatly reduce plutonium, higher actinides and environmentally hazardous fission products from the waste stream destined for permanent storage. ATW does not eliminate the need for, but instead enhances the viability of permanent waste repositories. Far from being limited to waste destruction, the ATW concept also brings to the table new technologies that could be relevant for next-generation power producing reactors. In the ATW concept, spent fuel would be shipped to the ATW site where the plutonium, transuranics and selected long-lived fission products would be destroyed by fission or transmutation in their first and only pass through the

  7. Social comparison modulates reward-driven attentional capture.

    PubMed

    Jiao, Jun; Du, Feng; He, Xiaosong; Zhang, Kan

    2015-10-01

    It is well established that attention can be captured by task irrelevant and non-salient objects associated with value through reward learning. However, it is unknown whether social comparison influences reward-driven attentional capture. The present study created four social contexts to examine whether different social comparisons modulate the reward-driven capture of attention. The results showed that reward-driven attentional capture varied with different social comparison conditions. Most prominently, reward-driven attentional capture is dramatically reduced in the disadvantageous social comparison context, in which an individual is informed that the other participant is earning more monetary reward for performing the same task. These findings suggest that social comparison can affect the reward-driven capture of attention. PMID:25711184

  8. Avalanches in tip-driven interfaces in random media

    NASA Astrophysics Data System (ADS)

    Aragón, L. E.; Kolton, A. B.; Le Doussal, P.; Wiese, K. J.; Jagla, E. A.

    2016-01-01

    We analyse by numerical simulations and scaling arguments the avalanche statistics of 1-dimensional elastic interfaces in random media driven at a single point. Both global and local avalanche sizes are power-law distributed, with universal exponents given by the depinning roughness exponent ζ and the interface dimension d, and distinct from their values in the uniformly driven case. A crossover appears between uniformly driven behaviour for small avalanches, and point-driven behaviour for large avalanches. The scale of the crossover is controlled by the ratio between the stiffness of the pulling spring and the elasticity of the interface; it is visible both in the global and local avalanche-size distributions, as in the average spatial avalanche shape. Our results are relevant to model experiments involving locally driven elastic manifolds at low temperatures, such as magnetic domain walls or vortex lines in superconductors.

  9. How surfactants influence evaporation-driven flows

    NASA Astrophysics Data System (ADS)

    Liepelt, Robert; Marin, Alvaro; Rossi, Massimiliano; Kähler, Christian J.

    2014-11-01

    Capillary flows appear spontaneously in sessile evaporating drops and give rise to particle accumulation around the contact lines, commonly known as coffee-stain effect (Deegan et al., Nature, 1997). On the other hand, out-of-equilibrium thermal effects may induce Marangoni flows in the droplet's surface that play an important role in the flow patterns and in the deposits left on the substrate. Some authors have argued that contamination or the presence of surfactants might reduce or eventually totally annul the Marangoni flow (Hu & Larson, J. Phys. Chem. B, 2006). On the contrary, others have shown an enhancement of the reverse surface flow (Sempels et al., Nat. Commun., 2012). In this work, we employ Astigmatic Particle Tracking Velocimetry (APTV) to obtain the 3D3C evaporation-driven flow in both bulk and droplet's surface, using surfactants of different ionic characters and solubility. Our conclusions lead to a complex scenario in which different surfactants and concentrations yield very different surface-flow patterns, which eventually might influence the colloidal deposition patterns.

  10. Modernizing Eligibility Criteria for Molecularly Driven Trials.

    PubMed

    Kim, Edward S; Bernstein, David; Hilsenbeck, Susan G; Chung, Christine H; Dicker, Adam P; Ersek, Jennifer L; Stein, Steven; Khuri, Fadlo R; Burgess, Earle; Hunt, Kelly; Ivy, Percy; Bruinooge, Suanna S; Meropol, Neal; Schilsky, Richard L

    2015-09-01

    As more clinical trials of molecularly targeted agents evolve, the number of eligibility criteria seems to be increasing. The importance and utility of eligibility criteria must be considered in the context of the fundamental goal of a clinical trial: to understand the risks and benefits of a treatment in the intended-use patient population. Although eligibility criteria are necessary to define the population under study and conduct trials safely, excessive requirements may severely restrict the population available for study, and often, this population is not reflective of the general population for which the drug would be prescribed. The American Society of Clinical Oncology Cancer Research Committee, which comprises academic faculty, industry representatives, and patient advocates, evaluated this issue. Evaluation results were mixed. Most physicians agreed that excessive eligibility criterias slow study enrollment rates and prolong the duration of enrollment; however, this hypothesis was difficult to validate with the data examined. We propose the organization of a public workshop, with input from regulatory bodies and key stakeholders, with the goal of developing an algorithmic approach to determining eligibility criteria for individual study protocols, which may help guide future investigators and companies in streamlining eligibility criteria in the era of molecularly driven therapy. PMID:26195710

  11. Dynamics of Actively Driven Crosslinked Microtubule Networks

    NASA Astrophysics Data System (ADS)

    Yadav, Vikrant; Stanhope, Kasimira; Evans, Arthur A.; Ross, Jennifer L.

    We have designed a model experiment to explore dynamics of crosslinked active microtubule clusters crosslinked with MAP65. Microtubule clusters are allowed to settle on a slide coated with kinesin-1 molecular motors, which move microtubules. We systematically tune either concentration of cross linkers bound to microtubule (ρc) or the global concentration of microtubules (ρMT) . We quantified the shape of the cluster by measuring the standard deviation (σ) of the cluster outline. At low ρMTor ρc the network is in an expanding state. At higher ρMTor ρc expansion slows down, reaches zero at a critical density, and become negative indicating contraction. Further increase of ρMTor ρc halts any kind of dynamics. The ρMT-ρc phase space shows distinct regions of extensile, contractile and static regimes. We model these results using active hydrodynamic theory. Microtubules are modeled as active rods whereas effect of crosslinkers is modeled using a collision term that prefers anti-parallel alignment of microtubules. A linearized analysis of hydrodynamic equation predicts existence of density driven expanding, contracting, and static phases for microtubule clusters.

  12. Data driven propulsion system weight prediction model

    NASA Technical Reports Server (NTRS)

    Gerth, Richard J.

    1994-01-01

    The objective of the research was to develop a method to predict the weight of paper engines, i.e., engines that are in the early stages of development. The impetus for the project was the Single Stage To Orbit (SSTO) project, where engineers need to evaluate alternative engine designs. Since the SSTO is a performance driven project the performance models for alternative designs were well understood. The next tradeoff is weight. Since it is known that engine weight varies with thrust levels, a model is required that would allow discrimination between engines that produce the same thrust. Above all, the model had to be rooted in data with assumptions that could be justified based on the data. The general approach was to collect data on as many existing engines as possible and build a statistical model of the engines weight as a function of various component performance parameters. This was considered a reasonable level to begin the project because the data would be readily available, and it would be at the level of most paper engines, prior to detailed component design.

  13. Passive bioventing driven by natural air exchange

    SciTech Connect

    Foor, D.C.; Zwick, T.C.; Hinchee, R.E.; Hoeppel, R.E.; Kyburg, C.; Bowling, L.

    1995-12-31

    Bioventing wells installed in the vadose zone of petroleum-contaminated sites at the Marine Corps Air Ground Combat Center (MCAGCC) in Twentynine Palms, California, naturally inhale and exhale air. This natural air exchange appears to be driven primarily by barometric pressure changes. The natural air exchange was utilized to engineer a passive bioventing system in which a valve allows only air injection and prevents soil gas extraction. The system is effective in aerating petroleum-contaminated, oxygen-limited subsurface soils. This aeration resulted in enhanced biological activity and site remediation. The bioventing wells (vent wells) were fitted with a passive valve mechanism that opens when the atmospheric pressure overcomes the internal vent well pressure. When the valve is open it permits atmospheric air to enter the vent well and infiltrate into the soil, thereby stimulating bioremediation. When the vent well pressure overcomes atmospheric pressure, the valve is closed and inhibits soil gas extraction. The vent wells are installed in a coarse sand where the depth to groundwater is approximately 220 ft (67 m). Generally, deeper vent wells produce greater flowrates. Passive airflow rates of up to 7 cfm (12 m{sup 3}/h) have been achieved at the bioventing wells.

  14. Data-Driven Classification of Animal Behavior

    NASA Astrophysics Data System (ADS)

    Berman, Gordon; Bialek, William; Shaevitz, Joshua

    2012-02-01

    The last decades have seen an explosion in our ability to characterize the molecular, cellular and genetic building blocks of life; the ingredients out of which we try to explain the rich and compelling behavior of living organisms. Our characterization of behavior itself, however, has advanced more slowly. Since modern ethology was founded over a century ago, behavioral experiments have focused largely on a restricted set of behaviors within the scope of a limited environment. Moreover, the set of behaviors to be examined is often user-defined, creating the potential for human bias and anthropomorphism. The research presented here describes a data-driven methodology for analyzing animal behavior, focusing on the fruit fly, Drosophila melanogaster, as a model system. Towards this end, we have built an imaging system that can track single flies as they move about a relatively unencumbered environment. Utilizing this capacity to generate large data sets of animal behavior, we have developed a method for automatically identifying behavioral states using techniques from image analysis, machine learning, and nonlinear dynamics. Identifying these states provides the starting point for many analyses and creates the possibility for automatic phenotyping of subtle behavioral traits.

  15. Auxin-driven patterning with unidirectional fluxes

    PubMed Central

    Cieslak, Mikolaj; Runions, Adam; Prusinkiewicz, Przemyslaw

    2015-01-01

    The plant hormone auxin plays an essential role in the patterning of plant structures. Biological hypotheses supported by computational models suggest that auxin may fulfil this role by regulating its own transport, but the plausibility of previously proposed models has been questioned. We applied the notion of unidirectional fluxes and the formalism of Petri nets to show that the key modes of auxin-driven patterning—the formation of convergence points and the formation of canals—can be implemented by biochemically plausible networks, with the fluxes measured by dedicated tally molecules or by efflux and influx carriers themselves. Common elements of these networks include a positive feedback of auxin efflux on the allocation of membrane-bound auxin efflux carriers (PIN proteins), and a modulation of this allocation by auxin in the extracellular space. Auxin concentration in the extracellular space is the only information exchanged by the cells. Canalization patterns are produced when auxin efflux and influx act antagonistically: an increase in auxin influx or concentration in the extracellular space decreases the abundance of efflux carriers in the adjacent segment of the membrane. In contrast, convergence points emerge in networks in which auxin efflux and influx act synergistically. A change in a single reaction rate may result in a dynamic switch between these modes, suggesting plausible molecular implementations of coordinated patterning of organ initials and vascular strands predicted by the dual polarization theory. PMID:26116915

  16. Streamer Waves Driven by Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Chen, Yao; Song, Hong-Qiang; Li, Bo; Xia, Li-Dong; Wu, Zhao; Fu, Hui

    Between July 5th and July 7th 2004, two intriguing fast coronal mass ejection(CME)-streamer interaction events were recorded by the Large Angle and Spectrometric Coronagraph (LASCO). At the beginning of the events, the streamer was pushed aside from their equilibrium position upon the impact of the rapidly outgoing and expanding ejecta; then, the streamer structure, mainly the bright streamer belt, exhibited elegant large scale sinusoidal wavelike motions. The motions were apparently driven by the restoring magnetic forces resulting from the CME impingement, suggestive of magnetohydrodynamic kink mode propagating outwards along the plasma sheet of the streamer. The mode is supported collectively by the streamer structure and is therefore named "streamer wave" in the present study. With the whitelight coronagraph data, we show that the streamer wave has a period of about 1 hour, a wavelength varying from 2 to 4 solar radii, an amplitude of about a few tens of solar radii, and a propagating phase speed in the range 300 to 500 km/s. We also find that there is a tendency for the phase speed to decline with increasing heliocentric distance. These observations provide good examples of large scale wave phenomena carried by corona structures, and have significance in developing seismological techniques for diagnosing plasma and magnetic parameters in the outer corona.

  17. Streamer Waves Driven by Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Song, H. Q.; Li, B.; Xia, L. D.; Wu, Z.; Fu, H.; Li, Xing

    2010-05-01

    Between 2004 July 5 and July 7, two intriguing fast coronal mass ejection (CME)-streamer interaction events were recorded by the Large Angle and Spectrometric Coronagraph. At the beginning of the events, the streamer was pushed aside from its equilibrium position upon the impact of the rapidly outgoing and expanding ejecta; then, the streamer structure, mainly the bright streamer belt, exhibited elegant large-scale sinusoidal wavelike motions. The motions were apparently driven by the restoring magnetic forces resulting from the CME impingement, suggestive of magnetohydrodynamic kink mode propagating outward along the plasma sheet of the streamer. The mode is supported collectively by the streamer-plasma sheet structure and is therefore named "streamer wave" in the present study. With the white light coronagraph data, we show that the streamer wave has a period of about 1 hr, a wavelength varying from 2 to 4 solar radii, an amplitude of about a few tens of solar radii, and a propagating phase speed in the range 300-500 km s-1. We also find that there is a tendency for the phase speed to decline with increasing heliocentric distance. These observations provide good examples of large-scale wave phenomena carried by coronal structures and have significance in developing seismological techniques for diagnosing plasma and magnetic parameters in the outer corona.

  18. Surface Tension Driven Convection Experiment (STDCE)

    NASA Technical Reports Server (NTRS)

    Ostrach, Simon; Kamotani, Y.; Pline, A.

    1994-01-01

    Results are reported of the Surface Tension Driven Convection Experiment (STDCE) aboard the USML-1 (first United States Microgravity Laboratory) Spacelab which was launched on June 25, 1992. In the experiment 10 cSt silicone oil was placed in an open circular container which was 10 cm wide by 5 cm deep. The fluid was heated either by a cylindrical heater (1.11 cm dia.) located along the container centerline or by a CO2 laser beam to induce thermocapillary flow. The flow field was studied by flow visualization. Several thermistor probes were placed in the fluid to measure the temperature distribution. The temperature distribution along the liquid free surface was measured by an infrared imager. Tests were conducted over a range of heating powers, laser beam diameters, and free surface shapes. In conjunction with the experiments an extensive numerical modeling of the flow was conducted. In this paper some results of the velocity and temperature measurements with flat and curved free surfaces are presented and they are shown to agree well with the numerical predictions.

  19. A quasilinear formulation of turbulence driven current

    SciTech Connect

    McDevitt, C. J.; Tang, Xian-Zhu; Guo, Zehua

    2014-02-15

    Non-inductive current drive mechanisms, such as the familiar neoclassical bootstrap current correspond to an essential component to the realization of steady state tokamak operation. In this work, we discuss a novel collisionless mechanism through which a mean plasma current may be driven in the presence of microturbulence. In analogy with the traditional neoclassical bootstrap current drive mechanism, in which the collisional equilibrium established between trapped and passing electrons results in the formation of a steady state plasma current, here we show that resonant scattering of electrons by drift wave microturbulence provides an additional means of determining the equilibrium between trapped and passing electrons. The resulting collisionless equilibrium is shown to result in the formation of an equilibrium current whose magnitude is a function of the thermodynamic forces. A mean field formulation is utilized to incorporate the above components into a unified framework through which both collisional as well as collisionless current drive mechanisms may be self-consistently treated. Utilizing a linearized Fokker-Planck collision operator, the plasma current in the presence of both collisions as well as turbulent stresses is computed, allowing for the relative strength of these two mechanisms to be quantified as a function of collisionality and fluctuation amplitude.

  20. Driven synchronization in random networks of oscillators.

    PubMed

    Hindes, Jason; Myers, Christopher R

    2015-07-01

    Synchronization is a universal phenomenon found in many non-equilibrium systems. Much recent interest in this area has overlapped with the study of complex networks, where a major focus is determining how a system's connectivity patterns affect the types of behavior that it can produce. Thus far, modeling efforts have focused on the tendency of networks of oscillators to mutually synchronize themselves, with less emphasis on the effects of external driving. In this work, we discuss the interplay between mutual and driven synchronization in networks of phase oscillators of the Kuramoto type, and explore how the structure and emergence of such states depend on the underlying network topology for simple random networks with a given degree distribution. We find a variety of interesting dynamical behaviors, including bifurcations and bistability patterns that are qualitatively different for heterogeneous and homogeneous networks, and which are separated by a Takens-Bogdanov-Cusp singularity in the parameter region where the coupling strength between oscillators is weak. Our analysis is connected to the underlying dynamics of oscillator clusters for important states and transitions. PMID:26232970

  1. Periodically driven DNA: Theory and simulation

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjay; Kumar, Ravinder; Janke, Wolfhard

    2016-01-01

    We propose a generic model of driven DNA under the influence of an oscillatory force of amplitude F and frequency ν and show the existence of a dynamical transition for a chain of finite length. We find that the area of the hysteresis loop, Aloop, scales with the same exponents as observed in a recent study based on a much more detailed model. However, towards the true thermodynamic limit, the high-frequency scaling regime extends to lower frequencies for larger chain length L and the system has only one scaling (Aloop≈ν-1F2 ). Expansion of an analytical expression for Aloop obtained for the model system in the low-force regime revealed that there is a new scaling exponent associated with force (Aloop≈ν-1F2.5 ), which has been validated by high-precision numerical calculation. By a combination of analytical and numerical arguments, we also deduce that for large but finite L , the exponents are robust and independent of temperature and friction coefficient.

  2. Accelerator Driven Nuclear Energy: The Thorium Option

    ScienceCinema

    Raja, Rajendran

    2010-01-08

    Conventional nuclear reactors use enriched Uranium as fuel and produce nuclear waste which needs to be stored away for over 10,000 years.   At the current rate of use, existing sources of Uranium will last for 50-100 years.  We describe a solution to the problem that uses particle accelerators to produce fast neutrons that can be used to burn existing nuclear waste and produce energy.  Such systems, initially proposed by Carlo Rubbia and collaborators in the 1990's, are being seriously considered by many countries as a possible solution to the green energy problem.  Accelerator driven reactors operate in a sub-critical regime and, thus, are safer and can obtain energy from plentiful elements such as Thorium-232 and Uranium-238. What is missing is the high intensity (10MW) accelerator that produces 1 GeV protons. We will describe scenarios which if implemented will make such systems a reality.  

  3. A swing driven by liquid crystals

    NASA Astrophysics Data System (ADS)

    Cheng, Cheng

    Angular momentum in liquid crystals exists as flow, director reorientation, etc. However, it is hard to observe and measure angular momentum in liquid crystals by a direct mechanical approach. Torsion pendulum is a general tool to measure angular momentum by torque balance. Our torsion pendulum can harvest the angular momentum in liquid crystals to make it observable. The oscillation of the pendulum keeps increasing by constructively adding a small angular momentum of liquid crystals each period at the resonant frequency of the pendulum. Its similar to a swing driven by a force at its resonant frequency. For the torsion pendulum, a cage made of two aluminum discs, in which a liquid crystal cell is placed, is suspended between two thin tungsten wires. A gold mirror, which is a part of the optical lever system, is attached on one tungsten wire. As first demonstration, we fabricate a circular hybrid liquid crystal cell, which can induce concentric backflows to generate angular momentum. The alignment on the planar substrate is concentric and tangential. Due to the coupling between director rotation and flow, the induced backflow goes around the cell when we add electrical pulses between top and bottom substrates. The oscillation is observed by a position sensitive detector and analyzed on the basis of Eriksen-Leslie theory. With vacuum condition and synchronous driving system, the oscillation signal is improved. We demonstrate that this torsion pendulum can sensitively detect the angular momentum in liquid crystals.

  4. Dislocation-driven surface dynamics on solids.

    PubMed

    Kodambaka, S; Khare, S V; Swiech, W; Ohmori, K; Petrov, I; Greene, J E

    2004-05-01

    Dislocations are line defects that bound plastically deformed regions in crystalline solids. Dislocations terminating on the surface of materials can strongly influence nanostructural and interfacial stability, mechanical properties, chemical reactions, transport phenomena, and other surface processes. While most theoretical and experimental studies have focused on dislocation motion in bulk solids under applied stress and step formation due to dislocations at surfaces during crystal growth, very little is known about the effects of dislocations on surface dynamics and morphological evolution. Here we investigate the near-equilibrium dynamics of surface-terminated dislocations using low-energy electron microscopy. We observe, in real time, the thermally driven nucleation and shape-preserving growth of spiral steps rotating at constant temperature-dependent angular velocities around cores of dislocations terminating on the (111) surface of TiN in the absence of applied external stress or net mass change. We attribute this phenomenon to point-defect migration from the bulk to the surface along dislocation lines. Our results demonstrate that dislocation-mediated surface roughening can occur even in the absence of deposition or evaporation, and provide fundamental insights into mechanisms controlling nanostructural stability. PMID:15129275

  5. Data flow machine for data driven computing

    DOEpatents

    Davidson, George S.; Grafe, Victor G.

    1995-01-01

    A data flow computer which of computing is disclosed which utilizes a data driven processor node architecture. The apparatus in a preferred embodiment includes a plurality of First-In-First-Out (FIFO) registers, a plurality of related data flow memories, and a processor. The processor makes the necessary calculations and includes a control unit to generate signals to enable the appropriate FIFO register receiving the result. In a particular embodiment, there are three FIFO registers per node: an input FIFO register to receive input information form an outside source and provide it to the data flow memories; an output FIFO register to provide output information from the processor to an outside recipient; and an internal FIFO register to provide information from the processor back to the data flow memories. The data flow memories are comprised of four commonly addressed memories. A parameter memory holds the A and B parameters used in the calculations; an opcode memory holds the instruction; a target memory holds the output address; and a tag memory contains status bits for each parameter. One status bit indicates whether the corresponding parameter is in the parameter memory and one status but to indicate whether the stored information in the corresponding data parameter is to be reused. The tag memory outputs a "fire" signal (signal R VALID) when all of the necessary information has been stored in the data flow memories, and thus when the instruction is ready to be fired to the processor.

  6. Ultrafast electronic dynamics driven by nuclear motion

    NASA Astrophysics Data System (ADS)

    Vendrell, Oriol

    2016-05-01

    The transfer of electrical charge on a microscopic scale plays a fundamental role in chemistry, in biology, and in technological applications. In this contribution, we will discuss situations in which nuclear motion plays a central role in driving the electronic dynamics of photo-excited or photo-ionized molecular systems. In particular, we will explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K-shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we will illustrate how the double hole can be transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. We thank the Hamburg Centre for Ultrafast Imaging and the Volkswagen Foundation for financial support.

  7. Query-Driven Visualization and Analysis

    SciTech Connect

    Ruebel, Oliver; Bethel, E. Wes; Prabhat, Mr.; Wu, Kesheng

    2012-11-01

    This report focuses on an approach to high performance visualization and analysis, termed query-driven visualization and analysis (QDV). QDV aims to reduce the amount of data that needs to be processed by the visualization, analysis, and rendering pipelines. The goal of the data reduction process is to separate out data that is "scientifically interesting'' and to focus visualization, analysis, and rendering on that interesting subset. The premise is that for any given visualization or analysis task, the data subset of interest is much smaller than the larger, complete data set. This strategy---extracting smaller data subsets of interest and focusing of the visualization processing on these subsets---is complementary to the approach of increasing the capacity of the visualization, analysis, and rendering pipelines through parallelism. This report discusses the fundamental concepts in QDV, their relationship to different stages in the visualization and analysis pipelines, and presents QDV's application to problems in diverse areas, ranging from forensic cybersecurity to high energy physics.

  8. Capillarity driven motion of solid film wedges

    SciTech Connect

    Wong, H.; Miksis, M.J.; Voorhees, P.W.; Davis, S.H.

    1997-06-01

    A solid film freshly deposited on a substrate may form a non-equilibrium contact angle with the substrate, and will evolve. This morphological evolution near the contact line is investigated by studying the motion of a solid wedge on a substrate. The contact angle of the wedge changes at time t = 0 from the wedge angle {alpha} to the equilibrium contact angle {beta}, and its effects spread into the wedge via capillarity-driven surface diffusion. The film profiles at different times are found to be self-similar, with the length scale increasing as t{sup 1 4}. The self-similar film profile is determined numerically by a shooting method for {alpha} and {beta} between 0 and 180. In general, the authors find that the film remains a wedge when {alpha} = {beta}. For {alpha} < {beta}, the film retracts, whereas for {alpha} > {beta}, the film extends. For {alpha} = 90{degree}, the results describe the growth of grain-boundary grooves for arbitrary dihedral angles. For {beta} = 90{degree}, the solution also applies to a free-standing wedge, and the thin-wedge profiles agree qualitatively with those observed in transmission electron microscope specimens.

  9. Cyclic Game Dynamics Driven by Iterated Reasoning

    PubMed Central

    Frey, Seth; Goldstone, Robert L.

    2013-01-01

    Recent theories from complexity science argue that complex dynamics are ubiquitous in social and economic systems. These claims emerge from the analysis of individually simple agents whose collective behavior is surprisingly complicated. However, economists have argued that iterated reasoning–what you think I think you think–will suppress complex dynamics by stabilizing or accelerating convergence to Nash equilibrium. We report stable and efficient periodic behavior in human groups playing the Mod Game, a multi-player game similar to Rock-Paper-Scissors. The game rewards subjects for thinking exactly one step ahead of others in their group. Groups that play this game exhibit cycles that are inconsistent with any fixed-point solution concept. These cycles are driven by a “hopping” behavior that is consistent with other accounts of iterated reasoning: agents are constrained to about two steps of iterated reasoning and learn an additional one-half step with each session. If higher-order reasoning can be complicit in complex emergent dynamics, then cyclic and chaotic patterns may be endogenous features of real-world social and economic systems. PMID:23441191

  10. Auxin-driven patterning with unidirectional fluxes.

    PubMed

    Cieslak, Mikolaj; Runions, Adam; Prusinkiewicz, Przemyslaw

    2015-08-01

    The plant hormone auxin plays an essential role in the patterning of plant structures. Biological hypotheses supported by computational models suggest that auxin may fulfil this role by regulating its own transport, but the plausibility of previously proposed models has been questioned. We applied the notion of unidirectional fluxes and the formalism of Petri nets to show that the key modes of auxin-driven patterning-the formation of convergence points and the formation of canals-can be implemented by biochemically plausible networks, with the fluxes measured by dedicated tally molecules or by efflux and influx carriers themselves. Common elements of these networks include a positive feedback of auxin efflux on the allocation of membrane-bound auxin efflux carriers (PIN proteins), and a modulation of this allocation by auxin in the extracellular space. Auxin concentration in the extracellular space is the only information exchanged by the cells. Canalization patterns are produced when auxin efflux and influx act antagonistically: an increase in auxin influx or concentration in the extracellular space decreases the abundance of efflux carriers in the adjacent segment of the membrane. In contrast, convergence points emerge in networks in which auxin efflux and influx act synergistically. A change in a single reaction rate may result in a dynamic switch between these modes, suggesting plausible molecular implementations of coordinated patterning of organ initials and vascular strands predicted by the dual polarization theory. PMID:26116915

  11. Supernovae-driven Winds in Isolated Galaxies.

    NASA Astrophysics Data System (ADS)

    Dubois, Y.; Teyssier, R.

    2006-06-01

    The hierarchical model of galaxy formation, despite its many successes, still suffers from the so--called ``angular momentum'' and ``overcooling'' problems. Supernovae--driven winds and their associated feedback on galaxy formation was proposed as a possible solution. It turned out that a proper modelling of supernovae explosions within a turbulent InterStellar Medium (ISM) is a difficult task. Recent advances have been obtained using a multiphase approach to solve for the thermal state of the ISM, plus some additional recipes to account for the kinetic effect of supernovae on the galactic gas. We describe here our implementation of supernovae feedback within the RAMSES code, and apply it to the formation and evolution of isolated galaxies of various masses and angular momenta. We have explored under what conditions a galactic wind can develop, if one considers only a quiescent mode of star formation. It turns out that, because of the ram pressure of infalling material from the gaseous halo, only moderately efficient winds appear, and in rather low mass (<1011 M_⊙) dark matter haloes.

  12. Optimal design of capacitor-driven coilgun

    NASA Astrophysics Data System (ADS)

    Kim, Seog-Whan; Jung, Hyun-Kyo; Hahn, Song-Yop

    1994-03-01

    This paper presents an analysis and optimal design of a capacitor-driven inductive coilgun. An equivalent circuit is used for a launch simulation of the coilgun. The circuit equations are solved together with the equation of motion of the projectile by using the Runge-Kutta method. The numerical results are compared with the experimental values to verify the usefulness of the developed simulation program. It is shown that the numerical and the experimental results are in a good agreement. In the design of the system the optimization is achieved by employing the genetic algorithm. The resultant specifications of the coilgun optimally designed by the proposed algorithm are tested by experiment. Finally the obtained results are compared with those designed by approximate equations and by linear search methods as well. It is found that the proposed algorithm gives a better result in the energy efficiency of the system, namely it enables one to obtain a higher muzzle velocity of the projectile with the same amount of energy.

  13. Linac-driven spallation-neutron source

    SciTech Connect

    Jason, A.J.

    1995-05-01

    Strong interest has arisen in accelerator-driven spallation-neutron sources that surpass existing facilities (such as ISIS at Rutherford or LANSCE at Los Alamos) by more than an order of magnitude in beam power delivered to the spallation target. The approach chosen by Los Alamos (as well as the European Spallation Source) provides the full beam energy by acceleration in a linac as opposed to primary acceleration in a synchrotron or other circular device. Two modes of neutron production are visualized for the source. A short-pulse mode produces 1 MW of beam power (at 60 pps) in pulses, of length less than 1 ms, by compression of the linac macropulse through multi-turn injection in an accumulator ring. A long-pulse mode produces a similar beam power with 1-ms-long pulses directly applied to a target. This latter mode rivals the performance of existing reactor facilities to very low neutron energies. Combination with the short-pulse mode addresses virtually all applications.

  14. Driven motion of vortices in superconductors

    SciTech Connect

    Crabtree, G.W.; Leaf, G.K.; Kaper, H.G.; Vinokur, V.M.; Koshelev, A.E.; Braun, D.W.; Levine, D.M.

    1995-09-01

    The driven motion of vortices in the solid vortex state is analyzed with the time-dependent Ginzburg-Landau equations. In large-scale numerical simulations, carried out on the IBM Scalable POWERparallel (SP) system at Argonne National Laboratory, many hundreds of vortices are followed as they move under the influence of a Lorentz force induced by a transport current in the presence of a planar defect (similar to a twin boundary in YBa{sub 2}CU{sub 3}O{sub 7}). Correlations in the positions and velocities of the vortices in plastic and elastic motion are identified and compared. Two types of plastic motion are observed. Organized plastic motion displaying long-range orientational correlation and shorter-range velocity correlation occurs when the driving forces are small compared to the pinning forces in the twin boundary. Disorganized plastic motion displaying no significant correlation in either the velocities or orientation of the vortex system occurs when the driving and pinning forces axe of the same order.

  15. A quasilinear formulation of turbulence driven current

    NASA Astrophysics Data System (ADS)

    McDevitt, C. J.; Tang, Xian-Zhu; Guo, Zehua

    2014-02-01

    Non-inductive current drive mechanisms, such as the familiar neoclassical bootstrap current correspond to an essential component to the realization of steady state tokamak operation. In this work, we discuss a novel collisionless mechanism through which a mean plasma current may be driven in the presence of microturbulence. In analogy with the traditional neoclassical bootstrap current drive mechanism, in which the collisional equilibrium established between trapped and passing electrons results in the formation of a steady state plasma current, here we show that resonant scattering of electrons by drift wave microturbulence provides an additional means of determining the equilibrium between trapped and passing electrons. The resulting collisionless equilibrium is shown to result in the formation of an equilibrium current whose magnitude is a function of the thermodynamic forces. A mean field formulation is utilized to incorporate the above components into a unified framework through which both collisional as well as collisionless current drive mechanisms may be self-consistently treated. Utilizing a linearized Fokker-Planck collision operator, the plasma current in the presence of both collisions as well as turbulent stresses is computed, allowing for the relative strength of these two mechanisms to be quantified as a function of collisionality and fluctuation amplitude.

  16. A Quasilinear Formulation of Turbulence Driven Current

    NASA Astrophysics Data System (ADS)

    McDevitt, C. J.; Tang, X. Z.; Guo, Z. H.

    2012-10-01

    Non-inductive current drive mechanisms such as the familiar bootstrap current correspond to an essential component to the realization of steady state tokamak operation. In this work we discuss a novel collisionless mechanism through which a mean plasma current may be driven in the presence of microturbulence (as seen in [1]). In analogy with the traditional bootstrap current drive mechanism, in which the collisional equilibrium established between trapped and passing particles results in the formation of a steady state plasma current, here we show that velocity space scattering by drift wave microturbulence is capable of modifying the equilibrium between trapped and passing particles leading to the generation of a mean plasma current. In the collisionless limit, this current drive mechanism can in turn be balanced either by turbulence mediated electron-ion momentum exchange or radial electron momentum transport. A mean field formulation is utilized to incorporate the above components into a unified framework through which both collisional as well as collisionless current drive mechanisms may be self-consistently treated. [4pt] [1] W. X. Wang et al., 53rd APS-DPP, Salt Lake City, Utah, 2011

  17. Laser-driven nonlinear cluster dynamics

    SciTech Connect

    Fennel, Th.; Meiwes-Broer, K.-H.; Tiggesbaeumker, J.; Reinhard, P.-G.; Dinh, P. M.; Suraud, E.

    2010-04-15

    Laser excitation of nanometer-sized atomic and molecular clusters offers various opportunities to explore and control ultrafast many-particle dynamics. Whereas weak laser fields allow the analysis of photoionization, excited-state relaxation, and structural modifications on these finite quantum systems, large-amplitude collective electron motion and Coulomb explosion can be induced with intense laser pulses. This review provides an overview of key phenomena arising from laser-cluster interactions with focus on nonlinear optical excitations and discusses the underlying processes according to the current understanding. A general survey covers basic cluster properties and excitation mechanisms relevant for laser-driven cluster dynamics. Then, after an excursion in theoretical and experimental methods, results for single-photon and multiphoton excitations are reviewed with emphasis on signatures from time- and angular-resolved photoemission. A key issue of this review is the broad spectrum of phenomena arising from clusters exposed to strong fields, where the interaction with the laser pulse creates short-lived and dense nanoplasmas. The implications for technical developments such as the controlled generation of ion, electron, and radiation pulses will be addressed along with corresponding examples. Finally, future prospects of laser-cluster research as well as experimental and theoretical challenges are discussed.

  18. Surface Tension Driven Convection Experiment (STDCE)

    NASA Technical Reports Server (NTRS)

    Ostrach, S.; Kamotani, Y.

    1996-01-01

    This document reports the results obtained from the Surface Tension Driven Convection Experiment (STDCE) conducted aboard the USML-1 Spacelab in 1992. The experiments used 10 cSt silicone oil placed in an open circular container that was 10 cm wide and 5 cm deep. Thermocapillary flow was induced by using either a cylindrical heater placed along the container centerline or by a CO2 laser. The tests were conducted under various power settings, laser beam diameters, and free surface shapes. Thermistors located at various positions in the test section recorded the temperature of the fluid, heater, walls, and air. An infrared imager was used to measure the free surface temperature. The flow field was studied by flow visualization and the data was analyzed by a PTV technique. The results from the flow visualization and the temperature measurements are compared with the numerical analysis that was conducted in conjunction with the experiment. The compared results include the experimental and numerical velocity vector plots, the streamline plots, the fluid temperature, and the surface temperature distribution.

  19. STREAMER WAVES DRIVEN BY CORONAL MASS EJECTIONS

    SciTech Connect

    Chen, Y.; Song, H. Q.; Li, B.; Xia, L. D.; Wu, Z.; Fu, H.; Li Xing

    2010-05-01

    Between 2004 July 5 and July 7, two intriguing fast coronal mass ejection (CME)-streamer interaction events were recorded by the Large Angle and Spectrometric Coronagraph. At the beginning of the events, the streamer was pushed aside from its equilibrium position upon the impact of the rapidly outgoing and expanding ejecta; then, the streamer structure, mainly the bright streamer belt, exhibited elegant large-scale sinusoidal wavelike motions. The motions were apparently driven by the restoring magnetic forces resulting from the CME impingement, suggestive of magnetohydrodynamic kink mode propagating outward along the plasma sheet of the streamer. The mode is supported collectively by the streamer-plasma sheet structure and is therefore named 'streamer wave' in the present study. With the white light coronagraph data, we show that the streamer wave has a period of about 1 hr, a wavelength varying from 2 to 4 solar radii, an amplitude of about a few tens of solar radii, and a propagating phase speed in the range 300-500 km s{sup -1}. We also find that there is a tendency for the phase speed to decline with increasing heliocentric distance. These observations provide good examples of large-scale wave phenomena carried by coronal structures and have significance in developing seismological techniques for diagnosing plasma and magnetic parameters in the outer corona.

  20. Hydrodynamically Driven Colloidal Assembly in Dip Coating

    NASA Astrophysics Data System (ADS)

    Colosqui, Carlos E.; Morris, Jeffrey F.; Stone, Howard A.

    2013-05-01

    We study the hydrodynamics of dip coating from a suspension and report a mechanism for colloidal assembly and pattern formation on smooth substrates. Below a critical withdrawal speed where the coating film is thinner than the particle diameter, capillary forces induced by deformation of the free surface prevent the convective transport of single particles through the meniscus beneath the film. Capillary-induced forces are balanced by hydrodynamic drag only after a minimum number of particles assemble within the meniscus. The particle assembly can thus enter the thin film where it moves at nearly the withdrawal speed and rapidly separates from the next assembly. The interplay between hydrodynamic and capillary forces produces periodic and regular structures below a critical ratio Ca2/3/Bo<0.7, where Ca and Bo are the capillary and Bond numbers, respectively. An analytical model and numerical simulations are presented for the case of two-dimensional flow with circular particles in suspension. The hydrodynamically driven assembly documented here is consistent with stripe pattern formations observed experimentally in dip coating.

  1. Measurements of gravity driven granular channel flows

    NASA Astrophysics Data System (ADS)

    Facto, Kevin

    This dissertation presents experiments that studied two gravity driven granular channel flows. The first experiment used magnetic resonance imaging to measure the density and displacement distributions of poppy seeds flowing in a rough walled channel. Time-averaged measurements of normalized velocity and density showed little flow speed dependence. Instantaneous measurements, however, showed marked velocity dependence in the displacement distributions. There was evidence of aperiodic starting and stopping at lower flow speeds and the onset of density waves on a continuous flow at higher speeds. The second experiment measured forces in all three spatial directions at the boundary of a flow of steel balls. The relationship between the normal and the tangential forces were examined statistically and compared to the Coulomb friction model. For both large and small forces, the tangential and normal forces are unrelated, as there appears to be a strong tendency for the tangential force to maintain a value that will bear the weight the weight of the particles in flow.

  2. A colalborative environment for information driven safeguards

    SciTech Connect

    Scott, Mark R; Michel, Kelly D

    2010-09-15

    For two decades, the IAEA has recognized the need for a comprehensive and strongly integrated Knowledge Management system to support its Information Driven Safeguards activities. In the past, plans for the development of such a system have progressed slowly due to concerns over costs and feasibility. In recent years, Los Alamos National Laboratory has developed a knowledge management system that could serve as the basis for an IAEA Collaborative Environment (ICE). The ICE derivative knowledge management system described in this paper addresses the challenge of living in an era of information overload coupled with certain knowledge shortfalls. The paper describes and defines a system that is flexible, yet ensures coordinated and focused collaboration, broad data evaluation capabilities, architected and organized work flows, and improved communications. The paper and demonstration of ICE will utilize a hypothetical scenario to highlight the functional features that facilitate collaboration amongst and between information analysts and inspectors. The scenario will place these two groups into a simulated planning exercise for a safeguards inspection drawing upon past data acquisitions, inspection reports, analyst conclusions, and a coordinated walk-through of a 3-D model of the facility. Subsequent to the conduct of the simulated facility inspection, the detection of an anomaly and pursuit of follow up activities will illustrate the event notification, information sharing, and collaborative capabilities of the system. The use of a collaborative environment such as ICE to fulfill the complicated knowledge management demands of the Agency and facilitate the completion of annual State Evaluation Reports will also be addressed.

  3. Contrast Driven Elastica for Image Segmentation.

    PubMed

    El-Zehiry, Noha Youssry; Grady, Leo

    2016-06-01

    Minimization of boundary curvature is a classic regularization technique for image segmentation in the presence of noisy image data. Techniques for minimizing curvature have historically been derived from gradient descent methods which could be trapped by a local minimum and, therefore, required a good initialization. Recently, combinatorial optimization techniques have overcome this barrier by providing solutions that can achieve a global optimum. However, curvature regularization methods can fail when the true object has high curvature. In these circumstances, existing methods depend on a data term to overcome the high curvature of the object. Unfortunately, the data term may be ambiguous in some images, which causes these methods also to fail. To overcome these problems, we propose a contrast driven elastica model (including curvature), which can accommodate high curvature objects and an ambiguous data model. We demonstrate that we can accurately segment extremely challenging synthetic and real images with ambiguous data discrimination, poor boundary contrast, and sharp corners. We provide a quantitative evaluation of our segmentation approach when applied to a standard image segmentation data set. PMID:27019488

  4. Computational dynamics of acoustically driven microsphere systems

    NASA Astrophysics Data System (ADS)

    Glosser, Connor; Piermarocchi, Carlo; Li, Jie; Dault, Dan; Shanker, B.

    2016-01-01

    We propose a computational framework for the self-consistent dynamics of a microsphere system driven by a pulsed acoustic field in an ideal fluid. Our framework combines a molecular dynamics integrator describing the dynamics of the microsphere system with a time-dependent integral equation solver for the acoustic field that makes use of fields represented as surface expansions in spherical harmonic basis functions. The presented approach allows us to describe the interparticle interaction induced by the field as well as the dynamics of trapping in counter-propagating acoustic pulses. The integral equation formulation leads to equations of motion for the microspheres describing the effect of nondissipative drag forces. We show (1) that the field-induced interactions between the microspheres give rise to effective dipolar interactions, with effective dipoles defined by their velocities and (2) that the dominant effect of an ultrasound pulse through a cloud of microspheres gives rise mainly to a translation of the system, though we also observe both expansion and contraction of the cloud determined by the initial system geometry.

  5. Nonequilibrium transitions driven by external dichotomous noise

    NASA Astrophysics Data System (ADS)

    Behn, U.; Schiele, K.; Teubel, A.; Kühnel, A.

    1987-06-01

    The stationary probability density P s for a class of nonlinear one-dimensional models driven by a dichotomous Markovian process (DMP) I t , can be calculated explicitly. For the specific case of the Stratonovich model, x=ax - -x 3 +I t x, the qualitative shape of P s and its support is discussed in the whole parameter region. The location of the maxima of P s shows a behavior similar to order parameters in continuous phase transitions. The possibility of a noiseinduced change from continuous to a discontinuous transition in an extended model, in which the DMP couples also to the cubic term, is discussed. The time-dependent moments can be represented as an infinite series of terms, which are determined by a recursion formula. For negative even moments the series terminates and the long-time behavior can be obtained analytically. As a function of the physical parameters, qualitative changes of this behavior may occur which can be partially related to the behavior of P s . All results reproduce those for Gaussian white noise in the corresponding limit. The influence of the finite correlation time and the discreteness of the space of states of the DMP are discussed. An extensive list of references is contained in U. Behn, K. Schiele, and A. Teubel, Wiss. Z. Karl-Marx-Univ. Leipzig, Mathem.-Naturwiss. R. 34:602 (1985).

  6. Current driven asymmetric domain wall propagation

    NASA Astrophysics Data System (ADS)

    Garg, Chirag; Pushp, Aakash; Phung, Timothy; Yang, See-Hun; Hughes, Brian P.; Rettner, Charles; Parkin, Stuart S. P.

    In ultrathin magnetic heterostructures, the presence of spin-orbit coupling gives rise to chiral Neel walls which are stabilized by the Dzyaloshinskii-Moriya Interaction (DMI), and also to a highly efficient chiral spin torque mechanism. In straight nanowires, the current-driven propagation of alternating Néel DWs without the presence of an in-plane field is equivalent, leading to the lock-step motion of several DWs in a nanowire. Here, we show that by engineering the structure in which the domain walls propagate, which in our case is in the shape of a Y-shaped junction, the DW propagation process becomes selective to the polarity of the DWs even in the absence of any externally applied magnetic fields. We remarkably find that after splitting at the Y-shaped junction, the DW velocity in one branch remains largely unaffected compared to its initial velocity whereas simultaneously the DW velocity in the other branch decreases by as much as 10-90%. We show that this large change in the DW velocity in a particular branch depends on the relative angle between the local magnetization of the DW and the spin current emanating from the underlying heavy-metal layer in these nanowires.

  7. Computational dynamics of acoustically driven microsphere systems.

    PubMed

    Glosser, Connor; Piermarocchi, Carlo; Li, Jie; Dault, Dan; Shanker, B

    2016-01-01

    We propose a computational framework for the self-consistent dynamics of a microsphere system driven by a pulsed acoustic field in an ideal fluid. Our framework combines a molecular dynamics integrator describing the dynamics of the microsphere system with a time-dependent integral equation solver for the acoustic field that makes use of fields represented as surface expansions in spherical harmonic basis functions. The presented approach allows us to describe the interparticle interaction induced by the field as well as the dynamics of trapping in counter-propagating acoustic pulses. The integral equation formulation leads to equations of motion for the microspheres describing the effect of nondissipative drag forces. We show (1) that the field-induced interactions between the microspheres give rise to effective dipolar interactions, with effective dipoles defined by their velocities and (2) that the dominant effect of an ultrasound pulse through a cloud of microspheres gives rise mainly to a translation of the system, though we also observe both expansion and contraction of the cloud determined by the initial system geometry. PMID:26871188

  8. Data flow machine for data driven computing

    DOEpatents

    Davidson, G.S.; Grafe, V.G.

    1988-07-22

    A data flow computer and method of computing is disclosed which utilizes a data driven processor node architecture. The apparatus in a preferred embodiment includes a plurality of First-In-First-Out (FIFO) registers, a plurality of related data flow memories, and a processor. The processor makes the necessary calculations and includes a control unit to generate signals to enable the appropriate FIFO register receiving the result. In a particular embodiment, there are three FIFO registers per node: an input FIFO register to receive input information from an outside source and provide it to the data flow memories; an output FIFO register to provide output information from the processor to an outside recipient; and an internal FIFO register to provide information from the processor back to the data flow memories. The data flow memories are comprised of four commonly addressed memories. A parameter memory holds the A and B parameters used in the calculations; an opcode memory holds the instruction; a target memory holds the output address; and a tag memory contains status bits for each parameter. One status bit indicates whether the corresponding parameter is in the parameter memory and one status bit to indicate whether the stored information in the corresponding data parameter is to be reused. The tag memory outputs a ''fire'' signal (signal R VALID) when all of the necessary information has been stored in the data flow memories, and thus when the instruction is ready to be fired to the processor. 11 figs.

  9. Nuclear Powered Laser Driven Plasma Propulsion System

    NASA Astrophysics Data System (ADS)

    Kammash, T.

    A relativistic plasma thruster that could open up the solar system to near-term human exploration is presented. It is based on recent experimental and theoretical research, which show that ultrafast (very short pulse length) lasers can accelerate charged particles to relativistic speeds. In table top-type experiments charge-neutral proton beams containing more than 1014 particles with mean energies of tens of MeV's have been produced when high intensity lasers with femtosecond (10-15 s) pulse lengths are made to strike thin solid targets. When viewed from a propulsion standpoint such systems can produce specific impulses of several million seconds albeit at modest thrusts and require nuclear power systems to drive them. Several schemes are proposed to enhance the thrust and make these systems suitable for manned interplanetary missions. In this paper we set forth the physics principles that make relativistic plasma driven by ultrafast lasers particularly attractive for propulsion applications. We introduce the “Laser Accelerated Plasma Propulsion System” LAPPS, and demonstrate its potential propulsive capability by addressing an interstellar mission to the Oort Cloud, and a planetary mission to Mars. We show that the first can be carried out in a human's lifetime and the second in a matter of months. In both instances we identify the major technological problems that must be addressed if this system is to evolve into a leading contender among the advance propulsion concepts currently under consideration.

  10. DUST-DRIVEN WIND FROM DISK GALAXIES

    SciTech Connect

    Sharma, Mahavir; Nath, Biman B.; Shchekinov, Yuri E-mail: biman@rri.res.in

    2011-08-01

    We study gaseous outflows from disk galaxies driven by radiation pressure on dust grains. We include the effect of bulge and dark matter halo and show that the existence of such an outflow implies a maximum value of disk mass-to-light ratio. We show that the terminal wind speed is proportional to the disk rotation speed in the limit of a cold gaseous outflow, and that in general there is a contribution from the gas sound speed. Using the mean opacity of dust grains and the evolution of the luminosity of a simple stellar population, we then show that the ratio of the wind terminal speed (v{sub {infinity}}) to the galaxy rotation speed (v{sub c}) ranges between 2 and 3 for a period of {approx}10 Myr after a burst of star formation, after which it rapidly decays. This result is independent of any free parameter and depends only on the luminosity of the stellar population and the relation between disk and dark matter halo parameters. We briefly discuss the possible implications of our results.

  11. Field-driven dynamics of nematic microcapillaries.

    PubMed

    Khayyatzadeh, Pouya; Fu, Fred; Abukhdeir, Nasser Mohieddin

    2015-12-01

    Polymer-dispersed liquid-crystal (PDLC) composites long have been a focus of study for their unique electro-optical properties which have resulted in various applications such as switchable (transparent or translucent) windows. These composites are manufactured using desirable "bottom-up" techniques, such as phase separation of a liquid-crystal-polymer mixture, which enable production of PDLC films at very large scales. LC domains within PDLCs are typically spheroidal, as opposed to rectangular for an LCD panel, and thus exhibit substantially different behavior in the presence of an external field. The fundamental difference between spheroidal and rectangular nematic domains is that the former results in the presence of nanoscale orientational defects in LC order while the latter does not. Progress in the development and optimization of PDLC electro-optical properties has progressed at a relatively slow pace due to this increased complexity. In this work, continuum simulations are performed in order to capture the complex formation and electric field-driven switching dynamics of approximations of PDLC domains. Using a simplified elliptic cylinder (microcapillary) geometry as an approximation of spheroidal PDLC domains, the effects of geometry (aspect ratio), surface anchoring, and external field strength are studied through the use of the Landau-de Gennes model of the nematic LC phase. PMID:26764713

  12. MICROFLARE ACTIVITY DRIVEN BY FORCED MAGNETIC RECONNECTION

    SciTech Connect

    Jess, D. B.; Mathioudakis, M.; Crockett, P. J.; Keenan, F. P.; Browning, P. K.

    2010-03-20

    High cadence, multiwavelength, optical observations of a solar active region, obtained with the Swedish Solar Telescope, are presented. Two magnetic bright points are seen to separate in opposite directions at a constant velocity of 2.8 km s{sup -1}. After a separation distance of {approx}4400 km is reached, multiple Ellerman bombs are observed in both H{alpha} and Ca-K images. As a result of the Ellerman bombs, periodic velocity perturbations in the vicinity of the magnetic neutral line, derived from simultaneous Michelson Doppler Imager data, are generated with amplitude {+-}6 km s{sup -1} and wavelength {approx}1000 km. The velocity oscillations are followed by an impulsive brightening visible in H{alpha} and Ca-K, with a peak intensity enhancement of 63%. We interpret these velocity perturbations as the magnetic field deformation necessary to trigger forced reconnection. A time delay of {approx}3 minutes between the H{alpha}-wing and Ca-K observations indicates that the observed magnetic reconnection occurs at a height of {approx}200 km above the solar surface. These observations are consistent with theoretical predictions and provide the first observational evidence of microflare activity driven by forced magnetic reconnection.

  13. Transient Mixing Driven by Buoyancy Flows

    NASA Technical Reports Server (NTRS)

    Duval, W. M. B.; Batur, C.; Zhong, H.

    2002-01-01

    Mixing driven by buoyancy-induced flows is of particular interest to microgravity processes, as the body force that governs the intensity of flow fields can be directly controlled. We consider a model experimental system to explore the dynamics of mixing which employs two miscible liquids inside a cavity separated initially by a divider. The two liquids are oriented vertically inside a rectangular cavity with constant width and height, and varying depths to span the range of a Hele-Shaw cell to a 3-D configuration. The two miscible liquids can be sufficiently diluted and died, for example water and deuterium oxide, such that a distinct interface exists across the divider. The transient mixing characteristic of the two fluids is addressed by following the Lagrangian history of the interface for various aspect ratios in the z-plane (depth variation) as well as a range of pulling velocities of the divider. The mixing characteristics of the two fluids are quantified from measurement of the length stretch of the interface and its flow field using respectively image processing techniques and Particle Imaging Velocimetry. Scaling analysis shows that the length stretch depends on four governing parameters, namely the Grashof number (Gr), Schmidt number (Sc), aspect ratio (Ar), and Reynolds number (Re). Variation of the Schmidt number is taken into account through thermophysical property variation. Thus our problem reduces to a codimension three bifurcation in parametric space for Gr, Ar, and Re.

  14. Photonic Crystal Laser-Driven Accelerator Structures

    SciTech Connect

    Cowan, Benjamin M.

    2007-08-22

    Laser-driven acceleration holds great promise for significantly improving accelerating gradient. However, scaling the conventional process of structure-based acceleration in vacuum down to optical wavelengths requires a substantially different kind of structure. We require an optical waveguide that (1) is constructed out of dielectric materials, (2) has transverse size on the order of a wavelength, and (3) supports a mode with speed-of-light phase velocity in vacuum. Photonic crystals---structures whose electromagnetic properties are spatially periodic---can meet these requirements. We discuss simulated photonic crystal accelerator structures and describe their properties. We begin with a class of two-dimensional structures which serves to illustrate the design considerations and trade-offs involved. We then present a three-dimensional structure, and describe its performance in terms of accelerating gradient and efficiency. We discuss particle beam dynamics in this structure, demonstrating a method for keeping a beam confined to the waveguide. We also discuss material and fabrication considerations. Since accelerating gradient is limited by optical damage to the structure, the damage threshold of the dielectric is a critical parameter. We experimentally measure the damage threshold of silicon for picosecond pulses in the infrared, and determine that our structure is capable of sustaining an accelerating gradient of 300 MV/m at 1550 nm. Finally, we discuss possibilities for manufacturing these structures using common microfabrication techniques.

  15. Patch-primitive driven compressive ghost imaging.

    PubMed

    Hu, Xuemei; Suo, Jinli; Yue, Tao; Bian, Liheng; Dai, Qionghai

    2015-05-01

    Ghost imaging has rapidly developed for about two decades and attracted wide attention from different research fields. However, the practical applications of ghost imaging are still largely limited, by its low reconstruction quality and large required measurements. Inspired by the fact that the natural image patches usually exhibit simple structures, and these structures share common primitives, we propose a patch-primitive driven reconstruction approach to raise the quality of ghost imaging. Specifically, we resort to a statistical learning strategy by representing each image patch with sparse coefficients upon an over-complete dictionary. The dictionary is composed of various primitives learned from a large number of image patches from a natural image database. By introducing a linear mapping between non-overlapping image patches and the whole image, we incorporate the above local prior into the convex optimization framework of compressive ghost imaging. Experiments demonstrate that our method could obtain better reconstruction from the same amount of measurements, and thus reduce the number of requisite measurements for achieving satisfying imaging quality. PMID:25969205

  16. Periodically driven DNA: Theory and simulation.

    PubMed

    Kumar, Sanjay; Kumar, Ravinder; Janke, Wolfhard

    2016-01-01

    We propose a generic model of driven DNA under the influence of an oscillatory force of amplitude F and frequency ν and show the existence of a dynamical transition for a chain of finite length. We find that the area of the hysteresis loop, A_{loop}, scales with the same exponents as observed in a recent study based on a much more detailed model. However, towards the true thermodynamic limit, the high-frequency scaling regime extends to lower frequencies for larger chain length L and the system has only one scaling (A_{loop}≈ν^{-1}F^{2}). Expansion of an analytical expression for A_{loop} obtained for the model system in the low-force regime revealed that there is a new scaling exponent associated with force (A_{loop}≈ν^{-1}F^{2.5}), which has been validated by high-precision numerical calculation. By a combination of analytical and numerical arguments, we also deduce that for large but finite L, the exponents are robust and independent of temperature and friction coefficient. PMID:26871010

  17. Acceleration efficiency in line-driven flows

    NASA Technical Reports Server (NTRS)

    Gayley, Kenneth G.; Owocki, Stanley P.

    1994-01-01

    We reexamine the physics of flow driving by line scattering of a continuum radiation source to determine the degree to which such line scattering can heat as well as accelerate the flow. Within the framework of the Sobolev theory for line transfer, we argue that the finite thermal width of the line scattering profile can lead to a significant 'Doppler heating' via photon frequency redistribution within a Sobolev resonance layer. Quantitative computation of this heating shows, however, that it is largely canceled by a corresponding cooling by the diffuse radiation. The resulting reduction in net Doppler heating or cooling means that the overall effect is only of limited importance in the energy balance of line-driven stellar winds. Through simple scaling relations, we compare the effect to other competing heating or cooling terms, including the ion-drag frictional heating recently discussed by Springmann and Pauldrach. We also provide a physical explanation of the unexpected cooling effect, and comment that its near cancellation of the anticipated heating provides another example of the tendency for ideal Sobolev theory to apply to a higher order than expected.

  18. Contour-Driven Atlas-Based Segmentation.

    PubMed

    Wachinger, Christian; Fritscher, Karl; Sharp, Greg; Golland, Polina

    2015-12-01

    We propose new methods for automatic segmentation of images based on an atlas of manually labeled scans and contours in the image. First, we introduce a Bayesian framework for creating initial label maps from manually annotated training images. Within this framework, we model various registration- and patch-based segmentation techniques by changing the deformation field prior. Second, we perform contour-driven regression on the created label maps to refine the segmentation. Image contours and image parcellations give rise to non-stationary kernel functions that model the relationship between image locations. Setting the kernel to the covariance function in a Gaussian process establishes a distribution over label maps supported by image structures. Maximum a posteriori estimation of the distribution over label maps conditioned on the outcome of the atlas-based segmentation yields the refined segmentation. We evaluate the segmentation in two clinical applications: the segmentation of parotid glands in head and neck CT scans and the segmentation of the left atrium in cardiac MR angiography images. PMID:26068202

  19. Driven Polymer Translocation into a Crosslinked Gel

    NASA Astrophysics Data System (ADS)

    Sean, David; Slater, Gary

    2015-03-01

    In a typical polymer translocation setup, a thin membrane is used to separate two chambers and a polyelectrolyte is driven by an electric field to translocate from one side of the membrane to the other via a small nanopore. However, the high translocation rate that results from the forces required to drive this process makes optical and/or electrical analysis of the translocating polymer challenging. Using coarse-grained Langevin Dynamics simulations we investigate how the translocation process can be slowed down by placing a crosslinked gel on the trans-side of the membrane. Since the driving electric field is localized in the neighborhood of the nanopore, electrophoretic migration is only achieved by a ``pushing'' action from the polymer segment residing in the nanopore. For the case of a flexible polymer we find that the polymer fills the gel pores via multiple ``herniation'' processes, whereas for a semi-flexible chain in a tight gel there are no hernias and the polymer follows a smooth curvilinear path. Moreover, for the case of a semi-flexible polymer the gel makes the translocation process more uniform by reducing the acceleration at the end of the process.

  20. Pressure driven flow in porous tubular membranes

    NASA Astrophysics Data System (ADS)

    Tilton, Nils; Martinand, Denis; Serre, Eric; Lueptow, Richard

    2011-11-01

    We consider the steady laminar flow of a Newtonian incompressible fluid in a porous tubular membrane with pressure-driven transmembrane flow. Due to its fundamental importance to membrane filtration systems, this flow has been studied extensively both analytically and numerically, yet a robust analytic solution has not been found. The problem is challenging due to the coupling between the transmembrane pressure and velocity with the simultaneous coupling between the axial pressure gradient and the axial velocity. We present a robust analytical solution which incorporates Darcy's law on the membrane surface. The solution is in the form of an asymptotic expansion about a small parameter related to the membrane permeability. We verify the analytical solution with comparison to 2-D spectral direct numerical simulations of ultrafiltration and microfiltration systems with typical operating conditions, as well as extreme cases of cross-flow reversal and axial flow exhaustion. In all cases, the agreement between the analytical and numerical results is excellent. Finally, we use the analytical and numerical results to provide guidelines about when common simplifying assumptions about the permeate flow may be made. Specifically, the assumptions of a parabolic axial velocity profile and uniform transmembrane velocity are valid only for small permeabilities.