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Sample records for artificial numerical length

  1. Introducing artificial length scales to tailor magnetic properties

    NASA Astrophysics Data System (ADS)

    Fassbender, J.; Strache, T.; Liedke, M. O.; Markó, D.; Wintz, S.; Lenz, K.; Keller, A.; Facsko, S.; Mönch, I.; McCord, J.

    2009-12-01

    Magnetism is a collective phenomenon. Hence, a local variation on the nanoscale of material properties, which act on the magnetic properties, affects the overall magnetism in an intriguing way. Of particular importance are the length scales on which a material property changes. These might be related to the exchange length, the domain wall width, a typical roughness correlation length, or a length scale introduced by patterning of the material. Here we report on the influence of two artificially created length scales: (i) ion erosion templates that serve as a source of a predefined surface morphology (ripple structure) and hence allow for the investigation of roughness phenomena. It is demonstrated that the ripple wave length can be easily tuned over a wide range (25-175 nm) by varying the primary ion erosion energy. The effect of this ripple morphology on the induced uniaxial magnetic anisotropy in soft magnetic Permalloy films is studied. Only below a ripple wavelength threshold (≈60 nm) is a significant induced magnetic anisotropy found. Above this threshold the corrugated Permalloy film acts as a flat film. This cross-over is discussed in the frame of dipolar interactions giving rise to the induced anisotropies. (ii) Ion implantation through a lithographically defined mask, which is used for a magnetic property patterning on various length scales. The resulting magnetic properties are neither present in non-implanted nor in homogeneously implanted films. Here new insight is gained by the comparison of different stripe patterning widths ranging from 1 to 10 μm. In addition, the appearance of more complicated magnetic domain structures, i.e. spin-flop domain configurations and head-on domain walls, during hard axis magnetization reversal is demonstrated. In both cases the magnetic properties, the magnetization reversal process as well as the magnetic domain configurations depend sensitively on the artificially introduced length scale.

  2. Numerical study of a microscopic artificial swimmer

    NASA Astrophysics Data System (ADS)

    Gauger, Erik; Stark, Holger

    2006-08-01

    We present a detailed numerical study of a microscopic artificial swimmer realized recently by Dreyfus in experiments [Dreyfus , Nature 437, 862 (2005)]. It consists of an elastic filament composed of superparamagnetic particles that are linked together by DNA strands. Attached to a load particle, the resulting swimmer is actuated by an oscillating external magnetic field so that it performs a nonreciprocal motion in order to move forward. We model the superparamagnetic filament by a bead-spring configuration that resists bending like a rigid rod and whose beads experience friction with the surrounding fluid and hydrodynamic interactions with each other. We show that, aside from finite-size effects, its dynamics is governed by the dimensionless sperm number, the magnitude of the magnetic field, and the angular amplitude of the field’s oscillating direction. Then we study the mean velocity and the efficiency of the swimmer as a function of these parameters and the size of the load particle. In particular, we clarify that the real velocity of the swimmer is influenced by two main factors, namely the shape of the beating filament (determined by the sperm number and the magnetic-field strength) and the oscillation frequency. Furthermore, the load size influences the performance of the swimmer and has to be chosen as a compromise between the largest swimming velocity and the best efficiency. Finally, we demonstrate that the direction of the swimming velocity changes in a symmetry-breaking transition when the angular amplitude of the field’s oscillating direction is increased, in agreement with experiments.

  3. Numerical evaluation of gas core length in free surface vortices

    NASA Astrophysics Data System (ADS)

    Cristofano, L.; Nobili, M.; Caruso, G.

    2014-11-01

    The formation and evolution of free surface vortices represent an important topic in many hydraulic intakes, since strong whirlpools introduce swirl flow at the intake, and could cause entrainment of floating matters and gas. In particular, gas entrainment phenomena are an important safety issue for Sodium cooled Fast Reactors, because the introduction of gas bubbles within the core causes dangerous reactivity fluctuation. In this paper, a numerical evaluation of the gas core length in free surface vortices is presented, according to two different approaches. In the first one, a prediction method, developed by the Japanese researcher Sakai and his team, has been applied. This method is based on the Burgers vortex model, and it is able to estimate the gas core length of a free surface vortex starting from two parameters calculated with single-phase CFD simulations. The two parameters are the circulation and the downward velocity gradient. The other approach consists in performing a two-phase CFD simulation of a free surface vortex, in order to numerically reproduce the gas- liquid interface deformation. Mapped convergent mesh is used to reduce numerical error and a VOF (Volume Of Fluid) method was selected to track the gas-liquid interface. Two different turbulence models have been tested and analyzed. Experimental measurements of free surface vortices gas core length have been executed, using optical methods, and numerical results have been compared with experimental measurements. The computational domain and the boundary conditions of the CFD simulations were set consistently with the experimental test conditions.

  4. Numerical Simulation of Flow Through an Artificial Heart

    NASA Technical Reports Server (NTRS)

    Rogers, Stuart E.; Kutler, Paul; Kwak, Dochan; Kiris, Cetin

    1989-01-01

    A solution procedure was developed that solves the unsteady, incompressible Navier-Stokes equations, and was used to numerically simulate viscous incompressible flow through a model of the Pennsylvania State artificial heart. The solution algorithm is based on the artificial compressibility method, and uses flux-difference splitting to upwind the convective terms; a line-relaxation scheme is used to solve the equations. The time-accuracy of the method is obtained by iteratively solving the equations at each physical time step. The artificial heart geometry involves a piston-type action with a moving solid wall. A single H-grid is fit inside the heart chamber. The grid is continuously compressed and expanded with a constant number of grid points to accommodate the moving piston. The computational domain ends at the valve openings where nonreflective boundary conditions based on the method of characteristics are applied. Although a number of simplifing assumptions were made regarding the geometry, the computational results agreed reasonably well with an experimental picture. The computer time requirements for this flow simulation, however, are quite extensive. Computational study of this type of geometry would benefit greatly from improvements in computer hardware speed and algorithm efficiency enhancements.

  5. A hybrid artificial bee colony algorithm for numerical function optimization

    NASA Astrophysics Data System (ADS)

    Alqattan, Zakaria N.; Abdullah, Rosni

    2015-02-01

    Artificial Bee Colony (ABC) algorithm is one of the swarm intelligence algorithms; it has been introduced by Karaboga in 2005. It is a meta-heuristic optimization search algorithm inspired from the intelligent foraging behavior of the honey bees in nature. Its unique search process made it as one of the most competitive algorithm with some other search algorithms in the area of optimization, such as Genetic algorithm (GA) and Particle Swarm Optimization (PSO). However, the ABC performance of the local search process and the bee movement or the solution improvement equation still has some weaknesses. The ABC is good in avoiding trapping at the local optimum but it spends its time searching around unpromising random selected solutions. Inspired by the PSO, we propose a Hybrid Particle-movement ABC algorithm called HPABC, which adapts the particle movement process to improve the exploration of the original ABC algorithm. Numerical benchmark functions were used in order to experimentally test the HPABC algorithm. The results illustrate that the HPABC algorithm can outperform the ABC algorithm in most of the experiments (75% better in accuracy and over 3 times faster).

  6. Numerical Simulation Of Flow Through An Artificial Heart

    NASA Technical Reports Server (NTRS)

    Rogers, Stuart; Kutler, Paul; Kwak, Dochan; Kiris, Centin

    1991-01-01

    Research in both artificial hearts and fluid dynamics benefits from computational studies. Algorithm that implements Navier-Stokes equations of flow extended to simulate flow of viscous, incompressible blood through articifial heart. Ability to compute details of such flow important for two reasons: internal flows with moving boundaries of academic interest in their own right, and many of deficiencies of artificial hearts attributable to dynamics of flow.

  7. Construction and characterization of bacterial artificial chromosomes (BACs) containing herpes simplex virus full-length genomes.

    PubMed

    Nagel, Claus-Henning; Pohlmann, Anja; Sodeik, Beate

    2014-01-01

    Bacterial artificial chromosomes (BACs) are suitable vectors not only to maintain the large genomes of herpesviruses in Escherichia coli but also to enable the traceless introduction of any mutation using modern tools of bacterial genetics. To clone a herpes simplex virus genome, a BAC replication origin is first introduced into the viral genome by homologous recombination in eukaryotic host cells. As part of their nuclear replication cycle, genomes of herpesviruses circularize and these replication intermediates are then used to transform bacteria. After cloning, the integrity of the recombinant viral genomes is confirmed by restriction length polymorphism analysis and sequencing. The BACs may then be used to design virus mutants. Upon transfection into eukaryotic cells new herpesvirus strains harboring the desired mutations can be recovered and used for experiments in cultured cells as well as in animal infection models. PMID:24671676

  8. Numerical solution of differential equations by artificial neural networks

    NASA Technical Reports Server (NTRS)

    Meade, Andrew J., Jr.

    1995-01-01

    Conventionally programmed digital computers can process numbers with great speed and precision, but do not easily recognize patterns or imprecise or contradictory data. Instead of being programmed in the conventional sense, artificial neural networks (ANN's) are capable of self-learning through exposure to repeated examples. However, the training of an ANN can be a time consuming and unpredictable process. A general method is being developed by the author to mate the adaptability of the ANN with the speed and precision of the digital computer. This method has been successful in building feedforward networks that can approximate functions and their partial derivatives from examples in a single iteration. The general method also allows the formation of feedforward networks that can approximate the solution to nonlinear ordinary and partial differential equations to desired accuracy without the need of examples. It is believed that continued research will produce artificial neural networks that can be used with confidence in practical scientific computing and engineering applications.

  9. A numerical investigation of the prompt oblique detonation wave sustained by a finite-length wedge

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Han, Xudong; Yao, Songbai; Wang, Jianping

    2016-03-01

    The prompt oblique detonation wave (PODW) sustained by a finite-length wedge is investigated by numerical simulation. The numerical results show that it is possible to stabilize a PODW on a finite-length wedge shorter than the induction length of the mixture behind the inert shock by numerically imposing a premature initiation of combustion in the initial flow field. The fully coupled and the partially coupled PODWs are observed in the numerical results. For the fully coupled PODW, the upstream facing transverse waves (UF TW) are swept downstream and consequently a fully coupled PODW can persist. For the partially coupled PODW, the UF TWs propagate upstream and the downstream facing transverse waves are weakened by the expansion wave emanating from the corner. As a result, a partially coupled PODW forms. Further, it is found that the stability of the partially coupled PODW is weak. The configuration of the partially coupled PODW can be altered by local explosions occurring downstream.

  10. Bit-parallel ASCII code artificial numeric keypad

    SciTech Connect

    Hale, G.M.

    1981-03-01

    Seven integrated circuits and a voltage regulator are combined with twelve reed relays to allow the ASCII encoded numerals 0 through 9 and characters ''.'' and R or S to momentarily close switches to an applications device, simulating keypad switch closures. This invention may be used as a PARALLEL TLL (Transistor Transistor Logic) data acqusition interface to a standard Hewlett-Packard HP-97 Calculator modified with a cable.

  11. Length of Hospital Stay Prediction at the Admission Stage for Cardiology Patients Using Artificial Neural Network.

    PubMed

    Tsai, Pei-Fang Jennifer; Chen, Po-Chia; Chen, Yen-You; Song, Hao-Yuan; Lin, Hsiu-Mei; Lin, Fu-Man; Huang, Qiou-Pieng

    2016-01-01

    For hospitals' admission management, the ability to predict length of stay (LOS) as early as in the preadmission stage might be helpful to monitor the quality of inpatient care. This study is to develop artificial neural network (ANN) models to predict LOS for inpatients with one of the three primary diagnoses: coronary atherosclerosis (CAS), heart failure (HF), and acute myocardial infarction (AMI) in a cardiovascular unit in a Christian hospital in Taipei, Taiwan. A total of 2,377 cardiology patients discharged between October 1, 2010, and December 31, 2011, were analyzed. Using ANN or linear regression model was able to predict correctly for 88.07% to 89.95% CAS patients at the predischarge stage and for 88.31% to 91.53% at the preadmission stage. For AMI or HF patients, the accuracy ranged from 64.12% to 66.78% at the predischarge stage and 63.69% to 67.47% at the preadmission stage when a tolerance of 2 days was allowed. PMID:27195660

  12. Parametric effects of CFL number and artificial smoothing on numerical solutions using implicit approximate factorization algorithm

    NASA Technical Reports Server (NTRS)

    Daso, E. O.

    1986-01-01

    An implicit approximate factorization algorithm is employed to quantify the parametric effects of Courant number and artificial smoothing on numerical solutions of the unsteady 3-D Euler equations for a windmilling propeller (low speed) flow field. The results show that propeller global or performance chracteristics vary strongly with Courant number and artificial dissipation parameters, though the variation is such less severe at high Courant numbers. Candidate sets of Courant number and dissipation parameters could result in parameter-dependent solutions. Parameter-independent numerical solutions can be obtained if low values of the dissipation parameter-time step ratio are used in the computations. Furthermore, it is realized that too much artificial damping can degrade numerical stability. Finally, it is demonstrated that highly resolved meshes may, in some cases, delay convergence, thereby suggesting some optimum cell size for a given flow solution. It is suspected that improper boundary treatment may account for the cell size constraint.

  13. Numerical Comparison of Artificial Recharge by Small-diameter Wells to Common Systems

    NASA Astrophysics Data System (ADS)

    Händel, F.; Liu, G.; Dietrich, P.; Liedl, R.; Fank, J.; Fank, A.; Butler, J. J.

    2013-12-01

    Scarcity of potable water has reached to a critical level all around the world. To address the temporal inequality of demand and availability of water resources, as well as additional purposes like enhancing water quality, artificial recharge is increasingly used. For shallow infiltration, such recharge methods as surface infiltration basins and trenches are commonly applied. However, these methods have significant disadvantages, e.g., enhanced clogging, evaporation, and an increased need of land use. Therefore, a new method for artificial recharge using shallow small-diameter wells is investigated. Such wells can be installed by Direct Push (DP) and water is allowed to infiltrate into aquifers by natural gravity, so that their installation and operation costs are very low. In this work, this method is compared numerically to a surface infiltration basin and a system applying horizontal filter pipes. For this, the work is divided into two parts. First, a rigorous comparison is done between the DP well and the infiltration basin. The simulated aquifer is composed of an unsaturated zone of 12 m and a saturated zone of 8 m. The results show the dependency of both methods on different components of the hydraulic conductivity, and highlight the advantages of the DP well over the basin. A small number of 5-cm shallow wells of 12 m length can be used to recharge water at the same infiltration rate as from a 60 m2 basin. When a layer of low hydraulic conductivity is present, the infiltration capacity of surface basins is significantly reduced while the adverse impacts on the wells are less pronounced due to the horizontal flow above the low conductivity layer (larger distance of water movement away from the screen). In the second part of this work, the DP wells will be compared to an operating horizontal, vadose zone artificial recharge system in Southern Styria, Austria. The water table is 3 m deep and horizontal filter pipes are used to recharge water into the shallow

  14. Numerical Modeling of Dependence of Separative Power of the Gas Centrifuge on the Length of Rotor

    NASA Astrophysics Data System (ADS)

    Bogovalov, S. V.; Borisevich, V. D.; Borman, V. D.; Tronin, I. V.; Tronin, V. N.

    Numerical modelling and optimization of the gas flow and isotope separation in the Iguasu gas centrifuge (GC) for uranium enrichment have been performed for different lengths of the rotor. The calculations show that the specific separative power of the GC reduces with the length of the rotor. We show that the reduction of the specific separative power is connected with the growth of the pressure in the optimal regime and corresponding growth of temperature to prevent the working gas sublimation. The specific separative power remains constant with the growth of the rotor length provided that the temperature of the rotor is taken to be constant.

  15. Coupling artificial intelligence and numerical computation for engineering design (Invited paper)

    NASA Astrophysics Data System (ADS)

    Tong, S. S.

    1986-01-01

    The possibility of combining artificial intelligence (AI) systems and numerical computation methods for engineering designs is considered. Attention is given to three possible areas of application involving fan design, controlled vortex design of turbine stage blade angles, and preliminary design of turbine cascade profiles. Among the AI techniques discussed are: knowledge-based systems; intelligent search; and pattern recognition systems. The potential cost and performance advantages of an AI-based design-generation system are discussed in detail.

  16. Length of Selection Around Candidate Genes for Artificial Selection During Domestication and Crop Improvement in Maize

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genomic screens for artificial selection have been successful in identifying candidate genes for agronomic traits in maize (Zea mays L). However, the validity of the candidates identified requires that selection sweeps are very short, only containing the candidate gene with the nearest neighboring g...

  17. Numerical modeling of artificial ionospheric layers driven by high-power HF-heating

    NASA Astrophysics Data System (ADS)

    Milikh, G. M.; Eliasson, B.; Shao, X.; Mishin, E. V.; Papadopoulos, K.

    2012-12-01

    We present a multi-scale dynamic model for the creation and propagation of artificial plasma layers in the ionosphere observed during high-power high frequency heating experiments at HAARP. Ordinary mode electromagnetic waves excite parametric instabilities and strong Langmuir turbulence near the reflection point. The coupling between high frequency electromagnetic and Langmuir waves and low-frequency ion acoustic waves is numerically simulated using a generalized Zakharov equation. The acceleration of plasma electrons is described by a Fokker-Planck model with an effective diffusion coefficient constructed using the simulated Langmuir wave spectrum. The propagation of the accelerated electrons through the non-uniform ionosphere is simulated by a kinetic model accounting for elastic and inelastic collisions with neutrals. The resulting ionization of neutral gas increases the plasma density below the acceleration region, so that the pump wave is reflected at a lower altitude. This leads to a new turbulent layer at the lower altitude, resulting in a descending artificial ionized layer, that moves from near 230 km to about 150 km. At the terminal altitude, ionization, recombination, and ambipolar diffusion reach equilibrium, so the descent stops. The modeling results reproduce artificial ionospheric layers produced for similar sets of parameters during the high-power HF experiments at HAARP.

  18. Numerical modeling of artificial ionospheric layers driven by high-power HF-heating

    NASA Astrophysics Data System (ADS)

    Eliasson, Bengt; Shao, Xi; Milikh, G.; Mishin, E. V.; Papadopoulos, K.

    2012-10-01

    We present a multi-scale dynamic model for the creation and propagation of artificial plasma layers in the ionosphere observed during high-power high frequency (HF) heating experiments at HAARP. Ordinary mode electromagnetic waves excite parametric instabilities and strong Langmuir turbulence near the reflection point. The coupling between high frequency electromagnetic and Langmuir waves and low-frequency ion acoustic waves is numerically simulated using a generalized Zakharov equation. The acceleration of plasma electrons is described by a Fokker-Planck model with an effective diffusion coefficient constructed using the simulated Langmuir wave spectrum. The propagation of the accelerated electrons through the non-uniform ionosphere is simulated by a kinetic model accounting for elastic and inelastic collisions with neutrals. The resulting ionization of neutral gas increases the plasma density below the acceleration region, so that the pump wave is reflected at a lower altitude. This leads to a new turbulent layer at the lower altitude, resulting in a descending artificial ionized layer that moves from near 230 km to about 150 km. The modeling results reproduce artificial ionospheric layers produced for similar sets of parameters during the high-power HF experiments at HAARP.

  19. Numerical modeling of artificial ionospheric layers driven by high-power HF heating

    NASA Astrophysics Data System (ADS)

    Eliasson, B.; Shao, X.; Milikh, G.; Mishin, E. V.; Papadopoulos, K.

    2012-10-01

    We present a multi-scale dynamic model for the creation and propagation of artificial plasma layers in the ionosphere observed during high-power high-frequency (HF) heating experiments at HAARP. Ordinary (O) mode electromagnetic (EM) waves excite parametric instabilities and strong Langmuir turbulence (SLT) near the reflection point. The coupling between high-frequency electromagnetic and Langmuir waves and low-frequency ion acoustic waves is numerically simulated using a generalized Zakharov equation. The acceleration of plasma electrons is described by a Fokker-Planck model with an effective diffusion coefficient constructed using the simulated Langmuir wave spectrum. The propagation of the accelerated electrons through the non-uniform ionosphere is simulated by a kinetic model accounting for elastic and inelastic collisions with neutrals. The resulting ionization of neutral gas increases the plasma density below the acceleration region, so that the pump wave is reflected at a lower altitude. This leads to a new turbulent layer at the lower altitude, resulting in a descending artificial ionized layer (DAIL), that moves from near 230 km to about 150 km. At the terminal altitude, ionization, recombination, and ambipolar diffusion reach equilibrium, so the descent stops. The modeling results reproduce artificial ionospheric layers produced for similar sets of parameters during the high-power HF experiments at HAARP.

  20. Euler solutions for blunt bodies using triangular meshes - Artificial viscosity forms and numerical boundary conditions

    NASA Technical Reports Server (NTRS)

    Winterstein, R.; Hafez, M.

    1993-01-01

    A finite volume method is used to calculate compressible inviscid flows over blunt bodies using, in general, unstructured grids. Artificial viscosity forms are derived based on a simplified least squares procedure. The extra second order terms are consistent with the governing equations, hence a systematic treatment of the numerical boundary conditions can be easily implemented. A special treatment of blunt bodies may be required. The discrete equations are linearized and the resulting system is solved by a relaxation method. Preliminary results indicate that the effect of the numerical dissipation is minimal. For subsonic flows over smooth bodies, the solution is practically vorticity-free and the total pressure loss is of the same order as the truncation error. Finally, some extensions of the present method are briefly discussed.

  1. Evolution of length scales and statistics of Richtmyer-Meshkov instability from direct numerical simulations.

    PubMed

    Tritschler, V K; Zubel, M; Hickel, S; Adams, N A

    2014-12-01

    In this study we present direct numerical simulation results of the Richtmyer-Meshkov instability (RMI) initiated by Ma=1.05,Ma=1.2, and Ma=1.5 shock waves interacting with a perturbed planar interface between air and SF(6). At the lowest shock Mach number the fluids slowly mix due to viscous diffusion, whereas at the highest shock Mach number the mixing zone becomes turbulent. When a minimum critical Taylor microscale Reynolds number is exceeded, an inertial range spectrum emerges, providing further evidence of transition to turbulence. The scales of turbulent motion, i.e., the Kolmogorov length scale, the Taylor microscale, and the integral length, scale are presented. The separation of these scales is found to increase as the Reynolds number is increased. Turbulence statistics, i.e., the probability density functions of the velocity and its longitudinal and transverse derivatives, show a self-similar decay and thus that turbulence evolving from RMI is not fundamentally different from isotropic turbulence, though nominally being only isotropic and homogeneous in the transverse directions. PMID:25615181

  2. A simple numerical model for membrane oxygenation of an artificial lung machine

    NASA Astrophysics Data System (ADS)

    Subraveti, Sai Nikhil; Sai, P. S. T.; Viswanathan Pillai, Vinod Kumar; Patnaik, B. S. V.

    2015-11-01

    Optimal design of membrane oxygenators will have far reaching ramification in the development of artificial heart-lung systems. In the present CFD study, we simulate the gas exchange between the venous blood and air that passes through the hollow fiber membranes on a benchmark device. The gas exchange between the tube side fluid and the shell side venous liquid is modeled by solving mass, momentum conservation equations. The fiber bundle was modelled as a porous block with a bundle porosity of 0.6. The resistance offered by the fiber bundle was estimated by the standard Ergun correlation. The present numerical simulations are validated against available benchmark data. The effect of bundle porosity, bundle size, Reynolds number, non-Newtonian constitutive relation, upstream velocity distribution etc. on the pressure drop, oxygen saturation levels etc. are investigated. To emulate the features of gas transfer past the alveoli, the effect of pulsatility on the membrane oxygenation is also investigated.

  3. Analysis and design of numerical schemes for gas dynamics. 2: Artificial diffusion and discrete shock structure

    NASA Technical Reports Server (NTRS)

    Jameson, Antony

    1994-01-01

    The effect of artificial diffusion on discrete shock structures is examined for a family of schemes which includes scalar diffusion, convective upwind and split pressure (CUSP) schemes, and upwind schemes with characteristics splitting. The analysis leads to conditions on the diffusive flux such that stationary discrete shocks can contain a single interior point. The simplest formulation which meets these conditions is a CUSP scheme in which the coefficients of the pressure differences is fully determined by the coefficient of convective diffusion. It is also shown how both the characteristic and CUSP schemes can be modified to preserve constant stagnation enthalpy in steady flow, leading to four variants, the E and H-characteristic schemes, and the E and H-CUSP schemes. Numerical results are presented which confirm the properties of these schemes.

  4. Proof of concept of an artificial muscle: theoretical model, numerical model, and hardware experiment.

    PubMed

    Haeufle, D F B; Günther, M; Blickhan, R; Schmitt, S

    2011-01-01

    Recently, the hyperbolic Hill-type force-velocity relation was derived from basic physical components. It was shown that a contractile element CE consisting of a mechanical energy source (active element AE), a parallel damper element (PDE), and a serial element (SE) exhibits operating points with hyperbolic force-velocity dependency. In this paper, the contraction dynamics of this CE concept were analyzed in a numerical simulation of quick release experiments against different loads. A hyperbolic force-velocity relation was found. The results correspond to measurements of the contraction dynamics of a technical prototype. Deviations from the theoretical prediction could partly be explained by the low stiffness of the SE, which was modeled analog to the metal spring in the hardware prototype. The numerical model and hardware prototype together, are a proof of this CE concept and can be seen as a well-founded starting point for the development of Hill-type artificial muscles. This opens up new vistas for the technical realization of natural movements with rehabilitation devices. PMID:22275541

  5. Numerical modelling of the flow and isotope separation in centrifuge Iguasu for different lengths of the rotor

    NASA Astrophysics Data System (ADS)

    Bogovalov, S. V.; Borisevich, V. D.; Borman, V. D.; Tronin, I. V.; Tronin, V. N.

    2016-06-01

    Numerical modelling and optimization of the gas flow and isotope separation in the Iguasu gas centrifuge (GC) for uranium enrichment have been performed for different lengths of the rotor. The calculations show that the specific separative power of the GC reduces with the length of the rotor. We show that the reduction of the specific separative power is connected with the growth of the pressure in the optimal regime and corresponding growth of temperature to prevent the working gas sublimation. The specific separative power remains constant with the growth of the rotor length provided that the temperature of the gas is taken to be constant.

  6. Run-length encoding graphic rules, biochemically editable designs and steganographical numeric data embedment for DNA-based cryptographical coding system.

    PubMed

    Kawano, Tomonori

    2013-03-01

    There have been a wide variety of approaches for handling the pieces of DNA as the "unplugged" tools for digital information storage and processing, including a series of studies applied to the security-related area, such as DNA-based digital barcodes, water marks and cryptography. In the present article, novel designs of artificial genes as the media for storing the digitally compressed data for images are proposed for bio-computing purpose while natural genes principally encode for proteins. Furthermore, the proposed system allows cryptographical application of DNA through biochemically editable designs with capacity for steganographical numeric data embedment. As a model case of image-coding DNA technique application, numerically and biochemically combined protocols are employed for ciphering the given "passwords" and/or secret numbers using DNA sequences. The "passwords" of interest were decomposed into single letters and translated into the font image coded on the separate DNA chains with both the coding regions in which the images are encoded based on the novel run-length encoding rule, and the non-coding regions designed for biochemical editing and the remodeling processes revealing the hidden orientation of letters composing the original "passwords." The latter processes require the molecular biological tools for digestion and ligation of the fragmented DNA molecules targeting at the polymerase chain reaction-engineered termini of the chains. Lastly, additional protocols for steganographical overwriting of the numeric data of interests over the image-coding DNA are also discussed. PMID:23750303

  7. Effect of coherence length and numerical aperture on the formation of OCT signals from model biotissues

    NASA Astrophysics Data System (ADS)

    Kirillin, Mikhail Y.; Priezzhev, Alexander V.; Myllyla, Risto

    2007-05-01

    Maximal depth of non-distorted imaging is an important characteristic, which shows the efficiency of an application of a certain OCT setup for imaging the given object. This characteristic depends on the setup parameters and the properties of the studied object. The definition of the maximal depth of non-distorted imaging based on the classifications of photons contributing to the signal in dependence on the relations of their optical travel pathlength in the object and maximal reached depth was used in this work. We studied the effect of the coherence length and the detection angle on the formation of OCT signals and images from model biotissues as well as on the maximal depth of non-distorted imaging. The signals and images were obtained by implementing the Monte Carlo technique developed in our earlier works. The following single- and multilayer biotissue phantoms were considered as the studied objects: erythrocyte suspension at physiological hematocrit (35%), 2% intralipid solution reported to have optical properties close to those of skin in optical and NIR range, and multilayer human skin phantoms. For the simulations, the parameters of the OCT setup were chosen in accordance with real ones. The wavelengths of the light sources were chosen 820 and 910 nm. The conducted simulations show that a decrease in the detection angle and an increase in the coherence length increase the maximal probing depth in the studied objects due to smaller role of multiple scattering photons in the formation of the OCT signals. The obtained value of maximal depth of non-distorted imaging varies in the range from 50 to 600 μm depending on the values of the setup parameters.

  8. Run-length encoding graphic rules, biochemically editable designs and steganographical numeric data embedment for DNA-based cryptographical coding system

    PubMed Central

    Kawano, Tomonori

    2013-01-01

    There have been a wide variety of approaches for handling the pieces of DNA as the “unplugged” tools for digital information storage and processing, including a series of studies applied to the security-related area, such as DNA-based digital barcodes, water marks and cryptography. In the present article, novel designs of artificial genes as the media for storing the digitally compressed data for images are proposed for bio-computing purpose while natural genes principally encode for proteins. Furthermore, the proposed system allows cryptographical application of DNA through biochemically editable designs with capacity for steganographical numeric data embedment. As a model case of image-coding DNA technique application, numerically and biochemically combined protocols are employed for ciphering the given “passwords” and/or secret numbers using DNA sequences. The “passwords” of interest were decomposed into single letters and translated into the font image coded on the separate DNA chains with both the coding regions in which the images are encoded based on the novel run-length encoding rule, and the non-coding regions designed for biochemical editing and the remodeling processes revealing the hidden orientation of letters composing the original “passwords.” The latter processes require the molecular biological tools for digestion and ligation of the fragmented DNA molecules targeting at the polymerase chain reaction-engineered termini of the chains. Lastly, additional protocols for steganographical overwriting of the numeric data of interests over the image-coding DNA are also discussed. PMID:23750303

  9. Numerical Study of Artificial Seal Formation to Remedy Leakage from Geological CO2 Storage Reservoirs

    NASA Astrophysics Data System (ADS)

    Ito, T.; Tanaka, H.; Xu, T.

    2011-12-01

    In the Carbon dioxide Capture and Storage (CCS), the CO2 is captured from emission source and stored into geological reservoirs at a depth below 800 m. The injected CO2 is less dense than water, and as a result, it tends to migrate upward. For trapping to inhibit the upward migration of CO2, the reservoirs should be covered with a sufficiently impermeable seal, i.e. caprock. However, the caprock may contain imperfections such as faults and fractures which will play a role of a high permeability path to arise leakage of the injected CO2 from the reservoirs. Pressurization with the injected CO2 can create fissures that may transmit CO2 through the caprock (Zoback and Zinke, 2002). Preparing for such risk of CO2 leakage through pre-existing and/or induced fractures, the International Energy Agency (IEA) has pointed out the importance of establishing a ready-to-use strategy for remediation of leakage from CO2 storage reservoirs (IEA, 2007). As one possibility to realize the strategy, we have proposed a concept to use an aqueous solution (Ito et al., 2006). The solution will have a sufficiently-low viscosity for passing through even small aperture, and it will not impact formation permeability as long as the solution is left as it is. When the solution encounters dissolved CO2, precipitation will occur due to chemical reaction. As a result, the permeability will be reduced by filling the pores and fractures in the rocks with the precipitates. In the present study, we demonstrated first this idea through laboratory experiments simulating subsurface condition at 1000 m deep, i.e. 10 MPa and 40 deg. C, and using a silicate solution reacting with CO2. In this case, the solution - CO2 reaction will produce precipitates of amorphous silica. The results of laboratory experiments show that the present method led to a 99 % permeability reduction in a glass-bead artificial rock even its initially-high permeability of few darcy. Such reduction of permeability was reproduced

  10. Radio wave refraction caused by artificial disturbances of the ionosphere - A numerical experiment

    NASA Astrophysics Data System (ADS)

    Ivanov, V. B.; Svistunov, K. V.

    The method of trajectory calculations is used to study short-wave propagation in the ionosphere, in the presence of large-scale inhomogeneities, due to plasma heating by means of high-power transmissions. It is shown that the refraction caused by the artificial disturbances can result in variations of the radio path distances, the occurrence of ricochet trajectories, and the focusing and defocusing of the radiation.

  11. Artificial compressibility methods for numerical solutions of transonic full potential equation

    NASA Technical Reports Server (NTRS)

    Hafez, M.; Murman, E.; South, J.

    1979-01-01

    New methods for transonic flow computations based on the full potential equation in conservation form are presented. The idea is to modify slightly the density (due to the artificial viscosity in the supersonic region), and solve the resulting elliptic-like problem iteratively. It is shown that standard discretization techniques (central differencing) as well as some standard iterative procedures (SOR, ADI, and explicit methods) are applicable to the modified transonic mixed-type equation. Calculations of transonic flows around cylinders and airfoils are discussed with special emphasis on the explicit methods that are suitable for vector processing on the STAR 100 computer.

  12. THEONA—a numerical-analytical theory of motion of artificial satellites of celestial bodies

    NASA Astrophysics Data System (ADS)

    Golikov, A. R.

    2012-11-01

    Basic principles of operation of the numerical-analytical theory THEONA (THéorie Numérique-Analytique) are presented, as well as force models taken into account and special functions used. Possibilities of applying the THEONA in problems of ballistic and navigation support are discussed. The accuracy of predicting the motion of the Earth's satellites is estimated for various classes of orbits.

  13. Confocal imaging and numerical simulations of converging flows in artificial microvessels

    NASA Astrophysics Data System (ADS)

    Hitt, Darren L.; Lowe, Mary L.

    1997-03-01

    A number of computational and experimental studies on flows in venular bifurcations have concentrated on the distribution of blood components and the formation of a 'separation surface' between two converging flows with different red blood cell concentrations and viscosities. To better understand these phenomena, we have used microfabrication techniques to construct artificial venular bifurcations with physiologically realistic dimensions. The current apparatus consists of a single bifurcation formed from tubes with semicircular cross sections of radius 50 (mu) . The vessels are fabricated from two glass slides using an abrasive etching process and a low melting point glass as sealant. Using a laser scanning confocal microscope, we have obtained the first three-dimensional images of flow structures in microscopic vessels; in particular we have imaged the separation surface for converging Newtonian fluids. A quantitative comparison is made between finite element simulations and experimental results of the position of the separation surface for different inlet flow ratios. Computed positions of the separation surface at the mid- depth of the outlet branch are in excellent agrement with experiment results obtained by confocal microscopy.

  14. Using an Artificial Neural Networks (ANNs) Model for Prediction of Intensive Care Unit (ICU) Outcome and Length of Stay at Hospital in Traumatic Patients

    PubMed Central

    Gholipour, Changiz; Rahim, Fakher; Fakhree, Abolghasem

    2015-01-01

    Introduction Currently applications of artificial neural network (ANN) models in outcome predicting of patients have made considerable strides in clinical medicine. This project aims to use a neural network for predicting survival and length of stay of patients in the ward and the intensive care unit (ICU) of trauma patients and to obtain predictive power of the current method. Materials and Methods We used Neuro-Solution software (NS), a leading-edge neural network software for data mining to create highly accurate and predictive models using advanced preprocessing techniques, intelligent automated neural network topology through cutting-edge distributed computing. This ANN model was used based on back-propagation, feed forward, and fed by Trauma and injury severity score (TRISS) components, biochemical findings, risk factors and outcome of 95 patients. In the next step a trained ANN was used to predict outcome, ICU and ward length of stay for 30 test group patients by processing primary data. Results The sensitivity and specificity of an ANN for predicting the outcome of traumatic patients in this study calculated 75% and 96.26%, respectively. 93.33% of outcome predictions obtained by ANN were correct. In 3.33% of predictions, results of ANN were optimistic and 3.33% of cases predicted ANN results were worse than the actual outcome of patients. Neither difference in average length of stay in the ward and ICU with predicted ANN results, were statistically significant. Correlation coefficient of two variables of ANN prediction and actual length of stay in hospital was equal to 0.643. Conclusion Using ANN model based on clinical and biochemical variables in patients with moderate to severe traumatic injury, resulted in satisfactory outcome prediction when applied to a test set. PMID:26023581

  15. Numerical analysis of blood flow in the clearance regions of a continuous flow artificial heart pump.

    PubMed

    Anderson, J; Wood, H G; Allaire, P E; Olsen, D B

    2000-06-01

    The CFVAD3 is the third prototype of a continuous flow ventricular assist device being developed for implantation in humans. The pump consists of a fully shrouded 4-blade impeller supported by magnetic bearings. On either side of this suspended rotating impeller is a small clearance region through which the blood flows. The spacing and geometry of these clearance regions are very important to the successful operation of this blood pump. Computational fluid dynamics (CFD) solutions for this flow were obtained using TascFlow, a software package available from AEA Technology, U.K. Flow in these clearance regions was studied parametrically by varying the size of the clearance, the blood flow rate into the pump, and the rotational speed of the pump. The numerical solutions yield the direction and magnitude of the flow and the dynamic pressure. Experimentally measured pump flow rates are compared to the numerical study. The results of the study provide guidance for improving pump efficiency. It is determined that current clearances can be significantly reduced to improve pump efficiency without negative impacts. PMID:10886072

  16. Numerical modelling of chirality-induced bi-directional swimming of artificial flagella.

    PubMed

    Namdeo, S; Khaderi, S N; Onck, P R

    2014-02-01

    Biomimetic micro-swimmers can be used for various medical applications, such as targeted drug delivery and micro-object (e.g. biological cells) manipulation, in lab-on-a-chip devices. Bacteria swim using a bundle of flagella (flexible hair-like structures) that form a rotating cork-screw of chiral shape. To mimic bacterial swimming, we employ a computational approach to design a bacterial (chirality-induced) swimmer whose chiral shape and rotational velocity can be controlled by an external magnetic field. In our model, we numerically solve the coupled governing equations that describe the system dynamics (i.e. solid mechanics, fluid dynamics and magnetostatics). We explore the swimming response as a function of the characteristic dimensionless parameters and put special emphasis on controlling the swimming direction. Our results provide fundamental physical insight on the chirality-induced propulsion, and it provides guidelines for the design of magnetic bi-directional micro-swimmers. PMID:24511253

  17. River flow forecasting with artificial neural networks using satellite observed precipitation pre-processed with flow length and travel time information: case study of the Ganges river basin

    NASA Astrophysics Data System (ADS)

    Akhtar, M. K.; Corzo, G. A.; van Andel, S. J.; Jonoski, A.

    2009-09-01

    This paper explores the use of flow length and travel time as a pre-processing step for incorporating spatial precipitation information into Artificial Neural Network (ANN) models used for river flow forecasting. Spatially distributed precipitation is commonly required when modelling large basins, and it is usually incorporated in distributed physically-based hydrological modelling approaches. However, these modelling approaches are recognised to be quite complex and expensive, especially due to the data collection of multiple inputs and parameters, which vary in space and time. On the other hand, ANN models for flow forecasting are frequently developed only with precipitation and discharge as inputs, usually without taking into consideration the spatial variability of precipitation. Full inclusion of spatially distributed inputs into ANN models still leads to a complex computational process that may not give acceptable results. Therefore, here we present an analysis of the flow length and travel time as a basis for pre-processing remotely sensed (satellite) rainfall data. This pre-processed rainfall is used together with local stream flow measurements of previous days as input to ANN models. The case study for this modelling approach is the Ganges river basin. A comparative analysis of multiple ANN models with different hydrological pre-processing is presented. The ANN showed its ability to forecast discharges 3-days ahead with an acceptable accuracy. Within this forecast horizon, the influence of the pre-processed rainfall is marginal, because of dominant influence of strongly auto-correlated discharge inputs. For forecast horizons of 7 to 10 days, the influence of the pre-processed rainfall is noticeable, although the overall model performance deteriorates. The incorporation of remote sensing data of spatially distributed precipitation information as pre-processing step showed to be a promising alternative for the setting-up of ANN models for river flow

  18. River flow forecasting with Artificial Neural Networks using satellite observed precipitation pre-processed with flow length and travel time information: case study of the Ganges river basin

    NASA Astrophysics Data System (ADS)

    Akhtar, M. K.; Corzo, G. A.; van Andel, S. J.; Jonoski, A.

    2009-04-01

    This paper explores the use of flow length and travel time as a pre-processing step for incorporating spatial precipitation information into Artificial Neural Network (ANN) models used for river flow forecasting. Spatially distributed precipitation is commonly required when modelling large basins, and it is usually incorporated in distributed physically-based hydrological modelling approaches. However, these modelling approaches are recognised to be quite complex and expensive, especially due to the data collection of multiple inputs and parameters, which vary in space and time. On the other hand, ANN models for flow forecasting are frequently developed only with precipitation and discharge as inputs, usually without taking into consideration the spatial variability of precipitation. Full inclusion of spatially distributed inputs into ANN models still leads to a complex computational process that may not give acceptable results. Therefore, here we present an analysis of the flow length and travel time as a basis for pre-processing remotely sensed (satellite) rainfall data. This pre-processed rainfall is used together with local stream flow measurements of previous days as input to ANN models. The case study for this modelling approach is the Ganges river basin. A comparative analysis of multiple ANN models with different hydrological pre-processing is presented. The ANN showed its ability to forecast discharges 3-days ahead with an acceptable accuracy. Within this forecast horizon, the influence of the pre-processed rainfall is marginal, because of dominant influence of strongly auto-correlated discharge inputs. For forecast horizons of 7 to 10 days, the influence of the pre-processed rainfall is noticeable, although the overall model performance deteriorates. The incorporation of remote sensing data of spatially distributed precipitation information as pre-processing step showed to be a promising alternative for the setting-up of ANN models for river flow

  19. A novel numerical technique for the high-precision simulation of flow processes related to artificial recharge

    NASA Astrophysics Data System (ADS)

    Stevens, David; Orsini, Paolo; Power, Henry; Morvan, Herve; Bensabat, Jacob

    2010-05-01

    This paper presents a novel numerical technique for large-scale groundwater flow simulations, in the frame of artificial recharge planning. The implementation is demonstrated using two test-sites from the EU funded GABARDINE project (FP6): The Sindos test site, near Thessaloniki, Greece, examines the infiltration of water towards the water table, through several unsaturated soil layers. The test site at Campina de Faro, Portugal, investigates phreatic surface movement around a large-diameter well. For both test cases a numerical simulation is constructed, and the local subsurface flow regime is investigated. Numerical methods for solving PDEs using interpolation with radial basis functions (RBFs) will typically provide high accuracy solutions, achieve excellent convergence rates, and offer great flexibility with regards to the enforcement of arbitrary boundary conditions. However, RBF methods have traditionally been limited to the solution of small academic problems, due to issues of computational cost and numerical conditioning. Recent developments in locally supported RBF methods have led to techniques which can be scaled to the largest problem sizes, while maintaining many of the flexibilities of traditional RBF methods. As a contribution to the GABARDINE project, two such numerical techniques have been developed; the meshless LHI method and the control-volume based CV-RBF method. These numerical techniques are capable of modelling flow and transport in heterogeneous porous media, and are of order-N computational complexity, allowing problems to be solved on large and irregular datasets. For both numerical techniques, the RBF Hermitian collocation method is utilised to perform interpolation at the local level, allowing the simultaneous imposition of pressure and mass-flux matching conditions at soil-layer interfaces. The non-overlapping stencil configuration then allows the accurate capture of non-smooth solution profiles across layer interfaces, to a high

  20. Application of a roughness-length representation to parameterize energy loss in 3-D numerical simulations of large rivers

    NASA Astrophysics Data System (ADS)

    Sandbach, S. D.; Lane, S. N.; Hardy, R. J.; Amsler, M. L.; Ashworth, P. J.; Best, J. L.; Nicholas, A. P.; Orfeo, O.; Parsons, D. R.; Reesink, A. J. H.; Szupiany, R. N.

    2012-12-01

    Recent technological advances in remote sensing have enabled investigation of the morphodynamics and hydrodynamics of large rivers. However, measuring topography and flow in these very large rivers is time consuming and thus often constrains the spatial resolution and reach-length scales that can be monitored. Similar constraints exist for computational fluid dynamics (CFD) studies of large rivers, requiring maximization of mesh- or grid-cell dimensions and implying a reduction in the representation of bedform-roughness elements that are of the order of a model grid cell or less, even if they are represented in available topographic data. These "subgrid" elements must be parameterized, and this paper applies and considers the impact of roughness-length treatments that include the effect of bed roughness due to "unmeasured" topography. CFD predictions were found to be sensitive to the roughness-length specification. Model optimization was based on acoustic Doppler current profiler measurements and estimates of the water surface slope for a variety of roughness lengths. This proved difficult as the metrics used to assess optimal model performance diverged due to the effects of large bedforms that are not well parameterized in roughness-length treatments. However, the general spatial flow patterns are effectively predicted by the model. Changes in roughness length were shown to have a major impact upon flow routing at the channel scale. The results also indicate an absence of secondary flow circulation cells in the reached studied, and suggest simpler two-dimensional models may have great utility in the investigation of flow within large rivers.

  1. Evaluation of bone remodeling around single dental implants of different lengths: a mechanobiological numerical simulation and validation using clinical data.

    PubMed

    Sotto-Maior, Bruno Salles; Mercuri, Emílio Graciliano Ferreira; Senna, Plinio Mendes; Assis, Neuza Maria Souza Picorelli; Francischone, Carlos Eduardo; Del Bel Cury, Altair Antoninha

    2016-01-01

    Algorithmic models have been proposed to explain adaptive behavior of bone to loading; however, these models have not been applied to explain the biomechanics of short dental implants. Purpose of present study was to simulate bone remodeling around single implants of different lengths using mechanoregulatory tissue differentiation model derived from the Stanford theory, using finite elements analysis (FEA) and to validate the theoretical prediction with the clinical findings of crestal bone loss. Loading cycles were applied on 7-, 10-, or 13-mm-long dental implants to simulate daily mastication and bone remodeling was assessed by changes in the strain energy density of bone after a 3, 6, and 12 months of function. Moreover, clinical findings of marginal bone loss in 45 patients rehabilitated with same implant designs used in the simulation (n = 15) were computed to validate the theoretical results. FEA analysis showed that although the bone density values reduced over time in the cortical bone for all groups, bone remodeling was independent of implant length. Clinical data showed a similar pattern of bone resorption compared with the data generated from mathematical analyses, independent of implant length. The results of this study showed that the mechanoregulatory tissue model could be employed in monitoring the morphological changes in bone that is subjected to biomechanical loads. In addition, the implant length did not influence the bone remodeling around single dental implants during the first year of loading. PMID:26249362

  2. Accuracy In Numerical Prediction Of Cavity Length and Vapor Cloud Shedding Frequency Of Cavitating Flows Over Various Geometries.

    NASA Astrophysics Data System (ADS)

    Jayaprakash, Arvind; Mahalatkar, Kathikeya

    2006-11-01

    Standard two-equation turbulence models have been found to be incapable of predicting cavitating flow due to high compressibility in the vapor region. In order to predict the dynamics of vapor cloud shedding, Courtier-Delgosha (J. of Fluid Eng, 125, 2003) suggested a modification for the eddy viscosity for k-epsilon turbulence model. Though the modification works in capturing the dynamic behavior of cavitation sheet, the accuracy of cavity length and frequency is not achieved for a wide range of cavitation numbers. This is due to the complex flow features present during a cavitating flow and the incapability of Couitier-Delgosh's turbulence modification to account for these factors. A tuning factor is introduced in the turbulence modification of Coutier-Delgosha, which can be adjusted for different types of geometries. This modified form is then tuned and tested on prediction of cavitating flow over several geometries including NACA 0015 hydrofoil, Convergent-Divergent Nozzle, and Wedge. Good comparisons for both cavity length and frequency of vapor cloud shedding were obtained for wide range of cavitation numbers in all the geometries. The commercial CFD software Fluent has been used for this analysis. Comparisons of cavity length and vapor cloud shedding frequency as predicted by the present turbulence modification and those observed in experimental studies will be presented.

  3. Steady-state response attenuation of a linear oscillator-nonlinear absorber system by using an adjustable-length pendulum in series: Numerical and experimental results

    NASA Astrophysics Data System (ADS)

    Eason, R. P.; Sun, C.; Dick, A. J.; Nagarajaiah, S.

    2015-05-01

    Response attenuation of a linear primary structure (PS)-nonlinear tuned mass damper (NTMD) dynamic system with and without an adaptive-length pendulum tuned mass damper (ALPTMD) in a series configuration is studied by using numerical and experimental methods. In the PS-NTMD system, coexisting high and low amplitude solutions are observed in the experiment, validating previous numerical efforts. In order to eliminate the potentially dangerous high amplitude solutions, a series ALPTMD with a mass multiple orders of magnitude smaller than the PS is added to the NTMD. The ALPTMD is used in order to represent the steady-state behavior of a smart tuned mass damper (STMD). In the experiment, the length of the pendulum is adjusted such that its natural frequency matches the dominant frequency of the harmonic ground motions. In the present study, the proposed ALPTMD can be locked so that it is unable to oscillate and influence the dynamics of the system in order to obtain the benefits provided by the NTMD. The experimental data show good qualitative agreement with numerical predictions computed with parameter continuation and time integration methods. Activation of the ALPTMD can successfully prevent the transition of the response from the low amplitude solution to the high amplitude solution or return the response from the high amplitude solution to the low amplitude solution, thereby protecting the PS.

  4. Numerical Simulation and Artificial Neural Network Modeling for Predicting Welding-Induced Distortion in Butt-Welded 304L Stainless Steel Plates

    NASA Astrophysics Data System (ADS)

    Narayanareddy, V. V.; Chandrasekhar, N.; Vasudevan, M.; Muthukumaran, S.; Vasantharaja, P.

    2016-02-01

    In the present study, artificial neural network modeling has been employed for predicting welding-induced angular distortions in autogenous butt-welded 304L stainless steel plates. The input data for the neural network have been obtained from a series of three-dimensional finite element simulations of TIG welding for a wide range of plate dimensions. Thermo-elasto-plastic analysis was carried out for 304L stainless steel plates during autogenous TIG welding employing double ellipsoidal heat source. The simulated thermal cycles were validated by measuring thermal cycles using thermocouples at predetermined positions, and the simulated distortion values were validated by measuring distortion using vertical height gauge for three cases. There was a good agreement between the model predictions and the measured values. Then, a multilayer feed-forward back propagation neural network has been developed using the numerically simulated data. Artificial neural network model developed in the present study predicted the angular distortion accurately.

  5. Numerical estimates of secular effects in the translational-rotational motion of an orbital station with artificial gravity

    NASA Astrophysics Data System (ADS)

    Koenov, D. Z.

    The coefficients of the secular terms in the translational-rotational motion of an orbital station with artificial gravity were determined. It is shown that the mean anomaly M = 1 of the mass center of the station for every mean solar day increases by about 5179.25 deg. This indicates that the station makes more than 14 revolutions about the earth in the course of a mean solar day.

  6. Comparative evaluation of numerical model and artificial neural network for simulating groundwater flow in Kathajodi-Surua Inter-basin of Odisha, India

    NASA Astrophysics Data System (ADS)

    Mohanty, S.; Jha, Madan K.; Kumar, Ashwani; Panda, D. K.

    2013-07-01

    In view of worldwide concern for the sustainability of groundwater resources, basin-wide modeling of groundwater flow is essential for the efficient planning and management of groundwater resources in a groundwater basin. The objective of the present study is to evaluate the performance of finite difference-based numerical model MODFLOW and the artificial neural network (ANN) model developed in this study in simulating groundwater levels in an alluvial aquifer system. Calibration of the MODFLOW was done by using weekly groundwater level data of 2 years and 4 months (February 2004 to May 2006) and validation of the model was done using 1 year of groundwater level data (June 2006 to May 2007). Calibration of the model was performed by a combination of trial-and-error method and automated calibration code PEST with a mean RMSE (root mean squared error) value of 0.62 m and a mean NSE (Nash-Sutcliffe efficiency) value of 0.915. Groundwater levels at 18 observation wells were simulated for the validation period. Moreover, artificial neural network models were developed to predict groundwater levels in 18 observation wells in the basin one time step (i.e., week) ahead. The inputs to the ANN model consisted of weekly rainfall, evaporation, river stage, water level in the drain, pumping rate of the tubewells and groundwater levels in these wells at the previous time step. The time periods used in the MODFLOW were also considered for the training and testing of the developed ANN models. Out of the 174 data sets, 122 data sets were used for training and 52 data sets were used for testing. The simulated groundwater levels by MODFLOW and ANN model were compared with the observed groundwater levels. It was found that the ANN model provided better prediction of groundwater levels in the study area than the numerical model for short time-horizon predictions.

  7. Oxygenation to Bovine Blood in Artificial Heart and Lung Using Vibrating Flow Pump: Experiment and Numerical Analysis Based on Non-Newtonian Model

    NASA Astrophysics Data System (ADS)

    Shintaku, Hirofumi; Yonemura, Tsubasa; Tsuru, Kazuaki; Isoyama, Takashi; Yambe, Tomoyuki; Kawano, Satoyuki

    In this study, we construct an experimental apparatus for a prototype artificial heart and lung (AHL) by installing hollow fibers into the cylindrical tube of the vibrating flow pump (VFP). The oxygenation characteristics are investigated both by experiments using bovine blood and by numerical analyses based on the computational fluid dynamics. The analyses are carried out at the Reynolds numbers Re ranged from O(1) to O(103), which are determined based on the experimental conditions. The blood flow and the diffusion of oxygen gas are analyzed based on the Newtonian/non-Newtonian, unsteady, incompressible and axisymmetric Navier-Stokes equations, and the advection-diffusion equation. The results show that the oxygenation rate increases in proportion to Re1/3, where the phenomenon corresponds to the decreasing thickness of the concentration boundary layer with Re. Although the effects of the vibrating flow and the rheology of the blood are clearly appeared on the velocity field, their effects on the gas exchange are relatively small at the ranges of prescribed Reynolds numbers. Furthermore, the numerical results in terms of the oxygenation rate are compared with the experimental ones. The basic design data of VFP were accumulated for the development of AHL in the clinical applications.

  8. Optimal Length of Low Reynolds Number Nanopropellers.

    PubMed

    Walker, D; Kübler, M; Morozov, K I; Fischer, P; Leshansky, A M

    2015-07-01

    Locomotion in fluids at the nanoscale is dominated by viscous drag. One efficient propulsion scheme is to use a weak rotating magnetic field that drives a chiral object. From bacterial flagella to artificial drills, the corkscrew is a universally useful chiral shape for propulsion in viscous environments. Externally powered magnetic micro- and nanomotors have been recently developed that allow for precise fuel-free propulsion in complex media. Here, we combine analytical and numerical theory with experiments on nanostructured screw-propellers to show that the optimal length is surprisingly short-only about one helical turn, which is shorter than most of the structures in use to date. The results have important implications for the design of artificial actuated nano- and micropropellers and can dramatically reduce fabrication times, while ensuring optimal performance. PMID:26030270

  9. Effect of Coulomb screening length on nuclear "pasta" simulations

    NASA Astrophysics Data System (ADS)

    Alcain, P. N.; Giménez Molinelli, P. A.; Nichols, J. I.; Dorso, C. O.

    2014-05-01

    We study the role of the effective Coulomb interaction strength and length on the dynamics of nucleons in conditions according to those in a neutron star's crust. Calculations were made with a semiclassical molecular dynamics model, studying isospin symmetric matter at subsaturation densities and low temperatures. The electrostatic interaction between protons is included as a screened Coulomb potential in the spirit of the Thomas-Fermi approximation, but the screening length is artificially varied to explore its effect on the formation of the nonhomogeneous nuclear structures known as "nuclear pasta." As the screening length increases, we can see a transition from a one-per-cell pasta regime (due exclusively to finite-size effects) to a more appealing multiple pasta per simulation box. This qualitative difference in the structure of neutron star matter at low temperatures shows that special caution should be taken when the screening length is estimated for numerical simulations.

  10. Artificial Limbs

    MedlinePlus

    ... you are missing an arm or leg, an artificial limb can sometimes replace it. The device, which ... activities such as walking, eating, or dressing. Some artificial limbs let you function nearly as well as ...

  11. Artificial Intelligence.

    ERIC Educational Resources Information Center

    Waltz, David L.

    1982-01-01

    Describes kinds of results achieved by computer programs in artificial intelligence. Topics discussed include heuristic searches, artificial intelligence/psychology, planning program, backward chaining, learning (focusing on Winograd's blocks to explore learning strategies), concept learning, constraint propagation, language understanding…

  12. Artificial Intelligence.

    ERIC Educational Resources Information Center

    Information Technology Quarterly, 1985

    1985-01-01

    This issue of "Information Technology Quarterly" is devoted to the theme of "Artificial Intelligence." It contains two major articles: (1) Artificial Intelligence and Law" (D. Peter O'Neill and George D. Wood); (2) "Artificial Intelligence: A Long and Winding Road" (John J. Simon, Jr.). In addition, it contains two sidebars: (1) "Calculating and…

  13. Numerical study of sub-millimeter Gunn oscillations in InP and GaN vertical diodes: Dependence on bias, doping, and length

    NASA Astrophysics Data System (ADS)

    García, S.; Íñiguez-de-la-Torre, I.; Pérez, S.; Mateos, J.; González, T.

    2013-08-01

    In this work, we report on Monte Carlo simulations of InP and GaN vertical Gunn diodes to optimize their oscillation frequency and DC to AC conversion efficiency. We show that equivalent operating conditions are achieved by the direct application of a sinusoidal AC voltage superimposed to the DC bias and by the simulation of the intrinsic device coupled with the consistent solution of a parallel RLC resonant circuit connected in series. InP diodes with active region about 1 μm offer a conversion efficiency up to 5.5% for frequencies around 225 GHz. By virtue of the larger saturation velocity, for a given diode length, oscillation frequencies in GaN diodes are higher than for InP structures. Current oscillations at frequencies as high as 675 GHz, with 0.1% efficiency, are predicted at the sixth generation band in a 0.9 μm-long GaN diode, corroborating the suitability of GaN to operate near the THz band. At the first generation band, structures with notch, in general, provide lower oscillation frequencies and efficiencies in comparison with the same structures without notch. However, a higher number of generation bands are originated in notched diodes, thus, typically reaching larger frequencies. Self-heating effects reduce the performance, but in GaN diodes the efficiency is not significantly degraded.

  14. Comparison of Artificial Compressibility Methods

    NASA Technical Reports Server (NTRS)

    Kiris, Cetin; Housman, Jeffrey; Kwak, Dochan

    2004-01-01

    Various artificial compressibility methods for calculating the three-dimensional incompressible Navier-Stokes equations are compared. Each method is described and numerical solutions to test problems are conducted. A comparison based on convergence behavior, accuracy, and robustness is given.

  15. Stability Affects of Artificial Viscosity in Detonation Modeling

    SciTech Connect

    Vitello, P; Souers, P C

    2002-06-03

    Accurate multi-dimensional modeling of detonation waves in solid HE materials is a difficult task. To treat applied problems which contain detonation waves one must consider reacting flow with a wide range of length-scales, non-linear equations of state (EOS), and material interfaces at which the detonation wave interacts with other materials. To be useful numerical models of detonation waves must be accurate, stable, and insensitive to details of the modeling such as the mesh spacing, and mesh aspect ratio for multi-dimensional simulations. Studies we have performed show that numerical simulations of detonation waves can be very sensitive to the form of the artificial viscosity term used. The artificial viscosity term is included in our ALE hydrocode to treat shock discontinuities. We show that a monotonic, second order artificial viscosity model derived from an approximate Riemann solver scheme can strongly damp unphysical oscillations in the detonation wave reaction zone, improving the detonation wave boundary wall interaction. These issues are demonstrated in 2D model simulations presented of the 'Bigplate' test. Results using LX-I 7 explosives are compared with numerical simulation results to demonstrate the affects of the artificial viscosity model.

  16. An artificial compound eye of photon Sieves

    NASA Astrophysics Data System (ADS)

    Jiang, Wenbo; Hu, Song; He, Yu; Bu, Yun

    2015-11-01

    The compound eye of insects has numerous extraordinary optical performances, such as minimum chromatic aberration, wide-angle field of view, and high sensitivity to the incidence light. Inspired by these unique performances, we present a novel artificial compound eye of photon sieves in this paper, where the photon sieves play the roles of insects' ommatidia. These photon sieves have the same focal length. The incidence light can be focused into the same focal plane and produce the superposition effect, the utilization ratio of energy can be largely improved. Through the numerical simulation, the results show that this novel structure has similar focusing performance with the conventional photon sieves, but has higher utilization ratio of energy and wider angle field of view than that of the conventional photon sieves. Our findings provide a new direction for optics and biology researchers, which will be beneficial for medical imaging, astronomy, etc.

  17. Artificial gravity experiment satellites

    NASA Astrophysics Data System (ADS)

    Harada, Tadashi

    1992-07-01

    An overview of the conceptual study of an artificial gravity experiment satellite based on the assumption of a launch by the H-2 launch vehicle with a target launch date in the Year 2000 is presented. While many satellites provided with artificial gravity have been reported in relation to a manned Mars exploration spacecraft mission, the review has been conducted on missions and test subjects only for experimental purposes. Mission requirements were determined based on the results of reviews on the mission, test subjects, and model missions. The system baseline and development plan were based on the results of a study on conceptual structure and scale of the system, including measures to generate artificial gravity. Approximate scale of the system and arm length, mission orbit, visibility of the operation orbit from ground stations in Japan, and satellite attitude on the mission orbit are outlined.

  18. Artificial Intelligence.

    ERIC Educational Resources Information Center

    Smith, Linda C.; And Others

    1988-01-01

    A series of articles focuses on artificial intelligence research and development to enhance information systems and services. Topics discussed include knowledge base designs, expert system development tools, natural language processing, expert systems for reference services, and the role that artificial intelligence concepts should have in…

  19. Artificial intelligence

    SciTech Connect

    Firschein, O.

    1984-01-01

    This book presents papers on artificial intelligence. Topics considered include knowledge engineering, expert systems, applications of artificial intelligence to scientific reasoning, planning and problem solving, error recovery in robots through failure reason analysis, programming languages, natural language, speech recognition, map-guided interpretation of remotely-sensed imagery, and image understanding architectures.

  20. Artificial Intelligence.

    ERIC Educational Resources Information Center

    Thornburg, David D.

    1986-01-01

    Overview of the artificial intelligence (AI) field provides a definition; discusses past research and areas of future research; describes the design, functions, and capabilities of expert systems and the "Turing Test" for machine intelligence; and lists additional sources for information on artificial intelligence. Languages of AI are also briefly…

  1. Numerical Model of Full Cardiac Cycle Hemodynamics in a Total Artificial Heart and the Effect of Its Size on Platelet Activation

    PubMed Central

    Marom, Gil; Chiu, Wei-Che; Crosby, Jessica R.; DeCook, Katrina J.; Prabhakar, Saurabh; Horner, Marc; Slepian, Marvin J.; Bluestein, Danny

    2014-01-01

    The SynCardia total artificial heart (TAH) is the only FDA approved device for replacing hearts in patients with congestive heart failure. It pumps blood via pneumatically driven diaphragms and controls the flow with mechanical valves. While it has been successfully implanted in more than 1,300 patients, its size precludes implantation in smaller patients. This study’s aim was to evaluate the viability of scaled-down TAHs by quantifying thrombogenic potentials from flow patterns. Simulations of systole were first conducted with stationary valves, followed by an advanced full-cardiac-cycle model with moving valves. All the models included deforming diaphragms and platelet suspension in the blood flow. Flow stress-accumulations were computed for the platelet trajectories and thrombogenic potentials were assessed. The simulations successfully captured complex flow patterns during various phases of the cardiac-cycle. Increased stress-accumulations, but within the safety margin of acceptable thrombogenicity, were found in smaller TAHs, indicating that they are clinically viable. PMID:25354999

  2. Numerical model of full-cardiac cycle hemodynamics in a total artificial heart and the effect of its size on platelet activation.

    PubMed

    Marom, Gil; Chiu, Wei-Che; Crosby, Jessica R; DeCook, Katrina J; Prabhakar, Saurabh; Horner, Marc; Slepian, Marvin J; Bluestein, Danny

    2014-12-01

    The SynCardia total artificial heart (TAH) is the only Food and Drug Administration (FDA) approved device for replacing hearts in patients with congestive heart failure. It pumps blood via pneumatically driven diaphragms and controls the flow with mechanical valves. While it has been successfully implanted in more than 1300 patients, its size precludes implantation in smaller patients. This study's aim was to evaluate the viability of scaled-down TAHs by quantifying thrombogenic potentials from flow patterns. Simulations of systole were first conducted with stationary valves, followed by an advanced full-cardiac cycle model with moving valves. All the models included deforming diaphragms and platelet suspension in the blood flow. Flow stress accumulations were computed for the platelet trajectories and thrombogenic potentials were assessed. The simulations successfully captured complex flow patterns during various phases of the cardiac cycle. Increased stress accumulations, but within the safety margin of acceptable thrombogenicity, were found in smaller TAHs, indicating that they are clinically viable. PMID:25354999

  3. Numerical Simulation of Ground-Water Flow and Assessment of the Effects of Artificial Recharge in the Rialto-Colton Basin, San Bernardino County, California

    USGS Publications Warehouse

    Woolfenden, Linda R.; Koczot, Kathryn M.

    2001-01-01

    The Rialto?Colton Basin, in western San Bernardino County, California, was chosen for storage of imported water because of the good quality of native ground water, the known storage capacity for additional ground-water storage in the basin, and the availability of imported water. To supplement native ground-water resources and offset overdraft conditions in the basin during dry periods, artificial-recharge operations during wet periods in the Rialto?Colton Basin were begun in 1982 to store surplus imported water. Local water purveyors recognized that determining the movement and ultimate disposition of the artificially recharged imported water would require a better understanding of the ground-water flow system. In this study, a finite-difference model was used to simulate ground-water flow in the Rialto?Colton Basin to gain a better understanding of the ground-water flow system and to evaluate the hydraulic effects of artificial recharge of imported water. The ground-water basin was simulated as four horizontal layers representing the river- channel deposits and the upper, middle, and lower water-bearing units. Several flow barriers bordering and internal to the Rialto?Colton Basin influence the direction of ground-water flow. Ground water may flow relatively unrestricted in the shallow parts of the flow system; however, the faults generally become more restrictive at depth. A particle-tracking model was used to simulate advective transport of imported water within the ground-water flow system and to evaluate three artificial-recharge alternatives. The ground-water flow model was calibrated to transient conditions for 1945?96. Initial conditions for the transient-state simulation were established by using 1945 recharge and discharge rates, and assuming no change in storage in the basin. Average hydrologic conditions for 1945?96 were used for the predictive simulations (1997?2027). Ground-water-level measurements made during 1945 were used for comparison with the

  4. Artificial urushi.

    PubMed

    Kobayashi, S; Uyama, H; Ikeda, R

    2001-11-19

    A new concept for the design and laccase-catalyzed preparation of "artificial urushi" from new urushiol analogues is described. The curing proceeded under mild reaction conditions to produce the very hard cross-linked film (artificial urushi) with a high gloss surface. A new cross-linkable polyphenol was synthesized by oxidative polymerization of cardanol, a phenol derivative from cashew-nut-shell liquid, by enzyme-related catalysts. The polyphenol was readily cured to produce the film (also artificial urushi) showing excellent dynamic viscoelasticity. PMID:11763444

  5. Intracardiac calipers for artificial chordae replacement in mitral valve repair.

    PubMed

    Doi, Atsuo; Iida, Hiroshi; Sunazawa, Toru

    2009-01-01

    Length adjustment of artificial chordae is crucial in the outcome of anterior mitral valve repair. Herein, a simple and reproducible method of artificial chordal replacement using polytetrafluoroethylene suture is described. With this technique, the length of the neo-chordae is easily decided and the knot can be tied surely without change in the length using only one instrument. PMID:19101333

  6. Artificial noses.

    PubMed

    Stitzel, Shannon E; Aernecke, Matthew J; Walt, David R

    2011-08-15

    The mammalian olfactory system is able to detect many more odorants than the number of receptors it has by utilizing cross-reactive odorant receptors that generate unique response patterns for each odorant. Mimicking the mammalian system, artificial noses combine cross-reactive sensor arrays with pattern recognition algorithms to create robust odor-discrimination systems. The first artificial nose reported in 1982 utilized a tin-oxide sensor array. Since then, however, a wide range of sensor technologies have been developed and commercialized. This review highlights the most commonly employed sensor types in artificial noses: electrical, gravimetric, and optical sensors. The applications of nose systems are also reviewed, covering areas such as food and beverage quality control, chemical warfare agent detection, and medical diagnostics. A brief discussion of future trends for the technology is also provided. PMID:21417721

  7. Artificial Intelligence.

    ERIC Educational Resources Information Center

    Wash, Darrel Patrick

    1989-01-01

    Making a machine seem intelligent is not easy. As a consequence, demand has been rising for computer professionals skilled in artificial intelligence and is likely to continue to go up. These workers develop expert systems and solve the mysteries of machine vision, natural language processing, and neural networks. (Editor)

  8. Artificial Intelligence.

    PubMed

    Lawrence, David R; Palacios-González, César; Harris, John

    2016-04-01

    It seems natural to think that the same prudential and ethical reasons for mutual respect and tolerance that one has vis-à-vis other human persons would hold toward newly encountered paradigmatic but nonhuman biological persons. One also tends to think that they would have similar reasons for treating we humans as creatures that count morally in our own right. This line of thought transcends biological boundaries-namely, with regard to artificially (super)intelligent persons-but is this a safe assumption? The issue concerns ultimate moral significance: the significance possessed by human persons, persons from other planets, and hypothetical nonorganic persons in the form of artificial intelligence (AI). This article investigates why our possible relations to AI persons could be more complicated than they first might appear, given that they might possess a radically different nature to us, to the point that civilized or peaceful coexistence in a determinate geographical space could be impossible to achieve. PMID:26957450

  9. Comparison of Artificial Compressibility Methods

    NASA Technical Reports Server (NTRS)

    Kiris, Cetin; Housman, Jeffrey; Kwak, Dochan

    2003-01-01

    Various artificial compressibility methods for calculating three-dimensional, steady and unsteady, laminar and turbulent, incompressible Navier-Stokes equations are compared in this work. Each method is described in detail along with appropriate physical and numerical boundary conditions. Analysis of well-posedness and numerical solutions to test problems for each method are provided. A comparison based on convergence behavior, accuracy, stability and robustness is used to establish the relative positive and negative characteristics of each method.

  10. Artificial mismatch hybridization

    DOEpatents

    Guo, Zhen; Smith, Lloyd M.

    1998-01-01

    An improved nucleic acid hybridization process is provided which employs a modified oligonucleotide and improves the ability to discriminate a control nucleic acid target from a variant nucleic acid target containing a sequence variation. The modified probe contains at least one artificial mismatch relative to the control nucleic acid target in addition to any mismatch(es) arising from the sequence variation. The invention has direct and advantageous application to numerous existing hybridization methods, including, applications that employ, for example, the Polymerase Chain Reaction, allele-specific nucleic acid sequencing methods, and diagnostic hybridization methods.

  11. Artificial halos

    NASA Astrophysics Data System (ADS)

    Selmke, Markus

    2015-09-01

    Judged by their frequency and beauty, ice halos easily rival rainbows as a prominent atmospheric optics phenomenon. This article presents experimental halo demonstrations of varying complexity. Using a single commercially available hexagonal glass prism, a variety of artificial halos can be simulated. The experiments include laser beam path analysis, a modified classic spinning prism experiment, and a novel Monte-Carlo machine for three-dimensional rotations. Each of these experiments emulates different conditions of certain halo displays, and in combination, they allow a thorough understanding of these striking phenomena.

  12. Numerical model of the earth artificial satellite.New version. (Russian Title: Численная модель движения ИСЗ. Новая версия . 2007. Т.50. № 12/2. С. 60-65.)

    NASA Astrophysics Data System (ADS)

    Bordovitsyna, T. V.; Baturin, A. P.; Avdyushev, V., A.; Kulikova, P. V.

    2007-12-01

    Describing of the new version of the program complex "Numerical model of the earth artificial satellite (EAS) motion" is present. Modifications are connected with increasing models of forces acting at earth's artificial satellite. Models are constructed with agreement of IERS standart-2003 and national atmospheric GOST P25645.166-2004. The program complex may be used for the calculation space positions of EAS and the improvement of their orbit.

  13. Artificial rheotaxis

    PubMed Central

    Palacci, Jérémie; Sacanna, Stefano; Abramian, Anaïs; Barral, Jérémie; Hanson, Kasey; Grosberg, Alexander Y.; Pine, David J.; Chaikin, Paul M.

    2015-01-01

    Motility is a basic feature of living microorganisms, and how it works is often determined by environmental cues. Recent efforts have focused on developing artificial systems that can mimic microorganisms, in particular their self-propulsion. We report on the design and characterization of synthetic self-propelled particles that migrate upstream, known as positive rheotaxis. This phenomenon results from a purely physical mechanism involving the interplay between the polarity of the particles and their alignment by a viscous torque. We show quantitative agreement between experimental data and a simple model of an overdamped Brownian pendulum. The model notably predicts the existence of a stagnation point in a diverging flow. We take advantage of this property to demonstrate that our active particles can sense and predictably organize in an imposed flow. Our colloidal system represents an important step toward the realization of biomimetic microsystems with the ability to sense and respond to environmental changes. PMID:26601175

  14. Artificial Hydrogenases

    PubMed Central

    Barton, Bryan E.; Olsen, Matthew T.; Rauchfuss, Thomas B.

    2010-01-01

    Decades of biophysical study on the hydrogenase (H2ase) enzymes have yielded sufficient information to guide the synthesis of analogues of their active sites. Three families of enzymes serve as inspiration for this work: the [FeFe]-, [NiFe]-, and [Fe]-H2ases, all of which feature iron centers bound to both CO and thiolate. Artificial H2ases effect the oxidation of H2 of H2 and the reverse reaction, the reduction of protons. These reactions occur via the intermediacy of metal hydrides. The inclusion of amine bases within the catalysts is an important design feature that is emulated in related bioinspired catalysts. Continuing challenges are the low reactivity of H2 towards biomimetic H2ases. PMID:20356731

  15. Artificial rheotaxis.

    PubMed

    Palacci, Jérémie; Sacanna, Stefano; Abramian, Anaïs; Barral, Jérémie; Hanson, Kasey; Grosberg, Alexander Y; Pine, David J; Chaikin, Paul M

    2015-05-01

    Motility is a basic feature of living microorganisms, and how it works is often determined by environmental cues. Recent efforts have focused on developing artificial systems that can mimic microorganisms, in particular their self-propulsion. We report on the design and characterization of synthetic self-propelled particles that migrate upstream, known as positive rheotaxis. This phenomenon results from a purely physical mechanism involving the interplay between the polarity of the particles and their alignment by a viscous torque. We show quantitative agreement between experimental data and a simple model of an overdamped Brownian pendulum. The model notably predicts the existence of a stagnation point in a diverging flow. We take advantage of this property to demonstrate that our active particles can sense and predictably organize in an imposed flow. Our colloidal system represents an important step toward the realization of biomimetic microsystems with the ability to sense and respond to environmental changes. PMID:26601175

  16. Artificial Respiration and Artificial Circulation

    PubMed Central

    Brook, Joseph; Brook, Morris H.; Lopez, Jose F.

    1965-01-01

    A training program in the newer methods of treatment of acute cardiopulmonary emergencies which was developed at the University Hospital, University of Saskatchewan, is reported. Artificial respiration by the chance rescuer, primary and secondary resuscitation, and post-resuscitation measures involving the use of special drugs and equipment by trained personnel are described. Figures and tables designed for wall-mounting and ready reference in an emergency situation are presented. Firstaid ventilatory adjuncts for use by trained personnel are classified and critically appraised, and the propriety of their use is emphasized. A plea is made to the medical profession and allied agencies to assume the responsibility of spreading knowledge of the new techniques more widely. Unless effective treatment is instituted early enough to prevent death or permanent anoxic damage to heart and brain, follow-through therapy will often be fruitless. PMID:14339303

  17. Artificial hair sensor designs for flow measurement of UAVs with different scales

    NASA Astrophysics Data System (ADS)

    Su, Weihua; Reich, Gregory W.

    2016-04-01

    Artificial hair sensors have been developed in the Air Force Research Laboratory for use in prediction of local flow around airfoils and subsequent use in gust rejection applications. The on-going sensor development is based on a micro-sized unmanned vehicle, resulting in a sensor design that is sensitive in that aircraft's nominal flight condition (speed). However, the active, or operating, region of the artificial hair sensor concept is highly dependent on the geometry and properties of the hair, capillary, and carbon nanotubes that make up the sensor design. This paper aims at expanding the flow measurement concept using artificial hair sensors to UAVs with different dimensions by properly sizing the parameters of the sensors, according to the nominal flight conditions of the UAVs. In this work, the hair, made of glass fiber, will be modeled as a cantilever beam with an elastic foundation, subject to external distributed aerodynamic drag. Hair length, diameter, capillary depth, and carbon nanotube length will be scaled by keeping the maximum strain of the carbon nanotubes constant for different sensors under different working conditions. Numerical studies will demonstrate the feasibility of the scaling methodology by designing artificial hair sensors for UAVs with different dimensions and flight conditions, starting from a baseline sensor design.

  18. Numerical simulation of the system artificial satellites motion by parallel computing. (Russian Title: Численное моделирование движения систем ИСЗ в среде параллельных вычислений)

    NASA Astrophysics Data System (ADS)

    Bordovitsyna, T. V.; Avdyushev, V. A.; Chuvashov, I. N.; Aleksandrova, A. G.; Tomilova, I. V.

    2009-11-01

    In this paper features of numerical simulation of the large-scale system artificial satellites motion by parallel computing is discussed per example instantiation program complex "Numerical model of the system artificial satellites motion" in cluster "Skiff Cyberia". It is shown that using of parallel computing allows to implement simultaneously high-precision numerical simulation of the motion of large-scale system artificial satellites. It opens comprehensive facilities in solve direct and regressive problems of dynamics such satellite system as GLONASS and objects of space debris.

  19. Computed Flow Through An Artificial Heart And Valve

    NASA Technical Reports Server (NTRS)

    Rogers, Stuart E.; Kwak, Dochan; Kiris, Cetin; Chang, I-Dee

    1994-01-01

    NASA technical memorandum discusses computations of flow of blood through artificial heart and through tilting-disk artificial heart valve. Represents further progress in research described in "Numerical Simulation of Flow Through an Artificial Heart" (ARC-12478). One purpose of research to exploit advanced techniques of computational fluid dynamics and capabilities of supercomputers to gain understanding of complicated internal flows of viscous, essentially incompressible fluids like blood. Another to use understanding to design better artificial hearts and valves.

  20. Effective Cavity Length of Gyrotrons

    NASA Astrophysics Data System (ADS)

    Thumm, Manfred

    2014-12-01

    Megawatt-class gyrotron oscillators for electron cyclotron heating and non-inductive current drive (ECH&CD) in magnetically confined thermonuclear fusion plasmas have relatively low cavity quality factors in the range of 1000 to 2000. The effective length of their cavities cannot be simply deduced from the cavity electric field profile, since this has by far not a Gaussian shape. The present paper presents a novel method to estimate the effective length of a gyrotron cavity just from the eigenvalue of the operating TEm,n mode, the cavity radius and the exact oscillation frequency which may be numerically computed or precisely measured. This effective cavity length then can be taken to calculate the Fresnel parameter in order to confirm that the cavity is not too short so that the transverse structure of any mode in the cavity is the same as that of the corresponding mode in a long circular waveguide with the same diameter.

  1. Arc Length Gone Global

    ERIC Educational Resources Information Center

    Boudreaux, Gregory M.; Wells, M. Scott

    2007-01-01

    Everyone with a thorough knowledge of single variable calculus knows that integration can be used to find the length of a curve on a given interval, called its arc length. Fortunately, if one endeavors to pose and solve more interesting problems than simply computing lengths of various curves, there are techniques available that do not require an…

  2. Computed Flow Through An Artificial Heart Valve

    NASA Technical Reports Server (NTRS)

    Rogers, Stewart E.; Kwak, Dochan; Kiris, Cetin; Chang, I-Dee

    1994-01-01

    Report discusses computations of blood flow through prosthetic tilting disk valve. Computational procedure developed in simulation used to design better artificial hearts and valves by reducing or eliminating following adverse flow characteristics: large pressure losses, which prevent hearts from working efficiently; separated and secondary flows, which causes clotting; and high turbulent shear stresses, which damages red blood cells. Report reiterates and expands upon part of NASA technical memorandum "Computed Flow Through an Artificial Heart and Valve" (ARC-12983). Also based partly on research described in "Numerical Simulation of Flow Through an Artificial Heart" (ARC-12478).

  3. Measuring Thermodynamic Length

    SciTech Connect

    Crooks, Gavin E

    2007-09-07

    Thermodynamic length is a metric distance between equilibrium thermodynamic states. Among other interesting properties, this metric asymptotically bounds the dissipation induced by a finite time transformation of a thermodynamic system. It is also connected to the Jensen-Shannon divergence, Fisher information, and Rao's entropy differential metric. Therefore, thermodynamic length is of central interestin understanding matter out of equilibrium. In this Letter, we will consider how to denethermodynamic length for a small system described by equilibrium statistical mechanics and how to measure thermodynamic length within a computer simulation. Surprisingly, Bennett's classic acceptance ratio method for measuring free energy differences also measures thermodynamic length.

  4. Inflatable artificial sphincter

    MedlinePlus

    ... works well. When you need to urinate, the cuff of the artificial sphincter can be relaxed so ... pain. An artificial sphincter has three parts: A cuff, which fits around your urethra, the tube that ...

  5. Artificial graphene with tunable interactions.

    PubMed

    Uehlinger, Thomas; Jotzu, Gregor; Messer, Michael; Greif, Daniel; Hofstetter, Walter; Bissbort, Ulf; Esslinger, Tilman

    2013-11-01

    We create an artificial graphene system with tunable interactions and study the crossover from metallic to Mott insulating regimes, both in isolated and coupled two-dimensional honeycomb layers. The artificial graphene consists of a two-component spin mixture of an ultracold atomic Fermi gas loaded into a hexagonal optical lattice. For strong repulsive interactions, we observe a suppression of double occupancy and measure a gapped excitation spectrum. We present a quantitative comparison between our measurements and theory, making use of a novel numerical method to obtain Wannier functions for complex lattice structures. Extending our studies to time-resolved measurements, we investigate the equilibration of the double occupancy as a function of lattice loading time. PMID:24237536

  6. Neandertal clavicle length

    PubMed Central

    Trinkaus, Erik; Holliday, Trenton W.; Auerbach, Benjamin M.

    2014-01-01

    The Late Pleistocene archaic humans from western Eurasia (the Neandertals) have been described for a century as exhibiting absolutely and relatively long clavicles. This aspect of their body proportions has been used to distinguish them from modern humans, invoked to account for other aspects of their anatomy and genetics, used in assessments of their phylogenetic polarities, and used as evidence for Late Pleistocene population relationships. However, it has been unclear whether the usual scaling of Neandertal clavicular lengths to their associated humeral lengths reflects long clavicles, short humeri, or both. Neandertal clavicle lengths, along with those of early modern humans and latitudinally diverse recent humans, were compared with both humeral lengths and estimated body masses (based on femoral head diameters). The Neandertal do have long clavicles relative their humeri, even though they fall within the ranges of variation of early and recent humans. However, when scaled to body masses, their humeral lengths are relatively short, and their clavicular lengths are indistinguishable from those of Late Pleistocene and recent modern humans. The few sufficiently complete Early Pleistocene Homo clavicles seem to have relative lengths also well within recent human variation. Therefore, appropriately scaled clavicular length seems to have varied little through the genus Homo, and it should not be used to account for other aspects of Neandertal biology or their phylogenetic status. PMID:24616525

  7. Numeric Databases in the 80s.

    ERIC Educational Resources Information Center

    Fried, John B.; Kovacs, Gabor J.

    1982-01-01

    Defining a numeric database as a computer-readable collection of data predominantly numeric in nature, this article reviews techniques and technologies having a positive influence on the growth of numeric databases, such as videotex, mini- and microcomputers, artificial intelligence, improved software, telecommunications, and office automation.…

  8. Spiral swimming of an artificial micro-swimmer

    NASA Astrophysics Data System (ADS)

    Keaveny, Eric E.; Maxey, Martin R.

    A device constructed from a filament of paramagnetic beads connected to a human red blood cell will swim when subject to an oscillating magnetic field. Bending waves propagate from the tip of the tail toward the red blood cell in a fashion analogous to flagellum beating, making the artificial swimmer a candidate for studying what has been referred to as micro-swimming. In this study, we demonstrate that under the influence of a rotating field the artificial swimmer will perform -type swimming. We conduct numerical simulations of the swimmer where the paramagnetic tail is represented as a series of rigid spheres connected by flexible but inextensible links. An optimal range of parameters governing the relative strength of viscous, elastic and magnetic forces is identified for swimming speed. A parameterization of the motion is extracted and examined as a function of the driving frequency. With a continuous elastica/resistive force model, we obtain an expression for the swimming speed in the low-frequency limit. Using this expression we explore further the effects of the applied field, the ratio of the transverse field to the constant field, and the ratio of the radius of the sphere to the length of the filament tail on the resulting dynamics.

  9. Elastic-Tether Suits for Artificial Gravity and Exercise

    NASA Technical Reports Server (NTRS)

    Torrance, Paul; Biesinger, Paul; Rybicki, Daniel D.

    2005-01-01

    Body suits harnessed to systems of elastic tethers have been proposed as means of approximating the effects of normal Earth gravitation on crewmembers of spacecraft in flight to help preserve the crewmembers physical fitness. The suits could also be used on Earth to increase effective gravitational loads for purposes of athletic training. The suit according to the proposal would include numerous small tether-attachment fixtures distributed over its outer surface so as to distribute the artificial gravitational force as nearly evenly as possible over the wearer s body. Elastic tethers would be connected between these fixtures and a single attachment fixture on a main elastic tether that would be anchored to a fixture on or under a floor. This fixture might include multiple pulleys to make the effective length of the main tether great enough that normal motions of the wearer cause no more than acceptably small variations in the total artificial gravitational force. Among the problems in designing the suit would be equalizing the load in the shoulder area and keeping tethers out of the way below the knees to prevent tripping. The solution would likely include running tethers through rings on the sides. Body suits with a weight or water ballast system are also proposed for very slight spinning space-station scenarios, in which cases the proposed body suits will easily be able to provide the equivalency of a 1-G or even greater load.

  10. Some orbital characteristics of lunar artificial satellites

    NASA Astrophysics Data System (ADS)

    Carvalho, J. P. S.; Vilhena de Moraes, R.; Prado, A. F. B. A.

    2010-12-01

    In this paper we present an analytical theory with numerical simulations to study the orbital motion of lunar artificial satellites. We consider the problem of an artificial satellite perturbed by the non-uniform distribution of mass of the Moon and by a third-body in elliptical orbit (Earth is considered). Legendre polynomials are expanded in powers of the eccentricity up to the degree four and are used for the disturbing potential due to the third-body. We show a new approximated equation to compute the critical semi-major axis for the orbit of the satellite. Lie-Hori perturbation method up to the second-order is applied to eliminate the terms of short-period of the disturbing potential. Coupling terms are analyzed. Emphasis is given to the case of frozen orbits and critical inclination. Numerical simulations for hypothetical lunar artificial satellites are performed, considering that the perturbations are acting together or one at a time.

  11. Critical Length Limiting Superlow Friction

    NASA Astrophysics Data System (ADS)

    Ma, Ming; Benassi, Andrea; Vanossi, Andrea; Urbakh, Michael

    2015-02-01

    Since the demonstration of superlow friction (superlubricity) in graphite at nanoscale, one of the main challenges in the field of nano- and micromechanics was to scale this phenomenon up. A key question to be addressed is to what extent superlubricity could persist, and what mechanisms could lead to its failure. Here, using an edge-driven Frenkel-Kontorova model, we establish a connection between the critical length above which superlubricity disappears and both intrinsic material properties and experimental parameters. A striking boost in dissipated energy with chain length emerges abruptly due to a high-friction stick-slip mechanism caused by deformation of the slider leading to a local commensuration with the substrate lattice. We derived a parameter-free analytical model for the critical length that is in excellent agreement with our numerical simulations. Our results provide a new perspective on friction and nanomanipulation and can serve as a theoretical basis for designing nanodevices with superlow friction, such as carbon nanotubes.

  12. Improving designer productivity. [artificial intelligence

    NASA Technical Reports Server (NTRS)

    Hill, Gary C.

    1992-01-01

    Designer and design team productivity improves with skill, experience, and the tools available. The design process involves numerous trials and errors, analyses, refinements, and addition of details. Computerized tools have greatly speeded the analysis, and now new theories and methods, emerging under the label Artificial Intelligence (AI), are being used to automate skill and experience. These tools improve designer productivity by capturing experience, emulating recognized skillful designers, and making the essence of complex programs easier to grasp. This paper outlines the aircraft design process in today's technology and business climate, presenting some of the challenges ahead and some of the promising AI methods for meeting these challenges.

  13. Coefficients of Effective Length.

    ERIC Educational Resources Information Center

    Edwards, Roger H.

    1981-01-01

    Under certain conditions, a validity Coefficient of Effective Length (CEL) can produce highly misleading results. A modified coefficent is suggested for use when empirical studies indicate that underlying assumptions have been violated. (Author/BW)

  14. Length Paradox in Relativity

    ERIC Educational Resources Information Center

    Martins, Roberto de A.

    1978-01-01

    Describes a thought experiment using a general analysis approach with Lorentz transformations to show that the apparent self-contradictions of special relativity concerning the length-paradox are really non-existant. (GA)

  15. [Sonographic leg length measurement].

    PubMed

    Holst, A; Thomas, W

    1989-03-01

    After brief presentation of the clinical and radiological methods to measure the leg length and the leg length difference the authors outline the new diagnostic method for measuring the leg length and the leg length difference by means of real time sonography. Postmortem tests and clinical examples show that ultrasound is ideal to determine exactly the length of femur and tibia. The joint gaps on the hip, knee and upper ankle joint can be demonstrated by means of a 5 MHz linear scanner. A 1 mm strong metal bar on the skin and under the scanner is placed at right angles to the longitudinal axis of the body so that the bar can be seen in the centre. A measuring device gives the distances of the joint gaps in cm so that the difference correspond to the real length of femur and tibia. This standardised measuring is done by a particularly developed bearing and measuring device. The results of the sonographical measurements on 20 corpses and checking after consecutive dissections showed in 75% of cases a 100% sonographic measuring accuracy of the total leg length. The separately considered results for femur (85%) and tibia (90) were even better. The maximum sonographic measuring fault was 1.0 cm for the femur (in one case) and 0.5 cm for the tibia, respectively. All sonographic measurements were performed with the Sonoline SL-1 of the Siemens Company (Erlangen, W-Germany). Thus, sonographical measuring of the leg length offers a reliable, non-invasive method that can be repeated as often as necessary and is simply executed.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2652268

  16. Editorial: Redefining Length

    SciTech Connect

    Sprouse, Gene D.

    2011-07-15

    Technological changes have moved publishing to electronic-first publication where the print version has been relegated to simply another display mode. Distribution in HTML and EPUB formats, for example, changes the reading environment and reduces the need for strict pagination. Therefore, in an effort to streamline the calculation of length, the APS journals will no longer use the printed page as the determining factor for length. Instead the journals will now use word counts (or word equivalents for tables, figures, and equations) to establish length; for details please see http://publish.aps.org/authors/length-guide. The title, byline, abstract, acknowledgment, and references will not be included in these counts allowing authors the freedom to appropriately credit coworkers, funding sources, and the previous literature, bringing all relevant references to the attention of readers. This new method for determining length will be easier for authors to calculate in advance, and lead to fewer length-associated revisions in proof, yet still retain the quality of concise communication that is a virtue of short papers.

  17. Artificial Intelligence in Astronomy

    NASA Astrophysics Data System (ADS)

    Devinney, E. J.; Prša, A.; Guinan, E. F.; Degeorge, M.

    2010-12-01

    From the perspective (and bias) as Eclipsing Binary researchers, we give a brief overview of the development of Artificial Intelligence (AI) applications, describe major application areas of AI in astronomy, and illustrate the power of an AI approach in an application developed under the EBAI (Eclipsing Binaries via Artificial Intelligence) project, which employs Artificial Neural Network technology for estimating light curve solution parameters of eclipsing binary systems.

  18. An artificial muscle computer

    NASA Astrophysics Data System (ADS)

    Marc O'Brien, Benjamin; Alexander Anderson, Iain

    2013-03-01

    We have built an artificial muscle computer based on Wolfram's "2, 3" Turing machine architecture, the simplest known universal Turing machine. Our computer uses artificial muscles for its instruction set, output buffers, and memory write and addressing mechanisms. The computer is very slow and large (0.15 Hz, ˜1 m3); however by using only 13 artificial muscle relays, it is capable of solving any computable problem given sufficient memory, time, and reliability. The development of this computer shows that artificial muscles can think—paving the way for soft robots with reflexes like those seen in nature.

  19. Artificial insemination in poultry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Artificial insemination is a relative simple yet powerful tool geneticists can employ for the propagation of economically important traits in livestock and poultry. In this chapter, we address the fundamental methods of the artificial insemination of poultry, including semen collection, semen evalu...

  20. Equine artificial insemination.

    PubMed

    Merkt, H

    1976-07-24

    The use and techniques of artificial insemination for horses in Germany over the last 30 years is described. Artificial insemination appears to produce pregnancy percentages equal to those from normal breeding methods and its continued availability under veterinary supervision is recommended in conditions where disease, disability or distance debar normal service. PMID:960520

  1. DIC image reconstruction using an energy minimization framework to visualize optical path length distribution.

    PubMed

    Koos, Krisztian; Molnár, József; Kelemen, Lóránd; Tamás, Gábor; Horvath, Peter

    2016-01-01

    Label-free microscopy techniques have numerous advantages such as low phototoxicity, simple setup and no need for fluorophores or other contrast materials. Despite their advantages, most label-free techniques cannot visualize specific cellular compartments or the location of proteins and the image formation limits quantitative evaluation. Differential interference contrast (DIC) is a qualitative microscopy technique that shows the optical path length differences within a specimen. We propose a variational framework for DIC image reconstruction. The proposed method largely outperforms state-of-the-art methods on synthetic, artificial and real tests and turns DIC microscopy into an automated high-content imaging tool. Image sets and the source code of the examined algorithms are made publicly available. PMID:27453091

  2. DIC image reconstruction using an energy minimization framework to visualize optical path length distribution

    PubMed Central

    Koos, Krisztian; Molnár, József; Kelemen, Lóránd; Tamás, Gábor; Horvath, Peter

    2016-01-01

    Label-free microscopy techniques have numerous advantages such as low phototoxicity, simple setup and no need for fluorophores or other contrast materials. Despite their advantages, most label-free techniques cannot visualize specific cellular compartments or the location of proteins and the image formation limits quantitative evaluation. Differential interference contrast (DIC) is a qualitative microscopy technique that shows the optical path length differences within a specimen. We propose a variational framework for DIC image reconstruction. The proposed method largely outperforms state-of-the-art methods on synthetic, artificial and real tests and turns DIC microscopy into an automated high-content imaging tool. Image sets and the source code of the examined algorithms are made publicly available. PMID:27453091

  3. Wave Speeds, Riemann Solvers and Artificial Viscosity

    SciTech Connect

    Rider, W.J.

    1999-07-18

    A common perspective on the numerical solution of the equation Euler equations for shock physics is examined. The common viewpoint is based upon the selection of nonlinear wavespeeds upon which the dissipation (implicit or explicit) is founded. This perspective shows commonality between Riemann solver based method (i.e. Godunov-type) and artificial viscosity (i.e. von Neumann-Richtmyer). As an example we derive an improved nonlinear viscous stabilization of a Richtmyer-Lax-Wendroff method. Additionally, we will define a form of classical artificial viscosity based upon the HLL Riemann solver.

  4. Onion artificial muscles

    NASA Astrophysics Data System (ADS)

    Chen, Chien-Chun; Shih, Wen-Pin; Chang, Pei-Zen; Lai, Hsi-Mei; Chang, Shing-Yun; Huang, Pin-Chun; Jeng, Huai-An

    2015-05-01

    Artificial muscles are soft actuators with the capability of either bending or contraction/elongation subjected to external stimulation. However, there are currently no artificial muscles that can accomplish these actions simultaneously. We found that the single layered, latticed microstructure of onion epidermal cells after acid treatment became elastic and could simultaneously stretch and bend when an electric field was applied. By modulating the magnitude of the voltage, the artificial muscle made of onion epidermal cells would deflect in opposing directions while either contracting or elongating. At voltages of 0-50 V, the artificial muscle elongated and had a maximum deflection of -30 μm; at voltages of 50-1000 V, the artificial muscle contracted and deflected 1.0 mm. The maximum force response is 20 μN at 1000 V.

  5. Document Length Normalization.

    ERIC Educational Resources Information Center

    Singhal, Amit; And Others

    1996-01-01

    Describes a study that investigated document retrieval relevance based on document length in an experimental text collection. Topics include term weighting and document ranking, retrieval strategies such as the vector-space cosine match, and a modified technique called the pivoted cosine normalization. (LRW)

  6. Impedance of finite length resistive cylinder

    NASA Astrophysics Data System (ADS)

    Krinsky, S.; Podobedov, B.; Gluckstern, R. L.

    2004-11-01

    We determine the impedance of a cylindrical metal tube (resistor) of radius a, length g, and conductivity σ attached at each end to perfect conductors of semi-infinite length. Our main interest is in the asymptotic behavior of the impedance at high frequency (k≫1/a). In the equilibrium regime, ka2≪g, the impedance per unit length is accurately described by the well-known result for an infinite length tube with conductivity σ. In the transient regime, ka2≫g, where the contribution of transition radiation arising from the discontinuity in conductivity is important, we derive an analytic expression for the impedance and compute the short-range wakefield. The analytic results are shown to agree with numerical evaluation of the impedance.

  7. Artificial ecosystem selection.

    PubMed

    Swenson, W; Wilson, D S; Elias, R

    2000-08-01

    Artificial selection has been practiced for centuries to shape the properties of individual organisms, providing Darwin with a powerful argument for his theory of natural selection. We show that the properties of whole ecosystems can also be shaped by artificial selection procedures. Ecosystems initiated in the laboratory vary phenotypically and a proportion of the variation is heritable, despite the fact that the ecosystems initially are composed of thousands of species and millions of individuals. Artificial ecosystem selection can be used for practical purposes, illustrates an important role for complex interactions in evolution, and challenges a widespread belief that selection is most effective at lower levels of the biological hierarchy. PMID:10890915

  8. 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.

  9. Intelligence: Real or artificial?

    PubMed Central

    Schlinger, Henry D.

    1992-01-01

    Throughout the history of the artificial intelligence movement, researchers have strived to create computers that could simulate general human intelligence. This paper argues that workers in artificial intelligence have failed to achieve this goal because they adopted the wrong model of human behavior and intelligence, namely a cognitive essentialist model with origins in the traditional philosophies of natural intelligence. An analysis of the word “intelligence” suggests that it originally referred to behavior-environment relations and not to inferred internal structures and processes. It is concluded that if workers in artificial intelligence are to succeed in their general goal, then they must design machines that are adaptive, that is, that can learn. Thus, artificial intelligence researchers must discard their essentialist model of natural intelligence and adopt a selectionist model instead. Such a strategic change should lead them to the science of behavior analysis. PMID:22477051

  10. Artificial Sweeteners and Cancer

    MedlinePlus

    ... artificial sweeteners and cancer? Saccharin Studies in laboratory rats during the early 1970s linked saccharin with the ... cause cancer in laboratory animals .” Subsequent studies in rats showed an increased incidence of urinary bladder cancer ...

  11. Introduction to artificial intelligence

    SciTech Connect

    Gevarter, W.B.

    1987-09-01

    The author discusses the development of artificial intelligence (AI). He explains the basic elements of AI: Heuristic search, knowledge representation, AI languages and tools, Natural Language Processing, computer vision, expert systems and problem solving and planning.

  12. Artificial light sources.

    PubMed

    Anderson, T F

    1986-04-01

    A wide variety of artificial light sources exists for use in the diagnosis and treatment of photosensitivity disorders. A discussion of the advantages and disadvantages of these light sources (including gas discharge arcs, fluorescent lamps, and other apparatus) illustrates the importance of matching the emission spectrum of the light source, the spectral response of the radiometer, and the photobiologic action spectrum. Environmental and occupational exposure to artificial light sources may contribute to photosensitivity disorders. PMID:3955892

  13. Physics of Artificial Gravity

    NASA Technical Reports Server (NTRS)

    Bukley, Angie; Paloski, William; Clement, Gilles

    2006-01-01

    This chapter discusses potential technologies for achieving artificial gravity in a space vehicle. We begin with a series of definitions and a general description of the rotational dynamics behind the forces ultimately exerted on the human body during centrifugation, such as gravity level, gravity gradient, and Coriolis force. Human factors considerations and comfort limits associated with a rotating environment are then discussed. Finally, engineering options for designing space vehicles with artificial gravity are presented.

  14. Heidegger and artificial intelligence

    SciTech Connect

    Diaz, G.

    1987-01-01

    The discipline of Artificial Intelligence, in its quest for machine intelligence, showed great promise as long as its areas of application were limited to problems of a scientific and situation neutral nature. The attempts to move beyond these problems to a full simulation of man's intelligence has faltered and slowed it progress, largely because of the inability of Artificial Intelligence to deal with human characteristic, such as feelings, goals, and desires. This dissertation takes the position that an impasse has resulted because Artificial Intelligence has never been properly defined as a science: its objects and methods have never been identified. The following study undertakes to provide such a definition, i.e., the required ground for Artificial Intelligence. The procedure and methods employed in this study are based on Heidegger's philosophy and techniques of analysis as developed in Being and Time. Results of this study show that both the discipline of Artificial Intelligence and the concerns of Heidegger in Being and Time have the same object; fundamental ontology. The application of Heidegger's conclusions concerning fundamental ontology unites the various aspects of Artificial Intelligence and provides the articulation which shows the parts of this discipline and how they are related.

  15. Artificial tears potpourri: a literature review.

    PubMed

    Moshirfar, Majid; Pierson, Kasey; Hanamaikai, Kamalani; Santiago-Caban, Luis; Muthappan, Valliammai; Passi, Samuel F

    2014-01-01

    Numerous brands and types of artificial tears are available on the market for the treatment of dysfunctional tear syndrome. Past literature has focused on comparing the components of these products on patient's clinical improvement. The wide array of products on the market presents challenges to both clinicians and patients when trying to choose between available tear replacement therapies. Different formulations affect patients based on etiology and severity of disease. In order to provide an unbiased comparison between available tear replacement therapies, we conducted a literature review of existing studies and National Institutes of Health clinical trials on commercially available, brand name artificial tears. Outcomes evaluated in each study, as well as the percent of patients showing clinical and symptomatic improvement, were analyzed. Fifty-one studies evaluating different brands of artificial tears, and their efficacy were identified. Out of the 51 studies, 18 were comparison studies testing brand name artificial tears directly against each other. Nearly all formulations of artificial tears provided significant benefit to patients with dysfunctional tear syndrome, but some proved superior to others. From the study data, a recommended treatment flowchart was derived. PMID:25114502

  16. Artificial tears potpourri: a literature review

    PubMed Central

    Moshirfar, Majid; Pierson, Kasey; Hanamaikai, Kamalani; Santiago-Caban, Luis; Muthappan, Valliammai; Passi, Samuel F

    2014-01-01

    Numerous brands and types of artificial tears are available on the market for the treatment of dysfunctional tear syndrome. Past literature has focused on comparing the components of these products on patient’s clinical improvement. The wide array of products on the market presents challenges to both clinicians and patients when trying to choose between available tear replacement therapies. Different formulations affect patients based on etiology and severity of disease. In order to provide an unbiased comparison between available tear replacement therapies, we conducted a literature review of existing studies and National Institutes of Health clinical trials on commercially available, brand name artificial tears. Outcomes evaluated in each study, as well as the percent of patients showing clinical and symptomatic improvement, were analyzed. Fifty-one studies evaluating different brands of artificial tears, and their efficacy were identified. Out of the 51 studies, 18 were comparison studies testing brand name artificial tears directly against each other. Nearly all formulations of artificial tears provided significant benefit to patients with dysfunctional tear syndrome, but some proved superior to others. From the study data, a recommended treatment flowchart was derived. PMID:25114502

  17. A variable mixing-length ratio for convection theory

    NASA Technical Reports Server (NTRS)

    Chan, K. L.; Wolff, C. L.; Sofia, S.

    1981-01-01

    It is argued that a natural choice for the local mixing length in the mixing-length theory of convection has a value proportional to the local density scale height of the convective bubbles. The resultant variable mixing-length ratio (the ratio between the mixing length and the pressure scale height) of this theory is enhanced in the superadiabatic region and approaches a constant in deeper layers. Numerical tests comparing the new mixing length successfully eliminate most of the density inversion that typically plagues conventional results. The new approach also seems to indicate the existence of granular motion at the top of the convection zone.

  18. Artificial Compressibility with Entropic Damping

    NASA Astrophysics Data System (ADS)

    Clausen, Jonathan; Roberts, Scott

    2012-11-01

    Artificial Compressibility (AC) methods relax the strict incompressibility constraint associated with the incompressible Navier-Stokes equations. Instead, they rely on an artificial equation of state relating pressure and density fluctuations through a numerical Mach number. Such methods are not new: the first AC methods date back to Chorin (1967). More recent applications can be found in the lattice-Boltzmann method, which is a kinetic/mesoscopic method that converges to an AC form of the Navier-Stokes equations. With computing hardware trending towards massively parallel architectures in order to achieve high computational throughput, AC style methods have become attractive due to their local information propagation and concomitant parallelizable algorithms. In this work, we examine a damped form of AC in the context of finite-difference and finite-element methods, with a focus on achieving time-accurate simulations. Also, we comment on the scalability of the various algorithms. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  19. Computational Hemodynamics Involving Artificial Devices

    NASA Technical Reports Server (NTRS)

    Kwak, Dochan; Kiris, Cetin; Feiereisen, William (Technical Monitor)

    2001-01-01

    This paper reports the progress being made towards developing complete blood flow simulation capability in human, especially, in the presence of artificial devices such as valves and ventricular assist devices. Devices modeling poses unique challenges different from computing the blood flow in natural hearts and arteries. There are many elements needed such as flow solvers, geometry modeling including flexible walls, moving boundary procedures and physiological characterization of blood. As a first step, computational technology developed for aerospace applications was extended in the recent past to the analysis and development of mechanical devices. The blood flow in these devices is practically incompressible and Newtonian, and thus various incompressible Navier-Stokes solution procedures can be selected depending on the choice of formulations, variables and numerical schemes. Two primitive variable formulations used are discussed as well as the overset grid approach to handle complex moving geometry. This procedure has been applied to several artificial devices. Among these, recent progress made in developing DeBakey axial flow blood pump will be presented from computational point of view. Computational and clinical issues will be discussed in detail as well as additional work needed.

  20. Length Scales in Bayesian Automatic Adaptive Quadrature

    NASA Astrophysics Data System (ADS)

    Adam, Gh.; Adam, S.

    2016-02-01

    Two conceptual developments in the Bayesian automatic adaptive quadrature approach to the numerical solution of one-dimensional Riemann integrals [Gh. Adam, S. Adam, Springer LNCS 7125, 1-16 (2012)] are reported. First, it is shown that the numerical quadrature which avoids the overcomputing and minimizes the hidden floating point loss of precision asks for the consideration of three classes of integration domain lengths endowed with specific quadrature sums: microscopic (trapezoidal rule), mesoscopic (Simpson rule), and macroscopic (quadrature sums of high algebraic degrees of precision). Second, sensitive diagnostic tools for the Bayesian inference on macroscopic ranges, coming from the use of Clenshaw-Curtis quadrature, are derived.

  1. Length of stain dosimeter

    NASA Technical Reports Server (NTRS)

    Lueck, Dale E. (Inventor)

    1994-01-01

    Payload customers for the Space Shuttle have recently expressed concerns about the possibility of their payloads at an adjacent pad being contaminated by plume effluents from a shuttle at an active pad as they await launch on an inactive pad. As part of a study to satisfy such concerns a ring of inexpensive dosimeters was deployed around the active pad at the inter-pad distance. However, following a launch, dosimeters cannot be read for several hours after the exposure. As a consequence factors such as different substrates, solvent systems, and possible volatilization of HCl from the badges were studied. This observation led to the length of stain (LOS) dosimeters of this invention. Commercial passive LOS dosimeters are sensitive only to the extent of being capable of sensing 2 ppm to 20 ppm if the exposure is 8 hours. To map and quantitate the HCl generated by Shuttle launches, and in the atmosphere within a radius of 1.5 miles from the active pad, a sensitivity of 2 ppm HCl in the atmospheric gases on an exposure of 5 minutes is required. A passive length of stain dosimeter has been developed having a sensitivity rendering it capable of detecting a gas in a concentration as low as 2 ppm on an exposure of five minutes.

  2. An artificial energy method for calculating flows with shocks

    NASA Technical Reports Server (NTRS)

    Rose, M. E.

    1980-01-01

    The artificial-viscosity method, first proposed by von Neumann and Richtmyer, introduces an artificial viscous pressure term in regions of compression such that an increase in entropy occurs in shock transition zones. The paper describes how dissipative flows can be induced by reducing the total energy available for adiabatic processes in shock zones. A class of inviscid fluid flows, called semiflows, is described in which the flows exhibit thermodynamic differences. Induced dissipative flows modify the pressure in regions of compression in a manner analogous to the artificial-viscosity method and for a gas, the effect is equivalent to suitably modifying the gas constant in the equation of state. By employing MacCormack's method and the usual non-adiabatic equations, numerical solutions of a Riemann problem are compared with the modified artificial energy method, showing that the dissipation effect predicted by the analytical formulation is reflected in the numerical method as well.

  3. Numerical Development

    ERIC Educational Resources Information Center

    Siegler, Robert S.; Braithwaite, David W.

    2016-01-01

    In this review, we attempt to integrate two crucial aspects of numerical development: learning the magnitudes of individual numbers and learning arithmetic. Numerical magnitude development involves gaining increasingly precise knowledge of increasing ranges and types of numbers: from non-symbolic to small symbolic numbers, from smaller to larger…

  4. Artificial consciousness, artificial emotions, and autonomous robots.

    PubMed

    Cardon, Alain

    2006-12-01

    Nowadays for robots, the notion of behavior is reduced to a simple factual concept at the level of the movements. On another hand, consciousness is a very cultural concept, founding the main property of human beings, according to themselves. We propose to develop a computable transposition of the consciousness concepts into artificial brains, able to express emotions and consciousness facts. The production of such artificial brains allows the intentional and really adaptive behavior for the autonomous robots. Such a system managing the robot's behavior will be made of two parts: the first one computes and generates, in a constructivist manner, a representation for the robot moving in its environment, and using symbols and concepts. The other part achieves the representation of the previous one using morphologies in a dynamic geometrical way. The robot's body will be seen for itself as the morphologic apprehension of its material substrata. The model goes strictly by the notion of massive multi-agent's organizations with a morphologic control. PMID:17016730

  5. An artificial molecular pump.

    PubMed

    Cheng, Chuyang; McGonigal, Paul R; Schneebeli, Severin T; Li, Hao; Vermeulen, Nicolaas A; Ke, Chenfeng; Stoddart, J Fraser

    2015-06-01

    Carrier proteins consume fuel in order to pump ions or molecules across cell membranes, creating concentration gradients. Their control over diffusion pathways, effected entirely through noncovalent bonding interactions, has inspired chemists to devise artificial systems that mimic their function. Here, we report a wholly artificial compound that acts on small molecules to create a gradient in their local concentration. It does so by using redox energy and precisely organized noncovalent bonding interactions to pump positively charged rings from solution and ensnare them around an oligomethylene chain, as part of a kinetically trapped entanglement. A redox-active viologen unit at the heart of a dumbbell-shaped molecular pump plays a dual role, first attracting and then repelling the rings during redox cycling, thereby enacting a flashing energy ratchet mechanism with a minimalistic design. Our artificial molecular pump performs work repetitively for two cycles of operation and drives rings away from equilibrium toward a higher local concentration. PMID:25984834

  6. Artificial muscles on heat

    NASA Astrophysics Data System (ADS)

    McKay, Thomas G.; Shin, Dong Ki; Percy, Steven; Knight, Chris; McGarry, Scott; Anderson, Iain A.

    2014-03-01

    Many devices and processes produce low grade waste heat. Some of these include combustion engines, electrical circuits, biological processes and industrial processes. To harvest this heat energy thermoelectric devices, using the Seebeck effect, are commonly used. However, these devices have limitations in efficiency, and usable voltage. This paper investigates the viability of a Stirling engine coupled to an artificial muscle energy harvester to efficiently convert heat energy into electrical energy. The results present the testing of the prototype generator which produced 200 μW when operating at 75°C. Pathways for improved performance are discussed which include optimising the electronic control of the artificial muscle, adjusting the mechanical properties of the artificial muscle to work optimally with the remainder of the system, good sealing, and tuning the resonance of the displacer to minimise the power required to drive it.

  7. Doped Artificial Spin Ice

    NASA Astrophysics Data System (ADS)

    Olson Reichhardt, Cynthia; Libal, Andras; Reichhardt, Charles

    We examine square and kagome artificial spin ice for colloids confined in arrays of double-well traps. Unlike magnetic artificial spin ices, colloidal and vortex artificial spin ice realizations allow creation of doping sites through double occupation of individual traps. We find that doping square and kagome ice geometries produces opposite effects. For square ice, doping creates local excitations in the ground state configuration that produce a local melting effect as the temperature is raised. In contrast, the kagome ice ground state can absorb the doping charge without generating non-ground-state excitations, while at elevated temperatures the hopping of individual colloids is suppressed near the doping sites. These results indicate that in the square ice, doping adds degeneracy to the ordered ground state and creates local weak spots, while in the kagome ice, which has a highly degenerate ground state, doping locally decreases the degeneracy and creates local hard regions.

  8. Artificial intelligence in nanotechnology

    NASA Astrophysics Data System (ADS)

    Sacha, G. M.; Varona, P.

    2013-11-01

    During the last decade there has been increasing use of artificial intelligence tools in nanotechnology research. In this paper we review some of these efforts in the context of interpreting scanning probe microscopy, the study of biological nanosystems, the classification of material properties at the nanoscale, theoretical approaches and simulations in nanoscience, and generally in the design of nanodevices. Current trends and future perspectives in the development of nanocomputing hardware that can boost artificial-intelligence-based applications are also discussed. Convergence between artificial intelligence and nanotechnology can shape the path for many technological developments in the field of information sciences that will rely on new computer architectures and data representations, hybrid technologies that use biological entities and nanotechnological devices, bioengineering, neuroscience and a large variety of related disciplines.

  9. An artificial molecular pump

    NASA Astrophysics Data System (ADS)

    Cheng, Chuyang; McGonigal, Paul R.; Schneebeli, Severin T.; Li, Hao; Vermeulen, Nicolaas A.; Ke, Chenfeng; Stoddart, J. Fraser

    2015-06-01

    Carrier proteins consume fuel in order to pump ions or molecules across cell membranes, creating concentration gradients. Their control over diffusion pathways, effected entirely through noncovalent bonding interactions, has inspired chemists to devise artificial systems that mimic their function. Here, we report a wholly artificial compound that acts on small molecules to create a gradient in their local concentration. It does so by using redox energy and precisely organized noncovalent bonding interactions to pump positively charged rings from solution and ensnare them around an oligomethylene chain, as part of a kinetically trapped entanglement. A redox-active viologen unit at the heart of a dumbbell-shaped molecular pump plays a dual role, first attracting and then repelling the rings during redox cycling, thereby enacting a flashing energy ratchet mechanism with a minimalistic design. Our artificial molecular pump performs work repetitively for two cycles of operation and drives rings away from equilibrium toward a higher local concentration.

  10. A physically consistent model for artificial dissipation in transonic potential flow computations

    NASA Technical Reports Server (NTRS)

    Dulikravich, George S.; Mortara, Karl W.; Marraffa, Lionel

    1988-01-01

    The effect that artificial dissipation has on numerical solutions of the transonic Full Potential Equation (FPE) are investigated by comparing the artificially dissipative FPE to a Physically Dissipative Potential (PDP) equation. Analytic expressions were derived from the variables C and M sub c that are used in the artificial density formulation. It was shown that these new values generate artificial dissipation which is equivalent to the physical dissipation existing in the PDP equation. The new expression for the variables C and M sub c can easily be incorporated into the existing full potential codes which are based either on the artificial density or on the artificial viscosity formulation. A comparison of Physically Dissipative Potential (PDP), Artificial Density or Viscosity (ADV), Artificial Mass Flux (AMF), and ADV with variable C and M sub c formulation (MCC) is also presented.

  11. Incompressible viscous flow computations for the pump components and the artificial heart

    NASA Technical Reports Server (NTRS)

    Kiris, Cetin

    1992-01-01

    A finite-difference, three-dimensional incompressible Navier-Stokes formulation to calculate the flow through turbopump components is utilized. The solution method is based on the pseudocompressibility approach and uses an implicit-upwind differencing scheme together with the Gauss-Seidel line relaxation method. Both steady and unsteady flow calculations can be performed using the current algorithm. In this work, the equations are solved in steadily rotating reference frames by using the steady-state formulation in order to simulate the flow through a turbopump inducer. Eddy viscosity is computed by using an algebraic mixing-length turbulence model. Numerical results are compared with experimental measurements and a good agreement is found between the two. Included in the appendix is a paper on incompressible viscous flow through artificial heart devices with moving boundaries. Time-accurate calculations, such as impeller and diffusor interaction, will be reported in future work.

  12. Nature-inspired micro-fluidic manipulation using artificial cilia

    NASA Astrophysics Data System (ADS)

    den Toonder, Jaap; de Goede, Judith; Khatavkar, Vinayak; Anderson, Patrick

    2006-11-01

    One particular micro-fluidics manipulation mechanism ``designed'' by nature is that due to a covering of beating cilia over the external surface of micro-organisms (e.g. Paramecium). A cilium can be viewed as a small hair or flexible rod (in protozoa: typical length 10 μm and diameter 0.1 μm) which is attached to the surface. We have developed polymer micro-actuators, made with standard micro-technology processing, which respond to an applied electrical or magnetic field by changing their shape. The shape and size of the polymer actuators mimics that of cilia occurring in nature. We have shown experimentally that, indeed, our artificial cilia can induce significant flow velocities of at least 75 μm/s in a fluid with a viscosity of 10 mPas. In this paper we will give an overview of our activities in developing the polymer actuators and the corresponding technology, show experimental and numerical fluid flow results, and finally assess the feasibility of applying this new and attractive micro-fluidic actuation method in functional biosensors.

  13. Artificial intelligence. Second edition

    SciTech Connect

    Winston, P.H.

    1984-01-01

    This book introduces the basic concepts of the field of artificial intelligence. It contains material covering the latest advances in control, representation, language, vision, and problem solving. Problem solving in design and analysis systems is addressed. Mitcell's version-space learning procedure, Morevec's reduced-images stereo procedure, and the Strips problem solver are covered.

  14. The Artificial Planet

    NASA Astrophysics Data System (ADS)

    Glover, D. R.

    An interim milestone for interstellar space travel is proposed: the artificial planet. Interstellar travel will require breakthroughs in the areas of propulsion systems, energy systems, construction of large space structures, protection from space & radiation effects, space agriculture, closed environmental & life support systems, and many other areas. Many difficult problems can be attacked independently of the propulsion and energy challenges through a project to establish an artificial planet in our solar system. Goals of the project would include construction of a large space structure, development of space agriculture, demonstration of closed environmental & life support systems over long time periods, selection of gravity level for long-term spacecraft, demonstration of a self-sufficient colony, and optimization of space colony habitat. The artificial planet would use solar energy as a power source. The orbital location will be selected to minimize effects of the Earth, yet be close enough for construction, supply, and rescue operations. The artificial planet would start out as a construction station and evolve over time to address progressive goals culminating in a self-sufficient space colony.

  15. Micromachined Artificial Haircell

    NASA Technical Reports Server (NTRS)

    Liu, Chang (Inventor); Engel, Jonathan (Inventor); Chen, Nannan (Inventor); Chen, Jack (Inventor)

    2010-01-01

    A micromachined artificial sensor comprises a support coupled to and movable with respect to a substrate. A polymer, high-aspect ratio cilia-like structure is disposed on and extends out-of-plane from the support. A strain detector is disposed with respect to the support to detect movement of the support.

  16. Artificial intelligence and robotics

    SciTech Connect

    Peden, I.C.; Braddock, J.V.; Brown, W.; Langendorf, R.M.

    1982-09-01

    This report examines the state-of-the-art in artificial intelligence and robotics technologies and their potential in terms of Army needs. Assessment includes battlefield technology, research and technology insertions, management considerations and recommendations related to research and development personnel, and recommendations regarding the Army's involvement in the automated plant.

  17. Terahertz Artificial Dielectric Lens

    NASA Astrophysics Data System (ADS)

    Mendis, Rajind; Nagai, Masaya; Wang, Yiqiu; Karl, Nicholas; Mittleman, Daniel M.

    2016-03-01

    We have designed, fabricated, and experimentally characterized a lens for the THz regime based on artificial dielectrics. These are man-made media that mimic properties of naturally occurring dielectric media, or even manifest properties that cannot generally occur in nature. For example, the well-known dielectric property, the refractive index, which usually has a value greater than unity, can have a value less than unity in an artificial dielectric. For our lens, the artificial-dielectric medium is made up of a parallel stack of 100 μm thick metal plates that form an array of parallel-plate waveguides. The convergent lens has a plano-concave geometry, in contrast to conventional dielectric lenses. Our results demonstrate that this lens is capable of focusing a 2 cm diameter beam to a spot size of 4 mm, at the design frequency of 0.17 THz. The results further demonstrate that the overall power transmission of the lens can be better than certain conventional dielectric lenses commonly used in the THz regime. Intriguingly, we also observe that under certain conditions, the lens boundary demarcated by the discontinuous plate edges actually resembles a smooth continuous surface. These results highlight the importance of this artificial-dielectric technology for the development of future THz-wave devices.

  18. Artificial Intelligence and CALL.

    ERIC Educational Resources Information Center

    Underwood, John H.

    The potential application of artificial intelligence (AI) to computer-assisted language learning (CALL) is explored. Two areas of AI that hold particular interest to those who deal with language meaning--knowledge representation and expert systems, and natural-language processing--are described and examples of each are presented. AI contribution…

  19. Applications of artificial intelligence

    SciTech Connect

    Gilmore, J.F.

    1984-01-01

    This book presents papers given at a conference on expert systems and artificial intelligence. Topics considered at the conference included the location of multiple faults by diagnostic expert systems, knowledge-based systems, natural language, image processing, computer vision, and identification systems.

  20. Terahertz Artificial Dielectric Lens.

    PubMed

    Mendis, Rajind; Nagai, Masaya; Wang, Yiqiu; Karl, Nicholas; Mittleman, Daniel M

    2016-01-01

    We have designed, fabricated, and experimentally characterized a lens for the THz regime based on artificial dielectrics. These are man-made media that mimic properties of naturally occurring dielectric media, or even manifest properties that cannot generally occur in nature. For example, the well-known dielectric property, the refractive index, which usually has a value greater than unity, can have a value less than unity in an artificial dielectric. For our lens, the artificial-dielectric medium is made up of a parallel stack of 100 μm thick metal plates that form an array of parallel-plate waveguides. The convergent lens has a plano-concave geometry, in contrast to conventional dielectric lenses. Our results demonstrate that this lens is capable of focusing a 2 cm diameter beam to a spot size of 4 mm, at the design frequency of 0.17 THz. The results further demonstrate that the overall power transmission of the lens can be better than certain conventional dielectric lenses commonly used in the THz regime. Intriguingly, we also observe that under certain conditions, the lens boundary demarcated by the discontinuous plate edges actually resembles a smooth continuous surface. These results highlight the importance of this artificial-dielectric technology for the development of future THz-wave devices. PMID:26973294

  1. Artificial intelligence within AFSC

    NASA Technical Reports Server (NTRS)

    Gersh, Mark A.

    1990-01-01

    Information on artificial intelligence research in the Air Force Systems Command is given in viewgraph form. Specific research that is being conducted at the Rome Air Development Center, the Space Technology Center, the Human Resources Laboratory, the Armstrong Aerospace Medical Research Laboratory, the Armamant Laboratory, and the Wright Research and Development Center is noted.

  2. Database in Artificial Intelligence.

    ERIC Educational Resources Information Center

    Wilkinson, Julia

    1986-01-01

    Describes a specialist bibliographic database of literature in the field of artificial intelligence created by the Turing Institute (Glasgow, Scotland) using the BRS/Search information retrieval software. The subscription method for end-users--i.e., annual fee entitles user to unlimited access to database, document provision, and printed awareness…

  3. Terahertz Artificial Dielectric Lens

    PubMed Central

    Mendis, Rajind; Nagai, Masaya; Wang, Yiqiu; Karl, Nicholas; Mittleman, Daniel M.

    2016-01-01

    We have designed, fabricated, and experimentally characterized a lens for the THz regime based on artificial dielectrics. These are man-made media that mimic properties of naturally occurring dielectric media, or even manifest properties that cannot generally occur in nature. For example, the well-known dielectric property, the refractive index, which usually has a value greater than unity, can have a value less than unity in an artificial dielectric. For our lens, the artificial-dielectric medium is made up of a parallel stack of 100 μm thick metal plates that form an array of parallel-plate waveguides. The convergent lens has a plano-concave geometry, in contrast to conventional dielectric lenses. Our results demonstrate that this lens is capable of focusing a 2 cm diameter beam to a spot size of 4 mm, at the design frequency of 0.17 THz. The results further demonstrate that the overall power transmission of the lens can be better than certain conventional dielectric lenses commonly used in the THz regime. Intriguingly, we also observe that under certain conditions, the lens boundary demarcated by the discontinuous plate edges actually resembles a smooth continuous surface. These results highlight the importance of this artificial-dielectric technology for the development of future THz-wave devices. PMID:26973294

  4. Artificial limb connection

    NASA Technical Reports Server (NTRS)

    Owens, L. J.

    1974-01-01

    Connection simplifies and eases donning and removing artificial limb; eliminates harnesses and clamps; and reduces skin pressures by allowing bone to carry all tensile and part of compressive loads between prosthesis and stump. Because connection is modular, it is easily modified to suit individual needs.

  5. Artificial Gravity Research Plan

    NASA Technical Reports Server (NTRS)

    Gilbert, Charlene

    2014-01-01

    This document describes the forward working plan to identify what countermeasure resources are needed for a vehicle with an artificial gravity module (intermittent centrifugation) and what Countermeasure Resources are needed for a rotating transit vehicle (continuous centrifugation) to minimize the effects of microgravity to Mars Exploration crewmembers.

  6. Biologically inspired robots as artificial inspectors

    NASA Astrophysics Data System (ADS)

    Bar-Cohen, Yoseph

    2002-06-01

    Imagine an inspector conducting an NDE on an aircraft where you notice something is different about him - he is not real but rather he is a robot. Your first reaction would probably be to say 'it's unbelievable but he looks real' just as you would react to an artificial flower that is a good imitation. This science fiction scenario could become a reality at the trend in the development of biologically inspired technologies, and terms like artificial intelligence, artificial muscles, artificial vision and numerous others are increasingly becoming common engineering tools. For many years, the trend has been to automate processes in order to increase the efficiency of performing redundant tasks where various systems have been developed to deal with specific production line requirements. Realizing that some parts are too complex or delicate to handle in small quantities with a simple automatic system, robotic mechanisms were developed. Aircraft inspection has benefitted from this evolving technology where manipulators and crawlers are developed for rapid and reliable inspection. Advancement in robotics towards making them autonomous and possibly look like human, can potentially address the need to inspect structures that are beyond the capability of today's technology with configuration that are not predetermined. The operation of these robots may take place at harsh or hazardous environments that are too dangerous for human presence. Making such robots is becoming increasingly feasible and in this paper the state of the art will be reviewed.

  7. Physiological Considerations of Artificial Gravity

    NASA Technical Reports Server (NTRS)

    Cramer, D. B.

    1985-01-01

    Reasons for the development of artificial gravity environments on spacecraft are outlined. The physiological effects of weightlessness on the human cardiovascular skeletal, and vestibular systems are enumerated. Design options for creating artificial gravity environments are shown.

  8. Dual band metamaterial perfect absorber based on artificial dielectric "molecules".

    PubMed

    Liu, Xiaoming; Lan, Chuwen; Li, Bo; Zhao, Qian; Zhou, Ji

    2016-01-01

    Dual band metamaterial perfect absorbers with two absorption bands are highly desirable because of their potential application areas such as detectors, transceiver system, and spectroscopic imagers. However, most of these dual band metamaterial absorbers proposed were based on resonances of metal patterns. Here, we numerically and experimentally demonstrate a dual band metamaterial perfect absorber composed of artificial dielectric "molecules" with high symmetry. The artificial dielectric "molecule" consists of four "atoms" of two different sizes corresponding to two absorption bands with near unity absorptivity. Numerical and experimental absorptivity verify that the dual-band metamaterial absorber is polarization insensitive and can operate in wide-angle incidence. PMID:27406699

  9. Artificial fibrous proteins: a review.

    PubMed

    Heslot, H

    1998-01-01

    Several kinds of natural fibrous proteins have been chosen as models: silk fibroin from Bombyx mori, silks from various species of spiders and collagens. The dragline silk of the spider Nephila clavipes is able to stretch by 30% before breaking and has a high tensile strength. It is stronger per unit weight than high tensile steel. Although the partial sequence of the two components of dragline silk is known, its molecular structure is still far from being clearly established. It is however demonstrated that it contains beta-sheet crystals composed of polyalanine residues. Artificial fibrous proteins have been prepared in vivo using either Escherichia coli or the yeast Pichia pastoris. As these proteins contain repetitive sequences, there is a risk of deletion at the DNA level. This difficulty has been solved by making use of the genetic code degeneracy. One group has successfully synthesized silk-like polymers; prolastin polymers containing both silk-like and elastin-like blocks; proNectin polymers containing the RGD triplet coming from fibronectin and able to fix numerous mammalian cell types; and synthetic collagen analogs. Some of these polymers have been spun into fibers that, up-to-now, do not display any measurable molecular orientation. Another group has studied artificial fibrous proteins able to form beta-sheet crystals of defined thickness and bearing functional groups at their surface, for instance Glu residues, selenomethionine or p-fluorophenylalanine. Apart from university laboratories, a venture capital society, an industrial research center and a US army research center are quite active in this field. A number of patents has been deposited. PMID:9587659

  10. Artificial Intelligence and Information Retrieval.

    ERIC Educational Resources Information Center

    Teodorescu, Ioana

    1987-01-01

    Compares artificial intelligence and information retrieval paradigms for natural language understanding, reviews progress to date, and outlines the applicability of artificial intelligence to question answering systems. A list of principal artificial intelligence software for database front end systems is appended. (CLB)

  11. Rearing insects on artificial diets

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Insects are reared in the laboratory for various purposes. They may be reared either on their natural food or artificial diets. Developing artificial diets may be difficult and time consuming but once optimized, artificial diets usually are simple to prepare and easy to use. Because they are process...

  12. Physiological Considerations of Artificial Gravity

    NASA Technical Reports Server (NTRS)

    Cramer, D. B.

    1985-01-01

    Weightlessness produces significant physiological changes. Whether these changes will stabilize or achieve medical significance is not clear. Artificial gravity is the physiological countermeasure, and the tether system represents an attractive approach to artificial gravity. The need for artificial gravity is examined.

  13. Swimming dynamics of bidirectional artificial flagella.

    PubMed

    Namdeo, S; Khaderi, S N; Onck, P R

    2013-10-01

    We study magnetic artificial flagella whose swimming speed and direction can be controlled using light and magnetic field as external triggers. The dependence of the swimming velocity on the system parameters (e.g., length, stiffness, fluid viscosity, and magnetic field) is explored using a computational framework in which the magnetostatic, fluid dynamic, and solid mechanics equations are solved simultaneously. A dimensionless analysis is carried out to obtain an optimal combination of system parameters for which the swimming velocity is maximal. The swimming direction reversal is addressed by incorporating photoresponsive materials, which in the photoactuated state can mimic natural mastigonemes. PMID:24229282

  14. Numerical Integration

    ERIC Educational Resources Information Center

    Sozio, Gerry

    2009-01-01

    Senior secondary students cover numerical integration techniques in their mathematics courses. In particular, students would be familiar with the "midpoint rule," the elementary "trapezoidal rule" and "Simpson's rule." This article derives these techniques by methods which secondary students may not be familiar with and an approach that…

  15. Numerical Relativity

    NASA Technical Reports Server (NTRS)

    Baker, John G.

    2009-01-01

    Recent advances in numerical relativity have fueled an explosion of progress in understanding the predictions of Einstein's theory of gravity, General Relativity, for the strong field dynamics, the gravitational radiation wave forms, and consequently the state of the remnant produced from the merger of compact binary objects. I will review recent results from the field, focusing on mergers of two black holes.

  16. Artificial neural superposition eye.

    PubMed

    Brückner, Andreas; Duparré, Jacques; Dannberg, Peter; Bräuer, Andreas; Tünnermann, Andreas

    2007-09-17

    We propose an ultra-thin imaging system which is based on the neural superposition compound eye of insects. Multiple light sensitive pixels in the footprint of each lenslet of this multi-channel configuration enable the parallel imaging of the individual object points. Together with the digital superposition of related signals this multiple sampling enables advanced functionalities for artificial compound eyes. Using this technique, color imaging and a circumvention for the trade-off between resolution and sensitivity of ultra-compact camera devices have been demonstrated in this article. The optical design and layout of such a system is discussed in detail. Experimental results are shown which indicate the attractiveness of microoptical artificial compound eyes for applications in the field of machine vision, surveillance or automotive imaging. PMID:19547555

  17. Whither Artificial Reproduction?

    PubMed Central

    Percival-Smith, Robin

    1985-01-01

    Artificial reproduction now offers sub fertile couples a number of options which raise scientific and ethical questions. This article discusses the Canadian and British experiences in formulating regulations and legislation in this important field. Current work on mammalian embryo research foretells the direction which human research will take. This article stresses the need for family physicians' participation in the ethical decisions that accompany these new developments. PMID:21274181

  18. Applications Of Artificial Intelligence

    NASA Astrophysics Data System (ADS)

    Trivedi, Mohan M.; Gilmore, John F.

    1986-03-01

    Intelligence evolves out of matter, so said the Sankhya philosophers of ancient India. The discipline of artificial intelligence (Al), which was established some 30 years ago, has confirmed the validity of the above assertion. Recently, a number of AI applications have been successfully demonstrated, generating a great deal of excitement and interest in scientific and technical circles. In this special issue of Optical Engineering a representative set of applications that incorporate Al principles is presented.

  19. Developing better artificial bones.

    PubMed

    Flinn, Edward D

    2003-01-01

    Researchers at the Center for Commercial Applications of Combustion in Space at the Colorado School of Mines are preparing the Space-DRUMS (Dynamically Responding Ultrasonic Matrix Systems) materials processing facility for transport to the International Space Station. The Space-DRUMS uses acoustic pressure beams to maintain the position of a suspended liquid or solid. Space-DRUMS will be used to extend experiments with tricalcium phosphate in the development of artificial bone material. PMID:12524712

  20. Artificial gravity Mars spaceship

    NASA Technical Reports Server (NTRS)

    Clark, Benton C.

    1989-01-01

    Experience gained in the study of artificial gravity for a manned trip to Mars is reviewed, and a snowflake-configured interplanetary vehicle cluster of habitat modules, descent vehicles, and propulsion systems is presented. An evolutionary design is described which permits sequential upgrading from five to nine crew members, an increase of landers from one to as many a three per mission, and an orderly, phased incorporation of advanced technologies as they become available.

  1. [Liver and artificial liver].

    PubMed

    Chamuleau, R A

    1998-06-01

    Despite good results of orthotopic liver transplantation in patients with fulminant hepatic failure the need still exists for an effective and safe artificial liver, able to temporarily take over the complex liver function so as to bridge the gap with transplantation or regeneration. Attempts to develop non-biological artificial livers have failed, mostly when controlled clinical trials were performed. In the last decade several different types of bioartificial livers have been devised, in which the biocomponent consists of freshly isolated porcine hepatocytes or a human hepatoblastoma cell line. The majority use semipermeable hollow fibers known from artificial kidney devices. The liver cells may lie either inside or outside the lumen of these fibers. In vitro analysis of liver function and animal experimental work showing that the bioartificial liver increases survival justify clinical application. Bioartificial livers are connected to patients extracorporeally by means of plasmapheresis circuit for periods of about 6 hours. In different trials about 40 patients with severe liver failure have been treated. No important adverse effects have not been reported in these phase I trials. Results of controlled studies are urgently needed. As long as no satisfactory immortalised human liver cell line with good function is available, porcine hepatocytes will remain the first choice, provided transmission of porcine pathogens to man is prevented. PMID:9752034

  2. Polish artificial heart program.

    PubMed

    El Fray, Miroslawa; Czugala, Monika

    2012-01-01

    Despite significant advances in the development of artificial heart substitutes, anthrombogenic materials and surfaces remain to be the main challenge for implants, which can prevent thrombosis that leads to rejection. The goal of material engineering is essentially to design polymeric materials of high durability and optimal thrombogenicity in mechanical heart prosthesis, being developed recently in a frame of the polish artificial heart program. For these reasons, various surface modifications are being continuously developed for a 'gold standard' material, which is a polyurethane (PU) thermoplastic elastomer and they will be shortly reviewed. However, new polymeric materials can meet medical word's attention if they are able to provide similar or better characteristics in term of bulk and surface properties. Specifically, if they will show appropriate surface topography, which is the most influential in determining the response of live tissues toward biomaterials. Nanostructured polyester thermoplastic elastomers of high biodurability as an alternative to PU materials for artificial heart are challenging new materials, and they will be discussed briefly. PMID:22110047

  3. IMPEDANCE OF FINITE LENGTH RESISTOR

    SciTech Connect

    KRINSKY, S.; PODOBEDOV, B.; GLUCKSTERN, R.L.

    2005-05-15

    We determine the impedance of a cylindrical metal tube (resistor) of radius a, length g, and conductivity {sigma}, attached at each end to perfect conductors of semi-infinite length. Our main interest is in the asymptotic behavior of the impedance at high frequency, k >> 1/a. In the equilibrium regime, , the impedance per unit length is accurately described by the well-known result for an infinite length tube with conductivity {sigma}. In the transient regime, ka{sup 2} >> g, we derive analytic expressions for the impedance and wakefield.

  4. Insect attachment on crystalline bioinspired wax surfaces formed by alkanes of varying chain lengths

    PubMed Central

    Böhm, Sandro; Jacky, Nadine; Maier, Louis-Philippe; Dening, Kirstin; Pechook, Sasha; Pokroy, Boaz; Gorb, Stanislav

    2014-01-01

    Summary The impeding effect of plant surfaces covered with three-dimensional wax on attachment and locomotion of insects has been shown previously in numerous experimental studies. The aim of this study was to examine the effect of different parameters of crystalline wax coverage on insect attachment. We performed traction experiments with the beetle Coccinella septempunctata and pull-off force measurements with artificial adhesive systems (tacky polydimethylsiloxane semi-spheres) on bioinspired wax surfaces formed by four alkanes of varying chain lengths (C36H74, C40H82, C44H90, and C50H102). All these highly hydrophobic coatings were composed of crystals having similar morphologies but differing in size and distribution/density, and exhibited different surface roughness. The crystal size (length and thickness) decreased with an increase of the chain length of the alkanes that formed these surfaces, whereas the density of the wax coverage, as well as the surface roughness, showed an opposite relationship. Traction tests demonstrated a significant, up to 30 fold, reduction of insect attachment forces on the wax surfaces when compared with the reference glass sample. Attachment of the beetles to the wax substrates probably relied solely on the performance of adhesive pads. We found no influence of the wax coatings on the subsequent attachment ability of beetles. The obtained data are explained by the reduction of the real contact between the setal tips of the insect adhesive pads and the wax surfaces due to the micro- and nanoscopic roughness introduced by wax crystals. Experiments with polydimethylsiloxane semi-spheres showed much higher forces on wax samples when compared to insect attachment forces measured on these surfaces. We explain these results by the differences in material properties between polydimethylsiloxane probes and tenent setae of C. septempunctata beetles. Among wax surfaces, force experiments showed stronger insect attachment and higher pull

  5. Line Lengths and Starch Scores.

    ERIC Educational Resources Information Center

    Moriarty, Sandra E.

    1986-01-01

    Investigates readability of different line lengths in advertising body copy, hypothesizing a normal curve with lower scores for shorter and longer lines, and scores above the mean for lines in the middle of the distribution. Finds support for lower scores for short lines and some evidence of two optimum line lengths rather than one. (SKC)

  6. Novel sensors for the Artificial Mouth

    NASA Astrophysics Data System (ADS)

    Djeghlaf, Lyes; Mielle, Patrick; Maratray, Jacques; Launay, Jérôme; Temple-Boyer, Pierre; Salles, Christian

    2011-09-01

    Similarly to human chewing, tasty compounds are released in saliva during the food piece mastication in the `Artificial Mouth', and so, are available continuously. Glutamate is present in numerous food, as taste enhancer, has a nice and sought "umami" taste, specific receptors and different inter individual sensitivities, and is a fair marker of the release of tasty compounds. The three sensors (for pH, salt, or glutamate concentration) have the same size, so they are easily interchangeable. Up to now, only one kind of parameter may be analysed at a time by the different sensors. Nevertheless, combined electrodes may be developed in the future.

  7. Artificial intelligence in hematology.

    PubMed

    Zini, Gina

    2005-10-01

    Artificial intelligence (AI) is a computer based science which aims to simulate human brain faculties using a computational system. A brief history of this new science goes from the creation of the first artificial neuron in 1943 to the first artificial neural network application to genetic algorithms. The potential for a similar technology in medicine has immediately been identified by scientists and researchers. The possibility to store and process all medical knowledge has made this technology very attractive to assist or even surpass clinicians in reaching a diagnosis. Applications of AI in medicine include devices applied to clinical diagnosis in neurology and cardiopulmonary diseases, as well as the use of expert or knowledge-based systems in routine clinical use for diagnosis, therapeutic management and for prognostic evaluation. Biological applications include genome sequencing or DNA gene expression microarrays, modeling gene networks, analysis and clustering of gene expression data, pattern recognition in DNA and proteins, protein structure prediction. In the field of hematology the first devices based on AI have been applied to the routine laboratory data management. New tools concern the differential diagnosis in specific diseases such as anemias, thalassemias and leukemias, based on neural networks trained with data from peripheral blood analysis. A revolution in cancer diagnosis, including the diagnosis of hematological malignancies, has been the introduction of the first microarray based and bioinformatic approach for molecular diagnosis: a systematic approach based on the monitoring of simultaneous expression of thousands of genes using DNA microarray, independently of previous biological knowledge, analysed using AI devices. Using gene profiling, the traditional diagnostic pathways move from clinical to molecular based diagnostic systems. PMID:16203606

  8. Length sensing and control for Einstein Telescope Low Frequency

    NASA Astrophysics Data System (ADS)

    Adya, Vaishali; Leavey, Sean; Lück, Harald; Gräf, Christian; Hild, Stefan

    2016-05-01

    In this paper we describe a feasible length sensing and control scheme for the low frequency interferometers of the Einstein Telescope (ET-LF) along with the techniques used to optimise several optical parameters, including the length of the recycling cavities and the modulation frequencies, using two numerical interferometer simulation packages: Optickle and Finesse. The investigations have suggested the use of certain combinations of sidebands to obtain independent information about the different degrees of freedom.

  9. Artificial gravity field

    NASA Astrophysics Data System (ADS)

    Markley, Larry C.; Lindner, John F.

    Using computer algebra to run Einstein's equations "backward", from field to source rather than from source to field, we design an artificial gravity field for a space station or spaceship. Everywhere inside astronauts experience normal Earth gravity, while outside they float freely. The stress-energy that generates the field contains exotic matter of negative energy density but also relies importantly on pressures and shears, which we describe. The same techniques can be readily used to design other interesting spacetimes and thereby elucidate the connection between the source and field in general relativity.

  10. Plasmonic nanostructures: artificial molecules.

    PubMed

    Wang, Hui; Brandl, Daniel W; Nordlander, Peter; Halas, Naomi J

    2007-01-01

    This Account describes a new paradigm for the relationship between the geometry of metallic nanostructures and their optical properties. While the interaction of light with metallic nanoparticles is determined by their collective electronic or plasmon response, a compelling analogy exists between plasmon resonances of metallic nanoparticles and wave functions of simple atoms and molecules. Based on this insight, an entire family of plasmonic nanostructures, artificial molecules, has been developed whose optical properties can be understood within this picture: nanoparticles (nanoshells, nanoeggs, nanomatryushkas, nanorice), multi-nanoparticle assemblies (dimers, trimers, quadrumers), and a nanoparticle-over-metallic film, an electromagnetic analog of the spinless Anderson model. PMID:17226945

  11. Analytical solution of average path length for Apollonian networks

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongzhi; Chen, Lichao; Zhou, Shuigeng; Fang, Lujun; Guan, Jihong; Zou, Tao

    2008-01-01

    With the help of recursion relations derived from the self-similar structure, we obtain the solution of average path length, dmacr t , for Apollonian networks. In contrast to the well-known numerical result dmacr t∝(lnNt)3/4 [J. S. Andrade, Jr. , Phys. Rev. Lett. 94, 018702 (2005)], our rigorous solution shows that the average path length grows logarithmically as dmacr t∝lnNt in the infinite limit of network size Nt . The extensive numerical calculations completely agree with our closed-form solution.

  12. Spreading lengths of Hermite polynomials

    NASA Astrophysics Data System (ADS)

    Sánchez-Moreno, P.; Dehesa, J. S.; Manzano, D.; Yáñez, R. J.

    2010-03-01

    The Renyi, Shannon and Fisher spreading lengths of the classical or hypergeometric orthogonal polynomials, which are quantifiers of their distribution all over the orthogonality interval, are defined and investigated. These information-theoretic measures of the associated Rakhmanov probability density, which are direct measures of the polynomial spreading in the sense of having the same units as the variable, share interesting properties: invariance under translations and reflections, linear scaling and vanishing in the limit that the variable tends towards a given definite value. The expressions of the Renyi and Fisher lengths for the Hermite polynomials are computed in terms of the polynomial degree. The combinatorial multivariable Bell polynomials, which are shown to characterize the finite power of an arbitrary polynomial, play a relevant role for the computation of these information-theoretic lengths. Indeed these polynomials allow us to design an error-free computing approach for the entropic moments (weighted Lq-norms) of Hermite polynomials and subsequently for the Renyi and Tsallis entropies, as well as for the Renyi spreading lengths. Sharp bounds for the Shannon length of these polynomials are also given by means of an information-theoretic-based optimization procedure. Moreover, the existence of a linear correlation between the Shannon length (as well as the second-order Renyi length) and the standard deviation is computationally proved. Finally, the application to the most popular quantum-mechanical prototype system, the harmonic oscillator, is discussed and some relevant asymptotical open issues related to the entropic moments, mentioned previously, are posed.

  13. Numerical anomalies mimicking physical effects

    NASA Astrophysics Data System (ADS)

    Menikoff, R.

    Numerical simulations of flows with shock waves typically use finite-difference shock-capturing algorithms. These algorithms give a shock a numerical width in order to generate the entropy increase that must occur across a shock wave. For algorithms in conservation form, steady-state shock waves are insensitive to the numerical dissipation because of the Hugoniot jump conditions. However, localized numerical errors occur when shock waves interact. Examples are the 'excess wall heating' in the Noh problem (shock reflected from rigid wall), errors when a shock impacts a material interface or an abrupt change in mesh spacing, and the start-up error from initializing a shock as a discontinuity. This class of anomalies can be explained by the entropy generation that occurs in the transient flow when a shock profile is formed or changed. The entropy error is localized spatially but under mesh refinement does not decrease in magnitude. Similar effects have been observed in shock tube experiments with partly dispersed shock waves. In this case, the shock has a physical width due to a relaxation process. An entropy anomaly from a transient shock interaction is inherent in the structure of the conservation equations for fluid flow. The anomaly can be expected to occur whenever heat conduction can be neglected and a shock wave has a non-zero width, whether the width is physical or numerical. Thus, the numerical anomaly from an artificial shock width mimics a real physical effect.

  14. When does length cause the word length effect?

    PubMed

    Jalbert, Annie; Neath, Ian; Bireta, Tamra J; Surprenant, Aimée M

    2011-03-01

    The word length effect, the finding that lists of short words are better recalled than lists of long words, has been termed one of the benchmark findings that any theory of immediate memory must account for. Indeed, the effect led directly to the development of working memory and the phonological loop, and it is viewed as the best remaining evidence for time-based decay. However, previous studies investigating this effect have confounded length with orthographic neighborhood size. In the present study, Experiments 1A and 1B revealed typical effects of length when short and long words were equated on all relevant dimensions previously identified in the literature except for neighborhood size. In Experiment 2, consonant-vowel-consonant (CVC) words with a large orthographic neighborhood were better recalled than were CVC words with a small orthographic neighborhood. In Experiments 3 and 4, using two different sets of stimuli, we showed that when short (1-syllable) and long (3-syllable) items were equated for neighborhood size, the word length effect disappeared. Experiment 5 replicated this with spoken recall. We suggest that the word length effect may be better explained by the differences in linguistic and lexical properties of short and long words rather than by length per se. These results add to the growing literature showing problems for theories of memory that include decay offset by rehearsal as a central feature. PMID:21171805

  15. Applicability of nonresonant artificial diamagnetics

    NASA Astrophysics Data System (ADS)

    Jelinek, L.; Lapine, M.; McPhedran, R. C.

    2014-09-01

    Artificial diamagnetics are prominent for achieving extraordinarily strong diamagnetism in a wide frequency range. However, as far as the magnetic fields outside the artificial medium are concerned, bulk conductors show a very similar pattern. The question arises whether the complicated internal structure of artificial diamagnetics can, to this end, be replaced by a simpler object. We show that for an electrically small body, internal structuring is likely to make the effective diamagnetic response weaker than that of a simple conducting object.

  16. The total artificial heart

    PubMed Central

    Cook, Jason A.; Shah, Keyur B.; Quader, Mohammed A.; Cooke, Richard H.; Kasirajan, Vigneshwar; Rao, Kris K.; Smallfield, Melissa C.; Tchoukina, Inna

    2015-01-01

    The total artificial heart (TAH) is a form of mechanical circulatory support in which the patient’s native ventricles and valves are explanted and replaced by a pneumatically powered artificial heart. Currently, the TAH is approved for use in end-stage biventricular heart failure as a bridge to heart transplantation. However, with an increasing global burden of cardiovascular disease and congestive heart failure, the number of patients with end-stage heart failure awaiting heart transplantation now far exceeds the number of available hearts. As a result, the use of mechanical circulatory support, including the TAH and left ventricular assist device (LVAD), is growing exponentially. The LVAD is already widely used as destination therapy, and destination therapy for the TAH is under investigation. While most patients requiring mechanical circulatory support are effectively treated with LVADs, there is a subset of patients with concurrent right ventricular failure or major structural barriers to LVAD placement in whom TAH may be more appropriate. The history, indications, surgical implantation, post device management, outcomes, complications, and future direction of the TAH are discussed in this review. PMID:26793338

  17. Development of artificial empathy.

    PubMed

    Asada, Minoru

    2015-01-01

    We have been advocating cognitive developmental robotics to obtain new insight into the development of human cognitive functions by utilizing synthetic and constructive approaches. Among the different emotional functions, empathy is difficult to model, but essential for robots to be social agents in our society. In my previous review on artificial empathy (Asada, 2014b), I proposed a conceptual model for empathy development beginning with emotional contagion to envy/schadenfreude along with self/other differentiation. In this article, the focus is on two aspects of this developmental process, emotional contagion in relation to motor mimicry, and cognitive/affective aspects of the empathy. It begins with a summary of the previous review (Asada, 2014b) and an introduction to affective developmental robotics as a part of cognitive developmental robotics focusing on the affective aspects. This is followed by a review and discussion on several approaches for two focused aspects of affective developmental robotics. Finally, future issues involved in the development of a more authentic form of artificial empathy are discussed. PMID:25498950

  18. Modelling fuel cell performance using artificial intelligence

    NASA Astrophysics Data System (ADS)

    Ogaji, S. O. T.; Singh, R.; Pilidis, P.; Diacakis, M.

    Over the last few years, fuel cell technology has been increasing promisingly its share in the generation of stationary power. Numerous pilot projects are operating worldwide, continuously increasing the amount of operating hours either as stand-alone devices or as part of gas turbine combined cycles. An essential tool for the adequate and dynamic analysis of such systems is a software model that enables the user to assess a large number of alternative options in the least possible time. On the other hand, the sphere of application of artificial neural networks has widened covering such endeavours of life such as medicine, finance and unsurprisingly engineering (diagnostics of faults in machines). Artificial neural networks have been described as diagrammatic representation of a mathematical equation that receives values (inputs) and gives out results (outputs). Artificial neural networks systems have the capacity to recognise and associate patterns and because of their inherent design features, they can be applied to linear and non-linear problem domains. In this paper, the performance of the fuel cell is modelled using artificial neural networks. The inputs to the network are variables that are critical to the performance of the fuel cell while the outputs are the result of changes in any one or all of the fuel cell design variables, on its performance. Critical parameters for the cell include the geometrical configuration as well as the operating conditions. For the neural network, various network design parameters such as the network size, training algorithm, activation functions and their causes on the effectiveness of the performance modelling are discussed. Results from the analysis as well as the limitations of the approach are presented and discussed.

  19. Applications of network analysis for adaptive management of artificial drainage systems in landscapes vulnerable to sea level rise

    NASA Astrophysics Data System (ADS)

    Poulter, Benjamin; Goodall, Jonathan L.; Halpin, Patrick N.

    2008-08-01

    SummaryThe vulnerability of coastal landscapes to sea level rise is compounded by the existence of extensive artificial drainage networks initially built to lower water tables for agriculture, forestry, and human settlements. These drainage networks are found in landscapes with little topographic relief where channel flow is characterized by bi-directional movement across multiple time-scales and related to precipitation, wind, and tidal patterns. The current configuration of many artificial drainage networks exacerbates impacts associated with sea level rise such as salt-intrusion and increased flooding. This suggests that in the short-term, drainage networks might be managed to mitigate sea level rise related impacts. The challenge, however, is that hydrologic processes in regions where channel flow direction is weakly related to slope and topography require extensive parameterization for numerical models which is limited where network size is on the order of a hundred or more kilometers in total length. Here we present an application of graph theoretic algorithms to efficiently investigate network properties relevant to the management of a large artificial drainage system in coastal North Carolina, USA. We created a digital network model representing the observation network topology and four types of drainage features (canal, collector and field ditches, and streams). We applied betweenness-centrality concepts (using Dijkstra's shortest path algorithm) to determine major hydrologic flowpaths based off of hydraulic resistance. Following this, we identified sub-networks that could be managed independently using a community structure and modularity approach. Lastly, a betweenness-centrality algorithm was applied to identify major shoreline entry points to the network that disproportionately control water movement in and out of the network. We demonstrate that graph theory can be applied to solving management and monitoring problems associated with sea level rise

  20. Artificial organs: recent progress in artificial hearing and vision.

    PubMed

    Ifukube, Tohru

    2009-01-01

    Artificial sensory organs are a prosthetic means of sending visual or auditory information to the brain by electrical stimulation of the optic or auditory nerves to assist visually impaired or hearing-impaired people. However, clinical application of artificial sensory organs, except for cochlear implants, is still a trial-and-error process. This is because how and where the information transmitted to the brain is processed is still unknown, and also because changes in brain function (plasticity) remain unknown, even though brain plasticity plays an important role in meaningful interpretation of new sensory stimuli. This article discusses some basic unresolved issues and potential solutions in the development of artificial sensory organs such as cochlear implants, brainstem implants, artificial vision, and artificial retinas. PMID:19330498

  1. Target fishes on artificial reefs: evidences of impacts over nearby natural environments.

    PubMed

    Simon, Thiony; Pinheiro, Hudson Tercio; Joyeux, Jean-Christophe

    2011-10-01

    Topics in artificial reef research have included a wide number of themes but a major portion of published works are about the attraction that artificial reefs exert over fishes that reside in natural reefs. In the present work, underwater visual censuses of fishes were conducted at both artificial and natural reefs, aiming at verifying whether fishes are attracted or and produced on artificial reefs. Length frequency, mean biomass and frequency of occurrence of four fish genera targeted by local fisheries (Caranx, Haemulon, Lutjanus and Mycteroperca) were compared between two artificial and two natural reefs. Evidences of both production and attraction of target reef fishes by artificial reefs were found. Production is evidenced by the enormous abundance of recruits of a single grunt species, the tomtate (Haemulon aurolineatum Cuvier). The high concentration of adults of predator demersal fishes (Mycteroperca spp. and Lutjanus spp.), present at low density on natural reefs, is the main evidence for attraction by artificial reefs. Results are inconclusive for the pelagic predators Caranx spp. The attraction that artificial reefs exert over large demersal predators can negatively affect nearby natural areas through shifts in predation, competition or nutrient input. Production can affect benthic communities in soft bottoms adjacent to artificial reefs by foraging of reef-associated fishes. Even when unplanned for fisheries purposes artificial reefs are often submitted to commercial and recreational fisheries and, due to the strong attraction they exert over large predators, these structures need harvest regulations. PMID:21871652

  2. Dynamics of neutral atoms in artificial magnetic field

    NASA Astrophysics Data System (ADS)

    Yu, Zi-Fa; Hu, Fang-Qi; Zhang, Ai-Xia; Xue, Ju-Kui

    2016-02-01

    Cyclotron dynamics of neutral atoms in a harmonic trap potential with artificial magnetic field is studied theoretically. The cyclotron orbit is obtained analytically and confirmed numerically. When the external harmonic potential is absent, artificial magnetic field can result in the singly periodic circular motion of Bose gas with the emergence of a Lorentz-like force, which is similar to particles with electric charge moving in a magnetic field. However, the coupling between artificial magnetic field and harmonic trap potential leads to rich and complex cyclotron trajectory, which depends on √{B2 + 1 }, where B is the rescaled artificial magnetic field. When √{B2 + 1 } is a rational number, the cyclotron orbit is multiply periodic and closed. However, when √{B2 + 1 } is an irrational number, the cyclotron orbit is quasiperiodic, i.e., the cyclotron motion of Bose gas is limited in a annular region, and eventually, the motion is ergodic in this region. Furthermore, the cyclotron orbits also depend on the initial conditions of Bose gas. Thus, the cyclotron dynamics of Bose gas can be manipulated in a controllable way by changing the artificial magnetic field, harmonic trap potential and initial conditions. Our results provide a direct theoretical evidence for the cyclotron dynamics of neutral atoms in the artificial gauge field.

  3. Experimental and Theoretical Studies of Photonic Band gaps in Artificial Opals

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Yin, Ming; Arammash, Fouzi; Datta, Timir

    2014-03-01

    Photonic band structure and band gap were numerically computed for a number of closed packed simple cubic and Hexagonal arrangements of non-conducting spheres using ``Finite Difference Time Domain Method''. Photonic gaps were found to exist in the simple cubic overlapping spheres with index of refraction (n) >3.2. Gap increased linearly from 0.117- 0.161 (1/micron) as lattice constant decreased from 0.34 to 0.18 (micron). For less than 3.2 no gap was obtained. Also, no gaps were obtained for hexagonal packing. UV-VIS reflectivity and transmission measurements of polycrystalline bulk artificial opals of silica (SiO2) spheres, ranging from 250nm to 300nm in sphere diameter indicate a reflection peak in the 500-600 nm regimes. Consistent with photonic band gap behavior we find that reflectivity is enhanced in the same wavelength where transmission is reduced. To the best of our knowledge this is the first observation of photonic gap in the visible wave length under ambient conditions. The wave length at the reflectance peak increases with the diameter of the SiO2 spheres, and is approximately twice the diameter following Bragg reflection. DOD Award No 60177-RT-H from ARO.

  4. Artificial sweeteners - a review.

    PubMed

    Chattopadhyay, Sanchari; Raychaudhuri, Utpal; Chakraborty, Runu

    2014-04-01

    Now a days sugar free food are very much popular because of their less calorie content. So food industry uses various artificial sweeteners which are low in calorie content instead of high calorie sugar. U.S. Food and Drug Administration has approved aspartame, acesulfame-k, neotame, cyclamate and alitame for use as per acceptable daily intake (ADI) value. But till date, breakdown products of these sweeteners have controversial health and metabolic effects. On the other hand, rare sugars are monosaccharides and have no known health effects because it does not metabolize in our body, but shows same sweet taste and bulk property as sugar. Rare sugars have no such ADI value and are mainly produced by using bioreactor and so inspite of high demand, rare sugars cannot be produced in the desired quantities. PMID:24741154

  5. Artificial Molecular Machines.

    PubMed

    Balzani; Credi; Raymo; Stoddart

    2000-10-01

    The miniaturization of components used in the construction of working devices is being pursued currently by the large-downward (top-down) fabrication. This approach, however, which obliges solid-state physicists and electronic engineers to manipulate progressively smaller and smaller pieces of matter, has its intrinsic limitations. An alternative approach is a small-upward (bottom-up) one, starting from the smallest compositions of matter that have distinct shapes and unique properties-namely molecules. In the context of this particular challenge, chemists have been extending the concept of a macroscopic machine to the molecular level. A molecular-level machine can be defined as an assembly of a distinct number of molecular components that are designed to perform machinelike movements (output) as a result of an appropriate external stimulation (input). In common with their macroscopic counterparts, a molecular machine is characterized by 1) the kind of energy input supplied to make it work, 2) the nature of the movements of its component parts, 3) the way in which its operation can be monitored and controlled, 4) the ability to make it repeat its operation in a cyclic fashion, 5) the timescale needed to complete a full cycle of movements, and 6) the purpose of its operation. Undoubtedly, the best energy inputs to make molecular machines work are photons or electrons. Indeed, with appropriately chosen photochemically and electrochemically driven reactions, it is possible to design and synthesize molecular machines that do work. Moreover, the dramatic increase in our fundamental understanding of self-assembly and self-organizational processes in chemical synthesis has aided and abetted the construction of artificial molecular machines through the development of new methods of noncovalent synthesis and the emergence of supramolecular assistance to covalent synthesis as a uniquely powerful synthetic tool. The aim of this review is to present a unified view of the field

  6. Molecular artificial photosynthesis.

    PubMed

    Berardi, Serena; Drouet, Samuel; Francàs, Laia; Gimbert-Suriñach, Carolina; Guttentag, Miguel; Richmond, Craig; Stoll, Thibaut; Llobet, Antoni

    2014-11-21

    The replacement of fossil fuels by a clean and renewable energy source is one of the most urgent and challenging issues our society is facing today, which is why intense research has been devoted to this topic recently. Nature has been using sunlight as the primary energy input to oxidise water and generate carbohydrates (solar fuel) for over a billion years. Inspired, but not constrained, by nature, artificial systems can be designed to capture light and oxidise water and reduce protons or other organic compounds to generate useful chemical fuels. This tutorial review covers the primary topics that need to be understood and mastered in order to come up with practical solutions for the generation of solar fuels. These topics are: the fundamentals of light capturing and conversion, water oxidation catalysis, proton and CO2 reduction catalysis and the combination of all of these for the construction of complete cells for the generation of solar fuels. PMID:24473472

  7. Compact artificial hand

    NASA Technical Reports Server (NTRS)

    Wiker, G. A.; Mann, W. A. (Inventor)

    1979-01-01

    A relatively simple, compact artificial hand, is described which includes hooks pivotally mounted on first frame to move together and apart. The first frame is rotatably mounted on a second frame to enable "turning at the wrist" movement without limitation. The second frame is pivotally mounted on a third frame to permit 'flexing at the wrist' movement. A hook-driving motor is fixed to the second frame but has a shaft that drives a speed reducer on the first frame which, in turn, drives the hooks. A second motor mounted on the second frame, turns a gear on the first frame to rotate the first frame and the hooks thereon. A third motor mounted on the third frame, turns a gear on a second frame to pivot it.

  8. Mechanical performance of artificial pneumatic muscles to power an ankle-foot orthosis.

    PubMed

    Gordon, Keith E; Sawicki, Gregory S; Ferris, Daniel P

    2006-01-01

    We developed a powered ankle-foot orthosis that uses artificial pneumatic muscles to produce active plantar flexor torque. The purpose of this study was to quantify the mechanical performance of the orthosis during human walking. Three subjects walked at a range of speeds wearing ankle-foot orthoses with either one or two artificial muscles working in parallel. The orthosis produced similar total peak plantar flexor torque and network across speeds independent of the number of muscles used. The orthosis generated approximately 57% of the peak ankle plantar flexor torque during stance and performed approximately 70% of the positive plantar flexor work done during normal walking. Artificial muscle bandwidth and force-length properties were the two primary factors limiting torque production. The lack of peak force and work differences between single and double muscle conditions can be explained by force-length properties. Subjects altered their ankle kinematics between conditions resulting in changes in artificial muscle length. In the double muscle condition greater plantar flexion yielded shorter artificial muscles lengths and decreased muscle forces. This finding emphasizes the importance of human testing in the design and development of robotic exoskeleton devices for assisting human movement. The results of this study outline the mechanical performance limitations of an ankle-foot orthosis powered by artificial pneumatic muscles. This orthosis could be valuable for gait rehabilitation and for studies investigating neuromechanical control of human walking. PMID:16023126

  9. In Pursuit of Artificial Intelligence.

    ERIC Educational Resources Information Center

    Watstein, Sarah; Kesselman, Martin

    1986-01-01

    Defines artificial intelligence and reviews current research in natural language processing, expert systems, and robotics and sensory systems. Discussion covers current commercial applications of artificial intelligence and projections of uses and limitations in library technical and public services, e.g., in cataloging and online information and…

  10. Generalized Adaptive Artificial Neural Networks

    NASA Technical Reports Server (NTRS)

    Tawel, Raoul

    1993-01-01

    Mathematical model of supervised learning by artificial neural network provides for simultaneous adjustments of both temperatures of neurons and synaptic weights, and includes feedback as well as feedforward synaptic connections. Extension of mathematical model described in "Adaptive Neurons For Artificial Neural Networks" (NPO-17803). Dynamics of neural network represented in new model by less-restrictive continuous formalism.

  11. Artificial Ligaments: Promise or Panacea?

    ERIC Educational Resources Information Center

    Lubell, Adele

    1987-01-01

    The Food and Drug Administration has approved a prosthetic ligament for limited use in persons with damaged anterior cruciate ligaments (ACL). This article addresses ligament repair, ACL tears, current treatment, development of the Gore-Tex artificial ligament, other artificial ligaments in process, and arguments for and against their use.…

  12. A Primer on Artificial Intelligence.

    ERIC Educational Resources Information Center

    Leal, Ralph A.

    A survey of literature on recent advances in the field of artificial intelligence provides a comprehensive introduction to this field for the non-technical reader. Important areas covered are: (1) definitions, (2) the brain and thinking, (3) heuristic search, and (4) programing languages used in the research of artificial intelligence. Some…

  13. Artificial Intelligence and Language Comprehension.

    ERIC Educational Resources Information Center

    National Inst. of Education (DHEW), Washington, DC. Basic Skills Group. Learning Div.

    The three papers in this volume concerning artificial intelligence and language comprehension were commissioned by the National Institute of Education to further the understanding of the cognitive processes that enable people to comprehend what they read. The first paper, "Artificial Intelligence and Language Comprehension," by Terry Winograd,…

  14. Instructional Applications of Artificial Intelligence.

    ERIC Educational Resources Information Center

    Halff, Henry M.

    1986-01-01

    Surveys artificial intelligence and the development of computer-based tutors and speculates on the future of artificial intelligence in education. Includes discussion of the definitions of knowledge, expert systems (computer systems that solve tough technical problems), intelligent tutoring systems (ITS), and specific ITSs such as GUIDON, MYCIN,…

  15. Thermal responses of shape memory alloy artificial anal sphincters

    NASA Astrophysics Data System (ADS)

    Luo, Yun; Takagi, Toshiyuki; Matsuzawa, Kenichi

    2003-08-01

    This paper presents a numerical investigation of the thermal behavior of an artificial anal sphincter using shape memory alloys (SMAs) proposed by the authors. The SMA artificial anal sphincter has the function of occlusion at body temperature and can be opened with a thermal transformation induced deformation of SMAs to solve the problem of severe fecal incontinence. The investigation of its thermal behavior is of great importance in terms of practical use in living bodies as a prosthesis. In this work, a previously proposed phenomenological model was applied to simulate the thermal responses of SMA plates that had undergone thermally induced transformation. The numerical approach for considering the thermal interaction between the prosthesis and surrounding tissues was discussed based on the classical bio-heat equation. Numerical predictions on both in vitro and in vivo cases were verified by experiments with acceptable agreements. The thermal responses of the SMA artificial anal sphincter were discussed based on the simulation results, with the values of the applied power and the geometric configuration of thermal insulation as parameters. The results obtained in the present work provided a framework for the further design of SMA artificial sphincters to meet demands from the viewpoint of thermal compatibility as prostheses.

  16. Conservative smoothing versus artificial viscosity

    SciTech Connect

    Guenther, C.; Hicks, D.L.; Swegle, J.W.

    1994-08-01

    This report was stimulated by some recent investigations of S.P.H. (Smoothed Particle Hydrodynamics method). Solid dynamics computations with S.P.H. show symptoms of instabilities which are not eliminated by artificial viscosities. Both analysis and experiment indicate that conservative smoothing eliminates the instabilities in S.P.H. computations which artificial viscosities cannot. Questions were raised as to whether conservative smoothing might smear solutions more than artificial viscosity. Conservative smoothing, properly used, can produce more accurate solutions than the von Neumann-Richtmyer-Landshoff artificial viscosity which has been the standard for many years. The authors illustrate this using the vNR scheme on a test problem with known exact solution involving a shock collision in an ideal gas. They show that the norms of the errors with conservative smoothing are significantly smaller than the norms of the errors with artificial viscosity.

  17. Persistence Length of Stable Microtubules

    NASA Astrophysics Data System (ADS)

    Hawkins, Taviare; Mirigian, Matthew; Yasar, M. Selcuk; Ross, Jennifer

    2011-03-01

    Microtubules are a vital component of the cytoskeleton. As the most rigid of the cytoskeleton filaments, they give shape and support to the cell. They are also essential for intracellular traffic by providing the roadways onto which organelles are transported, and they are required to reorganize during cellular division. To perform its function in the cell, the microtubule must be rigid yet dynamic. We are interested in how the mechanical properties of stable microtubules change over time. Some ``stable'' microtubules of the cell are recycled after days, such as in the axons of neurons or the cilia and flagella. We measured the persistence length of freely fluctuating taxol-stabilized microtubules over the span of a week and analyzed them via Fourier decomposition. As measured on a daily basis, the persistence length is independent of the contour length. Although measured over the span of the week, the accuracy of the measurement and the persistence length varies. We also studied how fluorescently-labeling the microtubule affects the persistence length and observed that a higher labeling ratio corresponded to greater flexibility. National Science Foundation Grant No: 0928540 to JLR.

  18. Does length or neighborhood size cause the word length effect?

    PubMed

    Jalbert, Annie; Neath, Ian; Surprenant, Aimée M

    2011-10-01

    Jalbert, Neath, Bireta, and Surprenant (2011) suggested that past demonstrations of the word length effect, the finding that words with fewer syllables are recalled better than words with more syllables, included a confound: The short words had more orthographic neighbors than the long words. The experiments reported here test two predictions that would follow if neighborhood size is a more important factor than word length. In Experiment 1, we found that concurrent articulation removed the effect of neighborhood size, just as it removes the effect of word length. Experiment 2 demonstrated that this pattern is also found with nonwords. For Experiment 3, we factorially manipulated length and neighborhood size, and found only effects of the latter. These results are problematic for any theory of memory that includes decay offset by rehearsal, but they are consistent with accounts that include a redintegrative stage that is susceptible to disruption by noise. The results also confirm the importance of lexical and linguistic factors on memory tasks thought to tap short-term memory. PMID:21461875

  19. When Does Length Cause the Word Length Effect?

    ERIC Educational Resources Information Center

    Jalbert, Annie; Neath, Ian; Bireta, Tamra J.; Surprenant, Aimee M.

    2011-01-01

    The word length effect, the finding that lists of short words are better recalled than lists of long words, has been termed one of the benchmark findings that any theory of immediate memory must account for. Indeed, the effect led directly to the development of working memory and the phonological loop, and it is viewed as the best remaining…

  20. Continuously variable focal length lens

    DOEpatents

    Adams, Bernhard W; Chollet, Matthieu C

    2013-12-17

    A material preferably in crystal form having a low atomic number such as beryllium (Z=4) provides for the focusing of x-rays in a continuously variable manner. The material is provided with plural spaced curvilinear, optically matched slots and/or recesses through which an x-ray beam is directed. The focal length of the material may be decreased or increased by increasing or decreasing, respectively, the number of slots (or recesses) through which the x-ray beam is directed, while fine tuning of the focal length is accomplished by rotation of the material so as to change the path length of the x-ray beam through the aligned cylindrical slows. X-ray analysis of a fixed point in a solid material may be performed by scanning the energy of the x-ray beam while rotating the material to maintain the beam's focal point at a fixed point in the specimen undergoing analysis.

  1. Ultrathin Alvarez lens system actuated by artificial muscles.

    PubMed

    Petsch, S; Grewe, A; Köbele, L; Sinzinger, S; Zappe, H

    2016-04-01

    A key feature of Alvarez lenses is that they may be tuned in focal length using lateral rather than axial translation, thus reducing the overall length of a focus-tunable optical system. Nevertheless the bulk of classical microsystems actuators limits further miniaturization. We present here a new, ultrathin focus-tunable Alvarez lens fabricated using molding techniques and actuated using liquid crystal elastomer (LCE) artificial muscle actuators. The large deformation generated by the LCE actuators permits the integration of the actuators in-plane with the mechanical and optical system and thus reduces the device thickness to only 1.6 mm. Movement of the Alvarez lens pair of 178 μm results in a focal length change of 3.3 mm, based on an initial focal length of 28.4 mm. This design is of considerable interest for realization of ultraflat focus-tunable and zoom systems. PMID:27139677

  2. Graduated compression stockings: knee length or thigh length.

    PubMed

    Benkö, T; Cooke, E A; McNally, M A; Mollan, R A

    2001-02-01

    The mechanisms by which graduated compression stockings prevent deep venous thrombosis are not completely understood. In the current study the physiologic effect of low-pressure graduated compression stockings on the venous blood flow in the lower limb and the practical aspects of their use were assessed. Patients having elective orthopaedic surgery at a university orthopaedic department were randomized into five groups to wear two different types of graduated compression stockings in thigh and knee lengths. Patients in the fifth control group did not wear graduated compression stockings. Venous occlusion strain gauge plethysmography was used to measure venous flow. After 20-minutes bed rest there was a highly significant increase in venous capacitance and venous outflow in patients in all of the four groups wearing stockings. There was no difference in the mean of the percentage change of venous capacitance in patients in the four groups wearing stockings. The knee length Brevet stockings were less efficient in increasing the venous outflow. There was no significant change in the venous capacitance and venous outflow in patients in the control group. Visual assessment of the fit and use of stockings was done, and patients' subjective opinion of comfort was sought. The knee length graduated compression stockings wrinkled significantly less, and significantly fewer patients reported discomfort with them. All stockings were reported to be difficult to use. Thigh and knee length stockings have a significant effect on decreasing venous stasis of the lower limb. Knee length graduated compression stockings are similarly efficient in decreasing venous stasis, but they are more comfortable to wear, and they wrinkle less. PMID:11210954

  3. Coherence length of neutron superfluids

    SciTech Connect

    De Blasio, F.V.; Hjorth-Jensen, M.; Lazzari, G.; Baldo, M.; Schulze, H.

    1997-10-01

    The coherence length of superfluid neutron matter is calculated from the microscopic BCS wave function of a Cooper pair in momentum space making use of recent nucleon-nucleon potential models and including polarization (RPA) effects. We find as our main result that the coherence length is proportional to the Fermi momentum to pairing gap ratio, in good agreement with simple estimates used in the literature, with a nearly interaction independent constant of proportionality. Our calculations can be applied to the problem of inhomogeneous superfluidity of hadronic matter in the crust of a neutron star. {copyright} {ital 1997} {ital The American Physical Society}

  4. Overview of bunch length measurements.

    SciTech Connect

    Lumpkin, A. H.

    1999-02-19

    An overview of particle and photon beam bunch length measurements is presented in the context of free-electron laser (FEL) challenges. Particle-beam peak current is a critical factor in obtaining adequate FEL gain for both oscillators and self-amplified spontaneous emission (SASE) devices. Since measurement of charge is a standard measurement, the bunch length becomes the key issue for ultrashort bunches. Both time-domain and frequency-domain techniques are presented in the context of using electromagnetic radiation over eight orders of magnitude in wavelength. In addition, the measurement of microbunching in a micropulse is addressed.

  5. Optimization of the artificial urinary sphincter: modelling and experimental validation

    NASA Astrophysics Data System (ADS)

    Marti, Florian; Leippold, Thomas; John, Hubert; Blunschi, Nadine; Müller, Bert

    2006-03-01

    The artificial urinary sphincter should be long enough to prevent strangulation effects of the urethral tissue and short enough to avoid the improper dissection of the surrounding tissue. To optimize the sphincter length, the empirical three-parameter urethra compression model is proposed based on the mechanical properties of the urethra: wall pressure, tissue response rim force and sphincter periphery length. In vitro studies using explanted animal or human urethras and different artificial sphincters demonstrate its applicability. The pressure of the sphincter to close the urethra is shown to be a linear function of the bladder pressure. The force to close the urethra depends on the sphincter length linearly. Human urethras display the same dependences as the urethras of pig, dog, sheep and calf. Quantitatively, however, sow urethras resemble best the human ones. For the human urethras, the mean wall pressure corresponds to (-12.6 ± 0.9) cmH2O and (-8.7 ± 1.1) cmH2O, the rim length to (3.0 ± 0.3) mm and (5.1 ± 0.3) mm and the rim force to (60 ± 20) mN and (100 ± 20) mN for urethra opening and closing, respectively. Assuming an intravesical pressure of 40 cmH2O, and an external pressure on the urethra of 60 cmH2O, the model leads to the optimized sphincter length of (17.3 ± 3.8) mm.

  6. The artificial leaf.

    PubMed

    Nocera, Daniel G

    2012-05-15

    To convert the energy of sunlight into chemical energy, the leaf splits water via the photosynthetic process to produce molecular oxygen and hydrogen, which is in a form of separated protons and electrons. The primary steps of natural photosynthesis involve the absorption of sunlight and its conversion into spatially separated electron-hole pairs. The holes of this wireless current are captured by the oxygen evolving complex (OEC) of photosystem II (PSII) to oxidize water to oxygen. The electrons and protons produced as a byproduct of the OEC reaction are captured by ferrodoxin of photosystem I. With the aid of ferrodoxin-NADP(+) reductase, they are used to produce hydrogen in the form of NADPH. For a synthetic material to realize the solar energy conversion function of the leaf, the light-absorbing material must capture a solar photon to generate a wireless current that is harnessed by catalysts, which drive the four electron/hole fuel-forming water-splitting reaction under benign conditions and under 1 sun (100 mW/cm(2)) illumination. This Account describes the construction of an artificial leaf comprising earth-abundant elements by interfacing a triple junction, amorphous silicon photovoltaic with hydrogen- and oxygen-evolving catalysts made from a ternary alloy (NiMoZn) and a cobalt-phosphate cluster (Co-OEC), respectively. The latter captures the structural and functional attributes of the PSII-OEC. Similar to the PSII-OEC, the Co-OEC self-assembles upon oxidation of an earth-abundant metal ion from 2+ to 3+, may operate in natural water at room temperature, and is self-healing. The Co-OEC also activates H(2)O by a proton-coupled electron transfer mechanism in which the Co-OEC is increased by four hole equivalents akin to the S-state pumping of the Kok cycle of PSII. X-ray absorption spectroscopy studies have established that the Co-OEC is a structural relative of Mn(3)CaO(4)-Mn cubane of the PSII-OEC, where Co replaces Mn and the cubane is extended in a

  7. Effects of the pitch length of superhydrophobic surfaces on the effective slip length and skin-friction drag

    NASA Astrophysics Data System (ADS)

    Jung, Taeyong; Choi, Haecheon; Kim, John

    2015-11-01

    Many numerical studies have been conducted to investigate the effect of the grating parameters of superhydrophobic surfaces, such as the pitch length and gas fraction, on the slip velocity and its effect on skin-friction drag. However, the pitch lengths considered numerically so far are much larger, varying from p+ = O (10) to O (102) in wall units, than those in experiments (p+ = O (1)). In the present study, we perform a direct numerical simulation of turbulent channel flow over superhydrophobic surfaces with longitudinal microgrates having the actual grating parameters of p+ = 3.8. The air layer inside the cavity (d+ = 18; d+ is the cavity depth) is also solved with the assumption of zero interface curvature. The minimal flow unit by Jimenez & Moin (1991) is adopted to resolve the small pitch length. Since small pitch length is accompanied by small cavity width, the growth of the slip velocity at the air-water interface is inhibited. As a result, the slip velocity (us+) is less than 2 for p+ = 3.8, whereas us+ is greater than 15 for p+ = 540. The effective slip length is an order of the viscous sublayer thickness, and the drag reduction is less than 20%. The detailed results for the cases of p+ ~ O (1) to O (102) will be presented. Supported by NRF-2012M2A8A4055647.

  8. Amplification of large artificial chromosomes.

    PubMed Central

    Smith, D R; Smyth, A P; Moir, D T

    1990-01-01

    Yeast artificial chromosome cloning is an attractive technology for genomic mapping studies because very large DNA segments can be readily propagated. However, detailed analyses often require the extensive application of blotting-hybridization techniques because artificial chromosomes are normally present at only one copy per haploid genome. We have developed a cloning vector and host strain that alleviate this problem by permitting copy number amplification of artificial chromosomes. The vector includes a conditional centromere that can be turned on or off by changing the carbon source. Strong selective pressure for extra copies of the artificial chromosome can be applied by selecting for the expression of a heterologous thymidine kinase gene. When this system was used, artificial chromosomes ranging from about 100 to 600 kilobases in size were readily amplified 10- to 20-fold. The selective conditions did not induce obvious rearrangements in any of the clones tested. Reactivation of the centromere in amplified artificial chromosome clones resulted in stable maintenance of an elevated copy number for 20 generations. Applications of copy number control to various aspects of artificial chromosome analysis are addressed. Images PMID:2236036

  9. Numerical simulation of flow through biofluid devices

    NASA Technical Reports Server (NTRS)

    Rogers, Stuart E.; Kwak, Dochan; Kiris, Cetin; Chang, I-Dee

    1990-01-01

    The results of a numerical simulation of flow through an artificial heart and through an artificial tilting-disk heart valve are presented. The simulation involves solving the incompressible Navier-Stokes equations; the solution process is described. The details and difficulties of modeling these particular geometries are discussed. The artificial heart geometry uses a single moving grid, and the valve computation uses an overlaid-grid approach with one moving grid and one stationary grid. The equations must be solved iteratively for each discrete time step of the computations, requiring a significant amount of computing time. It is particularly difficult to analyze and present the fluid physics represented by these calculations because of the time-varying nature of the flow, and because the flows are internal. Three-dimensional graphics and scientific visualization techniques have become instrumental in solving these problems.

  10. Quantum criticality with two length scales

    NASA Astrophysics Data System (ADS)

    Shao, Hui; Guo, Wenan; Sandvik, Anders W.

    2016-04-01

    The theory of deconfined quantum critical (DQC) points describes phase transitions at absolute temperature T = 0 outside the standard paradigm, predicting continuous transformations between certain ordered states where conventional theory would require discontinuities. Numerous computer simulations have offered no proof of such transitions, instead finding deviations from expected scaling relations that neither were predicted by the DQC theory nor conform to standard scenarios. Here we show that this enigma can be resolved by introducing a critical scaling form with two divergent length scales. Simulations of a quantum magnet with antiferromagnetic and dimerized ground states confirm the form, proving a continuous transition with deconfined excitations and also explaining anomalous scaling at T > 0. Our findings revise prevailing paradigms for quantum criticality, with potential implications for many strongly correlated materials.

  11. Quantum criticality with two length scales.

    PubMed

    Shao, Hui; Guo, Wenan; Sandvik, Anders W

    2016-04-01

    The theory of deconfined quantum critical (DQC) points describes phase transitions at absolute temperature T = 0 outside the standard paradigm, predicting continuous transformations between certain ordered states where conventional theory would require discontinuities. Numerous computer simulations have offered no proof of such transitions, instead finding deviations from expected scaling relations that neither were predicted by the DQC theory nor conform to standard scenarios. Here we show that this enigma can be resolved by introducing a critical scaling form with two divergent length scales. Simulations of a quantum magnet with antiferromagnetic and dimerized ground states confirm the form, proving a continuous transition with deconfined excitations and also explaining anomalous scaling at T > 0. Our findings revise prevailing paradigms for quantum criticality, with potential implications for many strongly correlated materials. PMID:26989196

  12. Superconducting vortex pinning with artificial magnetic nanostructures.

    SciTech Connect

    Velez, M.; Martin, J. I.; Villegas, J. E.; Hoffmann, A.; Gonzalez, E. M.; Vicent, J. L.; Schuller, I. K.; Univ. de Oviedo-CINN; Unite Mixte de Physique CNRS Univ. Paris-Sud; Univ.Complutense de Madrid; Univ. California at San Diego

    2008-11-01

    This review is dedicated to summarizing the recent research on vortex dynamics and pinning effects in superconducting films with artificial magnetic structures. The fabrication of hybrid superconducting/magnetic systems is presented together with the wide variety of properties that arise from the interaction between the superconducting vortex lattice and the artificial magnetic nanostructures. Specifically, we review the role that the most important parameters in the vortex dynamics of films with regular array of dots play. In particular, we discuss the phenomena that appear when the symmetry of a regular dot array is distorted from regularity towards complete disorder including rectangular, asymmetric, and aperiodic arrays. The interesting phenomena that appear include vortex-lattice reconfigurations, anisotropic dynamics, channeling, and guided motion as well as ratchet effects. The different regimes are summarized in a phase diagram indicating the transitions that take place as the characteristic distances of the array are modified respect to the superconducting coherence length. Future directions are sketched out indicating the vast open area of research in this field.

  13. Artificial Bee Colony Optimization for Short-Term Hydrothermal Scheduling

    NASA Astrophysics Data System (ADS)

    Basu, M.

    2014-12-01

    Artificial bee colony optimization is applied to determine the optimal hourly schedule of power generation in a hydrothermal system. Artificial bee colony optimization is a swarm-based algorithm inspired by the food foraging behavior of honey bees. The algorithm is tested on a multi-reservoir cascaded hydroelectric system having prohibited operating zones and thermal units with valve point loading. The ramp-rate limits of thermal generators are taken into consideration. The transmission losses are also accounted for through the use of loss coefficients. The algorithm is tested on two hydrothermal multi-reservoir cascaded hydroelectric test systems. The results of the proposed approach are compared with those of differential evolution, evolutionary programming and particle swarm optimization. From numerical results, it is found that the proposed artificial bee colony optimization based approach is able to provide better solution.

  14. Artificial polarization components

    NASA Astrophysics Data System (ADS)

    Cescato, L.; Gluch, Ekkehard; Stork, Wilhelm; Streibl, Norbert

    1990-07-01

    High frequency surface relief structures are optically anisotropic and show interesting polarisation properties 1 . These properties can be used to produce polarizations components such as wave plates polarizers. polarizing beamsplitters etc. Our experimental results show that even gratings with relatively low spatial frequency ( periods A ) exhibit a strong phase retardation and can be used as quarter-wave plates. k INTRODUC11ON The artificial birefringence exhibited by ultrahigh frequency gratings of dielectric materials can be used to produce various polarization components2 . Such components have applications in integrated optics as well as in free space optics. In order to produce the high spatial frequencies complex processes such as electron-beam lithography and reactive ion etching are needed. We show in this paper that sinusoidal holographic gratings in photoresist exhibit also a strong phase ret even at relatively long periods. L EXPERIMENTAL MEASUREMENTS To obtain the phase retardation of a lower frequency ( period A ) grating a simple setup as used by Enger and 2 can be applied. In our case however there are three measurements necessary to obtain the phase retardation because transmission of the two perpendicularly polarized beams is different from each other. I GRATING PRODUCTION grating 2 3 4 5 6 7 8 9 period (pmj 0. 74 0. 74 0. 61 0. 54 0. 46 0. 32 0. 54 0. 54 0. 54 ne (sec) 60

  15. Artificial frustrated spin systems

    NASA Astrophysics Data System (ADS)

    Perrin, Y.; Chioar, I. A.; Nguyen, V. D.; Lacour, D.; Hehn, M.; Montaigne, F.; Canals, B.; Rougemaille, N.

    2015-09-01

    Complex architectures of nanostructures are routinely elaborated using bottom-up or nanofabrication processes. This technological capability allows scientists to engineer materials with properties that do not exist in nature, but also to manufacture model systems to explore fundamental issues in condensed matter physics. Two-dimensional frustrated arrays of magnetic nanostructures are one class of systems for which theoretical predictions can be tested experimentally. These systems have been the subject of intense research in the last few years and allowed the investigation of a rich physics and fascinating phenomena, such as the exploration of the extensively degenerate ground-state manifolds of spin ice systems, the evidence of new magnetic phases in purely two-dimensional lattices, and the observation of pseudoexcitations involving classical analogues of magnetic monopoles. We show here, experimentally and theoretically, that simple magnetic geometries can lead to unconventional, non-collinear spin textures. For example, kagome arrays of inplane magnetized nano-islands do not show magnetic order. Instead, these systems are characterized by spin textures with intriguing properties, such as chirality, coexistence of magnetic order and disorder, and charge crystallization. Magnetic frustration effects in lithographically patterned kagome arrays of nanomagnets with out-of-plane magnetization also lead to an unusal, and still unknown, magnetic ground state manifold. Besides the influence of the lattice geometry, the micromagnetic nature of the elements constituting the arrays introduce the concept of chiral magnetic monopoles, bringing additional complexity into the physics of artificial frustrated spin systems.

  16. Artificial dexterous hand

    NASA Technical Reports Server (NTRS)

    Lee, Sukhan (Inventor)

    1990-01-01

    An artificial dexterous hand is provided for grasping and manipulating objects. The hand includes left and right thumbs that are operatively connected to an engagement assembly which causes movement of the left and right thumbs. The left thumb has a left thumb base and is movable about three separate first left thumb axes which run through the left thumb base. Correspondingly, the right thumb has a right thumb base and is movable about three separate first right thumb axes which run through the right thumb base. The engagement assembly has a gear assembly which is operatively connected to a motor assembly. Upon actuation by the motor assembly, the gear assembly causes movement of the left and right thumbs about the first left thumb axes and first right thumb axes respectively. The hand can also have a center finger which is operatively connected to the engagement assembly and which is interposed between the left and right thumbs. The finger has a finger base and is movable about two separate first finger axes running through the finger base. Therefore, upon actuation by the motor assembly, the gear assembly will also cause movement of the finger about the first finger axes.

  17. Artificial dexterous hand

    NASA Technical Reports Server (NTRS)

    Lee, Sukhan (Inventor)

    1990-01-01

    An artificial dexterous hand is provided for conformally engaging and manipulating objects. The hand includes an articulated digit which is connected to an engagement sub-assembly and has a first shape adaption mechanism associated with it. The digit has a digit base and first and second phalanges. The digit base is operatively interconnected to the first phalange by a base joint having a base pulley. The phalanges are operatively interconnected by a separate first phalange joint having a first phalange pulley. The engagement sub-assembly includes a tendon, which is received by the base pulley and by the first phalange pulley, and an actuation device for selectively tensioning the tendon. The first shape adaption mechanism is responsive to and receives the tendon. It is also situated between the base joint and the first phalange joint and is connected to the first phalange. Upon actuation by the actuation device, the phalanges are caused to pivot relative to the base joint and the second phalange is caused to pivot relative to the first phalange. At the same time, the first shape adaption mechanism controls the sequence of the aforementioned pivoting of the phalanges through application of braking force to the tendon.

  18. Nanostructured artificial nacre

    NASA Astrophysics Data System (ADS)

    Tang, Zhiyong; Kotov, Nicholas A.; Magonov, Sergei; Ozturk, Birol

    2003-06-01

    Finding a synthetic pathway to artificial analogs of nacre and bones represents a fundamental milestone in the development of composite materials. The ordered brick-and-mortar arrangement of organic and inorganic layers is believed to be the most essential strength- and toughness-determining structural feature of nacre. It has also been found that the ionic crosslinking of tightly folded macromolecules is equally important. Here, we demonstrate that both structural features can be reproduced by sequential deposition of polyelectrolytes and clays. This simple process results in a nanoscale version of nacre with alternating organic and inorganic layers. The macromolecular folding effect reveals itself in the unique saw-tooth pattern of differential stretching curves attributed to the gradual breakage of ionic crosslinks in polyelectrolyte chains. The tensile strength of the prepared multilayers approached that of nacre, whereas their ultimate Young modulus was similar to that of lamellar bones. Structural and functional resemblance makes clay- polyelectrolyte multilayers a close replica of natural biocomposites. Their nanoscale nature enables elucidation of molecular processes occurring under stress.

  19. Folding of Layers of Finite Length

    NASA Astrophysics Data System (ADS)

    Schmid, D. W.; Podladchikov, Yu. Yu.; Marques, F.

    All existing folding theories assume that the layers are infinitely long or, which is mathematically equivalent, that the compression is directly applied to the lateral boundaries. These assumptions are not always justified for natural geological sys- tems. In fact we can observe that on all scales, from veins to sub-ducting slabs, the layers are of finite length and that there are no distinct, rigid walls pushing the lay- ers from the side. Using the method of Muskhelishvili we have derived the complete two-dimensional solution of an elliptic object embedded in a matrix and subject to far field boundary conditions; pure shear, simple shear and arbitrary combinations thereof. The rheology of the matrix is viscous, the layer may behave either elastically or viscous. Using the values from this background state analysis, stress, pressure and strain rate, we performed the classical linear stability analysis to examine the mech- anism of folding in the described setup. The resulting expressions maximum growth rates and dominant wavelengths are applicable to general geological systems; in the limit of an infinite aspect ratio of the layer the classical expressions of Biot are ob- tained for all other cases new expressions result. Our main results are: 1. Folding of finite length layers is controlled by the ratio of aspect ratio to competence contrast. 2. The described setup explains why in nature only folds can be observed with a rela- tively small wavelength to thickness ratio, suggesting small viscosity contrast 3. The problem of the unknown compressive stress value for the elastic layer is solved. 4. For finite length elastic layers the dominant wavelength selection shows a cubic, instead of square, root dependence. 5. A complete table, describing the folding in all the possible limits is presented and the applicability to natural systems discussed. All the presented results were checked numerically and/or with analogue models.

  20. Artificial Reefs and Ocean Dumping.

    ERIC Educational Resources Information Center

    Glueck, Richard D.

    1983-01-01

    Activities and instructional strategies for two multigrade lessons are provided. Activity objectives include describing an artificial reef (such as a sunken ocean liner) as an ecosystem, knowing animal types in the ecosystem, and describing a food web. (JN)

  1. Inflatable artificial sphincter - series (image)

    MedlinePlus

    An artificial sphincter consists of three parts: a cuff that fits around the bladder neck a pressure regulating balloon a pump that inflates the cuff. To treat urinary incontinence, the cuff is placed ...

  2. Artificial intelligence: Principles and applications

    SciTech Connect

    Yazdami, M.

    1985-01-01

    The book covers the principles of AI, the main areas of application, as well as considering some of the social implications. The applications chapters have a common format structured as follows: definition of the topic; approach with conventional computing techniques; why 'intelligence' would provide a better approach; and how AI techniques would be used and the limitations. The contents discussed are: Principles of artificial intelligence; AI programming environments; LISP, list processing and pattern-making; AI programming with POP-11; Computer processing of natural language; Speech synthesis and recognition; Computer vision; Artificial intelligence and robotics; The anatomy of expert systems - Forsyth; Machine learning; Memory models of man and machine; Artificial intelligence and cognitive psychology; Breaking out of the chinese room; Social implications of artificial intelligence; and Index.

  3. Artificial photosynthesis for solar fuels.

    PubMed

    Styring, Stenbjörn

    2012-01-01

    This contribution was presented as the closing lecture at the Faraday Discussion 155 on artificial photosynthesis, held in Edinburgh Scotland, September 5-7 2011. The world needs new, environmentally friendly and renewable fuels to exchange for fossil fuels. The fuel must be made from cheap and "endless" resources that are available everywhere. The new research area of solar fuels aims to meet this demand. This paper discusses why we need a solar fuel and why electricity is not enough; it proposes solar energy as the major renewable energy source to feed from. The scientific field concerning artificial photosynthesis expands rapidly and most of the different scientific visions for solar fuels are briefly overviewed. Research strategies and the development of artificial photosynthesis research to produce solar fuels are overviewed. Some conceptual aspects of research for artificial photosynthesis are discussed in closer detail. PMID:22470985

  4. Darwin, artificial selection, and poverty.

    PubMed

    Sanchez, Luis

    2010-03-01

    This paper argues that the processes of evolutionary selection are becoming increasingly artificial, a trend that goes against the belief in a purely natural selection process claimed by Darwin's natural selection theory. Artificial selection is mentioned by Darwin, but it was ignored by Social Darwinists, and it is all but absent in neo-Darwinian thinking. This omission results in an underestimation of probable impacts of artificial selection upon assumed evolutionary processes, and has implications for the ideological uses of Darwin's language, particularly in relation to poverty and other social inequalities. The influence of artificial selection on genotypic and phenotypic adaptations arguably represents a substantial shift in the presumed path of evolution, a shift laden with both biological and political implications. PMID:20812798

  5. An artificial gravity demonstration experiment

    NASA Technical Reports Server (NTRS)

    Rupp, C.; Lemke, L.; Penzo, P.

    1989-01-01

    An artificial gravity experiment which is tethered to a Delta second stage and which uses the Small Expendable Deployer System is proposed. Following tether deployment, the Delta vehicle performs the required spin-up maneuver and can then be passivated. A surplus reentry vehicle houses the artificial gravity life science experiments. When the experiments are completed, the reentry phase of the experiment is initiated by synchronizing the spin of the configuration with the required deorbit impulse.

  6. Actuator device for artificial leg

    NASA Technical Reports Server (NTRS)

    Burch, J. L. (Inventor)

    1976-01-01

    An actuator device is described for moving an artificial leg of a person having a prosthesis replacing an entire leg and hip joint. The device includes a first articulated hip joint assembly carried by the natural leg and a second articulated hip joint assembly carried by the prosthesis whereby energy from the movement of the natural leg is transferred by a compressible fluid from the first hip joint assembly to the second hip joint assembly for moving the artificial leg.

  7. The total artificial heart.

    PubMed

    Meyer, A; Slaughter, M

    2011-09-01

    In the 1960s, cardiac surgeons and biomedical engineers pioneered the development of total artificial hearts (TAH) for the treatment of left and right heart failure. As we mark the 10th anniversary of the first implantation of the AbioCor device, the use of TAH has been limited, having failed to reach its envisioned potential and promise as an alternative therapy to heart transplantation. The Syncardia/CardioWest device, originally developed 30 years ago as the Jarvik TAH and later renamed the CardioWest TAH, continues to be used clinically in over 50 centers within the US and Europe having supported over 900 patients worldwide. Syncardia continues to develop TAH technology as evidenced by their recent introduction of a new portable pneumatic driver that enables patients to be discharged from the hospital. In contrast to TAH devices, continuous flow ventricular assist devices (VAD) have made tremendous technological strides and are rapidly gaining widespread clinical acceptance. The VAD technology has demonstrated extraordinary safety and reliability records through evolving technologies, advanced biocompatible materials, and improved patient management. Subsequently, the number of TAH implantations remains low compared to the growth in LVAD implants. Nonetheless, the Syncardia/CardioWest TAH remains an important and viable option for patients with severe biventricular failure and end organ dysfunction. Overall, a 79% survival rate has been achieved in patients supported with a Syncardia/CardioWest TAH as bridge-to-transplantation. In this review article, a brief history on the evolution of TAH devices, their current use and emerging use of evolving continuous flow VAD technology as chronic biventricular and TAH device systems are presented. PMID:21775941

  8. Magnetically-actuated artificial cilia for microfluidic propulsion.

    PubMed

    Khaderi, S N; Craus, C B; Hussong, J; Schorr, N; Belardi, J; Westerweel, J; Prucker, O; Rühe, J; den Toonder, J M J; Onck, P R

    2011-06-21

    In this paper we quantitatively analyse the performance of magnetically-driven artificial cilia for lab-on-a-chip applications. The artificial cilia are fabricated using thin polymer films with embedded magnetic nano-particles and their deformation is studied under different external magnetic fields and flows. A coupled magneto-mechanical solid-fluid model that accurately captures the interaction between the magnetic field, cilia and fluid is used to simulate the cilia motion. The elastic and magnetic properties of the cilia are obtained by fitting the results of the computational model to the experimental data. The performance of the artificial cilia with a non-uniform cross-section is characterised using the numerical model for two channel configurations that are of practical importance: an open-loop and a closed-loop channel. We predict that the flow and pressure head generated by the artificial cilia can be as high as 18 microlitres per minute and 3 mm of water, respectively. We also study the effect of metachronal waves on the flow generated and show that the fluid propelled increases drastically compared to synchronously beating cilia, and is unidirectional. This increase is significant even when the phase difference between adjacent cilia is small. The obtained results provide guidelines for the optimal design of magnetically-driven artificial cilia for microfluidic propulsion. PMID:21331419

  9. Hiding the squid: patterns in artificial cephalopod skin

    PubMed Central

    Fishman, Aaron; Rossiter, Jonathan; Homer, Martin

    2015-01-01

    Cephalopods employ their chromomorphic skins for rapid and versatile active camouflage and signalling effects. This is achieved using dense networks of pigmented, muscle-driven chromatophore cells which are neurally stimulated to actuate and affect local skin colouring. This allows cephalopods to adopt numerous dynamic and complex skin patterns, most commonly used to blend into the environment or to communicate with other animals. Our ultimate goal is to create an artificial skin that can mimic such pattern generation techniques, and that could produce a host of novel and compliant devices such as cloaking suits and dynamic illuminated clothing. This paper presents the design, mathematical modelling and analysis of a dynamic biomimetic pattern generation system using bioinspired artificial chromatophores. The artificial skin is made from electroactive dielectric elastomer: a soft, planar-actuating smart material that we show can be effective at mimicking the actuation of biological chromatophores. The proposed system achieves dynamic pattern generation by imposing simple local rules into the artificial chromatophore cells so that they can sense their surroundings in order to manipulate their actuation. By modelling sets of artificial chromatophores in linear arrays of cells, we explore the capability of the system to generate a variety of dynamic pattern types. We show that it is possible to mimic patterning seen in cephalopods, such as the passing cloud display, and other complex dynamic patterning. PMID:26063823

  10. Welding arc length control system

    NASA Technical Reports Server (NTRS)

    Iceland, William F. (Inventor)

    1993-01-01

    The present invention is a welding arc length control system. The system includes, in its broadest aspects, a power source for providing welding current, a power amplification system, a motorized welding torch assembly connected to the power amplification system, a computer, and current pick up means. The computer is connected to the power amplification system for storing and processing arc weld current parameters and non-linear voltage-ampere characteristics. The current pick up means is connected to the power source and to the welding torch assembly for providing weld current data to the computer. Thus, the desired arc length is maintained as the welding current is varied during operation, maintaining consistent weld penetration.

  11. Softness Correlations Across Length Scales

    NASA Astrophysics Data System (ADS)

    Ivancic, Robert; Shavit, Amit; Rieser, Jennifer; Schoenholz, Samuel; Cubuk, Ekin; Durian, Douglas; Liu, Andrea; Riggleman, Robert

    In disordered systems, it is believed that mechanical failure begins with localized particle rearrangements. Recently, a machine learning method has been introduced to identify how likely a particle is to rearrange given its local structural environment, quantified by softness. We calculate the softness of particles in simulations of atomic Lennard-Jones mixtures, molecular Lennard-Jones oligomers, colloidal systems and granular systems. In each case, we find that the length scale characterizing spatial correlations of softness is approximately a particle diameter. These results provide a rationale for why localized rearrangements--whose size is presumably set by the scale of softness correlations--might occur in disordered systems across many length scales. Supported by DOE DE-FG02-05ER46199.

  12. Variable focal length deformable mirror

    DOEpatents

    Headley, Daniel; Ramsey, Marc; Schwarz, Jens

    2007-06-12

    A variable focal length deformable mirror has an inner ring and an outer ring that simply support and push axially on opposite sides of a mirror plate. The resulting variable clamping force deforms the mirror plate to provide a parabolic mirror shape. The rings are parallel planar sections of a single paraboloid and can provide an on-axis focus, if the rings are circular, or an off-axis focus, if the rings are elliptical. The focal length of the deformable mirror can be varied by changing the variable clamping force. The deformable mirror can generally be used in any application requiring the focusing or defocusing of light, including with both coherent and incoherent light sources.

  13. Biothermal sensing of a torsional artificial muscle

    NASA Astrophysics Data System (ADS)

    Lee, Sung-Ho; Kim, Tae Hyeob; Lima, Márcio D.; Baughman, Ray H.; Kim, Seon Jeong

    2016-02-01

    originating from the carbon nanotubes. This biothermal sensing of a torsional artificial muscle offers a versatile platform for the recognition of various types of biomolecules by replacing the enzyme, because an exothermic reaction is a general property accompanying a biochemical transformation. Electronic supplementary information (ESI) available: Experimental sections; a schematic drawing of the custom-built flow injection system; the change in the length of the yarn correlated with the wetting and drying of the entrapped PNIPAm-GOx particle versus time; the particle size distribution of PNIPAm-GOx hydrogel in a pure PBS solution and in a PBS solution containing 100 mM glucose at 36 °C biothermal sensing torsional actuation of a carbon nanotube yarn (video). See DOI: 10.1039/c5nr07195j

  14. Correcting wave predictions with artificial neural networks

    NASA Astrophysics Data System (ADS)

    Makarynskyy, O.; Makarynska, D.

    2003-04-01

    The predictions of wind waves with different lead times are necessary in a large scope of coastal and open ocean activities. Numerical wave models, which usually provide this information, are based on deterministic equations that do not entirely account for the complexity and uncertainty of the wave generation and dissipation processes. An attempt to improve wave parameters short-term forecasts based on artificial neural networks is reported. In recent years, artificial neural networks have been used in a number of coastal engineering applications due to their ability to approximate the nonlinear mathematical behavior without a priori knowledge of interrelations among the elements within a system. The common multilayer feed-forward networks, with a nonlinear transfer functions in the hidden layers, were developed and employed to forecast the wave characteristics over one hour intervals starting from one up to 24 hours, and to correct these predictions. Three non-overlapping data sets of wave characteristics, both from a buoy, moored roughly 60 miles west of the Aran Islands, west coast of Ireland, were used to train and validate the neural nets involved. The networks were trained with error back propagation algorithm. Time series plots and scatterplots of the wave characteristics as well as tables with statistics show an improvement of the results achieved due to the correction procedure employed.

  15. Length scales and self-organization in dense suspension flows

    NASA Astrophysics Data System (ADS)

    Düring, Gustavo; Lerner, Edan; Wyart, Matthieu

    2014-02-01

    Dense non-Brownian suspension flows of hard particles display mystifying properties: As the jamming threshold is approached, the viscosity diverges, as well as a length scale that can be identified from velocity correlations. To unravel the microscopic mechanism governing dissipation and its connection to the observed correlation length, we develop an analogy between suspension flows and the rigidity transition occurring when floppy networks are pulled, a transition believed to be associated with the stress stiffening of certain gels. After deriving the critical properties near the rigidity transition, we show numerically that suspension flows lie close to it. We find that this proximity causes a decoupling between viscosity and the correlation length of velocities ξ, which scales as the length lc characterizing the response to a local perturbation, previously predicted to follow lc˜1/√zc-z ˜p0.18, where p is the dimensionless particle pressure, z is the coordination of the contact network made by the particles, and zc is twice the spatial dimension. We confirm these predictions numerically and predict the existence of a larger length scale lr˜√p with mild effects on velocity correlation and of a vanishing strain scale δγ ˜1/p that characterizes decorrelation in flow.

  16. ASAP- ARTIFICIAL SATELLITE ANALYSIS PROGRAM

    NASA Technical Reports Server (NTRS)

    Kwok, J.

    1994-01-01

    The Artificial Satellite Analysis Program (ASAP) is a general orbit prediction program which incorporates sufficient orbit modeling accuracy for mission design, maneuver analysis, and mission planning. ASAP is suitable for studying planetary orbit missions with spacecraft trajectories of reconnaissance (flyby) and exploratory (mapping) nature. Sample data is included for a geosynchronous station drift cycle study, a Venus radar mapping strategy, a frozen orbit about Mars, and a repeat ground trace orbit. ASAP uses Cowell's method in the numerical integration of the equations of motion. The orbital mechanics calculation contains perturbations due to non-sphericity (up to a 40 X 40 field) of the planet, lunar and solar effects, and drag and solar radiation pressure. An 8th order Runge-Kutta integration scheme with variable step size control is used for efficient propagation. The input includes the classical osculating elements, orbital elements of the sun relative to the planet, reference time and dates, drag coefficient, gravitational constants, and planet radius, rotation rate, etc. The printed output contains Cartesian coordinates, velocity, equinoctial elements, and classical elements for each time step or event step. At each step, selected output is added to a plot file. The ASAP package includes a program for sorting this plot file. LOTUS 1-2-3 is used in the supplied examples to graph the results, but any graphics software package could be used to process the plot file. ASAP is not written to be mission-specific. Instead, it is intended to be used for most planetary orbiting missions. As a consequence, the user has to have some basic understanding of orbital mechanics to provide the correct input and interpret the subsequent output. ASAP is written in FORTRAN 77 for batch execution and has been implemented on an IBM PC compatible computer operating under MS-DOS. The ASAP package requires a math coprocessor and a minimum of 256K RAM. This program was last

  17. Transformation optics with artificial Riemann sheets

    NASA Astrophysics Data System (ADS)

    Xu, Lin; Chen, Huanyang

    2013-11-01

    The two original versions of ‘invisibility’ cloaks (Leonhardt 2006 Science 312 1777-80 and Pendry et al 2006 Science 312 1780-2) show perfect cloaking but require unphysical singularities in material properties. A non-Euclidean version of cloaking (Leonhardt 2009 Science 323 110-12) was later presented to address these problems, using a very complicated non-Euclidean geometry. In this work, we combine the two original approaches to transformation optics into a more general concept: transformation optics with artificial Riemann sheets. Our method is straightforward and can be utilized to design new kinds of cloaks that can work not only in the realm of geometric optics but also using wave optics. The physics behind this design is similar to that of the conformal cloak for waves. The resonances in the interior region make the phase delay disappear and induce the cloaking effect. Numerical simulations confirm our theoretical results.

  18. Simulations of artificial swimmers in confined flows

    NASA Astrophysics Data System (ADS)

    Brandt, Luca; Zhu, Lailai; Gjølberg, Eerik

    2012-11-01

    Miniature swimmming robots are potentially powerful for microobject manipulation, such as flow control in lab-on-a-chip, localized drug delivery and screening for diseases. Magnetically driven artificial bacterial flagella (ABF) performing helical motion is advantegous due to high swimming speed and accurate control. Using boundary element method, we numerically investigate the propulsion of ABF in free space and near solid boundaries. Step-out at high actuation frequencies, wobbling and near-wall drifting are documented, in qualitative agreement with recent experiments. We aim to explore the effect of swimmer shape on the performance, thus benefiting design of efficient microswimmers. Propulsion of ABF confined by a solid wall with and without background shear flow is also studied, with a focus on wall-induced hydrodynamic interaction and its influence on the stability of the motion. Funding by VR (the Swedish Research Council) and Linne flow centre at KTH is acknowledged.

  19. Mesh deformation based on artificial neural networks

    NASA Astrophysics Data System (ADS)

    Stadler, Domen; Kosel, Franc; Čelič, Damjan; Lipej, Andrej

    2011-09-01

    In the article a new mesh deformation algorithm based on artificial neural networks is introduced. This method is a point-to-point method, meaning that it does not use connectivity information for calculation of the mesh deformation. Two already known point-to-point methods, based on interpolation techniques, are also presented. In contrast to the two known interpolation methods, the new method does not require a summation over all boundary nodes for one displacement calculation. The consequence of this fact is a shorter computational time of mesh deformation, which is proven by different deformation tests. The quality of the deformed meshes with all three deformation methods was also compared. Finally, the generated and the deformed three-dimensional meshes were used in the computational fluid dynamics numerical analysis of a Francis water turbine. A comparison of the analysis results was made to prove the applicability of the new method in every day computation.

  20. Attitude stability analyses for small artificial satellites

    NASA Astrophysics Data System (ADS)

    Silva, W. R.; Zanardi, M. C.; Formiga, J. K. S.; Cabette, R. E. S.; Stuchi, T. J.

    2013-10-01

    The objective of this paper is to analyze the stability of the rotational motion of a symmetrical spacecraft, in a circular orbit. The equilibrium points and regions of stability are established when components of the gravity gradient torque acting on the spacecraft are included in the equations of rotational motion, which are described by the Andoyer's variables. The nonlinear stability of the equilibrium points of the rotational motion is analysed here by the Kovalev-Savchenko theorem. With the application of the Kovalev-Savchenko theorem, it is possible to verify if they remain stable under the influence of the terms of higher order of the normal Hamiltonian. In this paper, numerical simulations are made for a small hypothetical artificial satellite. Several stable equilibrium points were determined and regions around these points have been established by variations in the orbital inclination and in the spacecraft principal moment of inertia. The present analysis can directly contribute in the maintenance of the spacecraft's attitude.

  1. Potential application of artificial concepts to aerodynamic simulation

    NASA Technical Reports Server (NTRS)

    Kutler, P.; Mehta, U. B.; Andrews, A.

    1984-01-01

    The concept of artificial intelligence as it applies to computational fluid dynamics simulation is investigated. How expert systems can be adapted to speed the numerical aerodynamic simulation process is also examined. A proposed expert grid generation system is briefly described which, given flow parameters, configuration geometry, and simulation constraints, uses knowledge about the discretization process to determine grid point coordinates, computational surface information, and zonal interface parameters.

  2. Local Flow Field and Slip Length of Superhydrophobic Surfaces.

    PubMed

    Schäffel, David; Koynov, Kaloian; Vollmer, Doris; Butt, Hans-Jürgen; Schönecker, Clarissa

    2016-04-01

    While the global slippage of water past superhydrophobic surfaces has attracted wide interest, the local distribution of slip still remains unclear. Using fluorescence correlation spectroscopy, we performed detailed measurements of the local flow field and slip length for water in the Cassie state on a microstructured superhydrophobic surface. We revealed that the local slip length is finite, nonconstant, anisotropic, and sensitive to the presence of surfactants. In combination with numerical calculations of the flow, we can explain all these properties by the local hydrodynamics. PMID:27081981

  3. Local Flow Field and Slip Length of Superhydrophobic Surfaces

    NASA Astrophysics Data System (ADS)

    Schäffel, David; Koynov, Kaloian; Vollmer, Doris; Butt, Hans-Jürgen; Schönecker, Clarissa

    2016-04-01

    While the global slippage of water past superhydrophobic surfaces has attracted wide interest, the local distribution of slip still remains unclear. Using fluorescence correlation spectroscopy, we performed detailed measurements of the local flow field and slip length for water in the Cassie state on a microstructured superhydrophobic surface. We revealed that the local slip length is finite, nonconstant, anisotropic, and sensitive to the presence of surfactants. In combination with numerical calculations of the flow, we can explain all these properties by the local hydrodynamics.

  4. Propagation of numerical noise in particle-in-cell tracking

    NASA Astrophysics Data System (ADS)

    Kesting, Frederik; Franchetti, Giuliano

    2015-11-01

    Particle-in-cell (PIC) is the most used algorithm to perform self-consistent tracking of intense charged particle beams. It is based on depositing macroparticles on a grid, and subsequently solving on it the Poisson equation. It is well known that PIC algorithms occupy intrinsic limitations as they introduce numerical noise. Although not significant for short-term tracking, this becomes important in simulations for circular machines over millions of turns as it may induce artificial diffusion of the beam. In this work, we present a modeling of numerical noise induced by PIC algorithms, and discuss its influence on particle dynamics. The combined effect of particle tracking and noise created by PIC algorithms leads to correlated or decorrelated numerical noise. For decorrelated numerical noise we derive a scaling law for the simulation parameters, allowing an estimate of artificial emittance growth. Lastly, the effect of correlated numerical noise is discussed, and a mitigation strategy is proposed.

  5. Telomere length in Hepatitis C.

    PubMed

    Kitay-Cohen, Y; Goldberg-Bittman, L; Hadary, R; Fejgin, M D; Amiel, A

    2008-11-01

    Telomeres are nucleoprotein structures located at the termini of chromosomes that protect the chromosomes from fusion and degradation. Hepatocyte cell-cycle turnover may be a primary mechanism of telomere shortening in hepatitis C virus (HCV) infection, inducing fibrosis and cellular senescence. HCV infection has been recognized as potential cause of B-cell lymphoma and hepatocellular carcinoma. The present study sought to assess relative telomere length in leukocytes from patients with chronic HCV infection, patients after eradication of HCV infection (in remission), and healthy controls. A novel method of manual evaluation was applied. Leukocytes derived from 22 patients with chronic HCV infection and age- and sex-matched patients in remission and healthy control subjects were subjected to a fluorescence-in-situ protocol (DAKO) to determine telomere fluorescence intensity and number. The relative, manual, analysis of telomere length was validated against findings on applied spectral imaging (ASI) in a random sample of study and control subjects. Leukocytes from patients with chronic HCV infection had shorter telomeres than leukocytes from patients in remission and healthy controls. On statistical analysis, more cells with low signal intensity on telomere FISH had shorter telomeres whereas more cells with high signal intensity had longer telomeres. The findings were corroborated by the ASI telomere software. Telomere shortening in leukocytes from patients with active HCV infection is probably due to the lower overall telomere level rather than higher cell cycle turnover. Manual evaluation is an accurate and valid method of assessing relative telomere length between patients with chronic HCV infection and healthy subjects. PMID:18992639

  6. The NIST Length Scale Interferometer

    PubMed Central

    Beers, John S.; Penzes, William B.

    1999-01-01

    The National Institute of Standards and Technology (NIST) interferometer for measuring graduated length scales has been in use since 1965. It was developed in response to the redefinition of the meter in 1960 from the prototype platinum-iridium bar to the wavelength of light. The history of the interferometer is recalled, and its design and operation described. A continuous program of modernization by making physical modifications, measurement procedure changes and computational revisions is described, and the effects of these changes are evaluated. Results of a long-term measurement assurance program, the primary control on the measurement process, are presented, and improvements in measurement uncertainty are documented.

  7. The Length of Time's Arrow

    SciTech Connect

    Feng, Edward H.; Crooks, Gavin E.

    2008-08-21

    An unresolved problem in physics is how the thermodynamic arrow of time arises from an underlying time reversible dynamics. We contribute to this issue by developing a measure of time-symmetry breaking, and by using the work fluctuation relations, we determine the time asymmetry of recent single molecule RNA unfolding experiments. We define time asymmetry as the Jensen-Shannon divergencebetween trajectory probability distributions of an experiment and its time-reversed conjugate. Among other interesting properties, the length of time's arrow bounds the average dissipation and determines the difficulty of accurately estimating free energy differences in nonequilibrium experiments.

  8. The artificial compression method for computation of shocks and contact discontinuities. I - Single conservation laws

    NASA Technical Reports Server (NTRS)

    Harten, A.

    1977-01-01

    The paper discusses the use of the artificial compression method for the computation of discontinuous solutions of a single conservation law by finite difference methods. The single conservation law has either a shock or a contact discontinuity. Any monotone finite difference scheme applied to the original equation smears the discontinuity, while the same scheme applied to the equation modified by an artificial compression flux produces steady progressing profiles. If L is any finite difference scheme in conservation form and C is an artificial compressor, the split flux artificial compression method CL is a corrective scheme: L smears the discontinuity while propagating it; C compresses the smeared transition toward a sharp discontinuity. Numerical implementation of artificial compression is described.

  9. Natural channel protein inserts and functions in a completely artificial, solid-supported bilayer membrane

    PubMed Central

    Zhang, Xiaoyan; Fu, Wangyang; Palivan, Cornelia G.; Meier, Wolfgang

    2013-01-01

    Reconstitution of membrane proteins in artificial membrane systems creates a platform for exploring their potential for pharmacological or biotechnological applications. Previously, we demonstrated amphiphilic block copolymers as promising building blocks for artificial membranes with long-term stability and tailorable structural parameters. However, the insertion of membrane proteins has not previously been realized in a large-area, stable, and solid-supported artificial membrane. Here, we show the first, preliminary model of a channel membrane protein that is functionally incorporated in a completely artificial polymer, tethered, solid-supported bilayer membrane (TSSBM). Unprecedented ionic transport characteristics that differ from previous results on protein insertion into planar, free-standing membranes, are identified. Our findings mark a change in understanding protein insertion and ion flow within natural channel proteins when inserted in an artificial TSSBM, thus holding great potential for numerous applications such as drug screening, trace analyzing, and biosensing. PMID:23846807

  10. Suppressing the numerical Cherenkov radiation in the Yee numerical scheme

    NASA Astrophysics Data System (ADS)

    Nuter, Rachel; Tikhonchuk, Vladimir

    2016-01-01

    The next generation of laser facilities will routinely produce relativistic particle beams from the interaction of intense laser pulses with solids and/or gases. Their modeling with Particle-In-Cell (PIC) codes needs dispersion-free Maxwell solvers in order to properly describe the interaction of electromagnetic waves with relativistic particles. A particular attention is devoted to the suppression of the numerical Cherenkov instability, responsible for the noise generation. It occurs when the electromagnetic wave is artificially slowed down because of the finite mesh size, thus allowing for the high energy particles to propagate with super-luminous velocities. In the present paper, we show how a slight increase of the light velocity in the Maxwell's equations enables to suppress this instability while keeping a good overall precision of calculations.