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Sample records for complex duct simulating

  1. Complex bile duct injuries: management

    PubMed Central

    Ardiles, V.; Pekolj, J.

    2008-01-01

    Background. Laparoscopic cholecystectomy is the present treatment of choice for patients with gallbladder stones, despite its being associated with a higher incidence of biliary injuries compared with the open procedure. Injuries occurring during the laparoscopic approach seem to be more complex. A complex biliary injury is a disease that is difficult to diagnose and treat. We considered complex injuries: 1) injuries that involve the confluence; 2) injuries in which repair attempts have failed; 3) any bile duct injury associated with a vascular injury; 4) or any biliary injury in association with portal hypertension or secondary biliary cirrhosis. The present review is an evaluation of our experience in the treatment of these complex biliary injuries and an analysis of the international literature on the management of patients. PMID:18695753

  2. A Comparison of Simulation Capabilities for Ducts

    SciTech Connect

    Miller, William A.; Smith, Matt K.; Gu, Lixing; New, Joshua Ryan

    2014-11-01

    Typically, the cheapest way to install a central air conditioning system in residential buildings is to place the ductwork in the attic. Energy losses due to duct-attic interactions can be great, but current whole-house models are unable to capture the dynamic multi-mode physics of the interactions. The building industry is notoriously fragmented and unable to devote adequate research resources to solve this problem. Builders are going to continue to put ducts in the attic because floor space is too expensive to closet them within living space, and there are both construction and aesthetic issues with other approaches such as dropped ceilings. Thus, there is a substantial need to publicly document duct losses and the cost of energy used by ducts in attics so that practitioners, builders, homeowners and state and federal code officials can make informed decisions leading to changes in new construction and additional retrofit actions. Thus, the goal of this study is to conduct a comparison of AtticSim and EnergyPlus simulation algorithms to identify specific features for potential inclusion in EnergyPlus that would allow higher-fidelity modeling of HVAC operation and duct transport of conditioned air. It is anticipated that the resulting analysis from these simulation tools will inform energy decisions relating to the role of ducts in future building energy codes and standards.

  3. Unsteady flowfield simulation of ducted prop-fan configurations

    NASA Technical Reports Server (NTRS)

    Janus, J. M.; Horstman, Howard Z.; Whitfield, David L.

    1992-01-01

    A technique for the simulation of unsteady flows in and around complex rotating machinery is presented. Additional domain decomposition mechanisms are introduced which extend the range of applicability of software developed for the time-accurate simulation of rotating machinery flowfields. The flow models uses the unsteady 3D Euler equations, discretized as a finite-volume method, utilizing a high-resolution approximate Riemann solver for cell interface flux definitions. Multiblock domain decomposition is used to partition the field radially, axially, as well as circumferentially into an ordered arrangement of blocks which exhibit varying degrees of similarity. A general high-order numerical scheme is applied to satisfy the geometric conservation law. Two configurations are presented - ducted single rotation prop-fan and a rotor-deswirl vane combination which form a single stage fan. Comparisons are made to other numerical solutions for these geometries and to available experimental data.

  4. Unsteady flowfield simulation of ducted prop-fan configurations

    NASA Technical Reports Server (NTRS)

    Janus, J. M.; Horstman, Howard Z.; Whitfield, David L.

    1992-01-01

    A technique for the simulation of unsteady flows in and around complex rotating machinery is presented. Additional domain decomposition mechanisms are introduced which extend the range of applicability of software developed for the time-accurate simulation of rotating machinery flowfields. The flow models uses the unsteady 3D Euler equations, discretized as a finite-volume method, utilizing a high-resolution approximate Riemann solver for cell interface flux definitions. Multiblock domain decomposition is used to partition the field radially, axially, as well as circumferentially into an ordered arrangement of blocks which exhibit varying degrees of similarity. A general high-order numerical scheme is applied to satisfy the geometric conservation law. Two configurations are presented - ducted single rotation prop-fan and a rotor-deswirl vane combination which form a single stage fan. Comparisons are made to other numerical solutions for these geometries and to available experimental data.

  5. Flow Simulation of Supersonic Inlet with Bypass Annular Duct

    NASA Technical Reports Server (NTRS)

    Kim, HyoungJin; Kumano, Takayasu; Liou, Meng-Sing; Povinelli, Louis A.; Conners, Timothy R.

    2011-01-01

    A relaxed isentropic compression supersonic inlet is a new concept that produces smaller cowl drag than a conventional inlet, but incurs lower total pressure recovery and increased flow distortion in the (radially) outer flowpath. A supersonic inlet comprising a bypass annulus to the relaxed isentropic compression inlet dumps out airflow of low quality through the bypass duct. A reliable computational fluid dynamics solution can provide considerable useful information to ascertain quantitatively relative merits of the concept, and further provide a basis for optimizing the design. For a fast and reliable performance evaluation of the inlet performance, an equivalent axisymmetric model whose area changes accounts for geometric and physical (blockage) effects resulting from the original complex three-dimensional configuration is proposed. In addition, full three-dimensional calculations are conducted for studying flow phenomena and verifying the validity of the equivalent model. The inlet-engine coupling is carried out by embedding numerical propulsion system simulation engine data into the flow solver for interactive boundary conditions at the engine fan face and exhaust plane. It was found that the blockage resulting from complex three-dimensional geometries in the bypass duct causes significant degradation of inlet performance by pushing the terminal normal shock upstream.

  6. Numerical simulation of duct flow with fog droplets

    NASA Astrophysics Data System (ADS)

    Suryan, Abhilash; Lee, J. K.; Kim, D. S.; Kim, H. D.

    2010-12-01

    Evaporative cooling is a widely used air cooling technique. In this method, evaporation of a liquid in the surrounding air cools the air in contact with it. In the current investigation, numerical simulations are carried out to visualize the evaporation and dynamics of tiny water droplets of different diameters in a long air duct. The effect of initial droplet size on the temperature and relative humidity distribution of the air stream in the duct is investigated. Three different initial conditions of air are considered to verify the influence of ambient conditions. Droplet spray patterns are also analyzed to identify the suitable locations for the spray nozzles within the duct. The results obtained are displayed in a series of plots to provide a clear understanding of the evaporative cooling process as well as the droplet dynamics within the ducts.

  7. Remote sensing of atmospheric duct parameters using simulated annealing

    NASA Astrophysics Data System (ADS)

    Zhao, Xiao-Feng; Huang, Si-Xun; Xiang, Jie; Shi, Wei-Lai

    2011-09-01

    Simulated annealing is one of the robust optimization schemes. Simulated annealing mimics the annealing process of the slow cooling of a heated metal to reach a stable minimum energy state. In this paper, we adopt simulated annealing to study the problem of the remote sensing of atmospheric duct parameters for two different geometries of propagation measurement. One is from a single emitter to an array of radio receivers (vertical measurements), and the other is from the radar clutter returns (horizontal measurements). Basic principles of simulated annealing and its applications to refractivity estimation are introduced. The performance of this method is validated using numerical experiments and field measurements collected at the East China Sea. The retrieved results demonstrate the feasibility of simulated annealing for near real-time atmospheric refractivity estimation. For comparison, the retrievals of the genetic algorithm are also presented. The comparisons indicate that the convergence speed of simulated annealing is faster than that of the genetic algorithm, while the anti-noise ability of the genetic algorithm is better than that of simulated annealing.

  8. Numerical simulation of laminar flow in a curved duct

    SciTech Connect

    Lopez, A.R.; Oberkampf, W.L.

    1995-01-01

    This paper describes numerical simulations that were performed to study laminar flow through a square duct with a 900 bend. The purpose of this work was two fold. First, an improved understanding was desired of the flow physics involved in the generation of secondary vortical flows in three-dimensions. Second, adaptive gridding techniques for structured grids in three- dimensions were investigated for the purpose of determining their utility in low Reynolds number, incompressible flows. It was also of interest to validate the commercial computer code CFD-ACE. Velocity predictions for both non-adaptive and adaptive grids are compared with experimental data. Flow visualization was used to examine the characteristics of the flow though the curved duct in order to better understand the viscous flow physics of this problem. Generally, moderate agreement with the experimental data was found but shortcomings in the experiment were demonstrated. The adaptive grids did not produce the same level of accuracy as the non-adaptive grid with a factor of four more grid points.

  9. Large Eddy Simulation of turbulent heat transfer in a rotating square duct

    NASA Astrophysics Data System (ADS)

    Qin, Zhaohui; Pletcher, Richard

    2004-11-01

    Turbulent heat transfer in a rotating square duct is an important topic with numerous applications such as turbine blade cooling and automobile brake cooling. Without rotation, Prandtl's secondary flow of the second kind is known to have a significant impact on the transport of heat and momentum in turbulent duct flows. With rotation, Coriolis force and centrifugal buoyancy force cause more complicated secondary flow pattern and, as a consequence, modify heat transfer coefficients. The objective of this study is to expand the capability of the current LES code to correctly predict complex turbulent flow phenomena and to gain a better understanding of the physics of turbulent flow in rotating passages. A finite volume LU-SGS scheme is used to simulate compressible three-dimensional turbulent flow at low Mach numbers. Time derivative preconditioning is employed to deal with the low Mach number situation. A localized dynamic subgrid-scale (SGS) model is used to evaluate the unresolved stresses. The calculation domain is divided into two parts. In the first part periodic boundary conditions are applied and this provides the fully developed inlet flow for the second part in which the heat transfer conditions are imposed. Characteristic out-flow conditions are used in the second part. This allows the flow to develop further as it responds to the heating condition. The code is parallelized using MPI (Message Passing Interface). To verify the code, we calculated isothermal rotating duct cases and compared our results with DNS and experimental results. Then heated duct flow cases were simulated and the results were compared to available data. Good agreement has been obtained.

  10. Numerical Simulation of Acoustic Propagation in a Lined Duct

    NASA Astrophysics Data System (ADS)

    Biringen, S.; Reichert, R. S.; Yu, J.; Zorumski, W. E.

    1996-11-01

    An inviscid, spatial time-domain numerical simulation is employed to compute acoustic wave propagation in a duct treated with an acoustic liner. The motivation is to assess the effects on sound attenuation of bias flow passed through the liner for application to noise suppression in jet engine nacelles. Physically, the liner is composed of porous sheets with backing air cavities. The mathematical model lumps the liner presence into a continuous empirical source term which modifies the right-hand side of the momentum equations. Thus, liner effects are felt interior to the domain rather than through boundary conditions. This source term determines the time-domain effects of the frequency-domain resistance and reactance of the liner's component sheets. The source term constants are matched to frequency-domain impedance data via a one-dimensional numerical impedance tube simulation. Nonlinear behavior of the liner at high sound pressure levels is included in the form of the source term. Sound pressure levels and axially transmitted power are computed to assess the effect of various magnitudes of bias flow on attenuation.

  11. Simulation of linear aeracoustic propagation in lined ducts with discontinuous Galerkin method

    NASA Astrophysics Data System (ADS)

    Peyret, Christophe; Delorme, Philippe

    2004-05-01

    The simulation of the acoustic propagation inside a lined duct with nonuniform flow still presents problems when geometry is complex. To handle computations on a complex geometry, without consequential effort, unstructured meshes are required. Assuming irrotational flow and acoustic perturbation, a well-posed finite element method based on the potential equation is established. But, the effect of the thin boundary layer is then neglected, which is not relevant to the acoustical processes occurring near the lining. Recent works have focused on the tremendous interest of the Galerkin discontinuous method (GDM) to solve Euler's linearized equations. The GDM can handle computations on unstructured meshes and introduces low numerical dissipation. Very recent mathematical works have established, for the GDM, a well-posed boundary condition to simulate the lining effect. Results computed with the GDM are presented for a uniform cross section lined duct with a shear flow and are found to be in good agreement with the modal analysis results, thereby validating the boundary condition. To illustrate the flexibility of the method other applications dealing with instabilities, air-wing diffraction, and atmospheric propagation are also presented.

  12. Whistler propagation in ionospheric density ducts: Simulations and DEMETER observations

    NASA Astrophysics Data System (ADS)

    Woodroffe, J. R.; Streltsov, A. V.; Vartanyan, A.; Milikh, G. M.

    2013-11-01

    On 16 October 2009, the Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite observed VLF whistler wave activity coincident with an ionospheric heating experiment conducted at HAARP. At the same time, density measurements by DEMETER indicate the presence of multiple field-aligned enhancements. Using an electron MHD model, we show that the distribution of VLF power observed by DEMETER is consistent with the propagation of whistlers from the heating region inside the observed density enhancements. We also discuss other interesting features of this event, including coupling of the lower hybrid and whistler modes, whistler trapping in artificial density ducts, and the interference of whistlers waves from two adjacent ducts.

  13. Computing simulated endolymphatic flow thermodynamics during the caloric test using normal and hydropic duct models.

    PubMed

    Rey-Martinez, Jorge; McGarvie, Leigh; Pérez-Fernández, Nicolás

    2017-03-01

    The obtained simulations support the underlying hypothesis that the hydrostatic caloric drive is dissipated by local convective flow in a hydropic duct. To develop a computerized model to simulate and predict the internal fluid thermodynamic behavior within both normal and hydropic horizontal ducts. This study used a computational fluid dynamics software to simulate the effects of cooling and warming of two geometrical models representing normal and hydropic ducts of one semicircular horizontal canal during 120 s. Temperature maps, vorticity, and velocity fields were successfully obtained to characterize the endolymphatic flow during the caloric test in the developed models. In the normal semicircular canal, a well-defined endolymphatic linear flow was obtained, this flow has an opposite direction depending only on the cooling or warming condition of the simulation. For the hydropic model a non-effective endolymphatic flow was predicted; in this model the velocity and vorticity fields show a non-linear flow, with some vortices formed inside the hydropic duct.

  14. Simulations of detonation wave propagation in rectangular ducts using a three-dimensional WENO scheme

    SciTech Connect

    Dou, Hua-Shu; Tsai, Her Mann; Khoo, Boo Cheong; Qiu, Jianxian

    2008-09-15

    This paper reports high resolution simulations using a fifth-order weighted essentially non-oscillatory (WENO) scheme with a third-order TVD Runge-Kutta time stepping method to examine the features of detonation front and physics in square ducts. The simulations suggest that two and three-dimensional detonation wave front formations are greatly enhanced by the presence of transverse waves. The motion of transverse waves generates triple points (zones of high pressure and large velocity coupled together), which cause the detonation front to become locally overdriven and thus form ''hot spots.'' The transversal motion of these hot spots maintains the detonation to continuously occur along the whole front in two and three dimensions. The present simulations indicate that the influence of the transverse waves on detonation is more profound in three dimensions and the pattern of quasi-steady detonation fronts also depends on the duct size. For a ''narrow'' duct (4L x 4L where L is the half-reaction length), the detonation front displays a distinctive ''spinning'' motion about the axial direction with a well-defined period. For a wider duct (20L x 20L), the detonation front exhibits a ''rectangular mode'' periodically, with the front displaying ''convex'' and ''concave'' shapes one following the other and the transverse waves on the four walls being partly out-of-phase with each other. (author)

  15. Male penile propulsion into spiraled spermathecal ducts of female chrysomelid beetles: A numerical simulation approach.

    PubMed

    Filippov, Alexander; Kovalev, Alexander; Matsumura, Yoko; Gorb, Stanislav N

    2015-11-07

    Genital diversification in animals is an interesting evolutionary phenomenon. Sexual selection is the main driving force behind the diversification. However, evolutionary mechanisms that have established and maintained variations in genitalia shape parameters observed in related species are not well understood. Here, for the first time, we used numerical simulations to test the hypothesis that variations in female spermathecal duct shapes among related beetle species mechanically interfere with penile propulsion in varying ways. Our numerical simulations showed that high curvature of the spiraled spermathecal ducts of the female have effects with a threshold-based interaction on male penile insertion. The relative size of spirals observed in the beetle, Cassida rubiginosa, studied here is not small enough to interfere with penile propulsion. But the model revealed that propulsion is impeded by the presence of reverse turns in spermathecal ducts. This type of morphology leads to an increase in the velocity of the propulsion but also to an increase in the propulsion energy cost for males. Our results showed that quantitative differences in spermathecal duct shape can mediate qualitative differences in penile motion. This explains, in part, the mechanism behind origin and maintenance of genital divergence among closely related species in general.

  16. Direct numerical simulation of turbulent flow in a rotating square duct

    SciTech Connect

    Dai, Yi-Jun; Huang, Wei-Xi Xu, Chun-Xiao; Cui, Gui-Xiang

    2015-06-15

    A fully developed turbulent flow in a rotating straight square duct is simulated by direct numerical simulations at Re{sub τ} = 300 and 0 ≤ Ro{sub τ} ≤ 40. The rotating axis is parallel to two opposite walls of the duct and normal to the main flow. Variations of the turbulence statistics with the rotation rate are presented, and a comparison with the rotating turbulent channel flow is discussed. Rich secondary flow patterns in the cross section are observed by varying the rotation rate. The appearance of a pair of additional vortices above the pressure wall is carefully examined, and the underlying mechanism is explained according to the budget analysis of the mean momentum equations.

  17. Simulations of a Normal Shock Train in a Constant Area Duct Using Wall-Modeled LES

    NASA Astrophysics Data System (ADS)

    Vane, Zachary; Bermejo-Moreno, Ivan; Lele, Sanjiva

    2013-11-01

    Large-Eddy Simulations (LES) of a turbulent boundary layer interacting with a normal shock train in a constant area duct (STCAD) are performed using an unstructured solver. Comparisons between wall-modeled LES (WMLES) and wall-resolved LES (WRLES) calculations of a spanwise-periodic flow at M = 1.61 and Re = 16,200 are used to evaluate an equilibrium wall-model's ability to replicate the wall-resolved results. The WMLES approach is then used for simulations at the flow conditions (M = 1.61, Re = 162,000) of the Carroll & Dutton STCAD experiments where traditional WRLES was inaccessible. Spanwise-periodic WMLES calculations were unable to duplicate the experimental wall pressure and Laser Doppler Velocimetry data obtained along the spanwise center plane of the duct. Investigations of the full, low aspect ratio duct geometry were then performed using WMLES. Comparisons with experimental data provide an assessment of the wall-model's ability to simulate realistic, high Reynolds number, non-equilibrium flows. However, the lack of information with respect to the sidewall boundary layers from the experiment led to a WMLES parameter study of the effects of boundary layer confinement on the shock train. Initial results suggest that the tunnel blockage due to the boundary layer displacement thickness determines many of the STCAD's characteristics. A possible improvement to the wall-model through the inclusion of previously omitted non-equilibrium terms is currently being pursued.

  18. Complex malformations of the urogenital tract in a female dog: Gartner duct cyst, ipsilateral renal agenesis, and ipsilateral hydrometra.

    PubMed

    Fujita, Atsushi; Tsuboi, Masaya; Uchida, Kazuyuki; Nishimura, Ryohei

    2016-05-01

    A 10-month-old female toy poodle was referred to the University of Tokyo Veterinary Medical Center with a urogenital anomaly found during sterilization. An exploratory laparotomy revealed a cyst adhering to the cervix and a unilateral renal agenesis. Histopathology and immunohistochemical analysis of the cyst was consistent with remnants of the Wolffian duct or a Gartner duct cyst. This is a rare case of a canine Gartner duct cyst with renal agenesis and uterine anomaly. We discuss the similarity of this case to that of humans and introduce a classification in the literature for these complex urogenital malformations for further clinical research into the precise diagnosis and appropriate surgical planning.

  19. Investigation of particle-laden flow in a straight duct using large eddy simulation

    SciTech Connect

    Fairweather, M.; Yao, J.

    2007-07-01

    A particle-laden turbulent flow in a square duct is predicted using large eddy simulation (LES). The simulation is performed for a Reynolds number of 35,500, and correctly predicts the existence of secondary flows and their effects on the mean flow. The results are also in good qualitative agreement with experimental data obtained at different Reynolds numbers. One-way coupling is assumed between solid particles and the fluid, and a particle equation of motion, including Stokes drag, lift, buoyancy and gravity force terms, solved using a Lagrangian particle tracking technique. Three sizes of particle (1, 50 and 100 {mu}m) are considered, and results demonstrate that size has a significant effect on particle dispersion and deposition in the duct flow. As particle size increases, therefore, they tend to settle on the floor of the duct, with less dispersion in the fluid phase. The study demonstrates the usefulness of LES for nuclear waste processing applications since secondary flows occur in many practically-relevant flows, and since it is desirable that the two-phase waste mixture is kept as homogeneous as possible to prevent, or at least discourage, the settling out of solid particles to form a bed which can promote pipe blockages. (authors)

  20. Numerical Simulation of Noise from Supersonic Jets Passing Through a Rigid Duct

    NASA Technical Reports Server (NTRS)

    Kandula, Max

    2012-01-01

    The generation, propagation and radiation of sound from a perfectly expanded Mach 2.5 cold supersonic jet flowing through an enclosed rigid-walled duct with an upstream J-deflector have been numerically simulated with the aid of OVERFLOW Navier-Stokes CFD code. A one-equation turbulence model is considered. While the near-field sound sources are computed by the CFD code, the far-field sound is evaluated by Kirchhoff surface integral formulation. Predictions of the farfield directivity of the OASPL (Overall Sound Pressure Level) agree satisfactorily with the experimental data previously reported by the author. Calculations also suggest that there is significant entrainment of air into the duct, with the mass flow rate of entrained air being about three times the jet exit mass flow rate.

  1. Measurement of flowfield in a simulated solid-propellant ducted rocket combustor using laser Doppler velocimetry

    SciTech Connect

    Hsieh, W.H.; Yang, V.; Chuang, C.L.; Yang, A.S.; Cherng, D.L.

    1989-01-01

    A two-component LDV system was used to obtain detailed flow velocity and turbulence measurements in order to study the flow characteristics in a simulated solid-propellant ducted rocket combustor. The vortical structures near the dome region, the size of the recirculation zone, and the location of the reattachment point are all shown to be strongly affected by the jet momentum of both ram air and fuel streams. It is found that the turbulence intensity is anisotropic throughout the front portion of the simulated conbustor, and that the measured Reynolds stress conmponent distribution is well correlated with the local mean velocity vector distribution. 25 refs.

  2. Hybrid palliation in complex congenital heart malformation with duct-dependent isolated pulmonary artery.

    PubMed

    Marrone, Chiara; Santoro, Giuseppe; Palladino, Maria Teresa; Caianiello, Giuseppe; Russo, Maria Giovanna; Calabrò, Raffaele

    2011-06-02

    A 2 month-old infant with severe congestive heart failure due to unrestrictive ventricular septal defect and absence of the left pulmonary artery was submitted to a hybrid transcatheter-surgical palliation consisting in percutaneous re-canalization of the occluded arterial duct-left pulmonary artery complex and surgical banding of the right pulmonary artery. The post-operative course was uneventful and the baby was discharged in a few days under mild anti-congestive therapy. This hybrid approach was highly effective in stabilizing this critical infant in view of a later and safer surgical repair.

  3. Study on numerical simulation of flowfield in afterburner for ducted rocket

    NASA Astrophysics Data System (ADS)

    Ding, Xiaoyu; Jin, Xing; Zhang, Peng

    2015-03-01

    Ducted rocket has been widely concerned on account of its high specific impulse, combustion stability and convenient maintenance which mixes the exhaust from a fuel gas generator with air from air inlet, and burns to produce thrust. It is necessary to establish two-dimensional or three-dimensional numerical models based on computational fluid dynamics to study on the flowfield in afterburner which is the key of ducted rocket because of expensive experiments, which is aimed at providing theoretical foundation for ducted rocket's development. In this paper, the gas-phase turbulent combustion process in afterburner with dual inlet three-dimensional mode was simulated numerically by solving Favre-averaged compressible turbulent N-S equations, the renormalization group (RNG) k-ɛ turbulence model was applied to simulate the turbulent flow, and Eddy-Dissipation Model (EDM) was applied to simulate gas combustion. Through simulation, situation analysis of flowfield in afterburner was done, and the influence of mixing combustion on afterburner was studied by taking air inlet angles and air-fuel ratio into account respectively. The results indicate that the distribution of temperature in afterburner is nonuniform, the backflow and axial swirl produced by gas mixing have an important influence on afterburner combustion. As air inlet angle is increased, the intensity of gas mixing is enhanced which is beneficial for afterburner combustion. That increasing air-fuel ratio is able to strength contact of oxygen with fuel gas, so that more fuel gas is consumed in the same location which is more beneficial for afterburner combustion.

  4. Far-field noise and internal modes from a ducted propeller at simulated aircraft takeoff conditions

    NASA Astrophysics Data System (ADS)

    Woodward, Richard P.; Bock, Lawrence A.; Heidelberg, Laurence J.; Hall, David G.

    The ducted propeller offers structural and acoustic benefits typical of conventional turbofan engines while retaining much of the aeroacoustic benefits of the unducted propeller. A model Advanced Ducted Propeller (ADP) was tested in the NASA Lewis Low-Speed Anechoic Wind Tunnel at a simulated takeoff velocity of Mach 0.2. The ADP model was designed and manufactured by the Pratt and Whitney Division of United Technologies. The 16-blade rotor ADP was tested with 22- and 40-vane stators to achieve cut-on and cut-off criterion with respect to propagation of the fundamental rotor-stator interaction tone. Additional test parameters included three inlet lengths, three nozzle sizes, two spinner configurations, and two rotor rub strip configurations. The model was tested over a range of rotor blade setting angles and propeller axis angles-of-attack. Acoustic data were taken with a sideline translating microphone probe and with a unique inlet microphone probe which identified inlet rotating acoustic modes. The beneficial acoustic effects of cut-off were clearly demonstrated. A 5 dB fundamental tone reduction was associated with the long inlet and 40-vane sector, which may relate to inlet duct geometry. The fundamental tone level was essentially unaffected by propeller axis angle-of-attack at rotor speeds of at least 96 percent design.

  5. Far-field noise and internal modes from a ducted propeller at simulated aircraft takeoff conditions

    NASA Technical Reports Server (NTRS)

    Woodward, Richard P.; Bock, Lawrence A.; Heidelberg, Laurence J.; Hall, David G.

    1992-01-01

    The ducted propeller offers structural and acoustic benefits typical of conventional turbofan engines while retaining much of the aeroacoustic benefits of the unducted propeller. A model Advanced Ducted Propeller (ADP) was tested in the NASA Lewis Low-Speed Anechoic Wind Tunnel at a simulated takeoff velocity of Mach 0.2. The ADP model was designed and manufactured by the Pratt and Whitney Division of United Technologies. The 16-blade rotor ADP was tested with 22- and 40-vane stators to achieve cut-on and cut-off criterion with respect to propagation of the fundamental rotor-stator interaction tone. Additional test parameters included three inlet lengths, three nozzle sizes, two spinner configurations, and two rotor rub strip configurations. The model was tested over a range of rotor blade setting angles and propeller axis angles-of-attack. Acoustic data were taken with a sideline translating microphone probe and with a unique inlet microphone probe which identified inlet rotating acoustic modes. The beneficial acoustic effects of cut-off were clearly demonstrated. A 5 dB fundamental tone reduction was associated with the long inlet and 40-vane sector, which may relate to inlet duct geometry. The fundamental tone level was essentially unaffected by propeller axis angle-of-attack at rotor speeds of at least 96 percent design.

  6. Eulerian-Lagrangian Simulations of Bubbly Flows in A Vertical Square Duct

    NASA Astrophysics Data System (ADS)

    Liu, Rui; Vanka, Surya P.; Thomas, Brian G.

    2013-11-01

    We report results of Eulerian-Lagrangian simulations of developing upward and downward bubbly flows in a vertical square duct with a bulk Reynolds number of 5000. The continuous fluid is simulated with DNS, solving the Navier-Stokes equations by a second-order accurate finite volume fractional step method. Bubbles of sizes comparable to the Kolmogorov scale are injected at the duct entrance with a mean bulk volume fraction below 10-2. A two-way coupling approach is adopted for the interaction between the continuous fluid phase and dispersed bubble phase. The bubbles are tracked by a Lagrangian method including drag and lift forces due to buoyancy and Saffman lift. A in-house code, CU-FLOW, implemented on Graphic Processing Unit (GPU) is used for simulations in this work. The preferential distributions of bubbles and their impact on local turbulence structures and their effects on turbulent kinetic energy budgets are studied. Results between an upward flow and a downward flow with the bubbles are compared. Work Supported by Continuous Casting Consortium at UIUC.

  7. Aerodynamic analysis and simulation of a twin-tail tilt-duct unmanned aerial vehicle

    NASA Astrophysics Data System (ADS)

    Abdollahi, Cyrus

    The tilt-duct vertical takeoff and landing (VTOL) concept has been around since the early 1960s; however, to date the design has never passed the research phase and development phase. Nearly 50 years later, American Dynamics Flight Systems (ADFS) is developing the AD-150, a 2,250lb weight class unmanned aerial vehicle (UAV) configured with rotating ducts on each wingtip. Unlike its predecessor, the Doak VZ-4, the AD-150 features a V tail and wing sweep -- both of which affect the aerodynamic behavior of the aircraft. Because no aircraft of this type has been built and tested, vital aerodynamic research was conducted on the bare airframe behavior (without wingtip ducts). Two weeks of static and dynamic testing were performed on a 3/10th scale model at the University of Maryland's 7' x 10' low speed wind tunnel to facilitate the construction of a nonlinear flight simulator. A total of 70 dynamic tests were performed to obtain damping parameter estimates using the ordinary least squares methodology. Validation, based on agreement between static and dynamic estimates of the pitch and yaw stiffness terms, showed an average percent error of 14.0% and 39.6%, respectively. These inconsistencies were attributed to: large dynamic displacements not encountered during static testing, regressor collinearity, and, while not conclusively proven, differences in static and dynamic boundary layer development. Overall, the damping estimates were consistent and repeatable, with low scatter over a 95% confidence interval. Finally, a basic open loop simulation was executed to demonstrate the instability of the aircraft. As a result, it is recommended that future work be performed to determine trim points and linear models for controls development.

  8. Simple vs complex congenital nasolacrimal duct obstructions: etiology, management and outcomes.

    PubMed

    Ali, Mohammad Javed; Kamal, Saurabh; Gupta, Adit; Ali, Mohammad Hasnat; Naik, Milind N

    2015-02-01

    The aim of this study was to report the comparative clinical profiles and outcomes of simple and complex congenital nasolacrimal duct obstruction (CNLDO). The study was a retrospective chart review of all patients presenting with CNLDO from a single surgeon's (M.J.A.) database. All patients underwent irrigation and probing under nasal endoscopic guidance. A detailed lacrimal system evaluation was performed, intraoperative findings including nasal endoscopy were documented, and etiologies of complex CNLDO were noted. Outcome measures were comparative profiles, and anatomical success and functional success of the interventions. Statistical analyses were performed using the Shapiro-Wilk test, Fisher's exact test, and Wilcoxon rank sum test. Ninety-five eyes of 81 patients with simple CNLDO and 100 eyes of 83 patients with complex CNLDO were compared. The mean age at presentation was 17.6 months in simple CNLDO and 45.6 months in complex cases (p < 0.001). Epiphora and discharge were the most common symptoms; 89.4% among simple cases and 92% in the complex group. The most common causes of complex CNLDO were bony obstructions (23%), craniofacial syndromes (12%), and buried probe (10%). At a mean follow-up of 5.85 months for simple CNLDO and 4.68 months for complex CNLDO, anatomical success and functional success was noted in 97.8% and 94.7%, respectively, in simple CNLDO, and in 58% and 51%, respectively, in complex CNDLO (p < 0.001). Bony obstruction, craniofacial syndrome, and buried probe were the most common reasons for a complex CNLDO, noted commonly in older children, with irrigation and probing having much poorer outcomes when compared with simpler obstructions. © 2014 ARS-AAOA, LLC.

  9. Computer-Simulation Surrogates for Optimization: Application to Trapezoidal Ducts and Axisymmetric Bodies

    NASA Technical Reports Server (NTRS)

    Otto, John C.; Paraschivoiu, Marius; Yesilyurt, Serhat; Patera, Anthony T.

    1995-01-01

    Engineering design and optimization efforts using computational systems rapidly become resource intensive. The goal of the surrogate-based approach is to perform a complete optimization with limited resources. In this paper we present a Bayesian-validated approach that informs the designer as to how well the surrogate performs; in particular, our surrogate framework provides precise (albeit probabilistic) bounds on the errors incurred in the surrogate-for-simulation substitution. The theory and algorithms of our computer{simulation surrogate framework are first described. The utility of the framework is then demonstrated through two illustrative examples: maximization of the flowrate of fully developed ow in trapezoidal ducts; and design of an axisymmetric body that achieves a target Stokes drag.

  10. Large eddy simulation of particle-laden flow in a duct with a 90° bend

    NASA Astrophysics Data System (ADS)

    Njobuenwu, D. O.; Fairweather, M.

    2011-12-01

    Large eddy simulation (LES) of particle-laden turbulent flow is studied for a square duct with a 90° bend and a radius of curvature of 1.5 times the duct width, and for a Reynolds number based on the bulk flow velocity of 100,000. A Lagrangian particle tracking technique is used to study the motion of particles experiencing drag, shear lift, buoyancy and gravitational forces in the flow. LES predictions capture important physical aspects of these flows known to occur in practice, unlike alternative Reynolds-averaged Navier-Stokes (RANS) approaches, such as flow separation in the boundary layers around the bend entrance on the concave wall of the bend, and around the bend exit on the convex wall. The LES predicted flow and particle statistics are generally in good agreement with both experimental data used for validation purposes and RANS solutions, with r.m.s. fluctuating velocity predictions from the LES in particular being superior to values derived using the RANS technique.

  11. Far-field noise and internal modes from a ducted propeller at simulated aircraft takeoff conditions

    NASA Astrophysics Data System (ADS)

    Woodward, Richard P.; Bock, Lawrence A.; Heidelberg, Laurence J.; Hall, David G.

    1992-01-01

    The ducted propeller offers structural and acoustic benefits typical of conventional turbofan engines while retaining much of the aeroacoustic benefits of the unducted propeller. A model Advanced Ducted Propeller (ADP) was tested in the NASA Lewis Low-Speed Anechoic Wind Tunnel at a simulated takeoff velocity of Mach 0.2. The ADP model was designed and manufactured by the Pratt and Whitney Division of United Technologies. The 16-blade rotor ADP was tested with 22- and 40-vane stators to achieve cut-on and cut-off criterion with respect to propagation of the fundamental rotor-stator interaction tone. Additional test parameters included three inlet lengths, three nozzle sizes, two spinner configurations, and two rotor rub strip configurations. The model was tested over a range of rotor blade setting angles and propeller axis angles-of-attack. Acoustic data were taken with a sideline translating microphone probe and with a unique inlet microphone probe which identified inlet rotating acoustic modes. The beneficial acoustic effects of cut-off were clearly demonstrated. A 5 dB fundamental tone reduction was associated with the long inlet and 40-vane sector, which may relate to inlet propeller axis angle-of-attack at rotor speeds of at least 96 percent design.

  12. PIV velocity measurements in the wake of an obstruction simulating a Taylor bubble in a duct

    SciTech Connect

    Vassallo, P.; Kumar, R.

    1997-06-01

    Mean velocity measurements in the wake of an obstruction simulating a Taylor bubble (or slug) have been obtained using Particle Image Velocimetry (PIV) in a duct. Two flow rates were established: one represented the flow behind a large gas slug rising in quiescent fluid and the other represented an idealized slug rising with a higher relative velocity, as typically found in higher void fraction churn-turbulent flow. The results indicate that, in a reference frame fixed to the slug, the flow around the sides of the slug behaves like wall bounded jets which eventually merge downstream of the slug. The ratio of wake volume to slug volume is nearly the same for both Reynolds numbers tested (i.e., 3.0 at Re = 3,628 and 2.9 at Re = 7.257) although the measurements suggest that the wake size decreases somewhat as the Reynolds number is increased.

  13. Large-Eddy Simulation of a Shock Train in a Duct with Side Walls

    NASA Astrophysics Data System (ADS)

    Morgan, Brandon; Duraisamy, Karthik; Lele, Sanjiva

    2012-11-01

    Large-eddy simulation (LES) is utilized to investigate the three-dimensionality of a shock train in a constant-area isolator model with fully resolved side walls (M∞ = 1.61, Reθ ~ 1660). Flow conditions and geometry are selected to match experimental conditions investigated by Carroll (1988); although Reynolds number is reduced to ensure adequate mesh resolution. Simulations with spanwise periodic boundary conditions are first performed, the results of which are compared to experiment and validated with a three-level grid refinement study. The same shock train interaction is then simulated in a three-dimensional, low-aspect ratio rectangular duct geometry with particular emphasis placed on characterizing secondary corner flows and the effects of these corner flows on the location and structure of the shock train. It is found, for instance, that location of the initial shock is particularly sensitive to the effects of spanwise confinement. Most significantly, it is observed that the same pressure ratio which results in a stable shock train with periodic boundary conditions may result in isolator unstart when side-wall effects are fully resolved.

  14. Intervention using a novel biodegradable hollow stent containing polylactic acid-polyprolactone-polyethylene glycol complexes against lacrimal duct obstruction disease

    PubMed Central

    Liu, Rong; Hu, Weikun; Zhang, Lei; Xiang, Nan

    2017-01-01

    Lacrimal duct obstruction disease (LDOD) is a common ophthalmologic disease. Stent implantation surgery is one of the most effective therapies. In this study, we intended to find out the satisfactory biodegradable stents containing poly-L-lactic acid-polycaprolactone-polyethylene glycol (PLLA- PCL- PEG) complexes for therapeutic application in LDOD. Stents made of PLLA- PCL- PEG complexes in various ratios, were prepared and used in vitro to determine stents with appropriate mechanical properties and shorter range of bio-degradation for study in vivo. Thirty-two rabbits were randomized into eight groups of four eyes each in advance for test in vivo. The selected stents were implanted into the left lacrimal ducts of 16 rabbits and silica gel stents as the control for the other 16 rabbits. At four points in time (1, 4, 10 and 16 weeks after the implantation), weight loss rate (WLR) of the stents was measured and analysed. To access the change of lacrimal duct, fluorescein excretion test, lacrimal duct endoscopy and histopathological testing were conducted. The stent containing PLLA: PCL6: 4+ 15%PEG was selected for study in vivo. Analysis of weight loss rate (WLR), fluorescein excretion test, lacrimal duct endoscopy and histopathological testing indicated that the selected stent was biodegradable and caused minimal stimulation and earlier tissue restoration in the lacrimal epithelium compared with the silica gel stent used as the control. The study results suggest that the PLLA: PCL6: 4+ 15% PEG stent is a satisfactory biodegradable stent as a promising alternative for therapeutic application in LDOD, which showed tissue compatibility, biodegradation and adequate mechanical intensity. PMID:28570687

  15. Intervention using a novel biodegradable hollow stent containing polylactic acid-polyprolactone-polyethylene glycol complexes against lacrimal duct obstruction disease.

    PubMed

    Zhan, Xinyuan; Guo, Xin; Liu, Rong; Hu, Weikun; Zhang, Lei; Xiang, Nan

    2017-01-01

    Lacrimal duct obstruction disease (LDOD) is a common ophthalmologic disease. Stent implantation surgery is one of the most effective therapies. In this study, we intended to find out the satisfactory biodegradable stents containing poly-L-lactic acid-polycaprolactone-polyethylene glycol (PLLA- PCL- PEG) complexes for therapeutic application in LDOD. Stents made of PLLA- PCL- PEG complexes in various ratios, were prepared and used in vitro to determine stents with appropriate mechanical properties and shorter range of bio-degradation for study in vivo. Thirty-two rabbits were randomized into eight groups of four eyes each in advance for test in vivo. The selected stents were implanted into the left lacrimal ducts of 16 rabbits and silica gel stents as the control for the other 16 rabbits. At four points in time (1, 4, 10 and 16 weeks after the implantation), weight loss rate (WLR) of the stents was measured and analysed. To access the change of lacrimal duct, fluorescein excretion test, lacrimal duct endoscopy and histopathological testing were conducted. The stent containing PLLA: PCL6: 4+ 15%PEG was selected for study in vivo. Analysis of weight loss rate (WLR), fluorescein excretion test, lacrimal duct endoscopy and histopathological testing indicated that the selected stent was biodegradable and caused minimal stimulation and earlier tissue restoration in the lacrimal epithelium compared with the silica gel stent used as the control. The study results suggest that the PLLA: PCL6: 4+ 15% PEG stent is a satisfactory biodegradable stent as a promising alternative for therapeutic application in LDOD, which showed tissue compatibility, biodegradation and adequate mechanical intensity.

  16. Effects of friction and heat conduction on sound propagation in ducts. [analyzing complex aerodynamic noise problems

    NASA Technical Reports Server (NTRS)

    Huerre, P.; Karamcheti, K.

    1976-01-01

    The theory of sound propagation is examined in a viscous, heat-conducting fluid, initially at rest and in a uniform state, and contained in a rigid, impermeable duct with isothermal walls. Topics covered include: (1) theoretical formulation of the small amplitude fluctuating motions of a viscous, heat-conducting and compressible fluid; (2) sound propagation in a two dimensional duct; and (3) perturbation study of the inplane modes.

  17. Numerical Simulation of Turbulent Bubbly Flow in a Vertical Square Duct

    NASA Astrophysics Data System (ADS)

    Vanka, Pratap; Kumar, Purushotam; Jin, Kai

    2016-11-01

    We numerically investigate the dynamics of a large number of gas bubbles in a turbulent liquid flow in a confined vertical square duct, a problem of interest to many industrial equipment. The fluid flow is simulated by Direct Numerical Simulations and the motions of the bubbles are resolved by an accurate Volume of Fluid (VOF) technique. The flow is considered periodic in the streamwise direction with an imposed pressure gradient. The surface tension force is incorporated through a Sharp Surface Force (SSF) method that is observed to generate only very small spurious velocities at the interface. The algorithm has been programmed on a multiple-GPU computer in a data parallel mode. The turbulence driven secondary flows are first ensured to agree with previous DNS/LES by other researchers. A very fine grid with 192 x 192 x 768 control volumes is used to resolve the liquid flow as well as 864 bubbles using 12 grid points across each bubble in all directions. The computations are carried out to 1.5 million time steps. It is seen that the bubbles preferentially migrate to walls, starting from a uniform layout. We present instantaneous and time mean velocities, turbulence statistics and compare them with unladen flow as well as with a bubbly flow in a planar channel.

  18. Simulations of Three-dimensional Droplet Deformation in a Square-Duct at Moderate Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Horwitz, Jeremy; Kumar, Purushotam; Vanka, Pratap

    2013-11-01

    We present results of numerical simulations of deformation of a confined droplet in a three-dimensional square-duct flow using a multiphase Lattice Boltzmann Method. We have studied the effects of capillary number, Reynolds number, and viscosity ratio on the droplet deformation characteristics. Unlike in the Stokes' limit where deformation is governed by a competition between viscous shear and interfacial tension, at higher Reynolds numbers, inertial effects play an increasingly important role. We observe that the deformation history is non-monotonic and contains an overshoot before relaxing to a steady deformed state. In contrast, the capillary number is seen to affect the magnitude of the deformation history and the time at which the peak deformation occurs. The viscosity ratio has a relatively modest effect on the magnitude of the deformation compared with the effects of Reynolds and capillary numbers. However, compared with the Reynolds number, the viscosity ratio and capillary number have a significant effect on the time to reach a steady state. University of Illinois at Urbana-Champaign, Air Conditioning and Refrigeration Center.

  19. The propagation and attenuation of complex acoustic waves in treated circular and annular ducts

    NASA Technical Reports Server (NTRS)

    Reethof, G.

    1976-01-01

    The propagation of plane waves and higher order acoustic modes in a circular multisectioned duct was studied. A unique source array consisting of two concentric rings of sources, providing phase and amplitude control in the radial, as well as circumferential direction, was developed to generate plane waves and both spinning and nonspinning higher order modes. Measurements of attenuation and radial mode shapes were taken with finite length liners between the hard wall sections of an anechoically terminated duct. Materials tested as liners included a glass fiber material and both sintered fiber metals and perforated sheet metals with a honeycomb backing. The fundamental acoustic properties of these materials were studied with emphasis on the attenuation of sound by the liners and the determination of local versus extended reaction behavior for the boundary condition. The experimental results were compared with a mathematical model for the multisectioned duct.

  20. Aircraft Ducting

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Templeman Industries developed the Ultra-Seal Ducting System, an environmental composite air duct with a 50 percent weight savings over current metallic ducting, but could not find a commercial facility with the ability to test it. Marshall Space Flight Center conducted a structural evaluation of the duct, equivalent to 86 years of take-offs and landings in an aircraft. Boeing Commercial Airplane Group and McDonnell Douglas Corporation are currently using the ducts.

  1. Effectiveness of a serpentine inlet duct flow control scheme at design and off-design simulated flight conditions

    NASA Astrophysics Data System (ADS)

    Rabe, Angela C.

    An experimental investigation was conducted in a static ground test facility to determine the flow quality of a serpentine inlet duct incorporating active flow control for several simulated flight conditions. The total pressure distortion at the aerodynamic interface plane (AIP) was then used to predict the resulting stability for a compression system. This study was conducted using a model of a compact, low observable, engine inlet duct developed by Lockheed Martin. A flow control technique using air injection through microjets at 1% of the inlet mass flow rate was developed by Lockheed Martin to improve the quality of the flow exiting the inlet duct. Both the inlet duct and the flow control technique were examined at cruise condition and off-design simulated flight conditions (angle of attack and asymmetric distortion). All of the experimental tests were run at an inlet throat Mach number of 0.55 and a resulting Reynolds number of 1.76*105 based on the hydraulic diameter at the inlet throat. For each of the flight conditions tested, the flow control scheme was found to improve the flow uniformity and reduce the inlet distortion at the AIP. For simulated cruise condition, the total pressure recovery was improved by ˜2% with the addition of flow control. For the off-design conditions of angle of attack and asymmetric distortion, the total pressure recovery was improved by 1.5% and 2% respectively. All flight conditions tested showed a reduction in circumferential distortion intensity with flow control. The cruise condition case showed reduced maximum circumferential distortion of 70% with the addition of flow control. A reduction in maximum circumferential distortion of 40% occurred for the angle of attack case with flow control, and 30% for the asymmetric distortion case with flow control. The inlet total pressure distortion was used to predict the changes in stability margin of a compression system due to design and off-design flight conditions and the

  2. Numerical simulation of a shock wave/turbulent boundary layer interaction in a duct

    NASA Technical Reports Server (NTRS)

    Yang, Wei-Li; Greber, Isaac

    1993-01-01

    A numerical investigation of the interaction of an incident oblique shock wave with a turbulent duct flow is presented. The investigation consists of solving the three-dimensional, unsteady, compressible, mass averaged Navier-Stokes equations, using an implicit finite volume, lower-upper time marching code and incorporates the three-dimensional Baldwin-Lomax turbulence model. Computed results are obtained Mach number 2.9 for a turning angle of 13 degrees and Reynolds number based on duct width of 1.36 x 10 exp 7. Under various inlet conditions, the results clearly depict the flow characteristics, including the shock geometry, the separated flow region, the wall pressure distribution, and the skin friction distribution. The findings provide a physical understanding of the three-dimensional vortex structure of the flow in a duct in which a shock wave interacts with a turbulent boundary layer. The results show that the ratio of the boundary layer thickness to the duct width is the critical parameter in determining the separation structure.

  3. Wall-modeled large-eddy simulations of shock/turbulent-boundary layer interaction in a duct

    NASA Astrophysics Data System (ADS)

    Bermejo-Moreno, Ivan; Larsson, Johan; Campo, Laura; Bodart, Julien; Helmer, David; Ham, Frank; Eaton, John K.

    2012-11-01

    We present wall-modeled LES of the interaction of an oblique shock wave and a turbulent boundary layer in a low-aspect-ratio duct, following the experiment by Campo, Helmer & Eaton, 2012. A M = 2 . 05 air stream is deflected by a small compression wedge that spans the top wall of the duct at 20°, generating an oblique shock that reflects off the turbulent boundary layer at the bottom wall. The Reynolds number of the incoming flow based on the boundary layer momentum thickness is Reθ = 6 , 500 . Simulations are performed with a control-volume-based, finite-volume solver of the filtered, compressible Navier-Stokes equations, utilizing a grid-based blend of non-dissipative central and dissipative upwind fluxes, Vreman (2004) subgrid scale model and ENO shock-capturing scheme, active only near shocks. An equilibrium wall model (Kawai and Larsson, 2012) is used. Turbulence is generated at the inflow from experimental data. Simulation results are compared to PIV data on four planes normal to the spanwise coordinate. A grid-convergence study is performed. Two heights of the compression wedge are considered, resulting in an increased strength of the interaction. Simulation results are also used to study the evolution of corner flows, complementing experimental findings. The authors acknowledge financial support provided by the USDoE under the Predictive Science Academic Alliance Program (PSAAP) at Stanford University.

  4. Numerical Simulation of Flow Through Equilateral Triangular Duct Under Constant Wall Heat Flux Boundary Condition

    NASA Astrophysics Data System (ADS)

    Kumar, Rajneesh; Kumar, Anoop; Goel, Varun

    2017-06-01

    The force convective heat transfer in an equilateral triangular duct of different wall heat flux configurations was analysed for the laminar hydro-dynamically developed and thermally developing flow by the use of finite volume method. Unstructured meshing was generated by multi-block technique and set of governing equations were discretized using second-order accurate up-wind scheme and numerically solved by SIMPLE Algorithm. For ensuring accuracy, grid independence study was also done. Numerical methodology was verified by comparing results with previous work and predicted results showed good agreement with them (within error of ±5 %). The different combinations of constant heat flux boundary condition were analysed and their effect on heat transfer and fluid flow for different Reynolds number was also studied. The results of different combinations were compared with the case of force convective heat transfer in the equilateral triangular duct with constant heat flux on all three walls.

  5. A finite element simulation of sound attenuation in a finite duct with a peripherally variable liner

    NASA Technical Reports Server (NTRS)

    Watson, W. R.

    1977-01-01

    Using multimodal analysis, a variational finite element method is presented for analyzing sound attenuation in a three-dimensional finite duct with a peripherally variable liner in the absence of flow. A rectangular element, with cubic shaped functions, is employed. Once a small portion of a peripheral liner is removed, the attenuation rate near the frequency where maximum attenuation occurs drops significantly. The positioning of the liner segments affects the attenuation characteristics of the liner. Effects of the duct termination are important in the low frequency ranges. The main effect of peripheral variation of the liner is a broadening of the attenuation characteristics in the midfrequency range. Because of matrix size limitations of the presently available computer program, the eigenvalue equations should be solved out of core in order to handle realistic sources.

  6. 2D-simulation of stationary MHD flows in the ducts of rectangular cross-section

    NASA Astrophysics Data System (ADS)

    Khalzov, Ivan; Ilgisonis, Victor

    2005-10-01

    The numerical code for a calculation of 2D stationary MHD flows of incompressible conducting viscous fluids (liquid metals) in straight and circular ducts of rectangular cross-section is developed. The flows are driven by the electrical current perpendicular both to the duct axis and to the external magnetic field. The code generalizes the well-known iterative Gauss-Seidel method for the case of systems of elliptic equations. The algorithm developed allows us to carry out the calculations of stationary flows in a wide range of Hartmann (Ha=110^3) and Reynolds (Re=110^6) numbers. The numerical results are presented for the experimental device, which is under construction in Russia.

  7. Lensing duct

    DOEpatents

    Beach, Raymond J. , Benett

    1994-01-01

    A lensing duct to condense (intensify) light using a combination of front surface lensing and reflective waveguiding. The duct tapers down from a wide input side to a narrow output side, with the input side being lens-shaped and coated with an antireflective coating for more efficient transmission into the duct. The four side surfaces are uncoated, preventing light from escaping by total internal reflection as it travels along the duct (reflective waveguiding). The duct has various applications for intensifying light, such as in the coupling of diode array pump light to solid state lasing materials, and can be fabricated from inexpensive glass and plastic.

  8. Lensing duct

    DOEpatents

    Beach, R.J.; Benett, W.J.

    1994-04-26

    A lensing duct to condense (intensify) light using a combination of front surface lensing and reflective waveguiding is described. The duct tapers down from a wide input side to a narrow output side, with the input side being lens-shaped and coated with an antireflective coating for more efficient transmission into the duct. The four side surfaces are uncoated, preventing light from escaping by total internal reflection as it travels along the duct (reflective waveguiding). The duct has various applications for intensifying light, such as in the coupling of diode array pump light to solid state lasing materials, and can be fabricated from inexpensive glass and plastic. 3 figures.

  9. Simulation Analysis of Air Flow and Turbulence Statistics in a Rib Grit Roughened Duct

    PubMed Central

    Vogiatzis, I. I.; Denizopoulou, A. C.; Ntinas, G. K.; Fragos, V. P.

    2014-01-01

    The implementation of variable artificial roughness patterns on a surface is an effective technique to enhance the rate of heat transfer to fluid flow in the ducts of solar air heaters. Different geometries of roughness elements investigated have demonstrated the pivotal role that vortices and associated turbulence have on the heat transfer characteristics of solar air heater ducts by increasing the convective heat transfer coefficient. In this paper we investigate the two-dimensional, turbulent, unsteady flow around rectangular ribs of variable aspect ratios by directly solving the transient Navier-Stokes and continuity equations using the finite elements method. Flow characteristics and several aspects of turbulent flow are presented and discussed including velocity components and statistics of turbulence. The results reveal the impact that different rib lengths have on the computed mean quantities and turbulence statistics of the flow. The computed turbulence parameters show a clear tendency to diminish downstream with increasing rib length. Furthermore, the applied numerical method is capable of capturing small-scale flow structures resulting from the direct solution of Navier-Stokes and continuity equations. PMID:25057511

  10. Simulation analysis of air flow and turbulence statistics in a rib grit roughened duct.

    PubMed

    Vogiatzis, I I; Denizopoulou, A C; Ntinas, G K; Fragos, V P

    2014-01-01

    The implementation of variable artificial roughness patterns on a surface is an effective technique to enhance the rate of heat transfer to fluid flow in the ducts of solar air heaters. Different geometries of roughness elements investigated have demonstrated the pivotal role that vortices and associated turbulence have on the heat transfer characteristics of solar air heater ducts by increasing the convective heat transfer coefficient. In this paper we investigate the two-dimensional, turbulent, unsteady flow around rectangular ribs of variable aspect ratios by directly solving the transient Navier-Stokes and continuity equations using the finite elements method. Flow characteristics and several aspects of turbulent flow are presented and discussed including velocity components and statistics of turbulence. The results reveal the impact that different rib lengths have on the computed mean quantities and turbulence statistics of the flow. The computed turbulence parameters show a clear tendency to diminish downstream with increasing rib length. Furthermore, the applied numerical method is capable of capturing small-scale flow structures resulting from the direct solution of Navier-Stokes and continuity equations.

  11. Multiscale simulation of complex coacervates

    NASA Astrophysics Data System (ADS)

    Hoffmann, Kyle Q.; Whitmer, Jonathan K.; Qin, Jian; Priftis, Dimitris; Perry, Sarah; Leon, Lorraine; Kade, Matthew; Tirrell, Matthew; de Pablo, Juan J.

    2014-03-01

    Aqueous solutions of polymers having opposite charge can separate into a coacervate phase and a supernatant water phase.The conditions leading to such behavior, including chain lenght, ionization fraction, ionic strength, molecular structure, and temperature are poorly understood. Though thermodynamic models of this phase separation exist, they offer little descriptive power for the mechanism of complex coacervation, and the internal structure of the coacervate and precipitate phases. Here we use atomic-level and coarse-grained representations of polypeptides to study features of the phase diagram, scaling relations, and microstructure of complex coacervates, comparing results to experimental data and model calculations.

  12. Scissors Duct

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Stennis Space Center engineers are preparing to conduct water tests on an updated version of the scissors duct component of the J-2X engine. Measuring about 2 feet long and about 8 inches in diameter, the duct on the J-2X predecessor, the J-2, connected its fuel turbo pumps to the flight vehicle's upper stage run tanks. According to NASA's J-2X project manager at SSC, Gary Benton, the water tests should establish the limits of the duct's ability to withstand vibration.

  13. Scissors Duct

    NASA Image and Video Library

    2007-06-26

    Stennis Space Center engineers are preparing to conduct water tests on an updated version of the scissors duct component of the J-2X engine. Measuring about 2 feet long and about 8 inches in diameter, the duct on the J-2X predecessor, the J-2, connected its fuel turbo pumps to the flight vehicle's upper stage run tanks. According to NASA's J-2X project manager at SSC, Gary Benton, the water tests should establish the limits of the duct's ability to withstand vibration.

  14. Duct closure

    DOEpatents

    Vowell, Kennison L.

    1987-01-01

    A closure for an inclined duct having an open upper end and defining downwardly extending passageway. The closure includes a cap for sealing engagement with the open upper end of the duct. Associated with the cap are an array of vertically aligned plug members, each of which has a cross-sectional area substantially conforming to the cross-sectional area of the passageway at least adjacent the upper end of the passageway. The plug members are interconnected in a manner to provide for free movement only in the plane in which the duct is inclined. The uppermost plug member is attached to the cap means and the cap means is in turn connected to a hoist means which is located directly over the open end of the duct.

  15. Molecular simulation and modeling of complex I.

    PubMed

    Hummer, Gerhard; Wikström, Mårten

    2016-07-01

    Molecular modeling and molecular dynamics simulations play an important role in the functional characterization of complex I. With its large size and complicated function, linking quinone reduction to proton pumping across a membrane, complex I poses unique modeling challenges. Nonetheless, simulations have already helped in the identification of possible proton transfer pathways. Simulations have also shed light on the coupling between electron and proton transfer, thus pointing the way in the search for the mechanistic principles underlying the proton pump. In addition to reviewing what has already been achieved in complex I modeling, we aim here to identify pressing issues and to provide guidance for future research to harness the power of modeling in the functional characterization of complex I. This article is part of a Special Issue entitled Respiratory complex I, edited by Volker Zickermann and Ulrich Brandt.

  16. Hydrogen peroxide vapour for decontaminating air-conditioning ducts and rooms of an emergency complex in northern India: time to move on.

    PubMed

    Taneja, N; Biswal, M; Kumar, A; Edwin, A; Sunita, T; Emmanuel, R; Gupta, A K; Sharma, M

    2011-07-01

    Overcrowding and patient overload in emergency services areas often mean that inadequate attention is paid to thorough cleaning, disinfection of rooms and air-conditioning ducts, which would require closing the area concerned. Over a period of time, this leads to accumulation of lint, fibre, dust and fungal growth. This study assessed the effectiveness of hydrogen peroxide fog to decontaminate the air-conditioning ducts as well as for room disinfection without having to close down the area. The Postgraduate Institute of Medical Education and Research emergency complex, Chandigarh, is distributed over three floors housing nine air-handling units (AHUs) and seven wards. The work was carried out over a period of seven days and involved cleaning of air-conditioning ducts and wards, cleaning and disinfection of fittings and furniture, vacuuming and fogging of AHU, ducts and room air. Fogging was done with 20% Ecoshield fog, a complex formulation of stabilised hydrogen peroxide 11% w/v with 0.015% w/v silver nitrate. Pre- and post-fogging samples were taken for microbiological culture, and air samples were also collected. Hydrogen peroxide fogging was highly effective for disinfection of room air, furniture and other articles. It decontaminated the air-conditioning ducts effectively, was rapid and cheaper than formalin, and no adverse effects were noted. There was minimum disturbance to the patients and the treated areas were ready to be populated again after 5-6h. Hydrogen peroxide has the advantage of being safer, less irritating, and has shorter cycle times compared with formalin fumigation which is more commonly practised in India. Copyright © 2011 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

  17. Development of simulation computer complex specification

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The Training Simulation Computer Complex Study was one of three studies contracted in support of preparations for procurement of a shuttle mission simulator for shuttle crew training. The subject study was concerned with definition of the software loads to be imposed on the computer complex to be associated with the shuttle mission simulator and the development of procurement specifications based on the resulting computer requirements. These procurement specifications cover the computer hardware and system software as well as the data conversion equipment required to interface the computer to the simulator hardware. The development of the necessary hardware and software specifications required the execution of a number of related tasks which included, (1) simulation software sizing, (2) computer requirements definition, (3) data conversion equipment requirements definition, (4) system software requirements definition, (5) a simulation management plan, (6) a background survey, and (7) preparation of the specifications.

  18. Simulation forecasts complex flow streams from Ekofisk

    SciTech Connect

    Arnes, F.C.; Lillejord, H.

    1996-10-28

    A commercial steady-state process flowsheet simulation program serves as the basis for a rigorous calculation model for predicting produced flow rates from the Ekofisk complex in the Norwegian sector of the North Sea. The complex is the center of an extensive gathering system that collects oil and gas streams from several producing fields. Prior to running a production forecast, the simulation model is initiated by matching several years of production. Once the simulation model matches historical production data within acceptable limits, it then is driven by production forecasts from reservoir simulations to develop long-term forecasts of gas, NGL, and oil production. The paper describes the Ekofisk field, the process simulation, implementation of the model, and problems encountered.

  19. Turbofan Duct Propagation Model

    NASA Technical Reports Server (NTRS)

    Lan, Justin H.; Posey, Joe W. (Technical Monitor)

    2001-01-01

    The CDUCT code utilizes a parabolic approximation to the convected Helmholtz equation in order to efficiently model acoustic propagation in acoustically treated, complex shaped ducts. The parabolic approximation solves one-way wave propagation with a marching method which neglects backwards reflected waves. The derivation of the parabolic approximation is presented. Several code validation cases are given. An acoustic lining design process for an example aft fan duct is discussed. It is noted that the method can efficiently model realistic three-dimension effects, acoustic lining, and flow within the computational capabilities of a typical computer workstation.

  20. COPASI--a COmplex PAthway SImulator.

    PubMed

    Hoops, Stefan; Sahle, Sven; Gauges, Ralph; Lee, Christine; Pahle, Jürgen; Simus, Natalia; Singhal, Mudita; Xu, Liang; Mendes, Pedro; Kummer, Ursula

    2006-12-15

    Simulation and modeling is becoming a standard approach to understand complex biochemical processes. Therefore, there is a big need for software tools that allow access to diverse simulation and modeling methods as well as support for the usage of these methods. Here, we present COPASI, a platform-independent and user-friendly biochemical simulator that offers several unique features. We discuss numerical issues with these features; in particular, the criteria to switch between stochastic and deterministic simulation methods, hybrid deterministic-stochastic methods, and the importance of random number generator numerical resolution in stochastic simulation. The complete software is available in binary (executable) for MS Windows, OS X, Linux (Intel) and Sun Solaris (SPARC), as well as the full source code under an open source license from http://www.copasi.org.

  1. Evaluation of panel code predictions with experimental results of inlet performance for a 17-inch ducted prop/fab simulator operating at Mach 0.2

    NASA Technical Reports Server (NTRS)

    Boldman, D. R.; Iek, C.; Hwang, D. P.; Jeracki, R. J.; Larkin, M.; Sorin, G.

    1991-01-01

    An axisymmetric panel code was used to evaluate a series of ducted propeller inlets. The inlets were tested in the Lewis 9 by 15 Foot Low Speed Wind Tunnel. Three basic inlets having ratios of shroud length to propeller diameter of 0.2, 0.4, and 0.5 were tested with the Pratt and Whitney ducted prop/fan simulator. A fourth hybrid inlet consisting of the shroud from the shortest basic inlet coupled with the spinner from the largest basic inlet was also tested. This later configuration represented the shortest overall inlet. The simulator duct diameter at the propeller face was 17.25 inches. The short and long spinners provided hub-to-tip ratios of 0.44 at the propeller face. The four inlets were tested at a nominal free stream Mach number of 0.2 and at angles of attack from 0 degrees to 35 degrees. The panel code method incorporated a simple two-part separation model which yielded conservative estimates of inlet separation.

  2. High Performance Computing for complex fluids simulation

    NASA Astrophysics Data System (ADS)

    Ismail, Mourad; Chabannes, Vincent; Doyeux, Vincent; Priem, Stéphane; Prud'Homme, Christophe; Feelpp Team

    2014-11-01

    In order to better understand the behavior of complex fluids in general and blood flow in particular, several models have been proposed by considering blood as a Newtonian fluid (governed by the Stokes equations or Navier-Stokes) in which are immersed deformable entities. These particles contain a second fluid of different viscosity and density from outer fluid. This context, I will present some models based on the same principle and will show its validations using some known benchmarks. I will also talk briefly about High Performance Computing in the framework of complex fluids simulations. http://www.feelpp.org/

  3. Efficiency of the confocal method of laser endomicroscopy in complex diagnoses of diseases of common bile duct

    NASA Astrophysics Data System (ADS)

    Anaskin, S. G.; Panchenkov, D. N.; Chertyuk, V. B.; Sazonov, D. V.; Zabozlayev, F. G.; Danilevskaya, O. V.; Mokshina, N. V.; Korniletsky, I. D.

    2017-01-01

    One of the more frequent manifestations of diseases of the bile ducts are its’ strictures or stenoses that could be of either malignant or benign nature. Current methods of diagnosing this pathology include computer tomography (CT) scan, magnetic resonance cholangiopancreatography (MRCP), endoscopic ultrasound (EUS) and endoscopic retrograde cholangiopancreatography (ERCP). However, these methods are not always informative, which makes this a current and topical problem. A fundamentally new method that broadens the capabilities of ERCP when diagnosing diseases of the bile duct accompanied by the development of strictures or stenoses is probe-based confocal laser endomicroscopy (pCLE). The method is based on the principle of confocal fluorescence microscopy. The most elaborate complications arise with the presence of the pre-existing pancreatobiliary pathology: pseudotumoral chronic pancreatitis, acute cholangitis, etc. Early stage cholangiocarcinoma diagnosis can be difficult (and not always possible) even with the help of modern research methods. For the timely diagnostic it is advantageous to conduct pCLE and targeted biopsy of the zone with most manifested changes. In all instances, the first use of the pCLE method for diagnostic purposes allowed us to clarify and correctly verify the diagnosis. When concerning the diseases of the bile duct, the modern stage of pCLE development can be of critical importance when other methods are not effective.

  4. Computational Aerodynamic Simulations of an 840 ft/sec Tip Speed Advanced Ducted Propulsor Fan System Model for Acoustic Methods Assessment and Development

    NASA Technical Reports Server (NTRS)

    Tweedt, Daniel L.

    2014-01-01

    Computational Aerodynamic simulations of an 840 ft/sec tip speed, Advanced Ducted Propulsor fan system were performed at five different operating points on the fan operating line, in order to provide detailed internal flow field information for use with fan acoustic prediction methods presently being developed, assessed and validated. The fan system is a sub-scale, lownoise research fan/nacelle model that has undergone extensive experimental testing in the 9- by 15- foot Low Speed Wind Tunnel at the NASA Glenn Research Center, resulting in quality, detailed aerodynamic and acoustic measurement data. Details of the fan geometry, the computational fluid dynamics methods, the computational grids, and various computational parameters relevant to the numerical simulations are discussed. Flow field results for three of the five operating conditions simulated are presented in order to provide a representative look at the computed solutions. Each of the five fan aerodynamic simulations involved the entire fan system, excluding a long core duct section downstream of the core inlet guide vane. As a result, only fan rotational speed and system bypass ratio, set by specifying static pressure downstream of the core inlet guide vane row, were adjusted in order to set the fan operating point, leading to operating points that lie on a fan operating line and making mass flow rate a fully dependent parameter. The resulting mass flow rates are in good agreement with measurement values. The computed blade row flow fields for all five fan operating points are, in general, aerodynamically healthy. Rotor blade and fan exit guide vane flow characteristics are good, including incidence and deviation angles, chordwise static pressure distributions, blade surface boundary layers, secondary flow structures, and blade wakes. Examination of the computed flow fields reveals no excessive boundary layer separations or related secondary-flow problems. A few spanwise comparisons between

  5. Small duct primary sclerosing cholangitis without inflammatory bowel disease is genetically different from large duct disease.

    PubMed

    Naess, Sigrid; Björnsson, Einar; Anmarkrud, Jarl A; Al Mamari, Said; Juran, Brian D; Lazaridis, Konstantinos N; Chapman, Roger; Bergquist, Annika; Melum, Espen; Marsh, Steven G E; Schrumpf, Erik; Lie, Benedicte A; Boberg, Kirsten M; Karlsen, Tom H; Hov, Johannes R

    2014-11-01

    Small duct primary sclerosing cholangitis (PSC) is phenotypically a mild version of large duct PSC, but it is unknown whether these phenotypes share aetiology. We aimed to characterize their relationship by investigating genetic associations in the human leucocyte antigen (HLA) complex, which represent the strongest genetic risk factors in large duct PSC. Four classical HLA loci (HLA-A, HLA-B, HLA-C and HLA-DRB1) were genotyped in 87 small duct PSC patients, 485 large duct PSC patients and 1117 controls across three geographical regions. HLA-DRB1*13:01 (OR = 2.0, 95% CI 1.2-3.4, P = 0.01) and HLA-B*08 (OR = 1.6, 95% CI 1.1-2.4, P = 0.02) were significantly associated with small duct PSC compared with healthy controls. Based on the observed frequency of HLA-B*08 in small duct PSC, the strongest risk factor in large duct PSC, an estimated 32% (95% CI 4-65%) of this population can be hypothesized to represent early stages or mild variants of large duct PSC. This subgroup may be constituted by small duct PSC patients with inflammatory bowel disease (IBD), which greatly resembled large duct PSC in its HLA association. In contrast, small duct PSC without IBD was only associated with HLA-DRB1*13:01(P = 0.03) and was otherwise distinctly dissimilar from large duct PSC. Small duct PSC with IBD resembles large duct PSC in its HLA association and may represent early stages or mild variants of large duct disease. Different HLA associations in small duct PSC without IBD could indicate that this subgroup is a different entity. HLA-DRB1*13:01 may represent a specific risk factor for inflammatory bile duct disease. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  6. Simulating Vibrations in a Complex Loaded Structure

    NASA Technical Reports Server (NTRS)

    Cao, Tim T.

    2005-01-01

    The Dynamic Response Computation (DIRECT) computer program simulates vibrations induced in a complex structure by applied dynamic loads. Developed to enable rapid analysis of launch- and landing- induced vibrations and stresses in a space shuttle, DIRECT also can be used to analyze dynamic responses of other structures - for example, the response of a building to an earthquake, or the response of an oil-drilling platform and attached tanks to large ocean waves. For a space-shuttle simulation, the required input to DIRECT includes mathematical models of the space shuttle and its payloads, and a set of forcing functions that simulates launch and landing loads. DIRECT can accommodate multiple levels of payload attachment and substructure as well as nonlinear dynamic responses of structural interfaces. DIRECT combines the shuttle and payload models into a single structural model, to which the forcing functions are then applied. The resulting equations of motion are reduced to an optimum set and decoupled into a unique format for simulating dynamics. During the simulation, maximum vibrations, loads, and stresses are monitored and recorded for subsequent analysis to identify structural deficiencies in the shuttle and/or payloads.

  7. Software for Simulating a Complex Robot

    NASA Technical Reports Server (NTRS)

    Goza, S. Michael

    2003-01-01

    RoboSim (Robot Simulation) is a computer program that simulates the poses and motions of the Robonaut a developmental anthropomorphic robot that has a complex system of joints with 43 degrees of freedom and multiple modes of operation and control. RoboSim performs a full kinematic simulation of all degrees of freedom. It also includes interface components that duplicate the functionality of the real Robonaut interface with control software and human operators. Basically, users see no difference between the real Robonaut and the simulation. Consequently, new control algorithms can be tested by computational simulation, without risk to the Robonaut hardware, and without using excessive Robonaut-hardware experimental time, which is always at a premium. Previously developed software incorporated into RoboSim includes Enigma (for graphical displays), OSCAR (for kinematical computations), and NDDS (for communication between the Robonaut and external software). In addition, RoboSim incorporates unique inverse-kinematical algorithms for chains of joints that have fewer than six degrees of freedom (e.g., finger joints). In comparison with the algorithms of OSCAR, these algorithms are more readily adaptable and provide better results when using equivalent sets of data.

  8. Toward simulating complex systems with quantum effects

    NASA Astrophysics Data System (ADS)

    Kenion-Hanrath, Rachel Lynn

    Quantum effects like tunneling, coherence, and zero point energy often play a significant role in phenomena on the scales of atoms and molecules. However, the exact quantum treatment of a system scales exponentially with dimensionality, making it impractical for characterizing reaction rates and mechanisms in complex systems. An ongoing effort in the field of theoretical chemistry and physics is extending scalable, classical trajectory-based simulation methods capable of capturing quantum effects to describe dynamic processes in many-body systems; in the work presented here we explore two such techniques. First, we detail an explicit electron, path integral (PI)-based simulation protocol for predicting the rate of electron transfer in condensed-phase transition metal complex systems. Using a PI representation of the transferring electron and a classical representation of the transition metal complex and solvent atoms, we compute the outer sphere free energy barrier and dynamical recrossing factor of the electron transfer rate while accounting for quantum tunneling and zero point energy effects. We are able to achieve this employing only a single set of force field parameters to describe the system rather than parameterizing along the reaction coordinate. Following our success in describing a simple model system, we discuss our next steps in extending our protocol to technologically relevant materials systems. The latter half focuses on the Mixed Quantum-Classical Initial Value Representation (MQC-IVR) of real-time correlation functions, a semiclassical method which has demonstrated its ability to "tune'' between quantum- and classical-limit correlation functions while maintaining dynamic consistency. Specifically, this is achieved through a parameter that determines the quantumness of individual degrees of freedom. Here, we derive a semiclassical correction term for the MQC-IVR to systematically characterize the error introduced by different choices of simulation

  9. Bile Duct Cancer (Cholangiocarcinoma)

    MedlinePlus

    ... Types of Cancer > Bile Duct Cancer (Cholangiocarcinoma) Bile Duct Cancer (Cholangiocarcinoma) This is Cancer.Net’s Guide to Bile Duct Cancer (Cholangiocarcinoma). Use the menu below to choose ...

  10. Mammary Duct Ectasia

    MedlinePlus

    ... tenderness or inflammation of the clogged duct (periductal mastitis). Mammary duct ectasia most often occurs in women ... that's turned inward (inverted) A bacterial infection called mastitis also may develop in the affected milk duct, ...

  11. Simulating Complex Window Systems using BSDF Data

    SciTech Connect

    Konstantoglou, Maria; Jonsson, Jacob; Lee, Eleanor

    2009-06-22

    Nowadays, virtual models are commonly used to evaluate the performance of conventional window systems. Complex fenestration systems can be difficult to simulate accurately not only because of their geometry but also because of their optical properties that scatter light in an unpredictable manner. Bi-directional Scattering Distribution Functions (BSDF) have recently been developed based on a mixture of measurements and modelling to characterize the optics of such systems. This paper describes the workflow needed to create then use these BSDF datasets in the Radiance lighting simulation software. Limited comparisons are made between visualizations produced using the standard ray-tracing method, the BSDF method, and that taken in a full-scale outdoor mockup.

  12. Minimum-complexity helicopter simulation math model

    NASA Technical Reports Server (NTRS)

    Heffley, Robert K.; Mnich, Marc A.

    1988-01-01

    An example of a minimal complexity simulation helicopter math model is presented. Motivating factors are the computational delays, cost, and inflexibility of the very sophisticated math models now in common use. A helicopter model form is given which addresses each of these factors and provides better engineering understanding of the specific handling qualities features which are apparent to the simulator pilot. The technical approach begins with specification of features which are to be modeled, followed by a build up of individual vehicle components and definition of equations. Model matching and estimation procedures are given which enable the modeling of specific helicopters from basic data sources such as flight manuals. Checkout procedures are given which provide for total model validation. A number of possible model extensions and refinement are discussed. Math model computer programs are defined and listed.

  13. Simulating Operation of a Complex Sensor Network

    NASA Technical Reports Server (NTRS)

    Jennings, Esther; Clare, Loren; Woo, Simon

    2008-01-01

    Simulation Tool for ASCTA Microsensor Network Architecture (STAMiNA) ["ASCTA" denotes the Advanced Sensors Collaborative Technology Alliance.] is a computer program for evaluating conceptual sensor networks deployed over terrain to provide military situational awareness. This or a similar program is needed because of the complexity of interactions among such diverse phenomena as sensing and communication portions of a network, deployment of sensor nodes, effects of terrain, data-fusion algorithms, and threat characteristics. STAMiNA is built upon a commercial network-simulator engine, with extensions to include both sensing and communication models in a discrete-event simulation environment. Users can define (1) a mission environment, including terrain features; (2) objects to be sensed; (3) placements and modalities of sensors, abilities of sensors to sense objects of various types, and sensor false alarm rates; (4) trajectories of threatening objects; (5) means of dissemination and fusion of data; and (6) various network configurations. By use of STAMiNA, one can simulate detection of targets through sensing, dissemination of information by various wireless communication subsystems under various scenarios, and fusion of information, incorporating such metrics as target-detection probabilities, false-alarm rates, and communication loads, and capturing effects of terrain and threat.

  14. Simulating the dynamics of complex plasmas.

    PubMed

    Schwabe, M; Graves, D B

    2013-08-01

    Complex plasmas are low-temperature plasmas that contain micrometer-size particles in addition to the neutral gas particles and the ions and electrons that make up the plasma. The microparticles interact strongly and display a wealth of collective effects. Here we report on linked numerical simulations that reproduce many of the experimental results of complex plasmas. We model a capacitively coupled plasma with a fluid code written for the commercial package comsol. The output of this model is used to calculate forces on microparticles. The microparticles are modeled using the molecular dynamics package lammps, which we extended to include the forces from the plasma. Using this method, we are able to reproduce void formation, the separation of particles of different sizes into layers, lane formation, vortex formation, and other effects.

  15. Simulation of complex three-dimensional flows

    NASA Technical Reports Server (NTRS)

    Diewert, G. S.; Rothmund, H. J.; Nakahashi, K.

    1985-01-01

    The concept of splitting is used extensively to simulate complex three dimensional flows on modern computer architectures. Used in all aspects, from initial grid generation to the determination of the final converged solution, splitting is used to enhance code vectorization, to permit solution driven grid adaption and grid enrichment, to permit the use of concurrent processing, and to enhance data flow through hierarchal memory systems. Three examples are used to illustrate these concepts to complex three dimensional flow fields: (1) interactive flow over a bump; (2) supersonic flow past a blunt based conical afterbody at incidence to a free stream and containing a centered propulsive jet; and (3) supersonic flow past a sharp leading edge delta wing at incidence to the free stream.

  16. FDLBM simulation of double-diffusive mixed convection of shear-thinning fluids between two-square concentric duct annuli

    NASA Astrophysics Data System (ADS)

    Kefayati, GH. R.

    2015-11-01

    Double-diffusive mixed convection of pseudoplastic fluids between two-square concentric duct annuli has been analyzed by FDLBM. Results indicate that the augmentation of Richardson number decreases heat and mass transfer. The fall of the power law index declines heat and mass transfer at Ri = 0.00062 and 0.01. The increase in the size of the adiabatic body enhances the heat and mass transfer in the lid-driven enclosure generally.

  17. Reliability of Complex Nonlinear Numerical Simulations

    NASA Technical Reports Server (NTRS)

    Yee, H. C.

    2004-01-01

    This work describes some of the procedure to ensure a higher level of confidence in the predictability and reliability (PAR) of numerical simulation of multiscale complex nonlinear problems. The focus is on relating PAR of numerical simulations with complex nonlinear phenomena of numerics. To isolate sources of numerical uncertainties, the possible discrepancy between the chosen partial differential equation (PDE) model and the real physics and/or experimental data is set aside. The discussion is restricted to how well numerical schemes can mimic the solution behavior of the underlying PDE model for finite time steps and grid spacings. The situation is complicated by the fact that the available theory for the understanding of nonlinear behavior of numerics is not at a stage to fully analyze the nonlinear Euler and Navier-Stokes equations. The discussion is based on the knowledge gained for nonlinear model problems with known analytical solutions to identify and explain the possible sources and remedies of numerical uncertainties in practical computations. Examples relevant to turbulent flow computations are included.

  18. Cost analysis of robot-assisted choledochotomy and common bile duct exploration as an option for complex choledocholithiasis.

    PubMed

    Almamar, Ahmed; Alkhamesi, Nawar A; Davies, Ward T; Schlachta, Christopher M

    2017-08-15

    The aim of this study is to evaluate the clinical outcomes and cost-effectiveness of elective, robot-assisted choledochotomy and common bile duct exploration (RCD/CBDE) compared to open surgery for ERCP refractory choledocholithiasis. A prospective database of all RCD/CBDE has been maintained since our first procedure in April 2007 though April 2016. With ethics approval, this database was compared with all contemporaneous elective open procedures (OCD/CBDE) performed since March 2005. Emergency procedures were excluded from analysis. Cost analysis was calculated using a micro-costing approach. Outcomes were analyzed on the basis of intent-to-treat. A p value of 0.05 denoted statistical significance. A total of 80 cases were performed since 2005 compromising 50 consecutive, unselected RCD/CBDE and 30 OCD/CBDE. Comparing RCD/CBDE to OCD/CBDE there were no significant differences between groups with respect to age (65 ± 20 vs. 67 ± 18 years, p = 0.09), gender (14/30 vs. 16/25 male/female, p = 0.52), ASA class or co-morbidities. The mean duration of surgery for RCD/CBDE trended longer compared to OCD/CBDE (205 ± 70 min vs. 174 ± 73 min, p = 0.08). However, there was significant reduction in postoperative complications with RCD/CBDE versus OCD/CBDE (22% vs. 56%, p = 0.002). Median hospital stay was also significantly reduced (6 vs 12 days, p = 0.01). The net overall hospital cost for RCD/CBDE was lower ($8449.88 CAD vs. $11671.2 CAD). In this single-centre, cohort study, robotic-assisted CD/CBDE for ERCP refractory common bile duct stones provides the dominating strategy of improved patient outcomes with a reduction of overall cost.

  19. Direct Numerical Simulation of Complex Turbulence

    NASA Astrophysics Data System (ADS)

    Hsieh, Alan

    Direct numerical simulations (DNS) of spanwise-rotating turbulent channel flow were conducted. The data base obtained from these DNS simulations were used to investigate the turbulence generation cycle for simple and complex turbulence. For turbulent channel flow, three theoretical models concerning the formation and evolution of sublayer streaks, three-dimensional hairpin vortices and propagating plane waves were validated using visualizations from the present DNS data. The principal orthogonal decomposition (POD) method was used to verify the existence of the propagating plane waves; a new extension of the POD method was derived to demonstrate these plane waves in a spatial channel model. The analyses of coherent structures was extended to complex turbulence and used to determine the proper computational box size for a minimal flow unit (MFU) at Rob < 0.5. Proper realization of Taylor-Gortler vortices in the highly turbulent pressure region was demonstrated to be necessary for acceptably accurate MFU turbulence statistics, which required a minimum spanwise domain length Lz = pi. A dependence of MFU accuracy on Reynolds number was also discovered and MFU models required a larger domain to accurately approximate higher-Reynolds number flows. In addition, the results obtained from the DNS simulations were utilized to evaluate several turbulence closure models for momentum and thermal transport in rotating turbulent channel flow. Four nonlinear eddy viscosity turbulence models were tested and among these, Explicit Algebraic Reynolds Stress Models (EARSM) obtained the Reynolds stress distributions in best agreement with DNS data for rotational flows. The modeled pressure-strain functions of EARSM were shown to have strong influence on the Reynolds stress distributions near the wall. Turbulent heatflux distributions obtained from two explicit algebraic heat flux models consistently displayed increasing disagreement with DNS data with increasing rotation rate. Results

  20. Fully nonlinear time-domain simulation of a backward bent duct buoy floating wave energy converter using an acceleration potential method

    NASA Astrophysics Data System (ADS)

    Lee, Kyoung-Rok; Koo, Weoncheol; Kim, Moo-Hyun

    2013-12-01

    A floating Oscillating Water Column (OWC) wave energy converter, a Backward Bent Duct Buoy (BBDB), was simulated using a state-of-the-art, two-dimensional, fully-nonlinear Numerical Wave Tank (NWT) technique. The hydrodynamic performance of the floating OWC device was evaluated in the time domain. The acceleration potential method, with a full-updated kernel matrix calculation associated with a mode decomposition scheme, was implemented to obtain accurate estimates of the hydrodynamic force and displacement of a freely floating BBDB. The developed NWT was based on the potential theory and the boundary element method with constant panels on the boundaries. The mixed Eulerian-Lagrangian (MEL) approach was employed to capture the nonlinear free surfaces inside the chamber that interacted with a pneumatic pressure, induced by the time-varying airflow velocity at the air duct. A special viscous damping was applied to the chamber free surface to represent the viscous energy loss due to the BBDB's shape and motions. The viscous damping coefficient was properly selected using a comparison of the experimental data. The calculated surface elevation, inside and outside the chamber, with a tuned viscous damping correlated reasonably well with the experimental data for various incident wave conditions. The conservation of the total wave energy in the computational domain was confirmed over the entire range of wave frequencies.

  1. Aerial Survey of Ames Research Center - Flight Simulation Complex' Flight simulators create an

    NASA Technical Reports Server (NTRS)

    1967-01-01

    Aerial Survey of Ames Research Center - Flight Simulation Complex' Flight simulators create an authentic aircraft environment by generating the appropriate physical cues that provide the sensations of flight.

  2. Duct Joining System

    DOEpatents

    Proctor, John P.

    2001-02-27

    A duct joining system for providing an air-tight seal and mechanical connection for ducts and fittings is disclosed. The duct joining system includes a flexible gasket affixed to a male end of a duct or fitting. The flexible gasket is affixed at an angle relative to normal of the male end of the duct. The female end of the other duct includes a raised bead in which the flexible gasket is seated when the ducts are properly joined. The angled flexible gasket seated in the raised bead forms an air-tight seal as well as fastens or locks the male end to the female end. Alternatively, when a flexible duct is used, a band clamp with a raised bead is clamped over the female end of the flexible duct and over the male end of a fitting to provide an air tight seal and fastened connection.

  3. Duct joining system

    DOEpatents

    Proctor, John P.; deKieffer, Robert C.

    2001-01-01

    A duct joining system for providing an air-tight seal and mechanical connection for ducts and fittings is disclosed. The duct joining system includes a flexible gasket affixed to a male end of a duct or fitting. The flexible gasket is affixed at an angle relative to normal of the male end of the duct. The female end of the other duct includes a raised bead in which the flexible gasket is seated when the ducts are properly joined. The angled flexible gasket seated in the raised bead forms an air-tight seal as well as fastens or locks the male end to the female end. Alternatively, when a flexible duct is used, a band clamp with a raised bead is clamped over the female end of the flexible duct and over the male end of a fitting to provide an air tight seal and fastened connection.

  4. Large-eddy simulation of turbulent flow and structures in a square duct roughened with perpendicular and V-shaped ribs

    NASA Astrophysics Data System (ADS)

    Fang, Xingjun; Yang, Zixuan; Wang, Bing-Chen; Tachie, Mark F.; Bergstrom, Donald J.

    2017-06-01

    In this paper, highly disturbed turbulent flows confined within a square duct with uniformly spaced V-shaped ribs mounted on one wall are investigated using large-eddy simulation (LES). Two V-shaped (6 0° and 4 5°) rib cases are studied in comparison with the perpendicular (9 0°) rib case. The LES results are validated against a set of water-channel measurement data newly acquired by the authors. The effects of different shaped ribs on turbulent flow are systematically studied in terms of the mean velocity field, turbulence statistics, and coherent structures. The results show that strong secondary flows in the pattern of a pair of large symmetrical streamwise-elongated vortices exist in all three rib cases. The impacts of rib geometry on turbulent coherent structures are investigated using vortex identifiers, temporal autocorrections, spatial two-point autocorrelations, and velocity spectra.

  5. Turbulent Flow Simulations in Complex Multilouvered Fins

    NASA Astrophysics Data System (ADS)

    Tafti, Danesh

    2000-11-01

    Air-side resistance makes up roughly 80resistance in compact heat exchangers. Multilouvered fins find widespread use in the automotive and HVAC industry for heat transfer augmentation. We will describe the computational methodology for simulating the complex three-dimensional geometry and present results at a Reynolds number of 1100 based on louver pitch and the average flow velocity. The three-dimensionality in the louver geometry occurs along the height of the fin, where the angled louver transitions to the flat landing and joins with the tube surface. The transition region is characterized by a swept leading edge and decreasing flow area between louvers. Results show the formation of spanwise vortices at the leading edge of the angled portion of the louver which convect downstream in the vicinity of the louver surface. Further there is evidence of a separate louver wake instability which interacts with the vortices shed from the leading edge. In the transition region, a high energy streamwise vortex jet is formed. The jet forms in the vicinity of the louver junction with the flat landing and is drawn under the louver in the transition region. The passage of the jet in the vicinity of the louver surface produces a high pressure stagnant zone directly under the jet with a net effect of reducing heat transfer. On the other hand, the top surface of the louver in the transition region experiences high velocities in the vicinity of the surface and exhibits much higher heat transfer coefficients than the bottom surface.

  6. Hollow lensing duct

    DOEpatents

    Beach, Raymond J.; Honea, Eric C.; Bibeau, Camille; Mitchell, Scott; Lang, John; Maderas, Dennis; Speth, Joel; Payne, Stephen A.

    2000-01-01

    A hollow lensing duct to condense (intensify) light using a combination of focusing using a spherical or cylindrical lens followed by reflective waveguiding. The hollow duct tapers down from a wide input side to a narrow output side, with the input side consisting of a lens that may be coated with an antireflective coating for more efficient transmission into the duct. The inside surfaces of the hollow lens duct are appropriately coated to be reflective, preventing light from escaping by reflection as it travels along the duct (reflective waveguiding). The hollow duct has various applications for intensifying light, such as in the coupling of diode array pump light to solid state lasing materials.

  7. Rocket-in-a-Duct Performance Analysis

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.; Reed, Brian D.

    1999-01-01

    An axisymmetric, 110 N class, rocket configured with a free expansion between the rocket nozzle and a surrounding duct was tested in an altitude simulation facility. The propellants were gaseous hydrogen and gaseous oxygen and the hardware consisted of a heat sink type copper rocket firing through copper ducts of various diameters and lengths. A secondary flow of nitrogen was introduced at the blind end of the duct to mix with the primary rocket mass flow in the duct. This flow was in the range of 0 to 10% of the primary massflow and its effect on nozzle performance was measured. The random measurement errors on thrust and massflow were within +/-1%. One dimensional equilibrium calculations were used to establish the possible theoretical performance of these rocket-in-a-duct nozzles. Although the scale of these tests was small, they simulated the relevant flow expansion physics at a modest experimental cost. Test results indicated that lower performance was obtained at higher free expansion area ratios and longer ducts, while, higher performance was obtained with the addition of secondary flow. There was a discernable peak in specific impulse efficiency at 4% secondary flow. The small scale of these tests resulted in low performance efficiencies, but prior numerical modeling of larger rocket-in-a-duct engines predicted performance that was comparable to that of optimized rocket nozzles. This remains to be proven in large-scale, rocket-in-a-duct tests.

  8. Bile Duct Diseases

    MedlinePlus

    ... gallbladder pushes the bile into tubes called bile ducts. They carry the bile to your small intestine. ... and wastes. Different diseases can block the bile ducts and cause a problem with the flow of ...

  9. Bile Duct Cancer

    MedlinePlus

    ... to diagnose bile duct cancer may include a physical exam, imaging tests of the liver and bile ducts, blood tests, and a biopsy. Treatments include surgery, radiation therapy, and chemotherapy. NIH: National Cancer Institute

  10. Bile duct stricture

    MedlinePlus

    ... occur after surgery to remove the gallbladder. Other causes of this condition include: Cancer of the bile duct, liver or pancreas Damage and scarring due to a gallstone in the bile duct Damage or scarring after ...

  11. Curved Duct Noise Prediction Using the Fast Scattering Code

    NASA Technical Reports Server (NTRS)

    Dunn, M. H.; Tinetti, Ana F.; Farassat, F.

    2007-01-01

    Results of a study to validate the Fast Scattering Code (FSC) as a duct noise predictor, including the effects of curvature, finite impedance on the walls, and uniform background flow, are presented in this paper. Infinite duct theory was used to generate the modal content of the sound propagating within the duct. Liner effects were incorporated via a sound absorbing boundary condition on the scattering surfaces. Simulations for a rectangular duct of constant cross-sectional area have been compared to analytical solutions and experimental data. Comparisons with analytical results indicate that the code can properly calculate a given dominant mode for hardwall surfaces. Simulated acoustic behavior in the presence of lined walls (using hardwall duct modes as incident sound) is consistent with expected trends. Duct curvature was found to enhance weaker modes and reduce pressure amplitude. Agreement between simulated and experimental results for a straight duct with hard walls (no flow) was excellent.

  12. Duct Flow Control System.

    DTIC Science & Technology

    is ejected under pressure tangentially of local duct surfaces through Coanda affected slots at the trailing edge of the duct from which only the...channel passages in order to modify the flow stream through the duct so as to perform certain functions such as thrust control and steerage control effects enhancing vehicle maneuverability.

  13. Blocked Tear Duct

    MedlinePlus

    Blocked tear duct Overview By Mayo Clinic Staff When you have a blocked tear duct, your tears can't drain normally, leaving you ... in the tear drainage system. A blocked tear duct is common in newborns. The condition usually gets ...

  14. Experimental evaluation of a pilot multinozzle-duct apparatus

    NASA Technical Reports Server (NTRS)

    Puster, R. L.

    1979-01-01

    A pilot multinozzle and duct were tested at ambient enthalpy to evaluate the suitability of such apparatus for testing thermal protection system panels mounted in the sidewalls of the duct downstream of the nozzle array. The flow field in the duct was complex: effects of wakes and shock waves from the nozzle dominated the flow field; the wakes continually mixed with the surrounding fluid; the boundary layer on the sidewalls of the duct was nonuniform; and near the exit of the duct the sidewall pressure variation was as much as 8.5 percent about the mean wall pressure. Starting loads on the duct walls were higher than those of a similar conventional nozzle and duct. It was concluded that the multinozzle-duct apparatus was not suitable for testing TPS panels, although the design and flow-field information should be of interest to designers of high-energy gasdynamic lasers.

  15. Comprehensive Report of Fan Performance From Duct Rake Instrumentation on 1.294 Pressure Ratio, 806 ft/sec Tip Speed Turbofan Simulator Models

    NASA Technical Reports Server (NTRS)

    Jeracki, Robert J.

    2006-01-01

    A large scale model representative of an advanced ducted propulsor-type, low-noise, very high bypass ratio turbofan engine was tested for acoustics, aerodynamic performance, and off-design operability in the NASA Glenn 9- by 15-Foot Low-Speed Wind Tunnel. The test was part of NASA s Advanced Subsonic Technology Noise Reduction Program. The low tip speed fan, nacelle, and un-powered core passage were simulated. As might be expected, the effect of stall management casing treatment was a performance penalty. Reducing the recirculating flow at the fan tip reduced the penalty while still providing sufficient stall margin. Two fans were tested with the same aerodynamic design; one with graphite composite material, and the other with solid titanium. There were surprising performance differences between the two fans, though both blades showed some indication of transitional flow near the tips. Though the pressure and temperature ratios were low for this fan design, the techniques used to improve thermocouple measurement accuracy gave repeatable data with adiabatic efficiencies agreeing within 1 percent. The measured fan adiabatic efficiency at simulated takeoff conditions was 93.7 percent and matched the design intent.

  16. Thrust control system design of ducted rockets

    NASA Astrophysics Data System (ADS)

    Chang, Juntao; Li, Bin; Bao, Wen; Niu, Wenyu; Yu, Daren

    2011-07-01

    The investigation of the thrust control system is aroused by the need for propulsion system of ducted rockets. Firstly the dynamic mathematical models of gas flow regulating system, pneumatic servo system and ducted rocket engine were established and analyzed. Then, to conquer the discussed problems of thrust control, the idea of information fusion was proposed to construct a new feedback variable. With this fused feedback variable, the thrust control system was designed. According to the simulation results, the introduction of the new fused feedback variable is valid in eliminating the contradiction between rapid response and stability for the thrust control system of ducted rockets.

  17. Stochastic Simulation of Complex Fluid Flows

    DTIC Science & Technology

    The PI has developed novel numerical algorithms and computational codes to simulate the Brownian motion of rigidparticles immersed in a viscous fluid...processes and to the design of novel nanofluid materials. Therandom Brownian motion of particles in fluid can be accounted for in fluid-structure

  18. Finite-difference theory for sound propagation in a lined duct with uniform flow using the wave envelope concept

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.

    1977-01-01

    Finite difference equations are derived for sound propagation in a two dimensional, straight, soft wall duct with a uniform flow by using the wave envelope concept. This concept reduces the required number of finite difference grid points by one to two orders of magnitude depending on the length of the duct and the frequency of the sound. The governing acoustic difference equations in complex notation are derived. An exit condition is developed that allows a duct of finite length to simulate the wave propagation in an infinitely long duct. Sample calculations presented for a plane wave incident upon the acoustic liner show the numerical theory to be in good agreement with closed form analytical theory. Complete pressure and velocity printouts are given to some sample problems and can be used to debug and check future computer programs.

  19. Chimaera simulation of complex states of flowing matter.

    PubMed

    Succi, S

    2016-11-13

    We discuss a unified mesoscale framework (chimaera) for the simulation of complex states of flowing matter across scales of motion. The chimaera framework can deal with each of the three macro-meso-micro levels through suitable 'mutations' of the basic mesoscale formulation. The idea is illustrated through selected simulations of complex micro- and nanoscale flows.This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'. © 2016 The Author(s).

  20. Chimaera simulation of complex states of flowing matter

    NASA Astrophysics Data System (ADS)

    Succi, S.

    2016-11-01

    We discuss a unified mesoscale framework (chimaera) for the simulation of complex states of flowing matter across scales of motion. The chimaera framework can deal with each of the three macro-meso-micro levels through suitable `mutations' of the basic mesoscale formulation. The idea is illustrated through selected simulations of complex micro- and nanoscale flows. This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'.

  1. Lightweight Valve Closes Duct Quickly

    NASA Technical Reports Server (NTRS)

    Fournier, Walter L.; Burgy, N. Frank

    1991-01-01

    Expanding balloon serves as lightweight emergency valve to close wide duct. Uninflated balloon stored in housing of duct. Pad resting on burst diaphragm protects balloon from hot gases in duct. Once control system triggers valve, balloon inflates rapidly to block duct. Weighs much less than does conventional butterfly, hot-gas, or poppet valve capable of closing duct of equal diameter.

  2. Lightweight Valve Closes Duct Quickly

    NASA Technical Reports Server (NTRS)

    Fournier, Walter L.; Burgy, N. Frank

    1991-01-01

    Expanding balloon serves as lightweight emergency valve to close wide duct. Uninflated balloon stored in housing of duct. Pad resting on burst diaphragm protects balloon from hot gases in duct. Once control system triggers valve, balloon inflates rapidly to block duct. Weighs much less than does conventional butterfly, hot-gas, or poppet valve capable of closing duct of equal diameter.

  3. Designing Better Scaffolding in Teaching Complex Systems with Graphical Simulations

    ERIC Educational Resources Information Center

    Li, Na

    2013-01-01

    Complex systems are an important topic in science education today, but they are usually difficult for secondary-level students to learn. Although graphic simulations have many advantages in teaching complex systems, scaffolding is a critical factor for effective learning. This dissertation study was conducted around two complementary research…

  4. Designing Better Scaffolding in Teaching Complex Systems with Graphical Simulations

    ERIC Educational Resources Information Center

    Li, Na

    2013-01-01

    Complex systems are an important topic in science education today, but they are usually difficult for secondary-level students to learn. Although graphic simulations have many advantages in teaching complex systems, scaffolding is a critical factor for effective learning. This dissertation study was conducted around two complementary research…

  5. A molecular simulation study on salt response of polyelectrolyte complexes

    NASA Astrophysics Data System (ADS)

    Antila, Hanne; van Tassel, Paul; Sammalkorpi, Maria

    2015-03-01

    In aqueous solutions, oppositely charged polymers, polyelectrolytes (PEs) form complexes which are known to be sensitive to added salt with responses ranging from shrinking to full destabilization of the complex. As a specific application of PE complexes, the complex formation of DNA with polycations has been demonstrated to be an effective means of transfecting genetic material in gene therapy. We use all-atom molecular dynamics and coarse-grained Monte Carlo simulations to investigate the effect of excess salt on DNA-polycation complex stability. The detailed all-atom simulations demonstrate the mechanism of polycation and ion species specific salt-driven dissociation involving charge reversal. More generally, other possible mechanisms of salt driven dissociation exist as well. The coarse grained approach, which describes the PE complex as oppositely charged, rigid rods and ions as hard spheres, provides a more complete understanding of PE interactions in salt, and suggests possible mechanisms leading to repulsion between the oppositely charged polyelectrolytes.

  6. Geomechanical numerical simulations of complex geologic structures

    SciTech Connect

    Arguello, J.G.; Stone, C.M.; Lorenz, J.C.

    1996-05-01

    Ability to predict mechanical response of rock in three dimensions over the spatial and time scales of geologic interest would give the oil and gas industry the ability to reduce risk on prospects, improve pre-project initial reserve estimates, and lower operating costs. A program has recently been initiated, under the auspices of the Advanced Computational Technology Initiative (ACTI), to achieve such a computational technology breakthrough by adapting the unique advanced quasistatic finite element technology developed by Sandia to the mechanics applications important to exploration and production activities within the oil and gas industry. As a precursor to that program, in an effort to evaluate the feasibility of the approach, several complex geologic structures of interest were analyzed with the existing two-dimensional quasistatic finite element code, SANTOS, developed at Sandia. Examples are presented and discussed.

  7. Simulation and display of macromolecular complexes

    NASA Technical Reports Server (NTRS)

    Nir, S.; Garduno, R.; Rein, R.; Macelroy, R. D.

    1977-01-01

    In association with an investigation of the interaction of proteins with DNA and RNA, an interactive computer program for building, manipulating, and displaying macromolecular complexes has been designed. The system provides perspective, planar, and stereoscopic views on the computer terminal display, as well as views for standard and nonstandard observer locations. The molecule or its parts may be rotated and/or translated in any direction; bond connections may be added or removed by the viewer. Molecular fragments may be juxtaposed in such a way that given bonds are aligned, and given planes and points coincide. Another subroutine provides for the duplication of a given unit such as a DNA or amino-acid base.

  8. Advanced Duct Sealing Testing

    SciTech Connect

    Sherman, Max H.; Walker, Iain S.

    2003-08-01

    Duct leakage has been identified as a major source of energy loss in residential buildings. Most duct leakage occurs at the connections to registers, plenums or branches in the duct system. At each of these connections a method of sealing the duct system is required. Typical sealing methods include tapes or mastics applied around the joints in the system. Field examinations of duct systems have typically shown that these seals tend to fail over extended periods of time. The Lawrence Berkeley National Laboratory has been testing sealant durability for several years. Typical duct tape (i.e. fabric backed tapes with natural rubber adhesives) was found to fail more rapidly than all other duct sealants. This report summarizes the results of duct sealant durability testing of five UL 181B-FX listed duct tapes (three cloth tapes, a foil tape and an Oriented Polypropylene (OPP) tape). One of the cloth tapes was specifically developed in collaboration with a tape manufacturer to perform better in our durability testing. The first test involved the aging of common ''core-to-collar joints'' of flexible duct to sheet metal collars, and sheet metal ''collar-to-plenum joints'' pressurized with 200 F (93 C) air. The second test consisted of baking duct tape specimens in a constant 212 F (100 C) oven following the UL 181B-FX ''Temperature Test'' requirements. Additional tests were also performed on only two tapes using sheet metal collar-to-plenum joints. Since an unsealed flexible duct joint can have a variable leakage depending on the positioning of the flexible duct core, the durability of the flexible duct joints could not be based on the 10% of unsealed leakage criteria. Nevertheless, the leakage of the sealed specimens prior to testing could be considered as a basis for a failure criteria. Visual inspection was also documented throughout the tests. The flexible duct core-to-collar joints were inspected monthly, while the sheet metal collar-to-plenum joints were inspected

  9. Duct Tape Durability Testing

    SciTech Connect

    Sherman, Max H.; Walker, Iain S.

    2004-04-01

    Duct leakage is a major source of energy loss in residential buildings. Most duct leakage occurs at the connections to registers, plenums, or branches in the duct system. At each of these connections, a method of sealing the duct system is required. Typical sealing methods include tapes or mastics applied around the joints in the system. Field examinations of duct systems have shown that taped seals tend to fail over extended periods of time. The Lawrence Berkeley National Laboratory (LBNL) has been testing sealant durability for several years using accelerated test methods and found that typical duct tape (i.e., cloth-backed tapes with natural rubber adhesives) fails more rapidly than other duct sealants. This report summarizes the results of duct sealant durability testing over two years for four UL 181B-FX listed duct tapes (two cloth tapes, a foil tape and an Oriented Polypropylene (OPP) tape). One of the cloth tapes was specifically developed in collaboration with a tape manufacturer to perform better in our durability testing. The tests involved the aging of common ''core-to-collar joints'' of flexible duct to sheet metal collars. Periodic air leakage tests and visual inspection were used to document changes in sealant performance. After two years of testing, the flex-to-collar connections showed little change in air leakage, but substantial visual degradation from some products. A surprising experimental result was failure of most of the clamps used to mechanically fasten the connections. This indicates that the durability of clamps also need to be addressed ensure longevity of the duct connection. An accelerated test method developed during this study has been used as the basis for an ASTM standard (E2342-03).

  10. Hybrid functionals for simulating complex oxides

    NASA Astrophysics Data System (ADS)

    Franchini, Cesare

    Hybrid functionals are a class of exchange-correlation (XC) functionals in density functional theory (DFT) that are constructed by a suitable mixing of local/semi-local XC functionals (LDA/GGA) with a certain portion of the exact Hartree-Fock exchange. After being used for years in the chemistry community for studying molecular properties, hybrid functionals are being increasingly widely used for solid state problems, for which standard LDA/GGA approximations provide a defective description. In particular, hybrid functionals appear to account well for the complicated coupling between lattice, charge and spin degrees of freedom in transition metal oxides, a class of materials that has recently attracted a lot of interest due to its technological relevance (all-oxides electronics), the large spectrum of functionalities, and the many challenging issues related to strong electronic correlation. The purpose of this talk is to present the essential ideas and physical picture of hybrid functionals and to present a map of recent applications to complex oxides aiming to cover an ample spectra of cases (sp , 3 d, 4 d and 5 d compounds) and to discuss an extended array of physical phenomena including: metal-to-insulator transitions, electron localization, bandgap prediction, polarons, multiferroism, and spin-orbit coupling.

  11. Numerical Simulation of Complex Turbomachinery Flows

    NASA Technical Reports Server (NTRS)

    Chernobrovkin, A. A.; Lakshiminarayana, B.

    1999-01-01

    An unsteady, multiblock, Reynolds Averaged Navier Stokes solver based on Runge-Kutta scheme and Pseudo-time step for turbo-machinery applications was developed. The code was validated and assessed against analytical and experimental data. It was used to study a variety of physical mechanisms of unsteady, three-dimensional, turbulent, transitional, and cooling flows in compressors and turbines. Flow over a cylinder has been used to study effects of numerical aspects on accuracy of prediction of wake decay and transition, and to modify K-epsilon models. The following simulations have been performed: (a) Unsteady flow in a compressor cascade: Three low Reynolds number turbulence models have been assessed and data compared with Euler/boundary layer predictions. Major flow features associated with wake induced transition were predicted and studied; (b) Nozzle wake-rotor interaction in a turbine: Results compared to LDV data in design and off-design conditions, and cause and effect of unsteady flow in turbine rotors were analyzed; (c) Flow in the low-pressure turbine: Assessed capability of the code to predict transitional, attached and separated flows at a wide range of low Reynolds numbers and inlet freestream turbulence intensity. Several turbulence and transition models have been employed and comparisons made to experiments; (d) leading edge film cooling at compound angle: Comparisons were made with experiments, and the flow physics of the associated vortical structures were studied; and (e) Tip leakage flow in a turbine. The physics of the secondary flow in a rotor was studied and sources of loss identified.

  12. Loft duct project report

    SciTech Connect

    Reed, J.R.

    1993-06-01

    On October 16, 1992, during a routine examination of the loft of Building 332, the Building Coordinator observed cracks in the welds of the duct work that services the fume hoods for Rooms 1313, 1321, and 1329. Further examination revealed cracks in the weld of the duct work that services the gloveboxes in Rooms 1321 and 1329. Upon discovery of the cracked welds, facility management immediately took the following two actions: Because one crack in the fume hood exhaust extended 70% around the duct circumference, a 1-ton chain fall was used to secure the duct to the roof support structure to prevent the duct from falling if the duct completely fractured. The Facility Manager suspended plutonium handling operations in the gloveboxes and work in the fume hoods in the affected rooms until the situation could be thoroughly investigated. Building 332 is ventilated by drawing conditioned air from the building hallways into the laboratories, hoods, and gloveboxes. This air is filtered through two sets of high-efficiency particulate air (HEPA) filters before being exhausted from the facility. Figure 1 is a schematic of the typical air flow pattern for the facility. All affected duct work is located in the loft of the facility or pressure zone 4. This ducting is fabricated from 12-, 14- and 16-gauge, 304 stainless-steel sheet stock and joined by the Gas Tungsten Arc Welding (GTAW) process.

  13. Ducted auroral kilometric radiation

    NASA Technical Reports Server (NTRS)

    Calvert, W.

    1982-01-01

    Certain discrete, intense wave signals attributed to auroral kilometric radiation (AKR) were observed with ISEE-l while it was within the plasmaspheric shadow zone for direct propagation. It is believed that wave ducting by thin depletions of the plasma density aligned with the magnetic field accounts for such signals, and that their discrete nature is caused by the satellite intercepting individual ducts. These ducts, which were also observed as coincident decreases of the upper hybrid resonance frequency, appeared to be twenty-percent depletions roughly one hundred kilometers across. The AKR, which is emitted approximately perpendicular to the magnetic field, apparently entered these ducts equatorward of the source after the waves had been refracted parallel to the duct axis. A diffuse background was also observed which is consistent with the leakage from similar ducts at lower L-values. These observations establish the existence of ducted AKR, its signature on the satellite wave spectrograms, and new evidence for depletion ducts within the plasmasphere.

  14. Simulation of complex phenomena in optical fibres

    NASA Astrophysics Data System (ADS)

    Allington-Smith, Jeremy; Murray, Graham; Lemke, Ulrike

    2012-12-01

    Optical fibres are essential for many types of highly multiplexed and precision spectroscopy. The success of the new generation of multifibre instruments under construction to investigate fundamental problems in cosmology, such as the nature of dark energy, requires accurate modellization of the fibre system to achieve their signal-to-noise ratio (SNR) goals. Despite their simple construction, fibres exhibit unexpected behaviour including non-conservation of etendue (focal ratio degradation, FRD) and modal noise. Furthermore, new fibre geometries (non-circular or tapered) have become available to improve the scrambling properties that, together with modal noise, limit the achievable SNR in precision spectroscopy. These issues have often been addressed by extensive tests on candidate fibres and their terminations, but these are difficult and time-consuming. Modelling by ray tracing and wave analysis is possible with commercial software packages, but these do not address the more complex features, in particular FRD. We use a phase-tracking ray-tracing method to provide a practical description of FRD derived from our previous experimental work on circular fibres and apply it to non-standard fibres. This allows the relationship between scrambling and FRD to be quantified for the first time. We find that scrambling primarily affects the shape of the near-field pattern but has negligible effect on the barycentre. FRD helps to homogenize the near-field pattern but does not make it completely uniform. Fibres with polygonal cross-section improve scrambling without amplifying the FRD. Elliptical fibres, in conjunction with tapering, may offer an efficient means of image slicing to improve the product of resolving power and throughput, but the result is sensitive to the details of illumination. We also investigated the performance of fibres close to the limiting numerical aperture since this may affect the uniformity of the SNR for some prime focus fibre instrumentation.

  15. Thermal performance of residential duct systems in basements

    SciTech Connect

    Treidler, B.; Modera, M.

    1994-02-01

    There are many unanswered questions about the typical effects of duct system operation on the infiltration rates and energy usage of single- family residences with HVAC systems in their basements. In this paper, results from preliminary field studies and computer simulations are used to examine the potential for improvements in efficiency of air distribution systems in such houses. The field studies comprise thermal and flow measurements on four houses in Maryland. The houses were found to have significant envelope leakage, duct leakage, and duct conduction losses. Simulations of a basement house, the characteristics of which were chosen from the measured houses, were performed to assess the energy savings potential for basement house. The simulations estimate that a nine percent reduction in space conditioning energy use is obtained by sealing eighty percent of the duct leaks and insulating ducts to an R-value of 0.88 {degree}C{center_dot}m{sup 2}/W (5{degree}F{center_dot}ft{sup 2}{center_dot}h/BTU) where they are exposed in the basement. To determine the maximum possible reduction m energy use, simulations were run with all ducts insulated to 17.6 {degree}C{center_dot}m{sup 2}/W (100 {degree}F{center_dot}ft{sup 2}{center_dot}h/BTU) and with no duct leakage. A reduction of energy use by 14% is obtained by using perfect ducts instead of nominal ducts.

  16. Simulation and analysis of complex human tasks for manufacturing

    NASA Astrophysics Data System (ADS)

    Badler, Norman I.; Becket, Welton M.; Webber, Bonnie L.

    1995-11-01

    We discuss how the combination of a realistic human figure with a high-level behavioral control interface allow the construction of detailed simulations of humans performing manual tasks from which inferences about human performance requirements can be made. The Jack human modeling environment facilitates the real-time simulation of humans performing sequences of tasks such as walking, lifting, reaching, and grasping in a complex simulation environment. Analysis capabilities include strength, reachability, and visibility; moreover results from these tests can affect an unfolding simulation.

  17. Low loss duct burner

    SciTech Connect

    Mar, H. M.; Reider, S. B.

    1985-07-09

    A jet propulsion engine with a fan bypass duct includes a duct burner with a plurality of flame stabilizers therein each mounted to inner case and outer case members through spherical bearings. Each of the stabilizers consists of two blade members having integral arms thereon actuated by fore and aft motion of an external actuating ring to assume an expanded position to increase duct turbulence for mixing air flow therethrough with a fuel supply and into a retracted position against each other to reduce pressure drop under nonafterburning operation. Each of the flame stabilizer blades has a platform that controls communication between a hot air source and a duct for improving fuel vaporization during afterburner operation thereby to increase afterburning limits; the platforms close communication between the hot air source and the duct during nonafterburning operation when flame stabilization is not required.

  18. Complex Organics from Laboratory Simulated Interstellar Ices

    NASA Technical Reports Server (NTRS)

    Dworkin, J. P.

    2003-01-01

    Many of the volatiles in interstellar dense clouds exist in ices surrounding dust grains. The low temperatures of these ices (T < 50 K) preclude most chemical reactions, but photolysis can drive reactions that produce a suite of new species, many of which are complex organics. We study the UV and proton radiation processing of interstellar ice analogs to explore links between interstellar chemistry, the organics in comets and meteorites, and the origin of life on Earth. The high D/H ratios in some interstellar species, and the knowledge that many of the organics in primitive meteorites are D-enriched, suggest that such links are plausible. Once identified, these species may serve as markers of interstellar heritage of cometary dust and meteorites. Of particular interest are our findings that UV photolysis of interstellar ice analogs produce molecules of importance in current living organisms, including quinones, amphiphiles, and amino acids. Quinones are essential in vital metabolic roles such as electron transport. Studies show that quinones should be made wherever polycyclic aromatic hydrocarbons are photolyzed in interstellar ices. In the case of anthracene-containing ices, we have observed the production of 9-anthrone and 9,10 anthraquinone, both of which have been observed in the Murchison meteorite. Amphiphiles are also made when mixed molecular ices are photolyzed. These amphiphiles self-assemble into fluorescent vesicles when placed in liquid water, as do Murchison extracts. Both have the ability to trap an ionic dye. Photolysis of plausible ices can also produce alanine, serine, and glycine as well as a number of small alcohols and amines. Flash heating of the room temperature residue generated by such experiments generates mass spectral distributions similar to those of IDPs. The detection of high D/H ratios in some interstellar molecular species, and the knowledge that many of the organics, such as hydroxy and amino acids, in primitive meteorites are D

  19. Complex Organics from Laboratory Simulated Interstellar Ices

    NASA Technical Reports Server (NTRS)

    Dworkin, J. P.

    2003-01-01

    Many of the volatiles in interstellar dense clouds exist in ices surrounding dust grains. The low temperatures of these ices (T < 50 K) preclude most chemical reactions, but photolysis can drive reactions that produce a suite of new species, many of which are complex organics. We study the UV and proton radiation processing of interstellar ice analogs to explore links between interstellar chemistry, the organics in comets and meteorites, and the origin of life on Earth. The high D/H ratios in some interstellar species, and the knowledge that many of the organics in primitive meteorites are D-enriched, suggest that such links are plausible. Once identified, these species may serve as markers of interstellar heritage of cometary dust and meteorites. Of particular interest are our findings that UV photolysis of interstellar ice analogs produce molecules of importance in current living organisms, including quinones, amphiphiles, and amino acids. Quinones are essential in vital metabolic roles such as electron transport. Studies show that quinones should be made wherever polycyclic aromatic hydrocarbons are photolyzed in interstellar ices. In the case of anthracene-containing ices, we have observed the production of 9-anthrone and 9,10 anthraquinone, both of which have been observed in the Murchison meteorite. Amphiphiles are also made when mixed molecular ices are photolyzed. These amphiphiles self-assemble into fluorescent vesicles when placed in liquid water, as do Murchison extracts. Both have the ability to trap an ionic dye. Photolysis of plausible ices can also produce alanine, serine, and glycine as well as a number of small alcohols and amines. Flash heating of the room temperature residue generated by such experiments generates mass spectral distributions similar to those of IDPs. The detection of high D/H ratios in some interstellar molecular species, and the knowledge that many of the organics, such as hydroxy and amino acids, in primitive meteorites are D

  20. Ranking important nodes in complex networks by simulated annealing

    NASA Astrophysics Data System (ADS)

    Sun, Yu; Yao, Pei-Yang; Wan, Lu-Jun; Shen, Jian; Zhong, Yun

    2017-02-01

    In this paper, based on simulated annealing a new method to rank important nodes in complex networks is presented. First, the concept of an importance sequence (IS) to describe the relative importance of nodes in complex networks is defined. Then, a measure used to evaluate the reasonability of an IS is designed. By comparing an IS and the measure of its reasonability to a state of complex networks and the energy of the state, respectively, the method finds the ground state of complex networks by simulated annealing. In other words, the method can construct a most reasonable IS. The results of experiments on real and artificial networks show that this ranking method not only is effective but also can be applied to different kinds of complex networks. Project supported by the National Natural Science Foundation of China (Grant No. 61573017) and the Natural Science Foundation of Shaanxi Province, China (Grant No. 2016JQ6062).

  1. Development testing of throttleable ducted rockets

    NASA Astrophysics Data System (ADS)

    Besser, Hans-Ludwig

    1992-09-01

    Throttleability, being a current requirement for modern air-breathing missile propulsion systems, adds considerable complexity to the development of ducted rockets. Problems are especially inherent in the development of the following: (1) pressure sensitive propellants; (2) hot gas valves (especially for particle laden flow); and (3) ramcombustors featuring high performance over widely varying operating conditions. The use of propellant ingredients with high heating value but unfavorable combustion characteristics, like boron, is an additional challenge in the development of high energy ducted rocket systems. Extensive testing and a well conceived test philosophy are needed to achieve satisfactory development results. MBB, together with its subsidiary Bayem-Chemie, has been engaged in the field of throttleable ducted rockets for more than a decade. This paper summarizes test procedures which were established to address the strongly interrelated development problems and presents examples of test results derived from the development of a ducted rocket engine for a supersonic antiship missile.

  2. A phased approach to enable hybrid simulation of complex structures

    NASA Astrophysics Data System (ADS)

    Spencer, Billie F.; Chang, Chia-Ming; Frankie, Thomas M.; Kuchma, Daniel A.; Silva, Pedro F.; Abdelnaby, Adel E.

    2014-08-01

    Hybrid simulation has been shown to be a cost-effective approach for assessing the seismic performance of structures. In hybrid simulation, critical parts of a structure are physically tested, while the remaining portions of the system are concurrently simulated computationally, typically using a finite element model. This combination is realized through a numerical time-integration scheme, which allows for investigation of full system-level responses of a structure in a cost-effective manner. However, conducting hybrid simulation of complex structures within large-scale testing facilities presents significant challenges. For example, the chosen modeling scheme may create numerical inaccuracies or even result in unstable simulations; the displacement and force capacity of the experimental system can be exceeded; and a hybrid test may be terminated due to poor communication between modules (e.g., loading controllers, data acquisition systems, simulation coordinator). These problems can cause the simulation to stop suddenly, and in some cases can even result in damage to the experimental specimens; the end result can be failure of the entire experiment. This study proposes a phased approach to hybrid simulation that can validate all of the hybrid simulation components and ensure the integrity large-scale hybrid simulation. In this approach, a series of hybrid simulations employing numerical components and small-scale experimental components are examined to establish this preparedness for the large-scale experiment. This validation program is incorporated into an existing, mature hybrid simulation framework, which is currently utilized in the Multi-Axial Full-Scale Sub-Structuring Testing and Simulation (MUST-SIM) facility of the George E. Brown Network for Earthquake Engineering Simulation (NEES) equipment site at the University of Illinois at Urbana-Champaign. A hybrid simulation of a four-span curved bridge is presented as an example, in which three piers are

  3. Complexity and significance in computer simulations of physiological systems.

    PubMed

    Kootsey, J M

    1987-06-01

    Complexity in a theoretical model may or may not be associated with a high level of arbitrariness, depending on how the model is constructed. In this paper I use examples from cardiac electrophysiology to illustrate two techniques for maintaining significance in complex simulations. First, the approaches of analysis and synthesis are compared as methods of constructing models of complex systems. When a model is constructed by synthesis of known principles, facts, and subunits, it may have any degree of complexity without losing significance; the same is not true for analysis models. Significance can also be maintained by assembling a limited model to test a specific hypothesis of mechanism.

  4. Entropy and enthalpy of polyelectrolyte complexation: Langevin dynamics simulations.

    PubMed

    Ou, Zhaoyang; Muthukumar, M

    2006-04-21

    We report a systematic study by Langevin dynamics simulation on the energetics of complexation between two oppositely charged polyelectrolytes of same charge density in dilute solutions of a good solvent with counterions and salt ions explicitly included. The enthalpy of polyelectrolyte complexation is quantified by comparisons of the Coulomb energy before and after complexation. The entropy of polyelectrolyte complexation is determined directly from simulations and compared with that from a mean-field lattice model explicitly accounting for counterion adsorption. At weak Coulomb interaction strengths, e.g., in solvents of high dielectric constant or with weakly charged polyelectrolytes, complexation is driven by a negative enthalpy due to electrostatic attraction between two oppositely charged chains, with counterion release entropy playing only a subsidiary role. In the strong interaction regime, complexation is driven by a large counterion release entropy and opposed by a positive enthalpy change. The addition of salt reduces the enthalpy of polyelectrolyte complexation by screening electrostatic interaction at all Coulomb interaction strengths. The counterion release entropy also decreases in the presence of salt, but the reduction only becomes significant at higher Coulomb interaction strengths. More significantly, in the range of Coulomb interaction strengths appropriate for highly charged polymers in aqueous solutions, complexation enthalpy depends weakly on salt concentration and counterion release entropy exhibits a large variation as a function of salt concentration. Our study quantitatively establishes that polyelectrolyte complexation in highly charged Coulomb systems is of entropic origin.

  5. Applying Integrative Learning Strategies and Complexity Theory to Design Simulations for Care of Complex Patients.

    PubMed

    Dunn, Karen S; Riley-Doucet, Cheryl K

    Nurse educators use a variety of clinical simulation strategies to promote cognitive, psychomotor, and affective learning. Statistically significant increases in self-confidence levels were found among senior-level nursing students in the assessment and management of medical and psychiatric symptoms after participating in strategically designed, complex, student-led clinical simulations. Having students role play simulation scenarios that are developed from real-life clinical experiences is a cost-effective interactive strategy that enhances their communication and technical skills.

  6. Large-Eddy Simulation of turbine wake in complex terrain

    NASA Astrophysics Data System (ADS)

    Berg, J.; Troldborg, N.; Sørensen, N. N.; Patton, E. G.; Sullivan, P. P.

    2017-05-01

    We present Large-Eddy Simulation results of a turbine wake in realistic complex terrain with slopes above 0.5. By comparing simulations including and without the wind turbine we can estimate the induction factor, a, and we show how the presence of a strong recirculation zone in the terrain dictates the positioning of the wake. This last finding is in contrast to what would happen in gentle terrain with no substantial increase of turbulent kinetic energy in the terrain induced wakes.

  7. Cystic duct carcinoma mimicking a middle bile duct tumour

    PubMed Central

    Francisco, Elsa; Mendes, Miguel; Vale, Sílvio; Esteves, Joana

    2015-01-01

    Cystic duct carcinoma was defined by Farrar as a tumour restricted to the cystic duct, making it a rare disease. The authors describe a case of a cystic duct carcinoma that fulfils Farrar’s strict diagnostic criteria and that became clinically relevant by compressing the common hepatic duct, thus causing cholestasis. A cholecystectomy was performed with en bloc resection of the cystic and extrahepatic bile duct with a regional lymphadenectomy. PMID:25819819

  8. Simulating complex ion channel kinetics with IonChannelLab

    PubMed Central

    Covarrubias, Manuel; Sánchez-Rodríguez, Jorge E; Perez-Cornejo, Patricia; Arreola, Jorge

    2010-01-01

    In-silico simulation based on Markov chains is a powerful way to describe and predict the activity of many transport proteins including ion channels. However, modeling and simulation using realistic models of voltage- or ligand-gated ion channels exposed to a wide range of experimental conditions require building complex kinetic schemes and solving complicated differential equations. To circumvent these problems, we developed IonChannelLab a software tool that includes a user-friendly Graphical User Interface and a simulation library. This program supports channels with Ohmic or Goldman-Hodgkin-Katz behavior and can simulate the time-course of ionic and gating currents, single channel behavior and steady-state conditions. The program allows the simulation of experiments where voltage, ligand and ionic concentration are varied independently or simultaneously. PMID:20935453

  9. Quantum simulations of small electron-hole complexes

    SciTech Connect

    Lee, M.A.; Kalia, R.K.; Vashishta, P.D.

    1984-09-01

    The Green's Function Monte Carlo method is applied to the calculation of the binding energies of electron-hole complexes in semiconductors. The quantum simulation method allows the unambiguous determination of the ground state energy and the effects of band anisotropy on the binding energy. 22 refs., 1 fig.

  10. Complex Equilibria Changing in Photochemical Reaction: Computerized Evaluation and Simulation.

    ERIC Educational Resources Information Center

    Horvath, Otto; Papp, Sandor

    1988-01-01

    States that if photochemical reactions can be followed spectrophotometrically, reactivities can be estimated by evaluating data from only one curve. Studies such a system using computerized evaluation and simulation. Uses chlorocuprate(II) complexes in acetonitrile solutions for the model systems. (MVL)

  11. Complex Equilibria Changing in Photochemical Reaction: Computerized Evaluation and Simulation.

    ERIC Educational Resources Information Center

    Horvath, Otto; Papp, Sandor

    1988-01-01

    States that if photochemical reactions can be followed spectrophotometrically, reactivities can be estimated by evaluating data from only one curve. Studies such a system using computerized evaluation and simulation. Uses chlorocuprate(II) complexes in acetonitrile solutions for the model systems. (MVL)

  12. Physical Simulation of Investment Casting of Complex Shape Parts

    NASA Astrophysics Data System (ADS)

    Rahimian, Mehdi; Milenkovic, Srdjan; Maestro, Laura; De Azua, Aitor Eguidazu Ruiz; Sabirov, Ilchat

    2015-05-01

    Development of investment casting process has been a challenge for manufacturers of complex shape parts. Numerous experimental casting trials are typically carried out to determine the optimum casting parameters for fabrication of high-quality products. In this work, it is demonstrated that physical simulation of investment casting can successfully predict microstructure and hardness in as-cast complex shape parts. The physical simulation tool consists of a thermal model and melting/solidification experiments in thermo-mechanical simulator. The thermal model is employed to predict local cooling rate during solidification at each point of a casting. Melting/solidification experiments are carried out under controlled cooling rates estimated by the thermal model. Microstructural and mechanical characterization of the solidified specimens is performed; the obtained results predict the local microstructure and mechanical properties of the casting. This concept is applied to investment casting of complex shape nozzle guide vanes from Mar-M247 Ni-based superalloy. Experimental casting trials are performed and the outcomes of physical simulation tool are validated against experimental results. It is shown that phase composition, secondary dendrite arm spacing, grain size, γ/ γ' eutectic size and volume fraction, size and shape of carbide particles, and local microhardness can be predicted at each point of the casting via physical simulation.

  13. Thermal performance of residential duct systems in basements

    NASA Astrophysics Data System (ADS)

    Treidler, Burke; Modera, Mark

    1994-01-01

    There are many unanswered questions about the typical effects of duct system operation on the infiltration rates and energy usage of single-family residences with HVAC systems in their basements. Results from preliminary field studies and computer simulations are used to examine the potential for improvements in efficiency of air distribution systems in such houses. The field studies comprise thermal and flow measurements on four houses in Maryland. The houses were found to have significant envelope leakage, duct leakage, and duct conduction losses. Simulations of a basement house, the characteristics of which were chosen from the measured houses, were performed to assess the energy savings potential for basement house. The simulations estimate that a nine percent reduction in space conditioning energy use is obtained by sealing eighty percent of the duct leaks and insulating ducks to an R-value of 0.88 (C x sq. m)/W(100 F x sq. ft x h/BTU) where they are exposed in the basement. To determine the maximum possible reduction in energy use, simulations were run with all ducts insulated to (17.6 C x sq m)/W(100 F x sq. ft x h/BTU) and with no duct leakage. A reduction of energy use by 14% is obtained by using perfect ducts instead of normal ducts.

  14. Accessory Pancreatic Duct Patterns and Their Clinical Implications

    PubMed Central

    Prasanna, Lokadolalu Chandracharya; Rajagopal, KV; Thomas, Huban R

    2015-01-01

    Context and Objective: Accessory pancreatic duct (APD) designed to reduce the pressure of major pancreatic duct by forming a secondary drainage channel. Few studies have mentioned the variant types of accessory ducts and their mode of formation, some of these have a clear clinical significance. Present study is aimed to evaluate the possible variations in the APD and its terminations. Materials and Methods: Forty formalin fixed adult human pancreas with duodenum in situ specimens were studied by injecting 1% aqueous eosin, followed by piece meal dissection of the head of the pancreas from posterior surface. Formation, tributaries, relations, and the termination of the accessory pancreatic duct were noted and photographed. Results: Accessory ducts revealed 50% belonged to long type, 22.5% were of short and ansa pancreatica type each, and embryonic type of duct pattern was seen in 5% specimens. 75% of long type ducts showed positive patency with eosin dye, followed by ansa type (44.4%), and least patency was found in short type (22.2%). With regard to the patency of the accessory pancreatic ducts towards their termination, we found 52.5% of the accessory ducts and 5% of the embryonic type pancreatic ducts were patent and in 42.5% of the specimen the ducts were obliterated. In 85% of specimens the minor duodenal papillae was anterosuperior to the major papilla and superior to the major papillae in 10% of the cases, and in 5% minor papillae was absent. The average distance between the two papillae was 2.35 cm. Conclusion: The knowledge of the complex anatomical relations of the gland with its duct, duodenum and bile ducts are essential for the surgeons and sinologists to plan and perform both the diagnostic as well as therapeutic procedures effectively. PMID:25954609

  15. 91. VIEW OF OBSOLETE AIRCONDITIONING DUCTS LOCATED IN NORTHWEST CORNER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    91. VIEW OF OBSOLETE AIR-CONDITIONING DUCTS LOCATED IN NORTHWEST CORNER OF ROOM, ABOVE SLC-3E AUTOPILOT EQUIPMENT. DIGITAL COUNTDOWN AND HOLD CLOCKS ON WALL LEFT OF DUCTS - Vandenberg Air Force Base, Space Launch Complex 3, Launch Operations Building, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  16. A versatile tunnel acts as a flexible duct

    NASA Technical Reports Server (NTRS)

    Brown, N. D.; Costakos, N. C.; Jeppesen, G. L.

    1980-01-01

    Tunnel activated by cable assembly can be expanded, contracted, and bent similar to flexible duct without uncoupling at either end. Tunnel was developed to join reusable space vehicle with cargo module and could be modified to be used as hydraulic or pneumatic hose or duct connecting complex moveable joints in remote manipulators and earth moving machinery.

  17. Atomistic Simulation of Lignocellulosic Biomass and Associated Cellulosomal Protein Complexes

    SciTech Connect

    Petridis, Loukas; Crowley, Michael F; Smith, Jeremy C

    2010-01-01

    Computer simulations have been performed to obtain an atomic-level understanding of lignocellulose structure and the assembly of its associated cellulosomal protein complexes. First, a CHARMM molecular mechanics force field for lignin is derived and validated by performing a molecular dynamics simulation of a crystal of a lignin fragment molecule and comparing simulation-derived structural features with experimental results. Together with the existing force field for polysaccharides, this work provides the basis for full simulations of lignocellulose. Second, the underlying molecular mechanism governing the assembly of various cellulosomal modules is investigated by performing a novel free-energy calculation of the cohesin-dockerin dissociation. Our calculation indicates a free-energy barrier of ~17 kcal/mol and further reveals a stepwise dissociation pathway involving both the central -sheet interface and its adjacent solvent-exposed loop/turn regions clustered at both ends of the -barrel structure.

  18. Complex molecular assemblies at hand via interactive simulations.

    PubMed

    Delalande, Olivier; Férey, Nicolas; Grasseau, Gilles; Baaden, Marc

    2009-11-30

    Studying complex molecular assemblies interactively is becoming an increasingly appealing approach to molecular modeling. Here we focus on interactive molecular dynamics (IMD) as a textbook example for interactive simulation methods. Such simulations can be useful in exploring and generating hypotheses about the structural and mechanical aspects of biomolecular interactions. For the first time, we carry out low-resolution coarse-grain IMD simulations. Such simplified modeling methods currently appear to be more suitable for interactive experiments and represent a well-balanced compromise between an important gain in computational speed versus a moderate loss in modeling accuracy compared to higher resolution all-atom simulations. This is particularly useful for initial exploration and hypothesis development for rare molecular interaction events. We evaluate which applications are currently feasible using molecular assemblies from 1900 to over 300,000 particles. Three biochemical systems are discussed: the guanylate kinase (GK) enzyme, the outer membrane protease T and the soluble N-ethylmaleimide-sensitive factor attachment protein receptors complex involved in membrane fusion. We induce large conformational changes, carry out interactive docking experiments, probe lipid-protein interactions and are able to sense the mechanical properties of a molecular model. Furthermore, such interactive simulations facilitate exploration of modeling parameters for method improvement. For the purpose of these simulations, we have developed a freely available software library called MDDriver. It uses the IMD protocol from NAMD and facilitates the implementation and application of interactive simulations. With MDDriver it becomes very easy to render any particle-based molecular simulation engine interactive. Here we use its implementation in the Gromacs software as an example.

  19. Route complexity and simulated physical ageing negatively influence wayfinding.

    PubMed

    Zijlstra, Emma; Hagedoorn, Mariët; Krijnen, Wim P; van der Schans, Cees P; Mobach, Mark P

    2016-09-01

    The aim of this age-simulation field experiment was to assess the influence of route complexity and physical ageing on wayfinding. Seventy-five people (aged 18-28) performed a total of 108 wayfinding tasks (i.e., 42 participants performed two wayfinding tasks and 33 performed one wayfinding task), of which 59 tasks were performed wearing gerontologic ageing suits. Outcome variables were wayfinding performance (i.e., efficiency and walking speed) and physiological outcomes (i.e., heart and respiratory rates). Analysis of covariance showed that persons on more complex routes (i.e., more floor and building changes) walked less efficiently than persons on less complex routes. In addition, simulated elderly participants perform worse in wayfinding than young participants in terms of speed (p < 0.001). Moreover, a linear mixed model showed that simulated elderly persons had higher heart rates and respiratory rates compared to young people during a wayfinding task, suggesting that simulated elderly consumed more energy during this task. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Large-Eddy Simulations of Flows in Complex Terrain

    NASA Astrophysics Data System (ADS)

    Kosovic, B.; Lundquist, K. A.

    2011-12-01

    Large-eddy simulation as a methodology for numerical simulation of turbulent flows was first developed to study turbulent flows in atmospheric by Lilly (1967). The first LES were carried by Deardorff (1970) who used these simulations to study atmospheric boundary layers. Ever since, LES has been extensively used to study canonical atmospheric boundary layers, in most cases flat plate boundary layers under the assumption of horizontal homogeneity. Carefully designed LES of canonical convective and neutrally stratified and more recently stably stratified atmospheric boundary layers have contributed significantly to development of better understanding of these flows and their parameterizations in large scale models. These simulations were often carried out using codes specifically designed and developed for large-eddy simulations of horizontally homogeneous flows with periodic lateral boundary conditions. Recent developments in multi-scale numerical simulations of atmospheric flows enable numerical weather prediction (NWP) codes such as ARPS (Chow and Street, 2009), COAMPS (Golaz et al., 2009) and Weather Research and Forecasting model, to be used nearly seamlessly across a wide range of atmospheric scales from synoptic down to turbulent scales in atmospheric boundary layers. Before we can with confidence carry out multi-scale simulations of atmospheric flows, NWP codes must be validated for accurate performance in simulating flows over complex or inhomogeneous terrain. We therefore carry out validation of WRF-LES for simulations of flows over complex terrain using data from Askervein Hill (Taylor and Teunissen, 1985, 1987) and METCRAX (Whiteman et al., 2008) field experiments. WRF's nesting capability is employed with a one-way nested inner domain that includes complex terrain representation while the coarser outer nest is used to spin up fully developed atmospheric boundary layer turbulence and thus represent accurately inflow to the inner domain. LES of a

  1. The future of simulation technologies for complex cardiovascular procedures.

    PubMed

    Cates, Christopher U; Gallagher, Anthony G

    2012-09-01

    Changing work practices and the evolution of more complex interventions in cardiovascular medicine are forcing a paradigm shift in the way doctors are trained. Implantable cardioverter defibrillator (ICD), transcatheter aortic valve implantation (TAVI), carotid artery stenting (CAS), and acute stroke intervention procedures are forcing these changes at a faster pace than in other disciplines. As a consequence, cardiovascular medicine has had to develop a sophisticated understanding of precisely what is meant by 'training' and 'skill'. An evolving conclusion is that procedure training on a virtual reality (VR) simulator presents a viable current solution. These simulations should characterize the important performance characteristics of procedural skill that have metrics derived and defined from, and then benchmarked to experienced operators (i.e. level of proficiency). Simulation training is optimal with metric-based feedback, particularly formative trainee error assessments, proximate to their performance. In prospective, randomized studies, learners who trained to a benchmarked proficiency level on the simulator performed significantly better than learners who were traditionally trained. In addition, cardiovascular medicine now has available the most sophisticated virtual reality simulators in medicine and these have been used for the roll-out of interventions such as CAS in the USA and globally with cardiovascular society and industry partnered training programmes. The Food and Drug Administration has advocated the use of VR simulation as part of the approval of new devices and the American Board of Internal Medicine has adopted simulation as part of its maintenance of certification. Simulation is rapidly becoming a mainstay of cardiovascular education, training, certification, and the safe adoption of new technology. If cardiovascular medicine is to continue to lead in the adoption and integration of simulation, then, it must take a proactive position in the

  2. Scale Model Experiments on Sound Propagation From a Mach 2.5 Cold Nitrogen Jet Flowing Through a Rigid-Walled Duct With a J-Deflector

    NASA Technical Reports Server (NTRS)

    Kandula, Max; Vu, Bruce

    2003-01-01

    The Launch Systems Testbed (LST) represents the evolution of vibroacoustics research and development work performed at NASA John F. Kennedy Space Center (KSC) over the last 15 years. The LST is located at the Launch Equipment Test Facility (LETF) in the KSC industrial complex. The LETF is operated by Sierra Lobo, Inc., as a member of University-Affiliated Technology Development Contract (USTDC) to KSC Spaceport and Engineering and Technology Directorate (YA), with ASRC Aerospace Corporation as a the prime contractor. Trajectory Simulation Mechanism (TSM) is a major component of the LST, developed specifically to simulate nonstationary acoustic loads on launch pad structures, vehicles, and payloads. TSM enhances the capabilities within LST for simulating launch environments of future vehicles. The scaled launch environments will be used to predict the full-scale launch environment via an appropriate scaling procedure. Air Force Research Laboratory (AFRL) has tasked NASA KSC to perform a basic technology test program in support of developing a low-cost clean pad (incorporating passive mitigation techniques) for future launch vehicles. The overall goal of the program is to develop innovative launch exhaust management systems, which effectively reduce launch acoustic environment with innovative duct designs, while eliminating traditional sound suppression water systems. Passive techniques, such as nontraditional duct geometries, resonators, and diffusers, etc., will be investigated. The overall goals are to advance innovative concepts for a clean pad while developing ideas to reduce transmitted sound via investigation and modeling of jet exhaust acoustic and flow field characteristics. The series of tests outlined in this report represent baseline tests and are geared towards defining the acoustic load environment on the TSM pad for open and closed duct configurations. This report summarizes the cold jet acoustic testing for Mach 2.5 supersonic nitrogen jet issuing

  3. CORNICE DUCT SYSTEM

    SciTech Connect

    Wayne Place; Chuck Ladd; TC Howard

    2002-12-01

    SYNERGETICS, INC., is in the process of designing, developing, and testing an air handling duct system that integrates the air duct with the cornice trim of interior spaces. The device has the advantage that the normal thermal losses from ducts into unconditioned attics and crawl spaces can be totally eliminated by bringing the ducts internal to the conditioned space. The following report details work conducted in the second budget period to develop the Cornice Duct System into a viable product for use in a variety of residential or small commercial building settings. A full-scale prototype has been fabricated and tested in a laboratory test building. Based on the results of that testing, the prototype design as been refined, fabricated, installed, and extensively tested in a residential laboratory house. The testing indicates that the device gives substantially superior performance to a standard air distribution system in terms of energy performance and thermal comfort. A patent has been submitted, refined based on feedback from the patent office, and resubmitted. Additional refinements to the design will lead to additional claims being added to the patent in the near future. Designs are being finalized for a refined version that will be fabricated and tested in the same residential laboratory house. Work is expected to be complete on this project in April of 2003.

  4. Simulation of guide-wire navigation in complex vascular structures

    NASA Astrophysics Data System (ADS)

    Guilloux, Vincent; Haigron, Pascal; Goksu, Cemil; Kulik, Carine; Lucas, Antoine

    2006-03-01

    The course and the success of an endovascular intervention can be influenced by the choice of the guidewire and primary by its ability to access to the lesion. The simulation of catheterism in complex vasculature is of main interest to aid the surgery planning. The overall objective of the simulation is to improve the choice of guidewire (with the simulation of its intrinsic features: torque, shape, rigidity, elasticity) as well as its navigation within patient specific vasculature. We propose a new approach for the simulation of guidewire navigation. It is based on: (i) the modeling of guidewire using "multi-body" approach and the representation of its internal characteristics, (ii) the modeling of artery as a surface mesh, (iii) the simulation of the interactions of the guidewire with its environment (artery and clinician). In this study, strength and elasticity of the guidewire are modeled. Only the "push" action performed by the clinician is considered. The global behavior of the guidewire is simulated by means of retraction and relaxation processes. To interact with the artery walls, methods based on the graphics hardware have been developed (i) to detect the collisions between the guidewire and the artery walls (ii) to find the direction of the retraction process which define the local reaction of the guidewire. All these methods have been tested in a qualitative validation on a patient vasculature.

  5. A perspective on modeling and simulation of complex dynamical systems

    NASA Astrophysics Data System (ADS)

    Åström, K. J.

    2011-09-01

    There has been an amazing development of modeling and simulation from its beginning in the 1920s, when the technology was available only at a handful of University groups who had access to a mechanical differential analyzer. Today, tools for modeling and simulation are available for every student and engineer. This paper gives a perspective on the development with particular emphasis on technology and paradigm shifts. Modeling is increasingly important for design and operation of complex natural and man-made systems. Because of the increased use of model based control such as Kalman filters and model predictive control, models are also appearing as components of feedback systems. Modeling and simulation are multidisciplinary, it is used in a wide variety of fields and their development have been strongly influenced by mathematics, numerics, computer science and computer technology.

  6. Numerical simulation and optimization of casting process for complex pump

    NASA Astrophysics Data System (ADS)

    Liu, Xueqin; Dong, Anping; Wang, Donghong; Lu, Yanling; Zhu, Guoliang

    2017-09-01

    The complex shape of the casting pump body has large complicated structure and uniform wall thickness, which easy give rise to casting defects. The numerical simulation software ProCAST is used to simulate the initial top gating process, after analysis of the material and structure characteristics of the high-pressure pump. The filling process was overall smooth, not there the water shortage phenomenon. But the circular shrinkage defects appear at the bottom of casting during solidification process. Then, the casting parameters were optimized and adding cold iron in the bottom. The shrinkage weight was reduced from 0.00167g to 0.0005g. The porosity volume was reduced from 1.39cm3 to 0.41cm3. The optimization scheme is simulated and actual experimented. The defect has been significantly improved.

  7. Large-scale simulations of complex physical systems

    NASA Astrophysics Data System (ADS)

    Belić, A.

    2007-04-01

    Scientific computing has become a tool as vital as experimentation and theory for dealing with scientific challenges of the twenty-first century. Large scale simulations and modelling serve as heuristic tools in a broad problem-solving process. High-performance computing facilities make possible the first step in this process - a view of new and previously inaccessible domains in science and the building up of intuition regarding the new phenomenology. The final goal of this process is to translate this newly found intuition into better algorithms and new analytical results. In this presentation we give an outline of the research themes pursued at the Scientific Computing Laboratory of the Institute of Physics in Belgrade regarding large-scale simulations of complex classical and quantum physical systems, and present recent results obtained in the large-scale simulations of granular materials and path integrals.

  8. Large-scale simulations of complex physical systems

    SciTech Connect

    Belic, A.

    2007-04-23

    Scientific computing has become a tool as vital as experimentation and theory for dealing with scientific challenges of the twenty-first century. Large scale simulations and modelling serve as heuristic tools in a broad problem-solving process. High-performance computing facilities make possible the first step in this process - a view of new and previously inaccessible domains in science and the building up of intuition regarding the new phenomenology. The final goal of this process is to translate this newly found intuition into better algorithms and new analytical results.In this presentation we give an outline of the research themes pursued at the Scientific Computing Laboratory of the Institute of Physics in Belgrade regarding large-scale simulations of complex classical and quantum physical systems, and present recent results obtained in the large-scale simulations of granular materials and path integrals.

  9. Simulations of Sea Level Rise Effects on Complex Coastal Systems

    NASA Astrophysics Data System (ADS)

    Niedoroda, A. W.; Ye, M.; Saha, B.; Donoghue, J. F.; Reed, C. W.

    2009-12-01

    It is now established that complex coastal systems with elements such as beaches, inlets, bays, and rivers adjust their morphologies according to time-varying balances in between the processes that control the exchange of sediment. Accelerated sea level rise introduces a major perturbation into the sediment-sharing systems. A modeling framework based on a new SL-PR model which is an advanced version of the aggregate-scale CST Model and the event-scale CMS-2D and CMS-Wave combination have been used to simulate the recent evolution of a portion of the Florida panhandle coast. This combination of models provides a method to evaluate coefficients in the aggregate-scale model that were previously treated as fitted parameters. That is, by carrying out simulations of a complex coastal system with runs of the event-scale model representing more than a year it is now possible to directly relate the coefficients in the large-scale SL-PR model to measureable physical parameters in the current and wave fields. This cross-scale modeling procedure has been used to simulate the shoreline evolution at the Santa Rosa Island, a long barrier which houses significant military infrastructure at the north Gulf Coast. The model has been used to simulate 137 years of measured shoreline change and to extend these to predictions of future rates of shoreline migration.

  10. On the propagation of long waves in acoustically treated, curved ducts

    NASA Technical Reports Server (NTRS)

    Rostafinski, W.

    1981-01-01

    A two dimensional study is presented on the behavior of long waves in lined, curved ducts. The analysis includes a comparison between the propagation in curved and straight lined ducts. A parametric study was conducted over a range of wall admittance and duct wall separation. The complex eigenvalues of the characteristic equation, which in the case of a curved duct are also the angular wavenumbers, were obtained by successive approximations.

  11. Particle deposition in ventilation ducts

    SciTech Connect

    Sippola, Mark Raymond

    2002-09-01

    Exposure to airborne particles is detrimental to human health and indoor exposures dominate total exposures for most people. The accidental or intentional release of aerosolized chemical and biological agents within or near a building can lead to exposures of building occupants to hazardous agents and costly building remediation. Particle deposition in heating, ventilation and air-conditioning (HVAC) systems may significantly influence exposures to particles indoors, diminish HVAC performance and lead to secondary pollutant release within buildings. This dissertation advances the understanding of particle behavior in HVAC systems and the fates of indoor particles by means of experiments and modeling. Laboratory experiments were conducted to quantify particle deposition rates in horizontal ventilation ducts using real HVAC materials. Particle deposition experiments were conducted in steel and internally insulated ducts at air speeds typically found in ventilation ducts, 2-9 m/s. Behaviors of monodisperse particles with diameters in the size range 1-16 μm were investigated. Deposition rates were measured in straight ducts with a fully developed turbulent flow profile, straight ducts with a developing turbulent flow profile, in duct bends and at S-connector pieces located at duct junctions. In straight ducts with fully developed turbulence, experiments showed deposition rates to be highest at duct floors, intermediate at duct walls, and lowest at duct ceilings. Deposition rates to a given surface increased with an increase in particle size or air speed. Deposition was much higher in internally insulated ducts than in uninsulated steel ducts. In most cases, deposition in straight ducts with developing turbulence, in duct bends and at S-connectors at duct junctions was higher than in straight ducts with fully developed turbulence. Measured deposition rates were generally higher than predicted by published models. A model incorporating empirical equations based on the

  12. Duct thermal performance models for large commercial buildings

    SciTech Connect

    Wray, Craig P.

    2003-10-01

    Despite the potential for significant energy savings by reducing duct leakage or other thermal losses from duct systems in large commercial buildings, California Title 24 has no provisions to credit energy-efficient duct systems in these buildings. A substantial reason is the lack of readily available simulation tools to demonstrate the energy-saving benefits associated with efficient duct systems in large commercial buildings. The overall goal of the Efficient Distribution Systems (EDS) project within the PIER High Performance Commercial Building Systems Program is to bridge the gaps in current duct thermal performance modeling capabilities, and to expand our understanding of duct thermal performance in California large commercial buildings. As steps toward this goal, our strategy in the EDS project involves two parts: (1) developing a whole-building energy simulation approach for analyzing duct thermal performance in large commercial buildings, and (2) using the tool to identify the energy impacts of duct leakage in California large commercial buildings, in support of future recommendations to address duct performance in the Title 24 Energy Efficiency Standards for Nonresidential Buildings. The specific technical objectives for the EDS project were to: (1) Identify a near-term whole-building energy simulation approach that can be used in the impacts analysis task of this project (see Objective 3), with little or no modification. A secondary objective is to recommend how to proceed with long-term development of an improved compliance tool for Title 24 that addresses duct thermal performance. (2) Develop an Alternative Calculation Method (ACM) change proposal to include a new metric for thermal distribution system efficiency in the reporting requirements for the 2005 Title 24 Standards. The metric will facilitate future comparisons of different system types using a common ''yardstick''. (3) Using the selected near-term simulation approach, assess the impacts of

  13. Governance of complex systems: results of a sociological simulation experiment.

    PubMed

    Adelt, Fabian; Weyer, Johannes; Fink, Robin D

    2014-01-01

    Social sciences have discussed the governance of complex systems for a long time. The following paper tackles the issue by means of experimental sociology, in order to investigate the performance of different modes of governance empirically. The simulation framework developed is based on Esser's model of sociological explanation as well as on Kroneberg's model of frame selection. The performance of governance has been measured by means of three macro and two micro indicators. Surprisingly, central control mostly performs better than decentralised coordination. However, results not only depend on the mode of governance, but there is also a relation between performance and the composition of actor populations, which has yet not been investigated sufficiently. Practitioner Summary: Practitioners can gain insights into the functioning of complex systems and learn how to better manage them. Additionally, they are provided with indicators to measure the performance of complex systems.

  14. Effectiveness of duct cleaning methods on newly installed duct surfaces.

    PubMed

    Holopainen, R; Asikainen, V; Tuomainen, M; Björkroth, M; Pasanen, P; Seppänen, O

    2003-09-01

    Two kinds of air duct cleaning methods, mechanical brushing with different brushes and compressed air cleaning, were compared in the laboratory and in newly built buildings. The ducts were contaminated either with test dust or with dust originated from a construction site. The amount of dust on the duct surface was measured with the vacuum test method and estimated visually before and after the cleaning. In addition, the cleaning times of the different techniques were compared and the amount of residual oil in the ducts was measured in the laboratory test. The brushing methods were more efficient in metal ducts, and compressed air cleaning was more efficient in plastic ducts. After the duct cleaning the mean amount of residual dust on the surface of the ducts was ducts contaminated at construction site and ducts cleaned in the laboratory or in the building site, respectively. The oil residues and the dust stuck onto the oil were difficult to scrape off and remove, and none of the cleaning methods were capable of cleaning the oily duct surfaces efficiently enough. Thus new installations should consist only of oil-free ducts.

  15. Computer Simulations and Theoretical Studies of Complex Systems: from complex fluids to frustrated magnets

    NASA Astrophysics Data System (ADS)

    Choi, Eunsong

    Computer simulations are an integral part of research in modern condensed matter physics; they serve as a direct bridge between theory and experiment by systemactically applying a microscopic model to a collection of particles that effectively imitate a macroscopic system. In this thesis, we study two very differnt condensed systems, namely complex fluids and frustrated magnets, primarily by simulating classical dynamics of each system. In the first part of the thesis, we focus on ionic liquids (ILs) and polymers--the two complementary classes of materials that can be combined to provide various unique properties. The properties of polymers/ILs systems, such as conductivity, viscosity, and miscibility, can be fine tuned by choosing an appropriate combination of cations, anions, and polymers. However, designing a system that meets a specific need requires a concrete understanding of physics and chemistry that dictates a complex interplay between polymers and ionic liquids. In this regard, molecular dynamics (MD) simulation is an efficient tool that provides a molecular level picture of such complex systems. We study the behavior of Poly (ethylene oxide) (PEO) and the imidazolium based ionic liquids, using MD simulations and statistical mechanics. We also discuss our efforts to develop reliable and efficient classical force-fields for PEO and the ionic liquids. The second part is devoted to studies on geometrically frustrated magnets. In particular, a microscopic model, which gives rise to an incommensurate spiral magnetic ordering observed in a pyrochlore antiferromagnet is investigated. The validation of the model is made via a comparison of the spin-wave spectra with the neutron scattering data. Since the standard Holstein-Primakoff method is difficult to employ in such a complex ground state structure with a large unit cell, we carry out classical spin dynamics simulations to compute spin-wave spectra directly from the Fourier transform of spin trajectories. We

  16. Prediction of ducted fan performance

    NASA Technical Reports Server (NTRS)

    Mendenhall, M. R.; Spangler, S. B.

    1972-01-01

    Computer program to predict performance of ducted fan combination at specified advance ratio and angle of attack is described. Parameters affecting performance of ducted fan are presented. Information obtained from computer program is explained for various conditions considered.

  17. What Is Bile Duct Cancer?

    MedlinePlus

    ... the liver. Types of bile duct cancer by cell type Bile duct cancers can also be divided ... Our Volunteers More ACS Sites Bookstore Shop Cancer Atlas Press Room Cancer Statistics Center Volunteer Learning Center ...

  18. Methods for simulating the dynamics of complex biological processes.

    PubMed

    Schilstra, Maria J; Martin, Stephen R; Keating, Sarah M

    2008-01-01

    In this chapter, we provide the basic information required to understand the central concepts in the modeling and simulation of complex biochemical processes. We underline the fact that most biochemical processes involve sequences of interactions between distinct entities (molecules, molecular assemblies), and also stress that models must adhere to the laws of thermodynamics. Therefore, we discuss the principles of mass-action reaction kinetics, the dynamics of equilibrium and steady state, and enzyme kinetics, and explain how to assess transition probabilities and reactant lifetime distributions for first-order reactions. Stochastic simulation of reaction systems in well-stirred containers is introduced using a relatively simple, phenomenological model of microtubule dynamic instability in vitro. We demonstrate that deterministic simulation [by numerical integration of coupled ordinary differential equations (ODE)] produces trajectories that would be observed if the results of many rounds of stochastic simulation of the same system were averaged. In Section V, we highlight several practical issues with regard to the assessment of parameter values. We draw some attention to the development of a standard format for model storage and exchange, and provide a list of selected software tools that may facilitate the model building process, and can be used to simulate the modeled systems.

  19. Effectiveness of duct sealing and duct insulation in multi-family buildings. Final report

    SciTech Connect

    Karins, N.H.; Tuluca, A.; Modera, M.

    1997-07-01

    This research investigated the cost-effectiveness of sealing and insulating the accessible portions of duct systems exposed to unconditioned areas in multifamily housing. Airflow and temperature measurements were performed in 25 apartments served by 10 systems a 9 multi-family properties. The measurements were performed before and after each retrofit, and included apartment airflow (supply and return), duct system temperatures, system fan flow and duct leakage area. The costs for each retrofit were recorded. The data were analyzed and used to develop a prototypical multifamily house. This prototype was used in energy simulations (DOE-2.1E) and air infiltration simulations (COMIS 2.1). The simulations were performed for two climates: New York City and Albany. In each climate, one simulation was performed assuming the basement was tight, and another assuming the basement was leaky. Simulation results and average retrofit costs were used to calculate cost-effectiveness. The results of the analysis indicate that sealing leaks of the accessible ductwork is cost-effective under all conditions simulated (simple payback was between 3 and 4 years). Insulating the accessible ductwork, however, is only cost-effective for buildings with leaky basement, in both climates (simple paybacks were less than 5 years). The simple payback period for insulating the ducts in buildings with tight basements was greater than 10 years, the threshold of cost-effectiveness for this research. 13 refs., 5 figs., 27 tabs.

  20. 76. DETAIL OF AIRCONDITIONING DUCT BETWEEN PORTABLE PAYLOAD AIRCONDITIONING SYSTEM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    76. DETAIL OF AIR-CONDITIONING DUCT BETWEEN PORTABLE PAYLOAD AIR-CONDITIONING SYSTEM AND LSB (BLDG. 770) - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 West, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  1. 54. DETAIL OF AIRCONDITIONING EXHAUST DUCTS ON NORTH FACE OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    54. DETAIL OF AIR-CONDITIONING EXHAUST DUCTS ON NORTH FACE OF ERECT UMBILICAL MAST - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 West, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  2. 23. A detailed interior view of the duct and delivery ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    23. A detailed interior view of the duct and delivery equipment situated in the upper grain conveyor structure of Elevator and Silo Complex B (1932). - Quaker Oats Cereal Factory, Southeast corner of Broadway & Mill Streets, Akron, Summit County, OH

  3. 40. VIEW INTO MST CUPOLA FROM STATION 124. DUCT HEATER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    40. VIEW INTO MST CUPOLA FROM STATION 124. DUCT HEATER FOR STATION 135 AT TOP LEFT OF PHOTOGRAPH. - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 East, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  4. 12. SANDSORTING BUILDING, THIRD FLOOR, VIBRATING SCREENS ON RIGHT, DUCT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. SAND-SORTING BUILDING, THIRD FLOOR, VIBRATING SCREENS ON RIGHT, DUCT FOR DUST COLLECTION SYSTEM IN FOREGROUND, LOOKING NORTH - Mill "C" Complex, Sand-Sorting Building, South of Dee Bennet Road, near Illinois River, Ottawa, La Salle County, IL

  5. Malignant tumors of Stensen's duct.

    PubMed

    Steiner, M; Gould, A R; Miller, R L; Johnson, J A

    1999-01-01

    A rare case of squamous cell carcinoma arising in Stensen's duct is reported. The literature concerning malignant neoplasia originating in this site is reviewed, with attention given to the histopathologic diversity of neoplasms occurring in the duct, criteria for determination of origin in the duct, and outcomes of therapy.

  6. Isolated Pancreatic Uncinate Duct IPMN.

    PubMed

    Maker, Ajay V; Maker, Vijay K

    2017-04-01

    The ventral pancreas originally forms as an evagination of the common bile duct at 32 days gestation and its duct, the uncinate duct, eventually rotates with the ventral anlage to join the dorsal pancreas and fuse with the main pancreatic duct. Thus, though often considered a "branch" duct of the pancreas, embryologically, the uncinate duct is the "main" pancreatic duct of the ventral pancreas. This concept is not fully addressed in the current definitions of intraductal papillary mucinous neoplasms of the pancreas (IPMN) where international consensus guidelines consider the main-duct IPMN as high risk for malignancy and most small branch-duct IPMN as low risk for malignancy. Thus, it is important to recognize that isolated uncinate-duct IPMN can occur and, based on its embryologic origin and increased association with high-grade dysplasia and invasive cancer, may be managed conceptually as a main duct type of disease rather than a branch duct until better biomarkers of malignancy are discovered. The images provide an example of this unique disease process.

  7. Simulating an Extreme Wind Event in a Topographically Complex Region

    NASA Astrophysics Data System (ADS)

    Lennard, Christopher

    2014-07-01

    Complex topography modifies local weather characteristics such as air temperature, rainfall and airflow within a larger regional extent. The Cape Peninsula around Cape Town, South Africa, is a complex topographical feature responsible for the modification of rainfall and wind fields largely downstream of the Peninsula. During the passage of a cold front on 2 October 2002, an extreme wind event associated with tornado-like damage occurred in the suburb of Manenberg, however synoptic conditions did not indicate convective activity typically associated with a tornado. A numerical regional climate model was operated at very high horizontal resolution (500 m) to investigate the dynamics of the event. The model simulated an interaction between the topography of the peninsula and an airflow direction change associated with the passage of the cold front. A small region of cyclonic circulation was simulated over Manenberg that was embedded in an area of negative vorticity and a leeward gravity wave. The feature lasted 14 min and moved in a north to south direction. Vertically, it was not evident above 220 m. The model assessment describes this event as a shallow but intense cyclonic vortex generated in the lee of the peninsula through an interaction between the peninsula and a change in wind direction as the cold front made landfall. The model did not simulate wind speeds associated with the observed damage suggesting that the horizontal grid resolution ought to be at the scale of the event to more completely understand such microscale airflow phenomena.

  8. Duct Leakage Repeatability Testing

    SciTech Connect

    Walker, Iain; Sherman, Max

    2014-08-01

    The purpose of this report is to evaluate the repeatability of the three most significant measurement techniques for duct leakage using data from the literature and recently obtained field data. We will also briefly discuss the first two factors. The main question to be answered by this study is to determine if differences in the repeatability of these tests methods is sufficient to indicate that any of these methods is so poor that it should be excluded from consideration as an allowed procedure in codes and standards. The three duct leak measurement methods assessed in this report are the two duct pressurization methods that are commonly used by many practitioners and the DeltaQ technique. These are methods B, C and A, respectively of the ASTM E1554 standard. Although it would be useful to evaluate other duct leak test methods, this study focused on those test methods that are commonly used and are required in various test standards, such as BPI (2010), RESNET (2014), ASHRAE 62.2 (2013), California Title 24 (CEC 2012), DOE Weatherization and many other energy efficiency programs.

  9. Admission mixing duct assembly

    NASA Technical Reports Server (NTRS)

    Orlando, Robert J. (Inventor); Dunbar, Lawrence W. (Inventor)

    1995-01-01

    A variable cycle jet engine is provided with a mixing duct assembly which mixes core engine exhaust gas with bypass air when the engine is operating in a turbofan mode and which blocks flow from the core engine and isolates the core engine from the bypass flow when the engine is operating as a ramjet.

  10. Auditory perception of note transitions in simulated complex bowing patterns.

    PubMed

    Schoonderwaldt, Erwin; Demoucron, Matthias; Altenmüller, Eckart; Leman, Marc

    2013-06-01

    Recent motion-capture measurements of violin bowing revealed an interesting coordination behavior in fast repetitive bowing patterns involving bow changes and string crossings; bow changes were consistently lagging behind string crossings, and the relative timing appeared to be an integral part of the bow-movement patterns. The aim of the current study was to investigate if there might be a perceptual explanation for the observed coordination behavior. For this purpose a virtual violin was used, controlled by simulated bowing gestures. A simplified coordination model is presented, which was implemented to allow real-time control of complex bowing patterns. This synthesis approach was employed in a perceptual experiment in which the participants were asked to optimize the sound by adjusting a slider controlling the main coordination parameters. It was found that the resulting coordination patterns were similar to those observed in performance, implying that complex bowing trajectories for an important part emerge from auditory-motor interaction. Further analysis of the responses shed light on temporal and spatial constraints of the simulated gestures associated with the note transitions. The results raise interesting questions with regard to auditory-motor interaction in complex instrumental control gestures.

  11. Aspect ratio effect on particle transport in turbulent duct flows

    NASA Astrophysics Data System (ADS)

    Noorani, A.; Vinuesa, R.; Brandt, L.; Schlatter, P.

    2016-11-01

    The dynamics of dilute micron-sized spherical inertial particles in turbulent duct flows is studied by means of direct numerical simulations of the carrier phase turbulence with one-way coupled Lagrangian particles. The geometries are a square and a rectangular duct with width-to-height aspect ratio AR of 3 operating at Reτ,c = 360 (based on the centerplane friction velocity and duct half-height). The present study is designed to determine the effect of turbulence-driven secondary motion on the particle dynamics. Our results show that a weak cross-flow secondary motion significantly changes the cross-sectional map of the particle concentration, mean velocity, and fluctuations. As the geometry of the duct is widened from AR = 1 to 3, the secondary vortex on the horizontal wall significantly expands in the spanwise direction, and although the kinetic energy of the secondary flow increases close to the corner, it decays towards the duct centreplane in the AR = 3 case so as the turbulent carrier phase approaches the behavior in spanwise-periodic channel flows, a fact that significantly affects the particle statistics. In the square duct the particle concentration in the viscous sublayer is maximum at the duct centreplane, whereas the maximum is found closer to the corner, at a distance of |z/h| ≈ 1.25 from the centreplane, in the AR = 3 case. Interestingly the centreplane concentration in the rectangular duct is around 3 times lower than that in the square duct. Moreover, a second peak in the accumulation distribution is found right at the corners for both ducts. At this location the concentration increases with particle inertia. The secondary motion changes also the cross-stream map of the particle velocities significantly in comparison to the fluid flow statistics. These directly affect the particle velocity fluctuations such that multiple peaks appear near the duct walls for the particle streamwise and wall-normal velocity fluctuations.

  12. High performance ultrasonic field simulation on complex geometries

    NASA Astrophysics Data System (ADS)

    Chouh, H.; Rougeron, G.; Chatillon, S.; Iehl, J. C.; Farrugia, J. P.; Ostromoukhov, V.

    2016-02-01

    Ultrasonic field simulation is a key ingredient for the design of new testing methods as well as a crucial step for NDT inspection simulation. As presented in a previous paper [1], CEA-LIST has worked on the acceleration of these simulations focusing on simple geometries (planar interfaces, isotropic materials). In this context, significant accelerations were achieved on multicore processors and GPUs (Graphics Processing Units), bringing the execution time of realistic computations in the 0.1 s range. In this paper, we present recent works that aim at similar performances on a wider range of configurations. We adapted the physical model used by the CIVA platform to design and implement a new algorithm providing a fast ultrasonic field simulation that yields nearly interactive results for complex cases. The improvements over the CIVA pencil-tracing method include adaptive strategies for pencil subdivisions to achieve a good refinement of the sensor geometry while keeping a reasonable number of ray-tracing operations. Also, interpolation of the times of flight was used to avoid time consuming computations in the impulse response reconstruction stage. To achieve the best performance, our algorithm runs on multi-core superscalar CPUs and uses high performance specialized libraries such as Intel Embree for ray-tracing, Intel MKL for signal processing and Intel TBB for parallelization. We validated the simulation results by comparing them to the ones produced by CIVA on identical test configurations including mono-element and multiple-element transducers, homogeneous, meshed 3D CAD specimens, isotropic and anisotropic materials and wave paths that can involve several interactions with interfaces. We show performance results on complete simulations that achieve computation times in the 1s range.

  13. Cornice Duct System

    SciTech Connect

    Wayne Place; Chuck Ladd

    2004-10-29

    SYNERGETICS, INC., has designed, developed, and tested an air handling duct system that integrates the air duct with the cornice trim of interior spaces. The device has the advantage that the normal thermal losses from ducts into unconditioned attics and crawl spaces can be totally eliminated by bringing the ducts internal to the conditioned space. The following report details work conducted in the second budget period to develop the Cornice Duct System into a viable product for use in a variety of residential or small commercial building settings. A full-scale prototype has been fabricated and tested in a laboratory test building at the Daylighting Facility at North Carolina State University., Based on the results of that testing, the prototype design as been refined, fabricated, installed, and extensively tested in a residential laboratory house. The testing indicates that the device gives substantially superior performance to a standard air distribution system in terms of energy performance and thermal comfort. Patent Number US 6,511,373 B2 has been granted on the version of the device installed and tested in the laboratory house. (A copy of that patent is attached.) Refinements to the device have been carried through two additional design iterations, with a particular focus on reducing installation time and cost and refining the air control system. These new designs have been fabricated and tested and show substantial promise. Based on these design and testing iterations, a final design is proposed as part of this document. That final design is the basis for a continuation in part currently being filed with the U.5, Patent office.

  14. Effect of flow on the acoustic resonances of an open-ended duct

    NASA Technical Reports Server (NTRS)

    Ingard, U.; Singhal, V. K.

    1975-01-01

    The effect of flow on the acoustic resonances of an open-ended, hard-walled duct is analyzed. The flow produces acoustic losses both in the interior of the duct and at the ends. Unless the duct is very long, typically 100 times the diameter, the losses at the ends dominate. At flow Mach numbers in excess of 0.4 the losses are so large that axial duct resonances are almost completely suppressed. The plane-wave Green's function for the duct with flow is expressed in terms of the (experimentally determined) pressure reflection coefficients at the ends of the duct, and the flow dependence of the complex eigenfrequencies of the duct is obtained. Some observations concerning the noise produced by the flow in the duct are also reported.

  15. Quantifying uncertainty and computational complexity for pore-scale simulations

    NASA Astrophysics Data System (ADS)

    Chen, C.; Yuan, Z.; Wang, P.; Yang, X.; Zhenyan, L.

    2016-12-01

    Pore-scale simulation is an essential tool to understand the complex physical process in many environmental problems, from multi-phase flow in the subsurface to fuel cells. However, in practice, factors such as sample heterogeneity, data sparsity and in general, our insufficient knowledge of the underlying process, render many simulation parameters and hence the prediction results uncertain. Meanwhile, most pore-scale simulations (in particular, direct numerical simulation) incur high computational cost due to finely-resolved spatio-temporal scales, which further limits our data/samples collection. To address those challenges, we propose a novel framework based on the general polynomial chaos (gPC) and build a surrogate model representing the essential features of the underlying system. To be specific, we apply the novel framework to analyze the uncertainties of the system behavior based on a series of pore-scale numerical experiments, such as flow and reactive transport in 2D heterogeneous porous media and 3D packed beds. Comparing with recent pore-scale uncertainty quantification studies using Monte Carlo techniques, our new framework requires fewer number of realizations and hence considerably reduce the overall computational cost, while maintaining the desired accuracy.

  16. Simulation and Processing Seismic Data in Complex Geological Models

    NASA Astrophysics Data System (ADS)

    Forestieri da Gama Rodrigues, S.; Moreira Lupinacci, W.; Martins de Assis, C. A.

    2014-12-01

    Seismic simulations in complex geological models are interesting to verify some limitations of seismic data. In this project, different geological models were designed to analyze some difficulties encountered in the interpretation of seismic data. Another idea is these data become available for LENEP/UENF students to test new tools to assist in seismic data processing. The geological models were created considering some characteristics found in oil exploration. We simulated geological medium with volcanic intrusions, salt domes, fault, pinch out and layers more distante from surface (Kanao, 2012). We used the software Tesseral Pro to simulate the seismic acquisitions. The acquisition geometries simulated were of the type common offset, end-on and split-spread. (Figure 1) Data acquired with constant offset require less processing routines. The processing flow used with tools available in Seismic Unix package (for more details, see Pennington et al., 2005) was geometric spreading correction, deconvolution, attenuation correction and post-stack depth migration. In processing of the data acquired with end-on and split-spread geometries, we included velocity analysis and NMO correction routines. Although we analyze synthetic data and carefully applied each processing routine, we can observe some limitations of the seismic reflection in imaging thin layers, great surface depth layers, layers with low impedance contrast and faults.

  17. Simulations of Instabilities in Complex Valve and Feed Systems

    NASA Technical Reports Server (NTRS)

    Ahuja, Vineet; Hosangadi, Ashvin; Shipman, Jeremy; Cavallo, Peter A.

    2006-01-01

    CFD analyses are playing an increasingly important role in identifying and characterizing flow induced instabilities in rocket engine test facilities and flight systems. In this paper, we analyze instability mechanisms that range from turbulent pressure fluctuations due to vortex shedding in structurally complex valve systems to flow resonance in plug cavities to large scale pressure fluctuations due to collapse of cavitation induced vapor clouds. Furthermore, we discuss simulations of transient behavior related to valve motion that can serve as guidelines for valve scheduling. Such predictions of valve response to varying flow conditions is of crucial importance to engine operation and testing.

  18. Computer simulation of supramolecular assembly by metal-ligand complexation

    NASA Astrophysics Data System (ADS)

    Wang, Shihu; Chen, Chun-Chung; Dormidontova, Elena E.

    2006-03-01

    Monte Carlo simulations were employed to study the supramolecular assembly of oligomers end-functionalized by ligands capable of complexation with metal ions. The properties of these metallo-supramolecular polymers strongly depend on the oligomer concentration, strength of complexation, and metal-to- ligand ratio. At high oligomer concentration the average molecular weight exhibits a maximum near the stoichiometric composition and decreases for higher or lower metal content. On the other hand, at low oligomer concentration the molecular weight shows a local minimum around the stoichiometric composition. This unusual behavior is attributed to the larger population of small rings around the stoichiometric composition, which make up a significant fraction of the overall molecular weight at low oligomer concentration. This effect is especially pronounced at low temperature, where the fraction of rings is higher. The fraction of chains and rings for different concentrations, temperatures and oligomer lengths were calculated and compared with experimental data.

  19. An efficient algorithm for corona simulation with complex chemical models

    NASA Astrophysics Data System (ADS)

    Villa, Andrea; Barbieri, Luca; Gondola, Marco; Leon-Garzon, Andres R.; Malgesini, Roberto

    2017-05-01

    The simulation of cold plasma discharges is a leading field of applied sciences with many applications ranging from pollutant control to surface treatment. Many of these applications call for the development of novel numerical techniques to implement fully three-dimensional corona solvers that can utilize complex and physically detailed chemical databases. This is a challenging task since it multiplies the difficulties inherent to a three-dimensional approach by the complexity of databases comprising tens of chemical species and hundreds of reactions. In this paper a novel approach, capable of reducing significantly the computational burden, is developed. The proposed method is based on a proper time stepping algorithm capable of decomposing the original problem into simpler ones: each of them has then been tackled with either finite element, finite volume or ordinary differential equations solvers. This last solver deals with the chemical model and its efficient implementation is one of the main contributions of this work.

  20. Reciprocity principle in duct acoustics

    NASA Technical Reports Server (NTRS)

    Cho, Y. C.

    1979-01-01

    Various reciprocity relations in duct acoustics have been derived on the basis of the spatial reciprocity principle implied in Green's functions for linear waves. The derivation includes the reciprocity relations between mode conversion coefficients for reflection and transmission in nonuniform ducts, and the relation between the radiation of a mode from an arbitrarily terminated duct and the absorption of an externally incident plane wave by the duct. Such relations are well defined as long as the systems remain linear, regardless of acoustic properties of duct nonuniformities which cause the mode conversions.

  1. Molecular dynamics simulations of DNA-polycation complexes

    NASA Astrophysics Data System (ADS)

    Ziebarth, Jesse; Wang, Yongmei

    2008-03-01

    A necessary step in the preparation of DNA for use in gene therapy is the packaging of DNA with a vector that can condense DNA and provide protection from degrading enzymes. Because of the immunoresponses caused by viral vectors, there has been interest in developing synthetic gene therapy vectors, with polycations emerging as promising candidates. Molecular dynamics simulations of the DNA duplex CGCGAATTCGCG in the presence of 20 monomer long sequences of the polycations, poly-L-lysine (PLL) and polyethyleneimine (PEI), with explicit counterions and TIP3P water, are performed to provide insight into the structure and formation of DNA polyplexes. After an initial separation of approximately 50 å, the DNA and polycation come together and form a stable complex within 10 ns. The DNA does not undergo any major structural changes upon complexation and remains in the B-form. In the formed complex, the charged amine groups of the polycation mainly interact with DNA phosphate groups, and rarely occupy electronegative sites in either the major or minor grooves. Differences between complexation with PEI and PLL will be discussed.

  2. The Crucible simulation: Behavioral simulation improves clinical leadership skills and understanding of complex health policy change.

    PubMed

    Cohen, Daniel; Vlaev, Ivo; McMahon, Laurie; Harvey, Sarah; Mitchell, Andy; Borovoi, Leah; Darzi, Ara

    2017-05-11

    The Health and Social Care Act 2012 represents the most complex National Health Service reforms in history. High-quality clinical leadership is important for successful implementation of health service reform. However, little is known about the effectiveness of current leadership training. This study describes the use of a behavioral simulation to improve the knowledge and leadership of a cohort of medical doctors expected to take leadership roles in the National Health Service. A day-long behavioral simulation (The Crucible) was developed and run based on a fictitious but realistic health economy. Participants completed pre- and postsimulation questionnaires generating qualitative and quantitative data. Leadership skills, knowledge, and behavior change processes described by the "theory of planned behavior" were self-assessed pre- and postsimulation. Sixty-nine medical doctors attended. Participants deemed the simulation immersive and relevant. Significant improvements were shown in perceived knowledge, capability, attitudes, subjective norms, intentions, and leadership competency following the program. Nearly one third of participants reported that they had implemented knowledge and skills from the simulation into practice within 4 weeks. This study systematically demonstrates the effectiveness of behavioral simulation for clinical management training and understanding of health policy reform. Potential future uses and strategies for analysis are discussed. High-quality care requires understanding of health systems and strong leadership. Policymakers should consider the use of behavioral simulation to improve understanding of health service reform and development of leadership skills in clinicians, who readily adopt skills from simulation into everyday practice.

  3. Building Blocks for Reliable Complex Nonlinear Numerical Simulations. Chapter 2

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Mansour, Nagi N. (Technical Monitor)

    2001-01-01

    This chapter describes some of the building blocks to ensure a higher level of confidence in the predictability and reliability (PAR) of numerical simulation of multiscale complex nonlinear problems. The focus is on relating PAR of numerical simulations with complex nonlinear phenomena of numerics. To isolate sources of numerical uncertainties, the possible discrepancy between the chosen partial differential equation (PDE) model and the real physics and/or experimental data is set aside. The discussion is restricted to how well numerical schemes can mimic the solution behavior of the underlying PDE model for finite time steps and grid spacings. The situation is complicated by the fact that the available theory for the understanding of nonlinear behavior of numerics is not at a stage to fully analyze the nonlinear Euler and Navier-Stokes equations. The discussion is based on the knowledge gained for nonlinear model problems with known analytical solutions to identify and explain the possible sources and remedies of numerical uncertainties in practical computations. Examples relevant to turbulent flow computations are included.

  4. Building Blocks for Reliable Complex Nonlinear Numerical Simulations

    NASA Technical Reports Server (NTRS)

    Yee, H. C.

    2005-01-01

    This chapter describes some of the building blocks to ensure a higher level of confidence in the predictability and reliability (PAR) of numerical simulation of multiscale complex nonlinear problems. The focus is on relating PAR of numerical simulations with complex nonlinear phenomena of numerics. To isolate sources of numerical uncertainties, the possible discrepancy between the chosen partial differential equation (PDE) model and the real physics and/or experimental data is set aside. The discussion is restricted to how well numerical schemes can mimic the solution behavior of the underlying PDE model for finite time steps and grid spacings. The situation is complicated by the fact that the available theory for the understanding of nonlinear behavior of numerics is not at a stage to fully analyze the nonlinear Euler and Navier-Stokes equations. The discussion is based on the knowledge gained for nonlinear model problems with known analytical solutions to identify and explain the possible sources and remedies of numerical uncertainties in practical computations.

  5. Building Blocks for Reliable Complex Nonlinear Numerical Simulations

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Mansour, Nagi N. (Technical Monitor)

    2002-01-01

    This talk describes some of the building blocks to ensure a higher level of confidence in the predictability and reliability (PAR) of numerical simulation of multiscale complex nonlinear problems. The focus is on relating PAR of numerical simulations with complex nonlinear phenomena of numerics. To isolate sources of numerical uncertainties, the possible discrepancy between the chosen partial differential equation (PDE) model and the real physics and/or experimental data is set aside. The discussion is restricted to how well numerical schemes can mimic the solution behavior of the underlying PDE model for finite time steps and grid spacings. The situation is complicated by the fact that the available theory for the understanding of nonlinear behavior of numerics is not at a stage to fully analyze the nonlinear Euler and Navier-Stokes equations. The discussion is based on the knowledge gained for nonlinear model problems with known analytical solutions to identify and explain the possible sources and remedies of numerical uncertainties in practical computations. Examples relevant to turbulent flow computations are included.

  6. GPU-enabled molecular dynamics simulations of ankyrin kinase complex

    NASA Astrophysics Data System (ADS)

    Gautam, Vertika; Chong, Wei Lim; Wisitponchai, Tanchanok; Nimmanpipug, Piyarat; Zain, Sharifuddin M.; Rahman, Noorsaadah Abd.; Tayapiwatana, Chatchai; Lee, Vannajan Sanghiran

    2014-10-01

    The ankyrin repeat (AR) protein can be used as a versatile scaffold for protein-protein interactions. It has been found that the heterotrimeric complex between integrin-linked kinase (ILK), PINCH, and parvin is an essential signaling platform, serving as a convergence point for integrin and growth-factor signaling and regulating cell adhesion, spreading, and migration. Using ILK-AR with high affinity for the PINCH1 as our model system, we explored a structure-based computational protocol to probe and characterize binding affinity hot spots at protein-protein interfaces. In this study, the long time scale dynamics simulations with GPU accelerated molecular dynamics (MD) simulations in AMBER12 have been performed to locate the hot spots of protein-protein interaction by the analysis of the Molecular Mechanics-Poisson-Boltzmann Surface Area/Generalized Born Solvent Area (MM-PBSA/GBSA) of the MD trajectories. Our calculations suggest good binding affinity of the complex and also the residues critical in the binding.

  7. Field theoretic simulations of the interfacial properties of complex coacervates

    NASA Astrophysics Data System (ADS)

    Riggleman, Robert; Fredrickson, Glenn

    2011-03-01

    Many biological processes and emerging technologies, such as wet adhesives and biosensors, rely on the association between oppositely charged polyelectrolytes. Such association is driven not only by the electrostatic interactions between the polyelectrolytes, but there is also a substantial entropy gain associated with counterion release upon complexation. In some cases, the association between oppositely charged polymers can lead to a solid precipitate while others can result in a fluid phase rich in polyelectrolytes (coacervate phase) coexisting with a polyelectrolyte-dilute solvent phase. For many of the applications seeking to exploit coacervation, characterization of the interface between the solvent phase and the coacervate is of paramount importance. In this talk, we will present the results of field-theoretic simulations for a coarse-grained polyelectrolyte model that exhibits complex coacervation. Our simulations sample the fully-fluctuating fields in three-dimensions and provide a detailed characterization of the interface between the solvent and the coacervate phase for symmetric polyelectrolytes (where both the polycations and the polyanions carry identical charge densities) as a function of salt concentration and strength of the electrostatic fields. Finally, we characterize the interfacial properties for a select set of asymmetric conditions.

  8. Numerical simulation of radiation fog in complex terrain

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Musson-Genon, L.; Carissimo, B.; Dupont, E.

    2009-09-01

    The interest for micro-scale modeling of the atmosphere is growing for environmental applications related, for example, to energy production, transport and urban development. The turbulence in the stable layers where pollutant dispersion is low and can lead to strong pollution events. This could be further complicated by the presence of clouds or fog and is specifically difficult in urban or industrial area due to the presence of buildings. In this context, radiation fog formation and dissipation over complex terrain were therefore investigated with a state-of-the-art model. This study is divided into two phases. The first phase is a pilot stage, which consist of employing a database from the ParisFog campaign which took place in the south of Paris during winter 2006-07 to assess the ability of the cloud model to reproduce the detailed structure of radiation fog. The second phase use the validated model for the study of influence of complex terrain on fog evolution. Special attention is given to the detailed and complete simulations and validation technique used is to compare the simulated results using the 3D cloud model of computational fluid dynamical software Code_Saturne with one of the best collected in situ data during the ParisFog campaign. Several dynamical, microphysical parameterizations and simulation conditions have been described. The resulting 3D cloud model runs at a horizontal resolution of 30 m and a vertical resolution comparable to the 1D model. First results look very promising and are able to reproduce the spatial distribution of fog. The analysis of the behavior of the different parameterized physical processes suggests that the subtle balance between the various processes is achieved.

  9. Complicated bile duct stones

    PubMed Central

    Roy, Ashwin; Martin, Derrick

    2013-01-01

    Common bile duct stones (CBDSs) are solid deposits that can either form within the gallbladder or migrate to the common bile duct (CBD), or form de novo in the biliary tree. In the USA around 15% of the population have gallstones and of these, 3% present with symptoms annually. Because of this, there have been major advancements in the management of gallstones and related conditions. Management is based on the patient's risk profile; young and healthy patients are likely to be recommended for surgery and elderly patients with comorbidities are usually recommended for endoscopic procedures. Imaging of gallstones has advanced in the last 30 years with endoscopic retrograde cholangiopancreatography evolving from a diagnostic to a therapeutic procedure in removing CBDSs. We present a complicated case of a patient with a CBDS and periampullary diverticulum and discuss the techniques used to diagnose and remove the stone from the biliary system. PMID:23946532

  10. The anatomy of fluid-yielding ducts in breast cancer.

    PubMed

    Twelves, Dominique; Nerurkar, Ashutosh; Osin, Peter; Ward, Ann; Isacke, Clare M; Gui, Gerald P H

    2012-04-01

    The concept of an intraductal approach to evaluate the breast microenvironment assumes direct access to the cancer-containing duct. Central duct access to the cancer-affected lobe is essential if cytology or cell markers are to be useful indicators of pre-malignant change. Access to the cancer-bearing lobe would be less important if field change effects of malignant change were predominantly supra-lobar. The aim of this study was to determine how often duct lavage fluid drains the breast cancer-affected segment. 58 patients undergoing mastectomy for breast cancer were recruited among which 47 had at least one fluid-yielding duct. Following duct lavage, fluid-yielding ducts were perfused ex vivo with Polyurethane Elastomer (PU4ii) resin. Specimens were sliced sagittally, and the extent of resin perfusion and anatomical relationship to the cancer-affected segment was recorded. Computed tomography (CT) scanning was performed on selected mastectomies before cut-up for a feasibility study of 3D duct reconstruction. The median number of fluid-yielding ducts cannulated per cancer-affected breast was 2 (range 1-4). 35/47 (74%) mastectomy specimens were successfully cannulated for resin perfusion. 29/35 (83%) showed tracing of the cancer-affected duct system, 6/35 resin perfusions traced duct systems unaffected by cancer and 12/35 perfusions extravasated. The proportion of sagittal breast slices perfused by resin was 13-68% (median 43%). Volume rendering CT showed it is feasible to produce a simulated image of the perfused ducts. Duct access to the cancer-containing segment is feasible in the majority of patients. Fluid-yielding ducts proportionately drain a significant volume of the breast. Large symptomatic cancers may cause obstruction with distal collapse. Further quantitative study of breast perfusion CT scans may be helpful for estimating the volume fraction of breast tissue perfused by fluid-yielding ducts. The intraductal approach is a valid concept for biomarker

  11. The Eemian climate simulated by two models of different complexities

    NASA Astrophysics Data System (ADS)

    Nikolova, Irina; Yin, Qiuzhen; Berger, Andre; Singh, Umesh; Karami, Pasha

    2013-04-01

    The Eemian period, also known as MIS-5, experienced warmer than today climate, reduction in ice sheets and important sea-level rise. These interesting features have made the Eemian appropriate to evaluate climate models when forced with astronomical and greenhouse gas forcings different from today. In this work, we present the simulated Eemian climate by two climate models of different complexities, LOVECLIM (LLN Earth system model of intermediate complexity) and CCSM3 (NCAR atmosphere-ocean general circulation model). Feedbacks from sea ice, vegetation, monsoon and ENSO phenomena are discussed to explain the regional similarities/dissimilarities in both models with respect to the pre-industrial (PI) climate. Significant warming (cooling) over almost all the continents during boreal summer (winter) leads to a largely increased (reduced) seasonal contrast in the northern (southern) hemisphere, mainly due to the much higher (lower) insolation received by the whole Earth in boreal summer (winter). The arctic is warmer than at PI through the whole year, resulting from its much higher summer insolation and its remnant effect in the following fall-winter through the interactions between atmosphere, ocean and sea ice. Regional discrepancies exist in the sea-ice formation zones between the two models. Excessive sea-ice formation in CCSM3 results in intense regional cooling. In both models intensified African monsoon and vegetation feedback are responsible for the cooling during summer in North Africa and on the Arabian Peninsula. Over India precipitation maximum is found further west, while in Africa the precipitation maximum migrates further north. Trees and grassland expand north in Sahel/Sahara, trees being more abundant in the results from LOVECLIM than from CCSM3. A mix of forest and grassland occupies continents and expand deep in the high northern latitudes in line with proxy records. Desert areas reduce significantly in Northern Hemisphere, but increase in North

  12. Numerical Methods and Simulations of Complex Multiphase Flows

    NASA Astrophysics Data System (ADS)

    Brady, Peter

    Multiphase flows are an important part of many natural and technological phenomena such as ocean-air coupling (which is important for climate modeling) and the atomization of liquid fuel jets in combustion engines. The unique challenges of multiphase flow often make analytical solutions to the governing equations impossible and experimental investigations very difficult. Thus, high-fidelity numerical simulations can play a pivotal role in understanding these systems. This dissertation describes numerical methods developed for complex multiphase flows and the simulations performed using these methods. First, the issue of multiphase code verification is addressed. Code verification answers the question "Is this code solving the equations correctly?" The method of manufactured solutions (MMS) is a procedure for generating exact benchmark solutions which can test the most general capabilities of a code. The chief obstacle to applying MMS to multiphase flow lies in the discontinuous nature of the material properties at the interface. An extension of the MMS procedure to multiphase flow is presented, using an adaptive marching tetrahedron style algorithm to compute the source terms near the interface. Guidelines for the use of the MMS to help locate coding mistakes are also detailed. Three multiphase systems are then investigated: (1) the thermocapillary motion of three-dimensional and axisymmetric drops in a confined apparatus, (2) the flow of two immiscible fluids completely filling an enclosed cylinder and driven by the rotation of the bottom endwall, and (3) the atomization of a single drop subjected to a high shear turbulent flow. The systems are simulated numerically by solving the full multiphase Navier-Stokes equations coupled to the various equations of state and a level set interface tracking scheme based on the refined level set grid method. The codes have been parallelized using MPI in order to take advantage of today's very large parallel computational

  13. Monte Carlo simulations of systems with complex energy landscapes

    NASA Astrophysics Data System (ADS)

    Wüst, T.; Landau, D. P.; Gervais, C.; Xu, Y.

    2009-04-01

    Non-traditional Monte Carlo simulations are a powerful approach to the study of systems with complex energy landscapes. After reviewing several of these specialized algorithms we shall describe the behavior of typical systems including spin glasses, lattice proteins, and models for "real" proteins. In the Edwards-Anderson spin glass it is now possible to produce probability distributions in the canonical ensemble and thermodynamic results of high numerical quality. In the hydrophobic-polar (HP) lattice protein model Wang-Landau sampling with an improved move set (pull-moves) produces results of very high quality. These can be compared with the results of other methods of statistical physics. A more realistic membrane protein model for Glycophorin A is also examined. Wang-Landau sampling allows the study of the dimerization process including an elucidation of the nature of the process.

  14. Stereoscopy for visual simulation of materials of complex appearance

    NASA Astrophysics Data System (ADS)

    da Graça, Fernando; Paljic, Alexis; Lafon-Pham, Dominique; Callet, Patrick

    2014-03-01

    The present work studies the role of stereoscopy on perceived surface aspect of computer generated complex materials. The objective is to investigate if, and how, the additional information conveyed by the binocular vision affects the observer judgment on the evaluation of flake density in an effect paint simulation. We have set up a heuristic flake model with a Voronoi: modelization of flakes. The model was implemented in our rendering engine using global illumination, ray tracing, with an off axis-frustum method for the calculation of stereo images. We conducted a user study based on a flake density discrimination task to determine perception thresholds (JNDs). Results show that stereoscopy slightly improves density perception. We propose an analysis methodology based on granulometry. This allows for a discussion of the results on the basis of scales of observation.

  15. MOLECULAR SIMULATION OF PHASE EQUILIBRIA FOR COMPLEX FLUIDS

    SciTech Connect

    Athanassios Z. Panagiotopoulos

    2009-09-09

    The general area of this project was the development and application of novel molecular simulation methods for prediction of thermodynamic and structural properties of complex polymeric, surfactant and ionic fluids. Over this project period, we have made considerable progress in developing novel algorithms to meet the computational challenges presented by the strong or long-range interactions in these systems and have generated data for well-defined mod-els that can be used to test theories and compare to experimental data. Overall, 42 archival papers and many invited and contributed presentations and lectures have been based on work supported by this project. 6 PhD, 1 M.S. and 2 postdoctoral students have been associated with this work, as listed in the body of the report.

  16. Linearized simulation of flow over wind farms and complex terrains.

    PubMed

    Segalini, Antonio

    2017-04-13

    The flow over complex terrains and wind farms is estimated here by numerically solving the linearized Navier-Stokes equations. The equations are linearized around the unperturbed incoming wind profile, here assumed logarithmic. The Boussinesq approximation is used to model the Reynolds stress with a prescribed turbulent eddy viscosity profile. Without requiring the boundary-layer approximation, two new linear equations are obtained for the vertical velocity and the wall-normal vorticity, with a reduction in the computational cost by a factor of 8 when compared with a primitive-variables formulation. The presence of terrain elevation is introduced as a vertical coordinate shift, while forestry or wind turbines are included as body forces, without any assumption about the wake structure for the turbines. The model is first validated against some available experiments and simulations, and then a simulation of a wind farm over a Gaussian hill is performed. The speed-up effect of the hill is clearly beneficial in terms of the available momentum upstream of the crest, while downstream of it the opposite can be said as the turbines face a decreased wind speed. Also, the presence of the hill introduces an additional spanwise velocity component that may also affect the turbines' operations. The linear superposition of the flow over the hill and the flow over the farm alone provided a first estimation of the wind speed along the farm, with discrepancies of the same order of magnitude for the spanwise velocity. Finally, the possibility of using a parabolic set of equations to obtain the turbulent kinetic energy after the linearized model is investigated with promising results.This article is part of the themed issue 'Wind energy in complex terrains'.

  17. Linearized simulation of flow over wind farms and complex terrains

    NASA Astrophysics Data System (ADS)

    Segalini, Antonio

    2017-03-01

    The flow over complex terrains and wind farms is estimated here by numerically solving the linearized Navier-Stokes equations. The equations are linearized around the unperturbed incoming wind profile, here assumed logarithmic. The Boussinesq approximation is used to model the Reynolds stress with a prescribed turbulent eddy viscosity profile. Without requiring the boundary-layer approximation, two new linear equations are obtained for the vertical velocity and the wall-normal vorticity, with a reduction in the computational cost by a factor of 8 when compared with a primitive-variables formulation. The presence of terrain elevation is introduced as a vertical coordinate shift, while forestry or wind turbines are included as body forces, without any assumption about the wake structure for the turbines. The model is first validated against some available experiments and simulations, and then a simulation of a wind farm over a Gaussian hill is performed. The speed-up effect of the hill is clearly beneficial in terms of the available momentum upstream of the crest, while downstream of it the opposite can be said as the turbines face a decreased wind speed. Also, the presence of the hill introduces an additional spanwise velocity component that may also affect the turbines' operations. The linear superposition of the flow over the hill and the flow over the farm alone provided a first estimation of the wind speed along the farm, with discrepancies of the same order of magnitude for the spanwise velocity. Finally, the possibility of using a parabolic set of equations to obtain the turbulent kinetic energy after the linearized model is investigated with promising results. This article is part of the themed issue 'Wind energy in complex terrains'.

  18. Sound radiation from annular ducts/nozzles using modal decomposition of in-duct acoustic power

    NASA Technical Reports Server (NTRS)

    Salikuddin, M.

    1983-01-01

    Using a refined acoustic impulse technique, an experimental program was carried out to determine the proper procedure for measuring the acoustic power for both incident and reflected sound fields for annular ducts with and without nozzles at various flow conditions. Several radial and azimuthal pressure measurements were made, and using these complex pressure data, the modal content of the pressure field was determined. A mathematical approach for the modal decomposition of annular duct acoustic power was developed. The acoustic power due to each individual mode and also their total sum were derived. The acoustic characteristics of annular duct-nozzle systems were studied at various flow conditions. The results derived from the experiments include the termination reflection coefficient, the normalized transmission coefficients, the power transfer functions and the power imbalance.

  19. Soil signature simulation of complex mixtures and particle size distributions

    NASA Astrophysics Data System (ADS)

    Carson, Tyler; Bachmann, Charles M.; Salvaggio, Carl

    2015-09-01

    Soil reflectance signatures were modeled using the digital imaging and remote sensing image generation model and Blender three-dimensional (3-D) graphic design software. Using these tools, the geometry, radiometry, and chemistry of quartz and magnetite were exploited to model the presence of particle size and porosity effects in the visible and the shortwave infrared spectrum. Using the physics engines within the Blender 3-D graphic design software, physical representations of granular soil scenes were created. Each scene characterized a specific particle distribution and density. Chemical and optical properties of pure quartz and magnetite were assigned to particles in the scene based on particle size. This work presents a model to describe an observed phase-angle dependence of beach sand density. Bidirectional reflectance signatures were simulated for targets of varying size distribution and density. This model provides validation for a phenomenological trade space between density and particle size distribution in complex, heterogeneous soil mixtures. It also confirms the suggestion that directional reflectance signatures can be defined by intimate mixtures that depend on pore spacing. The study demonstrated that by combining realistic target geometry and spectral measurements of pure quartz and magnetite, effects of soil particle size and density could be modeled without functional data fitting or rigorous analysis of material dynamics. This research does not use traditional function-based models for simulation. The combination of realistic geometry, physically viable particle structure, and first-principles ray-tracing enables the ability to represent signature changes that have been observed in experimental observations.

  20. Global-Scale Hydrology: Simple Characterization of Complex Simulation

    NASA Technical Reports Server (NTRS)

    Koster, Randal D.

    1999-01-01

    Atmospheric general circulation models (AGCMS) are unique and valuable tools for the analysis of large-scale hydrology. AGCM simulations of climate provide tremendous amounts of hydrological data with a spatial and temporal coverage unmatched by observation systems. To the extent that the AGCM behaves realistically, these data can shed light on the nature of the real world's hydrological cycle. In the first part of the seminar, I will describe the hydrological cycle in a typical AGCM, with some emphasis on the validation of simulated precipitation against observations. The second part of the seminar will focus on a key goal in large-scale hydrology studies, namely the identification of simple, overarching controls on hydrological behavior hidden amidst the tremendous amounts of data produced by the highly complex AGCM parameterizations. In particular, I will show that a simple 50-year-old climatological relation (and a recent extension we made to it) successfully predicts, to first order, both the annual mean and the interannual variability of simulated evaporation and runoff fluxes. The seminar will conclude with an example of a practical application of global hydrology studies. The accurate prediction of weather statistics several months in advance would have tremendous societal benefits, and conventional wisdom today points at the use of coupled ocean-atmosphere-land models for such seasonal-to-interannual prediction. Understanding the hydrological cycle in AGCMs is critical to establishing the potential for such prediction. Our own studies show, among other things, that soil moisture retention can lead to significant precipitation predictability in many midlatitude and tropical regions.

  1. Global-Scale Hydrology: Simple Characterization of Complex Simulation

    NASA Technical Reports Server (NTRS)

    Koster, Randal D.

    1999-01-01

    Atmospheric general circulation models (AGCMS) are unique and valuable tools for the analysis of large-scale hydrology. AGCM simulations of climate provide tremendous amounts of hydrological data with a spatial and temporal coverage unmatched by observation systems. To the extent that the AGCM behaves realistically, these data can shed light on the nature of the real world's hydrological cycle. In the first part of the seminar, I will describe the hydrological cycle in a typical AGCM, with some emphasis on the validation of simulated precipitation against observations. The second part of the seminar will focus on a key goal in large-scale hydrology studies, namely the identification of simple, overarching controls on hydrological behavior hidden amidst the tremendous amounts of data produced by the highly complex AGCM parameterizations. In particular, I will show that a simple 50-year-old climatological relation (and a recent extension we made to it) successfully predicts, to first order, both the annual mean and the interannual variability of simulated evaporation and runoff fluxes. The seminar will conclude with an example of a practical application of global hydrology studies. The accurate prediction of weather statistics several months in advance would have tremendous societal benefits, and conventional wisdom today points at the use of coupled ocean-atmosphere-land models for such seasonal-to-interannual prediction. Understanding the hydrological cycle in AGCMs is critical to establishing the potential for such prediction. Our own studies show, among other things, that soil moisture retention can lead to significant precipitation predictability in many midlatitude and tropical regions.

  2. Numerical simulation of the falling snow deposition over complex terrain

    NASA Astrophysics Data System (ADS)

    Wang, Zhengshi; Huang, Ning

    2017-01-01

    Snow is one of the most dynamic natural elements on the Earth's surface, and the variations in its distribution in time and space profoundly affect the hydrological cycle, climate system, and ecological evolution as well as other natural processes. Most previous studies have paid less attention to the process determining the distribution of snow on the ground as a result of the effect of nonuniform mountain wind on the trajectories of snow particles. In this paper, we present a numerical study on the falling snow deposition process involving snow particles of mixed grain sizes over complex terrain. A three-dimensional large-eddy simulation code was used to predict the wind field by considering the fluid-solid coupling effect, and the Lagrangian particle tracking method was employed to track the movement of each tracking snow particle. The grid resolution and model parameters were determined by the best fit with the field experiment, and the coupling effect between snow particles and wind field was found to be nonnegligible when the drifting snow occurred. In general, the preferential deposition on a single ridge showed a tendency from windward slope toward leeward slope with the increasing advection, while it was hard to describe the snow distribution over complex terrains with a unified deposition model due to the interaction of surrounding topographies and different atmospheric stabilities, and the particle tracking approach was substantially suitable for this issue. Our study significantly improved the understanding of the evolution of snow distributions at high levels of resolution.

  3. Constant-complexity stochastic simulation algorithm with optimal binning.

    PubMed

    Sanft, Kevin R; Othmer, Hans G

    2015-08-21

    At the molecular level, biochemical processes are governed by random interactions between reactant molecules, and the dynamics of such systems are inherently stochastic. When the copy numbers of reactants are large, a deterministic description is adequate, but when they are small, such systems are often modeled as continuous-time Markov jump processes that can be described by the chemical master equation. Gillespie's Stochastic Simulation Algorithm (SSA) generates exact trajectories of these systems, but the amount of computational work required for each step of the original SSA is proportional to the number of reaction channels, leading to computational complexity that scales linearly with the problem size. The original SSA is therefore inefficient for large problems, which has prompted the development of several alternative formulations with improved scaling properties. We describe an exact SSA that uses a table data structure with event time binning to achieve constant computational complexity with respect to the number of reaction channels for weakly coupled reaction networks. We present a novel adaptive binning strategy and discuss optimal algorithm parameters. We compare the computational efficiency of the algorithm to existing methods and demonstrate excellent scaling for large problems. This method is well suited for generating exact trajectories of large weakly coupled models, including those that can be described by the reaction-diffusion master equation that arises from spatially discretized reaction-diffusion processes.

  4. Constant-complexity stochastic simulation algorithm with optimal binning

    SciTech Connect

    Sanft, Kevin R.; Othmer, Hans G.

    2015-08-21

    At the molecular level, biochemical processes are governed by random interactions between reactant molecules, and the dynamics of such systems are inherently stochastic. When the copy numbers of reactants are large, a deterministic description is adequate, but when they are small, such systems are often modeled as continuous-time Markov jump processes that can be described by the chemical master equation. Gillespie’s Stochastic Simulation Algorithm (SSA) generates exact trajectories of these systems, but the amount of computational work required for each step of the original SSA is proportional to the number of reaction channels, leading to computational complexity that scales linearly with the problem size. The original SSA is therefore inefficient for large problems, which has prompted the development of several alternative formulations with improved scaling properties. We describe an exact SSA that uses a table data structure with event time binning to achieve constant computational complexity with respect to the number of reaction channels for weakly coupled reaction networks. We present a novel adaptive binning strategy and discuss optimal algorithm parameters. We compare the computational efficiency of the algorithm to existing methods and demonstrate excellent scaling for large problems. This method is well suited for generating exact trajectories of large weakly coupled models, including those that can be described by the reaction-diffusion master equation that arises from spatially discretized reaction-diffusion processes.

  5. Asymptomatic common bile duct stones.

    PubMed

    Rosseland, A R; Glomsaker, T B

    2000-11-01

    Patients with asymptomatic bile duct stones exhibit typical signs, such as elevated liver function tests, dilated bile ducts on ultrasound, a history of jaundice, or pancreatitis. The incidence of asymptomatic bile duct stones is about 10%, but up to 2% of patients show no signs of the disease. Bile duct stones can be diagnosed by using clinical judgement, scoring systems, or discriminant function tests. Which diagnostic modality is most reliable, cost-effective and safe, varies with different hospitals. Which therapy is most effective, safe and the cheapest also varies with different departments, but in the future an increasing number of departments will use the one-stage laparoscopic approach.

  6. Numerical simulation of three-dimensional mixed convection heat transfer from an array of discrete heat sources in a horizontal rectangular duct

    SciTech Connect

    Mahaney, H.V.; Ramadhyani, S.; Incropera, F.P. . School of Mechanical Engineering)

    1989-01-01

    Using a vectorized finite-difference marching technique, the steady-state continuity, momentum, and energy equations are solved numerically to evaluate the effects of buoyancy-induced secondary flow on forced flow in a horizontal rectangular duct with a four-row array of 12 heat sources flush mounted to the bottom wall. Secondary flows, in the form of longitudinal vortices, initially develop at spanwise positions corresponding to the edges of the heat sources. Additional plumes and vortices subsequently develop across the heater width, leading to the eventual formation of large-scale circulation patterns. For a fixed Rayleigh number and decreasing Reynolds number, the row-average Nusselt numbers decrease, reach a minimum, and subsequently increase due to bouyancy effects. Thus, due to buoyancy-induced secondary flow, conditions exist for which heat transfer may be enhanced by reducing the flow rate and hence the pump ower requiement. Heat transfer enhancement above the forced convection limit, as well as the Reynolds number range for which enhancement occurs, increases with increasing Raleigh number. Appropriate scaling parameters are introduced to characterize the strength of the buoyancy-induced secondary flow and to delineate conditions for which it is significant.

  7. Simulating Ecological Complexity Using the Example of Pesticides in Ecosystems.

    ERIC Educational Resources Information Center

    Muir, Patricia S.; McCune, Bruce

    1993-01-01

    Describes a simulation exercise developed for an introductory biology course for nonmajors. The simulation focuses on the control of western spruce budworms in forests of the western United States. A nonlinear, multivariate simulation model is used. (PR)

  8. LISP based simulation generators for modeling complex space processes

    NASA Technical Reports Server (NTRS)

    Tseng, Fan T.; Schroer, Bernard J.; Dwan, Wen-Shing

    1987-01-01

    The development of a simulation assistant for modeling discrete event processes is presented. Included are an overview of the system, a description of the simulation generators, and a sample process generated using the simulation assistant.

  9. Stopping duct quacks: Longevity of residential duct sealants

    SciTech Connect

    Sherman, Max H.; Walker, Iain S.; Dickerhoff, Darryl J.

    2000-08-01

    Duct leakage has been identified as a major source of energy loss in residential buildings. Most duct leakage occurs at the connections to registers, plenums or branches in the duct system. At each of these connections a method of sealing the duct system is required. Typical sealing methods include tapes or mastics applied around the joints in the system. Field examinations of duct systems have shown that these seals tend to fail over time periods ranging from days to years. We have used several test methods over the last few years to evaluate the longevity of duct sealants when subjected to temperatures and pressures representative of those found in the field. Traditional cloth duct tapes have been found to significantly under-perform other sealants and have been banned from receiving duct tightness credits in California's energy code (California Energy Commission 1998). Our accelerated testing apparatus has been redesigned since its first usage for improved performance. The methodology is currently under consideration by the American Society for Testing and Materials (ASTM) as a potential new test method. This report will summarize the set of measurements to date, review the status of the test apparatus and test method, and summarize the applications of these results to codes and standards.

  10. Use of the Environmental Simulation Program (ESP) to Simulate Complex Waste Treatment Processes

    SciTech Connect

    MacLean, G. T.; Ho, Q. T.; Berger, S. R. K.

    2003-02-26

    The Environmental Simulation Program is a process simulator designed for aqueous based chemical processes. ESP, which is produced by OLI Systems, Inc., utilizes sophisticated activity coefficient models and predictive equations that result in the ability to simulate very complex electrolyte systems (OLI, 2002). The software comes with databanks of regressed parameters for a large number of aqueous, vapor, and solid species covering most of the elements. ESP has been used extensively at the U. S. Department of Energy Hanford Site to predict nuclear waste slurry vapor-liquid-solid equilibrium. It has and is being used to model leaching and washing of nuclear waste sludges, evaporation of nuclear waste solutions, crystallization of salts, precipitation of plutonium and other metals from waste solutions, and other processing of dilute and concentrated aqueous solutions, sludges, and slurries. The software is also used extensively to rationalize the characterization of nuclear wastes using limited data from analyses of waste samples. The OLI provided databanks suffer from a legacy interaction model that limits the accuracy when neutral solutes are important. Also, the nitrate-nitrite systems typically found in nuclear wastes are not properly parameterized in ESP databases because of the existence of sodium nitrate and nitrite ion pairs. Properties databanks for ESP have been developed at Flour Federal Services that eliminate the legacy model and provide more accurate simulation results than the OLI supplied databases for such concentrated solutions and slurries.

  11. Intrahepatic Transposition of Bile Ducts

    PubMed Central

    Delić, Jasmin; Savković, Admedina; Isaković, Eldar; Marković, Sergije; Bajtarevic, Alma; Denjalić, Amir

    2012-01-01

    Objective. To describe the intrahepatic bile duct transposition (anatomical variation occurring in intrahepatic ducts) and to determine the frequency of this variation. Material and Methods. The researches were performed randomly on 100 livers of adults, both sexes. Main research methods were anatomical macrodissection. As a criterion for determination of variations in some parts of bile tree, we used the classification of Segmentatio hepatis according to Couinaud (1957) according to Terminologia Anatomica, Thieme Stuugart: Federative Committee on Anatomical Terminology, 1988. Results. Intrahepatic transposition of bile ducts was found in two cases (2%), out of total examined cases (100): right-left transposition (right segmental bile duct, originating from the segment VIII, joins the left liver duct-ductus hepaticus sinister) and left-right intrahepatic transposition (left segmental bile duct originating from the segment IV ends in right liver duct-ductus hepaticus dexter). Conclusion. Safety and success in liver transplantation to great extent depends on knowledge of anatomy and some common embryological anomalies in bile tree. Variations in bile tree were found in 24–43% of cases, out of which 1–22% are the variations of intrahepatic bile ducts. Therefore, good knowledge on ductal anatomy enables good planning, safe performance of therapeutic and operative procedures, and decreases the risk of intraoperative and postoperative complications. PMID:22550601

  12. Particulate mixing in a turbulent serpentine duct

    NASA Astrophysics Data System (ADS)

    Huang, X.; Durbin, P. A.

    2012-01-01

    Direct numerical simulations of particles in a serpentine duct were conducted at bulk flow Stokes numbers between 0.125 and 6. The geometrical curvature causes particles to depart direction from the mean flow. Above a Stokes number of about unity, a reflection layer forms along the outer curve of the bend. Reflectional mixing creates regions of nearly uniform particle mean velocity and kinetic energy. Particles leave the inner bend in a plume that separates from the inner wall at low Stokes number. At higher Stokes number, the plume splits in two, adding an upper part consisting of ballistic particles, that do not follow the geometrical curvature. When the Stokes number is low, the instantaneous 3-D distribution of particles visualizes wall streaks. But at higher Stokes number, particles disperse out of the reflection layer and form large scale puffs in the central portion of the duct.

  13. Lagrangian simulation of mixing and reactions in complex geochemical systems

    NASA Astrophysics Data System (ADS)

    Engdahl, Nicholas B.; Benson, David A.; Bolster, Diogo

    2017-04-01

    Simulations of detailed geochemical systems have traditionally been restricted to Eulerian reactive transport algorithms. This note introduces a Lagrangian method for modeling multicomponent reaction systems. The approach uses standard random walk-based methods for the particle motion steps but allows the particles to interact with each other by exchanging mass of their various chemical species. The colocation density of each particle pair is used to calculate the mass transfer rate, which creates a local disequilibrium that is then relaxed back toward equilibrium using the reaction engine PhreeqcRM. The mass exchange is the only step where the particles interact and the remaining transport and reaction steps are entirely independent for each particle. Several validation examples are presented, which reproduce well-known analytical solutions. These are followed by two demonstration examples of a competitive decay chain and an acid-mine drainage system. The source code, entitled Complex Reaction on Particles (CRP), and files needed to run these examples are hosted openly on GitHub (https://github.com/nbengdahl/CRP), so as to enable interested readers to readily apply this approach with minimal modifications.

  14. Laparoscopic common bile duct exploration.

    PubMed

    Stoker, M E; Leveillee, R J; McCann, J C; Maini, B S

    1991-10-01

    Operative common bile duct exploration, performed in conjunction with cholecystectomy, has been considered the treatment of choice for choledocholithiasis in the presence of an intact gallbladder. With the advent of laparoscopic cholecystectomy, the management of common bile duct stones has been affected. More emphasis is being placed on endoscopic sphincterotomy and options other than operative common duct exploration. Because of this increasing demand, we have developed a new technique for laparoscopic common bile duct exploration performed in the same operative setting as laparoscopic cholecystectomy. A series of five patients who successfully underwent common bile duct exploration, flexible choledochoscopy with stone extraction, and T-tube drainage, all using laparoscopic technique, is reported. Mean postoperative length of hospital stay was 4.6 days. Outpatient T-tube cholangiography was performed in all cases and revealed normal ductal anatomy with no retained stones. Follow-up ranged from 6 weeks to 4 months, and all patients were asymptomatic and had normal liver function tests.

  15. Ascariasis of the pancreatic duct.

    PubMed

    Klimovskij, Michail; Dulskas, Audrius; Kraulyte, Zita; Mikalauskas, Saulius

    2015-09-15

    Ascariasis is a common helminthic disease worldwide, although Lithuania and other European countries are not considered endemic areas. The presence of the Ascaris worm in the biliary tree causes choledocholithiasis-like symptoms. We report a case of pancreatic duct ascariasis causing such symptoms. A 73-year-old Lithuanian woman underwent endoscopic retrograde cholangiopancreatography (ERCP) suspecting choledocholithiasis. Contrast injection into the common bile duct demonstrated a slightly dilated biliary tree without any filling defects, and the tail of an Ascaris worm protruding from the opening of the papilla Vater. The worm was captured by a snare but escaped deep into the duct. After a small wirsungotomy the worm was retrieved from the pancreatic duct. The patient received a 150 mg dose of levamisole orally repeated 7 days later and was discharged after complete resolution of symptoms. This first reported sporadic case of pancreatic duct ascariasis in Lithuania was successfully treated with ERCP and Levamisole.

  16. Subsonic Flows through S-Ducts with Flow Control

    NASA Astrophysics Data System (ADS)

    Chen, Yi

    An inlet duct of an aircraft connects the air intake mounted on the fuselage to the engine within the aircraft body. The ideal outflow quality of the duct is steady, uniform and of high total pressure. Recently compact S-shaped inlet ducts are drawing more attention in the design of UAVs with short propulsion system. Compact ducts usually involve strong streamwise adverse pressure gradient and transverse secondary flow, leading to large-scale harmful vortical structures in the outflow. To improve the outflow quality modern flow control techniques have to be applied. Before designing successful flow control methods a solid understanding of the baseline flow field with the duct is crucial. In this work the fundamental mechanism of how the three dimensional flow topology evolves when the relevant parameters such as the duct geometry and boundary layer thickness are varied, is studied carefully. Two distinct secondary-flow patterns are identified. For the first time the sensitivity of the flow topology to the inflow boundary layer thickness in long ducts is clearly addressed. The interaction between the transverse motion induced by the transverse pressure gradient and the streamwise separation is revealed as the crucial reason for the various flow patterns existing in short ducts. A non-symmetric flow pattern is identified for the first time in both experiments and simulations in short ducts in which the intensity of the streamwise separation and the transverse invasion are in the same order of magnitude. A theory of energy accumulation and solution bifurcation is used to give a reasonable explanation for this non-symmetry. After gaining the knowledge of where and how the harmful vortical structures are generated several flow control techniques are tested to achieve a better outflow quality. The analysis of the flow control cases also provides a deeper insight into the behavior of the three-dimensional flow within the ducts. The conventional separation control method

  17. Hydrodynamic Modeling, Optimization and Performance Assessment for Ducted and Non-ducted Tidal Turbines

    NASA Astrophysics Data System (ADS)

    Shives, Michael Robert

    This thesis examines methods for designing and analyzing kinetic turbines based on blade element momentum (BEM) theory and computational fluid dynamics (CFD). The underlying goal of the work was to assess the potential augmentation of power production associated with enclosing the turbine in an expanding duct. Thus, a comparison of the potential performance of ducted and non-ducted turbines was carried out. This required defining optimal turbine performance for both concepts. BEM is the typical tool used for turbine optimization and is very well established in the context of wind turbine design. BEM was suitable for conventional turbines, but could not account for the influence of ducts, and no established methodology for designing ducted turbines could be found in the literature. Thus, methods were established to design and analyze ducted turbines based on an extended version of BEM (with CFD-derived coefficients), and based on CFD simulation. Additional complications arise in designing tidal turbines because traditional techniques for kinetic turbine design have been established for wind turbines, which are similar in their principle of operation but are driven by flows with inherently different boundary conditions than tidal currents. The major difference is that tidal flows are bounded by the ocean floor, the water surface and channel walls. Thus, analytical and CFD-based methods were established to account for the effects of these boundaries (called blockage effects) on the optimal design and performance of turbines. Additionally, tidal flows are driven by changes in the water surface height in the ocean and their velocity is limited by viscous effects. Turbines introduced into a tidal flow increase the total drag in the system and reduce the total flow in a region (e.g. a tidal channel). An analytical method to account for this was taken from the field of tidal resource assessment, and along with the methods to account for ducts and blockage effects, was

  18. What Happens After Treatment for Bile Duct Cancer?

    MedlinePlus

    ... After Treatment What Happens After Treatment for Bile Duct Cancer? For some people with bile duct cancer, ... Bile Duct Cancer Stops Working More In Bile Duct Cancer About Bile Duct Cancer Causes, Risk Factors, ...

  19. Chemical complexity in astrophysical simulations: optimization and reduction techniques

    NASA Astrophysics Data System (ADS)

    Grassi, T.; Bovino, S.; Schleicher, D.; Gianturco, F. A.

    2013-05-01

    Chemistry plays a key role in the evolution of the interstellar medium, so it is highly important to follow its evolution in numerical simulations. However, it could easily dominate the computational cost when applied to large systems. In this paper we discuss two approaches to reduce these costs: (i) based on computational strategies, and (ii) based on the properties and on the topology of the chemical network. The first methods are more robust, while the second are meant to be giving important information on the structure of large, complex networks. We first discuss the numerical solvers for integrating the system of ordinary differential equations (ODE) associated with the chemical network, and then we propose a buffer method that decreases the computational time spent in solving the ODE system. We further discuss a flux-based method that allows one to determine and then cut on the fly the less active reactions. In addition we also present a topological approach for selecting the most probable species that will be active during the chemical evolution, thus gaining information on the chemical network that otherwise would be difficult to retrieve. This topological technique can also be used as an a priori reduction method for any size network. We implemented these methods into a 1D Lagrangian hydrodynamical code to test their effects: both classes lead to large computational speed-ups, ranging from ×2 to ×5. We have also tested some hybrid approaches finding that coupling the flux method with a buffer strategy gives the best trade-off between robustness and speed-up of calculations.

  20. CFD-Based Design of Turbopump Inlet Duct for Reduced Dynamic Loads

    NASA Technical Reports Server (NTRS)

    Rothermel, Jeffry; Dorney, Suzanne M.; Dorney, Daniel J.

    2003-01-01

    Numerical simulations have been completed for a variety of designs for a 90 deg elbow duct. The objective is to identify a design that minimizes the dynamic load entering a LOX turbopump located at the elbow exit. Designs simulated to date indicate that simpler duct geometries result in lower losses. Benchmark simulations have verified that the compressible flow codes used in this study are applicable to these incompressible flow simulations.

  1. CFD-based Design of LOX Pump Inlet Duct for Reduced Dynamic Loads

    NASA Technical Reports Server (NTRS)

    Rothermel, Jeffry; Dorney, Daniel J.; Dorney, Suzanne M.

    2003-01-01

    Numerical simulations have been completed for a variety of designs for a 90 deg elbow duct. The objective is to identify a design that minimizes the dynamic load entering a LOX turbopump located at the elbow exit. Designs simulated to date indicate that simpler duct geometries result in lower losses. Benchmark simulations have verified that the compressible flow code used in this study is applicable to these incompressible flow simulations.

  2. SMALL, GEOLOGICALLY COMPLEX RESERVOIRS CAN BENEFIT FROM RESERVOIR SIMULATION

    SciTech Connect

    Richard E. Bennett

    2002-06-24

    The Cascade Sand zone of the Mission-Visco Lease in the Cascade Oil field of Los Angeles County, California, has been under water flood since 1970. Increasing water injection to increase oil production rates was being considered as an opportunity to improve oil recovery. However, a secondary gas cap had formed in the up-dip portion of the reservoir with very low gas cap pressures, creating concern that oil could be displaced into the gas cap resulting in the loss of recoverable oil. Therefore, injecting gas into the gas cap to keep the gas cap pressurized and restrict the influx of oil during water injection was also being considered. Further, it was recognized that the reservoir geology in the gas cap area is very complex with numerous folding and faulting and thus there are potential pressure barriers in several locations throughout the reservoir. With these conditions in mind, there were concerns regarding well to well continuity in the gas cap, which could interfere with the intended repressurization impact. Concerns about the pattern of gas flow from well to well, the possibilities of cycling gas without the desired increased pressure, and the possible loss of oil displaced into the gas cap resulted in the decision to conduct a gas tracer survey in an attempt to better define inter-well communication. Following the gas tracer survey, a reservoir model would be developed to integrate the findings of the gas tracer survey, known geologic and reservoir data, and historic production data. The reservoir model would be used to better define the reservoir characteristics and provide information that could help optimize the waterflood-gas injection project under consideration for efficient water and gas injection management to increase oil production. However, due to inadequate gas sampling procedures in the field and insufficiently developed laboratory analytical techniques, the laboratory was unable to detect the tracer in the gas samples taken. At that point, focus

  3. Intraductal tubular neoplasms of the bile ducts.

    PubMed

    Katabi, Nora; Torres, Javiera; Klimstra, David S

    2012-11-01

    metastases, 1 after local intraductal recurrence. However, the occurrence of metastasis in 3 of these patients was quite late (average, 52 mo). Intraductal tubular neoplasm of the bile ducts is a biliary intraductal neoplasm with a distinctive histologic pattern resembling the recently described intraductal tubulopapillary neoplasm of the pancreas. Immunohistochemical features are similar to those of other pancreatobiliary-type carcinomas. However, this tumor may be hard to recognize as intraductal because of its complex architecture. When the tumor is entirely intraductal, the outcome appears to be favorable, but metastases can occur when invasive carcinoma is present, even after many years.

  4. PMR Graphite Engine Duct Development

    NASA Technical Reports Server (NTRS)

    Stotler, C. L.; Yokel, S. A.

    1989-01-01

    The objective was to demonstrate the cost and weight advantages that could be obtained by utilizing the graphite/PMR15 material system to replace titanium in selected turbofan engine applications. The first component to be selected as a basis for evaluation was the outer bypass duct of the General Electric F404 engine. The operating environment of this duct was defined and then an extensive mechanical and physical property test program was conducted using material made by processing techniques which were also established by this program. Based on these properties, design concepts to fabricate a composite version of the duct were established and two complete ducts fabricated. One of these ducts was proof pressure tested and then run successfully on a factory test engine for over 1900 hours. The second duct was static tested to 210 percent design limit load without failure. An improved design was then developed which utilized integral composite end flanges. A complete duct was fabricated and successfully proof pressure tested. The net results of this effort showed that a composite version of the outer duct would be 14 percent lighter and 30 percent less expensive that the titanium duct. The other type of structure chosen for investigation was the F404 fan stator assembly, including the fan stator vanes. It was concluded that it was feasible to utilize composite materials for this type structure but that the requirements imposed by replacing an existing metal design resulted in an inefficient composite design. It was concluded that if composites were to be effectively used in this type structure, the design must be tailored for composite application from the outset.

  5. A non-local computational boundary condition for duct acoustics

    NASA Technical Reports Server (NTRS)

    Zorumski, William E.; Watson, Willie R.; Hodge, Steve L.

    1994-01-01

    A non-local boundary condition is formulated for acoustic waves in ducts without flow. The ducts are two dimensional with constant area, but with variable impedance wall lining. Extension of the formulation to three dimensional and variable area ducts is straightforward in principle, but requires significantly more computation. The boundary condition simulates a nonreflecting wave field in an infinite duct. It is implemented by a constant matrix operator which is applied at the boundary of the computational domain. An efficient computational solution scheme is developed which allows calculations for high frequencies and long duct lengths. This computational solution utilizes the boundary condition to limit the computational space while preserving the radiation boundary condition. The boundary condition is tested for several sources. It is demonstrated that the boundary condition can be applied close to the sound sources, rendering the computational domain small. Computational solutions with the new non-local boundary condition are shown to be consistent with the known solutions for nonreflecting wavefields in an infinite uniform duct.

  6. 14 CFR 29.1103 - Induction systems ducts and air duct systems.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Induction systems ducts and air duct... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Induction System § 29.1103 Induction systems ducts and air duct systems. (a) Each induction system duct upstream of the...

  7. Observationally constrained modeling of sound in curved ocean internal waves: examination of deep ducting and surface ducting at short range.

    PubMed

    Duda, Timothy F; Lin, Ying-Tsong; Reeder, D Benjamin

    2011-09-01

    A study of 400 Hz sound focusing and ducting effects in a packet of curved nonlinear internal waves in shallow water is presented. Sound propagation roughly along the crests of the waves is simulated with a three-dimensional parabolic equation computational code, and the results are compared to measured propagation along fixed 3 and 6 km source/receiver paths. The measurements were made on the shelf of the South China Sea northeast of Tung-Sha Island. Construction of the time-varying three-dimensional sound-speed fields used in the modeling simulations was guided by environmental data collected concurrently with the acoustic data. Computed three-dimensional propagation results compare well with field observations. The simulations allow identification of time-dependent sound forward scattering and ducting processes within the curved internal gravity waves. Strong acoustic intensity enhancement was observed during passage of high-amplitude nonlinear waves over the source/receiver paths, and is replicated in the model. The waves were typical of the region (35 m vertical displacement). Two types of ducting are found in the model, which occur asynchronously. One type is three-dimensional modal trapping in deep ducts within the wave crests (shallow thermocline zones). The second type is surface ducting within the wave troughs (deep thermocline zones). © 2011 Acoustical Society of America

  8. Examining Factors that Affect Performance in Complex Simulation Environments

    ERIC Educational Resources Information Center

    Mayrath, Michael Charles

    2009-01-01

    This study examined the effects of manipulating the modality (text-only, voice-only, voice+text) of a tutorial and restriction (restricted vs. unrestricted) of a simulation's interface on retention and transfer of tutorial content. The tutorial prepared novice students to use Packet Tracer, a simulation developed by Cisco that teaches network…

  9. Examining Factors that Affect Performance in Complex Simulation Environments

    ERIC Educational Resources Information Center

    Mayrath, Michael Charles

    2009-01-01

    This study examined the effects of manipulating the modality (text-only, voice-only, voice+text) of a tutorial and restriction (restricted vs. unrestricted) of a simulation's interface on retention and transfer of tutorial content. The tutorial prepared novice students to use Packet Tracer, a simulation developed by Cisco that teaches network…

  10. Sound propagation in choked ducts

    NASA Technical Reports Server (NTRS)

    Hersh, A. S.; Liu, C. Y.

    1976-01-01

    The linearized equations describing the propagation of sound in variable area ducts containing flow are shown to be singular when the duct mean flow is sonic. The singularity is removed when previously ignored nonlinear terms are retained. The results of a numerical study, for the case of plane waves propagating in a one-dimensional converging-diverging duct, show that the sound field is adequately described by the linearized equations only when the axial mean flow Mach number at the duct throat M sub th 0.6. For M sub th 0.6, the numerical results showed that acoustic energy flux was not conserved. An attempt was made to extend the study to include the nonlinear behavior of the sound field. Meaningful results were not obtained due, primarily, to numerical difficulties.

  11. Paraganglioma of the bile duct.

    PubMed

    Caceres, M; Mosquera, L F; Shih, J A; O'Leary, J P

    2001-05-01

    We report the case of a 28-year-old woman with a 3-month history of right upper quadrant abdominal pain. Medical history and physical examination were unremarkable. Abdominal ultrasonography showed a dilated gallbladder, suggestive of gallstones, without bile duct dilatation. Serum chemistry values were normal. Laparoscopic cholecystectomy was planned, and a mass encircling the common bile duct was found. The procedure was converted to an open operation, and cholecystectomy, mass excision, and hepaticojejunostomy were done. The specimen was interpreted as paraganglioma of the bile duct. There were no manifestations of catecholamine hypersecretion or signs of biliary obstruction. Six years later, the patient is asymptomatic without signs of recurrence. This is the third report of paraganglioma of the hepatic ducts. We describe the clinical and pathologic findings and therapeutic approach in this unusual case and review the literature.

  12. Articulated transition duct in turbomachine

    DOEpatents

    Flanagan, James Scott; McMahan, Kevin Weston; LeBegue, Jeffrey Scott; Pentecost, Ronnie Ray

    2014-04-29

    Turbine systems are provided. A turbine system includes a transition duct comprising an inlet, an outlet, and a duct passage extending between the inlet and the outlet and defining a longitudinal axis, a radial axis, and a tangential axis. The outlet of the transition duct is offset from the inlet along the longitudinal axis and the tangential axis. The duct passage includes an upstream portion and a downstream portion. The upstream portion extends from the inlet between an inlet end and an aft end. The downstream portion extends from the outlet between an outlet end and a head end. The turbine system further includes a joint coupling the aft end of the upstream portion and the head end of the downstream portion together. The joint is configured to allow movement of the upstream portion and the downstream portion relative to each other about or along at least one axis.

  13. Bile Duct Diseases - Multiple Languages

    MedlinePlus

    ... Supplements Videos & Tools You Are Here: Home → Multiple Languages → All Health Topics → Bile Duct Diseases URL of this page: https://medlineplus.gov/languages/bileductdiseases.html Other topics A-Z Expand Section ...

  14. Locating Anomalies in Complex Data Sets Using Visualization and Simulation

    NASA Technical Reports Server (NTRS)

    Panetta, Karen

    2001-01-01

    The research goals are to create a simulation framework that can accept any combination of models written at the gate or behavioral level. The framework provides the ability to fault simulate and create scenarios of experiments using concurrent simulation. In order to meet these goals we have had to fulfill the following requirements. The ability to accept models written in VHDL, Verilog or the C languages. The ability to propagate faults through any model type. The ability to create experiment scenarios efficiently without generating every possible combination of variables. The ability to accept adversity of fault models beyond the single stuck-at model. Major development has been done to develop a parser that can accept models written in various languages. This work has generated considerable attention from other universities and industry for its flexibility and usefulness. The parser uses LEXX and YACC to parse Verilog and C. We have also utilized our industrial partnership with Alternative System's Inc. to import vhdl into our simulator. For multilevel simulation, we needed to modify the simulator architecture to accept models that contained multiple outputs. This enabled us to accept behavioral components. The next major accomplishment was the addition of "functional fault models". Functional fault models change the behavior of a gate or model. For example, a bridging fault can make an OR gate behave like an AND gate. This has applications beyond fault simulation. This modeling flexibility will make the simulator more useful for doing verification and model comparison. For instance, two or more versions of an ALU can be comparatively simulated in a single execution. The results will show where and how the models differed so that the performance and correctness of the models may be evaluated. A considerable amount of time has been dedicated to validating the simulator performance on larger models provided by industry and other universities.

  15. Flow duct for nuclear reactors

    DOEpatents

    Straalsund, Jerry L.

    1978-01-01

    Improved liquid sodium flow ducts for nuclear reactors are described wherein the improvement comprises varying the wall thickness of each of the walls of a polygonal tubular duct structure so that each of the walls is of reduced cross-section along the longitudinal center line and of a greater cross-section along wall junctions with the other walls to form the polygonal tubular configuration.

  16. Fan/Ram Duct Program

    DTIC Science & Technology

    1973-10-01

    turbofan engine shutoff scheme, the ram duct flow conditions, and the Ian duct shutoff vane area transi- tion schedule. This loss will be...airflow. The performance of the turbofan is neglected until the main engine burner is ignited. At that time it is assumed that the turbo - fan...B. Transient Operation . . .. TRANSIENT TRANSITION TEST CASES A. Turbofan to Ramjet B. Ramjet to Turbo fan CONCLUSIONS AND RECOMMENDATIONS

  17. TWO NEW DUCT LEAKAGE TESTS

    SciTech Connect

    ANDREWS,J.W.

    1998-12-01

    Two variations on the tests for duct leakage currently embodied in ASHRAE Standard 152P (Method of Test for Determining the Design and Seasonal Efficiencies of Residential Thermal Distribution Systems) are presented. Procedures are derived for calculating supply and return duct leakage to/from outside using these new variations. Results of these tests are compared with the original ones in Standard 152P on the basis of data collected in three New York State homes.

  18. Flexible Borescope For Inspecting Ducts

    NASA Technical Reports Server (NTRS)

    Shinozaki, Keith; Armstrong, Mike P.; Urquidi, Ron

    1995-01-01

    Borescope and associated equipment developed specifically for use in optical inspection of inside of flexible joints in rocket-engine fuel duct. Apparatus includes assembly, characterized as "mouse/canoe," at sensing end of 10-ft borescope cable. Borescope tip rides in mouse/canoe. The mouse/canoe made laterally compressible, to facilitate movement past constrictions and provides fixed distance from inspection point permitting accurate description in duct inspected.

  19. Duct Leakage Repeatability Testing

    SciTech Connect

    Walker, Iain; Sherman, Max

    2014-01-01

    Duct leakage often needs to be measured to demonstrate compliance with requirements or to determine energy or Indoor Air Quality (IAQ) impacts. Testing is often done using standards such as ASTM E1554 (ASTM 2013) or California Title 24 (California Energy Commission 2013 & 2013b), but there are several choices of methods available within the accepted standards. Determining which method to use or not use requires an evaluation of those methods in the context of the particular needs. Three factors that are important considerations are the cost of the measurement, the accuracy of the measurement and the repeatability of the measurement. The purpose of this report is to evaluate the repeatability of the three most significant measurement techniques using data from the literature and recently obtained field data. We will also briefly discuss the first two factors. The main question to be answered by this study is to determine if differences in the repeatability of these tests methods is sufficient to indicate that any of these methods is so poor that it should be excluded from consideration as an allowed procedure in codes and standards.

  20. Turbofan aft duct suppressor study

    NASA Technical Reports Server (NTRS)

    Syed, A. A.; Motsinger, R. E.; Fiske, G. H.; Joshi, M. C.; Kraft, R. E.

    1983-01-01

    Suppressions due to acoustic treatment in the annular exhaust duct of a model fan were theoretically predicted and compared with measured suppressions. The predictions are based on the modal analysis of sound propagation in a straight annular flow duct with segmented treatment. Modal distributions of the fan noise source (fan-stator interaction only) were measured using in-duct modal probes. The flow profiles were also measured in the vicinity of the modal probes. The acoustic impedance of the single degree of freedom treatment was measured in the presence of grazing flow. The measured values of mode distribution of the fan noise source, the flow velocity profile and the acoustic impedance of the treatment in the duct were used as input to the prediction program. The predicted suppressions, under the assumption of uniform flow in the duct, compared well with the suppressions measured in the duct for all test conditions. The interaction modes generated by the rotor-stator interaction spanned a cut-off ratio range from nearly 1 to 7.

  1. STEPS: Modeling and Simulating Complex Reaction-Diffusion Systems with Python.

    PubMed

    Wils, Stefan; De Schutter, Erik

    2009-01-01

    We describe how the use of the Python language improved the user interface of the program STEPS. STEPS is a simulation platform for modeling and stochastic simulation of coupled reaction-diffusion systems with complex 3-dimensional boundary conditions. Setting up such models is a complicated process that consists of many phases. Initial versions of STEPS relied on a static input format that did not cleanly separate these phases, limiting modelers in how they could control the simulation and becoming increasingly complex as new features and new simulation algorithms were added. We solved all of these problems by tightly integrating STEPS with Python, using SWIG to expose our existing simulation code.

  2. Challenges in Integrating a Complex Systems Computer Simulation in Class: An Educational Design Research

    ERIC Educational Resources Information Center

    Loke, Swee-Kin; Al-Sallami, Hesham S.; Wright, Daniel F. B.; McDonald, Jenny; Jadhav, Sheetal; Duffull, Stephen B.

    2012-01-01

    Complex systems are typically difficult for students to understand and computer simulations offer a promising way forward. However, integrating such simulations into conventional classes presents numerous challenges. Framed within an educational design research, we studied the use of an in-house built simulation of the coagulation network in four…

  3. Challenges in Integrating a Complex Systems Computer Simulation in Class: An Educational Design Research

    ERIC Educational Resources Information Center

    Loke, Swee-Kin; Al-Sallami, Hesham S.; Wright, Daniel F. B.; McDonald, Jenny; Jadhav, Sheetal; Duffull, Stephen B.

    2012-01-01

    Complex systems are typically difficult for students to understand and computer simulations offer a promising way forward. However, integrating such simulations into conventional classes presents numerous challenges. Framed within an educational design research, we studied the use of an in-house built simulation of the coagulation network in four…

  4. Magnetically induced instabilities in duct flows

    NASA Astrophysics Data System (ADS)

    Bühler, L.; Arlt, T.; Boeck, T.; Braiden, L.; Chowdhury, V.; Krasnov, D.; Mistrangelo, C.; Molokov, S.; Priede, J.

    2017-07-01

    The occurrence of magnetically induced instability in magnetohydrodynamic duct flows is studied for Hunt flow, where one pair of walls parallel to the magnetic field is electrically insulating and the Hartmann walls perpendicular to the field are electrically conducting. The onset of time-dependent flow patterns and their intensity depends on the strength of the magnetic field and on the flow rate in terms of the Hartmann and Reynolds numbers, respectively. The problem is studied by a complementary approach using laboratory experiments, linear stability analysis and high-resolution direct numerical simulations.

  5. Radiation of sound from unflanged cylindrical ducts

    NASA Technical Reports Server (NTRS)

    Hartharan, S. L.; Bayliss, A.

    1983-01-01

    Calculations of sound radiated from unflanged cylindrical ducts are presented. The numerical simulation models the problem of an aero-engine inlet. The time dependent linearized Euler equations are solved from a state of rest until a harmonic solution is attained. A fourth order accurate finite difference scheme is used and solutions are obtained from a fully vectorized Cyber-203 computer program. Cases of both plane waves and spin modes are treated. Spin modes model the sound generated by a turbofan engine. Boundary conditions for both plane waves and spin modes are treated. Solutions obtained are compared with experiments conducted at NASA Langley Research Center.

  6. [The graphic model of algorithm for the abdominal part of the thoracic duct].

    PubMed

    Zykov, D S

    2001-01-01

    Fifty seven cadavers of adults have been studied with complex of anatomic techniques. Syntopy of abdominal part of the thoracic duct has been explored. Landmarks for reconstruction of the graphic model allowing preoperative and intraoperative determination of an optimal access to the abdominal part of the thoracic duct were suggested.

  7. Anatomy of the nipple and breast ducts

    PubMed Central

    Urban, Cícero; Vallejo, André

    2016-01-01

    Over time, variations of mastectomy came up and started allowing the oncological safety and the possibility of an immediate breast reconstruction. Nipple sparing mastectomy (NSM) procedures have strongly increased in frequency and have become one of the best alternatives to treat breast cancer, also improving overall aesthetic outcomes and the achievement of contralateral breast symmetry. The nipple areola-complex (NAC) must be considered the identity of the breast concerning self-esteem of patients. This paper will remind the main anatomical topics around the nipple and breast ducts. PMID:26855906

  8. Numerical simulations of complex fluid-fluid interface dynamics

    NASA Astrophysics Data System (ADS)

    Krüger, T.; Frijters, S.; Günther, F.; Kaoui, B.; Harting, J.

    2013-05-01

    Interfaces between two fluids are ubiquitous and of special importance for industrial applications, e.g., stabilisation of emulsions. The dynamics of fluid-fluid interfaces is difficult to study because these interfaces are usually deformable and their shapes are not known a priori. Since experiments do not provide access to all observables of interest, computer simulations pose attractive alternatives to gain insight into the physics of interfaces. In the present article, we restrict ourselves to systems with dimensions comparable to the lateral interface extensions. We provide a critical discussion of three numerical schemes coupled to the lattice Boltzmann method as a solver for the hydrodynamics of the problem: (a) the immersed boundary method for the simulation of vesicles and capsules, the Shan-Chen pseudopotential approach for multi-component fluids in combination with (b) an additional advection-diffusion component for surfactant modelling and (c) a molecular dynamics algorithm for the simulation of nanoparticles acting as emulsifiers.

  9. Discovering the Complexity of Supernovae through Three-Dimensional Simulations

    NASA Astrophysics Data System (ADS)

    Blondin, John M.

    2006-12-01

    Computational physics has played a key role in our understanding of core-collapse supernovae, beginning with the seminal work of Colgate and White in 1966. There is a growing body of evidence that these supernova explosions are inherently asymmetric, and today's computing platforms provide sufficient power to begin to study the origin of this asymmetry using multidimensional simulations. We will show how the jump to full three-dimensional simulations has revealed new insights to this age-old problem of how a massive star explodes, as well as providing more realistic models of the expanding relic blastwave. Unexpected results from these multidimensional simulations include the spinning up of pulsars via shocked accretion flow and the formation of 'jets' in otherwise spherical explosions.

  10. A SYSTEMIZATION AND PENETRATION STUDY FOR STRAIGHT CYLINDRICAL DUCTS,

    DTIC Science & Technology

    DUCTS, *NEUTRON BEAMS, DUCTED BODIES, ALUMINUM, NEUTRON DETECTORS, POLONIUM , BERYLLIUM, SOURCES, NEUTRON SCATTERING, SHIELDING, WATER, NEUTRON TRANSPORT THEORY, ISOTROPISM, DUCT BENDS, NEUTRON FLUX, PENETRATION.

  11. Observations and laboratory simulations of tornadoes in complex topographical regions

    NASA Astrophysics Data System (ADS)

    Karstens, Christopher Daniel

    Aerial photos taken along the damage paths of the Joplin, MO, and Tuscaloosa-Birmingham, AL, tornadoes of 2011 captured and preserved several unique patterns of damage. In particular, a few distinct tree-fall patterns were noted along the Tuscaloosa-Birmingham tornado track that appeared highly influenced by the underlying topography. One such region was the focus of a damage survey and motivated laboratory vortex simulations with a 3-D foam representation of the underlying topography, in addition to simulations performed with idealized 2D topographic features, using Iowa State University's tornado simulator. The purpose of this dissertation is to explore various aspects related to the interaction of a tornado or a tornado-like vortex with its underlying topography. Three topics are examined: 1) Analysis of tornado-induced tree-fall using aerial photography from the Joplin, MO, and Tuscaloosa-Birmingham, AL, tornadoes of 2011, 2) Laboratory investigation of topographical influences on a simulated tornado-like vortex, and 3) On the use of non-standard EF-scale damage indicators to categorize tornadoes.

  12. A Computer Simulated Experiment in Complex Order Kinetics

    ERIC Educational Resources Information Center

    Merrill, J. C.; And Others

    1975-01-01

    Describes a computer simulation experiment in which physical chemistry students can determine all of the kinetic parameters of a reaction, such as order of the reaction with respect to each reagent, forward and reverse rate constants for the overall reaction, and forward and reverse activation energies. (MLH)

  13. Stress Training and Simulator Complexity: Why Sometimes More Is Less

    ERIC Educational Resources Information Center

    Tichon, Jennifer G.; Wallis, Guy M.

    2010-01-01

    Through repeated practice under conditions similar to those in real-world settings, simulator training prepares an individual to maintain effective performance under stressful work conditions. Interfaces offering high fidelity and immersion can more closely reproduce real-world experiences and are generally believed to result in better learning…

  14. A Computer Simulated Experiment in Complex Order Kinetics

    ERIC Educational Resources Information Center

    Merrill, J. C.; And Others

    1975-01-01

    Describes a computer simulation experiment in which physical chemistry students can determine all of the kinetic parameters of a reaction, such as order of the reaction with respect to each reagent, forward and reverse rate constants for the overall reaction, and forward and reverse activation energies. (MLH)

  15. Towards large eddy and direct simulation of complex turbulent flows

    NASA Technical Reports Server (NTRS)

    Moin, Parviz

    1991-01-01

    Recent advances in the methodology for direct numerical simulation of turbulent flows and some of the current applications are reviewed. It is argued that high-order finite difference schemes yield solutions with comparable accuracy to the spectral methods with the same number of degrees of freedom. The effects of random inflow conditions on the downstream evolution of turbulence are discussed.

  16. Fan Performance From Duct Rake Instrumentation on a 1.294 Pressure Ratio, 725 ft/sec Tip Speed Turbofan Simulator Using Vaned Passage Casing Treatment

    NASA Technical Reports Server (NTRS)

    Fite, E. Brian

    2006-01-01

    A 1.294 pressure ratio, 725 ft/sec tip speed, variable pitch low noise fan was designed and tested in the NASA Glenn 9- by 15-foot Wind Tunnel. The design included a casing treatment that used recirculation to extend the fan stall line and provide an acceptable operating range. Overall aerodynamic experimental results are presented for this low tip speed, low noise fan without casing treatment as well as using several variants of the casing treatment that moved the air extraction and insertion axial locations. Measurements were made to assess effects on performance, operability, and noise. An unusual instability was discovered near the design operating line and is documented in the fan operating range. Measurements were made to compare stall margin improvements as well as measure the performance impact of the casing treatments. Experimental results in the presence of simulated inlet distortion, via screens, are presented for the baseline and recirculation casing treatment configurations. Estimates are made for the quantity of recirculation weight flow based on limited instrumentation in the recirculation system along with discussion of results and conclusions

  17. Learning to manage complexity through simulation: students' challenges and possible strategies.

    PubMed

    Gormley, Gerard J; Fenwick, Tara

    2016-06-01

    Many have called for medical students to learn how to manage complexity in healthcare. This study examines the nuances of students' challenges in coping with a complex simulation learning activity, using concepts from complexity theory, and suggests strategies to help them better understand and manage complexity.Wearing video glasses, participants took part in a simulation ward-based exercise that incorporated characteristics of complexity. Video footage was used to elicit interviews, which were transcribed. Using complexity theory as a theoretical lens, an iterative approach was taken to identify the challenges that participants faced and possible coping strategies using both interview transcripts and video footage.Students' challenges in coping with clinical complexity included being: a) unprepared for 'diving in', b) caught in an escalating system, c) captured by the patient, and d) unable to assert boundaries of acceptable practice.Many characteristics of complexity can be recreated in a ward-based simulation learning activity, affording learners an embodied and immersive experience of these complexity challenges. Possible strategies for managing complexity themes include: a) taking time to size up the system, b) attuning to what emerges, c) reducing complexity, d) boundary practices, and e) working with uncertainty. This study signals pedagogical opportunities for recognizing and dealing with complexity.

  18. Visual Analytics for Complex Engineering Systems: Hybrid Visual Steering of Simulation Ensembles.

    PubMed

    Matković, Krešimir; Gračanin, Denis; Splechtna, Rainer; Jelović, Mario; Stehno, Benedikt; Hauser, Helwig; Purgathofer, Werner

    2014-12-01

    In this paper we propose a novel approach to hybrid visual steering of simulation ensembles. A simulation ensemble is a collection of simulation runs of the same simulation model using different sets of control parameters. Complex engineering systems have very large parameter spaces so a naïve sampling can result in prohibitively large simulation ensembles. Interactive steering of simulation ensembles provides the means to select relevant points in a multi-dimensional parameter space (design of experiment). Interactive steering efficiently reduces the number of simulation runs needed by coupling simulation and visualization and allowing a user to request new simulations on the fly. As system complexity grows, a pure interactive solution is not always sufficient. The new approach of hybrid steering combines interactive visual steering with automatic optimization. Hybrid steering allows a domain expert to interactively (in a visualization) select data points in an iterative manner, approximate the values in a continuous region of the simulation space (by regression) and automatically find the "best" points in this continuous region based on the specified constraints and objectives (by optimization). We argue that with the full spectrum of optimization options, the steering process can be improved substantially. We describe an integrated system consisting of a simulation, a visualization, and an optimization component. We also describe typical tasks and propose an interactive analysis workflow for complex engineering systems. We demonstrate our approach on a case study from automotive industry, the optimization of a hydraulic circuit in a high pressure common rail Diesel injection system.

  19. Computer simulation of the precordial QRS complex: effects of simulated changes in ventricular wall thickness and volume.

    PubMed

    Salu, Y; Marcus, M L

    1976-12-01

    The cardiac electric field generated by depolarization of the human ventricle is simulated with a computer model which utilizes 1,500 dipoles. The configuration of the ventricles utilized in the model assumed that the cross-sectional shape of the left ventricle was circular and the right ventricular free wall was a portion of an ellipse. The torso was assumed to be homogeneous and infinite. The activation sequence was based on the measurements of Durrer. The depolarizational wave was simulated by dipole layers. The output of the model is presented as a standard multilead precordial ECG. The ECG complexes generated by the model closely resemble the precordial QRS complexes of normal man. Simulated increases in wall thickness (1 to 2.2 X control) were associated with changes in the calculated precordial QRS complexes which were characteristic of left ventricular hypertrophy. Voltage (R in V5 or V6 and S in V1) and QRS duration increased linearly as a function of calculated left ventricular mass. Increases in ventricular activation time were related nonlinearly to changes in left ventricular mass and did not occur in the absence of a simulated increase in wall thickness. The effects of simulated changes in left ventricular volume (0.6 to 3.0 X control) on the QRS complex were mainly dependent on the resultant increase in left ventricular mass. This model may be useful in simulating the precordial QRS complexes that result from isolated or combined changes in ventricular volume or wall thickness or other disorders of the heart. Furthermore, it may be useful whenever a simulation of a QRS generator is needed.

  20. 29. DETAIL OF OUTLET DUCTS FOR MST AIRCONDITIONING SYSTEM IN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    29. DETAIL OF OUTLET DUCTS FOR MST AIR-CONDITIONING SYSTEM IN NORTHWEST CORNER OF SLC-3W MST STATION 70.5 (LOWEST PAYLOAD SERVICE STATION). NOTE RING ATTACHMENT FOR PERSONNEL SAFETY HARNESS IN LEFT FOREGROUND. - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 West, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  1. 24. AIRCONDITIONING DUCT, WINCH CONTROL BOX, AND SPEAKER AT STATION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    24. AIR-CONDITIONING DUCT, WINCH CONTROL BOX, AND SPEAKER AT STATION 85.5 OF MST. FOLDED-UP PLATFORM ON RIGHT OF PHOTO. - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 East, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  2. 22. A closeup interior view of the duct work and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    22. A close-up interior view of the duct work and mechanical equipment used in the delivery of the grain to the upper level grain conveyor system for Elevator and Silo Complex B (1932). - Quaker Oats Cereal Factory, Southeast corner of Broadway & Mill Streets, Akron, Summit County, OH

  3. Smoothed Profile Method to Simulate Colloidal Particles in Complex Fluids

    NASA Astrophysics Data System (ADS)

    Yamamoto, Ryoichi; Nakayama, Yasuya; Kim, Kang

    A new direct numerical simulation scheme, called "Smoothed Profile (SP) method," is presented. The SP method, as a direct numerical simulation of particulate flow, provides a way to couple continuum fluid dynamics with rigid-body dynamics through smoothed profile of colloidal particle. Our formulation includes extensions to colloids in multicomponent solvents such as charged colloids in electrolyte solutions. This method enables us to compute the time evolutions of colloidal particles, ions, and host fluids simultaneously by solving Newton, advection-diffusion, and Navier-Stokes equations so that the electro-hydrodynamic couplings can be fully taken into account. The electrophoretic mobilities of charged spherical particles are calculated in several situations. The comparisons with approximation theories show quantitative agreements for dilute dispersions without any empirical parameters.

  4. Three dimensional direct numerical simulation of complex jet flows

    NASA Astrophysics Data System (ADS)

    Shin, Seungwon; Kahouadji, Lyes; Juric, Damir; Chergui, Jalel; Craster, Richard; Matar, Omar

    2016-11-01

    We present three-dimensional simulations of two types of very challenging jet flow configurations. The first consists of a liquid jet surrounded by a faster coaxial air flow and the second consists of a global rotational motion. These computations require a high spatial resolution and are performed with a newly developed high performance parallel code, called BLUE, for the simulation of two-phase, multi-physics and multi-scale incompressible flows, tested on up to 131072 threads with excellent scalability performance. The method for the treatment of the fluid interfaces uses a hybrid Front Tracking/Level Set technique that defines the interface both by a discontinuous density field as well as by a local triangular Lagrangian mesh. Coriolis forces are taken into account and solved via an exact time-integration method that ensures numerical accuracy and stability. EPSRC UK Programme Grant EP/K003976/1.

  5. Integrating Multibody Simulation and CFD: toward Complex Multidisciplinary Design Optimization

    NASA Astrophysics Data System (ADS)

    Pieri, Stefano; Poloni, Carlo; Mühlmeier, Martin

    This paper describes the use of integrated multidisciplinary analysis and optimization of a race car model on a predefined circuit. The objective is the definition of the most efficient geometric configuration that can guarantee the lowest lap time. In order to carry out this study it has been necessary to interface the design optimization software modeFRONTIER with the following softwares: CATIA v5, a three dimensional CAD software, used for the definition of the parametric geometry; A.D.A.M.S./Motorsport, a multi-body dynamic simulation software; IcemCFD, a mesh generator, for the automatic generation of the CFD grid; CFX, a Navier-Stokes code, for the fluid-dynamic forces prediction. The process integration gives the possibility to compute, for each geometrical configuration, a set of aerodynamic coefficients that are then used in the multiboby simulation for the computation of the lap time. Finally an automatic optimization procedure is started and the lap-time minimized. The whole process is executed on a Linux cluster running CFD simulations in parallel.

  6. Simulating and mapping spatial complexity using multi-scale techniques

    USGS Publications Warehouse

    De Cola, L.

    1994-01-01

    A central problem in spatial analysis is the mapping of data for complex spatial fields using relatively simple data structures, such as those of a conventional GIS. This complexity can be measured using such indices as multi-scale variance, which reflects spatial autocorrelation, and multi-fractal dimension, which characterizes the values of fields. These indices are computed for three spatial processes: Gaussian noise, a simple mathematical function, and data for a random walk. Fractal analysis is then used to produce a vegetation map of the central region of California based on a satellite image. This analysis suggests that real world data lie on a continuum between the simple and the random, and that a major GIS challenge is the scientific representation and understanding of rapidly changing multi-scale fields. -Author

  7. Numerical simulation of flow in centrifugal pump with complex impeller

    NASA Astrophysics Data System (ADS)

    Cui, Bao-ling; Lin, Yong-gang; Jin, Ying-zi

    2011-03-01

    Based on the Navier-Stokes equations and the Spalart-Allmaras turbulence model, three dimensional turbulent flow fields in centrifugal pump with long-mid-short blade complex impeller are calculated and analyzed numerically. The relative velocity and pressure distributions in the flowpart are obtained. It is found that the flow in the passage of the complex impeller is unsymmetrical due to the joint action between volute and impeller. The back-flow region is at inlet of long-blade suction side, near middle part of long-blade pressure side and outlet of short-blade suction side. The flow near volute throat is affected greatly by volute. The relative velocity is large and it is easy to bring back flow at outlet of the complex impeller near volute throat. The static and total pressure rise uniformly from inlet to outlet in the impeller. At impeller outlet, the pressure periodically decreases from pressure side to suction side, and then the static pressure sharply rise near the throat. The experimental results show that the back flow in the impeller has an important influence on the performance of pump.

  8. Duct leakage measurement and analysis

    SciTech Connect

    Swim, W.B.; Griggs, E.I.

    1995-08-01

    Leakage measurements were made on 6-in. (150-mm) and 10-in. (250-mm) round and 14-in. by 6-in. (350-mm by 150-mm) and 22-in. by 8-in. (560-mm by 200-mm) rectangular ducts for both positive and negative internal pressures. The data were found to fit a power law model, with the leakage rate (Q) increasing with a power, n, of static pressure difference ({Delta}p), i.e., Q {proportional_to} ({Delta}p){sup n}. A convenient leakage prediction equation, Q = C ({Delta}p*){sup n}, uses a normalized pressure difference, {Delta}p* = {Delta}p/{Delta}p{sub ref}, with {Delta}p in in. wg (Pa) and a reference pressure difference, {Delta}p{sub ref}, of 1 in. wg (250 Pa). C{sub D}, the recommended design values of C for a repetitive element of a duct system--one duct section and one joint, ranged from 0.01 cfm (0.005 L/s) for a Vanstone flanged joint to 18.5 cfm (8.7 L/s) for an unsealed 22-in. by 8-in (560-mm by 200-mm) duct with a slip-and-drive joint. Most test ducts had C{sub D} values of 6 to 8 cfm (3 to 4 L/s) and had values of n close to 0.58. Joints were found to account for most of the leakage, and thus most of the value of C{sub D}, in unsealed ducts, with seams contributing only 10% to 38% of the total.

  9. Viscous flow computations for elliptical two-duct version of the SSME hot gas manifold

    NASA Technical Reports Server (NTRS)

    Roger, R. P.

    1986-01-01

    The objective of the effort was to numerically simulate viscous subsonic flow in a proposed elliptical two-duct version of the fuel side Hot Gas Manifold (HGM) for the Space Shuttle Main Engine (SSME). The numerical results were to complement both water flow and air flow experiments in the two-duct geometry performed at NASA-MSFC and Rocketdyne. The three-dimensional character of the HGM consists of two essentially different geometries. The first part of the construction is a concentric shell duct structure which channels the gases from a turbine exit into the second part comprised of two cylindrically shaped transfer ducts. The initial concentric shell portion can be further subdivided into a turnaround section and a bowl section. The turnaround duct (TAD) changes the direction of the mean flow by 180 degress from a smaller radius to a larger radius duct which discharges into the bowl. The cylindrical transfer ducts are attached to the bowl on one side thus providing a plane of symmetry midway between the two. Centerline flow distance from the TAD inlet to the transfer duct exit is approximately two feet. Details of the approach used to numerically simulate laminar or turbulent flow in the HGM geometry are presented. Computational results are presented and discussed.

  10. Duct- to islet-cell differentiation and islet growth in the pancreas of duct-ligated adult rats.

    PubMed

    Wang, R N; Klöppel, G; Bouwens, L

    1995-12-01

    We investigated the growth of islet beta and alpha cells in adult rats which had undergone partial pancreatic duct ligation. Whereas the non-ligated head portion of the pancreas remained unaffected in terms of histology and cell population dynamics, the ligated tail part of the pancreas showed pronounced changes in histology and cell growth. These changes included replacement of exocrine acini by ductal complexes and significant growth of islet cells. Using immunocytochemistry and morphometry, we found that the beta-cell population had nearly doubled within 1 week and that a smaller, but also significant growth of the alpha-cell population had occurred. In addition, small islets and islet-cell clusters were more numerous in the pancreatic tail, indicating islet neogenesis. The bromodeoxyuridine (BrdU) pulse labelling index of beta and alpha cells increased five fold and threefold, respectively, in the tail. However, the observed beta-cell labelling index remained below 1% which was largely insufficient to explain the increased number of beta cells. This indicates that recruitment from a proliferating stem-cell compartment was the main source for the beta-cell hyperplasia. A tenfold-elevated BrdU labelling index (18%) was observed in the duct-cell compartment which was identified by specific immunostaining for cytokeratin 20. Transitional cytodifferentiation forms between duct cells expressing cytokeratin 20 and beta cells expressing insulin, or alpha cells expressing glucagon, were demonstrated by double immunostaining. Pancreatic duct ligation also induced the expression of the beta-cell-specific glucose transporter type 2 (GLUT-2) in duct cells, indicating their metaplastic state. We concluded that in this adult rat model, the proliferation and differentiation of exocrine duct cells represents the major mechanism of endocrine beta-cell neogenesis. Our study thus demonstrates that in normal adult rats islet-cell neogenesis can be reactivated by stimulation of

  11. Technology Solutions Case Study: New Insights for Improving the Designs of Flexible Duct Junction Boxes

    SciTech Connect

    2014-01-01

    In this project, IBACOS explored the relationships between pressure and physical configurations of flexible duct junction boxes by using computational fluid dynamics simulations to predict individual box parameters and total system pressure, thereby ensuring improved HVAC performance.

  12. Flexible Space-Filling Designs for Complex System Simulations

    DTIC Science & Technology

    2013-06-01

    ACKNOWLEDGEMENTS I want to thank Gene Paulo for supporting me as my Dissertation Advisor, but also for being such a good friend and mentor. I hope we can...two uniform grids of 11 points 71 that range from –1 to 1, one grid for the true model and one grid for the predicted model ( Goel , Tushar, Raphael...simulation models early in the architectural design of a ship. The traditional naval architect paradigm is to design the weapon systems, radars , or any

  13. Mouse Acetylcholinesterase Unliganded and in Complex with Huperzine A: A Comparison of Molecular Dynamics Simulations

    SciTech Connect

    Tara, Sylvia; Straatsma, TP; Mccammon, Andy

    1999-06-01

    A 1 ns molecular dynamics simulation of unliganded mouse acetylcholinesterase (AChE) is compared to a previous simulation of mouse AChE complexed with Huperzine A (HupA). Several common features are observed. In both simulations, the active site gorge fluctuates in size during the 1 ns trajectory, and is completely pinched off several times. Many of the residues in the gorge that formed hydrogen bonds with HupA in the simulation of the complex, now form hydrogen bonds with other protein residues and water molecules in the gorge. The opening of a "backdoor" entrance to the active site that was found in the simulation of the complex is also observed in the unliganded simulation. Differences between the two simulations include overall lower structural RMS deviations for residues in the gorge in the unliganded simulation, a smaller diameter of the gorge in the absence of HupA, and the disappearance of a side channel that was frequently present in the liganded simulation. The differences between the two simulations can be attributed, in part, to the interaction of AChE with HupA.

  14. What Should You Ask Your Doctor about Bile Duct Cancer?

    MedlinePlus

    ... What Should You Ask Your Doctor About Bile Duct Cancer? It is important to have frank, open ... Doctor About Bile Duct Cancer? More In Bile Duct Cancer About Bile Duct Cancer Causes, Risk Factors, ...

  15. What's New in Bile Duct Cancer Research and Treatment?

    MedlinePlus

    ... Bile Duct Cancer About Bile Duct Cancer What’s New in Bile Duct Cancer Research and Treatment? Bile ... is tumor blood vessels. Bile duct tumors need new blood vessels to grow beyond a certain size. ...

  16. What Are the Key Statistics about Bile Duct Cancer?

    MedlinePlus

    ... About Bile Duct Cancer What Are the Key Statistics About Bile Duct Cancer? Bile duct cancer (cholangiocarcinoma) ... it is when it is found. For survival statistics, see “ Survival statistics for bile duct cancers .” Visit ...

  17. Simulation of a Complex Groundwater System and an Application

    NASA Astrophysics Data System (ADS)

    Premchitt, Jerasak; Das Gupta, Ashim

    1981-06-01

    A hydrologic model of an extensive groundwater basin was developed for the study of land subsidence due to deep well pumping in Bangkok, Thailand. It is a quasi-three-dimensional flow model with relevant modifications to suit the hydrogeologic situations in the problem area. The troublesome effect of yield from aquitard is discarded, while the field information on subsurface strata is fully utilized to establish a realistic model. The subsurface is considered to be a single hydraulically connected body stratified into model layers for convenience in the simulation. Pumping can be imposed at any depth, and discharge rates can be arbitrary. Any number of model layers can be incorporated, with coupling being provided through the leakage flux. The power and flexibility of the model is demonstrated in the simulation of groundwater flow regime in the Lower Central Plain of Thailand for a time period of 45 years. At first the model is calibrated with available field measurements in the past, and it is then extended for the prediction of future situations. The model represents the actual field situation. The mathematical process is simple, and it would require less computing effort than the equivalent full three-dimensional model or the quasi-three-dimensional model with one-dimensional elements to represent aquitards.

  18. Stabilizing simulations of complex stochastic representations for quantum dynamical systems

    NASA Astrophysics Data System (ADS)

    Perret, C.; Petersen, W. P.

    2011-03-01

    Path integral representations of quantum dynamics can often be formulated as stochastic differential equations (SDEs). In a series of papers, Corney and Drummond (2004 Phys. Rev. Lett. 93 260401), Deuar and Drummond (2001 Comput. Phys. Commun. 142 442-5), Drummond and Gardnier (1980 J. Phys. A: Math. Gen. 13 2353-68), Gardiner and Zoller (2004 Quantum Noise: A Handbook of Markovian and Non-Markovian Quantum Stochastic Methods with Applications to Quantum Optics (Springer Series in Synergetics) 3rd edn (Berlin: Springer)) and Gilchrist et al (1997 Phys. Rev. A 55 3014-32) and their collaborators have derived SDEs from coherent states representations for density matrices. Computationally, these SDEs are attractive because they seem simple to simulate. They can be quite unstable, however. In this paper, we consider some of the instabilities and propose a few remedies. Particularly, because the variances of the simulated paths typically grow exponentially, the processes become de-localized in relatively short times. Hence, the issues of boundary conditions and stable integration methods become important. We use the Bose-Einstein Hamiltonian as an example. Our results reveal that it is possible to significantly extend integration times and show the periodic structure of certain functionals.

  19. Simulations of photochemical smog formation in complex urban areas

    NASA Astrophysics Data System (ADS)

    Muilwijk, C.; Schrijvers, P. J. C.; Wuerz, S.; Kenjereš, S.

    2016-12-01

    In the present study we numerically investigated the dispersion of photochemical reactive pollutants in complex urban areas by applying an integrated Computational Fluid Dynamics (CFD) and Computational Reaction Dynamics (CRD) approach. To model chemical reactions involved in smog generation, the Generic Reaction Set (GRS) approach is used. The GRS model was selected since it does not require detailed modeling of a large set of reactive components. Smog formation is modeled first in the case of an intensive traffic emission, subjected to low to moderate wind conditions in an idealized two-dimensional street canyon with a building aspect ratio (height/width) of one. It is found that Reactive Organic Components (ROC) play an important role in the chemistry of smog formation. In contrast to the NOx/O3 photochemical steady state model that predicts a depletion of the (ground level) ozone, the GRS model predicts generation of ozone. Secondly, the effect of direct sunlight and shadow within the street canyon on the chemical reaction dynamics is investigated for three characteristic solar angles (morning, midday and afternoon). Large differences of up to one order of magnitude are found in the ozone production for different solar angles. As a proof of concept for real urban areas, the integrated CFD/CRD approach is applied for a real scale (1 × 1 km2) complex urban area (a district of the city of Rotterdam, The Netherlands) with high traffic emissions. The predicted pollutant concentration levels give realistic values that correspond to moderate to heavy smog. It is concluded that the integrated CFD/CRD method with the GRS model of chemical reactions is both accurate and numerically robust, and can be used for modeling of smog formation in complex urban areas.

  20. Affections of the salivary ducts in buffaloes

    PubMed Central

    Misk, N.A.; Misk, T.N.; Semieka, M.A.; Ahmed, A.F.

    2014-01-01

    The aim of the present study was to determine different affections of the salivary ducts in buffaloes with special reference to diagnosis and treatment. The study was carried out on 39 buffaloes suffering from different affections of the salivary ducts. The recorded affections of the salivary ducts in buffaloes include; ectasia of the parotid duct (21 cases), parotid duct fistula (15 cases) and sialocele (3 cases). Each case was subjected to full study including case history, clinical examination, diagnosis, and treatment whenever possible. Exploratory puncture and radiography were used for confirmation of diagnosis. Intraoral marsupialization was performed for treatment of parotid duct ectasia. Salivary fistula was corrected by one of two successful techniques; the first by reconstruction of the parotid duct and the second by ligation of the parotid duct just caudal to the fistula opening. Sialoceles were corrected by removal of the mandibular salivary gland of the affected side. PMID:26623341

  1. Performance Study of a Ducted Fan System

    NASA Technical Reports Server (NTRS)

    Abrego, Anita I.; Bulaga, Robert W.; Rutkowski, Michael (Technical Monitor)

    2002-01-01

    An experimental investigation was completed in the NASA Ames 7- by 10-Foot Wind Tunnel with the objective of determining the performance characteristics of a ducted fan. The model was an annular duct with a 38-in diameter, 10-in chord, and a 5-bladed fixed-pitch fan. Model variations included duct angle of attack, exit vane flap length, flap deflection angle, and duct chord length. Duct performance data were obtained for axial and forward flight test conditions. Axial flow test data showed figure of merit decreases with increasing advance ratio. Forward flight data showed an increasing propulsive force with decreasing duct angle of attack. Exit vane flap deflection angle and flap chord length were shown to be an effective way of providing side force. Extending the duct chord did not effect the duct performance.

  2. Affections of the salivary ducts in buffaloes.

    PubMed

    Misk, N A; Misk, T N; Semieka, M A; Ahmed, A F

    2014-01-01

    The aim of the present study was to determine different affections of the salivary ducts in buffaloes with special reference to diagnosis and treatment. The study was carried out on 39 buffaloes suffering from different affections of the salivary ducts. The recorded affections of the salivary ducts in buffaloes include; ectasia of the parotid duct (21 cases), parotid duct fistula (15 cases) and sialocele (3 cases). Each case was subjected to full study including case history, clinical examination, diagnosis, and treatment whenever possible. Exploratory puncture and radiography were used for confirmation of diagnosis. Intraoral marsupialization was performed for treatment of parotid duct ectasia. Salivary fistula was corrected by one of two successful techniques; the first by reconstruction of the parotid duct and the second by ligation of the parotid duct just caudal to the fistula opening. Sialoceles were corrected by removal of the mandibular salivary gland of the affected side.

  3. Laparoscopic management of enlarged cystic duct.

    PubMed

    Nowzaradan, Y; Meador, J; Westmoreland, J

    1992-12-01

    After laparoscopic exploration of the common bile duct, or when a patient has acute cholecystitis, the cystic duct is sometimes edematous and too large to be ligated safely with an Endoclip. In such cases, ligation of the cystic duct with an Endoloop offers a solution to the problem. The standard technique for application of an Endoloop consists of dividing the cystic duct and then applying the Endoloop. This becomes more difficult if, after the cystic duct is divided, loss of traction on the common bile duct results in retraction of the divided cystic stump outside of the laparoscopic field of view. To avoid this difficulty, the authors apply an Endoloop with the grasping forceps on the cystic duct before the duct is divided so that it cannot retract from operative view and for this task developed an instrument that allows simultaneous introduction of both grasping forceps and the Endoloop through a single port.

  4. Common and Uncommon Anatomical Variants of Intrahepatic Bile Ducts in Magnetic Resonance Cholangiopancreatography and its Clinical Implication

    PubMed Central

    Sarawagi, Radha; Sundar, Shyam; Raghuvanshi, Sameer; Gupta, Sanjeev Kumar; Jayaraman, Gopal

    2016-01-01

    Summary Background Preoperative knowledge of intrahepatic bile duct (IHD) anatomy is critical for planning liver resections, liver transplantations and complex biliary reconstructive surgery. The purpose of our study was to demonstrate the imaging features of various anatomical variants of IHD using magnetic resonance cholangio-pancreatography (MRCP) and their prevalence in our population. Material/Methods This observational clinical evaluation study included 224 patients who were referred for MRCP. MRCP was performed in a 1.5-Tesla magnet (Philips) with SSH MRCP 3DHR and SSHMRCP rad protocol. A senior radiologist assessed the biliary passage for anatomical variations. Results The branching pattern of the right hepatic duct (RHD) was typical in 55.3% of subjects. The most common variant was right posterior sectoral duct (RPSD) draining into the left hepatic duct (LHD) in 27.6% of subjects. Trifurcation pattern was noted in 9.3% of subjects. In 4% of subjects, RPSD was draining into the common hepatic duct (CHD) and in 0.8% of subjects into the cystic duct. Other variants were noted in 2.6% of subjects. In 4.9% of cases there was an accessory duct. The most common type of LHD branching pattern was a common trunk of segment 2 and 3 ducts joining the segment 4 duct in 67.8% of subjects. In 23.2% of subjects, segment 2 duct united with the common trunk of segment 3 and 4 and in 3.4% of subjects segment 2, 3, and 4 ducts united together to form LHD. Other uncommon branching patterns of LHD were seen in 4.9% of subjects. Conclusions Intrahepatic bile duct anatomy is complex with many common and uncommon variations. MRCP is a reliable non-invasive imaging method for demonstration of bile duct morphology, which is useful to plan complex surgeries and to prevent iatrogenic injuries. PMID:27298653

  5. Complex organics in laboratory simulations of interstellar/cometary ices

    NASA Astrophysics Data System (ADS)

    Bernstein, M. P.; Allamandola, L. J.; Sandford, S. A.

    1997-05-01

    We present the photochemical and thermal evolution of both non-polar and polar ices representative of interstellar and pre-cometary grains. Ultraviolet photolysis of the non-polar ices comprised of O_2, N_2, and CO produces CO_2, N_2O, O_3, CO_3, HCO, H_2CO, and possibly NO and NO_2. When polar ice analogs (comprised of H_2O, CH_3OH, CO, and NH_3) are exposed to UV radiation, simple molecules are formed including: H_2, H_2CO, CO_2, CO, CH_4, and HCO. (the formyl radical). Warming produces moderately complex species such as CH_3CH_2OH (ethanol), HC(=O)NH_2 (formamide), CH_3C(=O)NH_2 (acetamide), R-CN and/or R-NC (nitriles and/or isonitriles). Several of these are already known to be in the interstellar medium, and their presence indicates the importance of grain processing. Infrared spectroscopy, ^1H and^13 C nuclear magnetic resonance (NMR) spectroscopy, and gas chromatography-mass spectrometry demonstrate that after warming to room temperature what remains is an organic residue composed primarily of hexamethylenetetramine (HMT, C_6H_12N_4) and other complex organics including the amides above and polyoxymethylene (POM) and its derivatives. The formation of these organic species from simple starting mixtures under conditions germane to astrochemistry may have important implications for the organic chemistry of interstellar ice grains, comets and the origins of life.

  6. Complex organics in laboratory simulations of interstellar/cometary ices.

    PubMed

    Bernstein, M P; Allamandola, L J; Sandford, S A

    1997-01-01

    We present the photochemical and thermal evolution of both non-polar and polar ices representative of interstellar and pre-cometary grains. Ultraviolet photolysis of the non-polar ices comprised of O2, N2, and CO produces CO2, N2O, O3, CO3, HCO, H2CO, and possibly NO and NO2. When polar ice analogs (comprised of H2O, CH3OH, CO, and NH3) are exposed to UV radiation, simple molecules are formed including: H2, H2CO, CO2, CO, CH4, and HCO (the formyl radical). Warming produces moderately complex species such as CH3CH2OH (ethanol), HC(=O)NH2 (formamide), CH3C(=O)NH2 (acetamide), R-CN and/or R-NC (nitriles and/or isonitriles). Several of these are already known to be in the interstellar medium, and their presence indicates the importance of grain processing. Infrared spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, and gas chromatography-mass spectrometry demonstrate that after warming to room temperature what remains is an organic residue composed primarily of hexamethylenetetramine (HMT, C6H12N4) and other complex organics including the amides above and polyoxymethylene (POM) and its derivatives. The formation of these organic species from simple starting mixtures under conditions germane to astrochemistry may have important implications for the organic chemistry of interstellar ice grains, comets and the origins of life.

  7. Molecular dynamics simulations of a membrane protein/amphipol complex.

    PubMed

    Perlmutter, Jason D; Popot, Jean-Luc; Sachs, Jonathan N

    2014-10-01

    Amphipathic polymers known as "amphipols" provide a highly stabilizing environment for handling membrane proteins in aqueous solutions. A8-35, an amphipol with a polyacrylate backbone and hydrophobic grafts, has been extensively characterized and widely employed for structural and functional studies of membrane proteins using biochemical and biophysical approaches. Given the sensitivity of membrane proteins to their environment, it is important to examine what effects amphipols may have on the structure and dynamics of the proteins they complex. Here we present the first molecular dynamics study of an amphipol-stabilized membrane protein, using Escherichia coli OmpX as a model. We begin by describing the structure of the complexes formed by supplementing OmpX with increasing amounts of A8-35, in order to determine how the amphipol interacts with the transmembrane and extramembrane surfaces of the protein. We then compare the dynamics of the protein in either A8-35, a detergent, or a lipid bilayer. We find that protein dynamics on all accessible length scales is restrained by A8-35, which provides a basis to understanding some of the stabilizing and functional effects of amphipols that have been experimentally observed.

  8. A new approach for turbulent simulations in complex geometries

    NASA Astrophysics Data System (ADS)

    Israel, Daniel M.

    Historically turbulence modeling has been sharply divided into Reynolds averaged Navier-Stokes (RANS), in which all the turbulent scales of motion are modeled, and large-eddy simulation (LES), in which only a portion of the turbulent spectrum is modeled. In recent years there have been numerous attempts to couple these two approaches either by patching RANS and LES calculations together (zonal methods) or by blending the two sets of equations. In order to create a proper bridging model, that is, a single set of equations which captures both RANS and LES like behavior, it is necessary to place both RANS and LES in a more general framework. The goal of the current work is threefold: to provide such a framework, to demonstrate how the Flow Simulation Methodology (FSM) fits into this framework, and to evaluate the strengths and weaknesses of the current version of the FSM. To do this, first a set of filtered Navier-Stokes (FNS) equations are introduced in terms of an arbitrary generalized filter. Additional exact equations are given for the second order moments and the generalized subfilter dissipation rate tensor. This is followed by a discussion of the role of implicit and explicit filters in turbulence modeling. The FSM is then described with particular attention to its role as a bridging model. In order to evaluate the method a specific implementation of the FSM approach is proposed. Simulations are presented using this model for the case of a separating flow over a "hump" with and without flow control. Careful attention is paid to error estimation, and, in particular, how using flow statistics and time series affects the error analysis. Both mean flow and Reynolds stress profiles are presented, as well as the phase averaged turbulent structures and wall pressure spectra. Using the phase averaged data it is possible to examine how the FSM partitions the energy between the coherent resolved scale motions, the random resolved scale fluctuations, and the subfilter

  9. Simulation of the kinetics of oxygen complexes in crystalline silicon

    NASA Astrophysics Data System (ADS)

    Joo Lee, Young; von Boehm, J.; Nieminen, R. M.

    2002-10-01

    The formation kinetics of thermal double donors (TDD's) is studied by a general kinetic model with parameters based on accurate ab initio total-energy calculations. The kinetic model includes all relevant association, dissociation, and restructuring processes. The simulated kinetics agrees qualitatively and in most cases quantitatively with the experimentally found consecutive kinetics of TDD's. It also supports our earlier assignments of the ring-type oxygen chains to TDD's [Pesola et al., Phys. Rev. Lett. 84, 5343 (2000)]. We demonstrate with the kinetic model that the most common assumption that only the O2 dimer acts as a fast diffusing species would lead to an unrealistic steady increase of the concentration of O3. The neglect of restructuring processes leads to an anomalous increase of oxygen dimers and negligible concentrations of TDD's. The capture of interstitial oxygens by diffusing oxygen chains and the escaping of interstitial oxygens from the chains fully dominate the formation kinetics.

  10. Laboratory production of complex organics in simulated interstellar ices

    NASA Astrophysics Data System (ADS)

    Dworkin, J.; Bernstein, M.; Ashbourn, S.; Iraci, L.; Cooper, G.; Sandford, S.; Allamandola, L.

    1 see www.astrochem.org for more information. Bernstein, M., Dworkin, J., Sandford, S., &Allamandola, L. (2001). Ultraviolet Ir- radiation of Naphthalene in H2O Ice: Implications for Meteorites and Biogenesis. Meteoritics and Planetary Science36, 351-358. Bernstein, M., Dworkin, J., Sandford, S., Cooper, G. &Allamandola, L. (2002) The Formation of Racemic Amino Acids byUltraviolet Photolysis of Interstellar Ice Analogs. Nature, 416, 401U403 Dworkin, J., Deamer, D., Sandford, S., &Allamandola, L. (2001). Self-Assembling Amphiphilic Molecules: Synthesis in Simulated Interstellar/Precometary Ices. Proc. Nat. Acad. Sci. USA 98, 815-819. Krishnamurthy, R., Epstein, S., Cronin, J., Pizzarello, S. &Yuen, G. (1992) Isotopic and molecular analyses of hydrocarbons and monocarboxylic acids of the Murchison meteorite. Geochim. Cosmochim. Acta 56, 4045-4058. Sandford, S. A., Bernstein, M. P., &Dworkin, J. P. (2001). Assessment of the interstellar processes leading to deuterium enrichment in meteoritic organics. Meteoritics and Planetary Sci- ence36, 1117-1133.

  11. Wind-farm simulation over moderately complex terrain

    NASA Astrophysics Data System (ADS)

    Segalini, Antonio; Castellani, Francesco

    2017-05-01

    A comparison between three independent software to estimate the power production and the flow field in a wind farm is conducted, validating them against SCADA (Supervisory, Control And Data Acquisition) data. The three software were ORFEUS, WindSim and WAsP: ORFEUS and WAsP are linearised solvers, while WindSim is fully nonlinear. A wake model (namely a prescribed velocity deficit associated to the turbines) is used by WAsP, while ORFEUS and WindSim use the actuator-disc method to account for the turbines presence. The comparison indicates that ORFEUS and WAsP perform slightly better than WindSim in the assessment of the polar efficiency. The wakes simulated with ORFEUS appear more persistent than the ones of WindSim, which uses a two-equation closure model for the turbulence effects.

  12. Automatic Assessment of Complex Task Performance in Games and Simulations. CRESST Report 775

    ERIC Educational Resources Information Center

    Iseli, Markus R.; Koenig, Alan D.; Lee, John J.; Wainess, Richard

    2010-01-01

    Assessment of complex task performance is crucial to evaluating personnel in critical job functions such as Navy damage control operations aboard ships. Games and simulations can be instrumental in this process, as they can present a broad range of complex scenarios without involving harm to people or property. However, "automatic"…

  13. Effect of motion cues during complex curved approach and landing tasks: A piloted simulation study

    NASA Technical Reports Server (NTRS)

    Scanlon, Charles H.

    1987-01-01

    A piloted simulation study was conducted to examine the effect of motion cues using a high fidelity simulation of commercial aircraft during the performance of complex approach and landing tasks in the Microwave Landing System (MLS) signal environment. The data from these tests indicate that in a high complexity MLS approach task with moderate turbulence and wind, the pilot uses motion cues to improve path tracking performance. No significant differences in tracking accuracy were noted for the low and medium complexity tasks, regardless of the presence of motion cues. Higher control input rates were measured for all tasks when motion was used. Pilot eye scan, as measured by instrument dwell time, was faster when motion cues were used regardless of the complexity of the approach tasks. Pilot comments indicated a preference for motion. With motion cues, pilots appeared to work harder in all levels of task complexity and to improve tracking performance in the most complex approach task.

  14. Genetic simulation tools for post-genome wide association studies of complex diseases.

    PubMed

    Chen, Huann-Sheng; Hutter, Carolyn M; Mechanic, Leah E; Amos, Christopher I; Bafna, Vineet; Hauser, Elizabeth R; Hernandez, Ryan D; Li, Chun; Liberles, David A; McAllister, Kimberly; Moore, Jason H; Paltoo, Dina N; Papanicolaou, George J; Peng, Bo; Ritchie, Marylyn D; Rosenfeld, Gabriel; Witte, John S; Gillanders, Elizabeth M; Feuer, Eric J

    2015-01-01

    Genetic simulation programs are used to model data under specified assumptions to facilitate the understanding and study of complex genetic systems. Standardized data sets generated using genetic simulation are essential for the development and application of novel analytical tools in genetic epidemiology studies. With continuing advances in high-throughput genomic technologies and generation and analysis of larger, more complex data sets, there is a need for updating current approaches in genetic simulation modeling. To provide a forum to address current and emerging challenges in this area, the National Cancer Institute (NCI) sponsored a workshop, entitled "Genetic Simulation Tools for Post-Genome Wide Association Studies of Complex Diseases" at the National Institutes of Health (NIH) in Bethesda, Maryland on March 11-12, 2014. The goals of the workshop were to (1) identify opportunities, challenges, and resource needs for the development and application of genetic simulation models; (2) improve the integration of tools for modeling and analysis of simulated data; and (3) foster collaborations to facilitate development and applications of genetic simulation. During the course of the meeting, the group identified challenges and opportunities for the science of simulation, software and methods development, and collaboration. This paper summarizes key discussions at the meeting, and highlights important challenges and opportunities to advance the field of genetic simulation. © 2014 WILEY PERIODICALS, INC.

  15. Genetic Simulation Tools for Post-Genome Wide Association Studies of Complex Diseases

    PubMed Central

    Amos, Christopher I.; Bafna, Vineet; Hauser, Elizabeth R.; Hernandez, Ryan D.; Li, Chun; Liberles, David A.; McAllister, Kimberly; Moore, Jason H.; Paltoo, Dina N.; Papanicolaou, George J.; Peng, Bo; Ritchie, Marylyn D.; Rosenfeld, Gabriel; Witte, John S.

    2014-01-01

    Genetic simulation programs are used to model data under specified assumptions to facilitate the understanding and study of complex genetic systems. Standardized data sets generated using genetic simulation are essential for the development and application of novel analytical tools in genetic epidemiology studies. With continuing advances in high-throughput genomic technologies and generation and analysis of larger, more complex data sets, there is a need for updating current approaches in genetic simulation modeling. To provide a forum to address current and emerging challenges in this area, the National Cancer Institute (NCI) sponsored a workshop, entitled “Genetic Simulation Tools for Post-Genome Wide Association Studies of Complex Diseases” at the National Institutes of Health (NIH) in Bethesda, Maryland on March 11-12, 2014. The goals of the workshop were to: (i) identify opportunities, challenges and resource needs for the development and application of genetic simulation models; (ii) improve the integration of tools for modeling and analysis of simulated data; and (iii) foster collaborations to facilitate development and applications of genetic simulation. During the course of the meeting the group identified challenges and opportunities for the science of simulation, software and methods development, and collaboration. This paper summarizes key discussions at the meeting, and highlights important challenges and opportunities to advance the field of genetic simulation. PMID:25371374

  16. Large eddy simulation for atmospheric boundary layer flow over flat and complex terrains

    NASA Astrophysics Data System (ADS)

    Han, Yi; Stoellinger, Michael; Naughton, Jonathan

    2016-09-01

    In this work, we present Large Eddy Simulation (LES) results of atmospheric boundary layer (ABL) flow over complex terrain with neutral stratification using the OpenFOAM-based simulator for on/offshore wind farm applications (SOWFA). The complete work flow to investigate the LES for the ABL over real complex terrain is described including meteorological-tower data analysis, mesh generation and case set-up. New boundary conditions for the lateral and top boundaries are developed and validated to allow inflow and outflow as required in complex terrain simulations. The turbulent inflow data for the terrain simulation is generated using a precursor simulation of a flat and neutral ABL. Conditionally averaged met-tower data is used to specify the conditions for the flat precursor simulation and is also used for comparison with the simulation results of the terrain LES. A qualitative analysis of the simulation results reveals boundary layer separation and recirculation downstream of a prominent ridge that runs across the simulation domain. Comparisons of mean wind speed, standard deviation and direction between the computed results and the conditionally averaged tower data show a reasonable agreement.

  17. Numerical simulation of laminar reacting flows with complex chemistry

    SciTech Connect

    Day, Marcus S.; Bell, John B.

    1999-12-01

    We present an adaptive algorithm for low Mach number reacting flows with complex chemistry. Our approach uses a form of the low Mach number equations that discretely conserves both mass and energy. The discretization methodology is based on a robust projection formulation that accommodates large density contrasts. The algorithm uses an operator-split treatment of stiff reaction terms and includes effects of differential diffusion. The basic computational approach is embedded in an adaptive projection framework that uses structured hierarchical grids with subcycling in time that preserves the discrete conservation properties of the underlying single-grid algorithm. We present numerical examples illustrating the performance of the method on both premixed and non-premixed flames.

  18. Towards numerical simulation of bubbly flows in complex geometries

    NASA Astrophysics Data System (ADS)

    Mattson, Michael; Mahesh, Krishnan

    2008-11-01

    We are developing the LES capability for bubbly flows in complex geometries using unstructured grids and an Euler--Lagrangian methodology. Two Lagrangian bubble models are considered: (i) the bubbles are treated as a dispersed phase in the carrier fluid, and individual bubbles are point particles governed by an equation for bubble motion and (ii) the force coupling method by Maxey et al. [Fluid Dyn. Res., 32 (1997), 143-156]. The evolution of the bubble radius (assuming spherical bubbles) is governed by the Rayleigh--Plesset equation and integrated using a Runge--Kutta integrator with adaptive time-stepping. The talk will discuss numerical issues and contrast results between the two methodologies. Numerical results ranging from the motion of individual bubbles in channels and around bodies to drag reduction by bubbles in turbulent channel flow will be presented.

  19. Design and performance of duct acoustic treatment

    NASA Technical Reports Server (NTRS)

    Motsinger, R. E.; Kraft, R. E.

    1991-01-01

    The procedure for designing acoustic treatment panels used to line the walls of aircraft engine ducts and for estimating the resulting suppression of turbofan engine duct noise is discussed. This procedure is intended to be used for estimating noise suppression of existing designs or for designing new acoustic treatment panels and duct configurations to achieve desired suppression levels.

  20. 46 CFR 116.610 - Ventilation ducts.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... served by the ventilation duct for shutting off the passage of air through the ventilation duct in the... side of the boundary. A fire damper blade need not be insulated; and (7) Ducts serving cargo spaces... at least 11 USSG and not more than 3.2 millimeters (0.125 inch) gap between the blade and casing; (2...

  1. Duct injection technology prototype development

    SciTech Connect

    Harper, S.L. . Research and Development Div.)

    1991-08-01

    This report describes a test program conducted to determine the corrosion rate of materials in the dry scrubber or duct injection systems. Four materials were evaluated: 1010 carbon steel, Corten, 317SS and Hastelloy C-276. The results show that acidic conditions result in higher corrosion rates than alkaline conditions for all the materials. The carbon steel, Corten and stainless steel show moderate to heavy pitting attack in the acidic environment. For the alkaline conditions, the corrosion rates of carbon steel and Corten were higher than the stainless steel or Hastelloy C-276. Also, the corrosion rate of abraded specimens were four time those of unabraded specimens in the flue gas. It is probable that areas of wall-wetting and plugging in the duct injection process will exhibit high rates of corrosion for the carbon steel, Corten, and stainless steel materials. General corrosion and pitting corrosion will predominate. Additionally, abraded duct areas will corrode at a significantly higher rate than unabraded duct materials. 6 refs., 11 figs., 7 tabs.

  2. Wind Turbine With Concentric Ducts

    NASA Technical Reports Server (NTRS)

    Muhonen, A. J.

    1983-01-01

    Wind Turbine device is relatively compact and efficient. Converging inner and outer ducts increase pressure difference across blades of wind turbine. Turbine shaft drives alternator housed inside exit cone. Suitable for installation on such existing structures as water towers, barns, houses, and commercial buildings.

  3. Teaching and Assessing Complex Skills in Simulation With Application to Rifle Marksmanship Training

    DTIC Science & Technology

    2009-12-01

    Interservice /Industry Training, Simulation, and Education Conference (I/ITSEC) 2009 2009 Paper No. 9086 Page 1 of 10 Teaching and Assessing Complex...integrate key areas of knowledge related to skill acquisition and expertise, address strategies for teaching and assessing complex skills, and examine the...complex skill development, based upon learning principles and enhanced performance feedback. Our emphasis is on teaching the “warrior” skills needed for

  4. Enhancing Complex System Performance Using Discrete-Event Simulation

    SciTech Connect

    Allgood, Glenn O; Olama, Mohammed M; Lake, Joe E

    2010-01-01

    In this paper, we utilize discrete-event simulation (DES) merged with human factors analysis to provide the venue within which the separation and deconfliction of the system/human operating principles can occur. A concrete example is presented to illustrate the performance enhancement gains for an aviation cargo flow and security inspection system achieved through the development and use of a process DES. The overall performance of the system is computed, analyzed, and optimized for the different system dynamics. Various performance measures are considered such as system capacity, residual capacity, and total number of pallets waiting for inspection in the queue. These metrics are performance indicators of the system's ability to service current needs and respond to additional requests. We studied and analyzed different scenarios by changing various model parameters such as the number of pieces per pallet ratio, number of inspectors and cargo handling personnel, number of forklifts, number and types of detection systems, inspection modality distribution, alarm rate, and cargo closeout time. The increased physical understanding resulting from execution of the queuing model utilizing these vetted performance measures identified effective ways to meet inspection requirements while maintaining or reducing overall operational cost and eliminating any shipping delays associated with any proposed changes in inspection requirements. With this understanding effective operational strategies can be developed to optimally use personnel while still maintaining plant efficiency, reducing process interruptions, and holding or reducing costs.

  5. Parallel Cartesian grid refinement for 3D complex flow simulations

    NASA Astrophysics Data System (ADS)

    Angelidis, Dionysios; Sotiropoulos, Fotis

    2013-11-01

    A second order accurate method for discretizing the Navier-Stokes equations on 3D unstructured Cartesian grids is presented. Although the grid generator is based on the oct-tree hierarchical method, fully unstructured data-structure is adopted enabling robust calculations for incompressible flows, avoiding both the need of synchronization of the solution between different levels of refinement and usage of prolongation/restriction operators. The current solver implements a hybrid staggered/non-staggered grid layout, employing the implicit fractional step method to satisfy the continuity equation. The pressure-Poisson equation is discretized by using a novel second order fully implicit scheme for unstructured Cartesian grids and solved using an efficient Krylov subspace solver. The momentum equation is also discretized with second order accuracy and the high performance Newton-Krylov method is used for integrating them in time. Neumann and Dirichlet conditions are used to validate the Poisson solver against analytical functions and grid refinement results to a significant reduction of the solution error. The effectiveness of the fractional step method results in the stability of the overall algorithm and enables the performance of accurate multi-resolution real life simulations. This material is based upon work supported by the Department of Energy under Award Number DE-EE0005482.

  6. Study on simulation and experiment of laser micro-Doppler effect for detecting complex vibration

    NASA Astrophysics Data System (ADS)

    Yuan, Shuai; Zhang, Juan; Liu, Mei-juan; Zhang, Jun

    2013-08-01

    The spectrum of radar signal will be modulated by moving target or vibration and turning part of the target, this is called micro-Doppler effect. It is a new way of using micro-Doppler effect to realize the feature extraction and target recognition. Because the complex vibration target has more complicated frequency component than the single frequency target, so it is very useful to do the research of simulation and experiment of laser micro-Doppler effect for detecting complex vibration. In this paper, the research on simulation and experiment of laser micro-Doppler effect for detecting complex vibration of moving target was developed based on the simulation research of micro-Doppler effect in lidar. Firstly, the geometry of complex vibrating target detection in radar was established. Secondly, the simulation and experiment signal sources were compared and also the returned signals in radar of the simulation and experiment were compared, the compared results showed that the two complex signal sources were very similar, and the frequency change trend of returned signals in radar was the same. Thirdly, joint time-frequency analysis method of the reassigned smoothed pseudo Wigner-Ville distribution (RSPWVD) was introduced to analyze the signals. The results showed that in RSPWVD, the waveform of the vibration target, the target vibration period, the Doppler frequency shift and the target's speed can be got. The simulation results and the experiment results got by the RSPWVD had the basically same frequency characteristics. So the RSPWVD can reflect very well the micro-Doppler characteristics of moving target's complex vibration. In conclusion it proved the validity of the simulated model, also it proved that using this time-frequency method to analyze the micro-Doppler signal of complex vibration was correct. And it laid the foundation of further using lidar to realize the classification and identification of target.

  7. Classification and management of bile duct injuries

    PubMed Central

    Mercado, Miguel Angel; Domínguez, Ismael

    2011-01-01

    To review the classification and general guidelines for treatment of bile duct injury patients and their long term results. In a 20-year period, 510 complex circumferential injuries have been referred to our team for repair at the Instituto Nacional de Ciencias Médicas y Nutrición “Salvador Zubirán” hospital in Mexico City and 198 elsewhere (private practice). The records at the third level Academic University Hospital were analyzed and divided into three periods of time: GI-1990-99 (33 cases), GII- 2000-2004 (139 cases) and GIII- 2004-2008 (140 cases). All patients were treated with a Roux en Y hepatojejunostomy. A decrease in using transanastomotic stents was observed (78% vs 2%, P = 0.0001). Partial segment IV and V resection was more frequently carried out (45% vs 75%, P = 0.2) (to obtain a high bilioenteric anastomosis). Operative mortality (3% vs 0.7%, P = 0.09), postoperative cholangitis (54% vs 13%, P = 0.0001), anastomosis strictures (30% vs 5%, P = 0.0001), short and long term complications and need for reoperation (surgical or radiological) (45% vs 11%, P = 0.0001) were significantly less in the last period. The authors concluded that transition to a high volume center has improved long term results for bile duct injury repair. Even interested and tertiary care centers have a learning curve. PMID:21528093

  8. Simulation of groundwater flow in the glacial aquifer system of northeastern Wisconsin with variable model complexity

    USGS Publications Warehouse

    Juckem, Paul F.; Clark, Brian R.; Feinstein, Daniel T.

    2017-05-04

    The U.S. Geological Survey, National Water-Quality Assessment seeks to map estimated intrinsic susceptibility of the glacial aquifer system of the conterminous United States. Improved understanding of the hydrogeologic characteristics that explain spatial patterns of intrinsic susceptibility, commonly inferred from estimates of groundwater age distributions, is sought so that methods used for the estimation process are properly equipped. An important step beyond identifying relevant hydrogeologic datasets, such as glacial geology maps, is to evaluate how incorporation of these resources into process-based models using differing levels of detail could affect resulting simulations of groundwater age distributions and, thus, estimates of intrinsic susceptibility.This report describes the construction and calibration of three groundwater-flow models of northeastern Wisconsin that were developed with differing levels of complexity to provide a framework for subsequent evaluations of the effects of process-based model complexity on estimations of groundwater age distributions for withdrawal wells and streams. Preliminary assessments, which focused on the effects of model complexity on simulated water levels and base flows in the glacial aquifer system, illustrate that simulation of vertical gradients using multiple model layers improves simulated heads more in low-permeability units than in high-permeability units. Moreover, simulation of heterogeneous hydraulic conductivity fields in coarse-grained and some fine-grained glacial materials produced a larger improvement in simulated water levels in the glacial aquifer system compared with simulation of uniform hydraulic conductivity within zones. The relation between base flows and model complexity was less clear; however, the relation generally seemed to follow a similar pattern as water levels. Although increased model complexity resulted in improved calibrations, future application of the models using simulated particle

  9. Training on a new, portable, simple simulator transfers to performance of complex bronchoscopy procedures.

    PubMed

    Krogh, Charlotte Loumann; Konge, Lars; Bjurström, Johanna; Ringsted, Charlotte

    2013-07-01

    Virtual-reality (VR) simulation provides a safe and effective learning environment prior to practicing on patients. However, existing bronchoscopy simulators are expensive and not easily portable. The aim of this study was to assess the effect of self-directed training on a new, portable, simple simulator measured by transfer of skills to performance of more complex bronchoscopy procedures on an advanced VR simulator. Twenty medical students participated in the study. After a general introduction to bronchoscopy, they were randomised into two groups, receiving either self-directed bronchoscopy training using a portable, simple simulator or no manual training. Subsequently, all participants were tested on complex scenarios in an advanced VR simulator using a validated bronchoscopy quality test. Bronchoscopy quality scores were compared using independent samples t-test and correlated with a previously established pass-fail standard. The intervention group spent an average of 71-min training on the new simulator. The intervention group performed significantly better than the control group, mean bronchoscopy quality score 0.55 [standard deviation (SD) 0.16] vs 0.36 (SD 0.10), P = 0.005, effect size = 1.47. Eight out of 10 participants in the intervention group passed the test compared with only 1 out of 10 in the control group. The effect of a brief, self-directed training session using a portable, simple simulator was substantial and transferred to performance of more complex skills. © 2012 John Wiley & Sons Ltd.

  10. Building complex simulations rapidly using MATRIX(x): The Space Station redesign

    NASA Astrophysics Data System (ADS)

    Carrington, C. K.

    MSFC's quick response to the Space Station redesign effort last year required the development of a computer simulation to model the attitude and station-keeping dynamics of a complex body with rotating solar arrays in orbit around the Earth. The simulation was written using a rapid-prototyping graphical simulation and design tool called MATRIX(x) and provided the capability to quickly remodel complex configuration changes by icon manipulation using a mouse. The simulation determines time-dependent inertia properties, and models forces and torques from gravity-gradient, solar radiation, and aerodynamic disturbances. Surface models are easily built from a selection of beams, plates, tetrahedrons, and cylinders. An optimization scheme was written to determine the torque equilibrium attitudes that balance gravity-gradient and aerodynamic torques over an orbit, and propellant-usage estimates were determined. The simulation has been adapted to model the attitude dynamics for small spacecraft.

  11. Symptomatic and incidental mammary duct ectasia.

    PubMed Central

    Browning, J; Bigrigg, A; Taylor, I

    1986-01-01

    The histology obtained from 1256 female patients undergoing breast surgery was reviewed. Mammary duct ectasia was noted in 51 (4.2%) patients who had associated symptoms and in 103 (8.1%) patients where duct ectasia was recognized as an incidental finding. The syndrome is defined by primary (nipple change or sepsis) and secondary (pain and lump) symptoms. Formal duct excision gives good results for symptomatic duct ectasia. It is postulated that many women have nonsymptomatic mammary duct ectasia. Secondary infection gives rise to nipple change, lump and pain. In the severe form abscess and fistula formation occurs which necessitates repeated surgical treatment, and rarely mastectomy. PMID:3806542

  12. Experimental and Numerical Study on Performance of Ducted Hydrokinetic Turbines with Pre-Swirl Stator Blades.

    NASA Astrophysics Data System (ADS)

    Gish, Andrew

    2015-11-01

    Ducts (also called shrouds) have been shown to improve performance of hydrokinetic turbines in some situations, bringing the power coefficient (Cp) closer to the Betz limit. Here we investigate optimization of the duct design as well as the addition of stator blades upstream of the turbine rotor to introduce pre-swirl in the flow. A small scale three-bladed turbine was tested in a towing tank. Three cases (bare turbine, with duct, and with duct and stators) were tested over a range of flow speeds. Important parameters include duct cross-sectional shape, blade-duct gap, stator cross-sectional shape, and stator angle. For each test, Cp was evaluated as a function of tip speed ratio (TSR). Experimental results were compared with numerical simulations. Results indicate that ducts and stators can improve performance at slower flow speeds and lower the stall speed compared to a bare turbine, but may degrade performance at higher speeds. Ongoing efforts to optimize duct and stator configurations will be discussed.

  13. Performance and Flowfield Measurements on a 10-inch Ducted Rotor VTOL UAV

    NASA Technical Reports Server (NTRS)

    Martin, Preston; Tung, Chee

    2004-01-01

    A ducted fan VTOL UAV with a 10-inch diameter rotor was tested in the US Army 7-by 10-Foot Wind Tunnel. The test conditions covered a range of angle of attack from 0 to 110 degrees to the freestream. The tunnel velocity was varied from 0 (simulating a hover condition) to 128 ft/sec in propeller mode. A six-component internal balance measured the aerodynamic loads for a range of model configurations. including the isolated rotor, the isolated duct, and the full configuration of the duct and rotor. For some conditions, hotwire velocity surveys were conducted along the inner and outer surface of the duct and across the downstream wake. In addition, fluorescent oil flow visualization allowed the flow separation patterns inside and outside of the duct to be mapped for a few test conditions. Two different duct shapes were tested to determine the performance effects of leading edge radius. For each duct, a range of rotor tip gap from 1%R to 4.5%R was tested to determine the performance penalty in hover and axial flight. Measured results are presented in terms of hover performance, hover performance in a crosswind, and high angle of attack performance in propeller mode. In each case, the effects of both tip gap and duct leading edge radius are illustrated using measurements. Some of the hover performance issues were also studied using a simple analytical method, and the results agreed with the measurements.

  14. Promoting Conceptual Change for Complex Systems Understanding: Outcomes of an Agent-Based Participatory Simulation

    NASA Astrophysics Data System (ADS)

    Rates, Christopher A.; Mulvey, Bridget K.; Feldon, David F.

    2016-08-01

    Components of complex systems apply across multiple subject areas, and teaching these components may help students build unifying conceptual links. Students, however, often have difficulty learning these components, and limited research exists to understand what types of interventions may best help improve understanding. We investigated 32 high school students' understandings of complex systems components and whether an agent-based simulation could improve their understandings. Pretest and posttest essays were coded for changes in six components to determine whether students showed more expert thinking about the complex system of the Chesapeake Bay watershed. Results showed significant improvement for the components Emergence ( r = .26, p = .03), Order ( r = .37, p = .002), and Tradeoffs ( r = .44, p = .001). Implications include that the experiential nature of the simulation has the potential to support conceptual change for some complex systems components, presenting a promising option for complex systems instruction.

  15. The Detection of Radiated Modes from Ducted Fan Engines

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Nark, Douglas M.; Thomas, Russell H.

    2001-01-01

    The bypass duct of an aircraft engine is a low-pass filter allowing some spinning modes to radiate outside the duct. The knowledge of the radiated modes can help in noise reduction, as well as the diagnosis of noise generation mechanisms inside the duct. We propose a nonintrusive technique using a circular microphone array outside the engine measuring the complex noise spectrum on an arc of a circle. The array is placed at various axial distances from the inlet or the exhaust of the engine. Using a model of noise radiation from the duct, an overdetermined system of linear equations is constructed for the complex amplitudes of the radial modes for a fixed circumferential mode. This system of linear equations is generally singular, indicating that the problem is illposed. Tikhonov regularization is employed to solve this system of equations for the unknown amplitudes of the radiated modes. An application of our mode detection technique using measured acoustic data from a circular microphone array is presented. We show that this technique can reliably detect radiated modes with the possible exception of modes very close to cut-off.

  16. Qualitative and Quantitative Protein Complex Prediction Through Proteome-Wide Simulations.

    PubMed

    Rizzetto, Simone; Priami, Corrado; Csikász-Nagy, Attila

    2015-10-01

    Despite recent progress in proteomics most protein complexes are still unknown. Identification of these complexes will help us understand cellular regulatory mechanisms and support development of new drugs. Therefore it is really important to establish detailed information about the composition and the abundance of protein complexes but existing algorithms can only give qualitative predictions. Herein, we propose a new approach based on stochastic simulations of protein complex formation that integrates multi-source data--such as protein abundances, domain-domain interactions and functional annotations--to predict alternative forms of protein complexes together with their abundances. This method, called SiComPre (Simulation based Complex Prediction), achieves better qualitative prediction of yeast and human protein complexes than existing methods and is the first to predict protein complex abundances. Furthermore, we show that SiComPre can be used to predict complexome changes upon drug treatment with the example of bortezomib. SiComPre is the first method to produce quantitative predictions on the abundance of molecular complexes while performing the best qualitative predictions. With new data on tissue specific protein complexes becoming available SiComPre will be able to predict qualitative and quantitative differences in the complexome in various tissue types and under various conditions.

  17. Potassium transport in the mammalian collecting duct.

    PubMed

    Muto, S

    2001-01-01

    The mammalian collecting duct plays a dominant role in regulating K(+) excretion by the nephron. The collecting duct exhibits axial and intrasegmental cell heterogeneity and is composed of at least two cell types: collecting duct cells (principal cells) and intercalated cells. Under normal circumstances, the collecting duct cell in the cortical collecting duct secretes K(+), whereas under K(+) depletion, the intercalated cell reabsorbs K(+). Assessment of the electrochemical driving forces and of membrane conductances for transcellular and paracellular electrolyte movement, the characterization of several ATPases, patch-clamp investigation, and cloning of the K(+) channel have provided important insights into the role of pumps and channels in those tubule cells that regulate K(+) secretion and reabsorption. This review summarizes K(+) transport properties in the mammalian collecting duct. Special emphasis is given to the mechanisms of how K(+) transport is regulated in the collecting duct.

  18. Stenting of the arterial duct: a new approach to palliation for pulmonary atresia.

    PubMed Central

    Gibbs, J L; Rothman, M T; Rees, M R; Parsons, J M; Blackburn, M E; Ruiz, C E

    1992-01-01

    OBJECTIVE--To assess the possibility of maintaining ductal patency in neonates with complex pulmonary atresia by percutaneous implantation of balloon expandable stents. PATIENTS--Two duct-dependent neonates with long segment pulmonary atresia, right sided aortic arch, and left sided arterial duct. RESULTS--Stents with final diameter of 3.5 or 4 mm and initial length of 7 or 15 mm were successfully positioned in the arterial duct. Two stents were required in one child and four in the other in order to stent the entire length of the duct. After the procedures the ducts remained widely patent and arterial oxygen saturations remained above 80%. Complications of the procedures included perforation of a peripheral pulmonary artery and cardiac perforation, both caused by guide wire manipulation. Both babies died suddenly, one at five weeks, and the other at nine days after successful stenting of the duct. Both ducts were patent at necropsy; the exact cause of one death was not clearly defined, but the second seemed to be caused by pneumococcal septicaemia. CONCLUSIONS--Stenting of the arterial duct is technically feasible. It provides adequate palliation for neonates with pulmonary atresia at least in the short term and it seems to result in balanced, central perfusion of both pulmonary arteries. This preliminary report suggests that this previously untried technique may prove to be a promising and attractive alternative to neonatal aortopulmonary shunt operation. Images PMID:1372815

  19. Mechanism of dynamic near-infrared fluorescence cholangiography of extrahepatic bile ducts and applications in detecting bile duct injuries using indocyanine green in animal models.

    PubMed

    Gao, Yang; Li, Min; Song, Zi-Fang; Cui, Le; Wang, Bi-Rong; Lou, Xiao-Ding; Zhou, Tao; Zhang, Yong; Zheng, Qi-Chang

    2017-02-01

    Fluorescence intraoperative cholangiography (IOC) is a potential alternative for identifying anatomical variation and preventing iatrogenic bile duct injuries by using the near-infrared probe indocyanine green (ICG). However, the dynamic process and mechanism of fluorescence IOC have not been elucidated in previous publications. Herein, the optical properties of the complex of ICG and bile, dynamic fluorescence cholangiography and iatrogenic bile duct injuries were investigated. The emission spectrum of ICG in bile peaked at 844 nm and ICG had higher tissue penetration. Extrahepatic bile ducts could fluoresce 2 min after intravenous injection, and the fluorescence intensity reached a peak at 8 min. In addition, biliary dynamics were observed owing to ICG excretion from the bile ducts into the duodenum. Quantitative analysis indicated that ICG-guided fluorescence IOC possessed a high signal to noise ratio compared to the surrounding peripheral tissue and the portal vein. Fluorescence IOC was based on rapid uptake of circulating ICG in plasma by hepatic cells, excretion of ICG into the bile and then its interaction with protein molecules in the bile. Moreover, fluorescence IOC was sensitive to detect bile duct ligation and acute bile duct perforation using ICG in rat models. All of the results indicated that fluorescence IOC using ICG is a valid alternative for the cholangiography of extrahepatic bile ducts and has potential for measurement of biliary dynamics.

  20. Numerical study of acoustic instability in a partly lined flow duct using the full linearized Navier-Stokes equations

    NASA Astrophysics Data System (ADS)

    Xin, Bo; Sun, Dakun; Jing, Xiaodong; Sun, Xiaofeng

    2016-07-01

    Lined ducts are extensively applied to suppress noise emission from aero-engines and other turbomachines. The complex noise/flow interaction in a lined duct possibly leads to acoustic instability in certain conditions. To investigate the instability, the full linearized Navier-Stokes equations with eddy viscosity considered are solved in frequency domain using a Galerkin finite element method to compute the sound transmission in shear flow in the lined duct as well as the flow perturbation over the impedance wall. A good agreement between the numerical predictions and the published experimental results is obtained for the sound transmission, showing that a transmission peak occurs around the resonant frequency of the acoustic liner in the presence of shear flow. The eddy viscosity is an important influential factor that plays the roles of both providing destabilizing and making coupling between the acoustic and flow motions over the acoustic liner. Moreover, it is shown from the numerical investigation that the occurrence of the sound amplification and the magnitude of transmission coefficient are closely related to the realistic velocity profile, and we find it essential that the actual variation of the velocity profile in the axial direction over the liner surface be included in the computation. The simulation results of the periodic flow patterns possess the proper features of the convective instability over the liner, as observed in Marx et al.'s experiment. A quantitative comparison between numerical and experimental results of amplitude and phase of the instability is performed. The corresponding eigenvalues achieve great agreement.

  1. Spectral light source distribution variations to enhance discrimination of the common bile duct from surroundings in reflectance hyperspectral images

    NASA Astrophysics Data System (ADS)

    Litorja, Maritoni; Fein, Mira; Wehner, Eleanor; Schwarz, Roderich; Zuzak, Karel; Livingston, Edward

    2013-03-01

    The classification of anatomical features using hyperspectral imaging has been a common goal in biomedical hyperspectral imaging. Identification and location of the common bile duct is critical in cholecystectomies, one of the most common surgical procedures. In this study, surgical images where the common bile duct is visible to the surgeon during open surgeries of patients with normal bile ducts were acquired. The effect of the spectral distribution of simulated light sources on the scene color are explored with the objective of providing the optimum spectral light distribution that can enhance contrast between the common bile duct and surrounding tissue through luminance and color differences.

  2. Simulating gene-gene and gene-environment interactions in complex diseases: Gene-Environment iNteraction Simulator 2

    PubMed Central

    2012-01-01

    Background The analysis of complex diseases is an important problem in human genetics. Because multifactoriality is expected to play a pivotal role, many studies are currently focused on collecting information on the genetic and environmental factors that potentially influence these diseases. However, there is still a lack of efficient and thoroughly tested statistical models that can be used to identify implicated features and their interactions. Simulations using large biologically realistic data sets with known gene-gene and gene-environment interactions that influence the risk of a complex disease are a convenient and useful way to assess the performance of statistical methods. Results The Gene-Environment iNteraction Simulator 2 (GENS2) simulates interactions among two genetic and one environmental factor and also allows for epistatic interactions. GENS2 is based on data with realistic patterns of linkage disequilibrium, and imposes no limitations either on the number of individuals to be simulated or on number of non-predisposing genetic/environmental factors to be considered. The GENS2 tool is able to simulate gene-environment and gene-gene interactions. To make the Simulator more intuitive, the input parameters are expressed as standard epidemiological quantities. GENS2 is written in Python language and takes advantage of operators and modules provided by the simuPOP simulation environment. It can be used through a graphical or a command-line interface and is freely available from http://sourceforge.net/projects/gensim. The software is released under the GNU General Public License version 3.0. Conclusions Data produced by GENS2 can be used as a benchmark for evaluating statistical tools designed for the identification of gene-gene and gene-environment interactions. PMID:22698142

  3. Simulating gene-gene and gene-environment interactions in complex diseases: Gene-Environment iNteraction Simulator 2.

    PubMed

    Pinelli, Michele; Scala, Giovanni; Amato, Roberto; Cocozza, Sergio; Miele, Gennaro

    2012-06-14

    The analysis of complex diseases is an important problem in human genetics. Because multifactoriality is expected to play a pivotal role, many studies are currently focused on collecting information on the genetic and environmental factors that potentially influence these diseases. However, there is still a lack of efficient and thoroughly tested statistical models that can be used to identify implicated features and their interactions. Simulations using large biologically realistic data sets with known gene-gene and gene-environment interactions that influence the risk of a complex disease are a convenient and useful way to assess the performance of statistical methods. The Gene-Environment iNteraction Simulator 2 (GENS2) simulates interactions among two genetic and one environmental factor and also allows for epistatic interactions. GENS2 is based on data with realistic patterns of linkage disequilibrium, and imposes no limitations either on the number of individuals to be simulated or on number of non-predisposing genetic/environmental factors to be considered. The GENS2 tool is able to simulate gene-environment and gene-gene interactions. To make the Simulator more intuitive, the input parameters are expressed as standard epidemiological quantities. GENS2 is written in Python language and takes advantage of operators and modules provided by the simuPOP simulation environment. It can be used through a graphical or a command-line interface and is freely available from http://sourceforge.net/projects/gensim. The software is released under the GNU General Public License version 3.0. Data produced by GENS2 can be used as a benchmark for evaluating statistical tools designed for the identification of gene-gene and gene-environment interactions.

  4. Parotid salivary duct sialocele associated with glandular duct stenosis in a cat.

    PubMed

    Vallefuoco, Rosario; Jardel, Nicolas; El Mrini, Meryem; Stambouli, Fouzia; Cordonnier, Nathalie

    2011-10-01

    Feline parotid salivary duct sialocele is an uncommon disorder that has been previously reported in association with traumatic rupture of the duct in only two cats. Both cases were successfully treated by proximal duct ligation. We describe the successful surgical treatment of a parotid duct sialocele, secondary to spontaneous salivary duct stenosis, in an adult domestic shorthair cat. The cat was referred for assessment of a recurrent fluid-filled swelling on the left side of the face. Cytology of the aspirated fluid was consistent with serous saliva. The anatomical localisation of the lesion and the nature of the fluid were indicative of parotid gland/duct involvement. Retrograde sialography by parotid duct cannulation was unsuccessful because the left parotid duct opening was stenosed and obstructed by scar tissue. Surgical exploration revealed a parotid salivary duct sialocele, which was completely removed along with the parotid gland without complications.

  5. Tear-ducts in wine

    NASA Astrophysics Data System (ADS)

    Bush, John W. M.

    1999-11-01

    We examine the radial spoke pattern evident in the meniscus region in glasses of strong alcoholic beverages exhibiting the `tears-in-wine' phenomenon. We demonstrate that the pattern results from ridge-like elevations of the free surface which are supported by evaporatively-driven Marangoni convection in the meniscus region. Vortices associated with the convective motions are aligned in the radial direction by the surface tension gradient responsible for the generation of tears. The radial flow is focussed into the ridges, which thus serve as the principal conduits of fluid for the tears; consequently, we refer to the ridges as `tear-ducts'. The phenomenon is examined experimentally, and a numerical model of evaporatively-driven Marangoni convection is developed which reproduces the salient features of the tear-duct phenomenon.

  6. HAARP-Induced Ionospheric Ducts

    SciTech Connect

    Milikh, Gennady; Vartanyan, Aram

    2011-01-04

    It is well known that strong electron heating by a powerful HF-facility can lead to the formation of electron and ion density perturbations that stretch along the magnetic field line. Those density perturbations can serve as ducts for ELF waves, both of natural and artificial origin. This paper presents observations of the plasma density perturbations caused by the HF-heating of the ionosphere by the HAARP facility. The low orbit satellite DEMETER was used as a diagnostic tool to measure the electron and ion temperature and density along the satellite orbit overflying close to the magnetic zenith of the HF-heater. Those observations will be then checked against the theoretical model of duct formation due to HF-heating of the ionosphere. The model is based on the modified SAMI2 code, and is validated by comparison with well documented experiments.

  7. Designing insulation for cryogenic ducts

    NASA Astrophysics Data System (ADS)

    Love, C. C.

    1984-03-01

    It is pointed out that the great temperature difference between the outside of a cryogenic duct and the liquified gas it carries can cause a high heat input unless blocked by a high thermal resistance. High thermal resistance for lines needing maximum insulation is provided by metal vacuum jackets. Low-density foam is satisfactory in cases in which higher heat input can be tolerated. Attention is given to the heat transfer through a duct vacuum jacket, the calculation of heat input and the exterior surface's steady-state temperature for various thicknesses of insulation, the calculation of the heat transfer through gimbal jackets, and design specifications regarding the allowable pressure rise in the jacket's annular space.

  8. πBUSS: a parallel BEAST/BEAGLE utility for sequence simulation under complex evolutionary scenarios.

    PubMed

    Bielejec, Filip; Lemey, Philippe; Carvalho, Luiz Max; Baele, Guy; Rambaut, Andrew; Suchard, Marc A

    2014-05-07

    Simulated nucleotide or amino acid sequences are frequently used to assess the performance of phylogenetic reconstruction methods. BEAST, a Bayesian statistical framework that focuses on reconstructing time-calibrated molecular evolutionary processes, supports a wide array of evolutionary models, but lacked matching machinery for simulation of character evolution along phylogenies. We present a flexible Monte Carlo simulation tool, called πBUSS, that employs the BEAGLE high performance library for phylogenetic computations to rapidly generate large sequence alignments under complex evolutionary models. πBUSS sports a user-friendly graphical user interface (GUI) that allows combining a rich array of models across an arbitrary number of partitions. A command-line interface mirrors the options available through the GUI and facilitates scripting in large-scale simulation studies. πBUSS may serve as an easy-to-use, standard sequence simulation tool, but the available models and data types are particularly useful to assess the performance of complex BEAST inferences. The connection with BEAST is further strengthened through the use of a common extensible markup language (XML), allowing to specify also more advanced evolutionary models. To support simulation under the latter, as well as to support simulation and analysis in a single run, we also add the πBUSS core simulation routine to the list of BEAST XML parsers. πBUSS offers a unique combination of flexibility and ease-of-use for sequence simulation under realistic evolutionary scenarios. Through different interfaces, πBUSS supports simulation studies ranging from modest endeavors for illustrative purposes to complex and large-scale assessments of evolutionary inference procedures. Applications are not restricted to the BEAST framework, or even time-measured evolutionary histories, and πBUSS can be connected to various other programs using standard input and output format.

  9. Applications of the COG multiparticle Monte Carlo transport code to simulated imaging of complex objects

    SciTech Connect

    Buck, R M; Hall, J M

    1999-06-01

    COG is a major multiparticle simulation code in the LLNL Monte Carlo radiation transport toolkit. It was designed to solve deep-penetration radiation shielding problems in arbitrarily complex 3D geometries, involving coupled transport of photons, neutrons, and electrons. COG was written to provide as much accuracy as the underlying cross-sections will allow, and has a number of variance-reduction features to speed computations. Recently COG has been applied to the simulation of high- resolution radiographs of complex objects and the evaluation of contraband detection schemes. In this paper we will give a brief description of the capabilities of the COG transport code and show several examples of neutron and gamma-ray imaging simulations. Keywords: Monte Carlo, radiation transport, simulated radiography, nonintrusive inspection, neutron imaging.

  10. Visualization of complex processes in lipid systems using computer simulations and molecular graphics.

    PubMed

    Telenius, Jelena; Vattulainen, Ilpo; Monticelli, Luca

    2009-01-01

    Computer simulation has become an increasingly popular tool in the study of lipid membranes, complementing experimental techniques by providing information on structure and dynamics at high spatial and temporal resolution. Molecular visualization is the most powerful way to represent the results of molecular simulations, and can be used to illustrate complex transformations of lipid aggregates more easily and more effectively than written text. In this chapter, we review some basic aspects of simulation methodologies commonly employed in the study of lipid membranes and we describe a few examples of complex phenomena that have been recently investigated using molecular simulations. We then explain how molecular visualization provides added value to computational work in the field of biological membranes, and we conclude by listing a few molecular graphics packages widely used in scientific publications.

  11. To Duct or Not to Duct: Evaluating the Space Conditioning Impacts of Heat Pump Water Heaters in the PNNL Lab Homes

    SciTech Connect

    Widder, Sarah H.; Parker, Graham B.; Peeks, B.; Sullivan, Greg; Shaffer, Scott

    2014-08-22

    Heat pump water heaters (HPWH) are a promising technology for substantially reducing water heating-related energy use in the residential sector. However, concerns have been raised regarding the impact of HPWHs on space conditioning energy when installed in conditioned space, primarily in northern climates. For example, the Northwest Energy Efficiency Alliance (NEEA’s) Northern Climate HPWH Specification, which describes the characteristics a HPWH must have to be incentivized in cold climates in the Pacific Northwest (PNW), requires exhaust ducting for their Tier II-specified products and both supply and exhaust ducting for the Tier III-specified product (NEEA 2013). However, these concerns and installation recommendations are based on modeling and comparative field data are not available to verify modeled performance. This study examines the overall performance and operation of two GE GeoSpring HPWHs in conditioned space in the matched pair of PNNL Lab Homes with no ducting, exhaust ducting, and full ducting (supply and exhaust) and explores the interactions between the HPWH and the home’s heating/cooling system. The data collected in this field evaluation suggest that previous modeling may not completely characterize the complex interactions of HPWHs, HVAC systems, and ducting. This report discusses the impact on space conditioning and water heater energy use of configuring an HPWH with exhaust only ducting or full ducting, as compared to an unducted HPWH. Additional cost analysis is necessary to assess the cost effectiveness of ducting and to make formal recommendations regarding appropriate installation of HPWHs in more varied scenarios.

  12. Simulation of complex data structures for planning of studies with focus on biomarker comparison.

    PubMed

    Schulz, Andreas; Zöller, Daniela; Nickels, Stefan; Beutel, Manfred E; Blettner, Maria; Wild, Philipp S; Binder, Harald

    2017-06-13

    There are a growing number of observational studies that do not only focus on single biomarkers for predicting an outcome event, but address questions in a multivariable setting. For example, when quantifying the added value of new biomarkers in addition to established risk factors, the aim might be to rank several new markers with respect to their prediction performance. This makes it important to consider the marker correlation structure for planning such a study. Because of the complexity, a simulation approach may be required to adequately assess sample size or other aspects, such as the choice of a performance measure. In a simulation study based on real data, we investigated how to generate covariates with realistic distributions and what generating model should be used for the outcome, aiming to determine the least amount of information and complexity needed to obtain realistic results. As a basis for the simulation a large epidemiological cohort study, the Gutenberg Health Study was used. The added value of markers was quantified and ranked in subsampling data sets of this population data, and simulation approaches were judged by the quality of the ranking. One of the evaluated approaches, the random forest, requires original data at the individual level. Therefore, also the effect of the size of a pilot study for random forest based simulation was investigated. We found that simple logistic regression models failed to adequately generate realistic data, even with extensions such as interaction terms or non-linear effects. The random forest approach was seen to be more appropriate for simulation of complex data structures. Pilot studies starting at about 250 observations were seen to provide a reasonable level of information for this approach. We advise to avoid oversimplified regression models for simulation, in particular when focusing on multivariable research questions. More generally, a simulation should be based on real data for adequately reflecting

  13. On the neutrons streaming in straight duct

    PubMed

    Jehouani; Boulkheir; Ichaoui

    2000-10-01

    The main aim of this study is to evaluate the thermal neutron streaming through a straight cylindrical duct by using the Monte Carlo method and evaluating the neutron reflection by the duct wall to the total flux at the exit of the duct. The duct walls are made separately of iron and aluminum. We have considered 10 groups of energy between 10(-5) and 10 eV. For a point source at the mouth of the duct, we have determined the direct and the reflected part of the total thermal neutron flux at the exit of the duct for different lengths and different radii of the duct. For a punctual source, we have found that the major contribution to the total flux of neutrons at the exit is due to the neutron reflection by walls, and the reflection contribution decreases when the neutron energy decreases. For a constant length of the duct, the reflected part decreases when the duct radius increases, while for the disk shaped source, we have found the opposite phenomenon. The transmitted neutron flux distribution at the exit of the duct is determined for a disk shaped source for different neutron energies and different distances from the exit center.

  14. Modeling particle loss in ventilation ducts

    SciTech Connect

    Sippola, Mark R.; Nazaroff, William W.

    2003-04-01

    Empirical equations were developed and applied to predict losses of 0.01-100 {micro}m airborne particles making a single pass through 120 different ventilation duct runs typical of those found in mid-sized office buildings. For all duct runs, losses were negligible for submicron particles and nearly complete for particles larger than 50 {micro}m. The 50th percentile cut-point diameters were 15 {micro}m in supply runs and 25 {micro}m in return runs. Losses in supply duct runs were higher than in return duct runs, mostly because internal insulation was present in portions of supply duct runs, but absent from return duct runs. Single-pass equations for particle loss in duct runs were combined with models for predicting ventilation system filtration efficiency and particle deposition to indoor surfaces to evaluate the fates of particles of indoor and outdoor origin in an archetypal mechanically ventilated building. Results suggest that duct losses are a minor influence for determining indoor concentrations for most particle sizes. Losses in ducts were of a comparable magnitude to indoor surface losses for most particle sizes. For outdoor air drawn into an unfiltered ventilation system, most particles smaller than 1 {micro}m are exhausted from the building. Large particles deposit within the building, mostly in supply ducts or on indoor surfaces. When filters are present, most particles are either filtered or exhausted. The fates of particles generated indoors follow similar trends as outdoor particles drawn into the building.

  15. Investigation of hydrodynamics and heat transfer at liquid metal downflow in a rectangular duct in a coplanar magnetic field

    NASA Astrophysics Data System (ADS)

    Poddubnyi, I. I.; Razuvanov, N. G.

    2016-02-01

    Hydrodynamics and heat transfer in a liquid metal downflow in a rectangular duct with an aspect ratio of approximately 3/1 in a coplanar magnetic field (MF) are studied upon inhomogeneous (one-sided) heating of the duct. The flow in the heat-transfer duct of the cooling system of a liquid-metal blanket module of the tokamak-type thermonuclear reactor is modeled. Experiments were carried out at the mercury magnetohydrodynamic (MHD) test facility, which is a part of the MHD-complex of Moscow Power Engineering Institute-Joint Institute for High Temperatures of the Russian Academy of Sciences. A probe technique is used for measurements in the flow. The studies are performed within the following ranges of regime parameters: Reynolds numbers Re = 10000-55000, Hartmann numbers Ha = 0-800, and Grashof numbers Grq = 0-6 × 108. Averaged profiles of velocity, temperature, temperature fluctuations of the flow, and duct wall temperature are presented for two typical flow regimes. Detailed measurements are performed in the duct cross-section distant from the heating beginning in the region of homogeneous MF. MF leads to the turbulent transport suppression, owing to which the temperature on the heated wall increases. A considerable influence of the heat-gravitational counter-convection, the interaction of which with the external MF leads in some regimes to the appearance and development of instabilities in the laminarized flow, is revealed under the downflow conditions. Generation of large-scale secondary vortices with the axis parallel to the MF induction causes temperature fluctuations of the abnormal intensity that considerably exceeds the level of turbulent fluctuations. Such temperature fluctuations easily penetrate into the duct wall and can lead to the fatigue breakdown of thermonuclear reactor cooling paths. Ranges of unallowable regime parameters are determined and the boundary in coordinates Gr-Re is presented, where this effect is revealed or vanishes. The numerical

  16. Simulation assisted characterization of kaolinite-methanol intercalation complexes synthesized using cost-efficient homogenization method

    NASA Astrophysics Data System (ADS)

    Makó, Éva; Kovács, András; Ható, Zoltán; Kristóf, Tamás

    2015-12-01

    Recent experimental and simulation findings with kaolinite-methanol intercalation complexes raised the question of the existence of more stable structures in wet and dry state, which has not been fully cleared up yet. Experimental and molecular simulation analyses were used to investigate different types of kaolinite-methanol complexes, revealing their real structures. Cost-efficient homogenization methods were applied to synthesize the kaolinite-dimethyl sulfoxide and kaolinite-urea pre-intercalation complexes of the kaolinite-methanol ones. The tested homogenization method required an order of magnitude lower amount of reagents than the generally applied solution method. The influence of the type of pre-intercalated molecules and of the wetting or drying (at room temperature and at 150 °C) procedure on the intercalation was characterized experimentally by X-ray diffraction and thermal analysis. Consistent with the suggestion from the present simulations, 1.12-nm and 0.83-nm stable kaolinite-methanol complexes were identified. For these complexes, our molecular simulations predict either single-layered structures of mobile methanol/water molecules or non-intercalated structures of methoxy-functionalized kaolinite. We found that the methoxy-modified kaolinite can easily be intercalated by liquid methanol.

  17. Conformational contribution to thermodynamics of binding in protein-peptide complexes through microscopic simulation.

    PubMed

    Das, Amit; Chakrabarti, J; Ghosh, Mahua

    2013-03-19

    We extract the thermodynamics of conformational changes in biomacromolecular complexes from the distributions of the dihedral angles of the macromolecules. These distributions are obtained from the equilibrium configurations generated via all-atom molecular dynamics simulations. The conformational thermodynamics data we obtained for calmodulin-peptide complexes using our methodology corroborate well with the experimentally observed conformational and binding entropies. The conformational free-energy changes and their contributions for different peptide-binding regions of calmodulin are evaluated microscopically.

  18. Compressive sensing based spinning mode detections by in-duct microphone arrays

    NASA Astrophysics Data System (ADS)

    Yu, Wenjun; Huang, Xun

    2016-05-01

    This paper presents a compressive sensing based experimental method for detecting spinning modes of sound waves propagating inside a cylindrical duct system. This method requires fewer dynamic pressure sensors than the number required by the Shannon-Nyquist sampling theorem so long as the incident waves are sparse in spinning modes. In this work, the proposed new method is firstly validated by preparing some of the numerical simulations with representative set-ups. Then, a duct acoustic testing rig with a spinning mode synthesiser and an in-duct microphone array is built to experimentally demonstrate the new approach. Both the numerical simulations and the experiment results are satisfactory, even when the practical issue of the background noise pollution is taken into account. The approach is beneficial for sensory array tests of silent aeroengines in particular and some other engineering systems with duct acoustics in general.

  19. Non-Newtonian bile flow in elastic cystic duct: one- and three-dimensional modeling.

    PubMed

    Li, W G; Luo, X Y; Chin, S B; Hill, N A; Johnson, A G; Bird, N C

    2008-11-01

    Bile flow is thought to play an essential role in the pathophysiological genesis of cholelithiasis (gallstone formation) and in gallbladder pain. In this paper, we extend our previous study of the human biliary system (Li et al., 2007, J. Biomech. Eng., 129:164-173) to include two important factors: the non-Newtonian properties of bile, and elastic deformation of the cystic duct. A one-dimensional (1D) model is analyzed and compared with three-dimensional (3D) fluid-structure interaction simulations. It is found that non-Newtonian bile raises resistance to the flow of bile, which can be augmented significantly by the elastic deformation (collapse) of the cystic duct. We also show that the 1D model predicts the pressure drop of the cystic duct flow well for all cases considered (Newtonian or non-Newtonian flow, rigid or elastic ducts), when compared with the full 3D simulations.

  20. Pressure losses across multiple fittings in ventilation ducts.

    PubMed

    Ai, Z T; Mak, C M

    2013-01-01

    The accurate prediction of pressure losses across in-duct fittings is of significance in relation to the accurate sizing and good energy efficiency of air-delivery systems. Current design guides provide design methods and data for the prediction of pressure losses only for a single and isolated fitting. This study presents an investigation of pressure losses across multiple interactive in-duct fittings in a ventilation duct. A laboratory measurement of pressure losses across one fitting and multiple fittings in a ventilation duct is carried out. The pressure loss across multiple interactive fittings is lower than that across multiple similar individual fittings, while the percentage decrease is dependent on the configuration and combination of the fittings. This implies that the pressure loss across multiple closely mounted fittings calculated by summing the pressure losses across individual fittings, as provided in the ASHRAE handbook and the CIBSE guide, is overpredicted. The numerical prediction of the pressure losses across multiple fittings using the large-eddy simulation (LES) model shows good agreement with the measured data, suggesting that this model is a useful tool in ductwork design and can help to save experimental resources and improve experimental accuracy and reliability.

  1. Pressure Losses across Multiple Fittings in Ventilation Ducts

    PubMed Central

    Ai, Z. T.; Mak, C. M.

    2013-01-01

    The accurate prediction of pressure losses across in-duct fittings is of significance in relation to the accurate sizing and good energy efficiency of air-delivery systems. Current design guides provide design methods and data for the prediction of pressure losses only for a single and isolated fitting. This study presents an investigation of pressure losses across multiple interactive in-duct fittings in a ventilation duct. A laboratory measurement of pressure losses across one fitting and multiple fittings in a ventilation duct is carried out. The pressure loss across multiple interactive fittings is lower than that across multiple similar individual fittings, while the percentage decrease is dependent on the configuration and combination of the fittings. This implies that the pressure loss across multiple closely mounted fittings calculated by summing the pressure losses across individual fittings, as provided in the ASHRAE handbook and the CIBSE guide, is overpredicted. The numerical prediction of the pressure losses across multiple fittings using the large-eddy simulation (LES) model shows good agreement with the measured data, suggesting that this model is a useful tool in ductwork design and can help to save experimental resources and improve experimental accuracy and reliability. PMID:24385871

  2. Formation of Complex Amino Acid Precursors in Simulated Primitive Atmosphere and Their Alteration under Simulated Submarine Hydrothermal Conditions

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kensei; Kurihara, Hironari; Hirako, Tomoaki; Obayashi, Yumiko; Kaneko, Takeo; Takano, Yoshinori; Yoshimura, Yoshitaka

    Since late 1970's a great number of submarine hydrothermal systems (SHSs) has been dis-covered, and they are considered possible sites of chemical evolution and generation of life on the Earth since their discovery in late 1970s. A number of experiments simulating the con-ditions of SHSs were conducted, and abiotic production and polymerization of amino acids were reported. Free amino acids were frequently used as starting materials to examine possible organic reactions in the simulation experiments. In our early studies, not free amino acids but complex amino acids precursors with large molecular weights were formed abiotically from simulated primitive Earth atmosphere (a mixture of CO, N2 and H2 O) (Takano et al., 2004). Such complex organics (hereafter referred as to CNWs) should have been delivered to SHSs in Primitive Ocean, where they were subjected to further alteration. We examined possible alteration of the complex organics in high-temperature high-pressure environments by the su-percritical water flow reactor (SCWFR) (Islam et al.. 2003) and an autoclave. CNWs were quite hydrophilic compounds whose molecular weights were ca. 3000. After heating 573 K for 2 min in the SCWFR, aggregates of organics were formed, which were separated from aque-ous solution with a Nucleopore filter (pore size: 200 nm). We propose the following scenario of chemical evolution: (1) Complex organics including amino acid precursors were formed in primitive atmosphere and/or extraterrestrial environments, (ii) they were delivered to primor-dial SHSs, (iii) hydrothermal alteration occurred in SHSs to give organic aggregates, (iv) quite primitive molecular systems with subtle biological functions were generated in the competition among such aggregates. References: Islam, Md. N., Kaneko, T., and Kobayashi, K (2003). Reactions of Amino Acids with a Newly ConstructedSupercritical Water Flow Reactor Simulating Submarine Hydrothermal Systems. Bull. Chem. Soc. Jpn., 76, 1171. Takano, Y

  3. Bile Ducts in Regenerative Liver Nodules of Alagille Patients Are Not the Result of Genetic Mosaicism.

    PubMed

    Rougemont, Anne-Laure; Alvarez, Fernando; McLin, Valérie A; Guiochon-Mantel, Anne; Bouligand, Jérome; Clément, Sophie; Tonson La Tour, Aude; Wildhaber, Barbara E; Rubbia-Brandt, Laura; Sartelet, Hervé

    2015-07-01

    Alagille syndrome (ALGS) is a complex, multisystem disease associated with mutations in the JAG1 gene. In the liver, ALGS is characterized by paucity of intrahepatic bile ducts. Gene dosage analysis performed on a large, central regenerative nodule with preserved interlobular bile ducts of 2 unrelated ALGS patients, and on surrounding cirrhotic and ductopenic liver parenchyma, showed in both cases complete JAG1 heterozygous deletion in the regenerative nodule and the ductopenic liver, with no differences in gene dosage. Thus, JAG1 mosaicism and differential haploinsufficiency do not explain the presence of bile ducts in centrally located regenerative nodules.

  4. Risk Factors associated with Paraurethral Duct Dilatation following Gonococcal Paraurethral Duct Infection in Men

    PubMed Central

    Fan, Wenge; Zhang, Qingsong; Wang, Lin; Ye, Xun; Jiang, Tingwang

    2016-01-01

    No studies have explored the risk factors for paraurethral duct dilatation following paraurethral duct infection by Neisseria gonorrhoeae in men undergoing ceftriaxone therapy. The present study was performed to explore the risk factors for paraurethral duct dilatation following paraurethral duct infection by N. gonorrhoeae in men undergoing ceftriaxone therapy and thus guide clinical interventions. We compared the demographic, behavioral, and clinical data of men with paraurethral duct infection by N. gonorrhoeae with and without dilatation of the paraurethral duct. Univariate analysis showed significant differences in age, disease course of the infected paraurethral duct, Chlamydia trachomatis infection in the paraurethral duct, and a history of paraurethral duct infection by N. gonorrhoeae between the patient and control groups (P<0.05). Multivariate logistic regression analysis showed consistent results (P<0.05). This study that shows delayed treatment may be a major risk factor for paraurethral duct dilatation secondary to paraurethral duct infection by N. gonorrhoeae in men. Age, C. trachomatis infection in the paraurethral duct, and a history of paraurethral duct infection by N. gonorrhoeae are also risk factors. Thus, educating patients to undergo timely therapy and treating the C. trachomatis infection may be effective interventions. PMID:27861521

  5. Thrive or overload? The effect of task complexity on novices' simulation-based learning.

    PubMed

    Haji, Faizal A; Cheung, Jeffrey J H; Woods, Nicole; Regehr, Glenn; de Ribaupierre, Sandrine; Dubrowski, Adam

    2016-09-01

    Fidelity is widely viewed as an important element of simulation instructional design based on its purported relationship with transfer of learning. However, higher levels of fidelity may increase task complexity to a point at which novices' cognitive resources become overloaded. In this experiment, we investigate the effects of variations in task complexity on novices' cognitive load and learning during simulation-based procedural skills training. Thirty-eight medical students were randomly assigned to simulation training on a simple or complex lumbar puncture (LP) task. Participants completed four practice trials on this task (skill acquisition). After 10 days of rest, all participants completed one additional trial on their assigned task (retention) and one trial on a 'very complex' simulation designed to be similar to the complex task (transfer). We assessed LP performance and cognitive load on each trial using multiple measures. In both groups, LP performance improved significantly during skill acquisition (p ≤ 0.047, f = 0.29-0.96) and was maintained at retention. The simple task group demonstrated superior performance compared with the complex task group throughout these phases (p ≤ 0.002, d = 1.13-2.31). Cognitive load declined significantly in the simple task group (p < 0.009, f = 0.48-0.76), but not in the complex task group during skill acquisition, and remained lower at retention (p ≤ 0.024, d = 0.78-1.39). Between retention and transfer, LP performance declined and cognitive load increased in the simple task group, whereas both remained stable in the complex task group. At transfer, no group differences were observed in LP performance and cognitive load, except that the simple task group made significantly fewer breaches of sterility (p = 0.023, d = 0.80). Reduced task complexity was associated with superior LP performance and lower cognitive load during skill acquisition and retention, but mixed results on transfer to a more

  6. Predicting Turbulent Convective Heat Transfer in Fully Developed Duct Flows

    NASA Technical Reports Server (NTRS)

    Rokni, Masoud; Gatski, Thomas B.

    2001-01-01

    The performance of an explicit algebraic stress model (EASM) is assessed in predicting the turbulent flow and forced heat transfer in both straight and wavy ducts, with rectangular, trapezoidal and triangular cross-sections, under fully developed conditions. A comparison of secondary flow patterns. including velocity vectors and velocity and temperature contours, are shown in order to study the effect of waviness on flow dynamics, and comparisons between the hydraulic parameters. Fanning friction factor and Nusselt number, are also presented. In all cases. isothermal conditions are imposed on the duct walls, and the turbulent heat fluxes are modeled using gradient-diffusion type models. The formulation is valid for Reynolds numbers up to 10(exp 5) and this minimizes the need for wall functions that have been used with mixed success in previous studies of complex duct flows. In addition, the present formulation imposes minimal demand on the number of grid points without any convergence or stability problems. Criteria in terms of heat transfer and friction factor needed to choose the optimal wavy duct cross-section for industrial applications among the ones considered are discussed.

  7. Perturbations From Ducts on the Modes of Acoustic Thermometers

    PubMed Central

    Gillis, K. A.; Lin, H.; Moldover, M. R.

    2009-01-01

    We examine the perturbations of the modes of an acoustic thermometer caused by circular ducts used either for gas flow or as acoustic waveguides coupled to remote transducers. We calculate the acoustic admittance of circular ducts using a model based on transmission line theory. The admittance is used to calculate the perturbations to the resonance frequencies and half-widths of the modes of spherical and cylindrical acoustic resonators as functions of the duct’s radius, length, and the locations of the transducers along the duct's length. To verify the model, we measured the complex acoustic admittances of a series of circular tubes as a function of length between 200 Hz and 10 kHz using a three-port acoustic coupler. The absolute magnitude of the specific acoustic admittance is approximately one. For a 1.4 mm inside-diameter, 1.4 m long tube, the root mean square difference between the measured and modeled specific admittances (both real and imaginary parts) over this frequency range was 0.018. We conclude by presenting design considerations for ducts connected to acoustic thermometers. PMID:27504227

  8. A novel multiblock immersed boundary method for large eddy simulation of complex arterial hemodynamics

    NASA Astrophysics Data System (ADS)

    Anupindi, Kameswararao; Delorme, Yann; Shetty, Dinesh A.; Frankel, Steven H.

    2013-12-01

    Computational fluid dynamics (CFD) simulations are becoming a reliable tool to understand hemodynamics, disease progression in pathological blood vessels and to predict medical device performance. Immersed boundary method (IBM) emerged as an attractive methodology because of its ability to efficiently handle complex moving and rotating geometries on structured grids. However, its application to study blood flow in complex, branching, patient-specific anatomies is scarce. This is because of the dominance of grid nodes in the exterior of the fluid domain over the useful grid nodes in the interior, rendering an inevitable memory and computational overhead. In order to alleviate this problem, we propose a novel multiblock based IBM that preserves the simplicity and effectiveness of the IBM on structured Cartesian meshes and enables handling of complex, anatomical geometries at a reduced memory overhead by minimizing the grid nodes in the exterior of the fluid domain. As pathological and medical device hemodynamics often involve complex, unsteady transitional or turbulent flow fields, a scale resolving turbulence model such as large eddy simulation (LES) is used in the present work. The proposed solver (here after referred as WenoHemo), is developed by enhancing an existing in-house high-order incompressible flow solver that was previously validated for its numerics and several LES models by Shetty et al. (2010) [33]. In the present work, WenoHemo is systematically validated for additional numerics introduced, such as IBM and the multiblock approach, by simulating laminar flow over a sphere and laminar flow over a backward facing step respectively. Then, we validate the entire solver methodology by simulating laminar and transitional flow in abdominal aortic aneurysm (AAA). Finally, we perform blood flow simulations in the challenging clinically relevant thoracic aortic aneurysm (TAA), to gain insights into the type of fluid flow patterns that exist in pathological

  9. Phenol-benzene complexation dynamics: quantum chemistry calculation, molecular dynamics simulations, and two dimensional IR spectroscopy.

    PubMed

    Kwac, Kijeong; Lee, Chewook; Jung, Yousung; Han, Jaebeom; Kwak, Kyungwon; Zheng, Junrong; Fayer, M D; Cho, Minhaeng

    2006-12-28

    Molecular dynamics (MD) simulations and quantum mechanical electronic structure calculations are used to investigate the nature and dynamics of the phenol-benzene complex in the mixed solvent, benzene/CCl4. Under thermal equilibrium conditions, the complexes are continuously dissociating and forming. The MD simulations are used to calculate the experimental observables related to the phenol hydroxyl stretching mode, i.e., the two dimensional infrared vibrational echo spectrum as a function of time, which directly displays the formation and dissociation of the complex through the growth of off-diagonal peaks, and the linear absorption spectrum, which displays two hydroxyl stretch peaks, one for the complex and one for the free phenol. The results of the simulations are compared to previously reported experimental data and are found to be in quite reasonable agreement. The electronic structure calculations show that the complex is T shaped. The classical potential used for the phenol-benzene interaction in the MD simulations is in good accord with the highest level of the electronic structure calculations. A variety of other features is extracted from the simulations including the relationship between the structure and the projection of the electric field on the hydroxyl group. The fluctuating electric field is used to determine the hydroxyl stretch frequency-frequency correlation function (FFCF). The simulations are also used to examine the number distribution of benzene and CCl4 molecules in the first solvent shell around the phenol. It is found that the distribution is not that of the solvent mole fraction of benzene. There are substantial probabilities of finding a phenol in either a pure benzene environment or a pure CCl4 environment. A conjecture is made that relates the FFCF to the local number of benzene molecules in phenol's first solvent shell.

  10. Lipid Clustering Correlates with Membrane Curvature as Revealed by Molecular Simulations of Complex Lipid Bilayers

    PubMed Central

    Koldsø, Heidi; Shorthouse, David; Hélie, Jean; Sansom, Mark S. P.

    2014-01-01

    Cell membranes are complex multicomponent systems, which are highly heterogeneous in the lipid distribution and composition. To date, most molecular simulations have focussed on relatively simple lipid compositions, helping to inform our understanding of in vitro experimental studies. Here we describe on simulations of complex asymmetric plasma membrane model, which contains seven different lipids species including the glycolipid GM3 in the outer leaflet and the anionic lipid, phosphatidylinositol 4,5-bisphophate (PIP2), in the inner leaflet. Plasma membrane models consisting of 1500 lipids and resembling the in vivo composition were constructed and simulations were run for 5 µs. In these simulations the most striking feature was the formation of nano-clusters of GM3 within the outer leaflet. In simulations of protein interactions within a plasma membrane model, GM3, PIP2, and cholesterol all formed favorable interactions with the model α-helical protein. A larger scale simulation of a model plasma membrane containing 6000 lipid molecules revealed correlations between curvature of the bilayer surface and clustering of lipid molecules. In particular, the concave (when viewed from the extracellular side) regions of the bilayer surface were locally enriched in GM3. In summary, these simulations explore the nanoscale dynamics of model bilayers which mimic the in vivo lipid composition of mammalian plasma membranes, revealing emergent nanoscale membrane organization which may be coupled both to fluctuations in local membrane geometry and to interactions with proteins. PMID:25340788

  11. Lipid clustering correlates with membrane curvature as revealed by molecular simulations of complex lipid bilayers.

    PubMed

    Koldsø, Heidi; Shorthouse, David; Hélie, Jean; Sansom, Mark S P

    2014-10-01

    Cell membranes are complex multicomponent systems, which are highly heterogeneous in the lipid distribution and composition. To date, most molecular simulations have focussed on relatively simple lipid compositions, helping to inform our understanding of in vitro experimental studies. Here we describe on simulations of complex asymmetric plasma membrane model, which contains seven different lipids species including the glycolipid GM3 in the outer leaflet and the anionic lipid, phosphatidylinositol 4,5-bisphophate (PIP2), in the inner leaflet. Plasma membrane models consisting of 1500 lipids and resembling the in vivo composition were constructed and simulations were run for 5 µs. In these simulations the most striking feature was the formation of nano-clusters of GM3 within the outer leaflet. In simulations of protein interactions within a plasma membrane model, GM3, PIP2, and cholesterol all formed favorable interactions with the model α-helical protein. A larger scale simulation of a model plasma membrane containing 6000 lipid molecules revealed correlations between curvature of the bilayer surface and clustering of lipid molecules. In particular, the concave (when viewed from the extracellular side) regions of the bilayer surface were locally enriched in GM3. In summary, these simulations explore the nanoscale dynamics of model bilayers which mimic the in vivo lipid composition of mammalian plasma membranes, revealing emergent nanoscale membrane organization which may be coupled both to fluctuations in local membrane geometry and to interactions with proteins.

  12. New Insights To Simulate the Luminescence Properties of Pt(II) Complexes Using Quantum Calculations.

    PubMed

    Massuyeau, Florian; Faulques, Eric; Latouche, Camille

    2017-03-24

    The present manuscript reports a thorough quantum investigation on the luminescence properties of three monoplatinum(II) complexes. First, the simulated bond lengths at the ground state are compared to the observed ones, and the simulated electronic transitions are compared to the reported ones in the literature in order to assess our methodology. In a second time we show that geometries from the first triplet excited state are similar to the ground state ones. Simulations of the phosphorescence spectra from the first triplet excited states have been performed taking into account the vibronic coupling effects together with mode-mixing (Dushinsky) and solvent effects. Our simulations are compared with the observed ones already reported in the literature and are in good agreement. The calculations demonstrate that the normal modes of low energy are of great importance on the phosphorescence signature. When temperature effects are taken into account, the simulated phosphorescence spectra are drastically improved. An analysis of the computational time shows that the vibronic coupling simulation is cost-effective and thus can be extended to treat large transition metal complexes. In addition to the intrinsic importance of the investigated targets, this work provides a robust method to simulate phosphorescence spectra and to increase the duality experiment-theory.

  13. NASA Operational Simulator (NOS) for V&V of complex systems

    NASA Astrophysics Data System (ADS)

    Zemerick, Scott A.; Morris, Justin R.; Bailey, Brandon T.

    2013-05-01

    This paper describes the development, capabilities and utility of the NASA Operational Simulator (NOS), a generic software-only simulation architecture developed for NASA missions. NOS was developed by the NASA's Independent Verification and Validation (IV&V) Independent Test Capability (ITC) team and is primarily utilized by software developers and (independent) testers to verify the functionality of a spacecraft's flight software from a system-wide perspective. NOS was initially developed in support of a software-only simulator for the Global Precipitation Measurement (GPM) mission to support verification and validation activities for NASA's IV&V Program. Due to the successes of the GPM simulator (GO-SIM), the NOS architecture is being reused to develop a simulation environment in support of the James Webb Space Telescope (JWST). While NOS has primarily been utilized on NASA missions, its generic architecture can be easily applied across domains to support V&V of complex systems.

  14. Towards socio-material approaches in simulation-based education: lessons from complexity theory.

    PubMed

    Fenwick, Tara; Dahlgren, Madeleine Abrandt

    2015-04-01

    Review studies of simulation-based education (SBE) consistently point out that theory-driven research is lacking. The literature to date is dominated by discourses of fidelity and authenticity - creating the 'real' - with a strong focus on the developing of clinical procedural skills. Little of this writing incorporates the theory and research proliferating in professional studies more broadly, which show how professional learning is embodied, relational and situated in social - material relations. A key concern for medical educators concerns how to better prepare students for the unpredictable and dynamic ambiguity of professional practice; this has stimulated the movement towards socio-material theories in education that address precisely this question. Among the various socio-material theories that are informing new developments in professional education, complexity theory has been of particular importance for medical educators interested in updating current practices. This paper outlines key elements of complexity theory, illustrated with examples from empirical study, to argue its particular relevance for improving SBE. Complexity theory can make visible important material dynamics, and their problematic consequences, that are not often noticed in simulated experiences in medical training. It also offers conceptual tools that can be put to practical use. This paper focuses on concepts of emergence, attunement, disturbance and experimentation. These suggest useful new approaches for designing simulated settings and scenarios, and for effective pedagogies before, during and following simulation sessions. Socio-material approaches such as complexity theory are spreading through research and practice in many aspects of professional education across disciplines. Here, we argue for the transformative potential of complexity theory in medical education using simulation as our focus. Complexity tools open questions about the socio-material contradictions inherent in

  15. Molecular dynamic simulations of protein/RNA complexes: CRISPR/Csy4 endoribonuclease.

    PubMed

    Estarellas, Carolina; Otyepka, Michal; Koča, Jaroslav; Banáš, Pavel; Krepl, Miroslav; Šponer, Jiří

    2015-05-01

    Many prokaryotic genomes comprise Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) offering defense against foreign nucleic acids. These immune systems are conditioned by the production of small CRISPR-derived RNAs matured from long RNA precursors. This often requires a Csy4 endoribonuclease cleaving the RNA 3'-end. We report extended explicit solvent molecular dynamic (MD) simulations of Csy4/RNA complex in precursor and product states, based on X-ray structures of product and inactivated precursor (55 simulations; ~3.7μs in total). The simulations identify double-protonated His29 and deprotonated terminal phosphate as the likely dominant protonation states consistent with the product structure. We revealed potential substates consistent with Ser148 and His29 acting as the general base and acid, respectively. The Ser148 could be straightforwardly deprotonated through solvent and could without further structural rearrangements deprotonate the nucleophile, contrasting similar studies investigating the general base role of nucleobases in ribozymes. We could not locate geometries consistent with His29 acting as general base. However, we caution that the X-ray structures do not always capture the catalytically active geometries and then the reactive structures may be unreachable by the simulation technique. We identified potential catalytic arrangement of the Csy4/RNA complex but we also report limitations of the simulation technique. Even for the dominant protonation state we could not achieve full agreement between the simulations and the structural data. Potential catalytic arrangement of the Csy4/RNA complex is found. Further, we provide unique insights into limitations of simulations of protein/RNA complexes, namely, the influence of the starting experimental structures and force field limitations. This article is part of a Special Issue entitled Recent developments of molecular dynamics. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. [Common bile duct stones and their complications].

    PubMed

    Millat, B; Borie, F

    2000-12-01

    At the time of cholecystectomy for symptomatic cholelithiasis, 7-20% of patients have common bile duct stones. Nearly one third of them are asymptomatic. Routine cholangiography during cholecystectomy allows the diagnosis and treatment of common bile duct stones during the same operation. Selective indication for the diagnosis of common bile duct stones based on the positive predictive value of indicators limits treatment to symptomatic cases. No single indicator is however completely accurate in predicting common bile duct stones and the natural history of asymptomatic cases is uncertain. Endoscopic stone extraction preceding cholecystectomy is not superior to one-stage surgical treatment. Diagnosis and treatment of common bile duct stones are feasible laparoscopically. Complications of common bile duct stones are cholangitis and acute pancreatitis; if severe, they require specific therapeutic approaches.

  17. Specific transduction and labeling of pancreatic ducts by targeted recombinant viral infusion into mouse pancreatic ducts.

    PubMed

    Guo, Ping; Xiao, Xiangwei; El-Gohary, Yousef; Criscimanna, Angela; Prasadan, Krishna; Rymer, Christopher; Shiota, Chiyo; Wiersch, John; Gaffar, Iliana; Esni, Farzad; Gittes, George K

    2013-11-01

    Specific labeling of pancreatic ducts has proven to be quite difficult. Such labeling has been highly sought after because of the power it would confer to studies of pancreatic ductal carcinogenesis, as well as studies of the source of new insulin-producing β-cells. Cre-loxp recombination could, in theory, lineage-tag pancreatic ducts, but results have been conflicting, mainly due to low labeling efficiencies. Here, we achieved a high pancreatic duct labeling efficiency using a recombinant adeno-associated virus (rAAV) with a duct-specific sox9 promoter infused into the mouse common biliary/pancreatic duct. We saw rapid, diffuse duct-specific labeling, with 50 and 89% labeling in the pancreatic tail and head region, respectively. This highly specific labeling of ducts should greatly enhance our ability to study the role of pancreatic ducts in numerous aspects of pancreatic growth, development and function.

  18. Ramjet bypass duct and preburner configuration

    NASA Technical Reports Server (NTRS)

    Orlando, Robert J. (Inventor)

    1994-01-01

    A combined turbofan and ramjet aircraft engine includes a forward bypass duct which allows the engine to operate more efficiently during the turbofan mode of operation. By mounting a ramjet preburner in the forward duct and isolating this duct from the turbofan bypass air, a transition from turbofan operation to ramjet operation can take place at lower flight Mach numbers without incurring pressure losses or blockage in the turbofan bypass air.

  19. Inference, simulation, modeling, and analysis of complex networks, with special emphasis on complex networks in systems biology

    NASA Astrophysics Data System (ADS)

    Christensen, Claire Petra

    Across diverse fields ranging from physics to biology, sociology, and economics, the technological advances of the past decade have engendered an unprecedented explosion of data on highly complex systems with thousands, if not millions of interacting components. These systems exist at many scales of size and complexity, and it is becoming ever-more apparent that they are, in fact, universal, arising in every field of study. Moreover, they share fundamental properties---chief among these, that the individual interactions of their constituent parts may be well-understood, but the characteristic behaviour produced by the confluence of these interactions---by these complex networks---is unpredictable; in a nutshell, the whole is more than the sum of its parts. There is, perhaps, no better illustration of this concept than the discoveries being made regarding complex networks in the biological sciences. In particular, though the sequencing of the human genome in 2003 was a remarkable feat, scientists understand that the "cellular-level blueprints" for the human being are cellular-level parts lists, but they say nothing (explicitly) about cellular-level processes. The challenge of modern molecular biology is to understand these processes in terms of the networks of parts---in terms of the interactions among proteins, enzymes, genes, and metabolites---as it is these processes that ultimately differentiate animate from inanimate, giving rise to life! It is the goal of systems biology---an umbrella field encapsulating everything from molecular biology to epidemiology in social systems---to understand processes in terms of fundamental networks of core biological parts, be they proteins or people. By virtue of the fact that there are literally countless complex systems, not to mention tools and techniques used to infer, simulate, analyze, and model these systems, it is impossible to give a truly comprehensive account of the history and study of complex systems. The author

  20. Simulation of Lamb wave propagation for the characterization of complex structures.

    PubMed

    Agostini, Valentina; Delsanto, Pier Paolo; Genesio, Ivan; Olivero, Dimitri

    2003-04-01

    Reliable numerical simulation techniques represent a very valuable tool for analysis. For this purpose we investigated the applicability of the local interaction simulation approach (LISA) to the study of the propagation of Lamb waves in complex structures. The LISA allows very fast and flexible simulations, especially in conjunction with parallel processing, and it is particularly useful for complex (heterogeneous, anisotropic, attenuative, and/or nonlinear) media. We present simulations performed on a glass fiber reinforced plate, initially undamaged and then with a hole passing through its thickness (passing-by hole). In order to give a validation of the method, the results are compared with experimental data. Then we analyze the interaction of Lamb waves with notches, delaminations, and complex structures. In the first case the discontinuity due to a notch generates mode conversion, which may be used to predict the defect shape and size. In the case of a single delamination, the most striking "signature" is a time-shift delay, which may be observed in the temporal evolution of the signal recorded by a receiver. We also present some results obtained on a geometrically complex structure. Due to the inherent discontinuities, a wealth of propagation mechanisms are observed, which can be exploited for the purpose of quantitative nondestructive evaluation (NDE).

  1. Toward a Common Structure in Demographic Educational Modeling and Simulation: A Complex Systems Approach

    ERIC Educational Resources Information Center

    Guevara, Porfirio

    2014-01-01

    This article identifies elements and connections that seem to be relevant to explain persistent aggregate behavioral patterns in educational systems when using complex dynamical systems modeling and simulation approaches. Several studies have shown what factors are at play in educational fields, but confusion still remains about the underlying…

  2. Appreciating the Complexity of Project Management Execution: Using Simulation in the Classroom

    ERIC Educational Resources Information Center

    Hartman, Nathan S.; Watts, Charles A.; Treleven, Mark D.

    2013-01-01

    As the popularity and importance of project management increase, so does the need for well-prepared project managers. This article discusses our experiences using a project management simulation in undergraduate and MBA classes to help students better grasp the complexity of project management. This approach gives students hands-on experience with…

  3. Using multi-criteria analysis of simulation models to understand complex biological systems

    Treesearch

    Maureen C. Kennedy; E. David. Ford

    2011-01-01

    Scientists frequently use computer-simulation models to help solve complex biological problems. Typically, such models are highly integrated, they produce multiple outputs, and standard methods of model analysis are ill suited for evaluating them. We show how multi-criteria optimization with Pareto optimality allows for model outputs to be compared to multiple system...

  4. Appreciating the Complexity of Project Management Execution: Using Simulation in the Classroom

    ERIC Educational Resources Information Center

    Hartman, Nathan S.; Watts, Charles A.; Treleven, Mark D.

    2013-01-01

    As the popularity and importance of project management increase, so does the need for well-prepared project managers. This article discusses our experiences using a project management simulation in undergraduate and MBA classes to help students better grasp the complexity of project management. This approach gives students hands-on experience with…

  5. Anatomical assessment of bile ducts of Luschka in human fetuses.

    PubMed

    Kocabiyik, Necdet; Yalcin, Bülent; Kilbas, Zafer; Karadeniz, Sinan R; Kurt, Bülent; Comert, Ayhan; Ozan, Hasan

    2009-08-01

    Bile ducts of Luschka (also called subvesical or supravesicular ducts) can cause bile leakage during laparoscopic cholecystectomy, especially if surgery is carried out in ignorance of such variations. The aim of this study was to clarify the clinical anatomy of these ducts in human fetuses and frequency of the ducts locating near gallbladder fossa. Thirty-two fetal cadaver livers were dissected and the gallbladders were separated from the livers and ducts were investigated under a surgical microscope. All observed ducts were examined microscopically and connective tissue cords were excluded. Bile ducts of Luschka locating near cystic fossa were found in 7 of 32 fetuses (21.9%). Three of the seven ducts ran towards to liver segment 5 (S5); three ducts were found in the gallbladder fossa; and one duct ran towards to liver segment 4 (S4). Also it was found that three of the seven ducts drained into the subsegmental duct of S5, two ducts drained into the right hepatic duct, one duct drained into the right anterior branch bile duct, and one duct drained into the subsegmental duct of S4. Subvesical ducts running along the gallbladder fossa between the gallbladder and the liver parenchyma were found in a relatively high incidence in fetuses than adults. Awareness and knowledge about incidence of such ducts alerts the surgeon during laparoscopic cholecystectomy. Therefore morbidity due to bile leaks can be reduced.

  6. Simulations of one- and two-dimensional complex plasmas using a modular, object-oriented code

    NASA Astrophysics Data System (ADS)

    Jefferson, R. A.; Cianciosa, M.; Thomas, E.

    2010-11-01

    In a complex plasma, charged microparticles ("dust") are added to a background of ions, electrons, and neutral particles. This dust fully interacts with the surrounding plasma and self-consistently alters the plasma environment leading to the emergence of new plasma behavior. Numerical tools that complement experimental investigations can provide important insights into the properties of complex plasmas. This paper discusses a newly developed code, named DEMON (dynamic exploration of microparticle clouds optimized numerically), for simulating a complex plasma. The DEMON code models the behavior of the charged particle component of a complex plasma in a uniform plasma background. The key feature of the DEMON code is the use of a modular force model that allows a wide variety of experimental configurations to be studied without varying the core code infrastructure. Examples of the flexibility of this modular approach are presented using examples of one- and two-dimensional complex plasmas.

  7. Discrete event simulation as a tool in optimization of a professional complex adaptive system.

    PubMed

    Nielsen, Anders Lassen; Hilwig, Helmer; Kissoon, Niranjan; Teelucksingh, Surujpal

    2008-01-01

    Similar urgent needs for improvement of health care systems exist in the developed and developing world. The culture and the organization of an emergency department in developing countries can best be described as a professional complex adaptive system, where each agent (employee) are ignorant of the behavior of the system as a whole; no one understands the entire system. Each agent's action is based on the state of the system at the moment (i.e. lack of medicine, unavailable laboratory investigation, lack of beds and lack of staff in certain functions). An important question is how one can improve the emergency service within the given constraints. The use of simulation signals is one new approach in studying issues amenable to improvement. Discrete event simulation was used to simulate part of the patient flow in an emergency department. A simple model was built using a prototyping approach. The simulation showed that a minor rotation among the nurses could reduce the mean number of visitors that had to be refereed to alternative flows within the hospital from 87 to 37 on a daily basis with a mean utilization of the staff between 95.8% (the nurses) and 87.4% (the doctors). We conclude that even faced with resource constraints and lack of accessible data discrete event simulation is a tool that can be used successfully to study the consequences of changes in very complex and self organizing professional complex adaptive systems.

  8. Simulation of unsaturated flow in complex fractures using smoothed particle hydrodynamics

    SciTech Connect

    Tartakovsky, Alexandre M.; Meakin, Paul

    2005-08-01

    Smoothed particle hydrodynamics (SPH) models were used to simulate unsaturated flow in fractures with complex geometries. SPH is a fully Lagrangian particle-based method that allows the dynamics of interfaces separating fluids to be modeled without employing complex front tracking schemes. In SPH simulations, the fluid density field is represented by a superposition of weighting functions centered on particles which represent the fluids. The pressure is related to the fluid density through an equation of state, and the particles move in response to the pressure gradient. SPH does not require the construction of grids that would otherwise introduce numerical dispersion. The model can be used to simulate complex free-surface flow phenomenon such as invasion of wetting and nonwetting fluids into three-dimensional fractures. These processes are a severe challenge for grid-based methods. Surface tension was simulated by using a van der Waals equation of state and a combination of short-range repulsive and longer-range attractive interactions between fluid particles. The wetting behavior was simulated using similar interactions between mobile fluid particles and stationary boundary particles. The fracture geometry was generated from self-affine fractal surfaces. The fractal model was based on a large body of experimental work, which indicates that fracture surfaces have a self-affine fractal geometry characterized by a material independent (quasi universal) Hurst exponent of about 0.75.

  9. Experimental verification of effect of horizontal inhomogeneity of evaporation duct on electromagnetic wave propagation

    NASA Astrophysics Data System (ADS)

    Shi, Yang; Kun-De, Yang; Yi-Xin, Yang; Yuan-Liang, Ma

    2015-04-01

    The evaporation duct which forms above the ocean surface has a significant influence on electromagnetic wave propagation above 2 GHz over the ocean. The effects of horizontal inhomogeneity of evaporation duct on electromagnetic wave propagation are investigated, both in numerical simulation and experimental observation methods, in this paper. Firstly, the features of the horizontal inhomogeneity of the evaporation duct are discussed. Then, two typical inhomogeneous cases are simulated and compared with the homogeneous case. The result shows that path loss is significantly higher than that in the homogeneous case when the evaporation duct height (EDH) at the receiver is lower than that at the transmitter. It is also concluded that the horizontal inhomogeneity of the evaporation duct has a significant influence when the EDH is low or when the electromagnetic wave frequency is lower than 13 GHz. Finally, experimental data collected on a 149-km long propagation path in the South China Sea in 2013 are used to verify the conclusion. The experimental results are consistent with the simulation results. The horizontal inhomogeneity of evaporation duct should be considered when modeling electromagnetic wave propagation over the ocean. Project supported by the National Natural Science Foundation of China (Grant No. 11174235) and the Fundamental Research Funds for the Central Universities (Grant No. 3102014JC02010301).

  10. Circumportal pancreas with retroportal main pancreatic duct.

    PubMed

    Hashimoto, Yasushi; Ross, Andrew S; Traverso, L William

    2009-08-01

    There have been 6 cases of circumportal pancreas reported, and 2 of them had the main pancreatic duct in a retroportal dorsal portion. This extremely uncommon anomaly is asymptomatic and therefore incidentally discovered. For the surgeon, it is important to discover this during pancreatic resection so the pancreatic duct can be closed and fistula is avoided. We describe the third case where a circumportal pancreas had its main pancreatic duct passing under the portal vein. The duct was identified and ligated. A fistula did not occur.

  11. Lightweight Forms for Epoxy/Aramid Ducts

    NASA Technical Reports Server (NTRS)

    Mix, E. W.; Anderson, A. N.; Bedford, Donald L., Sr.

    1986-01-01

    Aluminum mandrels easy to remove. Lightweight aluminum mandrel for shaping epoxy/aramid ducts simplifies and speeds production. In new process, glass-reinforced epoxy/aramid cloth wrapped on aluminum mandrel. Stainless-steel flanges and other hardware fitted on duct and held by simple tooling. Entire assembly placed in oven to cure epoxy. After curing, assembly placed in alkaline bath dissolves aluminum mandrel in about 4 hours. Epoxy/aramid shell ready for use as duct. Aluminum mandrel used to make ducts of various inside diameters up to 6 in. Standard aluminum forms used. Conventional tube-bending equipment produces requisite curves in mandrels.

  12. Generator stator core vent duct spacer posts

    DOEpatents

    Griffith, John Wesley; Tong, Wei

    2003-06-24

    Generator stator cores are constructed by stacking many layers of magnetic laminations. Ventilation ducts may be inserted between these layers by inserting spacers into the core stack. The ventilation ducts allow for the passage of cooling gas through the core during operation. The spacers or spacer posts are positioned between groups of the magnetic laminations to define the ventilation ducts. The spacer posts are secured with longitudinal axes thereof substantially parallel to the core axis. With this structure, core tightness can be assured while maximizing ventilation duct cross section for gas flow and minimizing magnetic loss in the spacers.

  13. Supercritical carbon dioxide interpolymer complexes improve survival of B. longum Bb-46 in simulated gastrointestinal fluids.

    PubMed

    Thantsha, Mapitsi S; Cloete, Thomas E; Moolman, Francis S; Labuschagne, Philip W

    2009-01-31

    Gastric acidity is the main factor affecting viability of probiotics in the gastrointestinal tract (GIT). This study investigated the survival in simulated gastrointestinal fluids of Bifidobacterium longum Bb-46 encapsulated in interpolymer complexes formed in supercritical carbon dioxide (scCO(2)). Bacteria were exposed sequentially to simulated gastric fluid (SGF, pH 2) for 2 h and simulated intestinal fluid (SIF, pH 6.8) for 6 or 24 h. Total encapsulated bacteria were determined by suspending 1 g of product in SIF for 6 h at 37 degrees C prior to plating out. Plates were incubated anaerobically at 37 degrees C for 72 h. The interpolymer complex displayed pH-responsive release properties, with little to no release in SGF and substantial release in SIF. There was a limited reduction in viable counts at the end of exposure period due to encapsulation. Protection efficiency of the interpolymer complex was improved by addition of glyceryl monostearate (GMS). Gelatine capsules delayed release of bacteria from the interpolymer complex thus minimizing time of exposure to the detrimental conditions. Use of poly(caprolactone) (PCL), ethylene oxide-propylene oxide triblock copolymer (PEO-PPO-PEO) decreased the protection efficiency of the matrix. Interpolymer complex encapsulation showed potential for protection of probiotics and therefore for application in food and pharmaceuticals.

  14. Solute transport with equilibrium aqueous complexation and either sorption or ion exchange: Simulation methodology and applications

    USGS Publications Warehouse

    Lewis, F.M.; Voss, C.I.; Rubin, J.

    1987-01-01

    Methodologies that account for specific types of chemical reactions in the simulation of solute transport can be developed so they are compatible with solution algorithms employed in existing transport codes. This enables the simulation of reactive transport in complex multidimensional flow regimes, and provides a means for existing codes to account for some of the fundamental chemical processes that occur among transported solutes. Two equilibrium-controlled reaction systems demonstrate a methodology for accommodating chemical interaction into models of solute transport. One system involves the sorption of a given chemical species, as well as two aqueous complexations in which the sorbing species is a participant. The other reaction set involves binary ion exchange coupled with aqueous complexation involving one of the exchanging species. The methodology accommodates these reaction systems through the addition of nonlinear terms to the transport equations for the sorbing species. Example simulation results show (1) the effect equilibrium chemical parameters have on the spatial distributions of concentration for complexing solutes; (2) that an interrelationship exists between mechanical dispersion and the various reaction processes; (3) that dispersive parameters of the porous media cannot be determined from reactive concentration distributions unless the reaction is accounted for or the influence of the reaction is negligible; (4) how the concentration of a chemical species may be significantly affected by its participation in an aqueous complex with a second species which also sorbs; and (5) that these coupled chemical processes influencing reactive transport can be demonstrated in two-dimensional flow regimes. ?? 1987.

  15. Evaluation of soil flushing of complex contaminated soil: an experimental and modeling simulation study.

    PubMed

    Yun, Sung Mi; Kang, Christina S; Kim, Jonghwa; Kim, Han S

    2015-04-28

    The removal of heavy metals (Zn and Pb) and heavy petroleum oils (HPOs) from a soil with complex contamination was examined by soil flushing. Desorption and transport behaviors of the complex contaminants were assessed by batch and continuous flow reactor experiments and through modeling simulations. Flushing a one-dimensional flow column packed with complex contaminated soil sequentially with citric acid then a surfactant resulted in the removal of 85.6% of Zn, 62% of Pb, and 31.6% of HPO. The desorption distribution coefficients, KUbatch and KLbatch, converged to constant values as Ce increased. An equilibrium model (ADR) and nonequilibrium models (TSNE and TRNE) were used to predict the desorption and transport of complex contaminants. The nonequilibrium models demonstrated better fits with the experimental values obtained from the column test than the equilibrium model. The ranges of KUbatch and KLbatch were very close to those of KUfit and KLfit determined from model simulations. The parameters (R, β, ω, α, and f) determined from model simulations were useful for characterizing the transport of contaminants within the soil matrix. The results of this study provide useful information for the operational parameters of the flushing process for soils with complex contamination. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Simulation of complex glazing products; from optical data measurements to model based predictive controls

    SciTech Connect

    Kohler, Christian

    2012-04-01

    Complex glazing systems such as venetian blinds, fritted glass and woven shades require more detailed optical and thermal input data for their components than specular non light-redirecting glazing systems. Various methods for measuring these data sets are described in this paper. These data sets are used in multiple simulation tools to model the thermal and optical properties of complex glazing systems. The output from these tools can be used to generate simplified rating values or as an input to other simulation tools such as whole building annual energy programs, or lighting analysis tools. I also describe some of the challenges of creating a rating system for these products and which factors affect this rating. A potential future direction of simulation and building operations is model based predictive controls, where detailed computer models are run in real-time, receiving data for an actual building and providing control input to building elements such as shades.

  17. Managing complexity in simulations of land surface and near-surface processes

    DOE PAGES

    Coon, Ethan T.; Moulton, J. David; Painter, Scott L.

    2016-01-12

    Increasing computing power and the growing role of simulation in Earth systems science have led to an increase in the number and complexity of processes in modern simulators. We present a multiphysics framework that specifies interfaces for coupled processes and automates weak and strong coupling strategies to manage this complexity. Process management is enabled by viewing the system of equations as a tree, where individual equations are associated with leaf nodes and coupling strategies with internal nodes. A dynamically generated dependency graph connects a variable to its dependencies, streamlining and automating model evaluation, easing model development, and ensuring models aremore » modular and flexible. Additionally, the dependency graph is used to ensure that data requirements are consistent between all processes in a given simulation. Here we discuss the design and implementation of these concepts within the Arcos framework, and demonstrate their use for verification testing and hypothesis evaluation in numerical experiments.« less

  18. A low-complexity method to generate delay power profile in wideband high frequency channel simulator

    NASA Astrophysics Data System (ADS)

    Liu, Yu-juan; Chen, Jin; Zhang, Yu-ming

    2011-10-01

    Delay power profile (DPP) characterizes the delay dispersion in wide-band high frequency (WBHF) channels, which determines whether the WBHF channel simulator can be used for the evaluation of WBHF communication systems. Newton's iterative method is commonly used to generate DPP for WBHF channels. But it has large computational complexity, so is not fit for applying to the implementation of WBHF channel simulators. We propose a new method to generate DPP based on look-up table. Compared to Newton's iterative method, Look-up table needs fewer multiplications and additions operations and avoids log operations, having lower computational complexity. Simulation results demonstrate that the decline of precision of DPP brought by look-up table can be neglected if the memory resources are great.

  19. Managing complexity in simulations of land surface and near-surface processes

    SciTech Connect

    Coon, Ethan T.; Moulton, J. David; Painter, Scott L.

    2016-01-12

    Increasing computing power and the growing role of simulation in Earth systems science have led to an increase in the number and complexity of processes in modern simulators. We present a multiphysics framework that specifies interfaces for coupled processes and automates weak and strong coupling strategies to manage this complexity. Process management is enabled by viewing the system of equations as a tree, where individual equations are associated with leaf nodes and coupling strategies with internal nodes. A dynamically generated dependency graph connects a variable to its dependencies, streamlining and automating model evaluation, easing model development, and ensuring models are modular and flexible. Additionally, the dependency graph is used to ensure that data requirements are consistent between all processes in a given simulation. Here we discuss the design and implementation of these concepts within the Arcos framework, and demonstrate their use for verification testing and hypothesis evaluation in numerical experiments.

  20. Design of an anemometer to characterize the flow in the ducts of a hydrogenerator rotor rim

    NASA Astrophysics Data System (ADS)

    Venne, Kevin; Mydlarski, Laurent; Torriano, Federico; Charest-Fournier, Jean-Philippe; Hudon, Claude; Morissette, Jean-Francois

    2016-11-01

    Due to its complex geometry, the airflow within hydrogenerators is difficult to characterize. And although CFD can be a reliable engineering tool, its application to the field of hydrogenerators is very recent and has certain inherent limitations, which are due in part to geometrical and flow complexities, including the coexistence of moving (rotor) and stationary (stator) components. For this reason, experimental measurements are required to validate the CFD simulations of such complex flows. To this end, a 1:4 scale model of a hydrogenerator was constructed at the IREQ (Hydro-Québec Research Institute) to better understand the flow dynamics in the rotor and stator components, and to help benchmark its CFD simulations. However, new flow sensors must be developed to quantify the flow in the confined and harsh regions of hydrogenerators. Of particular interest is the flow within the rotor rim ducts, since it is directly responsible for cooling one of the most critical components, the poles. This rather complex task required the design of an anemometer that had to be accurate, durable, cost-effective, easy to install, and able to withstand the extreme conditions (temperatures of 50°C, centrifugal forces of 300g, etc.) found in hydrogenerators. This paper presents two preliminary designs of such sensors and a series of tests that were performed to calibrate and test them. Funding graciously provided by the NSERC and FRQNT.

  1. Laparoscopic common bile duct exploration.

    PubMed

    Petelin, J B

    2003-11-01

    Herein I describe my >12-year experience with laparoscopic common bile duct exploration (LCBDE). From 21 September 1989 through 31 December 2001, 3,580 patients presented with symptomatic biliary tract disease. Laparoscopic cholecystecomy (LC) was attempted in 3,544 of them (99.1%) and completed in 3,527 (99.5%). Laparoscopic cholangiograms (IOC) were performed in 3,417 patients (96.4%); in 344 cases (9.7%), the IOC was abnormal. Forty-nine patients (1.4%) underwent preoperative endoscopic retrograde cholangiopancreatography (ERCP), and 33 patients (0.9%) underwent postoperative ERCP. LCBDE was attempted in 326 cases and completed in 321 (98.5%). It was successful in clearing the duct in 317 of the 344 patients with abnormal cholangiograms (92.2%). The mean operating time for all patients undergoing LC with or without cholangiograms or LCBDE or other additional surgery was 56.9 min. Mean length of stay was 22.1 h. The mean operating time for LC only patients ( n = 2530)--that is, those not undergoing LCBDE or any other additional procedure--was 47.6 min; their mean postoperative length of stay was 17.2 h. Ductal exploration was performed via the cystic duct in 269 patients, (82.5%) and through a choledochotomy in 57 patients (17.5%). T-tubes were used in patients in whom there was concern for possible retained debris or stones, distal spasm, pancreatitis, or general poor tissue quality secondary to malnutrition or infection. In cases where choledochotomy was used, a T-tube was placed in 38 patients (67%), and primary closure without a T-tube was done in 19 (33%). There were no complications in the group of patients who underwent choledochotomy and primary ductal closure without T-tube placement or in the group in whom T-tubes were placed. Common bile duct (CBD) stones still occur in 10% of patients. These stones are identified by IOC. IOC can be performed in >96.4% of cases of LC. LCBDE was successful in clearing these stones in 97.2% of patients in whom it was

  2. Structure, Spectra, and DFT Simulation of Nickel Benzazolate Complexes with Tris(2-aminoethyl)amine Ligand.

    PubMed

    Cerezo, Javier; Requena, Alberto; Zúñiga, José; Piernas, María José; Santana, M Dolores; Pérez, José; García, Luís

    2017-03-20

    Benzazolate complexes of Ni(II), [Ni(pbz)(tren)]ClO4 (pbz = 2-(2'-hydroxyphenyl)-benzimidazole (pbm), 1, 2-(2'-hydroxyphenyl)-benzoxazole (pbx), 2, 2-(2'-hydroxyphenyl)-benzothiazole (pbt), 3; tren = tris(2-aminoethyl)amine), are prepared by self-assembly reaction and structurally characterized. Theoretical DFT simulations are carried out to reproduce the features of their crystal structures and their spectroscopic and photophysic properties. The three complexes are moderately luminescent at room temperature both in acetonitrile solution and in the solid state. The simulations indicate that the absorption spectrum is dominated by two well-defined transitions, and the electronic density concentrates in three MOs around the benzazole ligands. The Stokes shifts of the emission spectra of complexes 1-3 are determined by optimizing the electronic excited state.

  3. Comparison of Measured and Numerically Simulated Turbulence Statistics in a Convective Boundary Layer Over Complex Terrain

    SciTech Connect

    Rai, Raj K.; Berg, Larry K.; Kosović, Branko; Mirocha, Jeffrey D.; Pekour, Mikhail S.; Shaw, William J.

    2016-11-25

    High resolution numerical simulation can provide insight into important physical processes that occur within the planetary boundary layer (PBL). The present work employs large eddy simulation (LES) using the Weather Forecasting and Research (WRF) model, with the LES domain nested within mesoscale simulation, to simulate real conditions in the convective PBL over an area of complex terrain. A multiple nesting approach has been used to downsize the grid spacing from 12.15 km (mesoscale) to 0.03 km (LES). A careful selection of grid spacing in the WRF Meso domain has been conducted to minimize artifacts in the WRF-LES solutions. The WRF-LES results have been evaluated with in situ and remote sensing observations collected during the US Department of Energy-supported Columbia BasinWind Energy Study (CBWES). Comparison of the first- and second-order moments, turbulence spectrum, and probability density function (PDF) of wind speed shows good agreement between the simulations and data. Furthermore, the WRF-LES variables show a great deal of variability in space and time caused by the complex topography in the LES domain. The WRF-LES results show that the flow structures, such as roll vortices and convective cells, vary depending on both the location and time of day. In addition to basic studies related to boundary-layer meteorology, results from these simulations can be used in other applications, such as studying wind energy resources, atmospheric dispersion, fire weather etc.

  4. Dirty ducting poses significant risks.

    PubMed

    Norman, Richard

    2010-06-01

    Richard Norman, managing director of ventilation system cleaning specialist Indepth Hygiene, discusses the importance of ensuring that such systems are properly cleaned in healthcare facilities, especially, he argues, as dust and debris on internal surfaces of ducting are potentially "ideal nutrients" for the growth of microorganisms such as MRSA and Clostridium difficile. In addition he warns that, if not properly and regularly cleaned, grease extract ventilation systems linked to catering facilities are a potential source of danger to hospital patients, staff, and visitors alike.

  5. Causes and Prevention of Laparoscopic Bile Duct Injuries

    PubMed Central

    Way, Lawrence W.; Stewart, Lygia; Gantert, Walter; Liu, Kingsway; Lee, Crystine M.; Whang, Karen; Hunter, John G.

    2003-01-01

    recognize a problem. Even when irregularities were identified, corrective feedback did not occur, which is characteristic of human thinking under firmly held assumptions. These findings illustrate the complexity of human error in surgery while simultaneously providing insights. They demonstrate that automatically attributing technical complications to behavioral factors that rely on the assumption of control is likely to be wrong. Finally, this study shows that there are only a few points within laparoscopic cholecystectomy where the complication-causing errors occur, which suggests that focused training to heighten vigilance might be able to decrease the incidence of bile duct injury. PMID:12677139

  6. Volterra representation enables modeling of complex synaptic nonlinear dynamics in large-scale simulations

    PubMed Central

    Hu, Eric Y.; Bouteiller, Jean-Marie C.; Song, Dong; Baudry, Michel; Berger, Theodore W.

    2015-01-01

    Chemical synapses are comprised of a wide collection of intricate signaling pathways involving complex dynamics. These mechanisms are often reduced to simple spikes or exponential representations in order to enable computer simulations at higher spatial levels of complexity. However, these representations cannot capture important nonlinear dynamics found in synaptic transmission. Here, we propose an input-output (IO) synapse model capable of generating complex nonlinear dynamics while maintaining low computational complexity. This IO synapse model is an extension of a detailed mechanistic glutamatergic synapse model capable of capturing the input-output relationships of the mechanistic model using the Volterra functional power series. We demonstrate that the IO synapse model is able to successfully track the nonlinear dynamics of the synapse up to the third order with high accuracy. We also evaluate the accuracy of the IO synapse model at different input frequencies and compared its performance with that of kinetic models in compartmental neuron models. Our results demonstrate that the IO synapse model is capable of efficiently replicating complex nonlinear dynamics that were represented in the original mechanistic model and provide a method to replicate complex and diverse synaptic transmission within neuron network simulations. PMID:26441622

  7. Chapter 3: Atomistic Simulation of Lignocellulosic Biomass and Associated Cellulosomal Protein Complexes

    SciTech Connect

    Petridis, L.; Xu, J.; Crowley, M. F.; Smith, J. C.; Cheng, X.

    2010-01-01

    Computer simulations have been performed to obtain an atomic-level understanding of lignocellulose structure and the assembly of its associated cellulosomal protein complexes. First, a CHARMM molecular mechanics force field for lignin is derived and validated by performing a molecular dynamics simulation of a crystal of a lignin fragment molecule and comparing simulation-derived structural features with experimental results. Together with the existing force field for polysaccharides, this work provides the basis for full simulations of lignocellulose. Second, the underlying molecular mechanism governing the assembly of various cellulosomal modules is investigated by performing a novel free-energy calculation of the cohesin-dockerin dissociation. Our calculation indicates a free-energy barrier of {approx}17 kcal/mol and further reveals a stepwise dissociation pathway involving both the central {beta}-sheet interface and its adjacent solvent-exposed loop/turn regions clustered at both ends of the {beta}-barrel structure.

  8. Restricted dynamics of water around a protein-carbohydrate complex: Computer simulation studies

    NASA Astrophysics Data System (ADS)

    Jana, Madhurima; Bandyopadhyay, Sanjoy

    2012-08-01

    Water-mediated protein-carbohydrate interaction is a complex phenomenon responsible for different biological processes in cellular environment. One of the unexplored but important issues in this area is the role played by water during the recognition process and also in controlling the microscopic properties of the complex. In this study, we have carried out atomistic molecular dynamics simulations of a protein-carbohydrate complex formed between the hyaluronan binding domain of the murine Cd44 protein and the octasaccharide hyaluronan in explicit water. Efforts have been made to explore the heterogeneous influence of the complex on the dynamic properties of water present in different regions around it. It is revealed from our analyses that the heterogeneous dynamics of water around the complex are coupled with differential time scales of formation and breaking of hydrogen bonds at the interface. Presence of a highly rigid thin layer of motionally restricted water molecules bridging the protein and the carbohydrate in the common region of the complex has been identified. Such water molecules are expected to play a crucial role in controlling properties of the complex. Importantly, it is demonstrated that the formation of the protein-carbohydrate complex affects the transverse and longitudinal degrees of freedom of the interfacial water molecules in a heterogeneous manner.

  9. Measure Guideline: Sealing and Insulating of Ducts in Existing Homes

    SciTech Connect

    Aldrich, R.; Puttagunta, S.

    2011-12-01

    This document begins with a discussion on potential cost and performance benefits of duct sealing and insulating. It continues with a review of typical duct materials and components and the overall procedures for assessing and improving the duct system.

  10. Measure Guideline. Sealing and Insulating Ducts in Existing Homes

    SciTech Connect

    Aldrich, R.; Puttagunta, S.

    2011-12-01

    This document begins with a discussion on potential cost and performance benefits of duct sealing and insulating. It continues with a review of typical duct materials and components and the overall procedures for assessing and improving the duct system.

  11. Numerical simulation of swirling flow in complex hydroturbine draft tube using unsteady statistical turbulence models

    SciTech Connect

    Paik, Joongcheol; Sotiropoulos, Fotis; Sale, Michael J

    2005-06-01

    A numerical method is developed for carrying out unsteady Reynolds-averaged Navier-Stokes (URANS) simulations and detached-eddy simulations (DESs) in complex 3D geometries. The method is applied to simulate incompressible swirling flow in a typical hydroturbine draft tube, which consists of a strongly curved 90 degree elbow and two piers. The governing equations are solved with a second-order-accurate, finite-volume, dual-time-stepping artificial compressibility approach for a Reynolds number of 1.1 million on a mesh with 1.8 million nodes. The geometrical complexities of the draft tube are handled using domain decomposition with overset (chimera) grids. Numerical simulations show that unsteady statistical turbulence models can capture very complex 3D flow phenomena dominated by geometry-induced, large-scale instabilities and unsteady coherent structures such as the onset of vortex breakdown and the formation of the unsteady rope vortex downstream of the turbine runner. Both URANS and DES appear to yield the general shape and magnitude of mean velocity profiles in reasonable agreement with measurements. Significant discrepancies among the DES and URANS predictions of the turbulence statistics are also observed in the straight downstream diffuser.

  12. Analysis on Turbulent Flows using Large-eddy Simulation on the Seaside Complex Terrain

    NASA Astrophysics Data System (ADS)

    Kamio, T.; Iida, M.; Arakawa, C.

    2014-12-01

    The purpose of this study is the Large-eddy Simulation (LES) of the turbulent wind on the complex terrain, and the first results of the simulation are described. The authors tried to apply the LES code, which was developed as an atmospheric simulator in Japan Agency for the Marine-Earth Science and Technology (JAMSTEC), to the wind prediction for the wind energy. On the wind simulation, the highest problem would be the boundary conditions, and the case in this paper was simplified one. The case study in this paper is the west wind on a complex terrain site, which is the wind from sea for the site. The steady flow was employed for the inlet condition, because the wind on the sea is the low turbulent wind, and almost all the turbulence would be generated by the roughness of the ground surface. The wall function was employed as the surface condition on the ground surface. The computational domain size was about 8 × 3 × 2.5 km3, and the minimum cell size was about 10 × 10 × 3 m3. The computational results, the vertical profile of the averaged wind speed and the turbulence intensity, agreed with the measurement by the meteorological masts. Moreover, the authors tried the analysis of the turbulence characteristics. The power spectrum density model, and the cross spectrum analyses gave the knowledge of the turbulent characteristics on the complex terrain and the hints for the domain and grid of the numerical analysis.

  13. Radiated noise of ducted fans

    NASA Technical Reports Server (NTRS)

    Eversman, Walter

    1992-01-01

    The differences in the radiated acoustic fields of ducted and unducted propellers of the same thrust operating under similar conditions are investigated. An FEM model is created for the generation, propagation, and radiation of steady, rotor alone noise and exit guide vane interaction noise of a ducted fan. For a specified number of blades, angular mode harmonic, and rotor angular velocity, the acoustic field is described in a cylindrical coordinate system reduced to only the axial and radial directions. It is found that, contrary to the usual understanding of the Tyler and Sofrin (1962) result, supersonic tip speed rotor noise can be cut off if the tip Mach number is only slightly in excess of unity and if the number of blades is relatively small. If there are many blades, the fundamental angular mode number is large, and the Tyler and Sofrin result for thin annuli becomes more relevant. Shrouding of subsonic tip speed propellers is a very effective means of controlling rotor alone noise.

  14. Radiated noise of ducted fans

    NASA Astrophysics Data System (ADS)

    Eversman, Walter

    The differences in the radiated acoustic fields of ducted and unducted propellers of the same thrust operating under similar conditions are investigated. An FEM model is created for the generation, propagation, and radiation of steady, rotor alone noise and exit guide vane interaction noise of a ducted fan. For a specified number of blades, angular mode harmonic, and rotor angular velocity, the acoustic field is described in a cylindrical coordinate system reduced to only the axial and radial directions. It is found that, contrary to the usual understanding of the Tyler and Sofrin (1962) result, supersonic tip speed rotor noise can be cut off if the tip Mach number is only slightly in excess of unity and if the number of blades is relatively small. If there are many blades, the fundamental angular mode number is large, and the Tyler and Sofrin result for thin annuli becomes more relevant. Shrouding of subsonic tip speed propellers is a very effective means of controlling rotor alone noise.

  15. Radiated noise of ducted fans

    NASA Technical Reports Server (NTRS)

    Eversman, Walter

    1992-01-01

    The differences in the radiated acoustic fields of ducted and unducted propellers of the same thrust operating under similar conditions are investigated. An FEM model is created for the generation, propagation, and radiation of steady, rotor alone noise and exit guide vane interaction noise of a ducted fan. For a specified number of blades, angular mode harmonic, and rotor angular velocity, the acoustic field is described in a cylindrical coordinate system reduced to only the axial and radial directions. It is found that, contrary to the usual understanding of the Tyler and Sofrin (1962) result, supersonic tip speed rotor noise can be cut off if the tip Mach number is only slightly in excess of unity and if the number of blades is relatively small. If there are many blades, the fundamental angular mode number is large, and the Tyler and Sofrin result for thin annuli becomes more relevant. Shrouding of subsonic tip speed propellers is a very effective means of controlling rotor alone noise.

  16. Flexible simulation framework to couple processes in complex 3D models for subsurface utilization assessment

    NASA Astrophysics Data System (ADS)

    Kempka, Thomas; Nakaten, Benjamin; De Lucia, Marco; Nakaten, Natalie; Otto, Christopher; Pohl, Maik; Tillner, Elena; Kühn, Michael

    2016-04-01

    Utilization of the geological subsurface for production and storage of hydrocarbons, chemical energy and heat as well as for waste disposal requires the quantification and mitigation of environmental impacts as well as the improvement of georesources utilization in terms of efficiency and sustainability. The development of tools for coupled process simulations is essential to tackle these challenges, since reliable assessments are only feasible by integrative numerical computations. Coupled processes at reservoir to regional scale determine the behaviour of reservoirs, faults and caprocks, generally demanding for complex 3D geological models to be considered besides available monitoring and experimenting data in coupled numerical simulations. We have been developing a flexible numerical simulation framework that provides efficient workflows for integrating the required data and software packages to carry out coupled process simulations considering, e.g., multiphase fluid flow, geomechanics, geochemistry and heat. Simulation results are stored in structured data formats to allow for an integrated 3D visualization and result interpretation as well as data archiving and its provision to collaborators. The main benefits in using the flexible simulation framework are the integration of data geological and grid data from any third party software package as well as data export to generic 3D visualization tools and archiving formats. The coupling of the required process simulators in time and space is feasible, while different spatial dimensions in the coupled simulations can be integrated, e.g., 0D batch with 3D dynamic simulations. User interaction is established via high-level programming languages, while computational efficiency is achieved by using low-level programming languages. We present three case studies on the assessment of geological subsurface utilization based on different process coupling approaches and numerical simulations.

  17. Monte Carlo simulations of flexible polyanions complexing with whey proteins at their isoelectric point

    NASA Astrophysics Data System (ADS)

    de Vries, R.

    2004-02-01

    Electrostatic complexation of flexible polyanions with the whey proteins α-lactalbumin and β-lactoglobulin is studied using Monte Carlo simulations. The proteins are considered at their respective isoelectric points. Discrete charges on the model polyelectrolytes and proteins interact through Debye-Hückel potentials. Protein excluded volume is taken into account through a coarse-grained model of the protein shape. Consistent with experimental results, it is found that α-lactalbumin complexes much more strongly than β-lactoglobulin. For α-lactalbumin, strong complexation is due to localized binding to a single large positive "charge patch," whereas for β-lactoglobulin, weak complexation is due to diffuse binding to multiple smaller charge patches.

  18. Molecular dynamics simulations of bovine cathepsin B and its complex with CA074.

    PubMed

    Yamamoto, A; Tomoo, K; Miyagawa, H; Takaoka, Y; Sumiya, S; Kitamura, K; Ishida, T

    2000-04-01

    To promote our better understanding of the dynamic stability of the bovine cathepsin B structure, which is characterized by an extra disulfide bond at Cys148-Cys252 from the other species, and of the binding stability of CA074 (a cathepsin B-specific inhibitor), molecular dynamics (MD) simulations were performed for the enzyme and its CA074 complex, assuming a system in aqueous solution at 300 K. The MD simulation covering 400 ps indicated that the existence of a Cys148-Cys252 disulfide bond increases the conformational flexibility of the occluding loop, although the conformational stability of the overall structure is little affected. The structural characteristics of the complex elucidated by X-ray analysis were suggested to be also intrinsic and stable in the dynamic state; the hydrogen bonding/electrostatic interactions between the main and side chains of CA074 and the Sn and Sn' subsites of the enzyme were maintained throughout the MD simulation. Furthermore, the simulation made clear that the binding of CA074 significantly restricted the conformational flexibility of the substrate binding region, especially the occluding loop, of cathepsin B. Statistical analyses during the simulation suggest that the selectivity of CA074 for cathepsin B stems from the tight P1'-S1' and P2'-S2' interactions, assisted in particular by double hydrogen bonds between the carboxyl two oxygens of the CA074 C-terminus and the imidazole NH groups of His110 and His111 residues.

  19. Distributed Model Complexity Versus Radar-Rainfall Input Uncertainty for Flow Simulation

    NASA Astrophysics Data System (ADS)

    Carpenter, T. M.; Georgakakos, K. P.

    2002-05-01

    The NOAA-organized Distributed Model Intercomparison Project (DMIP) has created the opportunity to study the issues pertaining to flow simulation by distributed hydrologic models with varying formulation and complexity. In this study, we examine the response of a given distributed hydrologic model under realistic conditions of uncertainty in radar-rainfall input and parameters. We extend the research reported in Carpenter et al., 2001, by (a) refining the characterization of the input uncertainty, (b) allowing for uncertainty in several soil-model parameters simultaneously, and (c) performing an inter comparison of flow simulations generated by spatially distributed and spatially lumped models to assess the likelihood that a more complex model structure would lead to significantly different flow simulations given the expected model input uncertainty. A Monte Carlo framework is used to perform the sensitivity runs and probabilistic measures are employed to determine significant sensitivities in simulated flow ensembles. The application watersheds include the DMIP basins: the Illinois River in Oklahoma, the Blue River in Oklahoma and the Elk River in Missouri. The sensitivity results are summarized in terms of simulated flow variability and assessed with regard to the basin size, peak flow, and input uncertainty. Reference: Carpenter, T.M., K.P. Georgakakos, and J.A. Sperfslage, 2001: On the parametric and NEXRAD-radar sensitivities of a distributed hydrologic model suitable for operational use. J. Hydrology, 253, 169-193.

  20. Non-linear duct acoustics and its application to fan noise

    NASA Technical Reports Server (NTRS)

    Vaidya, P. G.

    1977-01-01

    Quite often the scalar Helmholtz equation is assumed to be the fundamental equation of duct acoustics and various relations are derived from it. An investigation is, therefore, conducted regarding the underlying assumptions leading to the Helmholtz equation. It is found that serious errors, even well below 186 dB, are possible if the assumption of linearity were to be made. In duct acoustics these errors are highest near the cutoff points and in the case of ducts with transonic flow. It is pointed out that serious errors could arise if a nonlinear problem is analyzed by linear methods. At times, an entire phenomenon remains unpredictable by linear methods. Attention is given to the characteristics of nonlinear systems, the phenomenon of multiple pure tones in the case of noise from the aircraft engine fans, the limitations of the conventional acoustics equation, duct shape and nonlinearity, and the numerical simulation of a fan with 8 blades.

  1. Borescope Device Takes Impressions In Ducts

    NASA Technical Reports Server (NTRS)

    Walter, Richard F.; Turner, Laura J.

    1990-01-01

    Maneuverable device built around borescope equipped to make impression molds of welded joints in interior surfaces of ducts. Molds then examined to determine degress of mismatch in welds. Inserted in duct, and color-coded handles on ends of cables used to articulate head to maneuver around corners. Use of device fairly easy and requires little training.

  2. Clinical results of common bile duct exploration.

    PubMed

    Petelin, J B

    1993-06-01

    Laparoscopic common bile duct exploration has been successfully performed in hundreds of patients throughout the world since early 1990. The author reviews his personal experience with this procedure and compares it with the experience of others as reported in the literature. A variety of methods of managing common duct pathology has been employed. These include balloon-catheter manipulation, fluoroscopically-guided basket extraction, and choledochoscopy. The relative contributions of each of these modalities to the total framework of laparoscopic treatment of common bile duct stones is presented. By these techniques, 83 out of 86 patients had their common duct explored successfully. The author concludes that, based on accumulated experience, most, if not all, common duct stones can be treated and/or removed laparoscopically. In more than 90% of the cases, this can be accomplished through a cystic duct approach, although direct access to the common duct via choledochotomy is also possible. A rational protocol for management of common duct pathology is presented.

  3. 46 CFR 116.610 - Ventilation ducts.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... type of piping, chamber, or conduit used for ventilation. (b) A ventilation duct, and materials incidental to its installation, must be made of noncombustible material. (c) Combustibles and other foreign materials are not allowed within ventilation ducts. However, metal piping and electrical wiring installed in...

  4. Predicting vibrational failure of flexible ducting

    NASA Technical Reports Server (NTRS)

    Henry, R. H.

    1971-01-01

    Technique applies to liquid or gas transfer through flexible ducting and proves valuable in high velocity fluid flow cases. Fluid mechanism responsible for free bellows vibrational excitation also causes flexible hose oscillation. Static pressure stress influences flexible ducting fatigue life and is considered separately.

  5. Double-duct liquid metal magnetohydrodynamic engine

    DOEpatents

    Haaland, Carsten M.

    1997-01-01

    An internal combustion, liquid metal (LM) magnetohydrodynamic (MHD) engine and an alternating current (AC) magnetohydrodynamic generator, are used in combination to provide useful AC electric energy output. The engine design has four pistons and a double duct configuration, with each duct containing sodium potassium liquid metal confined between free pistons located at either end of the duct. The liquid metal is forced to flow back and forth in the duct by the movement of the pistons, which are alternatively driven by an internal combustion process. In the MHD generator, the two LM-MHD ducts pass in close proximity through a Hartmann duct with output transformer. AC power is produced by operating the engine with the liquid metal in the two generator ducts always flowing in counter directions. The amount of liquid metal maintained in the ducts may be varied. This provides a variable stroke length for the pistons. The engine/generator provides variable AC power at variable frequencies that correspond to the power demands of the vehicular propulsion. Also the engine should maintain nearly constant efficiency throughout the range of power usage. Automobiles and trucks could be powered by the invention, with no transmission or power converter devices being required.

  6. Double-duct liquid metal magnetohydrodynamic engine

    DOEpatents

    Haaland, Carsten M.

    1995-01-01

    An internal combustion, liquid metal (LM) magnetohydrodynamic (MHD) engine and an alternating current (AC) magnetohydrodynamic generator, are used in combination to provide useful AC electric energy output. The engine design has-four pistons and a double duct configuration, with each duct containing sodium potassium liquid metal confined between free pistons located at either end of the duct. The liquid metal is forced to flow back and forth in the duct by the movement of the pistons, which are alternatively driven by an internal combustion process. In the MHD generator, the two LM-MHD ducts pass in close proximity through a Hartmann duct with output transformer. AC power is produced by operating the engine with the liquid metal in the two generator ducts always flowing in counter directions. The amount of liquid metal maintained in the ducts may be varied. This provides a variable stroke length for the pistons. The engine/generator provides variable AC power at variable frequencies that correspond to the power demands of the vehicular propulsion. Also the engine should maintain nearly constant efficiency throughout the range of power usage. Automobiles and trucks could be powered by the invention, with no transmission or power converter devices being required.

  7. Surgical management of Stenson’s duct injury by using double J stent urethral catheter

    PubMed Central

    Aloosi, Suha N.; Khoshnaw, Najmaddin; Ali, Shakhawan M.; Muhammad, Belal A.

    2015-01-01

    Background Parotid duct or gland injury can be caused by assault with a knife, bottle, electrical-saw, road traffic accident, or rarely gunshot and fractures of the facial skeleton. The injury can be in the form of laceration, ductal exposure, total cutting, or crushing of the duct. These conditions are difficult to diagnose because of complex anatomy and variable forms of the injury. A successful management of parotid duct injuries depends on early diagnosis and appropriate intervention; improper surgery may lead to complications such as sialocele or salivary fistula Case report A 27-years-old man was presented to the maxillofacial unit, complaining of bleeding over the right side of his face after accidental exposure to a chain-saw three hours before admission. On examination, a 6 cm deep lacerated wound was found over the right buccal area, suspecting facial nerve-buccal branch and parotid duct injury. Under general anesthesia the parotid duct injury diagnosed, microsurgical anastomosis of the cut-ends of the parotid duct performed using the double J catheter. Sutures and JJ stent removed seven and twenty postoperative days respectively. After a proper supportive treatment a complete healing of the duct was obtained with normal amount of saliva. Conclusions Herein, we described an easy yet efficient technique in management of parotid duct injury using a JJ stent which is often used for urethra. We think that use of JJ stent is a valuable technique to be used in the diagnosis and surgical repair of the parotid duct during traumatic facial and/or parotid injuries. PMID:26555062

  8. A Project Management Approach to Using Simulation for Cost Estimation on Large, Complex Software Development Projects

    NASA Technical Reports Server (NTRS)

    Mizell, Carolyn; Malone, Linda

    2007-01-01

    It is very difficult for project managers to develop accurate cost and schedule estimates for large, complex software development projects. None of the approaches or tools available today can estimate the true cost of software with any high degree of accuracy early in a project. This paper provides an approach that utilizes a software development process simulation model that considers and conveys the level of uncertainty that exists when developing an initial estimate. A NASA project will be analyzed using simulation and data from the Software Engineering Laboratory to show the benefits of such an approach.

  9. Use of simulation to understand the effects of task complexity and time away on clinical confidence.

    PubMed

    Cohen, Elaine; Ononye, Chiagozie; Salud, Jonathan; Kwan, Calvin; Salud, Lawrence; Pugh, Carla

    2013-01-01

    In prior studies, mannequin-based simulation training has been used to help decrease student anxiety toward intimate clinical examinations. Using time away as an independent variable, the aim of this study was to assess decay of clinical confidence for four procedural tasks that vary in procedural complexity. Clinical confidence with intimate examinations, after a standardized mannequin-based simulation curriculum, decays over time. This decay is noted after two months of time away. Longer periods of time away did not show increased differences.

  10. Solving complex maintenance planning optimization problems using stochastic simulation and multi-criteria fuzzy decision making

    SciTech Connect

    Tahvili, Sahar; Österberg, Jonas; Silvestrov, Sergei; Biteus, Jonas

    2014-12-10

    One of the most important factors in the operations of many cooperations today is to maximize profit and one important tool to that effect is the optimization of maintenance activities. Maintenance activities is at the largest level divided into two major areas, corrective maintenance (CM) and preventive maintenance (PM). When optimizing maintenance activities, by a maintenance plan or policy, we seek to find the best activities to perform at each point in time, be it PM or CM. We explore the use of stochastic simulation, genetic algorithms and other tools for solving complex maintenance planning optimization problems in terms of a suggested framework model based on discrete event simulation.

  11. New cannulation method for pancreatic duct cannulation-bile duct guidewire-indwelling method

    PubMed Central

    Sakai, Yuji; Ishihara, Takeshi; Tsuyuguchi, Toshio; Tawada, Katsunobu; Saito, Masayoshi; Kurosawa, Jo; Tamura, Ryo; Togo, Seiko; Mikata, Rintaro; Tada, Motohisa; Yokosuka, Osamu

    2011-01-01

    The patient was a 58-year-old male with symptomatic alcoholic chronic pancreatitis. Since a 10 mm calculus was observed in the pancreatic body and abdominal pain occurred due to congestion of pancreatic juice, endoscopic retrograde cholangiopancreatography was conducted for assessment of the pancreatic duct and treatment of pancreatic calculus. Pancreatogram was slightly and insufficiently obtained by injecting the contrast media via the common channel of the duodenal main papilla. We tried to cannulate selectively into the pancreatic duct for a clear image. However, the selective cannulation of the pancreatic duct was difficult because of instability of the papilla. On the other hand, selective cannulation of the bile duct was relatively easily achieved. Therefore, after the imaging of the bile duct, a guidewire was retained in the bile duct to immobilize the duodenal papilla and cannulation of the pancreatic duct was attempted. As a result, selective pancreatic duct cannulation became possible. It is considered that the bile duct guidewire-indwelling method may serve as one of the useful techniques for cases whose selective pancreatic duct cannulation is difficult (“selective pancreatic duct difficult cannulation case”). PMID:22110840

  12. Docking and molecular dynamics simulations of the ternary complex nisin2:lipid II

    PubMed Central

    Mulholland, Sam; Turpin, Eleanor R.; Bonev, Boyan B.; Hirst, Jonathan D.

    2016-01-01

    Lanthionine antibiotics are an important class of naturally-occurring antimicrobial peptides. The best-known, nisin, is a commercial food preservative. However, structural and mechanistic details on nisin-lipid II membrane complexes are currently lacking. Recently, we have developed empirical force-field parameters to model lantibiotics. Docking and molecular dynamics (MD) simulations have been used to study the nisin2:lipid II complex in bacterial membranes, which has been put forward as the building block of nisin/lipid II binary membrane pores. An Ile1Trp mutation of the N-terminus of nisin has been modelled and docked onto lipid II models; the computed binding affinity increased compared to wild-type. Wild-type nisin was also docked onto three different lipid II structures and a stable 2:1 nisin:lipid II complex formed. This complex was inserted into a membrane. Six independent MD simulations revealed key interactions in the complex, specifically the N-terminal engagement of nisin with lipid II at the pyrophosphate and C-terminus of the pentapeptide chain. Nisin2 inserts into the membrane and we propose this as the first step in pore formation, mediated by the nisin N-terminus–lipid II pentapeptide hydrogen bond. The lipid II undecaprenyl chain adopted different conformations in the presence of nisin, which may also have implications for pore formation. PMID:26888784

  13. Simulation modelling as a tool to diagnose the complex networks of security systems

    NASA Astrophysics Data System (ADS)

    Iskhakov, S. Y.; Shelupanov, A. A.; Meshcheryakov, R. V.

    2017-01-01

    In the article, the questions of modelling of complex security system networks are considered. The simulation model of operation of similar complexes and approbation of the offered approach to identification of the incidents are presented. The approach is based on detection of uncharacteristic alterations of the network operation mode. The results of the experiment allow one to draw a conclusion on possibility of the offered model application to analyse the current status of heterogeneous security systems. Also, it is confirmed that the application of short-term forecasting methods for the analysis of monitoring system data allows one to automate the process of formation the criteria to reveal the incidents.

  14. Donepezil and flight simulator performance: effects on retention of complex skills.

    PubMed

    Yesavage, J A; Mumenthaler, M S; Taylor, J L; Friedman, L; O'Hara, R; Sheikh, J; Tinklenberg, J; Whitehouse, P J

    2002-07-09

    We report a randomized, double-blind, parallel group, placebo-controlled study to test the effects of the acetylcholinesterase inhibitor, donepezil (5 mg/d for 30 days), on aircraft pilot performance in 18 licensed pilots with mean age of 52 years. After 30 days of treatment, the donepezil group showed greater ability to retain the capacity to perform a set of complex simulator tasks than the placebo group, p < 0.05. Donepezil appears to have beneficial effects on retention of training on complex aviation tasks in nondemented older adults.

  15. Deposition Velocities of Non-Newtonian Slurries in Pipelines: Complex Simulant Testing

    SciTech Connect

    Poloski, Adam P.; Bonebrake, Michael L.; Casella, Andrew M.; Johnson, Michael D.; Toth, James J.; Adkins, Harold E.; Chun, Jaehun; Denslow, Kayte M.; Luna, Maria; Tingey, Joel M.

    2009-07-01

    ) was performed at each yield stress condition. Unlike the previous simulant, the sizes and densities of the particles that can deposit in the piping are a result of the simulant precipitation process; there is expected to be a complex mixture of particles of various sizes and densities that make it difficult to predict a stability map. The objective of the testing is to observe whether behavior consistent with the stability-map concept occurs in complex simulants with mixtures of different sizes and densities.

  16. Uniformly spaced field-aligned ionization ducts

    NASA Technical Reports Server (NTRS)

    Gross, S. H.; Muldrew, D. B.

    1984-01-01

    A number of interesting cases of combination mode ducted echoes for mid- and low-latitude regions are presented that show nearly uniformly spaced multiple combination mode traces on the ionograms in the frequency range above 1 MHz. These traces suggest that a parallel system of field-aligned ducts is present. Ray tracing studies are made to determine the structure that would explain the observations using the electron density profile derivable from the vertical trace and assuming field-aligned ducts. Spacing perpendicular to the ducts is found to be as much as 70 km. Some of these parallel duct structures are found to extend to the conjugate hemisphere, possibly to the F peak.

  17. Laparoscopic approach to common duct pathology.

    PubMed

    Petelin, J B

    1993-04-01

    The author reviews his experience with the laparoscopic management of common duct pathology and compares it with the experience of others as reported in the literature. Routine intraoperative cholangiography is advocated. A variety of methods of managing common duct stones laparoscopically is presented. These include balloon-catheter manipulation, fluoroscopically guided basket extraction, and choledochoscopic evaluation and removal of stones. The accumulated experience indicates that more than 90% of common duct stones can be removed laparoscopically via the cystic duct. This approach significantly reduces the need for either preoperative or postoperative endoscopic retrograde cholangiopancreatography. Although laparoscopic choledochotomy has been employed in a number of cases and can be performed with a high degree of safety and efficacy, it is needed only infrequently. This form of management results in decreased dependence upon T-tubes, thereby reducing postoperative morbidity and the length of hospitalization. A rational protocol for the management of common duct pathology is presented.

  18. Fluidic-Driven Ducted Heat Ejector

    NASA Astrophysics Data System (ADS)

    Gerty, Donavon; Mahalingam, Raghav; Glezer, Ari

    2003-11-01

    A high-aspect ratio miniature air duct is developed for forced convection heat rejection from electronic hardware within sealed enclosures. Relatively high heat transfer coefficient is achieved at low volume flow rates by a thin oscillating reed that is mounted across the span of the duct, parallel to its (wide) walls. The flow is induced by the time-periodic shedding of tip vortices at the edge of the reed which continue to propagate downstream along the duct. The interaction of these vortices with vorticity concentrations along the duct surfaces and the structure of the ensuing flow are investigated using high-resolution phase-locked and time-averaged particle image velocimetry. The dependence of the global flow and heat transfer from the duct walls on the frequency and amplitude of the reed motion are also characterized.

  19. An eddy viscosity calculation method for a turbulent duct flow

    NASA Technical Reports Server (NTRS)

    Antonia, R. A.; Bisset, D. K.; Kim, J.

    1991-01-01

    The mean velocity profile across a fully developed turbulent duct flow is obtained from an eddy viscosity relation combined with an empirical outer region wake function. Results are in good agreement with experiments and with direct numerical simulations in the same flow at two Reynolds numbers. In particular, the near-wall trend of the Reynolds shear stress and its variation with Reynolds number are similar to those of the simulations. The eddy viscosity method is more accurate than previous mixing length or implicit function methods.

  20. Electromagnetic propagation in PEC and absorbing curved S-ducts

    NASA Technical Reports Server (NTRS)

    Baumeister, Kenneth J.

    1988-01-01

    A finite-element Galerkin formulation has been developed to study transverse magnetic (TM) wave propagation in 2-D S-curved ducts with both perfectly conducting and absorbing walls. The reflection and transmission at the entrances and the exits of the curved ducts are determined by coupling the finite-element solutions in the curved ducts to the eigenfunctions of an infinite, uniform, perfectly conducting duct. Example solutions are presented for a double mitred and S-ducts of various lengths. The length of the S-duct is found to significantly effect the reflective characteristics of the duct. Also, the effect of curvature on an absorbing duct is illustrated.

  1. The application of the transfer matrix and matrix condensation methods with finite elements to duct acoustics

    NASA Astrophysics Data System (ADS)

    Craggs, A.

    1989-08-01

    When making an acoustic finite element model of a duct system, the resulting matrices can be very large due to the length of ductwork, the complex changes in geometry and the numerous junctions, and a full model may require several thousand nodes. In this paper two techniques are given for reducing the size of the matrices; the transfer matrix method and the condensed stiffness matrix approach—both of which lead to equations expressed in terms of the input and output nodes only. The methods are demonstrated with examples on a straight section of duct and a branched duct network. The substantial reductions in computer memory shown imply that duct acoustic problems can be studied using a desktop work station.

  2. Integrating surrogate models into subsurface simulation framework allows computation of complex reactive transport scenarios

    NASA Astrophysics Data System (ADS)

    De Lucia, Marco; Kempka, Thomas; Jatnieks, Janis; Kühn, Michael

    2017-04-01

    .: "Flexible Simulation Framework to Couple Processes in Complex 3D Models for Subsurface Utilization Assessment.", Energy Procedia, 97, 2016 p. 494-501.

  3. The Development of the Ducted Fan Noise Propagation and Radiation Code CDUCT-LaRC

    NASA Technical Reports Server (NTRS)

    Nark, Douglas M.; Farassat, F.; Pope, D. Stuart; Vatsa, Veer

    2003-01-01

    The development of the ducted fan noise propagation and radiation code CDUCT-LaRC at NASA Langley Research Center is described. This code calculates the propagation and radiation of given acoustic modes ahead of the fan face or aft of the exhaust guide vanes in the inlet or exhaust ducts, respectively. This paper gives a description of the modules comprising CDUCT-LaRC. The grid generation module provides automatic creation of numerical grids for complex (non-axisymmetric) geometries that include single or multiple pylons. Files for performing automatic inviscid mean flow calculations are also generated within this module. The duct propagation is based on the parabolic approximation theory of R. P. Dougherty. This theory allows the handling of complex internal geometries and the ability to study the effect of non-uniform (i.e. circumferentially and axially segmented) liners. Finally, the duct radiation module is based on the Ffowcs Williams-Hawkings (FW-H) equation with a penetrable data surface. Refraction of sound through the shear layer between the external flow and bypass duct flow is included. Results for benchmark annular ducts, as well as other geometries with pylons, are presented and compared with available analytical data.

  4. - - and Cross-Joints of Lined Ducts

    NASA Astrophysics Data System (ADS)

    Mechel, F. P.

    1998-10-01

    Much effort has been spent to increase the attenuation of lined ducts at low frequencies with only a minor increase of the blocking of the duct by thick silencers, in order to keep the stationary flow of the resistance of the silencer at low values. There exists a similar problem at high frequencies, where the attenuation goes down at about the square of the inverse frequency as soon as the frequency limit of ray formation is exceeded at which the free duct is about half a wavelength wide. The principal remedy of the problem, to choose narrow ducts, would increase the aerodynamic resistance. The ray-acoustical background of the low attenuation at high frequency suggests using the existing corners of the ductwork into which the silencer is inserted for the generation of high-frequency attenuation. A naı̈ve idea is to assume that the exciting sound ray of the inlet duct should be absorbed by an absorber on the corner wall opposite this duct, thereby avoiding the excitation of the outlet branch of the duct. Such a corner absorber could be applied in wide ducts also. This paper presents theories of joints of acoustically lined ducts with separate sound absorbers at the corner walls. The numerical results will show that high transmission losses can indeed be achieved at high frequencies, but the mechanism of the corner attenuation is not so much the absorption by the corner absorber, but more the (cut-off) attenuation of higher modes in the lined outlet branch of the duct.

  5. Molecular Dynamics Simulations of l-RNA Involving Homo- and Heterochiral Complexes.

    PubMed

    Dudek, Marta; Trylska, Joanna

    2017-03-14

    l-RNA is a mirror image of the naturally occurring d-RNA. We present the first simulations of l-RNA/d-RNA complexes in the AMBER ff10 force field that we modified to account for l-ribonucleotides. To validate the modifications we performed molecular dynamics simulations of several homo- and heterochiral RNA complexes. We did not observe any canonical base pairing in the l-/d-systems, but we found many repeatable geometric patterns that suggest possible structural motifs between the heterochiral RNA strands. The microscopic picture of l-RNA/d-RNA interface could help formulate the rules for designing l-RNAs with desired affinity toward specific d-RNA motifs.

  6. Multi-Agent-Based Simulation of a Complex Ecosystem of Mental Health Care.

    PubMed

    Kalton, Alan; Falconer, Erin; Docherty, John; Alevras, Dimitris; Brann, David; Johnson, Kyle

    2016-02-01

    This paper discusses the creation of an Agent-Based Simulation that modeled the introduction of care coordination capabilities into a complex system of care for patients with Serious and Persistent Mental Illness. The model describes the engagement between patients and the medical, social and criminal justice services they interact with in a complex ecosystem of care. We outline the challenges involved in developing the model, including process mapping and the collection and synthesis of data to support parametric estimates, and describe the controls built into the model to support analysis of potential changes to the system. We also describe the approach taken to calibrate the model to an observable level of system performance. Preliminary results from application of the simulation are provided to demonstrate how it can provide insights into potential improvements deriving from introduction of care coordination technology.

  7. Three-body interactions in complex fluids: Virial coefficients from simulation finite-size effects

    SciTech Connect

    Ashton, Douglas J.; Wilding, Nigel B.

    2014-06-28

    A simulation technique is described for quantifying the contribution of three-body interactions to the thermodynamical properties of coarse-grained representations of complex fluids. The method is based on a new approach for determining virial coefficients from the measured volume-dependent asymptote of a certain structural function. By comparing the third virial coefficient B{sub 3} for a complex fluid with that of an approximate coarse-grained model described by a pair potential, three body effects can be quantified. The strategy is applicable to both Molecular Dynamics and Monte Carlo simulation. Its utility is illustrated via measurements of three-body effects in models of star polymers and in highly size-asymmetrical colloid-polymer mixtures.

  8. Multi-cavity complex controller with vector simulator for TESLA technology linear accelerator

    NASA Astrophysics Data System (ADS)

    Czarski, Tomasz; Pozniak, Krzysztof T.; Romaniuk, Ryszard S.; Szewinski, Jaroslaw

    2008-01-01

    A digital control, as the main part of the Low Level RF system, for superconducting cavities of a linear accelerator is presented. The FPGA based controller, supported by MATLAB system, was developed to investigate a novel firmware implementation. The complex control algorithm based on the non-linear system identification is the proposal verified by the preliminary experimental results. The general idea is implemented as the Multi-Cavity Complex Controller (MCC) and is still under development. The FPGA based controller executes procedure according to the prearranged control tables: Feed-Forward, Set-Point and Corrector unit, to fulfill the required cavity performance: driving in the resonance during filling and field stabilization for the flattop range. Adaptive control algorithm is applied for the feed-forward and feedback modes. The vector Simulator table has been introduced for an efficient verification of the FPGA controller structure. Experimental results of the internal simulation, are presented for a cavity representative condition.

  9. 3-D FDTD simulation of shear waves for evaluation of complex modulus imaging.

    PubMed

    Orescanin, Marko; Wang, Yue; Insana, Michael

    2011-02-01

    The Navier equation describing shear wave propagation in 3-D viscoelastic media is solved numerically with a finite differences time domain (FDTD) method. Solutions are formed in terms of transverse scatterer velocity waves and then verified via comparison to measured wave fields in heterogeneous hydrogel phantoms. The numerical algorithm is used as a tool to study the effects on complex shear modulus estimation from wave propagation in heterogeneous viscoelastic media. We used an algebraic Helmholtz inversion (AHI) technique to solve for the complex shear modulus from simulated and experimental velocity data acquired in 2-D and 3-D. Although 3-D velocity estimates are required in general, there are object geometries for which 2-D inversions provide accurate estimations of the material properties. Through simulations and experiments, we explored artifacts generated in elastic and dynamic-viscous shear modulus images related to the shear wavelength and average viscosity.

  10. Comparison of the Actuator Line Model with Fully Resolved Simulations in Complex Environmental Conditions

    NASA Astrophysics Data System (ADS)

    Weihing, Pascal; Schulz, Christoph; Lutz, Thorsten; Krämer, Ewald

    2017-05-01

    In the present paper the actuator line method is compared with fully resolved wind turbine simulations in offshore and complex terrain applications. In such flow fields, which are characterized by non-homogeneous and unsteady velocity distributions in the rotor plane, unsteady aerodynamic effects are likely and it is unclear how these characterize the wake development and load behavior of the wind turbine. The wake properties and loads are therefore compared for the case of a 5 MW wind turbine operating in a typical maritime atmosphere and a 2.4 MW onshore turbine located at a complex terrain site downstream of an escarpment. It was found that the actuator line predicts the wake structure, wake deflection and wake deficit in good agreement with the fully resolved simulation. However, an overestimation of velocity fluctuations was observed.

  11. Average-Case Complexity Versus Approximate Simulation of Commuting Quantum Computations

    NASA Astrophysics Data System (ADS)

    Bremner, Michael J.; Montanaro, Ashley; Shepherd, Dan J.

    2016-08-01

    We use the class of commuting quantum computations known as IQP (instantaneous quantum polynomial time) to strengthen the conjecture that quantum computers are hard to simulate classically. We show that, if either of two plausible average-case hardness conjectures holds, then IQP computations are hard to simulate classically up to constant additive error. One conjecture relates to the hardness of estimating the complex-temperature partition function for random instances of the Ising model; the other concerns approximating the number of zeroes of random low-degree polynomials. We observe that both conjectures can be shown to be valid in the setting of worst-case complexity. We arrive at these conjectures by deriving spin-based generalizations of the boson sampling problem that avoid the so-called permanent anticoncentration conjecture.

  12. AN AGENT-BASED SIMULATION STUDY OF A COMPLEX ADAPTIVE COLLABORATION NETWORK

    SciTech Connect

    Ozmen, Ozgur; Smith, Jeffrey; Yilmaz, Levent

    2013-01-01

    One of the most significant problems in organizational scholarship is to discern how social collectives govern, organize, and coordinate the actions of individuals to achieve collective outcomes. The collectives are usually interpreted as complex adaptive systems (CAS). The understanding of CAS is more likely to arise with the help of computer-based simulations. In this tutorial, using agent-based modeling approach, a complex adaptive social communication network model is introduced. The objective is to present the underlying dynamics of the system in a form of computer simulation that enables analyzing the impacts of various mechanisms on network topologies and emergent behaviors. The ultimate goal is to further our understanding of the dynamics in the system and facilitate developing informed policies for decision-makers.

  13. Simulations reveal that the HIV-1 gp120-CD4 complex dissociates via complex pathways and is a potential target of the polyamidoamine (PAMAM) dendrimer

    NASA Astrophysics Data System (ADS)

    Nandy, Bidisha; Bindu, D. Hima; Dixit, Narendra M.; Maiti, Prabal K.

    2013-07-01

    The polyamidoamine (PAMAM) dendrimer prevents HIV-1 entry into target cells in vitro. Its mechanism of action, however, remains unclear and precludes the design of potent dendrimers targeting HIV-1 entry. We employed steered molecular dynamics simulations to examine whether the HIV-1 gp120-CD4 complex is a target of PAMAM. Our simulations mimicked single molecule force spectroscopy studies of the unbinding of the gp120-CD4 complex under the influence of a controlled external force. We found that the complex dissociates via complex pathways and defies the standard classification of adhesion molecules as catch and slip bonds. When the force loading rate was large, the complex behaved as a slip bond, weakening gradually. When the loading rate was small, the complex initially strengthened, akin to a catch bond, but eventually dissociated over shorter separations than with large loading rates. PAMAM docked to gp120 and destabilized the gp120-CD4 complex. The rupture force of the complex was lowered by PAMAM. PAMAM disrupted salt bridges and hydrogen bonds across the gp120-CD4 interface and altered the hydration pattern of the hydrophobic cavity in the interface. In addition, intriguingly, PAMAM suppressed the distinction in the dissociation pathways of the complex between the small and large loading rate regimes. Taken together, our simulations reveal that PAMAM targets the gp120-CD4 complex at two levels: it weakens the complex and also alters its dissociation pathway, potentially inhibiting HIV-1 entry.

  14. A novel multiblock immersed boundary method for large eddy simulation of complex arterial hemodynamics

    PubMed Central

    Shetty, Dinesh A.; Frankel, Steven H.

    2013-01-01

    Computational fluid dynamics (CFD) simulations are becoming a reliable tool to understand hemodynamics, disease progression in pathological blood vessels and to predict medical device performance. Immersed boundary method (IBM) emerged as an attractive methodology because of its ability to efficiently handle complex moving and rotating geometries on structured grids. However, its application to study blood flow in complex, branching, patient-specific anatomies is scarce. This is because of the dominance of grid nodes in the exterior of the fluid domain over the useful grid nodes in the interior, rendering an inevitable memory and computational overhead. In order to alleviate this problem, we propose a novel multiblock based IBM that preserves the simplicity and effectiveness of the IBM on structured Cartesian meshes and enables handling of complex, anatomical geometries at a reduced memory overhead by minimizing the grid nodes in the exterior of the fluid domain. As pathological and medical device hemodynamics often involve complex, unsteady transitional or turbulent flow fields, a scale resolving turbulence model such as large eddy simulation (LES) is used in the present work. The proposed solver (here after referred as WenoHemo), is developed by enhancing an existing in-house high order incompressible flow solver that was previously validated for its numerics and several LES models by Shetty et al. [Journal of Computational Physics 2010; 229 (23), 8802-8822]. In the present work, WenoHemo is systematically validated for additional numerics introduced, such as IBM and the multiblock approach, by simulating laminar flow over a sphere and laminar flow over a backward facing step respectively. Then, we validate the entire solver methodology by simulating laminar and transitional flow in abdominal aortic aneurysm (AAA). Finally, we perform blood flow simulations in the challenging clinically relevant thoracic aortic aneurysm (TAA), to gain insights into the type of

  15. A novel multiblock immersed boundary method for large eddy simulation of complex arterial hemodynamics.

    PubMed

    Anupindi, Kameswararao; Delorme, Yann; Shetty, Dinesh A; Frankel, Steven H

    2013-12-01

    Computational fluid dynamics (CFD) simulations are becoming a reliable tool to understand hemodynamics, disease progression in pathological blood vessels and to predict medical device performance. Immersed boundary method (IBM) emerged as an attractive methodology because of its ability to efficiently handle complex moving and rotating geometries on structured grids. However, its application to study blood flow in complex, branching, patient-specific anatomies is scarce. This is because of the dominance of grid nodes in the exterior of the fluid domain over the useful grid nodes in the interior, rendering an inevitable memory and computational overhead. In order to alleviate this problem, we propose a novel multiblock based IBM that preserves the simplicity and effectiveness of the IBM on structured Cartesian meshes and enables handling of complex, anatomical geometries at a reduced memory overhead by minimizing the grid nodes in the exterior of the fluid domain. As pathological and medical device hemodynamics often involve complex, unsteady transitional or turbulent flow fields, a scale resolving turbulence model such as large eddy simulation (LES) is used in the present work. The proposed solver (here after referred as WenoHemo), is developed by enhancing an existing in-house high order incompressible flow solver that was previously validated for its numerics and several LES models by Shetty et al. [Journal of Computational Physics 2010; 229 (23), 8802-8822]. In the present work, WenoHemo is systematically validated for additional numerics introduced, such as IBM and the multiblock approach, by simulating laminar flow over a sphere and laminar flow over a backward facing step respectively. Then, we validate the entire solver methodology by simulating laminar and transitional flow in abdominal aortic aneurysm (AAA). Finally, we perform blood flow simulations in the challenging clinically relevant thoracic aortic aneurysm (TAA), to gain insights into the type of

  16. Simulation and fitting of complex reaction network TPR: The key is the objective function

    SciTech Connect

    Savara, Aditya Ashi

    2016-07-07

    In this research, a method has been developed for finding improved fits during simulation and fitting of data from complex reaction network temperature programmed reactions (CRN-TPR). It was found that simulation and fitting of CRN-TPR presents additional challenges relative to simulation and fitting of simpler TPR systems. The method used here can enable checking the plausibility of proposed chemical mechanisms and kinetic models. The most important finding was that when choosing an objective function, use of an objective function that is based on integrated production provides more utility in finding improved fits when compared to an objective function based on the rate of production. The response surface produced by using the integrated production is monotonic, suppresses effects from experimental noise, requires fewer points to capture the response behavior, and can be simulated numerically with smaller errors. For CRN-TPR, there is increased importance (relative to simple reaction network TPR) in resolving of peaks prior to fitting, as well as from weighting of experimental data points. Using an implicit ordinary differential equation solver was found to be inadequate for simulating CRN-TPR. Lastly, the method employed here was capable of attaining improved fits in simulation and fitting of CRN-TPR when starting with a postulated mechanism and physically realistic initial guesses for the kinetic parameters.

  17. Simulation and fitting of complex reaction network TPR: The key is the objective function

    DOE PAGES

    Savara, Aditya Ashi

    2016-07-07

    In this research, a method has been developed for finding improved fits during simulation and fitting of data from complex reaction network temperature programmed reactions (CRN-TPR). It was found that simulation and fitting of CRN-TPR presents additional challenges relative to simulation and fitting of simpler TPR systems. The method used here can enable checking the plausibility of proposed chemical mechanisms and kinetic models. The most important finding was that when choosing an objective function, use of an objective function that is based on integrated production provides more utility in finding improved fits when compared to an objective function based onmore » the rate of production. The response surface produced by using the integrated production is monotonic, suppresses effects from experimental noise, requires fewer points to capture the response behavior, and can be simulated numerically with smaller errors. For CRN-TPR, there is increased importance (relative to simple reaction network TPR) in resolving of peaks prior to fitting, as well as from weighting of experimental data points. Using an implicit ordinary differential equation solver was found to be inadequate for simulating CRN-TPR. Lastly, the method employed here was capable of attaining improved fits in simulation and fitting of CRN-TPR when starting with a postulated mechanism and physically realistic initial guesses for the kinetic parameters.« less

  18. Simulation and fitting of complex reaction network TPR: The key is the objective function

    NASA Astrophysics Data System (ADS)

    Savara, Aditya

    2016-11-01

    A method has been developed for finding improved fits during simulation and fitting of data from complex reaction network temperature programmed reactions (CRN-TPR). It was found that simulation and fitting of CRN-TPR presents additional challenges relative to simulation and fitting of simpler TPR systems. The method used here can enable checking the plausibility of proposed chemical mechanisms and kinetic models. The most important finding was that when choosing an objective function, use of an objective function that is based on integrated production provides more utility in finding improved fits when compared to an objective function based on the rate of production. The response surface produced by using the integrated production is monotonic, suppresses effects from experimental noise, requires fewer points to capture the response behavior, and can be simulated numerically with smaller errors. For CRN-TPR, there is increased importance (relative to simple reaction network TPR) in resolving of peaks prior to fitting, as well as from weighting of experimental data points. Using an implicit ordinary differential equation solver was found to be inadequate for simulating CRN-TPR. The method employed here was capable of attaining improved fits in simulation and fitting of CRN-TPR when starting with a postulated mechanism and physically realistic initial guesses for the kinetic parameters.

  19. Simulation and fitting of complex reaction network TPR: The key is the objective function

    SciTech Connect

    Savara, Aditya Ashi

    2016-07-07

    In this research, a method has been developed for finding improved fits during simulation and fitting of data from complex reaction network temperature programmed reactions (CRN-TPR). It was found that simulation and fitting of CRN-TPR presents additional challenges relative to simulation and fitting of simpler TPR systems. The method used here can enable checking the plausibility of proposed chemical mechanisms and kinetic models. The most important finding was that when choosing an objective function, use of an objective function that is based on integrated production provides more utility in finding improved fits when compared to an objective function based on the rate of production. The response surface produced by using the integrated production is monotonic, suppresses effects from experimental noise, requires fewer points to capture the response behavior, and can be simulated numerically with smaller errors. For CRN-TPR, there is increased importance (relative to simple reaction network TPR) in resolving of peaks prior to fitting, as well as from weighting of experimental data points. Using an implicit ordinary differential equation solver was found to be inadequate for simulating CRN-TPR. Lastly, the method employed here was capable of attaining improved fits in simulation and fitting of CRN-TPR when starting with a postulated mechanism and physically realistic initial guesses for the kinetic parameters.

  20. Monitoring of Grouting Compactness in a Post-Tensioning Tendon Duct Using Piezoceramic Transducers.

    PubMed

    Jiang, Tianyong; Kong, Qingzhao; Wang, Wenxi; Huo, Linsheng; Song, Gangbing

    2016-08-22

    A post-tensioning tendon duct filled with grout can effectively prevent corrosion of the reinforcement, maintain bonding behavior between the reinforcement and concrete, and enhance the load bearing capacity of concrete structures. In practice, grouting of the post-tensioning tendon ducts always causes quality problems, which may reduce structural integrity and service life, and even cause accidents. However, monitoring of the grouting compactness is still a challenge due to the invisibility of the grout in the duct during the grouting process. This paper presents a stress wave-based active sensing approach using piezoceramic transducers to monitor the grouting compactness in real time. A segment of a commercial tendon duct was used as research object in this study. One lead zirconate titanate (PZT) piezoceramic transducer with marble protection, called a smart aggregate (SA), was bonded on the tendon and installed in the tendon duct. Two PZT patch sensors were mounted on the top outside surface of the duct, and one PZT patch sensor was bonded on the bottom outside surface of the tendon duct. In the active sensing approach, the SA was used as an actuator to generate a stress wave and the PZT sensors were utilized to detect the wave response. Cement or grout in the duct functions as a wave conduit, which can propagate the stress wave. If the cement or grout is not fully filled in the tendon duct, the top PZT sensors cannot receive much stress wave energy. The experimental procedures simulated four stages during the grout pouring process, which includes empty status, half grouting, 90% grouting, and full grouting of the duct. Experimental results show that the bottom PZT sensor can detect the signal when the grout level increases towards 50%, when a conduit between the SA and PZT sensor is formed. The top PZT sensors cannot receive any signal until the grout process is completely finished. The wavelet packet-based energy analysis was adopted in this research to

  1. Monitoring of Grouting Compactness in a Post-Tensioning Tendon Duct Using Piezoceramic Transducers

    PubMed Central

    Jiang, Tianyong; Kong, Qingzhao; Wang, Wenxi; Huo, Linsheng; Song, Gangbing

    2016-01-01

    A post-tensioning tendon duct filled with grout can effectively prevent corrosion of the reinforcement, maintain bonding behavior between the reinforcement and concrete, and enhance the load bearing capacity of concrete structures. In practice, grouting of the post-tensioning tendon ducts always causes quality problems, which may reduce structural integrity and service life, and even cause accidents. However, monitoring of the grouting compactness is still a challenge due to the invisibility of the grout in the duct during the grouting process. This paper presents a stress wave-based active sensing approach using piezoceramic transducers to monitor the grouting compactness in real time. A segment of a commercial tendon duct was used as research object in this study. One lead zirconate titanate (PZT) piezoceramic transducer with marble protection, called a smart aggregate (SA), was bonded on the tendon and installed in the tendon duct. Two PZT patch sensors were mounted on the top outside surface of the duct, and one PZT patch sensor was bonded on the bottom outside surface of the tendon duct. In the active sensing approach, the SA was used as an actuator to generate a stress wave and the PZT sensors were utilized to detect the wave response. Cement or grout in the duct functions as a wave conduit, which can propagate the stress wave. If the cement or grout is not fully filled in the tendon duct, the top PZT sensors cannot receive much stress wave energy. The experimental procedures simulated four stages during the grout pouring process, which includes empty status, half grouting, 90% grouting, and full grouting of the duct. Experimental results show that the bottom PZT sensor can detect the signal when the grout level increases towards 50%, when a conduit between the SA and PZT sensor is formed. The top PZT sensors cannot receive any signal until the grout process is completely finished. The wavelet packet-based energy analysis was adopted in this research to

  2. Inertial migration in dilute and semidilute suspensions of rigid particles in laminar square duct flow

    NASA Astrophysics Data System (ADS)

    Kazerooni, H. Tabaei; Fornari, W.; Hussong, J.; Brandt, L.

    2017-08-01

    We study the inertial migration of finite-size neutrally buoyant spherical particles in dilute and semidilute suspensions in laminar square duct flow. We perform several direct numerical simulations using an immersed boundary method to investigate the effects of the bulk Reynolds number Reb, particle Reynolds number Rep, and duct to particle size ratio h /a at different solid volume fractions ϕ , from very dilute conditions to 20 % . We show that the bulk Reynolds number Reb is the key parameter in inertial migration of particles in dilute suspensions. At low solid volume fraction (ϕ =0.4 % ), low bulk Reynolds number (Reb=144 ), and h /a =9 particles accumulate at the center of the duct walls. As Reb is increased, the focusing position moves progressively toward the corners of the duct. At higher volume fractions, ϕ =5 % , 10 % , and 20 % , and in wider ducts (h /a =18 ) with Reb=550 , particles are found to migrate away from the duct core toward the walls. In particular, for ϕ =5 % and 10 % , particles accumulate preferentially at the corners. At the highest volume fraction considered, ϕ =20 % , particles sample all the volume of the duct, with a lower concentration at the duct core. For all cases, we find that particles reside longer times at the corners than at the wall centers. In a duct with lower duct to particle size ratio h /a =9 (i.e., with larger particles), ϕ =5 % , and high bulk Reynolds number Reb=550 , we find a particle concentration pattern similar to that in the ducts with h /a =9 regardless of the solid volume fraction ϕ . Instead, for lower Bulk Reynolds number Reb=144 , h /a =9 , and ϕ =5 % , a different particle distribution is observed in comparison to a dilute suspension ϕ =0.4 % . Hence, the volume fraction plays a key role in defining the final distribution of particles in semidilute suspensions at low bulk Reynolds number. The presence of particles induces secondary cross-stream motions in the duct cross section, for all ϕ . The

  3. Assessment of complex dissociative disorder patients and simulated dissociation in forensic contexts.

    PubMed

    Brand, Bethany L; Webermann, Aliya R; Frankel, A Steven

    Few assessors receive training in assessing dissociation and complex dissociative disorders (DDs). Potential differential diagnoses include anxiety, mood, psychotic, substance use, and personality disorders, as well as exaggeration and malingering. Individuals with DDs typically elevate on many clinical and validity scales on psychological tests, yet research indicates that they can be distinguished from DD simulators. Becoming informed about the testing profiles of DD individuals and DD simulators can improve the accuracy of differential diagnoses in forensic settings. In this paper, we first review the testing profiles of individuals with complex DDs and contrast them with DD simulators on assessment measures used in forensic contexts, including the Minnesota Multiphasic Personality Inventory-2 (MMPI-2), Personality Assessment Inventory (PAI), and the Structured Inventory of Reported Symptoms (SIRS), as well as dissociation-specific measures such as the Dissociative Experiences Scale (DES) and Structured Clinical Interview for DSM-IV Dissociative Disorders (SCID-D-R). We then provide recommendations for assessing complex trauma and dissociation through the aforementioned assessments. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Molecular dynamics simulations of DNA/PEI complexes: effect of PEI branching and protonation state.

    PubMed

    Sun, Chongbo; Tang, Tian; Uludağ, Hasan; Cuervo, Javier E

    2011-06-08

    Complexes formed by DNA and polyethylenimine (PEI) are of great research interest because of their application in gene therapy. In this work, we carried out all-atom molecular dynamics simulations to study eight types of DNA/PEI complexes, each of which was formed by one DNA duplex d(CGCGAATTCGCG)(2) and one PEI. We used eight different PEIs with four different degrees of branching and two protonation ratios of amine groups (23% and 46%) in the simulations to investigate how the branching degree and protonation state can affect the binding. We found that 46% protonated PEIs form more stable complexes with DNA, and the binding is achieved mainly through direct interaction between the protonated amine groups on PEI and the electronegative oxygens on the DNA backbone, with some degree of interaction with electronegative groove nitrogens/oxygens. For the 23% protonated PEIs, indirect interaction mediated by one or more water molecules plays an important role in binding. Compared with the protonation state, the degree of branching has a smaller effect on binding, which essentially diminishes at the protonation ratio of 46%. These simulations shed light on the detailed mechanism(s) of PEI binding to DNA, and may facilitate the design of PEI-based gene delivery carriers.

  5. The Geometric Cluster Algorithm: Rejection-Free Monte Carlo Simulation of Complex Fluids

    NASA Astrophysics Data System (ADS)

    Luijten, Erik

    2005-03-01

    The study of complex fluids is an area of intense research activity, in which exciting and counter-intuitive behavior continue to be uncovered. Ironically, one of the very factors responsible for such interesting properties, namely the presence of multiple relevant time and length scales, often greatly complicates accurate theoretical calculations and computer simulations that could explain the observations. We have recently developed a new Monte Carlo simulation methodootnotetextJ. Liu and E. Luijten, Phys. Rev. Lett.92, 035504 (2004); see also Physics Today, March 2004, pp. 25--27. that overcomes this problem for several classes of complex fluids. Our approach can accelerate simulations by orders of magnitude by introducing nonlocal, collective moves of the constituents. Strikingly, these cluster Monte Carlo moves are proposed in such a manner that the algorithm is rejection-free. The identification of the clusters is based upon geometric symmetries and can be considered as the off-latice generalization of the widely-used Swendsen--Wang and Wolff algorithms for lattice spin models. While phrased originally for complex fluids that are governed by the Boltzmann distribution, the geometric cluster algorithm can be used to efficiently sample configurations from an arbitrary underlying distribution function and may thus be applied in a variety of other areas. In addition, I will briefly discuss various extensions of the original algorithm, including methods to influence the size of the clusters that are generated and ways to introduce density fluctuations.

  6. Specific DNA recognition by the Antp homeodomain: MD simulations of specific and nonspecific complexes.

    PubMed

    Gutmanas, Aleksandras; Billeter, Martin

    2004-12-01

    Four molecular dynamics simulation trajectories of complexes between the wild-type or a mutant Antennapedia homeodomain and 2 DNA sequences were generated in order to probe the mechanisms governing the specificity of DNA recognition. The starting point was published affinity measurements showing that a single protein mutation combined with a replacement of 2 base pairs yields a new high-affinity complex, whereas the other combinations, with changes on only 1 macromolecule, exhibited lower affinity. The simulations of the 4 complexes yielded fluctuating networks of interaction. On average, these networks differ significantly, explaining the switch of affinity caused by the alterations in the macromolecules. The network of mostly hydrogen-bonding interactions involving several water molecules, which was suggested both by X-ray and NMR structures of the wild-type homeodomain and its DNA operator sequence, could be reproduced in the trajectory. More interestingly, the high-affinity complex with alterations in both the protein and the DNA yielded again a dynamic but very tight network of intermolecular interactions, however, attributing a significantly stronger role to direct hydrophobic interactions at the expense of water bridges. The other 2 homeodomain-DNA complexes, with only 1 molecule altered, show on average over the trajectories a clearly reduced number of protein-DNA interactions. The observations from these simulations suggest specific experiments and thus close the circle formed by biochemical, structural, and computational studies. The shift from a water-dominated to a more "dry" interface may prove important in the design of proteins binding DNA in a specific manner.

  7. When can a high-resolution simulation over complex terrain be called LES?

    NASA Astrophysics Data System (ADS)

    Cuxart, Joan

    2015-12-01

    The ceaseless rise of computational power leads to a continuous increase of the resolution of the numerical models of the atmosphere. It is found today that operational models are run at horizontal resolutions near 1 km whereas research exercises for flows over complex terrain use resolutions at the hectometer scale. Horizontal resolutions of 100 m or finer have been used to perform Large-Eddy Simulations (LES) for some specific regimes like, e.g., the atmospheric boundary-layer in idealized configurations. However, to use the name "Large-Eddy Simulation" implies to be able to resolve at least the largest turbulent energetic eddies, which is almost impossible to reach with resolutions of the order of 100m for a real case, where many different processes occur linked to different scales, many of them even smaller than 100 m. Therefore, LES is an inappropriate denomination for these numerical exercises, that may simply be called High-Resolution Mesoscale Simulations.

  8. Comparison of Measured and Numerically Simulated Turbulence Statistics in a Convective Boundary Layer Over Complex Terrain

    NASA Astrophysics Data System (ADS)

    Rai, Raj K.; Berg, Larry K.; Kosović, Branko; Mirocha, Jeffrey D.; Pekour, Mikhail S.; Shaw, William J.

    2016-11-01

    The Weather Research and Forecasting (WRF) model can be used to simulate atmospheric processes ranging from quasi-global to tens of m in scale. Here we employ large-eddy simulation (LES) using the WRF model, with the LES-domain nested within a mesoscale WRF model domain with grid spacing decreasing from 12.15 km (mesoscale) to 0.03 km (LES). We simulate real-world conditions in the convective planetary boundary layer over an area of complex terrain. The WRF-LES model results are evaluated against observations collected during the US Department of Energy-supported Columbia Basin Wind Energy Study. Comparison of the first- and second-order moments, turbulence spectrum, and probability density function of wind speed shows good agreement between the simulations and observations. One key result is to demonstrate that a systematic methodology needs to be applied to select the grid spacing and refinement ratio used between domains, to avoid having a grid resolution that falls in the grey zone and to minimize artefacts in the WRF-LES model solutions. Furthermore, the WRF-LES model variables show large variability in space and time caused by the complex topography in the LES domain. Analyses of WRF-LES model results show that the flow structures, such as roll vortices and convective cells, vary depending on both the location and time of day as well as the distance from the inflow boundaries.

  9. Comparison of Measured and Numerically Simulated Turbulence Statistics in a Convective Boundary Layer Over Complex Terrain

    NASA Astrophysics Data System (ADS)

    Rai, Raj K.; Berg, Larry K.; Kosović, Branko; Mirocha, Jeffrey D.; Pekour, Mikhail S.; Shaw, William J.

    2017-04-01

    The Weather Research and Forecasting (WRF) model can be used to simulate atmospheric processes ranging from quasi-global to tens of m in scale. Here we employ large-eddy simulation (LES) using the WRF model, with the LES-domain nested within a mesoscale WRF model domain with grid spacing decreasing from 12.15 km (mesoscale) to 0.03 km (LES). We simulate real-world conditions in the convective planetary boundary layer over an area of complex terrain. The WRF-LES model results are evaluated against observations collected during the US Department of Energy-supported Columbia Basin Wind Energy Study. Comparison of the first- and second-order moments, turbulence spectrum, and probability density function of wind speed shows good agreement between the simulations and observations. One key result is to demonstrate that a systematic methodology needs to be applied to select the grid spacing and refinement ratio used between domains, to avoid having a grid resolution that falls in the grey zone and to minimize artefacts in the WRF-LES model solutions. Furthermore, the WRF-LES model variables show large variability in space and time caused by the complex topography in the LES domain. Analyses of WRF-LES model results show that the flow structures, such as roll vortices and convective cells, vary depending on both the location and time of day as well as the distance from the inflow boundaries.

  10. Modelling and simulation of complex sociotechnical systems: envisioning and analysing work environments

    PubMed Central

    Hettinger, Lawrence J.; Kirlik, Alex; Goh, Yang Miang; Buckle, Peter

    2015-01-01

    Accurate comprehension and analysis of complex sociotechnical systems is a daunting task. Empirically examining, or simply envisioning the structure and behaviour of such systems challenges traditional analytic and experimental approaches as well as our everyday cognitive capabilities. Computer-based models and simulations afford potentially useful means of accomplishing sociotechnical system design and analysis objectives. From a design perspective, they can provide a basis for a common mental model among stakeholders, thereby facilitating accurate comprehension of factors impacting system performance and potential effects of system modifications. From a research perspective, models and simulations afford the means to study aspects of sociotechnical system design and operation, including the potential impact of modifications to structural and dynamic system properties, in ways not feasible with traditional experimental approaches. This paper describes issues involved in the design and use of such models and simulations and describes a proposed path forward to their development and implementation. Practitioner Summary: The size and complexity of real-world sociotechnical systems can present significant barriers to their design, comprehension and empirical analysis. This article describes the potential advantages of computer-based models and simulations for understanding factors that impact sociotechnical system design and operation, particularly with respect to process and occupational safety. PMID:25761227

  11. GPU simulation of nonlinear propagation of dual band ultrasound pulse complexes

    SciTech Connect

    Kvam, Johannes Angelsen, Bjørn A. J.; Elster, Anne C.

    2015-10-28

    In a new method of ultrasound imaging, called SURF imaging, dual band pulse complexes composed of overlapping low frequency (LF) and high frequency (HF) pulses are transmitted, where the frequency ratio LF:HF ∼ 1 : 20, and the relative bandwidth of both pulses are ∼ 50 − 70%. The LF pulse length is hence ∼ 20 times the HF pulse length. The LF pulse is used to nonlinearly manipulate the material elasticity observed by the co-propagating HF pulse. This produces nonlinear interaction effects that give more information on the propagation of the pulse complex. Due to the large difference in frequency and pulse length between the LF and the HF pulses, we have developed a dual level simulation where the LF pulse propagation is first simulated independent of the HF pulse, using a temporal sampling frequency matched to the LF pulse. A separate equation for the HF pulse is developed, where the the presimulated LF pulse modifies the propagation velocity. The equations are adapted to parallel processing in a GPU, where nonlinear simulations of a typical HF beam of 10 MHz down to 40 mm is done in ∼ 2 secs in a standard GPU. This simulation is hence very useful for studying the manipulation effect of the LF pulse on the HF pulse.

  12. The identification of complex interactions in epidemiology and toxicology: a simulation study of boosted regression trees

    PubMed Central

    2014-01-01

    Background There is a need to evaluate complex interaction effects on human health, such as those induced by mixtures of environmental contaminants. The usual approach is to formulate an additive statistical model and check for departures using product terms between the variables of interest. In this paper, we present an approach to search for interaction effects among several variables using boosted regression trees. Methods We simulate a continuous outcome from real data on 27 environmental contaminants, some of which are correlated, and test the method’s ability to uncover the simulated interactions. The simulated outcome contains one four-way interaction, one non-linear effect and one interaction between a continuous variable and a binary variable. Four scenarios reflecting different strengths of association are simulated. We illustrate the method using real data. Results The method succeeded in identifying the true interactions in all scenarios except where the association was weakest. Some spurious interactions were also found, however. The method was also capable to identify interactions in the real data set. Conclusions We conclude that boosted regression trees can be used to uncover complex interaction effects in epidemiological studies. PMID:24993424

  13. CHARMM-GUI Martini Maker for modeling and simulation of complex bacterial membranes with lipopolysaccharides.

    PubMed

    Hsu, Pin-Chia; Bruininks, Bart M H; Jefferies, Damien; Cesar Telles de Souza, Paulo; Lee, Jumin; Patel, Dhilon S; Marrink, Siewert J; Qi, Yifei; Khalid, Syma; Im, Wonpil

    2017-10-15

    A complex cell envelope, composed of a mixture of lipid types including lipopolysaccharides, protects bacteria from the external environment. Clearly, the proteins embedded within the various components of the cell envelope have an intricate relationship with their local environment. Therefore, to obtain meaningful results, molecular simulations need to mimic as far as possible this chemically heterogeneous system. However, setting up such systems for computational studies is far from trivial, and consequently the vast majority of simulations of outer membrane proteins still rely on oversimplified phospholipid membrane models. This work presents an update of CHARMM-GUI Martini Maker for coarse-grained modeling and simulation of complex bacterial membranes with lipopolysaccharides. The qualities of the outer membrane systems generated by Martini Maker are validated by simulating them in bilayer, vesicle, nanodisc, and micelle environments (with and without outer membrane proteins) using the Martini force field. We expect this new feature in Martini Maker to be a useful tool for modeling large, complicated bacterial outer membrane systems in a user-friendly manner. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  14. The influence of simulation model complexity on the estimation of internal loading in gymnastics landings.

    PubMed

    Mills, Chris; Pain, Matthew T G; Yeadon, Maurice R

    2008-01-01

    Evaluating landing technique using a computer simulation model of a gymnast and landing mat could be a useful tool when attempting to assess injury risk. The aims of this study were: (1) to investigate whether a subject-specific torque-driven or a subject-specific muscle-driven model of a gymnast is better at matching experimental ground reaction forces and kinematics during gymnastics landings, (2) to calculate their respective simulation run times and (3) to determine what level of model complexity is required to assess injury risk. A subject-specific planar seven-link wobbling mass model of a gymnast and a multi-layer model of a landing mat were developed for this study. Subject-specific strength parameters were determined which defined the maximum voluntary torque/angle/angular velocity relationship about each joint. This relationship was also used to produce subject-specific 'lumped' muscle models for each joint. Kinetic and kinematic data were obtained during landings from backward and forward rotating gymnastics vaults. Both torque-driven and muscle-driven models were capable of producing simulated landings that matched the actual performances (with overall percentage differences between 10.1% and 18.2%). The torque-driven model underestimated the internal loading on joints and bones, resulting in joint reaction forces that were less than 50% of those calculated using the muscle-driven model. Simulation time increased from approximately 3 min (torque driven) to more than 10 min (muscle driven) as model complexity increased. The selection of a simulation model for assessing injury risk must consider the need for determining realistic internal forces as the priority despite increases in simulation run time.

  15. Dispersion of particles in complex terrain: comparisons between WRF LES and simulations using different PBL schemes

    NASA Astrophysics Data System (ADS)

    Xue, L.; Kosovic, B.; Tessendorf, S. A.; Rasmussen, R.

    2015-12-01

    A key process in wintertime orographic cloud seeding using ground-based generators is the dispersion of silver iodide particles released from the generators in the mountainous area. The dispersion features determine the targeting efficiency and ultimately the seeding effect on the ground under favorable seeding conditions. Previous field experiments showed that the silver iodide plumes were narrow (spread angle was around 20 degrees) and were confined within the mountainous boundary layer (usually lower than 1 km AGL). The numerical simulation of the particle dispersion in complex terrain using weather models is challenging due to the stable atmosphere in winter, the unresolved terrain-flow interaction, and the inherent numerical diffusion close to the source point in the Eulerian framework. A recent study by Xue et al. (2014) showed that Large Eddy Simulation (LES) of the particle dispersion in complex terrain with grid spacing of 100 m could reproduce most observed features while simulations using PBL schemes with 500 m grid spacing had difficulty reproducing the vertical dispersion. This study will simulate the same case using the Weather Research and Forecasting (WRF) model in LES mode and with several PBL schemes. The differences between the LES-simulated dispersion results and the PBL results will be analyzed and presented. Especially, the difference attributed to the unrepresented sub-grid scale (SGS) topography information in the PBL will be studied in detail. The ultimate goal of this study is to incorporate the dispersion due to turbulent kinetic energy induced by SGS topography into the existing PBL schemes to better simulate the process in mountainous regions.

  16. Investigation in the 7-By-10 Foot Wind Tunnel of Ducts for Cooling Radiators Within an Airplane Wing, Special Report

    NASA Technical Reports Server (NTRS)

    Harris, Thomas A.; Recant, Isidore G.

    1938-01-01

    An investigation was made in the NACA 7- by 10-foot wind tunnel of a large-chord wing model with a duct to house a simulated radiator suitable for a liquid-cooled engine. The duct was expanded to reduce the radiator losses, and the installation of the duct and radiator was made entirely within the wing to reduce form and interference drag. The tests were made using a two-dimensional flow set-up with a full-span duct and radiator. Section aerodynamic characteristics of the basic airfoil are given and also curves showing the characteristics of the various duct-radiator combinations. An expression for efficiency, the primary criterion of merit of any duct, and the effect of the several design parameters of the duct-radiator arrangement are discussed. The problem of throttling is considered and a discussion of the power required for cooling is included. It was found that radiators could be mounted in the wing and efficiently pass enough air for cooling with duct outlets located at any point from 0.25c to 0.70c from the wing leading edge on the upper surface. The duct-inlet position was found to be critical and, for maximum efficiency, had to be at the stagnation point of the airfoil and to change with flight attitude. The flow could be efficiently throttled only by a simultaneous variation of duct inlet and outlet sizes and of inlet position. It was desirable to round both inlet and outlet lips. With certain arrangements of duct, the power required for cooling at high speed was a very low percentage of the engine power.

  17. Advanced Turbofan Duct Liner Concepts

    NASA Technical Reports Server (NTRS)

    Bielak, Gerald W.; Premo, John W.; Hersh, Alan S.

    1999-01-01

    The Advanced Subsonic Technology Noise Reduction Program goal is to reduce aircraft noise by 10 EPNdB by the year 2000 relative, to 1992 technology. The improvement goal for nacelle attenuation is 25% relative to 1992 technology by 1997 and 50% by 2000. The Advanced Turbofan Duct Liner Concepts Task work by Boeing presented in this document was in support of these goals. The basis for the technical approach was a Boeing study conducted in 1993-94 under NASA/FAA contract NAS1-19349, Task 6, investigating broadband acoustic liner concepts. As a result of this work, it was recommended that linear double layer, linear and perforate triple layer, parallel element, and bulk absorber liners be further investigated to improve nacelle attenuations. NASA LaRC also suggested that "adaptive" liner concepts that would allow "in-situ" acoustic impedance control also be considered. As a result, bias flow and high-temperature liner concepts were also added to the investigation. The major conclusion from the above studies is that improvements in nacelle liner average acoustic impedance characteristics alone will not result in 25% increased nacelle noise reduction relative to 1992 technology. Nacelle design advancements currently being developed by Boeing are expected to add 20-40% more acoustic lining to hardwall regions in current inlets, which is predicted to result in and additional 40-80% attenuation improvement. Similar advancements are expected to allow 10-30% more acoustic lining in current fan ducts with 10-30% more attenuation expected. In addition, Boeing is currently developing a scarf inlet concept which is expected to give an additional 40-80% attenuation improvement for equivalent lining areas.

  18. Self-assembly of polyelectrolyte surfactant complexes using large scale MD simulation

    NASA Astrophysics Data System (ADS)

    Goswami, Monojoy; Sumpter, Bobby

    2014-03-01

    Polyelectrolytes (PE) and surfactants are known to form interesting structures with varied properties in aqueous solutions. The morphological details of the PE-surfactant complexes depend on a combination of polymer backbone, electrostatic interactions and hydrophobic interactions. We study the self-assembly of cationic PE and anionic surfactants complexes in dilute condition. The importance of such complexes of PE with oppositely charged surfactants can be found in biological systems, such as immobilization of enzymes in polyelectrolyte complexes or nonspecific association of DNA with protein. Many useful properties of PE surfactant complexes come from the highly ordered structures of surfactant self-assembly inside the PE aggregate which has applications in industry. We do large scale molecular dynamics simulation using LAMMPS to understand the structure and dynamics of PE-surfactant systems. Our investigation shows highly ordered pearl-necklace structures that have been observed experimentally in biological systems. We investigate many different properties of PE-surfactant complexation for different parameter ranges that are useful for pharmaceutical, engineering and biological applications.

  19. FACET: A simulation software framework for modeling complex societal processes and interactions

    SciTech Connect

    Christiansen, J. H.

    2000-06-02

    FACET, the Framework for Addressing Cooperative Extended Transactions, was developed at Argonne National Laboratory to address the need for a simulation software architecture in the style of an agent-based approach, but with sufficient robustness, expressiveness, and flexibility to be able to deal with the levels of complexity seen in real-world social situations. FACET is an object-oriented software framework for building models of complex, cooperative behaviors of agents. It can be used to implement simulation models of societal processes such as the complex interplay of participating individuals and organizations engaged in multiple concurrent transactions in pursuit of their various goals. These transactions can be patterned on, for example, clinical guidelines and procedures, business practices, government and corporate policies, etc. FACET can also address other complex behaviors such as biological life cycles or manufacturing processes. To date, for example, FACET has been applied to such areas as land management, health care delivery, avian social behavior, and interactions between natural and social processes in ancient Mesopotamia.

  20. Clinical significance of main pancreatic duct dilation on computed tomography: Single and double duct dilation

    PubMed Central

    Edge, Mark D; Hoteit, Maarouf; Patel, Amil P; Wang, Xiaoping; Baumgarten, Deborah A; Cai, Qiang

    2007-01-01

    AIM: To study the patients with main pancreatic duct dilation on computed tomography (CT) and thereby to provide the predictive criteria to identify patients at high risk of significant diseases, such as pancreatic cancer, and to avoid unnecessary work up for patients at low risk of such diseases. METHODS: Patients with dilation of the main pancreatic duct on CT at Emory University Hospital in 2002 were identified by computer search. Clinical course and ultimate diagnosis were obtained in all the identified patients by abstraction of their computer database records. RESULTS: Seventy-seven patients were identified in this study. Chronic pancreatitis and pancreatic cancer were the most common causes of the main pancreatic duct dilation on CT. Although the majority of patients with isolated dilation of the main pancreatic duct (single duct dilation) had chronic pancreatitis, one-third of patients with single duct dilation but without chronic pancreatitis had pancreatic malignancies, whereas most of patients with concomitant biliary duct dilation (double duct dilation) had pancreatic cancer. CONCLUSION: Patients with pancreatic double duct dilation need extensive work up and careful follow-up since a majority of these patients are ultimately diagnosed with pancreatic cancer. Patients with single duct dilation, especially such patients without any evidence of chronic pancreatitis, also need careful follow-up since the possibility of pancreatic malignancy, including adenocarcinoma and intraductal papillary mucinous tumors, is still high. PMID:17461473

  1. Magnetic Resonance (MR) Cholangiopancreatography Demonstration of the Cystic Duct Entering the Right Hepatic Duct

    PubMed Central

    D’Angelo, Tommaso; Racchiusa, Sergio; Mazziotti, Silvio; Cicero, Giuseppe

    2017-01-01

    Patient: Female, 51 Final Diagnosis: Cystic duct draining into the right hepatic biliary duct Symptoms: Recurrent abdominal pain Medication: — Clinical Procedure: MR-cholangiopancreatography Specialty: Radiology Objective: Congenital defects/diseases Background: MR cholangiopancreatography is widely performed before laparoscopic cholecystectomy to rule out choledocholithiasis and to avoid iatrogenic injuries that may be related to the high frequency of anatomical variations of the biliary tree. Although most of these variants have already been demonstrated surgically and by endoscopic retrograde cholangiopancreatography and CT cholangiography, there are no references in which MR cholangiopancreatography has shown a cystic duct draining into the right hepatic biliary duct. Case Report: A 51-year-old woman with a history of recurrent abdominal pain underwent an abdominal ultrasound in an outside center, which revealed gallbladder cholelithiasis. In this patient, an MR cholangiopancreatography was performed and the laboratory data were obtained. Laboratory findings showed only a mild increase of cholestasis. MRCP did not reveal significant dilatation of intra- or extrahepatic biliary ducts, while the cystic duct showed an atypical insertion, draining directly into the right hepatic duct. Conclusions: To avoid unintentional bile duct injuries, MRCP evaluation of the biliary anatomy is particularly important for pre-operative evaluation of patients undergoing laparoscopic cholecystectomy. In particular, in the case we describe, the right hepatic duct might have been mistaken for the cystic duct, with potentially severe surgical complications and clinical consequences. PMID:28275221

  2. Characterization of the secondary flow in hexagonal ducts

    NASA Astrophysics Data System (ADS)

    Marin, O.; Vinuesa, R.; Obabko, A. V.; Schlatter, P.

    2016-12-01

    In this work we report the results of DNSs and LESs of the turbulent flow through hexagonal ducts at friction Reynolds numbers based on centerplane wall shear and duct half-height Reτ,c ≃ 180, 360, and 550. The evolution of the Fanning friction factor f with Re is in very good agreement with experimental measurements. A significant disagreement between the DNS and previous RANS simulations was found in the prediction of the in-plane velocity, and is explained through the inability of the RANS model to properly reproduce the secondary flow present in the hexagon. The kinetic energy of the secondary flow integrated over the cross-sectional area yz decreases with Re in the hexagon, whereas it remains constant with Re in square ducts at comparable Reynolds numbers. Close connection between the values of Reynolds stress u w ¯ on the horizontal wall close to the corner and the interaction of bursting events between the horizontal and inclined walls is found. This interaction leads to the formation of the secondary flow, and is less frequent in the hexagon as Re increases due to the 120∘ aperture of its vertex, whereas in the square duct the 90∘ corner leads to the same level of interaction with increasing Re. Analysis of turbulence statistics at the centerplane and the azimuthal variance of the mean flow and the fluctuations shows a close connection between hexagonal ducts and pipe flows, since the hexagon exhibits near-axisymmetric conditions up to a distance of around 0.15DH measured from its center. Spanwise distributions of wall-shear stress show that in square ducts the 90∘ corner sets the location of a high-speed streak at a distance zv+≃50 from it, whereas in hexagons the 120∘ aperture leads to a shorter distance of zv+≃38 . At these locations the root mean square of the wall-shear stresses exhibits an inflection point, which further shows the connections between the near-wall structures and the large-scale motions in the outer flow.

  3. Characterization of the secondary flow in hexagonal ducts

    SciTech Connect

    Marin, O.; Vinuesa, R.; Obabko, A. V.; Schlatter, P.

    2016-12-06

    In this work we report the results of DNSs and LESs of the turbulent flow through hexagonal ducts at friction Reynolds numbers based on centerplane wall shear and duct half-height Reτ,c ≃ 180, 360, and 550. The evolution of the Fanning friction factor f with Re is in very good agreement with experimental measurements. A significant disagreement between the DNS and previous RANS simulations was found in the prediction of the in-plane velocity, and is explained through the inability of the RANS model to properly reproduce the secondary flow present in the hexagon. The kinetic energy of the secondary flow integrated over the cross-sectional area < K >yz decreases with Re in the hexagon, whereas it remains constant with Re in square ducts at comparable Reynolds numbers. Close connection between the values of Reynolds stress uw¯ on the horizontal wall close to the corner and the interaction of bursting events between the horizontal and inclined walls is found. This interaction leads to the formation of the secondary flow, and is less frequent in the hexagon as Re increases due to the 120° aperture of its vertex, whereas in the square duct the 90° corner leads to the same level of interaction with increasing Re. Analysis of turbulence statistics at the centerplane and the azimuthal variance of the mean flow and the fluctuations shows a close connection between hexagonal ducts and pipe flows, since the hexagon exhibits near-axisymmetric conditions up to a distance of around 0.15DH measured from its center. Spanwise distributions of wall-shear stress show that in square ducts the 90° corner sets the location of a high-speed streak at a distance z+v≃50 from it, whereas in hexagons the 120° aperture leads to a shorter distance of z+v≃38. Finally, at these locations the root mean square of the wall-shear stresses exhibits an inflection point, which

  4. Characterization of the secondary flow in hexagonal ducts

    DOE PAGES

    Marin, O.; Vinuesa, R.; Obabko, A. V.; ...

    2016-12-06

    In this work we report the results of DNSs and LESs of the turbulent flow through hexagonal ducts at friction Reynolds numbers based on centerplane wall shear and duct half-height Reτ,c ≃ 180, 360, and 550. The evolution of the Fanning friction factor f with Re is in very good agreement with experimental measurements. A significant disagreement between the DNS and previous RANS simulations was found in the prediction of the in-plane velocity, and is explained through the inability of the RANS model to properly reproduce the secondary flow present in the hexagon. The kinetic energy of the secondary flowmore » integrated over the cross-sectional area < K >yz decreases with Re in the hexagon, whereas it remains constant with Re in square ducts at comparable Reynolds numbers. Close connection between the values of Reynolds stress uw¯ on the horizontal wall close to the corner and the interaction of bursting events between the horizontal and inclined walls is found. This interaction leads to the formation of the secondary flow, and is less frequent in the hexagon as Re increases due to the 120° aperture of its vertex, whereas in the square duct the 90° corner leads to the same level of interaction with increasing Re. Analysis of turbulence statistics at the centerplane and the azimuthal variance of the mean flow and the fluctuations shows a close connection between hexagonal ducts and pipe flows, since the hexagon exhibits near-axisymmetric conditions up to a distance of around 0.15DH measured from its center. Spanwise distributions of wall-shear stress show that in square ducts the 90° corner sets the location of a high-speed streak at a distance z+v≃50 from it, whereas in hexagons the 120° aperture leads to a shorter distance of z+v≃38. Finally, at these locations the root mean square of the wall-shear stresses exhibits an inflection point, which further shows the connections between the near-wall structures and the large-scale motions in the outer flow.« less

  5. The role of microphysical processes on the mesoscale simulation over the complex terrain, the Himalayas

    NASA Astrophysics Data System (ADS)

    Shrestha, R. K.; Gallagher, M. W.; Connolly, P.

    2010-12-01

    The objective of this study is to evaluate the impact of the four different cloud microphysical schemes (WSM3, WSM6, Morrison double moment and Lin scheme) within the Weather Research and Forecasting model (WRF), as part of simulations of mesoscale weather systems across complex terrain in the Nepalese Himalayas. The Himalayas is characterized by a complex and rugged topography, with altitudes varying e.g. 70m in Southeastern Nepal, to the highest peak of the world, 8850m (Mt. Everest), and which extends from West to East covering many South and Central Asian countries: Afghanistan, Pakistan, China, India, Nepal, Bhutan, and Myanmar. Circulation in such a complex environment is complicated due to obstruction of flows by mountain ranges which in turn have wide ranging effects on cloud and rain formation and distribution. Monsoon rain is intrinsically linked to people’s daily life across the South Asia since more than 80% people depend on agriculture and majority of the agricultural systems are rainfall dependent. Modeling of the key microphysical process in this complex terrain provides insight into the general understanding of the processes and their spatial patterns, however there are many uncertainties in general. These uncertainties are even more pronounced when such models are applied to the complex terrain characteristic of the Himalayas. Numerical experiments are designed using the WRF model, with three nested domains (27, 9 and 3 km grid spacing). The performance of the four categories of microphysical schemes is examined in model experiments for (i) monsoon onset, (ii) monsoon decay and (iii) winter rainfall. The simulated results are compared with limited observed meteorological parameters such as rainfall, temperature, wind speed and wind direction, from ground-based meteorological stations situated within the high resolution (3km x 3km) domain. Results show that a) Simulated rainfall is very sensitive to the chosen microphysical scheme with rainfall

  6. URDME: a modular framework for stochastic simulation of reaction-transport processes in complex geometries

    PubMed Central

    2012-01-01

    Background Experiments in silico using stochastic reaction-diffusion models have emerged as an important tool in molecular systems biology. Designing computational software for such applications poses several challenges. Firstly, realistic lattice-based modeling for biological applications requires a consistent way of handling complex geometries, including curved inner- and outer boundaries. Secondly, spatiotemporal stochastic simulations are computationally expensive due to the fast time scales of individual reaction- and diffusion events when compared to the biological phenomena of actual interest. We therefore argue that simulation software needs to be both computationally efficient, employing sophisticated algorithms, yet in the same time flexible in order to meet present and future needs of increasingly complex biological modeling. Results We have developed URDME, a flexible software framework for general stochastic reaction-transport modeling and simulation. URDME uses Unstructured triangular and tetrahedral meshes to resolve general geometries, and relies on the Reaction-Diffusion Master Equation formalism to model the processes under study. An interface to a mature geometry and mesh handling external software (Comsol Multiphysics) provides for a stable and interactive environment for model construction. The core simulation routines are logically separated from the model building interface and written in a low-level language for computational efficiency. The connection to the geometry handling software is realized via a Matlab interface which facilitates script computing, data management, and post-processing. For practitioners, the software therefore behaves much as an interactive Matlab toolbox. At the same time, it is possible to modify and extend URDME with newly developed simulation routines. Since the overall design effectively hides the complexity of managing the geometry and meshes, this means that newly developed methods may be tested in a realistic

  7. URDME: a modular framework for stochastic simulation of reaction-transport processes in complex geometries.

    PubMed

    Drawert, Brian; Engblom, Stefan; Hellander, Andreas

    2012-06-22

    Experiments in silico using stochastic reaction-diffusion models have emerged as an important tool in molecular systems biology. Designing computational software for such applications poses several challenges. Firstly, realistic lattice-based modeling for biological applications requires a consistent way of handling complex geometries, including curved inner- and outer boundaries. Secondly, spatiotemporal stochastic simulations are computationally expensive due to the fast time scales of individual reaction- and diffusion events when compared to the biological phenomena of actual interest. We therefore argue that simulation software needs to be both computationally efficient, employing sophisticated algorithms, yet in the same time flexible in order to meet present and future needs of increasingly complex biological modeling. We have developed URDME, a flexible software framework for general stochastic reaction-transport modeling and simulation. URDME uses Unstructured triangular and tetrahedral meshes to resolve general geometries, and relies on the Reaction-Diffusion Master Equation formalism to model the processes under study. An interface to a mature geometry and mesh handling external software (Comsol Multiphysics) provides for a stable and interactive environment for model construction. The core simulation routines are logically separated from the model building interface and written in a low-level language for computational efficiency. The connection to the geometry handling software is realized via a Matlab interface which facilitates script computing, data management, and post-processing. For practitioners, the software therefore behaves much as an interactive Matlab toolbox. At the same time, it is possible to modify and extend URDME with newly developed simulation routines. Since the overall design effectively hides the complexity of managing the geometry and meshes, this means that newly developed methods may be tested in a realistic setting already at

  8. Atomic Simulation of Complex DNA DSBs and the Interactions with the Ku70/80 Heterodimer

    NASA Technical Reports Server (NTRS)

    Hu, Shaowen; Cucinotta, Francis A.

    2011-01-01

    DNA double strand breaks (DSBs) induced by ionizing radiation (IR) usually contain modified bases such as 8-oxo-7,8-dihydroguanine (8-oxoG) and thymine glycol, apurinic/apyrimidinic (AP) sites, 2-deoxyribonolactone, or single-strand breaks (SSBs). The presence of such lesions in close proximity to the DSB terminus makes the DNA nicks more difficult to repair and rejoin than endogenously induced simple DSBs, and as such a major determinant of the biological effects of high linear energy transfer (LET) radiation as encountered in space travel. In this study we conducted molecular dynamics simulations on a series of DNA duplexes with various complex lesions of 8-oxoG and AP sites, in an effort to investigate the effects of such lesions to the structural integrity and stability of DNA after insulted by IR. We also simulated the interaction of such complex DSBs with the Ku70/80 heterodimer, the first protein in mammalian cells to embark the non-homologous end joining (NHEJ) DNA repair pathway. The results indicate, compared to DNA with simple DSBs, the complex lesions can enhance the hydrogen bonds opening rate at the DNA terminus, and increase the mobility of the whole duplex, thus they present more deleterious effects to the genome integrity if not captured and repaired promptly in cells. Simulations also demonstrate the binding of Ku drastically reduces structural disruption and flexibility caused by the complex lesions, and the interactions of Ku with complex DSBs have a different potential energy landscape from the bound structure with simple DSB. In all complex DSBs systems, the binding of DSB terminus with Ku70 is softened while the binding of the middle duplex with Ku80 is tightened. This energy shift may help the Ku protein to secure at the DSB terminus for a longer time, so that other end processing factors or repair pathways can proceed at the lesions before NHEJ repair process starts. These atomic simulations may provide valuable new insight into the

  9. Direct dynamics simulation of dissociation of the [CH3--I--OH]- ion-molecule complex.

    PubMed

    Xie, Jing; McClellan, Miranda; Sun, Rui; Kohale, Swapnil C; Govind, Niranjan; Hase, William L

    2015-02-05

    Direct dynamics simulations were used to study dissociation of the [CH3--I--OH](-) complex ion, which was observed in a previous study of the OH(-) + CH3I gas phase reaction ( J. Phys. Chem. A 2013 , 117 , 7162 ). Restricted B97-1 simulations were performed to study dissociation at 65, 75, and 100 kcal/mol and the [CH3--I--OH](-) ion dissociated exponentially, in accord with RRKM theory. For these energies the major dissociation products are CH3I + OH(-), CH2I(-) + H2O, and CH3OH + I(-). Unrestricted B97-1 and restricted and unrestricted CAM-B3LYP simulations were also performed at 100 kcal/mol to compare with the restricted B97-1 results. The {CH3I + OH(-)}:{CH2I(-) + H2O}:{CH3OH + I(-)} product ratio is 0.72:0.15:0.13, 0.81:0.05:0.14, 0.71:0.19:0.10, and 0.83:0.13:0.04 for the restricted B97-1, unrestricted B97-1, restricted CAM-B3LYP, and unrestricted CAM-B3LYP simulations, respectively. Other product channels found are CH2 + I(-) + H2O, CH2 + I(-)(H2O), CH4 + IO(-), CH3(-) + IOH, and CH3 + IOH(-). The CH3(-) + IOH singlet products are only given by the restricted B97-1 simulation and the lower energy CH3 + IOH(-) doublet products are only formed by the unrestricted B97-1 simulation. Also studied were the direct and indirect atomic-level mechanisms for forming CH3I + OH(-), CH2I(-) + H2O, and CH3OH + I(-). The majority of CH3I + OH(-) were formed through a direct mechanism. For both CH2I(-) + H2O and CH3OH + I(-), the direct mechanism is overall more important than the indirect mechanisms, with the roundabout like mechanism the most important indirect mechanism at high excitation energies. Mechanism comparisons between the B97-1 and CAM-B3LYP simulations showed that formation of the CH3OH---I(-) complex is favored for the B97-1 simulations, whereas formation of the HO(-)---HCH2I complex is favored for the CAM-B3LYP simulations. The unrestricted simulations give a higher percentage of indirect mechanisms than the restricted simulations. The possible role of the

  10. Direct Dynamics Simulation of Dissociation of the [CH3--I--OH]- Ion-Molecule Complex

    SciTech Connect

    Xie, Jing; McClellan, Miranda; Sun, Rui; Kohale, Swapnil C.; Govind, Niranjan; Hase, William L.

    2015-02-05

    Direct dynamics simulations were used to study dissociation of the [CH3--I--OH]- complex ion, which was observed in a previous study of the OH- + CH3I gas phase reaction (J. Phys. Chem. A 2013, 117, 7162). Restricted B97-1 simulations were performed to study dissociation at 65, 75 and 100 kcal/mol and the [CH3--I--OH]- ion dissociated exponentially, in accord with RRKM theory. For these energies the major dissociation products are CH3I + OH-, CH2I- + H2O, and CH3OH + I-. Unrestricted B97-1 and restricted and unrestricted CAM-B3LYP simulations were also performed at 100 kcal/mol to compare with the restricted B97-1 results. The {CH3I + OH-}:{CH2I- + H2O}:{CH3OH + I-} product ratio is 0.72 : 0.15 : 0.13, 0.81 : 0.05 : 0.14, 0.71 : 0.19 : 0.10 , and 0.83 : 0.13 : 0.04 for the restricted B97-1, unrestricted B97-1, restricted CAM-B3LYP, and unrestricted CAM-B3LYP simulations, respectively. Other product channels found are CH2 + I- + H2O, CH2 + I-(H2O), CH4 + IO-, CH3 - + IOH, and CH3 + IOH-. The CH3 - + IOH singlet products are only given by the restricted B97-1 simulation and the lower energy CH3 + IOH- doublet products are only formed by the unrestricted B97-1 simulation. Also studied were the direct and indirect atomic-level mechanisms for forming CH3I + OH-, CH2I- + H2O, and CH3OH + I-. The majority of CH3I + OH- were formed through a direct mechanism. For both CH2I- + H2O and CH3OH + I-, the direct mechanism is overall more important than the indirect mechanisms, with the round-about like mechanism the most important indirect mechanism at high excitation energies. Mechanism comparisons between the B97-1 and CAM-B3LYP simulations showed that formation of the CH3OH---I- complex is favored for the B97-1 simulations, while formation of the HO----HCH2I complex is favored for the CAM-B3LYP simulations. The unrestricted simulations give a higher percentage of indirect mechanisms than the restricted simulations. The possible role of the self-interaction error in the

  11. How to solve complex problems in foundry plants - future of casting simulation -

    NASA Astrophysics Data System (ADS)

    Ohnaka, I.

    2015-06-01

    Although the computer simulation of casting has progressed dramatically over the last decades, there are still many challenges and problems. This paper discusses how to solve complex engineering problems in foundry plants and what we should do in the future, in particular, for casting simulation. First, problem solving procedures including application of computer simulation are demonstrated and various difficulties are pointed-out exemplifying mainly porosity defects in sand castings of spheroidal graphite cast irons. Next, looking back conventional scientific and engineering research to understand casting phenomena, challenges and problems are discussed from problem solving view point, followed by discussion on the issues we should challenge such as how to integrate huge amount of dispersed knowledge in various disciplines, differentiation of science-oriented and engineering-oriented models, professional ethics, how to handle fluctuating materials, initial and boundary conditions, error accumulation, simulation codes as black-box, etc. Finally some suggestions are made on how to challenge the issues such as promotion of research on the simulation based on the science- oriented model and publication of reliable data of casting phenomena in complicated-shaped castings including reconsideration of the evaluation system.

  12. Simulation in undergraduate paediatric nursing curriculum: Evaluation of a complex 'ward for a day' education program.

    PubMed

    Gamble, Andree S

    2017-03-01

    Simulation in health education has been shown to increase confidence, psychomotor and professional skills, and thus positively impact on student preparedness for clinical placement. It is recognised as a valuable tool to expose and engage students in realistic patient care encounters without the potential to cause patient harm. Although inherent challenges exist in the development and implementation of simulation, variability in clinical placement time, availability and quality dictates the need to provide students with learning opportunities they may otherwise not experience. With this, and a myriad of other issues providing the impetus for improved clinical preparation, 28 final semester undergraduate nursing students in a paediatric nursing course were involved in an extended multi-scenario simulated clinical shift prior to clinical placement. The simulation focussed on a complex ward experience, giving students the opportunity to demonstrate a variety of psychomotor skills, decision making, leadership, team work and other professional attributes integral for successful transition into the clinical arena. Evaluation data were collected at 3 intermittent points; post-simulation, post clinical placement, and 3 months after commencing employment as a Registered Nurse. Quantitative and qualitative analysis suggested positive impacts on critical nursing concepts and psychomotor skills resulted for participants in both clinical placement and beyond into the first months of employment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Efficient Constant-Time Complexity Algorithm for Stochastic Simulation of Large Reaction Networks.

    PubMed

    Thanh, Vo Hong; Zunino, Roberto; Priami, Corrado

    2017-01-01

    Exact stochastic simulation is an indispensable tool for a quantitative study of biochemical reaction networks. The simulation realizes the time evolution of the model by randomly choosing a reaction to fire and update the system state according to a probability that is proportional to the reaction propensity. Two computationally expensive tasks in simulating large biochemical networks are the selection of next reaction firings and the update of reaction propensities due to state changes. We present in this work a new exact algorithm to optimize both of these simulation bottlenecks. Our algorithm employs the composition-rejection on the propensity bounds of reactions to select the next reaction firing. The selection of next reaction firings is independent of the number reactions while the update of propensities is skipped and performed only when necessary. It therefore provides a favorable scaling for the computational complexity in simulating large reaction networks. We benchmark our new algorithm with the state of the art algorithms available in literature to demonstrate its applicability and efficiency.

  14. Simulation of metal-ligand self-assembly into spherical complex M6L8.

    PubMed

    Yoneya, Makoto; Yamaguchi, Tomohiko; Sato, Sota; Fujita, Makoto

    2012-09-05

    Molecular dynamics simulations were performed to study the self-assembly of a spherical complex through metal-ligand coordination interactions. M(6)L(8), a nanosphere with six palladium ions and eight pyridine-capped tridentate ligands, was selected as a target system. We successfully observed the spontaneous formation of spherical shaped M(6)L(8) cages over the course of our simulations, starting from random initial placement of the metals and ligands. To simulate spontaneous coordination bond formations and breaks, the cationic dummy atom method was employed to model nonbonded metal-ligand interactions. A coarse-grained solvent model was used to fill the gap between the time scale of the supramolecular self-assembly and that accessible by common molecular dynamics simulation. The simulated formation process occurred in the distinct three-stage (assembly, evolution, fixation) process that is well correlated with the experimental results. We found that the difference of the lifetime (or the ligand exchange rate) between the smaller-sized incomplete clusters and the completed M(6)L(8) nanospheres is crucially important in their supramolecular self-assembly.

  15. Simulation of dispersion in moderately complex terrain—Part B. The higher order closure dispersion model

    NASA Astrophysics Data System (ADS)

    Enger, Leif

    A three-dimensional higher-order closure dispersion model is presented. The model is used to simulate dispersion from point sources in complex terrain. The model uses mean and turbulence quantities simulated with the fluid dynamic model presented in Part A to simulate dispersion in a polar coordinate system with its origin in the point source. Different turbulent length scales are used for the vertical and horizontal fluxes. Simulation results are compared with data from tracer experiments performed in southern Sweden, the Vänersborg-Trollhättan region. The tracer experiments were performed during convective atmospheric conditions as well as during very stable conditions. The geographical area has terrain features that exert forcing on the meso-γ-scale. Within the area there is a relatively flat agricultural area, forested hills, a river valley and an extended lake area. The terrain height relief is typically 80 m. The simulations with the dispersion model performed in the Vänersborg-Trollhättan region show good agreement with measured data in the region for convective atmospheric conditions as well as for very stable conditions.

  16. Simulation of tracer dispersion from elevated and surface releases in complex terrain

    NASA Astrophysics Data System (ADS)

    Hernández, J. F.; Cremades, L.; Baldasano, J. M.

    A new version of an advanced mesoscale dispersion modeling system for simulating passive air pollutant dispersion in the real atmospheric planetary boundary layer (PBL), is presented. The system comprises a diagnostic mass-consistent meteorological model and a Lagrangian particle dispersion model (LADISMO). The former version of LADISMO, developed according to Zannetti (Air pollution modelling, 1990), was based on the Monte Carlo technique and included calculation of higher-order moments of vertical random forcing for convective conditions. Its ability to simulate complex flow dispersion has been stated in a previous paper (Hernández et al. 1995, Atmospheric Environment, 29A, 1331-1341). The new version follows Thomson's scheme (1984, Q. Jl Roy. Met. Soc.110, 1107-1120). It is also based on Langevin equation and follows the ideas given by Brusasca et al. (1992, Atmospheric Environment26A, 707-723) and Anfossi et al. (1992, Nuovo Cemento 15c, 139-158). The model is used to simulate the dispersion and predict the ground level concentration (g.l.c.) of a tracer (SF 6) released from both an elevated source ( case a) and a ground level source ( case b) in a highly complex mountainous terrain during neutral and synoptically dominated conditions ( case a) and light and apparently stable conditions ( case b). The last case is considered as being a specially difficult task to simulate. In fact, few works have reported situations with valley drainage flows in complex terrains and real stable atmospheric conditions with weak winds. The model assumes that nearly calm situations associated to strong stability and air stagnation, make the lowest layers of PBL poorly diffusive (Brusasca et al., 1992, Atmospheric Environment26A, 707-723). Model results are verified against experimental data from Guardo-90 tracer experiments, an intensive field campaign conducted in the Carrion river valley (Northern Spain) to study atmospheric diffusion within a steep walled valley in mountainous

  17. Atomic level insights into realistic molecular models of dendrimer-drug complexes through MD simulations

    NASA Astrophysics Data System (ADS)

    Jain, Vaibhav; Maiti, Prabal K.; Bharatam, Prasad V.

    2016-09-01

    Computational studies performed on dendrimer-drug complexes usually consider 1:1 stoichiometry, which is far from reality, since in experiments more number of drug molecules get encapsulated inside a dendrimer. In the present study, molecular dynamic (MD) simulations were implemented to characterize the more realistic molecular models of dendrimer-drug complexes (1:n stoichiometry) in order to understand the effect of high drug loading on the structural properties and also to unveil the atomistic level details. For this purpose, possible inclusion complexes of model drug Nateglinide (Ntg) (antidiabetic, belongs to Biopharmaceutics Classification System class II) with amine- and acetyl-terminated G4 poly(amidoamine) (G4 PAMAM(NH2) and G4 PAMAM(Ac)) dendrimers at neutral and low pH conditions are explored in this work. MD simulation analysis on dendrimer-drug complexes revealed that the drug encapsulation efficiency of G4 PAMAM(NH2) and G4 PAMAM(Ac) dendrimers at neutral pH was 6 and 5, respectively, while at low pH it was 12 and 13, respectively. Center-of-mass distance analysis showed that most of the drug molecules are located in the interior hydrophobic pockets of G4 PAMAM(NH2) at both the pH; while in the case of G4 PAMAM(Ac), most of them are distributed near to the surface at neutral pH and in the interior hydrophobic pockets at low pH. Structural properties such as radius of gyration, shape, radial density distribution, and solvent accessible surface area of dendrimer-drug complexes were also assessed and compared with that of the drug unloaded dendrimers. Further, binding energy calculations using molecular mechanics Poisson-Boltzmann surface area approach revealed that the location of drug molecules in the dendrimer is not the decisive factor for the higher and lower binding affinity of the complex, but the charged state of dendrimer and drug, intermolecular interactions, pH-induced conformational changes, and surface groups of dendrimer do play an

  18. How much complexity is needed in global model organic aerosol simulations?

    NASA Astrophysics Data System (ADS)

    Tsigaridis, K.; Daskalakis, N.; Kanakidou, M.

    2014-12-01

    The skill in simulating the global atmospheric distribution and fate of organic aerosols (OA) of thirty-one global chemistry/transport and general circulation models of various complexities will be presented. Significant differences between models are identified in the magnitude of primary emissions, secondary OA (SOA) formation, the number of OA species used, the complexity of OA parameterizations (gas-particle partitioning, chemical aging, multiphase chemistry, aerosol microphysics), and the OA physical, chemical and optical properties. The diversity of the global OA simulation results has increased since earlier AeroCom experiments, mainly due to the increasing complexity of the SOA parameterization in models, and the implementation of new, highly uncertain, OA sources. Diversity of over an order of magnitude exists in the modeled vertical distribution of OA concentrations pointing to uncertainties in the parameterization of the semi-volatile character of OA and its temperature dependence, as well as OA long-range transport. Fine aerosol organic carbon (OC) and OA observations from continuous monitoring networks and individual field campaigns have been used for model evaluation. Τhe combined model/measurements analysis suggests the existence of increased OA levels during summer due to biogenic SOA formation over large areas of the USA that can be of the same order of magnitude as the POA, even at urban locations, and contribute to the observed urban seasonal pattern. The global models are able to simulate the high secondary character of OA observed in the atmosphere as a result of SOA formation and of POA aging, although, the amount of OA present in the atmosphere remains largely underestimated. The models skill with increasing model complexity with regard to OC or OA mass concentration will be presented and thoroughly discussed. This work is part of AeroCom phase II.

  19. Duct Remediation Program: Remediation operations and implementation

    SciTech Connect

    Beckman, T.d.; Davis, M.M.; Karas, T.M.

    1992-11-01

    Plutonium holdup material has accumulated in the process ventilation duct systems at Rocky Flats. Non-Destructive Assay (NDA) measurements identified ducts containing this material. The Defense Nuclear Facility Safety Board and the Department of Energy established the criteria for remediation of these ducts. A remediation team was assembled and a program plan created. This program plan included activities such as fissile material accumulation identification, criticality safety assessments, radiation dose determinations, facility safety evaluations, prevention of future accumulation, and removal of holdup material. Several operational considerations had to be evaluated in determining completion of remediation.

  20. Magnetospheric whistler ducts observed by ISIS satellites

    NASA Technical Reports Server (NTRS)

    Ondoh, T.

    1976-01-01

    The latitudinal width of the magnetospheric whistler duct has been estimated by the first and final invariant latitudes of whistler echoes and the conservation of the magnetic flux for the centered dipole field, using 105 whistler echoes in ISIS VLF data received at Kashima, Japan for 1972-1973. The latitudinal distribution of whistler duct occurrence shows a maximum at invariant latitudes of 40-45 degrees near the maximum occurrence latitude of ground whistlers. The radial width of magnetospheric whistler duct in the geomagnetically equatorial plane increases with invariant latitude of the geomagnetic flux tube in which whistlers propagate.

  1. Paraurethral Skene's duct cyst in a newborn

    PubMed Central

    Moralioğlu, Serdar; Bosnalı, Oktav; Celayir, Ayşenur Cerrah; Şahin, Ceyhan

    2013-01-01

    Paraurethral or Skene's duct cysts are rare causes of interlabial masses in neonates. The diagnosis of Skene's duct cysts in the neonatal period is based on its location, in relation to the urethra, and the demonstration of transitional epithelium in the cyst wall. The distinguishing features of paraurethral cysts are the displacement of urethral meatus by the mass and a cyst containing milky fluid. Thus, we report a case of a Skene's duct cyst in a newborn which was treated by incision and drainage. PMID:24049387

  2. Magnetospheric whistler ducts observed by ISIS satellites

    NASA Technical Reports Server (NTRS)

    Ondoh, T.

    1976-01-01

    The latitudinal width of the magnetospheric whistler duct has been estimated by the first and final invariant latitudes of whistler echoes and the conservation of the magnetic flux for the centered dipole field, using 105 whistler echoes in ISIS VLF data received at Kashima, Japan for 1972-1973. The latitudinal distribution of whistler duct occurrence shows a maximum at invariant latitudes of 40-45 degrees near the maximum occurrence latitude of ground whistlers. The radial width of magnetospheric whistler duct in the geomagnetically equatorial plane increases with invariant latitude of the geomagnetic flux tube in which whistlers propagate.

  3. Nurse training with simulation: an innovative approach to teach complex microsurgery patient care.

    PubMed

    Flurry, Mitchell; Brooke, Sebastian; Micholetti, Brett; Natoli, Noel; Moyer, Kurtis; Mnich, Stephanie; Potochny, John

    2012-10-01

    Simulation has become an integral part of education at all levels within the medical field. The ability to allow personnel to practice and learn in a safe and controlled environment makes it a valuable tool for initial training and continued competence verification. An area of specific interest to the reconstructive microsurgeon is assurance that the nursing staff has adequate training and experience to provide optimum care for microsurgery patients. Plastic surgeons in institutions where few microsurgeries are performed face challenges teaching nurses how to care for these complex patients. Because no standard exists to educate microsurgery nurses, learning often happens by chance on-the-job encounters. Outcomes, therefore, may be affected by poor handoffs between inexperienced personnel. Our objective is to create a course that augments such random clinical experience and teaches the knowledge and skills necessary for successful microsurgery through simulated patient scenarios. Quality care reviews at our institution served as the foundation to develop an accredited nursing course providing clinical training for the care of microsurgery patients. The course combined lectures on microsurgery, pharmacology, and flap monitoring as well as simulated operating room, surgical intensive care unit, postanesthesia care unit, Trauma Bay, and Floor scenarios. Evaluation of participants included precourse examination, postcourse examination, and a 6-month follow-up. Average test scores were 72% precourse and 92% postcourse. Educational value, effectiveness of lectures and simulation, and overall course quality was rated very high or high by 86% of respondents; 0% respondents rated it as low. Six-month follow-up test score average was 88%. Learning to care for microsurgery patients should not be left to chance patient encounters on the job. Simulation provides a safe, reproducible, and controlled clinical experience. Our results show that simulation is a highly rated and

  4. An evaluation of a complex simulated scenario with final year undergraduate children's nursing students.

    PubMed

    Davies, Jane; Nathan, Martina; Clarke, Dave

    2012-01-01

    The last decade has witnessed the emergence of simulation as a useful, but sometimes challenging teaching methodology. This is supported by a number of sources of evidence, which focus strongly upon student evaluation of the learning experience. The challenges are equally worth consideration. These include issues such as the commissioning of space, staff expertise in resourcing and creating a situation which is as close to real practice as possible. It is against this backdrop, following a number of years developing innovative clinical simulation at Cardiff University; children's nursing students were exposed to a complex simulated clinical shift. The activities included: managing the clinical area; the transfer of a sick child; managing a medication error; subsequent discussion with the parents; and prioritising and organising care. The use of role-play was utilised throughout, to create a realistic experience and the simulation activity took place in two settings to enable the transfer from one area to another. The simulation experience was undertaken at the end of the third year undergraduate program by three cohorts of students (n = 41). Following the experience, data were collected through a post-simulation de-briefing and a Likert style questionnaire, enabling the collection of qualitative and quantitative data concerned with the student's experience of the simulation. Overwhelmingly, the results showed that this was a positive experience for the students, demonstrating a number of perceived improvements in the application of their clinical skills. These included: development of specific management skills; enhanced confidence; development of self-awareness; and the transferability of skills to practice. Students also demonstrated strong agreement in terms of the realism of the experience.

  5. Kinetic Energy Recovery from the Chimney Flue Gases Using Ducted Turbine System

    NASA Astrophysics Data System (ADS)

    Mann, Harjeet S.; Singh, Pradeep K.

    2017-03-01

    An innovative idea of extracting kinetic energy from man-made wind resources using ducted turbine system for on-site power generation is introduced in this paper. A horizontal axis ducted turbine is attached to the top of the chimney to harness the kinetic energy of flue gases for producing electricity. The turbine system is positioned beyond the chimney outlet, to avoid any negative impact on the chimney performance. The convergent-divergent duct causes increase in the flue gas velocity and hence enhances the performance of the turbine. It also acts as a safety cover to the energy recovery system. The results from the CFD based simulation analysis indicate that significant power 34 kW can be harnessed from the chimney exhaust. The effect of airfoils NACA4412 and NACA4416 and the diffuser angle on the power extraction by the energy recovery system using a 6-bladed ducted turbine has been studied with the CFD simulation. It is observed that the average flue gas velocity in the duct section at the throat is approximately twice that of the inlet velocity, whereas maximum velocity achieved is 2.6 times the inlet velocity. The simulated results show that about power may be extracted from the chimney flue gases of 660 MW power plant. The system can be retrofitted to existing chimneys of thermal power plants, refineries and other industries.

  6. Kinetic Energy Recovery from the Chimney Flue Gases Using Ducted Turbine System

    NASA Astrophysics Data System (ADS)

    Mann, Harjeet S.; Singh, Pradeep K.

    2017-03-01

    An innovative idea of extracting kinetic energy from man-made wind resources using ducted turbine system for on-site power generation is introduced in this paper. A horizontal axis ducted turbine is attached to the top of the chimney to harness the kinetic energy of flue gases for producing electricity. The turbine system is positioned beyond the chimney outlet, to avoid any negative impact on the chimney performance. The convergent-divergent duct causes increase in the flue gas velocity and hence enhances the performance of the turbine. It also acts as a safety cover to the energy recovery system. The results from the CFD based simulation analysis indicate that significant power 34 kW can be harnessed from the chimney exhaust. The effect of airfoils NACA4412 and NACA4416 and the diffuser angle on the power extraction by the energy recovery system using a 6-bladed ducted turbine has been studied with the CFD simulation. It is observed that the average flue gas velocity in the duct section at the throat is approximately twice that of the inlet velocity, whereas maximum velocity achieved is 2.6 times the inlet velocity. The simulated results show that about power may be extracted from the chimney flue gases of 660 MW power plant. The system can be retrofitted to existing chimneys of thermal power plants, refineries and other industries.

  7. Suppression of broadband noise radiated by a low-speed fan in a duct.

    PubMed

    Huang, L; Ma, X; Feng, L G

    2010-07-01

    Attenuation of ducted fan noise remains a technical challenge in the low frequency range as traditional duct lining becomes ineffective. This study proposes a reactive method to suppress the sound radiation from an axial-flow fan. The method is particularly effective in the low frequency region and covers a broad band. Its effect is derived from two mechanisms. One is the reduction in the confining effects of duct walls when the duct radius is increased; the other is the acoustic interference between the direct radiation from the fan and reflections by the duct junctions. This interference is always destructive for axial dipoles when the frequency approaches zero. This performance differs from normal passive control methods, which become totally ineffective toward zero frequency. An approximate plane-wave theory explains the essential physics of the method, and its quantitative prediction is found to agree well with a full numerical simulation using a spectral method of Chebyshev collocation. The latter is validated by experiment using an axial-flow fan in a duct of finite length. Broadband noise reduction is achieved while the flow speed is kept unchanged. Practical difficulties of implementation for a fan with high pressure increase are discussed.

  8. Simulating the Complex Cell Design of Trypanosoma brucei and Its Motility

    PubMed Central

    Alizadehrad, Davod; Krüger, Timothy; Engstler, Markus; Stark, Holger

    2015-01-01

    The flagellate Trypanosoma brucei, which causes the sleeping sickness when infecting a mammalian host, goes through an intricate life cycle. It has a rather complex propulsion mechanism and swims in diverse microenvironments. These continuously exert selective pressure, to which the trypanosome adjusts with its architecture and behavior. As a result, the trypanosome assumes a diversity of complex morphotypes during its life cycle. However, although cell biology has detailed form and function of most of them, experimental data on the dynamic behavior and development of most morphotypes is lacking. Here we show that simulation science can predict intermediate cell designs by conducting specific and controlled modifications of an accurate, nature-inspired cell model, which we developed using information from live cell analyses. The cell models account for several important characteristics of the real trypanosomal morphotypes, such as the geometry and elastic properties of the cell body, and their swimming mechanism using an eukaryotic flagellum. We introduce an elastic network model for the cell body, including bending rigidity and simulate swimming in a fluid environment, using the mesoscale simulation technique called multi-particle collision dynamics. The in silico trypanosome of the bloodstream form displays the characteristic in vivo rotational and translational motility pattern that is crucial for survival and virulence in the vertebrate host. Moreover, our model accurately simulates the trypanosome's tumbling and backward motion. We show that the distinctive course of the attached flagellum around the cell body is one important aspect to produce the observed swimming behavior in a viscous fluid, and also required to reach the maximal swimming velocity. Changing details of the flagellar attachment generates less efficient swimmers. We also simulate different morphotypes that occur during the parasite's development in the tsetse fly, and predict a flagellar

  9. A preliminary study on the application of remotely sensed SST in locating evaporation duct height

    NASA Astrophysics Data System (ADS)

    Baig, Muhammad Hasan Ali; Wang, Zhenhui; Zhang, Lifu; Yang, Lu

    2012-10-01

    Refractivity happens due to stratification in the lower boundary layer over oceans due to variability of moisture, temperature, wind and sea surface temperature which collectively may lead to generate evaporation duct. The evaporation duct has a significant impact on the spread of electromagnetic waves in the atmosphere over oceans both from the meteorological and military point of view. This ducting sometimes supports normal propagation of radar signals and sometimes may cause distortion and attenuation of signals depending on the height of evaporation duct. This leads to over-estimation and under-estimation of rainfall by weather radar meteorologically and for other targets militarily. The aim of this study was not only to locate evaporation duct height but also to check the efficiency of Weather Research and Forecasting Model (WRF) and Babin's model so that results may be used in applying correction measures for precise identification of targets by radar. In this study by utilizing the high vertical resolution of WRF for the simulation of different meteorological parameters, the Babin's method was used for calculating the evaporation duct height over South China Sea for the two months, April and July. Very clear duct heights were calculated at different areas over sea in different time domains. Study reveals that maximum height existed in the month of April although July was rich with different EDHs in different regions in contrast to April. It was found that in most of the cases EDH was higher or maximum when relative humidity was comparatively lower and air temperature and wind speed were comparatively higher. This study paves a way for futuristic study of evaporation duct monitoring and forecasting by assimilation of remote sensing data especially through that of Geostationary satellites by incorporating verification measures from radar.

  10. Scattering of acoustic duct modes by axial liner splices

    NASA Astrophysics Data System (ADS)

    Tam, Christopher K. W.; Ju, Hongbin; Chien, Eugene W.

    2008-03-01

    Recent engine test data and results of computational analysis show that the engine inlet acoustic liner splices have a significant impact on aircraft flight noise certification and cabin noise levels. The phenomenon of scattering of acoustic duct modes by axial liner splices is investigated. Previous studies, invariably, follow the frequency-domain approach. The present study, however, uses the time-domain approach. It is demonstrated that time-domain computation yields results that are in close agreement with frequency-domain results. The scattering phenomenon under consideration is very complex. This study concentrates on the effects of four parameters. They are the width of the splices, the frequency of the incident duct mode, the number of splices and the length of splices. Based on the computed results, the conditions under which scattered wave modes would significantly increase the intensity of transmitted waves are identified. It is also found that surface scattering by liner splices has the tendency to distribute energy equally to all the cut-on scattered azimuthal modes. On the other hand, for each scattered azimuthal mode, the high-order cut-on radial mode, generally, has the highest intensity. Moreover, scattering by liner splices is a local phenomenon. It is confined primarily to an area of the duct adjacent to the junction between the hard wall near the fan face and the spliced liner.

  11. Examination of Duct Physiology in the Human Mammary Gland

    PubMed Central

    Mills, Dixie; Gomberawalla, Ameer; Gordon, Eva J.; Tondre, Julie; Nejad, Mitra; Nguyen, Tinh; Pogoda, Janice M.; Rao, Jianyu; Chatterton, Robert; Henning, Susanne; Love, Susan M.

    2016-01-01

    Background The human breast comprise several ductal systems, or lobes, which contain a small amount of fluid containing cells, hormones, proteins and metabolites. The complex physiology of these ducts is likely a contributing factor to the development of breast cancer, especially given that the vast majority of breast cancers begin in a single lobular unit. Methods We examined the levels of total protein, progesterone, estradiol, estrone sulfate, dehydroepiandrosterone sulfate, and macrophages in ductal fluid samples obtained from 3 ducts each in 78 women, sampled twice over a 6 month period. Samples were processed for both cytological and molecular analysis. Intraclass correlation coefficients and mixed models were utilized to identify significant data. Results We found that the levels of these ductal fluid components were generally uncorrelated among ducts within a single breast and over time, suggesting that each lobe within the breast has a distinct physiology. However, we also found that estradiol was more correlated in women who were nulliparous or produced nipple aspirate fluid. Conclusions Our results provide evidence that the microenvironment of any given lobular unit is unique to that individual unit, findings that may provide clues about the initiation and development of ductal carcinomas. PMID:27073976

  12. Molecular Simulation of Copper Complexation by a Model of Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Newton, A. G.; Sposito, G.

    2008-12-01

    The coadsorption of cations and organic matter to mineral surfaces has been proposed as a mechanism to stabilize soil organic carbon and explain enhanced cation adsorption in soils. Spectroscopic investigations of coadsorption in copper (Cu)-organic ligand-mineral systems have provided conclusive evidence that ternary surface complexes do occur in instances where the simple organic ligand possesses a minimal number of homogeneous binding sites. Although the results of many experimental and spectroscopic investigations of ternary systems with dissolved organic matter (DOM) suggest that ternary surface complexes may be present, unambiguous conclusions cannot be drawn due to the nature of DOM and the heterogeneity of DOM binding sites. Molecular simulations of ternary surface complexes are powerful tools that can be used in the interpretation of spectroscopic data from these experimental systems. Molecular simulations of Cu-DOM coadsorption at mineral surfaces require a model of Cu-DOM that adequately reproduces the physical-chemical behavior of natural Cu-DOM. The Cu-saturated Schulten DOM molecule, whose charge from deprotonated carboxyl groups was balanced by Cu2+ ions, was modeled using the COMPASS forcefield and energy minimization and molecular dynamics algorithms. Compared to previous simulations of Na- and Ca-saturated Schulten DOM, the Cu-DOM was more compact and spherical, as demonstrated by the decreases in the surface area, surface area: volume ratio, porosity, and radius of gyration and by an increase in the volume. The Cu-DOM complex is more polar than Ca-DOM and less polar than Na-DOM, as indicated by the dipole moment and extent of hydrogen bonding. The Cu2+ ion coordination environment contains an average of four oxygen atoms at 2.04 Å from the metal center. These first shell atoms are primarily water and carboxylate oxygen, although oxygen atoms from carbonyl, phenolic, and esters functionalities as well as nitrogen groups are also present. The DOM

  13. In Defense of Simulating Complex and Tragic Historical Episodes: A Measured Response to the Outcry over a New England Slavery Simulation

    ERIC Educational Resources Information Center

    Wright-Maley, Cory

    2014-01-01

    A slavery simulation that took place as part of a field trip for students of a Hartford junior high academy led a father to file a human rights suit against the school district, and for one official to comment that simulations of complex and tragic human phenomena have "no place in an educational system." In light of these conclusions,…

  14. Traumatic resin ducts as indicators of bark beetle outbreaks

    Treesearch

    R. Justin DeRose; Matthew F. Bekker; James N. Long

    2017-01-01

    The formation of traumatic resin ducts (TRDs) represents an important induced defense in woody plants that enhances oleoresin production and flow in response to environmental perturbations. In some genera (Pinus), resin ducts are copious and conspicuous; however, in others (Picea), resin ducts are relatively rare. The occurrence and strength of resin ducts, in...

  15. Simulation of complex visibilities in synthetic aperture imaging radiometry with the aid of GPU

    NASA Astrophysics Data System (ADS)

    Anterrieu, Eric; Cabot, François

    2013-10-01

    The basic observables of an imaging interferometer by aperture synthesis are the complex visibilities. Under some conditions, they can be simulated with reference to the Van Cittert-Zernike theorem. However, owing to the underlying assumptions some important effects that may alter them cannot be taken into account. This paper is devoted to the numerical simulation of complex visibilities with very few assumptions. The emission is modelled with random short wave trains. Each wave is transported to the antennae, transmitted to the receivers and the corresponding signals are cross-correlated. From emission to correlation, perturbating effects can be introduced. However, owing to the amount of calculations to be performed, massive parallel architectures like that found in GPU are required. To illustrate this modelling, numerical simulations are carried out in the L-band in reference to the SMOS-next project led by the french space agency. The results are discussed and compared with the estimates provided by the Van Cittert-Zernike theorem.

  16. Large Eddy Simulation of Reacting Multiphase Flows in Complex Combustor Geometries

    NASA Astrophysics Data System (ADS)

    Apte, S.; Mahesh, K.; Iaccarino, G.; Constantinescu, G.; Ham, F.; Moin, P.

    2003-11-01

    We have developed a massively parallel computational tool (CDP) for large-eddy simulation (LES) of reacting multiphase flows in complex combustor geometries. A co-located, finite-volume scheme on unstructured grids is used to solve the low-Mach number equations for gaseous phase. The liquid phase is modeled by tracking a large number of computational particles in a Lagrangian framework with models for inter-phase mass, momentum, and energy transport. Complex physical phenomena of liquid atomization, droplet deformation, drag, and evaporation are captured using advanced subgrid models. A flamelet/progress variable appraoch by Pierce & Moin (2001) is used to compute non-premixed turbulent combustion. A series of validation studies in coaxial and realistic gas-turbine combustor geometries are performed to test the predictive capability of the solver. Specifically, simulations of non-premixed combustion, particle-laden swirling flows, droplet vaporization in coaxial-jet combustors and spray breakup in realistic injectors are performed and good agreement with avialable experimental data is obtained. This tool is now being used to perform simulations of turbulent spray flames in a realistic Pratt & Whitney gas-turbine combustion chamber using Department of Energy's computational resources under the Accelerated Strategic Computing Initiative (ASCI) project.

  17. Godunov method for multiprobe cryosurgery simulation with complex-shaped tumors

    NASA Astrophysics Data System (ADS)

    Tarwidi, D.

    2016-02-01

    Cryosurgery is a technique to eradicate abnormal biological tissues by freezing. The objective of cryosurgery is to maximize cryoinjury of tumor tissues while at the same time minimizing cryoinjury to the surrounding healthy tissues. The location and number of cryoprobes are important factors to obtain optimal cryosurgery in complex-shaped tumors. This paper presents multiprobe cryosurgery simulation with optimal cryoprobes location in target region. Bubble packing method is used to obtain optimal cryoprobes layout. We consider mathematical model of freezing by bioheat transfer equation in solid (frozen tissue), liquid (unfrozen tissue), and mushy region. This model is referred to as Stefan problem where the location of moving solid-mushy or mushy-liquid interface is not known and it is as part of the solution. We reformulate the bioheat equations into single enthalpy (energy) equation which can resolve the moving boundary between two phases. The first-order of Godunov method is adopted to obtain numerical solution of the phase change problem. This method is easily applied since we only solve one governing equation regardless the moving interface between two phases. For demonstration purposes, multiprobe cryosurgery for lung cancer case with complex geometry is simulated and interpreted. The numerical simulation for three to ten cryoprobes configuration shows that the nine cryoprobes layout has the smallest total defect in this case. The numerical results provide an important information for cryosurgeon before conducting effective cryosurgery protocol.

  18. Investigation of the interfacial tension of complex coacervates using field-theoretic simulations

    NASA Astrophysics Data System (ADS)

    Riggleman, Robert A.; Kumar, Rajeev; Fredrickson, Glenn H.

    2012-01-01

    Complex coacervation, a liquid-liquid phase separation that occurs when two oppositely charged polyelectrolytes are mixed in a solution, has the potential to be exploited for many emerging applications including wet adhesives and drug delivery vehicles. The ultra-low interfacial tension of coacervate systems against water is critical for such applications, and it would be advantageous if molecular models could be used to characterize how various system properties (e.g., salt concentration) affect the interfacial tension. In this article we use field-theoretic simulations to characterize the interfacial tension between a complex coacervate and its supernatant. After demonstrating that our model is free of ultraviolet divergences (calculated properties converge as the collocation grid is refined), we develop two methods for calculating the interfacial tension from field-theoretic simulations. One method relies on the mechanical interpretation of the interfacial tension as the interfacial pressure, and the second method estimates the change in free energy as the area between the two phases is changed. These are the first calculations of the interfacial tension from full field-theoretic simulation of which we are aware, and both the magnitude and scaling behaviors of our calculated interfacial tension agree with recent experiments.

  19. Investigation of the interfacial tension of complex coacervates using field-theoretic simulations

    SciTech Connect

    Kumar, Rajeev

    2012-01-01

    Complex coacervation, a liquid-liquid phase separation that occurs when two oppositely charged polyelectrolytes are mixed in a solution, has the potential to be exploited for many emerging applications including wet adhesives and drug delivery vehicles. The ultra-low interfacial tension of coacervate systems against water is critical for such applications, and it would be advantageous if molecular models could be used to characterize how various system properties (e.g., salt concentration) affect the interfacial tension. In this article we use field-theoretic simulations to characterize the interfacial tension between a complex coacervate and its supernatant. After demonstrating that our model is free of ultraviolet divergences (calculated properties converge as the collocation grid is refined), we develop two methods for calculating the interfacial tension from field-theoretic simulations. One method relies on the mechanical interpretation of the interfacial tension as the interfacial pressure, and the second method estimates the change in free energy as the area between the two phases is changed. These are the first calculations of the interfacial tension from full field theoretic simulation of which we are aware, and both the magnitude and scaling behaviors of our calculated interfacial tension agree with recent experiments.

  20. Investigation of the interfacial tension of complex coacervates using field-theoretic simulations.

    PubMed

    Riggleman, Robert A; Kumar, Rajeev; Fredrickson, Glenn H

    2012-01-14

    Complex coacervation, a liquid-liquid phase separation that occurs when two oppositely charged polyelectrolytes are mixed in a solution, has the potential to be exploited for many emerging applications including wet adhesives and drug delivery vehicles. The ultra-low interfacial tension of coacervate systems against water is critical for such applications, and it would be advantageous if molecular models could be used to characterize how various system properties (e.g., salt concentration) affect the interfacial tension. In this article we use field-theoretic simulations to characterize the interfacial tension between a complex coacervate and its supernatant. After demonstrating that our model is free of ultraviolet divergences (calculated properties converge as the collocation grid is refined), we develop two methods for calculating the interfacial tension from field-theoretic simulations. One method relies on the mechanical interpretation of the interfacial tension as the interfacial pressure, and the second method estimates the change in free energy as the area between the two phases is changed. These are the first calculations of the interfacial tension from full field-theoretic simulation of which we are aware, and both the magnitude and scaling behaviors of our calculated interfacial tension agree with recent experiments.