Low frequency oscillatory flow in a rotating curved pipe

Institute of Scientific and Technical Information of China (English)

陈华军; 章本照; 苏霄燕

2003-01-01

The low frequency oscillatory flow in a rotating curved pipe was studied by using the method of bi-parameter perturbation. Perturbation solutions up to the second order were obtained and the effects of rotationon the low frequency oscillatory flow were examined in detail, The results indicated that there exists evident difference between the low frequency oscillatory flow in a rotating curved pipe and in a curved pipe without ro-tation. During a period, four secondary vortexes may exist on the circular cross-section and the distribution of axial velocity and wall shear stress are related to the ratio of the Coriolis foree to centrifugal foree and the axial pressure gradient.

Low frequency oscillatory flow in a rotating curved pipe

Institute of Scientific and Technical Information of China (English)

陈华军; 章本照; 苏霄燕

2003-01-01

The low frequency oscillatory flow in a rotating curved pipe was studied by using the method of bi-parameter perturbation. Perturbation solutions up to the second order were obtained and the effects of rotation on the low frequency oscillatory flow were examined in detail. The results indicated that there exists evident difference between the low frequency oscillatory flow in a rotating curved pipe and in a curved pipe without rotation. During a period, four secondary vortexes may exist on the circular cross-section and the distribution of axial velocity and wall shear stress are related to the ratio of the Coriolis force to centrifugal force and the axial pressure gradient.

Stress strain flow curves for Cu-OFP

International Nuclear Information System (INIS)

Sandstroem, Rolf; Hallgren, Josefin

2009-04-01

Stress strain curves of oxygen free copper alloyed with phosphorus Cu-OFP have been determined in compression and tension. The compression tests were performed at room temperature for strain rates between 10 -5 and 10 -3 1/s. The tests in tension covered the temperature range 20 to 175 deg C for strain rates between 10 -7 and 5x10 -3 1/s. The results in compression and tension were close for similar strain rates. A model for stress strain curves has been formulated using basic dislocation mechanisms. The model has been set up in such a way that fitting of parameters to the curves is avoided. By using a fundamental creep model as a basis a direct relation to creep data has been established. The maximum engineering flow stress in tension is related to the creep stress giving the same strain rate. The model reproduces the measured flow curves as function of temperature and strain rate in the investigated interval. The model is suitable to use in finite-element computations of structures in Cu-OFP

Specification of Nonmonotonic Reasoning.

NARCIS (Netherlands)

Engelfriet, J.; Treur, J.

2000-01-01

Two levels of description of nonmonotonic reasoning are distinguished. For these levels semantical formalizations are given. The first Level is defined semantically by the notion of belief state frame, the second Level by the notion of reasoning frame. We introduce two specification languages to

Specification of Nonmonotonic Reasoning

NARCIS (Netherlands)

Engelfriet, J.; Treur, J.

1996-01-01

Two levels of description of nonmonotonic reasoning are distinguished. For these levels semantical formalizations are given. The first level is defined semantically by the notion of belief state frame, the second level by the notion of reasoning frame. We introduce two specification languages to

Relationship between spontaneous expiratory flow-volume curve pattern and air-flow obstruction in elderly COPD patients.

Science.gov (United States)

Nozoe, Masafumi; Mase, Kyoshi; Murakami, Shigefumi; Okada, Makoto; Ogino, Tomoyuki; Matsushita, Kazuhiro; Takashima, Sachie; Yamamoto, Noriyasu; Fukuda, Yoshihiro; Domen, Kazuhisa

2013-10-01

Assessment of the degree of air-flow obstruction is important for determining the treatment strategy in COPD patients. However, in some elderly COPD patients, measuring FVC is impossible because of cognitive dysfunction or severe dyspnea. In such patients a simple test of airways obstruction requiring only a short run of tidal breathing would be useful. We studied whether the spontaneous expiratory flow-volume (SEFV) curve pattern reflects the degree of air-flow obstruction in elderly COPD patients. In 34 elderly subjects (mean ± SD age 80 ± 7 y) with stable COPD (percent-of-predicted FEV(1) 39.0 ± 18.5%), and 12 age-matched healthy subjects, we measured FVC and recorded flow-volume curves during quiet breathing. We studied the SEFV curve patterns (concavity/convexity), spirometry results, breathing patterns, and demographics. The SEFV curve concavity/convexity prediction accuracy was examined by calculating the receiver operating characteristic curves, cutoff values, area under the curve, sensitivity, and specificity. Fourteen subjects with COPD had a concave SEFV curve. All the healthy subjects had convex SEFV curves. The COPD subjects who had concave SEFV curves often had very severe airway obstruction. The percent-of-predicted FEV(1)% (32.4%) was the most powerful SEFV curve concavity predictor (area under the curve 0.92, 95% CI 0.83-1.00), and had the highest sensitivity (0.93) and specificity (0.88). Concavity of the SEFV curve obtained during tidal breathing may be a useful test for determining the presence of very severe obstruction in elderly patients unable to perform a satisfactory FVC maneuver.

Secondary flow structures under stent-induced perturbations for cardiovascular flow in a curved artery model

International Nuclear Information System (INIS)

Glenn, Autumn L.; Bulusu, Kartik V.; Shu Fangjun; Plesniak, Michael W.

2012-01-01

Secondary flows within curved arteries with unsteady forcing result from amplified centrifugal instabilities and are expected to be driven by the rapid accelerations and decelerations inherent in physiological waveforms. These secondary flows may also affect the function of curved arteries through pro-atherogenic wall shear stresses, platelet residence time and other vascular response mechanisms. Planar PIV measurements were performed under multi-harmonic non-zero-mean and physiological carotid artery waveforms at various locations in a rigid bent-pipe curved artery model. Results revealed symmetric counter-rotating vortex pairs that developed during the acceleration phases of both multi-harmonic and physiological waveforms. An idealized stent model was placed upstream of the bend, which initiated flow perturbations under physiological inflow conditions. Changes in the secondary flow structures were observed during the systolic deceleration phase (t/T ≈ 0.20–0.50). Proper Orthogonal Decomposition (POD) analysis of the flow morphologies under unsteady conditions indicated similarities in the coherent secondary-flow structures and correlation with phase-averaged velocity fields. A regime map was created that characterizes the kaleidoscope of vortical secondary flows with multiple vortex pairs and interesting secondary flow morphologies. This regime map in the curved artery model was created by plotting the secondary Reynolds number against another dimensionless acceleration-based parameter marking numbered regions of vortex pairs.

Secondary flow structures under stent-induced perturbations for cardiovascular flow in a curved artery model

Energy Technology Data Exchange (ETDEWEB)

Glenn, Autumn L.; Bulusu, Kartik V. [Department of Mechanical and Aerospace Engineering, George Washington University, 801 22nd Street, NW., Washington, DC 20052 (United States); Shu Fangjun [Department of Mechanical and Aerospace Engineering, New Mexico State University, MSC 3450, P.O. Box 30001, Las Cruces, NM 88003-8001 (United States); Plesniak, Michael W., E-mail: plesniak@gwu.edu [Department of Mechanical and Aerospace Engineering, George Washington University, 801 22nd Street, NW., Washington, DC 20052 (United States)

2012-06-15

Secondary flows within curved arteries with unsteady forcing result from amplified centrifugal instabilities and are expected to be driven by the rapid accelerations and decelerations inherent in physiological waveforms. These secondary flows may also affect the function of curved arteries through pro-atherogenic wall shear stresses, platelet residence time and other vascular response mechanisms. Planar PIV measurements were performed under multi-harmonic non-zero-mean and physiological carotid artery waveforms at various locations in a rigid bent-pipe curved artery model. Results revealed symmetric counter-rotating vortex pairs that developed during the acceleration phases of both multi-harmonic and physiological waveforms. An idealized stent model was placed upstream of the bend, which initiated flow perturbations under physiological inflow conditions. Changes in the secondary flow structures were observed during the systolic deceleration phase (t/T Almost-Equal-To 0.20-0.50). Proper Orthogonal Decomposition (POD) analysis of the flow morphologies under unsteady conditions indicated similarities in the coherent secondary-flow structures and correlation with phase-averaged velocity fields. A regime map was created that characterizes the kaleidoscope of vortical secondary flows with multiple vortex pairs and interesting secondary flow morphologies. This regime map in the curved artery model was created by plotting the secondary Reynolds number against another dimensionless acceleration-based parameter marking numbered regions of vortex pairs.

Regularization of Nonmonotone Variational Inequalities

International Nuclear Information System (INIS)

Konnov, Igor V.; Ali, M.S.S.; Mazurkevich, E.O.

2006-01-01

In this paper we extend the Tikhonov-Browder regularization scheme from monotone to rather a general class of nonmonotone multivalued variational inequalities. We show that their convergence conditions hold for some classes of perfectly and nonperfectly competitive economic equilibrium problems

Applications of artificial neutral network for the prediction of flow boiling curves

International Nuclear Information System (INIS)

Su Guanghui; Jia Dounan; Fukuda, Kenji; Morita, Koji; Pidduck, Mark; Matsumoto, Tatsuya; Akasaka, Ryo

2002-01-01

An artificial neural network (ANN) was applied successfully to predict flow boiling curves. The databases used in the analysis are from the 1960's, including 1,305 data points which cover these parameter ranges: pressure P=100-1,000 kPa, mass flow rate G=40-500 kg/m 2 ·s, inlet subcooling ΔT sub =0-35degC, wall superheat ΔT w =10-300degC and heat flux Q=20-8,000 kW/m 2 . The proposed methodology allows us to achieve accurate results, thus it is suitable for the processing of the boiling curve data. The effects of the main parameters on flow boiling curves were analyzed using the ANN. The heat flux increases with increasing inlet subcooling for all heat transfer modes. Mass flow rate has no significant effects on nucleate boiling curves. The transition boiling and film boiling heat fluxes will increase with an increase in the mass flow rate. Pressure plays a predominant role and improves heat transfer in all boiling regions except the film boiling region. There are slight differences between the steady and the transient boiling curves in all boiling regions except the nucleate region. The transient boiling curve lies below the corresponding steady boiling curve. (author)

An analytical solution for Dean flow in curved ducts with rectangular cross section

Science.gov (United States)

Norouzi, M.; Biglari, N.

2013-05-01

In this paper, a full analytical solution for incompressible flow inside the curved ducts with rectangular cross-section is presented for the first time. The perturbation method is applied to solve the governing equations and curvature ratio is considered as the perturbation parameter. The previous perturbation solutions are usually restricted to the flow in curved circular or annular pipes related to the overly complex form of solutions or singularity situation for flow in curved ducts with non-circular shapes of cross section. This issue specifies the importance of analytical studies in the field of Dean flow inside the non-circular ducts. In this study, the main flow velocity, stream function of lateral velocities (secondary flows), and flow resistance ratio in rectangular curved ducts are obtained analytically. The effect of duct curvature and aspect ratio on flow field is investigated as well. Moreover, it is important to mention that the current analytical solution is able to simulate the Taylor-Görtler and Dean vortices (vortices in stable and unstable situations) in curved channels.

Prediction of flow boiling curves based on artificial neural network

International Nuclear Information System (INIS)

Wu Junmei; Xi'an Jiaotong Univ., Xi'an; Su Guanghui

2007-01-01

The effects of the main system parameters on flow boiling curves were analyzed by using an artificial neural network (ANN) based on the database selected from the 1960s. The input parameters of the ANN are system pressure, mass flow rate, inlet subcooling, wall superheat and steady/transition boiling, and the output parameter is heat flux. The results obtained by the ANN show that the heat flux increases with increasing inlet sub cooling for all heat transfer modes. Mass flow rate has no significant effects on nucleate boiling curves. The transition boiling and film boiling heat fluxes will increase with an increase of mass flow rate. The pressure plays a predominant role and improves heat transfer in whole boiling regions except film boiling. There are slight differences between the steady and the transient boiling curves in all boiling regions except the nucleate one. (authors)

AAAI Workshop on Nonmonotonic Reasoning

OpenAIRE

Etherington, David

1985-01-01

On October 17-19 1984 a workshop on non-monotonic reasoning was held at Mohonk Mountain House, outside New Paltz, New York. The workshop was organized by Raymond Reiter and Bonnie Webber, and was sponsored by the Association for the Advancement of Artificial Intelligence.

The holographic RG flow in a field theory on a curved background

International Nuclear Information System (INIS)

Cardoso, Gabriel Lopes; Luest, Dieter

2002-01-01

As shown by Freedman, Gubser, Pilch and Warner, the RG flow in N=4 super-Yang-Mills theory broken to an N=1 theory by the addition of a mass term can be described in terms of a supersymmetric domain wall solution in five-dimensional N=8 gauged supergravity. The FGPW flow is an example of a holographic RG flow in a field theory on a flat background. Here we put the field theory studied by Freedman, Gubser, Pilch and Warner on a curved AdS 4 background, and we construct the supersymmetric domain wall solution which describes the RG flow in this field theory. This solution is a curved (non-Ricci flat) domain wall solution. This example demonstrates that holographic RG flows in supersymmetric field theories on a curved AdS 4 background can be described in terms of curved supersymmetric domain wall solutions. (author)

Flow of viscous fluid along an exponentially stretching curved surface

Directory of Open Access Journals (Sweden)

N.F. Okechi

Full Text Available In this paper, we present the boundary layer analysis of flow induced by rapidly stretching curved surface with exponential velocity. The governing boundary value problem is reduced into self-similar form using a new similarity transformation. The resulting equations are solved numerically using shooting and Runge-Kutta methods. The numerical results depicts that the fluid velocity as well as the skin friction coefficient increases with the surface curvature, similar trend is also observed for the pressure. The dimensionless wall shear stress defined for this problem is greater than that of a linearly stretching curved surface, but becomes comparably less for a surface stretching with a power-law velocity. In addition, the result for the plane surface is a special case of this study when the radius of curvature of the surface is sufficiently large. The numerical investigations presented in terms of the graphs are interpreted with the help of underlying physics of the fluid flow and the consequences arising from the curved geometry. Keywords: Boundary layer flow, Curved surface, Exponential stretching, Curvature

Estimating daily flow duration curves from monthly streamflow data

CSIR Research Space (South Africa)

Smakhtin, VU

2000-01-01

Full Text Available The paper describes two techniques by which to establish 1-day (1d) flow duration curves at an ungauged site where only a simulated or calculated monthly flow time series is available. Both methods employ the straightforward relationships between...

Numerical Investigation on Fluid Flow in a 90-Degree Curved Pipe with Large Curvature Ratio

Directory of Open Access Journals (Sweden)

Yan Wang

2015-01-01

Full Text Available In order to understand the mechanism of fluid flows in curved pipes, a large number of theoretical and experimental researches have been performed. As a critical parameter of curved pipe, the curvature ratio δ has received much attention, but most of the values of δ are very small (δ<0.1 or relatively small (δ≤0.5. As a preliminary study and simulation this research studied the fluid flow in a 90-degree curved pipe of large curvature ratio. The Detached Eddy Simulation (DES turbulence model was employed to investigate the fluid flows at the Reynolds number range from 5000 to 20000. After validation of the numerical strategy, the pressure and velocity distribution, pressure drop, fluid flow, and secondary flow along the curved pipe were illustrated. The results show that the fluid flow in a curved pipe with large curvature ratio seems to be unlike that in a curved pipe with small curvature ratio. Large curvature ratio makes the internal flow more complicated; thus, the flow patterns, the separation region, and the oscillatory flow are different.

Regionalisation of low flow frequency curves for the Peninsular Malaysia

Science.gov (United States)

Mamun, Abdullah A.; Hashim, Alias; Daoud, Jamal I.

2010-02-01

SUMMARYRegional maps and equations for the magnitude and frequency of 1, 7 and 30-day low flows were derived and are presented in this paper. The river gauging stations of neighbouring catchments that produced similar low flow frequency curves were grouped together. As such, the Peninsular Malaysia was divided into seven low flow regions. Regional equations were developed using the multivariate regression technique. An empirical relationship was developed for mean annual minimum flow as a function of catchment area, mean annual rainfall and mean annual evaporation. The regional equations exhibited good coefficient of determination ( R2 > 0.90). Three low flow frequency curves showing the low, mean and high limits for each region were proposed based on a graphical best-fit technique. Knowing the catchment area, mean annual rainfall and evaporation in the region, design low flows of different durations can be easily estimated for the ungauged catchments. This procedure is expected to overcome the problem of data unavailability in estimating low flows in the Peninsular Malaysia.

Flow in curved ducts of varying cross-section

Science.gov (United States)

Sotiropoulos, F.; Patel, V. C.

1992-07-01

Two numerical methods for solving the incompressible Navier-Stokes equations are compared with each other by applying them to calculate laminar and turbulent flows through curved ducts of regular cross-section. Detailed comparisons, between the computed solutions and experimental data, are carried out in order to validate the two methods and to identify their relative merits and disadvantages. Based on the conclusions of this comparative study a numerical method is developed for simulating viscous flows through curved ducts of varying cross-sections. The proposed method is capable of simulating the near-wall turbulence using fine computational meshes across the sublayer in conjunction with a two-layer k-epsilon model. Numerical solutions are obtained for: (1) a straight transition duct geometry, and (2) a hydroturbine draft-tube configuration at model scale Reynolds number for various inlet swirl intensities. The report also provides a detailed literature survey that summarizes all the experimental and computational work in the area of duct flows.

Blood flow in curved pipe with radiative heat transfer

International Nuclear Information System (INIS)

Ogulu, A.; Bestman, A.R.

1992-03-01

Blood flow in a curved pipe such as the aorta is modelled in this study. The aorta is modelled as a curved pipe of slowly varying cross-section. Asymptotic series expansions about a small parameter δ, which is a measure of the curvature ratio is employed to obtain the velocity and temperature distributions. The study simulates the effect of radio-frequency heating, for instance during physiotherapy, on the flow of blood in the cardiovascular system assuming an external constant pressure gradient; and our results agree very well with results obtained by Pedley. (author). 9 refs, 2 figs

Modeling non-monotonic properties under propositional argumentation

Science.gov (United States)

Wang, Geng; Lin, Zuoquan

2013-03-01

In the field of knowledge representation, argumentation is usually considered as an abstract framework for nonclassical logic. In this paper, however, we'd like to present a propositional argumentation framework, which can be used to closer simulate a real-world argumentation. We thereby argue that under a dialectical argumentation game, we can allow non-monotonic reasoning even under classical logic. We introduce two methods together for gaining nonmonotonicity, one by giving plausibility for arguments, the other by adding "exceptions" which is similar to defaults. Furthermore, we will give out an alternative definition for propositional argumentation using argumentative models, which is highly related to the previous reasoning method, but with a simple algorithm for calculation.

Nonmonotonic magnetoresistance of a two-dimensional viscous electron-hole fluid in a confined geometry

Science.gov (United States)

Alekseev, P. S.; Dmitriev, A. P.; Gornyi, I. V.; Kachorovskii, V. Yu.; Narozhny, B. N.; Titov, M.

2018-02-01

Ultrapure conductors may exhibit hydrodynamic transport where the collective motion of charge carriers resembles the flow of a viscous fluid. In a confined geometry (e.g., in ultra-high-quality nanostructures), the electronic fluid assumes a Poiseuille-type flow. Applying an external magnetic field tends to diminish viscous effects leading to large negative magnetoresistance. In two-component systems near charge neutrality, the hydrodynamic flow of charge carriers is strongly affected by the mutual friction between the two constituents. At low fields, the magnetoresistance is negative, however, at high fields the interplay between electron-hole scattering, recombination, and viscosity results in a dramatic change of the flow profile: the magnetoresistance changes its sign and eventually becomes linear in very high fields. This nonmonotonic magnetoresistance can be used as a fingerprint to detect viscous flow in two-component conducting systems.

Obliquely Propagating Non-Monotonic Double Layer in a Hot Magnetized Plasma

International Nuclear Information System (INIS)

Kim, T.H.; Kim, S.S.; Hwang, J.H.; Kim, H.Y.

2005-01-01

Obliquely propagating non-monotonic double layer is investigated in a hot magnetized plasma, which consists of a positively charged hot ion fluid and trapped, as well as free electrons. A model equation (modified Korteweg-de Vries equation) is derived by the usual reductive perturbation method from a set of basic hydrodynamic equations. A time stationary obliquely propagating non-monotonic double layer solution is obtained in a hot magnetized-plasma. This solution is an analytic extension of the monotonic double layer and the solitary hole. The effects of obliqueness, external magnetic field and ion temperature on the properties of the non-monotonic double layer are discussed

A discrete wavelet spectrum approach for identifying non-monotonic trends in hydroclimate data

Science.gov (United States)

Sang, Yan-Fang; Sun, Fubao; Singh, Vijay P.; Xie, Ping; Sun, Jian

2018-01-01

The hydroclimatic process is changing non-monotonically and identifying its trends is a great challenge. Building on the discrete wavelet transform theory, we developed a discrete wavelet spectrum (DWS) approach for identifying non-monotonic trends in hydroclimate time series and evaluating their statistical significance. After validating the DWS approach using two typical synthetic time series, we examined annual temperature and potential evaporation over China from 1961-2013 and found that the DWS approach detected both the warming and the warming hiatus in temperature, and the reversed changes in potential evaporation. Further, the identified non-monotonic trends showed stable significance when the time series was longer than 30 years or so (i.e. the widely defined climate timescale). The significance of trends in potential evaporation measured at 150 stations in China, with an obvious non-monotonic trend, was underestimated and was not detected by the Mann-Kendall test. Comparatively, the DWS approach overcame the problem and detected those significant non-monotonic trends at 380 stations, which helped understand and interpret the spatiotemporal variability in the hydroclimatic process. Our results suggest that non-monotonic trends of hydroclimate time series and their significance should be carefully identified, and the DWS approach proposed has the potential for wide use in the hydrological and climate sciences.

Flow of liquid metals in curved channels under a transversely applied magnetic field, (3)

International Nuclear Information System (INIS)

Arai, Shigeki; Tomita, Yukio; Sudou, Kouzou.

1979-01-01

With the development of electromagnetic pumps in nuclear, metallurgical and casting industries, investigations of not only laminar flow but also transient and turbulent flows in magnetohydrodynamic (MHD) channels are the matters of much concern. However, it is no exaggeration to say that there was no investigation of transient and turbulent flows in curved MHD channels. In this report, the influences of Reynolds number, Hartmann number, radius of curvature and aspect ratio on the coefficient of friction in transient and turbulent flow channels are discussed. In transient flow region, the curve representing the product of the coefficient of channel friction in curved channels and Reynolds number has no clear transition point in the flow of comparatively small Hartmann number. However, as the intensity of magnetic field is increased, the curve transfers to the transition due to the effect of suppressing secondary flow, and if the magnetic field is further increased, it was found that it approached the crisis-free type transition. In turbulent flow region, the coefficient of channel friction can be expressed approximately by the empirical equation given first in this report. Also the effect of magnetic field on the turbulent flow in curved channels can be explained by using Hartmann effect, turbulence suppression effect, and the effect of suppressing secondary flow based on Lorentz's force. (Wakatsuki, Y.)

Irregular conformal block, spectral curve and flow equations

International Nuclear Information System (INIS)

Choi, Sang Kwan; Rim, Chaiho; Zhang, Hong

2016-01-01

Irregular conformal block is motivated by the Argyres-Douglas type of N=2 super conformal gauge theory. We investigate the classical/NS limit of irregular conformal block using the spectral curve on a Riemann surface with irregular punctures, which is equivalent to the loop equation of irregular matrix model. The spectral curve is reduced to the second order (Virasoro symmetry, SU(2) for the gauge theory) and third order (W_3 symmetry, SU(3)) differential equations of a polynomial with finite degree. The conformal and W symmetry generate the flow equations in the spectral curve and determine the irregular conformal block, hence the partition function of the Argyres-Douglas theory ala AGT conjecture.

Boiling curve in high quality flow boiling

International Nuclear Information System (INIS)

Shiralkar, B.S.; Hein, R.A.; Yadigaroglu, G.

1980-01-01

The post dry-out heat transfer regime of the flow boiling curve was investigated experimentally for high pressure water at high qualities. The test section was a short round tube located downstream of a hot patch created by a temperature controlled segment of tubing. Results from the experiment showed that the distance from the dryout point has a significant effect on the downstream temperatures and there was no unique boiling curve. The heat transfer coefficients measured sufficiently downstream of the dryout point could be correlated using the Heineman correlation for superheated steam, indicating that the droplet deposition effects could be neglected in this region

A discrete wavelet spectrum approach for identifying non-monotonic trends in hydroclimate data

Directory of Open Access Journals (Sweden)

Y.-F. Sang

2018-01-01

Full Text Available The hydroclimatic process is changing non-monotonically and identifying its trends is a great challenge. Building on the discrete wavelet transform theory, we developed a discrete wavelet spectrum (DWS approach for identifying non-monotonic trends in hydroclimate time series and evaluating their statistical significance. After validating the DWS approach using two typical synthetic time series, we examined annual temperature and potential evaporation over China from 1961–2013 and found that the DWS approach detected both the warming and the warming hiatus in temperature, and the reversed changes in potential evaporation. Further, the identified non-monotonic trends showed stable significance when the time series was longer than 30 years or so (i.e. the widely defined climate timescale. The significance of trends in potential evaporation measured at 150 stations in China, with an obvious non-monotonic trend, was underestimated and was not detected by the Mann–Kendall test. Comparatively, the DWS approach overcame the problem and detected those significant non-monotonic trends at 380 stations, which helped understand and interpret the spatiotemporal variability in the hydroclimatic process. Our results suggest that non-monotonic trends of hydroclimate time series and their significance should be carefully identified, and the DWS approach proposed has the potential for wide use in the hydrological and climate sciences.

Methods for estimating flow-duration curve and low-flow frequency statistics for ungaged locations on small streams in Minnesota

Science.gov (United States)

Ziegeweid, Jeffrey R.; Lorenz, David L.; Sanocki, Chris A.; Czuba, Christiana R.

2015-12-24

Knowledge of the magnitude and frequency of low flows in streams, which are flows in a stream during prolonged dry weather, is fundamental for water-supply planning and design; waste-load allocation; reservoir storage design; and maintenance of water quality and quantity for irrigation, recreation, and wildlife conservation. This report presents the results of a statewide study for which regional regression equations were developed for estimating 13 flow-duration curve statistics and 10 low-flow frequency statistics at ungaged stream locations in Minnesota. The 13 flow-duration curve statistics estimated by regression equations include the 0.0001, 0.001, 0.02, 0.05, 0.1, 0.25, 0.50, 0.75, 0.9, 0.95, 0.99, 0.999, and 0.9999 exceedance-probability quantiles. The low-flow frequency statistics include annual and seasonal (spring, summer, fall, winter) 7-day mean low flows, seasonal 30-day mean low flows, and summer 122-day mean low flows for a recurrence interval of 10 years. Estimates of the 13 flow-duration curve statistics and the 10 low-flow frequency statistics are provided for 196 U.S. Geological Survey continuous-record streamgages using streamflow data collected through September 30, 2012.

Spiral blood flows in an idealized 180-degree curved artery model

Science.gov (United States)

Bulusu, Kartik V.; Kulkarni, Varun; Plesniak, Michael W.

2017-11-01

Understanding of cardiovascular flows has been greatly advanced by the Magnetic Resonance Velocimetry (MRV) technique and its potential for three-dimensional velocity encoding in regions of anatomic interest. The MRV experiments were performed on a 180-degree curved artery model using a Newtonian blood analog fluid at the Richard M. Lucas Center at Stanford University employing a 3 Tesla General Electric (Discovery 750 MRI system) whole body scanner with an eight-channel cardiac coil. Analysis in two regions of the model-artery was performed for flow with Womersley number=4.2. In the entrance region (or straight-inlet pipe) the unsteady pressure drop per unit length, in-plane vorticity and wall shear stress for the pulsatile, carotid artery-based flow rate waveform were calculated. Along the 180-degree curved pipe (curvature ratio =1/7) the near-wall vorticity and the stretching of the particle paths in the vorticity field are visualized. The resultant flow behavior in the idealized curved artery model is associated with parameters such as Dean number and Womersley number. Additionally, using length scales corresponding to the axial and secondary flow we attempt to understand the mechanisms leading to the formation of various structures observed during the pulsatile flow cycle. Supported by GW Center for Biomimetics and Bioinspired Engineering (COBRE), MRV measurements in collaboration with Prof. John K. Eaton and, Dr. Chris Elkins at Stanford University.

POLARIZED LINE FORMATION IN NON-MONOTONIC VELOCITY FIELDS

Energy Technology Data Exchange (ETDEWEB)

Sampoorna, M.; Nagendra, K. N., E-mail: sampoorna@iiap.res.in, E-mail: knn@iiap.res.in [Indian Institute of Astrophysics, Koramangala, Bengaluru 560034 (India)

2016-12-10

For a correct interpretation of the observed spectro-polarimetric data from astrophysical objects such as the Sun, it is necessary to solve the polarized line transfer problems taking into account a realistic temperature structure, the dynamical state of the atmosphere, a realistic scattering mechanism (namely, the partial frequency redistribution—PRD), and the magnetic fields. In a recent paper, we studied the effects of monotonic vertical velocity fields on linearly polarized line profiles formed in isothermal atmospheres with and without magnetic fields. However, in general the velocity fields that prevail in dynamical atmospheres of astrophysical objects are non-monotonic. Stellar atmospheres with shocks, multi-component supernova atmospheres, and various kinds of wave motions in solar and stellar atmospheres are examples of non-monotonic velocity fields. Here we present studies on the effect of non-relativistic non-monotonic vertical velocity fields on the linearly polarized line profiles formed in semi-empirical atmospheres. We consider a two-level atom model and PRD scattering mechanism. We solve the polarized transfer equation in the comoving frame (CMF) of the fluid using a polarized accelerated lambda iteration method that has been appropriately modified for the problem at hand. We present numerical tests to validate the CMF method and also discuss the accuracy and numerical instabilities associated with it.

Effect of drag-reducing polymers on Tubing Performance Curve (TPC) in vertical gas-liquid flows

NARCIS (Netherlands)

Shoeibi Omrani, P.; Veltin, J.; Turkenburg, D.H.

2014-01-01

This paper discusses the effect of drag reducing polymers on the Tubing Performance Curve (TPC) of vertical air-water flows at near atmospheric conditions. The effect of polymer concentration, liquid and gas flow rates on the pressure drop curve (Tubing Performance Curve) was investigated

Tracer concentration curves and residence time analysis in technological flow systems. 2

International Nuclear Information System (INIS)

Pippel, W.

1976-01-01

Tracer concentration curves measured in flow systems by means of radioactive isotopes are treated as a two dimensional random process. Comparing them with the family distribution functions described in part I, it follows that only in case of ergodic behaviour of the system tracer curves can be considered as age distribution functions. The conception of ergodicity in residence time systems has been explained with the aid of a time function measurable by a special method of radioactive tracer technique and by the mean value of the residence time obtainable from this function. Furthermore, technological consequences in evaluating tracer concentration curves of real flow systems are discussed with respect to supposed ergodic or nonergodic behaviour. These considerations are of special importance for flow systems with temporary fluctuations in structure. (author)

Subtractive, divisive and non-monotonic gain control in feedforward nets linearized by noise and delays.

Science.gov (United States)

Mejias, Jorge F; Payeur, Alexandre; Selin, Erik; Maler, Leonard; Longtin, André

2014-01-01

The control of input-to-output mappings, or gain control, is one of the main strategies used by neural networks for the processing and gating of information. Using a spiking neural network model, we studied the gain control induced by a form of inhibitory feedforward circuitry-also known as "open-loop feedback"-, which has been experimentally observed in a cerebellum-like structure in weakly electric fish. We found, both analytically and numerically, that this network displays three different regimes of gain control: subtractive, divisive, and non-monotonic. Subtractive gain control was obtained when noise is very low in the network. Also, it was possible to change from divisive to non-monotonic gain control by simply modulating the strength of the feedforward inhibition, which may be achieved via long-term synaptic plasticity. The particular case of divisive gain control has been previously observed in vivo in weakly electric fish. These gain control regimes were robust to the presence of temporal delays in the inhibitory feedforward pathway, which were found to linearize the input-to-output mappings (or f-I curves) via a novel variability-increasing mechanism. Our findings highlight the feedforward-induced gain control analyzed here as a highly versatile mechanism of information gating in the brain.

Subtractive, divisive and non-monotonic gain control in feedforward nets linearized by noise and delays

Directory of Open Access Journals (Sweden)

Jorge F Mejias

2014-02-01

Full Text Available The control of input-to-output mappings, or gain control, is one of the main strategies used by neural networks for the processing and gating of information. Using a spiking neural network model, we studied the gain control induced by a form of inhibitory feedforward circuitry — also known as ’open-loop feedback’ —, which has been experimentally observed in a cerebellum-like structure in weakly electric fish. We found, both analytically and numerically, that this network displays three different regimes of gain control: subtractive, divisive, and non-monotonic. Subtractive gain control was obtained when noise is very low in the network. Also, it was possible to change from divisive to non-monotonic gain control by simply modulating the strength of the feedforward inhibition, which may be achieved via long-term synaptic plasticity. The particular case of divisive gain control has been previously observed in vivo in weakly electric fish. These gain control regimes were robust to the presence of temporal delays in the inhibitory feedforward pathway, which were found to linearize the input-to-output mappings (or f-I curves via a novel variability-increasing mechanism. Our findings highlight the feedforward-induced gain control analyzed here as a highly versatile mechanism of information gating in the brain.

Nonmonotonic belief state frames and reasoning frames

NARCIS (Netherlands)

Engelfriet, J.; Herre, H.; Treur, J.

1995-01-01

In this paper five levels of specification of nonmonotonic reasoning are distinguished. The notions of semantical frame, belief state frame and reasoning frame are introduced and used as a semantical basis for the first three levels. Moreover, the semantical connections between the levels are

Developing Turbulent Flow in Strongly Curved Passages of Square and Circular Cross-Section

Science.gov (United States)

1984-03-01

laser-velocimetry study known to us for developing tur- bulent flow in curved pipes, Enayet , et al. E113 investigated the motion in a 90* bend with Rc...flows are very similar, being De - Re (D/Rc) 1 / 2 6.8 x 104in Rowe’s bend and 2.6 x 104 in the bend of Enayet , et al., the difference in the maximum...a curved duct of square cross section. In addition to the data taken at three longitudioal stations in the curved pipe, (0 9 300, 60° and 900), Enayet

Modeling plasma flow in straight and curved solenoids

International Nuclear Information System (INIS)

Boercker, D.B.; Sanders, D.M.; Storer, J.; Falabella, S.

1991-01-01

The ''flux-tube'' model originated by Morozov is a very simple and numerically efficient method for simulating ion motion in plasma filters. In order to test its utility as a design tool, we compare the predictions of the model to recent experimental measurements of plasma flow in both straight and curved solenoids

Modelling Embedded Systems by Non-Monotonic Refinement

NARCIS (Netherlands)

Mader, Angelika H.; Marincic, J.; Wupper, H.

2008-01-01

This paper addresses the process of modelling embedded sys- tems for formal verification. We propose a modelling process built on non-monotonic refinement and a number of guidelines. The outcome of the modelling process is a model, together with a correctness argument that justifies our modelling

Nonmonotonic critical temperature in superconductor ferromagnet bilayers

NARCIS (Netherlands)

Fominov, Ya. V.; Fominov, I.V.; Chtchelkatchev, N.M.; Golubov, Alexandre Avraamovitch

2002-01-01

The critical temperature Tc of a superconductor/ferromagnet (SF) bilayer can exhibit nonmonotonic dependence on the thickness df of the F layer. SF systems have been studied for a long time; according to the experimental situation, a ¿dirty¿ limit is often considered which implies that the mean free

Non-monotone positive solutions of second-order linear differential equations: existence, nonexistence and criteria

Directory of Open Access Journals (Sweden)

Mervan Pašić

2016-10-01

Full Text Available We study non-monotone positive solutions of the second-order linear differential equations: $(p(tx'' + q(t x = e(t$, with positive $p(t$ and $q(t$. For the first time, some criteria as well as the existence and nonexistence of non-monotone positive solutions are proved in the framework of some properties of solutions $\\theta (t$ of the corresponding integrable linear equation: $(p(t\\theta''=e(t$. The main results are illustrated by many examples dealing with equations which allow exact non-monotone positive solutions not necessarily periodic. Finally, we pose some open questions.

Experimental study on the mean flow characteristics of forward-curved centrifugal fans

International Nuclear Information System (INIS)

Kwon, Eui Yong; Cho, Nam Hyo

2001-01-01

Measurements have been made in an automotive HVAC blower for two different centrifugal fans. This work is directed at improving the performance of a conventional forward-curved centrifugal fan for a given small blower casing. Mean velocities and pressure have been measured using a miniature five-hole probe and a pressure scanning unit connected to an online data acquisition system. First, we obtained the fan performance curves versus flow rates showing a significant attenuation of unstable nature achieved with the new fan rotor in the surging operation range. Second, aerodynamic characterizations were carried out by investigating the velocity and pressure fields in the casing flow passage for different fan operating conditions. The measurements showed that performance coefficients are strongly influnced by flow characteristics at the throat region. The main flow features were common in both fans, but improved performance is achieved with the new fan rotor, particularly in lower flow rate regions. Based on the measured results, design improvements were carried out in an acceptable operation range, which gave considerable insight into what features of flow behavior were most important

Neural network analysis of head-flow curves in deep well pumps

International Nuclear Information System (INIS)

Goelcue, Mustafa

2006-01-01

In impellers with splitter blades, the difficulty in calculation of the flow area of the impeller is because of the unknown flow rate occurring in the two separate areas when the splitter blades are added. Experimental studies were made to investigate the effects of splitter blade length on deep well pump performance for different numbers of blades. Head-flow curves of deep well pump impellers with splitter blades were investigated using artificial neural networks (ANNs). Gradient descent (GD), Gradient descent with momentum (GDM) and Levenberg-Marquardt (LM) learning algorithms were used in the networks. Experimental studies were completed to obtain training and test data. Blade number (z), non-dimensional splitter blade length (L-bar ) and flow rate (Q) were used as the input layer, while the output is head (H m ). For the testing data, the root mean squared error (RMSE), fraction of variance (R 2 ) and mean absolute percentage error (MAPE) were found to be 0.1285, 0.9999 and 1.6821%, respectively. With these results, we believe that the ANN can be used for prediction of head-flow curves as an appropriate method in deep well pump impellers with splitter blades.

A Simplified Micromechanical Modeling Approach to Predict the Tensile Flow Curve Behavior of Dual-Phase Steels

Science.gov (United States)

Nanda, Tarun; Kumar, B. Ravi; Singh, Vishal

2017-11-01

Micromechanical modeling is used to predict material's tensile flow curve behavior based on microstructural characteristics. This research develops a simplified micromechanical modeling approach for predicting flow curve behavior of dual-phase steels. The existing literature reports on two broad approaches for determining tensile flow curve of these steels. The modeling approach developed in this work attempts to overcome specific limitations of the existing two approaches. This approach combines dislocation-based strain-hardening method with rule of mixtures. In the first step of modeling, `dislocation-based strain-hardening method' was employed to predict tensile behavior of individual phases of ferrite and martensite. In the second step, the individual flow curves were combined using `rule of mixtures,' to obtain the composite dual-phase flow behavior. To check accuracy of proposed model, four distinct dual-phase microstructures comprising of different ferrite grain size, martensite fraction, and carbon content in martensite were processed by annealing experiments. The true stress-strain curves for various microstructures were predicted with the newly developed micromechanical model. The results of micromechanical model matched closely with those of actual tensile tests. Thus, this micromechanical modeling approach can be used to predict and optimize the tensile flow behavior of dual-phase steels.

Nonmonotonic Trust Management for P2P Applications

NARCIS (Netherlands)

Czenko, M.R.; Tran, H.M.; Doumen, J.M.; Etalle, Sandro; Hartel, Pieter H.; den Hartog, Jeremy

Community decisions about access control in virtual communities are non-monotonic in nature. This means that they cannot be expressed in current, monotonic trust management languages such as the family of Role Based Trust Management languages (RT). To solve this problem we propose RTo, which adds a

Analysis of flux-flow curves in superconductors as a function of temperature

International Nuclear Information System (INIS)

Boboshko, N.

1978-01-01

A phenomenological method to analyse the experimental data of flux-flow resistivity in superconductors as a function of temperature is proposed and successfully applied to existing data for t = kappa >= 0.07. An empirical curve relating the flux-flow resistivity with the Ginsburg-Landau parameter kappa was obtained. (author)

The effect of buoyancy on flow and heat transfer in curved pipes

OpenAIRE

Mochizuki, Munekazu; Ishigaki, Hiroshi; 望月 宗和; 石垣 博

1994-01-01

Fully developed laminar flow in a heated horizontal curved pipe is studied numerically. The thermal boundary conditions at the wall are uniform wall heat flux axially and uniform wall temperature peripherally. Flow and heat transfer are governed by Dean number, Prandtl number and buoyancy number. Detailed prediction of the friction factor, average heat transfer rate, velocity profile, temperature profile and secondary-flow streamlines are given.

Holographic RG flows on curved manifolds and quantum phase transitions

Science.gov (United States)

Ghosh, J. K.; Kiritsis, E.; Nitti, F.; Witkowski, L. T.

2018-05-01

Holographic RG flows dual to QFTs on maximally symmetric curved manifolds (dS d , AdS d , and S d ) are considered in the framework of Einstein-dilaton gravity in d + 1 dimensions. A general dilaton potential is used and the flows are driven by a scalar relevant operator. The general properties of such flows are analyzed and the UV and IR asymptotics computed. New RG flows can appear at finite curvature which do not have a zero curvature counterpart. The so-called `bouncing' flows, where the β-function has a branch cut at which it changes sign, are found to persist at finite curvature. Novel quantum first-order phase transitions are found, triggered by a variation in the d-dimensional curvature in theories allowing multiple ground states.

Non-monotonic field dependence of critical current in composite superconductors

International Nuclear Information System (INIS)

Andrianov, V.V.; Baev, V.P.; Ivanov, S.S.

1982-01-01

The nonmonotonic field dependence of critical current Im(B/sub a/ in composite superconductors is investigated experimentally for current and field varying simultaneously with final rates I and B/sub a/

Rarefaction effects in gas flows over curved surfaces

Science.gov (United States)

Dongari, Nishanth; White, Craig; Scanlon, Thomas J.; Zhang, Yonghao; Reese, Jason M.

2012-11-01

The fundamental test case of gas flow between two concentric rotating cylinders is considered in order to investigate rarefaction effects associated with the Knudsen layers over curved surfaces. We carry out direct simulation Monte Carlo simulations covering a wide range of Knudsen numbers and accommodation coefficients, and for various outer-to-inner cylinder radius ratios. Numerical data is compared with classical slip flow theory and a new power-law (PL) wall scaling model. The PL model incorporates Knudsen layer effects in near-wall regions by taking into account the boundary limiting effects on the molecular free paths. The limitations of both theoretical models are explored with respect to rarefaction and curvature effects. Torque and velocity profile comparisons also convey that mere prediction of integral flow parameters does not guarantee the accuracy of a theoretical model, and that it is important to ensure that prediction of the local flowfield is in agreement with simulation data.

Plasma flow in a curved magnetic field

International Nuclear Information System (INIS)

Lindberg, L.

1977-09-01

A beam of collisionless plasma is injected along a longitudinal magnetic field into a region of curved magnetic field. Two unpredicted phenomena are observed: The beam becomes deflected in the direction opposite to that in which the field is curved, and it contracts to a flat slab in the plane of curvature of the magnetic field. The phenomenon is of a general character and can be expected to occur in a very wide range of densities. The lower density limit is set by the condition for self-polarization, nm sub(i)/epsilon 0 B 2 >> 1 or, which is equivalent, c 2 /v 2 sub(A) >> 1, where c is the velocity of light, and v sup(A) the Alfven velocity. The upper limit is presumably set by the requirement ωsub(e)tau(e) >> 1. The phenomenon is likely to be of importance e.g. for injection of plasma into magnetic bottles and in space and solar physics. The paper illustrates the comlexity of plasma flow phenomena and the importance of close contact between experimental and theoretical work. (author)

Secondary flow in a curved artery model with Newtonian and non-Newtonian blood-analog fluids

Science.gov (United States)

Najjari, Mohammad Reza; Plesniak, Michael W.

2016-11-01

Steady and pulsatile flows of Newtonian and non-Newtonian fluids through a 180°-curved pipe were investigated using particle image velocimetry (PIV). The experiment was inspired by physiological pulsatile flow through large curved arteries, with a carotid artery flow rate imposed. Sodium iodide (NaI) and sodium thiocyanate (NaSCN) were added to the working fluids to match the refractive index (RI) of the test section to eliminate optical distortion. Rheological measurements revealed that adding NaI or NaSCN changes the viscoelastic properties of non-Newtonian solutions and reduces their shear-thinning property. Measured centerline velocity profiles in the upstream straight pipe agreed well with an analytical solution. In the pulsatile case, secondary flow structures, i.e. deformed-Dean, Dean, Wall and Lyne vortices, were observed in various cross sections along the curved pipe. Vortical structures at each cross section were detected using the d2 vortex identification method. Circulation analysis was performed on each vortex separately during the systolic deceleration phase, and showed that vortices split and rejoin. Secondary flow structures in steady flows were found to be morphologically similar to those in pulsatile flows for sufficiently high Dean number. supported by the George Washington University Center for Biomimetics and Bioinspired Engineering.

Unsteady motion and transition to turbulence in developing curved duct flow

International Nuclear Information System (INIS)

Arnal, M.; Firmino, F.; Humphrey, J.A.C.

1987-01-01

An experiment was performed to further the understanding of developing flows in curved ducts of square cross-section. Unlike most earlier works, attention was paid to investigating the time-dependent character of the motion. Mean and unsteady flow characteristics were determined using flow visualization and a laser-Doppler velocimeter. Only one velocity component, that aligned in the longitudinal (streamwise) coordinate direction, was measured. Notwithstanding, the time histories, autocorrelations and spectra derived reveal a time-periodic motion that becomes turbulent with increasing Reynolds number. The results are of intrinsic fundamental value and also illustrate the danger of imposing symmetry of the conservation equations on numerical solutions of this flow. 24 references

A Binomial Modeling Approach for Upscaling Colloid Transport Under Unfavorable Attachment Conditions: Emergent Prediction of Nonmonotonic Retention Profiles

Science.gov (United States)

Hilpert, Markus; Johnson, William P.

2018-01-01

We used a recently developed simple mathematical network model to upscale pore-scale colloid transport information determined under unfavorable attachment conditions. Classical log-linear and nonmonotonic retention profiles, both well-reported under favorable and unfavorable attachment conditions, respectively, emerged from our upscaling. The primary attribute of the network is colloid transfer between bulk pore fluid, the near-surface fluid domain (NSFD), and attachment (treated as irreversible). The network model accounts for colloid transfer to the NSFD of downgradient grains and for reentrainment to bulk pore fluid via diffusion or via expulsion at rear flow stagnation zones (RFSZs). The model describes colloid transport by a sequence of random trials in a one-dimensional (1-D) network of Happel cells, which contain a grain and a pore. Using combinatorial analysis that capitalizes on the binomial coefficient, we derived from the pore-scale information the theoretical residence time distribution of colloids in the network. The transition from log-linear to nonmonotonic retention profiles occurs when the conditions underlying classical filtration theory are not fulfilled, i.e., when an NSFD colloid population is maintained. Then, nonmonotonic retention profiles result potentially both for attached and NSFD colloids. The concentration maxima shift downgradient depending on specific parameter choice. The concentration maxima were also shown to shift downgradient temporally (with continued elution) under conditions where attachment is negligible, explaining experimentally observed downgradient transport of retained concentration maxima of adhesion-deficient bacteria. For the case of zero reentrainment, we develop closed-form, analytical expressions for the shape, and the maximum of the colloid retention profile.

A Nonmonotone Line Search Filter Algorithm for the System of Nonlinear Equations

Directory of Open Access Journals (Sweden)

Zhong Jin

2012-01-01

Full Text Available We present a new iterative method based on the line search filter method with the nonmonotone strategy to solve the system of nonlinear equations. The equations are divided into two groups; some equations are treated as constraints and the others act as the objective function, and the two groups are just updated at the iterations where it is needed indeed. We employ the nonmonotone idea to the sufficient reduction conditions and filter technique which leads to a flexibility and acceptance behavior comparable to monotone methods. The new algorithm is shown to be globally convergent and numerical experiments demonstrate its effectiveness.

Experimental investigation on in-plane/out-of-plane vortex-induced vibrations of curved cylinder in parallel and perpendicular flows

Science.gov (United States)

Srinil, Narakorn; Ma, Bowen; Zhang, Licong

2018-05-01

This study is motivated by an industrial need to better understand the vortex-induced vibration (VIV) of a curved structure subject to current flows with varying directions whose data for model calibration and validation are lacking. In this paper, new experimental investigations on the two-degree-of-freedom in-plane/out-of-plane VIV of a rigid curved circular cylinder immersed in steady and uniform free-stream flows are presented. The principal objective is to examine how the approaching flow direction versus the cylinder curvature plane affects cross-flow and in-line VIV and the associated hydrodynamic properties. This is achieved by testing the curved cylinder in 3 different flow orientations comprising the parallel flows aligned with the curvature vertical plane in convex and concave configurations, and the flows perpendicular to the curvature plane. The case of varying flow velocities in a subcritical flow range with a maximum Reynolds number of about 50,000 is considered for the curved cylinder with a low mass ratio and damping ratio. Experimental results are presented and discussed in terms of the cylinder response amplitudes, inclination angles, mean displacements, motion trajectories, oscillation frequencies, hydrodynamic forces, relative phases, fluid excitation and added inertia coefficients. Comparisons with other experimental results of curved and straight cylinder VIV are also presented. The experiments highlight the important effects of cylinder curvature versus flow orientation on the combined cross-flow/in-line VIV. The maximum (minimum) responses occur in the perpendicular (convex) flow case whereas the extended lower-branch responses occur in the concave flow case. For perpendicular flows, some meaningful features are observed, including the appearances of cross-flow mean displacements and asymmetric eight-shaped motion trajectories due to multiple 2:1:1 resonances where two out-of-plane and one in-plane dominant frequencies are simultaneously

Turbulent Heat Transfer in Curved Pipe Flow

Science.gov (United States)

Kang, Changwoo; Yang, Kyung-Soo

2013-11-01

In the present investigation, turbulent heat transfer in fully-developed curved pipe flow with axially uniform wall heat flux has been numerically studied. The Reynolds numbers under consideration are Reτ = 210 (DNS) and 1,000 (LES) based on the mean friction velocity and the pipe radius, and the Prandtl number (Pr) is 0.71. For Reτ = 210 , the pipe curvature (κ) was fixed as 1/18.2, whereas three cases of κ (0.01, 0.05, 0.1) were computed in the case of Reτ = 1,000. The mean velocity, turbulent intensities and heat transfer rates obtained from the present calculations are in good agreement with the previous numerical and experimental results. To elucidate the secondary flow structures due to the pipe curvature, the mean quantities and rms fluctuations of the flow and temperature fields are presented on the pipe cross-sections, and compared with those of the straight pipe flow. To study turbulence structures and their influence on turbulent heat transfer, turbulence statistics including but not limited to skewness and flatness of velocity fluctuations, cross-correlation coefficients, an Octant analysis, and turbulence budgets are presented and discussed. Based on our results, we attempt to clarify the effects of Reynolds number and the pipe curvature on turbulent heat transfer. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-0008457).

Nonmonotonic reasoning in description logics. Rational closure for the ABox

CSIR Research Space (South Africa)

Casini, G

2013-07-01

Full Text Available The introduction of defeasible reasoning in Description Logics has been a main research topic in the field in the last years. Despite the fact that various interesting formalizations of nonmonotonic reasoning for the TBox have been proposed...

Determination of minimum flood flow for regeneration of floodplain forest from inundated forest width-stage curve

Directory of Open Access Journals (Sweden)

Song-hao Shang

2010-09-01

Full Text Available Floods are essential for the regeneration and growth of floodplain forests in arid and semiarid regions. However, river flows, and especially flood flows, have decreased greatly with the increase of water diversion from rivers and/or reservoir regulation, resulting in severe deterioration of floodplain ecosystems. Estimation of the flood stage that will inundate the floodplain forest is necessary for the forest's restoration or protection. To balance water use for economic purposes and floodplain forest protection, the inundated forest width method is proposed for estimating the minimum flood stage for floodplain forests from the inundated forest width-stage curve. The minimum flood stage is defined as the breakpoint of the inundated forest width-stage curve, and is determined directly or analytically from the curve. For the analytical approach, the problem under consideration is described by a multi-objective optimization model, which can be solved by the ideal point method. Then, the flood flow at the minimum flood stage (minimum flood flow, which is useful for flow regulation, can be calculated from the stage-discharge curve. In order to protect the forest in a river floodplain in a semiarid area in Xinjiang subject to reservoir regulation upstream, the proposed method was used to determine the minimum flood stage and flow for the forest. Field survey of hydrology, topography, and forest distribution was carried out at typical cross sections in the floodplain. Based on the survey results, minimum flood flows for six typical cross sections were estimated to be between 306 m3/s and 393 m3/s. Their maximum, 393 m3/s, was considered the minimum flood flow for the study river reach. This provides an appropriate flood flow for the protection of floodplain forest and can be used in the regulation of the upstream reservoir.

The effect of the electrical double layer on hydrodynamic lubrication: a non-monotonic trend with increasing zeta potential

Directory of Open Access Journals (Sweden)

Dalei Jing

2017-07-01

Full Text Available In the present study, a modified Reynolds equation including the electrical double layer (EDL-induced electroviscous effect of lubricant is established to investigate the effect of the EDL on the hydrodynamic lubrication of a 1D slider bearing. The theoretical model is based on the nonlinear Poisson–Boltzmann equation without the use of the Debye–Hückel approximation. Furthermore, the variation in the bulk electrical conductivity of the lubricant under the influence of the EDL is also considered during the theoretical analysis of hydrodynamic lubrication. The results show that the EDL can increase the hydrodynamic load capacity of the lubricant in a 1D slider bearing. More importantly, the hydrodynamic load capacity of the lubricant under the influence of the EDL shows a non-monotonic trend, changing from enhancement to attenuation with a gradual increase in the absolute value of the zeta potential. This non-monotonic hydrodynamic lubrication is dependent on the non-monotonic electroviscous effect of the lubricant generated by the EDL, which is dominated by the non-monotonic electrical field strength and non-monotonic electrical body force on the lubricant. The subject of the paper is the theoretical modeling and the corresponding analysis.

An electronic implementation for Liao's chaotic delayed neuron model with non-monotonous activation function

International Nuclear Information System (INIS)

Duan Shukai; Liao Xiaofeng

2007-01-01

A new chaotic delayed neuron model with non-monotonously increasing transfer function, called as chaotic Liao's delayed neuron model, was recently reported and analyzed. An electronic implementation of this model is described in detail. At the same time, some methods in circuit design, especially for circuit with time delayed unit and non-monotonously increasing activation unit, are also considered carefully. We find that the dynamical behaviors of the designed circuits are closely similar to the results predicted by numerical experiments

Lung function in North American Indian children: reference standards for spirometry, maximal expiratory flow volume curves, and peak expiratory flow.

Science.gov (United States)

Wall, M A; Olson, D; Bonn, B A; Creelman, T; Buist, A S

1982-02-01

Reference standards of lung function was determined in 176 healthy North American Indian children (94 girls, 82 boys) 7 to 18 yr of age. Spirometry, maximal expiratory flow volume curves, and peak expiratory flow rate were measured using techniques and equipment recommended by the American Thoracic Society. Standing height was found to be an accurate predictor of lung function, and prediction equations for each lung function variable are presented using standing height as the independent variable. Lung volumes and expiratory flow rates in North American Indian children were similar to those previously reported for white and Mexican-American children but were greater than those in black children. In both boys and girls, lung function increased in a curvilinear fashion. Volume-adjusted maximal expiratory flow rates after expiring 50 or 75% of FVC tended to decrease in both sexes as age and height increased. Our maximal expiratory flow volume curve data suggest that as North American Indian children grow, lung volume increases at a slightly faster rate than airway size does.

Three-dimensional numerical modeling of turbulent single-phase and two-phase flow in curved pipes

International Nuclear Information System (INIS)

Xin, R.C.; Dong, Z.F.; Ebadian, M.A.

1996-01-01

In this study, three-dimensional single-phase and two-phase flows in curved pipes have been investigated numerically. Two different pipe configurations were computed. When the results of the single-phase flow simulation were compared with the experimental data, a fairly good agreement was achieved. A flow-developing process has been suggested in single-phase flow, in which the turbulence is stronger near the outer tube wall than near the inner tube wall. For two-phase flow, the Eulerian multiphase model was used to simulate the phase distribution of a three-dimensional gas-liquid bubble flow in curved pipe. The RNG/κ-ε turbulence model was used to determine the turbulence field. An inlet gas void fraction of 5 percent was simulated. The gas phase effects on the liquid phase flow velocity have been examined by comparing the results of single-phase flow and two-phase flow. The findings show that for the downward flow in the U bend, the gas concentrates at the inner portion of the cross section at φ = π/18 - π/6 in most cases. The results of the phase distribution simulation are compared to experimental observations qualitatively and topologically

Construction of estimated flow- and load-duration curves for Kentucky using the Water Availability Tool for Environmental Resources (WATER)

Science.gov (United States)

Unthank, Michael D.; Newson, Jeremy K.; Williamson, Tanja N.; Nelson, Hugh L.

2012-01-01

Flow- and load-duration curves were constructed from the model outputs of the U.S. Geological Survey's Water Availability Tool for Environmental Resources (WATER) application for streams in Kentucky. The WATER application was designed to access multiple geospatial datasets to generate more than 60 years of statistically based streamflow data for Kentucky. The WATER application enables a user to graphically select a site on a stream and generate an estimated hydrograph and flow-duration curve for the watershed upstream of that point. The flow-duration curves are constructed by calculating the exceedance probability of the modeled daily streamflows. User-defined water-quality criteria and (or) sampling results can be loaded into the WATER application to construct load-duration curves that are based on the modeled streamflow results. Estimates of flow and streamflow statistics were derived from TOPographically Based Hydrological MODEL (TOPMODEL) simulations in the WATER application. A modified TOPMODEL code, SDP-TOPMODEL (Sinkhole Drainage Process-TOPMODEL) was used to simulate daily mean discharges over the period of record for 5 karst and 5 non-karst watersheds in Kentucky in order to verify the calibrated model. A statistical evaluation of the model's verification simulations show that calibration criteria, established by previous WATER application reports, were met thus insuring the model's ability to provide acceptably accurate estimates of discharge at gaged and ungaged sites throughout Kentucky. Flow-duration curves are constructed in the WATER application by calculating the exceedence probability of the modeled daily flow values. The flow-duration intervals are expressed as a percentage, with zero corresponding to the highest stream discharge in the streamflow record. Load-duration curves are constructed by applying the loading equation (Load = Flow*Water-quality criterion) at each flow interval.

Flow and heat transfer in a curved channel

Science.gov (United States)

Brinich, P. F.; Graham, R. W.

1977-01-01

Flow and heat transfer in a curved channel of aspect ratio 6 and inner- to outer-wall radius ratio 0.96 were studied. Secondary currents and large longitudinal vortices were found. The heat-transfer rates of the outer and inner walls were independently controlled to maintain a constant wall temperature. Heating the inner wall increased the pressure drop along the channel length, whereas heating the outer wall had little effect. Outer-wall heat transfer was as much as 40 percent greater than the straight-channel correlation, and inner-wall heat transfer was 22 percent greater than the straight-channel correlation.

Bi-Hamiltonian operators, integrable flows of curves using moving frames and geometric map equations

International Nuclear Information System (INIS)

Anco, Stephen C

2006-01-01

Moving frames of various kinds are used to derive bi-Hamiltonian operators and associated hierarchies of multi-component soliton equations from group-invariant flows of non-stretching curves in constant-curvature manifolds and Lie-group manifolds. The hierarchy in the constant-curvature case consists of a vector mKdV equation coming from a parallel frame, a vector potential mKdV equation coming from a covariantly constant frame, and higher order counterparts generated by an underlying vector mKdV recursion operator. In the Lie-group case, the hierarchy comprises a group-invariant analogue of the vector NLS equation coming from a left-invariant frame, along with higher order counterparts generated by a recursion operator that is like a square root of the mKdV one. The corresponding respective curve flows are found to be given by geometric nonlinear PDEs, specifically mKdV and group-invariant analogues of Schroedinger maps. In all cases the hierarchies also contain variants of vector sine-Gordon equations arising from the kernel of the respective recursion operators. The geometric PDEs that describe the corresponding curve flows are shown to be wave maps

Bi-Hamiltonian operators, integrable flows of curves using moving frames and geometric map equations

Energy Technology Data Exchange (ETDEWEB)

Anco, Stephen C [Department of Mathematics, Brock University, St Catharines, ON (Canada)

2006-03-03

Moving frames of various kinds are used to derive bi-Hamiltonian operators and associated hierarchies of multi-component soliton equations from group-invariant flows of non-stretching curves in constant-curvature manifolds and Lie-group manifolds. The hierarchy in the constant-curvature case consists of a vector mKdV equation coming from a parallel frame, a vector potential mKdV equation coming from a covariantly constant frame, and higher order counterparts generated by an underlying vector mKdV recursion operator. In the Lie-group case, the hierarchy comprises a group-invariant analogue of the vector NLS equation coming from a left-invariant frame, along with higher order counterparts generated by a recursion operator that is like a square root of the mKdV one. The corresponding respective curve flows are found to be given by geometric nonlinear PDEs, specifically mKdV and group-invariant analogues of Schroedinger maps. In all cases the hierarchies also contain variants of vector sine-Gordon equations arising from the kernel of the respective recursion operators. The geometric PDEs that describe the corresponding curve flows are shown to be wave maps.

Design considerations and analysis planning of a phase 2a proof of concept study in rheumatoid arthritis in the presence of possible non-monotonicity.

Science.gov (United States)

Liu, Feng; Walters, Stephen J; Julious, Steven A

2017-10-02

It is important to quantify the dose response for a drug in phase 2a clinical trials so the optimal doses can then be selected for subsequent late phase trials. In a phase 2a clinical trial of new lead drug being developed for the treatment of rheumatoid arthritis (RA), a U-shaped dose response curve was observed. In the light of this result further research was undertaken to design an efficient phase 2a proof of concept (PoC) trial for a follow-on compound using the lessons learnt from the lead compound. The planned analysis for the Phase 2a trial for GSK123456 was a Bayesian Emax model which assumes the dose-response relationship follows a monotonic sigmoid "S" shaped curve. This model was found to be suboptimal to model the U-shaped dose response observed in the data from this trial and alternatives approaches were needed to be considered for the next compound for which a Normal dynamic linear model (NDLM) is proposed. This paper compares the statistical properties of the Bayesian Emax model and NDLM model and both models are evaluated using simulation in the context of adaptive Phase 2a PoC design under a variety of assumed dose response curves: linear, Emax model, U-shaped model, and flat response. It is shown that the NDLM method is flexible and can handle a wide variety of dose-responses, including monotonic and non-monotonic relationships. In comparison to the NDLM model the Emax model excelled with higher probability of selecting ED90 and smaller average sample size, when the true dose response followed Emax like curve. In addition, the type I error, probability of incorrectly concluding a drug may work when it does not, is inflated with the Bayesian NDLM model in all scenarios which would represent a development risk to pharmaceutical company. The bias, which is the difference between the estimated effect from the Emax and NDLM models and the simulated value, is comparable if the true dose response follows a placebo like curve, an Emax like curve, or log

Experimental Visualization of the Flow Structure for Jet in Crossflow with a Curved Hole Passage

Directory of Open Access Journals (Sweden)

Jun Yu Liang

2012-01-01

Full Text Available The objective of this paper is to investigate the influence of a hole curvature on the flow structure and characteristics downstream of JICF (jet in cross-Flow by means of smoke visualization and particle image velocimetry (PIV. The experiment was performed in a low speed wind tunnel with Reynolds numbers of about 480 and 1000, based on the hole diameter and main flow speed. Two geometries were tested: a circular hole with 90° curvature and a circular straight hole for comparison, under blowing ratios 0.5 and 1.0. The measurements were done in the symmetric plane and four cross-sections. The results show that the curved hole could decrease the mixing behavior of jet flow with the main flow as the hole leading edge also increases the chance of transportingthecoolant to the wall surface and the transverse coverage. The curved hole shows a high potential to increase the cooling effectiveness once it is applied to the turbine blades.

Multigenerational contaminant exposures produce non-monotonic, transgenerational responses in Daphnia magna

International Nuclear Information System (INIS)

Kimberly, David A.; Salice, Christopher J.

2015-01-01

Generally, ecotoxicologists rely on short-term tests that assume populations to be static. Conversely, natural populations may be exposed to the same stressors for many generations, which can alter tolerance to the same (or other) stressors. The objective of this study was to improve our understanding of how multigenerational stressors alter life history traits and stressor tolerance. After continuously exposing Daphnia magna to cadmium for 120 days, we assessed life history traits and conducted a challenge at higher temperature and cadmium concentrations. Predictably, individuals exposed to cadmium showed an overall decrease in reproductive output compared to controls. Interestingly, control D. magna were the most cadmium tolerant to novel cadmium, followed by those exposed to high cadmium. Our data suggest that long-term exposure to cadmium alter tolerance traits in a non-monotonic way. Because we observed effects after one-generation removal from cadmium, transgenerational effects may be possible as a result of multigenerational exposure. - Highlights: • Daphnia magna exposed to cadmium for 120 days. • D. magna exposed to cadmium had decreased reproductive output. • Control D. magna were most cadmium tolerant to novel cadmium stress. • Long-term exposure to cadmium alter tolerance traits in a non-monotonic way. • Transgenerational effects observed as a result of multigenerational exposure. - Adverse effects of long-term cadmium exposure persist into cadmium free conditions, as seen by non-monotonic responses when exposed to novel stress one generation removed.

Nonmonotonic low frequency losses in HTSCs

International Nuclear Information System (INIS)

Castro, H; Gerber, A; Milner, A

2007-01-01

A calorimetric technique has been used in order to study ac-field dissipation in ceramic BSCCO samples at low frequencies between 0.05 and 250 Hz, at temperatures from 65 to 90 K. In contrast to previous studies, where ac losses have been reported with a linear dependence on magnetic field frequency, we find a nonmonotonic function presenting various maxima. Frequencies corresponding to local maxima of dissipation depend on the temperature and the amplitude of the ac magnetic field. Flux creep is argued to be responsible for this behaviour. A simple model connecting the characteristic vortex relaxation times (flux creep) and the location of dissipation maxima versus frequency is proposed

Analytical solution of laminar-laminar stratified two-phase flows with curved interfaces

International Nuclear Information System (INIS)

Brauner, N.; Rovinsky, J.; Maron, D.M.

1995-01-01

The present study represents a complete analytical solution for laminar two-phase flows with curved interfaces. The solution of the Navier-Stokes equations for the two-phases in bipolar coordinates provides the 'flow monograms' describe the relation between the interface curvature and the insitu flow geometry when given the phases flow rates and viscosity ratios. Energy considerations are employed to construct the 'interface monograms', whereby the characteristic interfacial curvature is determined in terms of the phases insitu holdup, pipe diameter, surface tension, fluids/wall adhesion and gravitation. The two monograms are then combined to construct the system 'operational monogram'. The 'operational monogram' enables the determination of the interface configuration, the local flow characteristics, such as velocity profiles, wall and interfacial shear stresses distribution as well as the integral characteristics of the two-phase flow: phases insitu holdup and pressure drop

Analytical solution of laminar-laminar stratified two-phase flows with curved interfaces

Energy Technology Data Exchange (ETDEWEB)

Brauner, N.; Rovinsky, J.; Maron, D.M. [Tel-Aviv Univ. (Israel)

1995-09-01

The present study represents a complete analytical solution for laminar two-phase flows with curved interfaces. The solution of the Navier-Stokes equations for the two-phases in bipolar coordinates provides the `flow monograms` describe the relation between the interface curvature and the insitu flow geometry when given the phases flow rates and viscosity ratios. Energy considerations are employed to construct the `interface monograms`, whereby the characteristic interfacial curvature is determined in terms of the phases insitu holdup, pipe diameter, surface tension, fluids/wall adhesion and gravitation. The two monograms are then combined to construct the system `operational monogram`. The `operational monogram` enables the determination of the interface configuration, the local flow characteristics, such as velocity profiles, wall and interfacial shear stresses distribution as well as the integral characteristics of the two-phase flow: phases insitu holdup and pressure drop.

Non-monotonic reasoning in conceptual modeling and ontology design: A proposal

CSIR Research Space (South Africa)

Casini, G

2013-06-01

Full Text Available -1 2nd International Workshop on Ontologies and Conceptual Modeling (Onto.Com 2013), Valencia, Spain, 17-21 June 2013 Non-monotonic reasoning in conceptual modeling and ontology design: A proposal Giovanni Casini1 and Alessandro Mosca2 1...

Correlation between 2D and 3D flow curve modelling of DP steels using a microstructure-based RVE approach

International Nuclear Information System (INIS)

Ramazani, A.; Mukherjee, K.; Quade, H.; Prahl, U.; Bleck, W.

2013-01-01

A microstructure-based approach by means of representative volume elements (RVEs) is employed to evaluate the flow curve of DP steels using virtual tensile tests. Microstructures with different martensite fractions and morphologies are studied in two- and three-dimensional approaches. Micro sections of DP microstructures with various amounts of martensite have been converted to 2D RVEs, while 3D RVEs were constructed statistically with randomly distributed phases. A dislocation-based model is used to describe the flow curve of each ferrite and martensite phase separately as a function of carbon partitioning and microstructural features. Numerical tensile tests of RVE were carried out using the ABAQUS/Standard code to predict the flow behaviour of DP steels. It is observed that 2D plane strain modelling gives an underpredicted flow curve for DP steels, while the 3D modelling gives a quantitatively reasonable description of flow curve in comparison to the experimental data. In this work, a von Mises stress correlation factor σ 3D /σ 2D has been identified to compare the predicted flow curves of these two dimensionalities showing a third order polynomial relation with respect to martensite fraction and a second order polynomial relation with respect to equivalent plastic strain, respectively. The quantification of this polynomial correlation factor is performed based on laboratory-annealed DP600 chemistry with varying martensite content and it is validated for industrially produced DP qualities with various chemistry, strength level and martensite fraction.

Universal rescaling of flow curves for yield-stress fluids close to jamming

Science.gov (United States)

Dinkgreve, M.; Paredes, J.; Michels, M. A. J.; Bonn, D.

2015-07-01

The experimental flow curves of four different yield-stress fluids with different interparticle interactions are studied near the jamming concentration. By appropriate scaling with the distance to jamming all rheology data can be collapsed onto master curves below and above jamming that meet in the shear-thinning regime and satisfy the Herschel-Bulkley and Cross equations, respectively. In spite of differing interactions in the different systems, master curves characterized by universal scaling exponents are found for the four systems. A two-state microscopic theory of heterogeneous dynamics is presented to rationalize the observed transition from Herschel-Bulkley to Cross behavior and to connect the rheological exponents to microscopic exponents for the divergence of the length and time scales of the heterogeneous dynamics. The experimental data and the microscopic theory are compared with much of the available literature data for yield-stress systems.

An electronic implementation for Liao's chaotic delayed neuron model with non-monotonous activation function

Energy Technology Data Exchange (ETDEWEB)

Duan Shukai [Department of Computer Science and Engineering, Chongqing University, Chongqing 400044 (China); School of Electronic and Information Engineering, Southwest University, Chongqing 400715 (China)], E-mail: duansk@swu.edu.cn; Liao Xiaofeng [Department of Computer Science and Engineering, Chongqing University, Chongqing 400044 (China)], E-mail: xfliao@cqu.edu.cn

2007-09-10

A new chaotic delayed neuron model with non-monotonously increasing transfer function, called as chaotic Liao's delayed neuron model, was recently reported and analyzed. An electronic implementation of this model is described in detail. At the same time, some methods in circuit design, especially for circuit with time delayed unit and non-monotonously increasing activation unit, are also considered carefully. We find that the dynamical behaviors of the designed circuits are closely similar to the results predicted by numerical experiments.

Design considerations and analysis planning of a phase 2a proof of concept study in rheumatoid arthritis in the presence of possible non-monotonicity

Directory of Open Access Journals (Sweden)

Feng Liu

2017-10-01

Full Text Available Abstract Background It is important to quantify the dose response for a drug in phase 2a clinical trials so the optimal doses can then be selected for subsequent late phase trials. In a phase 2a clinical trial of new lead drug being developed for the treatment of rheumatoid arthritis (RA, a U-shaped dose response curve was observed. In the light of this result further research was undertaken to design an efficient phase 2a proof of concept (PoC trial for a follow-on compound using the lessons learnt from the lead compound. Methods The planned analysis for the Phase 2a trial for GSK123456 was a Bayesian Emax model which assumes the dose-response relationship follows a monotonic sigmoid “S” shaped curve. This model was found to be suboptimal to model the U-shaped dose response observed in the data from this trial and alternatives approaches were needed to be considered for the next compound for which a Normal dynamic linear model (NDLM is proposed. This paper compares the statistical properties of the Bayesian Emax model and NDLM model and both models are evaluated using simulation in the context of adaptive Phase 2a PoC design under a variety of assumed dose response curves: linear, Emax model, U-shaped model, and flat response. Results It is shown that the NDLM method is flexible and can handle a wide variety of dose-responses, including monotonic and non-monotonic relationships. In comparison to the NDLM model the Emax model excelled with higher probability of selecting ED90 and smaller average sample size, when the true dose response followed Emax like curve. In addition, the type I error, probability of incorrectly concluding a drug may work when it does not, is inflated with the Bayesian NDLM model in all scenarios which would represent a development risk to pharmaceutical company. The bias, which is the difference between the estimated effect from the Emax and NDLM models and the simulated value, is comparable if the true dose response

Thermal effects on the enhanced ductility in non-monotonic uniaxial tension of DP780 steel sheet

Science.gov (United States)

Majidi, Omid; Barlat, Frederic; Korkolis, Yannis P.; Fu, Jiawei; Lee, Myoung-Gyu

2016-11-01

To understand the material behavior during non-monotonic loading, uniaxial tension tests were conducted in three modes, namely, the monotonic loading, loading with periodic relaxation and periodic loading-unloadingreloading, at different strain rates (0.001/s to 0.01/s). In this study, the temperature gradient developing during each test and its contribution to increasing the apparent ductility of DP780 steel sheets were considered. In order to assess the influence of temperature, isothermal uniaxial tension tests were also performed at three temperatures (298 K, 313 K and 328 K (25 °C, 40 °C and 55 °C)). A digital image correlation system coupled with an infrared thermography was used in the experiments. The results show that the non-monotonic loading modes increased the apparent ductility of the specimens. It was observed that compared with the monotonic loading, the temperature gradient became more uniform when a non-monotonic loading was applied.

Wall roughness effects on flow and scouring in curved channels with gravel bed

OpenAIRE

Hersberger, Daniel S.

2002-01-01

Wall roughness effects on flow and scouring in curved channels with gravel bed In the narrow valleys in Alpine regions, rivers frequently flow across constructed zones, passing through villages and cities. Due to limited space, the protection from high floods often needs to be ensured by protection walls. During floods, these protection walls may be endangered by scour phenomena, especially if they are located in bends. In the past, the potential danger of underscoured structures was reduced ...

A fluid dynamical flow model for the central peak in the rotation curve of disk galaxies

International Nuclear Information System (INIS)

Bhattacharyya, T.; Basu, B.

1980-01-01

The rotation curve of the central region in some disk galaxies shows a linear rise, terminating at a peak (primary peak) which is then vollowed by a deep minimum. The curve then again rises to another peak at more or less half-way across the galactic radius. This latter peak is considered as the peak of the rotation curve in all large-scale analysis of galactic structure. The primary peak is usually ignored for the purpose. In this work an attempt has been made to look at the primary peak as the manifestation of the post-explosion flow pattern of gas in the deep central region of galaxies. Solving hydrodynamical equations of motion, a flow model has been derived which imitates very closely the actually observed linear rotational velocity, followed by the falling branch of the curve to minimum. The theoretical flow model has been compared with observed results for nine galaxies. The agreement obtained is extremely encouraging. The distance of the primary peak from the galactic centre has been shown to be correlated with the angular velocity in the linear part of the rotation curve. Here also, agreement is very good between theoretical and observed results. It is concluded that the distance of the primary peak from the centre not only speaks of the time that has elapsed since the explosion occurred in the nucleus, it also speaks of the potential capability of the nucleus of the galaxy for repeating explosions through some efficient process of mass replenishment at the core. (orig.)

Pressure drop-flow rate curves for single-phase steam in Combustion Engineering type steam generator U-tubes during severe accidents

Energy Technology Data Exchange (ETDEWEB)

Fynan, Douglas A.; Ahn, Kwang-Il, E-mail: kiahn@kaeri.re.kr

2016-12-15

Highlights: • Pressure drop-flow rate curves for superheated steam in U-tubes were generated. • Forward flow of hot steam is favored in the longer and taller U-tubes. • Reverse flow of cold steam is favored in short U-tubes. • Steam generator U-tube bundle geometry and tube diameter are important. • Need for correlation development for natural convention heat transfer coefficient. - Abstract: Characteristic pressure drop-flow rate curves are generated for all row numbers of the OPR1000 steam generators (SGs), representative of Combustion Engineering (CE) type SGs featuring square bend U-tubes. The pressure drop-flow rate curves are applicable to severe accident natural circulations of single-phase superheated steam during high pressure station blackout sequences with failed auxiliary feedwater and dry secondary side which are closely related to the thermally induced steam generator tube rupture event. The pressure drop-flow rate curves which determine the recirculation rate through the SG tubes are dependent on the tube bundle geometry and hydraulic diameter of the tubes. The larger CE type SGs have greater variation of tube length and height as a function of row number with forward flow of steam favored in the longer and taller high row number tubes and reverse flow favored in the short low row number tubes. Friction loss, natural convection heat transfer coefficients, and temperature differentials from the primary to secondary side are dominant parameters affecting the recirculation rate. The need for correlation development for natural convection heat transfer coefficients for external flow over tube bundles currently not modeled in system codes is discussed.

Rarefied gas flows through a curved channel: Application of a diffusion-type equation

Science.gov (United States)

Aoki, Kazuo; Takata, Shigeru; Tatsumi, Eri; Yoshida, Hiroaki

2010-11-01

Rarefied gas flows through a curved two-dimensional channel, caused by a pressure or a temperature gradient, are investigated numerically by using a macroscopic equation of convection-diffusion type. The equation, which was derived systematically from the Bhatnagar-Gross-Krook model of the Boltzmann equation and diffuse-reflection boundary condition in a previous paper [K. Aoki et al., "A diffusion model for rarefied flows in curved channels," Multiscale Model. Simul. 6, 1281 (2008)], is valid irrespective of the degree of gas rarefaction when the channel width is much shorter than the scale of variations of physical quantities and curvature along the channel. Attention is also paid to a variant of the Knudsen compressor that can produce a pressure raise by the effect of the change of channel curvature and periodic temperature distributions without any help of moving parts. In the process of analysis, the macroscopic equation is (partially) extended to the case of the ellipsoidal-statistical model of the Boltzmann equation.

On-line learning of non-monotonic rules by simple perceptron

OpenAIRE

Inoue, Jun-ichi; Nishimori, Hidetoshi; Kabashima, Yoshiyuki

1997-01-01

We study the generalization ability of a simple perceptron which learns unlearnable rules. The rules are presented by a teacher perceptron with a non-monotonic transfer function. The student is trained in the on-line mode. The asymptotic behaviour of the generalization error is estimated under various conditions. Several learning strategies are proposed and improved to obtain the theoretical lower bound of the generalization error.

Changes in the Flow-Volume Curve According to the Degree of Stenosis in Patients With Unilateral Main Bronchial Stenosis

Science.gov (United States)

Yoo, Jung-Geun; Yi, Chin A; Lee, Kyung Soo; Jeon, Kyeongman; Um, Sang-Won; Koh, Won-Jung; Suh, Gee Young; Chung, Man Pyo; Kwon, O Jung

2015-01-01

Objectives The shape of the flow-volume (F-V) curve is known to change to showing a prominent plateau as stenosis progresses in patients with tracheal stenosis. However, no study has evaluated changes in the F-V curve according to the degree of bronchial stenosis in patients with unilateral main bronchial stenosis. Methods We performed an analysis of F-V curves in 29 patients with unilateral bronchial stenosis with the aid of a graphic digitizer between January 2005 and December 2011. Results The primary diseases causing unilateral main bronchial stenosis were endobronchial tuberculosis (86%), followed by benign bronchial tumor (10%), and carcinoid (3%). All unilateral main bronchial stenoses were classified into one of five grades (I, ≤25%; II, 26%-50%; III, 51%-75%; IV, 76%-90%; V, >90% to near-complete obstruction without ipsilateral lung collapse). A monophasic F-V curve was observed in patients with grade I stenosis and biphasic curves were observed for grade II-IV stenosis. Both monophasic (81%) and biphasic shapes (18%) were observed in grade V stenosis. After standardization of the biphasic shape of the F-V curve, the breakpoints of the biphasic curve moved in the direction of high volume (x-axis) and low flow (y-axis) according to the progression of stenosis. Conclusion In unilateral bronchial stenosis, a biphasic F-V curve appeared when bronchial stenosis was >25% and disappeared when obstruction was near complete. In addition, the breakpoint moved in the direction of high volume and low flow with the progression of stenosis. PMID:26045916

Non-monotonic wetting behavior of chitosan films induced by silver nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Praxedes, A.P.P.; Webler, G.D.; Souza, S.T. [Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió, AL (Brazil); Ribeiro, A.S. [Instituto de Química e Biotecnologia, Universidade Federal de Alagoas, 57072-970 Maceió, AL (Brazil); Fonseca, E.J.S. [Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió, AL (Brazil); Oliveira, I.N. de, E-mail: italo@fis.ufal.br [Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió, AL (Brazil)

2016-05-01

Highlights: • The addition of silver nanoparticles modifies the morphology of chitosan films. • Metallic nanoparticles can be used to control wetting properties of chitosan films. • The contact angle shows a non-monotonic dependence on the silver concentration. - Abstract: The present work is devoted to the study of structural and wetting properties of chitosan-based films containing silver nanoparticles. In particular, the effects of silver concentration on the morphology of chitosan films are characterized by different techniques, such as atomic force microscopy (AFM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). By means of dynamic contact angle measurements, we study the modification on surface properties of chitosan-based films due to the addition of silver nanoparticles. The results are analyzed in the light of molecular-kinetic theory which describes the wetting phenomena in terms of statistical dynamics for the displacement of liquid molecules in a solid substrate. Our results show that the wetting properties of chitosan-based films are high sensitive to the fraction of silver nanoparticles, with the equilibrium contact angle exhibiting a non-monotonic behavior.

Change in the flow curves of non-Newtonian oils due to a magnetic field

International Nuclear Information System (INIS)

Veliev, F.G.

1979-01-01

The effect of a variable magnetic field on the rheological properties of non-Newtonian fluids is evaluated. Bituminous pitch oils were analyzed by recording the flow curves Q.Q(Δp) - the dependence of the volumetric flow rate on the pressure gradient - with and without a field. The results obtained indicate that variable magnetic fields can produce obvious changes in the rheological properties of bituminous pitch oils, although they are nonmagnetoactive and practically electrically nonconducting

Non-Monotonic Spatial Reasoning with Answer Set Programming Modulo Theories

OpenAIRE

Wałęga, Przemysław Andrzej; Schultz, Carl; Bhatt, Mehul

2016-01-01

The systematic modelling of dynamic spatial systems is a key requirement in a wide range of application areas such as commonsense cognitive robotics, computer-aided architecture design, and dynamic geographic information systems. We present ASPMT(QS), a novel approach and fully-implemented prototype for non-monotonic spatial reasoning -a crucial requirement within dynamic spatial systems- based on Answer Set Programming Modulo Theories (ASPMT). ASPMT(QS) consists of a (qualitative) spatial re...

Numerical Simulation of Heat and Flow Behaviors in Butt-fusion Welding Process of HDPE Pipes with Curved Fusion Surface

Energy Technology Data Exchange (ETDEWEB)

Yoo, Jae Hyun; Ahn, Kyung Hyun [Seoul National University, Seoul (Korea, Republic of); Choi, Sunwoong; Oh, Ju Seok [Hannam University, Daejeon (Korea, Republic of)

2017-08-15

Butt-fusion welding process is used to join the polymeric pipes. Recently, some researchers suggest the curved surface to enhance a welding quality. We investigated how curved welding surface affects heat and flow behaviors of polymer melt during the process in 2D axisymmetric domain with finite element method, and discussed the effect to the welding quality. In this study, we considered HDPE pipes. In heat soak stage, curved phase interface between the melt and solid is shown along the shape of welding surface. In jointing stage, squeezing flow is generated between curved welding surface and phase interface. The low shear rate in fusion domain reduces the alignment of polymer to the perpendicular direction of pipes, and then this phenomenon is expected to help to enhance the welding quality.

Nonmonotonic Thermal Casimir Force from Geometry-Temperature Interplay

International Nuclear Information System (INIS)

Weber, Alexej; Gies, Holger

2010-01-01

The geometry dependence of Casimir forces is significantly more pronounced in the presence of thermal fluctuations due to a generic geometry-temperature interplay. We show that the thermal force for standard sphere-plate or cylinder-plate geometries develops a nonmonotonic behavior already in the simple case of a fluctuating Dirichlet scalar. In particular, the attractive thermal force can increase for increasing distances below a critical temperature. This anomalous behavior is triggered by a reweighting of relevant fluctuations on the scale of the thermal wavelength. The essence of the phenomenon becomes transparent within the worldline picture of the Casimir effect.

Correlation between vortices and wall shear stress in a curved artery model under pulsatile flow conditions

Science.gov (United States)

Cox, Christopher; Plesniak, Michael W.

2017-11-01

One of the most physiologically relevant factors within the cardiovascular system is the wall shear stress. The wall shear stress affects endothelial cells via mechanotransduction and atherosclerotic regions are strongly correlated with curvature and branching in the human vasculature, where the shear stress is both oscillatory and multidirectional. Also, the combined effect of curvature and pulsatility in cardiovascular flows produces unsteady vortices. In this work, our goal is to assess the correlation between multiple vortex pairs and wall shear stress. To accomplish this, we use an in-house high-order flux reconstruction Navier-Stokes solver to simulate pulsatile flow of a Newtonian blood-analog fluid through a rigid 180° curved artery model. We use a physiologically relevant flow rate and generate results using both fully developed and uniform entrance conditions, the latter motivated by the fact that flow upstream to a curved artery may not be fully developed. Under these two inflow conditions, we characterize the evolution of various vortex pairs and their subsequent effect on several wall shear stress metrics. Supported by GW Center for Biomimetics and Bioinspired Engineering.

Secondary flow structures in a 180∘ elastic curved vessel with torsion under steady and pulsatile inflow conditions

Science.gov (United States)

Najjari, Mohammad Reza; Plesniak, Michael W.

2017-11-01

Secondary flow vortical structures were investigated in an elastic 180° curved pipe with and without torsion under steady and pulsatile flow using particle image velocimetry (PIV). The elastic thin-walled curved pipes were constructed using Sylgard 184, and inserted into a bath of refractive index matched fluid to perform PIV. A vortex identification method was employed to identify various vortical structures in the flow. The secondary flow structures in the planar compliant model with dilatation of 0.61%-3.23% under pulsatile flow rate were compared with the rigid vessel model results, and it was found that local vessel compliance has a negligible effect on secondary flow morphology. The secondary flow structures were found to be more sensitive to out of plane curvature (torsion) than to vessel compliance. Torsion distorts the symmetry of secondary flow and results in more complex vortical structures in both steady and pulsatile flows. In high Re number steady flow with torsion, a single dominant vortical structure can be detected at the middle of the 90° cross section. In pulsatile flow with torsion, the split-Dean and Lyne-type vortices with same rotation direction originating from opposite sides of the cross section tend to merge together. supported by GW Center for Biomimetics and Bioinspired Engineering.

Flow characteristics of developing laminar steady flows in a straight duct connected to a square curved duct

Energy Technology Data Exchange (ETDEWEB)

Sohn, Hyun Chull [Chosun Univ., Gwangju (Korea, Republic of)

2005-05-01

In the present study, the characteristics of developing steady laminar flows of a straight duct connected to a 180 .deg. curved duct were examined in the entrance region through experimental measurement. Flow characteristics such as shear stress distributions, pressure distributions and friction coefficient experimentally in a square cross-sectional straight duct by using the PIV system. For the PIV measurement by particles produced from mosquito coils particles. The experimental data were obtained at 9 points dividing the test sections by 400 mm. Experimental results can be summarized as follows. Critical Reynolds number, Re{sub cr} which indicates transition from laminar steady flow to transition steady flow was 2,150. Shear stress per unit length on the wall was stronger than that in the fully developed flow region. This was attributed to the fact that shear stress and pressure loss in the curvature of a duct were increased. Pressure distributions were gradually decreased irrespective of Reynolds number in the whole test section. This trends were in a good agreement with the reference results. Pipe friction coefficient in the steady state flow region was calculate from method of least squares. The co-relationship between fiction coefficient and Reynolds number was established as follow; {lambda}=56/Re.

Fluid flow profile in a packed bead column using residence time curves and radiotracer techniques

Energy Technology Data Exchange (ETDEWEB)

Almeida, Ana Paula F. de; Gonçalves, Eduardo Ramos; Brandão, Luis Eduardo B.; Salgado, Cesar M., E-mail: anacamiqui@gmail.com, E-mail: egoncalves@con.ufrj.br, E-mail: brandao@ien.gov.br, E-mail: otero@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

2017-07-01

Filling columns are extremely important in the chemical industry and are used for purification, separation and treatment processes of gas or liquid mixtures. The objective of this work is to study the hydrodynamics of the fluid for a characterization of aqueous phase flow patterns in the filling column, associating with the methodology of the Curves of Residence Time Distribution (RTD) to analyze and associate theoretical models that put as conditions column operating. RTD can be obtained by using the pulse-stimulus response technique which is characterized by the instantaneous injection of a radiotracer into the system input. In this work, 68Ga was used as radiotracer. Five shielded and collimated NaI (Tl) 1 x 1″ scintillator detectors were suitably positioned to record the movement of the radiotracer's path in the conveying line and filling column. Making possible the analysis of the RTD curve in the regions of interest. With the data generated by the NaI (Tl) detectors with the passage of the radiotracer in the transport line and inside the column, it was possible to evaluate the flow profile of the aqueous phase and to identify operational failures, such as internal conduit and the existence of a retention zone in the inside the column. Theoretical models were used for different flow flows: the piston flow and perfect mixing. (author)

Fluid flow profile in a packed bead column using residence time curves and radiotracer techniques

International Nuclear Information System (INIS)

Almeida, Ana Paula F. de; Gonçalves, Eduardo Ramos; Brandão, Luis Eduardo B.; Salgado, Cesar M.

2017-01-01

Filling columns are extremely important in the chemical industry and are used for purification, separation and treatment processes of gas or liquid mixtures. The objective of this work is to study the hydrodynamics of the fluid for a characterization of aqueous phase flow patterns in the filling column, associating with the methodology of the Curves of Residence Time Distribution (RTD) to analyze and associate theoretical models that put as conditions column operating. RTD can be obtained by using the pulse-stimulus response technique which is characterized by the instantaneous injection of a radiotracer into the system input. In this work, 68Ga was used as radiotracer. Five shielded and collimated NaI (Tl) 1 x 1″ scintillator detectors were suitably positioned to record the movement of the radiotracer's path in the conveying line and filling column. Making possible the analysis of the RTD curve in the regions of interest. With the data generated by the NaI (Tl) detectors with the passage of the radiotracer in the transport line and inside the column, it was possible to evaluate the flow profile of the aqueous phase and to identify operational failures, such as internal conduit and the existence of a retention zone in the inside the column. Theoretical models were used for different flow flows: the piston flow and perfect mixing. (author)

Three-dimensional flow analysis and improvement of slip factor model for forward-curved blades centrifugal fan

International Nuclear Information System (INIS)

Guo, En Min; Kim, Kwang Yong

2004-01-01

This work developed improved slip factor model and correction method to predict flow through impeller in forward-curved centrifugal fan. Both steady and unsteady three-dimensional CFD analyses were performed to validate the slip factor model and the correction method. The results show that the improved slip factor model presented in this paper could provide more accurate predictions for forward-curved centrifugal impeller than the other slip factor models since the present model takes into account the effect of blade curvature. The correction method is provided to predict mass-averaged absolute circumferential velocity at the exit of impeller by taking account of blockage effects induced by the large-scale backflow near the front plate and flow separation within blade passage. The comparison with CFD results also shows that the improved slip factor model coupled with the present correction method provides accurate predictions for mass-averaged absolute circumferential velocity at the exit of impeller near and above the flow rate of peak total pressure coefficient

Correction of Flow Curves and Constitutive Modelling of a Ti-6Al-4V Alloy

Directory of Open Access Journals (Sweden)

Ming Hu

2018-04-01

Full Text Available Isothermal uniaxial compressions of a Ti-6Al-4V alloy were carried out in the temperature range of 800–1050 °C and strain rate range of 0.001–1 s−1. The effects of friction between the specimen and anvils as well as the increase in temperature caused by the high strain rate deformation were considered, and flow curves were corrected as a result. Constitutive models were discussed based on the corrected flow curves. The correlation coefficient and average absolute relative error for the strain compensated Arrhenius-type constitutive model are 0.986 and 9.168%, respectively, while the values for a modified Johnson-Cook constitutive model are 0.924 and 22.673%, respectively. Therefore, the strain compensated Arrhenius-type constitutive model has a better prediction capability than a modified Johnson-Cook constitutive model.

The application of numerical debris flow modelling for the generation of physical vulnerability curves

Czech Academy of Sciences Publication Activity Database

Quan Luna, B.; Blahůt, Jan; van Westen, C.J.; Sterlacchini, S.; van Asch, T.W.J.; Akbas, S.O.

2011-01-01

Roč. 11, č. 7 (2011), s. 2047-2060 ISSN 1561-8633 Institutional research plan: CEZ:AV0Z30460519 Keywords : debris flow modelling * hazard * vulnerability curves Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.983, year: 2011 http://www.nat-hazards-earth-syst-sci.net/11/2047/2011/

Induction and Confirmation Theory: An Approach based on a Paraconsistent Nonmonotonic Logic

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Ricardo Sousa Silvestre

2010-12-01

Full Text Available This paper is an effort to realize and explore the connections that exist between nonmonotonic logic and confirmation theory. We pick up one of the most wide-spread nonmonotonic formalisms – default logic – and analyze to what extent and under what adjustments it could work as a logic of induction in the philosophical sense. By making use of this analysis, we extend default logic so as to make it able to minimally perform the task of a logic of induction, having as a result a system which we believe has interesting properties from the standpoint of theory of confirmation. It is for instance able to represent chains of inductive rules as well as to reason paraconsistently on the conclusions obtained from them. We then use this logic to represent some traditional ideas concerning confirmation theory, in particular the ones proposed by Carl Hempel in his classical paper “Studies in the Logic of Confirmation” of 1945 and the ones incorporated in the so-called abductive and hy-pothetico-deductive models.

Induction and Confirmation Theory: An Approach based on a Paraconsistent Nonmonotonic Logic

Directory of Open Access Journals (Sweden)

Ricardo Sousa Silvestre

2011-05-01

Full Text Available This paper is an effort to realize and explore the connections that exist between nonmonotonic logic and confirmation theory. We pick up one of the most wide-spread nonmonotonic formalisms – default logic – and analyze to what extent and under what adjustments it could work as a logic of induction in the philosophical sense. By making use of this analysis, we extend default logic so as to make it able to minimally perform the task of a logic of induction, having as a result a system which we believe has interesting properties from the standpoint of theory of confirmation. It is for instance able to represent chains of inductive rules as well as to reason paraconsistently on the conclusions obtained from them. We then use this logic to represent some traditional ideas concerning confirmation theory, in particular the ones proposed by Carl Hempel in his classical paper "Studies in the Logic of Confirmation" of 1945 and the ones incorporated in the so-called abductive and hy-pothetico-deductive models.

Analytical flow duration curves for summer streamflow in Switzerland

Science.gov (United States)

Santos, Ana Clara; Portela, Maria Manuela; Rinaldo, Andrea; Schaefli, Bettina

2018-04-01

This paper proposes a systematic assessment of the performance of an analytical modeling framework for streamflow probability distributions for a set of 25 Swiss catchments. These catchments show a wide range of hydroclimatic regimes, including namely snow-influenced streamflows. The model parameters are calculated from a spatially averaged gridded daily precipitation data set and from observed daily discharge time series, both in a forward estimation mode (direct parameter calculation from observed data) and in an inverse estimation mode (maximum likelihood estimation). The performance of the linear and the nonlinear model versions is assessed in terms of reproducing observed flow duration curves and their natural variability. Overall, the nonlinear model version outperforms the linear model for all regimes, but the linear model shows a notable performance increase with catchment elevation. More importantly, the obtained results demonstrate that the analytical model performs well for summer discharge for all analyzed streamflow regimes, ranging from rainfall-driven regimes with summer low flow to snow and glacier regimes with summer high flow. These results suggest that the model's encoding of discharge-generating events based on stochastic soil moisture dynamics is more flexible than previously thought. As shown in this paper, the presence of snowmelt or ice melt is accommodated by a relative increase in the discharge-generating frequency, a key parameter of the model. Explicit quantification of this frequency increase as a function of mean catchment meteorological conditions is left for future research.

Non-monotonic probability of thermal reversal in thin-film biaxial nanomagnets with small energy barriers

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N. Kani

2017-05-01

Full Text Available The goal of this paper is to investigate the short time-scale, thermally-induced probability of magnetization reversal for an biaxial nanomagnet that is characterized with a biaxial magnetic anisotropy. For the first time, we clearly show that for a given energy barrier of the nanomagnet, the magnetization reversal probability of an biaxial nanomagnet exhibits a non-monotonic dependence on its saturation magnetization. Specifically, there are two reasons for this non-monotonic behavior in rectangular thin-film nanomagnets that have a large perpendicular magnetic anisotropy. First, a large perpendicular anisotropy lowers the precessional period of the magnetization making it more likely to precess across the x^=0 plane if the magnetization energy exceeds the energy barrier. Second, the thermal-field torque at a particular energy increases as the magnitude of the perpendicular anisotropy increases during the magnetization precession. This non-monotonic behavior is most noticeable when analyzing the magnetization reversals on time-scales up to several tens of ns. In light of the several proposals of spintronic devices that require data retention on time-scales up to 10’s of ns, understanding the probability of magnetization reversal on the short time-scales is important. As such, the results presented in this paper will be helpful in quantifying the reliability and noise sensitivity of spintronic devices in which thermal noise is inevitably present.

Oscillation of Nonlinear Delay Differential Equation with Non-Monotone Arguments

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Özkan Öcalan

2017-07-01

Full Text Available Consider the first-order nonlinear retarded differential equation $$ x^{\\prime }(t+p(tf\\left( x\\left( \\tau (t\\right \\right =0, t\\geq t_{0} $$ where $p(t$ and $\\tau (t$ are function of positive real numbers such that $%\\tau (t\\leq t$ for$\\ t\\geq t_{0},\\ $and$\\ \\lim_{t\\rightarrow \\infty }\\tau(t=\\infty $. Under the assumption that the retarded argument is non-monotone, new oscillation results are given. An example illustrating the result is also given.

Non-monotonic behavior of electron temperature in argon inductively coupled plasma and its analysis via novel electron mean energy equation

Science.gov (United States)

Zhao, Shu-Xia

2018-03-01

In this work, the behavior of electron temperature against the power in argon inductively coupled plasma is investigated by a fluid model. The model properly reproduces the non-monotonic variation of temperature with power observed in experiments. By means of a novel electron mean energy equation proposed for the first time in this article, this electron temperature behavior is interpreted. In the overall considered power range, the skin effect of radio frequency electric field results in localized deposited power density, responsible for an increase of electron temperature with power by means of one parameter defined as power density divided by electron density. At low powers, the rate fraction of multistep and Penning ionizations of metastables that consume electron energy two times significantly increases with power, which dominates over the skin effect and consequently leads to the decrease of temperature with power. In the middle power regime, a transition region of temperature is given by the competition between the ionizing effect of metastables and the skin effect of electric field. The power location where the temperature alters its trend moves to the low power end as increasing the pressure due to the lack of metastables. The non-monotonic curve of temperature is asymmetric at the short chamber due to the weak role of skin effect in increasing the temperature and tends symmetric when axially prolonging the chamber. Still, the validity of the fluid model in this prediction is estimated and the role of neutral gas heating is guessed. This finding is helpful for people understanding the different trends of temperature with power in the literature.

Mapping axonal density and average diameter using non-monotonic time-dependent gradient-echo MRI

DEFF Research Database (Denmark)

Nunes, Daniel; Cruz, Tomás L; Jespersen, Sune N

2017-01-01

available in the clinic, or extremely long acquisition schemes to extract information from parameter-intensive models. In this study, we suggest that simple and time-efficient multi-gradient-echo (MGE) MRI can be used to extract the axon density from susceptibility-driven non-monotonic decay in the time...... the quantitative results are compared against ground-truth histology, they seem to reflect the axonal fraction (though with a bias, as evident from Bland-Altman analysis). As well, the extra-axonal fraction can be estimated. The results suggest that our model is oversimplified, yet at the same time evidencing......-dependent signal. We show, both theoretically and with simulations, that a non-monotonic signal decay will occur for multi-compartmental microstructures – such as axons and extra-axonal spaces, which we here used in a simple model for the microstructure – and that, for axons parallel to the main magnetic field...

Non-monotonic behaviour in relaxation dynamics of image restoration

International Nuclear Information System (INIS)

Ozeki, Tomoko; Okada, Masato

2003-01-01

We have investigated the relaxation dynamics of image restoration through a Bayesian approach. The relaxation dynamics is much faster at zero temperature than at the Nishimori temperature where the pixel-wise error rate is minimized in equilibrium. At low temperature, we observed non-monotonic development of the overlap. We suggest that the optimal performance is realized through premature termination in the relaxation processes in the case of the infinite-range model. We also performed Markov chain Monte Carlo simulations to clarify the underlying mechanism of non-trivial behaviour at low temperature by checking the local field distributions of each pixel

Heat transfer and pressure drop characteristics of the tube bank fin heat exchanger with fin punched with flow redistributors and curved triangular vortex generators

Science.gov (United States)

Liu, Song; Jin, Hua; Song, KeWei; Wang, LiangChen; Wu, Xiang; Wang, LiangBi

2017-10-01

The heat transfer performance of the tube bank fin heat exchanger is limited by the air-side thermal resistance. Thus, enhancing the air-side heat transfer is an effective method to improve the performance of the heat exchanger. A new fin pattern with flow redistributors and curved triangular vortex generators is experimentally studied in this paper. The effects of the flow redistributors located in front of the tube stagnation point and the curved vortex generators located around the tube on the characteristics of heat transfer and pressure drop are discussed in detail. A performance comparison is also carried out between the fins with and without flow redistributors. The experimental results show that the flow redistributors stamped out from the fin in front of the tube stagnation points can decrease the friction factor at the cost of decreasing the heat transfer performance. Whether the combination of the flow redistributors and the curved vortex generators will present a better heat transfer performance depends on the size of the curved vortex generators. As for the studied two sizes of vortex generators, the heat transfer performance is promoted by the flow redistributors for the fin with larger size of vortex generators and the performance is suppressed by the flow redistributors for the fin with smaller vortex generators.

Robust numerical methods for boundary-layer equations for a model problem of flow over a symmetric curved surface

NARCIS (Netherlands)

A.R. Ansari; B. Hossain; B. Koren (Barry); G.I. Shishkin (Gregori)

2007-01-01

textabstractWe investigate the model problem of flow of a viscous incompressible fluid past a symmetric curved surface when the flow is parallel to its axis. This problem is known to exhibit boundary layers. Also the problem does not have solutions in closed form, it is modelled by boundary-layer

Secondary flow vortical structures in a 180∘ elastic curved vessel with torsion under steady and pulsatile inflow conditions

Science.gov (United States)

Najjari, Mohammad Reza; Plesniak, Michael W.

2018-01-01

Secondary flow structures in a 180∘ curved pipe model of an artery are studied using particle image velocimetry. Both steady and pulsatile inflow conditions are investigated. In planar curved pipes with steady flow, multiple (two, four, six) vortices are detected. For pulsatile flow, various pairs of vortices, i.e., Dean, deformed-Dean, Lyne-type, and split-Dean, are present in the cross section of the pipe at 90∘ into the bend. The effects of nonplanar curvature (torsion) and vessel dilatation on these vortical structures are studied. Torsion distorts the symmetric secondary flows (which exist in planar curvatures) and can result in formation of more complex vortical structures. For example, the split-Dean and Lyne-type vortices with same rotation direction originating from opposite sides of the cross section tend to merge together in pulsatile flow. The vortical structures in elastic vessels with dilatation (0.61%-3.23%) are also investigated and the results are compared with rigid model results. It was found that the secondary flow structures in rigid and elastic models are similar, and hence the local compliance of the vessel does not affect the morphology of secondary flow structures.

Cuba: mitigation policies and the Environmental Kuznets curve

Directory of Open Access Journals (Sweden)

Yusimit Betancourt-Alayón

2017-12-01

Full Text Available This paper aims to determine whether there is for Cuba a growing non-monotonic relationship, known as the Environmental Kuznets Curve, between emissions of CO2, NOx and SO2 in relation to income levels as a measure of the degree of development a basic model from 1970 to 2010. In addition to exploring an extended model involving product structure and trade on emissions. These gases by the importance of the intensification of global warming and therefore in strengthening the climate change are studied. A positive relationship of emissions of the three gases with GDP, although with evidence of an emerging virtuous development path of emissions is obtained, in any case it is possible without a comprehensive development policy which is prioritized design mitigation options.

Parametric representation of centrifugal pump homologous curves

International Nuclear Information System (INIS)

Veloso, Marcelo A.; Mattos, Joao R.L. de

2015-01-01

Essential for any mathematical model designed to simulate flow transient events caused by pump operations is the pump performance data. The performance of a centrifugal pump is characterized by four basic quantities: the rotational speed, the volumetric flow rate, the dynamic head, and the hydraulic torque. The curves showing the relationships between these four variables are called the pump characteristic curves. The characteristic curves are empirically developed by the pump manufacturer and uniquely describe head and torque as functions of volumetric flow rate and rotation speed. Because of comprising a large amount of points, this configuration is not suitable for computational purposes. However, it can be converted to a simpler form by the development of the homologous curves, in which dynamic head and hydraulic torque ratios are expressed as functions of volumetric flow and rotation speed ratios. The numerical use of the complete set of homologous curves requires specification of sixteen partial curves, being eight for the dynamic head and eight for the hydraulic torque. As a consequence, the handling of homologous curves is still somewhat complicated. In solving flow transient problems that require the pump characteristic data for all the operation zones, the parametric form appears as the simplest way to deal with the homologous curves. In this approach, the complete characteristics of a pump can be described by only two closed curves, one for the dynamic head and other for the hydraulic torque, both in function of a single angular coordinate defined adequately in terms of the quotient between volumetric flow ratio and rotation speed ratio. The usefulness and advantages of this alternative method are demonstrated through a practical example in which the homologous curves for a pump of the type used in the main coolant loops of a pressurized water reactor (PWR) are transformed to the parametric form. (author)

Calibration of hydrological models using flow-duration curves

Directory of Open Access Journals (Sweden)

I. K. Westerberg

2011-07-01

Full Text Available The degree of belief we have in predictions from hydrologic models will normally depend on how well they can reproduce observations. Calibrations with traditional performance measures, such as the Nash-Sutcliffe model efficiency, are challenged by problems including: (1 uncertain discharge data, (2 variable sensitivity of different performance measures to different flow magnitudes, (3 influence of unknown input/output errors and (4 inability to evaluate model performance when observation time periods for discharge and model input data do not overlap. This paper explores a calibration method using flow-duration curves (FDCs to address these problems. The method focuses on reproducing the observed discharge frequency distribution rather than the exact hydrograph. It consists of applying limits of acceptability for selected evaluation points (EPs on the observed uncertain FDC in the extended GLUE approach. Two ways of selecting the EPs were tested – based on equal intervals of discharge and of volume of water. The method was tested and compared to a calibration using the traditional model efficiency for the daily four-parameter WASMOD model in the Paso La Ceiba catchment in Honduras and for Dynamic TOPMODEL evaluated at an hourly time scale for the Brue catchment in Great Britain. The volume method of selecting EPs gave the best results in both catchments with better calibrated slow flow, recession and evaporation than the other criteria. Observed and simulated time series of uncertain discharges agreed better for this method both in calibration and prediction in both catchments. An advantage with the method is that the rejection criterion is based on an estimation of the uncertainty in discharge data and that the EPs of the FDC can be chosen to reflect the aims of the modelling application, e.g. using more/less EPs at high/low flows. While the method appears less sensitive to epistemic input/output errors than previous use of limits of

Entropy Parameter M in Modeling a Flow Duration Curve

Directory of Open Access Journals (Sweden)

Yu Zhang

2017-12-01

Full Text Available A flow duration curve (FDC is widely used for predicting water supply, hydropower, environmental flow, sediment load, and pollutant load. Among different methods of constructing an FDC, the entropy-based method, developed recently, is appealing because of its several desirable characteristics, such as simplicity, flexibility, and statistical basis. This method contains a parameter, called entropy parameter M, which constitutes the basis for constructing the FDC. Since M is related to the ratio of the average streamflow to the maximum streamflow which, in turn, is related to the drainage area, it may be possible to determine M a priori and construct an FDC for ungauged basins. This paper, therefore, analyzed the characteristics of M in both space and time using streamflow data from 73 gauging stations in the Brazos River basin, Texas, USA. Results showed that the M values were impacted by reservoir operation and possibly climate change. The values were fluctuating, but relatively stable, after the operation of the reservoirs. Parameter M was found to change inversely with the ratio of average streamflow to the maximum streamflow. When there was an extreme event, there occurred a jump in the M value. Further, spatially, M had a larger value if the drainage area was small.

Unsteady laminar flow with convective heat transfer through a rotating curved square duct with small curvature

Energy Technology Data Exchange (ETDEWEB)

Mondal, Rabindra Nath, E-mail: rnmondal71@yahoo.com; Shaha, Poly Rani [Department of Mathematics, Jagannath University, Dhaka-1100 (Bangladesh); Roy, Titob [Department of Mathematics, Vikarunnesa Nun School and College, Boshundhara, Dhaka (Bangladesh); Yanase, Shinichiro, E-mail: yanase@okayama-u.ac.jp [Department of Mechanical and Systems Engineering, Okayama University, Okayama 700-8530 (Japan)

2016-07-12

Unsteady laminar flow with convective heat transfer through a curved square duct rotating at a constant angular velocity about the center of curvature is investigated numerically by using a spectral method, and covering a wide range of the Taylor number −300≤Tr≤1000 for the Dean number Dn = 1000. A temperature difference is applied across the vertical sidewalls for the Grashof number Gr = 100, where the outer wall is heated and the inner wall cooled, the top and bottom walls being adiabatic. Flow characteristics are investigated with the effects of rotational parameter, Tr, and the pressure-driven parameter, Dn, for the constant curvature 0.001. Time evolution calculations as well as their phase spaces show that the unsteady flow undergoes through various flow instabilities in the scenario ‘multi-periodic → chaotic → steady-state → periodic → multi-periodic → chaotic’, if Tr is increased in the positive direction. For negative rotation, however, time evolution calculations show that the flow undergoes in the scenario ‘multi-periodic → periodic → steady-state’, if Tr is increased in the negative direction. Typical contours of secondary flow patterns and temperature profiles are obtained at several values of Tr, and it is found that the unsteady flow consists of two- to six-vortex solutions if the duct rotation is involved. External heating is shown to generate a significant temperature gradient at the outer wall of the duct. This study also shows that there is a strong interaction between the heating-induced buoyancy force and the centrifugal-Coriolis instability in the curved channel that stimulates fluid mixing and consequently enhances heat transfer in the fluid.

Three dimensional numerical investigation of flow mixing in curved tubes and mass transfer in T-channel junction

International Nuclear Information System (INIS)

Pandey, Pradeep; Nayak, A.K.; Vijayan, P.K.

2014-01-01

Three dimensional flow patterns appearing in geometries such as curved pipes and T-channel junctions have important applications and are attractive for research. Unlike the flow in a straight tube, fluid motion in a curved tube is not parallel to the axis of bend, owing to the presence of centrifugal effects. It is characterized by a secondary flow in a cross-sectional plane normal to the main flow. Consequently, secondary flow separation near the inner wall is observed in the developing region. The strength of the secondary flow is greatly influenced by the curvature ratio and in turn, a non-dimensional parameter called the Dean Number. Secondary flow increases flow resistance, resulting in a larger pressure drop along the bend. The location of the maximum axial velocity gets shifted towards the outer wall. Flow in a T-channel junction is also a configuration of great significance. The simulations of the present work show that flow at low Reynolds numbers (Re ≤ 115) is steady and symmetric. For low Reynolds numbers, flow in the downstream channel remains highly segregated about the centerline. The appearance of vortices in the T-channel junction does little to redistribute concentration when flow remains symmetric. With increasing Reynolds number, transition takes place towards asymmetric flow. The incoming flow field gets redistributed at the center-plane and the dividing streamline becomes increasingly distorted. The flow field is characterized by thin elongated fluid interfaces across which momentum diffusion takes place. Flow at higher Reynolds numbers (Re ≥ 250) becomes unsteady in which unstable stagnation stream traces move periodically leftward and rightward at top and bottom walls. Trajectories of mass-less particles show greater dwelling in the junction as compared to those of finite mass particle. The numerical simulation is carried out in the present work using ANUPRAVAHA, a general purpose CFD solver developed at IIT Kanpur in collaboration with

Non-monotonic effect of growth temperature on carrier collection in SnS solar cells

International Nuclear Information System (INIS)

Chakraborty, R.; Steinmann, V.; Mangan, N. M.; Brandt, R. E.; Poindexter, J. R.; Jaramillo, R.; Mailoa, J. P.; Hartman, K.; Polizzotti, A.; Buonassisi, T.; Yang, C.; Gordon, R. G.

2015-01-01

We quantify the effects of growth temperature on material and device properties of thermally evaporated SnS thin-films and test structures. Grain size, Hall mobility, and majority-carrier concentration monotonically increase with growth temperature. However, the charge collection as measured by the long-wavelength contribution to short-circuit current exhibits a non-monotonic behavior: the collection decreases with increased growth temperature from 150 °C to 240 °C and then recovers at 285 °C. Fits to the experimental internal quantum efficiency using an opto-electronic model indicate that the non-monotonic behavior of charge-carrier collection can be explained by a transition from drift- to diffusion-assisted components of carrier collection. The results show a promising increase in the extracted minority-carrier diffusion length at the highest growth temperature of 285 °C. These findings illustrate how coupled mechanisms can affect early stage device development, highlighting the critical role of direct materials property measurements and simulation

Use of Gene Expression Programming in regionalization of flow duration curve

Science.gov (United States)

Hashmi, Muhammad Z.; Shamseldin, Asaad Y.

2014-06-01

In this paper, a recently introduced artificial intelligence technique known as Gene Expression Programming (GEP) has been employed to perform symbolic regression for developing a parametric scheme of flow duration curve (FDC) regionalization, to relate selected FDC characteristics to catchment characteristics. Stream flow records of selected catchments located in the Auckland Region of New Zealand were used. FDCs of the selected catchments were normalised by dividing the ordinates by their median value. Input for the symbolic regression analysis using GEP was (a) selected characteristics of normalised FDCs; and (b) 26 catchment characteristics related to climate, morphology, soil properties and land cover properties obtained using the observed data and GIS analysis. Our study showed that application of this artificial intelligence technique expedites the selection of a set of the most relevant independent variables out of a large set, because these are automatically selected through the GEP process. Values of the FDC characteristics obtained from the developed relationships have high correlations with the observed values.

Polar representation of centrifugal pump homologous curves

International Nuclear Information System (INIS)

Veloso, Marcelo Antonio; Mattos, Joao Roberto Loureiro de

2008-01-01

Essential for any mathematical model designed to simulate flow transient events caused by pump operations is the pump performance data. The performance of a centrifugal pump is characterized by four basic parameters: the rotational speed, the volumetric flow rate, the dynamic head, and the hydraulic torque. Any one of these quantities can be expressed as a function of any two others. The curves showing the relationships between these four variables are called the pump characteristic curves, also referred to as four-quadrant curves. The characteristic curves are empirically developed by the pump manufacturer and uniquely describe head and torque as functions of volumetric flow rate and rotation speed. Because of comprising a large amount of points, the four-quadrant configuration is not suitable for computational purposes. However, it can be converted to a simpler form by the development of the homologous curves, in which dynamic head and hydraulic torque ratios are expressed as functions of volumetric flow and rotation speed ratios. The numerical use of the complete set of homologous curves requires specification of sixteen partial curves, being eight for the dynamic head and eight for the hydraulic torque. As a consequence, the handling of homologous curves is still somewhat complicated. In solving flow transient problems that require the pump characteristic data for all the operation zones, the polar form appears as the simplest way to represent the homologous curves. In the polar method, the complete characteristics of a pump can be described by only two closed curves, one for the dynamic head and other for the hydraulic torque, both in function of a single angular coordinate defined adequately in terms of the quotient between volumetric flow ratio and rotation speed ratio. The usefulness and advantages of this alternative method are demonstrated through a practical example in which the homologous curves for a pump of the type used in the main coolant loops of a

Numerical study for Darcy-Forchheimer flow due to a curved stretching surface with Cattaneo-Christov heat flux and homogeneous-heterogeneous reactions

Directory of Open Access Journals (Sweden)

Tasawar Hayat

Full Text Available The current investigation presents Darcy-Forchheimer flow of viscous fluid caused by a curved stretching sheet. Flow for porous space is characterized by Darcy-Forchheimer relation. Concept of homogeneous and heterogeneous reactions is also utilized. Heat transfer for Cattaneo–Christov theory characterizing the feature of thermal relaxation is incorporated. Nonlinear differential systems are derived. Shooting algorithm is employed to construct the solutions for the resulting nonlinear system. The characteristics of various sundry parameters are studied and discussed. Skin friction coefficient and heat transfer rate are numerically described. Keywords: 2D flow, Curved stretching surface, Darcy-Forchheimer porous medium, Cattaneo-Christov heat flux, Homogeneous-heterogeneous reactions

Visualized study on specific points on demand curves and flow patterns in a single-side heated narrow rectangular channel

International Nuclear Information System (INIS)

Wang Junfeng; Huang Yanping; Wang Yanlin

2011-01-01

Highlights: → Specific points on the demand curve and flow patterns are visually studied. → Bubbly, churn, and annular flows were observed. → Onset of flow instability and bubbly-churn transition occurs at the same time. → The evolution of specific points and flow pattern transitions were examined. - Abstract: A simultaneous visualization and measurement study on some specific points on demand curves, such as onset of nucleate boiling (ONB), onset of significant void (OSV), onset of flow instability (OFI), and two-phase flow patterns in a single-side heated narrow rectangular channel, having a width of 40 mm and a gap of 3 mm, was carried out. New experimental approaches were adopted to identify OSV and OFI in a narrow rectangular channel. Under experimental conditions, the ONB could be predicted well by the Sato and Matsumura model. The OSV model of Bowring can reasonably predict the OSV if the single-side heated condition is considered. The OFI was close to the saturated boiling point and could be described accurately by Kennedy's correlation. The two-phase flow patterns observed in this experiment could be classified into bubbly, churn, and annular flow. Slug flow was never observed. The OFI always occurred when the bubbles at the channel exit began to coalesce, which corresponded to the beginning of the bubbly-churn transition in flow patterns. Finally, the evolution of specific points and flow pattern transitions were examined in a single-side heated narrow rectangular channel.

Marangoni instability in a thin film heated from below: Effect of nonmonotonic dependence of surface tension on temperature

Science.gov (United States)

Sarma, Rajkumar; Mondal, Pranab Kumar

2018-04-01

We investigate Marangoni instability in a thin liquid film resting on a substrate of low thermal conductivity and separated from the surrounding gas phase by a deformable free surface. Considering a nonmonotonic variation of surface tension with temperature, here we analytically derive the neutral stability curve for the monotonic and oscillatory modes of instability (for both the long-wave and short-wave perturbations) under the framework of linear stability analysis. For the long-wave instability, we derive a set of amplitude equations using the scaling k ˜(Bi) 1 /2 , where k is the wave number and Bi is the Biot number. Through this investigation, we demonstrate that for such a fluid layer upon heating from below, both monotonic and oscillatory instability can appear for a certain range of the dimensionless parameters, viz., Biot number (Bi ) , Galileo number (Ga ) , and inverse capillary number (Σ ) . Moreover, we unveil, through this study, the influential role of the above-mentioned parameters on the stability of the system and identify the critical values of these parameters above which instability initiates in the liquid layer.

Water quality, streamflow conditions, and annual flow-duration curves for streams of the San Juan–Chama Project, southern Colorado and northern New Mexico, 1935-2010

Science.gov (United States)

Falk, Sarah E.; Anderholm, Scott K.; Hafich, Katya A.

2013-01-01

The Albuquerque–Bernalillo County Water Utility Authority supplements the municipal water supply for the Albuquerque metropolitan area, in central New Mexico, with water diverted from the Rio Grande. Water diverted from the Rio Grande for municipal use is derived from the San Juan–Chama Project, which delivers water from streams in the southern San Juan Mountains in the Colorado River Basin in southern Colorado to the Rio Chama watershed and the Rio Grande Basin in northern New Mexico. The U.S. Geological Survey, in cooperation with Albuquerque–Bernalillo County Water Utility Authority, has compiled historical streamflow and water-quality data and collected new water-quality data to characterize the water quality and streamflow conditions and annual flow variability, as characterized by annual flow-duration curves, of streams of the San Juan–Chama Project. Nonparametric statistical methods were applied to calculate annual and monthly summary statistics of streamflow, trends in streamflow conditions were evaluated with the Mann–Kendall trend test, and annual variation in streamflow conditions was evaluated with annual flow-duration curves. The study area is located in northern New Mexico and southern Colorado and includes the Rio Blanco, Little Navajo River, and Navajo River, tributaries of the San Juan River in the Colorado River Basin located in the southern San Juan Mountains, and Willow Creek and Horse Lake Creek, tributaries of the Rio Chama in the Rio Grande Basin. The quality of water in the streams in the study area generally varied by watershed on the basis of the underlying geology and the volume and source of the streamflow. Water from the Rio Blanco and Little Navajo River watersheds, primarily underlain by volcanic deposits, volcaniclastic sediments and landslide deposits derived from these materials, was compositionally similar and had low specific-conductance values relative to the other streams in the study area. Water from the Navajo River

ASPMT(QS): Non-Monotonic Spatial Reasoning with Answer Set Programming Modulo Theories

OpenAIRE

Wałęga, Przemysław Andrzej; Bhatt, Mehul; Schultz, Carl

2015-01-01

The systematic modelling of \\emph{dynamic spatial systems} [9] is a key requirement in a wide range of application areas such as comonsense cognitive robotics, computer-aided architecture design, dynamic geographic information systems. We present ASPMT(QS), a novel approach and fully-implemented prototype for non-monotonic spatial reasoning ---a crucial requirement within dynamic spatial systems-- based on Answer Set Programming Modulo Theories (ASPMT). ASPMT(QS) consists of a (qualitative) s...

MHD convective flow of magnetite-Fe3O4 nanoparticles by curved stretching sheet

Directory of Open Access Journals (Sweden)

Tasawar Hayat

Full Text Available Present work is devoted to convective flow of ferrofluid due to non linear stretching curved sheet. Electrically conducting fluid is considered in the presence of uniform magnetic field. Nanofluid comprises water and magnetite-Fe3O4 as nanoparticles. Thermal radiation and heat generation/absorption are explained. Homotopy concept is utilized for the development of solutions. Highly nonlinear partial differential systems are reduced into the nonlinear ordinary differential system. Impact of non-dimensional radius of curvature and power law index on the physical quantities like fluid pressure, velocity and temperature field are examined. Computations for surface shear stress and heat transfer rate also analyzed. Keywords: MHD nanofluid, Thermal radiation, Porous medium, Convective boundary conditions, Non-linear curved stretching sheet

On conditions and parameters important to model sensitivity for unsaturated flow through layered, fractured tuff

International Nuclear Information System (INIS)

Prindle, R.W.; Hopkins, P.L.

1990-10-01

The Hydrologic Code Intercomparison Project (HYDROCOIN) was formed to evaluate hydrogeologic models and computer codes and their use in performance assessment for high-level radioactive-waste repositories. This report describes the results of a study for HYDROCOIN of model sensitivity for isothermal, unsaturated flow through layered, fractured tuffs. We investigated both the types of flow behavior that dominate the performance measures and the conditions and model parameters that control flow behavior. We also examined the effect of different conceptual models and modeling approaches on our understanding of system behavior. The analyses included single- and multiple-parameter variations about base cases in one-dimensional steady and transient flow and in two-dimensional steady flow. The flow behavior is complex even for the highly simplified and constrained system modeled here. The response of the performance measures is both nonlinear and nonmonotonic. System behavior is dominated by abrupt transitions from matrix to fracture flow and by lateral diversion of flow. The observed behaviors are strongly influenced by the imposed boundary conditions and model constraints. Applied flux plays a critical role in determining the flow type but interacts strongly with the composite-conductivity curves of individual hydrologic units and with the stratigraphy. One-dimensional modeling yields conservative estimates of distributions of groundwater travel time only under very limited conditions. This study demonstrates that it is wrong to equate the shortest possible water-travel path with the fastest path from the repository to the water table. 20 refs., 234 figs., 10 tabs

Modification of Flow Stress Curves and Constitutive Equations During Hot Compression Deformation of 5083 Aluminum Alloy

Directory of Open Access Journals (Sweden)

FU Ping

2017-08-01

Full Text Available The flow stress behavior of 5083 aluminum alloy was investigated under hot compression deformation at 523-723K,strain rates of 0.01-10s-1 and true strains of 0-0.7 with Gleeble-3800 thermal simulator. Based on the heat transfer effect on alloy deformation heat effect, the flow stress curves were corrected. The results show that influence of heat conduction can not be neglected and becomes more obvious with the increase of true strain. The corrected flow stress has little influence on the peak stress, but the steady flow stress softening trends to be diminished to some degree. The flow stress can be predicted by the Zener-Hollomon parameters in the constitutive equation. The corrected measured value exhibits a good agreement with the flow stress predicted by the constitutive equation, and the average relative error is only 5.21%.

Vulnerability curves vs. vulnerability indicators: application of an indicator-based methodology for debris-flow hazards

Science.gov (United States)

Papathoma-Köhle, Maria

2016-08-01

The assessment of the physical vulnerability of elements at risk as part of the risk analysis is an essential aspect for the development of strategies and structural measures for risk reduction. Understanding, analysing and, if possible, quantifying physical vulnerability is a prerequisite for designing strategies and adopting tools for its reduction. The most common methods for assessing physical vulnerability are vulnerability matrices, vulnerability curves and vulnerability indicators; however, in most of the cases, these methods are used in a conflicting way rather than in combination. The article focuses on two of these methods: vulnerability curves and vulnerability indicators. Vulnerability curves express physical vulnerability as a function of the intensity of the process and the degree of loss, considering, in individual cases only, some structural characteristics of the affected buildings. However, a considerable amount of studies argue that vulnerability assessment should focus on the identification of these variables that influence the vulnerability of an element at risk (vulnerability indicators). In this study, an indicator-based methodology (IBM) for mountain hazards including debris flow (Kappes et al., 2012) is applied to a case study for debris flows in South Tyrol, where in the past a vulnerability curve has been developed. The relatively "new" indicator-based method is being scrutinised and recommendations for its improvement are outlined. The comparison of the two methodological approaches and their results is challenging since both methodological approaches deal with vulnerability in a different way. However, it is still possible to highlight their weaknesses and strengths, show clearly that both methodologies are necessary for the assessment of physical vulnerability and provide a preliminary "holistic methodological framework" for physical vulnerability assessment showing how the two approaches may be used in combination in the future.

Large Airborne Full Tensor Gradient Data Inversion Based on a Non-Monotone Gradient Method

Science.gov (United States)

Sun, Yong; Meng, Zhaohai; Li, Fengting

2018-03-01

Following the development of gravity gradiometer instrument technology, the full tensor gravity (FTG) data can be acquired on airborne and marine platforms. Large-scale geophysical data can be obtained using these methods, making such data sets a number of the "big data" category. Therefore, a fast and effective inversion method is developed to solve the large-scale FTG data inversion problem. Many algorithms are available to accelerate the FTG data inversion, such as conjugate gradient method. However, the conventional conjugate gradient method takes a long time to complete data processing. Thus, a fast and effective iterative algorithm is necessary to improve the utilization of FTG data. Generally, inversion processing is formulated by incorporating regularizing constraints, followed by the introduction of a non-monotone gradient-descent method to accelerate the convergence rate of FTG data inversion. Compared with the conventional gradient method, the steepest descent gradient algorithm, and the conjugate gradient algorithm, there are clear advantages of the non-monotone iterative gradient-descent algorithm. Simulated and field FTG data were applied to show the application value of this new fast inversion method.

Non-monotonic Pre-fixed Points and Learning

Directory of Open Access Journals (Sweden)

Stefano Berardi

2013-08-01

Full Text Available We consider the problem of finding pre-fixed points of interactive realizers over arbitrary knowledge spaces, obtaining a relative recursive procedure. Knowledge spaces and interactive realizers are an abstract setting to represent learning processes, that can interpret non-constructive proofs. Atomic pieces of information of a knowledge space are stratified into levels, and evaluated into truth values depending on knowledge states. Realizers are then used to define operators that extend a given state by adding and possibly removing atoms: in a learning process states of knowledge change nonmonotonically. Existence of a pre-fixed point of a realizer is equivalent to the termination of the learning process with some state of knowledge which is free of patent contradictions and such that there is nothing to add. In this paper we generalize our previous results in the case of level 2 knowledge spaces and deterministic operators to the case of omega-level knowledge spaces and of non-deterministic operators.

Non-monotonic dose-response relationships and endocrine disruptors: a qualitative method of assessment

OpenAIRE

Lagarde, Fabien; Beausoleil, Claire; Belcher, Scott M; Belzunces, Luc P; Emond, Claude; Guerbet, Michel; Rousselle, Christophe

2015-01-01

International audience; Experimental studies investigating the effects of endocrine disruptors frequently identify potential unconventional dose-response relationships called non-monotonic dose-response (NMDR) relationships. Standardized approaches for investigating NMDR relationships in a risk assessment context are missing. The aim of this work was to develop criteria for assessing the strength of NMDR relationships. A literature search was conducted to identify published studies that repor...

Numerical investigation of the LM MHD flows in a curved duct with an FCI with varying slot locations

International Nuclear Information System (INIS)

Yang, Jong Hoon; Yan, Yue; Kim, Chang Nyung

2016-01-01

Highlights: • This study numerically investigates the liquid-metal magnetohydrodynamic flows in a curved duct with an FCI. • The effects of the location of FCI slot and of the curvature radius on the flow behavior are reviewed. • The influence of the FCI slot position on the equalization of the pressure in the inner fluid region (inside the FCI) and the gap fluid region (outer the FCI) is examined. - Abstract: This study numerically investigates the liquid-metal (LM) magnetohydrodynamic (MHD) flows in a curved duct with an FCI having three different slot locations and having no slot under a uniform magnetic field perpendicular to the duct. The flow velocity, current density, electric potential, Lorentz force, and pressure in different flow situations are presented in detail. The effects of the location of FCI slot and of the curvature radius on the flow behavior are reviewed. The flow field is examined with an introduction of the electric-field component and electro-motive component of the current, allowing us to analyze the interdependency of the flow variables. The effect of the FCI slot position on the equalization of the pressure in the inner fluid region (inside the FCI) and the gap fluid region (outer the FCI) is examined. The result shows that and the case with an FCI slot located in the neutral position yields the smallest pressure gradient in the main flow direction among the cases with an FCI slot, resulting in the smallest pressure drop. Also, in a flow situation with smaller radius of curvature with the FCI slot in the neutral position, the axial velocity near the inner (in terms of the curvature) part of a cross-section is higher than that near the outer part.

Dynamic Response and Optimal Design of Curved Metallic Sandwich Panels under Blast Loading

Science.gov (United States)

Yang, Shu; Han, Shou-Hong; Lu, Zhen-Hua

2014-01-01

It is important to understand the effect of curvature on the blast response of curved structures so as to seek the optimal configurations of such structures with improved blast resistance. In this study, the dynamic response and protective performance of a type of curved metallic sandwich panel subjected to air blast loading were examined using LS-DYNA. The numerical methods were validated using experimental data in the literature. The curved panel consisted of an aluminum alloy outer face and a rolled homogeneous armour (RHA) steel inner face in addition to a closed-cell aluminum foam core. The results showed that the configuration of a “soft” outer face and a “hard” inner face worked well for the curved sandwich panel against air blast loading in terms of maximum deflection (MaxD) and energy absorption. The panel curvature was found to have a monotonic effect on the specific energy absorption (SEA) and a nonmonotonic effect on the MaxD of the panel. Based on artificial neural network (ANN) metamodels, multiobjective optimization designs of the panel were carried out. The optimization results revealed the trade-off relationships between the blast-resistant and the lightweight objectives and showed the great use of Pareto front in such design circumstances. PMID:25126606

Dynamic response and optimal design of curved metallic sandwich panels under blast loading.

Science.gov (United States)

Qi, Chang; Yang, Shu; Yang, Li-Jun; Han, Shou-Hong; Lu, Zhen-Hua

2014-01-01

It is important to understand the effect of curvature on the blast response of curved structures so as to seek the optimal configurations of such structures with improved blast resistance. In this study, the dynamic response and protective performance of a type of curved metallic sandwich panel subjected to air blast loading were examined using LS-DYNA. The numerical methods were validated using experimental data in the literature. The curved panel consisted of an aluminum alloy outer face and a rolled homogeneous armour (RHA) steel inner face in addition to a closed-cell aluminum foam core. The results showed that the configuration of a "soft" outer face and a "hard" inner face worked well for the curved sandwich panel against air blast loading in terms of maximum deflection (MaxD) and energy absorption. The panel curvature was found to have a monotonic effect on the specific energy absorption (SEA) and a nonmonotonic effect on the MaxD of the panel. Based on artificial neural network (ANN) metamodels, multiobjective optimization designs of the panel were carried out. The optimization results revealed the trade-off relationships between the blast-resistant and the lightweight objectives and showed the great use of Pareto front in such design circumstances.

Dynamic Response and Optimal Design of Curved Metallic Sandwich Panels under Blast Loading

Directory of Open Access Journals (Sweden)

Chang Qi

2014-01-01

Full Text Available It is important to understand the effect of curvature on the blast response of curved structures so as to seek the optimal configurations of such structures with improved blast resistance. In this study, the dynamic response and protective performance of a type of curved metallic sandwich panel subjected to air blast loading were examined using LS-DYNA. The numerical methods were validated using experimental data in the literature. The curved panel consisted of an aluminum alloy outer face and a rolled homogeneous armour (RHA steel inner face in addition to a closed-cell aluminum foam core. The results showed that the configuration of a “soft” outer face and a “hard” inner face worked well for the curved sandwich panel against air blast loading in terms of maximum deflection (MaxD and energy absorption. The panel curvature was found to have a monotonic effect on the specific energy absorption (SEA and a nonmonotonic effect on the MaxD of the panel. Based on artificial neural network (ANN metamodels, multiobjective optimization designs of the panel were carried out. The optimization results revealed the trade-off relationships between the blast-resistant and the lightweight objectives and showed the great use of Pareto front in such design circumstances.

Flowing equation gradually varied in rectangles channels on depth curve; Ecuacion del flujo gradualmente variado en canales rectangulares de fondo curvo

Energy Technology Data Exchange (ETDEWEB)

Sotelo-Avila, G.; Gallegos-Silva, J. [Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)

2002-03-01

The study of channel flow usually have its basis in the hydrostatic distribution of pressure and the rectilinear flow hypotheses. It is from this hypothesis that the main flow equations are obtained. However, this is not applicable to a vertically curved flow that is present in a curved bed channel. This kind of channel is used to join two different slopes or in ski jumps. This kind of flow presents several changes from the rectilinear flow as in the velocity and pressure distributions and even in the energy loses. The authors of this article propose an equation of gradually varied flow for vertically-curved bed rectangular channels that adds a coefficient to modify the velocity in the calculus of the local friction gradient. With these results is possible now to analyze flow profiles in vertically-curved bed channels where before were used the methods for straight channels and therefore, increase accuracy. [Spanish] Las hipotesis del movimiento rectilineo y de distribucion hidrostatica de la presion son ciertamente las mas importantes en la hidraulica de canales, y de ellas se derivan los principales modelos de flujo que usualmente emplean. Sin embargo, no es valido aplicar la misma hipotesis y metodos de analisis al flujo curvilineo, que ocurre cuando el canal adopta curvaturas verticales en el fondo, las cuales inducen cambios importantes en la distribucion de la velocidad, presion y hasta en la perdida d energia. Tal es el caso de canales que contienen curvas verticales para unir tramos de distintas pendientes y producir el cambio en la direccion del flujo en cubetas deflectoras y vertedores en tunel. Los autores de este articulo proponen una ecuacion de flujo gradualmente variado en canales rectangulares de fondo curvo, esta es de gran utilidad en la determinacion del perfil del flujo con dichas caracteristicas, donde se plantea la adicion de un factor de amplificacion de la velocidad en el calculo del gradiente local de friccion, para tomar en cuenta el

ICP curve morphology and intracranial flow-volume changes

DEFF Research Database (Denmark)

Unnerbäck, Mårten; Ottesen, Johnny T.; Reinstrup, Peter

2018-01-01

proposed to shape the ICP curve. This study tested the hypothesis that the ICP curve correlates to intracranial volume changes. METHODS: Cine phase contrast magnetic resonance imaging (MRI) examinations were performed in neuro-intensive care patients with simultaneous ICP monitoring. The MRI was set......BACKGROUND: The intracranial pressure (ICP) curve with its different peaks has been extensively studied, but the exact physiological mechanisms behind its morphology are still not fully understood. Both intracranial volume change (ΔICV) and transmission of the arterial blood pressure have been...

Nonmonotonic Behavior of Supermultiplet Pattern Formation in a Noisy Lotka-Volterra System

International Nuclear Information System (INIS)

Fiasconaro, A.; Valenti, D.; Spagnolo, B.

2004-01-01

The noise-induced pattern formation in a population dynamical model of three interacting species in the coexistence regime is investigated. A coupled map lattice of Lotka-Volterra equations in the presence of multiplicative noise is used to analyze the spatiotemporal evolution. The spatial correlation of the species concentration as a function of time and of the noise intensity is investigated. A nonmonotonic behavior of the area of the patterns as a function of both noise intensity and evolution time is found. (author)

Computing daily mean streamflow at ungaged locations in Iowa by using the Flow Anywhere and Flow Duration Curve Transfer statistical methods

Science.gov (United States)

Linhart, S. Mike; Nania, Jon F.; Sanders, Curtis L.; Archfield, Stacey A.

2012-01-01

linear regression method and the daily mean streamflow for the 15th day of every other month. The Flow Duration Curve Transfer method was used to estimate unregulated daily mean streamflow from the physical and climatic characteristics of gaged basins. For the Flow Duration Curve Transfer method, daily mean streamflow quantiles at the ungaged site were estimated with the parameter-based regression model, which results in a continuous daily flow-duration curve (the relation between exceedance probability and streamflow for each day of observed streamflow) at the ungaged site. By the use of a reference streamgage, the Flow Duration Curve Transfer is converted to a time series. Data used in the Flow Duration Curve Transfer method were retrieved for 113 continuous-record streamgages in Iowa and within a 50-mile buffer of Iowa. The final statewide regression equations for Iowa were computed by using a weighted-least-squares multiple linear regression method and were computed for the 0.01-, 0.05-, 0.10-, 0.15-, 0.20-, 0.30-, 0.40-, 0.50-, 0.60-, 0.70-, 0.80-, 0.85-, 0.90-, and 0.95-exceedance probability statistics determined from the daily mean streamflow with a reporting limit set at 0.1 ft3/s. The final statewide regression equation for Iowa computed by using left-censored regression techniques was computed for the 0.99-exceedance probability statistic determined from the daily mean streamflow with a low limit threshold and a reporting limit set at 0.1 ft3/s. For the Flow Anywhere method, results of the validation study conducted by using six streamgages show that differences between the root-mean-square error and the mean absolute error ranged from 1,016 to 138 ft3/s, with the larger value signifying a greater occurrence of outliers between observed and estimated streamflows. Root-mean-square-error values ranged from 1,690 to 237 ft3/s. Values of the percent root-mean-square error ranged from 115 percent to 26.2 percent. The logarithm (base 10) streamflow percent root

Non-contact flow gauging for the extension and development of rating curves

Science.gov (United States)

Perks, Matthew; Large, Andy; Russell, Andy

2015-04-01

Accurate measurement of river discharge is fundamental to understanding hydrological processes, associated hazards and ecological responses within fluvial systems. Established protocols for determining river discharge are partial, predominantly invasive and logistically difficult during high flows. There is demand for new methods for accurate quantification of flow velocity under high-flow/flood conditions to in turn enable better post-event reconstruction of peak discharge. As a consequence considerable effort has been devoted to the development of innovative technologies for the representation of flow in open channels. Remotely operated fixed and mobile systems capable of providing quantitative estimates of instantaneous and time-averaged flow characteristics using non-contact methods has been a major development. Amongst the new approaches for stand-alone continuous monitoring of surface flows is Large Scale Particle Image Velocimetry (LSPIV). Here we adapt the LSPIV concept, to provide continuous discharge measurements in non-uniform channels with complex flow conditions. High Definition videos (1080p; 30fps) of the water surface are acquired at 5 minute intervals. The image is rectified to correct for perspective distortion using a new, open source tool which minimises errors resulting from oblique image capture. Naturally occurring artefacts on the water surface (e.g. bubbles, debris, etc.) are tracked with the Kanade-Lucas-Tomasi (KLT) algorithm. The data generated is in the form of a complex surface water velocity field which can be interrogated to extract a range of hydrological information such as the streamwise velocity at a cross-section of interest, or even allow the interrogation of hydrodynamic flow structures. Here we demonstrate that this approach is capable of generating river discharge data comparable to concurrent measurements made using existing, accepted technologies (e.g. ADCP). The outcome is better constraint and extension of rating curves

Axial velocity profiles and secondary flows of developing laminar flows in a straight connected exit region of a 180 .deg. square curved duct

Energy Technology Data Exchange (ETDEWEB)

Sohn, Hyun Chull; Lee, Heang Nam; Park, Gil Moon [Chosun Univ., Gwangju (Korea, Republic of)

2005-10-01

In the present study, characteristics of steady state laminar flows of a straight duct connected to a 180 .deg. curved duct were examined in the entrance region through experimental and numerical analyses. For the analysis, the governing equations of laminar flows in the Cartesian coordinate system were applied. Flow characteristics such as velocity profiles and secondary flows were investigated numerically and experimentally in a square cross-sectional straight duct by the PIV system and a CFD code (STARCD). For the PIV measurement, smoke particles produced from mosquito coils. The experimental data were obtained at 9 points dividing the test sections by 400 mm. Experimental and numerical results can be summarized as follows. 1) Reynolds number, Re was increased, dimensionless velocity profiles at the outer wall were increased due to the effect of the centrifugal force and secondary flows. 2) The intensity of a secondary flow became stronger at the inner wall rather than the outer wall regardless of Reynolds number. Especially, fluid dynamic phenomenon called conner impact were observed at dimensionless axial position, x/D{sub h}=50.

How do people learn from negative evidence? Non-monotonic generalizations and sampling assumptions in inductive reasoning.

Science.gov (United States)

Voorspoels, Wouter; Navarro, Daniel J; Perfors, Amy; Ransom, Keith; Storms, Gert

2015-09-01

A robust finding in category-based induction tasks is for positive observations to raise the willingness to generalize to other categories while negative observations lower the willingness to generalize. This pattern is referred to as monotonic generalization. Across three experiments we find systematic non-monotonicity effects, in which negative observations raise the willingness to generalize. Experiments 1 and 2 show that this effect emerges in hierarchically structured domains when a negative observation from a different category is added to a positive observation. They also demonstrate that this is related to a specific kind of shift in the reasoner's hypothesis space. Experiment 3 shows that the effect depends on the assumptions that the reasoner makes about how inductive arguments are constructed. Non-monotonic reasoning occurs when people believe the facts were put together by a helpful communicator, but monotonicity is restored when they believe the observations were sampled randomly from the environment. Copyright © 2015 Elsevier Inc. All rights reserved.

Determination of the equation parameters of carbon flow curves and estimated carbon flow and CO2 emissions from broiler production.

Science.gov (United States)

Henn, J D; Bockor, L; Borille, R; Coldebella, A; Ribeiro, A M L; Kessler, A M

2015-09-01

The objective of this study was to determine the equation parameters of carbon (i.e., C) flow curves and to estimate C flow and carbon dioxide (i.e., CO2) emissions from the production of 1- to 49-day-old broilers from different genetic strains. In total, 384 1-day-old chicks were used, distributed into 4 groups: high-performance males (Cobb-M) and females (Cobb-F), and intermediate-performance males (C44-M) and females (C44-F), with 6 replicates/treatment according to a completely randomized study design. Carbon intake and retention were calculated based on diet and body C composition, and expired C was stoichiometrically estimated as digestible C intake-C retention-C in the urine. Litter C emission was estimated as initial litter C+C in the excreta-final litter C. Carbon flow curves were determined fitting data by nonlinear regression using the Gompertz function. Expired CO2 was calculated based on expired C. The applied nonlinear model presented goodness-of-fit for all responses (R2>0.99). Carbon dioxide production was highly correlated with growth rate. At 42 d age, CO2 expiration (g/bird) was 3,384.4 for Cobb-M, 2,947.9 for Cobb-F, 2,512.5 for C44-M, and 2185.1 for C44-F. Age also significantly affected CO2 production: to achieve 2.0 kg BW, CO2 expiration (g/bird) was 1,794.3 for Cobb-M, 2,016.5 for Cobb-F, 2617.7 for C44-M, and 3,092.3 for C44-F. The obtained equations present high predictability to estimate individual CO2 emissions in strains of Cobb and C44 broilers of any weight, or age, reared between 1 and 49 d age. © 2015 Poultry Science Association Inc.

Surfactant Effect on the Average Flow Generation Near Curved Interface

Science.gov (United States)

Klimenko, Lyudmila; Lyubimov, Dmitry

2018-02-01

The present work is devoted to the average flow generation near curved interface with a surfactant adsorbed on the surface layer. The investigation was carried out for a liquid drop embedded in a viscous liquid with a different density. The liquid flows inside and outside the drop are generated by small amplitude and high frequency vibrations. Surfactant exchange between the drop surface and the surrounding liquid is limited by the process of adsorption-desorption. It was assumed that the surfactant is soluble in the surrounding liquid, but not soluble in the liquid drop. Surrounding liquid and the liquid in the drop are considered incompressible. Normal and shear viscous stresses balance at the interface is performed under the condition that the film thickness of the adsorbed surfactant is negligible. The problem is solved under assumption that the shape of the drop in the presence of adsorbed surfactant remains spherical symmetry. The effective boundary conditions for the tangential velocity jump and shear stress jump, describing the above generation have been obtained by matched asymptotic expansions method. The conditions under which the drop surface can be considered as a quasi-solid are determined. It is shown that in the case of the significant effect of surfactant on the surface tension, the dominant mechanism for the generation is the Schlichting mechanisms under vibrations.

Application of non-monotonic logic to failure diagnosis of nuclear power plant

International Nuclear Information System (INIS)

Takahashi, M.; Kitamura, M.; Sugiyama, K.

1989-01-01

A prototype diagnosis system for nuclear power plants was developed based on Truth Maintenance systems: TMS and Dempster-Shafer probability theory. The purpose of this paper is to establish basic technique for more intelligent, man-computer cooperative diagnosis system. The developed system is capable of carrying out the diagnostic inference under the imperfect observation condition with the help of the proposed belief revision procedure with TMS and the systematic uncertainty treatment with Dempster-Shafer theory. The usefulness and potentiality of the present non-monotonic logic were demonstrated through simulation experiments

A Nonmonotone Trust Region Method for Nonlinear Programming with Simple Bound Constraints

International Nuclear Information System (INIS)

Chen, Z.-W.; Han, J.-Y.; Xu, D.-C.

2001-01-01

In this paper we propose a nonmonotone trust region algorithm for optimization with simple bound constraints. Under mild conditions, we prove the global convergence of the algorithm. For the monotone case it is also proved that the correct active set can be identified in a finite number of iterations if the strict complementarity slackness condition holds, and so the proposed algorithm reduces finally to an unconstrained minimization method in a finite number of iterations, allowing a fast asymptotic rate of convergence. Numerical experiments show that the method is efficient

Cytotoxicity of binary mixtures of human pharmaceuticals in a fish cell line: approaches for non-monotonic concentration-response relationships.

Science.gov (United States)

Bain, Peter A; Kumar, Anupama

2014-08-01

Predicting the effects of mixtures of environmental micropollutants is a priority research area. In this study, the cytotoxicity of ten pharmaceuticals to the rainbow trout cell line RTG-2 was determined using the neutral red uptake assay. Fluoxetine (FL), propranolol (PPN), and diclofenac (DCF) were selected for further study as binary mixtures. Biphasic concentration-response relationships were observed in cells exposed to FL and PPN. In the case of PPN, microscopic examination revealed lysosomal swelling indicative of direct uptake and accumulation of the compound. Three equations describing non-monotonic concentration-response relationships were evaluated and one was found to consistently provide more accurate estimates of the median and 10% effect concentrations compared with a sigmoidal concentration-response model. Predictive modeling of the effects of binary mixtures of FL, PPN, and DCF was undertaken using an implementation of the concentration addition (CA) conceptual model incorporating non-monotonic concentration-response relationships. The cytotoxicity of the all three binary combinations could be adequately predicted using CA, suggesting that the toxic mode of action in RTG-2 cells is unrelated to the therapeutic mode of action of these compounds. The approach presented here is widely applicable to the study of mixture toxicity in cases where non-monotonic concentration-response relationships are observed. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

Curved-Duct

Directory of Open Access Journals (Sweden)

Je Hyun Baekt

2000-01-01

Full Text Available A numerical study is conducted on the fully-developed laminar flow of an incompressible viscous fluid in a square duct rotating about a perpendicular axis to the axial direction of the duct. At the straight duct, the rotation produces vortices due to the Coriolis force. Generally two vortex cells are formed and the axial velocity distribution is distorted by the effect of this Coriolis force. When a convective force is weak, two counter-rotating vortices are shown with a quasi-parabolic axial velocity profile for weak rotation rates. As the rotation rate increases, the axial velocity on the vertical centreline of the duct begins to flatten and the location of vorticity center is moved near to wall by the effect of the Coriolis force. When the convective inertia force is strong, a double-vortex secondary flow appears in the transverse planes of the duct for weak rotation rates but as the speed of rotation increases the secondary flow is shown to split into an asymmetric configuration of four counter-rotating vortices. If the rotation rates are increased further, the secondary flow restabilizes to a slightly asymmetric double-vortex configuration. Also, a numerical study is conducted on the laminar flow of an incompressible viscous fluid in a 90°-bend square duct that rotates about axis parallel to the axial direction of the inlet. At a 90°-bend square duct, the feature of flow by the effect of a Coriolis force and a centrifugal force, namely a secondary flow by the centrifugal force in the curved region and the Coriolis force in the downstream region, is shown since the centrifugal force in curved region and the Coriolis force in downstream region are dominant respectively.

Dip Phenomenon in High-Curved Turbulent Flows and Application of Entropy Theory

Directory of Open Access Journals (Sweden)

Donatella Termini

2018-03-01

Full Text Available The estimation of velocity profile in turbulent open channels is a difficult task due to the significant effects of the secondary flow. The present paper investigates the mechanism of the velocity-dip phenomenon, whereby the location of the maximum velocity appears to be below the free surface. Previous studies conducted in straight channels relate the mechanism of the velocity-dip phenomenon to secondary flow induced by anisotropy of turbulence. This work focuses on high-curved channels where the secondary motion, which is also induced by the channel’s curvature, evolves along the bend. The width-to-depth ratio, B/h, is one of the most important parameters that are affecting the secondary motion entity. In particular, the present study aims to investigate the evolution of the velocity-dip along the bend for two values of the width-to-depth ratio and the applicability of the entropic model for the dip-phenomenon estimation. The results show that the velocity-dip is more accentuated for low values of the width-to-depth ratio, where the secondary motion plays a fundamental role in the distribution of the downstream flow velocity, although the velocity-dip is also present when the aspect ratio is higher than 10. Furthermore, the velocity profiles that were estimated by applying the entropic model are in good agreement with the measured ones, especially for B/h < 10.

Multistability of neural networks with discontinuous non-monotonic piecewise linear activation functions and time-varying delays.

Science.gov (United States)

Nie, Xiaobing; Zheng, Wei Xing

2015-05-01

This paper is concerned with the problem of coexistence and dynamical behaviors of multiple equilibrium points for neural networks with discontinuous non-monotonic piecewise linear activation functions and time-varying delays. The fixed point theorem and other analytical tools are used to develop certain sufficient conditions that ensure that the n-dimensional discontinuous neural networks with time-varying delays can have at least 5(n) equilibrium points, 3(n) of which are locally stable and the others are unstable. The importance of the derived results is that it reveals that the discontinuous neural networks can have greater storage capacity than the continuous ones. Moreover, different from the existing results on multistability of neural networks with discontinuous activation functions, the 3(n) locally stable equilibrium points obtained in this paper are located in not only saturated regions, but also unsaturated regions, due to the non-monotonic structure of discontinuous activation functions. A numerical simulation study is conducted to illustrate and support the derived theoretical results. Copyright © 2015 Elsevier Ltd. All rights reserved.

Non-monotonicity and divergent time scale in Axelrod model dynamics

Science.gov (United States)

Vazquez, F.; Redner, S.

2007-04-01

We study the evolution of the Axelrod model for cultural diversity, a prototypical non-equilibrium process that exhibits rich dynamics and a dynamic phase transition between diversity and an inactive state. We consider a simple version of the model in which each individual possesses two features that can assume q possibilities. Within a mean-field description in which each individual has just a few interaction partners, we find a phase transition at a critical value qc between an active, diverse state for q < qc and a frozen state. For q lesssim qc, the density of active links is non-monotonic in time and the asymptotic approach to the steady state is controlled by a time scale that diverges as (q-qc)-1/2.

POSSIBLE RECESSION CURVE APPLICATIONS FOR RETENTION EVALUATION

Directory of Open Access Journals (Sweden)

Daniel Liberacki

2015-11-01

Full Text Available The objective of the article was to present possible applications of recession flow curve in a small lowland watershed retention discharge size evaluation. The examined woodland micro catchment area of 0.52 sq km is located in Puszcza Zielonka in central Wielkopolska. The Hutka catchment is typically woody with high retention abilities. The catchment of the Hutka watercourse is forested in 89%, the other 11% is covered by swamps and wasteland. The predominant sites are fresh mixed coniferous forest (BMśw, fresh coniferous forest (Bśw and alder carr forest (Ol. Landscape in catchment is characterized by a large number of interior depressions, filled partly with rainwater or peatbogs, with poorly developed natural drainage. The watercourses do not exceed 1 km in length, the mean width is approx. 0.5 m, while mean depth ranges from 0.2 to 0.3 m. During hydrological research conducted in 1997/1998–1999/2000, 35 major (characteristic raised water stages were observed in Hutka after substantial precipitation. The recession curve dating from 18–24 September 2000 has the α and n rates nearest to average. Comparing the model curve and the curve created by observing watercourse flow, one can notice their resemblance and that they have similar ordinate values as well as shape. In the case of other recession curves, the maximum differences of ordinate values are also about 0.1–0.2 l/s/km2. The measuured α and n rates do not reveal any regularities. There are no significant statistical Horton model parameter (for recession flow curves dependencies between α and n and e.g. initial flows (Qo or the whole period of high water waves (Qp. Consequently, calculated relation between these parameters is only an approximation for the general evaluation of the retention discharge in the catchment area towards retention with flow function.

A Journey Between Two Curves

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Sergey A. Cherkis

2007-03-01

Full Text Available A typical solution of an integrable system is described in terms of a holomorphic curve and a line bundle over it. The curve provides the action variables while the time evolution is a linear flow on the curve's Jacobian. Even though the system of Nahm equations is closely related to the Hitchin system, the curves appearing in these two cases have very different nature. The former can be described in terms of some classical scattering problem while the latter provides a solution to some Seiberg-Witten gauge theory. This note identifies the setup in which one can formulate the question of relating the two curves.

Numerical Simulation of the Vortex-Induced Vibration of A Curved Flexible Riser in Shear Flow

Science.gov (United States)

Zhu, Hong-jun; Lin, Peng-zhi

2018-06-01

A series of fully three-dimensional (3D) numerical simulations of flow past a free-to-oscillate curved flexible riser in shear flow were conducted at Reynolds number of 185-1015. The numerical results obtained by the two-way fluid-structure interaction (FSI) simulations are in good agreement with the experimental results reported in the earlier study. It is further found that the frequency transition is out of phase not only in the inline (IL) and crossflow (CF) directions but also along the span direction. The mode competition leads to the non-zero nodes of the rootmean- square (RMS) amplitude and the relatively chaotic trajectories. The fluid-structure interaction is to some extent reflected by the transverse velocity of the ambient fluid, which reaches the maximum value when the riser reaches the equilibrium position. Moreover, the local maximum transverse velocities occur at the peak CF amplitudes, and the values are relatively large when the vibration is in the resonance regions. The 3D vortex columns are shed nearly parallel to the axis of the curved flexible riser. As the local Reynolds number increases from 0 at the bottom of the riser to the maximum value at the top, the wake undergoes a transition from a two-dimensional structure to a 3D one. More irregular small-scale vortices appeared at the wake region of the riser, undergoing large amplitude responses.

Non-Monotonic Survival of Staphylococcus aureus with Respect to Ciprofloxacin Concentration Arises from Prophage-Dependent Killing of Persisters

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Elizabeth L. Sandvik

2015-11-01

Full Text Available Staphylococcus aureus is a notorious pathogen with a propensity to cause chronic, non-healing wounds. Bacterial persisters have been implicated in the recalcitrance of S. aureus infections, and this motivated us to examine the persistence of S. aureus to ciprofloxacin, a quinolone antibiotic. Upon treatment of exponential phase S. aureus with ciprofloxacin, we observed that survival was a non-monotonic function of ciprofloxacin concentration. Maximal killing occurred at 1 µg/mL ciprofloxacin, which corresponded to survival that was up to ~40-fold lower than that obtained with concentrations ≥ 5 µg/mL. Investigation of this phenomenon revealed that the non-monotonic response was associated with prophage induction, which facilitated killing of S. aureus persisters. Elimination of prophage induction with tetracycline was found to prevent cell lysis and persister killing. We anticipate that these findings may be useful for the design of quinolone treatments.

Natural rubber latex: determination and interpretation of flow curves

Directory of Open Access Journals (Sweden)

Harrison Lourenço Corrêa

2015-08-01

Full Text Available AbstractAs consumers become more demanding, the importance grows of guaranteeing the quality of products. The employment of reliable testing techniques that assure the origin and characteristics of the inputs used by industry is a key factor in this respect. In the rubber processing industry, the most commonly used characterization tests include determination of the total solids and dry rubber content, mechanical stability, odor, color and presence of volatile compounds, among others. For the most part, these tests are sufficient for the latex transformation industry. However, in situations where there is a need to know the behavior of latex in reaction to the mechanical forces of machines (mixers, pumps, etc., other tests must be used. Rheological tests to determine viscoelastic data by means of plotting flow curves combined with the application of theoretical models can provide important details for characterization of different types of latex. This article presents the protocol employed by the Rheology and Image Laboratory of Rio de Janeiro State University (UERJ for the rheological study of Brazilian latex. The samples analyzed came from the state of São Paulo.

Wall shear stress measurement of near-wall flow over inclined and curved boundaries by stereo interfacial particle image velocimetry

International Nuclear Information System (INIS)

Nguyen, Thien Duy; Wells, John Craig; Nguyen, Chuong Vinh

2010-01-01

In investigations of laminar or turbulent flows, wall shear is often important. Nevertheless, conventional particle image velocimetry (PIV) is difficult in near-wall regions. A near-wall measurement technique, named interfacial PIV (IPIV) [Nguyen, C., Nguyen, T., Wells, J., Nakayama, A., 2008. Proposals for PIV of near-wall flow over curved boundaries. In: Proceedings of 14th International Symposium on Applications of Laser Technique to Fluid Mechanics], handles curved boundaries by means of conformal transformation, directly measures the wall gradient, and yields the near-wall tangential velocity profile at one-pixel resolution. In this paper, we show the feasibility of extending IPIV to measure wall gradients by stereo reconstruction. First, we perform a test on synthetic images generated from a direct numerical simulation (DNS) snapshot of turbulent flow over sinusoidal bed. Comparative assessment of wall gradients derived by IPIV, stereo-IPIV and particle image distortion (PID) [Huang, H.T., Fiedler, H.E., Wang, J.J., 1993. Limitation and improvement of PIV. Experiments in Fluids 15(4), 263-273] is evaluated with DNS data. Also, the sensitivity of IPIV and stereo-IPIV results to the uncertainty of identified wall position is examined. As a practical application of IPIV and stereo-IPIV to experimental images, results from turbulent open channel flow over a backward-facing step are discussed in detail.

I-V curves of Y-Ba-Cu-O microbridges in the flux flow regime

International Nuclear Information System (INIS)

Kalisky, B.; Wolfus, Y.; Yeshurun, Y.; Koren, G.; Huebener, R.P.

2004-01-01

We report on measurements of I-V curves in microbridges of thin Y-Ba-Cu-O films of different thickness, in the presence of external magnetic fields up to 6 T. A discontinuity is observed at a critical voltage, V*, in the flux flow regime, reflecting an electronic instability, as predicted by Larkin and Ovchinnikov (LO), and in agreement with results reported by Doettinger et al. [Phys. Rev. Let. 73 (1994) 1691]. The critical voltage, V*, and the flux flow resistance, R 0 , in the limit V→0, are calculated by fitting the data to the LO model. We find that the vortex critical velocity, v*, at the instability, derived from V*, decreases with magnetic field and film thickness. These results, not predicted by the LO theory, reflect the dependence of the (spatially averaged) quasiparticle energy relaxation rate on magnetic field and film thickness

Regional variation of flow duration curves in the eastern United States: Process-based analyses of the interaction between climate and landscape properties

Science.gov (United States)

Wafa Chouaib; Peter V. Caldwell; Younes Alila

2018-01-01

This paper advances the physical understanding of the flow duration curve (FDC) regional variation. It provides a process-based analysis of the interaction between climate and landscape properties to explain disparities in FDC shapes. We used (i) long term measured flow and precipitation data over 73 catchments from the eastern US. (ii) We calibrated the...

Spatially-smooth regionalization of flow duration curves in non-pristine basins

Directory of Open Access Journals (Sweden)

D. Ganora

2016-05-01

Full Text Available The flow duration curve (FDC is a fundamental signature of the hydrological cycle to support water management strategies. Despite many studies on this topic, its estimation in ungauged basins is still a relevant issue as the FDC is controlled by different types of processes at different time-space scales, thus resulting quite sensitive to the specific case study. In this work, a regional spatially-smooth procedure to evaluate the annual FDC in ungauged basins is proposed, based on the estimation of the L-moments (mean, L-CV and L-skewness through regression models valid for the whole case study area. In this approach, homogeneous regions are no longer required and the L-moments are allowed to continuously vary along the river network, thus providing a final FDC smoothly evolving for different locations on the river. Regressions are based on a set of topographic, climatic, land use and vegetation descriptors at the basin scale. Moreover, the model ensures that the mean annual runoff is preserved at the river confluences, i.e. the sum of annual flows of the upstream reaches is equal to the predicted annual downstream flow. The proposed model is adapted to incorporate different "sub-models" to account for local information within the regional framework, where man-induced alterations are known, as common in non-pristine catchments. In particular, we propose a module to consider the impact of existing/designed water withdrawals on the L-moments of the FDC. The procedure has been applied to a dataset of daily observation of about 120 gauged basins on the upper Po river basin in North-Western Italy.

Internal m=1, n=1 helical mode in a tokamak with nonmonotonic current profile

International Nuclear Information System (INIS)

Kuvshinov, B.N.; Mikhajlovskij, A.B.

1988-01-01

Internal helical mode in a tokamak with two resonance surfaces, on which storing coefficient reduces to unity is studied theoretically. A general criterion for the investigated perturbations stability is obtained. Dispersion equation, describing both ideal and resistive helical modes, is derived. Analytic calculations for the case of perturbations localized near the tokamak axis are made. It is shown that in the framework of standard ideal hydrodynamics such perturbations are unstable at characteristic nonmonotonous profiles of the current

Frictional Torque Reduction in Taylor-Couette Flows with Riblet-Textured Rotors

Science.gov (United States)

Raayai, Shabnam; McKinley, Gareth

2017-11-01

Inspired by the riblets on the denticles of fast swimming shark species, periodic surface microtextures of different shapes have been studied under laminar and turbulent flow conditions to understand their drag reduction mechanism and to offer guides for designing optimized low-friction bio-inspired surfaces. Various reports over the past four decades have suggested that riblet surfaces can reduce the frictional drag force in high Reynolds number laminar and turbulent flow regimes. Here, we investigate the effect of streamwise riblets on torque reduction in steady flow between concentric cylinders, known as Taylor-Couette Flow. Using 3D printed riblet-textured rotors and a custom-built Taylor-Couette cell which can be mounted on a rheometer we measure the torque on the inner rotor as a function of three different dimensionless parameters; the Reynolds number of the flow, the sharpness of the riblets, and the size of the riblets with respect to the scale of the Taylor-Couette cell. Our experimental results in the laminar viscous flow regime show a reduction in torque up to 10% over a wide range of Reynolds numbers, that is a non-monotonic function of the aspect ratio and independent of Re. However, after transition to the Taylor vortex regime, the modification in torque becomes a function of the Reynolds number, while remaining a non-monotonic function of the aspect ratio. Using finite volume modelling of the geometry we discuss the changes in the Taylor-Couette flow in presence of the riblets compared to the case of smooth rotors and the resulting torque reduction as a function of the parameter space defined above.

Multistability of memristive Cohen-Grossberg neural networks with non-monotonic piecewise linear activation functions and time-varying delays.

Science.gov (United States)

Nie, Xiaobing; Zheng, Wei Xing; Cao, Jinde

2015-11-01

The problem of coexistence and dynamical behaviors of multiple equilibrium points is addressed for a class of memristive Cohen-Grossberg neural networks with non-monotonic piecewise linear activation functions and time-varying delays. By virtue of the fixed point theorem, nonsmooth analysis theory and other analytical tools, some sufficient conditions are established to guarantee that such n-dimensional memristive Cohen-Grossberg neural networks can have 5(n) equilibrium points, among which 3(n) equilibrium points are locally exponentially stable. It is shown that greater storage capacity can be achieved by neural networks with the non-monotonic activation functions introduced herein than the ones with Mexican-hat-type activation function. In addition, unlike most existing multistability results of neural networks with monotonic activation functions, those obtained 3(n) locally stable equilibrium points are located both in saturated regions and unsaturated regions. The theoretical findings are verified by an illustrative example with computer simulations. Copyright © 2015 Elsevier Ltd. All rights reserved.

Applying CFD in the Analysis of Heavy-Oil Transportation in Curved Pipes Using Core-Flow Technique

Directory of Open Access Journals (Sweden)

S Conceição

2017-06-01

Full Text Available Multiphase flow of oil, gas and water occurs in the petroleum industry from the reservoir to the processing units. The occurrence of heavy oils in the world is increasing significantly and points to the need for greater investment in the reservoirs exploitation and, consequently, to the development of new technologies for the production and transport of this oil. Therefore, it is interesting improve techniques to ensure an increase in energy efficiency in the transport of this oil. The core-flow technique is one of the most advantageous methods of lifting and transporting of oil. The core-flow technique does not alter the oil viscosity, but change the flow pattern and thus, reducing friction during heavy oil transportation. This flow pattern is characterized by a fine water pellicle that is formed close to the inner wall of the pipe, aging as lubricant of the oil flowing in the core of the pipe. In this sense, the objective of this paper is to study the isothermal flow of heavy oil in curved pipelines, employing the core-flow technique. A three-dimensional, transient and isothermal mathematical model that considers the mixture and k-e  turbulence models to address the gas-water-heavy oil three-phase flow in the pipe was applied for analysis. Simulations with different flow patterns of the involved phases (oil-gas-water have been done, in order to optimize the transport of heavy oils. Results of pressure and volumetric fraction distribution of the involved phases are presented and analyzed. It was verified that the oil core lubricated by a fine water layer flowing in the pipe considerably decreases pressure drop.

A numerical analysis on the curved bileaflet Mechanical Heart Valve (MHV) : leaflet motion and blood flow in an elastic blood vessel

International Nuclear Information System (INIS)

Bang, Jin Seok; Kim, Chang Nyung; Choi, Choeng Ryul

2005-01-01

In blood flow passing through the Mechanical Heart Valve (MHV) and elastic blood vessel, hemolysis and platelet activation causing thrombus formation can be seen owing to the shear stress in the blood. Also, fracture and deformation of leaflets can be observed depending on the shape and material properties of the leaflets which is opened and closed in a cycle. Hence, comprehensive study is needed on the hemodynamics which is associated with the motion of leaflet and elastic blood vessel in terms of fluid-structure interaction. In this paper, a numerical analysis has been performed for a three-dimensional pulsatile blood flow associated with the elastic blood vessel and curved bileaflet for multiple cycles in light of fluid-structure interaction. From this analysis fluttering phenomenon and rebound of the leaflet have been observed and recirculation and regurgitation have been found in the flow fields of the blood. Also, the pressure distribution and the radial displacement of the elastic blood vessel have been obtained. The motion of the leaflet and flow fields of the blood have shown similar tendency compared with the previous experiments carried out in other studies. The present study can contribute to the design methodology for the curved bileaflet mechanical heart valve. Furthermore, the proposed fluid-structure interaction method will be effectively used in various fields where the interaction between fluid flow and structure are involved

Raman D-band in the irradiated graphene: Origin of the non-monotonous dependence of its intensity with defect concentration

International Nuclear Information System (INIS)

Codorniu Pujals, Daniel

2013-01-01

Raman spectroscopy is one of the most used experimental techniques in studying irradiated carbon nanostructures, in particular graphene, due to its high sensibility to the presence of defects in the crystalline lattice. Special attention has been given to the variation of the intensity of the Raman D-band of graphene with the concentration of defects produced by irradiation. Nowadays, there are enough experimental evidences about the non-monotonous character of that dependence, but the explanation of this behavior is still controversial. In the present work we developed a simplified mathematical model to obtain a functional relationship between these two magnitudes and showed that the non-monotonous dependence is intrinsic to the nature of the D-band and that it is not necessarily linked to amorphization processes. The obtained functional dependence was used to fit experimental data taken from other authors. The determination coefficient of the fitting was 0.96.

The curve shortening problem

CERN Document Server

Chou, Kai-Seng

2001-01-01

Although research in curve shortening flow has been very active for nearly 20 years, the results of those efforts have remained scattered throughout the literature. For the first time, The Curve Shortening Problem collects and illuminates those results in a comprehensive, rigorous, and self-contained account of the fundamental results.The authors present a complete treatment of the Gage-Hamilton theorem, a clear, detailed exposition of Grayson''s convexity theorem, a systematic discussion of invariant solutions, applications to the existence of simple closed geodesics on a surface, and a new, almost convexity theorem for the generalized curve shortening problem.Many questions regarding curve shortening remain outstanding. With its careful exposition and complete guide to the literature, The Curve Shortening Problem provides not only an outstanding starting point for graduate students and new investigations, but a superb reference that presents intriguing new results for those already active in the field.

A Full-Vector Geomagnetic PSV Curve Derived from East Maui Volcano Lava Flows for the Last ~15,000 years

Science.gov (United States)

Herrero-Bervera, E.; Hagstrum, J. T.; Champion, D. E.; Dekkers, M. J.; Bohnel, H.

2012-12-01

We have studied the paleomagnetism and rock magnetism of oriented samples from 105 lava flows erupted by the East Maui Volcano, Hawai`i, (i.e. Hana Volcanics) in order to construct a directional and absolute paleointensity (full-vector) paleosecular variation (PSV) curve for the last ~15,000 years. The directional geomagnetic behavior for East Maui has already been published by Sherrod et al. [JGR, 111, 10,1029/2005JB003876, 2006], and Herrero-Bervera and Valet [PEPI, 161-267-280, 2007]. All lava flows were previously dated using radiocarbon methods and span the last ~15,000 years of geomagnetic behavior. In addition to demagnetization experiments (i.e. alternating field and thermal) we have determined Curie temperatures and hysteresis parameters to characterize composition and grain size of the magnetic grains contained by the sampled flows. Accordingly, most lava flow samples have two types of magnetic minerals in different proportions; low-Ti titanomagnetite with high Curie temperature and high-Ti titanomagnetite with low Curie temperature. During sample heating and cooling the temperature curves are often irreversible. Magnetic grains have sizes that are within the pseudo single domain range and include both single and multi domain particles. Absolute paleointensities (PI) of 37 flows were obtained using the multi-specimen parallel differential pTRM method [Dekkers and Böhnel, EPSL, 248, 508-517, 2006], mostly at temperatures between 170° and 250°C when high-Ti titanomagnetite was dominant. In a few samples with magnetic grains having near-magnetite compositions, higher temperatures could be used. For some of the samples the recently proposed domain-state correction [Fabian and Leonhardt, EPSL, 297, 84-94, 2010] was applied as well. In addition, we have been able to successfully obtain PIs by means of the Thellier-Coe protocol for 17 lava flows. Our paleointensity results correlate well with global absolute paleointensity determinations.

Angle β of greater than 80° at the start of spirometry may identify high-quality flow volume curves.

Science.gov (United States)

Lian, Ningfang; Li, Li; Ren, Weiying; Jiang, Zhilong; Zhu, Lei

2017-04-01

The American Thoracic Society (ATS) and European Respiratory Society (ERS) emphasize a satisfactory start in maximal expiratory flow-volume (MEFV) curves and highlight subjective parameters: performance without hesitation and expiration with maximum force. We described a new parameter, angle β for characterization of the start to the MEFV curve. Subjects completed the MEFV curve at least three times and at least two curves met ATS/ERS quality. Subjects were divided into normal, restrictive and obstructive groups according to pulmonary function test results. The tangent line was drawn at the start of the MEFV curve's ascending limb to the x-axis and the angle β between the tangent line and x-axis was obtained. The relationships between tangent of β, pulmonary function parameters (PFPs) and anthropometric data were assessed. The MEFV curves with insufficient explosion at the start were considered as poor-quality MEFV curves. In 998 subjects with high-quality spirometry, although PFP varied in relation to the three aspects: the angle β and its tangent were similar (P > 0.05), the tangent of β did not correlate with PFP or anthropometric measurements (P > 0.05) and the lower limit of normal (LLN) of the angle β was 80° in the group with high-quality spirometry (P < 0.05). Angle β derived from poor-quality MEFV curves was smaller than that from good quality one (P < 0.05). Angle β may function as a parameter to assess the expiratory efforts, which can be used to assess the quality of the MEFV curve start. © 2016 Asian Pacific Society of Respirology.

Numerical analysis of thermal creep flow in curved channels for designing a prototype of Knudsen micropump

International Nuclear Information System (INIS)

Leontidis, V; Baldas, L; Colin, S; Brandner, J J

2012-01-01

The possibility to generate a gas flow inside a channel just by imposing a tangential temperature gradient along the walls without the existence of an initial pressure difference is well known. The gas must be under rarefied conditions, meaning that the system must operate between the slip and the free molecular flow regimes, either at low pressure or/and at micro/nano-scale dimensions. This phenomenon is at the basis of the operation principle of Knudsen pumps, which are actually compressors without any moving parts. Nowadays, gas flows in the slip flow regime through microchannels can be modeled using commercial Computational Fluid Dynamics softwares, because in this regime the compressible Navier-Stokes equations with appropriate boundary conditions are still valid. A simulation procedure has been developed for the modeling of thermal creep flow using ANSYS Fluent®. The implementation of the boundary conditions is achieved by developing User Defined Functions (UDFs) by means of C++ routines. The complete first order velocity slip boundary condition, including the thermal creep effects due to the axial temperature gradient and the effect of the wall curvature, and the temperature jump boundary condition are applied. The developed simulation tool is used for the preliminary design of Knudsen micropumps consisting of a sequence of curved and straight channels.

Low dose effects and non-monotonic dose responses for endocrine active chemicals: Science to practice workshop: Workshop summary

DEFF Research Database (Denmark)

Beausoleil, Claire; Ormsby, Jean-Nicolas; Gies, Andreas

2013-01-01

A workshop was held in Berlin September 12–14th 2012 to assess the state of the science of the data supporting low dose effects and non-monotonic dose responses (“low dose hypothesis”) for chemicals with endocrine activity (endocrine disrupting chemicals or EDCs). This workshop consisted of lectu...

Transonic shock wave. Turbulent boundary layer interaction on a curved surface

NARCIS (Netherlands)

Nebbeling, C.; Koren, B.

1988-01-01

This paper describes an experimental investigation of a transonic shock wave - turbulent boundary layer interaction in a curved test section, in which the flow has been computed by a 2-D Euler flow method. The test section has been designed such that the flow near the shock wave on the convex curved

Unsteady fluid flow in a slightly curved annular pipe: The impact of the annulus on the flow physics

Science.gov (United States)

Messaris, Gerasimos A. T.; Karahalios, George T.

2017-02-01

The motivation of the present study is threefold. Mainly, the etiological explanation of the Womersley number based on physical reasoning. Next, the extension of a previous work [Messaris, Hadjinicolaou, and Karahalios, "Unsteady fluid flow in a slightly curved pipe: A comparative study of a matched asymptotic expansions solution with a single analytical solution," Phys. Fluids 28, 081901 (2016)] to the annular pipe flow. Finally, the discussion of the effect of the additional stresses generated by a catheter in an artery and exerted on the arterial wall during an in vivo catheterization. As it is known, the square of the Womersley number may be interpreted as an oscillatory Reynolds number which equals to the ratio of the inertial to the viscous forces. The adoption of a modified Womersley number in terms of the annular gap width seems therefore more appropriate to the description of the annular flow than an ordinary Womersley number defined in terms of the pipe radius. On this ground, the non-dimensional equations of motion are approximately solved by two analytical methods: a matched asymptotic expansions method and a single. In the first method, which is valid for very large values of the Womersley number, the flow region consists of the main core and the two boundary layers formed at the inner and outer boundaries. In the second, the fluid is considered as one region and the Womersley number can vary from finite values, such that they fit to the blood flow in the aorta and the main arteries, to infinity. The single solution predicts increasing circumferential and decreasing axial stresses with increasing catheter radius at a prescribed value of the Womersley parameter in agreement with analogous results from other theoretical and numerical solutions. It also predicts the formation of pinches on the secondary flow streamlines and a third boundary layer, additional to those formed at the boundary walls. Finally, we show that the insertion of a catheter in an

Non-monotonic resonance in a spatially forced Lengyel-Epstein model

Energy Technology Data Exchange (ETDEWEB)

Haim, Lev [Physics Department, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Department of Oncology, Soroka University Medical Center, Beer-Sheva 84101 (Israel); Hagberg, Aric [Center for Nonlinear Studies, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Meron, Ehud [Physics Department, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Department of Solar Energy and Environmental Physics, BIDR, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion 84990 (Israel)

2015-06-15

We study resonant spatially periodic solutions of the Lengyel-Epstein model modified to describe the chlorine dioxide-iodine-malonic acid reaction under spatially periodic illumination. Using multiple-scale analysis and numerical simulations, we obtain the stability ranges of 2:1 resonant solutions, i.e., solutions with wavenumbers that are exactly half of the forcing wavenumber. We show that the width of resonant wavenumber response is a non-monotonic function of the forcing strength, and diminishes to zero at sufficiently strong forcing. We further show that strong forcing may result in a π/2 phase shift of the resonant solutions, and argue that the nonequilibrium Ising-Bloch front bifurcation can be reversed. We attribute these behaviors to an inherent property of forcing by periodic illumination, namely, the increase of the mean spatial illumination as the forcing amplitude is increased.

Relationship between flow volume curve and CT findings in non-smoking patients with long histories of bronchial asthma

Energy Technology Data Exchange (ETDEWEB)

Kawamoto, Hitoshi; Kambe, Masayuki; Yamagata, Mitsunori; Nakajima, Hidekatsu [Hiroshima Univ. (Japan). School of Medicine; Yamane, Kousuke; Kuraoka, Toshihiko; Miyamura, Isao

2001-08-01

This study was conducted to verify whether bronchial asthma (BA) alone causes pulmonary emphysema (PE), and to examine the computed tomography (CT) findings in non-smokers with BA demonstrating the flow volume curve (FV curve) characteristic of PE. Non-smoking patients with a history of BA for more than 20 years were divided into 2 groups: the dogleg pattern group (n=5), with an FV curve characteristic of PE, and the concave pattern group (n=16) with an FV curve characteristic of BA. CT scans was performed using CT values (level, 900 H.U.; width, 400 H.U.) that facilitate detection of a low attenuation area (LAA), and using conventional CT values (level, 700 H.U.; width, 1,300 H.U.). LAA (including air trapping), thickness of the bronchial wall, and partial atelectasis were compared between the 2 groups. PE was not detected, although air trapping was found in all subjects. The thickness of the airway was greater in the dogleg pattern than in the concave pattern. The incidences of air trapping and partial atelectasis were higher in the former than in the latter. BA alone may not cause PE. Some BA patients without PE show the FV curve characteristic of PE, reflecting an increase in the thickness of the airway wall and a decrease in the pulmonary ventilation probably due to the air trapping and the partial atelectasis. (author)

Non-linear, non-monotonic effect of nano-scale roughness on particle deposition in absence of an energy barrier: Experiments and modeling

Science.gov (United States)

Jin, Chao; Glawdel, Tomasz; Ren, Carolyn L.; Emelko, Monica B.

2015-12-01

Deposition of colloidal- and nano-scale particles on surfaces is critical to numerous natural and engineered environmental, health, and industrial applications ranging from drinking water treatment to semi-conductor manufacturing. Nano-scale surface roughness-induced hydrodynamic impacts on particle deposition were evaluated in the absence of an energy barrier to deposition in a parallel plate system. A non-linear, non-monotonic relationship between deposition surface roughness and particle deposition flux was observed and a critical roughness size associated with minimum deposition flux or “sag effect” was identified. This effect was more significant for nanoparticles (<1 μm) than for colloids and was numerically simulated using a Convective-Diffusion model and experimentally validated. Inclusion of flow field and hydrodynamic retardation effects explained particle deposition profiles better than when only the Derjaguin-Landau-Verwey-Overbeek (DLVO) force was considered. This work provides 1) a first comprehensive framework for describing the hydrodynamic impacts of nano-scale surface roughness on particle deposition by unifying hydrodynamic forces (using the most current approaches for describing flow field profiles and hydrodynamic retardation effects) with appropriately modified expressions for DLVO interaction energies, and gravity forces in one model and 2) a foundation for further describing the impacts of more complicated scales of deposition surface roughness on particle deposition.

Evaluation of 133Xe clearance curves in the study of lingual blood flow in dogs

International Nuclear Information System (INIS)

Fazekas, A.; Posch, E.; Harsing, L.

1979-01-01

Lingual blood flow was studied in dogs by the 133 Xe clearance technique under control conditions, during epinephrine infusion and in response to a combined treatment with regitin and epinephrine. The composite washout curves recorded during control conditions could be resolved into three monoexponential components. It is suggested that the steep initial slope (component I) is caused by the fraction of blood that perfuses the A-V anastomoses of the tongue. Components II and III appear to indicate the perfusion rate of lingual mucosa and musculature, respectively. The disappearance of component I due to the effect of epinephrine infusion might indicate the closure of arterio-venous anastomoses containing alpha receptors. Regitin pretreatment could prevent the closure of the arterio-venous anastomoses elicited by epinephrine infusion. The beta receptor stimulating activity of epinephrine might account for the augmentation of blood flow to lingual musculature. (orig.) 891 AJ/orig. 892 BRE [de

Analytical modeling of complete Nukiyama curves corresponding to expected low void fraction at high subcooling and flow rate

International Nuclear Information System (INIS)

Schroeder-Richter, D.

1996-01-01

On the basis of a new hypothesis of thermodynamic states (the superheated wall layer is not metastable but saturated at locally elevated pressure), an analytical estimation is presented of the whole boiling curve [except critical heat flux (CHF), but fixed at this point, known by experiments or correlation]. The curvature of the boiling curve (bubbly flow) is deduced from thermodynamics of irreversible processes. The wall temperature corresponding to departure from nucleate boiling is calculated from balances of momentum at the interfaces, based on the assumption that the speed of sound may be a limit for maximum evaporation mass flux and thereby heat flux, i.e., CHF. Heat flux during transition boiling is determined from balance of energy at the rewetting front. The Leidenfrost temperature, as well as wall temperature at CHF, can be calculated analytically without using empirical coefficients. Heat flux of bubbly flow and transition boiling can be matched at any empirical CHF point. All these results are determined from properties of state alone, i.e., the models can be verified for all fluids including water and liquid metals (so far at moderate heat fluxes). 52 refs., 11 figs., 2 tabs

Power curve report

DEFF Research Database (Denmark)

Vesth, Allan; Kock, Carsten Weber

The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to Ref. [1]. A site calibration has been carried out; see Ref. [2], and the measured flow correction factors for different wind directions are used in the present...

Photoelectic BV Light Curves of Algol and the Interpretations of the Light Curves

Directory of Open Access Journals (Sweden)

Ho-Il Kim

1985-06-01

Full Text Available Standardized B and V photoelectric light curves of Algol are made with the observations obtained during 1982-84 with the 40-cm and the 61-cm reflectors of Yonsei University Observatory. These light curves show asymmetry between ascending and descending shoulders. The ascending shoulder is 0.02 mag brighter than descending shoulder in V light curve and 0.03 mag in B light curve. These asymmetric light curves are interpreted as the result of inhomogeneous energy distribution on the surface of one star of the eclipsing pair rather than the result of gaseous stream flowing from KOIV to B8V star. The 180-year periodicity, so called great inequality, are most likely the result proposed by Kim et al. (1983 that the abrupt and discrete mass losses of cooler component may be the cause of this orbital change. The amount of mass loss deduced from these discrete period changes turned out to be of the order of 10^(-6 - 10^(-5 Msolar.

Prediction of hydrographs and flow-duration curves in almost ungauged catchments: Which runoff measurements are most informative for model calibration?

Science.gov (United States)

Pool, Sandra; Viviroli, Daniel; Seibert, Jan

2017-11-01

Applications of runoff models usually rely on long and continuous runoff time series for model calibration. However, many catchments around the world are ungauged and estimating runoff for these catchments is challenging. One approach is to perform a few runoff measurements in a previously fully ungauged catchment and to constrain a runoff model by these measurements. In this study we investigated the value of such individual runoff measurements when taken at strategic points in time for applying a bucket-type runoff model (HBV) in ungauged catchments. Based on the assumption that a limited number of runoff measurements can be taken, we sought the optimal sampling strategy (i.e. when to measure the streamflow) to obtain the most informative data for constraining the runoff model. We used twenty gauged catchments across the eastern US, made the assumption that these catchments were ungauged, and applied different runoff sampling strategies. All tested strategies consisted of twelve runoff measurements within one year and ranged from simply using monthly flow maxima to a more complex selection of observation times. In each case the twelve runoff measurements were used to select 100 best parameter sets using a Monte Carlo calibration approach. Runoff simulations using these 'informed' parameter sets were then evaluated for an independent validation period in terms of the Nash-Sutcliffe efficiency of the hydrograph and the mean absolute relative error of the flow-duration curve. Model performance measures were normalized by relating them to an upper and a lower benchmark representing a well-informed and an uninformed model calibration. The hydrographs were best simulated with strategies including high runoff magnitudes as opposed to the flow-duration curves that were generally better estimated with strategies that captured low and mean flows. The choice of a sampling strategy covering the full range of runoff magnitudes enabled hydrograph and flow-duration curve

Nonmonotonic and anisotropic magnetoresistance effect in antiferromagnet CaMn2Bi2

Science.gov (United States)

Kawaguchi, N.; Urata, T.; Hatano, T.; Iida, K.; Ikuta, H.

2018-04-01

We found a large and unique magnetoresistance (MR) effect for CaMn2Bi2 . When the magnetic field was applied along the crystallographic c axis at low temperatures, the resistivity increased with the magnetic field and the MR ratio reached several hundred percent, but then it decreased with further increasing the applied field. In addition, the angle dependence measurement revealed a strong anisotropy. This compound is an antiferromagnetic semiconductor with a narrow band gap, and Mn atoms form a corrugated honeycomb lattice. Therefore, a frustration among the magnetic moments is expected, and we propose that our observations can be understood by a nonmonotonic modulation of magnetic fluctuation under the magnetic field.

Classification of pulsating flow patterns in curved pipes.

Science.gov (United States)

Tada, S; Oshima, S; Yamane, R

1996-08-01

The fully developed periodic laminar flow of incompressible Newtonian fluids through a pipe of circular cross section, which is coiled in a circle, was simulated numerically. The flow patterns are characterized by three parameters: the Womersley number Wo, the Dean number De, and the amplitude ratio beta. The effect of these parameters on the flow was studied in the range 2.19 secondary flow evolved with increasing Womersley number and Dean number is explained. The secondary flow patterns are classified into three main groups: the viscosity-dominated type, the inertia-dominated type, and the convection-dominated type. It was found that when the amplitude ratio of the volumetric flow rate is equal to 1.0, four to six vortices of the secondary flow appear at high Dean numbers, and the Lyne-type flow patterns disappear at beta > or = 0.50.

Numerical investigations of two-phase flow with dynamic capillary pressure in porous media via a moving mesh method

Science.gov (United States)

Zhang, Hong; Zegeling, Paul Andries

2017-09-01

Motivated by observations of saturation overshoot, this paper investigates numerical modeling of two-phase flow in porous media incorporating dynamic capillary pressure. The effects of the dynamic capillary coefficient, the infiltrating flux rate and the initial and boundary values are systematically studied using a traveling wave ansatz and efficient numerical methods. The traveling wave solutions may exhibit monotonic, non-monotonic or plateau-shaped behavior. Special attention is paid to the non-monotonic profiles. The traveling wave results are confirmed by numerically solving the partial differential equation using an accurate adaptive moving mesh solver. Comparisons between the computed solutions using the Brooks-Corey model and the laboratory measurements of saturation overshoot verify the effectiveness of our approach.

Comparison of catchment grouping methods for flow duration curve estimation at ungauged sites in France

Directory of Open Access Journals (Sweden)

E. Sauquet

2011-08-01

Full Text Available The study aims at estimating flow duration curves (FDC at ungauged sites in France and quantifying the associated uncertainties using a large dataset of 1080 FDCs. The interpolation procedure focuses here on 15 percentiles standardised by the mean annual flow, which is assumed to be known at each site. In particular, this paper discusses the impact of different catchment grouping procedures on the estimation of percentiles by regional regression models.

In a first step, five parsimonious FDC parametric models are tested to approximate FDCs at gauged sites. The results show that the model based on the expansion of Empirical Orthogonal Functions (EOF outperforms the other tested models. In the EOF model, each FDC is interpreted as a linear combination of regional amplitude functions with spatially variable weighting factors corresponding to the parameters of the model. In this approach, only one amplitude function is required to obtain a satisfactory fit with most of the observed curves. Thus, the considered model requires only two parameters to be applicable at ungauged locations.

Secondly, homogeneous regions are derived according to hydrological response, on the one hand, and geological, climatic and topographic characteristics on the other hand. Hydrological similarity is assessed through two simple indicators: the concavity index (IC representing the shape of the dimensionless FDC and the seasonality ratio (SR, which is the ratio of summer and winter median flows. These variables are used as homogeneity criteria in three different methods for grouping catchments: (i according to an a priori classification of French Hydro-EcoRegions (HERs, (ii by applying regression tree clustering and (iii by using neighbourhoods obtained by canonical correlation analysis.

Finally, considering all the data, and subsequently for each group obtained through the tested grouping techniques, we derive regression models between

Relaxation-type nonlocal inertial-number rheology for dry granular flows

Science.gov (United States)

Lee, Keng-lin; Yang, Fu-ling

2017-12-01

We propose a constitutive model to describe the nonlocality, hysteresis, and several flow features of dry granular materials. Taking the well-known inertial number I as a measure of sheared-induced local fluidization, we derive a relaxation model for I according to the evolution of microstructure during avalanche and dissipation processes. The model yields a nonmonotonic flow law for a homogeneous flow, accounting for hysteretic solid-fluid transition and intermittency in quasistatic flows. For an inhomogeneous flow, the model predicts a generalized Bagnold shear stress revealing the interplay of two microscopic nonlocal mechanisms: collisions among correlated structures and the diffusion of fluidization within the structures. In describing a uniform flow down an incline, the model reproduces the hysteretic starting and stopping heights and the Pouliquen flow rule for mean velocity. Moreover, a dimensionless parameter reflecting the nonlocal effect on the flow is discovered, which controls the transition between Bagnold and creeping flow dynamics.

Considerations for reference pump curves

International Nuclear Information System (INIS)

Stockton, N.B.

1992-01-01

This paper examines problems associated with inservice testing (IST) of pumps to assess their hydraulic performance using reference pump curves to establish acceptance criteria. Safety-related pumps at nuclear power plants are tested under the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (the Code), Section 11. The Code requires testing pumps at specific reference points of differential pressure or flow rate that can be readily duplicated during subsequent tests. There are many cases where test conditions cannot be duplicated. For some pumps, such as service water or component cooling pumps, the flow rate at any time depends on plant conditions and the arrangement of multiple independent and constantly changing loads. System conditions cannot be controlled to duplicate a specific reference value. In these cases, utilities frequently request to use pump curves for comparison of test data for acceptance. There is no prescribed method for developing a pump reference curve. The methods vary and may yield substantially different results. Some results are conservative when compared to the Code requirements; some are not. The errors associated with different curve testing techniques should be understood and controlled within reasonable bounds. Manufacturer's pump curves, in general, are not sufficiently accurate to use as reference pump curves for IST. Testing using reference curves generated with polynomial least squares fits over limited ranges of pump operation, cubic spline interpolation, or cubic spline least squares fits can provide a measure of pump hydraulic performance that is at least as accurate as the Code required method. Regardless of the test method, error can be reduced by using more accurate instruments, by correcting for systematic errors, by increasing the number of data points, and by taking repetitive measurements at each data point

Power Curve Measurements

DEFF Research Database (Denmark)

Federici, Paolo; Vesth, Allan

The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to Ref. [1]. A site calibration has been carried out; see Ref. [2], and the measured flow correction factors for different wind directions are used in the present...... analyze of power performance of the turbine....

Power Curve Measurements

DEFF Research Database (Denmark)

Villanueva, Héctor; Gómez Arranz, Paula

The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to Ref. [1]. A site calibration has been carried out; see Ref. [2], and the measured flow correction factors for different wind directions are used in the present...... analyze of power performance of the turbine...

Quantitative non-monotonic modeling of economic uncertainty by probability and possibility distributions

DEFF Research Database (Denmark)

Schjær-Jacobsen, Hans

2012-01-01

uncertainty can be calculated. The possibility approach is particular well suited for representation of uncertainty of a non-statistical nature due to lack of knowledge and requires less information than the probability approach. Based on the kind of uncertainty and knowledge present, these aspects...... to the understanding of similarities and differences of the two approaches as well as practical applications. The probability approach offers a good framework for representation of randomness and variability. Once the probability distributions of uncertain parameters and their correlations are known the resulting...... are thoroughly discussed in the case of rectangular representation of uncertainty by the uniform probability distribution and the interval, respectively. Also triangular representations are dealt with and compared. Calculation of monotonic as well as non-monotonic functions of variables represented...

Permanence of a Semi-Ratio-Dependent Predator-Prey System with Nonmonotonic Functional Response and Time Delay

Directory of Open Access Journals (Sweden)

Xuepeng Li

2009-01-01

Full Text Available Sufficient conditions for permanence of a semi-ratio-dependent predator-prey system with nonmonotonic functional response and time delay ̇1(=1([1(−11(1(−(−12(2(/(2+21(],  ̇2(=2([2(−21(2(/1(], are obtained, where 1( and 2( stand for the density of the prey and the predator, respectively, and ≠0 is a constant. (≥0 stands for the time delays due to negative feedback of the prey population.

Condition-based inspection/replacement policies for non-monotone deteriorating systems with environmental covariates

Energy Technology Data Exchange (ETDEWEB)

Zhao Xuejing [Universite de Technologie de Troyes, Institut Charles Delaunay and STMR UMR CNRS 6279, 12 rue Marie Curie, 10010 Troyes (France); School of mathematics and statistics, Lanzhou University, Lanzhou 730000 (China); Fouladirad, Mitra, E-mail: mitra.fouladirad@utt.f [Universite de Technologie de Troyes, Institut Charles Delaunay and STMR UMR CNRS 6279, 12 rue Marie Curie, 10010 Troyes (France); Berenguer, Christophe [Universite de Technologie de Troyes, Institut Charles Delaunay and STMR UMR CNRS 6279, 12 rue Marie Curie, 10010 Troyes (France); Bordes, Laurent [Universite de Pau et des Pays de l' Adour, LMA UMR CNRS 5142, 64013 PAU Cedex (France)

2010-08-15

The aim of this paper is to discuss the problem of modelling and optimising condition-based maintenance policies for a deteriorating system in presence of covariates. The deterioration is modelled by a non-monotone stochastic process. The covariates process is assumed to be a time-homogenous Markov chain with finite state space. A model similar to the proportional hazards model is used to show the influence of covariates on the deterioration. In the framework of the system under consideration, an appropriate inspection/replacement policy which minimises the expected average maintenance cost is derived. The average cost under different conditions of covariates and different maintenance policies is analysed through simulation experiments to compare the policies performances.

Condition-based inspection/replacement policies for non-monotone deteriorating systems with environmental covariates

International Nuclear Information System (INIS)

Zhao Xuejing; Fouladirad, Mitra; Berenguer, Christophe; Bordes, Laurent

2010-01-01

The aim of this paper is to discuss the problem of modelling and optimising condition-based maintenance policies for a deteriorating system in presence of covariates. The deterioration is modelled by a non-monotone stochastic process. The covariates process is assumed to be a time-homogenous Markov chain with finite state space. A model similar to the proportional hazards model is used to show the influence of covariates on the deterioration. In the framework of the system under consideration, an appropriate inspection/replacement policy which minimises the expected average maintenance cost is derived. The average cost under different conditions of covariates and different maintenance policies is analysed through simulation experiments to compare the policies performances.

Use of tidal breathing curves for evaluating expiratory airway obstruction in infants.

Science.gov (United States)

Hevroni, Avigdor; Goldman, Aliza; Blank-Brachfeld, Miriam; Abu Ahmad, Wiessam; Ben-Dov, Lior; Springer, Chaim

2018-01-15

To evaluate tidal breathing (TB) flow-volume and flow-time curves for identification of expiratory airway obstruction in infants. Pulmonary function tests were analyzed retrospectively in 156 infants aged 3-24 months with persistent or recurrent respiratory complaints. Parameters derived from TB curves were compared to maximal expiratory flow at functional residual capacity ([Formula: see text]maxFRC) measured by rapid thoracoabdominal compression technique. Analyzed parameters were: inspiratory time (t I ), expiratory time (t E ), tidal volume, peak tidal expiratory flow (PTEF), time to peak tidal expiratory flow (t PTEF ), expiratory flow when 50% and 25% of tidal volume remains in the lungs (FEF 50 , FEF 25 , respectively), and the ratios t PTEF /t E , t I /t E , FEF 50 /PTEF, and FEF 25 /PTEF. Statistical comparisons between flow indices and TB parameters were performed using mean squared error and Pearson's sample correlation coefficient. The study population was also divided into two groups based on severity of expiratory obstruction (above or below z-score for [Formula: see text]maxFRC of -2) to generate receiver operating characteristic (ROC) curves and calculate discriminatory values between the groups. TB parameters that were best correlated to [Formula: see text]maxFRC were: t PTEF /t E , FEF 50 /PTEF, and FEF 25 /PTEF, with r = 0.61, 0.67, 0.65, respectively (p < 0.0001 for all). ROC curves for FEF 50 /PTEF, FEF 25 /PTEF and t PTEF /t E showed areas under the curve of 0.813, 0.797, and 0.796, respectively. Cutoff value z-scores of -0.35, -0.34, and -0.43 for these three parameters, respectively, showed an 86% negative predictive value for severe airway obstructions. TB curves can assist in ruling out severe expiratory airway obstruction in infants.

Flow boundary conditions for chain-end adsorbing polymer blends.

Science.gov (United States)

Zhou, Xin; Andrienko, Denis; Delle Site, Luigi; Kremer, Kurt

2005-09-08

Using the phenol-terminated polycarbonate blend as an example, we demonstrate that the hydrodynamic boundary conditions for a flow of an adsorbing polymer melt are extremely sensitive to the structure of the epitaxial layer. Under shear, the adsorbed parts (chain ends) of the polymer melt move along the equipotential lines of the surface potential whereas the adsorbed additives serve as the surface defects. In response to the increase of the number of the adsorbed additives the surface layer becomes thinner and solidifies. This results in a gradual transition from the slip to the no-slip boundary condition for the melt flow, with a nonmonotonic dependence of the slip length on the surface concentration of the adsorbed ends.

Lectures on mean curvature flows

CERN Document Server

Zhu, Xi-Ping

2002-01-01

"Mean curvature flow" is a term that is used to describe the evolution of a hypersurface whose normal velocity is given by the mean curvature. In the simplest case of a convex closed curve on the plane, the properties of the mean curvature flow are described by Gage-Hamilton's theorem. This theorem states that under the mean curvature flow, the curve collapses to a point, and if the flow is diluted so that the enclosed area equals \\pi, the curve tends to the unit circle. In this book, the author gives a comprehensive account of fundamental results on singularities and the asymptotic behavior of mean curvature flows in higher dimensions. Among other topics, he considers in detail Huisken's theorem (a generalization of Gage-Hamilton's theorem to higher dimension), evolution of non-convex curves and hypersurfaces, and the classification of singularities of the mean curvature flow. Because of the importance of the mean curvature flow and its numerous applications in differential geometry and partial differential ...

Surfactants non-monotonically modify the onset of Faraday waves

Science.gov (United States)

Strickland, Stephen; Shearer, Michael; Daniels, Karen

2017-11-01

When a water-filled container is vertically vibrated, subharmonic Faraday waves emerge once the driving from the vibrations exceeds viscous dissipation. In the presence of an insoluble surfactant, a viscous boundary layer forms at the contaminated surface to balance the Marangoni and Boussinesq stresses. For linear gravity-capillary waves in an undriven fluid, the surfactant-induced boundary layer increases the amount of viscous dissipation. In our analysis and experiments, we consider whether similar effects occur for nonlinear Faraday (gravity-capillary) waves. Assuming a finite-depth, infinite-breadth, low-viscosity fluid, we derive an analytic expression for the onset acceleration up to second order in ɛ =√{ 1 / Re } . This expression allows us to include fluid depth and driving frequency as parameters, in addition to the Marangoni and Boussinesq numbers. For millimetric fluid depths and driving frequencies of 30 to 120 Hz, our analysis recovers prior numerical results and agrees with our measurements of NBD-PC surfactant on DI water. In both case, the onset acceleration increases non-monotonically as a function of Marangoni and Boussinesq numbers. For shallower systems, our model predicts that surfactants could decrease the onset acceleration. DMS-0968258.

Laser induced non-monotonic degradation in short-circuit current of triple-junction solar cells

Science.gov (United States)

Dou, Peng-Cheng; Feng, Guo-Bin; Zhang, Jian-Min; Song, Ming-Ying; Zhang, Zhen; Li, Yun-Peng; Shi, Yu-Bin

2018-06-01

In order to study the continuous wave (CW) laser radiation effects and mechanism of GaInP/GaAs/Ge triple-junction solar cells (TJSCs), 1-on-1 mode irradiation experiments were carried out. It was found that the post-irradiation short circuit current (ISC) of the TJSCs initially decreased and then increased with increasing of irradiation laser power intensity. To explain this phenomenon, a theoretical model had been established and then verified by post-damage tests and equivalent circuit simulations. Conclusion was drawn that laser induced alterations in the surface reflection and shunt resistance were the main causes for the observed non-monotonic decrease in the ISC of the TJSCs.

Evaluation of cerebral intravascular blood flow by time density curve study of intravenous digital subtraction angiography

Energy Technology Data Exchange (ETDEWEB)

Imamura, Toru; Kogure, Kyuya (Tohoku Univ., Sendai (Japan). School of Medicine); Sekine, Teiko; Satoh, Kei; Endoh, Minoru; Tsuburaya, Kenji; Hoshi, Akihiko

1992-01-01

Time density curve (TDC) can be reconstructed from the data of intravenous digital subtraction angiography (IVDSA). We evaluated peak time (PT) and modal transit time (MOTT) of the TDC as the probable indicator of cerebral intravascular blood flow. Cerebral IVDSA and single photon emission CT (SPECT) were performed on 12 patients with ischemic cerebrovascular disease, which consisted of 3 internal carotid artery (ICA) occlusions, one middle cerebral artery (MCA) occlusion, one anterior cerebral artery (ACA) branch occlusion and 7 lacunar infarctions. We classified former 4 patients as occlusion group and latter 8 as reference group. In 3 patients (2 ICA and one MCA occlusions), SPECT study revealed definite hypoaccumulation in the MCA territory of occlusive side. Two regions of interest (ROI) were placed on the territories of right and left middle cerebral arteries in the frontal view of cerebral IVDSA. Digital data processor fitted {gamma} curve to the TDC of each ROI, and calculated PT and MOTT. The absolute lateralities of PT and MOTT of MCA territory was significantly (p<0.05) larger in occlusion group than reference group. Patients with hypoaccumulation in SPECT had significantly (p<0.02) larger laterality of MOTT than patients with isoaccumulation. One ICA occluded patient without hypoaccumulation in corresponding MCA territory had relatively small laterality of MOTT similar to the patients of ACA branch occlusion and lacunar infarction. These results suggest that PT and MOTT are possible to detect the laterality of the intravascular blood flow in MCA territories caused by major artery occlusion. Cerebral TDC study of IVDSA may be useful in some clinical therapeutic situations such as hemodilution or intra-arterial thrombolysis, and worth further clinical evaluation. (author).

'More is less'. The tax effects of ignoring flow externalities

International Nuclear Information System (INIS)

Sandal, Leif K.; Steinshamn, Stein Ivar; Grafton, R. Quentin

2003-01-01

Using a model of non-linear, non-monotone decay of the stock pollutant, and starting from the same initial conditions, the paper shows that an optimal tax that corrects for both stock and flow externalities may result in a lower tax, fewer cumulative emissions (less decay in emissions) and higher output at the steady state than a corrective tax that ignores the flow externality. This 'more is less' result emphasizes that setting a corrective tax that ignores the flow externality, or imposing a corrective tax at too low a level where there exists only a stock externality, may affect both transitory and steady-state output, tax payments and cumulative emissions. The result has important policy implications for decision makers setting optimal corrective taxes and targeted emission limits whenever stock externalities exist

Two-Phase Annular Flow in Helical Coil Flow Channels in a Reduced Gravity Environment

Science.gov (United States)

Keshock, Edward G.; Lin, Chin S.

1996-01-01

A brief review of both single- and two-phase flow studies in curved and coiled flow geometries is first presented. Some of the complexities of two-phase liquid-vapor flow in curved and coiled geometries are discussed, and serve as an introduction to the advantages of observing such flows under a low-gravity environment. The studies proposed -- annular two-phase air-water flow in helical coil flow channels are described. Objectives of the studies are summarized.

Power Curve Measurements, FGW

DEFF Research Database (Denmark)

Vesth, Allan; Kock, Carsten Weber

The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to Ref. [1]. A site calibration has been carried out; see Ref. [2], and the measured flow correction factors for different wind directions are used in the present...... analyze of power performance of the turbine....

Power Curve Measurements FGW

DEFF Research Database (Denmark)

Federici, Paolo; Kock, Carsten Weber

The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to Ref. [1]. A site calibration has been carried out; see Ref. [2], and the measured flow correction factors for different wind directions are used in the present...... analyze of power performance of the turbine...

Consistent Valuation across Curves Using Pricing Kernels

Directory of Open Access Journals (Sweden)

Andrea Macrina

2018-03-01

Full Text Available The general problem of asset pricing when the discount rate differs from the rate at which an asset’s cash flows accrue is considered. A pricing kernel framework is used to model an economy that is segmented into distinct markets, each identified by a yield curve having its own market, credit and liquidity risk characteristics. The proposed framework precludes arbitrage within each market, while the definition of a curve-conversion factor process links all markets in a consistent arbitrage-free manner. A pricing formula is then derived, referred to as the across-curve pricing formula, which enables consistent valuation and hedging of financial instruments across curves (and markets. As a natural application, a consistent multi-curve framework is formulated for emerging and developed inter-bank swap markets, which highlights an important dual feature of the curve-conversion factor process. Given this multi-curve framework, existing multi-curve approaches based on HJM and rational pricing kernel models are recovered, reviewed and generalised and single-curve models extended. In another application, inflation-linked, currency-based and fixed-income hybrid securities are shown to be consistently valued using the across-curve valuation method.

Current density and polarization curves for radial flow field patterns applied to PEMFCs (Proton Exchange Membrane Fuel Cells)

International Nuclear Information System (INIS)

Cano-Andrade, S.; Hernandez-Guerrero, A.; Spakovsky, M.R. von; Damian-Ascencio, C.E.; Rubio-Arana, J.C.

2010-01-01

A numerical solution of the current density and velocity fields of a 3-D PEM radial configuration fuel cell is presented. The energy, momentum and electrochemical equations are solved using a computational fluid dynamics (CFD) code based on a finite volume scheme. There are three cases of principal interest for this radial model: four channels, eight channels and twelve channels placed in a symmetrical path over the flow field plate. The figures for the current-voltage curves for the three models proposed are presented, and the main factors that affect the behavior of each of the curves are discussed. Velocity contours are presented for the three different models, showing how the fuel cell behavior is affected by the velocity variations in the radial configuration. All these results are presented for the case of high relative humidity. The favorable results obtained for this unconventional geometry seems to indicate that this geometry could replace the conventional commercial geometries currently in use.

Effects of shear flow on phase nucleation and crystallization.

Science.gov (United States)

Mura, Federica; Zaccone, Alessio

2016-04-01

Classical nucleation theory offers a good framework for understanding the common features of new phase formation processes in metastable homogeneous media at rest. However, nucleation processes in liquids are ubiquitously affected by hydrodynamic flow, and there is no satisfactory understanding of whether shear promotes or slows down the nucleation process. We developed a classical nucleation theory for sheared systems starting from the molecular level of the Becker-Doering master kinetic equation and we analytically derived a closed-form expression for the nucleation rate. The theory accounts for the effect of flow-mediated transport of molecules to the nucleus of the new phase, as well as for the mechanical deformation imparted to the nucleus by the flow field. The competition between flow-induced molecular transport, which accelerates nucleation, and flow-induced nucleus straining, which lowers the nucleation rate by increasing the nucleation energy barrier, gives rise to a marked nonmonotonic dependence of the nucleation rate on the shear rate. The theory predicts an optimal shear rate at which the nucleation rate is one order of magnitude larger than in the absence of flow.

Investigation of intrarenal blood flow and urine flow aspects by scintillation camera

International Nuclear Information System (INIS)

Kawamura, J.; Hosokawa, S.; Yoshida, O.; Ishii, Y.; Torizuka, K.

1977-01-01

In order to clarify intrarenal dynamic processes related to regional distribution in patients with unilateral renal disease, two radioactive tracers, 133 Xe and /sup 99m/Tc-diethylenetriaminepentaacetic acid (/sup 99m/Tc-DTPA) were introduced into a renal artery and intrarenal blood flow and urine flow aspects were observed by scintillation camera. Cortical blood flow decreased and medullary blood flow relatively increased with the advance of renal damage. Urine flow curve from normal cortex showed two phasic patterns. One early phase might correspond to the appearance of the tracer through the proximal tubule and a second phase might correspond to the appearance of the tracer through the loop of Henle to the distal tubule. Under mannitol diuresis, two phasic urine flow curves from the cortex became obscured and the peak time of pelvic curve shifted to the earlier period. These studies were considered to be useful in evaluating unilateral renal function and might offer a good insight for intrarenal physiology concerning blood flow as well as urine flow

Assessing dose-response relationships for endocrine disrupting chemicals (EDCs): a focus on non-monotonicity.

Science.gov (United States)

Zoeller, R Thomas; Vandenberg, Laura N

2015-05-15

The fundamental principle in regulatory toxicology is that all chemicals are toxic and that the severity of effect is proportional to the exposure level. An ancillary assumption is that there are no effects at exposures below the lowest observed adverse effect level (LOAEL), either because no effects exist or because they are not statistically resolvable, implying that they would not be adverse. Chemicals that interfere with hormones violate these principles in two important ways: dose-response relationships can be non-monotonic, which have been reported in hundreds of studies of endocrine disrupting chemicals (EDCs); and effects are often observed below the LOAEL, including all environmental epidemiological studies examining EDCs. In recognition of the importance of this issue, Lagarde et al. have published the first proposal to qualitatively assess non-monotonic dose response (NMDR) relationships for use in risk assessments. Their proposal represents a significant step forward in the evaluation of complex datasets for use in risk assessments. Here, we comment on three elements of the Lagarde proposal that we feel need to be assessed more critically and present our arguments: 1) the use of Klimisch scores to evaluate study quality, 2) the concept of evaluating study quality without topical experts' knowledge and opinions, and 3) the requirement of establishing the biological plausibility of an NMDR before consideration for use in risk assessment. We present evidence-based logical arguments that 1) the use of the Klimisch score should be abandoned for assessing study quality; 2) evaluating study quality requires experts in the specific field; and 3) an understanding of mechanisms should not be required to accept observable, statistically valid phenomena. It is our hope to contribute to the important and ongoing debate about the impact of NMDRs on risk assessment with positive suggestions.

Distance of Sample Measurement Points to Prototype Catalog Curve

DEFF Research Database (Denmark)

Hjorth, Poul G.; Karamehmedovic, Mirza; Perram, John

2006-01-01

We discuss strategies for comparing discrete data points to a catalog (reference) curve by means of the Euclidean distance from each point to the curve in a pump's head H vs. flow Qdiagram. In particular we find that a method currently in use is inaccurate. We propose several alternatives...

Regional variation of flow duration curves in the eastern United States: Process-based analyses of the interaction between climate and landscape properties

Science.gov (United States)

Chouaib, Wafa; Caldwell, Peter V.; Alila, Younes

2018-04-01

This paper advances the physical understanding of the flow duration curve (FDC) regional variation. It provides a process-based analysis of the interaction between climate and landscape properties to explain disparities in FDC shapes. We used (i) long term measured flow and precipitation data over 73 catchments from the eastern US. (ii) We calibrated the Sacramento model (SAC-SMA) to simulate soil moisture and flow components FDCs. The catchments classification based on storm characteristics pointed to the effect of catchments landscape properties on the precipitation variability and consequently on the FDC shapes. The landscape properties effect was pronounce such that low value of the slope of FDC (SFDC)-hinting at limited flow variability-were present in regions of high precipitation variability. Whereas, in regions with low precipitation variability the SFDCs were of larger values. The topographic index distribution, at the catchment scale, indicated that saturation excess overland flow mitigated the flow variability under conditions of low elevations with large soil moisture storage capacity and high infiltration rates. The SFDCs increased due to the predominant subsurface stormflow in catchments at high elevations with limited soil moisture storage capacity and low infiltration rates. Our analyses also highlighted the major role of soil infiltration rates on the FDC despite the impact of the predominant runoff generation mechanism and catchment elevation. In conditions of slow infiltration rates in soils of large moisture storage capacity (at low elevations) and predominant saturation excess, the SFDCs were of larger values. On the other hand, the SFDCs decreased in catchments of prevalent subsurface stormflow and poorly drained soils of small soil moisture storage capacity. The analysis of the flow components FDCs demonstrated that the interflow contribution to the response was the higher in catchments with large value of slope of the FDC. The surface flow

RMS fatigue curves for random vibrations

International Nuclear Information System (INIS)

Brenneman, B.; Talley, J.G.

1984-01-01

Fatigue usage factors for deterministic or constant amplitude vibration stresses may be calculated with well known procedures and fatigue curves given in the ASME Boiler and Pressure Vessel Code. However, some phenomena produce nondeterministic cyclic stresses which can only be described and analyzed with statistical concepts and methods. Such stresses may be caused by turbulent fluid flow over a structure. Previous methods for solving this statistical fatigue problem are often difficult to use and may yield inaccurate results. Two such methods examined herein are Crandall's method and the ''3sigma'' method. The objective of this paper is to provide a method for creating ''RMS fatigue curves'' which accurately incorporate the requisite statistical information. These curves are given and may be used by analysts with the same ease and in the same manner as the ASME fatigue curves

Determining the spill flow discharge of combined sewer overflows using rating curves based on computational fluid dynamics instead of the standard weir equation.

Science.gov (United States)

Fach, S; Sitzenfrei, R; Rauch, W

2009-01-01

It is state of the art to evaluate and optimise sewer systems with urban drainage models. Since spill flow data is essential in the calibration process of conceptual models it is important to enhance the quality of such data. A wide spread approach is to calculate the spill flow volume by using standard weir equations together with measured water levels. However, these equations are only applicable to combined sewer overflow (CSO) structures, whose weir constructions correspond with the standard weir layout. The objective of this work is to outline an alternative approach to obtain spill flow discharge data based on measurements with a sonic depth finder. The idea is to determine the relation between water level and rate of spill flow by running a detailed 3D computational fluid dynamics (CFD) model. Two real world CSO structures have been chosen due to their complex structure, especially with respect to the weir construction. In a first step the simulation results were analysed to identify flow conditions for discrete steady states. It will be shown that the flow conditions in the CSO structure change after the spill flow pipe acts as a controlled outflow and therefore the spill flow discharge cannot be described with a standard weir equation. In a second step the CFD results will be used to derive rating curves which can be easily applied in everyday practice. Therefore the rating curves are developed on basis of the standard weir equation and the equation for orifice-type outlets. Because the intersection of both equations is not known, the coefficients of discharge are regressed from CFD simulation results. Furthermore, the regression of the CFD simulation results are compared with the one of the standard weir equation by using historic water levels and hydrographs generated with a hydrodynamic model. The uncertainties resulting of the wide spread use of the standard weir equation are demonstrated.

Nonmonotonic behaviour of superconducting critical temperature of Nb/CuNi bilayers with a nanometer range of layer thickness

International Nuclear Information System (INIS)

Morari, R.; Antropov, E.; Socrovisciuc, A.; Prepelitsa, A.; Zdravkov, V.I.; Tagirov, L.R.; Kupriyanov, M.Yu.; Sidorenko, A.S.

2009-01-01

Present work reports the result of the proximity effect investigation for superconducting Nb/CuNi-bilayers with the thickness of the ferromagnetic layer (Cu x Ni 1-x ) being in the sub-nanometer range. It was found a non-monotonic behavior of the critical temperature T c , i.e. its growth with the increasing of the ferromagnetic layer thickness dF, for the series of the samples with constant thickness of Nb layer, (d Nb = const). (authors)

The Effect of Turbulences Flow on a Gas-Liquid Mixing Process Downstream of a Curved Duct

Directory of Open Access Journals (Sweden)

Abdul Satar Jawad Mohammed

2018-02-01

Full Text Available An experimental investigation is carried out on the use of water injection on the humidification process of air with a steady flow that travels during the curved part of a duct with a constant cross section. The naturally generated turbulences will surely aid the mixing process between the injected water droplets and the air to enhance both the mass and heat transfer. The current investigation is regarded as a simulation of the inlet air cooling of the gas turbine which aims to specify the optimum atomizer position on the air cooling by the fogging technique. The experiments were carried out on a (50×50 cm wind tunnel with an average air velocity of (10 m/s. Experiments were conducted in a range of air to water flow ratio between 1000 and 2000, and an ambient temperature in a range of 30° to 50°C. At higher ambient temperature of 45.2oC (DBT, a temperature reduction of 26% and an increase in the relative humidity ratio of 2.13 were recorded at the flow ratio of 1000. Injecting water upward through the range of angles -25° to 75° showed less sensitivity to atomizer location regardless the radial position of the atomizer. This situation is most suitable for using atomizing array across the duct. The central location with tangential spray introduces the critical position for a single-point spray. Such position is promising the optimum atomizer place specified by a radii ratio of (r/rin=3 and tangential orientation to the direction of flow.

Annealing temperature dependent non-monotonic d{sup 0} ferromagnetism in pristine In{sub 2}O{sub 3} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Cao, Haiming; Xing, Pengfei, E-mail: pfxing@tju.edu.cn; Yao, Dongsheng; Wu, Ping

2017-05-01

Cubic bixbyite In{sub 2}O{sub 3} nanoparticles with room temperature d{sup 0} ferromagnetism were prepared by sol-gel method with the air annealing temperature ranging from 500 to 900 °C. X-ray diffraction, X-ray photoelectron spectroscopy, Raman-scattering and photoluminescence were carried out to demonstrate the presence of oxygen vacancies. The lattice constant, the atomic ratio of crystal O and In, the Raman peak at 369 cm{sup −1}, the PL emission peak at 396 nm and the saturation magnetization of d{sup 0} ferromagnetism all had a consistent non-monotonic change with the increasing annealing temperature. With further considering the relation between the grain size and the distribution of oxygen vacancies, we think that d{sup 0} ferromagnetism in our samples is directly related with the singly charged oxygen vacancies at the surface of In{sub 2}O{sub 3} nanoparticles. - Highlights: • Effect of air-annealing temperature on the d{sup 0} ferromagnetism of pure In{sub 2}O{sub 3}. • Oxygen-deficiency states of all samples were detected by Raman scattering and PL. • Ferromagnetism changes non-monotonically with the increasing annealing temperature. • d{sup 0} ferromagnetism in our In{sub 2}O{sub 3} nanoparticles is related with the surface V{sub O}{sup +}.

Numerical investigation of Dean vortices in a curved pipe

Science.gov (United States)

Bernad, S. I.; Totorean, A.; Bosioc, A.; Stanciu, R.; Bernad, E. S.

2013-10-01

This study is devoted to the three-dimensional numerical simulation of developing secondary flows of Newtonian fluid through a curved circular duct. The numerical simulations produced for different Dean numbers show clearly the presence of two steady Dean vortices. Therefore, results confirm that helical flow constitutes an important flow signature in vessels, and its strength as a fluid dynamic index.

Effect of Temperature Reversion on Hot Ductility and Flow Stress-Strain Curves of C-Mn Continuously Cast Steels

Science.gov (United States)

Dong, Zhihua; Li, Wei; Long, Mujun; Gui, Lintao; Chen, Dengfu; Huang, Yunwei; Vitos, Levente

2015-08-01

The influence of temperature reversion in secondary cooling and its reversion rate on hot ductility and flow stress-strain curve of C-Mn steel has been investigated. Tensile specimens were cooled at various regimes. One cooling regime involved cooling at a constant rate of 100 °C min-1 to the test temperature, while the others involved temperature reversion processes at three different reversion rates before deformation. After hot tensile test, the evolution of mechanical properties of steel was analyzed at various scales by means of microstructure observation, ab initio prediction, and thermodynamic calculation. Results indicated that the temperature reversion in secondary cooling led to hot ductility trough occurring at higher temperature with greater depth. With increasing temperature reversion rate, the low temperature end of ductility trough extended toward lower temperature, leading to wider hot ductility trough with slightly reducing depth. Microstructure examinations indicated that the intergranular fracture related to the thin film-like ferrite and (Fe,Mn)S particles did not changed with varying cooling regimes; however, the Widmanstatten ferrite surrounding austenite grains resulted from the temperature reversion process seriously deteriorated the ductility. In addition, after the temperature reversion in secondary cooling, the peak stress on the flow curve slightly declined and the peak of strain to peak stress occurred at higher temperature. With increasing temperature reversion rate, the strain to peak stress slightly increased, while the peak stress showed little variation. The evolution of plastic modulus and strain to peak stress of austenite with varying temperature was in line with the theoretical prediction on Fe.

Effect of Flow Direction on Relative Permeability Curves in Water/Gas Reservoir System: Implications in Geological CO2 Sequestration

Directory of Open Access Journals (Sweden)

Abdulrauf Rasheed Adebayo

2017-01-01

Full Text Available The effect of gravity on vertical flow and fluids saturation, especially when flow is against gravity, is not often a subject of interest to researchers. This is because of the notion that flow in subsurface formations is usually in horizontal direction and that vertical flow is impossible or marginal because of the impermeable shales or silts overlying them. The density difference between two fluids (usually oil and water flowing in the porous media is also normally negligible; hence gravity influence is neglected. Capillarity is also often avoided in relative permeability measurements in order to satisfy some flow equations. These notions have guided most laboratory core flooding experiments to be conducted in horizontal flow orientation, and the data obtained are as good as what the experiments tend to mimic. However, gravity effect plays a major role in gas liquid systems such as CO2 sequestration and some types of enhanced oil recovery techniques, particularly those involving gases, where large density difference exists between the fluid pair. In such cases, laboratory experiments conducted to derive relative permeability curves should take into consideration gravity effects and capillarity. Previous studies attribute directional dependence of relative permeability and residual saturations to rock anisotropy. It is shown in this study that rock permeability, residual saturation, and relative permeability depend on the interplay between gravity, capillarity, and viscous forces and also the direction of fluid flow even when the rock is isotropic. Rock samples representing different lithology and wide range of permeabilities were investigated through unsteady-state experiments covering drainage and imbibition in both vertical and horizontal flow directions. The experiments were performed at very low flow rates to capture capillarity. The results obtained showed that, for each homogeneous rock and for the same flow path along the core length

Exploring the physical controls of regional patterns of flow duration curves – Part 2: Role of seasonality, the regime curve, and associated process controls

Directory of Open Access Journals (Sweden)

M. Sivapalan

2012-11-01

Full Text Available The goal of this paper is to explore the process controls underpinning regional patterns of variations of streamflow regime behavior, i.e., the mean seasonal variation of streamflow within the year, across the continental United States. The ultimate motivation is to use the resulting process understanding to generate insights into the physical controls of another signature of streamflow variability, namely the flow duration curve (FDC. The construction of the FDC removes the time dependence of flows. Thus in order to better understand the physical controls in regions that exhibit strong seasonal dependence, the regime curve (RC, which is closely connected to the FDC, is studied in this paper and later linked back to the FDC. To achieve these aims a top-down modeling approach is adopted; we start with a simple two-stage bucket model, which is systematically enhanced through addition of new processes on the basis of model performance assessment in relation to observations, using rainfall-runoff data from 197 United States catchments belonging to the MOPEX dataset. Exploration of dominant processes and the determination of required model complexity are carried out through model-based sensitivity analyses, guided by a performance metric. Results indicated systematic regional trends in dominant processes: snowmelt was a key process control in cold mountainous catchments in the north and north-west, whereas snowmelt and vegetation cover dynamics were key controls in the north-east; seasonal vegetation cover dynamics (phenology and interception were important along the Appalachian mountain range in the east. A simple two-bucket model (with no other additions was found to be adequate in warm humid catchments along the west coast and in the south-east, with both regions exhibiting strong seasonality, whereas much more complex models are needed in the dry south and south-west. Agricultural catchments in the mid-west were found to be difficult to predict

Integrated analysis on static/dynamic aeroelasticity of curved panels based on a modified local piston theory

Science.gov (United States)

Yang, Zhichun; Zhou, Jian; Gu, Yingsong

2014-10-01

A flow field modified local piston theory, which is applied to the integrated analysis on static/dynamic aeroelastic behaviors of curved panels, is proposed in this paper. The local flow field parameters used in the modification are obtained by CFD technique which has the advantage to simulate the steady flow field accurately. This flow field modified local piston theory for aerodynamic loading is applied to the analysis of static aeroelastic deformation and flutter stabilities of curved panels in hypersonic flow. In addition, comparisons are made between results obtained by using the present method and curvature modified method. It shows that when the curvature of the curved panel is relatively small, the static aeroelastic deformations and flutter stability boundaries obtained by these two methods have little difference, while for curved panels with larger curvatures, the static aeroelastic deformation obtained by the present method is larger and the flutter stability boundary is smaller compared with those obtained by the curvature modified method, and the discrepancy increases with the increasing of curvature of panels. Therefore, the existing curvature modified method is non-conservative compared to the proposed flow field modified method based on the consideration of hypersonic flight vehicle safety, and the proposed flow field modified local piston theory for curved panels enlarges the application range of piston theory.

MHD Convective Flow of Jeffrey Fluid Due to a Curved Stretching Surface with Homogeneous-Heterogeneous Reactions.

Directory of Open Access Journals (Sweden)

Maria Imtiaz

Full Text Available This paper looks at the flow of Jeffrey fluid due to a curved stretching sheet. Effect of homogeneous-heterogeneous reactions is considered. An electrically conducting fluid in the presence of applied magnetic field is considered. Convective boundary conditions model the heat transfer analysis. Transformation method reduces the governing nonlinear partial differential equations into the ordinary differential equations. Convergence of the obtained series solutions is explicitly discussed. Characteristics of sundry parameters on the velocity, temperature and concentration profiles are analyzed by plotting graphs. Computations for pressure, skin friction coefficient and surface heat transfer rate are presented and examined. It is noted that fluid velocity and temperature through curvature parameter are enhanced. Increasing values of Biot number correspond to the enhancement in temperature and Nusselt number.

Couette flow regimes with heat transfer in rarefied gas

Energy Technology Data Exchange (ETDEWEB)

Abramov, A. A., E-mail: alabr54@mail.ru; Butkovskii, A. V., E-mail: albutkov@mail.ru [Zhukovski Central Aerohydrodynamics Institute (Russian Federation)

2013-06-15

Based on numerical solution of the Boltzmann equation by direct statistic simulation, the Couette flow with heat transfer is studied in a broad range of ratios of plate temperatures and Mach numbers of a moving plate. Flow regime classification by the form of the dependences of the energy flux and friction stress on the Knudsen number Kn is proposed. These dependences can be simultaneously monotonic and nonmonotonic and have maxima. Situations are possible in which the dependence of the energy flux transferred to a plate on Kn has a minimum, while the dependence of the friction stress is monotonic or even has a maximum. Also, regimes exist in which the dependence of the energy flux on Kn has a maximum, while the dependence of the friction stress is monotonic, and vice versa.

Non-monotonic spatial distribution of the interstellar dust in astrospheres: finite gyroradius effect

Science.gov (United States)

Katushkina, O. A.; Alexashov, D. B.; Izmodenov, V. V.; Gvaramadze, V. V.

2017-02-01

High-resolution mid-infrared observations of astrospheres show that many of them have filamentary (cirrus-like) structure. Using numerical models of dust dynamics in astrospheres, we suggest that their filamentary structure might be related to specific spatial distribution of the interstellar dust around the stars, caused by a gyrorotation of charged dust grains in the interstellar magnetic field. Our numerical model describes the dust dynamics in astrospheres under an influence of the Lorentz force and assumption of a constant dust charge. Calculations are performed for the dust grains with different sizes separately. It is shown that non-monotonic spatial dust distribution (viewed as filaments) appears for dust grains with the period of gyromotion comparable with the characteristic time-scale of the dust motion in the astrosphere. Numerical modelling demonstrates that the number of filaments depends on charge-to-mass ratio of dust.

Blood flow in the limbs of hemiplegic patients by 99mTc-HSA accumulation curve and digital plethysmography

International Nuclear Information System (INIS)

Kuriyama, Setsuro

1985-01-01

Using 99m Tc-Human-Serum-Albumin (HSA) accumulation curve we have studied the blood flow in the lower extremities of the hemiplegic patients. After injection of 5 - 10 mCi of 99m Tc-HSA into v. mediana cubiti by the Oldendolf method, we recorded the RI count from both knees. We have examined 68 hemiplegic patients (male: 26, female: 42, right: 31, left: 37, average age: 61.7 years, average Brunnstrom stage of the lower extremity: 3.73, average duration post-stroke: 20.2 months). We counted the accumulation of the isotope in both knees 1 and 30 minutes after injection, and calculated the percentage (partic side/right and left sides), and named them as ''1-minute value'' and ''30-minute value''. During the 15 months period after an attack, the paretic leg had more blood flow than the non-paretic leg. After 15 months after attack, on the contrary, the paretic leg had less blood flow than the non-paretic leg. This tendency is clear in the left-sided hemiplegic patients. There is no relation between the blood flow and age, and the Brunnstrom stage, and the ability to walk. Using digital plethysmography, we have studied the blood flow in the finger and toe, too. We have examined 57 hemiplegic patients. We have averaged the five hights of the wave (mV/V), and calculated the percentage involved (paretic side/right and left) and labled it ''the paretic blood flow value (of the finger and of the toe)''. During the 12 month period after an attack, the paretic side had more blood flow than the non-paratic side. After 15 month after an attack, on the contrary, the paretic side had less blood flow than the non-paretic side. This tendency is clear in the finger than the toe. There is no correlation between the blood flow and the age, and the Brunnstrom stage, and the ability to walk. (author)

Non-monotonic relationships between emotional arousal and memory for color and location.

Science.gov (United States)

Boywitt, C Dennis

2015-01-01

Recent research points to the decreased diagnostic value of subjective retrieval experience for memory accuracy for emotional stimuli. While for neutral stimuli rich recollective experiences are associated with better context memory than merely familiar memories this association appears questionable for emotional stimuli. The present research tested the implicit assumption that the effect of emotional arousal on memory is monotonic, that is, steadily increasing (or decreasing) with increasing arousal. In two experiments emotional arousal was manipulated in three steps using emotional pictures and subjective retrieval experience as well as context memory were assessed. The results show an inverted U-shape relationship between arousal and recognition memory but for context memory and retrieval experience the relationship was more complex. For frame colour, context memory decreased linearly while for spatial location it followed the inverted U-shape function. The complex, non-monotonic relationships between arousal and memory are discussed as possible explanations for earlier divergent findings.

Transmission of wave energy in curved ducts

Science.gov (United States)

Rostafinski, W.

1973-01-01

A formation of wave energy flow was developed for motion in curved ducts. A parametric study over a range of frequencies determined the ability of circular bends to transmit energy for the case of perfectly rigid walls.

Dynamos driven by poloidal flows in untwisted, curved and flat Riemannian diffusive flux tubes

International Nuclear Information System (INIS)

De Andrade, L.C.G.

2010-01-01

Recently Vishik anti-fast dynamo theorem has been tested against non-stretching flux tubes (Phys. Plasmas, 15 (2008)). In this paper, another anti dynamo theorem, called Cowling's theorem, which states that axisymmetric magnetic fields cannot support dynamo action, is carefully tested against thick tubular and curved Riemannian untwisted flows, as well as thin flux tubes in diffusive and diffusion less media. In the non-diffusive media Cowling's theorem is not violated in thin Riemann-flat untwisted flux tubes, where the Frenet curvature is negative. Nevertheless the diffusion action in the thin flux tube leads to a dynamo action driven by poloidal flows as shown by Love and Gubbins (Geophysical Res., 23 (1996) 857) in the context of geo dynamos. Actually it is shown that a slow dynamo action is obtained. In this case the Frenet and Riemann curvature still vanishes. In the case of magnetic filaments in diffusive media dynamo action is obtained when the Frenet scalar curvature is negative. Since the Riemann curvature tensor can be expressed in terms of the Frenet curvature of the magnetic flux tube axis, this result can be analogous to a recent result obtained by Chicone, Latushkin and Smith, which states that geodesic curvature in compact Riemannian manifolds can drive dynamo action in the manifold. It is also shown that in the absence of diffusion, magnetic energy does not grow but magnetic toroidal magnetic field can be generated by the poloidal field, what is called a plasma dynamo.

Sheared flow layer formation in tokamak plasmas with reversed magnetic shear

International Nuclear Information System (INIS)

Dong, J.Q.; Long, Y.X.; Mou, Z.Z.; Zhang, J.H.; Li, J.Q.

2005-01-01

Sheared flow layer (SFL) formation due to magnetic energy release through tearing-reconnections in tokamak plasmas is investigated. The characteristics of the SFLs created in the development of double tearing mode, mediated by electron viscosity in configurations with non-monotonic safety factor q profiles and, therefore, two rational flux surfaces of same q value, are analyzed in detail as an example. Quasi-linear simulations demonstrate that the sheared flows induced by the mode have desirable characteristics (lying at the boundaries of the magnetic islands), and sufficient levels required for internal transport barrier (ITB) formation. A possible correlation of the SFLs with experimental observations, that double transport barrier structures are preferentially formed in proximity of the two rational surfaces, is also proffered. (author)

Beyond Rating Curves: Time Series Models for in-Stream Turbidity Prediction

Science.gov (United States)

Wang, L.; Mukundan, R.; Zion, M.; Pierson, D. C.

2012-12-01

The New York City Department of Environmental Protection (DEP) manages New York City's water supply, which is comprised of over 20 reservoirs and supplies over 1 billion gallons of water per day to more than 9 million customers. DEP's "West of Hudson" reservoirs located in the Catskill Mountains are unfiltered per a renewable filtration avoidance determination granted by the EPA. While water quality is usually pristine, high volume storm events occasionally cause the reservoirs to become highly turbid. A logical strategy for turbidity control is to temporarily remove the turbid reservoirs from service. While effective in limiting delivery of turbid water and reducing the need for in-reservoir alum flocculation, this strategy runs the risk of negatively impacting water supply reliability. Thus, it is advantageous for DEP to understand how long a particular turbidity event will affect their system. In order to understand the duration, intensity and total load of a turbidity event, predictions of future in-stream turbidity values are important. Traditionally, turbidity predictions have been carried out by applying streamflow observations/forecasts to a flow-turbidity rating curve. However, predictions from rating curves are often inaccurate due to inter- and intra-event variability in flow-turbidity relationships. Predictions can be improved by applying an autoregressive moving average (ARMA) time series model in combination with a traditional rating curve. Since 2003, DEP and the Upstate Freshwater Institute have compiled a relatively consistent set of 15-minute turbidity observations at various locations on Esopus Creek above Ashokan Reservoir. Using daily averages of this data and streamflow observations at nearby USGS gauges, flow-turbidity rating curves were developed via linear regression. Time series analysis revealed that the linear regression residuals may be represented using an ARMA(1,2) process. Based on this information, flow-turbidity regressions with

Power flow modeling of Back-to-Back STATCOM: Comprehensive simulation studies including PV curves and PQ circles

Directory of Open Access Journals (Sweden)

Ahmet Mete Vural

2017-09-01

Full Text Available Power flow study in a power network embedded with FACTS device requires effort in program coding. Moreover, Newton-Raphson method should be modified by embedding injected power components into the algorithm. In this study, we have proposed a method for modeling of one of the newest FACTS concepts in power flow study without program coding or modification of existing Newton-Raphson algorithm. Real and reactive power injections for each voltage source converter of Back-to-Back Static Synchronous Compensator (BtB-STATCOM are PI regulated to their desired steady-state values. With this respect, reactive power injection of each voltage source converter as well as real power transfer among them can be assigned as control constraint. Operating losses are also taken into account in the proposed modeling approach. Furthermore, proposed model can be easily modified for the modeling of conventional STATCOM having only one voltage source converter or two STATCOMs operating independently. The proposed modeling approach is verified in PSCAD through a number of simulation scenarios in BtB-STATCOM and STATCOM embedded power systems, namely 1-Machine 4-Bus system and 3-Machine 7-Bus system. PV curves of local buses compensated by BtB-STATCOM and STATCOM are presented and compared. Steady-state performance of BtB-STATCOM and STATCOM is also compared in power flow handling.

On the connection between nonmonotonic taste behavior and molecular conformation in solution: The case of rebaudioside-A

Science.gov (United States)

Chopade, Prashant D.; Sarma, Bipul; Santiso, Erik E.; Simpson, Jeffrey; Fry, John C.; Yurttas, Nese; Biermann, Kari L.; Chen, Jie; Trout, Bernhardt L.; Myerson, Allan S.

2015-12-01

The diterpene steviol glycoside, rebaudioside A, is a natural high potency non-caloric sweetener extracted from the leaves of Stevia rebaudiana. This compound shows a parabolic change in sweet taste intensity with temperature which contrasts with the general finding for other synthetic or natural sweeteners whose sweet taste increases with temperature. The nonmonotonic taste behavior was determined by sensory analysis using large taste panels. The conformational landscape of rebaudioside A was established at a range of temperatures by means of nuclear magnetic resonance and molecular dynamics simulation. The relationship between various conformations and the observed sweetness of rebaudioside A is described.

On the connection between nonmonotonic taste behavior and molecular conformation in solution: The case of rebaudioside-A

International Nuclear Information System (INIS)

Chopade, Prashant D.; Sarma, Bipul; Santiso, Erik E.; Chen, Jie; Trout, Bernhardt L.; Myerson, Allan S.; Simpson, Jeffrey; Fry, John C.; Biermann, Kari L.; Yurttas, Nese

2015-01-01

The diterpene steviol glycoside, rebaudioside A, is a natural high potency non-caloric sweetener extracted from the leaves of Stevia rebaudiana. This compound shows a parabolic change in sweet taste intensity with temperature which contrasts with the general finding for other synthetic or natural sweeteners whose sweet taste increases with temperature. The nonmonotonic taste behavior was determined by sensory analysis using large taste panels. The conformational landscape of rebaudioside A was established at a range of temperatures by means of nuclear magnetic resonance and molecular dynamics simulation. The relationship between various conformations and the observed sweetness of rebaudioside A is described

On the connection between nonmonotonic taste behavior and molecular conformation in solution: The case of rebaudioside-A

Energy Technology Data Exchange (ETDEWEB)

Chopade, Prashant D.; Sarma, Bipul; Santiso, Erik E.; Chen, Jie; Trout, Bernhardt L.; Myerson, Allan S., E-mail: myerson@mit.edu [Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 66-568, Cambridge, Massachusetts 02139 (United States); Simpson, Jeffrey [Department of Chemistry Instrumentation Facility, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 18-0090, Cambridge, Massachusetts 02139 (United States); Fry, John C.; Biermann, Kari L. [Connect Consulting, 6 Hollands Field, Horsham RH123HQ (United Kingdom); Yurttas, Nese [Cargill, Inc., Global Food Technology, 2301 Crosby Road, Wayzata, Minnesota 55391 (United States)

2015-12-28

The diterpene steviol glycoside, rebaudioside A, is a natural high potency non-caloric sweetener extracted from the leaves of Stevia rebaudiana. This compound shows a parabolic change in sweet taste intensity with temperature which contrasts with the general finding for other synthetic or natural sweeteners whose sweet taste increases with temperature. The nonmonotonic taste behavior was determined by sensory analysis using large taste panels. The conformational landscape of rebaudioside A was established at a range of temperatures by means of nuclear magnetic resonance and molecular dynamics simulation. The relationship between various conformations and the observed sweetness of rebaudioside A is described.

Independent variable complexity for regional regression of the flow duration curve in ungauged basins

Science.gov (United States)

Fouad, Geoffrey; Skupin, André; Hope, Allen

2016-04-01

The flow duration curve (FDC) is one of the most widely used tools to quantify streamflow. Its percentile flows are often required for water resource applications, but these values must be predicted for ungauged basins with insufficient or no streamflow data. Regional regression is a commonly used approach for predicting percentile flows that involves identifying hydrologic regions and calibrating regression models to each region. The independent variables used to describe the physiographic and climatic setting of the basins are a critical component of regional regression, yet few studies have investigated their effect on resulting predictions. In this study, the complexity of the independent variables needed for regional regression is investigated. Different levels of variable complexity are applied for a regional regression consisting of 918 basins in the US. Both the hydrologic regions and regression models are determined according to the different sets of variables, and the accuracy of resulting predictions is assessed. The different sets of variables include (1) a simple set of three variables strongly tied to the FDC (mean annual precipitation, potential evapotranspiration, and baseflow index), (2) a traditional set of variables describing the average physiographic and climatic conditions of the basins, and (3) a more complex set of variables extending the traditional variables to include statistics describing the distribution of physiographic data and temporal components of climatic data. The latter set of variables is not typically used in regional regression, and is evaluated for its potential to predict percentile flows. The simplest set of only three variables performed similarly to the other more complex sets of variables. Traditional variables used to describe climate, topography, and soil offered little more to the predictions, and the experimental set of variables describing the distribution of basin data in more detail did not improve predictions

Flow boiling heat transfer on nanowire-coated surfaces with highly wetting liquid

International Nuclear Information System (INIS)

Shin, Sangwoo; Choi, Geehong; Kim, Beom Seok; Cho, Hyung Hee

2014-01-01

Owing to the recent advances in nanotechnology, one significant progress in energy technology is increased cooling ability. It has recently been shown that nanowires can improve pool boiling heat transfer due to the unique features such as enhanced wetting and enlarged nucleation sites. Applying such nanowires on a flow boiling, which is another major class of boiling phenomenon that is associated with forced convection, is yet immature and scarce despite its importance in various applications such as liquid cooling of energy, electronics and refrigeration systems. Here, we investigate flow boiling heat transfer on surfaces that are coated with SiNWs (silicon nanowires). Also, we use highly-wetting dielectric liquid, FC-72, as a working fluid. An interesting wetting behavior is observed where the presence of SiNWs reduces wetting and wicking that in turn leads to significant decrease of CHF (critical heat flux) compared to the plain surface, which opposes the current consensus. Also, the effects of nanowire length and Reynolds number on the boiling heat transfer are shown to be highly nonmonotonic. We attempt to explain such an unusual behavior on the basis of wetting, nucleation and forced convection, and we show that such factors are highly coupled in a way that lead to unusual behavior. - Highlights: • Observation of suppressed wettability in the presence of surface roughness (nanowires). • Significant reduction of critical heat flux in the presence of nanowires. • Nonmonotonic behavior of heat transfer coefficient vs. nanowire length and Reynolds number

Influence of discharge on fish habitat suitability curves in mountain watercourses in IFIM methodology

Directory of Open Access Journals (Sweden)

Macura Viliam

2018-03-01

Full Text Available In this study, the quality of the aquatic habitats of mountain and piedmont streams was evaluated using the ‘Instream Flow Incremental Methodology (IFIM’ decision-making tool. The quality of habitats was interpreted from the behaviour of bioindicators in the form of habitat suitability curves (HSCs. From 1995 until the present, 59 different reaches of 43 mountain streams in Slovakia and 3 validation reaches were evaluated, and the results analysed. The aim of this study was to generalize the parameters of the HSCs for the brown trout. The generalized curves will be useful for water management planning. It is difficult and time-consuming to take hydrometrical and ichthyological measurements at different water levels. Therefore, we developed a methodology for modifying suitability curves based on an ichthyological survey during a low flow and a flow at which fish lose the ability to resist the flow velocity. The study provides the information how such curves can be modified for a wider flow range. In summary, this study shows that generalized HSCs provide representative data that can be used to support both the design of river restoration and the assessment of the impacts of the water use or of climate change on stream habitat quality.

A New Result Concerning the Solvability of a Class of General Systems of Variational Equations with Nonmonotone Operators: Applications to Dirichlet and Neumann Nonlinear Problems

Directory of Open Access Journals (Sweden)

Luisa Toscano

2016-01-01

Full Text Available A new result of solvability for a wide class of systems of variational equations depending on parameters and governed by nonmonotone operators is found in a Banach real and reflexive space with applications to Dirichlet and Neumann problems related to nonlinear elliptic systems.

Developing Novel Reservoir Rule Curves Using Seasonal Inflow Projections

Science.gov (United States)

Tseng, Hsin-yi; Tung, Ching-pin

2015-04-01

Due to significant seasonal rainfall variations, reservoirs and their flexible operational rules are indispensable to Taiwan. Furthermore, with the intensifying impacts of climate change on extreme climate, the frequency of droughts in Taiwan has been increasing in recent years. Drought is a creeping phenomenon, the slow onset character of drought makes it difficult to detect at an early stage, and causes delays on making the best decision of allocating water. For these reasons, novel reservoir rule curves using projected seasonal streamflow are proposed in this study, which can potentially reduce the adverse effects of drought. This study dedicated establishing new rule curves which consider both current available storage and anticipated monthly inflows with leading time of two months to reduce the risk of water shortage. The monthly inflows are projected based on the seasonal climate forecasts from Central Weather Bureau (CWB), which a weather generation model is used to produce daily weather data for the hydrological component of the GWLF. To incorporate future monthly inflow projections into rule curves, this study designs a decision flow index which is a linear combination of current available storage and inflow projections with leading time of 2 months. By optimizing linear relationship coefficients of decision flow index, the shape of rule curves and the percent of water supply in each zone, the best rule curves to decrease water shortage risk and impacts can be developed. The Shimen Reservoir in the northern Taiwan is used as a case study to demonstrate the proposed method. Existing rule curves (M5 curves) of Shimen Reservoir are compared with two cases of new rule curves, including hindcast simulations and historic seasonal forecasts. The results show new rule curves can decrease the total water shortage ratio, and in addition, it can also allocate shortage amount to preceding months to avoid extreme shortage events. Even though some uncertainties in

Discrete mKdV and discrete sine-Gordon flows on discrete space curves

International Nuclear Information System (INIS)

Inoguchi, Jun-ichi; Kajiwara, Kenji; Matsuura, Nozomu; Ohta, Yasuhiro

2014-01-01

In this paper, we consider the discrete deformation of the discrete space curves with constant torsion described by the discrete mKdV or the discrete sine-Gordon equations, and show that it is formulated as the torsion-preserving equidistant deformation on the osculating plane which satisfies the isoperimetric condition. The curve is reconstructed from the deformation data by using the Sym–Tafel formula. The isoperimetric equidistant deformation of the space curves does not preserve the torsion in general. However, it is possible to construct the torsion-preserving deformation by tuning the deformation parameters. Further, it is also possible to make an arbitrary choice of the deformation described by the discrete mKdV equation or by the discrete sine-Gordon equation at each step. We finally show that the discrete deformation of discrete space curves yields the discrete K-surfaces. (paper)

Computer quantification of “angle of collapse” on maximum expiratory flow volume curve for diagnosing asthma-COPD overlap syndrome

Directory of Open Access Journals (Sweden)

Wang W

2016-12-01

Full Text Available Wei Wang, Mengshuang Xie, Shuang Dou, Liwei Cui, Wei Xiao Department of Pulmonary Medicine, Qilu Hospital, Shandong University, Jinan, People’s Republic of China Background: In a previous study, we demonstrated that asthma patients with signs of emphysema on quantitative computed tomography (CT fulfill the diagnosis of asthma-COPD overlap syndrome (ACOS. However, quantitative CT measurements of emphysema are not routinely available for patients with chronic airway disease, which limits their application. Spirometry was a widely used examination tool in clinical settings and shows emphysema as a sharp angle in the maximum expiratory flow volume (MEFV curve, called the “angle of collapse (AC”. The aim of this study was to investigate the value of the AC in the diagnosis of emphysema and ACOS. Methods: This study included 716 participants: 151 asthma patients, 173 COPD patients, and 392 normal control subjects. All the participants underwent pulmonary function tests. COPD and asthma patients also underwent quantitative CT measurements of emphysema. The AC was measured using computer models based on Matlab software. The value of the AC in the diagnosis of emphysema and ACOS was evaluated using receiver-operating characteristic (ROC curve analysis. Results: The AC of COPD patients was significantly lower than that of asthma patients and control subjects. The AC was significantly negatively correlated with emphysema index (EI; r=-0.666, P<0.001, and patients with high EI had a lower AC than those with low EI. The ROC curve analysis showed that the AC had higher diagnostic efficiency for high EI (area under the curve =0.876 than did other spirometry parameters. In asthma patients, using the AC ≤137° as a surrogate criterion for the diagnosis of ACOS, the sensitivity and specificity were 62.5% and 89.1%, respectively. Conclusion: The AC on the MEFV curve quantified by computer models correlates with the extent of emphysema. The AC may become a

Computational Stud of Flow in Curved Pipes with Circular-Section

OpenAIRE

Shirayama, Susumu; Kawamura, Tetsuya; Kuwahara, Kunio; 白山, 晋; 河村, 哲也; 桑原, 邦郎

1985-01-01

By solving the incompressible Navier-Stokes equations the flow field is calculated in a circular-sectioned pipe with a straight inlet or gradually enlarged inlet in the higher Dean number. With the straight inlet, a secondary flow of cross-stream planes was obtained and with the higher Dean number some different flow patterns were obtained. With the gradually enlarged inlet, the difference of flow patterns corresponding to Reynolds number could be simulated.

The Cyclic Stress-Strain Curve of Polycrystals

DEFF Research Database (Denmark)

Pedersen, Ole Bøcker; Rasmussen, K. V.; Winter, A. T.

1982-01-01

The internal stresses implied by the Sachs model are estimated for individual PSBs at low plastic strain amplitudes and for homogeneously sheared grains at higher plastic strain amplitudes. The analysis shows that the Sachs model can account semi-quantitatively for experimentally measured cyclic...... stress-strain curves for copper. A similar approximative analysis of the Taylor model cannot account for the data. An interesting feature of the Sachs model is that, although it is assumed that the flow condition is entirely controlled by the PSBs. the predicted cyclic stress-strain curve displays...

Effect of Pulse Polarity on Thresholds and on Non-monotonic Loudness Growth in Cochlear Implant Users.

Science.gov (United States)

Macherey, Olivier; Carlyon, Robert P; Chatron, Jacques; Roman, Stéphane

2017-06-01

Most cochlear implants (CIs) activate their electrodes non-simultaneously in order to eliminate electrical field interactions. However, the membrane of auditory nerve fibers needs time to return to its resting state, causing the probability of firing to a pulse to be affected by previous pulses. Here, we provide new evidence on the effect of pulse polarity and current level on these interactions. In experiment 1, detection thresholds and most comfortable levels (MCLs) were measured in CI users for 100-Hz pulse trains consisting of two consecutive biphasic pulses of the same or of opposite polarity. All combinations of polarities were studied: anodic-cathodic-anodic-cathodic (ACAC), CACA, ACCA, and CAAC. Thresholds were lower when the adjacent phases of the two pulses had the same polarity (ACCA and CAAC) than when they were different (ACAC and CACA). Some subjects showed a lower threshold for ACCA than for CAAC while others showed the opposite trend demonstrating that polarity sensitivity at threshold is genuine and subject- or electrode-dependent. In contrast, anodic (CAAC) pulses always showed a lower MCL than cathodic (ACCA) pulses, confirming previous reports. In experiments 2 and 3, the subjects compared the loudness of several pulse trains differing in current level separately for ACCA and CAAC. For 40 % of the electrodes tested, loudness grew non-monotonically as a function of current level for ACCA but never for CAAC. This finding may relate to a conduction block of the action potentials along the fibers induced by a strong hyperpolarization of their central processes. Further analysis showed that the electrodes showing a lower threshold for ACCA than for CAAC were more likely to yield a non-monotonic loudness growth. It is proposed that polarity sensitivity at threshold reflects the local neural health and that anodic asymmetric pulses should preferably be used to convey sound information while avoiding abnormal loudness percepts.

Effect of gas temperature on flow rate characteristics of an averaging pitot tube type flow meter

Energy Technology Data Exchange (ETDEWEB)

Yeo, Seung Hwa; Lee, Su Ryong; Lee, Choong Hoon [Seoul National University of Science and Technology, Seoul (Korea, Republic of)

2015-01-15

The flow rate characteristics passing through an averaging Pitot tube (APT) while constantly controlling the flow temperature were studied through experiments and CFD simulations. At controlled temperatures of 25, 50, 75, and 100 .deg .C, the flow characteristics, in this case the upstream, downstream and static pressure at the APT flow meter probe, were measured as the flow rate was increased. The flow rate through the APT flow meter was represented using the H-parameter (hydraulic height) obtained by a combination of the differential pressure and the air density measured at the APT flow meter probe. Four types of H-parameters were defined depending on the specific combination. The flow rate and the upstream, downstream and static pressures measured at the APT flow meter while changing the H-parameters were simulated by means of CFD. The flow rate curves showed different features depending on which type of H-parameter was used. When using the constant air density value in a standard state to calculate the H-parameters, the flow rate increased linearly with the H-parameter and the slope of the flow rate curve according to the H-parameter increased as the controlled target air temperature was increased. When using different air density levels corresponding to each target air temperature to calculate the H-parameter, the slope of the flow rate curve according to the H-parameter was constant and the flow rate curve could be represented by a single line. The CFD simulation results were in good agreement with the experimental results. The CFD simulations were performed while increasing the air temperature to 1200 K. The CFD simulation results for high air temperatures were similar to those at the low temperature ranging from 25 to 100 .deg. C.

Effect of gas temperature on flow rate characteristics of an averaging pitot tube type flow meter

International Nuclear Information System (INIS)

Yeo, Seung Hwa; Lee, Su Ryong; Lee, Choong Hoon

2015-01-01

The flow rate characteristics passing through an averaging Pitot tube (APT) while constantly controlling the flow temperature were studied through experiments and CFD simulations. At controlled temperatures of 25, 50, 75, and 100 .deg .C, the flow characteristics, in this case the upstream, downstream and static pressure at the APT flow meter probe, were measured as the flow rate was increased. The flow rate through the APT flow meter was represented using the H-parameter (hydraulic height) obtained by a combination of the differential pressure and the air density measured at the APT flow meter probe. Four types of H-parameters were defined depending on the specific combination. The flow rate and the upstream, downstream and static pressures measured at the APT flow meter while changing the H-parameters were simulated by means of CFD. The flow rate curves showed different features depending on which type of H-parameter was used. When using the constant air density value in a standard state to calculate the H-parameters, the flow rate increased linearly with the H-parameter and the slope of the flow rate curve according to the H-parameter increased as the controlled target air temperature was increased. When using different air density levels corresponding to each target air temperature to calculate the H-parameter, the slope of the flow rate curve according to the H-parameter was constant and the flow rate curve could be represented by a single line. The CFD simulation results were in good agreement with the experimental results. The CFD simulations were performed while increasing the air temperature to 1200 K. The CFD simulation results for high air temperatures were similar to those at the low temperature ranging from 25 to 100 .deg. C.

Guest Controlled Nonmonotonic Deep Cavity Cavitand Assembly State Switching.

Science.gov (United States)

Tang, Du; Barnett, J Wesley; Gibb, Bruce C; Ashbaugh, Henry S

2017-11-30

Octa-acid (OA) and tetra-endo-methyl octa-acid (TEMOA) are water-soluble, deep-cavity cavitands with nanometer-sized nonpolar pockets that readily bind complementary guests, such as n-alkanes. Experimentally, OA exhibits a progression of 1:1 to 2:2 to 2:1 host/guest complexes (X:Y where X is the number of hosts and Y is the number of guests) with increasing alkane chain length from methane to tetradecane. Differing from OA only by the addition of four methyl groups ringing the portal of the pocket, TEMOA exhibits a nonmonotonic progression of assembly states from 1:1 to 2:2 to 1:1 to 2:1 with increasing guest length. Here we present a systematic molecular simulation study to parse the molecular and thermodynamic determinants that distinguish the succession of assembly stoichiometries observed for these similar hosts. Potentials of mean force between hosts and guests, determined via umbrella sampling, are used to characterize association free energies. These free energies are subsequently used in a reaction network model to predict the equilibrium distributions of assemblies. Our models accurately reproduce the experimentally observed trends, showing that TEMOA's endo-methyl units constrict the opening of the binding pocket, limiting the conformations available to bound guests and disrupting the balance between monomeric complexes and dimeric capsules. The success of our simulations demonstrate their utility at interpreting the impact of even simple chemical modifications on supramolecular assembly and highlight their potential to aid bottom-up design.

Aspherical Supernovae: Effects on Early Light Curves

Science.gov (United States)

Afsariardchi, Niloufar; Matzner, Christopher D.

2018-04-01

Early light from core-collapse supernovae, now detectable in high-cadence surveys, holds clues to a star and its environment just before it explodes. However, effects that alter the early light have not been fully explored. We highlight the possibility of nonradial flows at the time of shock breakout. These develop in sufficiently nonspherical explosions if the progenitor is not too diffuse. When they do develop, nonradial flows limit ejecta speeds and cause ejecta–ejecta collisions. We explore these phenomena and their observational implications using global, axisymmetric, nonrelativistic FLASH simulations of simplified polytropic progenitors, which we scale to representative stars. We develop a method to track photon production within the ejecta, enabling us to estimate band-dependent light curves from adiabatic simulations. Immediate breakout emission becomes hidden as an oblique flow develops. Nonspherical effects lead the shock-heated ejecta to release a more constant luminosity at a higher, evolving color temperature at early times, effectively mixing breakout light with the early light curve. Collisions between nonradial ejecta thermalize a small fraction of the explosion energy; we will address emission from these collisions in a subsequent paper.

Rating curve estimation using Envisat virtual stations on the main Orinoco river

Directory of Open Access Journals (Sweden)

Juan León

2011-09-01

Full Text Available Rating curve estimation (height-stream relation made by hydrometric stations representing cross-sections of a river is one of hydrometrics’ fundamental tasks due to the fact that it leads to deducing a river’s average daily flow on that particular section. This information is fundamental in any attempt at hydrological modelling. However, the number of hydrological control stations monitoring large hydrological basins has been reduced worldwide. Space hydrology studies during the last five years have shown that satellite radar altimetry means that hydrological monitoring networks’ available information can be densified due to the introduction of so-called virtual stations and the joint use of such information along with in-situ measured flow records for estimating expenditure curves at these stations. This study presents the rating curves for 4 Envisat virtual stations located on the main stream of the Orinoco River. Virtual stations’ flows were estimated by using the Muskingum- Cunge 1D model. There was less than 1% error between measured and estimated flows. The methodology led to reducing average zero flow depth; in this case, it led to depths ranging from 11 to 20 meters being found along the 130 km of the Orinoco River represented by the virtual stations being considered.

Peristaltic flow of Powell-Eyring fluid in curved channel with heat transfer: A useful application in biomedicine.

Science.gov (United States)

Hina, S; Mustafa, M; Hayat, T; Alsaedi, A

2016-10-01

In this work, we explore the heat transfer characteristics in the peristaltic transport of Powell-Eyring fluid inside a curved channel with complaint walls. The study has motivation toward the understanding of blood flow in microcirculatory system. Formulation is developed in the existence of velocity slip and temperature jump conditions. Perturbation approach has been utilized to present series expressions of axial velocity and temperature distributions. Streamlines are prepared to analyze the interesting phenomenon of trapping. Moreover, the plots of heat transfer coefficient for a broad range of embedded parameters are presented and discussed. The results indicate that slip effects substantially influence the velocity and temperature distributions. Axial flow accelerates when slip parameter is incremented. Temperature rises and wall heat flux grows when viscous dissipation effect is strengthened. In contrast to the planar channels, here velocity and temperature functions do not exhibit symmetry with respect to the central line. In addition, bolus size and its shape are different in upper and lower portions of the channel. Heat transfer coefficient enlarges when the curvature effects are reduced. The behaviors of wall tension and wall mass parameters on the profiles are qualitatively similar. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Stair-Step Particle Flux Spectra on the Lunar Surface: Evidence for Nonmonotonic Potentials?

Science.gov (United States)

Collier, Michael R.; Newheart, Anastasia; Poppe, Andrew R.; Hills, H. Kent; Farrell, William M.

2016-01-01

We present examples of unusual "stair-step" differential flux spectra observed by the Apollo 14 Suprathermal Ion Detector Experiment on the lunar dayside surface in Earth's magnetotail. These spectra exhibit a relatively constant differential flux below some cutoff energy and then drop off precipitously, by about an order of magnitude or more, at higher energies. We propose that these spectra result from photoions accelerated on the lunar dayside by nonmonotonic potentials (i.e.,potentials that do not decay to zero monotonically) and present a model for the expected differential flux. The energy of the cutoff and the magnitude of the differential flux are related to the properties of the local space environment and are consistent with the observed flux spectra. If this interpretation is correct, these surface-based ion observations provide a unique perspective that both complements and enhances the conclusions obtained by remote-sensing orbiter observations on the Moon's exospheric and electrostatic properties.

Removing the impact of water abstractions on flow duration curves

Science.gov (United States)

Masoero, Alessandro; Ganora, Daniele; Galeati, Giorgio; Laio, Francesco; Claps, Pierluigi

2015-04-01

on few easy-access parameters, of correction of the water abstraction impact. The model, based on an exponential form of the river Flow Duration Curve (FDC), allows completely analytical solutions. Hence the method can be applied extensively. This is particularly relevant when working on a general outlook on water resources (regional or basin scale), given the high number of water abstractions that should be considered. The correction method developed is based on only two hard data that can be easily found: i) the design maximum discharge of the water intake and ii) the days of exercise, between a year. Following the same correction hypothesis also the abstracted discharge statistics have been reconstructed analytically and combined with the statistics of the receiving reach, that can be different from the original one. This information can be useful when we are assessing water availability in a river network interconnected by derivation channels. The goodness of the correction method proposed is proven by the application to a case study in North-West Italy, along a second order tributary of the Po River. Flow values recorded at the river gauge station were affected, significantly, by the presence of a 5 MW hydropower plant. Knowing the amount of water abstracted daily by the power plant we are able to reconstruct, empirically, the natural discharge on the river and compare its main statistics with the ones computed analytically using the proposed correction model. An extremely low difference between empirical and analytical reconstructed mean discharge and L-moment of variation was founded. Also, the importance of the day of exercise information was highlighted. The correction proposed in this work is able to give a correct indication of the non-impacted natural streamflows characteristics, especially in alpine regions where water abstraction impact is a main issue.

Classifying low flow hydrological regimes at a regional scale

Science.gov (United States)

Kirkby, M. J.; Gallart, F.; Kjeldsen, T. R.; Irvine, B. J.; Froebrich, J.; Lo Porto, A.; de Girolamo, A.; Mirage Team

2011-12-01

The paper uses a simple water balance model that partitions the precipitation between actual evapotranspiration, quick flow and delayed flow, and has sufficient complexity to capture the essence of climate and vegetation controls on this partitioning. Using this model, monthly flow duration curves have been constructed from climate data across Europe to address the relative frequency of ecologically critical low flow stages in semi-arid rivers, when flow commonly persists only in disconnected pools in the river bed. The hydrological model is based on a dynamic partitioning of precipitation to estimate water available for evapotranspiration and plant growth and for residual runoff. The duration curve for monthly flows has then been analysed to give an estimate of bankfull flow based on recurrence interval. Arguing from observed ratios of cross-sectional areas at flood and low flows, hydraulic geometry suggests that disconnected flow under "pool" conditions is approximately 0.1% of bankfull flow. Flow duration curves define a measure of bankfull discharge on the basis of frequency. The corresponding frequency for pools is then read from the duration curve, using this (0.1%) ratio to estimate pool discharge from bank full discharge. The flow duration curve then provides an estimate of the frequency of poorly connected pool conditions, corresponding to this discharge, that constrain survival of river-dwelling arthropods and fish. The methodology has here been applied across Europe at 15 km resolution, and the potential is demonstrated for applying the methodology under alternative climatic scenarios.

Computer registration of radioactive indicator-dilution curves.

Science.gov (United States)

Shepherd, A P; Perry, M A; Alexander, G M; Granger, D N; Riedel, G L; Kvietys, P R; Franke, C P

1983-12-01

A system is described for recording indicator-dilution curves produced by gamma radiation-emitting tracers. The system consists of a flow-through cuvette in a well counter, appropriate commercially available gamma radiation-detecting equipment, an Apple II computer, and a two-channel pulse-counting interface of our own design. With the counting interface and the software described here, an investigator can simultaneously record two indicator-dilution curves produced by gamma emitters. Instead of having to wait hours or days for results, the investigator can watch the data being recorded and display the results in graphic form almost immediately after each injection.

Rheology of dense granular flows in two dimensions: Comparison of fully two-dimensional flows to unidirectional shear flow

Science.gov (United States)

Bhateja, Ashish; Khakhar, Devang V.

2018-06-01

We consider the rheology of steady two-dimensional granular flows, in different geometries, using discrete element method-based simulations of soft spheres. The flow classification parameter (ψ ), which defines the local flow type (ranging from pure rotation to simple shear to pure extension), varies spatially, to a significant extent, in the flows. We find that the material behaves as a generalized Newtonian fluid. The μ -I scaling proposed by Jop et al. [Nature (London) 441, 727 (2006), 10.1038/nature04801] is found to be valid in both two-dimensional and unidirectional flows, as observed in previous studies; however, the data for each flow geometry fall on a different curve. The results for the two-dimensional silo flow indicate that the viscosity does not depend directly on the flow type parameter, ψ . We find that the scaling based on "granular fluidity" [Zhang and Kamrin, Phys. Rev. Lett. 118, 058001 (2017), 10.1103/PhysRevLett.118.058001] gives good collapse of the data to a single curve for all the geometries. The data for the variation of the solid faction with inertial number show a reasonable collapse for the different geometries.

Geomorphic versus land use controls on suspended sediment rating curves

Science.gov (United States)

Belmont, P.; Vaughan, A. A.; Fisher, A. C. N.

2017-12-01

The relation between river discharge (Q) and suspended sediment (SS) concentration reflects the degree to which sediment sources are accessed or depleted across the range of flow conditions. Increased availability of high resolution topography and land use data greatly enhance our ability to evaluate linkages between characteristics of these sediment rating curves (SRCs) and the geomorphic features that influence them. We evaluated Q-SS relations at 45 gages throughout Minnesota, USA representing a wide variety of landscape settings in terms of topography, land use, and geologic history. We characterized the SRCs according to the overall shape, steepness (exponent), vertical offset (coefficient) and SS concentration under low flow (90% exceedance) conditions. Rivers exhibited three distinct SRC shapes, simple power functions, threshold power functions and peaked power functions. We used random forest models to analyze relations between SRC parameters and attributes of the watershed as well as the near-channel environment. The model correctly classified 78% of SRC shapes and explained 60% of variance in the SRC exponent, 43% of the SRC coefficient for rising limb samples, and 45% of variance under low flow conditions. Notably, the random forest models predict that near-channel morphology predominately controls both the shape and steepness of the sediment rating curves. Land use predominately controls the vertical offset (coefficient) and SS concentration under low flow conditions. These findings suggest that land use and watershed restoration practices may have little capacity to alter the shape and steepness of these curves as these characteristics may be dictated by the geologic and geomorphic setting. Rather, human influences in the watershed may exhibit the greatest influence on suspended sediment concentrations at moderate to low flows. Criteria to evaluate improvements in water quality as a result of changes in land management might be most meaningful if they

Stage discharge curve for Guillemard Bridge streamflow sation based on rating curve method using historical flood event data

International Nuclear Information System (INIS)

Ros, F C; Sidek, L M; Desa, M N; Arifin, K; Tosaka, H

2013-01-01

The purpose of the stage-discharge curves varies from water quality study, flood modelling study, can be used to project climate change scenarios and so on. As the bed of the river often changes due to the annual monsoon seasons that sometimes cause by massive floods, the capacity of the river will changed causing shifting controlled to happen. This study proposes to use the historical flood event data from 1960 to 2009 in calculating the stage-discharge curve of Guillemard Bridge located in Sg. Kelantan. Regression analysis was done to check the quality of the data and examine the correlation between the two variables, Q and H. The mean values of the two variables then were adopted to find the value of difference between zero gauge height and the level of zero flow, 'a', K and 'n' to fit into rating curve equation and finally plotting the stage-discharge rating curve. Regression analysis of the historical flood data indicate that 91 percent of the original uncertainty has been explained by the analysis with the standard error of 0.085.

Surface representations of two- and three-dimensional fluid flow topology

Science.gov (United States)

Helman, James L.; Hesselink, Lambertus

1990-01-01

We discuss our work using critical point analysis to generate representations of the vector field topology of numerical flow data sets. Critical points are located and characterized in a two-dimensional domain, which may be either a two-dimensional flow field or the tangential velocity field near a three-dimensional body. Tangent curves are then integrated out along the principal directions of certain classes of critical points. The points and curves are linked to form a skeleton representing the two-dimensional vector field topology. When generated from the tangential velocity field near a body in a three-dimensional flow, the skeleton includes the critical points and curves which provide a basis for analyzing the three-dimensional structure of the flow separation. The points along the separation curves in the skeleton are used to start tangent curve integrations to generate surfaces representing the topology of the associated flow separations.

A stable route to high-{beta}{sub p} plasmas with non-monotonic q-profiles

Energy Technology Data Exchange (ETDEWEB)

Soeldner, F X; Baranov, Y; Bhatnagar, V P; Bickley, A J; Challis, C D; Fischer, B; Gormezano, C; Huysmans, G T.A.; Kerner, W; Rimini, F; Sips, A C.C.; Springmann, R; Taroni, A [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Goedbloed, J P; Holties, H A [Institute for Plasmas Physics, Nieuwegein (Netherlands); Parail, V V; Pereverzev, G V [Kurchatov Institute of Atomic Energy, Moscow (Russian Federation)

1994-07-01

Steady-state operation of tokamak reactors seems feasible in so-called Advanced Scenarios with high bootstrap current in high-beta{sub p} operation. The stabilization of such discharges with noninductive profile control will be attempted on JET in pursuit of previous high bootstrap current studies. Results of modelling studies of full noninductive current drive scenarios in JET and ITER are presented. Fast Waves (FW), Lower Hybrid (LH) Waves and Neutral Beam Injection (NBI) are used for heating and current drive, alternatively or in combination. A stable route to nonmonotonic q-profiles has been found with a specific ramp-up scenario which combines LH-current drive (LHCD) and a fast Ohmic ramp-up. A hollow current profile with deep shear reversal over the whole central region is thereby formed in an early low-beta phase and frozen in by additional heating. (authors). 5 refs., 4 figs.

Effective behavior of a free fluid in contact with a flow in a curved porous medium

DEFF Research Database (Denmark)

Dobberschütz, Sören

2015-01-01

The appropriate boundary condition between an unconfined incompressible viscous fluid and a porous medium is given by the law of Beavers and Joseph. The latter has been justified both experimentally and mathematically, using the method of periodic homogenization. However, all results so far deal...... only with the case of a planar boundary. In this work, we consider the case of a curved, macroscopically periodic boundary. By using a coordinate transformation, we obtain a description of the flow in a domain with a planar boundary, for which we derive the effective behavior: The effective velocity...... is continuous in normal direction. Tangential to the interface, a slip occurs. Additionally, a pressure jump occurs. The magnitude of the slip velocity as well as the jump in pressure can be determined with the help of a generalized boundary layer function. The results indicate the validity of a generalized...

Analytical extension of curved shock theory

Science.gov (United States)

Emanuel, G.

2018-03-01

Curved shock theory (CST) is limited to shock waves in a steady, two-dimensional or axisymmetric (2-Ax) flow of a perfect gas. A unique feature of CST is its use of intrinsic coordinates that result in an elegant and useful formulation for flow properties just downstream of a shock. For instance, the downstream effect of upstream vorticity, shock wave curvature, and the upstream pressure gradient along a streamline is established. There have been several attempts to extend CST, as mentioned in the text. Removal of the steady, 2-Ax, and perfect gas limitations, singly or in combination, requires an appropriate formulation of the shock wave's jump relations and the intrinsic coordinate Euler equations. Issues discussed include flow plane versus osculating plane, unsteady flow, vorticity, an imperfect gas, etc. The extension of CST utilizes concepts from differential geometry, such as the osculating plane, streamline torsion, and the Serret-Frenet equations.

Investigation on de-trapping mechanisms related to non-monotonic kink pattern in GaN HEMT devices

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Chandan Sharma

2017-08-01

Full Text Available This article reports an experimental approach to analyze the kink effect phenomenon which is usually observed during the GaN high electron mobility transistor (HEMT operation. De-trapping of charge carriers is one of the prominent reasons behind the kink effect. The commonly observed non-monotonic behavior of kink pattern is analyzed under two different device operating conditions and it is found that two different de-trapping mechanisms are responsible for a particular kink behavior. These different de-trapping mechanisms are investigated through a time delay analysis which shows the presence of traps with different time constants. Further voltage sweep and temperature analysis corroborates the finding that different de-trapping mechanisms play a role in kink behavior under different device operating conditions.

Investigation on de-trapping mechanisms related to non-monotonic kink pattern in GaN HEMT devices

Science.gov (United States)

Sharma, Chandan; Laishram, Robert; Amit, Rawal, Dipendra Singh; Vinayak, Seema; Singh, Rajendra

2017-08-01

This article reports an experimental approach to analyze the kink effect phenomenon which is usually observed during the GaN high electron mobility transistor (HEMT) operation. De-trapping of charge carriers is one of the prominent reasons behind the kink effect. The commonly observed non-monotonic behavior of kink pattern is analyzed under two different device operating conditions and it is found that two different de-trapping mechanisms are responsible for a particular kink behavior. These different de-trapping mechanisms are investigated through a time delay analysis which shows the presence of traps with different time constants. Further voltage sweep and temperature analysis corroborates the finding that different de-trapping mechanisms play a role in kink behavior under different device operating conditions.

Classifying low flow hydrological regimes at a regional scale

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M. J. Kirkby

2011-12-01

Full Text Available The paper uses a simple water balance model that partitions the precipitation between actual evapotranspiration, quick flow and delayed flow, and has sufficient complexity to capture the essence of climate and vegetation controls on this partitioning. Using this model, monthly flow duration curves have been constructed from climate data across Europe to address the relative frequency of ecologically critical low flow stages in semi-arid rivers, when flow commonly persists only in disconnected pools in the river bed. The hydrological model is based on a dynamic partitioning of precipitation to estimate water available for evapotranspiration and plant growth and for residual runoff. The duration curve for monthly flows has then been analysed to give an estimate of bankfull flow based on recurrence interval. Arguing from observed ratios of cross-sectional areas at flood and low flows, hydraulic geometry suggests that disconnected flow under "pool" conditions is approximately 0.1% of bankfull flow. Flow duration curves define a measure of bankfull discharge on the basis of frequency. The corresponding frequency for pools is then read from the duration curve, using this (0.1% ratio to estimate pool discharge from bank full discharge. The flow duration curve then provides an estimate of the frequency of poorly connected pool conditions, corresponding to this discharge, that constrain survival of river-dwelling arthropods and fish. The methodology has here been applied across Europe at 15 km resolution, and the potential is demonstrated for applying the methodology under alternative climatic scenarios.

Ferromagnetism in the Hubbard-Hirsch model

International Nuclear Information System (INIS)

Ivanov, V.A.; Zhuravlev, M.E.

1991-01-01

In the Hubbard model U=∞ the energy lowering due to exchange interaction of electrons of opposite spin in states with opposite bonding character is taken into account. In the electron concentration range 0< n<1 nonmonotonous dependence m(n) analogous to Slater-Pauling curves has been obtained. The Curle temperature having nonmonotonous dependence on n, saturated magnetization, the temperature dependences of magnetization have been obtained. (orig.)

Non-monotonic reorganization of brain networks with Alzheimer’s disease progression

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Hyoungkyu eKim

2015-06-01

Full Text Available Background: Identification of stage-specific changes in brain network of patients with Alzheimer’s disease (AD is critical for rationally designed therapeutics that delays the progression of the disease. However, pathological neural processes and their resulting changes in brain network topology with disease progression are not clearly known. Methods: The current study was designed to investigate the alterations in network topology of resting state fMRI among patients in three different clinical dementia rating (CDR groups (i.e., CDR = 0.5, 1, 2 and amnestic mild cognitive impairment (aMCI and age-matched healthy subject groups. We constructed cost networks from these 5 groups and analyzed their network properties using graph theoretical measures.Results: The topological properties of AD brain networks differed in a non-monotonic, stage-specific manner. Interestingly, local and global efficiency and betweenness of the network were rather higher in the aMCI and AD (CDR 1 groups than those of prior stage groups. The number, location, and structure of rich-clubs changed dynamically as the disease progressed.Conclusions: The alterations in network topology of the brain are quite dynamic with AD progression, and these dynamic changes in network patterns should be considered meticulously for efficient therapeutic interventions of AD.

The Hardy inequality and the heat flow in curved wedges

Czech Academy of Sciences Publication Activity Database

Krejčiřík, David

2016-01-01

Roč. 73, č. 2 (2016), s. 91-113 ISSN 0032-5155 R&D Projects: GA ČR(CZ) GA14-06818S Institutional support: RVO:61389005 Keywords : Hardy inequality * heat equation * large-time behaviour * curved wedges * Dirichlet Laplacian * conical singularities * Brownian motion * subcriticality Subject RIV: BE - Theoretical Physics Impact factor: 0.735, year: 2016

On the modelling of turbulent flows under strong buoyancy effects in cavities with curved boundaries; French title please

Energy Technology Data Exchange (ETDEWEB)

Viollet, P L; Goussebaile, J [E.D.F, Laboratoire National d' Hydraulique, Chatou (France)

1983-07-01

Finite-difference methods have been developed for the two-dimensional computation of non-isothermal unsteady flows inside cavities with curved boundaries. The algorithm uses either u, v, P or u, v, {psi} formulations, and arbitrary non orthogonal curvilinear grids may be used. The turbulence modelling is tested for the case of a stratified two-layer flow with shear and the k-{epsilon} eddy viscosity and algebraic-stress models are compared. An example of unsteady density currents in a U-shaped pipe is given with comparison of experimental results. (author) [French] Cette note decrit succinctement les methodes de differences finies qui ont ete developpees pour le calcul bidimensionnel d'ecoulements non isothermes dans les cavites presentant des frontieres courbes. L'algorithme utilise les variables u, v, P ou u, v, {psi} et des maillages curvilignes non orthogonaux quelconques peuvent etre utiliss. La simulation de turbulence a deux equations est testee pour le cas d'un ecoulement horizontal stratifie: le modele k-{epsilon} standard est compare au modele avec expressions algebriques des flux turbulents. Enfin, un exemple de courants de densite instationnaires dans une tuyauterie en forme de U, pour lequel des resultats experimentaux sont disponibles, est presente. (author)

Uncertainty estimation with bias-correction for flow series based on rating curve

Science.gov (United States)

Shao, Quanxi; Lerat, Julien; Podger, Geoff; Dutta, Dushmanta

2014-03-01

Streamflow discharge constitutes one of the fundamental data required to perform water balance studies and develop hydrological models. A rating curve, designed based on a series of concurrent stage and discharge measurements at a gauging location, provides a way to generate complete discharge time series with a reasonable quality if sufficient measurement points are available. However, the associated uncertainty is frequently not available even though it has a significant impact on hydrological modelling. In this paper, we identify the discrepancy of the hydrographers' rating curves used to derive the historical discharge data series and proposed a modification by bias correction which is also in the form of power function as the traditional rating curve. In order to obtain the uncertainty estimation, we propose a further both-side Box-Cox transformation to stabilize the regression residuals as close to the normal distribution as possible, so that a proper uncertainty can be attached for the whole discharge series in the ensemble generation. We demonstrate the proposed method by applying it to the gauging stations in the Flinders and Gilbert rivers in north-west Queensland, Australia.

Influence of fluid structure upon the shape of RTD curve at a sugar crystallizer

International Nuclear Information System (INIS)

Griffith, J.; Borroto, J.I.; Leclerc, J.P.

2004-01-01

The influence of fluid structure over the shape of the RTD curve at a pilot sugar crystallizer has been tested by the radiotracer method. For Newtonian pure molasses B sugar fluid the pattern flux was close to a perfect mixing cells with backmixing model with a back flow-rate ratio lower than one. In the case of molasses B transformed to a non-Newtonian fluid the pattern flux approaches the same model but with extreme values of the back flow-rate ration (higher than one). A direct relationship was founded between the back flow rate ratio and the flow index of the tested fluids, showing that a special attention has to be pay during data processing of the RTD curves for non-Newtonian fluids. (author)

Non-monotonic dose dependence of the Ge- and Ti-centres in quartz

International Nuclear Information System (INIS)

Woda, C.; Wagner, G.A.

2007-01-01

The dose response of the Ge- and Ti-centres in quartz is studied over a large dose range. After an initial signal increase in the low dose range, both defects show a pronounced decrease in signal intensities for high doses. The model by Euler and Kahan [1987. Radiation effects and anelastic loss in germanium-doped quartz. Phys. Rev. B 35 (9), 4351-4359], in which the signal drop is explained by an enhanced trapping of holes at the electron trapping site, is critically discussed. A generalization of the model is then developed, following similar considerations by Lawless et al. [2005. A model for non-monotonic dose dependence of thermoluminescence (TL). J. Phys. Condens. Matter 17, 737-753], who explained a signal drop in TL by an enhanced recombination rate with electrons at the recombination centre. Finally, an alternative model for the signal decay is given, based on the competition between single and double electron capture at the electron trapping site. From the critical discussion of the different models it is concluded that the double electron capture mechanism is the most probable effect for the dose response

Lagrangian Curves on Spectral Curves of Monopoles

International Nuclear Information System (INIS)

Guilfoyle, Brendan; Khalid, Madeeha; Ramon Mari, Jose J.

2010-01-01

We study Lagrangian points on smooth holomorphic curves in TP 1 equipped with a natural neutral Kaehler structure, and prove that they must form real curves. By virtue of the identification of TP 1 with the space LE 3 of oriented affine lines in Euclidean 3-space, these Lagrangian curves give rise to ruled surfaces in E 3 , which we prove have zero Gauss curvature. Each ruled surface is shown to be the tangent lines to a curve in E 3 , called the edge of regression of the ruled surface. We give an alternative characterization of these curves as the points in E 3 where the number of oriented lines in the complex curve Σ that pass through the point is less than the degree of Σ. We then apply these results to the spectral curves of certain monopoles and construct the ruled surfaces and edges of regression generated by the Lagrangian curves.

Effect of Non Submerged Vanes on Separation Zone at Strongly-curved Channel Bends, a Laboratory Scale Study

Directory of Open Access Journals (Sweden)

Ali Akbar Akhtari

2010-03-01

Full Text Available Bends along open channels always pose difficulties for water transfer systems. One undesirable effect of bends in such channels, i.e. separation of water from inner banks, was studied. For the purposes of this study, the literature on the subject was first reviewed, and a strongly-curved open channel was designed and constructed on the laboratory scale. Several tests were performed to evaluate the accuracy of the lab model, data homogeneity, and systematic errors. The model was then calibrated and the influence of curvature on flow pattern past the curve was investigated. Also, for the first time, the influence of separation walls on flow pattern was investigated. Experimental results on three strongly-curved open channels with a curvature radius to channel width ratio of 1.5 and curvature angles of 30°, 60°, and 90° showed that, in all the cases studied, the effect of flow separation could be observed immediately after the curve. In addition, the greatest effect of flow separation was seen at a distance equal to channel width from the bend end. In the presence of middle walls and flow separation, the effect of water separation reduced at the bend, especially for a curvature of 90°.

Opposed-flow Flame Spread Over Solid Fuels in Microgravity: the Effect of Confined Spaces

Science.gov (United States)

Wang, Shuangfeng; Hu, Jun; Xiao, Yuan; Ren, Tan; Zhu, Feng

2015-09-01

Effects of confined spaces on flame spread over thin solid fuels in a low-speed opposing flow is investigated by combined use of microgravity experiments and computations. The flame behaviors are observed to depend strongly on the height of the flow tunnel. In particular, a non-monotonic trend of flame spread rate versus tunnel height is found, with the fastest flame occurring in the 3 cm high tunnel. The flame length and the total heat release rate from the flame also change with tunnel height, and a faster flame has a larger length and a higher heat release rate. The computation analyses indicate that a confined space modifies the flow around the spreading flame. The confinement restricts the thermal expansion and accelerates the flow in the streamwise direction. Above the flame, the flow deflects back from the tunnel wall. This inward flow pushes the flame towards the fuel surface, and increases oxygen transport into the flame. Such a flow modification explains the variations of flame spread rate and flame length with tunnel height. The present results suggest that the confinement effects on flame behavior in microgravity should be accounted to assess accurately the spacecraft fire hazard.

Analysis on the time/activity curve of salivary gland scintigraphy in salivary gland diseases; The correlation between the pattern of time/activity curve and the amount of saliva

Energy Technology Data Exchange (ETDEWEB)

Suzuki, Kazufumi; Hosokawa, Yoichiro; Kaneko, Masanori; Ohmori, Keiichi; Minowa, Kazuyuki; Fukuda, Hiroshi; Yamasaki, Michio (Hokkaido Univ., Sapporo (Japan). School of Dentistry)

1992-04-01

Salivary gland scintigraphy with {sup 99m}TcO{sub 4}{sup -} is a simple method to evaluate salivary gland function and has been available as a technique using a time/activity curve for a number of years. But, there were few reports on the relationship between the various patterns of the time/activity curves and the salivary flow rate from the gland. This presents correlation between the time/activity curve pattern and the salivary flow rate from the parotid gland. Sixty-five patients complaining of xerostomia were examined. Sixty-two were female and 3 male (average age 45.6 years, range 17-69 years). Their diagnosis were 26 Sjoegren Syndrome, 28 suspicion of Sjoegren Syndrome and 11 parotiditis. The salivary flow rate from parotid gland was measured by stimulation with 10% citric acid using modified Carlson crittenden cup every 10 seconds for 5 min. 185 MBq {sup 99m}TcO{sub 4}{sup -} was injected intravenously and sequential scintigraphy was performed. Time/activity curves were recorded on film. Six kinds of basic patterns were as follows: normal pattern, median pattern, flat pattern and sloped pattern (Mita et al 1981), reaccumulation flat pattern and poor secretion (Stimulant secretory ratio: less than 70%) pattern by us. The amount of saliva was as follows: normal pattern (n=31), 5.4+0.4 ml; reaccumulation flat pattern (n=3), 4.2+0.6 ml; poor secretion pattern (n=18), 4.1+0.5 ml; median pattern (n=20), 3.5+0.5 ml; flat pattern (n=11), 2.6+0.5 ml and sloped pattern (n=1), 1.5 ml. Normal pattern versus poor secretion pattern, median pattern and flat pattern in the salivary flow rate were statistically significant as determined by Students' t-test. We assessed the correlation between the pattern of time/activity curve in the salivary gland scintigraphy and the amount of saliva. (author).

Determination of regional cerebral blood flow curves and parameters by computed γ camera

International Nuclear Information System (INIS)

Zhu Guohong

1988-01-01

Regional CBF curves and parameters were determined in 236 subjects by Sigma 438/MCS 560 computed γ camera. Each subject was given 99m TcO 4 -370 MBq intravenously. Four CBF curves and three parameters were derived by the computer.The results from 39 normal subjects, 22 patients with cerebral embolism, 53 patients with cerebrovascular sclerosis, 56 patients with diseases of cervical vertebrae, 10 patients with concussion and 5 patients with cerebral arteritis were analyzed

MOE-Analysis for Oversaturated Flow with Interrupted Facility and Heterogeneous Traffic for Urban Roads

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Hemant Kumar Sharma

2012-09-01

Full Text Available Speed-flow functions have been developed by several transportation experts to predict accurately the speed of urban road networks. HCM Speed-Flow Curve, BPR Curve, MTC Speed-Flow Curve, Akçelik Speed-Flow Curve are some extraordinary efforts to define the shape of speed-flow curves. However, the complexity of driver's behaviour, interactions among different type of vehicles, lateral clearance, co-relation of driver's psychology with vehicular characteristics and interdependence of various variables of traffic has led to continuous development and refinement of speed-flow curves. The problem gets more difficult in the case of urban roads with heterogeneous traffic, oversaturated flow and signalized network (which includes some unsignalized intersections as well. This paper presents analysis for various measures of effectiveness (MOE for urban roads with interrupted flow comprising heterogeneous traffic. Model has been developed for heterogeneous traffic under constraints of roadway geometry, vehicle characteristics, driving behaviour and traffic controls. The model developed in this paper predicts speed, delay, average queue and maximum queue estimates for urban roads and quantifies congestion for oversaturated conditions. The investigation details the oversaturated portion of flow in particular.

Milk emission curves in different parities in Italian Brown Swiss cattle

Directory of Open Access Journals (Sweden)

D. Vigo

2011-03-01

Full Text Available In modern dairy farm practice functional traits hold an increasing importance (Groen, 1997 and many population selection programs include traits related with milkability (Soelkner, 2002. Milkability affect farmer’s net profit (Sivarajasingam et al., 1984 and is one of the functional traits that affect involuntary culling (Frerking, 1999. Usually milkability is measured as milking speed, either recorded as slow, average, or fast, or as time in seconds from the seating of the teat cups until their removal. Since 1992, in the Italian Brown population, milking performance is recorded with electronic flowmeters and genetic evaluations of individuals are available for average milk flow. The flowmeter technology allows to collect information concerning the shape of milk releasing curves and to use it to implement a genetic selection program. A previous study showed heritability of 0.21 for maximum milk flow and 0.14 for time at stable flow with a genetic correlation between them of -0.65, values that suggest the possibility for selection on milking parameters (Santus and Bagnato 1998. Objective of this study is the investigation of variation of parameters describing the milking emission curves along the animal career and to address relationship between curve shapes with production and somatic cell count.

A study on the jet pump characteristic curve in boiling water reactor

International Nuclear Information System (INIS)

Liao, L.Y.

1990-01-01

The jet pump models of RELAP5/MOD2, RETRAN-02/MOD3, and RELAP4/MOD3 are compared. From the investigation of the momentum equations, it is found that the normal quadrant jet pump models of these codes are essentially the same. In this paper, it is found that the relationship between the flow ratio, M, and the heat ratio, N, is uniquely determined for a given jet pump geometry provided that the wall friction and gravitational head are neglected. In other words, under the given assumptions the M - N characteristic curve will not change with power level, recirculation pump speed and loop flow rate. The effect of the gravitational head on the M - N curve has been found to be significant for low flow conditions. As a result, a guideline has been given to the definition of the specific energy (or the head ratio). Sensitivity studies on the key parameters have been performed. It is found that the generic M - N curve should not be used for a jet pump which does not have the same nozzle to throat area ratio as that of the generic jet pump

universal specific energy curve for para- bolic open channels

African Journals Online (AJOL)

DEPT OF AGRICULTURAL ENGINEERING

UNIVERSAL SPECIFIC ENERGY CURVE FOR PARA-. BOLIC OPEN CHANNELS. K.O. Aiyesimoju. Department of Civil Engineering. University of Lagos. Lagos, Nigeria. ABSTRACT. From the general relationship between specific energy and flow depth for all open channels, the specific relationship for parabolic open ...

Curved butterfly bileaflet prosthetic cardiac valve

Science.gov (United States)

McQueen, David M.; Peskin, Charles S.

1991-06-25

An annular valve body having a central passageway for the flow of blood therethrough with two curved leaflets each of which is pivotally supported on an accentric positioned axis in the central passageway for moving between a closed position and an open position. The leaflets are curved in a plane normal to the eccentric axis and positioned with the convex side of the leaflets facing each other when the leaflets are in the open position. Various parameters such as the curvature of the leaflets, the location of the eccentric axis, and the maximum opening angle of the leaflets are optimized according to the following performance criteria: maximize the minimum peak velocity through the valve, maximize the net stroke volume, and minimize the mean forward pressure difference, thereby reducing thrombosis and improving the hemodynamic performance.

Creep measurements confirm steady flow after stress maximum in extension of branched polymer melts

DEFF Research Database (Denmark)

Javier Alvarez, Nicolas; Román Marín, José Manuel; Huang, Qian

2013-01-01

We provide conclusive evidence of nonmonotonic mechanical behavior in the extension of long-chain branched polymer melts. While nonmonotonic behavior is known to occur for solids, for the case of polymeric melts, this phenomenon is in direct contrast with current theoretical models. We rule out t...

APPLICATION OF A PRIMAL-DUAL INTERIOR POINT ALGORITHM USING EXACT SECOND ORDER INFORMATION WITH A NOVEL NON-MONOTONE LINE SEARCH METHOD TO GENERALLY CONSTRAINED MINIMAX OPTIMISATION PROBLEMS

Directory of Open Access Journals (Sweden)

INTAN S. AHMAD

2008-04-01

Full Text Available This work presents the application of a primal-dual interior point method to minimax optimisation problems. The algorithm differs significantly from previous approaches as it involves a novel non-monotone line search procedure, which is based on the use of standard penalty methods as the merit function used for line search. The crucial novel concept is the discretisation of the penalty parameter used over a finite range of orders of magnitude and the provision of a memory list for each such order. An implementation within a logarithmic barrier algorithm for bounds handling is presented with capabilities for large scale application. Case studies presented demonstrate the capabilities of the proposed methodology, which relies on the reformulation of minimax models into standard nonlinear optimisation models. Some previously reported case studies from the open literature have been solved, and with significantly better optimal solutions identified. We believe that the nature of the non-monotone line search scheme allows the search procedure to escape from local minima, hence the encouraging results obtained.

INEXTENSIBLE FLOWS OF CURVES IN THE EQUIFORM GEOMETRY OF THE PSEUDO-GALILEAN SPACE G13

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HANDAN OZTEKIN

2016-12-01

Full Text Available In this paper, we study inextensible ows of curves in 3-dimensional pseudo- Galilean space. We give necessary and sucient conditions for inextensible ows of curves according to equiform geometry in pseudo-Galilean space.

Semiparametric approach for non-monotone missing covariates in a parametric regression model

KAUST Repository

Sinha, Samiran

2014-02-26

Missing covariate data often arise in biomedical studies, and analysis of such data that ignores subjects with incomplete information may lead to inefficient and possibly biased estimates. A great deal of attention has been paid to handling a single missing covariate or a monotone pattern of missing data when the missingness mechanism is missing at random. In this article, we propose a semiparametric method for handling non-monotone patterns of missing data. The proposed method relies on the assumption that the missingness mechanism of a variable does not depend on the missing variable itself but may depend on the other missing variables. This mechanism is somewhat less general than the completely non-ignorable mechanism but is sometimes more flexible than the missing at random mechanism where the missingness mechansim is allowed to depend only on the completely observed variables. The proposed approach is robust to misspecification of the distribution of the missing covariates, and the proposed mechanism helps to nullify (or reduce) the problems due to non-identifiability that result from the non-ignorable missingness mechanism. The asymptotic properties of the proposed estimator are derived. Finite sample performance is assessed through simulation studies. Finally, for the purpose of illustration we analyze an endometrial cancer dataset and a hip fracture dataset.

Exploring the physical controls of regional patterns of flow duration curves – Part 4: A synthesis of empirical analysis, process modeling and catchment classification

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M. Sivapalan

2012-11-01

Full Text Available The paper reports on a four-pronged study of the physical controls on regional patterns of the flow duration curve (FDC. This involved a comparative analysis of long-term continuous data from nearly 200 catchments around the US, encompassing a wide range of climates, geology, and ecology. The analysis was done from three different perspectives – statistical analysis, process-based modeling, and data-based classification – followed by a synthesis, which is the focus of this paper. Streamflow data were separated into fast and slow flow responses, and associated signatures, and both total flow and its components were analyzed to generate patterns. Regional patterns emerged in all aspects of the study. The mixed gamma distribution described well the shape of the FDC; regression analysis indicated that certain climate and catchment properties were first-order controls on the shape of the FDC. In order to understand the spatial patterns revealed by the statistical study, and guided by the hypothesis that the middle portion of the FDC is a function of the regime curve (RC, mean within-year variation of flow, we set out to classify these catchments, both empirically and through process-based modeling, in terms of their regime behavior. The classification analysis showed that climate seasonality and aridity, either directly (empirical classes or through phenology (vegetation processes, were the dominant controls on the RC. Quantitative synthesis of these results determined that these classes were indeed related to the FDC through its slope and related statistical parameters. Qualitative synthesis revealed much diversity in the shapes of the FDCs even within each climate-based homogeneous class, especially in the low-flow tails, suggesting that catchment properties may have become the dominant controls. Thus, while the middle portion of the FDC contains the average response of the catchment, and is mainly controlled by climate, the tails of the FDC

Exploring the physical controls of regional patterns of flow duration curves – Part 3: A catchment classification system based on regime curve indicators

Directory of Open Access Journals (Sweden)

M. Sivapalan

2012-11-01

Full Text Available Predictions of hydrological responses in ungauged catchments can benefit from a classification scheme that can organize and pool together catchments that exhibit a level of hydrologic similarity, especially similarity in some key variable or signature of interest. Since catchments are complex systems with a level of self-organization arising from co-evolution of climate and landscape properties, including vegetation, there is much to be gained from developing a classification system based on a comparative study of a population of catchments across climatic and landscape gradients. The focus of this paper is on climate seasonality and seasonal runoff regime, as characterized by the ensemble mean of within-year variation of climate and runoff. The work on regime behavior is part of an overall study of the physical controls on regional patterns of flow duration curves (FDCs, motivated by the fact that regime behavior leaves a major imprint upon the shape of FDCs, especially the slope of the FDCs. As an exercise in comparative hydrology, the paper seeks to assess the regime behavior of 428 catchments from the MOPEX database simultaneously, classifying and regionalizing them into homogeneous or hydrologically similar groups. A decision tree is developed on the basis of a metric chosen to characterize similarity of regime behavior, using a variant of the Iterative Dichotomiser 3 (ID3 algorithm to form a classification tree and associated catchment classes. In this way, several classes of catchments are distinguished, in which the connection between the five catchments' regime behavior and climate and catchment properties becomes clearer. Only four similarity indices are entered into the algorithm, all of which are obtained from smoothed daily regime curves of climatic variables and runoff. Results demonstrate that climate seasonality plays the most significant role in the classification of US catchments, with rainfall timing and climatic aridity index

Ultrasonic velocity profiling rheometry based on a widened circular Couette flow

International Nuclear Information System (INIS)

Shiratori, Takahisa; Tasaka, Yuji; Oishi, Yoshihiko; Murai, Yuichi

2015-01-01

We propose a new rheometry for characterizing the rheological properties of fluids. The technique produces flow curves, which represent the relationship between the fluid shear rate and shear stress. Flow curves are obtained by measuring the circumferential velocity distribution of tested fluids in a circular Couette system, using an ultrasonic velocity profiling technique. By adopting a widened gap of concentric cylinders, a designed range of the shear rate is obtained so that velocity profile measurement along a single line directly acquires flow curves. To reduce the effect of ultrasonic noise on resultant flow curves, several fitting functions and variable transforms are examined to best approximate the velocity profile without introducing a priori rheological models. Silicone oil, polyacrylamide solution, and yogurt were used to evaluate the applicability of this technique. These substances are purposely targeted as examples of Newtonian fluids, shear thinning fluids, and opaque fluids with unknown rheological properties, respectively. We find that fourth-order Chebyshev polynomials provide the most accurate representation of flow curves in the context of model-free rheometry enabled by ultrasonic velocity profiling. (paper)

Population variability in biological adaptive responses to DNA damage and the shapes of carcinogen dose-response curves

International Nuclear Information System (INIS)

Conolly, Rory B.; Gaylor, David W.; Lutz, Werner K.

2005-01-01

Carcinogen dose-response curves for both ionizing radiation and chemicals are typically assumed to be linear at environmentally relevant doses. This assumption is used to ensure protection of the public health in the absence of relevant dose-response data. A theoretical justification for the assumption has been provided by the argument that low dose linearity is expected when an exogenous agent adds to an ongoing endogenous process. Here, we use computational modeling to evaluate (1) how two biological adaptive processes, induction of DNA repair and cell cycle checkpoint control, may affect the shapes of dose-response curves for DNA-damaging carcinogens and (2) how the resulting dose-response behaviors may vary within a population. Each model incorporating an adaptive process was capable of generating not only monotonic dose-responses but also nonmonotonic (J-shaped) and threshold responses. Monte Carlo analysis suggested that all these dose-response behaviors could coexist within a population, as the spectrum of qualitative differences arose from quantitative changes in parameter values. While this analysis is largely theoretical, it suggests that (a) accurate prediction of the qualitative form of the dose-response requires a quantitative understanding of the mechanism (b) significant uncertainty is associated with human health risk prediction in the absence of such quantitative understanding and (c) a stronger experimental and regulatory focus on biological mechanisms and interindividual variability would allow flexibility in regulatory treatment of environmental carcinogens without compromising human health

Flow visualization and relative permeability measurements in rough-walled fractures

International Nuclear Information System (INIS)

Persoff, P.; Pruess, K.

1993-01-01

Two-phase (gas-liquid) flow experiments were done in a natural rock fracture and transparent replicas of natural fractures. Liquid was injected at constant volume flow rate, and gas was injected at either constant mass flow rate or constant pressure. When gas was injected at constant mass flow rate, the gas inlet pressure, and inlet and outlet capillary pressures, generally did not reach steady state but cycled irregularly. Flow visualization showed that this cycling was due to repeated blocking and unblocking of gas flow paths by liquid. Relative permeabilities calculated from flow rate and pressure data show that the sum of the relative permeabilities of the two phases is much less than 1, indicating that each phase interferes strongly with the flow of the other. Comparison of the relative permeability curves with typical curves for porous media (Corey curves) show that the phase interference is stronger in fractures than in typical porous media

Estimation of Soil Water Retention Curve Using Fractal Dimension ...

African Journals Online (AJOL)

ADOWIE PERE

2017-12-01

Dec 1, 2017 ... ABSTRACT: The soil water retention curve (SWRC) is a fundamental hydraulic property majorly used to study flow transport in soils and calculate ... suitable to model the heterogeneous soil structure with tortuous pore space (Rieu ... so, soil texture determined according to the USDA texture classification.

Multistability and gluing bifurcation to butterflies in coupled networks with non-monotonic feedback

International Nuclear Information System (INIS)

Ma Jianfu; Wu Jianhong

2009-01-01

Neural networks with a non-monotonic activation function have been proposed to increase their capacity for memory storage and retrieval, but there is still a lack of rigorous mathematical analysis and detailed discussions of the impact of time lag. Here we consider a two-neuron recurrent network. We first show how supercritical pitchfork bifurcations and a saddle-node bifurcation lead to the coexistence of multiple stable equilibria (multistability) in the instantaneous updating network. We then study the effect of time delay on the local stability of these equilibria and show that four equilibria lose their stability at a certain critical value of time delay, and Hopf bifurcations of these equilibria occur simultaneously, leading to multiple coexisting periodic orbits. We apply centre manifold theory and normal form theory to determine the direction of these Hopf bifurcations and the stability of bifurcated periodic orbits. Numerical simulations show very interesting global patterns of periodic solutions as the time delay is varied. In particular, we observe that these four periodic solutions are glued together along the stable and unstable manifolds of saddle points to develop a butterfly structure through a complicated process of gluing bifurcations of periodic solutions

Electroosmotic Flow in Mixed Polymer Brush-Grafted Nanochannels

Directory of Open Access Journals (Sweden)

Qianqian Cao

2016-12-01

Full Text Available Mixed polymer brush-grafted nanochannels—where two distinct species of polymers are alternately grafted on the inner surface of nanochannels—are an interesting class of nanostructured hybrid materials. By using a coarse-grained molecular dynamics simulation method, we are able to simulate the electrokinetic transport dynamics of the fluid in such nanochannels as well as the conformational behaviors of the mixed polymer brush. We find that (1 the brush adopts vertically-layered and longitudinally-separated structures due to the coupling of electroosmotic flow (EOF and applied electric field; (2 the solvent quality affects the brush conformations and the transport properties of the EOF; (3 the EOF flux non-monotonically depends on the grafting density, although the EOF velocity in the central region of the channel monotonically depends on the grafting density.

Reference Curve for the Mean Uterine Artery Pulsatility Index in Singleton Pregnancies.

Science.gov (United States)

Weichert, Alexander; Hagen, Andreas; Tchirikov, Michael; Fuchs, Ilka B; Henrich, Wolfgang; Entezami, Michael

2017-05-01

Doppler sonography of the uterine artery (UA) is done to monitor pregnancies, because the detected flow patterns are useful to draw inferences about possible disorders of trophoblast invasion. Increased resistance in the UA is associated with an increased risk of preeclampsia and/or intrauterine growth restriction (IUGR) and perinatal mortality. In the absence of standardized figures, the normal ranges of the various available reference curves sometimes differ quite substantially from one another. The causes for this are differences in the flow patterns of the UA depending on the position of the pulsed Doppler gates as well as branching of the UA. Because of the discrepancies between the different reference curves and the practical problems this poses for guideline recommendations, we thought it would be useful to create our own reference curves for Doppler measurements of the UA obtained from a singleton cohort under standardized conditions. This retrospective cohort study was carried out in the Department of Obstetrics of the Charité - Universitätsmedizin Berlin, the Department for Obstetrics and Prenatal Medicine of the University Hospital Halle (Saale) and the Center for Prenatal Diagnostics and Human Genetics Kurfürstendamm 199. Available datasets from the three study locations were identified and reference curves were generated using the LMS method. Measured values were correlated with age of gestation, and a cubic model and Box-Cox power transformation (L), the median (M) and the coefficient of variation (S) were used to smooth the curves. 103 720 Doppler examinations of the UA carried out in singleton pregnancies from the 11th week of gestation (10 + 1 GW) were analyzed. The mean pulsatility index (Mean PI) showed a continuous decline over the course of pregnancy, dropping to a plateau of around 0.84 between the 23rd and 27th GW, after which it decreased again. Age of gestation, placental position, position of pulsed Doppler gates and branching of

An extended CFD model to predict the pumping curve in low pressure plasma etch chamber

Science.gov (United States)

Zhou, Ning; Wu, Yuanhao; Han, Wenbin; Pan, Shaowu

2014-12-01

Continuum based CFD model is extended with slip wall approximation and rarefaction effect on viscosity, in an attempt to predict the pumping flow characteristics in low pressure plasma etch chambers. The flow regime inside the chamber ranges from slip wall (Kn ˜ 0.01), and up to free molecular (Kn = 10). Momentum accommodation coefficient and parameters for Kn-modified viscosity are first calibrated against one set of measured pumping curve. Then the validity of this calibrated CFD models are demonstrated in comparison with additional pumping curves measured in chambers of different geometry configurations. More detailed comparison against DSMC model for flow conductance over slits with contraction and expansion sections is also discussed.

Renormalization group flows and fixed points for a scalar field in curved space with nonminimal F (ϕ )R coupling

Science.gov (United States)

Merzlikin, Boris S.; Shapiro, Ilya L.; Wipf, Andreas; Zanusso, Omar

2017-12-01

Using covariant methods, we construct and explore the Wetterich equation for a nonminimal coupling F (ϕ )R of a quantized scalar field to the Ricci scalar of a prescribed curved space. This includes the often considered nonminimal coupling ξ ϕ2R as a special case. We consider the truncations without and with scale- and field-dependent wave-function renormalization in dimensions between four and two. Thereby the main emphasis is on analytic and numerical solutions of the fixed point equations and the behavior in the vicinity of the corresponding fixed points. We determine the nonminimal coupling in the symmetric and spontaneously broken phases with vanishing and nonvanishing average fields, respectively. Using functional perturbative renormalization group methods, we discuss the leading universal contributions to the RG flow below the upper critical dimension d =4 .

Orbital Signatures from Observed Light Curves of Blazars

Indian Academy of Sciences (India)

2016-01-27

Jan 27, 2016 ... Variability in active galactic nuclei is observed in UV to X-ray emission based light curves. This could be attributed to orbital signatures of the plasma that constitutes the accretion flow on the putative disk or in the developing jet close to the inner region of the central black hole. We discuss some theoretical ...

Comparison of two methods to determine fan performance curves using computational fluid dynamics

Science.gov (United States)

Onma, Patinya; Chantrasmi, Tonkid

2018-01-01

This work investigates a systematic numerical approach that employs Computational Fluid Dynamics (CFD) to obtain performance curves of a backward-curved centrifugal fan. Generating the performance curves requires a number of three-dimensional simulations with varying system loads at a fixed rotational speed. Two methods were used and their results compared to experimental data. The first method incrementally changes the mass flow late through the inlet boundary condition while the second method utilizes a series of meshes representing the physical damper blade at various angles. The generated performance curves from both methods are compared with an experiment setup in accordance with the AMCA fan performance testing standard.

Environmentally-relevant concentrations of atrazine induce non-monotonic acceleration of developmental rate and increased size at metamorphosis in Rhinella arenarum tadpoles.

Science.gov (United States)

Brodeur, Julie C; Sassone, Alina; Hermida, Gladys N; Codugnello, Nadia

2013-06-01

Despite of the various studies reporting on the subject, anticipating the impacts of the widely-used herbicide atrazine on anuran tadpoles metamorphosis remains complex as increases or decreases of larval period duration are almost as frequently reported as an absence of effect. The aim of the present study was to examine the effects of environmentally-relevant concentrations of atrazine (0.1, 1, 10, 100, and 1000μg/L) on the timings of metamorphosis and body size at metamorphosis in the common South American toad, Rhinella arenarum (Anura: bufonidae). None of the atrazine concentrations tested significantly altered survival. Low atrazine concentrations in the range of 1-100μg/L were found to accelerate developmental rate in a non-monotonic U-shaped concentration-response relationship. This observed acceleration of the metamorphic process occurred entirely between stages 25 and 39; treated tadpoles proceeding through metamorphosis as control animals beyond this point. Together with proceeding through metamorphosis at a faster rate, tadpoles exposed to atrazine concentrations in the range of 1-100μg/L furthermore transformed into significantly larger metamorphs than controls, the concentration-response curve taking the form of an inverted U in this case. The no observed effect concentration (NOEC) was 0.1μg atrazine/L for both size at metamorphosis and timings of metamorphosis. Tadpoles exposed to 100μg/L 17β-estradiol presented the exact same alterations of developmental rate and body size as those treated with 1, 10 and 100μg/L of atrazine. Elements of the experimental design that facilitated the detection of alterations of metamorphosis at low concentrations of atrazine are discussed, together with the ecological significance of those findings. Copyright © 2013 Elsevier Inc. All rights reserved.

Fourier analysis of cerebrospinal fluid flow velocities: MR imaging study. The Scandinavian Flow Group

DEFF Research Database (Denmark)

Thomsen, C; Ståhlberg, F; Stubgaard, M

1990-01-01

images. The phase information in the resultant image was converted to flow velocity with a calibration curve with the slope 26.5 radian.m-1.sec. The velocity versus time function was Fourier transformed and a continuous curve was fitted to the measured data with use of the first three harmonics...

Assessment of CHF enhancement mechanisms in a curved, rectangular channel subjected to concave heating

International Nuclear Information System (INIS)

Sturgis, J.C.; Mudawar, I.

1999-01-01

An experimental study was undertaken to examine the enhancement in critical heat flux (CHF) provided by streamwise curvature. Curved and straight rectangular flow channels were fabricated with identical 5.0 x 2.5 mm cross sections and heated lengths of 101.6 mm in which the heat was applied to only one wall--the concave wall (32.3 mm radius) in the curved channel and a side wall in the straight. Tests were conducted using FC-72 liquid with mean inlet velocity and outlet subcooling of 0.25 to 10 m s -1 and 3 to 29 C, respectively. Centripetal acceleration for curved flow reached 315 times earth's gravitational acceleration. Critical heat flux was enhanced due to flow curvature at all conditions but the enhancement decreased with increasing subcooling. For near-saturated conditions, the enhancement was approximately 60% while for highly subcooled flow it was only 20%. The causes for the enhancement were identified as (1) increased pressure on the liquid-vapor interface at wetting fronts, (2) buoyancy forces and (3) increased subcooling at the concave wall. Flow visualization tests were conducted in transparent channels to explore the role of buoyancy forces in enhancing the critical heat flux. These forces were observed to remove vapor from the concave wall and distribute it throughout the cross section. Vapor removal was only effective at near-saturated conditions, yielding the observed substantial enhancement in CHF relative to the straight channel

Steady flow in shallow channel bends

NARCIS (Netherlands)

De Vriend, H.J.

1981-01-01

Making use of a mathematical model solving the complete NavierStokes equations for steady flow in coiled rectangular pipes, fully-developed laminar flow in shallow curved channels is analysed physically and mathematically. Transverse convection of momentum by the secondary flow is shown to cause

New Insight into Combined Model and Revised Model for RTD Curves in a Multi-strand Tundish

Science.gov (United States)

Lei, Hong

2015-12-01

The analysis for the residence time distribution (RTD) curve is one of the important experimental technologies to optimize the tundish design. But there are some issues about RTD analysis model. Firstly, the combined (or mixed) model and the revised model give different analysis results for the same RTD curve. Secondly, different upper limits of integral in the numerator for the mean residence time give different results for the same RTD curve. Thirdly, the negative dead volume fraction sometimes appears at the outer strand of the multi-strand tundish. In order to solve the above problems, it is necessary to have a deep insight into the RTD curve and to propose a reasonable method to analyze the RTD curve. The results show that (1) the revised model is not appropriate to treat with the RTD curve; (2) the conception of the visual single-strand tundish and the combined model with the dimensionless time at the cut-off point are applied to estimate the flow characteristics in the multi-strand tundish; and that (3) the mean residence time at each exit is the key parameter to estimate the similarity of fluid flow among strands.

Estimation of soil water retention curve using fractal dimension ...

African Journals Online (AJOL)

The soil water retention curve (SWRC) is a fundamental hydraulic property majorly used to study flow transport in soils and calculate plant-available water. Since, direct measurement of SWRC is time-consuming and expensive, different models have been developed to estimate SWRC. In this study, a fractal-based model ...

Transient Droplet Behavior and Droplet Breakup during Bulk and Confined Shear Flow in Blends with One Viscoelastic Component: Experiments, Modelling and Simulations

Science.gov (United States)

Cardinaels, Ruth; Verhulst, Kristof; Renardy, Yuriko; Moldenaers, Paula

2008-07-01

The transient droplet deformation and droplet orientation after inception of shear, the shape relaxation after cessation of shear and droplet breakup during shear, are microscopically studied, both under bulk and confined conditions. The studied blends contain one viscoelastic Boger fluid phase. A counter rotating setup, based on a Paar Physica MCR300, is used for the droplet visualisation. For bulk shear flow, it is shown that the droplet deformation during startup of shear flow and the shape relaxation after cessation of shear flow are hardly influenced by droplet viscoelasticity, even at moderate to high capillary and Deborah numbers. The effects of droplet viscoelasticity only become visible close to the critical conditions and a novel break-up mechanism is observed. Matrix viscoelasticity has a more pronounced effect, causing overshoots in the deformation and significantly inhibiting relaxation. However, different applied capillary numbers prior to cessation of shear flow, with the Deborah number fixed, still result in a single master curve for shape retraction, as in fully Newtonian systems. The long tail in the droplet relaxation can be qualitatively described with a phenomenological model for droplet deformation, when using a 5-mode Giesekus model for the fluid rheology. It is found that the shear flow history significantly affects the droplet shape evolution and the breakup process in blends with one viscoelastic component. Confining a droplet between two plates accelerates the droplet deformation kinetics, similar to fully Newtonian systems. However, the increased droplet deformation, due to wall effects, causes the steady state to be reached at a later instant in time. Droplet relaxation is less sensitive to confinement, leading to slower relaxation kinetics only for highly confined droplets. For the blend with a viscoelastic droplet, a non-monotonous trend is found for the critical capillary number as a function of the confinement ratio. Finally

Transient Droplet Behavior and Droplet Breakup during Bulk and Confined Shear Flow in Blends with One Viscoelastic Component: Experiments, Modelling and Simulations

International Nuclear Information System (INIS)

Cardinaels, Ruth; Verhulst, Kristof; Moldenaers, Paula; Renardy, Yuriko

2008-01-01

The transient droplet deformation and droplet orientation after inception of shear, the shape relaxation after cessation of shear and droplet breakup during shear, are microscopically studied, both under bulk and confined conditions. The studied blends contain one viscoelastic Boger fluid phase. A counter rotating setup, based on a Paar Physica MCR300, is used for the droplet visualisation. For bulk shear flow, it is shown that the droplet deformation during startup of shear flow and the shape relaxation after cessation of shear flow are hardly influenced by droplet viscoelasticity, even at moderate to high capillary and Deborah numbers. The effects of droplet viscoelasticity only become visible close to the critical conditions and a novel break-up mechanism is observed. Matrix viscoelasticity has a more pronounced effect, causing overshoots in the deformation and significantly inhibiting relaxation. However, different applied capillary numbers prior to cessation of shear flow, with the Deborah number fixed, still result in a single master curve for shape retraction, as in fully Newtonian systems. The long tail in the droplet relaxation can be qualitatively described with a phenomenological model for droplet deformation, when using a 5-mode Giesekus model for the fluid rheology. It is found that the shear flow history significantly affects the droplet shape evolution and the breakup process in blends with one viscoelastic component. Confining a droplet between two plates accelerates the droplet deformation kinetics, similar to fully Newtonian systems. However, the increased droplet deformation, due to wall effects, causes the steady state to be reached at a later instant in time. Droplet relaxation is less sensitive to confinement, leading to slower relaxation kinetics only for highly confined droplets. For the blend with a viscoelastic droplet, a non-monotonous trend is found for the critical capillary number as a function of the confinement ratio. Finally

Non-darcy flow behavior mean high-flux injection wells in porous and fractured formations

Energy Technology Data Exchange (ETDEWEB)

Wu, Yu-Shu

2003-04-25

This paper presents a study of non-Darcy fluid flow through porous and fractured rock, which may occur near wells during high-flux injection of waste fluids into underground formations. Both numerical and analytical models are used in this study. General non-Darcy flow is described using the Forchheimer equation, implemented in a three-dimensional, multiphase flow reservoir simulator. The non-Darcy flow through a fractured reservoir is handled using a general dual continuum approach, covering commonly used conceptual models, such as double porosity, dual permeability, explicit fracture, etc. Under single-phase flow conditions, an approximate analytical solution, as an extension of the Warren-Root solution, is discussed. The objectives of this study are (1) to obtain insights into the effect of non-Darcy flow on transient pressure behavior through porous and fractured reservoirs and (2) to provide type curves for well test analyses of non-Darcy flow wells. The type curves generated include various types of drawdown, injection, and buildup tests with non-Darcy flow occurring in porous and fractured reservoirs. In addition, non-Darcy flow into partially penetrating wells is also considered. The transient-pressure type curves for flow in fractured reservoirs are based on the double-porosity model. Type curves provided in this work for non-Darcy flow in porous and fractured reservoirs will find their applications in well test interpretation using a type-curve matching technique.

Law of mixture used to model the flow behavior of a duplex stainless steel at high temperatures

International Nuclear Information System (INIS)

Momeni, A.; Dehghani, K.; Poletti, M.C.

2013-01-01

In this investigation the flow curves of a duplex stainless steel were drawn by performing hot compression tests over a wide temperature range of 950–1200 °C and strain rates of 0.001–100 s −1 . The flow curves of ferrite and austenite phases in the duplex structure were depicted by conducting similar hot compression tests on two steels that were cast and prepared with the same chemical compositions. The flow curves of the austenitic steel were found typical of dynamic recrystallization. They were successfully modeled by using the experimental exponential equation proposed by Cingara and McQueen. The flow curves of the ferritic steel were typical of dynamic recovery. They were modeled by the dislocation density evolution function proposed by Estrin and Meckning. Comparing the flow curves of three studied steels, it was found that the flow curves of the duplex steel were very similar and close to those of the ferrite steel. It was understood that in a duplex structure of ferrite and austenite the flow behavior is mostly controlled by the softer phase, i.e. ferrite. The law of mixture was modified to consider the strain partitioning between ferrite and austenite. The distribution coefficients of ferrite and austenite were described and determined at different deformation conditions. The results of modeling satisfactorily predicted the experimental curves. It was shown that the influence of austenite on the flow behavior of the duplex structure is almost low. However, it increases as strain rate or temperature rises. - Highlights: ► Flow curves of austenite and ferrite in the duplex steel were modeled separately. ► The flow behavior of the duplex steel is mostly controlled by ferrite. ► The effect of austenite on flow curve increases with temperature and strain rate. ► The flow curve of the duplex steel is modeled by the modified law of mixture

Can Low-Resolution Airborne Laser Scanning Data Be Used to Model Stream Rating Curves?

Directory of Open Access Journals (Sweden)

Steve W. Lyon

2015-03-01

Full Text Available This pilot study explores the potential of using low-resolution (0.2 points/m2 airborne laser scanning (ALS-derived elevation data to model stream rating curves. Rating curves, which allow the functional translation of stream water depth into discharge, making them integral to water resource monitoring efforts, were modeled using a physics-based approach that captures basic geometric measurements to establish flow resistance due to implicit channel roughness. We tested synthetically thinned high-resolution (more than 2 points/m2 ALS data as a proxy for low-resolution data at a point density equivalent to that obtained within most national-scale ALS strategies. Our results show that the errors incurred due to the effect of low-resolution versus high-resolution ALS data were less than those due to flow measurement and empirical rating curve fitting uncertainties. As such, although there likely are scale and technical limitations to consider, it is theoretically possible to generate rating curves in a river network from ALS data of the resolution anticipated within national-scale ALS schemes (at least for rivers with relatively simple geometries. This is promising, since generating rating curves from ALS scans would greatly enhance our ability to monitor streamflow by simplifying the overall effort required.

Can low-resolution airborne laser scanning data be used to model stream rating curves?

Science.gov (United States)

Lyon, Steve; Nathanson, Marcus; Lam, Norris; Dahlke, Helen; Rutzinger, Martin; Kean, Jason W.; Laudon, Hjalmar

2015-01-01

This pilot study explores the potential of using low-resolution (0.2 points/m2) airborne laser scanning (ALS)-derived elevation data to model stream rating curves. Rating curves, which allow the functional translation of stream water depth into discharge, making them integral to water resource monitoring efforts, were modeled using a physics-based approach that captures basic geometric measurements to establish flow resistance due to implicit channel roughness. We tested synthetically thinned high-resolution (more than 2 points/m2) ALS data as a proxy for low-resolution data at a point density equivalent to that obtained within most national-scale ALS strategies. Our results show that the errors incurred due to the effect of low-resolution versus high-resolution ALS data were less than those due to flow measurement and empirical rating curve fitting uncertainties. As such, although there likely are scale and technical limitations to consider, it is theoretically possible to generate rating curves in a river network from ALS data of the resolution anticipated within national-scale ALS schemes (at least for rivers with relatively simple geometries). This is promising, since generating rating curves from ALS scans would greatly enhance our ability to monitor streamflow by simplifying the overall effort required.

An analysis on the environmental Kuznets curve of Chengdu

Science.gov (United States)

Gao, Zijian; Peng, Yue; Zhao, Yue

2017-12-01

In this paper based on the environmental and economic data of Chengdu from 2005 to 2014, the measurement models were established to analyze 3 kinds of environmental flow indicators and 4 kinds of environmental stock indicators to obtain their EKC evolution trajectories and characters. The results show that the relationship curve between the discharge of SO2 from industry and the GDP per capita is a positive U shape, just as the curve between discharge of COD from industry and the GDP per person. The relationship curve between the dust discharge from industry and the GDP per capita is an inverted N shape. In the central of the urban the relationship curve between the concentration of SO2 in the air and the GDP per person is a positive U shape. The relationship curves between the concentration of NO2 in the air and the GDP per person, between the concentration of the particulate matters and the GDP per person, and between the concentration of the fallen dusts and the GDP per person are fluctuating. So the EKC curves of the 7 kinds of environmental indicators are not accord with inverted U shape feature. In the development of this urban the environmental problems can’t be resolved only by economic growth. The discharge of industrial pollutants should be controlled to improve the atmospheric environmental quality and reduce the environmental risks.

Flow lab.: flow visualization and simulation

International Nuclear Information System (INIS)

Park, Chung Kyun; Cho, Won Jin; Hahn, Pil Soo

2005-01-01

The experimental setups for flow visualization and processes identification in laboratory scale (so called Flow Lab.) has developed to get ideas and answer fundamental questions of flow and migration in geologic media. The setup was made of a granite block of 50x50cm scale and a transparent acrylate plate. The tracers used in this experiments were tritiated water, anions, and sorbing cations as well as an organic dye, eosine, to visualize migration paths. The migration plumes were taken with a digital camera as a function of time and stored as digital images. A migration model was also developed to describe and identify the transport processes. Computer simulation was carried out not only for the hydraulic behavior such as distributions of pressure and flow vectors in the fracture but also for the migration plume and the elution curves

The mechanism of fracture for entangled polymer liquids in extensional flow

DEFF Research Database (Denmark)

Huang, Qian; Yu, Liyun; Wingstrand, Sara Lindeblad

In uniaxial extensional flow of entangled polymer liquids, different rupture modes may happen, including necking and fracture. Malkin andPetrie [1] proposed a ''master curve'' dividing the flow behavior into four zones based on the stretch rate: (I) Flow zone; (II) Transition zone; (III) Rubbery...... curve in Zone IV. However, with faster rate, a constant critical strain is observed, which is not shown in the original master curve. The value of the constant critical strain seems to be related to themaximum stretch ratio of the polymer chain (determined by Me), but not influenced by Z. The results...

Bacterial streamers in curved microchannels

Science.gov (United States)

Rusconi, Roberto; Lecuyer, Sigolene; Guglielmini, Laura; Stone, Howard

2009-11-01

Biofilms, generally identified as microbial communities embedded in a self-produced matrix of extracellular polymeric substances, are involved in a wide variety of health-related problems ranging from implant-associated infections to disease transmissions and dental plaque. The usual picture of these bacterial films is that they grow and develop on surfaces. However, suspended biofilm structures, or streamers, have been found in natural environments (e.g., rivers, acid mines, hydrothermal hot springs) and are always suggested to stem from a turbulent flow. We report the formation of bacterial streamers in curved microfluidic channels. By using confocal laser microscopy we are able to directly image and characterize the spatial and temporal evolution of these filamentous structures. Such streamers, which always connect the inner corners of opposite sides of the channel, are always located in the middle plane. Numerical simulations of the flow provide evidences for an underlying hydrodynamic mechanism behind the formation of the streamers.

Endocrine effects of chemicals: aspects of hazard identification and human health risk assessment.

Science.gov (United States)

Dekant, Wolfgang; Colnot, Thomas

2013-12-16

Hazard and risk assessment of chemicals with endocrine activity is hotly debated due to claimed non-monotonous dose-response curves in the low-dose region. In hazard identification a clear definition of "endocrine disruptors" (EDs) is required; this should be based on the WHO/IPCS definition of EDs and on adverse effects demonstrated in intact animals or humans. Therefore, endocrine effects are a mode of action potentially resulting in adverse effects; any classification should not be based on a mode of action, but on adverse effects. In addition, when relying on adverse effects, most effects reported in the low-dose region will not qualify for hazard identification since most have little relation to an adverse effect. Non-monotonous dose-response curves that had been postulated from limited, exploratory studies could also not be reproduced in targeted studies with elaborate quality assurance. Therefore, regulatory agencies or advisory bodies continue to apply the safety-factor method or the concept of "margin-of-exposure" based on no observed adverse effect levels (NOAELs) in the risk assessment of chemicals with weak hormonal activity. Consistent with this approach, tolerable levels regarding human exposure have been defined for such chemicals. To conclusively support non-monotonous dose-response curves, targeted experiments with a sufficient number of animals, determination of adverse endpoints, adequate statistics and quality control would be required. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Relative ages of lava flows at Alba Patera, Mars

International Nuclear Information System (INIS)

Schneeberger, D.M.; Pieri, D.C.

1987-01-01

Many large lava flows on the flanks of Alba Patera are astonishing in their volume and length. As a suite, these flows suggest tremendously voluminous and sustained eruptions, and provide dimensional boundary conditions typically a factor of 100 larger than terrestrial flows. One of the most striking features associated with Alba Patera is the large, radially oriented lava flows that exhibit a variety of flow morphologies. These include sheet flows, tube fed and tube channel flows, and undifferentiated flows. Three groups of flows were studied; flows on the northwest flank, southeast flank, and the intracaldera region. The lava flows discussed probably were erupted as a group during the same major volcanic episode as suggested by the data presented. Absolute ages are poorly constrained for both the individual flows and shield, due in part to disagreement as to which absolute age curve is representative for Mars. A relative age sequence is implied but lacks precision due to the closeness of the size frequency curves

Guidelines for using the Delphi Technique to develop habitat suitability index curves

Science.gov (United States)

Crance, Johnie H.

1987-01-01

Habitat Suitability Index (SI) curves are one method of presenting species habitat suitability criteria. The curves are often used with the Habitat Evaluation Procedures (HEP) and are necessary components of the Instream Flow Incremental Methodology (IFIM) (Armour et al. 1984). Bovee (1986) described three categories of SI curves or habitat suitability criteria based on the procedures and data used to develop the criteria. Category I curves are based on professional judgment, with 1ittle or no empirical data. Both Category II (utilization criteria) and Category III (preference criteria) curves have as their source data collected at locations where target species are observed or collected. Having Category II and Category III curves for all species of concern would be ideal. In reality, no SI curves are available for many species, and SI curves that require intensive field sampling often cannot be developed under prevailing constraints on time and costs. One alternative under these circumstances is the development and interim use of SI curves based on expert opinion. The Delphi technique (Pill 1971; Delbecq et al. 1975; Linstone and Turoff 1975) is one method used for combining the knowledge and opinions of a group of experts. The purpose of this report is to describe how the Delphi technique may be used to develop expert-opinion-based SI curves.

Search for scalar-tensor gravity theories with a non-monotonic time evolution of the speed-up factor

Energy Technology Data Exchange (ETDEWEB)

Navarro, A [Dept Fisica, Universidad de Murcia, E30071-Murcia (Spain); Serna, A [Dept Fisica, Computacion y Comunicaciones, Universidad Miguel Hernandez, E03202-Elche (Spain); Alimi, J-M [Lab. de l' Univers et de ses Theories (LUTH, CNRS FRE2462), Observatoire de Paris-Meudon, F92195-Meudon (France)

2002-08-21

We present a method to detect, in the framework of scalar-tensor gravity theories, the existence of stationary points in the time evolution of the speed-up factor. An attractive aspect of this method is that, once the particular scalar-tensor theory has been specified, the stationary points are found through a simple algebraic equation which does not contain any integration. By applying this method to the three classes of scalar-tensor theories defined by Barrow and Parsons, we have found several new cosmological models with a non-monotonic evolution of the speed-up factor. The physical interest of these models is that, as previously shown by Serna and Alimi, they predict the observed primordial abundance of light elements for a very wide range of baryon density. These models are then consistent with recent CMB and Lyman-{alpha} estimates of the baryon content of the universe.

Comparison of Themodynamic and Transport Property Models for Computing Equilibrium High Enthalpy Flows

Science.gov (United States)

Ramasahayam, Veda Krishna Vyas; Diwakar, Anant; Bodi, Kowsik

2017-11-01

To study the flow of high temperature air in vibrational and chemical equilibrium, accurate models for thermodynamic state and transport phenomena are required. In the present work, the performance of a state equation model and two mixing rules for determining equilibrium air thermodynamic and transport properties are compared with that of curve fits. The thermodynamic state model considers 11 species which computes flow chemistry by an iterative process and the mixing rules considered for viscosity are Wilke and Armaly-Sutton. The curve fits of Srinivasan, which are based on Grabau type transition functions, are chosen for comparison. A two-dimensional Navier-Stokes solver is developed to simulate high enthalpy flows with numerical fluxes computed by AUSM+-up. The accuracy of state equation model and curve fits for thermodynamic properties is determined using hypersonic inviscid flow over a circular cylinder. The performance of mixing rules and curve fits for viscosity are compared using hypersonic laminar boundary layer prediction on a flat plate. It is observed that steady state solutions from state equation model and curve fits match with each other. Though curve fits are significantly faster the state equation model is more general and can be adapted to any flow composition.

Advection endash diffusion around a curved obstacle

International Nuclear Information System (INIS)

Ahluwalia, D.S.; Keller, J.B.; Knessl, C.

1998-01-01

Advection and diffusion of a substance around a curved obstacle is analyzed when the advection velocity is large compared to the diffusion velocity, i.e., when the Peclet number is large. Asymptotic expressions for the concentration are obtained by the use of boundary layer theory, matched asymptotic expansions, etc. The results supplement and extend previous ones for straight obstacles. They apply to electrophoresis, the flow of ground water, chromatography, sedimentation, etc. copyright 1998 American Institute of Physics

Exploring the physical controls of regional patterns of flow duration curves – Part 1: Insights from statistical analyses

Directory of Open Access Journals (Sweden)

S. Ye

2012-11-01

Full Text Available The flow duration curve (FDC is a classical method used to graphically represent the relationship between the frequency and magnitude of streamflow. In this sense it represents a compact signature of temporal runoff variability that can also be used to diagnose catchment rainfall-runoff responses, including similarity and differences between catchments. This paper is aimed at extracting regional patterns of the FDCs from observed daily flow data and elucidating the physical controls underlying these patterns, as a way to aid towards their regionalization and predictions in ungauged basins. The FDCs of total runoff (TFDC using multi-decadal streamflow records for 197 catchments across the continental United States are separated into the FDCs of two runoff components, i.e., fast flow (FFDC and slow flow (SFDC. In order to compactly display these regional patterns, the 3-parameter mixed gamma distribution is employed to characterize the shapes of the normalized FDCs (i.e., TFDC, FFDC and SFDC over the entire data record. This is repeated to also characterize the between-year variability of "annual" FDCs for 8 representative catchments chosen across a climate gradient. Results show that the mixed gamma distribution can adequately capture the shapes of the FDCs and their variation between catchments and also between years. Comparison between the between-catchment and between-year variability of the FDCs revealed significant space-time symmetry. Possible relationships between the parameters of the fitted mixed gamma distribution and catchment climatic and physiographic characteristics are explored in order to decipher and point to the underlying physical controls. The baseflow index (a surrogate for the collective impact of geology, soils, topography and vegetation, as well as climate is found to be the dominant control on the shapes of the normalized TFDC and SFDC, whereas the product of maximum daily precipitation and the fraction of non-rainy days

Measurement of activated rCBF by the 133Xe inhalation technique: a comparison of total versus partial curve analysis

International Nuclear Information System (INIS)

Leli, D.A.; Katholi, C.R.; Hazelrig, J.B.; Falgout, J.C.; Hannay, H.J.; Wilson, E.M.; Wills, E.L.; Halsey, J.H. Jr.

1985-01-01

An initial assessment of the differential sensitivity of total versus partial curve analysis in estimating task related focal changes in cortical blood flow measured by the 133 Xe inhalation technique was accomplished by comparing the patterns during the performance of two sensorimotor tasks by normal subjects. The validity of these patterns was evaluated by comparing them to the activation patterns expected from activation studies with the intra-arterial technique and the patterns expected from neuropsychological research literature. Subjects were 10 young adult nonsmoking healthy male volunteers. They were administered two tasks having identical sensory and cognitive components but different response requirements (oral versus manual). The regional activation patterns produced by the tasks varied with the method of curve analysis. The activation produced by the two tasks was very similar to that predicted from the research literature only for total curve analysis. To the extent that the predictions are correct, these data suggest that the 133 Xe inhalation technique is more sensitive to regional flow changes when flow parameters are estimated from the total head curve. The utility of the total head curve analysis will be strengthened if similar sensitivity is demonstrated in future studies assessing normal subjects and patients with neurological and psychiatric disorders

Unsteady fluid flow in a slightly curved pipe: A comparative study of a matched asymptotic expansions solution with a single analytical solution

Energy Technology Data Exchange (ETDEWEB)

Messaris, Gerasimos A. T., E-mail: messaris@upatras.gr [Department of Physics, Division of Theoretical Physics, University of Patras, GR 265 04 Rion (Greece); School of Science and Technology, Hellenic Open University, 11 Sahtouri Street, GR 262 22 Patras (Greece); Hadjinicolaou, Maria [School of Science and Technology, Hellenic Open University, 11 Sahtouri Street, GR 262 22 Patras (Greece); Karahalios, George T. [Department of Physics, Division of Theoretical Physics, University of Patras, GR 265 04 Rion (Greece)

2016-08-15

The present work is motivated by the fact that blood flow in the aorta and the main arteries is governed by large finite values of the Womersley number α and for such values of α there is not any analytical solution in the literature. The existing numerical solutions, although accurate, give limited information about the factors that affect the flow, whereas an analytical approach has an advantage in that it can provide physical insight to the flow mechanism. Having this in mind, we seek analytical solution to the equations of the fluid flow driven by a sinusoidal pressure gradient in a slightly curved pipe of circular cross section when the Womersley number varies from small finite to infinite values. Initially the equations of motion are expanded in terms of the curvature ratio δ and the resulting linearized equations are solved analytically in two ways. In the first, we match the solution for the main core to that for the Stokes boundary layer. This solution is valid for very large values of α. In the second, we derive a straightforward single solution valid to the entire flow region and for 8 ≤ α < ∞, a range which includes the values of α that refer to the physiological flows. Each solution contains expressions for the axial velocity, the stream function, and the wall stresses and is compared to the analogous forms presented in other studies. The two solutions give identical results to each other regarding the axial flow but differ in the secondary flow and the circumferential wall stress, due to the approximations employed in the matched asymptotic expansion process. The results on the stream function from the second solution are in agreement with analogous results from other numerical solutions. The second solution predicts that the atherosclerotic plaques may develop in any location around the cross section of the aortic wall unlike to the prescribed locations predicted by the first solution. In addition, it gives circumferential wall stresses

Unsteady fluid flow in a slightly curved pipe: A comparative study of a matched asymptotic expansions solution with a single analytical solution

International Nuclear Information System (INIS)

Messaris, Gerasimos A. T.; Hadjinicolaou, Maria; Karahalios, George T.

2016-01-01

The present work is motivated by the fact that blood flow in the aorta and the main arteries is governed by large finite values of the Womersley number α and for such values of α there is not any analytical solution in the literature. The existing numerical solutions, although accurate, give limited information about the factors that affect the flow, whereas an analytical approach has an advantage in that it can provide physical insight to the flow mechanism. Having this in mind, we seek analytical solution to the equations of the fluid flow driven by a sinusoidal pressure gradient in a slightly curved pipe of circular cross section when the Womersley number varies from small finite to infinite values. Initially the equations of motion are expanded in terms of the curvature ratio δ and the resulting linearized equations are solved analytically in two ways. In the first, we match the solution for the main core to that for the Stokes boundary layer. This solution is valid for very large values of α. In the second, we derive a straightforward single solution valid to the entire flow region and for 8 ≤ α < ∞, a range which includes the values of α that refer to the physiological flows. Each solution contains expressions for the axial velocity, the stream function, and the wall stresses and is compared to the analogous forms presented in other studies. The two solutions give identical results to each other regarding the axial flow but differ in the secondary flow and the circumferential wall stress, due to the approximations employed in the matched asymptotic expansion process. The results on the stream function from the second solution are in agreement with analogous results from other numerical solutions. The second solution predicts that the atherosclerotic plaques may develop in any location around the cross section of the aortic wall unlike to the prescribed locations predicted by the first solution. In addition, it gives circumferential wall stresses

Unsteady fluid flow in a slightly curved pipe: A comparative study of a matched asymptotic expansions solution with a single analytical solution

Science.gov (United States)

Messaris, Gerasimos A. T.; Hadjinicolaou, Maria; Karahalios, George T.

2016-08-01

The present work is motivated by the fact that blood flow in the aorta and the main arteries is governed by large finite values of the Womersley number α and for such values of α there is not any analytical solution in the literature. The existing numerical solutions, although accurate, give limited information about the factors that affect the flow, whereas an analytical approach has an advantage in that it can provide physical insight to the flow mechanism. Having this in mind, we seek analytical solution to the equations of the fluid flow driven by a sinusoidal pressure gradient in a slightly curved pipe of circular cross section when the Womersley number varies from small finite to infinite values. Initially the equations of motion are expanded in terms of the curvature ratio δ and the resulting linearized equations are solved analytically in two ways. In the first, we match the solution for the main core to that for the Stokes boundary layer. This solution is valid for very large values of α. In the second, we derive a straightforward single solution valid to the entire flow region and for 8 ≤ α flows. Each solution contains expressions for the axial velocity, the stream function, and the wall stresses and is compared to the analogous forms presented in other studies. The two solutions give identical results to each other regarding the axial flow but differ in the secondary flow and the circumferential wall stress, due to the approximations employed in the matched asymptotic expansion process. The results on the stream function from the second solution are in agreement with analogous results from other numerical solutions. The second solution predicts that the atherosclerotic plaques may develop in any location around the cross section of the aortic wall unlike to the prescribed locations predicted by the first solution. In addition, it gives circumferential wall stresses augmented by approximately 100% with respect to the matched asymptotic expansions

Localization and Instability in Sheared Granular Materials: Role of Pore Fluids and Non-monotonic Rate Dependent Rheology

Science.gov (United States)

Ma, X.; Elbanna, A. E.; Kothari, K.

2017-12-01

Fault zone dynamics hold the key to resolving many outstanding geophysical problems including the heat flow paradox, discrepancy between fault static and dynamic strength, and energy partitioning. Most fault zones that generate tectonic events are gouge filled and fluid saturated posing the need for formulating gouge-specific constitutive models that capture spatially heterogeneous compaction and dilation, non-monotonic rate dependence, and transition between localized and distributed deformation. In this presentation, we focus primarily on elucidating microscopic underpinnings for shear banding and stick-slip instabilities in sheared saturated granular materials and explore their implications for earthquake dynamics. We use a non-equilibrium thermodynamics model, the Shear Transformation Zone theory, to investigate the dynamics of strain localization and its connection to stability of sliding in the presence and absence of pore fluids. We also consider the possible influence of self-induced mechanical vibrations as well as the role of external acoustic vibrations as analogue for triggering by a distant event. For the dry case, our results suggest that at low and intermediate strain rates, persistent shear bands develop only in the absence of vibrations. Vibrations tend to fluidize the granular network and de-localize slip at these rates. Stick-slip is only observed for rough grains and it is confined to the shear band. At high strain rates, stick-slip disappears and the different systems exhibit similar stress-slip response. Changing the vibration intensity, duration or time of application alters the system response and may cause long-lasting rheological changes. The presence of pore fluids modifies the stick slip pattern and may lead to both loss and development of slip instability depending on the value of the confining pressure, imposed strain rate and hydraulic parameters. We analyze these observations in terms of possible transitions between rate

Testicular blood flow in varicocele

International Nuclear Information System (INIS)

Iwamoto, Teruaki; Hirokawa, Makoto.

1986-01-01

Radioisotopic scrotal angiography was applied for study of testicular blood flow of patients with varicocele. Following iv. bolus injection of 10 ∼ 20 mCi of Tc human serum albumine, Tc RBC or Tc pertechnetate, time activity curve of radioactivity at corresponding bilateral areas of scrotum was simultaneously generated and compared. Eighty-four patients with overt varicocele (grade 2 and 3) at left side only, were selected for the present study and eight healthy young volunteers were studied as a control group. Three patterns of time activity curves were recognized. They are as follows. Type 1, where radioactivity was accumulated quickly in left side and then decreased gradually. Bilateral time activity curves were asymmetrical. Type 2, where time activity curves rose gradually and to a higher level at the left side than at the right side. Type 3, where bilateral time activity curves increased gradually, and symmetrically. All of the control group showed the same pattern as Type 3. Of the 84 patients examined, 34 patients showed Type 1, including 7 with grade 2 and 27 with grade 3. Twenty-four patients showed Type 2. consisting of 12 with grade 2 and 12 with grade 3. Twenty-six patients showed Type 3, consisting of 14 with grade 2 and 12 with grade 3. We presumed the following about testicular blood flow in varicocele: Type 1 pattern shows retrograde blood flow from the renal vein to the internal spermatic vein, Type 2 pattern shows poor venous return through the internal spermatic vein and Type 3 pattern shows good venous return though the presence of dilatated pampiniform plexus. (author)

Spatially varying dispersion to model breakthrough curves.

Science.gov (United States)

Li, Guangquan

2011-01-01

Often the water flowing in a karst conduit is a combination of contaminated water entering at a sinkhole and cleaner water released from the limestone matrix. Transport processes in the conduit are controlled by advection, mixing (dilution and dispersion), and retention-release. In this article, a karst transport model considering advection, spatially varying dispersion, and dilution (from matrix seepage) is developed. Two approximate Green's functions are obtained using transformation of variables, respectively, for the initial-value problem and for the boundary-value problem. A numerical example illustrates that mixing associated with strong spatially varying conduit dispersion can cause strong skewness and long tailing in spring breakthrough curves. Comparison of the predicted breakthrough curve against that measured from a dye-tracing experiment between Ames Sink and Indian Spring, Northwest Florida, shows that the conduit dispersivity can be as large as 400 m. Such a large number is believed to imply strong solute interaction between the conduit and the matrix and/or multiple flow paths in a conduit network. It is concluded that Taylor dispersion is not dominant in transport in a karst conduit, and the complicated retention-release process between mobile- and immobile waters may be described by strong spatially varying conduit dispersion. Copyright © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.

Long-term Behavior of Hydrocarbon Production Curves

Science.gov (United States)

Lovell, A.; Karra, S.; O'Malley, D.; Viswanathan, H. S.; Srinivasan, G.

2017-12-01

Recovering hydrocarbons (such as natural gas) from naturally-occurring formations with low permeability has had a huge impact on the energy sector, however, recovery rates are low due to poor understanding of recovery and transport mechanisms [1]. The physical mechanisms that control the production of hydrocarbon are only partially understood. Calculations have shown that the short-term behavior in the peak of the production curve is understood to come from the free hydrocarbons in the fracture networks, but the long-term behavior of these curves is often underpredicted [2]. This behavior is thought to be due to small scale processes - such as matrix diffusion, desorption, and connectivity in the damage region around the large fracture network. In this work, we explore some of these small-scale processes using discrete fracture networks (DFN) and the toolkit dfnWorks [3], the matrix diffusion, size of the damage region, and distribution of free gas between the fracture networks and rock matrix. Individual and combined parameter spaces are explored, and comparisons of the resulting production curves are made to experimental site data from the Haynesville formation [4]. We find that matrix diffusion significantly controls the shape of the tail of the production curve, while the distribution of free gas impacts the relative magnitude of the peak to the tail. The height of the damage region has no effect on the shape of the tail. Understanding the constrains of the parameter space based on site data is the first step in rigorously quantifying the uncertainties coming from these types of systems, which can in turn optimize and improve hydrocarbon recovery. [1] C. McGlade, et. al., (2013) Methods of estimating shale gas resources - comparison, evaluation, and implications, Energy, 59, 116-125 [2] S. Karra, et. al., (2015) Effect of advective flow in fractures and matrix diffusion on natural gas production, Water Resources Research, 51(10), 8646-8657 [3] J.D. Hyman, et

Fermions in curved spacetimes

Energy Technology Data Exchange (ETDEWEB)

Lippoldt, Stefan

2016-01-21

In this thesis we study a formulation of Dirac fermions in curved spacetime that respects general coordinate invariance as well as invariance under local spin base transformations. We emphasize the advantages of the spin base invariant formalism both from a conceptual as well as from a practical viewpoint. This suggests that local spin base invariance should be added to the list of (effective) properties of (quantum) gravity theories. We find support for this viewpoint by the explicit construction of a global realization of the Clifford algebra on a 2-sphere which is impossible in the spin-base non-invariant vielbein formalism. The natural variables for this formulation are spacetime-dependent Dirac matrices subject to the Clifford-algebra constraint. In particular, a coframe, i.e. vielbein field is not required. We disclose the hidden spin base invariance of the vielbein formalism. Explicit formulas for the spin connection as a function of the Dirac matrices are found. This connection consists of a canonical part that is completely fixed in terms of the Dirac matrices and a free part that can be interpreted as spin torsion. The common Lorentz symmetric gauge for the vielbein is constructed for the Dirac matrices, even for metrics which are not linearly connected. Under certain criteria, it constitutes the simplest possible gauge, demonstrating why this gauge is so useful. Using the spin base formulation for building a field theory of quantized gravity and matter fields, we show that it suffices to quantize the metric and the matter fields. This observation is of particular relevance for field theory approaches to quantum gravity, as it can serve for a purely metric-based quantization scheme for gravity even in the presence of fermions. Hence, in the second part of this thesis we critically examine the gauge, and the field-parametrization dependence of renormalization group flows in the vicinity of non-Gaussian fixed points in quantum gravity. While physical

The Characteristics of Turbulence in Curved Pipes under Highly Pulsatile Flow Conditions

Science.gov (United States)

Kalpakli, A.; Örlü, R.; Tillmark, N.; Alfredsson, P. Henrik

High speed stereoscopic particle image velocimetry has been employed to provide unique data from a steady and highly pulsatile turbulent flow at the exit of a 90 degree pipe bend. Both the unsteady behaviour of the Dean cells under steady conditions, the so called "swirl switching" phenomenon, as well as the secondary flow under pulsations have been reconstructed through proper orthogonal decomposition. The present data set constitutes - to the authors' knowledge - the first detailed investigation of a turbulent, pulsatile flow through a pipe bend.

Numerical analysis of Sakiadis flow problem considering Maxwell nanofluid

Directory of Open Access Journals (Sweden)

Mustafa Meraj

2017-01-01

Full Text Available This article investigates the flow of Maxwell nanofluid over a moving plate in a calm fluid. Novel aspects of Brownian motion and thermophoresis are taken into consideration. Revised model for passive control of nanoparticle volume fraction at the plate is used in this study. The formulated differential system is solved numerically by employing shooting approach together with fourth-fifth-order-Runge-Kutta integration procedure and Newton’s method. The solutions are greatly influenced with the variation of embedded parameters which include the local Deborah number, the Brownian motion parameter, the thermophoresis parameter, the Prandtl number, and the Schmidt number. We found that the variation in velocity distribution with an increase in local Deborah number is non-monotonic. Moreover, the reduced Nusselt number has a linear and direct relationship with the local Deborah number.

Mean flow produced by small-amplitude vibrations of a liquid bridge with its free surface covered with an insoluble surfactant

Science.gov (United States)

Carrión, Luis M.; Herrada, Miguel A.; Montanero, José M.; Vega, José M.

2017-09-01

As is well known, confined fluid systems subject to forced vibrations produce mean flows, called in this context streaming flows. These mean flows promote an overall mass transport in the fluid that has consequences in the transport of passive scalars and surfactants, when these are present in a fluid interface. Such transport causes surfactant concentration inhomogeneities that are to be counterbalanced by Marangoni elasticity. Therefore, the interaction of streaming flows and Marangoni convection is expected to produce new flow structures that are different from those resulting when only one of these effects is present. The present paper focuses on this interaction using the liquid bridge geometry as a paradigmatic system for the analysis. Such analysis is based on an appropriate post-processing of the results obtained via direct numerical simulation of the system for moderately small viscosity, a condition consistent with typical experiments of vibrated millimetric liquid bridges. It is seen that the flow patterns show a nonmonotone behavior as the Marangoni number is increased. In addition, the strength of the mean flow at the free surface exhibits two well-defined regimes as the forcing amplitude increases. These regimes show fairly universal power-law behaviors.

Bayesian analysis of stage-fall-discharge rating curves and their uncertainties

Science.gov (United States)

Mansanarez, Valentin; Le Coz, Jérôme; Renard, Benjamin; Lang, Michel; Pierrefeu, Gilles; Le Boursicaud, Raphaël; Pobanz, Karine

2016-04-01

Stage-fall-discharge (SFD) rating curves are traditionally used to compute streamflow records at sites where the energy slope of the flow is variable due to variable backwater effects. Building on existing Bayesian approaches, we introduce an original hydraulics-based method for developing SFD rating curves used at twin gauge stations and estimating their uncertainties. Conventional power functions for channel and section controls are used, and transition to a backwater-affected channel control is computed based on a continuity condition, solved either analytically or numerically. The difference between the reference levels at the two stations is estimated as another uncertain parameter of the SFD model. The method proposed in this presentation incorporates information from both the hydraulic knowledge (equations of channel or section controls) and the information available in the stage-fall-discharge observations (gauging data). The obtained total uncertainty combines the parametric uncertainty and the remnant uncertainty related to the model of rating curve. This method provides a direct estimation of the physical inputs of the rating curve (roughness, width, slope bed, distance between twin gauges, etc.). The performance of the new method is tested using an application case affected by the variable backwater of a run-of-the-river dam: the Rhône river at Valence, France. In particular, a sensitivity analysis to the prior information and to the gauging dataset is performed. At that site, the stage-fall-discharge domain is well documented with gaugings conducted over a range of backwater affected and unaffected conditions. The performance of the new model was deemed to be satisfactory. Notably, transition to uniform flow when the overall range of the auxiliary stage is gauged is correctly simulated. The resulting curves are in good agreement with the observations (gaugings) and their uncertainty envelopes are acceptable for computing streamflow records. Similar

Estimation of curve number by DAWAST model

Energy Technology Data Exchange (ETDEWEB)

Kim, Tai Cheol; Park, Seung Ki; Moon, Jong Pil [Chungnam National University, Taejon (Korea, Republic of)

1997-10-31

It is one of the most important factors to determine the effective rainfall for estimation of flood hydrograph in design schedule. SCS curve number (CN) method has been frequently used to estimate the effective rainfall of synthesized design flood hydrograph for hydraulic structures. But, it should be cautious to apply SCS-CN originally developed in U.S.A to watersheds in Korea, because characteristics of watersheds in Korea and cropping patterns especially like a paddy land cultivation are quite different from those in USA. New CN method has been introduced. Maximum storage capacity which was herein defined as U{sub max} can be calibrated from the stream flow data and converted to new CN-I of driest condition of soil moisture in the given watershed. Effective rainfall for design flood hydrograph can be estimated by the curve number developed in the watersheds in Korea. (author). 14 refs., 5 tabs., 3 figs.

Design of Gerotor Using Cycloid and Circular-Arc Curves

Energy Technology Data Exchange (ETDEWEB)

Choi, Tae Hoon; Kim, Moon Saeng; Jung, Sung Yuen; Kim, Chul [Pusan National University, Busan (Korea, Republic of); Lee, Geun Su [Samhan Co., Ltd, Seoul (Korea, Republic of)

2011-03-15

The new gerotor developed in this paper has an inner rotor in which a circular arc is inserted between the hypocycloid and epicycloid curves, whereas the outer rotor is designed using the simulation results for the rotor and a modification method. The new gerotor has no cusps and loops and no limit on the eccentricity. We increase the average flow rate by adding a new design parameter, {gamma}, which is the inclined angle of the inner rotor at the intersection of the hypocycloid and the circular arc. A calculation method to calculate the chamber area is also developed. This method can also be used to calculate the flow rate and flow rate irregularity when the contact points are unknown. The control of eccentricity and {gamma} is expected to lead to an efficient rotor.

General spectral flow formula for fixed maximal domain

DEFF Research Database (Denmark)

Booss-Bavnbek, Bernhelm; Zhu, Chaofeng

2005-01-01

of the resulting continuous family of (unbounded) self-adjoint Fredholm operators in terms of the Maslov index of two related curves of Lagrangian spaces. One curve is given by the varying domains, the other by the Cauchy data spaces. We provide rigorous definitions of the underlying concepts of spectral theory......We consider a continuous curve of linear elliptic formally self-adjoint differential operators of first order with smooth coefficients over a compact Riemannian manifold with boundary together with a continuous curve of global elliptic boundary value problems. We express the spectral flow...... and symplectic analysis and give a full (and surprisingly short) proof of our General Spectral Flow Formula for the case of fixed maximal domain. As a side result, we establish local stability of weak inner unique continuation property (UCP) and explain its role for parameter dependent spectral theory....

Boundary layer for non-newtonian fluids on curved surfaces

International Nuclear Information System (INIS)

Stenger, N.

1981-04-01

By using the basic equation of fluid motion (conservation of mass and momentum) the boundary layer parameters for a Non-Newtonian, incompressible and laminar fluid flow, has been evaluated. As a test, the flat plate boundary layer is first analized and afterwards, a case with pressure gradient, allowing separation, is studied. In the case of curved surfaces, the problem is first developed in general and afterwards particularized to a circular cylinder. Finally suction and slip in the flow interface are examined. The power law model is used to represent the stress strain relationship in Non-Newtonian flow. By varying the fluid exponent one can then, have an idea of how the Non-Newtonian behavior of the flow influences the parameters of the boundary layer. Two equations, in an appropriate coordinate system have been obtained after an order of magnitude analysis of the terms in the equations of motion is performed. (Author) [pt

Debris Flow Risk Management Framework and Risk Analysis in Taiwan, A Preliminary Study

Science.gov (United States)

Tsao, Ting-Chi; Hsu, Wen-Ko; Chiou, Lin-Bin; Cheng, Chin-Tung; Lo, Wen-Chun; Chen, Chen-Yu; Lai, Cheng-Nong; Ju, Jiun-Ping

2010-05-01

Taiwan is located on a seismically active mountain belt between the Philippine Sea plate and Eurasian plate. After 1999's Chi-Chi earthquake (Mw=7.6), landslide and debris flow occurred frequently. In Aug. 2009, Typhoon Morakot struck Taiwan and numerous landslides and debris flow events, some with tremendous fatalities, were observed. With limited resources, authorities should establish a disaster management system to cope with slope disaster risks more effectively. Since 2006, Taiwan's authority in charge of debris flow management, the Soil and Water Conservation Bureau (SWCB), completed the basic investigation and data collection of 1,503 potential debris flow creeks around Taiwan. During 2008 and 2009, a debris flow quantitative risk analysis (QRA) framework, based on landslide risk management framework of Australia, was proposed and conducted on 106 creeks of the 30 villages with debris flow hazard history. Information and value of several types of elements at risk (bridge, road, building and crop) were gathered and integrated into a GIS layer, with the vulnerability model of each elements at risk applied. Through studying the historical hazard events of the 30 villages, numerical simulations of debris flow hazards with different magnitudes (5, 10, 25, 50, 100 and 200 years return period) were conducted, the economic losses and fatalities of each scenario were calculated for each creek. When taking annual exceeding probability into account, the annual total risk of each creek was calculated, and the results displayed on a debris flow risk map. The number of fatalities and frequency were calculated, and the F-N curves of 106 creeks were provided. For F-N curves, the individual risk to life per year of 1.0E-04 and slope of 1, which matched with international standards, were considered to be an acceptable risk. Applying the results of the 106 creeks onto the F-N curve, they were divided into 3 categories: Unacceptable, ALARP (As Low As Reasonable Practicable) and

Non-monotonic piezoresistive behaviour of graphene nanoplatelet (GNP-polymer composite flexible films prepared by solvent casting

Directory of Open Access Journals (Sweden)

S. Makireddi

2017-07-01

Full Text Available Graphene-polymer nanocomposite films show good piezoresistive behaviour and it is reported that the sensitivity increases either with the increased sheet resistance or decreased number density of the graphene fillers. A little is known about this behaviour near the percolation region. In this study, graphene nanoplatelet (GNP/poly (methyl methacrylate (PMMA flexible films are fabricated via solution casting process at varying weight percent of GNP. Electrical and piezoresistive behaviour of these films is studied as a function of GNP concentration. Piezoresistive strain sensitivity of the films is measured by affixing the film to an aluminium specimen which is subjected to monotonic uniaxial tensile load. The change in resistance of the film with strain is monitored using a four probe. An electrical percolation threshold at 3 weight percent of GNP is observed. We report non-monotonic piezoresistive behaviour of these films as a function GNP concentration. We observe an increase in gauge factor (GF with unstrained resistance of the films up to a critical resistance corresponding to percolation threshold. Beyond this limit the GF decreases with unstrained resistance.

About the method of approximation of a simple closed plane curve with a sharp edge

Directory of Open Access Journals (Sweden)

Zelenyy A.S.

2017-02-01

Full Text Available it was noted in the article, that initially the problem of interpolation of the simple plane curve arose in the problem of simulation of subsonic flow around a body with the subsequent calculation of the velocity potential using the vortex panel method. However, as it turned out, the practical importance of this method is much wider. This algorithm can be successfully applied in any task that requires a discrete set of points which describe an arbitrary curve: potential function method, flow around an airfoil with the trailing edge (airfoil, liquid drop, etc., analytic expression, which is very difficult to obtain, creation of the font and logo and in some tasks of architecture and garment industry.

Curved anode wire chambers for x-ray diffraction applications

International Nuclear Information System (INIS)

Perez-Mendez, V.; Wiedenbeck, P.; Wagner, C.N.J.; Woelfel, E.

1983-01-01

Curved position sensitive proportional detectors are described. The first has a radius of curvature of 135 mm and a 60 0 angular range. The second has a radius of curvature of 360 mm and a 45 0 angular range. For high quantum efficiency for x-ray energies up to 60 keV, a relatively large x-ray path and high gas pressure are required. The anode wires are suspended in circular arcs by the interaction of a current flowing through them and a magnetic field provided by two permanent magnets placed above and below the wire running parallel to it over the full length of the curved chambers. Anode wire stability under the combined action of the magnetic and electrostatic forces is discussed

Observation of mass flux through hcp 4He off the melting curve

International Nuclear Information System (INIS)

Ray, M W; Hallock, R B

2009-01-01

Solid hcp 4 He has been created off the melting curve using two growth techniques. In an effort to observe the flow of 4 He through the solid, rather than squeezing the solid directly, the experimental apparatus allows injection of 4 He atoms from superfluid in porous Vycor directly into the solid. We will describe the apparatus and our observations. Evidence for the transport of mass through a sample cell filled with hcp solid 4 He off the melting curve is found. The temperature and pressure dependence of this behavior will be presented.

Experimental determination of sorption in fractured flow systems

Science.gov (United States)

Zimmerman, Mitchell D.; Bennett, Philip C.; Sharp, John M.; Choi, Wan-Joo

2002-09-01

Fracture "skins" are alteration zones on fracture surfaces created by a variety of biological, chemical, and physical processes. Skins increase surface area, where sorption occurs, compared to the unaltered rock matrix. This study examines the sorption of organic solutes on altered fracture surfaces in an experimental fracture-flow apparatus. Fracture skins containing abundant metal oxides, clays, and organic material from the Breathitt Formation (Kentucky, USA) were collected in a manner such that skin surface integrity was maintained. The samples were reassembled in the lab in a flow-through apparatus that simulated ˜2.7 m of a linear fracture "conduit." A dual-tracer injection scheme was utilized with the sorbing or reactive tracer compared to a non-reactive tracer (chloride) injected simultaneously. Sorption was assessed from the ratio of the first temporal moments of the breakthrough curves and from the loss of reactive tracer mass and evaluated as a function of flow velocity and solute type. The breakthrough curves suggest dual-flow regimes in the fracture with both sorbing and non-sorbing flow fields. Significant sorption occurs for the reactive components, and sorption increased with decreasing flow rate and decreasing compound solubility. Based on moment analysis, however, there was little retardation of the center of solute mass. These data suggest that non-equilibrium sorption processes dominate and that slow desorption and boundary layer diffusion cause extensive tailing in the breakthrough curves.

Are microbubbles free flowing tracers through the Myocardium? Comparison of indicator-dilution curves obtained from dye dilution and echo contrast using harmonic power Doppler imaging.

Science.gov (United States)

Tiemann, K; Schlosser, T; Pohl, C; Bimmel, D; Wietasch, G; Hoeft, A; Likungu, J; Vahlhaus, C; Kuntz, S; Nanda, N C; Becher, H; Lüderitz, B

2000-01-01

Harmonic power Doppler imaging (H-PDI) has been introduced into the field of contrast echocardiography as a contrast-specific imaging modality. However, there has been considerable skepticism as to whether H-PDI would be quantifiable, because it depends on the destruction of microbubbles and has more complex signal processing than gray scale imaging. The aim of the present study was to evaluate the relationship between the concentration of microbubbles and the resulting H-PDI signals even under conditions where bubble destruction is most likely. Furthermore, we evaluated whether microbubbles of Levovist freely pass the microcirculation, which is a prerequisite for the assessment of myocardial blood flow. A strong positive correlation was found between the H-PDI signals and the amount of microbubbles up to the onset of acoustic shadowing (r = 0. 968, Pgreen (ICG) in both a flow phantom and a working heart setup. The mean transit times (MTTs) through the myocardium of both agents were compared after a bolus injection into the left coronary artery. A close correlation was observed between 1/MTT and flow in both setups (r>0.98, Pgreen. We conclude that microbubbles fulfill the prerequisites of free flowing tracers through the myocardium. Furthermore, H-PDI technology allows a reliable assessment of time-concentration curves of air-filled microbubbles up to the onset of acoustic shadowing.

Three-dimensional effects of curved plasma actuators in quiescent air

International Nuclear Information System (INIS)

Wang Chincheng; Durscher, Ryan; Roy, Subrata

2011-01-01

This paper presents results on a new class of curved plasma actuators for the inducement of three-dimensional vortical structures. The nature of the fluid flow inducement on a flat plate, in quiescent conditions, due to four different shapes of dielectric barrier discharge (DBD) plasma actuators is numerically investigated. The three-dimensional plasma kinetic equations are solved using our in-house, finite element based, multiscale ionized gas (MIG) flow code. Numerical results show electron temperature and three dimensional plasma force vectors for four shapes, which include linear, triangular, serpentine, and square actuators. Three-dimensional effects such as pinching and spreading the neighboring fluid are observed for serpentine and square actuators. The mechanisms of vorticity generation for DBD actuators are discussed. Also the influence of geometric wavelength (λ) and amplitude (Λ) of the serpentine and square actuators on vectored thrust inducement is predicted. This results in these actuators producing significantly better flow mixing downstream as compared to the standard linear actuator. Increasing the wavelengths of serpentine and square actuators in the spanwise direction is shown to enhance the pinching effect giving a much higher vertical velocity. On the contrary, changing the amplitude of the curved actuator varies the streamwise velocity significantly influencing the near wall jet. Experimental data for a serpentine actuator are also reported for validation purpose.

A CLASS OF NONMONOTONE TRUST REGION ALGORITHMS FOR LINEARLY CONSTRAINED OPTIMIZATION%线性约束优化的一类非单调信赖域算法

Institute of Scientific and Technical Information of China (English)

葛恒武; 陈中文

2002-01-01

We present a class of nonmonotone trust region algorithms for linearly constrained optimization in this paper.The algorithm may adjust automatically the scope of the monotonicity by the degree that the quadratic model is "trusted".Under the suitable conditions,it is proved that any limit point of the infinite sequence generated by the algorithm is the Kuhn-Tucker point of the primal problem.Finally,some numerical results show that the new algorithm is very effective.

Motion of curves and solutions of two multi-component mKdV equations

International Nuclear Information System (INIS)

Yao Ruoxia; Qu Changzheng; Li Zhibin

2005-01-01

Two classes of multi-component mKdV equations have been shown to be integrable. One class called the multi-component geometric mKdV equation is exactly the system for curvatures of curves when the motion of the curves is governed by the mKdV flow. In this paper, exact solutions including solitary wave solutions of the two- and three-component mKdV equations are obtained, the symmetry reductions of the two-component geometric mKdV equation to ODE systems corresponding to it's Lie point symmetry groups are also given. Curves and their behavior corresponding to solitary wave solutions of the two-component geometric mKdV equation are presented

Supersonic flows past an obstacle in Yukawa liquids

Science.gov (United States)

Charan, Harish; Ganesh, Rajaraman

2018-04-01

Shock formation, when a supersonic flow passes a stationary obstacle, is ubiquitous in nature. Considering particles mediating via a Yukawa-type interaction as a prototype for a strongly coupled complex plasma, characterized by coupling strength (Γ, ratio of the average potential to kinetic energy per particle) and screening parameter (κ, ratio of the mean inter-particle distance to the shielding length), we address the fundamental problem of supersonic fluid flow U0, past a stationary obstacle immersed in this strongly coupled system. We here report the results on the bow shocks formed in Yukawa liquids when the liquid flows at speeds larger than the speed of sound in the system. Depending on the values of Mach number MC L=U/0 CL , where CL is the longitudinal speed of sound in the system, the bow shocks are found to be either traveling or localized. We find that for the transonic flows (0.8 ≲ MC L≲ 1.2), the bow shocks travel in the upstream direction opposite to the incoming fluid. The phase velocity of the traveling bow shocks is found to be a non-monotonous function of κ, varying as ∝1 /k1.11 at a fixed value of Γ, and is found to be independent of Γ at a fixed value of κ. It is observed that for the flow values with MC L>1.5 , the shock waves do not travel in the upstream direction but instead form a stationary arc like structure around the obstacle. For the fluid flows with 1 ≲ MC L≲ 2.6 , secondary bow shocks are seen to emerge behind the stationary obstacle which travel in the downstream direction, and the phase velocity of these secondary bow shocks is found to be equal to that of the primary bow shocks.

Transport on intermediate time scales in flows with cat's eye patterns

Science.gov (United States)

Pöschke, Patrick; Sokolov, Igor M.; Zaks, Michael A.; Nepomnyashchy, Alexander A.

2017-12-01

We consider the advection-diffusion transport of tracers in a one-parameter family of plane periodic flows where the patterns of streamlines feature regions of confined circulation in the shape of "cat's eyes," separated by meandering jets with ballistic motion inside them. By varying the parameter, we proceed from the regular two-dimensional lattice of eddies without jets to the sinusoidally modulated shear flow without eddies. When a weak thermal noise is added, i.e., at large Péclet numbers, several intermediate time scales arise, with qualitatively and quantitatively different transport properties: depending on the parameter of the flow, the initial position of a tracer, and the aging time, motion of the tracers ranges from subdiffusive to superballistic. We report on results of extensive numerical simulations of the mean-squared displacement for different initial conditions in ordinary and aged situations. These results are compared with a theory based on a Lévy walk that describes the intermediate-time ballistic regime and gives a reasonable description of the behavior for a certain class of initial conditions. The interplay of the walk process with internal circulation dynamics in the trapped state results at intermediate time scales in nonmonotonic characteristics of aging not captured by the Lévy walk model.

Unraveling the relationship between arterial flow and intra-aneurysmal hemodynamics.

Science.gov (United States)

Morales, Hernán G; Bonnefous, Odile

2015-02-26

Arterial flow rate affects intra-aneurysmal hemodynamics but it is not clear how their relationship is. This uncertainty hinders the comparison among studies, including clinical evaluations, like a pre- and post-treatment status, since arterial flow rates may differ at each time acquisition. The purposes of this work are as follows: (1) To study how intra-aneurysmal hemodynamics changes within the full physiological range of arterial flow rates. (2) To provide characteristic curves of intra-aneurysmal velocity, wall shear stress (WSS) and pressure as functions of the arterial flow rate. Fifteen image-based aneurysm models were studied using computational fluid dynamics (CFD) simulations. The full range of physiological arterial flow rates reported in the literature was covered by 11 pulsatile simulations. For each aneurysm, the spatiotemporal-averaged blood flow velocity, WSS and pressure were calculated. Spatiotemporal-averaged velocity inside the aneurysm linearly increases as a function of the mean arterial flow (minimum R(2)>0.963). Spatiotemporal-averaged WSS and pressure at the aneurysm wall can be represented by quadratic functions of the arterial flow rate (minimum R(2)>0.996). Quantitative characterizations of spatiotemporal-averaged velocity, WSS and pressure inside cerebral aneurysms can be obtained with respect to the arterial flow rate. These characteristic curves provide more information of the relationship between arterial flow and aneurysm hemodynamics since the full range of arterial flow rates is considered. Having these curves, it is possible to compare experimental studies and clinical evaluations when different flow conditions are used. Copyright © 2015 Elsevier Ltd. All rights reserved.

A parametric study on supersonic/hypersonic flutter behavior of aero-thermo-elastic geometrically imperfect curved skin panel

NARCIS (Netherlands)

Abbas, L.K.; Rui, X.; Marzocca, P.; Abdalla, M.; De Breuker, R.

2011-01-01

In this paper, the effect of the system parameters on the flutter of a curved skin panel forced by a supersonic/hypersonic unsteady flow is numerically investigated. The aeroelastic model investigated includes the third-order piston theory aerodynamics for modeling the flow-induced forces and the

Operation control of fluids pumping in curved pipes during annular flow: a numerical evaluation

Directory of Open Access Journals (Sweden)

T Andrade

2016-10-01

Full Text Available To generate projects which provide significant volume recovery from heavy oils reservoirs and improve existing projects, is important to develop new production and transport technologies, especially in the scenario of offshore fields. The core-flow technique is one of new technologies used in heavy oil transportation. This core-flow pattern is characterized by a water pellicle that is formed close or adjacent to the inner wall of the pipe, functioning as a lubricant. The oil flows in the center of the pipe causing a reduction in longitudinal pressure drop. In this sense, this work presents a numerical study of heavy oil annular flow (core-flow assisted by computational tool ANSYS CFX® Release 12.0. It was used a three-dimensional, transient and isothermal mathematical model considered by the mixture and turbulence - models to address the water-heavy oil two-phase flow, assuming laminar flow for oil phase and turbulent flow for water phase. Results of the pressure, velocity and volume fraction distributions of the phases and the pressure drop for different operation conditions are presented and evaluated. It was observed that the oil core flowing eccentrically in the pipe and stops of the water flux considerably increases the pressure drop in the pipe after the restart of the pump.

Development of a miniaturized mass-flow meter for an axial flow blood pump based on computational analysis.

Science.gov (United States)

Kosaka, Ryo; Nishida, Masahiro; Maruyama, Osamu; Yamane, Takashi

2011-09-01

In order to monitor the condition of patients with implantable left ventricular assist systems (LVAS), it is important to measure pump flow rate continuously and noninvasively. However, it is difficult to measure the pump flow rate, especially in an implantable axial flow blood pump, because the power consumption has neither linearity nor uniqueness with regard to the pump flow rate. In this study, a miniaturized mass-flow meter for discharged patients with an implantable axial blood pump was developed on the basis of computational analysis, and was evaluated in in-vitro tests. The mass-flow meter makes use of centrifugal force produced by the mass-flow rate around a curved cannula. An optimized design was investigated by use of computational fluid dynamics (CFD) analysis. On the basis of the computational analysis, a miniaturized mass-flow meter made of titanium alloy was developed. A strain gauge was adopted as a sensor element. The first strain gauge, attached to the curved area, measured both static pressure and centrifugal force. The second strain gauge, attached to the straight area, measured static pressure. By subtracting the output of the second strain gauge from the output of the first strain gauge, the mass-flow rate was determined. In in-vitro tests using a model circulation loop, the mass-flow meter was compared with a conventional flow meter. Measurement error was less than ±0.5 L/min and average time delay was 0.14 s. We confirmed that the miniaturized mass-flow meter could accurately measure the mass-flow rate continuously and noninvasively.

Blood flow determinations utilizing digital densitometry

International Nuclear Information System (INIS)

Lois, F.; Mankovich, N.J.; Gomes, A.S.

1987-01-01

A method of obtaining relative and absolute blood flow measurements from digital densitometry was evaluated with a simulated vessel phantom and a hydrodynamic model. A digital vascular imaging system capable of acquisition in 512 2 and 1024 2 mode was used. Relative and absolute blood flow were measured using parameters derived from the densitometric curve. Since application of densitometric data to absolute flow measurements requires the vessel diameter, an algorithm for vessel size determination was created. Gray scale changes were demonstrated to be linearly related to contrast concentration. The variance of vessel size determination was significantly different in all combinations of 1024 2 and 512 2 imaging with 15 cm or 35 cm field size. The error in vessel size determination was significantly less using the larger 1024 2 matrix and the smaller 15 cm image intensifier field size, as shown by the smaller variance. In relative flow determinations, there was good correlation between the flow and four parameters of the densitometric curve with no significant differences between 512 2 and 1024 2 imaging. Absolute flow determinations had slightly lower correlation to actual flow but were not significantly different from relative flow determinations. Relative and absolute blood flow determinations can be performed adequately with either 512 2 or 1024 2 imaging. The increased accuracy in vessel size determination with 1024 2 imaging makes this high resolution system potentially perferable to determine absolute blood flow. (orig.)

Kinetics of gravity-driven slug flow in partially wettable capillaries of varying cross section

Science.gov (United States)

Nissan, Alon; Wang, Qiuling; Wallach, Rony

2016-11-01

A mathematical model for slug (finite liquid volume) motion in not-fully-wettable capillary tubes with sinusoidally varying cross-sectional areas was developed. The model, based on the Navier-Stokes equation, accounts for the full viscous terms due to nonuniform geometry, the inertial term, the slug's front and rear meniscus hysteresis effect, and dependence of contact angle on flow velocity (dynamic contact angle). The model includes a velocity-dependent film that is left behind the advancing slug, reducing its mass. The model was successfully verified experimentally by recording slug movement in uniform and sinusoidal capillary tubes with a gray-scale high-speed camera. Simulation showed that tube nonuniformity has a substantial effect on slug flow pattern: in a uniform tube it is monotonic and depends mainly on the slug's momentary mass/length; an undulating tube radius results in nonmonotonic flow characteristics. The static nonzero contact angle varies locally in nonuniform tubes owing to the additional effect of wall slope. Moreover, the nonuniform cross-sectional area induces slug acceleration, deceleration, blockage, and metastable-equilibrium locations. Increasing contact angle further amplifies the geometry effect on slug propagation. The developed model provides a modified means of emulating slug flow in differently wettable porous media for intermittent inlet water supply (e.g., raindrops on the soil surface).

Transmission of wave energy in curved ducts. [acoustic propagation within rigid walls

Science.gov (United States)

Rostafinski, W.

1974-01-01

Investigation of the ability of circular bends to transmit acoustic energy flux. A formulation of wave-energy flow is developed for motion in curved ducts. A parametric study over a range of frequencies shows the ability of circular bends to transmit energy in the case of perfectly rigid walls.

Study on an Undershot Cross-Flow Water Turbine with Straight Blades

Directory of Open Access Journals (Sweden)

Yasuyuki Nishi

2015-01-01

Full Text Available Small-scale hydroelectric power generation has recently attracted considerable attention. The authors previously proposed an undershot cross-flow water turbine with a very low head suitable for application to open channels. The water turbine was of a cross-flow type and could be used in open channels with the undershot method, remarkably simplifying its design by eliminating guide vanes and the casing. The water turbine was fitted with curved blades (such as the runners of a typical cross-flow water turbine installed in tube channels. However, there was ambiguity as to how the blades’ shape influenced the turbine’s performance and flow field. To resolve this issue, the present study applies straight blades to an undershot cross-flow water turbine and examines the performance and flow field via experiments and numerical analyses. Results reveal that the output power and the turbine efficiency of the Straight Blades runner were greater than those of the Curved Blades runner regardless of the rotational speed. Compared with the Curved Blades runner, the output power and the turbine efficiency of the Straight Blades runner were improved by about 31.7% and about 67.1%, respectively.

Experimental results from a flowing-lithium target

International Nuclear Information System (INIS)

Annese, C.E.; Schwartz, K.E.

1982-01-01

Hydraulic stability of a free surface lithium jet was demonstrated at 260 0 C and from the middle-vacuum region of 0.01 Pa (10 - 4 Torr) up to 124 kPa (18 psia). The jet is formed by flowing lithium at rates to 0.04 m 3 /s (600 GPM) through a precisely defined nozzle which directs the flow along a curved wall where velocities of up to 17 m/s are attained. This nozzle and curved wall configuration form the basis of the Fusion Materials Irradiation Test (FMIT) Facility lithium target. A full-size experimental model of this target is presently under test with flowing lithium in the Experimental Lithium System (ELS). The FMIT is being developed for the Department of Energy by the Westinghouse Hanford Company at the Hanford Engineering Development Laboratory

Rational Degenerations of M-Curves, Totally Positive Grassmannians and KP2-Solitons

Science.gov (United States)

Abenda, Simonetta; Grinevich, Petr G.

2018-03-01

We establish a new connection between the theory of totally positive Grassmannians and the theory of M-curves using the finite-gap theory for solitons of the KP equation. Here and in the following KP equation denotes the Kadomtsev-Petviashvili 2 equation [see (1)], which is the first flow from the KP hierarchy. We also assume that all KP times are real. We associate to any point of the real totally positive Grassmannian Gr^{tp} (N,M) a reducible curve which is a rational degeneration of an M-curve of minimal genus {g=N(M-N)} , and we reconstruct the real algebraic-geometric data á la Krichever for the underlying real bounded multiline KP soliton solutions. From this construction, it follows that these multiline solitons can be explicitly obtained by degenerating regular real finite-gap solutions corresponding to smooth M-curves. In our approach, we rule the addition of each new rational component to the spectral curve via an elementary Darboux transformation which corresponds to a section of a specific projection Gr^{tp} (r+1,M-N+r+1)\\mapsto Gr^{tp} (r,M-N+r).

Centrifugal fingering in a curved Hele-Shaw cell: A generalized Euler's elastica shape for the two-fluid interface

Science.gov (United States)

Miranda, Jose; Brandao, Rodolfo

2017-11-01

We study a family of generalized elastica-like equilibrium shapes that arise at the interface separating two fluids in a curved rotating Hele-Shaw cell. This family of stationary interface solutions consists of shapes that balance the competing capillary and centrifugal forces in such a curved flow environment. We investigate how the emerging interfacial patterns are impacted by changes in the geometric properties of the curved Hele-Shaw cell. A vortex-sheet formalism is used to calculate the two-fluid interface curvature, and a gallery of possible shapes is provided to highlight a number of peculiar morphological features. A linear perturbation theory is employed to show that the most prominent aspects of these complex stationary patterns can be fairly well reproduced by the interplay of just two interfacial modes. The connection of these dominant modes to the geometry of the curved cell, as well as to the fluid dynamic properties of the flow, is discussed. We thank CNPq (Brazilian Research Council) for financial support under Grant No. 304821/2015-2.

Topological Sound and Flocking on Curved Surfaces

Science.gov (United States)

Shankar, Suraj; Bowick, Mark J.; Marchetti, M. Cristina

2017-07-01

Active systems on curved geometries are ubiquitous in the living world. In the presence of curvature, orientationally ordered polar flocks are forced to be inhomogeneous, often requiring the presence of topological defects even in the steady state because of the constraints imposed by the topology of the underlying surface. In the presence of spontaneous flow, the system additionally supports long-wavelength propagating sound modes that get gapped by the curvature of the underlying substrate. We analytically compute the steady-state profile of an active polar flock on a two-sphere and a catenoid, and show that curvature and active flow together result in symmetry-protected topological modes that get localized to special geodesics on the surface (the equator or the neck, respectively). These modes are the analogue of edge states in electronic quantum Hall systems and provide unidirectional channels for information transport in the flock, robust against disorder and backscattering.

Effect of region assignment on relative renal blood flow estimates using radionuclides

International Nuclear Information System (INIS)

Harris, C.C.; Ford, K.K.; Coleman, R.E.; Dunnick, N.R.

1984-01-01

To determine the value of the initial phase of the Tc-99m DTPA renogram in the direct estimation of relative renal blood flow in dogs, the ratios of the slopes of renal time-activity curves were compared with the ratios of measured blood flow. Radionuclide results were dependent on region-of-interest (ROI) and background ROI assignment, and correlated well with measured relative flow only with a maximum renal outline region. Curve slope ratios correlated well with measured flow ratios with and without background correction, while 1- to 2-minute uptake ratios correlated well only when corrected for background

A self-similar solution of a curved shock wave and its time-dependent force variation for a starting flat plate airfoil in supersonic flow

Directory of Open Access Journals (Sweden)

Zijun CHEN

2018-02-01

Full Text Available The problem of aeroelasticity and maneuvering of command surface and gust wing interaction involves a starting flow period which can be seen as the flow of an airfoil attaining suddenly an angle of attack. In the linear or nonlinear case, compressive Mach or shock waves are generated on the windward side and expansive Mach or rarefaction waves are generated on the leeward side. On each side, these waves are composed of an oblique steady state wave, a vertically-moving one-dimensional unsteady wave, and a secondary wave resulting from the interaction between the steady and unsteady ones. An analytical solution in the secondary wave has been obtained by Heaslet and Lomax in the linear case, and this linear solution has been borrowed to give an approximate solution by Bai and Wu for the nonlinear case. The structure of the secondary shock wave and the appearance of various force stages are two issues not yet considered in previous studies and has been studied in the present paper. A self-similar solution is obtained for the secondary shock wave, and the reason to have an initial force plateau as observed numerically is identified. Moreover, six theoretical characteristic time scales for pressure load variation are determined which explain the slope changes of the time-dependent force curve. Keywords: Force, Self-similar solution, Shock-shock interaction, Shock waves, Unsteady flow

Breakthrough curve of H/sub 2/-Ti-sponge adsorption system

Energy Technology Data Exchange (ETDEWEB)

Yasufuku, K [Kawasaki Heavy Industries Ltd., Kobe (Japan)

1977-11-01

Experimental work concerning H/sub 2/-Ti-sponge adsorption system has been undertaken at Kawasaki Heavy Industry Co. to obtain necessary data for the design of hydrogen removal tower (Ti-sponge trap) to be used as an purification component of a VHTR plant. In this study, the effects of equilibrium curve, H/sub 2/ inlet concentration, and the ratio of the solid-side capacity factor to the gas-side capacity factor on the breakthrough curve were investigated. The Freundlich's equation with the diffusion model of Carter et al. was numerically solved by the Crank-Nicholson method, and the results of calculations are presented. The flow diagram and the photographs of the facilities for He gas purification experiments are also presented.

Dynamics of embedded curves by doubly-nonlocal reaction-diffusion systems

Science.gov (United States)

von Brecht, James H.; Blair, Ryan

2017-11-01

We study a class of nonlocal, energy-driven dynamical models that govern the motion of closed, embedded curves from both an energetic and dynamical perspective. Our energetic results provide a variety of ways to understand physically motivated energetic models in terms of more classical, combinatorial measures of complexity for embedded curves. This line of investigation culminates in a family of complexity bounds that relate a rather broad class of models to a generalized, or weighted, variant of the crossing number. Our dynamic results include global well-posedness of the associated partial differential equations, regularity of equilibria for these flows as well as a more detailed investigation of dynamics near such equilibria. Finally, we explore a few global dynamical properties of these models numerically.

Steady flow in shallow channel bends

OpenAIRE

De Vriend, H.J.

1981-01-01

Making use of a mathematical model solving the complete NavierStokes equations for steady flow in coiled rectangular pipes, fully-developed laminar flow in shallow curved channels is analysed physically and mathematically. Transverse convection of momentum by the secondary flow is shown to cause important deformations of the main velocity distribution. The model is also used to investigate simplified computation methods for shallow channels. The usual 'shallow water approximation' is shown to...

Study for discharge coefficient of flow nozzles. Prediction by using numerical simulation

International Nuclear Information System (INIS)

Ikeda, Hiroshi; Sakai, Norio; Yamamoto, Yasushi; Arai, Kenji; Matsumoto, Masaaki

2008-01-01

In nuclear plant, as water feeding into reactor have much effect on thermal power of plant, it is important to measure accurately the flow rate of water. Flow nozzle is on of typical differential pressure type flow meters and the discharge coefficient is used to calculate the flow rate. This coefficient is given by actual experiment and theory. We studied the theoretical assumption of the discharge coefficient curve using numerical simulation and evaluated the effect of flow nozzle configuration on the coefficient numerically and experimentally. As the result, numerical simulation can predict the discharge coefficient of theoretical curve within 0.3%. And we found that the throat length and throat tapping location of flow nozzle have much effect on the coefficient. (author)

Inhibition of coronary blood flow by a vascular waterfall mechanism.

Science.gov (United States)

Downey, J M; Kirk, E S

1975-06-01

The mechanism whereby systole inhibits coronary blood flow was examined. A branch of the left coronary artery was maximally dilated with an adenosine infusion, and the pressure-flow relationship was obtained for beating and arrested states. The pressure-flow curve for the arrested state was shifted toward higher pressures and in the range of pressures above peak ventricular pressure was linear and parallel to that for the arrested state. Below this range the curve for the beating state converged toward that for the arrested state and was convex to the pressure axis. These results were compared with a model of the coronary vasculature that consisted of numerous parallel channels, each responding to local intramyocardial pressure by forming vascular waterfalls. When intramyocardial pressure in the model was assigned values from zero at the epicardium to peak ventricular pressure at the endocardium, pressure-flow curves similar to the experimental ones resulted. Thus, we conclude that systole inhibits coronary perfusion by the formation of vascular waterfalls and that the intramyocardial pressures responsible for this inhibition do not significantly exceed peak ventricular pressure.

Experimental study of turbulent flows through pipe bends

OpenAIRE

Kalpakli, Athanasia

2012-01-01

This thesis deals with turbulent flows in 90 degree curved pipes of circular cross-section. The flow cases investigated experimentally are turbulent flow with and without an additional motion, swirling or pulsating, superposed on the primary flow. The aim is to investigate these complex flows in detail both in terms of statistical quantities as well as vortical structures that are apparent when curvature is present. Such a flow field can contain strong secondary flow in a plane normal to the ...

Near-Wall Turbulence Modelling of Rotating and Curved Shear Flows

Energy Technology Data Exchange (ETDEWEB)

Pettersson, Bjoern Anders

1997-12-31

This thesis deals with verification and refinement of turbulence models within the framework of the Reynolds-averaged approach. It pays special attention to modelling the near-wall region, where the turbulence is strongly non-homogeneous and anisotropic. It also studies in detail the effects associated with an imposed rotation of the reference frame or streamline curvature. The objective with near-wall turbulence closure modelling is to formulate a set of equations governing single point turbulence statistics, which can be solved in the region of the flow which extends to the wall. This is in contrast to the commonly adopted wall-function approach in which the wall-boundary conditions are replaced by matching conditions in the logarithmic region. The near-wall models allow more flexibility by not requiring any such universal behaviour. Assessment of the novel elliptic relaxation approach to model the proximity of a solid boundary reveals an encouraging potential used in conjunction with second-moment and eddy-viscosity closures. The most natural level of closure modelling to predict flows affected by streamline curvatures or an imposed rotation of the reference frame is at the second-moment closure (SMC) level. Although SMCs naturally accounts for the effects of system rotation, the usual application of a scalar dissipation rate equation is shown to require ad hoc corrections in some cases in order to give good results. The elliptic relaxation approach is also used in conjunction with non-linear pressure-strain models and very encouraging results are obtained for rotating flows. Rotational induced secondary motions are vital to predicting the effects of system rotation. Some severe weaknesses of non-linear pressure-strain models are also indicated. Finally, a modelling methodology for anisotropic dissipation in nearly homogeneous turbulence are proposed. 84 refs., 56 figs., 16 tabs.

Stenting for curved lesions using a novel curved balloon: Preliminary experimental study.

Science.gov (United States)

Tomita, Hideshi; Higaki, Takashi; Kobayashi, Toshiki; Fujii, Takanari; Fujimoto, Kazuto

2015-08-01

Stenting may be a compelling approach to dilating curved lesions in congenital heart diseases. However, balloon-expandable stents, which are commonly used for congenital heart diseases, are usually deployed in a straight orientation. In this study, we evaluated the effect of stenting with a novel curved balloon considered to provide better conformability to the curved-angled lesion. In vitro experiments: A Palmaz Genesis(®) stent (Johnson & Johnson, Cordis Co, Bridgewater, NJ, USA) mounted on the Goku(®) curve (Tokai Medical Co. Nagoya, Japan) was dilated in vitro to observe directly the behavior of the stent and balloon assembly during expansion. Animal experiment: A short Express(®) Vascular SD (Boston Scientific Co, Marlborough, MA, USA) stent and a long Express(®) Vascular LD stent (Boston Scientific) mounted on the curved balloon were deployed in the curved vessel of a pig to observe the effect of stenting in vivo. In vitro experiments: Although the stent was dilated in a curved fashion, stent and balloon assembly also rotated conjointly during expansion of its curved portion. In the primary stenting of the short stent, the stent was dilated with rotation of the curved portion. The excised stent conformed to the curved vessel. As the long stent could not be negotiated across the mid-portion with the balloon in expansion when it started curving, the mid-portion of the stent failed to expand fully. Furthermore, the balloon, which became entangled with the stent strut, could not be retrieved even after complete deflation. This novel curved balloon catheter might be used for implantation of the short stent in a curved lesion; however, it should not be used for primary stenting of the long stent. Post-dilation to conform the stent to the angled vessel would be safer than primary stenting irrespective of stent length. Copyright © 2014 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

Energization of electrons in a plasma beam entering a curved magnetic field

International Nuclear Information System (INIS)

Brenning, N.; Lindberg, L.; Eriksson, A.

1980-09-01

Earlier experiments have indicated that suprathermal electrons appear when a collisionless plasma flowing along a magnetic field enters a region where the magnetic field is curved. In the present investigation newly developed methods of He-spectroscopy based on the absolute intensities of the He I 3889 A and He II 4686 A lines are utilized to study the electron temperature and to estimate the population of non-thermal electrons. The density of helium added for the diagnostic purpose is so low that the flow is not disturbed. It is found that the intrusion of the plasma into a curved or transverse field gives rise to a slight increase (15-20%) in the electron temperature and a remarkable increase in the fraction of non-thermal (>100 eV) electrons from below 1% to as much as 20-25% of the total electron population. There are also indications that the energization of electrons is particularly efficient on that side of the plasma beam which becomes polarized to a positive potential when entering the curved field. The experiments are confined to the case of weak magnetic field, i.e. only the electrons are magnetically confined. New details of the electric field and potential structure are presented and discussed. Electric field components parallel to the magnetic field are likely to energize the electrons, probably through the run-away phenomenon. (Auth.)

Evaluation of RI images of hepatic blood flow using Tc-99m PMT

Energy Technology Data Exchange (ETDEWEB)

Fujiwara, Hiromichi; Iwasaki, Naoya; Ichikawa, Kesato

1988-03-01

To evaluate the clinical significance of RI images of hepatic blood flow using Tc-99m-PMT, analysis of the RI images and estimation of hepatic blood flow were carried out in patients with various liver diseases (37 cases). After intravenous injection of Tc-99m-PMT, hepatic accumulation curve of ROI positioned at whole liver area and time activity curve of ROI positioned at celiac artery were obtained through scintillation camera images with the computer-analysed system. Hepatic blood flow coefficient (K) was calculated from the hepatic accumulation curve. Based on the differential curve calculated from the time activity curve, chronological images of arterial, portal, parenchymal and saturated parenchymal phases were obtained. Results ; 1) K was 0.50 + 0.04, 0.35 + 0.02 and 0.26 + 0.04/min in normal type, CH type and LC type respectively. These coefficients well correlated with clinical severity of hepatic diseases. 2) Perfusional phase images of the liver became poorer in accordance with progression of liver disease, while images of spleen, portal venous system and collateral channels were more clearly obtained in liver cirrhosis. This method was shown to have a potential to understanding of severity of liver disease and hepatic blood flow dynamics.

Temporal integration of loudness measured using categorical loudness scaling and matching procedures

DEFF Research Database (Denmark)

Valente, Daniel L.; Joshi, Suyash Narendra; Jesteadt, Walt

2011-01-01

integration of loudness and previously reported nonmonotonic behavior observed at mid-sound pressure level levels is replicated with this procedure. Stimuli that are assigned to the same category are effectively matched in loudness, allowing the measurement of temporal integration with CLS without curve...

Curve Boxplot: Generalization of Boxplot for Ensembles of Curves.

Science.gov (United States)

Mirzargar, Mahsa; Whitaker, Ross T; Kirby, Robert M

2014-12-01

In simulation science, computational scientists often study the behavior of their simulations by repeated solutions with variations in parameters and/or boundary values or initial conditions. Through such simulation ensembles, one can try to understand or quantify the variability or uncertainty in a solution as a function of the various inputs or model assumptions. In response to a growing interest in simulation ensembles, the visualization community has developed a suite of methods for allowing users to observe and understand the properties of these ensembles in an efficient and effective manner. An important aspect of visualizing simulations is the analysis of derived features, often represented as points, surfaces, or curves. In this paper, we present a novel, nonparametric method for summarizing ensembles of 2D and 3D curves. We propose an extension of a method from descriptive statistics, data depth, to curves. We also demonstrate a set of rendering and visualization strategies for showing rank statistics of an ensemble of curves, which is a generalization of traditional whisker plots or boxplots to multidimensional curves. Results are presented for applications in neuroimaging, hurricane forecasting and fluid dynamics.

Oscillatory flow in the human airways from the mouth through several bronchial generations

International Nuclear Information System (INIS)

Banko, Andrew J.; Coletti, Filippo; Elkins, Christopher J.; Eaton, John K.

2016-01-01

Highlights: • Oscillatory flow in the human airways is studied experimentally. • The realistic anatomy is obtained from the CT scan of a healthy adult. • Integral parameters are calculated to quantify streamwise and lateral dispersion. • Flow in real human anatomy is qualitatively different from idealized models. - Abstract: The time-varying flow is studied experimentally in an anatomically accurate model of the human airways from the mouth through several generations of bronchial branching. The airway geometry is obtained from the CT scan of a healthy adult male of normal height and build. The three-component, three-dimensional mean velocity field is obtained throughout the entire model using phase-locked Magnetic Resonance Velocimetry. A pulsatile pump drives a sinusoidal waveform (inhalation and exhalation) with frequency and stroke-length such that the mean trachea Reynolds number at peak inspiration is 4200 and the Womersley number is 7. Integral parameters are defined to quantify the degree of velocity profile non-uniformity (related to axial dispersion) and secondary flow strength (lateral dispersion). It is found that the extrathoracic airways significantly modify the tracheal flow and that the flow at the first bifurcation is highly asymmetric. The effect of flow oscillation is to produce time dependent flow features which are asymmetric with respect to the acceleration and deceleration periods surrounding peak inhalation and exhalation. This is most pronounced in regions of separation and on the secondary flow structure, which are sensitive to local attributes of the real anatomy. This is reflected in the integral parameters, which behave non-monotonically between successive bronchial generations. In general, the measured oscillatory flow in a realistic anatomy confirms many trends derived from idealized models but also possesses qualitatively different large scale flow structures as compared to idealized representations of the upper airways.

JUMPING THE CURVE

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René Pellissier

2012-01-01

Full Text Available This paper explores the notion ofjump ing the curve,following from Handy 's S-curve onto a new curve with new rules policies and procedures. . It claims that the curve does not generally lie in wait but has to be invented by leadership. The focus of this paper is the identification (mathematically and inferentially ofthat point in time, known as the cusp in catastrophe theory, when it is time to change - pro-actively, pre-actively or reactively. These three scenarios are addressed separately and discussed in terms ofthe relevance ofeach.

Mathematical modeling of two phase stratified flow in a microchannel with curved interface

Science.gov (United States)

Dandekar, Rajat; Picardo, Jason R.; Pushpavanam, S.

2017-11-01

Stratified or layered two-phase flows are encountered in several applications of microchannels, such as solvent extraction. Assuming steady, unidirectional creeping flow, it is possible to solve the Stokes equations by the method of eigenfunctions, provided the interface is flat and meets the wall with a 90 degree contact angle. However, in reality the contact angle depends on the pair of liquids and the material of the channel, and differs significantly from 90 degrees in many practical cases. For unidirectional flow, this implies that the interface is a circular arc (of constant curvature). We solve this problem within the framework of eigenfunctions, using the procedure developed by Shankar. We consider two distinct cases: (a) the interface meets the wall with the equilibrium contact angle; (b) the interface is pinned by surface treatment of the walls, so that the flow rates determine the apparent contact angle. We show that the contact angle appreciably affects the velocity profile and the volume fractions of the liquids, while limiting the range of flow rates that can be sustained without the interface touching the top/bottom walls. Non-intuitively, we find that the pressure drop is reduced when the more viscous liquid wets the wall.

Dual Smarandache Curves of a Timelike Curve lying on Unit dual Lorentzian Sphere

OpenAIRE

Kahraman, Tanju; Hüseyin Ugurlu, Hasan

2016-01-01

In this paper, we give Darboux approximation for dual Smarandache curves of time like curve on unit dual Lorentzian sphere. Firstly, we define the four types of dual Smarandache curves of a timelike curve lying on dual Lorentzian sphere.

Stochastic or statistic? Comparing flow duration curve models in ungauged basins and changing climates

Science.gov (United States)

Müller, M. F.; Thompson, S. E.

2015-09-01

The prediction of flow duration curves (FDCs) in ungauged basins remains an important task for hydrologists given the practical relevance of FDCs for water management and infrastructure design. Predicting FDCs in ungauged basins typically requires spatial interpolation of statistical or model parameters. This task is complicated if climate becomes non-stationary, as the prediction challenge now also requires extrapolation through time. In this context, process-based models for FDCs that mechanistically link the streamflow distribution to climate and landscape factors may have an advantage over purely statistical methods to predict FDCs. This study compares a stochastic (process-based) and statistical method for FDC prediction in both stationary and non-stationary contexts, using Nepal as a case study. Under contemporary conditions, both models perform well in predicting FDCs, with Nash-Sutcliffe coefficients above 0.80 in 75 % of the tested catchments. The main drives of uncertainty differ between the models: parameter interpolation was the main source of error for the statistical model, while violations of the assumptions of the process-based model represented the main source of its error. The process-based approach performed better than the statistical approach in numerical simulations with non-stationary climate drivers. The predictions of the statistical method under non-stationary rainfall conditions were poor if (i) local runoff coefficients were not accurately determined from the gauge network, or (ii) streamflow variability was strongly affected by changes in rainfall. A Monte Carlo analysis shows that the streamflow regimes in catchments characterized by a strong wet-season runoff and a rapid, strongly non-linear hydrologic response are particularly sensitive to changes in rainfall statistics. In these cases, process-based prediction approaches are strongly favored over statistical models.

Estimated damage from the Cascadia Subduction Zone tsunami: A model comparisons using fragility curves

Science.gov (United States)

Wiebe, D. M.; Cox, D. T.; Chen, Y.; Weber, B. A.; Chen, Y.

2012-12-01

Building damage from a hypothetical Cascadia Subduction Zone tsunami was estimated using two methods and applied at the community scale. The first method applies proposed guidelines for a new ASCE 7 standard to calculate the flow depth, flow velocity, and momentum flux from a known runup limit and estimate of the total tsunami energy at the shoreline. This procedure is based on a potential energy budget, uses the energy grade line, and accounts for frictional losses. The second method utilized numerical model results from previous studies to determine maximum flow depth, velocity, and momentum flux throughout the inundation zone. The towns of Seaside and Canon Beach, Oregon, were selected for analysis due to the availability of existing data from previously published works. Fragility curves, based on the hydrodynamic features of the tsunami flow (inundation depth, flow velocity, and momentum flux) and proposed design standards from ASCE 7 were used to estimate the probability of damage to structures located within the inundations zone. The analysis proceeded at the parcel level, using tax-lot data to identify construction type (wood, steel, and reinforced-concrete) and age, which was used as a performance measure when applying the fragility curves and design standards. The overall probability of damage to civil buildings was integrated for comparison between the two methods, and also analyzed spatially for damage patterns, which could be controlled by local bathymetric features. The two methods were compared to assess the sensitivity of the results to the uncertainty in the input hydrodynamic conditions and fragility curves, and the potential advantages of each method discussed. On-going work includes coupling the results of building damage and vulnerability to an economic input output model. This model assesses trade between business sectors located inside and outside the induction zone, and is used to measure the impact to the regional economy. Results highlight

Topographic instability of flow in a rotating fluid

Directory of Open Access Journals (Sweden)

K. I. Patarashvili

2006-01-01

Full Text Available Here are presented the results of experimental and theoretical studies on a stability of zonal geostrophic flows in the rotating layer of the shallow water. In the experiments, a special apparatus by Abastumani Astrophysical Observatory Georgian Academy of Science was used. This apparatus represents a paraboloid of rotation, which can be set in a regulable rotation around the vertical axis. Maximal diameter of the paraboloid is 1.2 m, radius of curvature in the pole is 0.698 m. In the paraboloid, water spreads on walls as a layer uniform on height under the period of rotation 1.677 s. Against a background of the rotating fluid, the zonal flows are formed by the source-sink system. It consists of two concentric circular perforations on the paraboloid bottom (width is 0.3 cm, radiuses are 8.4 and 57.3 cm, respectively; water can be pumped through them with various velocities and in all directions. It has been established that under constant vertical depth of the rotating fluid the zonal flows are stable. There are given the measurements of the radial profiles for the water level and velocity in the stationary regime. It has been found that zonal flows may lose stability under the presence of the radial gradient of full depth formed by a change of angular velocity of paraboloid rotation. An instability origin results in the loss of flow axial symmetry and in the appearance of self-excited oscillations in the zonal flow. At the given angular velocity of rotation, instability is observed only in the definite range of intensities of the source-sink system. The theoretical estimations are performed in the framework of the equations of the shallow water theory, including the terms describing the bottom friction. It has been shown that the instability of zonal flows found experimentally has a topographical nature and is related with non-monotone dependence of the potential vorticity on radius.

Influence of radial magnetic field on the peristaltic flow of Williamson fluid in a curved complaint walls channel

Directory of Open Access Journals (Sweden)

Tasawar Hayat

Full Text Available Peristaltic transport of Williamson fluid in a curved geometry is modeled. Problem formulation is completed by complaint walls of channel. Radial magnetic field in the analysis is taken into account. Resulting problem formulation is simplified using long wavelength and low Reynolds number approximations. Series solution is obtained for small Weissenberg number. Influences of different embedded parameters on the axial velocity and stream function are examined. As expected the velocity in curved channel is not symmetric. Axial velocity is noticed decreasing for Hartman number. Trapped bolus increases for Hartman and curvature parameters. Keywords: Williamson fluid, Curved channel, Radial magnetic field, Complaint walls

ECM using Edwards curves

DEFF Research Database (Denmark)

Bernstein, Daniel J.; Birkner, Peter; Lange, Tanja

2013-01-01

-arithmetic level are as follows: (1) use Edwards curves instead of Montgomery curves; (2) use extended Edwards coordinates; (3) use signed-sliding-window addition-subtraction chains; (4) batch primes to increase the window size; (5) choose curves with small parameters and base points; (6) choose curves with large...

A statistical method for estimating wood thermal diffusivity and probe geometry using in situ heat response curves from sap flow measurements.

Science.gov (United States)

Chen, Xingyuan; Miller, Gretchen R; Rubin, Yoram; Baldocchi, Dennis D

2012-12-01

The heat pulse method is widely used to measure water flux through plants; it works by using the speed at which a heat pulse is propagated through the system to infer the velocity of water through a porous medium. No systematic, non-destructive calibration procedure exists to determine the site-specific parameters necessary for calculating sap velocity, e.g., wood thermal diffusivity and probe spacing. Such parameter calibration is crucial to obtain the correct transpiration flux density from the sap flow measurements at the plant scale and subsequently to upscale tree-level water fluxes to canopy and landscape scales. The purpose of this study is to present a statistical framework for sampling and simultaneously estimating the tree's thermal diffusivity and probe spacing from in situ heat response curves collected by the implanted probes of a heat ratio measurement device. Conditioned on the time traces of wood temperature following a heat pulse, the parameters are inferred using a Bayesian inversion technique, based on the Markov chain Monte Carlo sampling method. The primary advantage of the proposed methodology is that it does not require knowledge of probe spacing or any further intrusive sampling of sapwood. The Bayesian framework also enables direct quantification of uncertainty in estimated sap flow velocity. Experiments using synthetic data show that repeated tests using the same apparatus are essential for obtaining reliable and accurate solutions. When applied to field conditions, these tests can be obtained in different seasons and can be automated using the existing data logging system. Empirical factors are introduced to account for the influence of non-ideal probe geometry on the estimation of heat pulse velocity, and are estimated in this study as well. The proposed methodology may be tested for its applicability to realistic field conditions, with an ultimate goal of calibrating heat ratio sap flow systems in practical applications.

Topological Sound and Flocking on Curved Surfaces

Directory of Open Access Journals (Sweden)

Suraj Shankar

2017-09-01

Full Text Available Active systems on curved geometries are ubiquitous in the living world. In the presence of curvature, orientationally ordered polar flocks are forced to be inhomogeneous, often requiring the presence of topological defects even in the steady state because of the constraints imposed by the topology of the underlying surface. In the presence of spontaneous flow, the system additionally supports long-wavelength propagating sound modes that get gapped by the curvature of the underlying substrate. We analytically compute the steady-state profile of an active polar flock on a two-sphere and a catenoid, and show that curvature and active flow together result in symmetry-protected topological modes that get localized to special geodesics on the surface (the equator or the neck, respectively. These modes are the analogue of edge states in electronic quantum Hall systems and provide unidirectional channels for information transport in the flock, robust against disorder and backscattering.

Nonequilibrium recombination after a curved shock wave

Science.gov (United States)

Wen, Chihyung; Hornung, Hans

2010-02-01

The effect of nonequilibrium recombination after a curved two-dimensional shock wave in a hypervelocity dissociating flow of an inviscid Lighthill-Freeman gas is considered. An analytical solution is obtained with the effective shock values derived by Hornung (1976) [5] and the assumption that the flow is ‘quasi-frozen’ after a thin dissociating layer near the shock. The solution gives the expression of dissociation fraction as a function of temperature on a streamline. A rule of thumb can then be provided to check the validity of binary scaling for experimental conditions and a tool to determine the limiting streamline that delineates the validity zone of binary scaling. The effects on the nonequilibrium chemical reaction of the large difference in free stream temperature between free-piston shock tunnel and equivalent flight conditions are discussed. Numerical examples are presented and the results are compared with solutions obtained with two-dimensional Euler equations using the code of Candler (1988) [10].

The feedback control research on straight and curved road with car-following model

Science.gov (United States)

Zheng, Yi-Ming; Cheng, Rong-Jun; Ge, Hong-Xia

2017-07-01

Taking account of the road consisting of curved part and straight part, an extended car-following model is proposed in this paper. A control signal including the velocity difference between the considered vehicle and the vehicle in front is taken into account. The control theory method is applied into analysis of the stability condition for the model. Numerical simulations are implemented to prove that the stability of the traffic flow strengthens effectively with an increase of the radius of curved road, and the control signal can suppress the traffic congestion. The results are in good agree with the theoretical analysis.

Technological change in energy systems. Learning curves, logistic curves and input-output coefficients

International Nuclear Information System (INIS)

Pan, Haoran; Koehler, Jonathan

2007-01-01

Learning curves have recently been widely adopted in climate-economy models to incorporate endogenous change of energy technologies, replacing the conventional assumption of an autonomous energy efficiency improvement. However, there has been little consideration of the credibility of the learning curve. The current trend that many important energy and climate change policy analyses rely on the learning curve means that it is of great importance to critically examine the basis for learning curves. Here, we analyse the use of learning curves in energy technology, usually implemented as a simple power function. We find that the learning curve cannot separate the effects of price and technological change, cannot reflect continuous and qualitative change of both conventional and emerging energy technologies, cannot help to determine the time paths of technological investment, and misses the central role of R and D activity in driving technological change. We argue that a logistic curve of improving performance modified to include R and D activity as a driving variable can better describe the cost reductions in energy technologies. Furthermore, we demonstrate that the top-down Leontief technology can incorporate the bottom-up technologies that improve along either the learning curve or the logistic curve, through changing input-output coefficients. An application to UK wind power illustrates that the logistic curve fits the observed data better and implies greater potential for cost reduction than the learning curve does. (author)

THE CARNEGIE SUPERNOVA PROJECT: LIGHT-CURVE FITTING WITH SNooPy

International Nuclear Information System (INIS)

Burns, Christopher R.; Persson, S. E.; Madore, Barry F.; Freedman, Wendy L.; Stritzinger, Maximilian; Phillips, M. M.; Boldt, Luis; Campillay, Abdo; Folatelli, Gaston; Gonzalez, Sergio; Krzeminski, Wojtek; Morrell, Nidia; Salgado, Francisco; Kattner, ShiAnne; Contreras, Carlos; Suntzeff, Nicholas B.

2011-01-01

In providing an independent measure of the expansion history of the universe, the Carnegie Supernova Project (CSP) has observed 71 high-z Type Ia supernovae (SNe Ia) in the near-infrared bands Y and J. These can be used to construct rest-frame i-band light curves which, when compared to a low-z sample, yield distance moduli that are less sensitive to extinction and/or decline-rate corrections than in the optical. However, working with NIR observed and i-band rest-frame photometry presents unique challenges and has necessitated the development of a new set of observational tools in order to reduce and analyze both the low-z and high-z CSP sample. We present in this paper the methods used to generate uBVgriYJH light-curve templates based on a sample of 24 high-quality low-z CSP SNe. We also present two methods for determining the distances to the hosts of SN Ia events. A larger sample of 30 low-z SNe Ia in the Hubble flow is used to calibrate these methods. We then apply the method and derive distances to seven galaxies that are so nearby that their motions are not dominated by the Hubble flow.

Development of Load Duration Curve System in Data Scarce Watersheds Based on a Distributed Hydrological Model

Science.gov (United States)

WANG, J.

2017-12-01

In stream water quality control, the total maximum daily load (TMDL) program is very effective. However, the load duration curves (LDC) of TMDL are difficult to be established because no sufficient observed flow and pollutant data can be provided in data-scarce watersheds in which no hydrological stations or consecutively long-term hydrological data are available. Although the point sources or a non-point sources of pollutants can be clarified easily with the aid of LDC, where does the pollutant come from and to where it will be transported in the watershed cannot be traced by LDC. To seek out the best management practices (BMPs) of pollutants in a watershed, and to overcome the limitation of LDC, we proposed to develop LDC based on a distributed hydrological model of SWAT for the water quality management in data scarce river basins. In this study, firstly, the distributed hydrological model of SWAT was established with the scarce-hydrological data. Then, the long-term daily flows were generated with the established SWAT model and rainfall data from the adjacent weather station. Flow duration curves (FDC) was then developed with the aid of generated daily flows by SWAT model. Considering the goal of water quality management, LDC curves of different pollutants can be obtained based on the FDC. With the monitored water quality data and the LDC curves, the water quality problems caused by the point or non-point source pollutants in different seasons can be ascertained. Finally, the distributed hydrological model of SWAT was employed again to tracing the spatial distribution and the origination of the pollutants of coming from what kind of agricultural practices and/or other human activities. A case study was conducted in the Jian-jiang river, a tributary of Yangtze river, of Duyun city, Guizhou province. Results indicate that this kind of method can realize the water quality management based on TMDL and find out the suitable BMPs for reducing pollutant in a watershed.

The S-Curve: China versus Its Major Trading Partners

OpenAIRE

Mohsen Bahmani-Oskooee; Ruixin Zhang

2013-01-01

China has been accused of manipulating its currency to gain international competitiveness and enjoy a trade surplus. The S-Curve is a hypothesis that could be used to test the effectiveness of currency devaluation or depreciation. It claims that while future values of the trade balance and current exchange rate are positively correlated, the past values of the trade balance and current exchange rate are negatively correlated. While China¡¯s aggregate trade flows with the rest of the world con...

Prediction of separation of gases and gaseous isotopes in a curved shock wave

International Nuclear Information System (INIS)

Tunstall, J.N.; Harris, W.L.; Childs, K.W.

1976-01-01

An examination of the species separation induced by a curved shock wave in a supersonic flow of a binary gas mixture has been undertaken. The objectives of this investigation are to determine the importance of physical mechanisms operative in such flows per the species separation and to develop a self-consistent model for predicting species separation in such flows. The formulation of the model examined in this paper is based on the continuum Navier-Stokes equations. The effects of a specified flow field downstream of the shock have been neglected. The parameters which characterize the separation induced by the shock have been identified. Results show a mathematically self-consistent and physically plausible dependence on the parameters which characterize the phenomenon. A comparison with existing theoretical models and experimental data shows good agreement

Normalization of flow-mediated dilation to shear stress area under the curve eliminates the impact of variable hyperemic stimulus.

Science.gov (United States)

Padilla, Jaume; Johnson, Blair D; Newcomer, Sean C; Wilhite, Daniel P; Mickleborough, Timothy D; Fly, Alyce D; Mather, Kieren J; Wallace, Janet P

2008-09-04

Normalization of brachial artery flow-mediated dilation (FMD) to individual shear stress area under the curve (peak FMD:SSAUC ratio) has recently been proposed as an approach to control for the large inter-subject variability in reactive hyperemia-induced shear stress; however, the adoption of this approach among researchers has been slow. The present study was designed to further examine the efficacy of FMD normalization to shear stress in reducing measurement variability. Five different magnitudes of reactive hyperemia-induced shear stress were applied to 20 healthy, physically active young adults (25.3 +/- 0. 6 yrs; 10 men, 10 women) by manipulating forearm cuff occlusion duration: 1, 2, 3, 4, and 5 min, in a randomized order. A venous blood draw was performed for determination of baseline whole blood viscosity and hematocrit. The magnitude of occlusion-induced forearm ischemia was quantified by dual-wavelength near-infrared spectrometry (NIRS). Brachial artery diameters and velocities were obtained via high-resolution ultrasound. The SSAUC was individually calculated for the duration of time-to-peak dilation. One-way repeated measures ANOVA demonstrated distinct magnitudes of occlusion-induced ischemia (volume and peak), hyperemic shear stress, and peak FMD responses (all p index of endothelial function.

Temperature dependence of the defect luminescence in La2Be2O5 single crystals

International Nuclear Information System (INIS)

Ogorodnikov, I.N.; Pustovarov, V.A.

2015-01-01

Temperature quenching (TQ) curves in the temperature range of 80–500 K have been studied for both the undoped, and doped with RE 3+ -ions (RE = Ce, Eu, Er, Pr, Nd) lanthanum beryllate (BLO) single crystals. Photoluminescence spectra and TQ-curves were recorded upon excitation in the absorption bands of the lattice defects. The reaction rate model has been developed to describe the experimental results. The model includes two competing processes with characteristic temperatures: thermal quenching of intracenter PL (T 1 ) and thermally stimulated migration of electronic excitations (T 2 ). The competition between these two processes leads to the observed non-monotonic TQ-curves. The rationalized formulas using three parameters (intensity, activation energy, characteristic temperature), were developed to describe each of these processes. Within the framework of the unified model, all the experimental results were described and the best fit parameters were obtained. Classification of the investigated lanthanum beryllate crystals was carried out in line with the best fit parameters obtained for the TQ-curves. - Highlights: • We studied La 2 Be 2 O 5 (BLO) single crystals (pristine and RE 3+ -doped). • We studied PL emission spectra of defects in BLO and BLO:RE 3+ . • Temperature quenching of the defect PL emission was studied at 80–500 K. • We developed the reaction rate model to describe non-monotonic TQ-curves. • TQ-curves were parameterized for BLO, BLO:RE 3+ (RE = Ce, Pr, Eu, Nd, Er).

Numerical analysis of unsteady conjugate heat transfer for initial evolution of thermal stratification in a curved pipe

International Nuclear Information System (INIS)

Jo, Jong Chull; Kim, Wee Kyung; Kim, Yun Il; Cho, Sang Jin; Choi, Seok Ki

2000-01-01

A detailed numerical analysis of initial evolution of thermal stratification in a curved pipe with a finite wall thickness is performed. A primary emphasis of the present study is placed on the investigation of the effect of existence of pipe wall thickness on the evolution of thermal stratification. A simple and convenient numerical method of treating the unsteady conjugate heat transfer in Cartesian as well as non-orthogonal coordinate systems is presented. The proposed unsteady conjugate heat transfer analysis method is implemented in a finite volume thermal-hydraulic computer code based on a cell-centered, non-staggered grid arrangement, the SIMPLEC algorithm and a higher-order bounded convection scheme. Calculations are performed for initial evolution of thermal stratification with high Richardson number in a curved pipe. The predicted results show that the thermally stratified flow and transient conjugate heat transfer in a curved pipe with a specified wall thickness can be satisfactorily analyzed by using the numerical method presented in this paper. As the result, the present analysis method is considered to be effective for the determination of transient temperature distributions in the wall of curved piping system subjected to internally thermal stratification. In addition, the method can be extended to be applicable for the simulation of turbulent flow of thermally stratified fluid

Computerised curve deconvolution of TL/OSL curves using a popular spreadsheet program.

Science.gov (United States)

Afouxenidis, D; Polymeris, G S; Tsirliganis, N C; Kitis, G

2012-05-01

This paper exploits the possibility of using commercial software for thermoluminescence and optically stimulated luminescence curve deconvolution analysis. The widely used software package Microsoft Excel, with the Solver utility has been used to perform deconvolution analysis to both experimental and reference glow curves resulted from the GLOw Curve ANalysis INtercomparison project. The simple interface of this programme combined with the powerful Solver utility, allows the analysis of complex stimulated luminescence curves into their components and the evaluation of the associated luminescence parameters.

Computerised curve deconvolution of TL/OSL curves using a popular spreadsheet program

International Nuclear Information System (INIS)

Afouxenidis, D.; Polymeris, G. S.; Tsirliganis, N. C.; Kitis, G.

2012-01-01

This paper exploits the possibility of using commercial software for thermoluminescence and optically stimulated luminescence curve deconvolution analysis. The widely used software package Microsoft Excel, with the Solver utility has been used to perform deconvolution analysis to both experimental and reference glow curves resulted from the Glow Curve Analysis Intercomparison project. The simple interface of this programme combined with the powerful Solver utility, allows the analysis of complex stimulated luminescence curves into their components and the evaluation of the associated luminescence parameters. (authors)

Improving H-Q rating curves in temprorary streams by using Acoustic Doppler Current meters

Science.gov (United States)

Marchand, P.; Salles, C.; Rodier, C.; Hernandez, F.; Gayrard, E.; Tournoud, M.-G.

2012-04-01

Intermittent rivers pose different challenges to stream rating due to high spatial and temporal gradients. Long dry periods, cut by short duration flush flood events explain the difficulty to obtain reliable discharge data, for low flows as well as for floods: problems occur with standard gauging, zero flow period, etc. Our study aims to test the use of an acoustic Doppler currentmeter (ADC) for improving stream rating curves in small catchments subject to large variations of discharge, solid transport and high eutrophication levels. The study is conducted at the outlet of the river Vène, a small coastal river (67 km2) located close to the city of Montpellier (France). The low flow period lasts for more than 6 month; during this period the river flow is sustained by effluents from urban sewage systems, which allows development of algae and macrophytes in the riverbed. The ADC device (Sontek ®Argonaut SW) is a pulsed Doppler current profiling system designed for measuring water velocity profiles and levels that are used to compute volumetric flow rates. It is designed for shallow waters (less than 4 meter depth). Its main advantages are its low cost and high accuracy (±1% of the measured velocity or ±0.05 m/sec, as reported by the manufacturer). The study will evaluate the improvement in rating curves in an intermittent flow context and the effect of differences in sensitivity between low and high water level, by comparing mean flow velocity obtained by ADC to direct discharges measurements. The study will also report long-term use of ADC device, by considering effects of biofilms, algae and macrophytes, as well as solid transport on the accuracy of the measurements. In conclusion, we show the possibility to improve stream rating and continuous data collection of an intermittent river by using a ADC with some precautions.

Evaluating Design Parameters for Breakthrough Curve Analysis and Kinetics of Fixed Bed Columns for Cu(II Cations Using Lignocellulosic Wastes

Directory of Open Access Journals (Sweden)

Zaira Zaman Chowdhury

2014-12-01

Full Text Available A continuous adsorption study for removal of Cu(II cations from wastewater using a fixed-bed column was conducted. A granular carbonaceous activated adsorbent produced by carbonization of the outer rind, or exocarp, of mangostene fruit shell was used for column packing. The effects of feed flow rate, influent cation concentration, and bed depth on the breakthrough curve were investigated at pH 5.5. Experimental analysis confirmed that the breakthrough curves were dependent on flow rate, initial concentration of Cu(II cations, and bed height related to the amount of activated carbon used for column packing. Thomas, Yoon–Nelson, and Adams–Bohart models were applied to analyze the breakthrough curves at different conditions. Linear regression analysis of experimental data demonstrated that Thomas and Yoon–Nelson models were appropriate to explain the breakthrough curve, while the Adams–Bohart model was only applicable to predict the initial part of the dynamic process. It was concluded that the column packed with fruit rind based activated carbon can be used to treat Cu(II-enriched wastewater.

Custom Type-Curve Generation for Pressure Transient Analysis of Elongated Linear Flow Systems Génération de courbes caractéristiques de réponse en pression pour des systèmes linéaires longs

Directory of Open Access Journals (Sweden)

Wagner P. B.

2006-11-01

Full Text Available When the drainage area of a flowing well is long and narrow, the pressure transient behavior of the well often cannot be analyzed by conventional means. Well tests which appear to exhibit linear flow behavior for extended periods, beyond the length of time which could be attributed to flow to a fracture, have been observed for both geothermal wells and for oil and gas wells. In geothermal formations and in some of the deep low-permeability gas fields the elongated reservoir shape results from long parallel faults which appear to bound the formations. Typically such wells are also penetrating natural fractures. In other reservoirs the elongated drainage shape is due to the river delta or alluvial environment in which the reservoir sands were originally deposited. Using a recently developed scheme for custom type curve generation for a wide variety of flow geometries, the particular behavior of the well producing from an elongated linear flow system is presented in detail. Cases examined include fractured wells of variable fracture length in varions positions within the flow channel and also of variable length. The effects of partial penetration are also demonstrated. This paper illustrates the use of custom type curves in computer-aided type-curve matching. With the help of relatively inexpensive computer graphics, custom type curves are displayed which exactly represent whatever is known about a particular drainage geometry, including such variables as formation thickness and areal extent, fracture length, partial penetration, and well location. Familles of curves can be generated and displayed along with the data to help determine unknown features of the reservoir geometry. An important contribution included in this work was the development of a set of orthogonal dimensionless parameters which facilitate the generation of familles of type curves which vary one reservoir shape parameter with implied effects on other parameters. The dimensionless

Role of mixed boundaries on flow in open capillary channels with curved air-water interfaces.

Science.gov (United States)

Zheng, Wenjuan; Wang, Lian-Ping; Or, Dani; Lazouskaya, Volha; Jin, Yan

2012-09-04

Flow in unsaturated porous media or in engineered microfluidic systems is dominated by capillary and viscous forces. Consequently, flow regimes may differ markedly from conventional flows, reflecting strong interfacial influences on small bodies of flowing liquids. In this work, we visualized liquid transport patterns in open capillary channels with a range of opening sizes from 0.6 to 5.0 mm using laser scanning confocal microscopy combined with fluorescent latex particles (1.0 μm) as tracers at a mean velocity of ∼0.50 mm s(-1). The observed velocity profiles indicate limited mobility at the air-water interface. The application of the Stokes equation with mixed boundary conditions (i.e., no slip on the channel walls and partial slip or shear stress at the air-water interface) clearly illustrates the increasing importance of interfacial shear stress with decreasing channel size. Interfacial shear stress emerges from the velocity gradient from the adjoining no-slip walls to the center where flow is trapped in a region in which capillary forces dominate. In addition, the increased contribution of capillary forces (relative to viscous forces) to flow on the microscale leads to increased interfacial curvature, which, together with interfacial shear stress, affects the velocity distribution and flow pattern (e.g., reverse flow in the contact line region). We found that partial slip, rather than the commonly used stress-free condition, provided a more accurate description of the boundary condition at the confined air-water interface, reflecting the key role that surface/interface effects play in controlling flow behavior on the nanoscale and microscale.

Transposing Concentration-Discharge Curves onto Unmonitored Catchments to Estimate Seasonal Nutrient Loads

Science.gov (United States)

Minaudo, C.; Moatar, F.; Abbott, B. W.; Dupas, R.; Gascuel-Odoux, C.; Pinay, G.; Roubeix, V.; Danis, P. A.

2017-12-01

Many lakes and reservoirs in Europe suffer from severe eutrophication. Accurate quantification of nutrient loads are critical for effective mitigation measures, but this information is often unknown. For example, in France, only 50 out of 481 lakes and reservoirs have national monitoring allowing estimation of interannual nitrogen and phosphorus loads, and even these loads are computed from low-frequency data. To address this lack of data, we developed a straightforward method to predict seasonal loads in lake tributaries. First, we analyzed concentration-discharge (C-Q) curves in monitored catchments and identified slopes, intercepts, and coefficient of variation of the log(C)-log(Q) regressions determined for both low and high flows, separated by the median daily flow [Moatar et al., 2017]. Then, we used stepwise multiple linear regression models to empirically link the characteristics of C-Q curves with a set of catchment descriptors such as land use, lithology, morphology indices, climate, and hydrological indicators. Modeled C-Q relationships were then used to estimate annual and seasonal nutrient loads in nearby and similar unmonitored catchments. We implemented this approach on a large dataset from France where stream flow was surveyed daily and water quality (suspended solids, nitrate, total phosphorus, and orthophosphate concentrations) was measured on a monthly basis at 233 stations over the past 20 years in catchments from 10 to 3000 km². The concentration at the median daily flow (seen here as a metric of the general level of contamination in a catchment) was predicted with uncertainty ranging between 30 and 100 %, depending on the variable. C-Q slopes were predicted with large errors, but a sensitivity analysis was conducted to determine the impact of C-Q slopes uncertainties on computed annual and seasonal loads. This approach allows estimation of seasonal and annual nutrient loads and could be potentially implemented to improve protection and

Laminar flow of a shear-thickening fluid in a 90∘ pipe bend

Science.gov (United States)

Marn, Jure; Ternik, Primož

2006-05-01

The non-Newtonian fluid flow in a sharp 90∘ curved pipe is studied numerically to obtain the pressure loss coefficient prompted by disagreement between the existing empirical correlations and results obtained by computer codes. This disagreement results from presumption of fully developed flow throughout the curvature (correlations) while the actual flow is partially developed for the Newtonian and sharp 90∘ curved bend non-Newtonian flows, and fully developed for slightly bent 90∘ curvature non-Newtonian flow. The Quadratic model is employed to accommodate the shear-thickening behavior of an electrostatic ash and water mixture. Numerical results are obtained for different values of Reynolds number. Finally, results for local pressure loss coefficient are compared with values obtained for the Power law rheological model.

Numerical investigation of MHD flow with Soret and Dufour effect

Science.gov (United States)

Hayat, Tasawar; Nasir, Tehreem; Khan, Muhammad Ijaz; Alsaedi, Ahmed

2018-03-01

This paper describes the flow due to an exponentially curved surface subject to Soret and Dufour effects. Nonlinear velocity is considered. Exponentially curved stretchable sheet induced the flow. Fluid is electrical conducting through constant applied magnetic field. The governing flow expressions are reduced to ordinary ones and then tackled by numerical technique (Built-in-Shooting). Impacts of various flow variables on the dimensionless velocity, concentration and temperature fields are graphically presented and discussed in detail. Skin friction coefficient and Sherwood and Nusselt numbers are studied through graphs. Furthermore it is observed that Soret and Dufour variables regulate heat and mass transfer rates. It is also noteworthy that velocity decays for higher magnetic variable. Skin friction magnitude decays via curvature and magnetic variables. Also mass transfer gradient or rate of mass transport enhances for higher estimations of curvature parameter and Schmidt number.

Creating drag and lift curves from soccer trajectories

Science.gov (United States)

Goff, John Eric; Kelley, John; Hobson, Chad M.; Seo, Kazuya; Asai, Takeshi; Choppin, S. B.

2017-07-01

Trajectory analysis is an alternative to using wind tunnels to measure a soccer ball’s aerodynamic properties. It has advantages over wind tunnel testing such as being more representative of game play. However, previous work has not presented a method that produces complete, speed-dependent drag and lift coefficients. Four high-speed cameras in stereo-calibrated pairs were used to measure the spatial co-ordinates for 29 separate soccer trajectories. Those trajectories span a range of launch speeds from 9.3 to 29.9 m s-1. That range encompasses low-speed laminar flow of air over a soccer ball, through the drag crises where air flow is both laminar and turbulent, and up to high-speed turbulent air flow. Results from trajectory analysis were combined to give speed-dependent drag and lift coefficient curves for the entire range of speeds found in the 29 trajectories. The average root mean square error between the measured and modelled trajectory was 0.028 m horizontally and 0.034 m vertically. The drag and lift crises can be observed in the plots of drag and lift coefficients respectively.

Direct Breakthrough Curve Prediction From Statistics of Heterogeneous Conductivity Fields

Science.gov (United States)

Hansen, Scott K.; Haslauer, Claus P.; Cirpka, Olaf A.; Vesselinov, Velimir V.

2018-01-01

This paper presents a methodology to predict the shape of solute breakthrough curves in heterogeneous aquifers at early times and/or under high degrees of heterogeneity, both cases in which the classical macrodispersion theory may not be applicable. The methodology relies on the observation that breakthrough curves in heterogeneous media are generally well described by lognormal distributions, and mean breakthrough times can be predicted analytically. The log-variance of solute arrival is thus sufficient to completely specify the breakthrough curves, and this is calibrated as a function of aquifer heterogeneity and dimensionless distance from a source plane by means of Monte Carlo analysis and statistical regression. Using the ensemble of simulated groundwater flow and solute transport realizations employed to calibrate the predictive regression, reliability estimates for the prediction are also developed. Additional theoretical contributions include heuristics for the time until an effective macrodispersion coefficient becomes applicable, and also an expression for its magnitude that applies in highly heterogeneous systems. It is seen that the results here represent a way to derive continuous time random walk transition distributions from physical considerations rather than from empirical field calibration.

Approximation by planar elastic curves

DEFF Research Database (Denmark)

Brander, David; Gravesen, Jens; Nørbjerg, Toke Bjerge

2016-01-01

We give an algorithm for approximating a given plane curve segment by a planar elastic curve. The method depends on an analytic representation of the space of elastic curve segments, together with a geometric method for obtaining a good initial guess for the approximating curve. A gradient......-driven optimization is then used to find the approximating elastic curve....

Assessment of Estimation Methods ForStage-Discharge Rating Curve in Rippled Bed Rivers

Directory of Open Access Journals (Sweden)

P. Maleki

2016-02-01

Full Text Available Introduction: Interactionbetweenwater flow characteristics andthe bed erodibilityplays an important role in sediment transport process. In order to reach stability, rivers with deposition or bottom erosion make a different bed form in the riverbed. One way to identify thebehavior of therivers is to study the structure and formation of bed forms within them. Ripples are the smallest of the bed forms. The longitudinal cross section of ripples are usually not symmetrical. The upstream face is long and has a gentle slope, and the downstream face is short and steep. The height of ripples is usually between 0.5 cm and 2 cm; the height ripple is not more than 5 cm. The wave lengths normally do not exceed 30cm, and they are usually within the range of 1 cm to 15 cm. Their occurrence is the result of the unstable viscous layer near the boundary. They can form in both shallow and deep water.With an increase of the flow velocity, the plan form of the ripples gradually develops form straight line to curves and then to a pattern like fish scales, symmetrical or unsymmetrical, as shown in Fig 1. Figure1-The patterndevelopment oftheripple Raudkivi (1966 was the first person that, the flow structure over ripples was investigated experimentally.Hethenestablishseveraldifferent conditionsonthemovingsandbedinanlaboratorychannelconsisted of a rectangular cross-section with base width of 70cm, wasable toform arow ofripples , he wassucceed toform arow ofripples.JafariMianaei and Keshavarzi(2008,studied the turbulentflow betweentwoartificialripples for investigate the change of kinetic energyandshearstress on overripples. The stage- discharge rating curve is one of the most important tools in the hydraulic studies. In alluvial rivers,bed rippled are formed and significantly affect the stage- discharge rating curve. In this research, the effects of two different type of ripples (parallel and flakeshape onthe hydraulic characteristicsof flow were experimentally studied

Bragg Curve Spectroscopy

International Nuclear Information System (INIS)

Gruhn, C.R.

1981-05-01

An alternative utilization is presented for the gaseous ionization chamber in the detection of energetic heavy ions, which is called Bragg Curve Spectroscopy (BCS). Conceptually, BCS involves using the maximum data available from the Bragg curve of the stopping heavy ion (HI) for purposes of identifying the particle and measuring its energy. A detector has been designed that measures the Bragg curve with high precision. From the Bragg curve the range from the length of the track, the total energy from the integral of the specific ionization over the track, the dE/dx from the specific ionization at the beginning of the track, and the Bragg peak from the maximum of the specific ionization of the HI are determined. This last signal measures the atomic number, Z, of the HI unambiguously

Determination of myocardial blood flow by videodensitometry

International Nuclear Information System (INIS)

Erikson, U.; Helmius, G.; Hennig, K.; Johansson, L.; Enghoff, E.; Ruhn, G.

1981-01-01

Videodensitometry has hitherto been used as a tool for measuring regional blood flow in the kidneys and lungs by means of the well known Stewart Hamilton curve (wash-out) technique. This preliminary report suggests the possibility of using this method to measure coronary blood flow. Thirty-six patients, 29 of whom had angina pectoris, underwent videodensitometry in connection with coronary angiography. (orig.) [de

Learning Curve? Which One?

Directory of Open Access Journals (Sweden)

Paulo Prochno

2004-07-01

Full Text Available Learning curves have been studied for a long time. These studies provided strong support to the hypothesis that, as organizations produce more of a product, unit costs of production decrease at a decreasing rate (see Argote, 1999 for a comprehensive review of learning curve studies. But the organizational mechanisms that lead to these results are still underexplored. We know some drivers of learning curves (ADLER; CLARK, 1991; LAPRE et al., 2000, but we still lack a more detailed view of the organizational processes behind those curves. Through an ethnographic study, I bring a comprehensive account of the first year of operations of a new automotive plant, describing what was taking place on in the assembly area during the most relevant shifts of the learning curve. The emphasis is then on how learning occurs in that setting. My analysis suggests that the overall learning curve is in fact the result of an integration process that puts together several individual ongoing learning curves in different areas throughout the organization. In the end, I propose a model to understand the evolution of these learning processes and their supporting organizational mechanisms.

Contractibility of curves

Directory of Open Access Journals (Sweden)

Janusz Charatonik

1991-11-01

Full Text Available Results concerning contractibility of curves (equivalently: of dendroids are collected and discussed in the paper. Interrelations tetween various conditions which are either sufficient or necessary for a curve to be contractible are studied.

Roc curves for continuous data

CERN Document Server

Krzanowski, Wojtek J

2009-01-01

Since ROC curves have become ubiquitous in many application areas, the various advances have been scattered across disparate articles and texts. ROC Curves for Continuous Data is the first book solely devoted to the subject, bringing together all the relevant material to provide a clear understanding of how to analyze ROC curves.The fundamental theory of ROC curvesThe book first discusses the relationship between the ROC curve and numerous performance measures and then extends the theory into practice by describing how ROC curves are estimated. Further building on the theory, the authors prese

Study of operational parameters on the performance of micro PEMFCs with different flow fields

International Nuclear Information System (INIS)

Hsieh, S.-S.; Yang, S.-H.; Kuo, J.-K.; Huang, C.-F.; Tsai, H.-H.

2006-01-01

The effects of different operating parameters on micro PEMFC performances were experimentally studied for three different flow field configurations (interdigitated, mesh, and serpentine). Experiments with different cell operating temperatures and different backpressures on the H 2 flow channels, as well as various combinations of these parameters, have been conducted for three different flow geometries. The micro PEMFCs were designed and fabricated inhouse through a deep UV lithography technique and the SU-8 photoresist was used as microstructure material for the fuel cell flow field plates. Results are presented in the form of polarization VI curves and PI curves under different operating conditions. The possible transport mechanisms associated with the parametric effects were discussed. In addition, it was found that among the three flow patterns considered, significant improvements can be reached with a specified flow geometry

Low flow and drought spatial analysis

International Nuclear Information System (INIS)

Dakova, Snejana

2004-01-01

The hydrological characteristics of Bulgarian rivers reflect to the climate variability. Nearly all precipitation is received during the spring and/or winter months, with negligible precipitations in summer. Thus, peak flows occur in spring and/or winter, and during the summer, the flow is significant lower with many rivers being ephemeral. Therefore, 2210 reservoirs for satisfaction the water needs have been constructed during the last sixty years. In spit of that, Bulgaria is facing to a new insufficiency of water. The recent climate change investigations and climate scenarios determine the area of Balkan Peninsula as territories with decreasing of rainfalls and increasing of air temperature. In view of that, research the low flow in the light of climate changing together with the water management is required. In this study the definitions of low flow and drought are developed using available data obtained in Bulgarian area, which has semiarid zone conditions. The difference between the terms of drought and low flow is describing and clarified also. The low flow and drought variables are investigated on two levels: first on long-year's variability using annual data and than monthly and seasonal data series-for enabling the within-year effects to be determined. The relationship between the probability of river's dry up and mean annual and seasonal rainfalls is quantified using multiple regressions applied to logarithmic- transformed data. This paper presets also analyses of minimum flow series with zero values. The exceed probability above which stream flow is zero and conditional probability of non-zero flow (non-zero-duration curve) is obtained by the principals of total probability. A different kind of adjusting duration curves are proposed depending of the number of zero values in the series.(Author)

Atlas of stress-strain curves

CERN Document Server

2002-01-01

The Atlas of Stress-Strain Curves, Second Edition is substantially bigger in page dimensions, number of pages, and total number of curves than the previous edition. It contains over 1,400 curves, almost three times as many as in the 1987 edition. The curves are normalized in appearance to aid making comparisons among materials. All diagrams include metric (SI) units, and many also include U.S. customary units. All curves are captioned in a consistent format with valuable information including (as available) standard designation, the primary source of the curve, mechanical properties (including hardening exponent and strength coefficient), condition of sample, strain rate, test temperature, and alloy composition. Curve types include monotonic and cyclic stress-strain, isochronous stress-strain, and tangent modulus. Curves are logically arranged and indexed for fast retrieval of information. The book also includes an introduction that provides background information on methods of stress-strain determination, on...

Higher dimensional curved domain walls on Kähler surfaces

Energy Technology Data Exchange (ETDEWEB)

Akbar, Fiki T., E-mail: ftakbar@fi.itb.ac.id [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10 Bandung, 40132 (Indonesia); Gunara, Bobby E., E-mail: bobby@fi.itb.ac.id [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10 Bandung, 40132 (Indonesia); Radjabaycolle, Flinn C. [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10 Bandung, 40132 (Indonesia); Departement of Physics, Faculty of Mathematics and Natural Sciences, Cendrawasih University, Jl. Kampwolker Kampus Uncen Baru Waena-Jayapura 99351 (Indonesia); Wijaya, Rio N. [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10 Bandung, 40132 (Indonesia)

2017-03-15

In this paper we study some aspects of curved BPS-like domain walls in higher dimensional gravity theory coupled to scalars where the scalars span a complex Kähler surface with scalar potential turned on. Assuming that a fake superpotential has a special form which depends on Kähler potential and a holomorphic function, we prove that BPS-like equations have a local unique solution. Then, we analyze the vacuum structure of the theory including their stability using dynamical system and their existence in ultraviolet-infrared regions using renormalization group flow.

Higher dimensional curved domain walls on Kähler surfaces

International Nuclear Information System (INIS)

Akbar, Fiki T.; Gunara, Bobby E.; Radjabaycolle, Flinn C.; Wijaya, Rio N.

2017-01-01

In this paper we study some aspects of curved BPS-like domain walls in higher dimensional gravity theory coupled to scalars where the scalars span a complex Kähler surface with scalar potential turned on. Assuming that a fake superpotential has a special form which depends on Kähler potential and a holomorphic function, we prove that BPS-like equations have a local unique solution. Then, we analyze the vacuum structure of the theory including their stability using dynamical system and their existence in ultraviolet-infrared regions using renormalization group flow.

Analysis of Flow Behavior for Acid Fracturing Wells in Fractured-Vuggy Carbonate Reservoirs

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Mingxian Wang

2018-01-01

Full Text Available This study develops a mathematical model for transient flow analysis of acid fracturing wells in fractured-vuggy carbonate reservoirs. This model considers a composite system with the inner region containing finite number of artificial fractures and wormholes and the outer region showing a triple-porosity medium. Both analytical and numerical solutions are derived in this work, and the comparison between two solutions verifies the model accurately. Flow behavior is analyzed thoroughly by examining the standard log-log type curves. Flow in this composite system can be divided into six or eight main flow regimes comprehensively. Three or two characteristic V-shaped segments can be observed on pressure derivative curves. Each V-shaped segment corresponds to a specific flow regime. One or two of the V-shaped segments may be absent in particular cases. Effects of interregional diffusivity ratio and interregional conductivity ratio on transient responses are strong in the early-flow period. The shape and position of type curves are also influenced by interporosity coefficients, storativity ratios, and reservoir radius significantly. Finally, we show the differences between our model and the similar model with single fracture or without acid fracturing and further investigate the pseudo-skin factor caused by acid fracturing.

Nonmonotonous changes of thymus nuclei lipid metabolism upon chronic gamma-radiation of rats at a dose-rate of 3 c Gy/Day

International Nuclear Information System (INIS)

Kulagina, T.P.; Kolomijtseva, I.K.; Moiseeva, S.A.; Kuzin, A.M.

2000-01-01

The dynamics of changes in the thymus nuclei lipid metabolism under chronic gamma-radiation in low doses with the dose rate of 3 cGy/day is studied. It is shown, that at the 25 cGy dose rate there takes place activation of exchange in the fatly-acid part of the phospholipid molecule with simultaneous activation of the cholesterol and fatty acids synthesis. The synthesis of cholesterol and fatty acids at 50 cGy remains activated, whereas metabolism of the fatty-acid part of the phospholipids molecule is sharply depressed. The identified changes reveal the similarity with the processes, proceeding by the apoptose induction. At the same time the dynamics of the thymocyte nuclei lipid exchange in the process of adaptation to the long radiation effect as nonmonotonous metabolic response to low dose impact is characterized for the first time [ru

Mathematics of flexible risers including pressure and internal flow affects

Energy Technology Data Exchange (ETDEWEB)

Seyed, F.B. (John Brown Engineers and Constructors Ltd., London (GB)); Patel, M.H. (University Coll., London (GB). Dept. of Mechanical Engineering)

1992-01-01

Derivations are presented for calculation of pressure and internal flow induced forces on flexible risers and other curved pipes using a mathematically rigorous approach. Approximate and exact methods are presented for calculation of pressure forces on straight and curved pipes in two dimensions. The mathematical identity of these equations with those for effective tension is illustrated. The force arising from the flow of an internal fluid of constant density is then calculated and combined with those for pressure forces in derivation of the catenary equations including pressure and internal flow terms. It is shown that internal flow contributes a new term to the expression for effective tension. These governing equations are then reduced for the specific cases of simple catenary, steep-S, lazy-S, steep-wave and lazy-wave risers. In each case, the solution method has been presented and the governing equilibrium and geometric compatability conditions cited. (author).

Nonlinear dynamics near the stability margin in rotating pipe flow

Science.gov (United States)

Yang, Z.; Leibovich, S.

1991-01-01

The nonlinear evolution of marginally unstable wave packets in rotating pipe flow is studied. These flows depend on two control parameters, which may be taken to be the axial Reynolds number R and a Rossby number, q. Marginal stability is realized on a curve in the (R, q)-plane, and the entire marginal stability boundary is explored. As the flow passes through any point on the marginal stability curve, it undergoes a supercritical Hopf bifurcation and the steady base flow is replaced by a traveling wave. The envelope of the wave system is governed by a complex Ginzburg-Landau equation. The Ginzburg-Landau equation admits Stokes waves, which correspond to standing modulations of the linear traveling wavetrain, as well as traveling wave modulations of the linear wavetrain. Bands of wavenumbers are identified in which the nonlinear modulated waves are subject to a sideband instability.

Tornado-Shaped Curves

Science.gov (United States)

Martínez, Sol Sáez; de la Rosa, Félix Martínez; Rojas, Sergio

2017-01-01

In Advanced Calculus, our students wonder if it is possible to graphically represent a tornado by means of a three-dimensional curve. In this paper, we show it is possible by providing the parametric equations of such tornado-shaped curves.

Mechanism of transition to turbulence in a circular cylinder wake in a channel

Directory of Open Access Journals (Sweden)

Molochnikov Valery

2017-01-01

Full Text Available Transition to turbulence in the circular cylinder wake has been studied experimentally and numerically at growing Reynolds number. Good agreement of calculation results with the flow visualization and measurements of instantaneous vector fields of velocity and vorticity has been demonstrated. The growing Reynolds number is shown to make large-scale vortex generation onset move upstream. It also triggers the transition to 3D flow pattern in the cylinder wake. This process is accompanied by non-monotonous behavior of the profiles of velocity and its turbulent fluctuations at equal distances from the cylinder. Non-monotonous behavior of the cylinder drag has been revealed for the Reynolds numbers ranging from 120 to 300.

Loschmidt echo for local perturbations: non-monotonic cross-over from the Fermi-golden-rule to the escape-rate regime

International Nuclear Information System (INIS)

Goussev, Arseni; Waltner, Daniel; Richter, Klaus; Jalabert, Rodolfo A

2008-01-01

We address the sensitivity of quantum mechanical time evolution by considering the time decay of the Loschmidt echo (LE) (or fidelity) for local perturbations of the Hamiltonian. Within a semiclassical approach, we derive analytical expressions for the LE decay for chaotic systems for the whole range from weak to strong local perturbations and identify different decay regimes which complement those known for the case of global perturbations. For weak perturbations, a Fermi-golden-rule (FGR)-type behavior is recovered. For strong perturbations, the escape-rate regime is reached, where the LE decays exponentially with a rate independent of the perturbation strength. The transition between the FGR regime and the escape-rate regime is non-monotonic, i.e. the rate of the exponential time-decay of the LE oscillates as a function of the perturbation strength. We further perform extensive quantum mechanical calculations of the LE based on numerical wave packet evolution, which strongly support our semiclassical theory. Finally, we discuss in some detail possible experimental realizations for observing the predicted behavior of the LE

A versatile curve-fit model for linear to deeply concave rank abundance curves

NARCIS (Netherlands)

Neuteboom, J.H.; Struik, P.C.

2005-01-01

A new, flexible curve-fit model for linear to concave rank abundance curves was conceptualized and validated using observational data. The model links the geometric-series model and log-series model and can also fit deeply concave rank abundance curves. The model is based ¿ in an unconventional way

Debris flow-induced topographic changes: effects of recurrent debris flow initiation.

Science.gov (United States)

Chen, Chien-Yuan; Wang, Qun

2017-08-12

Chushui Creek in Shengmu Village, Nantou County, Taiwan, was analyzed for recurrent debris flow using numerical modeling and geographic information system (GIS) spatial analysis. The two-dimensional water flood and mudflow simulation program FLO-2D were used to simulate debris flow induced by rainfall during typhoon Herb in 1996 and Mindulle in 2004. Changes in topographic characteristics after the debris flows were simulated for the initiation of hydrological characteristics, magnitude, and affected area. Changes in topographic characteristics included those in elevation, slope, aspect, stream power index (SPI), topographic wetness index (TWI), and hypsometric curve integral (HI), all of which were analyzed using GIS spatial analysis. The results show that the SPI and peak discharge in the basin increased after a recurrence of debris flow. The TWI was higher in 2003 than in 2004 and indicated higher potential of landslide initiation when the slope of the basin was steeper. The HI revealed that the basin was in its mature stage and was shifting toward the old stage. Numerical simulation demonstrated that the parameters' mean depth, maximum depth, affected area, mean flow rate, maximum flow rate, and peak flow discharge were increased after recurrent debris flow, and peak discharge occurred quickly.

Experimental investigation of torque scaling and coherent structures in turbulent Taylor–Couette flow

International Nuclear Information System (INIS)

Tokgoz, S; Elsinga, G E; Delfos, R; Westerweel, J

2011-01-01

The effect of flow structures to the torque values of fully turbulent Taylor-Couette flow was experimentally studied using tomographic PIV. The measurements were performed for various relative cylinder rotation speeds and Reynolds numbers, based on a study of Ravelet et al. (2010). We confirmed that the flow structures are strongly influenced by the rotation number. Our analyses using time-averaged mean flow showed the presence of Taylor vortices for the two smallest rotation numbers that were studied. Increasing the rotation number initially resulted in the shape deformation of the Taylor vortices. Further increment towards only outer cylinder rotation, showed transition to the dominance of the small scale vortices and absence of Taylor vortex-like structures. We compared the transition of the flow structures with the curves of dimensionless torque. Sudden changes of the flow structures confirmed the presence of transition points on the torque curve, where the dominance of small and large scale vortical structures on the mean flow interchanges.

In-Vehicle Dynamic Curve-Speed Warnings at High-Risk Rural Curves

Science.gov (United States)