Prandtl number of toroidal plasmas
Energy Technology Data Exchange (ETDEWEB)
Itoh, Kimitaka (National Inst. for Fusion Science, Nagoya (Japan)); Itoh, Sanae; Fukuyama, Atsushi; Yagi, Masatoshi; Azumi, Masafumi
1993-12-01
Theory of the L-mode confinement in toroidal plasmas is developed. The Prandtl number, the ratio between the ion viscosity and the thermal conductivity is obtained for the anomalous transport process which is caused by the self-sustained turbulence in the toroidal plasma. It is found that the Prandtl number is of order unity both for the ballooning mode turbulence in tokamaks and for the interchange mode turbulence in helical system. The influence on the anomalous transport and fluctuation level is evaluated. Hartmann number and magnetic Prandtl number are also discussed. (author).
Optimal Prandtl number for heat transfer in rotating Rayleigh-Bénard convection
Stevens, Richard Johannes Antonius Maria; Clercx, H.J.H.; Lohse, Detlef
2010-01-01
Numerical data for the heat transfer as a function of the Prandtl (Pr)and Rossby (Ro) numbers in turbulent rotating Rayleigh–Bénard convection are presented for Rayleigh number Ra = 10 8 When Ro is xed, the heat transfer enhancement with respect to the non-rotating value shows a maximum as a functi
Optimal Prandtl number for heat transfer in rotating Rayleigh-Benard convection
Stevens, Richard J A M; Lohse, Detlef
2009-01-01
Numerical data for the heat transfer as a function of the Prandtl (Pr) and Rossby (Ro) numbers in turbulent rotating Rayleigh-Benard convection are presented for Rayleigh number Ra = 10^8. When Ro is fixed the heat transfer enhancement with respect to the non-rotating value shows a maximum as function of Pr. This maximum is due to the reduced efficiency of Ekman pumping when Pr becomes too small or too large. When Pr becomes small, i.e. for large thermal diffusivity, the heat that is carried by the vertical vortices spreads out in the middle of the cell, and Ekman pumping thus becomes less efficient. For higher Pr the thermal boundary layers (BLs) are thinner than the kinetic BLs and therefore the Ekman vortices do not reach the thermal BL. This means that the fluid that is sucked into the vertical vortices is colder than for lower Pr which limits the efficiency of the upwards heat transfer.
Dynamos at extreme magnetic Prandtl numbers
Verma, Mahendra K
2015-01-01
We present a MHD shell model suitable for the computation of various energy fluxes of magnetohydrodynamic turbulence for very small and very large magnetic Prandtl numbers $\\mathrm{Pm}$; such computations are inaccessible to direct numerical simulations. For small $\\mathrm{Pm}$, we observe that the both kinetic and magnetic energy spectra scale as $k^{-5/3}$ in the inertial range, but the dissipative magnetic energy scales as $k^{-17/3}$. Here, the kinetic energy at large length scale feeds the large-scale magnetic field that cascades to small-scale magnetic field, which gets dissipated by Joule heating. The large $\\mathrm{Pm}$ dynamo has a similar behaviour except that the dissipative kinetic energy scales as $k^{-13/3}$. For this case, the large-scale velocity field transfers energy to large-scale magnetic field, which gets transferred to small-scale velocity and magnetic fields. The energy of the small-scale magnetic field also gets transferred to the small-scale velocity field. The energy accumulated at s...
Magnetic dynamo action at low magnetic Prandtl numbers.
Malyshkin, Leonid M; Boldyrev, Stanislav
2010-11-19
Amplification of magnetic field due to kinematic turbulent dynamo action is studied in the regime of small magnetic Prandtl numbers. Such a regime is relevant for planets and stars interiors, as well as for liquid-metal laboratory experiments. A comprehensive analysis based on the Kazantsev-Kraichnan model is reported, which establishes the dynamo threshold and the dynamo growth rates for varying kinetic helicity of turbulent fluctuations. It is proposed that in contrast with the case of large magnetic Prandtl numbers, the kinematic dynamo action at small magnetic Prandtl numbers is significantly affected by kinetic helicity, and it can be made quite efficient with an appropriate choice of the helicity spectrum.
Dissipation in dynamos at low and high magnetic Prandtl numbers
Brandenburg, A
2010-01-01
Using simulations of helically driven turbulence, it is shown that the ratio of kinetic to magnetic energy dissipation scales with the magnetic Prandtl number in power law fashion with an exponent of approximately 0.6. Over six orders of magnitude in the magnetic Prandtl number the magnetic field is found to be sustained by large-scale dynamo action of alpha-squared type. This work extends a similar finding for small magnetic Prandtl numbers to the regime of large magnetic Prandtl numbers. At large magnetic Prandtl numbers, most of the energy is dissipated viscously, lowering thus the amount of magnetic energy dissipation, which means that simulations can be performed at magnetic Reynolds numbers that are large compared to the usual limits imposed by a given resolution. This is analogous to an earlier finding that at small magnetic Prandtl numbers, most of the energy is dissipated resistively, lowering the amount of kinetic energy dissipation, so simulations can then be performed at much larger fluid Reynolds...
Diffusion in anisotropic fully developed turbulence: Turbulent Prandtl number
Jurčišinová, E.; Jurčišin, M.
2016-10-01
Using the field theoretic renormalization group technique in the leading order of approximation of a perturbation theory the influence of the uniaxial small-scale anisotropy on the turbulent Prandtl number in the framework of the model of a passively advected scalar field by the turbulent velocity field driven by the Navier-Stokes equation is investigated for spatial dimensions d >2 . The influence of the presence of the uniaxial small-scale anisotropy in the model on the stability of the Kolmogorov scaling regime is briefly discussed. It is shown that with increasing of the value of the spatial dimension the region of stability of the scaling regime also increases. The regions of stability of the scaling regime are studied as functions of the anisotropy parameters for spatial dimensions d =3 ,4 , and 5. The dependence of the turbulent Prandtl number on the anisotropy parameters is studied in detail for the most interesting three-dimensional case. It is shown that the anisotropy of turbulent systems can have a rather significant impact on the value of the turbulent Prandtl number, i.e., on the rate of the corresponding diffusion processes. In addition, the relevance of the so-called weak anisotropy limit results are briefly discussed, and it is shown that there exists a relatively large region of small absolute values of the anisotropy parameters where the results obtained in the framework of the weak anisotropy approximation are in very good agreement with results obtained in the framework of the model without any approximation. The dependence of the turbulent Prandtl number on the anisotropy parameters is also briefly investigated for spatial dimensions d =4 and 5. It is shown that the dependence of the turbulent Prandtl number on the anisotropy parameters is very similar for all studied cases (d =3 ,4 , and 5), although the numerical values of the corresponding turbulent Prandtl numbers are different.
Convection-driven spherical shell dynamos at varying Prandtl numbers
Käpylä, P J; Olspert, N; Warnecke, J; Brandenburg, A
2016-01-01
(abidged) Context: Stellar convection zones are characterized by vigorous high-Reynolds number turbulence at low Prandtl numbers. Aims: We study the dynamo and differential rotation regimes at varying levels of viscous, thermal, and magnetic diffusion. Methods: We perform three-dimensional simulations of stratified fully compressible magnetohydrodynamic convection in rotating spherical wedges at various thermal and magnetic Prandtl numbers. Results: We find that the rotation profiles for high thermal diffusivity show a monotonically increasing angular velocity from the bottom of the convection zone to the top and from the poles toward the equator. For sufficiently rapid rotation, a region of negative radial shear develops at mid-latitudes as the thermal diffusivity is decreased. This coincides with a change in the dynamo mode from poleward propagating activity belts to equatorward propagating ones. Furthermore, the cyclic solutions disappear at the highest magnetic Reynolds numbers. The total magnetic energy ...
Numerical demonstration of fluctuation dynamo at low magnetic Prandtl numbers.
Iskakov, A B; Schekochihin, A A; Cowley, S C; McWilliams, J C; Proctor, M R E
2007-05-18
Direct numerical simulations of incompressible nonhelical randomly forced MHD turbulence are used to demonstrate for the first time that the fluctuation dynamo exists in the limit of large magnetic Reynolds number Rm>1 and small magnetic Prandtl number Pmdynamo on the hydrodynamic Reynolds number Re is obtained for 1 less than or similar Re less than or similar 6700. In the limit Pmdynamo at large and moderate Prandtl numbers: Rmc less than or similar 200 for Re greater than or similar 6000 compared to Rmc approximately 60 for Pm>or=1. It is not yet possible to determine numerically whether the growth rate of the magnetic energy is proportional, Rm1/2 in the limit Rm-->infinity, as it should be if the dynamo is driven by the inertial-range motions at the resistive scale.
Viscosity, thermal diffusivity and Prandtl number of nanoparticle suspensions
Institute of Scientific and Technical Information of China (English)
WANG Buxuan; ZHOU Leping; PENG Xiaofeng
2004-01-01
Using our reported experimental data of effective thermal conductivity, specific heat capacity and viscosity for CuO nanoparticle suspensions, the corresponding thermal diffusivity and Prandtl number are calculated. With the hard sphere model and considering effects of particle clustering and surface adsorption, the increase of viscosity for nanoparticle suspension observed is explained. It is shown that the effective thermal conductivity will be strongly affected by the formation and correlated spatial distribution of nanoparticle clusters when compared to viscosity in hosting liquid.
Small-scale dynamo at low magnetic Prandtl numbers.
Schober, Jennifer; Schleicher, Dominik; Bovino, Stefano; Klessen, Ralf S
2012-12-01
The present-day Universe is highly magnetized, even though the first magnetic seed fields were most probably extremely weak. To explain the growth of the magnetic field strength over many orders of magnitude, fast amplification processes need to operate. The most efficient mechanism known today is the small-scale dynamo, which converts turbulent kinetic energy into magnetic energy leading to an exponential growth of the magnetic field. The efficiency of the dynamo depends on the type of turbulence indicated by the slope of the turbulence spectrum v(ℓ)∝ℓ^{ϑ}, where v(ℓ) is the eddy velocity at a scale ℓ. We explore turbulent spectra ranging from incompressible Kolmogorov turbulence with ϑ=1/3 to highly compressible Burgers turbulence with ϑ=1/2. In this work, we analyze the properties of the small-scale dynamo for low magnetic Prandtl numbers Pm, which denotes the ratio of the magnetic Reynolds number, Rm, to the hydrodynamical one, Re. We solve the Kazantsev equation, which describes the evolution of the small-scale magnetic field, using the WKB approximation. In the limit of low magnetic Prandtl numbers, the growth rate is proportional to Rm^{(1-ϑ)/(1+ϑ)}. We furthermore discuss the critical magnetic Reynolds number Rm_{crit}, which is required for small-scale dynamo action. The value of Rm_{crit} is roughly 100 for Kolmogorov turbulence and 2700 for Burgers. Furthermore, we discuss that Rm_{crit} provides a stronger constraint in the limit of low Pm than it does for large Pm. We conclude that the small-scale dynamo can operate in the regime of low magnetic Prandtl numbers if the magnetic Reynolds number is large enough. Thus, the magnetic field amplification on small scales can take place in a broad range of physical environments and amplify week magnetic seed fields on short time scales.
Small-scale dynamo at low magnetic Prandtl numbers
Schober, Jennifer; Schleicher, Dominik; Bovino, Stefano; Klessen, Ralf S.
2012-12-01
The present-day Universe is highly magnetized, even though the first magnetic seed fields were most probably extremely weak. To explain the growth of the magnetic field strength over many orders of magnitude, fast amplification processes need to operate. The most efficient mechanism known today is the small-scale dynamo, which converts turbulent kinetic energy into magnetic energy leading to an exponential growth of the magnetic field. The efficiency of the dynamo depends on the type of turbulence indicated by the slope of the turbulence spectrum v(ℓ)∝ℓϑ, where v(ℓ) is the eddy velocity at a scale ℓ. We explore turbulent spectra ranging from incompressible Kolmogorov turbulence with ϑ=1/3 to highly compressible Burgers turbulence with ϑ=1/2. In this work, we analyze the properties of the small-scale dynamo for low magnetic Prandtl numbers Pm, which denotes the ratio of the magnetic Reynolds number, Rm, to the hydrodynamical one, Re. We solve the Kazantsev equation, which describes the evolution of the small-scale magnetic field, using the WKB approximation. In the limit of low magnetic Prandtl numbers, the growth rate is proportional to Rm(1-ϑ)/(1+ϑ). We furthermore discuss the critical magnetic Reynolds number Rmcrit, which is required for small-scale dynamo action. The value of Rmcrit is roughly 100 for Kolmogorov turbulence and 2700 for Burgers. Furthermore, we discuss that Rmcrit provides a stronger constraint in the limit of low Pm than it does for large Pm. We conclude that the small-scale dynamo can operate in the regime of low magnetic Prandtl numbers if the magnetic Reynolds number is large enough. Thus, the magnetic field amplification on small scales can take place in a broad range of physical environments and amplify week magnetic seed fields on short time scales.
Scaling in large Prandtl number turbulent thermal convection
Dubrulle, B
2011-01-01
We study the scaling properties of heat transfer $Nu$ in turbulent thermal convection at large Prandtl number $Pr$ using a quasi-linear theory. We show that two regimes arise, depending on the Reynolds number $Re$. At low Reynolds number, $Nu Pr^{-1/2}$ and $Re$ are a function of $Ra Pr^{-3/2}$. At large Reynolds number $Nu Pr^{1/3}$ and $Re Pr$ are function only of $Ra Pr^{2/3}$ (within logarithmic corrections). In practice, since $Nu$ is always close to $Ra^{1/3}$, this corresponds to a much weaker dependence of the heat transfer in the Prandtl number at low Reynolds number than at large Reynolds number. This difference may solve an existing controversy between measurements in SF6 (large $Re$) and in alcohol/water (lower $Re$). We link these regimes with a possible global bifurcation in the turbulent mean flow. We further show how a scaling theory could be used to describe these two regimes through a single universal function. This function presents a bimodal character for intermediate range of Reynolds num...
Direct Transition to Spatiotemporal Chaos in Low Prandtl Number Fluids
Xi, H; Gunton, J D; Xi, Hao-wen; Li, Xiao-jun
1996-01-01
We present the first large scale numerical simulation of three-dimensional Rayleigh-Bénard convection near onset, under free-free boundary conditions for a fluid of Prandtl number $\\sigma=0.5$. We find that a spatiotemporally chaotic state emerges immediately above onset, which we investigate as a function of the reduced control parameter $\\epsilon$. We conclude that the transition from conduction to spatiotemporal chaos is second order and of ``mean field'' character. We also present a simple theory for the time-averaged convective current. Finally, we show that the time-averaged structure factor satisfies a scaling behavior with respect to the correlation length near onset.
Zero-Prandtl-number convection with slow rotation
Maity, Priyanka; Kumar, Krishna
2014-01-01
We present the results of our investigations of the primary instability and the flow patterns near onset in zero-Prandtl-number Rayleigh-B\\'enard convection with uniform rotation about a vertical axis. The investigations are carried out using direct numerical simulations of the hydrodynamic equations with stress-free horizontal boundaries in rectangular boxes of size $(2\\pi/k_x) \\times (2\\pi/k_y) \\times 1$ for different values of the ratio $\\eta = k_x/k_y$. The primary instability is found to...
Convection-driven spherical shell dynamos at varying Prandtl numbers
Käpylä, P. J.; Käpylä, M. J.; Olspert, N.; Warnecke, J.; Brandenburg, A.
2017-02-01
Context. Stellar convection zones are characterized by vigorous high-Reynolds number turbulence at low Prandtl numbers. Aims: We study the dynamo and differential rotation regimes at varying levels of viscous, thermal, and magnetic diffusion. Methods: We perform three-dimensional simulations of stratified fully compressible magnetohydrodynamic convection in rotating spherical wedges at various thermal and magnetic Prandtl numbers (from 0.25 to 2 and from 0.25 to 5, respectively). Differential rotation and large-scale magnetic fields are produced self-consistently. Results: We find that for high thermal diffusivity, the rotation profiles show a monotonically increasing angular velocity from the bottom of the convection zone to the top and from the poles toward the equator. For sufficiently rapid rotation, a region of negative radial shear develops at mid-latitudes as the thermal diffusivity is decreased, corresponding to an increase of the Prandtl number. This coincides with and results in a change of the dynamo mode from poleward propagating activity belts to equatorward propagating ones. Furthermore, the clearly cyclic solutions disappear at the highest magnetic Reynolds numbers and give way to irregular sign changes or quasi-stationary states. The total (mean and fluctuating) magnetic energy increases as a function of the magnetic Reynolds number in the range studied here (5-151), but the energies of the mean magnetic fields level off at high magnetic Reynolds numbers. The differential rotation is strongly affected by the magnetic fields and almost vanishes at the highest magnetic Reynolds numbers. In some of our most turbulent cases, however, we find that two regimes are possible, where either differential rotation is strong and mean magnetic fields are relatively weak, or vice versa. Conclusions: Our simulations indicate a strong nonlinear feedback of magnetic fields on differential rotation, leading to qualitative changes in the behaviors of large
Energy transfers in dynamos with small magnetic Prandtl numbers
Kumar, Rohit
2015-06-25
We perform numerical simulation of dynamo with magnetic Prandtl number Pm = 0.2 on 10243 grid, and compute the energy fluxes and the shell-to-shell energy transfers. These computations indicate that the magnetic energy growth takes place mainly due to the energy transfers from large-scale velocity field to large-scale magnetic field and that the magnetic energy flux is forward. The steady-state magnetic energy is much smaller than the kinetic energy, rather than equipartition; this is because the magnetic Reynolds number is near the dynamo transition regime. We also contrast our results with those for dynamo with Pm = 20 and decaying dynamo. © 2015 Taylor & Francis.
Zero-Prandtl-number convection with slow rotation
Maity, Priyanka; Kumar, Krishna
2014-10-01
We present the results of our investigations of the primary instability and the flow patterns near onset in zero-Prandtl-number Rayleigh-Bénard convection with uniform rotation about a vertical axis. The investigations are carried out using direct numerical simulations of the hydrodynamic equations with stress-free horizontal boundaries in rectangular boxes of size (2π/kx) × (2π/ky) × 1 for different values of the ratio η = kx/ky. The primary instability is found to depend on η and Ta. Wavy rolls are observed at the primary instability for smaller values of η (1/√{3} ≤ η ≤ 2 except at η = 1) and for smaller values of Ta. We observed Küppers-Lortz (KL) type patterns at the primary instability for η = 1/√{3} and Ta ≥ 40. The fluid patterns are found to exhibit the phenomenon of bursting, as observed in experiments [K. M. S. Bajaj, G. Ahlers, and W. Pesch, "Rayleigh-Bénard convection with rotation at small Prandtl numbers," Phys. Rev. E 65, 056309 (2002)]. Periodic wavy rolls are observed at onset for smaller values of Ta, while KL-type patterns are observed for Ta ≥ 100 for η =√{3}. In case of η = 2, wavy rolls are observed for smaller values of Ta and KL-type patterns are observed for 25 ≤ Ta ≤ 575. Quasi-periodically varying patterns are observed in the oscillatory regime (Ta > 575). The behavior is quite different at η = 1. A time dependent competition between two sets of mutually perpendicular rolls is observed at onset for all values of Ta in this case. Fluid patterns are found to burst periodically as well as chaotically in time. It involved a homoclinic bifurcation. We have also made a couple of low-dimensional models to investigate bifurcations for η = 1, which is used to investigate the sequence of bifurcations.
Li, Zheng; Zhang, Yuwen
2016-01-01
The purposes of this paper are testing an efficiency algorithm based on LBM and using it to analyze two-dimensional natural convection with low Prandtl number. Steady state or oscillatory results are obtained using double multiple-relaxation-time thermal lattice Boltzmann method. The velocity and temperature fields are solved using D2Q9 and D2Q5 models, respectively. With different Rayleigh number, the tested natural convection can either achieve to steady state or oscillatory. With fixed Rayleigh number, lower Prandtl number leads to a weaker convection effect, longer oscillation period and higher oscillation amplitude for the cases reaching oscillatory solutions. At fixed Prandtl number, higher Rayleigh number leads to a more notable convection effect and longer oscillation period. Double multiple-relaxation-time thermal lattice Boltzmann method is applied to simulate the low Prandtl number fluid natural convection. Rayleigh number and Prandtl number effects are also investigated when the natural convection...
Azimuthal Magnetorotational Instability at low and high magnetic Prandtl numbers
Guseva, A; Willis, A P; Avila, M
2016-01-01
The magnetorotational instability (MRI) is considered to be one of the most powerful sources of turbulence in hydrodynamically stable quasi-Keplerian flows, such as those governing accretion disk flows. Although the linear stability of these flows with applied external magnetic field has been studied for decades, the influence of the instability on the outward angular momentum transport, necessary for the accretion of the disk, is still not well known. In this work we model Keplerian rotation with Taylor-Couette flow and imposed azimuthal magnetic field using both linear and nonlinear approaches. We present scalings of instability with Hartmann and Reynolds numbers via linear analysis and direct numerical simulations (DNS) for the two magnetic Prandtl numbers of $1.4 \\cdot 10^{-6}$ and $1$. Inside of the instability domains modes with different axial wavenumbers dominate, resulting in sub-domains of instabilities, which appear different for each $Pm$. The DNS show the emergence of 1- and 2-frequency spatio-te...
Fluctuation dynamo and turbulent induction at small Prandtl number.
Eyink, Gregory L
2010-10-01
We study the Lagrangian mechanism of the fluctuation dynamo at zero Prandtl number and infinite magnetic Reynolds number, in the Kazantsev-Kraichnan model of white-noise advection. With a rough velocity field corresponding to a turbulent inertial range, flux freezing holds only in a stochastic sense. We show that field lines arriving to the same point which were initially separated by many resistive lengths are important to the dynamo. Magnetic vectors of the seed field that point parallel to the initial separation vector arrive anticorrelated and produce an "antidynamo" effect. We also study the problem of "magnetic induction" of a spatially uniform seed field. We find no essential distinction between this process and fluctuation dynamo, both producing the same growth rates and small-scale magnetic correlations. In the regime of very rough velocity fields where fluctuation dynamo fails, we obtain the induced magnetic energy spectra. We use these results to evaluate theories proposed for magnetic spectra in laboratory experiments of turbulent induction.
The Small-Scale Dynamo at Low Magnetic Prandtl Numbers
Schober, Jennifer; Bovino, Stefano; Klessen, Ralf S
2012-01-01
The present-day Universe is highly magnetized, even though the first magnetic seed fields were most probably extremely weak. To explain the growth of the magnetic field strength over many orders of magnitude fast amplification processes need to operate. The most efficient mechanism known today is the small-scale dynamo, which converts turbulent kinetic energy into magnetic energy leading to an exponential growth of the magnetic field. The efficiency of the dynamo depends on the type of turbulence indicated by the slope of the turbulence spectrum v(l) \\propto l^{theta}, where v(l) is the eddy velocity at a scale l. We explore turbulent spectra ranging from incompressible Kolmogorov turbulence with theta = 1/3 to highly compressible Burgers turbulence with theta = 1/2. In this work we analyze the properties of the small-scale dynamo for low magnetic Prandtl numbers Pm, which denotes the ratio of the magnetic Reynolds number, Rm, to the hydrodynamical one, Re. We solve the Kazantsev equation, which describes the...
Fluctuation Dynamo and Turbulent Induction at Small Prandtl Number
Eyink, Gregory L
2010-01-01
We study the Lagrangian mechanism of the fluctuation dynamo at zero Prandtl number and infinite magnetic Reynolds number, in the Kazantsev-Kraichnan model of white-noise advection. With a rough velocity field corresponding to a turbulent inertial-range, flux-freezing holds only in a stochastic sense. We show that field-lines arriving to the same point which were initially separated by many resistive lengths are important to the dynamo. Magnetic vectors of the seed field that point parallel to the initial separation vector arrive anti-correlated and produce an "anti-dynamo" effect. We also study the problem of "magnetic induction" of a spatially uniform seed field. We find no essential distinction between this process and fluctuation dynamo, both producing the same growth-rates and small-scale magnetic correlations. In the regime of very rough velocity fields where fluctuation dynamo fails, we obtain the induced magnetic energy spectra. We use these results to evaluate theories proposed for magnetic spectra in...
Jurčišinová, E; Jurčišin, M; Remecký, R
2011-10-01
The turbulent magnetic Prandtl number in the framework of the kinematic magnetohydrodynamic (MHD) turbulence, where the magnetic field behaves as a passive vector field advected by the stochastic Navier-Stokes equation, is calculated by the field theoretic renormalization group technique in the two-loop approximation. It is shown that the two-loop corrections to the turbulent magnetic Prandtl number in the kinematic MHD turbulence are less than 2% of its leading order value (the one-loop value) and, at the same time, the two-loop turbulent magnetic Prandtl number is the same as the two-loop turbulent Prandtl number obtained in the corresponding model of a passively advected scalar field. The dependence of the turbulent magnetic Prandtl number on the spatial dimension d is investigated and the source of the smallness of the two-loop corrections for spatial dimension d=3 is identified and analyzed.
Dynamos at extreme magnetic Prandtl numbers: insights from shell models
Verma, Mahendra K.; Kumar, Rohit
2016-12-01
We present an MHD shell model suitable for computation of various energy fluxes of magnetohydrodynamic turbulence for very small and very large magnetic Prandtl numbers $\\mathrm{Pm}$; such computations are inaccessible to direct numerical simulations. For small $\\mathrm{Pm}$, we observe that both kinetic and magnetic energy spectra scale as $k^{-5/3}$ in the inertial range, but the dissipative magnetic energy scales as $k^{-11/3}\\exp(-k/k_\\eta)$. Here, the kinetic energy at large length scale feeds the large-scale magnetic field that cascades to small-scale magnetic field, which gets dissipated by Joule heating. The large-$\\mathrm{Pm}$ dynamo has a similar behaviour except that the dissipative kinetic energy scales as $k^{-13/3}$. For this case, the large-scale velocity field transfers energy to the large-scale magnetic field, which gets transferred to small-scale velocity and magnetic fields; the energy of the small-scale magnetic field also gets transferred to the small-scale velocity field, and the energy thus accumulated is dissipated by the viscous force.
Zero-Prandtl-number convection with slow rotation
Maity, Priyanka
2014-01-01
We present the results of our investigations of the primary instability and the flow patterns near onset in zero-Prandtl-number Rayleigh-B\\'{e}nard convection with uniform rotation about a vertical axis. The investigations are carried out using direct numerical simulations of the hydrodynamic equations with stress-free horizontal boundaries in rectangular boxes of size $(2\\pi/k_x) \\times (2\\pi/k_y) \\times 1$ for different values of the ratio $\\eta = k_x/k_y$. The primary instability is found to depend on $\\eta$ and $Ta$. Wavy rolls are observed at the primary instability for smaller values of $\\eta$ ($1/\\sqrt{3} \\le \\eta \\le 2$ except at $\\eta = 1$) and for smaller values of $Ta$. We observed K\\"{u}ppers-Lortz (KL) type patterns at the primary instability for $\\eta = 1/\\sqrt{3}$ and $ Ta \\ge 40$. The fluid patterns are found to exhibit the phenomenon of bursting, as observed in experiments [Bajaj et al. Phys. Rev. E {\\bf 65}, 056309 (2002)]. Periodic wavy rolls are observed at onset for smaller values of $Ta$...
Viscous range of turbulent scalar of large Prandtl number
Qian, J.
1995-02-01
The analytical theory of a turbulent scalar, developed in previous papers is extended to the case of large Prandtl number. The fluctuation character of the least principal rate of strain gamma has an important effect upon the scalar spectrum. The scalar variance spectrum in the viscous range is F(k) = 4.472 (nu/epsilon)(exp 1/2) chi k(exp -1) H(x), X is identical to (k/k(sub b))(exp 2), H(x) is a dimensionless universal function and is determined by solving numerically the closed spectral dynamical equations. A simple fitting formula of the numerical result is H(x) = 0.7687 exp(- 3.79x) + 0.2313 exp(-11.13 x), which corresponds a two-values fluctuation model of gamma. Here upsilon is the kinematic viscosity, k(sub b) is identical to (epsilon/upsilon mu(exp 2))(exp 1/4) is the Batchelor wavenumber, mu is the scalar diffusivity, and epsilon and eni are respectively the energy and variance dissipation rates.
Transitional boundary layers in low-Prandtl-number convection
Schumacher, Jörg; Bandaru, Vinodh; Pandey, Ambrish; Scheel, Janet D.
2016-12-01
The boundary layer structure of the velocity and temperature fields in turbulent Rayleigh-Bénard flows in closed cylindrical cells of unit aspect ratio is revisited from a transitional and turbulent viscous boundary layer perspective. When the Rayleigh number is large enough, the dynamics at the bottom and top plates can be separated into an impact region of downwelling plumes, an ejection region of upwelling plumes, and an interior region away from the side walls. The latter is dominated by the shear of the large-scale circulation (LSC) roll, which fills the whole cell and continuously varies its orientation. The working fluid is liquid mercury or gallium at a Prandtl number Pr=0.021 for Rayleigh numbers 3 ×105≤Ra≤4 ×108 . The generated turbulent momentum transfer corresponds to macroscopic flow Reynolds numbers with 1.8 ×103≤Re≤4.6 ×104 . In highly resolved spectral element direct numerical simulations, we present the mean profiles of velocity, Reynolds stress, and temperature in inner viscous units and compare our findings with convection experiments and channel flow data. The complex three-dimensional and time-dependent structure of the LSC in the cell is compensated by a plane-by-plane symmetry transformation which aligns the horizontal velocity components and all its derivatives with the instantaneous orientation of the LSC. As a consequence, the torsion of the LSC is removed, and a streamwise direction in the shear flow can be defined. It is shown that the viscous boundary layers for the largest Rayleigh numbers are highly transitional and obey properties that are directly comparable to transitional channel flows at friction Reynolds numbers Reτ≲102 . The transitional character of the viscous boundary layer is also underlined by the strong enhancement of the fluctuations of the wall stress components with increasing Rayleigh number. An extrapolation of our analysis data suggests that the friction Reynolds number Reτ in the velocity boundary
Sustained Turbulence in Differentially Rotating Magnetized Fluids at Low Magnetic Prandtl Number
Nauman, Farrukh
2016-01-01
We show for the first time that sustained turbulence is possible at low magnetic Prandtl number for Keplerian flows with no mean magnetic flux. Our results indicate that increasing the vertical domain size is equivalent to increasing the dynamical range between the energy injection scale and the dissipative scale. This has important implications for a large variety of differentially rotating systems with low magnetic Prandtl number such as protostellar disks and laboratory experiments.
Sustained Turbulence in Differentially Rotating Magnetized Fluids at Low Magnetic Prandtl Number
DEFF Research Database (Denmark)
Nauman, Farrukh; Pessah, Martin E.
2016-01-01
We show for the first time that sustained turbulence is possible at low magnetic Prandtl number for Keplerian flows with no mean magnetic flux. Our results indicate that increasing the vertical domain size is equivalent to increasing the dynamical range between the energy injection scale...... and the dissipative scale. This has important implications for a large variety of differentially rotating systems with low magnetic Prandtl number such as protostellar disks and laboratory experiments....
High Prandtl number effect on Rayleigh-Bénard convection heat transfer at high Rayleigh number
Ma, Li; Li, Jing; Ji, Shui; Chang, Huajian
2017-02-01
This paper represents results of the Rayleigh-Bénard convection heat transfer in silicon oil confined by two horizontal plates, heated from below, and cooled from above. The Prandtl numbers considered as 100-10,000 corresponding to three types of silicon oil. The experiments covered a range of Rayleigh numbers from 2.14·109 to 2.27·1013. The data points that the Nusselt number dependents on the Rayleigh number, which is asymptotic to a 0.248 power. Furthermore, the experiment results can fit the data in low Rayleigh number well.
Jurčišinová, E; Jurčišin, M; Remecký, R; Zalom, P
2013-04-01
Using the field theoretic renormalization group technique, the influence of helicity (spatial parity violation) on the turbulent magnetic Prandtl number in the kinematic magnetohydrodynamic turbulence is investigated in the two-loop approximation. It is shown that the presence of helicity decreases the value of the turbulent magnetic Prandtl number and, at the same time, the two-loop helical contribution to the turbulent magnetic Prandtl number is at most 4.2% (in the case with the maximal helicity) of its nonhelical value. These results demonstrate, on one hand, the potential importance of the presence of asymmetries in processes in turbulent environments and, on the other hand, the rather strong stability of the properties of diffusion processes of the magnetic field in the conductive turbulent environment with the spatial parity violation in comparison to the corresponding systems without the spatial parity violation. In addition, obtained results are compared to the corresponding results found for the two-loop turbulent Prandtl number in the model of passively advected scalar field. It is shown that the turbulent Prandtl number and the turbulent magnetic Prandtl number, which are the same in fully symmetric isotropic turbulent systems, are essentially different when one considers the spatial parity violation. It means that the properties of the diffusion processes in the turbulent systems with a given symmetry breaking can considerably depend on the internal tensor structure of advected quantities.
Investigation of the helium proportion influence on the Prandtl number value of gas mixtures
Directory of Open Access Journals (Sweden)
S. A. Burtsev
2014-01-01
Full Text Available The paper investigates an influence of helium fraction (light gases on the Prandtl number value for binary and more complex gas mixtures.It is shown that a low value of the Prandtl number (Pr-number results in decreasing a temperature recovery factor value and, respectively, in reducing a recovery temperature value on the wall (thermoinsulated wall temperature with the compressive gas flow bypassing it. This, in turn, allows us to increase efficiency of gasdynamic energy separation in Leontyev's tube.The paper conducts a numerical research of the influence of binary and more complex gas mixture composition on the Prandtl number value. It is shown that a mixture of two gases with small and large molecular weight allows us to produce a mixture with a lower value of the Prandtl number in comparison with the initial gases. Thus, the value of Prandtl number decreases by 1.5-3.2 times in comparison with values for pure components (the more a difference of molar mass of components, the stronger is a decrease.The technique to determine the Prandtl number value for mixtures of gases in the wide range of temperatures and pressure is developed. Its verification based on experimental data and results of numerical calculations of other authors is executed. It is shown that it allows correct calculation of binary and more complex mixtures of gasesFor the mixtures of inert gases it has been obtained that the minimum value of the Prandtl number is as follows: for helium - xenon mixtures (He-Xe makes 0.2-0.22, for helium - krypton mixtures (He-Kr – 0.3, for helium - argon mixes (He-Ar – 0.41.For helium mixture with carbon dioxide the minimum value of the Prandtl number makes about 0.4, for helium mixture with N2 nitrogen the minimum value of the Prandtl number is equal to 0.48, for helium-methane (CH4 - 0.5 and helium – oxygen (O2 – 0.46.This decrease is caused by the fact that the thermal capacity of mixture changes under the linear law in regard to the
Convection-driven kinematic dynamos at low Rossby and magnetic Prandtl numbers
Calkins, Michael A; Nieves, David; Julien, Keith; Tobias, Steven M
2016-01-01
Most large-scale planetary magnetic fields are thought to be driven by low Rossby number convection of a low magnetic Prandtl number fluid. Here kinematic dynamo action is investigated with an asymptotic, rapidly rotating dynamo model for the plane layer geometry that is intrinsically low magnetic Prandtl number. The thermal Prandtl number and Rayleigh number are varied to illustrate fundamental changes in flow regime, ranging from laminar cellular convection to geostrophic turbulence in which an inverse energy cascade is present. A decrease in the efficiency of the convection to generate a dynamo, as determined by an increase in the critical magnetic Reynolds number, is observed as the buoyancy forcing is increased. This decreased efficiency may result from both the loss of correlations associated with the increasingly disordered states of flow that are generated, and boundary layer behavior that enhances magnetic diffusion locally. We find that the spatial characteristics of $\\alpha$, and thus the large-sca...
Calkins, Michael A; Tobias, Steven M; Aurnou, Jonathan M; Marti, Philippe
2015-01-01
The onset of dynamo action is investigated within the context of a newly developed low Rossby, low magnetic Prandtl number, convection-driven dynamo model. The model represents an asymptotically exact form of an $\\alpha^2$ mean field dynamo model in which the small-scale convection is represented explicitly by the finite amplitude, single mode convective solutions first investigated by Bassom and Zhang (Geophys.~Astrophys.~Fluid Dyn., \\textbf{76}, p.223, 1994). Both steady and oscillatory convection are considered for a variety of horizontal planforms. The kinematic helicity is observed to be a monotonically increasing function of the Rayleigh number; as a result, very small magnetic Prandtl number dynamos can be found for a sufficiently large Rayleigh number. All dynamos are found to be oscillatory with an oscillation frequency that increases as the strength of the convection is increased and the magnetic Prandtl number is reduced. Single mode solutions which exhibit boundary layer behavior in the kinematic ...
Energy Technology Data Exchange (ETDEWEB)
Yamamoto, Yoshinobu, E-mail: yamamotoy@yamanashi.ac.jp [Division of Mechanical Engineering, University of Yamanashi, 4-3-11 Takeda, Kofu 400-8511 (Japan); Kunugi, Tomoaki, E-mail: kunugi@nucleng.kyoto-u.ac.jp [Department of Nuclear Engineering, Kyoto University, C3-d2S06, Kyoto-Daigaku Katsura, Nishikyo-Ku 615-8540, Kyoto (Japan)
2016-11-01
Highlights: • We show the applicability to predict the heat transfer imposed on a uniform wall-normal magnetic field by means of the zero-equation heat transfer model. • Quasi-theoretical turbulent Prandtl numbers with various molecular Prandtl number fluids were obtained. • Improvements of the prediction accuracy in turbulent kinetic energy and turbulent dissipation rate under the magnetic fields were accomplished. - Abstract: Zero-equation heat transfer models based on the constant turbulent Prandtl number are evaluated using direct numerical simulation (DNS) data for fully developed channel flows imposed on a uniform wall-normal magnetic field. Quasi-theoretical turbulent Prandtl numbers are estimated by DNS data of various molecular Prandtl number fluids. From the viewpoint of highly-accurate magneto-hydrodynamic (MHD) heat transfer prediction, the parameters of the turbulent eddy viscosity of the k–É› model are optimized under the magnetic fields. Consequently, we use the zero-equation model based on a constant turbulent Prandtl number to demonstrate MHD heat transfer, and show the applicability of using this model to predict the heat transfer.
Gourdon, Mathias; Karlsson, Erik; Innings, Fredrik; Jongsma, Alfred; Vamling, Lennart
2016-02-01
In many industrial applications, falling film evaporation is an attractive technique for solvent removal due to high heat transfer and low residence times. Examples are the powder production in the dairy industry and in kraft pulp production process to remove water from so called black liquor. Common for both applications is that the fluids exhibit high viscosities in industrial practice. In this paper, results from experimental studies on both black liquor and a dairy product are reported for Prandtl numbers up to 800. The results are compared with several existing correlation in literature, and the need for a modified correlation is recognized especially to cover higher Prandtl-numbers. The following correlation for the turbulent flow region with 3 literature data from one additional study on two other fluids (propylene glycol and cyclohexanol) with fairly high Prandtl-numbers, from 40 to 58 and from 45 to 155 respectively and the agreement was within ±40 %.
Challenges in simulation and modeling of heat transfer in low-Prandtl number fluids
Energy Technology Data Exchange (ETDEWEB)
Groetzbach, G., E-mail: groetzbach@kit.edu [Karlsruher Inst. fuer Technologie (KIT), Inst. fuer Kern-und Energietechnik, Karlsruhe (Germany)
2011-07-01
Nuclear heat transfer applications with low-Prandtl number fluids are often in the transition range between conduction and convection dominated regimes. Most flows in reactors involve also anisotropic turbulent fluxes and strong buoyancy influences. The relevance and complexity of the required heat flux modelling is discussed depending on engineering issues. The needed acceptable models range from turbulent Prandtl number concepts, over algebraic flux models, to full second order models in RANS as well as in LES, all with special liquid metal extensions. Recommendations are deduced for the promising HYBRID models. The listed remaining challenges show the need for further development of models and instrumentation. (author)
The Numerical Study on the Influence of Prandtl Number and Height of the Enclosure
Energy Technology Data Exchange (ETDEWEB)
Moon, Je-Young; Chung, Bum-Jin [Kyung Hee University, Yongin (Korea, Republic of)
2016-10-15
This study investigated numerically the internal flow depending on Prandtl number of fluid and height of enclosure. The two-dimensional numerical simulations were performed for several heights of enclosure in the range between 0.01 m and 0.074 m. It corresponds to the aspect ratio (H/L) ranged from 0.07 to 0.5. Prandtl number was 0.2, 0.7 and 7. Rayleigh number based on the height of enclosure ranged between 8.49x10{sup 3} and 1.20x10{sup 8}. The numerical calculations were carried out using FLUENT 6.3. In order to confirm the influence of Prandtl number and height of side walls on the internal flow and heat transfer of the horizontal enclosure, the numerical study is carried out using the FLUENT 6.3. The numerical results for the condition of top cooling only agree well with Rayleigh-Benard natural convection. When the top and side walls were cooled, the internal flow of enclosure is more complex. The thickness of thermal and velocity boundary layer varies with Prandtl number. For Pr>1 the behavior of cells is unstable and irregular owing to the entrained plume, whereas the internal flow for Pr<1 is stable and regular. Also, the number of cells increases depending on decrease of height. As a result, the heat exchange increases.
Convection-driven kinematic dynamos at low Rossby and magnetic Prandtl numbers
Calkins, Michael A.; Long, Louie; Nieves, David; Julien, Keith; Tobias, Steven M.
2016-12-01
Most large-scale planetary magnetic fields are thought to be driven by low Rossby number convection of a low magnetic Prandtl number fluid. Here kinematic dynamo action is investigated with an asymptotic, rapidly rotating dynamo model for the plane layer geometry that is intrinsically low magnetic Prandtl number. The thermal Prandtl number and Rayleigh number are varied to illustrate fundamental changes in flow regime, ranging from laminar cellular convection to geostrophic turbulence in which an inverse energy cascade is present. A decrease in the efficiency of the convection to generate a dynamo, as determined by an increase in the critical magnetic Reynolds number, is observed as the buoyancy forcing is increased. This decreased efficiency may result from both the loss of correlations associated with the increasingly disordered states of flow that are generated, and boundary layer behavior that enhances magnetic diffusion locally. We find that the spatial characteristics of the large-scale magnetic field is dependent only weakly on changes in flow behavior. In contrast, the behavior of the small-scale magnetic field is directly dependent on, and therefore shows significant variations with, the small-scale convective flow field. However, our results are limited to the linear, kinematic dynamo regime; future simulations that include the Lorentz force are therefore necessary to assess the robustness of these results.
Global and local statistics in turbulent convection at low Prandtl numbers
Scheel, Janet D
2016-01-01
Statistical properties of turbulent Rayleigh-Benard convection at low Prandtl numbers (Pr), which are typical for liquid metals such as mercury, gallium or liquid sodium, are investigated in high-resolution three-dimensional spectral element simulations in a closed cylindrical cell with an aspect ratio of one and are compared to previous turbulent convection simulations in air. We compare the scaling of global momentum and heat transfer. The scaling exponents are found to be in agreement with experiments. Mean profiles of the root-mean-square velocity as well as the thermal and kinetic energy dissipation rates have growing amplitudes with decreasing Prandtl number which underlies a more vigorous bulk turbulence in the low-Pr regime. The skin-friction coefficient displays a Reynolds-number dependence that is close to that of an isothermal, intermittently turbulent velocity boundary layer. The thermal boundary layer thicknesses are larger as Pr decreases and conversely the velocity boundary layer thicknesses be...
A Fokker-Planck Model of the Boltzmann Equation with Correct Prandtl Number for Polyatomic Gases
Mathiaud, J.; Mieussens, L.
2017-09-01
We propose an extension of the Fokker-Planck model of the Boltzmann equation to get a correct Prandtl number in the Compressible Navier-Stokes asymptotics for polyatomic gases. This is obtained by replacing the diffusion coefficient (which is the equilibrium temperature) by a non diagonal temperature tensor, like the Ellipsoidal-Statistical model is obtained from the Bathnagar-Gross-Krook model of the Boltzmann equation, and by adding a diffusion term for the internal energy. Our model is proved to satisfy the properties of conservation and a H-theorem. A Chapman-Enskog analysis shows how to compute the transport coefficients of our model. Some numerical tests are performed to illustrate that a correct Prandtl number can be obtained.
Similarities between 2D and 3D convection for large Prandtl number
Indian Academy of Sciences (India)
PANDEY AMBRISH; VERMA MAHENDRA K; CHATTERJEE ANANDO G; DUTTA BIPLAB
2016-07-01
Using direct numerical simulations of Rayleigh–Bénard convection (RBC), we perform a comparative study of the spectra and fluxes of energy and entropy, and the scaling of large-scale quantities for large and infinite Prandtl numbers in two (2D) and three (3D) dimensions. We observe close similarities between the 2D and 3D RBC, in particular, the kinetic energy spectrum $E^{u}(k) ∼ k^{−13/3}$, and the entropy spectrum exhibits a dual branch with a dominant $k^{−2}$ spectrum. We showed that the dominant Fourier modes in 2D and 3D flows are very close. Consequently, the 3D RBC is quasi-two-dimensional, which is the reason for the similarities between the 2D and 3D RBC for large and infinite Prandtl numbers.
A Fokker-Planck Model of the Boltzmann Equation with Correct Prandtl Number for Polyatomic Gases
Mathiaud, J.; Mieussens, L.
2017-07-01
We propose an extension of the Fokker-Planck model of the Boltzmann equation to get a correct Prandtl number in the Compressible Navier-Stokes asymptotics for polyatomic gases. This is obtained by replacing the diffusion coefficient (which is the equilibrium temperature) by a non diagonal temperature tensor, like the Ellipsoidal-Statistical model is obtained from the Bathnagar-Gross-Krook model of the Boltzmann equation, and by adding a diffusion term for the internal energy. Our model is proved to satisfy the properties of conservation and a H-theorem. A Chapman-Enskog analysis shows how to compute the transport coefficients of our model. Some numerical tests are performed to illustrate that a correct Prandtl number can be obtained.
Anatomy of a laminar starting thermal plume at high Prandtl number
Davaille, Anne; Limare, Angela; Touitou, Floriane; Kumagai, Ichiro; Vatteville, Judith
2011-02-01
We present an experimental study of the dynamics of a plume generated from a small heat source in a high Prandtl number fluid with a strongly temperature-dependent viscosity. The velocity field was determined with particle image velocimetry, while the temperature field was measured using differential interferometry and thermochromic liquid crystals. The combination of these different techniques run simultaneously allows us to identify the different stages of plume development, and to compare the positions of key-features of the velocity field (centers of rotation, maximum vorticity locations, stagnation points) respective to the plume thermal anomaly, for Prandtl numbers greater than 103. We further show that the thermal structure of the plume stem is well predicted by the constant viscosity model of Batchelor (Q J R Met Soc 80: 339-358, 1954) for viscosity ratios up to 50.
Turbulent magnetic Prandtl numbers obtained with MHD Taylor-Couette flow experiments
Gellert, M
2008-01-01
The stability problem of MHD Taylor-Couette flows with toroidal magnetic fields is considered in dependence on the magnetic Prandtl number. Only the most uniform (but not current-free) field with B\\_in = B\\_out has been considered. For high enough Hartmann numbers the toroidal field is always unstable. Rigid rotation, however, stabilizes the magnetic (kink-)instability. The axial current which drives the instability is reduced by the electromotive force induced by the instability itself. Numerical simulations are presented to probe this effect as a possibility to measure the turbulent conductivity in a laboratory. It is shown numerically that in a sodium experiment (without rotation) an eddy diffusivity 4 times the molecular diffusivity appears resulting in a potential difference of ~34 mV/m. If the cylinders are rotating then also the eddy viscosity can be measured. Nonlinear simulations of the instability lead to a turbulent magnetic Prandtl number of 2.1 for a molecular magnetic Prandtl number of 0.01. The...
Simulation of Heat Transfer to the Gas Coolant with Low Prandtl Number Value
Directory of Open Access Journals (Sweden)
T. N. Kulikova
2015-01-01
Full Text Available The work concerns the simulating peculiarities of heat transfer to the gas coolants with low values of the Prandtl number, in particular, to the binary mixtures of inert gases.The paper presents simulation results of heat transfer to the fully established flow of a helium-xenon mixture in the round tube of 6 mm in diameter with the boundary condition of the second kind. It considers a flow of three helium-xenon mixtures with different helium content and molecular Prandtl numbers within the range 0.239–0.322 and with Reynolds numbers ranged from 10000 to 50000. During numerical simulation a temperature factor changed from 1.034 to 1.061. CFD-code STAR-CCM+ that is designed for solving a wide range of problems of hydrodynamics, heat transfer and stress was used as the primary software.The applicability of the five models for the turbulent Prandtl number is examined. It is shown that the choice of the model has a significant influence on the heat transfer coefficient. The paper presents structural characteristics of the flow in the wall region. It estimates a thermal stabilization section to be approximately as long as 30 diameters of tube.Simulation results are compared with the known data on heat transfer to gas coolants with low values of the Prandtl number. It is shown that V2F low-Reynolds number -ε turbulence model with an approximation for the turbulent Prandtl number used according Kays-CrawfordWeigand gives the best compliance with the results predicted by relationships of Kays W.M. and Petukhov B.S. The approximating correlation summarizes a set of simulation results.Application of the work results is reasonable when conducting the numerical simulation of heat transfer to binary gas mixtures in channels of different forms. The presented approximating correlation allows rapid estimate of heat transfer coefficients to the gas coolants with a low value of the molecular Prandl number within the investigated range with a flow through the
Subcritical convection in a rapidly rotating sphere at low Prandtl number
Guervilly, Celine
2016-01-01
We study non-linear convection in a low Prandtl number fluid ($Pr = 0.01-0.1$) in a rapidly rotating sphere with internal heating. We use a numerical model based on the quasi-geostrophic approximation, in which variations of the axial vorticity along the rotation axis are neglected, whereas the temperature field is fully three-dimensional. We identify two separate branches of convection close to onset: (i) a well-known weak branch for Ekman numbers greater than $10^{-6}$, which is continuous at the onset (supercritical bifurcation) and consists of a superposition of thermal Rossby waves, and (ii) a novel strong branch at lower Ekman numbers, which is discontinuous at the onset. The strong branch becomes subcritical for Ekman numbers of the order of $10^{-8}$. On the strong branch, the Reynolds number of the flow is greater than $10^3$, and a strong zonal flow with multiple jets develops, even close to the non-linear onset of convection. We find that the subcriticality is amplified by decreasing the Prandtl nu...
Effects of external environment on thermocapillary convection of high prandtl number fluid
Directory of Open Access Journals (Sweden)
Liang Ruquan
2016-01-01
Full Text Available Numerical simulations have been carried out to investigate the influence of external environment on thermocapillary convection in high Prandtl number (Pr=68 liquid. The geometric model of physical problem is that the the liquid bridge surrounded by ambient air under zero or ground gravity. The interface velocity, temperature, heat flux and flow pattern in the liquid bridge are presented and discussed under different conditions by changing the external environment. The buoyancy convection produces a symmetrical vortex in the liquid bridge. The ambient air affects the distributions of the temperature velocity and heat flux on the interface by changing the thermocapillary convection.
Jung, Eunbum; Lee, Wook; Kang, Seongwon; Iaccarino, Gianluca
2015-11-01
The turbulent Prandtl number (Prt) is an important parameter in turbulent flows used in many engineering models for heat transfer. In the present study, spatial variation of Prt in a wall-bounded turbulent flow is investigated using DNS. We derived a form of Prt applicable to a general flow configuration, using the least-square method in a manner consistent with the turbulent viscosity model in LES. For a flow subject to local acceleration and deceleration induced by the wall geometry, we performed a parametric study for the Reynolds number, Prandtl number and a geometric factor using DNS. A comparison of the data from DNS and RANS with a constant Prt indicates the potential of improved RANS predictions using the present variable Prt subject to the local flow field. Also, it is observed that the local pressure gradient has an important effect on the Prt field. From the flow statistics, a few flow variables showing higher correlations with Prt are identified. An elementary model for Prt is devised, and used for RANS prediction producing a more accurate prediction of the heat transfer rate. Corresponding author
Ochrymiuk, Tomasz
2016-06-01
Numerical simulations were performed to predict the film cooling effectiveness on the fiat plate with a three- dimensional discrete-hole film cooling arrangement. The effects of basic geometrical characteristics of the holes, i.e. diameter D, length L and pitch S/D were studied. Different turbulent heat transfer models based on constant and variable turbulent Prandtl number approaches were considered. The variability of the turbulent Prandtl number Pr t in the energy equation was assumed using an algebraic relation proposed by Kays and Crawford, or employing the Abe, Kondoh and Nagano eddy heat diffusivity closure with two differential transport equations for the temperature variance k θ and its destruction rate ɛ θ . The obtained numerical results were directly compared with the data that came from an experiment based on Transient Liquid Crystal methodology. All implemented models for turbulent heat transfer performed sufficiently well for the considered case. It was confirmed, however, that the two- equation closure can give a detailed look into film cooling problems without using any time-consuming and inherently unsteady models.
Turbulent magnetic field amplification from the smallest to the largest magnetic Prandtl numbers
Bovino, Stefano; Schober, Jennifer
2012-01-01
The small-scale dynamo provides a highly efficient mechanism for the conversion of turbulent into magnetic energy. In astrophysical environments, such turbulence often occurs at high Mach numbers, implying steep slopes in the turbulent spectra. It is thus a central question whether the small-scale dynamo can amplify magnetic fields in the interstellar or intergalactic media, where such Mach numbers occur. To address this long-standing issue, we employ the Kazantsev model for turbulent magnetic field amplification, systematically exploring the effect of different turbulent slopes, as expected for Kolmogorov, Burgers, the Larson laws and results derived from numerical simulations. With the framework employed here, we give the first solution encompassing the complete range of magnetic Prandtl numbers, including Pm > 1. We derive scaling laws of the growth rate as a function of hydrodynamic and magnetic Reynolds number for Pm > 1 for all types of turbulence. A central result concerns the regime of Pm ~ 1, where t...
Examining the Impact of Prandtl Number and Surface Convection Models on Deep Solar Convection
O'Mara, B. D.; Augustson, K.; Featherstone, N. A.; Miesch, M. S.
2015-12-01
Turbulent motions within the solar convection zone play a central role in the generation and maintenance of the Sun's magnetic field. This magnetic field reverses its polarity every 11 years and serves as the source of powerful space weather events, such as solar flares and coronal mass ejections, which can affect artificial satellites and power grids. The structure and inductive properties are linked to the amplitude (i.e. speed) of convective motion. Using the NASA Pleiades supercomputer, a 3D fluids code simulates these processes by evolving the Navier-Stokes equations in time and under an anelastic constraint. This code simulates the fluxes describing heat transport in the sun in a global spherical-shell geometry. Such global models can explicitly capture the large-scale motions in the deep convection zone but heat transport from unresolved small-scale convection in the surface layers must be parameterized. Here we consider two models for heat transport by surface convection, including a conventional turbulent thermal diffusion as well as an imposed flux that carries heat through the surface in a manner that is independent of the deep convection and the entropy stratification it establishes. For both models, we investigate the scaling of convective amplitude with decreasing diffusion (increasing Rayleigh number). If the Prandtl number is fixed, we find that the amplitude of convective motions increases with decreasing diffusion, possibly reaching an asymptotic value in the low diffusion limit. However, if only the thermal diffusion is decreased (keeping the viscosity fixed), we find that the amplitude of convection decreases with decreasing diffusion. Such a high-Prandtl-number, high-Peclet-number limit may be relevant for the Sun if magnetic fields mix momentum, effectively acting as an enhanced viscosity. In this case, our results suggest that the amplitude of large-scale convection in the Sun may be substantially less than in current models that employ an
A Study on Time-Scales Ratio and Turbulent Prandtl Number in Ducts of Industrial Applications
DEFF Research Database (Denmark)
Rokni, Masoud
2006-01-01
This investigation concerns numerical time-scales ratio and turbulent Prandtl number in fully developed turbulent ﬂows in ducts of various cross-sections. The low Reynolds number version of a non-linear eddy viscosity model is proposed to predict the Reynolds stresses and the temperature ﬁeld...... is solved using a two-equation heat ﬂux model. The computed results compare satisfactory with the available experimental data. The time-scale ratio R is deﬁned as the ratio between the dynamic time-scale (k/ε) and the scalar time-scale(0.5θθ/εθ). Based on existing DNS data and calculations in this work...
Heavy gas relaxation in a light gas shock wave at small Prandtl number
Fernandez-Feria, R.
2016-09-01
The shock wave structure of a binary mixture with very different molecular weights is analyzed using a two-fluid theory in the limit of small Prandtl (Pr) number of the light gas. In particular, the case in which both the density ratio and Λ =Pr/δ Sc are order unity or below is considered, where δ ≪1 is the molecular mass ratio and Sc is the Schmidt number. Approximate analytical solutions are given for weak, and for moderately strong, shock waves. In the former case the solution is continuous, while in the latter case the light gas shock exhibits a discontinuity and the heavy gas relaxes towards the final equilibrium state.
Geoid and topography for infinite Prandtl number convection in a spherical shell
Bercovici, D.; Schubert, G.; Zebib, A.
1988-01-01
Geoid anomalies and surface and lower-boundary topographies are calculated for numerically generated thermal convection for an infinite Prandtl number, Boussinesq, axisymmetric spherical fluid shell with constant gravity and viscosity, for heating both entirely from below and entirely from within. Convection solutions are obtained for Rayleigh numbers Ra up to 20 times the critical Ra in heating from below and 27 times critical for heating from within. Geoid parallels surface undulations, and boundary deformation generally increases with increasing cell wavelength. Dimensionless geoid and topography in heating from below are about 5 times greater than in heating from within. Values for heating from within correlate more closely with geophysical data than values from heating from below, suggesting a predominance of internal heating in the mantle. The study emphasizes that dynamically induced topography and geoid are sensitive to the mode of heating in the earth's mantle.
Helical turbulent Prandtl number in the A model of passive vector advection
Hnatič, M.; Zalom, P.
2016-11-01
Using the field theoretic renormalization group technique in the two-loop approximation, turbulent Prandtl numbers are obtained in the general A model of passive vector advected by fully developed turbulent velocity field with violation of spatial parity introduced via the continuous parameter ρ ranging from ρ =0 (no violation of spatial parity) to |ρ |=1 (maximum violation of spatial parity). Values of A represent a continuously adjustable parameter which governs the interaction structure of the model. In nonhelical environments, we demonstrate that A is restricted to the interval -1.723 ≤A ≤2.800 (rounded to 3 decimal places) in the two-loop order of the field theoretic model. However, when ρ >0.749 (rounded to 3 decimal places), the restrictions may be removed, which means that presence of helicity exerts a stabilizing effect onto the possible stationary regimes of the system. Furthermore, three physically important cases A ∈{-1 ,0 ,1 } are shown to lie deep within the allowed interval of A for all values of ρ . For the model of the linearized Navier-Stokes equations (A =-1 ) up to date unknown helical values of the turbulent Prandtl number have been shown to equal 1 regardless of parity violation. Furthermore, we have shown that interaction parameter A exerts strong influence on advection-diffusion processes in turbulent environments with broken spatial parity. By varying A continuously, we explain high stability of the kinematic MHD model (A =1 ) against helical effects as a result of its proximity to the A =0.912 (rounded to 3 decimal places) case where helical effects are completely suppressed. Contrary, for the physically important A =0 model, we show that it lies deep within the interval of models where helical effects cause the turbulent Prandtl number to decrease with |ρ | . We thus identify internal structure of interactions given by the parameter A , and not the vector character of the admixture itself being the dominant factor influencing
Helical turbulent Prandtl number in the A model of passive vector advection.
Hnatič, M; Zalom, P
2016-11-01
Using the field theoretic renormalization group technique in the two-loop approximation, turbulent Prandtl numbers are obtained in the general A model of passive vector advected by fully developed turbulent velocity field with violation of spatial parity introduced via the continuous parameter ρ ranging from ρ=0 (no violation of spatial parity) to |ρ|=1 (maximum violation of spatial parity). Values of A represent a continuously adjustable parameter which governs the interaction structure of the model. In nonhelical environments, we demonstrate that A is restricted to the interval -1.723≤A≤2.800 (rounded to 3 decimal places) in the two-loop order of the field theoretic model. However, when ρ>0.749 (rounded to 3 decimal places), the restrictions may be removed, which means that presence of helicity exerts a stabilizing effect onto the possible stationary regimes of the system. Furthermore, three physically important cases A∈{-1,0,1} are shown to lie deep within the allowed interval of A for all values of ρ. For the model of the linearized Navier-Stokes equations (A=-1) up to date unknown helical values of the turbulent Prandtl number have been shown to equal 1 regardless of parity violation. Furthermore, we have shown that interaction parameter A exerts strong influence on advection-diffusion processes in turbulent environments with broken spatial parity. By varying A continuously, we explain high stability of the kinematic MHD model (A=1) against helical effects as a result of its proximity to the A=0.912 (rounded to 3 decimal places) case where helical effects are completely suppressed. Contrary, for the physically important A=0 model, we show that it lies deep within the interval of models where helical effects cause the turbulent Prandtl number to decrease with |ρ|. We thus identify internal structure of interactions given by the parameter A, and not the vector character of the admixture itself being the dominant factor influencing diffusion
Johnston, Stephen; Fonda, Enrico; Sreenivasan, Katepalli R.; Ranjan, Devesh
2016-11-01
Both experiments and simulations on Rayleigh-Bénard convection with fluids of Prandtl numbers 5 and below have shown that the container shape influences the flow structure. Here, we investigate similar dependences of convection of fluids with Prandtl numbers of up to 104. The convection cells have aspect ratio of order unity, and we use cubic and cylindrical shapes. Visual analysis using a noninvasive photochromic dye technique indicates the distinct large-scale flow patterns in both square and cylindrical test cells. The stability of these flow patterns is explored. Also presented are results on the Nusselt-Rayleigh scaling for moderate Rayleigh numbers.
Institute of Scientific and Technical Information of China (English)
Lucia Fontana
2014-01-01
Simultaneous free convection above and below a uniformly heated horizontal plate has been widely investigated,both in the case of an isothermal surface,and of a uniformly heated surface,but always assuming only air as fluid (Pr=0.7).Nevertheless,there are works dealing with horizontal plates whose results show that the Nu dependence on Pr may not be simply expressed by a power law with the same exponent of the Gr one.So it was considered useful to study the Prandtl number influence in the case of the isothermal horizontal strip.Results show that,while for the lower surface of the strip the Nu dependence in Gr can be expressed by a power law with an exponent close to the Gr one,for the upper surface the exponent is sensibly different.Correlating equations related to the investigated situations are proposed.
Stefani, F; Giesecke, A; Weber, N; Weier, T
2016-01-01
The current-driven, kink-type Tayler instability (TI) is a key ingredient of the Tayler-Spruit dynamo model for the generation of stellar magnetic fields, but is also discussed as a mechanism that might hamper the up-scaling of liquid metal batteries. Under some circumstances, the TI involves a helical flow pattern which goes along with some alpha effect. Here we focus on the chiral symmetry breaking and the related impact on the alpha effect that would be needed to close the dynamo loop in the Tayler-Spruit model. For low magnetic Prandtl numbers, we observe intrinsic oscillations of the alpha effect. These oscillations serve then as the basis for a synchronized Tayler-Spruit dynamo model, which could possibly link the periodic tidal forces of planets with the oscillation periods of stellar dynamos.
Bagheri, Nader; Strataridakis, Constantine J.; White, Bruce R.
1990-01-01
Hot-wire anemometry measurements in an incompressible turbulent boundary laeyr flow over a heated flat plate at zero pressure gradient were made using an x-probe and temperature fluctuation probe. The experiments resulted in direct measurement of the turbulent Prandtl number as a function of height through the boundary layer for three temperature difference cases. Also, space-time correlations of temperature fluctuations T-prime were obtained with a pair of temperature fluctuation probes. The mean convection velocities of the T-prime large-scale structure are presented for the three temperature difference cases. The mean convection velocity of the T-prime structure is a function of position y(+) and is found to be independent of the temperature difference for the cases considered.
Thermal Conductivity of Pure Noble Gases at Low Density from Ab Initio Prandtl Number
Song, Bo; Wang, Xiaopo; Liu, Zhigang
2013-03-01
The experimental data reported in the literature after 2000 have been investigated for the viscosity and thermal conductivity of helium-4, neon, and argon at low density. The well-established values of thermal conductivity by transient hot-wire measurements are not reliable enough for noble gases in the low-pressure gas region. These facts motivate us to determine the thermal conductivity from accurate viscosity data and the ab initio Prandtl number, with an uncertainty of 0.25 % for temperatures ranging between 200 K and 700 K. The theoretical accuracy is superior to the accuracy of the best measurements. The calculated results are accurate enough to be applied as standard values for the thermal conductivity of helium-4, neon, and argon over the considered temperature range.
Model for modulated and chaotic waves in zero-Prandtl-number rotating convection
Indian Academy of Sciences (India)
Alaka Das; Krishna Kumar
2008-09-01
The effects of time-periodic forcing in a few-mode model for zero-Prandtl-number convection with rigid body rotation is investigated. The time-periodic modulation of the rotation rate about the vertical axis and gravity modulation are considered separately. In the presence of periodic variation of the rotation rate, the model shows modulated waves with a band of frequencies. The increase in the external forcing amplitude widens the frequency band of the modulated waves, which ultimately leads to temporally chaotic waves. The gravity modulation, on the other hand, with small frequencies, destroys the quasiperiodic waves at the onset and leads to chaos through intermittency. The spectral power density shows more power to a band of frequencies in the case of periodic modulation of the rotation rate. In the case of externally imposed vertical vibration, the spectral density has more power at lower frequencies. The two types of forcing show different routes to chaos.
Hu, Kainan; Zhang, Hongwu
2016-01-01
A lattice Boltzmann scheme associated with flexible Prandtl number and specific heat ratio is proposed, which is based on the polyatomic ellipsoidal statistics model(ES-BGK). The Prandtl number can be modified by a parameter of the Gaussian distribution and the specific heat ratio can be modified by additional free degrees. For the sake of constructing the scheme proposed, the Gaussian distribution is expanded on the Hermite polynomials and the general term formula for the Hermite coefficients of the Gaussian distribution is deduced. Benchmarks are carried out to verify the scheme proposed. The numerical results are in good agreement with the the analytical solutions.
Energy Technology Data Exchange (ETDEWEB)
Rabas, T.J.; Arman, B.
1992-08-01
This paper demonstrates that the heat-transfer performance of an enhanced tube with transverse, rectangular disruptions can be predicted with a numerical modeling method, an accomplishment not previously achieved. This computer code is then used to determine the influence of the Prandtl number. The numerical simulation demonstrated that six distinct regions exist: the three rib surfaces, the upstream and downstream recirculation regions, and the boundary-layer development zone. Three zones dominate the thermal performance: the rib top and downstream faces and the downstream recirculation zone. The thermal performance at the rib region begins to dominate tile overall performance as the Prandtl number becomes large. The contribution from the downstream recirculation zone becomes more important and dominates for low Prandtl number fluids such as air. The Reynolds number dependence at the rib region and the downstream recirculation zone is similar to that for reattaching flows with exponents in the 0.65 to 0.75 range. The location of the maximum in the recirculation moves closer to the rib with increasing Reynolds and Prandtl numbers and is bounded upstream by the location of the maximum wall shear stress and downstream by the reattachment length. The high turbulence level near the surface in this region is responsible for the heat-transfer enhancement.
Energy Technology Data Exchange (ETDEWEB)
Rabas, T.J.; Arman, B.
1992-01-01
This paper demonstrates that the heat-transfer performance of an enhanced tube with transverse, rectangular disruptions can be predicted with a numerical modeling method, an accomplishment not previously achieved. This computer code is then used to determine the influence of the Prandtl number. The numerical simulation demonstrated that six distinct regions exist: the three rib surfaces, the upstream and downstream recirculation regions, and the boundary-layer development zone. Three zones dominate the thermal performance: the rib top and downstream faces and the downstream recirculation zone. The thermal performance at the rib region begins to dominate tile overall performance as the Prandtl number becomes large. The contribution from the downstream recirculation zone becomes more important and dominates for low Prandtl number fluids such as air. The Reynolds number dependence at the rib region and the downstream recirculation zone is similar to that for reattaching flows with exponents in the 0.65 to 0.75 range. The location of the maximum in the recirculation moves closer to the rib with increasing Reynolds and Prandtl numbers and is bounded upstream by the location of the maximum wall shear stress and downstream by the reattachment length. The high turbulence level near the surface in this region is responsible for the heat-transfer enhancement.
Directory of Open Access Journals (Sweden)
K. S. Egorov
2015-01-01
Full Text Available The presented paper regards the influence of one of similarity criteria – the Prandtl number of gas (Pr - on the efficiency of the machine-less energetic separation device (Leontiev pipe, using numerical modeling in ANSYS software. This device, equally as Rank-Hilsch and Hartman-Schprenger pipes, is designed to separate one gas flow into two flows with different temperatures. One flow (supersonic streams out of the pipe with a temperature higher than initial and the other (subsonic flows out with a temperature lower than initial. This direction of energetic separation is true if the Prandtl number is less than 1 that corresponds to gases.The Prandtl number affects the efficiency of running Leontiev pipe indirectly both through a temperature difference on which a temperature recovery factor has an impact and through a thermal conductivity coefficient that shows the impact of heat transfer intensity between gas and solid wall.The Prandtl number range in the course of research was from 0.1 to 0.7. The Prandtl number value equal to 0.7 corresponds to the air or pure gases (for example, inert argon gas. The Prandtl number equal to 0.2 corresponds to the mixtures of inert gases such as helium-xenon.The numerical modeling completed for the supersonic flow with Mach number 2.0 shows that efficiency of the machine-less energetic separation device has been increased approximately 2 times with the Prandtl number decreasing from 0.7 to 0.2. Moreover, for the counter-flow scheme this effect is a little higher due to its larger heat efficiency in comparison with the straight-flow one.Also, the research shows that the main problem for the further increase of the Leontiev pipe efficiency is a small value of thermal conductivity coefficient, which requires an intensification of the heat exchange, especially in the supersonic flow. It can be obtained, for example, by using a system of oblique shock waves in the supersonic channel.
Near-wall variable-Prandtl-number turbulence model for compressible flows
Sommer, T. P.; So, R. M. C.; Zhang, H. S.
1993-01-01
A near-wall four-equation turbulence model is developed for the calculation of high-speed compressible turbulent boundary layers. The four equations used are the k-epsilon equations and the theta(exp 2)-epsilon (sub theta) equations. These equations are used to define the turbulent diffusivities for momentum and heat fluxes, thus allowing the assumption of dynamic similarity between momentum and heat transport to be relaxed. The Favre-averaged equations of motion are solved in conjunction with the four transport equations. Calculations are compared with measurements and with another model's predictions where the assumption of the constant turbulent Prandtl number is invoked. Compressible flat plate turbulent boundary layers with both adiabatic and constant temperature wall boundary conditions are considered. Results for the range of low Mach numbers and temperature ratios investigated are essentially the same as those obtained using an identical near-wall k-epsilon model. In general, there are significant improvements in the predictions of mean flow properties at high Mach numbers.
Homoclinic bifurcations in low-Prandtl-number Rayleigh-B\\'{e}nard convection with uniform rotation
Maity, P; Pal, P
2014-01-01
We present results of direct numerical simulations on homoclinic gluing and ungluing bifurcations in low-Prandtl-number ($ 0 \\leq Pr \\leq 0.025 $) Rayleigh-B\\'{e}nard system rotating slowly and uniformly about a vertical axis. We have performed simulations with \\textit{stress-free} top and bottom boundaries for several values of Taylor number ($5 \\leq Ta \\leq 50$) near the instability onset. We observe a single homoclinic ungluing bifurcation, marked by the spontaneous breaking of a larger limit cycle into two limit cycles with the variation of the reduced Rayleigh number $r$ for smaller values of $Ta (< 25)$. A pair of homoclinic bifurcations, instead of one bifurcation, is observed with variation of $r$ for slightly higher values of $Ta$ ($25 \\leq Ta \\leq 50$) in the same fluid dynamical system. The variation of the bifurcation threshold with $Ta$ is also investigated. We have also constructed a low-dimensional model which qualitatively captures the dynamics of the system near the homoclinic bifurcations...
Lin, Wenxian; Armfield, S W; Patterson, J C; Lei, Chengwang
2009-06-01
In this paper, the scalings incorporating the Prandtl number (Pr) dependence have been obtained by a scaling analysis for the unsteady natural convection boundary layer of an initially quiescent isothermal Newtonian fluid of Pr>1 produced by the sudden imposition of a higher temperature on a vertical plate. It is shown that the transient flow behavior of the resulting boundary layer can be described by a three-region structure and at the start-up stage the boundary layer development is one dimensional and independent of height due to the dominance of pure conduction; however, at steady state it becomes two dimensional and height dependent as the flow becomes dominated by convection. Numerical results demonstrate that the scalings representing the thermal boundary layer development accurately represent their Pr dependence over the whole stage of flow development. The scalings representing the viscous boundary layer development are generally in good agreement with the numerical results with the Pr variation over the whole stage of flow development, although there are small deviations from the numerical results with the Pr variation that are within acceptable limits for scaling.
The behavior of magnetic Prandtl number on the Rossby wave instability in the protoplanetary discs
Gholipour, Mahmoud; Ebadi, Hossein; Shaji, Zeynab
2017-07-01
In recent years, the Rossby wave instability (RWI) has become the target of intense theoretical and simulation investigations in dealing to some ambiguous problems such as the planet formation and angular momentum transport in the protoplanetary discs. The role of hydrodynamic turbulence on the RWI theory has been well understood by many theoretical and simulation works. However, less attention has been paid to the magnetohydrodynamic (MHD) turbulence in theoretical works related to the RWI. However, the turbulent magnetic Prandtl numbers (Prm), i.e., the ratio of the turbulent viscosity to the turbulent magnetic diffusivity, is one of the significant parameters in (MHD) turbulence. On the other hand, the gradient and strength of the toroidal magnetic field can affect some variables and parameters in the stationary and perturbation states in some radii which may be lead to important results. In this paper, the whole range of Prm is considered in details with considering the gradient and strength of the toroidal magnetic field. Although complicating the problem, it gives us a comprehensive view on the RWI occurrence in the cold and hot discs. The results show that the Prm can significantly control the RWI occurrence as well as the growth rate of unstable modes. While the magneto-rotational instability cannot be responsible for the angular momentum transport in the protoplanetary discs, our results indicate that the RWI is responsible about this subject in these discs.
Investigation of turbulent Prandtl number subject to local acceleration and deceleration
Jung, Eunbeom; Lee, Wook; Kang, Seongwon; Iaccarino, Gianluca
2016-11-01
The main objective of the present study is to analyze the turbulent Prandtl number (Prt) varying over space in a wall-bounded turbulent flow under local acceleration and deceleration. The Prt shows the opposite trends for the conditions of acceleration and deceleration. In order to explain these phenomena, the convection velocity from the space-time correlation is investigated. It is shown that small-scale motions experience larger acceleration and deceleration compared to large-scale ones. Also, a discrepancy between the momentum and heat transfer at small scales results in the spatially varying Prt. The budgets of the turbulent kinetic energy and temperature variance show a hint for the variation of Prt. The results from DNS and RANS with a constant Prt are compared and show that RANS prediction can be improved by using a modeled Prt. From the turbulent statistics, a few flow variables showing higher correlations with Prt are identified. Based on this, simple phenomenological models are devised and the corresponding simulations show a more accurate prediction of the heat transfer rate. Corresponding author.
Schober, Jennifer; Schleicher, Dominik; Federrath, Christoph; Klessen, Ralf; Banerjee, Robi
2012-02-01
The small-scale dynamo is a process by which turbulent kinetic energy is converted into magnetic energy, and thus it is expected to depend crucially on the nature of the turbulence. In this paper, we present a model for the small-scale dynamo that takes into account the slope of the turbulent velocity spectrum v(ℓ)proportional ℓ([symbol see text])V}, where ℓ and v(ℓ) are the size of a turbulent fluctuation and the typical velocity on that scale. The time evolution of the fluctuation component of the magnetic field, i.e., the small-scale field, is described by the Kazantsev equation. We solve this linear differential equation for its eigenvalues with the quantum-mechanical WKB approximation. The validity of this method is estimated as a function of the magnetic Prandtl number Pm. We calculate the minimal magnetic Reynolds number for dynamo action, Rm_{crit}, using our model of the turbulent velocity correlation function. For Kolmogorov turbulence ([symbol see text] = 1/3), we find that the critical magnetic Reynolds number is Rm(crit) (K) ≈ 110 and for Burgers turbulence ([symbol see text] = 1/2) Rm(crit)(B) ≈ 2700. Furthermore, we derive that the growth rate of the small-scale magnetic field for a general type of turbulence is Γ proportional Re((1-[symbol see text])/(1+[symbol see text])) in the limit of infinite magnetic Prandtl number. For decreasing magnetic Prandtl number (down to Pm >/~ 10), the growth rate of the small-scale dynamo decreases. The details of this drop depend on the WKB approximation, which becomes invalid for a magnetic Prandtl number of about unity.
Effects of Prandtl number on the laminar cross flow past a heated cylinder
Ajith Kumar, S.; Mathur, Manikandan; Sameen, A.; Anil Lal, S.
2016-11-01
Flow past a heated cylinder at constant surface temperature is computationally simulated and analyzed in the laminar regime at moderate buoyancy. The parameters governing the flow dynamics are the Reynolds number, Re, the Richardson number, Ri, and the Prandtl number, Pr. We perform our computations in the range 10 ≤ Re ≤ 35, for which the flow past an unheated cylinder results in a steady separation bubble, and vary the other two parameters in the range 0 ≤ Ri ≤ 2, 0.25 ≤ Pr ≤ 100. The heat transfer from the entire cylinder surface, quantified by the average Nusselt number Nuavg, is shown to obey Nuavg = 0.7435Re0.44Pr0.346 in the mixed convection regime we investigate. For a fixed Re and Pr, the flow downstream of the cylinder becomes asymmetric as Ri is increased from zero, followed by a complete disappearance of the vortices in the recirculation bubble beyond a threshold value of Ri. For a fixed Re and Ri, the vortices in the recirculation bubble are again observed to disappear beyond a threshold Pr, but with the reappearance of both the vortices above a larger threshold of Pr. In the limit of large Pr, the time-averaged flow outside the thermal boundary layer but within the near-wake region regains symmetry about the centerline and ultimately converges to a flow field similar to that of Ri = 0; in the far-wake region, however, we observe asymmetric vortex shedding for moderate Pr. The thermal plume structure in the cylinder wake is then discussed, and the plume generation is identified at points on the cylinder where the Nusselt number is a local minimum. The difference between the plume generation and the flow separation locations on the cylinder is shown to converge to zero in the limit of large Pr. We conclude by plotting the lift and drag coefficients as a function of Ri and Pr, observing that CD decreases with Ri for Pr Prt), where Prt ≈ 7.5.
Convection under rotation for Prandtl numbers near 1: K{umlt u}ppers-Lortz instability
Energy Technology Data Exchange (ETDEWEB)
Hu, Yuchou; Ecke, Robert E. [Condensed-Matter and Thermal Physics and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Ahlers, Guenter [Department of Physics and Center for Nonlinear Sciences, University of California at Santa Barbara, Santa Barbara, California 93106 (United States)] Pesch, Werner [Physikalisches Institut der Universitaet Bayreuth, 95440 Bayreuth (Germany)
1998-11-01
The K{umlt u}ppers-Lortz (KL) instability in Rayleigh-B{acute e}nard convection rotated about a vertical axis was studied experimentally using optical-shadowgraph imaging in the rotating frame for dimensionless rotation rates 6{lt}{Omega}{lt}20. Two cylindrical convection cells with radius-to-height ratios {Gamma}=40 and 23 were used. The cells contained CO{sub 2} at 33.1 bar and 16.6 bar with Prandtl numbers {sigma}=0.93 and {sigma}=0.83, respectively. Numerical solutions of the Boussinesq equations with parameter values corresponding to the experiments were obtained for comparison. For {Gamma}=40 and 8{lt}{Omega}{lt}10.5, the initial pattern above onset was time dependent. Its dynamics revealed a mixture of sidewall-nucleated domain-wall motion characteristic of the KL instability and of dislocation-defect motion. For {Omega}{gt}10.5, spontaneous formation of KL domain walls away from the sidewall was observed. For 8{lt}{Omega}{lt}12, there were differences between the two cells very close to onset, but for {epsilon}{approx_gt}0.02 the systems were qualitatively similar. For {Omega}{approx_gt}12 there was no qualitative difference in the behavior of the two cells at any {epsilon}. The average size of a domain containing rolls of approximately the same orientation decreased with increasing {Omega}, and the time dependence speeded up and became dominated by domain-wall propagation. The numerical solutions were qualitatively similar, although there was a tendency for the domains to be larger at the same {epsilon} and {Omega}. The replacement of domains of one orientation by those with another led to a rotation in Fourier space which was characterized by a rotation frequency {omega}{sub a} in the frame rotating at angular velocity {Omega}. Quantitative experimental measurements of {omega}{sub a}, of a correlation length {xi}, and of a domain-switching angle {Theta}{sub s} as functions of {epsilon}{equivalent_to}{Delta}T/{Delta}T{sub c}{minus}1 and {Omega} are
Progress in the prediction of non-unity Prandtl-number turbulent flows using TransAT
Energy Technology Data Exchange (ETDEWEB)
Lakehal, D.; Panyasantisuk, J.; Caviezel, D.; Labois, M.; Narayanan, C., E-mail: lakehal@ascomp.ch [ASCOMP GmbH Zurich (Switzerland)
2011-07-01
We report LES results of the flow and convective heat transfer in a heated channel at a wall shear Reynolds number of Reτ = 150 and 171. The results are compared with available DNS data for various Prandtl number fluids (Pr = 0.1-10). In order to deal with non-unity Pr fluid flows, we have extended the variant of the Dynamic sub-grid scale (SGS) model of Germano proposed by Lilly to the thermal field, whereby the motion of the unresolved fluid flow and thermal structures is dictated by the resolved thermal-flow field. The base LES strategy as built in the code TransAT has been first validated for a practical case: the thermal-flow in a T junction, showing time-averaged results with excellent agreement with the experiment. The extended SGS model to the thermal field delivers results in line with the DNS data of a heated channel flow, and reveals that the turbulent Prandtl number cannot be fixed in an ad-hoc manner, and is clearly dependent on both the fluid and flow properties. (author)
Schubert, G.; Zebib, A.
1980-01-01
A Galerkin technique is used to study the finite-amplitude axisymmetric steady convective motions of an infinite Prandtl number Boussinesq fluid in a spherical shell. Two types of heating are considered: in one case, convection is driven both by internal heat sources in the fluid and by an externally imposed temperature drop across the shell boundaries; in the other case, only internal heat sources drive convection and the lower boundary of the shell is adiabatic. Two distinct classes of axisymmetric steady states are found to be possible: states characterized by temperature and radial velocity fields that are symmetric about an equatorial plane; and a class of solutions that does not possess any symmetry properties about the equatorial plane.
Assessment of RANS at low Prandtl number and simulation of sodium boiling flows with a CMFD code
Energy Technology Data Exchange (ETDEWEB)
Mimouni, S., E-mail: stephane.mimouni@edf.fr; Guingo, M.; Lavieville, J.
2017-02-15
Highlights: • Modelling of boiling sodium flows in a multiphase flow solver. • Rod heated with a constant heat flux in a pipe liquid metal flow. • Sodium boiling flow around a rod heated with a constant heat. • Computations in progress in an assembly constituted of 19 pins equipped with a wrapped wire. - Abstract: In France, Sodium-cooled Fast Reactors (SFR) have recently received a renewed interest. In 2006, the decision was taken by the French Government to initiate research in order to build a first Generation IV prototype (called ASTRID) by 2020. The improvement in the safety of SFR is one of the key points in their conception. Accidental sequences may lead to a significant increase of reactivity. This is for instance the case when the sodium coolant is boiling within the fissile zone. As a consequence, incipient boiling superheat of sodium is an important parameter, as it can influence boiling process which may appear during some postulated accidents as the unexpected loss of flow (ULOF). The problem is that despite the reduction in core power, when boiling conditions are reached, the flow decreases progressively and vapour expands into the heating zone. A crucial investigating way is to optimize the design of the fissile assemblies of the core in order to lead to stable boiling during a ULOF accident, without voiding of the fissile zone. Moreover, in order to evaluate nuclear plant design and safety, a CFD tool has been developed at EDF in the framework of the nuclear industry. Advanced models dedicated to boiling flows have been implemented and validated against experimental data for ten years now including a wall law for boiling flows, wall transfer for nucleate boiling, turbulence and polydispersion model. This paper aims at evaluating the generalization of these models to SFR. At least two main issues are encountered. Firstly, at low Prandtl numbers such as those of liquid metal, classical approaches derived for unity or close to unity fail to
Schober, Jennifer; Federrath, Christoph; Klessen, Ralf; Banerjee, Robi
2011-01-01
The small-scale dynamo is a process by which turbulent kinetic energy is converted into magnetic energy, and thus is expected to depend crucially on the nature of turbulence. In this work, we present a model for the small-scale dynamo that takes into account the slope of the turbulent velocity spectrum v(l) ~ l^theta, where l and v(l) are the size of a turbulent fluctuation and the typical velocity on that scale. The time evolution of the fluctuation component of the magnetic field, i.e., the small-scale field, is described by the Kazantsev equation. We solve this linear differential equation for its eigenvalues with the quantum-mechanical WKB-approximation. The validity of this method is estimated as a function of the magnetic Prandtl number Pm. We calculate the minimal magnetic Reynolds number for dynamo action, Rm_crit, using our model of the turbulent velocity correlation function. For Kolmogorov turbulence (theta=1/3), we find that the critical magnetic Reynolds number is approximately 110 and for Burger...
Dynamo action at low magnetic Prandtl numbers: mean flow versus fully turbulent motions
Energy Technology Data Exchange (ETDEWEB)
Ponty, Y [CNRS UMR6202, Laboratoire Cassiopee, Observatoire de la Cote d' Azur, BP 4229, Nice Cedex 04 (France); Mininni, P D [NCAR, P O Box 3000, Boulder Colorado 80307-3000 (United States); Pinton, J-F [CNRS UMR5672, Laboratoire de Physique, Ecole Normale Superieure de Lyon, 46 Allee d' Italie, 69007 Lyon (France); Politano, H [CNRS UMR6202, Laboratoire Cassiopee, Observatoire de la Cote d' Azur, BP 4229, Nice Cedex 04 (France); Pouquet, A [NCAR, P O Box 3000, Boulder Colorado 80307-3000 (United States)
2007-08-15
We compute numerically the threshold for dynamo action in Taylor-Green (TG) swirling flows. Kinematic dynamo calculations, for which the flow field is fixed to its time average, are compared to dynamical runs, with the Navier-Stokes and induction equations jointly solved. The dynamo instability for the kinematic calculations is found to have two branches. The dynamical dynamo threshold at low Reynolds numbers lies within the low branch, while at high Reynolds numbers it gets closer to the high branch. Based on these results, the effect of the mean flow and of the turbulent fluctuations in TG dynamos are discussed.
Institute of Scientific and Technical Information of China (English)
甘延标; 许爱国; 张广财; 李英骏
2011-01-01
We further develop the lattice Boltzmann （LB） model [Physica A 382 （2007） 502] for compressible flows from two aspects. Firstly, we modify the Bhatnagar Gross Krook （BGK） collision term in the LB equation, which makes the model suitable for simulating flows with different Prandtl numbers. Secondly, the flux limiter finite difference （FLFD） scheme is employed to calculate the convection term of the LB equation, which makes the unphysical oscillations at discontinuities be effectively suppressed and the numerical dissipations be significantly diminished. The proposed model is validated by recovering results of some well-known benchmarks, including （i） The thermal Couette flow; （ii） One- and two-dlmenslonal FLiemann problems. Good agreements are obtained between LB results and the exact ones or previously reported solutions. The flexibility, together with the high accuracy of the new model, endows the proposed model considerable potential for tracking some long-standing problems and for investigating nonlinear nonequilibrium complex systems.
O'Mara, Bridget; Miesch, Mark S.; Featherstone, Nicholas A.; Augustson, Kyle C.
2016-10-01
Several lines of evidence suggest that the velocity amplitude in global simulations of solar convection, U, may be systematically over-estimated. Motivated by these recent results, we explore the factors that determine U and we consider how these might scale to solar parameter regimes. To this end, we decrease the thermal diffusivity κ along two paths in parameter space. If the kinematic viscosity ν is decreased proportionally with κ (fixing the Prandtl number Pr = ν / κ), we find that U increases but asymptotes toward a constant value, as found by Featherstone and Hindman (2016). However, if ν is held fixed while decreasing κ (increasing Pr), we find that U systematically decreases. We attribute this to an enhancement of the thermal content of downflow plumes, which allows them to carry the solar luminosity with slower flow speeds. We contrast this with the case of Rayleigh-Bénard convection which is not subject to this luminosity constraint. This dramatic difference in behavior for the two paths in parameter space (fixed Pr or fixed ν) persists whether the heat transport by unresolved, near-surface convection is modeled as a thermal conduction or as a fixed flux. The results suggest that if solar convection can operate in a high-Pr regime, then this might effectively limit the velocity amplitude. Small-scale magnetism is a possible source of enhanced viscosity that may serve to achieve this high-Pr regime.
Energy Technology Data Exchange (ETDEWEB)
Oishi, Jeffrey S.; /KIPAC, Menlo Park; Low, Mordecai-Mark Mac; /Amer. Museum Natural Hist.
2012-02-14
The magnetorotational instability (MRI) may dominate outward transport of angular momentum in accretion disks, allowing material to fall onto the central object. Previous work has established that the MRI can drive a mean-field dynamo, possibly leading to a self-sustaining accretion system. Recently, however, simulations of the scaling of the angular momentum transport parameter {alpha}{sub SS} with the magnetic Prandtl number Pm have cast doubt on the ability of the MRI to transport astrophysically relevant amounts of angular momentum in real disk systems. Here, we use simulations including explicit physical viscosity and resistivity to show that when vertical stratification is included, mean field dynamo action operates, driving the system to a configuration in which the magnetic field is not fully helical. This relaxes the constraints on the generated field provided by magnetic helicity conservation, allowing the generation of a mean field on timescales independent of the resistivity. Our models demonstrate the existence of a critical magnetic Reynolds number Rm{sub crit}, below which transport becomes strongly Pm-dependent and chaotic, but above which the transport is steady and Pm-independent. Prior simulations showing Pm-dependence had Rm < Rm{sub crit}. We conjecture that this steady regime is possible because the mean field dynamo is not helicity-limited and thus does not depend on the details of the helicity ejection process. Scaling to realistic astrophysical parameters suggests that disks around both protostars and stellar mass black holes have Rm >> Rm{sub crit}. Thus, we suggest that the strong Pm dependence seen in recent simulations does not occur in real systems.
Arabi, Pouria; Jafarpur, Khosrow
2016-08-01
In the present study, effect of different flow regimes on free convection heat transfer has been examined. In the light of this, a novel analytical method is developed to calculate free convection heat transfer from isothermal convex bodies with arbitrary shape over all range of Rayleigh number in fluids with any Prandtl number. The crux of this method is based on the concept of dynamic behaviors existing in natural convection flow. In the previous models the Body Gravity Function (BGF) and Turbulent Function (TF) have been taken as constant values. In this study, BGF accounts for the effect of body shape and orientation with respect to gravity vector in laminar free convection. Besides, TF accounts for the impact of Prandtl number, body shape and orientation with regard to gravity vector in turbulent free convection. By contrast, it is shown that these two parameters undergo a change through the variation of Rayleigh number and cannot be considered as a constant. These two parameters are modeled based upon the thermal resistance concept. Moreover, two transition criteria happening in free convection heat transfer will be obtained according to this new analytical method (conduction-laminar and laminar-turbulent transitions). Finally, three models (models 1, 2 and 3) are proposed for calculation free convection heat transfer and present results for ten isothermal convex bodies with various aspect ratios (0.298 ≤ √ A /P ≤ 2.470) have been compared with the available experimental and numerical data. Here, the results of model 2 are almost equal to those of model 3. Also, the results of model 1 are more precise than those of model 3 while the parameters computation of model 1 is more intricate in comparison with model 3. On the one hand, the model 1 has an average difference <6 % vis-à-vis numerical data in entire range of Rayleigh number (laminar and turbulent). On the other hand, the average difference of model 1 is not more than 8 % versus experimental data
Institute of Scientific and Technical Information of China (English)
孙祉伟; 韩金虎; 戴乐蓉; 解京昌; 胡文瑞
1997-01-01
A device of mercury liquid bridge of floating half-zone is designed to experimentally explore thermo-capillary convection and its instability of a low Prandtl number liquid. Noncontacted diagnostic techniques were developed to monitor surface flow and surface deformation. The surface flow and the influence of a growing surface film (or skin) on the flow were observed It is shown that the film is a key factor in changing the behavior associated with the thermocapillary convection. The experiment indicates that the critical Marangoni number should be much higher than that expected by the numerical simulation. The condition and process of surface film growth are discussed. The surface oscillation of the mercury bridge wrapped with "dirt-film" was observed, and the characteristics and the frequency associated with this oscillation are given.
Institute of Scientific and Technical Information of China (English)
H.Sun; C.F.Ma; 等
1997-01-01
Using seven working fluids,a systematic experimental study was performed to investigate the local convective heat transfer from vertical heaters to impinging circular submerged jets in the range of Reynolds number between 1.17×102 and 3.69×104 with the emphasis placed on the examination of Prandtl number dependence.Heat transfer coefficients at the stagnation point were collected and correlated with the plate held within and beyond the potential core.Radial distribution of the local heat transfer coefficient was measured with five test liquids.Based on the measured profiles of the local heat transfer,a correlation was developed to cover the entire range of the adial distance.Basides the present data,the correlations developed in this work were also compared with a large quantity of available data of circular air jets.General agreement was observed between the air data and the correlations.
Ahlers, Guenter; He, Xiaozhou
2014-01-01
We report on experimental determinations of the temperature field in the interior (bulk) of turbulent Rayleigh-Benard convection for a cylindrical sample with aspect ratio (diameter over height) of 0.50, both in the classical and in the ultimate state. The Prandtl number was close to 0.8. We find a "logarithmic layer" in which the temperature varies as A*ln(z/L) + B with the distance z from the bottom plate of the sample. The amplitude A varies with radial position r. In the classical state these results are in good agreement with direct numerical simulations (DNS); in the ultimate state there are as yet no DNS. A close analogy between the temperature field in the classical state and the "Law of the Wall" for the time-averaged down-stream velocity in shear flow is discussed.
Yu, Jia-Jia; Wu, Chun-Mei; Li, You-Rong; Chen, Jie-Chao
2016-08-01
A series of three-dimensional numerical simulations on thermal-solutal capillary-buoyancy flow in an annular pool were carried out. The pool was filled with silicon-germanium melt with an initial silicon mass fraction of 1.99%. The Prandtl number and the Lewis number of the working fluid are 6.37 × 10-3 and 2197.8, respectively. Both the radial temperature gradient and the solute concentration gradient were applied to the annular pool. The capillary ratio was assumed to be -1, which means that the solutal and thermal capillary effects were equal and opposite. Results show that the thermal-solutal capillary-buoyancy flow always occurs at this special case with the capillary ratio of -1, and even in a shallow annular pool with an aspect ratio of 0.05. With the increase of the thermal Marangoni number, four kinds of flow patterns appear orderly, including concentric rolls, petal-like, spoke, and rosebud-like patterns. These flow patterns are strongly influenced by the local interaction between the solutal and thermal capillary effects and the vertical solute concentration gradient near the outer cylinder. A small vortex driven by the dominant solutal capillary effect emerges near the inner cylinder, which is different from the flow pattern in a pure fluid. In addition, the critical thermal Marangoni number of the initial three-dimensional flow decreases with the increase of the aspect ratio of the annular pool.
Lorenz, J. J.; Yung, D. T.; Panchal, C. B.; Layton, G. E.
1982-01-01
An experimental investigation assessed the accuracy of existing heat-transfer correlations for turbulent flow of water in smooth tubes at Prandtl numbers (Pr) of 6.0 and 11.6. The best correlations were selected for use in designing ocean thermal energy conversion (OTEC) heat exchangers. Two shell-and-tube heat exchangers, a plain-tube evaporator and a plain-tube condenser, were tested to obtain data for water at Pr = 6.0 (800 F) and Pr = 11.6 (400 F), respectively. From measured values of the overall heat-transfer coefficients, the water-side coefficients were determined by the Wilson plot method. The results were used as a data base for evaluating seven widely used heat-transfer correlations. Overall, the best correlations were found to be Petukhov-Popov and Sleicher-Rouse, both of which agree within + or - 5% with the experimental data over the entire Reynolds number range. The Dittus-Boelter and Sieder-Tate correlations, popular with heat-transfer engineers, underpredict the data by 5% to 15% and thus are considered too conservative. Predictions from the Kays correlation compare favorably with the data at Pr = 6.0 but are slightly high (nonconservative) at Pr = 11.6. The Eagle Ferguson correlation is acceptable at Pr = 6.0 but a little too conservative at Pr = 11.6.
Yano, T.; Nishino, K.; Ueno, I.; Matsumoto, S.; Kamotani, Y.
2017-04-01
This paper reports the sensitivity of hydrothermal wave (HTW) instability of Marangoni convection to the interfacial heat transfer in liquid bridges (LBs) of high Prandtl number fluids (Pr = 67, 112, and 207) formed under the microgravity environment on the International Space Station. The data for instability are collected for a wide range of AR and for TC = 15 and 20 °C, where AR is the aspect ratio (=height/diameter) of the LB and TC is the cooled disk temperature. A significant decrease in critical oscillation frequency as well as an appreciable decrease in the critical Marangoni number is observed for AR > 1.25. This drastic change of instability mechanisms is associated with the reversal of axial traveling direction of HTWs and roll-structures as reported previously. It is found that this reversal is closely related to the interfacial heat transfer, which is evaluated numerically through accounting for both convective and radiative components. A heat transfer ratio, QI/QH, is introduced as a dimensionless parameter for interfacial heat transfer, where QI and QH are the heat transfer rates at the LB-gas and LB-heated disk interfaces, respectively. It is found that HTWs travel in the same direction as the surface flow for QI/QH > 0 (heat-loss condition) while in the opposite direction for QI/QH alters slightly but appreciably the basic temperature and flow field, the alteration that is not accounted for in the previous linear stability analyses for an infinite LB.
Park, Hae-Kyun; Chung, Bum-Jin
2016-12-01
The turbulent forced convection heat transfer of rectangular fins in a duct was investigated by varying the tip clearance and Pr. Mass transfer experiments using a H2SO4-CuSO4 electroplating system were performed based on the analogy between heat and mass transfers. FLUENT 6.3 was used for calculations. Turbulent models were tested and the Reynolds Stress Model was chosen, which showed a 1.15 % discrepancy with the existing correlation for a simple tube flow when Pr = 2, but 13 % when Pr = 2014. For a more complex fin channel, the discrepancy increased up to 30 %. The optimal tip clearances, corresponding to maximum heat transfer rates, did not vary with Pr, which is explained using the temperature contours. The results were also compared with the laminar case where Pr influenced the optimal tip clearance.
Directory of Open Access Journals (Sweden)
R.K. Abdul Razak
2017-06-01
Full Text Available This paper investigates the heat transfer and fluid flow characteristics of liquid metal coolants (such as Sodium, Sodium potassium, Bismuth, Lead, and Lead–bismuth flowing over a nuclear fuel element having non-uniform internal energy generation numerically using finite difference method. The Full Navier Stokes Equations governing the flow were converted into stream function-Vorticity form and solved simultaneously along with energy equation using central finite difference scheme. For the two dimensional steady state heat conduction and Stream-Function Equation, the discretization was done in the form suitable to solve using ‘Line-by-Line Gauss-Seidel’ solution technique whereas the discretization of Vorticity transport and energy equations were done using Alternating Direction Implicit (ADI scheme. After discretization the systems of equations were solved using ‘Thomas Algorithm’. The complete task was done by writing a computer code. The results were obtained in the form of variation of Maximum temperature in the fuel element (hot spots and its location, mean coolant temperature at the exit .The parameters considered for the study were aspect ratio of fuel element, Ar, conduction-convection parameter Ncc, total energy generation parameter Qt, and flow Reynolds number ReH. The results obtained can be used to minimize the Maximum temperature in the fuel element (hot spots.
Pr数对环形浅液池热毛细对流的影响%EFFECT OF PRANDTL NUMBER ON THERMOCAPILLARY CONVECTION IN SHALLOW ANNULAR POOLS
Institute of Scientific and Technical Information of China (English)
石万元; 李友荣; 彭岚
2011-01-01
In order to understand the effect of Prandtl (Pr) number on thermocapillary convection instability, the thermocapillary convection in shallow annular pools of silicon melt (Pr = 0.011) and silicone oils with Pr number ranging from 6.7 to 57.9 are investigated using linear stability analysis.The hydrothermal waves (HW) and their critical conditions for the incipience of HWs are determined,especially for those at high value of Pr number. The results indicate that the Mac increases sharply with increasing Pr number when Pr≤l5.9, while it increases slightly with increasing Pr number when Pr ＞ 15.9. When Pr≤15.9, there is only one group of HW in the pool. However, two groups of HW coexist in the pool and they interfere each other when Pr ＞ 15.9. With increasing Pr number, the arms of the main group of HW become longer and their propagation angles decrease gradually. The critical wave number mc and critical phase velocity wc decrease with increasing Pr number.%为了解流体普朗特数(Pr)对热毛细对流的影响,通过线性稳定性分析,确定了环形浅液池内硅熔体(Pr＝0.011)和几种硅油(Pr数从6.7至57.9)热毛细对流失稳的临界条件,获得了它们在临界条件下的热流体波,特别是高Pr数硅油的热流体波.结果发现:当Pr≤15.9时,临界Ma数随Pr数的增加迅速上升,此时环形池内只有一组热流体波,呈连续条纹状.当Pr＞15.9后,临界Ma数随Pr数的增加变缓,环形池内由波数相同、强弱和传播角不同的两组热流体波组成,二者相互干涉形成忽明忽暗、断断续续的条纹.随着Pr数的增加,其中占据主要地位的一组热流体波变得越来越长,传播角越来越小.临界波数mc和临界相速ωc随Pr数的增加而降低.
Convective Heat Transfer Analysis on Prandtl Fluid Model with Peristalsis
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A. Alsaedi
2013-01-01
Full Text Available The effects of magnetohydrodynamic (MHD on peristaltic transport of Prandtl fluid in a symmetric channel have been studied under the assumptions of long wave length and low-Reynolds number. Channel walls are considered compliant in nature. Series solutions of axial velocity, stream function and temperature are given by using regular perturbation technique for small values of Prandtl fluid parameter. The effects of physical parameters on the velocity, streamlines and temperature are examined by plotting graphs.
Energy Technology Data Exchange (ETDEWEB)
Rieger, M. [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires
1968-06-01
The heat transfer parameters were determined experimentally in electrically heated tube bundles for turbulent flow parallel to the axis. The tubes were arranged in a pattern of equilateral triangles. The ratios of the distance between the axes of the tubes to their external diameter were 1.60 and 1.25 in the two test sections studied. The experiments were carried out with distilled water and with a mixture of 60 per cent ethylene glycol and 40 per cent water. The values obtained for the Prandtl numbers in this way fell within the range from 2.3 to 18. The Reynolds numbers were varied between 10{sup 4} and 2.10{sup 5}. The relation between the mean heat transfer coefficients and the friction factor in the tube bundles was found from the experiments as: Nu = [Re Pr {zeta}/8]/[1+{radical}({zeta}/8) 8.8 (Pr-1.3) Pr{sup -0.22}]. The experimentally determined mean Nusselt numbers were also given by the following function: Nu = (0.0122 + 0.00245 p/d) Re{sup 0.86} Pr{sup 0.4}, with a maximum deviation of {+-}4 per cent. For certain local Nusselt numbers, deviations of up to 20 per cent with respect to the relations given were observed. (author) [French] Dans des faisceaux tubulaires a chauffage electrique parcourus par un ecoulement turbulent parallele a l'axe, on a determine experimentalement les parametres du transfert de chaleur. Les centres des sections droites des tubes etaient des sommets de triangles equilateraux. Les rapports de la distance a l'axe des tubes et leur diametre exterieur dans les deux veines de mesure etudiees etaient de 1.60 et 1.25. Des essais furent effectues avec de l'eau distillee ainsi qu'avec un melange de 60 pour cent de glycol ethylenique et 40 pour cent d'eau. Les valeurs des nombres de Prandtl obtenues ainsi etaient situees entre 2.3 a 18. On a fait varier les nombres de Reynolds entre 10{sup 4} et 2.10{sup 5}. La relation entre les nombres caracteristiques de transfert de chaleur moyens et la perte de charge dans
Prandtl-Batchelor flows revisited
Wijngaarden, van L.
2007-01-01
In this paper laminar flows are considered with closed streamlines. For such flows Prandtl [1905. Å°ber FlÃ¼ssigkeitsbewegung bei sehr kleiner Reibung. Verhandlungen des III. Internationalen Mathematiker Kongresses, Heidelberg, 1904, pp. 484-491, Teubner, Leizig. See Gesammelte Abhandlungen II, pp.
Generalized Ramsey numbers through adiabatic quantum optimization
Ranjbar, Mani; Macready, William G.; Clark, Lane; Gaitan, Frank
2016-09-01
Ramsey theory is an active research area in combinatorics whose central theme is the emergence of order in large disordered structures, with Ramsey numbers marking the threshold at which this order first appears. For generalized Ramsey numbers r( G, H), the emergent order is characterized by graphs G and H. In this paper we: (i) present a quantum algorithm for computing generalized Ramsey numbers by reformulating the computation as a combinatorial optimization problem which is solved using adiabatic quantum optimization; and (ii) determine the Ramsey numbers r({{T}}m,{{T}}n) for trees of order m,n = 6,7,8, most of which were previously unknown.
Automated Control Surface Design and Sizing for the Prandtl Plane
Van Ginneken, D.A.J.; Voskuijl, M.; Van Tooren, M.J.L.; Frediani, A.
2010-01-01
This paper presents a methodology for the design of the primary flight control surfaces, in terms of size, number and location, for fixed wing aircraft (conventional or unconventional). As test case, the methodology is applied to a 300 passenger variant of the Prandtl Plane. This box wing aircraft i
Prandtl and the G\\"ottingen School
Bodenschatz, Eberhard
2011-01-01
This is a historical review of "Prandtl and the G\\"ottingen School" from his first work in 1898 to after WWII. We report the development of the boundary layer theory and the investigations that lead Ludwig Prandtl in the spring of 1945 to use a energy cascade model to derive for fully developed turbulence the Kolmogrov length scale. Working at the end of WWII he was not aware of the work by Kolmogorov. Thus Ludwig Prandtl was before Onsager, von Weiz\\"acker, and Heisenberg in rederiving parts of K41 theory. In our historical analysis we rely heavily on exchanges between Ludwig Prandtl with Theodore von K\\'arm\\'an and Goeffrey Ingram Taylor and on the original notes by Ludwig Prandtl and others.
Optimal Strouhal number for swimming animals
Eloy, Christophe
2011-01-01
To evaluate the swimming performances of aquatic animals, an important dimensionless quantity is the Strouhal number, St = fA/U, with f the tail-beat frequency, A the peak-to-peak tail amplitude, and U the swimming velocity. Experiments with flapping foils have exhibited maximum propulsive efficiency in the interval 0.25 < St < 0.35 and it has been argued that animals likely evolved to swim in the same narrow interval. Using Lighthill's elongated-body theory to address undulatory propulsion, it is demonstrated here that the optimal Strouhal number increases from 0.15 to 0.8 for animals spanning from the largest cetaceans to the smallest tadpoles. To assess the validity of this model, the swimming kinematics of 53 different species of aquatic animals have been compiled from the literature and it shows that their Strouhal numbers are consistently near the predicted optimum.
Optimal Number of Questionnaire Response Categories
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W. Paul Jones
2013-05-01
Full Text Available Two multi-instrument investigations in a university clinic/lab provided an opportunity to explore the impact of reducing the number of response alternatives in a scale measuring vocational personality traits. In a simulation study, a standard computer-based administration provided a numeric scale for each item ranging from 0 to 10. The tests were then rescored to simulate the effect of only three choices. For the follow-up study, two versions of the scale were created, one with two response options and the other with six response options, and were randomly assigned to participants. Typical relationships were evident between the vocational personality traits and scores on standard measures of core personality traits with negligible impact from reducing the number of response alternatives. Neither the ability of the participants nor the self-reported distress had a measurable impact on the utility of the results with the reduction in response alternatives.
Guo, Yan
2010-01-01
This note concerns a nonlinear ill-posedness of the Prandtl equation and an invalidity of asymptotic boundary-layer expansions of incompressible fluid flows near a solid boundary. Our analysis is built upon recent remarkable linear ill-posedness results established by G\\'erard-Varet and Dormy [2], and an analysis in Guo and Tice [5]. We show that the asymptotic boundary-layer expansion is not valid for non-monotonic shear layer flows in Sobolev spaces. We also introduce a notion of Weak Lipschitz well-posedness and prove that the nonlinear Prandtl equation is not well-posed in this sense near non-stationary and non-monotonic shear flows. On the other hand, we are able to verify that Oleinik's monotonic solutions are well-posed.
Energetics of slope flows: linear and weakly nonlinear solutions of the extended Prandtl model
Güttler, Ivan; Marinović, Ivana; Večenaj, Željko; Grisogono, Branko
2016-07-01
The Prandtl model succinctly combines the 1D stationary boundary-layer dynamics and thermodynamics of simple anabatic and katabatic flows over uniformly inclined surfaces. It assumes a balance between the along-the-slope buoyancy component and adiabatic warming/cooling, and the turbulent mixing of momentum and heat. In this study, energetics of the Prandtl model is addressed in terms of the total energy (TE) concept. Furthermore, since the authors recently developed a weakly nonlinear version of the Prandtl model, the TE approach is also exercised on this extended model version, which includes an additional nonlinear term in the thermodynamic equation. Hence, interplay among diffusion, dissipation and temperature-wind interaction of the mean slope flow is further explored. The TE of the nonlinear Prandtl model is assessed in an ensemble of solutions where the Prandtl number, the slope angle and the nonlinearity parameter are perturbed. It is shown that nonlinear effects have the lowest impact on variability in the ensemble of solutions of the weakly nonlinear Prandtl model when compared to the other two governing parameters. The general behavior of the nonlinear solution is similar to the linear solution, except that the maximum of the along-the-slope wind speed in the nonlinear solution reduces for larger slopes. Also, the dominance of PE near the sloped surface, and the elevated maximum of KE in the linear and nonlinear energetics of the extended Prandtl model are found in the PASTEX-94 measurements. The corresponding level where KE>PE most likely marks the bottom of the sublayer subject to shear-driven instabilities. Finally, possible limitations of the weakly nonlinear solutions of the extended Prandtl model are raised. In linear solutions, the local storage of TE term is zero, reflecting the stationarity of solutions by definition. However, in nonlinear solutions, the diffusion, dissipation and interaction terms (where the height of the maximum interaction is
Optimization of Approximate Inhibitory Rules Relative to Number of Misclassifications
Alsolami, Fawaz
2013-10-04
In this work, we consider so-called nonredundant inhibitory rules, containing an expression “attribute:F value” on the right- hand side, for which the number of misclassifications is at most a threshold γ. We study a dynamic programming approach for description of the considered set of rules. This approach allows also the optimization of nonredundant inhibitory rules relative to the length and coverage. The aim of this paper is to investigate an additional possibility of optimization relative to the number of misclassifications. The results of experiments with decision tables from the UCI Machine Learning Repository show this additional optimization achieves a fewer misclassifications. Thus, the proposed optimization procedure is promising.
Optimization of approximate decision rules relative to number of misclassifications
Amin, Talha
2012-12-01
In the paper, we study an extension of dynamic programming approach which allows optimization of approximate decision rules relative to the number of misclassifications. We introduce an uncertainty measure J(T) which is a difference between the number of rows in a decision table T and the number of rows with the most common decision for T. For a nonnegative real number γ, we consider γ-decision rules that localize rows in subtables of T with uncertainty at most γ. The presented algorithm constructs a directed acyclic graph Δγ(T). Based on this graph we can describe the whole set of so-called irredundant γ-decision rules. We can optimize rules from this set according to the number of misclassifications. Results of experiments with decision tables from the UCI Machine Learning Repository are presented. © 2012 The authors and IOS Press. All rights reserved.
Optimal tooth numbers for compact standard spur gear sets
Savage, M.; Coy, J.; Townsend, D. P.
1981-01-01
The design of a standard gear mesh is treated with the objective of minimizing the gear size for a given ratio, pinion torque, and allowable tooth strength. Scoring, pitting fatigue, bending fatigue, and the kinematic limits of contact ratio and interference are considered. A design space is defined in terms of the number of teeth on the pinion and the diametral pitch. This space is then combined with the objective function of minimum center distance to obtain an optimal design region. This region defines the number of pinion teeth for the most compact design. The number is a function of the gear ratio only. A design example illustrating this procedure is also given.
Optimal number of stimulation contacts for coordinated reset neuromodulation
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Borys eLysyansky
2013-07-01
Full Text Available In this computational study we investigatecoordinated reset (CR neuromodulation designed for an effective controlof synchronization by multi-site stimulation of neuronal target populations. This method was suggested to effectively counteract pathological neuronal synchronycharacteristic for several neurological disorders. We studyhow many stimulation sites are required for optimal CR-induced desynchronization. We found that a moderate increase of the number of stimulation sitesmay significantly prolong the post-stimulation desynchronized transientafter the stimulation is completely switched off. This can, in turn,reduce the amount of the administered stimulation current for theintermittent ON-OFF CR stimulation protocol, where time intervalswith stimulation ON are recurrently followed by time intervals withstimulation OFF. In addition, we found that the optimal number ofstimulation sites essentially depends on how strongly the administeredcurrent decays within the neuronal tissue with increasing distancefrom the stimulation site. In particular, for a broad spatial stimulationprofile, i.e., for a weak spatial decay rate of the stimulation current,CR stimulation can optimally be delivered via a small number of stimulationsites. Our findings may contribute to an optimization of therapeutic applications of CR neuromodulation.
Haut, R. C.; Adcock, J. B.
1976-01-01
The dependency of Mach number on the Prandtl-Meyer function was numerically determined by iterating the Prandtl-Meyer function and applying the Muller method to converge on the Mach number for flows in cryogenic parahydrogen and nitrogen at various total pressures and total temperatures. The results are compared with the ideal diatomic gas values and are presented in tabular form.
Optimizing number of online ad impressions per user
Strehar, Davorin
2014-01-01
This thesis deals with the optimization of displaying online ads (frequency capping), where ad serving represents a cost, and clicks on the ads represent advertising revenue. In this case we would like to display the ad to the user so many times to have the biggest probability of the ad click. For this purpose, we converted the ad serving data to the appropriate format, analyzed it and used machine learning methods to make predictive models with the aim of predicting the optimal number of vie...
Gu, Guo-Ying; Yang, Mei-Ju; Zhu, Li-Min
2012-06-01
This paper presents a novel real-time inverse hysteresis compensation method for piezoelectric actuators exhibiting asymmetric hysteresis effect. The proposed method directly utilizes a modified Prandtl-Ishlinskii hysteresis model to characterize the inverse hysteresis effect of piezoelectric actuators. The hysteresis model is then cascaded in the feedforward path for hysteresis cancellation. It avoids the complex and difficult mathematical procedure for constructing an inversion of the hysteresis model. For the purpose of validation, an experimental platform is established. To identify the model parameters, an adaptive particle swarm optimization algorithm is adopted. Based on the identified model parameters, a real-time feedforward controller is implemented for fast hysteresis compensation. Finally, tests are conducted with various kinds of trajectories. The experimental results show that the tracking errors caused by the hysteresis effect are reduced by about 90%, which clearly demonstrates the effectiveness of the proposed inverse compensation method with the modified Prandtl-Ishlinskii model.
Ludwig Prandtl and the growth of fluid mechanics in Germany
Eckert, Michael
2017-07-01
Ludwig Prandtl (1875-1953) has been called the father of modern aerodynamics. His name is associated most famously with the boundary layer concept, but also with several other topics in 20th-century fluid mechanics, particularly turbulence (Prandtl's mixing length). Among his disciples are pioneers of modern fluid mechanics like Heinrich Blasius, Theodore von Kármán, and Walter Tollmien. Furthermore, Prandtl founded the Aerodynamische Versuchsanstalt (AVA) and the Kaiser-Wilhelm-Institut für Strömungsforschung in Göttingen, nuclei for the growth of fluid mechanics in Germany. In this article I trace this development on the basis of my recent biography of Prandtl.
Parametric dependences of momentum pinch and Prandtl number in JET
Tala, T.; Salmi, A.; Angioni, C.; Casson, F. J.; Corrigan, G.; Ferreira, J.; Giroud, C.; Mantica, P.; Naulin, V.; Peeters, A.G.; Solomon, W. M.; Strintzi, D.; Tsalas, M.; Versloot, T. W.; de Vries, P. C.; Zastrow, K. D.
2011-01-01
Several parametric scans have been performed to study momentum transport on JET. A neutral beam injection modulation technique has been applied to separate the diffusive and convective momentum transport terms. The magnitude of the inward momentum pinch depends strongly on the inverse density gradie
Parametric dependences of momentum pinch and Prandtl number in JET
DEFF Research Database (Denmark)
Tala, T.; Salmi, A.; Angioni, C.
2011-01-01
Several parametric scans have been performed to study momentum transport on JET. A neutral beam injection modulation technique has been applied to separate the diffusive and convective momentum transport terms. The magnitude of the inward momentum pinch depends strongly on the inverse density gra...
Parametric dependences of momentum pinch and Prandtl number in JET
Tala, T.; Salmi, A.; Angioni, C.; Casson, F. J.; Corrigan, G.; Ferreira, J.; Giroud, C.; Mantica, P.; Naulin, V.; Peeters, A.G.; Solomon, W. M.; Strintzi, D.; Tsalas, M.; Versloot, T. W.; de Vries, P. C.; Zastrow, K. D.
2011-01-01
Several parametric scans have been performed to study momentum transport on JET. A neutral beam injection modulation technique has been applied to separate the diffusive and convective momentum transport terms. The magnitude of the inward momentum pinch depends strongly on the inverse density
The required number of physicians: is it an optimal figure?
Forgacs, I
2002-01-01
Apart from the developing countries in which the number of physicians is extremely low, the number of physicians in the different countries shows a wide range even if it is comparing with the GDP or even with the number of nurses. According WHO data there are more than 500 physicians/100,000 inhabitants in Cuba and in Italy; more than 400 in Belarus and Norway, or in Spain and Georgia; more than 300 in 22 countries among them Belgium, France, Germany and Greece, Sweden, Switzerland, or Bulgaria, Czech, Hungary, Slovakia, Lithuania, etc. The number of doctors is below 300/100,000 inhabitants for example in such rich countries as the Netherlands, and the USA, and below 200 in the United Kingdom or in Japan. There is no correlation between the GDP and the number of doctors, as well as between the average life expectancy (or GBD, DALY, DALE) and the number of doctors. (On the other hand there is good correlation between GDP and life expectancy.) There is no correlation between GP-s and specialists, but it may be a weak correlation between the number of hospital beds and the number of doctors. It is difficult to find an optimal doctor/nurse ratio among the different countries; nevertheless the definition of "nurses" has a different meaning in the different countries. The burden of diseases, or the "patients" load" is also not an objective reference point, because the more the doctors, the more the patients. In the different countries there are different norms of the physicians' performances mainly decided by the health insurance funds. The different reimbursement systems, as the "per capita" at the GP-s, or the DRG at the hospital care, or the point-based remuneration at the specialist care are the real rate limiting factors for the number of physicians, which are not necessarily adequate to the professional requirements.
Optimal translational swimming of a sphere at low Reynolds number
Felderhof, B U
2015-01-01
Swimming velocity and rate of dissipation of a sphere with surface distortions are discussed on the basis of the Stokes equations of low Reynolds number hydrodynamics. At first the surface distortions are assumed to cause an irrotational axisymmetric flow pattern. The efficiency of swimming is optimized within this class of flows. Subsequently more general axisymmetric polar flows with vorticity are considered. This leads to a considerably higher maximum efficiency. An additional measure of swimming performance is proposed based on the energy consumption for given amplitude of stroke.
Optimal feeding is optimal swimming for all P\\'eclet numbers
Michelin, Sébastien
2011-01-01
Cells swimming in viscous fluids create flow fields which influence the transport of relevant nutrients, and therefore their feeding rate. We propose a modeling approach to the problem of optimal feeding at zero Reynolds number. We consider a simplified spherical swimmer deforming its shape tangentially in a steady fashion (so-called squirmer). Assuming that the nutrient is a passive scalar obeying an advection-diffusion equation, the optimal use of flow fields by the swimmer for feeding is determined by maximizing the diffusive flux at the organism surface for a fixed rate of energy dissipation in the fluid. The results are obtained through the use of an adjoint-based numerical optimization implemented by a Legendre polynomial spectral method. We show that, to within a negligible amount, the optimal feeding mechanism consists in putting all the energy expended by surface distortion into swimming - so-called treadmill motion - which is also the solution maximizing the swimming efficiency. Surprisingly, althou...
Menage a quoi? Optimal number of peer reviewers.
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Richard R Snell
Full Text Available Peer review represents the primary mechanism used by funding agencies to allocate financial support and by journals to select manuscripts for publication, yet recent Cochrane reviews determined literature on peer review best practice is sparse. Key to improving the process are reduction of inherent vulnerability to high degree of randomness and, from an economic perspective, limiting both the substantial indirect costs related to reviewer time invested and direct administrative costs to funding agencies, publishers and research institutions. Use of additional reviewers per application may increase reliability and decision consistency, but adds to overall cost and burden. The optimal number of reviewers per application, while not known, is thought to vary with accuracy of judges or evaluation methods. Here I use bootstrapping of replicated peer review data from a Post-doctoral Fellowships competition to show that five reviewers per application represents a practical optimum which avoids large random effects evident when fewer reviewers are used, a point where additional reviewers at increasing cost provides only diminishing incremental gains in chance-corrected consistency of decision outcomes. Random effects were most evident in the relative mid-range of competitiveness. Results support aggressive high- and low-end stratification or triaging of applications for subsequent stages of review, with the proportion and set of mid-range submissions to be retained for further consideration being dependent on overall success rate.
Menage a Quoi? Optimal Number of Peer Reviewers
Snell, Richard R.
2015-01-01
Peer review represents the primary mechanism used by funding agencies to allocate financial support and by journals to select manuscripts for publication, yet recent Cochrane reviews determined literature on peer review best practice is sparse. Key to improving the process are reduction of inherent vulnerability to high degree of randomness and, from an economic perspective, limiting both the substantial indirect costs related to reviewer time invested and direct administrative costs to funding agencies, publishers and research institutions. Use of additional reviewers per application may increase reliability and decision consistency, but adds to overall cost and burden. The optimal number of reviewers per application, while not known, is thought to vary with accuracy of judges or evaluation methods. Here I use bootstrapping of replicated peer review data from a Post-doctoral Fellowships competition to show that five reviewers per application represents a practical optimum which avoids large random effects evident when fewer reviewers are used, a point where additional reviewers at increasing cost provides only diminishing incremental gains in chance-corrected consistency of decision outcomes. Random effects were most evident in the relative mid-range of competitiveness. Results support aggressive high- and low-end stratification or triaging of applications for subsequent stages of review, with the proportion and set of mid-range submissions to be retained for further consideration being dependent on overall success rate. PMID:25830238
Hayat, T.; Zahir, Hina; Tanveer, Anum; Alsaedi, A.
2016-06-01
The objective of present analysis is to address the mixed convective peristaltic flow of Prandtl fluid in a planar channel with compliant walls. Effects of applied magnetic field and Hall current are retained. Heat transfer in fluid flow is characterized through convective boundary conditions. Impact of first order chemical reaction together with Soret effect is examined. Problems formulation in view of long wavelength and low Reynolds number consideration is developed. The graphs are obtained numerically for the velocity, temperature, concentration and heat transfer coefficient. Results for Hall parameter and Hartman number on velocity have opposite characteristics.
Determining the Optimal Number of Clusters with the Clustergram
Fluegemann, Joseph K.; Davies, Misty D.; Aguirre, Nathan D.
2011-01-01
Cluster analysis aids research in many different fields, from business to biology to aerospace. It consists of using statistical techniques to group objects in large sets of data into meaningful classes. However, this process of ordering data points presents much uncertainty because it involves several steps, many of which are subject to researcher judgment as well as inconsistencies depending on the specific data type and research goals. These steps include the method used to cluster the data, the variables on which the cluster analysis will be operating, the number of resulting clusters, and parts of the interpretation process. In most cases, the number of clusters must be guessed or estimated before employing the clustering method. Many remedies have been proposed, but none is unassailable and certainly not for all data types. Thus, the aim of current research for better techniques of determining the number of clusters is generally confined to demonstrating that the new technique excels other methods in performance for several disparate data types. Our research makes use of a new cluster-number-determination technique based on the clustergram: a graph that shows how the number of objects in the cluster and the cluster mean (the ordinate) change with the number of clusters (the abscissa). We use the features of the clustergram to make the best determination of the cluster-number.
Transportation optimization with fuzzy trapezoidal numbers based on possibility theory.
He, Dayi; Li, Ran; Huang, Qi; Lei, Ping
2014-01-01
In this paper, a parametric method is introduced to solve fuzzy transportation problem. Considering that parameters of transportation problem have uncertainties, this paper develops a generalized fuzzy transportation problem with fuzzy supply, demand and cost. For simplicity, these parameters are assumed to be fuzzy trapezoidal numbers. Based on possibility theory and consistent with decision-makers' subjectiveness and practical requirements, the fuzzy transportation problem is transformed to a crisp linear transportation problem by defuzzifying fuzzy constraints and objectives with application of fractile and modality approach. Finally, a numerical example is provided to exemplify the application of fuzzy transportation programming and to verify the validity of the proposed methods.
The same number of optimized parameters scheme for determining intermolecular interaction energies
DEFF Research Database (Denmark)
Kristensen, Kasper; Ettenhuber, Patrick; Eriksen, Janus Juul;
2015-01-01
We propose the Same Number Of Optimized Parameters (SNOOP) scheme as an alternative to the counterpoise method for treating basis set superposition errors in calculations of intermolecular interaction energies. The key point of the SNOOP scheme is to enforce that the number of optimized wave...
Economic considerations in the optimal size and number of reserve sites
Groeneveld, R.A.
2005-01-01
The debate among ecologists on the optimal number of reserve sites under a fixed maximum total reserve area-the single large or several small (SLOSS) problem-has so far neglected the economic aspects of the problem. This paper argues that economic considerations can affect the optimal number and siz
DEFF Research Database (Denmark)
Feng, Ju; Shen, Wen Zhong; Xu, Chang
2016-01-01
A new algorithm for multi-objective wind farm layout optimization is presented. It formulates the wind turbine locations as continuous variables and is capable of optimizing the number of turbines and their locations in the wind farm simultaneously. Two objectives are considered. One is to maximi...
PIV Analysis of Ludwig Prandtl's Historic Flow Visualization Films
Willert, Christian
2010-01-01
Around 1930 Ludwig Prandtl and his colleagues O. Tietjens and W. M\\"uller published two films with visualizations of flows around surface piercing obstacles to illustrate the unsteady process of flow separation. These visualizations were achieved by recording the motion of fine particles sprinkled onto the water surface in water channels. The resulting images meet the relevant criteria of properly seeded recordings for particle image velocimetry (PIV). Processing these image sequences with modern PIV algorithms allows the visualization of flow quantities (e.g. vorticity) that were unavailable prior to the development of the PIV technique. The accompanying fluid dynamics video consists of selected original film sequences overlaid with visualizations obtained through PIV processing.
A Self-Adaptive Fuzzy c-Means Algorithm for Determining the Optimal Number of Clusters
Wang, Zhihao; Yi, Jing
2016-01-01
For the shortcoming of fuzzy c-means algorithm (FCM) needing to know the number of clusters in advance, this paper proposed a new self-adaptive method to determine the optimal number of clusters. Firstly, a density-based algorithm was put forward. The algorithm, according to the characteristics of the dataset, automatically determined the possible maximum number of clusters instead of using the empirical rule n and obtained the optimal initial cluster centroids, improving the limitation of FCM that randomly selected cluster centroids lead the convergence result to the local minimum. Secondly, this paper, by introducing a penalty function, proposed a new fuzzy clustering validity index based on fuzzy compactness and separation, which ensured that when the number of clusters verged on that of objects in the dataset, the value of clustering validity index did not monotonically decrease and was close to zero, so that the optimal number of clusters lost robustness and decision function. Then, based on these studies, a self-adaptive FCM algorithm was put forward to estimate the optimal number of clusters by the iterative trial-and-error process. At last, experiments were done on the UCI, KDD Cup 1999, and synthetic datasets, which showed that the method not only effectively determined the optimal number of clusters, but also reduced the iteration of FCM with the stable clustering result. PMID:28042291
Energy Technology Data Exchange (ETDEWEB)
Smorodinskiy, B.I.
1984-01-01
A theoretical justification is given for a method for solving one of the common problems in whole number linear programming with Boolean variables. It is shown that a number of optimization problems in the oil industry can be reduced to this model.
Hansson-Sandsten, Maria
2010-05-01
The purpose of this paper is to present the optimal number of windows and window lengths using multiple window spectrogram for estimation of non-stationary processes with shorter or longer duration. Such processes could start in the EEG as a result of a stimuli, e.g., steady-state visual evoked potentials (SSVEP). In many applications, the Welch method is used with standard set-ups for window lengths and number of averaged spectra/spectrograms. This paper optimizes the window lengths and number of windows of the Welch method and other more recent, so called, multiple window or multitaper methods and compares the mean squared errors of these methods. Approximative formulas for the choice of optimal number of windows and window lengths are also given. Examples of spectrogram estimation of SSVEP are shown.
Mechanical Parameters of the Squeeze Film Curvilinear Bearing Lubricated with a Prandtl Fluid
Walicka, A.; Walicki, E.
2016-12-01
Based upon a Prandtl fluid flow model, a curvilinear squeeze film bearing is considered. The equations of motion are given in a specific coordinate system. After general considerations on the Prandtl fluid flow these equations are used to derive the Reynolds equation. The solution of this equation is obtained by a method of successive approximation. As a result one obtains formulae expressing the pressure distribution and load-carrying capacity. The numerical examples of the Prandtl fluid flow in gaps of two simple bearings are presented.
Aerodynamic Shape Optimization Using A Real-Number-Encoded Genetic Algorithm
Holst, Terry L.; Pulliam, Thomas H.
2001-01-01
A new method for aerodynamic shape optimization using a genetic algorithm with real number encoding is presented. The algorithm is used to optimize three different problems, a simple hill climbing problem, a quasi-one-dimensional nozzle problem using an Euler equation solver and a three-dimensional transonic wing problem using a nonlinear potential solver. Results indicate that the genetic algorithm is easy to implement and extremely reliable, being relatively insensitive to design space noise.
The optimal upper bound of the number of generalized Euler configurations
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Consider a generalized 3-body problem. The attraction force between any two bodies is proportional to the two "masses" and the b-th power of the mutual distance. Albouy and Fu have obtained the optimal upper bound of the number of generalized Euler configurations for the cases b 1 and b = 2, 3. This paper obtains the optimal upper bound for the remaining real values of b in a systematic way.
A multi-sequential number-theoretic optimization algorithm using clustering methods
Institute of Scientific and Technical Information of China (English)
XU Qing-song; LIANG Yi-zeng; HOU Zhen-ting
2005-01-01
A multi-sequential number-theoretic optimization method based on clustering was developed and applied to the optimization of functions with many local extrema. Details of the procedure to generate the clusters and the sequential schedules were given. The algorithm was assessed by comparing its performance with generalized simulated annealing algorithm in a difficult instructive example and a D-optimum experimental design problem. It is shown the presented algorithm to be more effective and reliable based on the two examples.
Energy Technology Data Exchange (ETDEWEB)
Wang, L.; Tang, X. [Univ. of Central Lancashire. Engineering and Physical Sciences, Preston (United Kingdom); Liu, X. [Univ. of Cumbria. Sustainable Engineering, Workington (United Kingdom)
2012-07-01
The aerodynamic performance of a wind turbine depends very much on its blade geometric design, typically based on the blade element momentum (BEM) theory, which divides the blade into several blade elements. In current blade design practices based on Schmitz rotor design theory, the blade geometric parameters including chord and twist angle distributions are determined based on airfoil aerodynamic data at a specific Reynolds number. However, rotating wind turbine blade elements operate at different Reynolds numbers due to variable wind speed and different blade span locations. Therefore, the blade design through Schmitz rotor theory at a specific Reynolds number does not necessarily provide the best power performance under operational conditions. This paper aims to provide an optimal blade design strategy for horizontal-axis wind turbines operating at different Reynolds numbers. A fixed-pitch variable-speed (FPVS) wind turbine with S809 airfoil is chosen as a case study and a Matlab program which considers Reynolds number effects is developed to determine the optimized chord and twist angle distributions of the blade. The performance of the optimized blade is compared with that of the preliminary blade which is designed based on Schmitz rotor design theory at a specific Reynolds number. The results demonstrate that the proposed blade design optimization strategy can improve the power performance of the wind turbine. This approach can be further developed for any practice of horizontal axis wind turbine blade design. (Author)
Directory of Open Access Journals (Sweden)
Ji-ting Qu
2013-01-01
Full Text Available A new optimal method is presented by combining the weight coefficient with the theory of force analogy method. Firstly, a new mathematical model of location index is proposed, which deals with the determination of a reasonable number of dampers according to values of the location index. Secondly, the optimal locations of dampers are given. It can be specific from stories to spans. Numerical examples are illustrated to verify the effectiveness and feasibility of the proposed mathematical model and optimal method. At last, several significant conclusions are given based on numerical results.
Optimization of β-decision rules relative to number of misclassifications
Zielosko, Beata
2012-01-01
In the paper, we present an algorithm for optimization of approximate decision rules relative to the number of misclassifications. The considered algorithm is based on extensions of dynamic programming and constructs a directed acyclic graph Δ β (T). Based on this graph we can describe the whole set of so-called irredundant β-decision rules. We can optimize rules from this set according to the number of misclassifications. Results of experiments with decision tables from the UCI Machine Learning Repository are presented. © 2012 Springer-Verlag.
Bilal, S.; Rehman, Khalil Ur; Malik, M. Y.; Hussain, Arif; Awais, M.
The current communication is carried to contemplate the unique and novel characteristics of nanofluids by constructing formulation of Prandtl fluid model. The fascinating aspects of thermo diffusion effects are also accounted in this communication. Mathematical modelling is performed by employing boundary layer approach. Afterwards, similarity variables are selected to convert dimensional non-linear system into dimensionless expressions. The solution of governing dimensionless problem is executed by shooting method (SM). Graphical evaluation is displayed to depict the intrinsic behavior of embedded parameters on dimensionless velocity, temperature, solutal concentration and nanoparticle concentration profiles. Furthermore, the numerical variation for skin friction coefficient, local Nusselt number, Sherwood number and nano Sherwood number is scrutinized through tables. The assurance of current analysis is affirmed by developing comparison with previous findings available in literature, which sets a benchmark for implementation of computational approach. It is inferred from the computation that concentration profile increases whereas Sherwood number decreases for progressive values of Dufour solutal number.
Gan, Jinqiang; Zhang, Xianmin; Wu, Heng
2016-03-01
In this paper, a generalized hysteresis model is developed to describe both rate-independent and rate-dependent hysteresis in piezoelectric actuators. Based on the classical Prandtl-Ishlinskii (P-I) model, the developed model adds a quadratic polynomial and makes other small changes. When it is used to describe rate-independent hysteresis, the parameters of the model are constants, which can be identified by self-adaptive particle swarm optimization. The effectiveness of this rate-independent modified P-I model is demonstrated by comparing simulation results of the developed model and the classic Prandtl-Ishlinskii model. Simulation results suggest that the rate-independent modified P-I model can describe hysteresis more precisely. Compared with the classical P-I model, the rate-independent modified P-I model reduces modeling error by more than 50%. When it is used to describe rate-independent hysteresis, a one-side operator is adopted and the parameters are functions with input frequency. The results of the experiments and simulations have shown that the proposed models can accurately describe both rate-independent and rate-dependent hysteresis in piezoelectric actuators.
An Approach to Determining the Optimal Cell Number of Manufacturing Cell Formation
Directory of Open Access Journals (Sweden)
Jianwei Wang
2013-04-01
Full Text Available An approach to determining the optimal cell number of manufacturing cell formation is presented. Firstly, the difference of weighting exponent, cluster center and metrics how to have an impact upon the clustering results and membership function are studied. Secondly, a method to determine the optimal m value is given. Two-order partial derivative of the objective function for FCM is calculated, and the variational weighting exponent m is obtained that can prevent the parameter from being the unique value and play an important role in the process of fuzzy clustering. Moreover, in order to avoid a single validity index can not assess correctly, partition coefficient (PC, classification entropy (CE, Fukuyama and Sugeno (FS and Xie and Beni (XB are considered as multi-performance indexes to evaluate the cluster validity, and then an optimal number c is chosen based on these validity measures. Finally, test exampls are given to illustrate the validity of the proposed approach.
Character-Size Optimization for Reducing the Number of EB Shots of MCC Lithographic Systems
Sugihara, Makoto
We propose a character size optimization technique to reduce the number of EB shots of multi-column-cell (MCC) lithographic systems in which transistor patterns are projected with multiple column cells in parallel. Each and every column cell is capable of projecting patterns with character projection (CP) and variable shaped beam (VSB) methods. Seeking the optimal character size of characters contributes to minimizing the number of EB shots and reducing the fabrication cost for ICs. Experimental results show that the character size optimization achieved 70.6% less EB shots in the best case with an available electron beam (EB) size. Our technique also achieved 40.6% less EB shots in the best case than a conventional character sizing technique.
A Novel Power Optimization Method by Minimum Comparator Number Algorithm for Pipeline ADCs
Institute of Scientific and Technical Information of China (English)
NING Ning; WU Shuang-yi; WANG Xiang-zhan; YANG Mo-hua
2007-01-01
The effects of stage numbers on power dissipation of pipeline analog-to-digital converter (ADC) are studied and a novel design method aiming for power optimization is presented. In this method, a minimum comparator number algorithm (MCNA) is first introduced,and then the optimum distribution of resolutions through pipeline ADC stages is deduced by MCNA. Based on the optimum stage-resolution distribution, an optimization method is established, which examines the precise function between ADC power and stage resolutions with a parameter of power ratio (Rp). For 10-bit pipeline ADC with scaling down technology, the simulation results by using MATLAB CAD tools show that an eight-stage topology with 1-bit RSD correction achieves the power optimization indicated by the power reduction ratio.
Directory of Open Access Journals (Sweden)
Taha Aziz
2013-01-01
Full Text Available The simplest equation method is employed to construct some new exact closed-form solutions of the general Prandtl's boundary layer equation for two-dimensional flow with vanishing or uniform mainstream velocity. We obtain solutions for the case when the simplest equation is the Bernoulli equation or the Riccati equation. Prandtl's boundary layer equation arises in the study of various physical models of fluid dynamics. Thus finding the exact solutions of this equation is of great importance and interest.
Alsolami, Fawaz
2013-01-01
This paper is devoted to the study of algorithms for sequential optimization of approximate inhibitory rules relative to the length, coverage and number of misclassifications. Theses algorithms are based on extensions of dynamic programming approach. The results of experiments for decision tables from UCI Machine Learning Repository are discussed. © 2013 Springer-Verlag.
Best Spatiotemporal Performance Sustained by Optimal Number of Random Shortcuts on Complex Networks
Institute of Scientific and Technical Information of China (English)
WANG Mao-Sheng; HOU Zhong-Huai; XIN Hou-Wen
2006-01-01
@@ The spatial synchronization and temporal coherence of FitzHugh-Nagumo (FHN) neurons on complex networks are numerically investigated. When an optimal number of random shortcuts are added to a regular neural chain,the system can reach a state which is nearly periodic in time and almost synchronized in space.
Tetrahedral Element Shape Optimization via the Jacobian Determinant and Condition Number
Energy Technology Data Exchange (ETDEWEB)
FREITAG,LORI A.; KNUPP,PATRICK
1999-09-27
We present a new shape measure for tetrahedral elements that is optimal in the sense that it gives the distance of a tetrahedron from the set of inverted elements. This measure is constructed from the condition number of the linear transformation between a unit equilateral tetrahedron and any tetrahedron with positive volume. We use this shape measure to formulate two optimization objective functions that are differentiated by their goal: the first seeks to improve the average quality of the tetrahedral mesh; the second aims to improve the worst-quality element in the mesh. Because the element condition number is not defined for tetrahedral with negative volume, these objective functions can be used only when the initial mesh is valid. Therefore, we formulate a third objective function using the determinant of the element Jacobian that is suitable for mesh untangling. We review the optimization techniques used with each objective function and present experimental results that demonstrate the effectiveness of the mesh improvement and untangling methods. We show that a combined optimization approach that uses both condition number objective functions obtains the best-quality meshes.
Tetrahedral element shape optimization via the Jacobian determinant and condition number.
Energy Technology Data Exchange (ETDEWEB)
Freitag, L. A.; Knupp, P. M.
1999-07-30
We present a new shape measure for tetrahedral elements that is optimal in the sense that it gives the distance of a tetrahedron from the set of inverted elements. This measure is constructed from the condition number of the linear transformation between a unit equilateral tetrahedron and any tetrahedron with positive volume. We use this shape measure to formulate two optimization objective functions that are differentiated by their goal: the first seeks to improve the average quality of the tetrahedral mesh; the second aims to improve the worst-quality element in the mesh. Because the element condition number is not defined for tetrahedral with negative volume, these objective functions can be used only when the initial mesh is valid. Therefore, we formulate a third objective function using the determinant of the element Jacobian that is suitable for mesh untangling. We review the optimization techniques used with each objective function and present experimental results that demonstrate the effectiveness of the mesh improvement and untangling methods. We show that a combined optimization approach that uses both condition number objective functions obtains the best-quality meshes.
Effect of number density on optimal design of gold nanoshells for plasmonic photothermal therapy.
Sikdar, Debabrata; Rukhlenko, Ivan D; Cheng, Wenlong; Premaratne, Malin
2013-01-01
Despite much research efforts being devoted to the design optimization of metallic nanoshells, no account is taken of the fact that the number of the nanoshells that can be delivered to a given cancerous site vary with their size. In this paper, we study the effect of the nanoshell number density on the absorption and scattering properties of a gold-nanoshell ensemble exposed to a broadband near-infrared radiation, and optimize the nanoshells' dimensions for efficient cancer treatment by analyzing a wide range of human tissues. We first consider the general situation in which the number of the delivered nanoshells decreases with their mean radius R as ∝ R(-β), and demonstrate that the optimal design of nanoshells required to treat cancer most efficiently depends critically on β. In the case of β = 2, the maximal energy absorbed (scattered) by the ensemble is achieved for the same dimensions that maximize the absorption (scattering) efficiency of a single nanoshell. We thoroughly study this special case by the example of gold nanoshells with silica core. To ensure that minimal thermal injury is caused to the healthy tissue surrounding a cancerous site, we estimate the optimal dimensions that minimize scattering by the nanoshells for a desired value of the absorption efficiency. The comparison of gold nanoshells with different cores shows that hollow nanoshells exhibiting relatively low absorption efficiency are less harmful to the healthy tissue and, hence, are preferred over the strongly absorbing nanoshells. For each of the cases analyzed, we provide approximate analytical expressions for the optimal nanoshell dimensions, which may be used as design guidelines by experimentalists, in order to optimize the synthesis of gold nanoshells for treating different types of human cancer at their various growth stages.
Optimizing the Number of Cooperating Terminals for Energy Aware Task Computing in Wireless Networks
DEFF Research Database (Denmark)
Olsen, Anders Brødløs; Fitzek, Frank H. P.; Koch, Peter
2005-01-01
is previously proposed (D2VS), where the overall idea of selective distribution of tasks among terminals is made. In this paper the optimal number of terminals for cooperative task computing in a wireless network will be investigated. The paper presents an energy model for the proposed scheme. Energy......It is generally accepted that energy consumption is a significant design constraint for mobile handheld systems, therefore motivations for methods optimizing the energy consumption making better use of the restricted battery resources are evident. A novel concept of distributed task computing...
The influence of surfactants on thermocapillary flow instabilities in low Prandtl melting pools
Kidess, Anton; Kenjereš, Saša; Kleijn, Chris R.
2016-06-01
Flows in low Prandtl number liquid pools are relevant for various technical applications and have so far only been investigated for the case of pure fluids, i.e., with a constant, negative surface tension temperature coefficient ∂γ/∂T. Real-world fluids containing surfactants have a temperature dependent ∂γ/∂T > 0, which may change sign to ∂γ/∂T forces are the main driving force, this can have a tremendous effect on the resulting flow patterns and the associated heat transfer. Here we investigate the stability of such flows for five Marangoni numbers in the range of 2.1 × 106 ≤ Ma ≤ 3.4 × 107 using dynamic large eddy simulations, which we validate against a high resolution direct numerical simulation. We find that the five cases span all flow regimes, i.e., stable laminar flow at Ma ≤ 2.1 × 106, transitional flow with rotational instabilities at Ma = 2.8 × 106 and Ma = 4.6 × 106, and turbulent flow at Ma = 1.8 × 107 and Ma = 3.4 × 107.
The influence of surfactants on thermocapillary flow instabilities in low Prandtl melting pools
Kidess, Anton; Kleijn, Chris R
2016-01-01
Flows in low Prandtl number liquid pools are relevant for various technical applications, and have so far only been investigated for the case of pure fluids, i.e. with a constant, negative surface tension temperature coefficient $\\partial\\gamma/\\partial T$. Real-world fluids containing surfactants have a temperature dependent $\\partial\\gamma/\\partial T > 0$, which may change sign to $\\partial\\gamma/\\partial T < 0$ at a critical temperature $T_c$. Where thermocapillary forces are the main driving force, this can have a tremendous effect on the resulting flow patterns and the associated heat transfer. Here we investigate the stability of such flows for five Marangoni numbers in the range of $2.1\\times 10^6 \\leq Ma \\leq 3.4\\times 10^7$ using dynamic large eddy simulations (LES), which we validate against a high resolution direct numerical simulation (DNS). We find that the five cases span all flow regimes, i.e. stable laminar flow at $Ma \\leq 2.1\\times 10^6$, transitional flow with rotational instabilities at...
1991-07-01
optimal number of sorties. The discrepancy between the two solutions is a result of rounding up the decision variables with real results in the 40 RMIP to...the next highest integer to ensure an aircraft is scheduled to meet a specifically tasked mission or an additionally tasked sortie. TABLE 1 RMIP /MIP...combinations. Of these 14, only three differ by more than one sortie. TABLE 2. SINGLE CYCLE/DOUBLE CYCLE F14 F18 A6 EA6 E2 S3 ES3 Cycle 1 RMIP 6/NA 8
Determination of the Optimal Fourier Number on the Dynamic Thermal Transmission
Bruzgevičius, P.; Burlingis, A.; Norvaišienė, R.
2016-12-01
This article represents the result of experimental research on transient heat transfer in a multilayered (heterogeneous) wall. Our non-steady thermal transmission simulation is based on a finite-difference calculation method. The value of a Fourier number shows the similarity of thermal variation in conditional layers of an enclosure. Most scientists recommend using no more than a value of 0.5 for the Fourier number when performing calculations on dynamic (transient) heat transfer. The value of the Fourier number is determined in order to acquire reliable calculation results with optimal accuracy. To compare the results of simulation with experimental research, a transient heat transfer calculation spreadsheet was created. Our research has shown that a Fourier number of around 0.5 or even 0.32 is not sufficient ({≈ }17 % of oscillation amplitude) for calculations of transient heat transfer in a multilayered wall. The least distorted calculation results were obtained when the multilayered enclosure was divided into conditional layers with almost equal Fourier number values and when the value of the Fourier number was around 1/6, i.e., approximately 0.17. Statistical deviation analysis using the Statistical Analysis System was applied to assess the accuracy of the spreadsheet calculation and was developed on the basis of our established methodology. The mean and median absolute error as well as their confidence intervals has been estimated by the two methods with optimal accuracy ({F}_{oMDF}= 0.177 and F_{oEPS}= 0.1633 values).
Liu, Tongjun; Wang, Tongcai; Luan, Weiling; Cao, Qimin
2017-01-01
Waste heat recovery through thermoelectric generators is a promising way to improve energy conversion efficiency. This paper proposes a type of heat pipe assisted thermoelectric generator (HP-TEG) system. The expandable evaporator and condenser surface of the heat pipe facilitates the intensive assembly of thermoelectric (TE) modules to compose a compact device. Compared with a conventional layer structure thermoelectric generator, this system is feasible for the installment of more TE couples, thus increasing power output. To investigate the performance of the HP-TEG and the optimal number of TE couples, a theoretical model was presented and verified by experiment results. Further theoretical analysis results showed the performance of the HP-TEG could be further improved by optimizing the parameters, including the inlet air temperature, the thermal resistance of the heating section, and thermal resistance of the cooling structure. Moreover, applying a proper number of TE couples is important to acquire the best power output performance.
The upper bound of the optimal number of clusters in fuzzy clustering
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The upper bound of the optimal number of clusters in clustering algorithm is studied in this paper. A new method is proposed to solve this issue. This method shows that the rule cmax≤n, which is popular in current papers, is reasonable in some sense. The above conclusion is tested and analyzed by some typical examples in the literature, which demonstrates the validity of the new method.
Multiobjective Design Optimization of Supersonic Jet Engine in Different Cruise Mach Numbers
Ogawa, Masamichi; Sato, Tetsuya; Kobayashi, Hiroaki; Taguchi, Hideyuki
The aim of this paper is to apply a multi-objective optimization generic algorithm (MOGA) to the conceptual design of the hypersonic/supersonic vehicles with different cruise Mach number. The pre-cooled turbojet engine is employed as a propulsion system and some engine parameters such as the precooler size, compressor size, compression ratio and fuel type are varied in the analysis. The result shows that the optimum cruise Mach number is about 4 if hydrogen fuel is used. Methane fuel instead of hydrogen reduces the vehicle gross weight by 33% in case of the Mach 2 vehicle.
Lift-optimal aspect ratio of a revolving wing at low Reynolds number
Jardin, Thierry; Colonius, Tim
2016-11-01
Lentink & Dickinson (2009) showed that rotational acceleration stabilized the leading-edge vortex on revolving, low-aspect-ratio wings, and hypothesized that a Rossby number of around 3, which is achieved during each half-stroke for a variety of hovering insects, seeds, and birds, represents a convergent high-lift solution across a range of scales in nature. Subsequent work has verified that, in particular, the Coriolis acceleration is responsible for LEV stabilization. Implicit in these results is that there exists an optimal aspect ratio for wings revolving about their root, because it is otherwise unclear why, apart from possible physiological reasons, the convergent solution would not occur for an even lower Rossby number. We perform direct numerical simulations of the flow past revolving wings where we vary the aspect ratio and Rossby numbers independently by displacing the wing root from the axis of rotation. We show that the optimal lift coefficient represents a compromise between competing trends where the coefficient of lift increases monotonically with aspect ratio, holding Rossby number constant, but decreases monotonically with Rossby number, when holding aspect ratio constant. For wings revolving about their root, this favors wings of aspect ratio between 3 and 4. The authors gratefully acknowledge support from Fondation ISAE-Supaero.
Are there optimal numbers of oocytes, spermatozoa and embryos in assisted reproduction?
Milachich, Tanya; Shterev, Atanas
2016-08-01
The aim of this overview is to discuss the current information about the search for the optimum yield of gametes in assisted reproduction, as one of the major pillars of IVF success. The first topic is focused on the number of male gametes and the possible impact of some genetic traits on these parameters. The number of spermatozoa did not seem to be crucial when there is no severe male factor of infertility. Genetic testing prior to using those sperm cells is very important. Different methods were applied in order to elect the "best" spermatozoa according to specific indications. The next problem discussed is the importance of the number of oocytes collected. Several studies have agreed that "15 oocytes is the perfect number," as the number of mature oocytes is more important. However, if elective single embryo transfer is performed, the optimal number of oocytes will enable a proper embryo selection. The third problem discussed concerns fertility preservation. Many educational programs promote and encourage procreation at maternal ages between 20-35 years, since assisted reproduction is unable to fully overcome the effects of female aging and fertility loss after that age. It is also strongly recommended to ensure a reasonable number of cryopreserved mature oocytes, preferably in younger ages (<35), for which an average of two stimulation cycles are likely required. For embryo cryopreservation, the "freeze all" strategy suggests the vitrification of good embryos, therefore quality is prior to number and patient recruitment for this strategy should be performed cautiously.
Assessment of fruit density and leaf number: fruit to optimize crop load of mangosteen
Directory of Open Access Journals (Sweden)
Sayan Sdoodee
2006-09-01
Full Text Available To optimize crop load of mangosteen, fruit density and leaf number: fruit were assessed using a framework of quadrat cube (0.5 x 0.5 x 0.5 m in 2 consecutive years (2004-2005. Twenty-four 14-year-old uniform trees, field grown at Songkhla province, were selected to arrange 4 levels of crop loads: 1 Extremely low crop load (T1 = 264±5 fruit pt-1, 2 Low crop load (T2 = 826±36 fruit pt-1, 3 Medium crop load (T3 = 1190±27 fruit pt-1 and 4 High crop load (T4 = 1719±36 fruit pt-1. By placing the quadrat cube on the tree canopy, leaves quadrat-1 and fruits quadrat-1 were counted. Relationship between fruits quadrat-1 and fruit number pt-1 was found, and leaf number: fruit was also related to fruit yield pt-1. These results indicate that the assessment of fruit density and leaf number: fruit is of benefit for crop load management. Thus, 9 fruits quadrat-1 and 18 leaves: fruit are recommended to optimize crop load of mangosteen.
Directory of Open Access Journals (Sweden)
Nicolae Petrescu
2010-01-01
Full Text Available This paper is intended to achieve a mathematical model for the optimal dimensioning of number and heights of somedams/thresholds during a downpour, a decrease of water flow rate being obtained and by the solid material depositionsbehind the constructions a new smaller slope of the valley that changes the torrential nature that had before theconstruction is obtained.The choice of the dam and its characteristic dimensions may be an optimization issue and the location of dams on thetorrential (rainfall aspect is dictated by the capabilities of the foundation and restraint so that the chosen solutions willhave to comply with these sites. Finally, the choice of optimal solution to limit torrential (rainfall aspect will be basedon a calculation where the number of thresholds / dams can be a variable related to this, their height properly varying.The calculation method presented is an attempt to demonstrate the multiple opportunities available to implement atechnical issue solving conditions offered by the mathematics against soil erosion, which now is currently very topicalon the environmental protection.
Feng, Ju; Shen, Wen Zhong; Xu, Chang
2016-09-01
A new algorithm for multi-objective wind farm layout optimization is presented. It formulates the wind turbine locations as continuous variables and is capable of optimizing the number of turbines and their locations in the wind farm simultaneously. Two objectives are considered. One is to maximize the total power production, which is calculated by considering the wake effects using the Jensen wake model combined with the local wind distribution. The other is to minimize the total electrical cable length. This length is assumed to be the total length of the minimal spanning tree that connects all turbines and is calculated by using Prim's algorithm. Constraints on wind farm boundary and wind turbine proximity are also considered. An ideal test case shows the proposed algorithm largely outperforms a famous multi-objective genetic algorithm (NSGA-II). In the real test case based on the Horn Rev 1 wind farm, the algorithm also obtains useful Pareto frontiers and provides a wide range of Pareto optimal layouts with different numbers of turbines for a real-life wind farm developer.
Huang, Xuan-Chao
2010-01-01
One of the main problems in all-optical packet-switched networks is the lack of optical buffers, and one feasible technology for the constructions of optical buffers is to use optical crossbar Switches and fiber Delay Lines (SDL). In this two-part paper, we consider SDL constructions of optical queues with a limited number of recirculations through the optical switches and the fiber delay lines. Such a problem arises from practical feasibility considerations. In Part I, we have proposed a class of greedy constructions for certain types of optical queues, including linear compressors, linear decompressors, and 2-to-1 FIFO multiplexers, and have shown that every optimal construction among our previous constructions of these types of optical queues under the constraint of a limited number of recirculations must be a greedy construction. In Part II, the present paper, we further show that there are at most two optimal constructions and give a simple algorithm to obtain the optimal construction(s). The main idea i...
The optimal number of lymph nodes removed in maximizing the survival of breast cancer patients
Peng, Lim Fong; Taib, Nur Aishah; Mohamed, Ibrahim; Daud, Noorizam
2014-07-01
The number of lymph nodes removed is one of the important predictors for survival in breast cancer study. Our aim is to determine the optimal number of lymph nodes to be removed for maximizing the survival of breast cancer patients. The study population consists of 873 patients with at least one of axillary nodes involved among 1890 patients from the University of Malaya Medical Center (UMMC) breast cancer registry. For this study, the Chi-square test of independence is performed to determine the significant association between prognostic factors and survival status, while Wilcoxon test is used to compare the estimates of the hazard functions of the two or more groups at each observed event time. Logistic regression analysis is then conducted to identify important predictors of survival. In particular, Akaike's Information Criterion (AIC) are calculated from the logistic regression model for all thresholds of node involved, as an alternative measure for the Wald statistic (χ2), in order to determine the optimal number of nodes that need to be removed to obtain the maximum differential in survival. The results from both measurements are compared. It is recommended that, for this particular group, the minimum of 10 nodes should be removed to maximize survival of breast cancer patients.
Optimizing the Number of Cooperating Terminals for Energy Aware Task Computing in Wireless Networks
DEFF Research Database (Denmark)
Olsen, Anders Brødløs; Fitzek, Frank H. P.; Koch, Peter
2005-01-01
It is generally accepted that energy consumption is a significant design constraint for mobile handheld systems, therefore motivations for methods optimizing the energy consumption making better use of the restricted battery resources are evident. A novel concept of distributed task computing...... consumption of the terminals with respect to their workload and the overhead of distributing tasks among terminals are taken into account. The paper shows, that the number of cooperating terminals is in general limited to a few, though alternating with respect to the various system parameters....
Directory of Open Access Journals (Sweden)
Dušan Malindžák
2008-12-01
Full Text Available Material transportation by belt conveyers is widely used in many industrial branches including mining plants. Belt conveyingdevelopment during the last year was oriented mainly on construction of belts. The consequence of this is the improvement of itsmanufacture qualities bringing down the costs for their exchange and maintenance.Despite the fact that there are some theoreticalcalculations based on a standards it is common in the industry that the belt is not properly selected or it is overdesigned or number of itstypes is too large what can lead to increased costs for its storage. The paper describes the optimization of number of belt types in miningcompany SIDERIT, s. r. o. Nižná Slaná by the method of modernization and unification of belts under practical skills and projectingbased on theoretical calculations.
Directory of Open Access Journals (Sweden)
Mahmood Shafiee
2013-01-01
Full Text Available In offshore wind turbines, the blades are among the most critical and expensive components that suffer from different types of damage due to the harsh maritime environment and high load. The blade damages can be categorized into two types: the minor damage, which only causes a loss in wind capture without resulting in any turbine stoppage, and the major (catastrophic damage, which stops the wind turbine and can only be corrected by replacement. In this paper, we propose an optimal number-dependent preventive maintenance (NDPM strategy, in which a maintenance team is transported with an ordinary or expedited lead time to the offshore platform at the occurrence of the Nth minor damage or the first major damage, whichever comes first. The long-run expected cost of the maintenance strategy is derived, and the necessary conditions for an optimal solution are obtained. Finally, the proposed model is tested on real data collected from an offshore wind farm database. Also, a sensitivity analysis is conducted in order to evaluate the effect of changes in the model parameters on the optimal solution.
An Optimization Model for Design of Asphalt Pavements Based on IHAP Code Number 234
Directory of Open Access Journals (Sweden)
Ali Reza Ghanizadeh
2016-01-01
Full Text Available Pavement construction is one of the most costly parts of transportation infrastructures. Incommensurate design and construction of pavements, in addition to the loss of the initial investment, would impose indirect costs to the road users and reduce road safety. This paper aims to propose an optimization model to determine the optimal configuration as well as the optimum thickness of different pavement layers based on the Iran Highway Asphalt Paving Code Number 234 (IHAP Code 234. After developing the optimization model, the optimum thickness of pavement layers for secondary rural roads, major rural roads, and freeways was determined based on the recommended prices in “Basic Price List for Road, Runway and Railway” of Iran in 2015 and several charts were developed to determine the optimum thickness of pavement layers including asphalt concrete, granular base, and granular subbase with respect to road classification, design traffic, and resilient modulus of subgrade. Design charts confirm that in the current situation (material prices in 2015, application of asphalt treated layer in pavement structure is not cost effective. Also it was shown that, with increasing the strength of subgrade soil, the subbase layer may be removed from the optimum structure of pavement.
Optimizing of large-number-patterns string matching algorithms based on definite-state automata
Institute of Scientific and Technical Information of China (English)
CHEN Xun-xun; FANG Bin-xing
2007-01-01
Because the small CACHE size of computers, the scanning speed of DFA based multi-pattern stringmatching algorithms slows down rapidly especially when the number of patterns is very large. For solving such problems, we cut down the scanning time of those algorithms (i.e. DFA based) by rearranging the states table and shrinking the DFA alphabet size. Both the methods can decrease the probability of large-scale random memory accessing and increase the probability of continuously memory accessing. Then the hitting rate of the CACHE is increased and the searching time of on the DFA is reduced. Shrinking the alphabet size of the DFA also reduces the storage complication. The AC + + algorithm, by optimizing the Aho-Corasick ( i. e. AC) algorithm using such methods, proves the theoretical analysis. And the experimentation results show that the scanning time of AC + + and the storage occupied is better than that of AC in most cases and the result is much attractive when the number of patterns is very large. Because DFA is a widely used base algorithm in may string matching algorithms, such as DAWG, SBOM etc. , the optimizing method discussed is significant in practice.
Yarmand, Hamed
2013-01-01
Stereotactic body radiotherapy (SBRT) is characterized by delivering a high amount of dose in a short period of time. In SBRT the dose is delivered using open fields (e.g., beam's-eye-view) known as "apertures". Mathematical methods can be used for optimizing treatment planning for delivery of sufficient dose to the cancerous cells while keeping the dose to surrounding organs at risk (OARs) minimal. Two important elements of a treatment plan are quality and delivery time. Quality of a plan is measured based on the target coverage and dose to OARs. Delivery time heavily depends on the number of beams used in the plan since the setup times for different beam directions constitute a large portion of the delivery time. Therefore the ideal plan, in which all potential beams can be used simultaneously, will be associated with a long impractical delivery time. We use the dose to OARs in the ideal plan to find the plan with the minimum number of beams which is guaranteed to be epsilon-optimal (i.e., a predetermined m...
Miniaturised Prandtl tube with integrated pressure sensors for micro-thruster plume characterisation
Dijkstra, Marcel; Ma, Kechun; de Boer, Meint J.; Groenesteijn, Jarno; Lötters, Joost Conrad; Wiegerink, Remco J.
2014-01-01
A miniaturised Prandtl-tube sensor incorporating a 6 mm long 40 μm diameter microchannel with integrated pressure sensors has been realised. The sensor has been designed for the characterisation of rarefied plume flow from a MEMS-based monopropellant propulsion system for high-accuracy attitude
Kranenburg, C.
1999-01-01
The Prandtl mixing-length model of turbulent exchange of mass and momentum is applied to calculate the entrainment of overlying water into a layer of suspended fine sediment at a horizontal bed. In the field the flow and turbulence in such a concentrated benthic suspension (CBS) are driven by a
Plunian, Franck; Stepanov, Rodion
2010-10-01
A phenomenology of isotropic magnetohydrodynamic (MHD) turbulence subject to both rotation and applied magnetic field is presented. It is assumed that the triple correlation decay time is the shortest between the eddy turn-over time and the ones associated to the rotating frequency and the Alfvén wave period. For Pm=1 it leads to four kinds of piecewise spectra, depending on four parameters: injection rate of energy, magnetic diffusivity, rotation rate, and applied field. With a shell model of MHD turbulence (including rotation and applied magnetic field), spectra for Pm ≤ 1 are presented, together with the ratio between magnetic and viscous dissipations.
Prandtl number effects in MRT lattice Boltzmann models for shocked and unshocked compressible fluids
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
This paper constructs a new multiple relaxation time lattice Boltzmann model which is not only for the shocked compressible fluids,but also for the unshocked compressible fluids.To make the model work for unshocked compressible fluids,a key step is to modify the collision operators of energy flux so that the viscous coefficient in momentum equation is consistent with that in energy equation even in the unshocked system.The unnecessity of the modification for systems under strong shock is analyzed.The model ...
Directory of Open Access Journals (Sweden)
Satwinder Singh
2016-01-01
Full Text Available A task-oriented design strategy is presented in this paper for service manipulators. The tasks are normally defined in the form of working locations where the end-effector can work while avoiding the obstacles. To acquire feasible solutions in cluttered environments, the robotic parameters (D-H parameters are allowed to take unconventional values. This enhances the solution space and it is observed that, by inducing this flexibility, the required number of degrees of freedom for fulfilling a given task can be reduced. A bilevel optimization problem is formulated with the outer layer utilizing the binary search method for minimizing the number of degrees of freedom. To enlarge the applicability domain of the proposed strategy, the upper limit of the number of joints is kept more than six. These allowable redundant joints would help in providing solution for intricate workcells. For each iteration of the upper level, a constrained nonlinear problem is solved for dimensional synthesis of the manipulator. The methodology is demonstrated through a case study of a realistic environment of a cluttered server room. A 7-link service arm, synthesized using the proposed method, is able to fulfill two different tasks effectively.
Incremental Optimization of Hub and Spoke Network for the Spokes’ Numbers and Flow
Directory of Open Access Journals (Sweden)
Yanfeng Wang
2015-01-01
Full Text Available Hub and spoke network problem is solved as part of a strategic decision making process which may have a profound effect on the future of enterprises. In view of the existing network structure, as time goes on, the number of spokes and the flow change because of different sources of uncertainty. Hence, the incremental optimization of hub and spoke network problem is considered in this paper, and the policy makers should adopt a series of strategies to cope with the change, such as setting up new hubs, adjusting the capacity level of original hubs, or closing some original hubs. The objective is to minimize the total cost, which includes the setup costs for the new hubs, the closure costs, and the adjustment costs for the original hubs as well as the flow routing costs. Two mixed-integer linear programming formulations are proposed and analyzed for this problem. China Deppon Logistics as an example is performed to present computational analysis, and we analyze the changes in the solutions driven by the number of spokes and the flow. The tests also allow an analysis to consider the effect of variation in parameters on network.
Methods for optimizing DNA extraction before quantifying oral bacterial numbers by real-time PCR.
Nadkarni, Mangala A; Martin, F Elizabeth; Hunter, Neil; Jacques, Nicholas A
2009-07-01
Methods for the optimal extraction of genomic DNA for real-time PCR enumeration of oral bacteria using the muramidase, mutanolysin, were developed using a simple in vitro oral flora model comprised of the facultative anaerobic gram-positive bacteria, Lactobacillus acidophilus and Streptococcus mutans, the gram-positive anaerobe, Parvimonas micra, and the gram-negative anaerobes, Porphyromonas gingivalis, Prevotella melaninogenica and Fusobacterium nucleatum. Traditional, as well as more elaborate, methods of quantifying bacterial numbers, including colony counting and estimation of DNA content using 4',6-diamino-2-phenylindole were compared in order to validate the real-time PCR approach. Evidence was obtained that P. gingivalis nuclease activity adversely affected the extraction of double-stranded DNA from this bacterium either alone or when it formed part of a consortium with the other bacteria. This nuclease activity could be overcome by treatment of the bacteria with either 20 mM diethyl pyrocarbonate or 70% ethanol at 4 degrees C overnight. A final purification of the DNA to remove any potential PCR inhibitors was added to the protocol in order to accurately quantify the amount of DNA by real-time PCR and hence the number of bacteria in a sample.
Optimization model using Markowitz model approach for reducing the number of dengue cases in Bandung
Yong, Benny; Chin, Liem
2017-05-01
Dengue fever is one of the most serious diseases and this disease can cause death. Currently, Indonesia is a country with the highest cases of dengue disease in Southeast Asia. Bandung is one of the cities in Indonesia that is vulnerable to dengue disease. The sub-districts in Bandung had different levels of relative risk of dengue disease. Dengue disease is transmitted to people by the bite of an Aedesaegypti mosquito that is infected with a dengue virus. Prevention of dengue disease is by controlling the vector mosquito. It can be done by various methods, one of the methods is fogging. The efforts made by the Health Department of Bandung through fogging had constraints in terms of limited funds. This problem causes Health Department selective in fogging, which is only done for certain locations. As a result, many sub-districts are not handled properly by the Health Department because of the unequal distribution of activities to prevent the spread of dengue disease. Thus, it needs the proper allocation of funds to each sub-district in Bandung for preventing dengue transmission optimally. In this research, the optimization model using Markowitz model approach will be applied to determine the allocation of funds should be given to each sub-district in Bandung. Some constraints will be added to this model and the numerical solution will be solved with generalized reduced gradient method using Solver software. The expected result of this research is the proportion of funds given to each sub-district in Bandung correspond to the level of risk of dengue disease in each sub-district in Bandung so that the number of dengue cases in this city can be reduced significantly.
Modal structural acoustic sensing with minimum number of optimally placed piezoelectric sensors
Loghmani, Ali; Danesh, Mohammad; Keshmiri, Mehdi
2016-02-01
Structural acoustic sensing is a method of obtaining radiated sound pressure from a vibrating structure using vibration information. Structural acoustic sensing is used in active structural acoustic control for attenuating the sound radiated from a structure. In this paper, a new approach called Modal Structural Acoustic Sensing (MSAS) is proposed for estimating the pressure radiated from a vibrating cylindrical shell using piezoelectric sensors. The motion equations of a cylindrical shell in conjunction with piezoelectric patches are derived based on the Donnel-Mushtari shell theory. The locations of the piezoelectric sensors are optimized by the Genetic Algorithm based on maximizing the observability gramian matrix. The Kirchhoff-Helmholtz integral is used for estimating the sound pressure radiated from the cylindrical shell. Numerical simulations are performed to demonstrate the advantages of the proposed approach in comparison with previous methods such as discrete structural acoustic sensing and distributed modal sensors. Results show that the MSAS can increase the estimation accuracy and decrease the controller dimensionality and the number of required sensors.
On the Global Existence and Uniqueness of Solutions to Prandtl's System
Institute of Scientific and Technical Information of China (English)
Xin Ying XU; Jun Ning ZHAO
2009-01-01
In this paper, we consider the Prandtl system for the non-stationary boundary layer in the vicinity of a point where the outer flow has zero velocity. It is assumed that U(t, x, y) = xmU1(t, x), where 0≤x≤L and m≥1. We establish the global existence of the weak solution to this problem. Moreover the uniqueness of the weak solution is proved.
Acker, A.
Under reasonably general assumptions, we prove the existence of convex classical solutions for the Prandtl-Batchelor free boundary problem in fluid dynamics, in which a flow of constant vorticity density is embedded in a potential flow, with a vortex sheet of constant vorticity density as the flow interface. These results apply to Batchelor flows which are confined to a bounded, convex vessel, and for which the limiting interior flow-speed exceeds the limiting exterior flow-speed along the interface.
Goldstein's solution of the problem of the aircraft propeller with a finite number of blades
Helmbold, H B
1931-01-01
This report examines the Betz theory on frictionless, lightly loaded propellers and Prandtl's addendum extended to moderately loaded propellers. The author then goes on to extend the discussion to Goldstein's solution for propellers with a finite number of blades.
Energy Technology Data Exchange (ETDEWEB)
Barragán, A. M., E-mail: ana.barragan@uclouvain.be; Differding, S.; Lee, J. A.; Sterpin, E. [Center of Molecular Imaging, Radiotherapy and Oncology, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels B-1200 (Belgium); Janssens, G. [Ion Beam Applications S.A., Louvain-la-Neuve 1348 (Belgium)
2015-04-15
Purpose: To prove the ability of protons to reproduce a dose gradient that matches a dose painting by numbers (DPBN) prescription in the presence of setup and range errors, by using contours and structure-based optimization in a commercial treatment planning system. Methods: For two patients with head and neck cancer, voxel-by-voxel prescription to the target volume (GTV{sub PET}) was calculated from {sup 18}FDG-PET images and approximated with several discrete prescription subcontours. Treatments were planned with proton pencil beam scanning. In order to determine the optimal plan parameters to approach the DPBN prescription, the effects of the scanning pattern, number of fields, number of subcontours, and use of range shifter were separately tested on each patient. Different constant scanning grids (i.e., spot spacing = Δx = Δy = 3.5, 4, and 5 mm) and uniform energy layer separation [4 and 5 mm WED (water equivalent distance)] were analyzed versus a dynamic and automatic selection of the spots grid. The number of subcontours was increased from 3 to 11 while the number of beams was set to 3, 5, or 7. Conventional PTV-based and robust clinical target volumes (CTV)-based optimization strategies were considered and their robustness against range and setup errors assessed. Because of the nonuniform prescription, ensuring robustness for coverage of GTV{sub PET} inevitably leads to overdosing, which was compared for both optimization schemes. Results: The optimal number of subcontours ranged from 5 to 7 for both patients. All considered scanning grids achieved accurate dose painting (1% average difference between the prescribed and planned doses). PTV-based plans led to nonrobust target coverage while robust-optimized plans improved it considerably (differences between worst-case CTV dose and the clinical constraint was up to 3 Gy for PTV-based plans and did not exceed 1 Gy for robust CTV-based plans). Also, only 15% of the points in the GTV{sub PET} (worst case) were
Amin, Talha
2013-01-01
In the paper, we present a comparison of dynamic programming and greedy approaches for construction and optimization of approximate decision rules relative to the number of misclassifications. We use an uncertainty measure that is a difference between the number of rows in a decision table T and the number of rows with the most common decision for T. For a nonnegative real number γ, we consider γ-decision rules that localize rows in subtables of T with uncertainty at most γ. Experimental results with decision tables from the UCI Machine Learning Repository are also presented. © 2013 Springer-Verlag.
Roccuzzo, Mario; Bonino, Francesca; Gaudioso, Luigi; Zwahlen, Marcel; Meijer, Henny J. A.
2012-01-01
Objectives The aim of this systematic review was to assess the optimal number of implants for removable reconstructions. Material and methods Medline and The Cochrane Central Register of Controlled Trials were searched and complemented by hand searching. All trials published in English to October
Roccuzzo, Mario; Bonino, Francesca; Gaudioso, Luigi; Zwahlen, Marcel; Meijer, Henny J. A.
2012-01-01
Objectives The aim of this systematic review was to assess the optimal number of implants for removable reconstructions. Material and methods Medline and The Cochrane Central Register of Controlled Trials were searched and complemented by hand searching. All trials published in English to October 20
Yarmand, Hamed; Winey, Brian; Craft, David
2013-09-07
Stereotactic body radiation therapy (SBRT) is characterized by delivering a high amount of dose in a short period of time. In SBRT the dose is delivered using open fields (e.g., beam's-eye-view) known as 'apertures'. Mathematical methods can be used for optimizing treatment planning for delivery of sufficient dose to the cancerous cells while keeping the dose to surrounding organs at risk (OARs) minimal. Two important elements of a treatment plan are quality and delivery time. Quality of a plan is measured based on the target coverage and dose to OARs. Delivery time heavily depends on the number of beams used in the plan as the setup times for different beam directions constitute a large portion of the delivery time. Therefore the ideal plan, in which all potential beams can be used, will be associated with a long impractical delivery time. We use the dose to OARs in the ideal plan to find the plan with the minimum number of beams which is guaranteed to be epsilon-optimal (i.e., a predetermined maximum deviation from the ideal plan is guaranteed). Since the treatment plan optimization is inherently a multi-criteria-optimization problem, the planner can navigate the ideal dose distribution Pareto surface and select a plan of desired target coverage versus OARs sparing, and then use the proposed technique to reduce the number of beams while guaranteeing epsilon-optimality. We use mixed integer programming (MIP) for optimization. To reduce the computation time for the resultant MIP, we use two heuristics: a beam elimination scheme and a family of heuristic cuts, known as 'neighbor cuts', based on the concept of 'adjacent beams'. We show the effectiveness of the proposed technique on two clinical cases, a liver and a lung case. Based on our technique we propose an algorithm for fast generation of epsilon-optimal plans.
Determining the optimal number of Kanban in multi-products supply chain system
Widyadana, G. A.; Wee, H. M.; Chang, Jer-Yuan
2010-02-01
Kanban, a key element of just-in-time system, is a re-order card or signboard giving instruction or triggering the pull system to manufacture or supply a component based on actual usage of material. There are two types of Kanban: production Kanban and withdrawal Kanban. This study uses optimal and meta-heuristic methods to determine the Kanban quantity and withdrawal lot sizes in a supply chain system. Although the mix integer programming method gives an optimal solution, it is not time efficient. For this reason, the meta-heuristic methods are suggested. In this study, a genetic algorithm (GA) and a hybrid of genetic algorithm and simulated annealing (GASA) are used. The study compares the performance of GA and GASA with that of the optimal method using MIP. The given problems show that both GA and GASA result in a near optimal solution, and they outdo the optimal method in term of run time. In addition, the GASA heuristic method gives a better performance than the GA heuristic method.
Harmening, Corinna; Neuner, Hans
2016-09-01
Due to the establishment of terrestrial laser scanner, the analysis strategies in engineering geodesy change from pointwise approaches to areal ones. These areal analysis strategies are commonly built on the modelling of the acquired point clouds. Freeform curves and surfaces like B-spline curves/surfaces are one possible approach to obtain space continuous information. A variety of parameters determines the B-spline's appearance; the B-spline's complexity is mostly determined by the number of control points. Usually, this number of control points is chosen quite arbitrarily by intuitive trial-and-error-procedures. In this paper, the Akaike Information Criterion and the Bayesian Information Criterion are investigated with regard to a justified and reproducible choice of the optimal number of control points of B-spline curves. Additionally, we develop a method which is based on the structural risk minimization of the statistical learning theory. Unlike the Akaike and the Bayesian Information Criteria this method doesn't use the number of parameters as complexity measure of the approximating functions but their Vapnik-Chervonenkis-dimension. Furthermore, it is also valid for non-linear models. Thus, the three methods differ in their target function to be minimized and consequently in their definition of optimality. The present paper will be continued by a second paper dealing with the choice of the optimal number of control points of B-spline surfaces.
Optimizing the number of steps in learning tasks for complex skills.
Nadolski, Rob; Kirschner, Paul A.; Van Merriënboer, Jeroen
2007-01-01
Background. Carrying out whole tasks is often too difficult for novice learners attempting to acquire complex skills. The common solution is to split up the tasks into a number of smaller steps. The number of steps must be optimised for efficient and effective learning. Aim. The aim of the study is
Adjoint optimization of natural convection problems: differentially heated cavity
Saglietti, Clio; Schlatter, Philipp; Monokrousos, Antonios; Henningson, Dan S.
2016-06-01
Optimization of natural convection-driven flows may provide significant improvements to the performance of cooling devices, but a theoretical investigation of such flows has been rarely done. The present paper illustrates an efficient gradient-based optimization method for analyzing such systems. We consider numerically the natural convection-driven flow in a differentially heated cavity with three Prandtl numbers (Pr=0.15{-}7 ) at super-critical conditions. All results and implementations were done with the spectral element code Nek5000. The flow is analyzed using linear direct and adjoint computations about a nonlinear base flow, extracting in particular optimal initial conditions using power iteration and the solution of the full adjoint direct eigenproblem. The cost function for both temperature and velocity is based on the kinetic energy and the concept of entransy, which yields a quadratic functional. Results are presented as a function of Prandtl number, time horizons and weights between kinetic energy and entransy. In particular, it is shown that the maximum transient growth is achieved at time horizons on the order of 5 time units for all cases, whereas for larger time horizons the adjoint mode is recovered as optimal initial condition. For smaller time horizons, the influence of the weights leads either to a concentric temperature distribution or to an initial condition pattern that opposes the mean shear and grows according to the Orr mechanism. For specific cases, it could also been shown that the computation of optimal initial conditions leads to a degenerate problem, with a potential loss of symmetry. In these situations, it turns out that any initial condition lying in a specific span of the eigenfunctions will yield exactly the same transient amplification. As a consequence, the power iteration converges very slowly and fails to extract all possible optimal initial conditions. According to the authors' knowledge, this behavior is illustrated here
modelling for optimal number of line storage reservoirs in a water ...
African Journals Online (AJOL)
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the reservoir system location be integrated into the ... systems experience (figure 1), storage facilities within the system .... Therefore, a computer programme for designing cost effective water distribution net works called Economic Number of.
A new definition of Bejan number
Directory of Open Access Journals (Sweden)
Awad Mohamed M.
2012-01-01
Full Text Available A new definition of Bejan number will be generated by replacing the thermal diffusivity with the mass diffusivity. For example, the Schmidt number is the mass transfer analog of the Prandtl number. For the case of Reynolds analogy (Sc = Pr = = 1, both current and new definitions of Bejan number are the same. This new definition is useful and needed for diffusion of mass (mass diffusion.
Heuristic approach to optimize the number of test cases for simple circuits
Directory of Open Access Journals (Sweden)
SM. Thamarai
2015-09-01
Full Text Available In this paper a new solution is proposed for testing simples two stage electronic circuits. It minimizes the number of tests to be performed to determine the genuinity of the circuit. The main idea behind the present research work is to identify the maximum number of indistinguishable faults present in the given circuit and minimize the number of test cases based on the number of faults that has been detected. Heuristic approach is used for test minimization part, which identifies the essential tests from overall test cases.From the results it is observed that, test minimization varies from 50% to 99% with the lowest one corresponding to a circuit with four gates .Test minimization is low in case of circuits with lesser input leads in gates compared to greater input leads in gates for the boolean expression with same number of symbols. Achievement of 99% reduction is due to the fact that the large number of tests find the same faults.The new approach is implemented for simple circuits. The results show potential for both smaller test sets and lower cpu times
Numerical investigation of homogeneous condensation in Prandtl-Meyer expansion flows
Cao, Y.; Cheng, W.; Luo, X.; Yang, J.
2017-03-01
The effect of heat addition induced by condensation of water vapor on Prandtl-Meyer flows is investigated numerically. Two configurations are considered to study the formation of the stationary waves and the movement of the oscillatory shocks caused by homogeneous condensation. One is a nozzle-shaped channel bounded by lower and upper walls, and the other is an upper unbounded corner expansion. For the first configuration, cases with a sharp corner and a rounded corner are compared to highlight the influence of the sharp corner, where the cooling rate is very large. The density variation in the zone near the corner is smoothed, and the influence on the flow structure caused by the sharp corner is very limited in the neighborhood of the sharp corner. For a relatively low initial saturation, the structures of the condensation shock in the numerical simulation agree well with the experimental results in the literature. The increase of the initial saturation makes the condensation shock move upstream, and eventually leads to an unsteady shock motion. The tendency is similar to that in the condensation process in nozzles. For the unbounded corner expansion, the wave structure forms a two-dimensional distribution. Multiple shock waves are observed in the numerical schlieren image, which are caused by a sequence of quenching (by the condensation shock) and rebuilding (by the Prandtl-Meyer expansion) of the condensation. This mutual interaction can also be recognized by the wavy shape of the nucleation rate distribution.
Numerical investigation of homogeneous condensation in Prandtl-Meyer expansion flows
Cao, Y.; Cheng, W.; Luo, X.; Yang, J.
2016-06-01
The effect of heat addition induced by condensation of water vapor on Prandtl-Meyer flows is investigated numerically. Two configurations are considered to study the formation of the stationary waves and the movement of the oscillatory shocks caused by homogeneous condensation. One is a nozzle-shaped channel bounded by lower and upper walls, and the other is an upper unbounded corner expansion. For the first configuration, cases with a sharp corner and a rounded corner are compared to highlight the influence of the sharp corner, where the cooling rate is very large. The density variation in the zone near the corner is smoothed, and the influence on the flow structure caused by the sharp corner is very limited in the neighborhood of the sharp corner. For a relatively low initial saturation, the structures of the condensation shock in the numerical simulation agree well with the experimental results in the literature. The increase of the initial saturation makes the condensation shock move upstream, and eventually leads to an unsteady shock motion. The tendency is similar to that in the condensation process in nozzles. For the unbounded corner expansion, the wave structure forms a two-dimensional distribution. Multiple shock waves are observed in the numerical schlieren image, which are caused by a sequence of quenching (by the condensation shock) and rebuilding (by the Prandtl-Meyer expansion) of the condensation. This mutual interaction can also be recognized by the wavy shape of the nucleation rate distribution.
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Sukhpreet Kaur Sidhu
2014-01-01
Full Text Available The drawbacks of the existing methods to obtain the fuzzy optimal solution of such linear programming problems, in which coefficients of the constraints are represented by real numbers and all the other parameters as well as variables are represented by symmetric trapezoidal fuzzy numbers, are pointed out, and to resolve these drawbacks, a new method (named as Mehar method is proposed for the same linear programming problems. Also, with the help of proposed Mehar method, a new method, much easy as compared to the existing methods, is proposed to deal with the sensitivity analysis of the same type of linear programming problems.
Le Bouquin, J B; Bouquin, Jean-Baptiste Le; Tatulli, Eric
2006-01-01
Incoming optical interferometers will allow spectro-imaging at high angular resolution. Non-homothetic Fizeau concept combines good sensitivity and high spectral resolution capabilities. However, one critical issue is the design of the beam recombination scheme, at the heart of the instrument. We tackle the possibility of reducing the number of pixels that are coding the fringes by compressing the pupil plane. Shrinking the number of pixels -- which drastically increases with the number of recombined telescopes -- is indeed a key issue that enables to reach higher limiting magnitude, but also allows to lower the required spectral resolution and fasten the fringes reading process. By means of numerical simulations, we study the performances of existing estimators of the visibility with respect to the compression process. We show that, not only the model based estimator lead to better signal to noise ratio (SNR) performances than the Fourier ones, but above all it is the only one which prevent from introducing ...
Lian, Jiazhang; Jin, Run; Zhao, Huimin
2016-11-01
The CEN/ARS-based low-copy plasmids and 2 μ-based high-copy plasmids have been broadly used for both fundamental studies and practical applications in Saccharomyces cerevisiae. However, the relative low copy numbers and narrow dynamic range limit their applications in many cases. In this study, the expression level of the selection marker proteins was engineered to increase the plasmid copy numbers. A series of plasmids with step-wise increased copy numbers were constructed. The copy number of the plasmids with engineered dominant markers (5-100 copies per cell) showed a positive correlation with the concentration of antibiotics supplemented to the growth media. Based on this finding, we developed a simple yet highly efficient strategy, named Pathway Optimization by Tuning Antibiotic Concentrations (POTAC) to rapidly balance the flux of multi-gene pathways at the DNA level in S. cerevisiae. As proof of concept, POTAC was used to optimize the lycopene and n-butanol biosynthetic pathways, increasing the production of lycopene and n-butanol by 10- and 100-fold, respectively. Additionally, multiplex genome integration with controllable copy numbers was attempted by combining the engineered dominant markers with the CRISPR/Cas9 system. Biotechnol. Bioeng. 2016;113: 2462-2473. © 2016 Wiley Periodicals, Inc.
Boskovic, Goran; Jovicic, Nebojsa
2015-12-01
This paper concerns the development of a methodology aimed at determining the optimal number of waste bins as well optimizing the location of collection points. The methodology was based on a geographic information system, which handled different sets of information, such as street directions, spatial location of objects and number of inhabitants, location of waste bins, and radius of their coverage. The study was conducted in a district in the central area of the city of Kragujevac. Due to a lack of information about the existing situation, all necessary data was collected by fieldwork and by using GPS equipment. By using the developed methodology, the results indicated a reduction of 24% in the number of collection points and 33.5% in the number of waste bins, without reducing the quality of the provided services. It has led to cost and time savings for waste collection and environmental benefits. All users of the services were covered within a 75-m radius, and the usage of bins is more efficient. According to the reduction in the number of waste bins, a total amount of €26,000 may be achieved. In addition, the time for waste collection was reduced, resulting in a €1700 saving per year in fuel costs, as well as 4.5 tons of emitted CO2 into the atmosphere. © The Author(s) 2015.
On the optimal number of scale points in graded paired comparisons
Beuckelaer, A. De; Toonen, S.; Davidov, E.
2013-01-01
In market research, it is common practice to measure individuals’ brand or product preference through graded paired comparisons (GPCs). One important decision concerns the (odd) number of scale points (e.g., five, seven, nine, or eleven) that has to be assigned to either brands or products in each
Wolterbeek, H.T.; Van der Meer, A.J.G.M.
2005-01-01
The lactate dehydrogenase (LDH) assay was addressed for its sensitivity, disturbances by foaming, and cell number and size. Cells were from a U-251 MG grade IV human glioblastoma brain tumor cell line used in 100-µl well volumes. Cells were counted by microscopy and Coulter counting; assays were LDH
Harmening, Corinna; Neuner, Hans
2017-03-01
Freeform surfaces like B-splines have proven to be a suitable tool to model laser scanner point clouds and to form the basis for an areal data analysis, for example an areal deformation analysis. A variety of parameters determine the B-spline's appearance, the B-spline's complexity being mostly determined by the number of control points. Usually, this parameter type is chosen by intuitive trial-and-error-procedures. In [10] the problem of finding an alternative to these trial-and-error-procedures was addressed for the case of B-spline curves: The task of choosing the optimal number of control points was interpreted as a model selection problem. Two model selection criteria, the Akaike and the Bayesian Information Criterion, were used to identify the B-spline curve with the optimal number of control points from a set of candidate B-spline models. In order to overcome the drawbacks of the information criteria, an alternative approach based on statistical learning theory was developed. The criteria were evaluated by means of simulated data sets. The present paper continues these investigations. If necessary, the methods proposed in [10] are extended to areal approaches so that they can be used to determine the optimal number of B-spline surface control points. Furthermore, the methods are evaluated by means of real laser scanner data sets rather than by simulated ones. The application of those methods to B-spline surfaces reveals the datum problem of those surfaces, meaning that location and number of control points of two B-splines surfaces are only comparable if they are based on the same parameterization. First investigations to solve this problem are presented.
Prathabrao, M.; Nawawi, Azli; Sidek, Noor Azizah
2017-04-01
Radio Frequency Identification (RFID) system has multiple benefits which can improve the operational efficiency of the organization. The advantages are the ability to record data systematically and quickly, reducing human errors and system errors, update the database automatically and efficiently. It is often more readers (reader) is needed for the installation purposes in RFID system. Thus, it makes the system more complex. As a result, RFID network planning process is needed to ensure the RFID system works perfectly. The planning process is also considered as an optimization process and power adjustment because the coordinates of each RFID reader to be determined. Therefore, algorithms inspired by the environment (Algorithm Inspired by Nature) is often used. In the study, PSO algorithm is used because it has few number of parameters, the simulation time is fast, easy to use and also very practical. However, PSO parameters must be adjusted correctly, for robust and efficient usage of PSO. Failure to do so may result in disruption of performance and results of PSO optimization of the system will be less good. To ensure the efficiency of PSO, this study will examine the effects of two parameters on the performance of PSO Algorithm in RFID tag coverage optimization. The parameters to be studied are the swarm size and iteration number. In addition to that, the study will also recommend the most optimal adjustment for both parameters that is, 200 for the no. iterations and 800 for the no. of swarms. Finally, the results of this study will enable PSO to operate more efficiently in order to optimize RFID network planning system.
Okariz, Ana; Guraya, Teresa; Iturrondobeitia, Maider; Ibarretxe, Julen
2017-02-01
The SIRT (Simultaneous Iterative Reconstruction Technique) algorithm is commonly used in Electron Tomography to calculate the original volume of the sample from noisy images, but the results provided by this iterative procedure are strongly dependent on the specific implementation of the algorithm, as well as on the number of iterations employed for the reconstruction. In this work, a methodology for selecting the iteration number of the SIRT reconstruction that provides the most accurate segmentation is proposed. The methodology is based on the statistical analysis of the intensity profiles at the edge of the objects in the reconstructed volume. A phantom which resembles a a carbon black aggregate has been created to validate the methodology and the SIRT implementations of two free software packages (TOMOJ and TOMO3D) have been used.
Optimal Length Scale for a Turbulent Dynamo.
Sadek, Mira; Alexakis, Alexandros; Fauve, Stephan
2016-02-19
We demonstrate that there is an optimal forcing length scale for low Prandtl number dynamo flows that can significantly reduce the required energy injection rate. The investigation is based on simulations of the induction equation in a periodic box of size 2πL. The flows considered are the laminar and turbulent ABC flows forced at different forcing wave numbers k_{f}, where the turbulent case is simulated using a subgrid turbulence model. At the smallest allowed forcing wave number k_{f}=k_{min}=1/L the laminar critical magnetic Reynolds number Rm_{c}^{lam} is more than an order of magnitude smaller than the turbulent critical magnetic Reynolds number Rm_{c}^{turb} due to the hindering effect of turbulent fluctuations. We show that this hindering effect is almost suppressed when the forcing wave number k_{f} is increased above an optimum wave number k_{f}L≃4 for which Rm_{c}^{turb} is minimum. At this optimal wave number, Rm_{c}^{turb} is smaller by more than a factor of 10 than the case forced in k_{f}=1. This leads to a reduction of the energy injection rate by 3 orders of magnitude when compared to the case where the system is forced at the largest scales and thus provides a new strategy for the design of a fully turbulent experimental dynamo.
Innovative processes impact on the factors optimal number formation of the enterprise location
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Franiv Ihor Andriiovych
2014-12-01
Full Text Available The aim of the article. Determination of the factors to locate enterprises for searching optimal location place, therefore grounding enterprise location place with one or several factors one should consider innovative development nowadays. The results of the analysis. The branches referring to this or that production group will always have relative character and will concern time period, because – various factors value can be changed under influence of innovation introduction. Technological and organizational changes of production with big probability impact effect its location. On the territory of some states or regions the enterprise can be built, which earlier it was not efficiently to build. Taking into account this “innovative prism” concerning enterprises location factor, we can form ten factors, which are taken by enterprises while searching their optimal location places. Direction of production attention to raw sources. The enterprises orient to be located close to raw sources and producing based due to this factor. Direction of attention to the raw sources is reasonably to conduct in the following cases. Firstly, raw procurement, processing or mining (minerals mining, sawmilling industry, fish-processing industry, etc. enterprises have raw orientation. Secondly, enterprises, which waste a lot of raw materials in relation to final product, i.e. material-intensive production, direct their attention to the raw sources. Thirdly, enterprises, processing raw, which is quickly spoiled: wine industry, food-canning industry, fish-processing industry, etc., are closely situated to the raw sources. Direction of the producing attention to electric power and fuel sources. Highly energy-intensive productions (fuel and energetic costs component is half of the whole costs for production have to direct their attention to close location to fuel bases (heat and power stations, petrochemical industry enterprises, etc. or close to the electric power
Multi-hop routing-based optimization of the number of cluster-heads in wireless sensor networks.
Nam, Choon Sung; Han, Young Shin; Shin, Dong Ryeol
2011-01-01
Wireless sensor networks require energy-efficient data transmission because the sensor nodes have limited power. A cluster-based routing method is more energy-efficient than a flat routing method as it can only send specific data for user requirements and aggregate similar data by dividing a network into a local cluster. However, previous clustering algorithms have some problems in that the transmission radius of sensor nodes is not realistic and multi-hop based communication is not used both inside and outside local clusters. As energy consumption based on clustering is dependent on the number of clusters, we need to know how many clusters are best. Thus, we propose an optimal number of cluster-heads based on multi-hop routing in wireless sensor networks. We observe that a local cluster made by a cluster-head influences the energy consumption of sensor nodes. We determined an equation for the number of packets to send and relay, and calculated the energy consumption of sensor networks using it. Through the process of calculating the energy consumption, we can obtain the optimal number of cluster-heads in wireless sensor networks.
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Antonio Berlanga
2004-07-01
Full Text Available The design of statistical classification systems for optical character recognition (OCR is a cumbersome task. This paper proposes a method using evolutionary strategies (ES to evolve and upgrade the set of parameters in an OCR system. This OCR is applied to identify the tail number of aircrafts moving on the airport. The proposed approach is discussed and some results are obtained using a benchmark data set. This research demonstrates the successful application of ES to a difficult, noisy, and real-world problem.
On identifying the optimal number of population clusters via the deviance information criterion.
Gao, Hong; Bryc, Katarzyna; Bustamante, Carlos D
2011-01-01
Inferring population structure using bayesian clustering programs often requires a priori specification of the number of subpopulations, K, from which the sample has been drawn. Here, we explore the utility of a common bayesian model selection criterion, the Deviance Information Criterion (DIC), for estimating K. We evaluate the accuracy of DIC, as well as other popular approaches, on datasets generated by coalescent simulations under various demographic scenarios. We find that DIC outperforms competing methods in many genetic contexts, validating its application in assessing population structure.
Schabrun, Siobhan M.
2017-01-01
The delivery of five stimuli to each cranial site is recommended during transcranial magnetic stimulation (TMS) mapping. However, this time-consuming practice restricts the use of TMS mapping beyond the research environment. While reducing the number of stimuli administered to each cranial site may improve efficiency and decrease physiological demand, doing so may also compromise the procedure's validity. Therefore, the aim of this study was to determine the minimum number of stimuli per cranial site required to obtain valid outcomes during TMS mapping. Map volume and centre of gravity (CoG) recordings obtained using five stimuli per cranial site were retrospectively compared to those obtained using one, two, three, and four stimuli per cranial site. For CoG longitude, one stimulus per cranial site produced valid recordings (ICC = 0.91, 95% CI 0.82 to 0.95). However, this outcome is rarely explored in isolation. As two stimuli per cranial site were required to obtain valid CoG latitude (ICC = 0.99, 95% CI 0.99 to 0.99) and map volume (ICC = 0.99, 95% CI 0.99 to 0.99) recordings, it is recommended that a minimum of two stimuli be delivered to each cranial site during TMS mapping in order to obtain valid outcomes. PMID:28331848
Optimizing the number of progenies and replications in plant breeding experiments
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João Luís da Silva Filho
2013-01-01
Full Text Available A determination criterion was proposed for the number of replications, r, and of evaluated progenies, Nr, given P experimentalplots, with Nr=P/r, and n progenies to be selected; its application was discussed in the selection of progenies of bulk populations,derived from two homozygous parents. For a known heritability at the plot level, h20, there is a critical n below which the gain isgreater with selection evaluating P/(r+1 progenies in r+1 than P/r progenies in r replications. Different h20 scenarios were simulatedin the F2 and F∞ generations, assuming no dominance. It was demonstrated that at any h20 , if n > 18.5% of P, larger gains are obtainedby assuming Nr = P, showing that the augmented block design could be used in the early stages of breeding programs. The higher h20,the higher must be the selection intensity to justify the use of additional replications.
Domingo-Perez, Francisco; Lazaro-Galilea, Jose Luis; Bravo, Ignacio; Gardel, Alfredo; Rodriguez, David
2016-06-22
This paper focuses on optimal sensor deployment for indoor localization with a multi-objective evolutionary algorithm. Our goal is to obtain an algorithm to deploy sensors taking the number of sensors, accuracy and coverage into account. Contrary to most works in the literature, we consider the presence of obstacles in the region of interest (ROI) that can cause occlusions between the target and some sensors. In addition, we aim to obtain all of the Pareto optimal solutions regarding the number of sensors, coverage and accuracy. To deal with a variable number of sensors, we add speciation and structural mutations to the well-known non-dominated sorting genetic algorithm (NSGA-II). Speciation allows one to keep the evolution of sensor sets under control and to apply genetic operators to them so that they compete with other sets of the same size. We show some case studies of the sensor placement of an infrared range-difference indoor positioning system with a fairly complex model of the error of the measurements. The results obtained by our algorithm are compared to sensor placement patterns obtained with random deployment to highlight the relevance of using such a deployment algorithm.
Rotating convection-driven dynamos at low Ekman number.
Rotvig, Jon; Jones, Chris A
2002-11-01
We present a fully 3D self-consistent convection-driven dynamo model with reference to the geodynamo. A relatively low Ekman number regime is reached, with the aim of investigating the dynamical behavior at low viscosity. This regime is computationally very demanding, which has prompted us to adopt a plane layer model with an inclined rotation vector, and to make use of efficiently parallelized code. No hyperdiffusion is used, all diffusive operators are in the classical form. Our model has infinite Prandtl number, a Rayleigh number that scales as E(-1/3) (E being the Ekman number), and a constant Roberts number. The optimized model allows us to study dynamos with Ekman numbers in the range [10(-5),10(-4)]. In this regime we find strong-field dynamos where the induced magnetic fields satisfy Taylor's constraint to good accuracy. The solutions are characterized by (i) a MAC balance within the bulk, i.e., Coriolis, pressure, Lorentz, and buoyancy forces are of comparable magnitude, while viscous forces are only significant in thin boundary layers, (ii) the Elsasser number is O(10), (iii) the strong magnetic fields cannot prevent small-scale structures from becoming dominant over the large-scale components, (iv) the Taylor-Proudman effect is detectable, (v) the Taylorization decreases as the Ekman number is lowered, and (vi) the ageostrophic velocity component makes up 80% of the flow.
The hydrophilic-lipophilic balance (HLB) number system was used to optimize a compatible non-ionic surfactant, TDA(polyoxyethylene tridecyl ether) in formulations for two Beauveria bassiana strains, NI8 and GHA. The optimal HLB number for TDA was determined on the basis of wetting times for conidia...
On the use of the Prandtl mixing length model in the cutting torch modeling
Energy Technology Data Exchange (ETDEWEB)
Mancinelli, B [Grupo de Descargas Electricas, Departamento Ing. Electromecanica, Universidad Tecnologica Nacional, Regional Venado Tuerto, Laprida 651, Venado Tuerto (2600), Santa Fe (Argentina); Minotti, F O; Kelly, H, E-mail: bmancinelli@arnet.com.ar [Instituto de Fisica del Plasma (CONICET), Departamento de Fisica, Facultad de Ciencias Exactas y Naturales (UBA) Ciudad Universitaria Pab. I, 1428 Buenos Aires (Argentina)
2011-05-01
The Prandtl mixing length model has been used to take into account the turbulent effects in a 30 A high-energy density cutting torch model. In particular, the model requires the introduction of only one adjustable coefficient c corresponding to the length of action of the turbulence. It is shown that the c value has little effect on the plasma temperature profiles outside the nozzle (the differences being less than 10 %), but severely affects the plasma velocity distribution, with differences reaching about 100% at the middle of the nozzle-anode gap. Within the experimental uncertainties it was also found that the value c = 0.08 allows to reproduce both, the experimental data of velocity and temperature
Dual solutions in MHD stagnation-point flow of Prandtl fluid impinging on shrinking sheet
Institute of Scientific and Technical Information of China (English)
N.S.AKBAR; Z.H.KHAN; R.U.HAQ; S.NADEEM
2014-01-01
The present article investigates the dual nature of the solution of the magneto-hydrodynamic (MHD) stagnation-point flow of a Prandtl fluid model towards a shrinking surface. The self-similar nonlinear ordinary differential equations are solved numerically by the shooting method. It is found that the dual solutions of the flow exist for cer-tain values of the velocity ratio parameter. The special case of the first branch solutions (the classical Newtonian fluid model) is compared with the present numerical results of stretching flow. The results are found to be in good agreement. It is also shown that the boundary layer thickness for the second solution is thicker than that for the first solution.
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Nelson Maculan
2003-01-01
Full Text Available We present integer linear models with a polynomial number of variables and constraints for combinatorial optimization problems in graphs: optimum elementary cycles, optimum elementary paths and optimum tree problems.Apresentamos modelos lineares inteiros com um número polinomial de variáveis e restrições para problemas de otimização combinatória em grafos: ciclos elementares ótimos, caminhos elementares ótimos e problemas em árvores ótimas.
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M. Varchola
2009-12-01
Full Text Available This paper deals with an evaluation platform for cryptographic True Random Number Generators (TRNGs based on the hardware implementation of statistical tests for FPGAs. It was developed in order to provide an automatic tool that helps to speed up the TRNG design process and can provide new insights on the TRNG behavior as it will be shown on a particular example in the paper. It enables to test sufﬁcient statistical properties of various TRNG designs under various working conditions on the ﬂy. Moreover, the tests are suitable to be embedded into cryptographic hardware products in order to recognize TRNG output of weak quality and thus increase its robustness and reliability. Tests are fully compatible with the FIPS 140 standard and are implemented by the VHDL language as an IP-Core for vendor independent FPGAs. A recent Flash based Actel Fusion FPGA was chosen for preliminary experiments. The Actel version of the tests possesses an interface to the Actel’s CoreMP7 softcore processor that is fully compatible with the industry standard ARM7TDMI. Moreover, identical tests suite was implemented to the Xilinx Virtex 2 and 5 in order to compare the performance of the proposed solution with the performance of already published one based on the same FPGAs. It was achieved 25% and 65% greater clock frequency respectively while consuming almost equal resources of the Xilinx FPGAs. On the top of it, the proposed FIPS 140 architecture is capable of processing one random bit per one clock cycle which results in 311.5 Mbps throughput for Virtex 5 FPGA.
Stefanski, Frederik; Minorowicz, Bartosz; Persson, Johan; Plummer, Andrew; Bowen, Chris
2017-01-01
The potential to actuate proportional flow control valves using piezoelectric ceramics or other smart materials has been investigated for a number of years. Although performance advantages compared to electromagnetic actuation have been demonstrated, a major obstacle has proven to be ferroelectric hysteresis, which is typically 20% for a piezoelectric actuator. In this paper, a detailed study of valve control methods incorporating hysteresis compensation is made for the first time. Experimental results are obtained from a novel spool valve actuated by a multi-layer piezoelectric ring bender. A generalised Prandtl-Ishlinskii model, fitted to experimental training data from the prototype valve, is used to model hysteresis empirically. This form of model is analytically invertible and is used to compensate for hysteresis in the prototype valve both open loop, and in several configurations of closed loop real time control system. The closed loop control configurations use PID (Proportional Integral Derivative) control with either the inverse hysteresis model in the forward path or in a command feedforward path. Performance is compared to both open and closed loop control without hysteresis compensation via step and frequency response results. Results show a significant improvement in accuracy and dynamic performance using hysteresis compensation in open loop, but where valve position feedback is available for closed loop control the improvements are smaller, and so conventional PID control may well be sufficient. It is concluded that the ability to combine state-of-the-art multi-layer piezoelectric bending actuators with either sophisticated hysteresis compensation or closed loop control provides a route for the creation of a new generation of high performance piezoelectric valves.
Energy Technology Data Exchange (ETDEWEB)
Riofrio, D; Luan, S [University of New Mexico, Albuquerque, New Mexico (United States); Zhou, J [William Beaumont Hospital, Royal Oak, MI (United States); Ma, L [UCSF Comprehensive Cancer Center, San Francisco, CA (United States)
2015-06-15
Purpose: In prostate HDR brachytherapy, interstitial implants are placed manually on the fly. The aim for this research is to develop a computer algorithm to find optimal and reliable implant trajectories using minimal number of implants. Methods: Our new algorithm mainly uses these key ideas: (1) positive charged static particles are uniformly placed on the surface of prostate and critical structures such as urethra, bladder, and rectum. (2) Positive charged kinetic particles are placed at a cross-section of the prostate with an initial velocity parallel to the principal implant direction. (3) The kinetic particles move through the prostate, interacting with each other, spreading out, while staying away from the prostate surface and critical structures. The initial velocity ensures that the trajectories observe the curvature constraints of typical implant procedures. (4) The finial trajectories of kinetic particles are smoothed using a third-degree polynomial regression, which become the implant trajectories. (5) The dwelling times and final dose distribution are calculated using least-distance programming. Results: (1) We experimented with previously treated cases. Our plan achieves all prescription goals while reducing the number of implants by 41%! Our plan also has less uniform target dose, which implies a higher dose is delivered to the prostate. (2) We expect future implant procedures will be performed under the guidance of such pre-calculated trajectories. To assess the applicability, we randomly perturb the tracks to mimic the manual implant errors. Our studies showed the impact of these perturbations are negligible, which is compensated by the least distance programming. Conclusions: We developed a new inverse planning system for prostate HDR therapy that can find optimal implant trajectories while minimizing the number of implants. For future work, we plan to integrate our new inverse planning system with an existing needle tracking system.
Energy Technology Data Exchange (ETDEWEB)
Wenterodt, Tammo
2013-08-14
The entropic potential concept as well as the energy devaluation number is developed. Their advantage over common evaluation criteria for heat exchangers is demonstrated. For that purpose, a new method for the automated geometry optimization of heat exchangers based on CFD calculations is presented. It is based on the description of surfaces by Fourier coefficients and their optimization by an evolutionary algorithm.
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LAELA SARI
2005-07-01
Full Text Available Aloe vera of the Aloeaceae is originated from Canary Island (West Africa. This plant is commonly know in Indonesia and cultivated in large fields or in the house yard for many purposes, such as ornamental and medicine plant. The industries using it as the principle raw material has became more important due to the significant benefits of this plant. This study is purposed to obtain the medium optimization for leaf numbers and shoot multiplication of Aloe vera by BAP and adenine supplement. The shoot of Aloe vera was taken from green house of Biotechnology-LIPI. Shoots sterilized by clorox (sodium hypochlorite solution 35% and 20% for 30 and 15 min. until get aseptic shoot (in vitro plants. The shoot isolated from in vitro plant into MS (Murashige and Skoog medium in different concentration of BAP and adenine. The research used factorial Completely Randomized Design with two factors (BAP concentration: 0; 0.5; 1; 1.5; 2 mg/L and adenine concentration 0; 10; 20 mg/L with 5 replicates. The results obtained have showed that addition 20 mg/L adenine to MS raise the numbers of leaf. The shoot multiplication has been augmented by addition of BAP 1 mg/L and adenine 20 mg/L. The results showed that BAP has a positive role in increasing shoot multiplication rate and that adenine has a synergic effect when added together with BAP.
Optimal Heat Transport in Rayleigh-B\\'enard Convection
Sondak, David; Waleffe, Fabian
2015-01-01
Steady flows that optimize heat transport are obtained for two-dimensional Rayleigh-B\\'enard convection with no-slip horizontal walls for a variety of Prandtl numbers $Pr$ and Rayleigh number up to $Ra\\sim 10^9$. Power law scalings of $Nu\\sim Ra^{\\gamma}$ are observed with $\\gamma\\approx 0.31$, where the Nusselt number $Nu$ is a non-dimensional measure of the vertical heat transport. Any dependence of the scaling exponent on $Pr$ is found to be extremely weak. On the other hand, the presence of two local maxima of $Nu$ with different horizontal wavenumbers at the same $Ra$ leads to the emergence of two different flow structures as candidates for optimizing the heat transport. For $Pr \\lesssim 7$, optimal transport is achieved at the smaller maximal wavenumber. In these fluids, the optimal structure is a plume of warm rising fluid which spawns left/right horizontal arms near the top of the channel, leading to downdrafts adjacent to the central updraft. For $Pr > 7$ at high-enough Ra, the optimal structure is a...
O'Mara, Bridget; Featherstone, Nicholas A; Augustson, K C
2016-01-01
Several lines of evidence suggest that the velocity amplitude in global simulations of solar convection, U, may be systematically over-estimated. Motivated by these recent results, we explore the factors that determine U and we consider how these might scale to solar parameter regimes. To this end, we decrease the thermal diffusivity $\\kappa$ along two paths in parameter space. If the kinematic viscosity $\
Zang, Xizhe; Liu, Yixiang; Heng, Shuai; Lin, Zhenkun; Zhao, Jie
2017-01-01
High-performance position control of pneumatic artificial muscles is limited by their inherent nonlinearity and hysteresis. This study aims to model the length/pressure hysteresis of a single pneumatic artificial muscle and to realize its accurate position tracking control with forward hysteresis compensation. The classical Prandtl-Ishlinskii model is widely used in hysteresis modelling and compensation. But it is only effective for symmetric hysteresis. Therefore, a modified Prandtl-Ishlinskii model is built to characterize the asymmetric length/pressure hysteresis of a single pneumatic artificial muscle, by replacing the classical play operators with two more flexible elementary operators to independently describe the ascending branch and descending branch of hysteresis loops. On the basis, a position tracking controller, which is composed of cascade forward hysteresis compensation and simple proportional pressure controller, is designed for the pneumatic artificial muscle. Experiment results show that the MPI model can reproduce the length/pressure hysteresis of the pneumatic artificial muscle, and the proposed controller for the pneumatic artificial muscle can track the reference position signals with high accuracy. By modelling the length/pressure hysteresis with the modified Prandtl-Ishlinskii model and using its inversion for compensation, precise position control of a single pneumatic artificial muscle is achieved.
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Aerodynamic performance of low-Reynolds-number high-lift airfoil makes a great impact on designing a high-efficiency propeller for low-dynamic vehicles in stratosphere. At high altitude,low-Reynolds-number airfoils are supposed to have high lift-drag ratio or high endurance factor at cruising attack angle along with good stall characteristics. To design such a high-performance low-Reynolds-number high-lift airfoil,the paper established a hierarchical multi-objective optimization platform by combing direct search optimization algorithm EXTREM and airfoil flow field solver XFOIL to automatically and quickly calculate aerodynamic performance function of airfoil by computer. It provides an effective solution to multi-point design problem of low-speed low-Reynolds-number airfoil. It can be seen from the results of three typical optimization examples,the new airfoil E387_OPT2,FX63-137_OPT2 and S1223_OPT2 based on hot low-Reynolds-number high-lift airfoils (Eppler 387 airfoil,Wortmann FX63-137 airfoil and S1223 airfoil) can meet the optimization design requirements and have very good aerodynamic characteristics in both design state and non-design state. Thus,the applicability and effectiveness of hierarchical multi-objective optimization platform are verified.
Directory of Open Access Journals (Sweden)
SHOJAEIAN, S.
2014-02-01
Full Text Available The presence of reactive component of current in transmission lines causes adverse impact on the network, including power losses, reduction of line capacity, and voltage drop. These adverse impacts can be reduced by using the first or second generation of FACTS devices. In this paper, these adverse impacts can be reduced optimally by using one of the modern optimization techniques, i.e., particle swarm optimization algorithm (PSO algorithm. By using this algorithm, the optimal size of the static VAr compensator (FACTS devices in a 30 bus IEEE test system is determined. At first, the load flow equations of the 30 bus IEEE test system is defined in the MATLAB software by means of dynamic programming method, and the number of SVCs will be determined by using the system sensitivity function (power losses and the sum of buses voltage drop square; then, the optimal sizes of the FACTS devices is obtained by means of PSO algorithm.
Wang, Yugang; Wu, Xinjun; Sun, Pengfei; Li, Jian
2015-02-03
Electromagnetic acoustic transducers (EMATs) can generate non-dispersive T(0,1) mode guided waves in a metallic pipe for nondestructive testing (NDT) by using a periodic permanent magnet (PPM) EMAT circular array. In order to enhance the excitation efficiency of the sensor, the effects of varying the number of elements of the array on the excitation efficiency is studied in this paper. The transduction process of the PPM EMAT array is studied based on 3-D finite element method (FEM). The passing signal amplitude of the torsional wave is obtained to represent the excitation efficiency of the sensor. Models with different numbers of elements are established and the results are compared to obtain an optimal element number. The simulation result is verified by experiments. It is shown that after optimization, the amplitudes of both the passing signal and defect signal with the optimal element number are increased by 29%, which verifies the feasibility of this optimal method. The essence of the optimization is to find the best match between the static magnetic field and the eddy current field in a limited circumferential space to obtain the maximum circumferential Lorentz force.
Carver, Charles S.; Scheier, Michael F.; Segerstrom, Suzanne C.
2010-01-01
Optimism is an individual difference variable that reflects the extent to which people hold generalized favorable expectancies for their future. Higher levels of optimism have been related prospectively to better subjective well-being in times of adversity or difficulty (i.e., controlling for previous well-being). Consistent with such findings, optimism has been linked to higher levels of engagement coping and lower levels of avoidance, or disengagement, coping. There is evidence that optimism is associated with taking proactive steps to protect one's health, whereas pessimism is associated with health-damaging behaviors. Consistent with such findings, optimism is also related to indicators of better physical health. The energetic, task-focused approach that optimists take to goals also relates to benefits in the socioeconomic world. Some evidence suggests that optimism relates to more persistence in educational efforts and to higher later income. Optimists also appear to fare better than pessimists in relationships. Although there are instances in which optimism fails to convey an advantage, and instances in which it may convey a disadvantage, those instances are relatively rare. In sum, the behavioral patterns of optimists appear to provide models of living for others to learn from. PMID:20170998
Institute of Scientific and Technical Information of China (English)
Qingqing Wang; Chun-Yi Su; Yonghong Tan
2005-01-01
The development of control techniques to mitigate the effects of unknown hysteresis preceding with plants has recently re-attracted significant attention. In this paper, we first give a brief review of presently developed hysteresis models and hysteresis compensating control methods.Then, with the use of the Prandtl-Ishlinskii hysteresis model, we propose a robust adaptive control scheme. The novelty is that the model of hysteresis nonlinearities is firstly fused with the available control techniques without necessarily constructing a hysteresis inverse. The global stability of the adaptive system and tracking a desired trajectory to a certain precision are achieved. Simulations performed on a nonlinear system illustrate and clarify the approach.
Pearce, Charles
2009-01-01
Focuses on mathematical structure, and on real-world applications. This book includes developments in several optimization-related topics such as decision theory, linear programming, turnpike theory, duality theory, convex analysis, and queuing theory.
Braess, Dietrich; Dette, Holger
2004-01-01
We consider maximin and Bayesian D -optimal designs for nonlinear regression models. The maximin criterion requires the specification of a region for the nonlinear parameters in the model, while the Bayesian optimality criterion assumes that a prior distribution for these parameters is available. It was observed empirically by many authors that an increase of uncertainty in the prior information (i.e. a larger range for the parameter space in the maximin criterion or a larger variance of the ...
Acker, A.
We give an analytical proof of the existence of convex classical solutions for the (convex) Prandtl-Batchelor free boundary problem in fluid dynamics. In this problem, a convex vortex core of constant vorticity μ >0 is embedded in a closed irrotational flow inside a closed, convex vessel in ℜ 2. The unknown boundary of the vortex core is a closed curve Γ along which (v+)^2-(v^-)^2=Λ , where v+ and v- denote, respectively, the exterior and interior flow-speeds along Γ and Λ is a given constant. Our existence results all apply to the natural multidimensional mathematical generalization of the above problem. The present existence theorems are the only ones available for the Prandtl-Batchelor problem for Λ >0, because (a) the author's prior existence treatment was restricted to the case where Λ <0, and because (b) there is no analytical existence theory available for this problem in the non-convex case, regardless of the sign of Λ .
Energy Technology Data Exchange (ETDEWEB)
van Hest, Maikel [National Renewable Energy Lab. (NREL), Golden, CO (United States)
2016-09-01
Suntricity Corporation and NREL will develop an optimal CZTS device structure. In this process absorber materials provided by Suntricity Corporation will be used for testing. For this purpose Suntricity Corporation will provide dried film precursors or ink precursors. NREL will process these into PV material and complete cells with buffer, window and contacts.
Institute of Scientific and Technical Information of China (English)
WANG JiaMin
2009-01-01
In this paper we consider a retail service facility with cross-trained workers who can perform operations in both the front room and back room. Workers are brought from the back room to the front room and vice versa depending on the number of customers in the system. A loss of productivity occurs when a worker returns to the back room. Two problems are studied. In the first problem, given the number of workers available, we determine an optimal deterministic switching policy so that the expected number of customers in queue is minimized subject to a constraint ensuring that there is a sufficient workforce to fulfill the functions in the back room. In the second problem, the number of workers needed is minimized subject to an additional constraint requiring that the expected number of customers waiting in queue is bounded above by a given threshold value. Exact solution procedures are developed and illustrative numerical examples are presented.
Ou, Kua-Chun; Wang, Chih-Yang; Liu, Kuan-Ting; Chen, Yi-Ling; Chen, Yi-Chen; Lai, Ming-Derg; Yen, Meng-Chi
2014-11-14
Transfer RNA (tRNA) abundance is one of the critical factors for the enhancement of protein productivity in prokaryotic and eukaryotic hosts. Gene copy number of tRNA and tRNA codon usage bias are generally used to match tRNA abundance of protein-expressing hosts and to optimize the codons of recombinant proteins. Because sufficient concentration of intracellular tRNA and optimized codons of recombinant proteins enhanced translation efficiency, we hypothesized that sufficient supplement of host's tRNA improved protein productivity in mammalian cells. First, the small tRNA sequencing results of CHO-K1 cells showed moderate positive correlation with gene copy number and codon usage bias. Modification of human interleukin-2 (IL-2) through codons with high gene copy number and high codon usage bias (IL-2 HH, modified on Leu, Thr, Glu) significantly increased protein productivity in CHO-K1 cells. In contrast, modification through codons with relatively high gene copy number and low codon usage bias (IL-2 HL, modified on Ala, Thr, Val), or relatively low gene copy number and low codon usage bias (IL-2 LH, modified on Ala, Thr, Val) did not increase IL-2 productivity significantly. Furthermore, supplement of the alanine tRNA or threonine tRNA increased IL-2 productivity of IL-2 HL. In summary, we revealed a potential strategy to enhance productivity of recombinant proteins, which may be applied in production of protein drug or design of DNA vaccine.
Directory of Open Access Journals (Sweden)
Muh. Ryman Napirah
2015-09-01
Full Text Available Background: The amount of labor in the laboratory unit hospital of Anutapura Palu workforce was 30 people, but there were still problems in terms of inspection of samples that only consisted of some people in a kind of examination while in terms of inspection of the sample was in need of power because the large number of visits from patients who require to carry out an examination of sample. One of manpower planning method is Workload Indicator Of Staffing Needed (WISN that calculated the optimal amount based on workload of employees. Objective: This study aimed at finding out of the optimal number of staff needed in The laboratory unit at RSU Anutapura using WISN method. Methods: This study was a quantitative study with descriptive approach. Data were collected using work sampling method, observation, and document review. Results: It showed that using productive time of the activities time total was 88,51% and using productive time of working hours was 114,240 minutes per year, workload standard is 5817.32 per year and the loose standard is 0,4 per year. Conclusion: Based on the analysis of the optimal number of staff needed using WISN method, it can be concluded that the laboratory unit still needs 8 people, and for manpower planning, things that need to consider are qualification and competence to get a good quality of labor.
Matsumoto, Takahiro; Yamaya, Taiga; Yoshida, Eiji; Nishikido, Fumihiko; Inadama, Naoko; Murayama, Hideo; Suga, Mikio
2014-01-01
We are developing a novel PET detector with 3D isotropic resolution called a crystal (X'tal) cube. The X'tal cube detector consists of a crystal block all 6 surfaces of which are covered with silicon photomultipliers (SiPMs). We have developed a prototype detector with 3D isotropic 1 mm resolution. On the other hand, when the X'tal cubes are arranged to form a PET scanner, insensitive inter-detector gaps made by the SiPM arrays should not be too wide, or, better yet, they should be removed. Reduction of the number of SiPMs will also be reflected in the production costs. Therefore, reducing the number of faces to be connected to the SiPMs has become our top priority. In this study, we evaluated the effect of reducing the number of SiPMs on the positioning accuracy through numerical simulations. Simulations were performed with the X'tal cube, which was composed of a 6 × 6 × 6 array of Lu2x Gd2(1-x)SiO5:Ce crystal elements with dimensions of (3.0 mm)(3). Each surface of the crystal block was covered with a 4 × 4 array of SiPMs, each of which had a (3.0 mm)(2) active area. For material between crystal elements, we compared two: optical glue and an air gap. The air gap showed a better crystal identification performance than did the optical glue, although a good crystal identification performance was obtained even with optical glue for the 6-face photodetection. In conclusion, the number of photodetection faces could be reduced to two when the gap material was air.
The optimal number of routine vaccines to order at health clinics in low or middle income countries.
Rajgopal, Jayant; Connor, Diana L; Assi, Tina-Marie; Norman, Bryan A; Chen, Sheng-I; Bailey, Rachel R; Long, Adrienne R; Wateska, Angela R; Bacon, Kristina M; Brown, Shawn T; Burke, Donald S; Lee, Bruce Y
2011-07-26
In a low or middle income country, determining the correct number of routine vaccines to order at a health clinic can be difficult, especially given the variability in the number of patients arriving, minimal vaccination days and resource (e.g., information technology and refrigerator space) constraints. We developed a spreadsheet model to determine the potential impact of different ordering policies, basing orders on the arrival rates seen in the previous 1, 3, 6, or 12 sessions, or on long-term historical averages (where these might be available) along with various buffer stock levels (range: 5-50%). Experiments varied patient arrival rates (mean range: 1-30 per session), arrival rate distributions (Poisson, Normal, and Uniform) and vaccine vial sizes (range: 1-dose to 10-dose vials). It was found that when the number of doses per vial is small and the expected number of patients is low, the ordering policy has a more significant impact on the ability to meet demand. Using data from more prior sessions to determine arrival rates generally equates to a better ability to meet demand, although the marginal benefit is relatively small after more than 6 sessions are averaged. As expected, the addition of more buffer is helpful in obtaining better performance; however, this advantage also has notable diminishing returns. In general, the long-term demand rate, the vial sizes of the vaccines used and the method of determining the patient arrival rate all have an effect on the ability of a clinic to maximize the demand that is met. Copyright © 2011 Elsevier Ltd. All rights reserved.
Institute of Scientific and Technical Information of China (English)
李连侠; 廖华胜; 刘达; 蒋胜银
2015-01-01
Energy dissipations induced by the hydraulic jump and the trajectory jet are the most widely known as the two dissipation modes at the downstream of flood discharging structures, which are often considered quite different even contradictory. However, such two energy dissipators can be used jointly and harmonically. In this paper, a new type of stilling basin with a shallow-water cushion and a triangular bottom deflector is proposed based on two different scale physical model tests of the flood discharging tunnel No.2 of Luding hydropower project. The experimental results show that the flow regime of the hydraulic jump in the presented stilling basin with bottom deflector enjoys a good and stable performance within a large range of flow rates and the energy dissipation rate is considerably high as compared to the conventional stilling basin even at a low Froude number. The results also indicate that the stilling basin with triangular bottom deflector has a better performance in improving the potential cavitation erosion according to the analysis of the pressure and the cavitation number compared to the trapezoidal one. The proposed new type of shallow-cushion stilling basin with a shallow-water cushion can be applied in similar energy dissipation projects with low Froude number and large range of flow rates.
de Beer, Jessica L; Akkerman, Onno W; Schürch, Anita C; Mulder, Arnout; van der Werf, Tjip S; van der Zanden, Adri G M; van Ingen, Jakko; van Soolingen, Dick
2014-05-01
Variable-number tandem-repeat (VNTR) typing with a panel of 24 loci is the current gold standard in the molecular typing of Mycobacterium tuberculosis complex isolates. However, because of technical problems, a part of the loci often cannot be amplified by multiplex PCRs. Therefore, a considerable number of single-locus PCRs have to be performed for the loci with missing results, which impairs the laboratory work flow. Therefore, the original in-house method described by Supply et al. in 2006 was reevaluated. We modified seven primers and the PCR master mixture and obtained a strongly optimized in-house 24-locus VNTR typing method. The percentage of instantly complete 24-locus VNTR patterns detected in the routine flow of typing activities increased to 84.7% from the 72.3% obtained with the typing conducted with the commercially available Genoscreen MIRU-VNTR typing kit. The analytical sensitivity of the optimized in-house method was assessed by serial dilutions of M. tuberculosis in bronchoalveolar lavage fluid. A 1:10 dilution of the different strains tested was the lowest dilution for the detection of a complete 24-locus VNTR pattern. The optimized in-house 24-locus VNTR typing method will reduce the turnaround time of typing significantly and also the financial burden of these activities.
Naik, Ganesh R; Al-Timemy, Ali H; Nguyen, Hung T
2016-08-01
Surface electromyography (sEMG)-based pattern recognition studies have been widely used to improve the classification accuracy of upper limb gestures. Information extracted from multiple sensors of the sEMG recording sites can be used as inputs to control powered upper limb prostheses. However, usage of multiple EMG sensors on the prosthetic hand is not practical and makes it difficult for amputees due to electrode shift/movement, and often amputees feel discomfort in wearing sEMG sensor array. Instead, using fewer numbers of sensors would greatly improve the controllability of prosthetic devices and it would add dexterity and flexibility in their operation. In this paper, we propose a novel myoelectric control technique for identification of various gestures using the minimum number of sensors based on independent component analysis (ICA) and Icasso clustering. The proposed method is a model-based approach where a combination of source separation and Icasso clustering was utilized to improve the classification performance of independent finger movements for transradial amputee subjects. Two sEMG sensor combinations were investigated based on the muscle morphology and Icasso clustering and compared to Sequential Forward Selection (SFS) and greedy search algorithm. The performance of the proposed method has been validated with five transradial amputees, which reports a higher classification accuracy ( > 95%). The outcome of this study encourages possible extension of the proposed approach to real time prosthetic applications.
Shammas, Nicolas W; Shammas, Gail A; Aasen, Nicole; Jarvis, Gary
2015-12-01
Rotational atherectomy with the use of the JetStream XC device is indicated for treatment of infrainguinal arterial obstructive disease. The number of blades-up (BU) runs needed for optimal tissue debulking in femoropopliteal in-stent restenosis (ISR) is unknown. In the present series, 6 patients (15 lesions) were treated for femoropopliteal ISR with the JetStream XC device. Minimal luminal diameter or percent stenosis improved significantly from baseline after 2 BU runs, but no further gain was seen between 2 and 4 BU runs (P > .05). However, adjunctive balloon angioplasty reduced percent stenosis significantly following BU runs. In conclusion, the JetStream XC device achieved optimal acute angiographic results in treating femoropopliteal ISR following 2 BU runs and adjunctive balloon angioplasty.
Numerical modeling of the impact of regenerator housing on the determination of Nusselt numbers
DEFF Research Database (Denmark)
Nielsen, Kaspar Kirstein; Nellis, G.F.; Klein, S.A.
2013-01-01
to the regenerator fluid is developed. The model is applied to a range of cases and it is shown that at low Reynolds numbers (well below 100) and at Prandtl numbers appropriate to liquids (7 for water) the regenerator housing may influence the experimental determination of Nusselt numbers significantly. The impact......It is suggested that the housing of regenerators may have a significant impact when experimentally determining Nusselt numbers at low Reynolds and large Prandtl numbers. In this paper, a numerical model that takes the regenerator housing into account as a domain that is thermally coupled...... of the housing on the performance during cyclic steady-state regenerator operation is quantified by comparing the regenerator effectiveness for cases where the wall is ignored and with cases where it is included. It is shown that the effectiveness may be decreased by as much as 18% for the cases considered here...
Directory of Open Access Journals (Sweden)
Maxim Ivanov
2015-10-01
Full Text Available A Chernobyl-derived 137Cs- fallout was associated with one or two rainfalls Because of that vast areas of the Europe affected by Chernobyl-derived fallout are characterized by non-uniform field of radionuclide contamination. It was assessed after detailed field investigation within few river basins of the Central Russia located in areas with different levels of Chernobyl contamination, that existing maps of radionuclide contamination composed during last two decades are not enough detailed for assessment of initial contamination field transformation by the lateral migration processes of the Chernobyl-derived 137Cs. This problem can be overcomed if additional soil sampling are undertaken in reference locations for correction of exiting radionuclide contamination maps. However it is necessary to evaluate the optimal number of bulk samples which should be taken in each sampling point for receiving statistically correct results of radionuclide concentration. Special investigation was undertaken in few catchments (S= 2-50 km2 of the Central Russia, located in areas with different levels of initial Chernobyl contamination, for evaluation the optimal number of samples, which should be taken in each sampling point for the determination of Cs-137 concentrations error not exceed 30 % on 95 % confidence level.
Peixoto, L A; Bhering, L L; Cruz, C D
2016-11-21
Genomic selection is a useful technique to assist breeders in selecting the best genotypes accurately. Phenotypic selection in the F2 generation presents with low accuracy as each genotype is represented by one individual; thus, genomic selection can increase selection accuracy at this stage of the breeding program. This study aimed to establish the optimal number of individuals required to compose the training population and to establish the amount of markers necessary to obtain the maximum accuracy by genomic selection methods in F2 populations. F2 populations with 1000 individuals were simulated, and six traits were simulated with different heritability values (5, 20, 40, 60, 80 and 99%). Ridge regression best linear unbiased prediction was used in all analyses. Genomic selection models were set by varying the number of individuals in the training population (2 to 1000 individuals) and markers (2 to 3060 markers). Phenotypic accuracy, genotypic accuracy, genetic variance, residual variance, and heritability were evaluated. Greater the number of individuals in the training population, higher was the accuracy; the values of genotypic and residual variances and heritability were close to the optimum value. Higher the heritability of the trait, higher is the number of markers necessary to obtain maximum accuracy, ranging from 200 for the trait with 5% heritability to 900 for the trait with 99% heritability. Therefore, genomic selection models for prediction in F2 populations must consist of 200 to 900 markers of major effect on the trait and more than 600 individuals in the training population.
Directory of Open Access Journals (Sweden)
Vahid Hassani
2012-01-01
Full Text Available One of the major problems occurring in many technical applications is the presence of the hysteretic behavior in sensors and actuators, which causes a nonlinear relationship between input and output variables in such devices. Since the nonlinear phenomenon of hysteresis degrades the performance of the piezoelectric materials and piezoelectric drive mechanisms, for example, in positioning control framework, it has to be characterized in order to mitigate the effect of the nonlinearity in the devices. This paper is aimed to characterize and model the hysteresis in typical piezoelectric actuators under load-free and preloaded circumstances incorporating the inertial effect of the system. For this purpose, the piezoelectric actuator is modeled as a mass-spring-damper system, which is expressed in terms of a stop operator as one of the essential yet efficient hysteresis operators in the Prandtl-Ishlinskii (PI model. The reason of utilizing the stop operator in this study is for the sake of control purposes, as the stop operator plays as the inverse of the play operator in the PI model and can be used in a feed-forward controller scheme to suppress the effect of hysteresis in general control framework. The results reveal that this model exhibits better correspondence to the measurement output compared to that of the classical PI model.
Rana, Parvez; Gautam, Basanta; Tokola, Timo
2016-07-01
Remote sensing-based inventories of above-ground forest biomass (AGB) require a set of training plots representative of the area to be studied, the collection of which is the most expensive part of the analysis. These are time-consuming and costly because the large variety in forest conditions requires more plots to adequately capture this variability. A field campaign in general is challenging and is hampered by the complex topographic conditions, limited accessibility, steep mountainous terrains which increase labor efforts and costs. In addition it is also depend on the ratio between size of study area and number of training plots. In this study, we evaluate the number of training areas (sample size) required to estimate AGB for an area in the southern part of Nepal using airborne laser scanning (ALS), RapidEye and Landsat data. Three experiments were conducted: (i) AGB model performance, based on all the field training plots; (ii) reduction of the sample size, based on the ALS metrics and the AGB distribution; and (iii) prediction of the optimal number of training plots, based on the correlation between the remote sensing and field data. The AGB model was fitted using the sparse Bayesian method. AGB model performance was validated using an independent validation dataset. The effect of the strategies for reducing the sample size was readily apparent for the ALS-based AGB prediction, but the RapidEye and Landsat sensor data failed to capture any such effect. The results indicate that adequate coverage of the variability in tree height and density was an important condition for selecting the training plots. In addition, the ALS-based AGB prediction required the smallest number of training plots and was also quite stable with a small number of field plots.
Directory of Open Access Journals (Sweden)
Nguyen Thi Hong
2016-05-01
Full Text Available Meteorological data play a particularly important role in hydrologic research because the climate and weather of an area exert a profound influence on most hydrologic processes. Meanwhile, hydrological data are critical for performing a range of purposes, including water resources assessment, impacts of climate change and flood forecasting and warning. It can be said that the prevention of disasters caused by floods and droughts would be impossible without rational forecasting technology based on an understanding of the rainfall-runoff phenomenon and statistical analysis of past hydrological data, which cannot be achieved without meteo-hydrological observations. The lack of adequate meteo-hydrological data affects the ability to model, predict and plan for catastrophic events such as floods and droughts which have obvious negative impacts on public health and socio-economic aspects. The accurate estimation of the spatial distribution of meteorological and hydrological parameters requires a dense network of instruments, which entails large installation and operational costs. It is thus necessary to optimize the number and location of meteo-hydrological stations. This paper presents a GIS-based approach to establishing an optimal meteo-hydrological station network on Vu Gia- Thu Bon river basin for developing an up-to-date real time flood warning system. Based on statistical analysis of the annual rainfall total data at 9 existing gauges in the study area from 1980 to 2013, it showed that the error of the existing network was about 7.47%. Considering 9 rain gauges as a standard representative of rainfall over the region, if the error decreases from 7.47% to 5%, the number of additional rain gauges should be 20. For adequate and economical network design, these additional rain gauges were spatially distributed between the different isohyetals after considering the relative distances between rain gauges, their accessibility, personnel required for
Inertia-less convectively-driven dynamo models in the limit of low Rossby number
Calkins, Michael A; Tobias, Steven M
2016-01-01
Compositional convection is thought to be an important energy source for magnetic field generation within planetary interiors. The Prandtl number, $Pr$, characterizing compositional convection is significantly larger than unity, suggesting that the inertial force may not be important on the small scales of convection. We develop asymptotic dynamo models for the case of small Rossby number and large Prandtl number in which inertia is absent on the convective scale. The relevant diffusivity parameter for this limit is the compositional Roberts number, $q = D/\\eta$, which is the ratio of compositional and magnetic diffusivities. Dynamo models are developed for both order one $q$ and the more geophysically relevant low $q$ limit. For both cases the ratio of magnetic to kinetic energy densities, $M$, is asymptotically large and reflects the fact that Alfv\\'en waves have been filtered from the dynamics. Taken together with previous investigations of asymptotic dynamo models for $Pr=O(1)$, our results show that the ...
Ferrari, Ricardo J
2013-02-01
Although anisotropic diffusion filters have been used extensively and with great success in medical image denoising, one limitation of this iterative approach, when used on fully automatic medical image processing schemes, is that the quality of the resulting denoised image is highly dependent on the number of iterations of the algorithm. Using many iterations may excessively blur the edges of the anatomical structures, while a few may not be enough to remove the undesirable noise. In this work, a mathematical model is proposed to automatically determine the number of iterations of the robust anisotropic diffusion filter applied to the problem of denoising three common human brain magnetic resonance (MR) images (T1-weighted, T2-weighted and proton density). The model is determined off-line by means of the maximization of the mean structural similarity index, which is used in this work as metric for quantitative assessment of the resulting processed images obtained after each iteration of the algorithm. After determining the model parameters, the optimal number of iterations of the algorithm is easily determined without requiring any extra computation time. The proposed method was tested on 3D synthetic and clinical human brain MR images and the results of qualitative and quantitative evaluation have shown its effectiveness.
Leading-edge boundary layer flow : Prandtl's vision, current developments and future perspectives.
Energy Technology Data Exchange (ETDEWEB)
Collis, Samuel Scott; Theofilis, Vassilis (U. Politecnica de Madrid, E-28040 Madrid, Spain); Fedorov, Alexander V. (Moscow Institute of Physics and Technology, 141700 Moscow Region, Russia)
2004-09-01
The first viscous compressible three-dimensional BiGlobal linear instability analysis of leading-edge boundary layer flow has been performed. Results have been obtained by independent application of asymptotic analysis and numerical solution of the appropriate partial-differential eigenvalue problem. It has been shown that the classification of three-dimensional linear instabilities of the related incompressible flow [13] into symmetric and antisymmetric mode expansions in the chordwise coordinate persists for compressible, subsonic flow-regime at sufficiently large Reynolds numbers.
Directory of Open Access Journals (Sweden)
Fernando Augusto de Souza
2014-07-01
Full Text Available The aim of this research was to evaluate the influence of the number and position of nutrient levels used in dose-response trials in the estimation of the optimal-level (OL and the goodness of fit on the models: quadratic polynomial (QP, exponential (EXP, linear response plateau (LRP and quadratic response plateau (QRP. It was used data from dose-response trials realized in FCAV-Unesp Jaboticabal considering the homogeneity of variances and normal distribution. The fit of the models were evaluated considered the following statistics: adjusted coefficient of determination (R²adj, coefficient of variation (CV and the sum of the squares of deviations (SSD.It was verified in QP and EXP models that small changes on the placement and distribution of the levels caused great changes in the estimation of the OL. The LRP model was deeply influenced by the absence or presence of the level between the response and stabilization phases (change in the straight to plateau. The QRP needed more levels on the response phase and the last level on stabilization phase to estimate correctly the plateau. It was concluded that the OL and the adjust of the models are dependent on the positioning and the number of the levels and the specific characteristics of each model, but levels defined near to the true requirement and not so spaced are better to estimate the OL.
Optimization and Optimal Control
Chinchuluun, Altannar; Enkhbat, Rentsen; Tseveendorj, Ider
2010-01-01
During the last four decades there has been a remarkable development in optimization and optimal control. Due to its wide variety of applications, many scientists and researchers have paid attention to fields of optimization and optimal control. A huge number of new theoretical, algorithmic, and computational results have been observed in the last few years. This book gives the latest advances, and due to the rapid development of these fields, there are no other recent publications on the same topics. Key features: Provides a collection of selected contributions giving a state-of-the-art accou
Félix-Urquídez, Dalmira; Pérez-Urquiza, Melina; Valdez Torres, José-Benigno; León-Félix, Josefina; García-Estrada, Raymundo; Acatzi-Silva, Abraham
2016-01-05
Certified reference materials (CRMs) are required to guarantee the reliability of analytical measurements. The CRMs available in the field of genetically modified organisms (GMOs) are characterized using real-time polymerase chain reaction (qPCR). This technology has limited application, because of its dependence on a calibrant. The objective of this study was to obtain a method with higher metrological quality, to characterize the CRMs for their contents of T-nos/hmg copy number ratio in maize. A duplex droplet digital PCR (ddPCR) assay was developed and optimized by a central composite design. The developed method achieved an absolute limit of detection (LOD) of 11 cP T-nos, a relative LOD of 0.034%, a limit of quantification (LOQ) of 23 cP (relative LOQ of 0.08%), and a dynamic range of 0.08%-100% T-nos/hmg ratio. The specificity and applicability of the assay were established for the analysis of low T-nos concentrations (0.9%) in several corn varieties. The convenience of DNA digestion to reduce measurement bias in the case of multiple-copy binding was confirmed through an enzymatic restriction assay. Given its overall performance, this method can be used to characterize CRM candidates for their contents of T-nos/hmg ratio.
Ma, Tian; Wang, Shouhong
2007-01-01
The main objective of this addendum to the mentioned article by Park is to provide some remarks on bifurcation theories for nonlinear partial differential equations (PDE) and their applications to fluid dynamics problems. We only wish to comment and list some related literatures, without any intention to provide a complete survey.
Optimization of a Low Delta T Rankine Power System.
1980-12-01
considered laminar for numerical evaluation. b. Salt Water Heat Transfer Coefficient, hj The simple empirical relation proposed by Sieder and Tate [Ref...proposed by Sieder and Tate [Ref. 3] will be used for laminar heat transfer in tubes and as defined by 1/3 113 0.14 Nusselt and Prandtl numbers are...bulk temperature. The effect of the viscosity ratio in the Sieder -Tate equation is considered negligible, and will hereafter be dropped from the
Optimally Stopped Optimization
Vinci, Walter; Lidar, Daniel A.
2016-11-01
We combine the fields of heuristic optimization and optimal stopping. We propose a strategy for benchmarking randomized optimization algorithms that minimizes the expected total cost for obtaining a good solution with an optimal number of calls to the solver. To do so, rather than letting the objective function alone define a cost to be minimized, we introduce a further cost-per-call of the algorithm. We show that this problem can be formulated using optimal stopping theory. The expected cost is a flexible figure of merit for benchmarking probabilistic solvers that can be computed when the optimal solution is not known and that avoids the biases and arbitrariness that affect other measures. The optimal stopping formulation of benchmarking directly leads to a real-time optimal-utilization strategy for probabilistic optimizers with practical impact. We apply our formulation to benchmark simulated annealing on a class of maximum-2-satisfiability (MAX2SAT) problems. We also compare the performance of a D-Wave 2X quantum annealer to the Hamze-Freitas-Selby (HFS) solver, a specialized classical heuristic algorithm designed for low-tree-width graphs. On a set of frustrated-loop instances with planted solutions defined on up to N =1098 variables, the D-Wave device is 2 orders of magnitude faster than the HFS solver, and, modulo known caveats related to suboptimal annealing times, exhibits identical scaling with problem size.
Wagner, Richard D., Jr.
1959-01-01
In a recent article on hypersonic flow, Lees and Kubota suggested a modification of the local-expansion method to predict the surface pressures in the region of a nose-cylinder junction where Newtonian theory fails. The modification consists of matching the Newtonian pressure distribution and the Prandtl-Meyer relation at the point on the nose surface where both the pressure and the pressure gradient, predicted by these two solution, are equal. With this approximation, the pressure distribution can be predicted quite accurately up to the nose-cylinder junction for blunt-nosed bodies of continuous curvature, provided centrifugal-force effects are negligible. The purpose of this note is to facilitate the application of Lees' suggestion and to draw attention to some of its consequences.
Goloviznin, V. M.; Korotkin, I. A.; Finogenov, S. A.
2016-12-01
Some numerical results for the two- and three-dimensional de Vahl Davis benchmark are presented. This benchmark describes thermal convection in a square (cubic) cavity with vertical heated walls in a wide range of Rayleigh numbers (104 to 1014), which covers both laminar and highly turbulent f lows. Turbulent f lows are usually described using a turbulence model with parameters that depend on the Rayleigh number and require adjustment. An alternative is Direct Numerical Simulation (DNS) methods, but they demand extremely large computational grids. Recently, there has been an increasing interest in DNS methods with an incomplete resolution, which, in some cases, are able to provide acceptable results without resolving Kolmogorov scales. On the basis of this approach, the so-called parameter-free computational techniques have been developed. These methods cover a wide range of Rayleigh numbers and allow computing various integral properties of heat transport on relatively coarse computational grids. In this paper, a new numerical method based on the CABARET scheme is proposed for solving the Navier-Stokes equations in the Boussinesq approximation. This technique does not involve a turbulence model or any tuning parameters and has a second-order approximation scheme in time and space on uniform and nonuniform grids with a minimal computational stencil. Testing the technique on the de Vahl Davis benchmark and a sequence of refined grids shows that the method yields integral heat f luxes with a high degree of accuracy for both laminar and highly turbulent f lows. For Rayleigh numbers up to 1014, a several percent accuracy is achieved on an extremely coarse grid consisting of 20 × 20 cells refined toward the boundary. No definite or comprehensive explanation of this computational phenomenon has been given. Cautious optimism is expressed regarding the perspectives of using the new method for thermal convection computations at low Prandtl numbers typical of liquid metals.
Energy Technology Data Exchange (ETDEWEB)
Brackney, Larry J. [National Renewable Energy Lab. (NREL), Golden, CO (United States)
2016-02-17
North East utility National Grid (NGrid) is developing a portfolio-scale application of OpenStudio designed to optimize incentive and marketing expenditures for their energy efficiency (EE) programs. NGrid wishes to leverage a combination of geographic information systems (GIS), public records, customer data, and content from the Building Component Library (BCL) to form a JavaScript Object Notation (JSON) input file that is consumed by an OpenStudio-based expert system for automated model generation. A baseline model for each customer building will be automatically tuned using electricity and gas consumption data, and a set of energy conservation measures (ECMs) associated with each NGrid incentive program will be applied to the model. The simulated energy performance and return on investment (ROI) will be compared with customer hurdle rates and available incentives to A) optimize the incentive required to overcome the customer hurdle rate and B) determine if marketing activity associated with the specific ECM is warranted for that particular customer. Repeated across their portfolio, this process will enable NGrid to substantially optimize their marketing and incentive expenditures, targeting those customers that will likely adopt and benefit from specific EE programs.
Energy Technology Data Exchange (ETDEWEB)
Keeling, V; Hossain, S; Hildebrand, K; Ahmad, S [University of Oklahoma Health Sciences Center, Oklahoma City, OK (United States); Larson, D; Ma, L [University of California San Francisco, San Francisco, CA (United States); Sahgal, A [University of Toronto, Toronto, ON (Canada)
2015-06-15
Purpose: To show improvements in dose conformity and normal brain tissue sparing using an optimal planning technique (OPT) against clinically acceptable planning technique (CAP) in the treatment of multiple brain metastases. Methods: A standardized international benchmark case with12 intracranial tumors was planned using two different VMAT optimization methods. Plans were split into four groups with 3, 6, 9, and 12 targets each planned with 3, 5, and 7 arcs using Eclipse TPS. The beam geometries were 1 full coplanar and half non-coplanar arcs. A prescription dose of 20Gy was used for all targets. The following optimization criteria was used (OPT vs. CAP): (No upper limit vs.108% upper limit for target volume), (priority 140–150 vs. 75–85 for normal-brain-tissue), and (selection of automatic sparing Normal-Tissue-Objective (NTO) vs. Manual NTO). Both had priority 50 to critical structures such as brainstem and optic-chiasm, and both had an NTO priority 150. Normal-brain-tissue doses along with Paddick Conformity Index (PCI) were evaluated. Results: In all cases PCI was higher for OPT plans. The average PCI (OPT,CAP) for all targets was (0.81,0.64), (0.81,0.63), (0.79,0.57), and (0.72,0.55) for 3, 6, 9, and 12 target plans respectively. The percent decrease in normal brain tissue volume (OPT/CAP*100) achieved by OPT plans was (reported as follows: V4, V8, V12, V16, V20) (184, 343, 350, 294, 371%), (192, 417, 380, 299, 360%), and (235, 390, 299, 281, 502%) for the 3, 5, 7 arc 12 target plans, respectively. The maximum brainstem dose decreased for the OPT plan by 4.93, 4.89, and 5.30 Gy for 3, 5, 7 arc 12 target plans, respectively. Conclusion: Substantial increases in PCI, critical structure sparing, and decreases in normal brain tissue dose were achieved by eliminating upper limits from optimization, using automatic sparing of normal tissue function with high priority, and a high priority to normal brain tissue.
Pourcel, Christine; Minandri, Fabrizia; Hauck, Yolande; D'Arezzo, Silvia; Imperi, Francesco; Vergnaud, Gilles; Visca, Paolo
2011-01-01
Acinetobacter baumannii is an important opportunistic pathogen responsible for nosocomial outbreaks, mostly occurring in intensive care units. Due to the multiplicity of infection sources, reliable molecular fingerprinting techniques are needed to establish epidemiological correlations among A. baumannii isolates. Multiple-locus variable-number tandem-repeat analysis (MLVA) has proven to be a fast, reliable, and cost-effective typing method for several bacterial species. In this study, an MLVA assay compatible with simple PCR- and agarose gel-based electrophoresis steps as well as with high-throughput automated methods was developed for A. baumannii typing. Preliminarily, 10 potential polymorphic variable-number tandem repeats (VNTRs) were identified upon bioinformatic screening of six annotated genome sequences of A. baumannii. A collection of 7 reference strains plus 18 well-characterized isolates, including unique types and representatives of the three international A. baumannii lineages, was then evaluated in a two-center study aimed at validating the MLVA assay and comparing it with other genotyping assays, namely, macrorestriction analysis with pulsed-field gel electrophoresis (PFGE) and PCR-based sequence group (SG) profiling. The results showed that MLVA can discriminate between isolates with identical PFGE types and SG profiles. A panel of eight VNTR markers was selected, all showing the ability to be amplified and good amounts of polymorphism in the majority of strains. Independently generated MLVA profiles, composed of an ordered string of allele numbers corresponding to the number of repeats at each VNTR locus, were concordant between centers. Typeability, reproducibility, stability, discriminatory power, and epidemiological concordance were excellent. A database containing information and MLVA profiles for several A. baumannii strains is available from http://mlva.u-psud.fr/. PMID:21147956
Steen, Anton; Buist, Girbe; Horsburgh, Gavin J; Venema, Gerard; Kuipers, Oscar P; Foster, Simon J; Kok, Jan
2005-06-01
AcmA, the major autolysin of Lactococcus lactis MG1363 is a modular protein consisting of an N-terminal active site domain and a C-terminal peptidoglycan-binding domain. The active site domain is homologous to that of muramidase-2 of Enterococcus hirae, however, RP-HPLC analysis of muropeptides released from Bacillus subtilis peptidoglycan, after digestion with AcmA, shows that AcmA is an N-acetylglucosaminidase. In the C-terminus of AcmA three highly similar repeated regions of 45 amino acid residues are present, which are separated by short nonhomologous sequences. The repeats of AcmA, which belong to the lysine motif (LysM) domain family, were consecutively deleted, removed, or, alternatively, one additional repeat was added, without destroying the cell wall-hydrolyzing activity of the enzyme in vitro, although AcmA activity was reduced in all cases. In vivo, proteins containing no or only one repeat did not give rise to autolysis of lactococcal cells, whereas separation of the producer cells from the chains was incomplete. Exogenously added AcmA deletion derivatives carrying two repeats or four repeats bound to lactococcal cells, whereas the derivative with no or one repeat did not. In conclusion, these results show that AcmA needs three LysM domains for optimal peptidoglycan binding and biological functioning.
Numerical simulations of high Knudsen number gas flows and microchannel electrokinetic liquid flows
Yan, Fang
Low pressure and microchannel gas flows are characterized by high Knudsen numbers. Liquid flows in microchannels are characterized by non-conventional driving potentials like electrokinetic forces. The main thrust of the dissertation is to investigate these two different kinds of flows in gases and liquids respectively. High Knudsen number (Kn) gas flows were characterized by 'rarified' or 'microscale' behavior. Because of significant non-continuum effect, traditional CFD techniques are often inaccurate for analyzing high Kn number gas flows. The direct simulation Monte Carlo (DSMC) method offers an alternative to traditional CFD which retains its validity in slip and transition flow regimes. To validate the DSMC code, comparisons of simulation results with theoretical analysis and experimental data are made. The DSMC method was first applied to compute low pressure, high Kn flow fields in partially heated two dimensional channels. The effects of varying pressure, inlet flow and gas transport properties (Kn, Reynolds number, Re and the Prandtl number, Pr respectively) on the wall heat transfer (Nusselt number, Nu) were examined. The DSMC method was employed to explore mixing gas flows in two dimensional microchannels. Mixing of two gas streams (H2 and O2) was considered within a microchannel. The effect of the inlet-outlet pressure difference, the pressure ratio of the incoming streams and the accommodation coefficient of the solid wall on mixing length were all examined. Parallelization of a three-dimensional DSMC code was implemented using OpenMP procedure on a shared memory multi-processor computer. The parallel code was used to simulate 3D high Kn number Couette flow and the flow characteristics are found to be very different from their continuum counterparts. A mathematical model describing electrokinetically driven mass transport phenomena in microfabricated chip devices will also be presented. The model accounts for the principal physical phenomena affecting
Ohteru, Shoko; Kishine, Keiji
The Burst ACK scheme enhances effective throughput by reducing ACK overhead when a transmitter sends sequentially multiple data frames to a destination. IEEE 802.11e is one such example. The size of the data frame body and the number of burst data frames are important burst transmission parameters that affect throughput. The larger the burst transmission parameters are, the better the throughput under error-free conditions becomes. However, large data frame could reduce throughput under error-prone conditions caused by signal-to-noise ratio (SNR) deterioration. If the throughput can be calculated from the burst transmission parameters and error rate, the appropriate ranges of the burst transmission parameters could be narrowed down, and the necessary buffer size for storing transmit data or received data temporarily could be estimated. In this paper, we present a method that features a simple algorithm for estimating the effective throughput from the burst transmission parameters and error rate. The calculated throughput values agree well with the measured ones for actual wireless boards based on the IEEE 802.11-based original MAC protocol. We also calculate throughput values for larger values of the burst transmission parameters outside the assignable values of the wireless boards and find the appropriate values of the burst transmission parameters.
Mendonça, J. Ricardo G.
2012-01-01
We define a new class of numbers based on the first occurrence of certain patterns of zeros and ones in the expansion of irracional numbers in a given basis and call them Sagan numbers, since they were first mentioned, in a special case, by the North-american astronomer Carl E. Sagan in his science-fiction novel "Contact." Sagan numbers hold connections with a wealth of mathematical ideas. We describe some properties of the newly defined numbers and indicate directions for further amusement.
Vorob'ev, Nikolai Nikolaevich
2011-01-01
Fibonacci numbers date back to an 800-year-old problem concerning the number of offspring born in a single year to a pair of rabbits. This book offers the solution and explores the occurrence of Fibonacci numbers in number theory, continued fractions, and geometry. A discussion of the ""golden section"" rectangle, in which the lengths of the sides can be expressed as a ration of two successive Fibonacci numbers, draws upon attempts by ancient and medieval thinkers to base aesthetic and philosophical principles on the beauty of these figures. Recreational readers as well as students and teacher
Number names and number understanding
DEFF Research Database (Denmark)
Ejersbo, Lisser Rye; Misfeldt, Morten
2014-01-01
through using mathematical names for the numbers such as one-ten-one for 11 and five-ten-six for 56. The project combines the renaming of numbers with supporting the teaching with the new number names. Our hypothesis is that Danish children have more difficulties learning and working with numbers, because...... the Danish number names are more complicated than in other languages. Keywords: A research project in grade 0 and 1th in a Danish school, Base-10 system, two-digit number names, semiotic, cognitive perspectives....
Petersen, T Kyle
2015-01-01
This text presents the Eulerian numbers in the context of modern enumerative, algebraic, and geometric combinatorics. The book first studies Eulerian numbers from a purely combinatorial point of view, then embarks on a tour of how these numbers arise in the study of hyperplane arrangements, polytopes, and simplicial complexes. Some topics include a thorough discussion of gamma-nonnegativity and real-rootedness for Eulerian polynomials, as well as the weak order and the shard intersection order of the symmetric group. The book also includes a parallel story of Catalan combinatorics, wherein the Eulerian numbers are replaced with Narayana numbers. Again there is a progression from combinatorics to geometry, including discussion of the associahedron and the lattice of noncrossing partitions. The final chapters discuss how both the Eulerian and Narayana numbers have analogues in any finite Coxeter group, with many of the same enumerative and geometric properties. There are four supplemental chapters throughout, ...
Canadian Journal of Physics. Volume 69, Number 2 (Revue Canadienne de Physique. Volume 69, Numero 2
1991-02-01
and hydrodynamics and hydromagnetics that are subject to wall cross-viscosity coefficients of the fluid. suction have been discussed by several... coefficients of k, we [12] t ( Rm 8Y2 obtain for the particular case Rm = 1 where [18] U’’o + U1o + s2Hio = 0 - 212 [19] R’o + Hlo + ulo =0 S= 2...Prandtl numbers. On prdsente une approche intgrale i l’analyse du frottement de surface dans l’dcoulement autour d’un coin, pour un fluide non newtonien A
Institute of Scientific and Technical Information of China (English)
无
2004-01-01
THE last digit of my home phone number in Beijing is 4. “So what?” European readers might ask.This was my attitude when I first lived in China; I couldn't understand why Chinese friends were so shocked at my indifference to the number 4. But China brings new discoveries every day, and I have since seen the light. I know now that Chinese people have their own ways of preserving their well being, and that they see avoiding the number 4 as a good way to stay safe.
Andrews, George E
1994-01-01
Although mathematics majors are usually conversant with number theory by the time they have completed a course in abstract algebra, other undergraduates, especially those in education and the liberal arts, often need a more basic introduction to the topic.In this book the author solves the problem of maintaining the interest of students at both levels by offering a combinatorial approach to elementary number theory. In studying number theory from such a perspective, mathematics majors are spared repetition and provided with new insights, while other students benefit from the consequent simpl
Barnes, John
2016-01-01
In this intriguing book, John Barnes takes us on a journey through aspects of numbers much as he took us on a geometrical journey in Gems of Geometry. Similarly originating from a series of lectures for adult students at Reading and Oxford University, this book touches a variety of amusing and fascinating topics regarding numbers and their uses both ancient and modern. The author intrigues and challenges his audience with both fundamental number topics such as prime numbers and cryptography, and themes of daily needs and pleasures such as counting one's assets, keeping track of time, and enjoying music. Puzzles and exercises at the end of each lecture offer additional inspiration, and numerous illustrations accompany the reader. Furthermore, a number of appendices provides in-depth insights into diverse topics such as Pascal’s triangle, the Rubik cube, Mersenne’s curious keyboards, and many others. A theme running through is the thought of what is our favourite number. Written in an engaging and witty sty...
Watanabe, Tatsuhiko; Kokubun, Yasuo
2014-04-07
The ultimate number of transmission channels in a fiber for the space division multiplexing (SDM) is shown by designing an air-hole-assisted double-cladding few-mode multi-core fiber. The propagation characteristics such as the dispersion and the mode field diameter are almost equalized for all cores owing to the double cladding structure, and the crosstalk between adjacent cores is extremely suppressed by the heterogeneous arrangement of cores and the air holes surrounding the cores. Optimizing the structure of the air-hole-assisted double-cladding, ultra dense core arrangements, e.g. 129 cores in a core accommodated area with 200 μm diameter, can be realized with low crosstalk of less than -34.3 dB at 100km transmission. In this design, each core supports 3 modes i.e. LP(01), LP(11a), and LP(11b) as the transmission channels, so that the number of transmission channels can be 3-hold greater than the number of cores. Therefore, 387 transmission channels can be realized.
Murty, M Ram
2014-01-01
This book provides an introduction to the topic of transcendental numbers for upper-level undergraduate and graduate students. The text is constructed to support a full course on the subject, including descriptions of both relevant theorems and their applications. While the first part of the book focuses on introducing key concepts, the second part presents more complex material, including applications of Baker’s theorem, Schanuel’s conjecture, and Schneider’s theorem. These later chapters may be of interest to researchers interested in examining the relationship between transcendence and L-functions. Readers of this text should possess basic knowledge of complex analysis and elementary algebraic number theory.
Suzuki, Rei; Irisawa, Atsushi; Bhutani, Manoop S; Hikichi, Takuto; Takagi, Tadayuki; Sato, Ai; Sato, Masaki; Ikeda, Tsunehiko; Watanabe, Ko; Nakamura, Jun; Tasaki, Kazuhiro; Obara, Katsutoshi; Ohira, Hiromasa
2012-11-01
A prior study with 22-gauge needles recommended more than seven needle passes for endoscopic ultrasound-guided fine-needle aspiration biopsy (EUS-FNA) of solid pancreatic lesions (SPL) without onsite cytopathology for optimal acquisition of cytopathological diagnosis. The feasibility of this recommendation should be re-evaluated considering the later development and popularity of 25-gauge EUS-FNA needles. We aimed to determine the optimal number of needle passes for cytopathological specimen acquisition with 25-gauge needles for EUS-FNA of SPL. A preliminary prospective study of 22 patients with an onsite cytopathology technician showed a sensitivity of 93.3% and a specificity of 100% with four needle passes that was not statistically different from five needle passes. Based on our preliminary study, we fixed the number of needle passes to four (Group A). As a control group, we carried out sampling in consecutive patients using 25-gauge needles with an onsite cytopathologist (Group B). Sampling rate, diagnostic value and complications were evaluated. We enrolled 20 patients in each group. Sampling rate was higher in Group B (20/20, 100%) than in Group A (19/20, 95%), but there was no statistical difference between them (P-value = 0.31). In Group A, sensitivity, specificity and accuracy were 100% among 19. In Group B, sensitivity was 94.1%, specificity 100%, accuracy 95%. There were also no statistical differences between the groups. No complications were seen. Our study suggests that four needle passes using a 25-gauge needle may be sufficient for EUS-FNA of SPL where onsite cytology is not available. © 2012 The Authors. Digestive Endoscopy © 2012 Japan Gastroenterological Endoscopy Society.
Thelin, John R.
2013-01-01
What topic would you choose if you had the luxury of writing forever? In this article, John Thelin provides his response: He would opt to write about the history of higher education in a way that relies on quantitative data. "Numbers, please!" is his research request in taking on a longitudinal study of colleges and universities over…
Thelin, John R.
2013-01-01
What topic would you choose if you had the luxury of writing forever? In this article, John Thelin provides his response: He would opt to write about the history of higher education in a way that relies on quantitative data. "Numbers, please!" is his research request in taking on a longitudinal study of colleges and universities over…
Galbraith, Mary J.
1974-01-01
Examination of models for representing integers demonstrates that formal operational thought is required for establishing the operations on integers. Advocated is the use of many models for introducing negative numbers but, apart from addition, it is recommended that operations on integers be delayed until the formal operations stage. (JP)
Chenal-Francisque, Viviane; Diancourt, Laure; Cantinelli, Thomas; Passet, Virginie; Tran-Hykes, Coralie; Bracq-Dieye, Hélène; Leclercq, Alexandre; Pourcel, Christine; Lecuit, Marc; Brisse, Sylvain
2013-06-01
Populations of the food-borne pathogen Listeria monocytogenes are genetically structured into a small number of major clonal groups, some of which have been implicated in multiple outbreaks. The goal of this study was to develop and evaluate an optimized multilocus variable number of tandem repeat (VNTR) analysis (MLVA) subtyping scheme for strain discrimination and clonal group identification. We evaluated 18 VNTR loci and combined the 11 best ones into two multiplexed PCR assays (MLVA-11). A collection of 255 isolates representing the diversity of clonal groups within phylogenetic lineages I and II, including representatives of epidemic clones, were analyzed by MLVA-11, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). MLVA-11 had less discriminatory power than PFGE, except for some clones, and was unable to distinguish some epidemiologically unrelated isolates. Yet it distinguished all major MLST clones and therefore constitutes a rapid method to identify epidemiologically relevant clonal groups. Given its high reproducibility and high throughput, MLVA represents a very attractive first-line screening method to alleviate the PFGE workload in outbreak investigations and listeriosis surveillance.
Institute of Scientific and Technical Information of China (English)
曾波; 石娟娟; 周雪玉
2015-01-01
以改善区间灰数预测模型的模拟及预测性能为目的，对区间灰数预测模型的参数优化方法进行研究，应用Cramer法则推导了核序列GM （1，1）模型通用形式的参数无偏估计新方法，从理论上证明了新方法对非齐次指数“核”序列的模拟无偏性，并在此基础上构建了一种新的区间灰数预测模型；通过与优化前的区间灰数预测模型模拟精度进行比较，结果表明新模型具有更为优秀的模拟及预测性能。此研究成果对丰富和完善灰色预测模型方法体系与拓展灰色模型应用范围，具有积极意义。%The parameter optimal method of interval grey number prediction model was studied to improve its simulative and predictive performance in this paper .It applied Cramer rule to deduce the novel unbiased estimation method of GM (1 ,1) model common form for interval grey numbers'kernel sequence , and the simulative unbiasedness of the novel method for nonhomogeneous exponent kernel sequences has been theoretically proven and a new interval grey number prediction model has been established . Comparing the simulative accuracy of the novel model with that of the previous interval grey model without parameter optimization reveals that the novel method has better performances in terms of modeling and prediction . The findings in this paper enrich the literature of grey prediction model and pave the way towards extending the application of grey model .
Directory of Open Access Journals (Sweden)
Ramachandra Prasad
2016-01-01
Full Text Available In this article, we investigate the nonlinear steady boundary layer flow and heat transfer of an incompressible Tangent Hyperbolicnon-Newtonian fluid from a vertical porous plate. The transformed conservation equations are solved numerically subject to physically appropriate boundary conditions using a second-order accurate implicit finite-difference Keller Box technique. The numerical code is validated with previous studies. The influence of a number of emerging non-dimensional parameters, namely the Weissenberg number (We, the power law index (n, Prandtl number (Pr, Biot number (, and dimensionless local suction parameter(on velocity and temperature evolution in the boundary layer regime are examined in detail. Furthermore the effects of these parameters on surface heat transfer rate and local skin friction are also investigated. Validation with earlier Newtonian studies is presented and excellent correlation achieved. It is found that velocity, Skin friction and Nusselt number (heat transfer rate are reduced with increasing Weissenberg number (We, whereas, temperature is enhanced. Increasing power law index (n enhances velocity and Nusselt number (heat transfer rate but temperature and Skin friction decrease. An increase in the Biot number ( is observed to enhance velocity, temperature, local skin friction and Nusselt number. An increasing Prandtl number, Pr, is found to decrease both velocity, temperature and skin friction but elevates heat transfer rate (Nusselt number. The study is relevant to chemical materials processing applications.
Number names and number understanding
DEFF Research Database (Denmark)
Ejersbo, Lisser Rye; Misfeldt, Morten
2014-01-01
This paper concerns the results from the first year of a three-year research project involving the relationship between Danish number names and their corresponding digits in the canonical base 10 system. The project aims to develop a system to help the students’ understanding of the base 10 syste...
Energy Technology Data Exchange (ETDEWEB)
Leon P, A. A.; Martinez B, M. R.; Hernandez P, C. F.; Espinoza G, J. G.; Castaneda M, V. H.; Solis S, L. O.; Castaneda M, R.; Ortiz R, J. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Av. Ramon Lopez Velarde 801, Col. Centro, 98000 Zacatecas, Zac. (Mexico); Mendez V, R. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas, Laboratorio de Patrones Neutronicos, Av. Complutense 22, 28040 Madrid (Spain); Gallego, E. [Universidad Politecnica de Madrid, Departamento de Ingenieria Nuclear, ETSI Industriales, Jose Gutierrez Abascal 2, 28006 Madrid (Spain); De Sousa L, M. A. [Centro de Desenvolvimento da Tecnologia Nuclear / CNEN, Av. Pte. Antonio Carlos 6627, 31270-901 Pampulha, Belo Horizonte, Minas Gerais (Brazil)
2016-10-15
The neutron spectrometry is an experimental process for determining the energy distribution called the Spectrum. Among the methods available for neutron spectrometry, one can mention the Bonner Sphere Spectrometric System as one of the most used, consisting of a detector placed in the center of a set of polyethylene spheres whose diameters range from 2 to 18 inches, however has some disadvantages such as the long periods of time to perform the measurements, the weight and the spheres number that vary according to the system. From this, alternative methods such as artificial neural networks are proposed. For this project neural networks of reverse propagation were used with the methodology of robust design of artificial neural networks, with the aid of a computational tool that maximizes the performance, making the time used for the training s of the network is the smallest possible and thus gets the orthogonal fixes quickly to determine the best network topology. The counting rates of a spectrometric system with 7 spheres, 2 spheres and one sphere of 5 and 8 inches were used. This methodology seeks to reduce the work used as in the spectrometric system formed by a greater number of spheres, since to enter less data in the counting rates to obtain the spectra with 60 energy levels saves time and space, because at having a smaller number of spheres its portability is easier to move from one place to another, for this we performed several experiments with different errors until we reached the optimal error so that the topology of the network was appropriate and find the best design parameters. A statistical software JMP was also used to obtain the best topologies and thus to retrain obtaining its best and worst spectra, in order to determine if the reduction is possible. (Author)
Directory of Open Access Journals (Sweden)
Renato Travassos Beltrame
2007-06-01
Full Text Available Purchase and maintenance of recipient females account for a large proportion of the costs and determine the number of calves that can be produced in an embryo transfer program. However, the large variability of embryo production by the donors and the need to purchase and synchronize the recipients before knowing the number of embryos collected make it difficult for the decision maker to identify the ideal number of recipient females to allocate. An ex-ante evaluation to determine the optimal number of recipient females was carried out through a sensitivity analysis for the ratio between the number of recipients and donors in a simulation model. The variability for the number of embryos collected was accounted for by applying the Monte Carlo simulation technique, assuming normal distribution and known values for mean and variance. The simulation considered monthly intervals between collections, during a 24 months program. The effect of embryo freezing on the number of pregnancies was considered by introducing a stock of frozen embryos into the mathematical model. Optimal recipient/donor ratio and the cost per pregnancy were compared for three recipient synchronization protocols (prostaglandin, progesterone - P4 and Ovsynch, based on the expected performance for synchronization, conception and transfer/treated rates for each protocol. Stochastic simulation associated with sensitivity analysis was effective in identifying the optimal donor to recipient ratio. Freezing embryos is effective to reduce the operational costs per pregnancy. The estimated optimal recipient/donor ratio was 20 for prostaglandin and 16.7 for the other protocols. The P4 protocol, although the most expensive, resulted in the lowest pregnancy cost estimation followed by prostaglandin and Ovsynch.A aquisição e manutenção de receptoras representam grande proporção dos custos e determinam o número de produtos gerados em um programa de transferência de embriões. Entretanto
Convective heat transport in stratified atmospheres at low and high Mach number
Anders, Evan H
2016-01-01
Convection in astrophysical systems is stratified and often occurs at high Rayleigh number (Ra) and low Mach number (Ma). Here we study stratified convection in the context of plane-parallel, polytropically stratified atmospheres. We hold the density stratification ($n_{\\rho}$) and Prandtl number (Pr) constant while varying Ma and Ra to determine the behavior of the Nusselt number (Nu), which quantifies the efficiency of convective heat transport. As Ra increases and $\\text{Ma} \\rightarrow 1$, a scaling of Nu $\\propto$ Ra$^{0.45}$ is observed. As Ra increases to a regime where Ma $\\geq 1$, this scaling gives way to a weaker Nu $\\propto$ Ra$^{0.19}$. In the regime of Ma $\\ll 1$, a consistent Nu $\\propto$ Ra$^{0.31}$ is retrieved, reminiscent of the Nu $\\propto$ Ra$^{2/7}$ seen in Rayleigh-B\\'{e}nard convection.
Applications of combinatorial optimization
Paschos, Vangelis Th
2013-01-01
Combinatorial optimization is a multidisciplinary scientific area, lying in the interface of three major scientific domains: mathematics, theoretical computer science and management. The three volumes of the Combinatorial Optimization series aims to cover a wide range of topics in this area. These topics also deal with fundamental notions and approaches as with several classical applications of combinatorial optimization. "Applications of Combinatorial Optimization" is presenting a certain number among the most common and well-known applications of Combinatorial Optimization.
Energy Technology Data Exchange (ETDEWEB)
Zhao, Chen-Ru; Zhang, Zhen [Institute of Nuclear and New Energy Technology of Tsinghua University, Advanced Nuclear Energy Technology Cooperation Innovation Centre, Key Laboratory of Advanced Nuclear Engineering and Safety, Ministry of Education, Beijing 100084 (China); Jiang, Pei-Xue, E-mail: jiangpx@tsinghua.edu.cn [Beijing Key Laboratory of CO_2 Utilization and Reduction Technology/Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China); Bo, Han-Liang [Institute of Nuclear and New Energy Technology of Tsinghua University, Advanced Nuclear Energy Technology Cooperation Innovation Centre, Key Laboratory of Advanced Nuclear Engineering and Safety, Ministry of Education, Beijing 100084 (China)
2017-03-15
Highlights: • Understanding of the mechanism of buoyancy effect on supercritical heat transfer. • Turbulence related parameters in upward and downward flows were compared. • Turbulent Prandtl number affected the prediction insignificantly. • Buoyancy production was insignificant compared with shear production. • Damping function had the greatest effect and is a priority for further modification. - Abstract: Heat transfer to supercritical pressure fluids was modeled for normal and buoyancy affected conditions using several low Reynolds number k-ε models, including the Launder and Sharma, Myong and Kasagi, and Abe, Kondoh and Nagano, with the predictions compared with experimental data. All three turbulence models accurately predicted the cases without heat transfer deterioration, but failed to accurately predict the cases with heat transfer deterioration although the general trends were captured, indicating that further improvements and modifications are needed for the low Reynolds number k-ε turbulence models to better predict buoyancy deteriorated heat transfer. Further investigations studied the influence of various aspects of the low Reynolds number k-ε turbulence models, including the turbulent Prandtl number, the buoyancy production of turbulent kinetic energy, and the damping function to provide guidelines for model development to more precisely predict buoyancy affected heat transfer. The results show that the turbulent Prandtl number and the buoyancy production of turbulent kinetic energy have little influence on the predictions for cases in this study, while new damping functions with carefully selected control parameters are needed in the low Reynolds number k-ε turbulence models to correctly predict the buoyancy effect for heat transfer simulations in various applications such as supercritical pressure steam generators (SPSGs) in the high temperature gas cooled reactor (HTR) and the supercritical pressure water reactor (SCWR).
Institute of Scientific and Technical Information of China (English)
程小燕; 薛彦涛
2012-01-01
With the development of the energy dissipation brace, this technology is more and more used in the new structures and the old structures' reinforcement and reconstruction design. In this paper, a series of formulas for determining, optimal numbers of braces under earthquake action are presented, based on the cooperation work principle of brace and frame in braced-frame structure and the code for seismic design of buildings. This method is accurate and convenient enough for use when the braced-frame structure are designed during the preliminary stage of design and the renovated and strengthened of existing frame structure.%随着耗能支撑的发展,支撑越来越多地应用于新建结构和旧有建筑的加固改造中.本文依据框架-支撑结构的协同工作原理,按照我国现行抗震设计规范对混凝土框架-支撑结构侧移变形的限值,推导出了满足层间位移角限值的支撑数量的计算公式,从而为框架-支撑结构的初步设计以及原有框架结构的改造加固提供参考.
Antenna optimization using Particle Swarm Optimization algorithm
Directory of Open Access Journals (Sweden)
Golubović Ružica M.
2006-01-01
Full Text Available We present the results for two different antenna optimization problems that are found using the Particle Swarm Optimization (PSO algorithm. The first problem is finding the maximal forward gain of a Yagi antenna. The second problem is finding the optimal feeding of a broadside antenna array. The optimization problems have 6 and 20 optimization variables, respectively. The preferred values of the parameters of the PSO algorithm are found for presented problems. The results show that the preferred parameters of PSO are somewhat different for optimization problems with different number of dimensions of the optimization space. The results that are found using the PSO algorithm are compared with the results that are found using other optimization algorithms, in order to estimate the efficiency of the PSO.
Institute of Scientific and Technical Information of China (English)
翟永玺; 张堃元; 王磊; 李永洲; 张林
2014-01-01
A parametric research on the curved compression surface with controllable Mach number distri-bution was commenced to find the effect regularity of design parameters on the performance parameters of curved compression surface. On this basis,a polynomial response surface proxy model was built to make a multi-objec-tive optimization,and a hypersonic curved shock two-dimensional inlet was designed based on the optimization result, the performance was compared with the three-ramp compression inlet which was designed under the same constraints. Results indicate among the design parameters, the initial compress angle θ and the factor C and factor md1 affect most. The flow coefficient of the innovative inlet is up to 0.769 at Mach 4,when Mach num-ber ranges from 4 to 7,the two inlets have equally the same mass capture ratio,while the innovative inlet has high total pressure recovery of throat and outlet section. Compared with the relative three-ramp inlet , the total pressure recovery of throat section of the innovative inlet increased by 6.5%at Mach 4, 8.4%at Mach 6, and 10.7%at Mach 7.%针对一种马赫数分布可控的二元高超弯曲压缩面进行参数化研究，获得其设计参数对压缩面性能的影响规律，在此基础上建立多项式响应面代理模型并进行多目标优化，基于优化结果设计了二元弯曲激波进气道，并与同等约束条件下的三楔进气道进行比较。结果表明：压缩面初始压缩角θ与马赫数梯度函数中的设计参数md1，C对压缩面性能影响最为显著；Ma∞=4.0时弯曲激波进气道流量系数达0.769，与三楔进气道相比，在Ma∞=4～7工作范围内的流量捕获能力相当，但其喉道、出口截面的总压恢复系数均高于三楔进气道，在Ma∞=4，6，7工况下，喉道截面总压恢复分别有6.5%，8.4%和10.7%的提高。
Rotating thermal convection at very large Rayleigh numbers
Weiss, Stephan; van Gils, Dennis; Ahlers, Guenter; Bodenschatz, Eberhard
2016-11-01
The large scale thermal convection systems in geo- and astrophysics are usually influenced by Coriolis forces caused by the rotation of their celestial bodies. To better understand the influence of rotation on the convective flow field and the heat transport at these conditions, we study Rayleigh-Bénard convection, using pressurized sulfur hexaflouride (SF6) at up to 19 bars in a cylinder of diameter D=1.12 m and a height of L=2.24 m. The gas is heated from below and cooled from above and the convection cell sits on a rotating table inside a large pressure vessel (the "Uboot of Göttingen"). With this setup Rayleigh numbers of up to Ra =1015 can be reached, while Ekman numbers as low as Ek =10-8 are possible. The Prandtl number in these experiment is kept constant at Pr = 0 . 8 . We report on heat flux measurements (expressed by the Nusselt number Nu) as well as measurements from more than 150 temperature probes inside the flow. We thank the Deutsche Forschungsgemeinschaft (DFG) for financial support through SFB963: "Astrophysical Flow Instabilities and Turbulence". The work of GA was supported in part by the US National Science Foundation through Grant DMR11-58514.
Institute of Scientific and Technical Information of China (English)
熊敏
2012-01-01
通过对10号优质碳素结构钢、玻璃熔封件的热应力计算,阐明了10号优质碳素结构钢、玻璃熔封结构的可行性。通过采取控制玻璃用量、合理设计孔口、烧结模具、优化工艺过程等手段,解决了熔封件玻璃开裂、漏气和管壳的抗蚀性等问题。机械和温度应力试验表明,采用该材料的金属电子封装外壳漏气速率不超过1×10-3Pa.cm3/s,并能承受24h盐雾试验。%Based on calculating the thermal stress of number ten high-quality carbon steel and glass sealing parts,the feasibility of the sealing structure is described.By controlling the glass dose,rational designing the aperture and sintering dies and optimizing the manufacture process,such problems as glass crack,air leakage and corrosion resistance of the metal package are resolved.Mechanical stress and temperate stress tests show that the air leakage rate of the electronic package is less than 10-3 Pa·cm3/s,and the package can withstand the 24-hour salt-fog test.
The dependence of Nusselt number on Reynolds number for a hot-wire sensor in supercritical CO2 flow
Vukoslavcevic, Petar; Wallace, James
2005-11-01
An analysis of the heat transfer mechanism around a hot-wire sensor in superctitical CO2 flow has been performed, and the dependence of the Nusselt number (Nu) on the Reynolds number (Re) has been determined. A special, closed flow loop, capable of inducing variable speed flow at different pressures and temperatures in the ranges of 0.15-2 m/s, 15-70^oC and 1-100 bar, has been used to create a supercritical CO2 flow around a hot-wire sensor operated in the constant temperature mode. The Nu and Re numbers were determined based on the known heat convected from the sensor, the flow speed and the sensor temperature and dimensions. The experiment was performed along a line of constant 80 bar pressure in the temperature range of 25-65^oC. It was found that, at a given pressure and temperature, the relation Nu=F(Re) has the classical form Nu=M+NRe^n, with the parameters M and N being functions of pressure and temperature. The dependence of these parameters on temperature was analyzed, and the most convenient reference temperature was chosen. In contrast to the operation of hot-wires in air and water, the dependence of the parameters M and N on the Prandtl number can result in nonunique solutions.
Institute of Scientific and Technical Information of China (English)
李友荣; 刘玉姗; 石万元
2009-01-01
利用线性稳定性理论分析了低Pr数(Pr=0.011)流体在环形液池内的热毛细对流,以此了解环形液池内热毛细对流的转变特性.液池外壁被加热,内壁被冷却,底部固壁和顶部自由表面均绝热.结果表明,随着液池深宽比的增加,临界Marangoni数和临界波数都逐渐减小,且当液池深宽比超过0.12后,临界波数基本不变;随着液池内外半径比的增加,临界Marangoni数会逐渐减小,但变化幅度不大,而临界波数有一个大的增加.
Energy Technology Data Exchange (ETDEWEB)
Rocha, Alan Carlos Bueno da
1997-07-01
A heat transfer (condenser) of a domestic freezer was tested in a vertical channel in order to study the influence of the chimney effect in the optimization of the heat transfer coefficient. The variation of the opening of the channel, position and the heating power of the heat exchanger in the heat transfer coefficient was considered. The influence of the surface emissivity on the heat transfer by thermal radiation was studied with the heat exchanger testes without paint and with black paint. The air velocity entering the channel was measured with a hot wire anemometer. In order to evaluate the chimney effect, the heat exchanger was testes in a open ambient. This situation simulates its operational conditions when installed on the freezer system. The variables collected in the experimental procedures was gathered in the form of dimensionless parameters as Nusselt, Rayleigh, Grashof and Prandtl numbers, and dimensional parameters of the convection. The results showed that the highest heat transfer value occurred when both a specific position and a specific channel opening were used. The experiments pointed out that the radiation contribution must be considered in heat transfer calculations. The conclusions showed that different channel openings can improve the heat transfer coefficient in this heat transfer exchanger. (author)
Institute of Scientific and Technical Information of China (English)
徐广斌; 刘惊雷
2015-01-01
challenging due to the number of possible solutions that need to be examined,which grows exponentially with the number of agents involved.Traditionally, there have been put forward many algorithms to solve this problem ranging from dynamic programming to improved dynamic programming,to integer programming,and all of these techniques suffer from having no constaints on the number of coalitions.However,in many real-world applications,there are inherent constraints on the number of coalitions.In this paper,we present the first systematic study of constraint on the number of coalition,and use the DP(dynamic programming)theory to develop an algorithm,which is named as CCDP(coalition constraint dynamic programming),for generating an optimal(welfare-maximizing)coalition structure.Furthermore,it is proved that the time complexity of this algorithm is O(3n ).In the end,we analyze and verify the influence of agent’s number and the size of values of constraints on the algorithm performance through detailed experiments.
Mechanical Design Optimization Using Advanced Optimization Techniques
Rao, R Venkata
2012-01-01
Mechanical design includes an optimization process in which designers always consider objectives such as strength, deflection, weight, wear, corrosion, etc. depending on the requirements. However, design optimization for a complete mechanical assembly leads to a complicated objective function with a large number of design variables. It is a good practice to apply optimization techniques for individual components or intermediate assemblies than a complete assembly. Analytical or numerical methods for calculating the extreme values of a function may perform well in many practical cases, but may fail in more complex design situations. In real design problems, the number of design parameters can be very large and their influence on the value to be optimized (the goal function) can be very complicated, having nonlinear character. In these complex cases, advanced optimization algorithms offer solutions to the problems, because they find a solution near to the global optimum within reasonable time and computational ...
Institute of Scientific and Technical Information of China (English)
冯宝军; 闰达文; 迟国泰
2012-01-01
现有研究把存、贷款利率视为常数，无法使资产配置的优化结果适应未来市场利率的变化。本文的资产负债管理优化模型通过资产与负债的区间数的持续期缺口建立了区间型利率风险免疫条件，使资产的最优配置在资产与负债的收益率变化时仍能免疫利率风险。研究表明本文引入的持效期缺口区间的偏向选择参数7决定预留缺口是赚钱还是亏钱。γ取值0．5时缺口区间两端点的绝对值最小；γ越大于0．5时，正缺口越大，在利率下降时就越赚钱。γ越小于0．5时，负缺口越大，在利率上升时就越赚钱。而区间长度选择参数γ决定损益的大小；揭示了在积极的利率风险管理策略中，选择较小的λ会获得较多的风险收益。另一方面，本文通过相关系数组合半绝对离差建立了非线性区间型组合风险的函数表达式，改变了现有研究线性区间型算法将各笔贷款风险进行简单线性加权、进而夸大了组合信用风险的弊端。%The unreasonable status that deposit and lending rates are considered as constants m existing literature couldn＇t immune future interest rate risk, in case deposit and lending rates would be changing. In our assets and liabilities optimization model, we construct the immune constrain of interval interest rate through duration gap of interval numbers of asset and liability, which makes the assets＇ allocation be immune to interest rate risk with a changing yield of asset and liability. The study shows that interval-biased selection parameter γ of duration gap decides whether the reserved gap makes money or loses money. The result is the interval-biased selection parameter γ of duration gap is 0.5, the absolute value of both ends of gap interval is in minimum; the more γ is greater than 0.5, the larger positive gap is, and more money is earned when interest rate declines ; The more γ is less than 0.5, the
Number of Compositions and Convolved Fibonacci numbers
Janjic, Milan
2010-01-01
We consider two type of upper Hessenberg matrices which determinants are Fibonacci numbers. Calculating sums of principal minors of the fixed order of the first type leads us to convolved Fibonacci numbers. Some identities for these and for Fibonacci numbers are proved. We also show that numbers of compositions of a natural number with fixed number of ones appear as coefficients of characteristic polynomial of a Hessenberg matrix which determinant is a Fibonacci number. We derive the explicit...
Number of Compositions and Convolved Fibonacci numbers
Janjic, Milan
2010-01-01
We consider two type of upper Hessenberg matrices which determinants are Fibonacci numbers. Calculating sums of principal minors of the fixed order of the first type leads us to convolved Fibonacci numbers. Some identities for these and for Fibonacci numbers are proved. We also show that numbers of compositions of a natural number with fixed number of ones appear as coefficients of characteristic polynomial of a Hessenberg matrix which determinant is a Fibonacci number. We derive the explicit formula for the number of such compositions, in terms of convolutions of Fibonacci numbers.
Laboratory-Scale Simulation of Spiral Plumes in Fluid with Hight Ptandtl Number
Sharifulin, A N
2013-01-01
We experimentally investigated the appearance of a plumes from local hot spot and study its interaction with cellular flow in closed cavity filled by silicon oil with Prandtl number Pr ~2*10^3 . Convective plume is generated by a local heat source, located on the top of the small rubber cylinder, which is located in the center of the bottom of the rectangular cell. Green laser has been used to simulate the hot-spot. Roll-type large-scale convective flow is generated by heating of the one vertical sides of cavity. Influence of power of hot point on the shape of plume has been investigated. It is shown that the presence of cellular convective motion may lead to the formation of a strange spiral convective plume. This plume looks like Archimedes spiral replaced on vertical plane. Physical mechanism of the formation of strange spiral plume and application of obtained results for mantle convection problems are discussed.
Pegging Numbers For Various Tree Graphs
Levavi, Ariel
2011-01-01
In the game of pegging, each vertex of a graph is considered a hole into which a peg can be placed. A pegging move is performed by jumping one peg over another peg, and then removing the peg that has been jumped over from the graph. We define the pegging number as the smallest number of pegs needed to reach all the vertices in a graph no matter what the distribution. Similarly, the optimal-pegging number of a graph is defined as the smallest distribution of pegs for which all the vertices in the graph can be reached. We obtain tight bounds on the pegging numbers and optimal-pegging numbers of complete binary trees and compute the optimal-pegging numbers of complete infinitary trees. As a result of these computations, we deduce that there is a tree whose optimal-pegging number is strictly increased by removing a leaf. We also compute the optimal-pegging number of caterpillar graphs and the tightest upper bound on the optimal-pegging numbers of lobster graphs.
Covering Numbers for Convex Functions
Guntuboyina, Adityanand
2012-01-01
In this paper we study the covering numbers of the space of convex and uniformly bounded functions in multi-dimension. We find optimal upper and lower bounds for the $\\epsilon$-covering number of $\\C([a, b]^d, B)$, in the $L_p$-metric, $1 \\le p 0$, and $\\C([a,b]^d, B)$ denotes the set of all convex functions on $[a, b]^d$ that are uniformly bounded by $B$. We summarize previously known results on covering numbers for convex functions and also provide alternate proofs of some known results. Our results have direct implications in the study of rates of convergence of empirical minimization procedures as well as optimal convergence rates in the numerous convexity constrained function estimation problems.
Energy Technology Data Exchange (ETDEWEB)
Christensen, Craig [National Renewable Energy Lab. (NREL), Golden, CO (United States)
2016-01-29
Opportunities for combining energy efficiency, demand response, and energy storage with PV are often missed, because the required knowledge and expertise for these different technologies exist in separate organizations or individuals. Furthermore, there is a lack of quantitative tools to optimize energy efficiency, demand response and energy storage with PV, especially for existing buildings. Our goal is to develop a modeling tool, BEopt-CA (Ex), with capabilities to facilitate identification and implementation of a balanced integration of energy efficiency (EE), demand response (DR), and energy storage (ES) with photovoltaics (PV) within the residential retrofit market. To achieve this goal, we will adapt and extend an existing tool -- BEopt -- that is designed to identify optimal combinations of efficiency and PV in new home designs. In addition, we will develop multifamily residential modeling capabilities for use in California, to facilitate integration of distributed solar power into the grid in order to maximize its value to California ratepayers. The project is follow-on research that leverages previous California Solar Initiative RD&D investment in the BEopt software. BEopt facilitates finding the least cost combination of energy efficiency and renewables to support integrated DSM (iDSM) and Zero Net Energy (ZNE) in California residential buildings. However, BEopt is currently focused on modeling single-family houses and does not include satisfactory capabilities for modeling multifamily homes. The project brings BEopt's existing modeling and optimization capabilities to multifamily buildings, including duplexes, triplexes, townhouses, flats, and low-rise apartment buildings.
Venter, Gerhard; Sobieszczanski-Sobieski Jaroslaw
2002-01-01
The purpose of this paper is to show how the search algorithm known as particle swarm optimization performs. Here, particle swarm optimization is applied to structural design problems, but the method has a much wider range of possible applications. The paper's new contributions are improvements to the particle swarm optimization algorithm and conclusions and recommendations as to the utility of the algorithm, Results of numerical experiments for both continuous and discrete applications are presented in the paper. The results indicate that the particle swarm optimization algorithm does locate the constrained minimum design in continuous applications with very good precision, albeit at a much higher computational cost than that of a typical gradient based optimizer. However, the true potential of particle swarm optimization is primarily in applications with discrete and/or discontinuous functions and variables. Additionally, particle swarm optimization has the potential of efficient computation with very large numbers of concurrently operating processors.
The stability of stratified spatially periodic shear flows at low Péclet number
Energy Technology Data Exchange (ETDEWEB)
Garaud, Pascale, E-mail: pgaraud@ucsc.edu [Department of Applied Mathematics and Statistics, Baskin School of Engineering, University of California at Santa Cruz, 1156 High Street, Santa Cruz, California 95064 (United States); Gallet, Basile [Service de Physique de l’Etat Condensé, DSM/IRAMIS, CNRS UMR 3680, CEA Saclay, 91191 Gif-sur-Yvette cedex (France); Bischoff, Tobias [Division of Geological and Planetary Sciences, California Institute of Technology, Mail Code 170-25, 1200 E. California Blvd., Pasadena, California 91125 (United States)
2015-08-15
This work addresses the question of the stability of stratified, spatially periodic shear flows at low Péclet number but high Reynolds number. This little-studied limit is motivated by astrophysical systems, where the Prandtl number is often very small. Furthermore, it can be studied using a reduced set of “low-Péclet-number equations” proposed by Lignières [“The small-Péclet-number approximation in stellar radiative zones,” Astron. Astrophys. 348, 933–939 (1999)]. Through a linear stability analysis, we first determine the conditions for instability to infinitesimal perturbations. We formally extend Squire’s theorem to the low-Péclet-number equations, which shows that the first unstable mode is always two-dimensional. We then perform an energy stability analysis of the low-Péclet-number equations and prove that for a given value of the Reynolds number, above a critical strength of the stratification, any smooth periodic shear flow is stable to perturbations of arbitrary amplitude. In that parameter regime, the flow can only be laminar and turbulent mixing does not take place. Finding that the conditions for linear and energy stability are different, we thus identify a region in parameter space where finite-amplitude instabilities could exist. Using direct numerical simulations, we indeed find that the system is subject to such finite-amplitude instabilities. We determine numerically how far into the linearly stable region of parameter space turbulence can be sustained.
Richardson, Thomas M.
2014-01-01
We introduce the super Patalan numbers, a generalization of the super Catalan numbers in the sense of Gessel, and prove a number of properties analagous to those of the super Catalan numbers. The super Patalan numbers generalize the super Catalan numbers similarly to how the Patalan numbers generalize the Catalan numbers.
Institute of Scientific and Technical Information of China (English)
刘城; 潘鑫; 闫清东; 魏巍
2012-01-01
As the conventional beam streamline theory cannot optimize the blade numbers of torque converter effectively, a 3-D flow field simulation platform for torque converter has been built. The design of experiment (DOE) was adopted to study the influence of blade number on the performance of torque converter, and the blade number was optimized utilizing the response surface methodology (RSM). The results indicate that the blade numbers of pump and turbine have a great influence on maximum efficiency and stall torque ratio, while the blade numbers of pump and stator are the main factors for stall pump torque coefficient. The performance of the torque converter with optimized blade numbers is improved evidently.%为解决一维束流理论难以有效地对液力变矩器叶片数进行优化的问题,建立液力变矩器三维流动设计分析平台,利用实验设计方法,研究了各叶片数对液力变矩器性能的影响,并在响应曲面基础上对叶片数进行了优化.结果表明,泵轮、涡轮叶片数对最高效率和起动转矩比有较大影响,泵轮、导轮叶片数对泵轮扭矩系数有较大影响.优化后,液力变矩器各性能指标均有提高.
Optimization : insights and applications
Brinkhuis, Jan
2005-01-01
This self-contained textbook is an informal introduction to optimization through the use of numerous illustrations and applications. The focus is on analytically solving optimization problems with a finite number of continuous variables. In addition, the authors provide introductions to classical and modern numerical methods of optimization and to dynamic optimization. The book's overarching point is that most problems may be solved by the direct application of the theorems of Fermat, Lagrange, and Weierstrass. The authors show how the intuition for each of the theoretical results can be s
Graben, Peter beim; Fröhlich, Flavio
2015-01-01
We optimally estimate the recurrence structure of a multivariate time series by Markov chains obtained from recurrence grammars. The goodness of fit is assessed with a utility function derived from the stochastic Markov transition matrix. It assumes a local maximum for the distance threshold of the optimal recurrence grammar. We validate our approach by means of the nonlinear Lorenz system and its linearized stochastic surrogates. Finally we apply our optimization procedure to the segmentation of neurophysiological time series obtained from anesthetized animals. We propose the number of optimal recurrence domains as a statistic for classifying an animals' state of consciousness.
Directory of Open Access Journals (Sweden)
L. I. Rozonoer
1999-01-01
Full Text Available Necessary and sufficient conditions for existence of optimal control for all initial data are proved for LQ-optimization problem. If these conditions are fulfilled, necessary and sufficient conditions of optimality are formulated. Basing on the results, some general hypotheses on optimal control in terms of Pontryagin's maximum condition and Bellman's equation are proposed.
Energy Technology Data Exchange (ETDEWEB)
James Demmel
2007-02-26
In many areas of science, physical experimentation may be too dangerous, too expensive or even impossible. Instead, large-scale simulations, validated by comparison with related experiments in well-understood laboratory contexts, are used by scientists to gain insight and confirmation of existing theories in such areas, without benefit of full experimental verification. The goal of the TOPS ISIC was to develop and implement algorithms and support scientific investigations performed by DOE-sponsored researchers. A major component of this effort is to provide software for large scale parallel computers capable of efficiently solving the enormous systems of equations arising from the nonlinear PDEs underlying these simulations. Several TOPS supported packages where designed in part (ScaLAPACK) or in whole (SuperLU) at Berkeley, and are widely used beyond SciDAC and DOE. Beyond continuing to develop these codes, our main effort focused on automatic performance tuning of the sparse matrix kernels (eg sparse-matrix-vector-multiply, or SpMV) at the core of many TOPS iterative solvers. Based on the observation that the fastest implementation of SpMV (and other kernels) can depend dramatically both on the computer and the matrix (the latter of which is not known until run-time), we developed and released a system called OSKI (Optimized Sparse Kernel Interface) that will automatically produce optimized version of SpMV (and other kernels), hiding complicated implementation details from the user. OSKI led to a 2x speedup in SpMV in a DOE accelerator design code, a 2x speedup in a commercial lithography simulation, and has been downloaded over 500 times. In addition to a stand-alone version, OSKI was also integrated into the TOPS-supported PETSc system.
On Number of Compositions of Natural Numbers
Janjic, Milan
2010-01-01
We first give a combinatorial interpretation of coefficients of Chebyshev polynomials, which allows us to connect them with compositions of natural numbers. Then we describe a relationship between the number of compositions of a natural number in which a certain number of parts are p-1, and other parts are not less than p with compositions in which all parts are not less than p. Then we find a relationship between principal minors of a type of Hessenberg matrices and compositions of natural numbers.
On Validating Boolean Optimizers
Morgado, Antonio
2011-01-01
Boolean optimization finds a wide range of application domains, that motivated a number of different organizations of Boolean optimizers since the mid 90s. Some of the most successful approaches are based on iterative calls to an NP oracle, using either linear search, binary search or the identification of unsatisfiable sub-formulas. The increasing use of Boolean optimizers in practical settings raises the question of confidence in computed results. For example, the issue of confidence is paramount in safety critical settings. One way of increasing the confidence of the results computed by Boolean optimizers is to develop techniques for validating the results. Recent work studied the validation of Boolean optimizers based on branch-and-bound search. This paper complements existing work, and develops methods for validating Boolean optimizers that are based on iterative calls to an NP oracle. This entails implementing solutions for validating both satisfiable and unsatisfiable answers from the NP oracle. The wo...
Institute of Scientific and Technical Information of China (English)
赵霞; 王召巴
2014-01-01
在设计和使用超声相控阵检测系统时，系统独立通道数直接影响着系统检测分辨力及系统成本。本文从相控阵系统检测分辨力的角度出发，分别分析研究了系统独立通道数与声束焦点宽度及检测偏转角的关系，得出系统独立通道数的设计准则。%In the design and use of ultrasonic phased array testing system,the system of independent channel number directly affects the detection resolution and system cost.This paper from the phased array system to detect the viewpoint of discrimination,respectively,to analyze the system of independent channel number and beam width and the relationship between focus detection angle,design criterion of independent channel number of the.
On Multiplying Negative Numbers.
Crowley, Mary L.; Dunn, Kenneth A.
1985-01-01
Comments on the history of negative numbers, some methods that can be used to introduce the multiplication of negative numbers to students, and an explanation of why the product of two negative numbers is a positive number are included. (MNS)
The small-scale dynamo: Breaking universality at high Mach numbers
Schleicher, Dominik R G; Federrath, Christoph; Bovino, Stefano; Schmidt, Wolfram
2013-01-01
(Abridged) The small-scale dynamo may play a substantial role in magnetizing the Universe under a large range of conditions, including subsonic turbulence at low Mach numbers, highly supersonic turbulence at high Mach numbers and a large range of magnetic Prandtl numbers Pm, i.e. the ratio of kinetic viscosity to magnetic resistivity. Low Mach numbers may in particular lead to the well-known, incompressible Kolmogorov turbulence, while for high Mach numbers, we are in the highly compressible regime, thus close to Burgers turbulence. In this study, we explore whether in this large range of conditions, a universal behavior can be expected. Our starting point are previous investigations in the kinematic regime. Here, analytic studies based on the Kazantsev model have shown that the behavior of the dynamo depends significantly on Pm and the type of turbulence, and numerical simulations indicate a strong dependence of the growth rate on the Mach number of the flow. Once the magnetic field saturates on the current ...
All Square Chiliagonal Numbers
A?iru, Muniru A.
2016-01-01
A square chiliagonal number is a number which is simultaneously a chiliagonal number and a perfect square (just as the well-known square triangular number is both triangular and square). In this work, we determine which of the chiliagonal numbers are perfect squares and provide the indices of the corresponding chiliagonal numbers and square…
Electrohydrodynamic deformation of drops and bubbles at large Reynolds numbers
Schnitzer, Ory
2015-11-01
In Taylor's theory of electrohydrodynamic drop deformation by a uniform electric field, inertia is neglected at the outset, resulting in fluid velocities that scale with E2, E being the applied-field magnitude. When considering strong fields and low viscosity fluids, the Reynolds number predicted by this scaling may actually become large, suggesting the need for a complementary large-Reynolds-number analysis. Balancing viscous and electrical stresses reveals that the velocity scales with E 4 / 3. Considering a gas bubble, the external flow is essentially confined to two boundary layers propagating from the poles to the equator, where they collide to form a radial jet. Remarkably, at leading order in the Capillary number the unique scaling allows through application of integral mass and momentum balances to obtain a closed-form expression for the O (E2) bubble deformation. Owing to a concentrated pressure load at the vicinity of the collision region, the deformed profile features an equatorial dimple which is non-smooth on the bubble scale. The dynamical importance of internal circulation in the case of a liquid drop leads to an essentially different deformation mechanism. This is because the external boundary layer velocity attenuates at a short distance from the interface, while the internal boundary-layer matches with a Prandtl-Batchelor (PB) rotational core. The dynamic pressure associated with the internal circulation dominates the interfacial stress profile, leading to an O (E 8 / 3) deformation. The leading-order deformation can be readily determined, up to the PB constant, without solving the circulating boundary-layer problem. To encourage attempts to verify this new scaling, we shall suggest a favourable experimental setup in which inertia is dominant, while finite-deformation, surface-charge advection, and gravity effects are negligible.
Optimization and optimal control in automotive systems
Kolmanovsky, Ilya; Steinbuch, Maarten; Re, Luigi
2014-01-01
This book demonstrates the use of the optimization techniques that are becoming essential to meet the increasing stringency and variety of requirements for automotive systems. It shows the reader how to move away from earlier approaches, based on some degree of heuristics, to the use of more and more common systematic methods. Even systematic methods can be developed and applied in a large number of forms so the text collects contributions from across the theory, methods and real-world automotive applications of optimization. Greater fuel economy, significant reductions in permissible emissions, new drivability requirements and the generally increasing complexity of automotive systems are among the criteria that the contributing authors set themselves to meet. In many cases multiple and often conflicting requirements give rise to multi-objective constrained optimization problems which are also considered. Some of these problems fall into the domain of the traditional multi-disciplinary optimization applie...
Surrogate Modeling for Geometry Optimization
DEFF Research Database (Denmark)
Rojas Larrazabal, Marielba de la Caridad; Abraham, Yonas; Holzwarth, Natalie;
2009-01-01
A new approach for optimizing the nuclear geometry of an atomic system is described. Instead of the original expensive objective function (energy functional), a small number of simpler surrogates is used.......A new approach for optimizing the nuclear geometry of an atomic system is described. Instead of the original expensive objective function (energy functional), a small number of simpler surrogates is used....
Directory of Open Access Journals (Sweden)
Öje Danell
1999-04-01
Full Text Available Optimal Production in Reindeer Husbandry.There are three ways to optimize the reindeer herd: 1 Adjusting the reindeer number to pasture resources. 2 Keeping as many productive animals in the herd as possible through slaughter. 3 Increasing the herd quality through selection.Renhjorden bör optimeras så att den fungerar som en "skördeapparat" for bete och lämnar största möjliga bidrag till försörjningen för dem som lever av renskötsel. Det finns minst tre sätt att optimera renhjorden, nämligen (1 anpassning av djurantalet till betesresurserna så att djurens kondition och därmed produktiviteten kan bibehållas på hög nivå, (2 utforma renhjordens struktur med hjalp av slaktuttaget så att den innehåller så stor andel produktiva djur som möjligt, och (3 förbättra djurmaterialets produktionsmässiga kvalitet genom urval baserat på registrerad produktion. Betesanpassningen är den mest grundläggande åtgärden och ger den snabbaste effekten. Även hjordstrukturering är en åtgärd som ger relativt snabb effekt och som dessutom kan beslutas och utforas av den enskilde djuraägaren utan att störa den kollektiva renskötseln. Urval är en åtgärd som ger effekt först på längre sikt och därför kräver en konsekvent insats under en längre tid.
Numbers Defy the Law of Large Numbers
Falk, Ruma; Lann, Avital Lavie
2015-01-01
As the number of independent tosses of a fair coin grows, the rates of heads and tails tend to equality. This is misinterpreted by many students as being true also for the absolute numbers of the two outcomes, which, conversely, depart unboundedly from each other in the process. Eradicating that misconception, as by coin-tossing experiments,…
Parameterizing by the Number of Numbers
Fellows, Michael R; Rosamond, Frances A
2010-01-01
The usefulness of parameterized algorithmics has often depended on what Niedermeier has called, "the art of problem parameterization". In this paper we introduce and explore a novel but general form of parameterization: the number of numbers. Several classic numerical problems, such as Subset Sum, Partition, 3-Partition, Numerical 3-Dimensional Matching, and Numerical Matching with Target Sums, have multisets of integers as input. We initiate the study of parameterizing these problems by the number of distinct integers in the input. We rely on an FPT result for ILPF to show that all the above-mentioned problems are fixed-parameter tractable when parameterized in this way. In various applied settings, problem inputs often consist in part of multisets of integers or multisets of weighted objects (such as edges in a graph, or jobs to be scheduled). Such number-of-numbers parameterized problems often reduce to subproblems about transition systems of various kinds, parameterized by the size of the system descripti...
DEFF Research Database (Denmark)
Clasen, Julie; Mellerup, Anders; Olsen, John Elmerdahl
2016-01-01
The primary objective of this study was to determine the minimum number of individual fecal samples to pool together in order to obtain a representative sample for herd level quantification of antimicrobial resistance (AMR) genes in a Danish pig herd, using a novel high-throughput qPCR assay....... The secondary objective was to assess the agreement between different methods of sample pooling. Quantification of AMR was achieved using a high-throughput qPCR method to quantify the levels of seven AMR genes (ermB, ermF, sulI, sulII, tet(M), tet(O) and tet(W)). A large variation in the levels of AMR genes...
Institute of Scientific and Technical Information of China (English)
张士强
2012-01-01
The injection molding gate had important influence on the molding quality of plastic intake manifold. To shorten the development cycle, reduce the cost and improve the product quality, the location and number of different gates for intake manifold injection molding were simulated and analyzed with the Moldflow software. The locations of potential bubble and welding mark were forecast, and finally the location and number of injection molding gates were determined, which avoided the complex process of the mould testing and repairing. The analysis results show that four point gates of regular geometric distribution is the best choice. The experiments prove that the quality of trial product sample is better with the improved mould.%为了研究注塑模具浇口对发动机塑料进气歧管成型质量的影响,缩短进气歧管开发周期,降低成本,提高产品质量,利用Moldflow软件对塑料进气歧管注塑成型中浇口位置及数量进行流动模拟分析,预测可能存在的气泡位置和熔接痕位置,通过比较分析来确定制品注塑成型中的浇口位置和数量.分析结果表明,采用呈规则几何形状分布的4个点浇口为最佳选择.试验证明:按照模拟结果制造模具,试制的产品样件质量较好.
Institute of Scientific and Technical Information of China (English)
孙丽君
2013-01-01
Wartime ammo transportation route selection and evaluation is a process of multi-objective decision. In order to select and evaluate the ammo transportation route systematic and scientifically,a target system was structured compounded by haulage time,safety and guarantee price. The TOPSIS evaluation methodology based on triangular fuzzy number was used to evaluate the selection of ammo transportation route. Result shows that,evaluate method of triangular fuzzy number based TOPSIS is suitable for wartime ammo transportation route selection and can provide scientific basis of army ammo guarantee.%战时弹药运输的路径选择评价是一个多属性决策过程，为了对弹药运输的路径进行系统科学地评价和选择，构建由运输时间、安全性和保障代价3个评价指标组成的指标体系，运用三角模糊数的TOPSIS评价方法，对弹药运输线路的选择进行了实证分析评价。分析结果表明：三角模糊数的TOPSIS评价方法对战时弹药运输的路径选择有较好的适用性，能有效为部队的弹药保障工作提供科学依据。
Laird, Philip
1992-01-01
We distinguish static and dynamic optimization of programs: whereas static optimization modifies a program before runtime and is based only on its syntactical structure, dynamic optimization is based on the statistical properties of the input source and examples of program execution. Explanation-based generalization is a commonly used dynamic optimization method, but its effectiveness as a speedup-learning method is limited, in part because it fails to separate the learning process from the program transformation process. This paper describes a dynamic optimization technique called a learn-optimize cycle that first uses a learning element to uncover predictable patterns in the program execution and then uses an optimization algorithm to map these patterns into beneficial transformations. The technique has been used successfully for dynamic optimization of pure Prolog.
Schneider, Johannes J
2007-01-01
This book addresses stochastic optimization procedures in a broad manner. The first part offers an overview of relevant optimization philosophies; the second deals with benchmark problems in depth, by applying a selection of optimization procedures. Written primarily with scientists and students from the physical and engineering sciences in mind, this book addresses a larger community of all who wish to learn about stochastic optimization techniques and how to use them.
2015-07-06
consider a probabilistically-constrained portfolio optimization problem [16] to determine a minimum cost distribution of a unit investment among n assets...present a branching technique (Section 5). Through computational experiments on the probabilistic portfolio optimization problem (3) and an optimal ...at one. 15 DISTRIBUTION A: Distribution approved for public release. 6.2 Probabilistic Portfolio Optimization The first class of instances we test
OPTIMAL DELAUNAY TRIANGULATIONS
Institute of Scientific and Technical Information of China (English)
Long Chen; Jin-chao Xu
2004-01-01
The Delaunay triangulation, in both classic and more generalized sense, is studied in this paper for minimizing the linear interpolation error (measure in Lp-norm) for a given function. The classic Delaunay triangulation can then be characterized as an optimal triangulation that minimizes the interpolation error for the isotropic function ‖x‖2 among all the triangulations with a given set of vertices. For a more general function, a functiondependent Delaunay triangulation is then defined to be an optimal triangulation that minimizes the interpolation error for this .function and its construction can be obtained by a simple lifting and projection procedure.The optimal Delaunay triangulation is the one that minimizes the interpolation error among all triangulations with the same number of vertices, i.e. the distribution of vertices are optimized in order to minimize the interpolation error. Such a function-dependent optimal Delaunay triangulation is proved to exist for any given convex continuous function.On an optimal Delaunay triangulation associated with f, it is proved that ▽f at the interior vertices can be exactly recovered by the function values on its neighboring vertices.Since the optimal Delaunay triangulation is difficult to obtain in practice, the concept of nearly optimal triangulation is introduced and two sufficient conditions are presented for a triangulation to be nearly optimal.
Number words and number symbols a cultural history of numbers
Menninger, Karl
1992-01-01
Classic study discusses number sequence and language and explores written numerals and computations in many cultures. "The historian of mathematics will find much to interest him here both in the contents and viewpoint, while the casual reader is likely to be intrigued by the author's superior narrative ability.
On the number of special numbers
Indian Academy of Sciences (India)
KEVSER AKTAS; M RAM MURTY
2017-06-01
For lack of a better word, a number is called special if it has mutually distinct exponents in its canonical prime factorizaton for all exponents. Let $V (x)$ be the number of special numbers $\\leq x$. We will prove that there is a constant $c$ > 1 such that $V (x) \\sim \\frac{cx}{log x}$. We will make some remarks on determining the error term at the end. Using the explicit abc conjecture, we will study the existence of 23 consecutive special integers.
Hybrid Batch Bayesian Optimization
Azimi, Javad; Fern, Xiaoli
2012-01-01
Bayesian Optimization aims at optimizing an unknown non-convex/concave function that is costly to evaluate. We are interested in application scenarios where concurrent function evaluations are possible. Under such a setting, BO could choose to either sequentially evaluate the function, one input at a time and wait for the output of the function before making the next selection, or evaluate the function at a batch of multiple inputs at once. These two different settings are commonly referred to as the sequential and batch settings of Bayesian Optimization. In general, the sequential setting leads to better optimization performance as each function evaluation is selected with more information, whereas the batch setting has an advantage in terms of the total experimental time (the number of iterations). In this work, our goal is to combine the strength of both settings. Specifically, we systematically analyze Bayesian optimization using Gaussian process as the posterior estimator and provide a hybrid algorithm t...
SAGD optimization under uncertainty
Energy Technology Data Exchange (ETDEWEB)
Gossuin, J.; Naccache, P. [Schlumberger SIS, Abingdon (United Kingdom); Bailley, W.; Couet, B. [Schlumberger-Doll Research, Cambridge, MA, (United States)
2011-07-01
In the heavy oil industry, the steam assisted gravity drainage process is often used to enhance oil recovery but this is a costly method and ways to make it more efficient are needed. Multiple methods have been developed to optimize the SAGD process but none of them explicitly considered uncertainty. This paper presents an optimization method in the presence of reservoir uncertainty. This process was tested on an SAGD model where three equi-probable geological models are possible. Preparatory steps were first performed to identify key variables and the optimization model was then proposed. The method was shown to be successful in handling a significant number of uncertainties, optimizing the SAGD process and preventing premature steam channels that can choke production. The optimization method presented herein was successfully applied to an SAGD process and was shown to provide better strategies than sensitivity analysis while handling more complex problems.
Smith, David Eugene; Ginsburg, Jekuthiel
Counting, naming numbers, numerals, computation, and fractions are the topics covered in this pamphlet. Number lore and interesting number properties are noted; the derivation of some arithmetic terms is briefly discussed. (DT)
Koninck, Jean-Marie De
2009-01-01
Who would have thought that listing the positive integers along with their most remarkable properties could end up being such an engaging and stimulating adventure? The author uses this approach to explore elementary and advanced topics in classical number theory. A large variety of numbers are contemplated: Fermat numbers, Mersenne primes, powerful numbers, sublime numbers, Wieferich primes, insolite numbers, Sastry numbers, voracious numbers, to name only a few. The author also presents short proofs of miscellaneous results and constantly challenges the reader with a variety of old and new n
Optimal Strategy in Basketball
Skinner, Brian
2015-01-01
This book chapter reviews some of the major principles associated with optimal strategy in basketball. In particular, we consider the principles of allocative efficiency (optimal allocation of shots between offensive options), dynamic efficiency (optimal shot selection in the face of pressure from the shot clock), and the risk/reward tradeoff (strategic manipulation of outcome variance). For each principle, we provide a simple example of a strategic problem and show how it can be described analytically. We then review general analytical results and provide an overview of existing statistical studies. A number of open challenges in basketball analysis are highlighted.
High Rayleigh number convection numerical experiments
Verzicco, Roberto
2002-03-01
temperature variance dissipations. The achieved results seem to support the idea that the observed transitional behaviors have to be attributed to the change in the topology of the mean flow rather than to a transition from a laminar to a turbulent state of the viscous boundary layers. Other issues accomplished by the simulation concern the study of the scaling properties of the turbulent quantities and length scales in terms of Ra. Finally, further details on the turbulence dynamics are obtained by the analysis of the power spectra and low order structure functions of both the temperature and the velocity components, computed from the numerical probes both within the bulk region and close to the walls. References Roche, PE; Castaing, B; Chabaud, B; Hebral, B. ``Observation of the 1/2 power law in Rayleigh-Benard convection'' Phys. Rev. E, 2001, 6304(4), p. 5303. Niemela, J.J.; Skrbek, L.; Sreenivasan, K.R. and Donnelly, R.J. ``Turbulent convection at very high Rayleigh numbers'' Nature, 405, 243-253 (11 May 2000). Verzicco, R. and Camussi, R. ``Prandtl number effects in convective turbulence'' J. of Fluid Mech., 383, (1999), 55-73.
Vazzana, Anthony; Garth, David
2007-01-01
One of the oldest branches of mathematics, number theory is a vast field devoted to studying the properties of whole numbers. Offering a flexible format for a one- or two-semester course, Introduction to Number Theory uses worked examples, numerous exercises, and two popular software packages to describe a diverse array of number theory topics.
Damian Slota; Roman Witula
2009-01-01
The scope of the paper is the definition and discussion of the polynomial generalizations of the {sc Fibonacci} numbers called here $delta$-{sc Fibonacci} numbers. Many special identities and interesting relations for these new numbers are presented. Also, different connections between $delta$-{sc Fibonacci} numbers and {sc Fibonacci} and {sc Lucas} numbersare proven in this paper.
Wilkie, James E. B.; Bodenhausen, Galen V.
2012-01-01
We examined the possibility that nonsocial, highly generic concepts are gendered. Specifically, we investigated the gender connotations of Arabic numerals. Across several experiments, we show that the number 1 and other odd numbers are associated with masculinity, whereas the number 2 and other even numbers are associated with femininity, in ways…
Wilkie, James E. B.; Bodenhausen, Galen V.
2012-01-01
We examined the possibility that nonsocial, highly generic concepts are gendered. Specifically, we investigated the gender connotations of Arabic numerals. Across several experiments, we show that the number 1 and other odd numbers are associated with masculinity, whereas the number 2 and other even numbers are associated with femininity, in ways…
Burkhart, Jerry
2009-01-01
Prime numbers are often described as the "building blocks" of natural numbers. This article shows how the author and his students took this idea literally by using prime factorizations to build numbers with blocks. In this activity, students explore many concepts of number theory, including the relationship between greatest common factors and…
Tan, Shanguang
2007-01-01
A new kind of numbers called Hyper Space Complex Numbers and its algebras are defined and proved. It is with good properties as the classic Complex Numbers, such as expressed in coordinates, triangular and exponent forms and following the associative and commutative laws of addition and multiplication. So the classic Complex Number is developed from in complex plane with two dimensions to in complex space with N dimensions and the number system is enlarged also.
Rips, Lance J; Thompson, Samantha
2014-03-01
Number systems-such as the natural numbers, integers, rationals, reals, or complex numbers-play a foundational role in mathematics, but these systems can present difficulties for students. In the studies reported here, we probed the boundaries of people's concept of a number system by asking them whether "number lines" of varying shapes qualify as possible number systems. In Experiment 1, participants rated each of a set of number lines as a possible number system, where the number lines differed in their structures (a single straight line, a step-shaped line, a double line, or two branching structures) and in their boundedness (unbounded, bounded below, bounded above, bounded above and below, or circular). Participants also rated each of a group of mathematical properties (e.g., associativity) for its importance to number systems. Relational properties, such as associativity, predicted whether participants believed that particular forms were number systems, as did the forms' ability to support arithmetic operations, such as addition. In Experiment 2, we asked participants to produce properties that were important for number systems. Relational, operation, and use-based properties from this set again predicted ratings of whether the number lines were possible number systems. In Experiment 3, we found similar results when the number lines indicated the positions of the individual numbers. The results suggest that people believe that number systems should be well-behaved with respect to basic arithmetic operations, and that they reject systems for which these operations produce ambiguous answers. People care much less about whether the systems have particular numbers (e.g., 0) or sets of numbers (e.g., the positives).
Transport numbers in transdermal iontophoresis.
Mudry, Blaise; Guy, Richard H; Delgado-Charro, M Begoña
2006-04-15
Parameters determining ionic transport numbers in transdermal iontophoresis have been characterized. The transport number of an ion (its ability to carry charge) is key to its iontophoretic delivery or extraction across the skin. Using small inorganic ions, the roles of molar fraction and mobility of the co- and counterions present have been demonstrated. A direct, constant current was applied across mammalian skin in vitro. Cations were anodally delivered from either simple M(+)Cl(-) solutions (single-ion case, M(+) = sodium, lithium, ammonium, potassium), or binary and quaternary mixtures thereof. Transport numbers were deduced from ion fluxes. In the single-ion case, maximum cationic fluxes directly related to the corresponding ionic aqueous mobilities were found. Addition of co-ions decreased the transport numbers of all cations relative to the single-ion case, the degree of effect depending upon the molar fraction and mobility of the species involved. With chloride as the principal counterion competing to carry current across the skin (the in vivo situation), a maximum limit on the single or collective cation transport number was 0.6-0.8. Overall, these results demonstrate how current flowing across the skin during transdermal iontophoresis is distributed between competing ions, and establish simple rules with which to optimize transdermal iontophoretic transport.
Jarvis, Frazer
2014-01-01
The technical difficulties of algebraic number theory often make this subject appear difficult to beginners. This undergraduate textbook provides a welcome solution to these problems as it provides an approachable and thorough introduction to the topic. Algebraic Number Theory takes the reader from unique factorisation in the integers through to the modern-day number field sieve. The first few chapters consider the importance of arithmetic in fields larger than the rational numbers. Whilst some results generalise well, the unique factorisation of the integers in these more general number fields often fail. Algebraic number theory aims to overcome this problem. Most examples are taken from quadratic fields, for which calculations are easy to perform. The middle section considers more general theory and results for number fields, and the book concludes with some topics which are more likely to be suitable for advanced students, namely, the analytic class number formula and the number field sieve. This is the fi...
Ruszczynski, Andrzej
2011-01-01
Optimization is one of the most important areas of modern applied mathematics, with applications in fields from engineering and economics to finance, statistics, management science, and medicine. While many books have addressed its various aspects, Nonlinear Optimization is the first comprehensive treatment that will allow graduate students and researchers to understand its modern ideas, principles, and methods within a reasonable time, but without sacrificing mathematical precision. Andrzej Ruszczynski, a leading expert in the optimization of nonlinear stochastic systems, integrates t
All square chiliagonal numbers
Aṣiru, Muniru A.
2016-10-01
A square chiliagonal number is a number which is simultaneously a chiliagonal number and a perfect square (just as the well-known square triangular number is both triangular and square). In this work, we determine which of the chiliagonal numbers are perfect squares and provide the indices of the corresponding chiliagonal numbers and square numbers. The study revealed that the determination of square chiliagonal numbers naturally leads to a generalized Pell equation x2 - Dy2 = N with D = 1996 and N = 9962, and has six fundamental solutions out of which only three yielded integer values for use as indices of chiliagonal numbers. The crossing/independent recurrence relations satisfied by each class of indices of the corresponding chiliagonal numbers and square numbers are obtained. Finally, the generating functions serve as a clothesline to hang up the indices of the corresponding chiliagonal numbers and square numbers for easy display and this was used to obtain the first few sequence of square chiliagonal numbers.
Directory of Open Access Journals (Sweden)
James W Vaupel
Full Text Available Semelparous organisms have a simple life cycle characterized by immediate death after reproduction. We assume that semelparous life histories can be separated into a juvenile non-reproductive period followed by an adult period during which reproduction is possible. We derive formulae for the optimal age and size at reproduction and for the optimal size of the offspring (e.g., seeds. Our main contribution is to determine the conditions under which the optimal size of the offspring does not depend on the optimal size at reproduction and vice versa.
King, Andrew
2008-01-01
Remember when an optimized website was one that merely didn't take all day to appear? Times have changed. Today, website optimization can spell the difference between enterprise success and failure, and it takes a lot more know-how to achieve success. This book is a comprehensive guide to the tips, techniques, secrets, standards, and methods of website optimization. From increasing site traffic to maximizing leads, from revving up responsiveness to increasing navigability, from prospect retention to closing more sales, the world of 21st century website optimization is explored, exemplified a
DEFF Research Database (Denmark)
Elvik, Rune; Bjørnskau, Torkel
2017-01-01
Highlights •26 studies of the safety-in-numbers effect are reviewed. •The existence of a safety-in-numbers effect is confirmed. •Results are consistent. •Causes of the safety-in-numbers effect are incompletely known.......Highlights •26 studies of the safety-in-numbers effect are reviewed. •The existence of a safety-in-numbers effect is confirmed. •Results are consistent. •Causes of the safety-in-numbers effect are incompletely known....
Chen, Shi-Chao
2011-01-01
A natural number $n$ is called {\\it multiperfect} or {\\it$k$-perfect} for integer $k\\ge2$ if $\\sigma(n)=kn$, where $\\sigma(n)$ is the sum of the positive divisors of $n$. In this paper, we establish the structure theorem of odd multiperfect numbers analogous as Euler's theorem on odd perfect numbers. We prove the divisibility of the Euler part of odd multiperfect numbers and characterize the forms of odd perfect numbers $n=\\pi^\\alpha M^2$ such that $\\pi\\equiv\\alpha(\\text{mod}8)$. We also present some examples to show the nonexistence of odd perfect numbers as applications.
Temperature variance profiles of turbulent thermal convection at high Rayleigh numbers
He, Xiaozhou; Bodenschatz, Eberhard; Ahlers, Guenter
2016-11-01
We present measurements of the Nusselt number Nu , and of the temperature variance σ2 as a function of vertical position z, in turbulent Rayleigh-Bénard convection of two cylindrical samples with aspect ratios (diameter D/height L) Γ = 0 . 50 and 0 . 33 . Both samples had D = 1 . 12 m but different L. We used compressed SF6 gas at pressures up to 19 bars as the fluid. The measurements covered the Rayleigh-number range 1013 < Ra < 5 ×1015 at a Prandtl number Pr = 0 . 80 . Near the side wall we found that σ2 is independent of Ra when plotted as a function of z / λ where λ ≡ L / (2 Nu) is a thermal boundary-layer thickness. The profiles σ2 (z / λ) for the two Γ values overlapped and followed a logarithmic function for 20 z / λ 120 . With the observed "-1"-scaling of the temperature power spectra and on the basis of the Perry-Townsend similarity hypothesis, we derived a fitting function σ2 =p1 ln (z / λ) +p2 +p3(z / λ) - 0 . 5 which describes the σ2 data up to z / λ = 1500 . Supported by the Max Planck Society, the Volkswagenstiftung, the DFD Sonderforschungsbereich SFB963, and NSF Grant DMR11-58514.
Directory of Open Access Journals (Sweden)
S. Abdul Gaffar
2015-01-01
Full Text Available Magnetic polymers are finding increasing applications in diverse fields of chemical and mechanical engineering. In this paper, we investigate the nonlinear steady boundary layer flow and heat transfer of such fluids from a nonisothermal wedge. The incompressible Eyring-Powell non-Newtonian fluid model is employed and a magnetohydrodynamic body force is included in the simulation. The transformed conservation equations are solved numerically subject to physically appropriate boundary conditions using a second-order accurate implicit finite difference Keller Box technique. The numerical code is validated with previous studies. The influence of a number of emerging nondimensional parameters, namely, the Eyring-Powell rheological fluid parameter (ε, local non-Newtonian parameter based on length scale (δ, Prandtl number (Pr, Biot number (γ, pressure gradient parameter (m, magnetic parameter (M, mixed convection parameter (λ, and dimensionless tangential coordinate (ξ, on velocity and temperature evolution in the boundary layer regime is examined in detail. Furthermore, the effects of these parameters on surface heat transfer rate and local skin friction are also investigated.
Discrete unified gas kinetic scheme for all Knudsen number flows: II. Compressible case
Guo, Zhaoli; Xu, Kun
2014-01-01
This paper is a continuation of our earlier work [Z.L. Guo {\\it et al.}, Phys. Rev. E {\\bf 88}, 033305 (2013)] where a multiscale numerical scheme based on kinetic model was developed for low speed isothermal flows with arbitrary Knudsen numbers. In this work, a discrete unified gas-kinetic scheme (DUGKS) for compressible flows with the consideration of heat transfer and shock discontinuity is developed based on the Shakhov model with an adjustable Prandtl number. The method is an explicit finite-volume scheme where the transport and collision processes are coupled in the evaluation of the fluxes at cell interfaces, so that the nice asymptotic preserving (AP) property is retained, such that the time step is limited only by the CFL number, the distribution function at cell interface recovers to the Chapman-Enskog one in the continuum limit while reduces to that of free-transport for free-molecular flow, and the time and spatial accuracy is of second-order accuracy in smooth region. These features make the DUGK...
Matsumoto, Kohji
2002-01-01
The book includes several survey articles on prime numbers, divisor problems, and Diophantine equations, as well as research papers on various aspects of analytic number theory such as additive problems, Diophantine approximations and the theory of zeta and L-function Audience Researchers and graduate students interested in recent development of number theory
Xu, Junyan
2012-01-01
We point out that the recursive formula that appears in Erickson's presentation "Fusible Numbers" is incorrect, and pose an alternate conjecture about the structure of fusible numbers. Although we are unable to solve the conjecture, we succeed in establishing some basic properties of fusible numbers. We suggest some possible approaches to the conjecture, and list further problems in the final chapter.
Landy, David; Silbert, Noah; Goldin, Aleah
2013-01-01
Despite their importance in public discourse, numbers in the range of 1 million to 1 trillion are notoriously difficult to understand. We examine magnitude estimation by adult Americans when placing large numbers on a number line and when qualitatively evaluating descriptions of imaginary geopolitical scenarios. Prior theoretical conceptions…
de Mestre, Neville
2008-01-01
Prime numbers are important as the building blocks for the set of all natural numbers, because prime factorisation is an important and useful property of all natural numbers. Students can discover them by using the method known as the Sieve of Eratosthenes, named after the Greek geographer and astronomer who lived from c. 276-194 BC. Eratosthenes…
Dynamic stochastic optimization
Ermoliev, Yuri; Pflug, Georg
2004-01-01
Uncertainties and changes are pervasive characteristics of modern systems involving interactions between humans, economics, nature and technology. These systems are often too complex to allow for precise evaluations and, as a result, the lack of proper management (control) may create significant risks. In order to develop robust strategies we need approaches which explic itly deal with uncertainties, risks and changing conditions. One rather general approach is to characterize (explicitly or implicitly) uncertainties by objec tive or subjective probabilities (measures of confidence or belief). This leads us to stochastic optimization problems which can rarely be solved by using the standard deterministic optimization and optimal control methods. In the stochastic optimization the accent is on problems with a large number of deci sion and random variables, and consequently the focus ofattention is directed to efficient solution procedures rather than to (analytical) closed-form solu tions. Objective an...
Bolt Thread Stress Optimization
DEFF Research Database (Denmark)
Pedersen, Niels Leergaard
2012-01-01
Designs of threaded fasteners are controlled by different standards, and the number of different thread definitions is large. The most commonly used thread is probably the metric ISO thread, and this design is therefore used in this paper. Thread root design controls the stress concentration factor...... of threads and therefore indirectly the bolt fatigue life. The root shape is circular, and from shape optimization for minimum stress concentration it is well known that the circular shape is seldom optimal. An axisymmetric Finite Element (FE) formulation is used to analyze the bolted connection, and a study...... is performed to establish the need for contact modeling with regard to finding the correct stress concentration factor. Optimization is performed with a simple parameterization with two design variables. Stress reduction of up to 9% is found in the optimization process, and some similarities are found...
Bolt Thread Stress Optimization
DEFF Research Database (Denmark)
Pedersen, Niels Leergaard
2012-01-01
Designs of threaded fasteners are controlled by different standards, and the number of different thread definitions is large. The most commonly used thread is probably the metric ISO thread, and this design is therefore used in this paper. Thread root design controls the stress concentration factor...... of threads and therefore indirectly the bolt fatigue life. The root shape is circular, and from shape optimization for minimum stress concentration it is well known that the circular shape is seldom optimal. An axisymmetric Finite Element (FE) formulation is used to analyze the bolted connection, and a study...... is performed to establish the need for contact modeling with regard to finding the correct stress concentration factor. Optimization is performed with a simple parameterization with two design variables. Stress reduction of up to 9% is found in the optimization process, and some similarities are found...
DEFF Research Database (Denmark)
Birkholm, Klavs
2010-01-01
En undersøgelse af anvendelsen af medicin til optimering af koncentration, hukommelse og følelsestonus. Efterfulgt af etiske overvejelser og anbefalinger til det politiske system......En undersøgelse af anvendelsen af medicin til optimering af koncentration, hukommelse og følelsestonus. Efterfulgt af etiske overvejelser og anbefalinger til det politiske system...
DEFF Research Database (Denmark)
A. Kristensen, Anders Schmidt; Damkilde, Lars
2007-01-01
. A way to solve the initial design problem namely finding a form can be solved by so-called topology optimization. The idea is to define a design region and an amount of material. The loads and supports are also fidefined, and the algorithm finds the optimal material distribution. The objective function...... dictates the form, and the designer can choose e.g. maximum stiness, maximum allowable stresses or maximum lowest eigenfrequency. The result of the topology optimization is a relatively coarse map of material layout. This design can be transferred to a CAD system and given the necessary geometrically...... refinements, and then remeshed and reanalysed in other to secure that the design requirements are met correctly. The output of standard topology optimization has seldom well-defined, sharp contours leaving the designer with a tedious interpretation, which often results in less optimal structures. In the paper...
Carver, Charles S.; Scheier, Michael F.
2014-01-01
Optimism is a cognitive construct (expectancies regarding future outcomes) that also relates to motivation: optimistic people exert effort, whereas pessimistic people disengage from effort. Study of optimism began largely in health contexts, finding positive associations between optimism and markers of better psychological and physical health. Physical health effects likely occur through differences in both health-promoting behaviors and physiological concomitants of coping. Recently, the scientific study of optimism has extended to the realm of social relations: new evidence indicates that optimists have better social connections, partly because they work harder at them. In this review, we examine the myriad ways this trait can benefit an individual, and our current understanding of the biological basis of optimism. PMID:24630971
Niederreiter, Harald
2015-01-01
This textbook effectively builds a bridge from basic number theory to recent advances in applied number theory. It presents the first unified account of the four major areas of application where number theory plays a fundamental role, namely cryptography, coding theory, quasi-Monte Carlo methods, and pseudorandom number generation, allowing the authors to delineate the manifold links and interrelations between these areas. Number theory, which Carl-Friedrich Gauss famously dubbed the queen of mathematics, has always been considered a very beautiful field of mathematics, producing lovely results and elegant proofs. While only very few real-life applications were known in the past, today number theory can be found in everyday life: in supermarket bar code scanners, in our cars’ GPS systems, in online banking, etc. Starting with a brief introductory course on number theory in Chapter 1, which makes the book more accessible for undergraduates, the authors describe the four main application areas in Chapters...
Optimality criteria: A basis for multidisciplinary design optimization
Venkayya, V. B.
1989-01-01
This paper presents a generalization of what is frequently referred to in the literature as the optimality criteria approach in structural optimization. This generalization includes a unified presentation of the optimality conditions, the Lagrangian multipliers, and the resizing and scaling algorithms in terms of the sensitivity derivatives of the constraint and objective functions. The by-product of this generalization is the derivation of a set of simple nondimensional parameters which provides significant insight into the behavior of the structure as well as the optimization algorithm. A number of important issues, such as, active and passive variables, constraints and three types of linking are discussed in the context of the present derivation of the optimality criteria approach. The formulation as presented in this paper brings multidisciplinary optimization within the purview of this extremely efficient optimality criteria approach.
DEFF Research Database (Denmark)
Jørgensen, Claus Bjørn; Suetens, Sigrid; Tyran, Jean-Robert
numbers based on recent drawings. While most players pick the same set of numbers week after week without regards of numbers drawn or anything else, we find that those who do change, act on average in the way predicted by the law of small numbers as formalized in recent behavioral theory. In particular......We investigate the “law of small numbers” using a unique panel data set on lotto gambling. Because we can track individual players over time, we can measure how they react to outcomes of recent lotto drawings. We can therefore test whether they behave as if they believe they can predict lotto......, on average they move away from numbers that have recently been drawn, as suggested by the “gambler’s fallacy”, and move toward numbers that are on streak, i.e. have been drawn several weeks in a row, consistent with the “hot hand fallacy”....
DEFF Research Database (Denmark)
Jørgensen, Claus Bjørn; Suetens, Sigrid; Tyran, Jean-Robert
We investigate the “law of small numbers” using a unique panel data set on lotto gambling. Because we can track individual players over time, we can measure how they react to outcomes of recent lotto drawings. We can therefore test whether they behave as if they believe they can predict lotto...... numbers based on recent drawings. While most players pick the same set of numbers week after week without regards of numbers drawn or anything else, we find that those who do change, act on average in the way predicted by the law of small numbers as formalized in recent behavioral theory. In particular......, on average they move away from numbers that have recently been drawn, as suggested by the “gambler’s fallacy”, and move toward numbers that are on streak, i.e. have been drawn several weeks in a row, consistent with the “hot hand fallacy”....
Cocos, Mihail
2011-01-01
In this paper we present a mathematical way of defining musical modes, we derive a formula for the total number of modes and define the musicality of a mode as the total number of harmonic chords whithin the mode. We also give an algorithm for the construction of a duet of melodic lines given a sequence of numbers and a mode. We attach the .mus files of the counterpoints obtained by using the sequence of primes and several musical modes.
Quantum Random Number Generators
Herrero-Collantes, Miguel; Garcia-Escartin, Juan Carlos
2016-01-01
Random numbers are a fundamental resource in science and engineering with important applications in simulation and cryptography. The inherent randomness at the core of quantum mechanics makes quantum systems a perfect source of entropy. Quantum random number generation is one of the most mature quantum technologies with many alternative generation methods. We discuss the different technologies in quantum random number generation from the early devices based on radioactive decay to the multipl...
1977-05-09
from one of the Moscow institutes. In childhood he played at hypnosis with his sister and hypnotized her. He studies In the 11th grade at night school...O R M I N G OR G. REPORT NUMBER 7. AUTHOR( s ) 8 C O N T R A C T OR GRANT NUMBER(e) Lev Kolodnyy 9. PERFORMING O R G A N I Z A T I O N NAME AND
Diamond, Harold G; Cheung, Man Ping
2016-01-01
"Generalized numbers" is a multiplicative structure introduced by A. Beurling to study how independent prime number theory is from the additivity of the natural numbers. The results and techniques of this theory apply to other systems having the character of prime numbers and integers; for example, it is used in the study of the prime number theorem (PNT) for ideals of algebraic number fields. Using both analytic and elementary methods, this book presents many old and new theorems, including several of the authors' results, and many examples of extremal behavior of g-number systems. Also, the authors give detailed accounts of the L^2 PNT theorem of J. P. Kahane and of the example created with H. L. Montgomery, showing that additive structure is needed for proving the Riemann hypothesis. Other interesting topics discussed are propositions "equivalent" to the PNT, the role of multiplicative convolution and Chebyshev's prime number formula for g-numbers, and how Beurling theory provides an interpretation of the ...
DEFF Research Database (Denmark)
Suetens, Sigrid; Galbo-Jørgensen, Claus B.; Tyran, Jean-Robert Karl
2016-01-01
as formalized in recent behavioral theory. In particular, players tend to bet less on numbers that have been drawn in the preceding week, as suggested by the ‘gambler’s fallacy’, and bet more on a number if it was frequently drawn in the recent past, consistent with the ‘hot-hand fallacy’.......We investigate the ‘law of small numbers’ using a data set on lotto gambling that allows us to measure players’ reactions to draws. While most players pick the same set of numbers week after week, we find that those who do change react on average as predicted by the law of small numbers...
Hirst, Keith
1994-01-01
Number and geometry are the foundations upon which mathematics has been built over some 3000 years. This book is concerned with the logical foundations of number systems from integers to complex numbers. The author has chosen to develop the ideas by illustrating the techniques used throughout mathematics rather than using a self-contained logical treatise. The idea of proof has been emphasised, as has the illustration of concepts from a graphical, numerical and algebraic point of view. Having laid the foundations of the number system, the author has then turned to the analysis of infinite proc
DEFF Research Database (Denmark)
Suetens, Sigrid; Galbo-Jørgensen, Claus B.; Tyran, Jean-Robert Karl
2016-01-01
We investigate the ‘law of small numbers’ using a data set on lotto gambling that allows us to measure players’ reactions to draws. While most players pick the same set of numbers week after week, we find that those who do change react on average as predicted by the law of small numbers...... as formalized in recent behavioral theory. In particular, players tend to bet less on numbers that have been drawn in the preceding week, as suggested by the ‘gambler’s fallacy’, and bet more on a number if it was frequently drawn in the recent past, consistent with the ‘hot-hand fallacy’....
Godefroy, Gilles
2004-01-01
Numbers are fascinating. The fascination begins in childhood, when we first learn to count. It continues as we learn arithmetic, algebra, geometry, and so on. Eventually, we learn that numbers not only help us to measure the world, but also to understand it and, to some extent, to control it. In The Adventure of Numbers, Gilles Godefroy follows the thread of our expanding understanding of numbers to lead us through the history of mathematics. His goal is to share the joy of discovering and understanding this great adventure of the mind. The development of mathematics has been punctuated by a n
Frajtova-Michalikova, Katarina; Spuchľakova, Erika; Misankova, Maria
2015-01-01
In this paper Portfolio Optimization techniques were used to determine the most favorable investment portfolio. In particular, stock indices of three companies, namely Microsoft Corporation, Christian Dior Fashion House and Shevron Corporation were evaluated. Using this data the amounts invested in each asset when a portfolio is chosen on the efficient frontier were calculated. In addition, the Portfolio with minimum variance, tangency portfolio and optimal Markowitz portfolio are presented.
Linkmann, Moritz; Berera, Arjun; Goldstraw, Erin E.
2017-01-01
This paper examines the behavior of the dimensionless dissipation rate Cɛ for stationary and nonstationary magnetohydrodynamic (MHD) turbulence in the presence of external forces. By combining with previous studies for freely decaying MHD turbulence, we obtain here both the most general model equation for Cɛ applicable to homogeneous MHD turbulence and a comprehensive numerical study of the Reynolds number dependence of the dimensionless total energy dissipation rate at unity magnetic Prandtl number. We carry out a series of medium to high resolution direct numerical simulations of mechanically forced stationary MHD turbulence in order to verify the predictions of the model equation for the stationary case. Furthermore, questions of nonuniversality are discussed in terms of the effect of external forces as well as the level of cross- and magnetic helicity. The measured values of the asymptote Cɛ ,∞ lie between 0.193 ≤Cɛ ,∞≤0.268 for free decay, where the value depends on the initial level of cross- and magnetic helicities. In the stationary case we measure Cɛ ,∞=0.223 .
Hyperquarks and generation number
Buchmann, Alfons J
2013-01-01
In a model in which quarks and leptons are built up from two spin 1/2 preons as fundamental entities, a new class of fermionic bound states (hyperquarks) arises. It turns out that these hyperquarks are necessary to fulfill the 't Hooft anomaly constraint, which then links the number of fermionic generations to the number of colors and hypercolors.
Multispecies quantum Hurwitz numbers
Harnad, J
2014-01-01
The construction of hypergeometric 2D Toda $\\tau$-functions as generating functions for quantum Hurwitz numbers is extended here to multispecies families. Both the enumerative geometrical significance of these multispecies quantum Hurwitz numbers as weighted enumerations of branched coverings of the Riemann sphere and their combinatorial significance in terms of weighted paths in the Cayley graph of $S_n$ are derived.
Onstad, Torgeir
1991-01-01
After a brief historical account of Leonardo Pisano Fibonacci, some basic results concerning the Fibonacci numbers are developed and proved, and entertaining examples are described. Connections are made between the Fibonacci numbers and the Golden Ratio, biological nature, and other combinatorics examples. (MDH)
DEFF Research Database (Denmark)
Levin, Bruce R; McCall, Ingrid C.; Perrot, Veronique
2017-01-01
We postulate that the inhibition of growth and low rates of mortality of bacteria exposed to ribosome-binding antibiotics deemed bacteriostatic can be attributed almost uniquely to these drugs reducing the number of ribosomes contributing to protein synthesis, i.e., the number of effective riboso...
Kolyada, Sergiy; Rybak, Oleksandr
2013-01-01
We introduce and study the Lyapunov numbers -- quantitative measures of the sensitivity of a dynamical system $(X,f)$ given by a compact metric space $X$ and a continuous map $f:X \\to X$. In particular, we prove that for a minimal topologically weakly mixing system all Lyapunov numbers are the same.
Kuipers, J; Vermaseren, J A M
2013-01-01
We describe the implementation of output code optimization in the open source computer algebra system FORM. This implementation is based on recently discovered techniques of Monte Carlo tree search to find efficient multivariate Horner schemes, in combination with other optimization algorithms, such as common subexpression elimination. For systems for which no specific knowledge is provided it performs significantly better than other methods we could compare with. Because the method has a number of free parameters, we also show some methods by which to tune them to different types of problems.
Rugani, Rosa; Sartori, Luisa
2016-01-01
Humans show a remarkable tendency to describe and think of numbers as being placed on a mental number line (MNL), with smaller numbers located on the left and larger ones on the right. Faster responses to small numbers are indeed performed on the left side of space, while responses to large numbers are facilitated on the right side of space (spatial-numerical association of response codes, SNARC effect). This phenomenon is considered the experimental demonstration of the MNL and has been extensively replicated throughout a variety of paradigms. Nevertheless, the majority of previous literature has mainly investigated this effect by means of response times and accuracy, whereas studies considering more subtle and automatic measures such as kinematic parameters are rare (e.g., in a reaching-to-grasp movement, the grip aperture is enlarged in responding to larger numbers than in responding to small numbers). In this brief review we suggest that numerical magnitude can also affect the what and how of action execution (i.e., temporal and spatial components of movement). This evidence could have large implications in the strongly debated issue concerning the effect of experience and culture on the orientation of MNL.
EXPERIMENTAL RETRIEVAL SYSTEMS STUDIES, REPORT NUMBER 3.
ANDERSON, RONALD R.; AND OTHERS
CONTENTS--(1) AN ASSOCIATIVITY TECHNIQUE FOR AUTOMATICALLY OPTIMIZING RETRIEVAL RESULTS BY RONALD R. ANDERSON. AN ASSOCIATIVE TECHNIQUE BY WHICH IT IS POSSIBLE TO AUTOMATICALLY EXPAND AND NARROW THE NUMBER OF DOCUMENTS RETRIEVED AND TO RETRIEVE DOCUMENTS RELATED TO A REQUEST EVEN THOUGH THEY MAY NOT BE INDEXED BY THE EXACT TERMS OF THE REQUEST IS…
Dudley, Underwood
2008-01-01
Ideal for a first course in number theory, this lively, engaging text requires only a familiarity with elementary algebra and the properties of real numbers. Author Underwood Dudley, who has written a series of popular mathematics books, maintains that the best way to learn mathematics is by solving problems. In keeping with this philosophy, the text includes nearly 1,000 exercises and problems-some computational and some classical, many original, and some with complete solutions. The opening chapters offer sound explanations of the basics of elementary number theory and develop the fundamenta
Kneusel, Ronald T
2015-01-01
This is a book about numbers and how those numbers are represented in and operated on by computers. It is crucial that developers understand this area because the numerical operations allowed by computers, and the limitations of those operations, especially in the area of floating point math, affect virtually everything people try to do with computers. This book aims to fill this gap by exploring, in sufficient but not overwhelming detail, just what it is that computers do with numbers. Divided into two parts, the first deals with standard representations of integers and floating point numb
Morrison, Greg
2010-01-01
We propose a simple real-valued generalization of the well known integer-valued Erdos number as a topological, non-metric measure of the `closeness' felt between two nodes in an undirected, weighted graph. These real-valued Erdos numbers are asymmetric and are able to distinguish between network topologies that standard distance metrics view as identical. We use this measure to study some simple analytically tractable networks, and show the utility of our measure to devise a ratings scheme based on the generalized Erdos number that we deploy on the data from the NetFlix prize, and find a significant improvement in our ratings prediction over a baseline.
Professor Stewart's incredible numbers
Stewart, Ian
2015-01-01
Ian Stewart explores the astonishing properties of numbers from 1 to10 to zero and infinity, including one figure that, if you wrote it out, would span the universe. He looks at every kind of number you can think of - real, imaginary, rational, irrational, positive and negative - along with several you might have thought you couldn't think of. He explains the insights of the ancient mathematicians, shows how numbers have evolved through the ages, and reveals the way numerical theory enables everyday life. Under Professor Stewart's guidance you will discover the mathematics of codes,
Sierpinski, Waclaw
1988-01-01
Since the publication of the first edition of this work, considerable progress has been made in many of the questions examined. This edition has been updated and enlarged, and the bibliography has been revised.The variety of topics covered here includes divisibility, diophantine equations, prime numbers (especially Mersenne and Fermat primes), the basic arithmetic functions, congruences, the quadratic reciprocity law, expansion of real numbers into decimal fractions, decomposition of integers into sums of powers, some other problems of the additive theory of numbers and the theory of Gaussian
Crossley, John N
1987-01-01
This book presents detailed studies of the development of three kinds of number. In the first part the development of the natural numbers from Stone-Age times right up to the present day is examined not only from the point of view of pure history but also taking into account archaeological, anthropological and linguistic evidence. The dramatic change caused by the introduction of logical theories of number in the 19th century is also treated and this part ends with a non-technical account of the very latest developments in the area of Gödel's theorem. The second part is concerned with the deve
Corry, Leo
2015-01-01
The world around us is saturated with numbers. They are a fundamental pillar of our modern society, and accepted and used with hardly a second thought. But how did this state of affairs come to be? In this book, Leo Corry tells the story behind the idea of number from the early days of the Pythagoreans, up until the turn of the twentieth century. He presents an overview of how numbers were handled and conceived in classical Greek mathematics, in the mathematics of Islam, in European mathematics of the middle ages and the Renaissance, during the scientific revolution, all the way through to the
LeVeque, William J
1996-01-01
This excellent textbook introduces the basics of number theory, incorporating the language of abstract algebra. A knowledge of such algebraic concepts as group, ring, field, and domain is not assumed, however; all terms are defined and examples are given - making the book self-contained in this respect.The author begins with an introductory chapter on number theory and its early history. Subsequent chapters deal with unique factorization and the GCD, quadratic residues, number-theoretic functions and the distribution of primes, sums of squares, quadratic equations and quadratic fields, diopha
Weiss, Edwin
1998-01-01
Careful organization and clear, detailed proofs characterize this methodical, self-contained exposition of basic results of classical algebraic number theory from a relatively modem point of view. This volume presents most of the number-theoretic prerequisites for a study of either class field theory (as formulated by Artin and Tate) or the contemporary treatment of analytical questions (as found, for example, in Tate's thesis).Although concerned exclusively with algebraic number fields, this treatment features axiomatic formulations with a considerable range of applications. Modem abstract te
Supersymmetric Displaced Number States
Directory of Open Access Journals (Sweden)
Fredy R. Zypman
2015-06-01
Full Text Available We introduce, generate and study a family of supersymmetric displaced number states (SDNS that can be considered generalized coherent states of the supersymmetric harmonic oscillator. The family is created from the seminal supersymmetric boson-fermion entangling annihilation operator introduced by Aragone and Zypman and later expanded by Kornbluth and Zypman. Using the momentum representation, the states are obtained analytically in compact form as displaced supersymmetric number states. We study their position-momentum uncertainties, and their bunchiness by classifying them according to their Mandel Q-parameter in phase space. We were also able to find closed form analytical representations in the space and number basis.
Cohn, Harvey
1980-01-01
""A very stimulating book ... in a class by itself."" - American Mathematical MonthlyAdvanced students, mathematicians and number theorists will welcome this stimulating treatment of advanced number theory, which approaches the complex topic of algebraic number theory from a historical standpoint, taking pains to show the reader how concepts, definitions and theories have evolved during the last two centuries. Moreover, the book abounds with numerical examples and more concrete, specific theorems than are found in most contemporary treatments of the subject.The book is divided into three parts
Pfyl, Frank A.; Presley, Leroy L.
1961-01-01
The local recovery factor was determined experimentally along the surface of a thin-walled 20 deg included angle cone for Mach numbers near 6.0 at stagnation temperatures between 1200 deg R and 2600 deg R. In addition, a similar cone configuration was tested at Mach numbers near 4.5 at stagnation temperatures of approximately 612 deg R. The local Reynolds number based on flow properties at the edge of the boundary layer ranged between 0.1 x 10(exp 4) and 3.5 x 10(exp 4) for tests at temperatures above 1200 deg R and between 6 x 10(exp 4) and 25 x 10(exp 4) for tests at temperatures near 612 deg R. The results indicated, generally, that the recovery factor can be predicted satisfactorily using the square root of the Prandtl number. No conclusion could be made as to the necessity of evaluating the Prandtl number at a reference temperature given by an empirical equation, as opposed to evaluating the Prandtl number at the wall temperature or static temperature of the gas at the cone surface. For the tests at temperatures above 1200 deg R (indicated herein as the tests conducted in the slip-flow region), two definite trends in the recovery data were observed - one of increasing recovery factor with decreasing stagnation pressure, which was associated with slip-flow effects and one of decreasing recovery factor with increasing temperature. The true cause of the latter trend could not be ascertained, but it was shown that this trend was not appreciably altered by the sources of error of the magnitude considered herein. The real-gas equations of state were used to determine accurately the local stream properties at the outer edge of the boundary layer of the cone. Included in the report, therefore, is a general solution for the conical flow of a real gas using the Beattie-Bridgeman equation of state. The largest effect of temperature was seen to be in the terms which were dependent upon the internal energy of the gas. The pressure and hence the pressure drag terms were
Schwartz, Richard Evan
2014-01-01
In the American Mathematical Society's first-ever book for kids (and kids at heart), mathematician and author Richard Evan Schwartz leads math lovers of all ages on an innovative and strikingly illustrated journey through the infinite number system. By means of engaging, imaginative visuals and endearing narration, Schwartz manages the monumental task of presenting the complex concept of Big Numbers in fresh and relatable ways. The book begins with small, easily observable numbers before building up to truly gigantic ones, like a nonillion, a tredecillion, a googol, and even ones too huge for names! Any person, regardless of age, can benefit from reading this book. Readers will find themselves returning to its pages for a very long time, perpetually learning from and growing with the narrative as their knowledge deepens. Really Big Numbers is a wonderful enrichment for any math education program and is enthusiastically recommended to every teacher, parent and grandparent, student, child, or other individual i...
DEFF Research Database (Denmark)
Wanscher, Jørgen Bundgaard; Sørensen, Majken Vildrik
2006-01-01
highly uniform multidimensional draws, which are highly relevant for todays traffic models. This paper shows among others combined shuffling and scrambling seems needless, that scrambling gives the lowest correlation and that there are detectable differences between random numbers, dependent...
Strawn, Candace A.
1998-01-01
Describes LOGO's turtle graphics capabilities based on a sixth-grade classroom's activities with negative numbers and Logo programming. A sidebar explains LOGO and offers suggestions to teachers for using LOGO effectively. (LRW)
Quantum random number generator
Pooser, Raphael C.
2016-05-10
A quantum random number generator (QRNG) and a photon generator for a QRNG are provided. The photon generator may be operated in a spontaneous mode below a lasing threshold to emit photons. Photons emitted from the photon generator may have at least one random characteristic, which may be monitored by the QRNG to generate a random number. In one embodiment, the photon generator may include a photon emitter and an amplifier coupled to the photon emitter. The amplifier may enable the photon generator to be used in the QRNG without introducing significant bias in the random number and may enable multiplexing of multiple random numbers. The amplifier may also desensitize the photon generator to fluctuations in power supplied thereto while operating in the spontaneous mode. In one embodiment, the photon emitter and amplifier may be a tapered diode amplifier.
Quantum random number generators
Herrero-Collantes, Miguel; Garcia-Escartin, Juan Carlos
2017-01-01
Random numbers are a fundamental resource in science and engineering with important applications in simulation and cryptography. The inherent randomness at the core of quantum mechanics makes quantum systems a perfect source of entropy. Quantum random number generation is one of the most mature quantum technologies with many alternative generation methods. This review discusses the different technologies in quantum random number generation from the early devices based on radioactive decay to the multiple ways to use the quantum states of light to gather entropy from a quantum origin. Randomness extraction and amplification and the notable possibility of generating trusted random numbers even with untrusted hardware using device-independent generation protocols are also discussed.
Solar Indices - Sunspot Numbers
National Oceanic and Atmospheric Administration, Department of Commerce — Collection includes a variety of indices related to solar activity contributed by a number of national and private solar observatories located worldwide. This...
Institute of Scientific and Technical Information of China (English)
陈欣欣; 于洪彦
2014-01-01
在心理学研究中，等级评定量表是研究数据的常用测量工具。然而，研究者们使用的等级评定量表的版式并不一致，尤其表现在使用的反应项的数目不同。关于最佳反应项数目的研究只局限于从被试的最终反应结果来进行分析，而没有从被试对量表的反应过程来进行分析。根据前人相关文献，设计6种反应项的量表，并通过眼动实验来测量被试的信息处理过程。通过对反应时、净默认反应方式、极端反应方式和选项比例变化的综合比较，我们得出最佳的量表反应项数目是5。%Rating scales are widely used measuring instruments in psychological researches.However, the formats of rat-ing scales are different in a great deal of researches, specifically differences in the number of response alternatives. Previous researches about what is the optimal number of response alternatives for a scale only focused on the analy-sis of participants'final response results, rather than on that of participants'information processing.According to the relevant previous literature, we used eye-tracking study to explore the issue by analyzing the information pro-cessing in six scales with different response alternatives.We compared the reaction times, net acquiescence re-sponse styles, extreme response styles and proportional changes in response alternatives of the six scales.Our re-sults suggested the optimal number is five.
Brown, Ezra; Brunson, Cornelius
2008-01-01
Fibonacci's forgotten number is the sexagesimal number 1;22,7,42,33,4,40, which he described in 1225 as an approximation to the real root of x[superscript 3] + 2x[superscript 2] + 10x - 20. In decimal notation, this is 1.36880810785...and it is correct to nine decimal digits. Fibonacci did not reveal his method. How did he do it? There is also a…
DEFF Research Database (Denmark)
Frandsen, P. E.; Jonasson, K.; Nielsen, Hans Bruun
1999-01-01
This lecture note is intended for use in the course 04212 Optimization and Data Fitting at the Technincal University of Denmark. It covers about 25% of the curriculum. Hopefully, the note may be useful also to interested persons not participating in that course. The aim of the note is to give...... an introduction to algorithms for unconstrained optimization. We present Conjugate Gradient, Damped Newton and Quasi Newton methods together with the relevant theoretical background. The reader is assumed to be familiar with algorithms for solving linear and nonlinear system of equations, at a level corresponding...
DEFF Research Database (Denmark)
Frandsen, P. E.; Jonasson, K.; Nielsen, Hans Bruun
1999-01-01
This lecture note is intended for use in the course 04212 Optimization and Data Fitting at the Technincal University of Denmark. It covers about 25% of the curriculum. Hopefully, the note may be useful also to interested persons not participating in that course. The aim of the note is to give...... an introduction to algorithms for unconstrained optimization. We present Conjugate Gradient, Damped Newton and Quasi Newton methods together with the relevant theoretical background. The reader is assumed to be familiar with algorithms for solving linear and nonlinear system of equations, at a level corresponding...
Directory of Open Access Journals (Sweden)
S. Abdul Gaffar
2015-12-01
Full Text Available In this article, we investigate the nonlinear steady boundary layer flow and heat transfer of an incompressible Tangent Hyperbolic fluid from a sphere. The transformed conservation equations are solved numerically subject to physically appropriate boundary conditions using implicit finite-difference Keller Box technique. The numerical code is validated with previous studies. The influence of a number of emerging non-dimensional parameters, namely Weissenberg number (We, power law index (n, Prandtl number (Pr, Biot number (γ and dimensionless tangential coordinate (ξ on velocity and temperature evolution in the boundary layer regime is examined in detail. Furthermore, the effects of these parameters on heat transfer rate and skin friction are also investigated. Validation with earlier Newtonian studies is presented and excellent correlation is achieved. It is found that the velocity, Skin friction and the Nusselt number (heat transfer rate are decreased with increasing Weissenberg number (We, whereas the temperature is increased. Increasing power law index (n increases the velocity and the Nusselt number (heat transfer rate but decreases the temperature and the Skin friction. An increase in the Biot number (γ is observed to increase velocity, temperature, local skin friction and Nusselt number. The study is relevant to chemical materials processing applications.
Energy Technology Data Exchange (ETDEWEB)
Nelson, R.N. (ed.)
1985-05-01
This publication lists all report number codes processed by the Office of Scientific and Technical Information. The report codes are substantially based on the American National Standards Institute, Standard Technical Report Number (STRN)-Format and Creation Z39.23-1983. The Standard Technical Report Number (STRN) provides one of the primary methods of identifying a specific technical report. The STRN consists of two parts: The report code and the sequential number. The report code identifies the issuing organization, a specific program, or a type of document. The sequential number, which is assigned in sequence by each report issuing entity, is not included in this publication. Part I of this compilation is alphabetized by report codes followed by issuing installations. Part II lists the issuing organization followed by the assigned report code(s). In both Parts I and II, the names of issuing organizations appear for the most part in the form used at the time the reports were issued. However, for some of the more prolific installations which have had name changes, all entries have been merged under the current name.
Wind Electrolysis: Hydrogen Cost Optimization
Energy Technology Data Exchange (ETDEWEB)
Saur, G.; Ramsden, T.
2011-05-01
This report describes a hydrogen production cost analysis of a collection of optimized central wind based water electrolysis production facilities. The basic modeled wind electrolysis facility includes a number of low temperature electrolyzers and a co-located wind farm encompassing a number of 3MW wind turbines that provide electricity for the electrolyzer units.
Optimal Preprocessing Of GPS Data
Wu, Sien-Chong; Melbourne, William G.
1994-01-01
Improved technique for preprocessing data from Global Positioning System receiver reduces processing time and number of data to be stored. Optimal in sense that it maintains strength of data. Also increases ability to resolve ambiguities in numbers of cycles of received GPS carrier signals.
Eckmann, B
2008-01-01
At the close of the 1980s, the independent contributions of Yann Brenier, Mike Cullen and John Mather launched a revolution in the venerable field of optimal transport founded by G Monge in the 18th century, which has made breathtaking forays into various other domains of mathematics ever since. The author presents a broad overview of this area.
DEFF Research Database (Denmark)
Bendsøe, Martin P.; Sigmund, Ole
2007-01-01
Taking as a starting point a design case for a compliant mechanism (a force inverter), the fundamental elements of topology optimization are described. The basis for the developments is a FEM format for this design problem and emphasis is given to the parameterization of design as a raster image...
Directory of Open Access Journals (Sweden)
Roberto da Costa Quinino
1999-08-01
Full Text Available Neste trabalho estudamos o número ótimo de classificações independentes por unidade produzida supondo que haja dois tipos de erro: o tipo I, no qual classifica-se um produto como não-conforme quando ele na realidade é conforme; e o tipo II, no qual classifica-se um produto como conforme quando na realidade é não-conforme. Desenvolvemos um modelo econômico para minimizar o custo médio total em função dos erros de classificação e do custo de cada classificação. Pela complexidade da função-objetivo associada ao modelo, utilizamos um procedimento exaustivo de busca juntamente com um limitante superior do valor ótimo. Todo o procedimento computacional teve uma implementação relativamente simples e está disponível como uma planilha eletrônica do Excel e um código do software estatístico Minitab.In this study we investigate the optimal number of independent classifications per unit produced when there are two types of classification errors: type I, where product is classified as conforming when it is not in reality, and type II, where product is classified as non-conforming when in reality it is conforming. We developed an economic model to minimize the total medium cost as a function of the classification errors and the cost of each classification. Due to the complexity of the objective function associated to the model, we used an exhaustive procedure with an upper bound of the optimal value. The procedure may be implemented easily and is available either as an Excel spreadsheet or as a macro of the statistical software Minitab.
Optimal Internet Media Selection
Peter J. Danaher; Janghyuk Lee; Laoucine Kerbache
2010-01-01
In this study we develop a method that optimally selects online media vehicles and determines the number of advertising impressions that should be purchased and then served from each chosen website. As a starting point, we apply Danaher's [Danaher, P. J. 2007. Modeling page views across multiple websites with an application to Internet reach and frequency prediction. (3) 422–437] multivariate negative binomial distribution (MNBD) for predicting online media exposure distributions. The MNBD is...
Alizée Dauvergne
2010-01-01
What makes the LHC the biggest particle accelerator in the world? Here are some of the numbers that characterise the LHC, and their equivalents in terms that are easier for us to imagine. Feature Number Equivalent Circumference ~ 27 km Distance covered by beam in 10 hours ~ 10 billion km a round trip to Neptune Number of times a single proton travels around the ring each second 11 245 Speed of protons first entering the LHC 299 732 500 m/s 99.9998 % of the speed of light Speed of protons when they collide 299 789 760 m/s 99.9999991 % of the speed of light Collision temperature ~ 1016 °C ove...
Chromosome numbers in Bromeliaceae
Directory of Open Access Journals (Sweden)
Cotias-de-Oliveira Ana Lúcia Pires
2000-01-01
Full Text Available The present study reports chromosome numbers of 17 species of Bromeliaceae, belonging to the genera Encholirium, Bromelia, Orthophytum, Hohenbergia, Billbergia, Neoglaziovia, Aechmea, Cryptanthus and Ananas. Most species present 2n = 50, however, Bromelia laciniosa, Orthophytum burle-marxii and O. maracasense are polyploids with 2n = 150, 2n = 100 and 2n = 150, respectively, while for Cryptanthus bahianus, 2n = 34 + 1-4B. B chromosomes were observed in Bromelia plumieri and Hohenbergia aff. utriculosa. The chromosome number of all species was determined for the first time, except for Billbergia chlorosticta and Cryptanthus bahianus. Our data supports the hypothesis of a basic number of x = 25 for the Bromeliaceae family and decreasing aneuploidy in the genus Cryptanthus.
Quantum random number generation
Ma, Xiongfeng; Yuan, Xiao; Cao, Zhu; Qi, Bing; Zhang, Zhen
2016-06-01
Quantum physics can be exploited to generate true random numbers, which have important roles in many applications, especially in cryptography. Genuine randomness from the measurement of a quantum system reveals the inherent nature of quantumness—coherence, an important feature that differentiates quantum mechanics from classical physics. The generation of genuine randomness is generally considered impossible with only classical means. On the basis of the degree of trustworthiness on devices, quantum random number generators (QRNGs) can be grouped into three categories. The first category, practical QRNG, is built on fully trusted and calibrated devices and typically can generate randomness at a high speed by properly modelling the devices. The second category is self-testing QRNG, in which verifiable randomness can be generated without trusting the actual implementation. The third category, semi-self-testing QRNG, is an intermediate category that provides a tradeoff between the trustworthiness on the device and the random number generation speed.
CONFUSION WITH TELEPHONE NUMBERS
Telecom Service
2002-01-01
he area code is now required for all telephone calls within Switzerland. Unfortunately this is causing some confusion. CERN has received complaints that incoming calls intended for CERN mobile phones are being directed to private subscribers. This is caused by mistakenly dialing the WRONG code (e.g. 022) in front of the mobile number. In order to avoid these problems, please inform your correspondents that the correct numbers are: 079 201 XXXX from Switzerland; 0041 79 201 XXXX from other countries. Telecom Service
CONFUSION WITH TELEPHONE NUMBERS
Telecom Service
2002-01-01
The area code is now required for all telephone calls within Switzerland. Unfortunately this is causing some confusion. CERN has received complaints that incoming calls intended for CERN mobile phones are being directed to private subscribers. This is caused by mistakenly dialing the WRONG code (e.g. 022) in front of the mobile number. In order to avoid these problems, please inform your correspondents that the correct numbers are: 079 201 XXXX from Switzerland; 0041 79 201 XXXX from other countries. Telecom Service
Earthquake number forecasts testing
Kagan, Yan Y.
2017-10-01
We study the distributions of earthquake numbers in two global earthquake catalogues: Global Centroid-Moment Tensor and Preliminary Determinations of Epicenters. The properties of these distributions are especially required to develop the number test for our forecasts of future seismic activity rate, tested by the Collaboratory for Study of Earthquake Predictability (CSEP). A common assumption, as used in the CSEP tests, is that the numbers are described by the Poisson distribution. It is clear, however, that the Poisson assumption for the earthquake number distribution is incorrect, especially for the catalogues with a lower magnitude threshold. In contrast to the one-parameter Poisson distribution so widely used to describe earthquake occurrences, the negative-binomial distribution (NBD) has two parameters. The second parameter can be used to characterize the clustering or overdispersion of a process. We also introduce and study a more complex three-parameter beta negative-binomial distribution. We investigate the dependence of parameters for both Poisson and NBD distributions on the catalogue magnitude threshold and on temporal subdivision of catalogue duration. First, we study whether the Poisson law can be statistically rejected for various catalogue subdivisions. We find that for most cases of interest, the Poisson distribution can be shown to be rejected statistically at a high significance level in favour of the NBD. Thereafter, we investigate whether these distributions fit the observed distributions of seismicity. For this purpose, we study upper statistical moments of earthquake numbers (skewness and kurtosis) and compare them to the theoretical values for both distributions. Empirical values for the skewness and the kurtosis increase for the smaller magnitude threshold and increase with even greater intensity for small temporal subdivision of catalogues. The Poisson distribution for large rate values approaches the Gaussian law, therefore its skewness
Samuel, Pierre
2008-01-01
Algebraic number theory introduces students not only to new algebraic notions but also to related concepts: groups, rings, fields, ideals, quotient rings and quotient fields, homomorphisms and isomorphisms, modules, and vector spaces. Author Pierre Samuel notes that students benefit from their studies of algebraic number theory by encountering many concepts fundamental to other branches of mathematics - algebraic geometry, in particular.This book assumes a knowledge of basic algebra but supplements its teachings with brief, clear explanations of integrality, algebraic extensions of fields, Gal
Iwaniec, Henryk
2004-01-01
Analytic Number Theory distinguishes itself by the variety of tools it uses to establish results, many of which belong to the mainstream of arithmetic. One of the main attractions of analytic number theory is the vast diversity of concepts and methods it includes. The main goal of the book is to show the scope of the theory, both in classical and modern directions, and to exhibit its wealth and prospects, its beautiful theorems and powerful techniques. The book is written with graduate students in mind, and the authors tried to balance between clarity, completeness, and generality. The exercis
2007-12-26
265–275. [7] H. G. Grundman, ‘ Sequences of consecutive Niven numbers’, Fibonacci Quart. 32 (1994), 174–175. [8] D. R. Heath-Brown and S. Konyagin...paper, we define a natural sequence in relation to q-Niven numbers. For a fixed but arbitrary k ∈ N and a base q ≥ 2, one may ask whether or not there...other words, ak is the smallest Niven number whose sum of the digits is a given positive integer k. We denote by ck the companion sequence ck = ak/k
Clette, Frédéric; Vaquero, José M; Cliver, Edward W
2014-01-01
Our knowledge of the long-term evolution of solar activity and of its primary modulation, the 11-year cycle, largely depends on a single direct observational record: the visual sunspot counts that retrace the last 4 centuries, since the invention of the astronomical telescope. Currently, this activity index is available in two main forms: the International Sunspot Number initiated by R. Wolf in 1849 and the Group Number constructed more recently by Hoyt and Schatten (1998a,b). Unfortunately, those two series do not match by various aspects, inducing confusions and contradictions when used in crucial contemporary studies of the solar dynamo or of the solar forcing on the Earth climate. Recently, new efforts have been undertaken to diagnose and correct flaws and biases affecting both sunspot series, in the framework of a series of dedicated Sunspot Number Workshops. Here, we present a global overview of our current understanding of the sunspot number calibration. While the early part of the sunspot record befor...
Babu, K S; Al-Binni, U; Banerjee, S; Baxter, D V; Berezhiani, Z; Bergevin, M; Bhattacharya, S; Brice, S; Brock, R; Burgess, T W; Castellanos, L; Chattopadhyay, S; Chen, M-C; Church, E; Coppola, C E; Cowen, D F; Cowsik, R; Crabtree, J A; Davoudiasl, H; Dermisek, R; Dolgov, A; Dutta, B; Dvali, G; Ferguson, P; Perez, P Fileviez; Gabriel, T; Gal, A; Gallmeier, F; Ganezer, K S; Gogoladze, I; Golubeva, E S; Graves, V B; Greene, G; Handler, T; Hartfiel, B; Hawari, A; Heilbronn, L; Hill, J; Jaffe, D; Johnson, C; Jung, C K; Kamyshkov, Y; Kerbikov, B; Kopeliovich, B Z; Kopeliovich, V B; Korsch, W; Lachenmaier, T; Langacker, P; Liu, C-Y; Marciano, W J; Mocko, M; Mohapatra, R N; Mokhov, N; Muhrer, G; Mumm, P; Nath, P; Obayashi, Y; Okun, L; Pati, J C; Pattie, R W; Phillips, D G; Quigg, C; Raaf, J L; Raby, S; Ramberg, E; Ray, A; Roy, A; Ruggles, A; Sarkar, U; Saunders, A; Serebrov, A; Shafi, Q; Shimizu, H; Shiozawa, M; Shrock, R; Sikdar, A K; Snow, W M; Soha, A; Spanier, S; Stavenga, G C; Striganov, S; Svoboda, R; Tang, Z; Tavartkiladze, Z; Townsend, L; Tulin, S; Vainshtein, A; Van Kooten, R; Wagner, C E M; Wang, Z; Wehring, B; Wilson, R J; Wise, M; Yokoyama, M; Young, A R
2013-01-01
This report, prepared for the Community Planning Study - Snowmass 2013 - summarizes the theoretical motivations and the experimental efforts to search for baryon number violation, focussing on nucleon decay and neutron-antineutron oscillations. Present and future nucleon decay search experiments using large underground detectors, as well as planned neutron-antineutron oscillation search experiments with free neutron beams are highlighted.
Alladi, Krishnaswami
2008-01-01
Contains chapters on number theory and related topics. This title covers topics that focus on multipartitions, congruences and identities, the formulas of Koshliakov and Guinand in Ramanujan's "Lost Notebook", alternating sign matrices and the Weyl character formulas, theta functions in complex analysis, and elliptic functions
Bell, Eric Temple
1991-01-01
From one of the foremost interpreters for lay readers of the history and meaning of mathematics: a stimulating account of the origins of mathematical thought and the development of numerical theory. It probes the work of Pythagoras, Galileo, Berkeley, Einstein, and others, exploring how ""number magic"" has influenced religion, philosophy, science, and mathematics
Schreuder, M.F.
2012-01-01
A low nephron number is, according to Brenner's hyperfiltration hypothesis, associated with hypertension, glomerular damage and proteinuria, and starts a vicious cycle that ends in renal failure over the long term. Nephron endowment is set during foetal life, and there is no formation of nephrons
Trudgian, Timothy
2009-01-01
One of the difficulties in any teaching of mathematics is to bridge the divide between the abstract and the intuitive. Throughout school one encounters increasingly abstract notions, which are more and more difficult to relate to everyday experiences. This article examines a familiar approach to thinking about negative numbers, that is an…
Haida Numbers and Calculation.
Cogo, Robert
Experienced traders in furs, blankets, and other goods, the Haidas of the 1700's had a well-developed decimal system for counting and calculating. Their units of linear measure included the foot, yard, and fathom, or six feet. This booklet lists the numbers from 1 to 20 in English and Haida; explains the Haida use of ten, hundred, and thousand…
Uniform random number generators
Farr, W. R.
1971-01-01
Methods are presented for the generation of random numbers with uniform and normal distributions. Subprogram listings of Fortran generators for the Univac 1108, SDS 930, and CDC 3200 digital computers are also included. The generators are of the mixed multiplicative type, and the mathematical method employed is that of Marsaglia and Bray.
Jorgensen, C.B.; Suetens, S.; Tyran, J.R.
2011-01-01
We investigate the "law of small numbers" using a unique panel data set on lotto gambling. Because we can track individual players over time, we can measure how they react to outcomes of recent lotto drawings. We can therefore test whether they behave as if they believe they can predict lotto
Ramsey numbers and adiabatic quantum computing.
Gaitan, Frank; Clark, Lane
2012-01-06
The graph-theoretic Ramsey numbers are notoriously difficult to calculate. In fact, for the two-color Ramsey numbers R(m,n) with m, n≥3, only nine are currently known. We present a quantum algorithm for the computation of the Ramsey numbers R(m,n). We show how the computation of R(m,n) can be mapped to a combinatorial optimization problem whose solution can be found using adiabatic quantum evolution. We numerically simulate this adiabatic quantum algorithm and show that it correctly determines the Ramsey numbers R(3,3) and R(2,s) for 5≤s≤7. We then discuss the algorithm's experimental implementation, and close by showing that Ramsey number computation belongs to the quantum complexity class quantum Merlin Arthur.
Totally optimal decision trees for Boolean functions
Chikalov, Igor
2016-07-28
We study decision trees which are totally optimal relative to different sets of complexity parameters for Boolean functions. A totally optimal tree is an optimal tree relative to each parameter from the set simultaneously. We consider the parameters characterizing both time (in the worst- and average-case) and space complexity of decision trees, i.e., depth, total path length (average depth), and number of nodes. We have created tools based on extensions of dynamic programming to study totally optimal trees. These tools are applicable to both exact and approximate decision trees, and allow us to make multi-stage optimization of decision trees relative to different parameters and to count the number of optimal trees. Based on the experimental results we have formulated the following hypotheses (and subsequently proved): for almost all Boolean functions there exist totally optimal decision trees (i) relative to the depth and number of nodes, and (ii) relative to the depth and average depth.
Aschepkov, Leonid T; Kim, Taekyun; Agarwal, Ravi P
2016-01-01
This book is based on lectures from a one-year course at the Far Eastern Federal University (Vladivostok, Russia) as well as on workshops on optimal control offered to students at various mathematical departments at the university level. The main themes of the theory of linear and nonlinear systems are considered, including the basic problem of establishing the necessary and sufficient conditions of optimal processes. In the first part of the course, the theory of linear control systems is constructed on the basis of the separation theorem and the concept of a reachability set. The authors prove the closure of a reachability set in the class of piecewise continuous controls, and the problems of controllability, observability, identification, performance and terminal control are also considered. The second part of the course is devoted to nonlinear control systems. Using the method of variations and the Lagrange multipliers rule of nonlinear problems, the authors prove the Pontryagin maximum principle for prob...
A copositive formulation for the stability number of infinite graphs
Dobre, Cristian; Dür, Mirjam; Frerick, Leonhard; Vallentin, Frank
2016-01-01
In the last decade, copositive formulations have been proposed for a variety of combinatorial optimization problems, for example the stability number (independence number). In this paper, we generalize this approach to infinite graphs and show that the stability number of an infinite graph is the
A copositive formulation for the stability number of infinite graphs
Dobre, Cristian; Dür, Mirjam; Frerick, Leonhard; Vallentin, Frank
2016-01-01
In the last decade, copositive formulations have been proposed for a variety of combinatorial optimization problems, for example the stability number (independence number). In this paper, we generalize this approach to infinite graphs and show that the stability number of an infinite graph is the
Trommer, Jochen
2005-01-01
In dieser Dissertation schlage ich eine Synthese (Distributed Optimality, DO) von Optimalitätstheorie und einem derivationellen, morphologischem Asatz, Distributed Morphology (DM; Halle & Marantz, 1993) vor. Durch die Integration von OT in DM wird es möglich, Phänomene, die in DM durch sprachspezifische Regeln oder Merkmale von lexikalischen Einträge erfasst werden, auf die Interaktion von verletzbaren, universellen Constraints zurückzuführen. Andererseits leistet auch DM zwei substantielle B...
Powell, Warren B
2012-01-01
Learn the science of collecting information to make effective decisions Everyday decisions are made without the benefit of accurate information. Optimal Learning develops the needed principles for gathering information to make decisions, especially when collecting information is time-consuming and expensive. Designed for readers with an elementary background in probability and statistics, the book presents effective and practical policies illustrated in a wide range of applications, from energy, homeland security, and transportation to engineering, health, and business. This book covers the
Directory of Open Access Journals (Sweden)
Yaping Hu
2015-01-01
the nonsmooth convex optimization problem. First, by using Moreau-Yosida regularization, we convert the original objective function to a continuously differentiable function; then we use approximate function and gradient values of the Moreau-Yosida regularization to substitute the corresponding exact values in the algorithm. The global convergence is proved under suitable assumptions. Numerical experiments are presented to show the effectiveness of this algorithm.
Aircraft technology portfolio optimization using ant colony optimization
Villeneuve, Frederic J.; Mavris, Dimitri N.
2012-11-01
Technology portfolio selection is a combinatorial optimization problem often faced with a large number of combinations and technology incompatibilities. The main research question addressed in this article is to determine if Ant Colony Optimization (ACO) is better suited than Genetic Algorithms (GAs) and Simulated Annealing (SA) for technology portfolio optimization when incompatibility constraints between technologies are present. Convergence rate, capability to find optima, and efficiency in handling of incompatibilities are the three criteria of comparison. The application problem consists of finding the best technology portfolio from 29 aircraft technologies. The results show that ACO and GAs converge faster and find optima more easily than SA, and that ACO can optimize portfolios with technology incompatibilities without using penalty functions. This latter finding paves the way for more use of ACO when the number of constraints increases, such as in the technology and concept selection for complex engineering systems.
Spagnolie, Saverio E.; Lauga, Eric
2010-03-01
Motile eukaryotic cells propel themselves in viscous fluids by passing waves of bending deformation down their flagella. An infinitely long flagellum achieves a hydrodynamically optimal low-Reynolds number locomotion when the angle between its local tangent and the swimming direction remains constant along its length. Optimal flagella therefore adopt the shape of a helix in three dimensions (smooth) and that of a sawtooth in two dimensions (nonsmooth). Physically, biological organisms (or engineered microswimmers) must expend internal energy in order to produce the waves of deformation responsible for the motion. Here we propose a physically motivated derivation of the optimal flagellum shape. We determine analytically and numerically the shape of the flagellar wave which leads to the fastest swimming for a given appropriately defined energetic expenditure. Our novel approach is to define an energy which includes not only the work against the surrounding fluid, but also (1) the energy stored elastically in the bending of the flagellum, (2) the energy stored elastically in the internal sliding of the polymeric filaments which are responsible for the generation of the bending waves (microtubules), and (3) the viscous dissipation due to the presence of an internal fluid. This approach regularizes the optimal sawtooth shape for two-dimensional deformation at the expense of a small loss in hydrodynamic efficiency. The optimal waveforms of finite-size flagella are shown to depend on a competition between rotational motions and bending costs, and we observe a surprising bias toward half-integer wave numbers. Their final hydrodynamic efficiencies are above 6%, significantly larger than those of swimming cells, therefore indicating available room for further biological tuning.
MacCarron, Pádraig; Dunbar, Robin
2016-01-01
The social brain hypothesis predicts that humans have an average of about 150 relationships at any given time. Within this 150, there are layers of friends of an ego, where the number of friends in a layer increases as the emotional closeness decreases. Here we analyse a mobile phone dataset, firstly, to ascertain whether layers of friends can be identified based on call frequency. We then apply different clustering algorithms to break the call frequency of egos into clusters and compare the number of alters in each cluster with the layer size predicted by the social brain hypothesis. In this dataset we find strong evidence for the existence of a layered structure. The clustering yields results that match well with previous studies for the innermost and outermost layers, but for layers in between we observe large variability.
Directory of Open Access Journals (Sweden)
Marco Ruffino
2001-12-01
Full Text Available In this paper I discuss the intuition behind Frege's and Russell's definitions of numbers as sets, as well as Benacerraf's criticism of it. I argue that Benacerraf's argument is not as strong as some philosophers tend to think. Moreover, I examine an alternative to the Fregean-Russellian definition of numbers proposed by Maddy, and point out some problems faced by it.Neste artigo discuto a intuição subjacente à definição de n∨meros como conjuntos proposta por Frege e Russell, assim como a crítica de Benacerraf a esta definição. Eu tento mostrar que o argumento de Benacerraf não é tão forte como alguns filósofos o tomaram. Adicionalmente, examino uma alternativa à definição de Frege e Russell proposta por Maddy, e indico algumas dificuldades encontrada pela mesma.
Sierpinski and Carmichael Numbers
2013-01-16
appear. 31 [21] E. M. Matveev, ‘An explicit lower bound for a homogeneous rational linear form in logarithms of algebraic numbers. II,’ Izv. Ross. Akad...Math. Comp. 37 (1981), 587–593. [23] C. Pontreau, ‘A Mordell- Lang plus Bogomolov type result for curves in G2m,’ Monatsh. Math. 157 (2009), 267–281. [24
Rocker, Graeme M; Verma, Jennifer Y; Demmons, Jillian; Mittmann, Nicole
2015-02-06
The 'Number Needed to Treat' (NNT) is a useful measure for estimating the number of patients that would need to receive a therapeutic intervention to avoid one of the adverse events that the treatment is designed to prevent. We explored the possibility of an adaption of NNT to estimate the 'Number Needed to $ave' (NN$) as a new, conceptual systems metric to estimate potential cost-savings to the health system from implementation of a treatment, or in this case, a program. We used the outcomes of the INSPIRED COPD Outreach ProgramTM to calculate that 26 patients would need to complete the program to avoid healthcare expenditures of $100,000, based on hospital bed days avoided. The NN$ does not translate into 'cost savings' per se, but redirection of resource expenditures for other purposes. We propose that the NN$ metric, if further developed, could help to inform system-level resource allocation decisions in a manner similar to the way that the NNT metric helps to inform individual-level treatment decisions.
Stability Analysis for Stochastic Optimization Problems
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Stochastic optimization offers a means of considering the objectives and constrains with stochastic parameters. However, it is generally difficult to solve the stochastic optimization problem by employing conventional methods for nonlinear programming when the number of random variables involved is very large. Neural network models and algorithms were applied to solve the stochastic optimization problem on the basis of the stability theory. Stability for stochastic programs was discussed. If random vector sequence converges to the random vector in the original problem in distribution, the optimal value of the corresponding approximation problems converges to the optimal value of the original stochastic optimization problem.
Drilling Path Optimization Based on Particle Swarm Optimization Algorithm
Institute of Scientific and Technical Information of China (English)
ZHU Guangyu; ZHANG Weibo; DU Yuexiang
2006-01-01
This paper presents a new approach based on the particle swarm optimization (PSO) algorithm for solving the drilling path optimization problem belonging to discrete space. Because the standard PSO algorithm is not guaranteed to be global convergence or local convergence, based on the mathematical algorithm model, the algorithm is improved by adopting the method of generate the stop evolution particle over again to get the ability of convergence to the global optimization solution. And the operators are improved by establishing the duality transposition method and the handle manner for the elements of the operator, the improved operator can satisfy the need of integer coding in drilling path optimization. The experiment with small node numbers indicates that the improved algorithm has the characteristics of easy realize, fast convergence speed, and better global convergence characteristics, hence the new PSO can play a role in solving the problem of drilling path optimization in drilling holes.
Generalizations of Euler Numbers and Euler Numbers of Higher Order
Institute of Scientific and Technical Information of China (English)
LUOQiu-ming; QIFeng
2005-01-01
The purpose of this paper is to define the generalized Euler numbers and the generalized Euler numbers of higher order, their recursion formula and some properties were established, accordingly Euler numbers and Euler numbers of higher order were extended.
LeVeque, William J
2002-01-01
Classic two-part work now available in a single volume assumes no prior theoretical knowledge on reader's part and develops the subject fully. Volume I is a suitable first course text for advanced undergraduate and beginning graduate students. Volume II requires a much higher level of mathematical maturity, including a working knowledge of the theory of analytic functions. Contents range from chapters on binary quadratic forms to the Thue-Siegel-Roth Theorem and the Prime Number Theorem. Includes numerous problems and hints for their solutions. 1956 edition. Supplementary Reading. List of Symb
Thurston, H A
2007-01-01
The teaching of mathematics has undergone extensive changes in approach, with a shift in emphasis from rote memorization to acquiring an understanding of the logical foundations and methodology of problem solving. This book offers guidance in that direction, exploring arithmetic's underlying concepts and their logical development.This volume's great merit lies in its wealth of explanatory material, designed to promote an informal and intuitive understanding of the rigorous logical approach to the number system. The first part explains and comments on axioms and definitions, making their subseq
Pati, Jogesh C.; Salam, Abdus
We suggest that baryon-number conservation may not be absolute and that an integrally charged quark may disintegrate into two leptons and an antilepton with a coupling strength G Bmp2≲ 10-9. On the other hand, if quarks are much heavier than low-lying hadrons, the decay of a three-quark system like the proton is highly forbidden (proton lifetime ≳ 1028 y). Motivation for these ideas appears to arise within a unified theory of hadrons and leptons and their gauge interactions. We emphasize the consequences of such a possibility for real quark searches.
Neukirch, Jürgen; Wingberg, Kay
2013-01-01
The second edition is a corrected and extended version of the first. It is a textbook for students, as well as a reference book for the working mathematician, on cohomological topics in number theory. The first part provides algebraic background: cohomology of profinite groups, duality groups, free products, and homotopy theory of modules, with new sections on spectral sequences and on Tate cohomology of profinite groups. The second part deals with Galois groups of local and global fields: Tate duality, structure of absolute Galois groups of local fields, extensions with restricted ramificatio
Quantum random number generator
Stipcevic, M
2006-01-01
We report upon a novel principle for realization of a fast nondeterministic random number generator whose randomness relies on intrinsic randomness of the quantum physical processes of photonic emission in semiconductors and subsequent detection by the photoelectric effect. Timing information of detected photons is used to generate binary random digits-bits. The bit extraction method based on restartable clock theoretically eliminates both bias and autocorrelation while reaching efficiency of almost 0.5 bits per random event. A prototype has been built and statistically tested.
New Optimization Algorithms in Physics
Hartmann, Alexander K
2004-01-01
Many physicists are not aware of the fact that they can solve their problems by applying optimization algorithms. Since the number of such algorithms is steadily increasing, many new algorithms have not been presented comprehensively until now. This presentation of recently developed algorithms applied in physics, including demonstrations of how they work and related results, aims to encourage their application, and as such the algorithms selected cover concepts and methods from statistical physics to optimization problems emerging in theoretical computer science.
Automatic differentiation using vectorized hyper dual numbers
Swaroop, Kshitiz
Sensitivity analysis is a method to measure the change in a dependent variable with respect to one or more independent variables with uses including optimization, design analysis and risk modeling. Conventional methods like finite difference suffer from both truncation, subtraction errors and cannot be used to simultaneously calculate derivatives of an output with respect to multiple inputs (commonly seen in optimization problems). Automatic Differentiation tackles all these issues successfully allowing us to calculate derivatives of any variable with respect to the independent variables in a computer program up to machine precision without any significant user input. Vectorized Hyper Dual Numbers, an extension of Hyper Dual Numbers, which allows the user to automatically calculate both the Hessian and derivative along with the function evaluation is developed for this thesis. The method is then used for the sizing and layup of a composite wind turbine blade as a proof of concept.
Parker, R Gary
1988-01-01
This book treats the fundamental issues and algorithmic strategies emerging as the core of the discipline of discrete optimization in a comprehensive and rigorous fashion. Following an introductory chapter on computational complexity, the basic algorithmic results for the two major models of polynomial algorithms are introduced--models using matroids and linear programming. Further chapters treat the major non-polynomial algorithms: branch-and-bound and cutting planes. The text concludes with a chapter on heuristic algorithms.Several appendixes are included which review the fundamental ideas o
Chvátal, V
2011-01-01
This book is a collection of six articles arising from the meeting of the NATO Advanced Study Institute (ASI) "Combinatorial Optimization: Methods and Applications," which was held at the University of Montreal in June 2006. This ASI consisted of seven series of five one-hour lectures and one series of four one-hour lectures. It was attended by some sixty students of graduate or postdoctoral level from fifteen countries worldwide. It includes topics such as: integer and mixed integer programming, facility location, branching on split disjunctions, convexity in combinatorial optimizat
Evaluation of a number skills development programme | Pietersen ...
African Journals Online (AJOL)
Evaluation of a number skills development programme. ... It was concluded that the use of concrete educational material should be central in the ... in the use of educational equipment and also to create an optimal learning environment.
Numerical calculation of economic uncertainty by intervals and fuzzy numbers
DEFF Research Database (Denmark)
Schjær-Jacobsen, Hans
2010-01-01
This paper emphasizes that numerically correct calculation of economic uncertainty with intervals and fuzzy numbers requires implementation of global optimization techniques in contrast to straightforward application of interval arithmetic. This is demonstrated by both a simple case from managerial...
Institute of Scientific and Technical Information of China (English)
陈志旺; 陈林; 白锌; 杨七; 赵方亮
2015-01-01
针对约束多目标区间优化问题,提出一种交互多属性决策NSGA-Ⅱ算法.该算法将非线性问题线性化,定义占优支配关系求出个体的序值,定义区间拥挤距离来区分具有相同序值个体的优劣,采用约束精英策略删除种群中不满足约束的个体.将选出的个体作为方案集,目标函数作为属性集,决策者对于各目标函数的偏好作为属性权重,构建一个多属性决策模型,在进化过程中融入该模型来选取符合决策者偏好的满意解.仿真实验验证了所提出方法的可行性和正确性.%For constrained multi-objective optimization problems with interval numbers, a kind of interactive multi-attribute decision-making NSGA-Ⅱ is proposed. In this algorithm, nonlinear optimization problems are transformed into linear ones.dominance relationship is defined to get the rank values of individuals and interval crowding distance is presented to distinguish the quality of the individuals with the same rank value. A constrained elite strategy is used to remove those individuals that do not satisfy the constraint from the population. A multi-attribute decision-making model(DMM) is built, which regards the selected individuals as the alternatives set, the objective function as the attributes set, and the preference of each objective function as the attribute weights. In the process of evolution, an interactive NSGA-Ⅱ incorporated with DMM is proposed to obtain satisfactory solutions which conform to the decision-makers preference. Simulation results show the feasibility and correctness of the proposed method.
Instant PageSpeed optimization
Jaiswal, Sanjeev
2013-01-01
Filled with practical, step-by-step instructions and clear explanations for the most important and useful tasks. Instant PageSpeed Optimization is a hands-on guide that provides a number of clear, step-by-step exercises for optimizing your websites for better performance and improving their efficiency.Instant PageSpeed Optimization is aimed at website developers and administrators who wish to make their websites load faster without any errors and consume less bandwidth. It's assumed that you will have some experience in basic web technologies like HTML, CSS3, JavaScript, and the basics of netw
Tagging, Encoding, and Jones Optimality
DEFF Research Database (Denmark)
Danvy, Olivier; Lopez, Pablo E. Martinez
2003-01-01
A partial evaluator is said to be Jones-optimal if the result of specializing a self-interpreter with respect to a source program is textually identical to the source program, modulo renaming. Jones optimality has already been obtained if the self-interpreter is untyped. If the selfinterpreter...... is typed, however, residual programs are cluttered with type tags. To obtain the original source program, these tags must be removed. A number of sophisticated solutions have already been proposed. We observe, however, that with a simple representation shift, ordinary partial evaluation is already Jones-optimal...
MPQC: Performance Analysis and Optimization
Energy Technology Data Exchange (ETDEWEB)
Sarje, Abhinav [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Williams, Samuel [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bailey, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2013-01-24
MPQC (Massively Parallel Quantum Chemistry) is a widely used computational quantum chemistry code. It is capable of performing a number of computations commonly occurring in quantum chemistry. In order to achieve better performance of MPQC, in this report we present a detailed performance analysis of this code. We then perform loop and memory access optimizations, and measure performance improvements by comparing the performance of the optimized code with that of the original MPQC code. We observe that the optimized MPQC code achieves a significant improvement in the performance through a better utilization of vector processing and memory hierarchies.
Aircraft Trajectory Optimization Using Parametric Optimization Theory
Valenzuela Romero, Alfonso
2012-01-01
In this thesis, a study of the optimization of aircraft trajectories using parametric optimization theory is presented. To that end, an approach based on the use of predefined trajectory patterns and parametric optimization is proposed. The trajectory pat
Earth Observing Satellite Orbit Design Via Particle Swarm Optimization
2014-08-01
Earth Observing Satellite Orbit Design Via Particle Swarm Optimization Sharon Vtipil ∗ and John G. Warner ∗ US Naval Research Laboratory, Washington...number of passes per day given a satellite’s orbital altitude and inclination. These are used along with particle swarm optimization to determine optimal...well suited to use within a meta-heuristic optimization method such as the Particle Swarm Optimizer (PSO). This method seeks to find the optimal set
Structural Optimization for Blast Mitigation Using HCA
2009-08-14
UNCLASSIFIED Structural Optimization for Blast Mitigation Using HCA University of Notre Dame John Goetz, Huade Tan, Andrés Tovar , John Renaud...John Goetz; Huande Tan; Andres Tovar ; John Renaud 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND...Overview: Algorithm • A continuum-based topology optimization – First utilized for bone remodeling ( Tovar ’04) – Extend bone remodeling technique for
AFRICAN BUFFALO OPTIMIZATION ico-pdf
Directory of Open Access Journals (Sweden)
Julius Beneoluchi Odili
2016-02-01
Full Text Available This is an introductory paper to the newly-designed African Buffalo Optimization (ABO algorithm for solving combinatorial and other optimization problems. The algorithm is inspired by the behavior of African buffalos, a species of wild cows known for their extensive migrant lifestyle. This paper presents an overview of major metaheuristic algorithms with the aim of providing a basis for the development of the African Buffalo Optimization algorithm which is a nature-inspired, population-based metaheuristic algorithm. Experimental results obtained from applying the novel ABO to solve a number of benchmark global optimization test functions as well as some symmetric and asymmetric Traveling Salesman’s Problems when compared to the results obtained from using other popular optimization methods show that the African Buffalo Optimization is a worthy addition to the growing number of swarm intelligence optimization techniques.
FFLP problem with symmetric trapezoidal fuzzy numbers
Directory of Open Access Journals (Sweden)
Reza Daneshrad
2015-04-01
Full Text Available The most popular approach for solving fully fuzzy linear programming (FFLP problems is to convert them into the corresponding deterministic linear programs. Khan et al. (2013 [Khan, I. U., Ahmad, T., & Maan, N. (2013. A simplified novel technique for solving fully fuzzy linear programming problems. Journal of Optimization Theory and Applications, 159(2, 536-546.] claimed that there had been no method in the literature to find the fuzzy optimal solution of a FFLP problem without converting it into crisp linear programming problem, and proposed a technique for the same. Others showed that the fuzzy arithmetic operation used by Khan et al. (2013 had some problems in subtraction and division operations, which could lead to misleading results. Recently, Ezzati et al. (2014 [Ezzati, R., Khorram, E., & Enayati, R. (2014. A particular simplex algorithm to solve fuzzy lexicographic multi-objective linear programming problems and their sensitivity analysis on the priority of the fuzzy objective functions. Journal of Intelligent and Fuzzy Systems, 26(5, 2333-2358.] defined a new operation on symmetric trapezoidal fuzzy numbers and proposed a new algorithm to find directly a lexicographic/preemptive fuzzy optimal solution of a fuzzy lexicographic multi-objective linear programming problem by using new fuzzy arithmetic operations, but their model was not fully fuzzy optimization. In this paper, a new method, by using Ezzati et al. (2014’s fuzzy arithmetic operation and a fuzzy version of simplex algorithm, is proposed for solving FFLP problem whose parameters are represented by symmetric trapezoidal fuzzy number without converting the given problem into crisp equivalent problem. By using the proposed method, the fuzzy optimal solution of FFLP problem can be easily obtained. A numerical example is provided to illustrate the proposed method.
[SIAM conference on optimization
Energy Technology Data Exchange (ETDEWEB)
1992-05-10
Abstracts are presented of 63 papers on the following topics: large-scale optimization, interior-point methods, algorithms for optimization, problems in control, network optimization methods, and parallel algorithms for optimization problems.
DEFF Research Database (Denmark)
Hansen, C. T.; Madsen, Kaj; Nielsen, Hans Bruun
1991-01-01
The paper treats a piping system, where the layout of the network is given but the diameters of the pipes should be chosen among a small number of different values. The cost of realizing the system should be minimized while keeping the energy heads at the nodes above some lower limits. A new...... algorithm using successive linear programming is presented. The performance of the algorithm is illustrated by optimizing a network with 201 pipes and 172 nodes. It is concluded that the new algorithm seems to be very efficient and stable, and that it always finds a solution with a cost near the best...
1988-01-01
TASK AREA & WORK UNIT NUMBERS Dipartimento di Matematica -G.--iattelnuoz .’ Universita di Roma "La Sapienze" rlnlRr% Pnmaq (Tt-al’g) I$. CONTROLLING...guaranteed. 3. Adminisrtrative actions The following investigators are working on the contract: (i) Francesco Zirilli Dipartimento di Matematica "G...Castelnuovo" Universiti di Roma "La Sapienza" 00185 Romna (Italy) (ii) Filippo Aluffi-Pentini Dipartimento di Matematica Universiti di Barn 80125 Bari (Italy
Beyond natural numbers: negative number representation in parietal cortex.
Blair, Kristen P; Rosenberg-Lee, Miriam; Tsang, Jessica M; Schwartz, Daniel L; Menon, Vinod
2012-01-01
Unlike natural numbers, negative numbers do not have natural physical referents. How does the brain represent such abstract mathematical concepts? Two competing hypotheses regarding representational systems for negative numbers are a rule-based model, in which symbolic rules are applied to negative numbers to translate them into positive numbers when assessing magnitudes, and an expanded magnitude model, in which negative numbers have a distinct magnitude representation. Using an event-related functional magnetic resonance imaging design, we examined brain responses in 22 adults while they performed magnitude comparisons of negative and positive numbers that were quantitatively near (difference 6). Reaction times (RTs) for negative numbers were slower than positive numbers, and both showed a distance effect whereby near pairs took longer to compare. A network of parietal, frontal, and occipital regions were differentially engaged by negative numbers. Specifically, compared to positive numbers, negative number processing resulted in greater activation bilaterally in intraparietal sulcus (IPS), middle frontal gyrus, and inferior lateral occipital cortex. Representational similarity analysis revealed that neural responses in the IPS were more differentiated among positive numbers than among negative numbers, and greater differentiation among negative numbers was associated with faster RTs. Our findings indicate that despite negative numbers engaging the IPS more strongly, the underlying neural representation are less distinct than that of positive numbers. We discuss our findings in the context of the two theoretical models of negative number processing and demonstrate how multivariate approaches can provide novel insights into abstract number representation.
NEMO Oceanic Model Optimization
Epicoco, I.; Mocavero, S.; Murli, A.; Aloisio, G.
2012-04-01
NEMO is an oceanic model used by the climate community for stand-alone or coupled experiments. Its parallel implementation, based on MPI, limits the exploitation of the emerging computational infrastructures at peta and exascale, due to the weight of communications. As case study we considered the MFS configuration developed at INGV with a resolution of 1/16° tailored on the Mediterranenan Basin. The work is focused on the analysis of the code on the MareNostrum cluster and on the optimization of critical routines. The first performance analysis of the model aimed at establishing how much the computational performance are influenced by the GPFS file system or the local disks and wich is the best domain decomposition. The results highlight that the exploitation of local disks can reduce the wall clock time up to 40% and that the best performance is achieved with a 2D decomposition when the local domain has a square shape. A deeper performance analysis highlights the obc_rad, dyn_spg and tra_adv routines are the most time consuming routines. The obc_rad implements the evaluation of the open boundaries and it has been the first routine to be optimized. The communication pattern implemented in obc_rad routine has been redesigned. Before the introduction of the optimizations all processes were involved in the communication, but only the processes on the boundaries have the actual data to be exchanged and only the data on the boundaries must be exchanged. Moreover the data along the vertical levels are "packed" and sent with only one MPI_send invocation. The overall efficiency increases compared with the original version, as well as the parallel speed-up. The execution time was reduced of about 33.81%. The second phase of optimization involved the SOR solver routine, implementing the Red-Black Successive-Over-Relaxation method. The high frequency of exchanging data among processes represent the most part of the overall communication time. The number of communication is
Lepton family number violation
Energy Technology Data Exchange (ETDEWEB)
Herczeg, P.
1999-03-01
At present there is evidence from neutrino oscillation searches that the neutrinos are in fact massive particles and that they mix. If confirmed, this would imply that the conservation of LFN is not exact. Lepton family number violation (LFNV) has been searched for with impressive sensitivities in many processes involving charged leptons. The present experimental limits on some of them (those which the author shall consider here) are shown in Table 1. These stringent limits are not inconsistent with the neutrino oscillation results since, given the experimental bounds on the masses of the known neutrinos and the neutrino mass squared differences required by the oscillation results, the effects of LFNV from neutrino mixing would be too small to be seen elsewhere (see Section 2). The purpose of experiments searching for LFNV involving the charged leptons is to probe the existence of other sources of LFNV. Such sources are present in many extensions of the SM. In this lecture the author shall discuss some of the possibilities, focusing on processes that require muon beams. Other LFNV processes, such as the decays of the kaons and of the {tau}, provide complementary information. In the next Section he shall consider some sources of LFNV that do not require an extension of the gauge group of the SM (the added leptons or Higgs bosons may of course originate from models with extended gauge groups). In Section 3 he discusses LFNV in left-right symmetric models. In Section 4 he considers LFNV in supersymmetric models, first in R-parity conserving supersymmetric grand unified models, and then in the minimal supersymmetric standard model with R-parity violation. The last section is a brief summary of the author`s conclusions.
Beyond Natural Numbers: Negative Number Representation in Parietal Cortex
Blair, Kristen P.; Rosenberg-Lee, Miriam; Tsang, Jessica M.; Schwartz, Daniel L.; Menon, Vinod
2012-01-01
Unlike natural numbers, negative numbers do not have natural physical referents. How does the brain represent such abstract mathematical concepts? Two competing hypotheses regarding representational systems for negative numbers are a rule-based model, in which symbolic rules are applied to negative numbers to translate them into positive numbers when assessing magnitudes, and an expanded magnitude model, in which negative numbers have a distinct magnitude representation. Using an event-relate...
On Fibonacci Numbers Which Are Elliptic Korselt Numbers
2014-11-17
On Fibonacci numbers which are elliptic Korselt numbers Florian Luca School of Mathematics University of the Witwatersrand P. O. Box Wits 2050, South...is a CM elliptic curve with CM field Q( √ −d), then the set of n for which the nth Fibonacci number Fn satisfies an elliptic Korselt criterion for Q...SUBTITLE On Fibonacci Numbers Which Are Elliptic Korselt Numbers 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d
Percents Are Not Natural Numbers
Jacobs, Jennifer A.
2013-01-01
Adults are prone to treating percents, one representational format of rational numbers, as novel cases of natural number. This suggests that percent values are not differentiated from natural numbers; a conceptual shift from the natural numbers to the rational numbers has not yet occurred. This is most surprising, considering people are inundated…
Automatic Planning of External Search Engine Optimization
Directory of Open Access Journals (Sweden)
Vita Jasevičiūtė
2015-07-01
Full Text Available This paper describes an investigation of the external search engine optimization (SEO action planning tool, dedicated to automatically extract a small set of most important keywords for each month during whole year period. The keywords in the set are extracted accordingly to external measured parameters, such as average number of searches during the year and for every month individually. Additionally the position of the optimized web site for each keyword is taken into account. The generated optimization plan is similar to the optimization plans prepared manually by the SEO professionals and can be successfully used as a support tool for web site search engine optimization.
Optimal Algorithm for Algebraic Factoring
Institute of Scientific and Technical Information of China (English)
支丽红
1997-01-01
This paper presents on optimized method for factoring multivariate polynomials over algebraic extension fields defined by an irreducible ascending set. The basic idea is to convert multivariate polynomials to univariate polynomials and algebraic extension fields to algebraic number fields by suitable integer substituteions.Then factorize the univariate polynomials over the algebraic number fields.Finally,construct mulativariate factors of the original polynomial by Hensel lemma and TRUEFACTOR test.Some examples with timing are included.
Casazza, Peter G; Krahmer, Felix; Kutyniok, Gitta
2010-01-01
Frames have established themselves as a means to derive redundant, yet stable decompositions of a signal for analysis or transmission, while also promoting sparse expansions. However, when the signal dimension is large, the computation of the frame measurements of a signal typically requires a large number of additions and multiplications, and this makes a frame decomposition intractable in applications with limited computing budget. To address this problem, in this paper, we introduce sparsity of a frame as a new paradigm. In our terminology, a sparse frame is a frame whose elements have a sparse representation in an orthonormal basis, thereby enabling low-complexity frame decompositions. To introduce a precise meaning of optimality, we take the sum of the numbers of vectors needed of this orthonormal basis when expanding each frame vector as sparsity measure. We then analyze the recently introduced algorithm Spectral Tetris for construction of unit norm tight frames and prove that the tight frames generated...
Series of Reciprocal Triangular Numbers
Bruckman, Paul; Dence, Joseph B.; Dence, Thomas P.; Young, Justin
2013-01-01
Reciprocal triangular numbers have appeared in series since the very first infinite series were summed. Here we attack a number of subseries of the reciprocal triangular numbers by methodically expressing them as integrals.
Tran, Chuong V; Yu, Xinwei
2012-06-01
We study incompressible magnetohydrodynamic turbulence in both two and three dimensions, with an emphasis on the number of degrees of freedom N. This number is estimated in terms of the magnetic Prandtl number Pr, kinetic Reynolds number Re, and magnetic Reynolds number Rm. Here Re and Rm are dynamic in nature, defined in terms of the kinetic and magnetic energy dissipation rates (or averages of the velocity and magnetic field gradients), viscosity and magnetic diffusivity, and the system size. It is found that for the two-dimensional case, N satisfies N≤PrRe(3/2)+Rm(3/2) for Pr>1 and N≤Re(3/2)+Pr(-1)Rm(3/2) for Pr≤1. In three dimensions, on the other hand, N satisfies N≤(PrRe(3/2)+Rm(3/2))(3/2) for Pr>1 and N≤(Re(3/2)+Pr(-1)Rm(3/2))(3/2) for Pr≤1. In the limit Pr→0, Re(3/2) dominates Pr(-1)Rm(3/2), and the present estimate for N appropriately reduces to Re(9/4) as in the case of usual Navier-Stokes turbulence. For Pr≈1, our results imply the classical spectral scaling of the energy inertial range and dissipation wave number (in the form of upper bounds). These bounds are consistent with the existing predictions in the literature for turbulence with or without Alfvén wave effects. We discuss the possibility of solution regularity, with an emphasis on the two-dimensional case in the absence of either one or both of the dissipation terms.
Axiomatic of Fuzzy Complex Numbers
Angel Garrido
2012-01-01
Fuzzy numbers are fuzzy subsets of the set of real numbers satisfying some additional conditions. Fuzzy numbers allow us to model very difficult uncertainties in a very easy way. Arithmetic operations on fuzzy numbers have also been developed, and are based mainly on the crucial Extension Principle. When operating with fuzzy numbers, the results of our calculations strongly depend on the shape of the membership functions of these numbers. Logically, less regular membership functions may lead ...
Route Optimization in Network Mobility
Directory of Open Access Journals (Sweden)
Md. Hasan Tareque
2013-01-01
Full Text Available NEtwork MObility (NEMO controls mobility of a number of mobile nodes in a comprehensive way using one or more mobile routers. To choose a route optimization scheme, it is very important to have a quantitative comparison of the available route optimization schemes. The focus of this paper is to analyze the degree of Route Optimization (RO, deploy-ability and type of RO supported by each class in general. The comparison shows the differences among the schemes in terms of issues, such as additional header, signaling and memory requirement. We classify the schemes established on the basic method for route optimization, and equal the schemes based on protocol overhead, such as header overhead, amount of signaling, and memory requirements. Lastly the performance of the classes of different schemes has to be estimated under norms such as available bandwidth, topology of the mobile network and mobility type.
Transport optimization on complex networks
Danila, Bogdan; Marsh, John A; Bassler, Kevin E
2007-01-01
We present a comparative study of the application of a recently introduced heuristic algorithm to the optimization of transport on three major types of complex networks. The algorithm balances network traffic iteratively by minimizing the maximum node betweenness with as little path lengthening as possible. We show that by using this optimal routing, a network can sustain significantly higher traffic without jamming than in the case of shortest path routing. A formula is proved that allows quick computation of the average number of hops along the path and of the average travel times once the betweennesses of the nodes are computed. Using this formula, we show that routing optimization preserves the small-world character exhibited by networks under shortest path routing, and that it significantly reduces the average travel time on congested networks with only a negligible increase in the average travel time at low loads. Finally, we study the correlation between the weights of the links in the case of optimal ...
Generation of sub-Poissonian photon number distribution
DEFF Research Database (Denmark)
Grønbech-Jensen, N.; Ramanujam, P. S.
1990-01-01
An optimization of a nonlinear Mach-Zehnder interferometer to produce sub-Poissonian photon number distribution is proposed. We treat the system quantum mechanically and estimate the mirror parameters, the nonlinearity of the medium in the interferometer, and the input power to obtain minimal...... output uncertainty in the photon number. The power efficiency of the system is shown to be high....
The Hull Method for Selecting the Number of Common Factors
Lorenzo-Seva, Urbano; Timmerman, Marieke E.; Kiers, Henk A. L.
2011-01-01
A common problem in exploratory factor analysis is how many factors need to be extracted from a particular data set. We propose a new method for selecting the number of major common factors: the Hull method, which aims to find a model with an optimal balance between model fit and number of parameters. We examine the performance of the method in an…
Number Games, Magnitude Representation, and Basic Number Skills in Preschoolers
Whyte, Jemma Catherine; Bull, Rebecca
2008-01-01
The effect of 3 intervention board games (linear number, linear color, and nonlinear number) on young children's (mean age = 3.8 years) counting abilities, number naming, magnitude comprehension, accuracy in number-to-position estimation tasks, and best-fit numerical magnitude representations was examined. Pre- and posttest performance was…
Pauli Pascal Pyramids, Pauli Fibonacci Numbers, and Pauli Jacobsthal Numbers
Horn, Martin Erik
2007-01-01
The three anti-commutative two-dimensional Pauli Pascal triangles can be generalized into multi-dimensional Pauli Pascal hyperpyramids. Fibonacci and Jacobsthal numbers are then generalized into Pauli Fibonacci numbers, Pauli Jacobsthal numbers, and Pauli Fibonacci numbers of higher order. And the question is: are Pauli rabbits killer rabbits?
Number Games, Magnitude Representation, and Basic Number Skills in Preschoolers
Whyte, Jemma Catherine; Bull, Rebecca
2008-01-01
The effect of 3 intervention board games (linear number, linear color, and nonlinear number) on young children's (mean age = 3.8 years) counting abilities, number naming, magnitude comprehension, accuracy in number-to-position estimation tasks, and best-fit numerical magnitude representations was examined. Pre- and posttest performance was…
On Types of Distance Fibonacci Numbers Generated by Number Decompositions
Directory of Open Access Journals (Sweden)
Anetta Szynal-Liana
2014-01-01
Full Text Available We introduce new types of distance Fibonacci numbers which are closely related with number decompositions. Using special decompositions of the number n we give a sequence of identities for them. Moreover, we give matrix generators for distance Fibonacci numbers and their direct formulas.
Optimal Foraging in Semantic Memory
Hills, Thomas T.; Jones, Michael N.; Todd, Peter M.
2012-01-01
Do humans search in memory using dynamic local-to-global search strategies similar to those that animals use to forage between patches in space? If so, do their dynamic memory search policies correspond to optimal foraging strategies seen for spatial foraging? Results from a number of fields suggest these possibilities, including the shared…