Probing the pairing interaction through two-neutron transfer reactions
Directory of Open Access Journals (Sweden)
Margueron J.
2012-12-01
Full Text Available The treatment of the pairing interaction in mean-field-based models is addressed. In particular, the possibility to use pair transfers as A tool to better constrain this interaction is discussed. First, pairing inter-actions with various density dependencies (surface/volume mixing are used in the microscopic Hartree-Fock-Bogoliubov + quasiparticle random-phase approximation model to generate the form factors to be used in reaction calculations. Cross sections for (p,t two-neutron transfer reactions are calculated in the one-step zero-range distorted-wave Born approximation for some Tin isotopes and for incident proton energies from 15 to 35 MeV. Three different surface/volume mixings of A zero-range density-dependent pairing interaction are employed in the microscopic calculations and the sensitivity of the cross sections to the different mixings is analyzed. Differences among the three different theoretical predictions are found espacially for the nucleus 136Sn and they are more important at the incident proton energy of 15 MeV. We thus indicate (p,t two-neutron transfer reactions with very neutron-rich Sn isotopes and at proton energies around 15 MeV as good experimental cases where the surface/volume mixing of the pairing interaction may be probed. In the second part of the manuscript, ground-state to ground-state transitions are investigated. Approximations made to estimate two-nucleon transfer probabilities in ground-state to ground-state transitions and the physical interpretation of these probabilities are discussed. Probabilities are often calculated by approximating both ground states of the initial nucleus A and of the final nucleus A±2 by the same quasiparticle vacuum. We analyze two improvements of this approach. First, the effect of using two different ground states with average numbers of particles A and A±2 is quantified. Second, by using projection techniques, the role of particle number restoration is analyzed. Our analysis
Spectroscopy of $^{46}$Ar by the (t,p) two-neutron transfer reaction
Nowak, K.; Hellgartner, S.; Mücher, D.; Bildstein, V.; Diriken, J.; Elseviers, J.; Gaffney, L.P.; Gernhäuser, R.; Iwanicki, J.; Johansen, J.G.; Huyse, M.; Konki, J.; Kröll, T.; Krücken, T.; Lutter, R.; Orlandi, R.; Pakarinen, J.; Raabe, R.; Reiter, P.; Roger, T.; Schrieder, G.; Seidlitz, M.; Sorlin, O.; Van Duppen, P.; Warr, N.; De Witte, H.; Zielinska, M.
2016-01-01
States in the $N=28$ nucleus $^{46}$Ar have been studied by a two-neutron transfer reaction at REX-ISOLDE (CERN). A beam of radioactive $^{44}$ at an energy of 2.16~AMeV and a tritium loaded titanium target were used to populate $^{46}$ by the t($^{44}$,p) two-neutron transfer reaction. Protons emitted from the target were identified in the T-REX silicon detector array. The excitation energies of states in $^{46}$ have been reconstructed from the measured angles and energies of recoil protons. Angular distributions for three final states were measured and based on the shape of the differential cross section an excited state at 3695~keV has been identified as $J^\\pi = 0^+$. The angular differential cross section for the population of different states are compared to calculations using a reaction model employing both sequential and direct transfer of two neutrons. Results are compared to shell model calculations using state-of-the-art effective interactions.
Discovery of the shape coexisting 0$^{+}$ state in $^{32}$Mg by a two neutron transfer reaction
Wimmer, K; Krücken, R; Bildstein, V; Gernhäuser, R; Bastin, B; Bree, N; Diriken, J; Van Duppen, P; Huyse, M; Patronis, N; Vermaelen, P; Voulot, D; Van de Walle, J; Wenander, F; Fraile, L M; Chapman, R; Hadinia, B; Orlandi, R; Smith, J F; Lutter, R; Thirolf, P G; Labiche, M; Blazhev, A; Kalkühler, M; Reiter, P; Seidlitz, M; Warr, N; Macchiavelli, A O; Jeppesen, H B; Fiori, E; Georgiev, G; Schrieder, G; Gupta, S Das; Bianco, G Lo; Nardelli, S; Butterworth, J; Johansen, J; Riisager, K
2010-01-01
The Island of Inversion nucleus $^{32}$Mg has been studied by a (t,p) two neutron transfer reaction in inverse kinematics at REX-ISOLDE. The shape coexistent excited 0$^{+}$ state in $^{32}$Mg has been identified by the characteristic angular distribution of the protons of the $\\Delta$L = 0 transfer. The excitation energy of 1058 keV is much lower than predicted by any theoretical model. The low $\\gamma$-ray intensity observed for the decay of this 0$^{+}$ state indicates a lifetime of more than 10 ns. Deduced spectroscopic amplitudes are compared with occupation numbers from shell model calculations.
Investigation of 0+ states in mercury isotopes after two-neutron transfer
Directory of Open Access Journals (Sweden)
Bernards C.
2014-03-01
Full Text Available Using the high-resolution Q3D magnetic spectrograph at the Maier-Leibnitz Laboratory (MLL Tandem accelerator in Munich, we studied 0+ excitations in the mercury isotopes 198Hg, 200Hg, and 202Hg after two-neutron transfer. We only observed 4-6 excited 0+ states per nucleus up to about 3-MeV excitation energy, far fewer than in other experiments of this (p, t campaign. The results reveal a sharp drop in the number of low-lying 0+ states towards the 208Pb shell closure. We discuss the low-energy 0+ state density as a function of the valence nucleon number Nval. The 0+ excitation energies and the measured (p, t transfer cross sections indicate a structural change throughout the Hg isotopes, with the most notable result being the peaking in the cross section of the low-lying excited 02+ state in 200Hg.
Two-neutron transfer reactions investigating shell stability and inverse kinematics capability
Energy Technology Data Exchange (ETDEWEB)
Mahgoub, Mahmoud; Bildstein, Vinzenz; Faestermann, Thomas; Gernhaeuser, Roman; Kroell, Thorsten; Kruecken, Reiner; Maier, Ludwig; Wirth, Hans [Physik-Department E12, TU Muenchen, Garching (Germany); Bohlen, Hans-Gerhard; Kokalova, Tzanka; Oertzen, Wolfram von; Wheldon, Carl [HMI, Berlin (Germany); Bucurescu, Dorel [NIPNE, Bucharest (Romania); Dorsch, Tatiana [Physik-Department E12, TU Muenchen, Garching (Germany); HMI, Berlin (Germany); Hertenberger, Ralf [Sektion Physik, LMU Muenchen (Germany)
2008-07-01
Neutron transfer reactions were used to study the stability of the magic number N=28. We investigated neutron pairing correlations using the two-neutron pickup reaction {sup 58}Ni((vector)p,t){sup 56}Ni depending on the fact that nuclei with high neutron pairing are good magic nuclei. The capability of inverse kinematics reactions to study exotic nuclei was tested by the neutron transfer reactions t({sup 40}Ar,p){sup 42} Ar using a tritium target and comparing the results and conclusions with the normal kinematics reactions. The results for the reactions on Ni and Ar compared to DWBA calculations will be presented. Future possibilities for the use of inverse kinematics to study exotic nuclei with radioactive beams are discussed.
One-and Two-Neutron Transfer Reactions in 11Be+208Pb and Mechanism of Lowering Fusion Barrier
Institute of Scientific and Technical Information of China (English)
WANG Ning; LI Zhu-Xia; WU Xi-Zhen; WANG Nan; SUN Xiu-Quan
2000-01-01
We study one-and two-neutron transfer reactions in 11Be+208Pb by using the quantum molecular dynamics model. We find that lowering about 1-2 MeV of the potential barrier of 208Pb for fusion is gained when two neutrons separated from 11Be enter into 208Pb. Whereas no significant change of potential barrier is found when only the halo neutron separated from 11Be enters into 208Pb. The dynamical interplay between suppression and enhancement effects on the fusion probability in reaction 11Be+208Pb stemming from the easy separation of halo neutron and the long extending of neutron distribution is discussed.
Reiter, P; Blazhev, A A; Kruecken, R; Franchoo, S; Mertzimekis, T; Darby, I G; Van de walle, J; Raabe, R; Elseviers, J; Gernhaeuser, R A; Sorlin, O H; Georgiev, G P; Bree, N C F; Habs, D; Chapman, R; Gaudefroy, L; Diriken, J V J; Jenkins, D G; Kroell, T; Axiotis, M; Huyse, M L; Patronis, N
We propose to perform the two-neutron transfer reaction $^{3}$H($^{66}$Ni, $^{68}$Ni)$p$ using the ISOLDE radioactive ion beam at 2.7 $A$ MeV and the MINIBALL + T-REX setup to characterize the 0$^{+}$ and 2$^{+}$ states in $^{68}$Ni.
Blazhev, A A; Nardelli, S; Kruecken, R; Voulot, D; Hadinia, B; Kalkuehler, M; Clement, E; Habs, D; Diriken, J V J; Wady, P T; Angus, L J
2008-01-01
We aim to study the structure of neutron-rich nuclei in the "island of inversion" where intruder $\\textit{fp}$-orbitals favouring deformed states compete with the normal spherical $\\textit{sd}$-orbitals. In particular, we search for the spherical 0$^{+}_{2}$ state in $^{32}$Mg which should coexist with the deformed ground state but has not been observed so far. We propose to populate this state by a (t,p) two-neutron transfer reaction with a $^{30}$Mg beam at around 2 MeV/u from REX-ISOLDE impinging on a tritium-loaded Ti target. The $\\gamma$-rays are detected by MINIBALL and the particles by our new set-up of segmented Si detectors. The results will shed new light on the breaking of the shell closure at $\\textit{N}$ = 20 in this region.
Local Transfer Coefficient, Smooth Channel
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R. T. Kukreja
1998-01-01
Full Text Available Naphthalene sublimation technique and the heat/mass transfer analogy are used to determine the detailed local heat/mass transfer distributions on the leading and trailing walls of a twopass square channel with smooth walls that rotates about a perpendicular axis. Since the variation of density is small in the flow through the channel, buoyancy effect is negligible. Results show that, in both the stationary and rotating channel cases, very large spanwise variations of the mass transfer exist in he turn and in the region immediately downstream of the turn in the second straight pass. In the first straight pass, the rotation-induced Coriolis forces reduce the mass transfer on the leading wall and increase the mass transfer on the trailing wall. In the turn, rotation significantly increases the mass transfer on the leading wall, especially in the upstream half of the turn. Rotation also increases the mass transfer on the trailing wall, more in the downstream half of the turn than in the upstream half of the turn. Immediately downstream of the turn, rotation causes the mass transfer to be much higher on the trailing wall near the downstream corner of the tip of the inner wall than on the opposite leading wall. The mass transfer in the second pass is higher on the leading wall than on the trailing wall. A slower flow causes higher mass transfer enhancement in the turn on both the leading and trailing walls.
AUTHOR|(CDS)2079390; Van Duppen, Piet
The region around the nucleus $^{68}$Ni, with a shell closure for its protons at Z=28 and a harmonic oscillator shell gap for its neutrons at N=40, has drawn considerable interest over the past decades. $^{68}$Ni has properties that are typical for a doubly-magic nucleus, such as a high excitation energy and low B($E2:2^{+} \\rightarrow 0^{+}$) transition probability for the first excited 2$^{+}$ level and a 0$^{+}$ level as the first excited state. However, it has been suggested that the magic properties of $^{68}$Ni arise due to the fact that the N=40 separates the negative parity $pf$-shell from the positive parity 1$g_{9/2}$ orbital, and indeed, recent mass measurements have not revealed a clear N = 40 energy gap. Despite all additional information that was acquired over the last decade the specific role of the N=40 is not yet understood and a new experimental approach to study $^{68}$Ni was proposed. Namely, a two-neutron transfer reaction on $^{66}$Ni to characterize and disentangle the structure of the ...
Information transfer through quantum channels
Energy Technology Data Exchange (ETDEWEB)
Kretschmann, D.
2007-03-12
This PhD thesis represents work done between Aug. 2003 and Dec. 2006 in Reinhard F. Werner's quantum information theory group at Technische Universitaet Braunschweig, and Artur Ekert's Centre for Quantum Computation at the University of Cambridge. My thesis falls into the field of abstract quantum information theory. This work investigates both fundamental properties of quantum channels and their asymptotic capacities for classical as well as quantum information transfer. Stinespring's theorem is the basic structure theorem for quantum channels. It implies that every quantum channel can be represented as a unitary evolution on an enlarged system. In Ch. 3 we present a continuity theorem for Stinespring's representation: two quantum channels are similar if and only if it is possible to find unitary implementations that are likewise similar, with dimension-independent norm bounds. The continuity theorem allows to derive a formulation of the information-disturbance tradeoff in terms of quantum channels, and a continuity estimate for the no-broadcasting principle. In Ch. 4 we then apply the continuity theorem to give a strengthened no-go proof for quantum bit commitment, an important cryptographic primitive. This result also provides a natural characterization of those protocols that fall outside the standard setting of unconditional security, and thus may allow secure bit commitment. We present a new such protocol whose security relies on decoherence in the receiver's lab. Ch. 5 reviews the capacities of quantum channels for the transfer of both classical and quantum information, and investigates several variations in the notion of channel capacity. Memory effects are then investigated in detail in Ch. 6. We advertise a model which is sufficiently general to encompass all causal automata: every quantum process in which the outputs up to any given time t do not depend on the inputs at times t'>t can be represented as a concatenated memory
Directory of Open Access Journals (Sweden)
Carbone D.
2016-01-01
Full Text Available The 13C(18O,16O15C reaction has been studied at 84 MeV incident energy. The ejectiles have been momentum analized by the MAGNEX spectrometer and 15C excitation energy spectra have been obtained up to about 20 MeV. In the region above the two-neutron separation energy, a bump has been observed at 13.7 MeV. The extracted cross section angular distribution for this structure, obtained by using different models for background, displays a clear oscillating pattern, typical of resonant state of the residual nucleus.
Eikonal reaction theory for two-neutron removal reactions
Minomo, K; Egashira, K; Ogata, K; Yahiro, M
2014-01-01
The eikonal reaction theory (ERT) proposed lately is a method of calculating one-neutron removal reactions at intermediate incident energies in which Coulomb breakup is treated accurately with the continuum discretized coupled-channels method. ERT is extended to two-neutron removal reactions. ERT reproduces measured one- and two-neutron removal cross sections for 6He scattering on 12C and 208Pb targets at 240 MeV/nucleon and also on a 28Si target at 52 MeV/nucleon. For the heavier target in which Coulomb breakup is important, ERT yields much better agreement with the measured cross sections than the Glauber model.
Boiling Heat Transfer on Porous Surfaces with Vapor Channels
Institute of Scientific and Technical Information of China (English)
吴伟; 杜建华; 王补宣
2002-01-01
Boiling heat transfer on porous coated surfaces with vapor channels was investigated experimentally to determine the effects of the size and density of the vapor channels on the boiling heat transfer. Observations showed that bubbles escaping from the channels enhanced the heat transfer. Three regimes were identified: liquid flooding, bubbles in the channel and the bottom drying out region. The maximum heat transfer occurred for an optimum vapor channel density and the boiling heat transfer performance was increased if the channels were open to the bottom of the porous coating.
Heat transfer to near-critical helium in horizontal channels
Energy Technology Data Exchange (ETDEWEB)
Dolgoy, M.L.; Kirichenko, Y.A.; Sklovsky, Y.B.; Troyanov, A.M.; Chernyakov, P.S. (AN Ukrainskoj SSR, Kharkov. Fiziko-Tekhnicheskij Inst. Nizkikh Temperatur)
1983-03-01
Experimental results on heat transfer and pressure losses during a forced motion of helium of near-critical state parameters in a horizontal channel are reported. A method of calculation of temperature and pressure distributions along the channel is proposed.
Core momentum distribution in two-neutron halo nuclei
Souza, Lucas A; Yamashita, Marcelo T; Frederico, Tobias; Tomio, Lauro
2015-01-01
The core momentum distribution of a weakly-bound neutron-neutron-core exotic nucleus is computed within a renormalized zero-range three-body model, with interactions in the s-wave channel. The halo wave-function in momentum space is obtained by using as inputs the two-body scattering lengths and the two-neutron separation energy. The core momentum densities are computed for $^{11}$Li, $^{14}$Be $^{20}$C and $^{22}$C. The model describes the experimental data for $^{11}$Li, $^{14}$Be and to some extend $^{20}$C. The recoil momentum distribution of the $^{20}$C from the breakup of $^{22}$C nucleus is computed for different two-neutron separation energies, and from the comparison with recent experimental data the two-neutron separation energy is estimated in the range $100\\lesssim S_{2n}\\lesssim 400$ KeV. The recoil momentum distribution depends weakly on the neutron-$^{20}$C scattering length, while the matter radius is strongly sensitive to it. The expected universality of the momentum distribution width is ve...
Two neutron correlations in photo-fission
Dale, D. S.; Kosinov, O.; Forest, T.; Burggraf, J.; Stave, S.; Warren, G.; Starovoitova, V.
2016-09-01
A large body of experimental work has established the strong kinematical correlation between fission fragments and fission neutrons. Here, we report on the progress of investigations of the potential for strong two neutron correlations arising from the nearly back-to-back nature of the two fission fragments that emit these neutrons in the photo-fission process. In initial measurements, a pulsed electron linear accelerator was used to generate bremsstrahlung photons that impinged upon an actinide target, and the energy and opening angle distributions of coincident neutrons were measured using a large acceptance neutron detector array. A planned comprehensive set of measurements of two neutron correlations in the photo-fission of actinides is expected to shed light on several fundamental aspects of the fission process including the multiplicity distributions associated with the light and heavy fission fragments, the nuclear temperatures of the fission fragments, and the mass distribution of the fission fragments as a function of energy released. In addition to these measurements providing important nuclear data, the unique kinematics of fission and the resulting two neutron correlations have the potential to be the basis for a new tool to detect fissionable materials. A key technical challenge of this program arises from the need to perform coincidence measurements with a low duty factor, pulsed electron accelerator. This has motivated the construction of a large acceptance neutron detector array, and the development of data analysis techniques to directly measure uncorrelated two neutron backgrounds.
Directory of Open Access Journals (Sweden)
Lovell A.E.
2016-01-01
Full Text Available Recently, the first example of two-neutron decay from the ground state of an unbound nucleus, 16Be, was seen (A. Spyrou, et. al., Phys. Rev. Lett. 108 102501 (2012. Three-body methods are ideal for exactly treating the degrees of freedom important for these decays. Using a basis expansion over hyperspherical harmonics and the hyperspherical R-matrix method, we construct a realistic model of 16Be in order to investigate its decay mode and the role of the two-neutron interaction. The neutron-14Be interaction is constrained using shell model predictions. We obtain a ground state for 16Be that is under-bound by approximately 0.7 MeV with a width of approximately 0.17 MeV. For such a system, an attractive three-body force must be included to reproduce the experimental ground state energy.
Lovell, A E; Thompson, I J
2015-01-01
Recently, the first example of two-neutron decay from the ground state of an unbound nucleus, $^{16}$Be, was seen. Three-body methods are ideal for exactly treating the degrees of freedom important for these decays. Using a basis expansion over hyperspherical harmonics and the hyperspherical R-matrix method, we construct a realistic model of $^{16}$Be in order to investigate its decay mode and the role of the two-neutron interaction. The neutron-$^{14}$Be interaction is constrained using shell model predictions. We obtain a ground state for $^{16}$Be that is over-bound by approximately 1 MeV with a width of approximately 0.23 MeV. This suggests, that for such systems, the three-body force needs to be repulsive.
The heat transfer characteristics of lightning return stroke channel
Dong, Caixia; Yuan, Ping; Cen, Jianyong; Wang, Xuejuan; Mu, Yali
2016-09-01
Based on the time-resolved spectra of lightning return stroke processes, the evolutional characteristics of thermal conductivity and thermal diffusivity of the discharge channels are discussed. The distribution of temperature along the radial direction of channels at the peak current stage of return stroke is also investigated, and then the heat transferring characteristics along radial direction of the channels are analyzed. The results show that a temperature gradient along radial direction of lightning channel is formed due to the outward heat transfer. The closer the distance is to the current core channel, the greater the temperature gradient is and the more heat is transferred along the radial direction of the channel. The heat transferring in per unit length of the channel and per unit time is in the order of 104 J/m ṡ s at the initial moment of lightning return stroke. After the peak current, the channel temperature decreases slowly and the heat transport coefficients vary as a monotonically decreasing function.
Multi-Channel Transfer Function with Dimensionality Reduction
Kim, Han Suk; Schulze, Jürgen P.; Cone, Angela C.; Sosinsky, Gina E.; Martone, Maryann E.
2010-01-01
The design of transfer functions for volume rendering is a difficult task. This is particularly true for multi-channel data sets, where multiple data values exist for each voxel. In this paper, we propose a new method for transfer function design. Our new method provides a framework to combine multiple approaches and pushes the boundary of gradient-based transfer functions to multiple channels, while still keeping the dimensionality of transfer functions to a manageable level, i.e., a maximum of three dimensions, which can be displayed visually in a straightforward way. Our approach utilizes channel intensity, gradient, curvature and texture properties of each voxel. The high-dimensional data of the domain is reduced by applying recently developed nonlinear dimensionality reduction algorithms. In this paper, we used Isomap as well as a traditional algorithm, Principle Component Analysis (PCA). Our results show that these dimensionality reduction algorithms significantly improve the transfer function design process without compromising visualization accuracy. In this publication we report on the impact of the dimensionality reduction algorithms on transfer function design for confocal microscopy data. PMID:20582228
Finite volume simulation for convective heat transfer in wavy channels
Aslan, Erman; Taymaz, Imdat; Islamoglu, Yasar
2016-03-01
The convective heat transfer characteristics for a periodic wavy channel have been investigated experimentally and numerically. Finite volume method was used in numerical study. Experiment results are used for validation the numerical results. Studies were conducted for air flow conditions where contact angle is 30°, and uniform heat flux 616 W/m2 is applied as the thermal boundary conditions. Reynolds number ( Re) is varied from 2000 to 11,000 and Prandtl number ( Pr) is taken 0.7. Nusselt number ( Nu), Colburn factor ( j), friction factor ( f) and goodness factor ( j/ f) against Reynolds number have been studied. The effects of the wave geometry and minimum channel height have been discussed. Thus, the best performance of flow and heat transfer characterization was determined through wavy channels. Additionally, it was determined that the computed values of convective heat transfer coefficients are in good correlation with experimental results for the converging diverging channel. Therefore, numerical results can be used for these channel geometries instead of experimental results.
Explicit Numerical Modeling of Heat Transfer in Glacial Channels
Jarosch, A. H.; Zwinger, T.
2015-12-01
Turbulent flow and heat transfer of water in englacial channels is explicitly modelelled and the numerical results are compared to the most commonly used heat transfer parameterization in glaciology, i.e. the Dittus-Boelter equation. The three-dimensional flow is simulated by solving the incompressible Navier-Stokes equations utilizing a variational multiscale method (VMS) turbulence model and the finite-element method (i.e. Elmer-FEM software), which also solves the heat equation. By studying a wide range of key parameters of the system, e.g. channel diameter, Reynolds number, water flux, water temperature and Darcy-Weisbach wall roughness (which is explicitly represented on the wall geometry), it is found that the Dittus-Boelter equation is inadequate for glaciological applications and a new, highly suitable heat transfer parameterization for englacial/subglacial channels will be presented. This new parameterization utilizes a standard combination of dimensionless numbers describing the flow and channel (i.e. Reynolds number, Prandtl number and Darcy-Weisbach roughness) to predict a suitable Nusselt number describing the effective heat transfer and thus can be readily used in existing englacial/subglacial hydrology models.
Experimental Assessment of Moisture Transfer in the Vertical Ventilated Channel
Directory of Open Access Journals (Sweden)
Musorina Tatyana
2016-01-01
Full Text Available This article considers the moisture transfer phenomenon in the vertical ventilated channel. Also the article considers innovative structures for the vertical ventilated channel.The negative factors connected with moisture accumulation and excessive moistening of a heat insulation are given. Optimum design parameters for definition of the most intensive moisture transfer are discovered: systems with and without grooved lines. Influence that existence of technological gaps (grooved lines has on the speed of air flows in a gap is investigated. Dependence of speed on width of the ventilated gap for a design with the opened and closed grooved lines is established empirically. The dehumidification properties of the vertical ventilated channel are described, as well as dependence of mass evaporation rate on time is established. Processes of drying-out in various conditions are compared.
RFID Ownership Transfer with Positive Secrecy Capacity Channels
Directory of Open Access Journals (Sweden)
Jorge Munilla
2016-12-01
Full Text Available RFID ownership transfer protocols (OTPs transfer tag ownership rights. Recently, there has been considerable interest in such protocols; however, guaranteeing privacy for symmetric-key settings without trusted third parties (TTPs is a challenge still unresolved. In this paper, we address this issue and show that it can be solved by using channels with positive secrecy capacity. We implement these channels with noisy tags and provide practical values, thus proving that perfect secrecy is theoretically possible. We then define a communication model that captures spatiotemporal events and describe a first example of symmetric-key based OTP that: (i is formally secure in the proposed communication model and (ii achieves privacy with a noisy tag wiretap channel without TTPs.
Flow characteristics and heat transfer in wavy walled channels
Mills, Zachary; Shah, Tapan; Monts, Vontravis; Warey, Alok; Balestrino, Sandro; Alexeev, Alexander
2013-11-01
Using lattice Boltzmann simulations, we investigated the effects of wavy channel geometry on the flow and heat transfer within a parallel plate heat exchanger. We observed three distinct flow regimes that include steady flow with and without recirculation and unsteady time-periodic flow. We determined the critical Reynolds numbers at which the flow transitions between different flow regimes. To validate our computational results, we compared the simulated flow structures with the structures observed in a flowing soap film. Furthermore, we examine the effects of the wavy channel geometry on the heat transfer. We find that the unsteady flow regime drastically enhances the rate of heat transfer and show that heat exchangers with wavy walls outperform currently used heat exchangers with similar volume and power characteristics. Results from our study point to a simple and efficient method for increasing performance in compact heat exchangers.
Single phase channel flow forced convection heat transfer
Energy Technology Data Exchange (ETDEWEB)
Hartnett, J.P.
1999-04-01
A review of the current knowledge of single phase forced convection channel flow of liquids (Pr > 5) is presented. Two basic channel geometries are considered, the circular tube and the rectangular duct. Both laminar flow and turbulent flow are covered. The review begins with a brief overview of the heat transfer behavior of Newtonian fluids followed by a more detailed presentation of the behavior of purely viscous and viscoelastic Non-Newtonian fluids. Recent developments dealing with aqueous solutions of high molecular weight polymers and aqueous solutions of surfactants are discussed. The review concludes by citing a number of challenging research opportunities.
Profiling optimization for big data transfer over dedicated channels
Energy Technology Data Exchange (ETDEWEB)
Yun, D. [New Jersey Institute of Technology; Wu, Qishi [University of Memphis; Rao, Nageswara S [ORNL; Kettimuthu, R. [Argonne National Laboratory (ANL); Jung, E. S. [Argonne National Laboratory (ANL)
2016-01-01
The transfer of big data is increasingly supported by dedicated channels in high-performance networks, where transport protocols play an important role in maximizing applicationlevel throughput and link utilization. The performance of transport protocols largely depend on their control parameter settings, but it is prohibitively time consuming to conduct an exhaustive search in a large parameter space to find the best set of parameter values. We propose FastProf, a stochastic approximation-based transport profiler, to quickly determine the optimal operational zone of a given data transfer protocol/method over dedicated channels. We implement and test the proposed method using both emulations based on real-life performance measurements and experiments over physical connections with short (2 ms) and long (380 ms) delays. Both the emulation and experimental results show that FastProf significantly reduces the profiling overhead while achieving a comparable level of end-to-end throughput performance with the exhaustive search-based approach.
Boiling heat transfer in horizontal and inclined rectangular channels
Energy Technology Data Exchange (ETDEWEB)
Morcos, S.M.; Mobarak, A.; Hilal, M.; Mohareb, M.R. (Cairo Univ. (Egypt))
1987-05-01
The present experimental investigation is concerned with boiling heat transfer of water inside both horizontal and inclined rectangular channels under a relatively low heat flux. These configurations simulate the absorber channel of line-focus solar concentrations under boiling conditions. The experimental facility includes electrically heated aluminum rectangular channels with aspect ratios of 2.67 and 0.37. The experimental results of the two-phase Nusselt number for the two aspect ratios and for the inclination angles 0, 15, 30, and 45 deg were correlated in terms of a ratio of the two-phase to the liquid-phase Reynolds number for the forced-convection vaporization region. The proposed correlations agree well with previous investigations. In the present work, classifications of the various flow patterns were made by direct observation through a glass window at the end of the test section.
Boiling heat transfer in a small horizontal rectangular channel
Energy Technology Data Exchange (ETDEWEB)
Tran, T.N.; Wambsganss, M.W.; Jendrzejczyk, J.A. [Argonne National Lab., IL (United States); France, D.M. [Illinois Univ., Chicago, IL (United States). Dept. of Mechanical Engineering
1993-08-01
Compact heat exchangers have traditionally found wide application in the transportation industry, where they are used as evaporators and condensers in vapor compression cycles for air conditioning and refrigeration. Such heat exchangers possess numerous attractive features including high thermal effectiveness, small size, low weight, design flexibility, and pure counterflow, and they can accommodate multiple streams. Today, there is a widespread interest in expanding the range of application of compact heat exchangers to include phase-change heat transfer in the process industries, among others. An overall objective of this effort is to provide the basis for establishing design technology in this area. In the present study, small channel flow boiling heat transfer was extended to a rectangular channel (4.06 {times} 1.70 mm) using refrigerant 12 (R-12). As with the circular tube studies, the flow channel wall was electrically heated providing a constant heat flux. Tests were performed over a quality range of 0.15 to 0.80, and large ranges of mass fluxes (50 to 400 kg/m{sup 2}s) and heat flux (4 to 34 kW/m{sup 2}). Heat transfer was measured and results are compared with correlation predictions.
Emergent universality in the two-neutron halo structure of 22C
Souza, L. A.; Garrido, E.; Frederico, T.
2016-12-01
The structure of the two-neutron halo 22C is investigated by means of a renormalized zero-range three-body model, with interactions in the s -wave channel, and a finite-range model with two- and three-body forces provided by the hyperspherical adiabatic expansion method. In both models the halo wave function in configuration space is obtained by using as inputs the two-body scattering lengths and the two-neutron separation energy. The halo-matter density is computed for 22C with different three-body forces and low-energy parameters, with two-neutron separation energy within the range 50 keV≤S2 n≤1000 keV. The halo-neutron density depends weakly on the neutron-20C scattering length as long as its absolute value is larger than the neutron-neutron one. The halo-neutron density is then analyzed by means of the root-mean-square radius, the probability density, and also the geometry, taking into account the angle between the two Jacobi coordinates. The results of finite-range and zero-range two-neutron-core models are compared. The effects in the halo structure of short-range and long-range three-body forces are studied, and the emergent universal behavior of the halo-neutron density and its geometry is pointed out.
Charge Transfer Channels in Formation of Exciplex in Polymer Blends
Institute of Scientific and Technical Information of China (English)
DOU Fei; ZHANG Xin-Ping
2011-01-01
The strong dependence of photoluminescence of charge transfer excited states or exciplex in a blend film of poly(9,9'-dioctylBuorene-co-benzothiadiazole) (F8BT) and poly(9,9'-dioctyl6uorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-l,4- phenylenediamine) (PFB) on the excitation wavelengths and morphology is investigated. The experimental results reveal that electron transfer in the LUMOs from PFB to F8BT is more efficient than hole transfer in the HOMOs from PFB to F8BT for the formation of exciplex at the interfacial junctions between these two types of molecules in the blend Sim. Furthermore, energy transfer from the blue-emitting PFB to the green-emitting F8BT at the interfaces introduces an additional two-step channel and thus enhances the formation of an exciplex. This is important for understanding of charge generation and separation in organic bulk heterojunctions and for design of optoelectronic devices.%@@ The strong dependence of photoluminescence of charge transfer excited states or exciplex in a blend film of poly(9,9'-dioctylfluorene-co-benzothiadiazole)(F8BT)and poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine)(PFB)on the excitation wavelengths and morphology is investigated.The experimental results reveal that electron transfer in the LUMOs from PFB to F8BT is more efficient than hole transfer in the HOMOs from PFB to F8BT for the formation of exciplex at the interfacial junctions between these two types of molecules in the blend film.Furthermore,energy transfer from the blue-emitting PFB to the green-emitting F8BT at the interfaces introduces an additional two-step channel and thus enhances the formation of an exciplex.This is important for understanding of charge generation and separation in organic bulk heterojunctions and for design of optoelectronic devices.
Chen, Xiaohua; Bu, Yuxiang
2007-08-08
The mechanism of proton transfer (PT)/electron transfer (ET) in acylamide units was explored theoretically using density functional theory in a representative model (a cyclic coupling mode between formamide and the N-dehydrogenated formamidic radical, FF). In FF, PT/ET normally occurs via a seven-center cyclic proton-coupled electron transfer (PCET) mechanism with a N-->N PT and an O-->O ET. However, when different hydrated metal ions are bound to the two oxygen sites of FF, the PT/ET mechanism may significantly change. In addition to their inhibition of PT/ET rate, the hydrated metal ions can effectively regulate the FF PT/ET cooperative mechanism to produce a single pathway hydrogen atom transfer (HAT) or a flexible proton coupled electron transfer (PCET) mechanism by changing the ET channel. The regulation essentially originates from the change in the O...O bond strength in the transition state, subject to the binding ability of the hydrated metal ions. In general, the high valent metal ions and those with large binding energies can promote HAT, and the low valent metal ions and those with small binding energies favor PCET. Hydration may reduce the Lewis acidity of cations, and thus favor PCET. Good correlations among the binding energies, barrier heights, spin density distributions, O...O contacts, and hydrated metal ion properties have been found, which can be used to interpret the transition in the PT/ET mechanism. These findings regarding the modulation of the PT/ET pathway via hydrated metal ions may provide useful information for a greater understanding of PT/ET cooperative mechanisms, and a possible method for switching conductance in nanoelectronic devices.
Pulse Method of Mass Transfer Intensification in Elastic Channels
Malyshev, V. L.
2016-01-01
The kinetics of internal mass transfer in the course of evaporation of liquids in elastic capillary systems in which the transverse dimensions of the pores can both decrease and increase on exposure to intense thermal effect is investigated. Structural transformations in a material arise as a result of its dehydration. It is assumed that the channel radius changes simultaneously over the entire length, synchronously with the interface motion. Three schemes are possible in principle: a uniform change during the process, a faster change in the initial stage, and, conversely, a faster change in the closing stage. The time-limited additional thermal effect during the period that makes the main contribution to the overall duration of the process is capable of substantially enhancing mass transfer with minimum energy consumption.
Efficient Quantum Information Transfer Through a Uniform Channel
Directory of Open Access Journals (Sweden)
Paola Verrucchi
2011-06-01
Full Text Available Effective quantum-state and entanglement transfer can be obtained by inducing a coherent dynamics in quantum wires with homogeneous intrawire interactions. This goal is accomplished by optimally tuning the coupling between the wire endpoints and the two qubits there attached. A general procedure to determine such value is devised, and scaling laws between the optimal coupling and the length of the wire are found. The procedure is implemented in the case of a wire consisting of a spin-1/2 XY chain: results for the time dependence of the quantities which characterize quantum-state and entanglement transfer are found of extremely good quality also for very long wires. The present approach does not require engineered intrawire interactions nor a specific initial pulse shaping, and can be applied to a vast class of quantum channels.
Forced Convective Heat Transfer in a Porous Plate Channel
Institute of Scientific and Technical Information of China (English)
PeixueJiang; ZhanWang; 等
1997-01-01
Fored convective heat transfer in a plate channel filled with metallic spherical particales was investigated experimentally and numerically.The test section ,58mm×80mm×50mm in size,was heated by a 0.4mm thick plate electrical heater,The coolant water flow rate ranged from 0.015 to 0.833 kg/s.The local wall temperature distribution was measured along with the inlet and outlet fliud temperatures and pressures.The results illustrate the heat transfer augmentation and increased pressure drop caused by the porous medium.The heat transfer coefficient was increased 5-12 times by the porous media although the hydraulic resistance was increased even more.The Nusselt number and the heat transfer coefficient increased with decreasing particle diameter,while the pressure drop decreased as the particle diameter increased.It was found that,for the conditions studied(metallic packed bed),the effect of thermal dispersion did not need to be considered in the physical model,as opposed to a non-metallic packed bed,where thermal dispersion is important.
Two neutron decay from the $2_1^+$ state of $^6$He
Kikuchi, Yuma; Minomo, Kosho; Ogata, Kazuyuki
2013-01-01
Decay mode of the $2_1^+$ resonant state of $^6$He populated by the $^6$He breakup reaction by $^{12}$C at 240 MeV/nucleon is investigated. The continuum-discretized coupled-channels method is adopted to describe the formation of the $2_1^+$ state, whereas its decay is described by the complex-scaled solutions of the Lippmann-Schwinger equation. From analysis of invariant mass spectra with respect to the $\\alpha$-$n$ and $n$-$n$ subsystems, coexistence of two decay modes is found. One is the simultaneous decay of two neutrons correlating with each other and the other is the emission of two neutrons to the opposite directions. The latter is found to be free from the final state interaction and suggests existence of a di-neutron in the $2_1^+$ state of $^6$He.
Coupled-channels description of the 40Ca+58,64Ni transfer and fusion reactions
Scamps, G; Hagino, K; Haas, F; Courtin, S
2016-01-01
Preliminary experimental data for nucleon transfer reactions of the 40Ca+58Ni and 40Ca+64Ni systems are analyzed with the coupled- channels approach. It is shown that a simple treatment for the transfer in the coupled-channels method cannot reproduce simultaneously the transfer probabilities and the sub-barrier enhancement of fusion cross sections.
Boltenko, E. A.; Varava, A. N.; Dedov, A. V.; Zakharenkov, A. V.; Komov, A. T.; Malakhovskii, S. A.
2015-03-01
Results from systematic investigations of heat transfer and pressure drop for water flow in an annular channel using an efficient method for enhancing heat transfer on a convex heating surface are presented. The main technical data of the thermal-hydraulic experimental setup are given together with a brief description of the control, monitoring, and physical parameters measurement and recording systems, as well as primary experimental data processing and storage system. The test section, the enhancement method based on setting up swirl flows, the geometrical characteristics of intensifiers, their schematic design, and installation technology are described. The experimental data are obtained in a wide range of coolant flow parameters under the conditions of single-phase convection with using intensifiers having different shapes. The test measurements carried out on a smooth annular channel showed good agreement with the classic correlations both for heat transfer and pressure drop, thereby confirming reliability of the experimental data. A considerable improvement in heat removal efficiency on the convex heating surface is obtained. The value of heat transfer coefficient is a factor of 1.8 higher than it is for smooth annular channels. The region of the values of intensifier geometrical characteristics and Reynolds numbers for which the growth of heat transfer prevails over the growth of pressure drop is established. It is shown that the maximums of heat transfer and pressure drop are observed at quite definite values of intensifier geometrical characteristics. The primary experimental data are processed and presented as a dependence of the Nusselt number on the Reynolds number for different values of the intensifier's relative fin height Ḣ. The value of Ḣ at which heat transfer reaches its maximum is found. The experiments were carried out in the pressure range p = 3.0-10.0 MPa and at the constant temperature of liquid at the test section inlet equal to 100
Observation of Ground-State Two-Neutron Decay
Thoennessen, M; Spyrou, A; Lunderberg, E; DeYoung, P A; Attanayake, H; Baumann, T; Bazin, D; Brown, B A; Christian, G; Divaratne, D; Grimes, S M; Haagsma, A; Finck, J E; Frank, N; Luther, B; Mosby, S; Nagi, T; Peaslee, G F; Peters, W A; Schiller, A; Smith, J K; Snyder, J; Strongman, M; Volya, A
2012-01-01
Neutron decay spectroscopy has become a successful tool to explore nuclear properties of nuclei with the largest neutron-to-proton ratios. Resonances in nuclei located beyond the neutron dripline are accessible by kinematic reconstruction of the decay products. The development of two-neutron detection capabilities of the Modular Neutron Array (MoNA) at NSCL has opened up the possibility to search for unbound nuclei which decay by the emission of two neutrons. Specifically this exotic decay mode was observed in 16Be and 26O.
COMPUTATION OF MOMENTUM TRANSFER COEFFICIENT AND CONVEYANCE CAPACITY IN COMPOUND CHANNELS
Institute of Scientific and Technical Information of China (English)
WANG Hua; YANG Ke-jun; CAO Shu-you; LIU Xing-nian
2007-01-01
The momentum transfer coefficient is an important parameter for determining the apparent shear stress at the vertical interface between the main channel and its associated flood plains, the cross-sectional mean velocity and the discharge capacity in compound channels. In this article, under the Boussinesq assumption and through analyzing the characteristics of velocity distribution in the interacting region between the main channel and its associated flood plain, the expression of momentum transfer coefficient was theoretically derived. On the basis of force balance, the expression of vertical apparent shear stress was obtained. By applying the experimental data from the British Engineering Research Council Flood Channel Facility (SERC-FCF), the relationship between the momentum transfer coefficient with the relative depth and the ratio of the flood plain width to the main channel width, was established, And hence the conveyance capacity in compound channels was calculated with Liu and Dong's method. The computed results show that the momentum transfer coefficient relationship obtained is viable.
Evaluation of correlations of flow boiling heat transfer of R22 in horizontal channels.
Zhou, Zhanru; Fang, Xiande; Li, Dingkun
2013-01-01
The calculation of two-phase flow boiling heat transfer of R22 in channels is required in a variety of applications, such as chemical process cooling systems, refrigeration, and air conditioning. A number of correlations for flow boiling heat transfer in channels have been proposed. This work evaluates the existing correlations for flow boiling heat transfer coefficient with 1669 experimental data points of flow boiling heat transfer of R22 collected from 18 published papers. The top two correlations for R22 are those of Liu and Winterton (1991) and Fang (2013), with the mean absolute deviation of 32.7% and 32.8%, respectively. More studies should be carried out to develop better ones. Effects of channel dimension and vapor quality on heat transfer are analyzed, and the results provide valuable information for further research in the correlation of two-phase flow boiling heat transfer of R22 in channels.
Two-neutron decay of excited states of 11Li
Smith, Jenna; MoNA Collaboration
2013-10-01
One prominent example of a Borromean nucleus is the two-neutron halo nucleus, 11Li. All excited states of this nucleus are unbound to two-neutron decay. Many theories propose that the two valence neutrons exhibit dineutron behavior in the ground state, but it is unclear what effect such a structure would have on the decay of the excited states. We have recently completed an experiment designed to study the decay of one of these excited states. Unbound 11Li was populated via a two-proton knockout from 13B. The two emitted neutrons were detected with the Modular Neutron Array (MoNA) and the Large-area multi-Institutional Scintillator Array (LISA) in coincidence with the daughter fragment, 9Li. Preliminary results will be discussed.
Directory of Open Access Journals (Sweden)
Szwast Maciej
2015-06-01
Full Text Available The paper presents the mathematical modelling of selected isothermal separation processes of gaseous mixtures, taking place in plants using membranes, in particular nonporous polymer membranes. The modelling concerns membrane modules consisting of two channels - the feeding and the permeate channels. Different shapes of the channels cross-section were taken into account. Consideration was given to co-current and counter-current flows, for feeding and permeate streams, respectively, flowing together with the inert gas receiving permeate. In the proposed mathematical model it was considered that pressure of gas changes along the length of flow channels was the result of both - the drop of pressure connected with flow resistance, and energy transfer by molecules of gas flowing in a given channel to molecules which penetrate this channel from the adjacent channel. The literature on membrane technology takes into account only the drop of pressure connected with flow resistance. Consideration given to energy transfer by molecules of gas flowing in a given channel to molecules which penetrate this channel from the adjacent channel constitute the essential novelty in the current study. The paper also presents results of calculations obtained by means of a computer program which used equations of the derived model. Physicochemical data concerning separation of the CO2/CH4 mixture with He as the sweep gas and data concerning properties of the membrane made of PDMS were assumed for calculations.
Investigation of Heat Transfer in Mini Channels using Planar Laser Induced Fluorescence
DEFF Research Database (Denmark)
Bøgild, Morten Ryge; Poulsen, Jonas Lundsted; Rath, Emil Zacho
2012-01-01
In this paper an experimental investigation of the heat transfer in mini channels with a hydraulic diameter of 889 m is conducted. The method used is planar laser induceduorescence (PLIF), which uses the principle of laser excitation of rhodamine B in water. The goal of this study is to validate...... the applicability of PLIF to determine the convective heat transfer coecient in mini channels against conventional correlations of the convective heat transfer coecient. The applicability of the conventional theory in micro and mini channels has been discussed by several researchers, but to the authors knowledge...
Comparative evaluation of three heat transfer enhancement strategies in a grooved channel
Energy Technology Data Exchange (ETDEWEB)
Herman, C.; Kang, E. [Dept. of Mechanical Engineering, Johns Hopkins Univ., Baltimore, MD (United States)
2001-09-01
Results of a comparative evaluation of three heat transfer enhancement strategies for forced convection cooling of a parallel plate channel populated with heated blocks, representing electronic components mounted on printed circuit boards, are reported. Heat transfer in the reference geometry, the asymmetrically heated parallel plate channel, is compared with that for the basic grooved channel, and the same geometry enhanced by cylinders and vanes placed above the downstream edge of each heated block. In addition to conventional heat transfer and pressure drop measurements, holographic interferometry combined with high-speed cinematography was used to visualize the unsteady temperature fields in the self-sustained oscillatory flow. The locations of increased heat transfer within one channel periodicity depend on the enhancement technique applied, and were identified by analyzing the unsteady temperature distributions visualized by holographic interferometry. This approach allowed gaining insight into the mechanisms responsible for heat transfer enhancement. Experiments were conducted at moderate flow velocities in the laminar, transitional and turbulent flow regimes. Reynolds numbers were varied in the range Re = 200-6500, corresponding to flow velocities from 0.076 to 2.36 m/s. Flow oscillations were first observed between Re = 1050 and 1320 for the basic grooved channel, and around Re = 350 and 450 for the grooved channels equipped with cylinders and vanes, respectively. At Reynolds numbers above the onset of oscillations and in the transitional flow regime, heat transfer rates in the investigated grooved channels exceeded the performance of the reference geometry, the asymmetrically heated parallel plate channel. Heat transfer in the grooved channels enhanced with cylinders and vanes showed an increase by a factor of 1.2-1.8 and 1.5-3.5, respectively, when compared to data obtained for the basic grooved channel; however, the accompanying pressure drop penalties
Comparative evaluation of three heat transfer enhancement strategies in a grooved channel
Herman, C.; Kang, E.
Results of a comparative evaluation of three heat transfer enhancement strategies for forced convection cooling of a parallel plate channel populated with heated blocks, representing electronic components mounted on printed circuit boards, are reported. Heat transfer in the reference geometry, the asymmetrically heated parallel plate channel, is compared with that for the basic grooved channel, and the same geometry enhanced by cylinders and vanes placed above the downstream edge of each heated block. In addition to conventional heat transfer and pressure drop measurements, holographic interferometry combined with high-speed cinematography was used to visualize the unsteady temperature fields in the self-sustained oscillatory flow. The locations of increased heat transfer within one channel periodicity depend on the enhancement technique applied, and were identified by analyzing the unsteady temperature distributions visualized by holographic interferometry. This approach allowed gaining insight into the mechanisms responsible for heat transfer enhancement. Experiments were conducted at moderate flow velocities in the laminar, transitional and turbulent flow regimes. Reynolds numbers were varied in the range Re=200-6500, corresponding to flow velocities from 0.076 to 2.36m/s. Flow oscillations were first observed between Re=1050 and 1320 for the basic grooved channel, and around Re=350 and 450 for the grooved channels equipped with cylinders and vanes, respectively. At Reynolds numbers above the onset of oscillations and in the transitional flow regime, heat transfer rates in the investigated grooved channels exceeded the performance of the reference geometry, the asymmetrically heated parallel plate channel. Heat transfer in the grooved channels enhanced with cylinders and vanes showed an increase by a factor of 1.2-1.8 and 1.5-3.5, respectively, when compared to data obtained for the basic grooved channel; however, the accompanying pressure drop penalties also
The effect of a magnetic field on heat transfer in a slotted channel
Energy Technology Data Exchange (ETDEWEB)
Evtushenko, I.A. [D.V. Efremov Scientific Research Institute of Electrophysical Apparatus, St. Petersburg, 189631 (Russian Federation); Hua, T.Q. [Argonne National Laboratory, Argonne, IL 60439 (United States); Kirillov, I.R. [D.V. Efremov Scientific Research Institute of Electrophysical Apparatus, St. Petersburg, 189631 (Russian Federation); Reed, Claude B. [Argonne National Laboratory, Argonne, IL 60439 (United States); Sidorenkov, S.S. [D.V. Efremov Scientific Research Institute of Electrophysical Apparatus, St. Petersburg, 189631 (Russian Federation)
1995-03-01
The results of numerical and experimental studies of liquid metal heat transfer in slotted channels in a transverse magnetic field are presented. Test results showed an improvement in heat transfer in a straight channel at low and moderate interaction parameter N. The Nusselt number at small N (around 120) was up to twofold higher than in turbulent flow without a magnetic field, the Peclet number being equal. This effect of heat transfer enhancement is caused by the generation and development of large-scale velocity fluctuations close to the heated wall area. Qualitative and quantitative correlations between heat transfer and velocity fluctuation characteristics are presented. (orig.).
The effect of a magnetic field on heat transfer in a slotted channel
Energy Technology Data Exchange (ETDEWEB)
Evtushenko, I.A.; Kirillov, I.R.; Sidorenkov, S.S. [D.V. Efremov Scientific Research Institute of Electrophysical Apparatus, St. Petersburg (Russian Federation); Hua, T.Q.; Reed, C.B. [Argonne National Lab., IL (United States)
1994-07-01
The results of numerical and experimental studies of liquid metal heat transfer in slotted channels in a transverse magnetic field are presented. Test results showed an improvement in heat transfer in a straight channel at low and moderate interaction parameter, N. The Nusselt number at small N (around 120) was up to 2 times higher than in turbulent flow without a magnetic field, Peclet number being equal. This effect of heat transfer enhancement is caused by the generation and development of large scale velocity fluctuations in the near heated wall area. Qualitative and quantitative correlations between heat transfer and velocity fluctuation characteristics are presented.
Monte Carlo simulations of dense gas flow and heat transfer in micro- and nano-channels
Institute of Scientific and Technical Information of China (English)
WANG Moran; LI Zhixin
2005-01-01
The dense gas flow and heat transfer in micro- and nano-channels was simulated using the Enskog simulation Monte Carlo (ESMC) method. The results were compared with those from the direct simulation Monte Carlo (DSMC) method and from the consistent Boltzmann algorithm (CBA). The dense gas flow and heat transfer characteristics were thus analyzed. The results showed that when the gas density was large enough, the finite gas density effect on the flow and heat transfer cannot be ignored, which decreased the skin friction coefficient and changed the heat transfer characteristics on the channel wall surfaces.
Heat transfer of bubbly flow on inner wall of annular channel
Directory of Open Access Journals (Sweden)
Lobanov Pavel
2017-01-01
Full Text Available Experimental investigations of heat transfer from the heated wall to the two-phase bubbly flow were performed in vertical annular channel using air-water system. The IR-thermography and miniature temperature sensors were used to measure heat transfer coefficients. The influence of bubbles on heat transfer is shown in comparison with the case of single phase flow. The presence of bubbles in the flow leads to heat transfer intensification in the annular channel even for low void fractions.
Mixed convection flow and heat transfer in a vertical wavy channel ...
African Journals Online (AJOL)
user
Keywords: convective flow; wavy channel; porous medium; traveling thermal waves. ... the problems of forced convection in composite fluids and porous layers. ... Processes involving heat and mass transfer are often encountered in the ...
Reinhardt, Colin N.; Tsintikidis, Dimitris; Hammel, Stephen; Kuga, Yasuo; Ritcey, James A.; Ishimaru, Akira
2012-03-01
Using an 850-nanometer-wavelength free-space optical (FSO)communications system of our own design, we acquired field data for the transmitted and received signals in fog at Point Loma, CA for a range of optical depths within the multiple-scattering regime. Statistical estimators for the atmospheric channel transfer function and the related coherency function were computed directly from the experimental data. We interpret the resulting channel transfer function estimates in terms of the physics of the atmospheric propagation channel and fog aerosol particle distributions. We investigate the behavior of the estimators using both real field-test data and simulated propagation data. We compare the field-data channel transfer function estimates against the outputs from a computationally-intensive radiative-transfer theory model-based approach, which we also developed previously for the FSO multiple-scattering atmospheric channel. Our results show that the data-driven channel transfer function estimates are in close agreement with the radiative transfer modeling, and provide comparable receiver signal detection performance improvements while being significantly less time and computationally-intensive.
Thermodynamic view of activation energies of proton transfer in various gramicidin A channels.
Chernyshev, Anatoly; Cukierman, Samuel
2002-01-01
The temperature dependencies (range: 5-45 degrees C) of single-channel proton conductances (g(H)) in native gramicidin A (gA) and in two diastereoisomers (SS and RR) of the dioxolane-linked gA channels were measured in glycerylmonooleate/decane (GMO) and diphytanoylphosphatidylcholine/decane (DiPhPC) bilayers. Linear Arrhenius plots (ln (g(H)) versus K(-1)) were obtained for the native gA and RR channels in both types of bilayers, and for the SS channel in GMO bilayers only. The Arrhenius plot for proton transfer in the SS channel in DiPhPC bilayers had a break in linearity around 20 degrees C. This break seems to occur only when protons are the permeating cations in the SS channel. The activation energies (E(a)) for proton transfer in various gA channels (approximately 15 kJ/mol) are consistent with the rate-limiting step being in the channel and/or at the membrane-channel/solution interface, and not in bulk solution. E(a) values for proton transfer in gA channels are considerably smaller than for the permeation of nonproton currents in gA as well as in various other ion channels. The E(a) values for proton transfer in native gA channels are nearly the same in both GMO and DiPhPC bilayers. In contrast, for the dioxolane linked gA dimers, E(a) values were strongly modulated by the lipid environment. The Gibbs activation free energies (Delta G(#)(o)) for protons in various gA channels are within the range of 27-29 kJ/mol in GMO bilayers and of 20-22 kJ/mol in DiPhPC bilayers. The largest difference between Delta G(#)(o) for proton currents occurs between native gA (or SS channels) and the RR channel. In general, the activation entropy (Delta S) is mostly responsible for the differences between g(H) values in various gA channels, and also in distinct bilayers. However, significant differences between the activation enthalpies (Delta H(#)(o)) for proton transfer in the SS and RR channels occur in distinct membranes.
Maldonado, Jaime J.
1994-01-01
Hypersonic vehicles are exposed to extreme thermal conditions compared to subsonic aircraft; therefore, some level of thermal management is required to protect the materials used. Normally, hypersonic vehicles experience the highest temperatures in the nozzle throat, and aircraft and propulsion system leading edges. Convective heat transfer augmentation techniques can be used in the thermal management system to increase heat transfer of the cooling channels in those areas. The techniques studied in this report are pin-fin, offset-fin, ribbed and straight roughened channel. A smooth straight channel is used as the baseline for comparing the techniques. SINDA '85, a lumped parameter finite difference thermal analyzer, is used to model the channels. Subroutines are added to model the fluid flow assuming steady one dimensional compressible flow with heat addition and friction. Correlations for convective heat transfer and friction are used in conjunction with the fluid flow analysis mentioned. As expected, the pin-fin arrangement has the highest heat transfer coefficient and the largest pressure drop. All the other devices fall in between the pin-fin and smooth straight channel. The selection of the best heat augmentation method depends on the design requirements. A good approach may be a channel using a combination of the techniques. For instance, several rows of pin-fins may be located at the region of highest heat flux, surrounded by some of the other techniques. Thus, the heat transfer coefficient is maximized at the region of highest heat flux while the pressure drop is not excessive.
Khushboo, Mandal, S.; Nath, S.; Madhavan, N.; Gehlot, J.; Jhingan, A.; Kumar, Neeraj; Banerjee, Tathagata; Kaur, Gurpreet; Rojeeta Devi, K.; Banerjee, A.; Neelam, Varughese, T.; Siwal, Davinder; Garg, R.; Mukul, Ish; Saxena, M.; Verma, S.; Kumar, S.; Behera, B. R.; Verma, P.
2017-07-01
Background: It is a well established fact that nuclear deformation and vibration influence fusion dynamics around the Coulomb barrier. This effect was observed for several systems with the inclusion of inelastic excitations in coupled-channels calculations. Sub-barrier fusion cross sections were also observed to be affected by neutron transfer in systems carrying positive Q value for transfer channels. However, recent experimental analysis with a few systems showed that inelastic excitations are enough to explain the sub-barrier fusion behavior, and no effect was noticed due to positive Q -value transfer channels. Purpose: The motivation behind present investigation is to explore the effects of colliding nuclei structure and the transfer channel on enhancement of sub-barrier fusion cross sections. Method: An experiment was performed with Heavy Ion Reaction Analyzer (HIRA) at New Delhi to measure the fusion cross sections for 28Si+Zr,9692 systems. These cross sections were later compared with quantum mechanical coupled-channels calculations. In order to explore the effects of nuclear deformation on fusion cross sections, the present data were compared with those of other researchers on fusion who have used various projectiles of different structural properties on a 96Zr target. Results: Experimental fusion cross sections have been extracted around the Coulomb barrier. In the coupled-channels framework, inclusion of inelastic excitations of both projectile (28Si) and targets (Zr,9692) could reproduce the experimental cross sections around the Coulomb barrier, but they deviated substantially in the sub-barrier region. This indicates that positive Q -value neutron transfer channels may need to be included in the calculations to reproduce the experimental cross sections at sub-barrier energies. Conclusions: The nuclear structure of interacting nuclei has a strong influence on sub-barrier fusion enhancement. The effect of multineutron transfer channels was observed to be
Numerical simulations of heat transfer in plane channel flow
Gharbi, Najla El; Benzaoui, Ahmed
2010-01-01
Reynolds-averaged Navier-Stokes (RANS) turbulence models (such as k-{\\epsilon} models) are still widely used for engineering applications because of their relatively simplicity and robustness. In fully developed plane channel flow (i.e. the flow between two infinitely large plates), even if available models and near-wall treatments provide adequate mean flow velocities, they fail to predict suitable turbulent kinetic energy "TKE" profiles near walls. TKE is involved in determination of eddy viscosity/diffusivity and could therefore provide inaccurate concentrations and temperatures. In order to improve TKE a User Define Function "UDF" based on an analytical profile for TKE was developed and implemented in Fluent. Mean streamwise velocity and turbulent kinetic energy "TKE" profiles were compared to DNS data for friction Reynolds number $Re_{\\tau}$ = 150. Simulation results for TKE show accurate profiles. Simulation results for horizontal heated channel flows obtained with Fluent are presented. Numerical result...
Characterization of nuclear sources via two-neutron intensity interferometry
Ghetti, R; Helgesson, J; De Filippo, E; Tagliente, G; Anzalone, A; Bellini, V; Carlén, L; Cavallaro, S; Celano, L; D'Erasmo, G; Di Santo, D; Fiore, E M; Fokin, A; Geraci, M; Jakobsson, B; Kuznetsov, A; Lanzanò, G; Mahboub, D; Murin, Yu A; Maartensson, J; Pagano, A; Palazzolo, F; Palomba, M; Pantaleo, A; Paticchio, V; Potenza, R; Riera, G; Siwek, A; Sperduto, M L; Sutera, C; Urrata, M; Westerberg, L
1999-01-01
The neutron energy spectrum and the two-neutron correlation function have been measured for the E/A=45 MeV Ni + Al reaction in order to assess the space-time characteristics of the neutron emitting source. When comparing the data to a statistical model, the kinetic energy spectra, the integrated correlation function as well as the longitudinal correlation function are reproduced by one single source. However, only the inclusion of a short-lived pre-equilibrium component can account for the stronger correlation exhibited by neutron pairs emitted with high total momentum. The correlation function from events defined as peripheral by constraints on the highest charge of the projectile-like fragment does show a significantly weaker correlation than the minimum bias sample.
Quantum Monte Carlo calculations of two neutrons in finite volume
Klos, P; Tews, I; Gandolfi, S; Gezerlis, A; Hammer, H -W; Hoferichter, M; Schwenk, A
2016-01-01
Ab initio calculations provide direct access to the properties of pure neutron systems that are challenging to study experimentally. In addition to their importance for fundamental physics, their properties are required as input for effective field theories of the strong interaction. In this work, we perform auxiliary-field diffusion Monte Carlo calculations of the ground and first excited state of two neutrons in a finite box, considering a simple contact potential as well as chiral effective field theory interactions. We compare the results against exact diagonalizations and present a detailed analysis of the finite-volume effects, whose understanding is crucial for determining observables from the calculated energies. Using the L\\"uscher formula, we extract the low-energy S-wave scattering parameters from ground- and excited-state energies for different box sizes.
Directory of Open Access Journals (Sweden)
James A. Parsons
2001-01-01
Full Text Available The effect of channel rotation on jet impingement cooling by arrays of circular jets in twin channels was studied. Impinging jet flows were in the direction of rotation in one channel and opposite to the direction of rotation in the other channel. The jets impinged normally on the smooth, heated target wall in each channel. The spent air exited the channels through extraction holes in each target wall, which eliminates cross flow on other jets. Jet rotation numbers and jet Reynolds numbers varied from 0.0 to 0.0028 and 5000 to 10,000, respectively. For the target walls with jet flow in the direction of rotation (or opposite to the direction of rotation, as rotation number increases heat transfer decreases up to 25% (or 15% as compared to corresponding results for non-rotating conditions. This is due to the changes in flow distribution and rotation induced Coriolis and centrifugal forces.
Knowledge Transfer Channels to Vietnam for Process Improvement
DEFF Research Database (Denmark)
Machikita, Tomohiro; Ueki, Yasushi
2013-01-01
Purpose In the globalized economy, it is becoming increasingly necessary for firms in emerging economies to adopt advanced knowledge and technology from external sources, both domestic and abroad. This paper aims to identify knowledge flows through domestic and international customer-supplier rel......-to-face interactions with downstream and upstream firms, and it offers a new development in the study of transfers of intangible assets within a supply chain in Asian emerging economies....
Convective Heat Transfer Augmentation by Flexible fins in Laminar Channel Pulsating flow
Joshi, Rakshitha U; Bhardwaj, Rajneesh
2015-01-01
Fluid-structure interaction (FSI) of thin flexible fins coupled with convective heat transfer has applications in energy harvesting and in understanding functioning of several biological systems. We numerically investigate FSI of the thin flexible fins involving large-scale flow-induced deformation as a potential heat transfer enhancement technique. An in-house, strongly-coupled fluid-structure interaction (FSI) solver is employed in which flow and structure solvers are based on sharp-interface immersed boundary and finite element method, respectively. We consider twin flexible fins in a heated channel with laminar pulsating cross flow. The vortex ring past the fin sweep higher sources of vorticity generated on the channel walls out into the downstream - promoting the mixing of the fluid. The moving fin assists in convective mixing, augmenting convection in bulk and at the walls; and thereby reducing thermal boundary layer thickness and improving heat transfer at the channel walls. The thermal augmentation is...
Evaluating Ubiquitous Media Usability Challenges: Content Transfer and Channel Switching Delays
DEFF Research Database (Denmark)
Fleury, Alexandre; Pedersen, Jakob Schou; Larsen, Lars Bo
2011-01-01
As ubiquitous media is developing rapidly, new HCI challenges emerge. In this paper, we address usability issues related to the transfer of content between fixed and mobile devices, as well as channel switching delays on mobile devices. We first provide an extensive review of the field. We...... a threshold level above which people appear to be annoyed when switching between TV channels on a mobile device, and investigate factors that may influence the perceived acceptability of such delay....
Pressure drop and mass transfer in two-pass ribbed channels
Chandra, P. R.; Han, J. C.
1989-01-01
The combined effects of the sharp 180-deg turn and of the rib configuration on the pressure drop and mass transfer characteristics in a two-pass square channel with a pair of opposite rib-roughened walls (to simulate turbine airfoil cooling passages) were determined for a Reynolds number range of 10,000-60,000. Heat transfer enhancements were compared for the first pass and for the two-pass channel with the sharp 180-deg turn. Correlations for the fully-developed friction factors and loss coefficients were obtained.
Heat transfer and friction factors in the ribbed square convergent and divergent channels
Lee, M. S.; Ahn, S. W.
2016-06-01
Heat transfer and friction factors are reported for the measurements of turbulent flows in the convergent and divergent square channels with one-sided ribbed wall as well as two opposite in-line ribbed walls. The study covers three different hydraulic diameter ratios between inlet and exit at the test section such as Dho/Dhi = 0.75, 1.0, and 1.33 and Reynolds numbers in the range of 25,000-79,000. The channels, composing of ten isolated copper sections in the length of test section of 1 m, have the hydraulic diameter of 87.5 mm for the straight channel (Dho/Dhi = 1.0); the rib height-to-hydraulic diameter is 0.114; the rib pitch-to-height ratio equals 10. On the contrary to public opinion that the friction factor depends on the portion of the ribbed area, the total friction factor in the two opposite ribbed walls are lower than in the one-sided ribbed wall in the divergent channel of Dho/Dhi = 1.33 because the total pressure, summing positive dynamic and negative static pressures, is acted. The results show that the two opposite ribbed divergent channel of Dho/Dhi = 1.33 provides the best heat transfer enhancement and the two opposite ribbed convergent channel of Dho/Dhi = 0.75 provides the worst friction factor enhancement, and the ribbed divergent channels are generally recommended.
CFD modeling of heat transfer in a rectangular channel with dimplepin finning
Directory of Open Access Journals (Sweden)
Spokoiny M. Yu.
2013-05-01
Full Text Available Using the CFD modeling method, the authors have investigated conjugate heat transfer in a rectangular channel with dimple-pin finning with hight of pins, depth of cavities and Reynolds number values varying in the range, characteristic for heat exchangers designed for liquid cooling of microelectronic devices, such as microprocessors. Criterion dependencies for calculation of heat transfer under these conditions have been obtained.
Dimensionality Reduction on Multi-Dimensional Transfer Functions for Multi-Channel Volume Data Sets
Kim, Han Suk; Schulze, Jürgen P.; Cone, Angela C.; Sosinsky, Gina E.; Martone, Maryann E.
2011-01-01
The design of transfer functions for volume rendering is a non-trivial task. This is particularly true for multi-channel data sets, where multiple data values exist for each voxel, which requires multi-dimensional transfer functions. In this paper, we propose a new method for multi-dimensional transfer function design. Our new method provides a framework to combine multiple computational approaches and pushes the boundary of gradient-based multi-dimensional transfer functions to multiple channels, while keeping the dimensionality of transfer functions at a manageable level, i.e., a maximum of three dimensions, which can be displayed visually in a straightforward way. Our approach utilizes channel intensity, gradient, curvature and texture properties of each voxel. Applying recently developed nonlinear dimensionality reduction algorithms reduces the high-dimensional data of the domain. In this paper, we use Isomap and Locally Linear Embedding as well as a traditional algorithm, Principle Component Analysis. Our results show that these dimensionality reduction algorithms significantly improve the transfer function design process without compromising visualization accuracy. We demonstrate the effectiveness of our new dimensionality reduction algorithms with two volumetric confocal microscopy data sets. PMID:21841914
An experimental investigation of heat-transfer and flow in channels with streamwise-periodic flow
Energy Technology Data Exchange (ETDEWEB)
Habib, M.A. (King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia)); Mobarak, A.M.; Attya, A.M.; Aly, A.Z. (Cairo Univ. (Egypt). Faculty of Engineering)
1992-11-01
We investigate the enhancement of heat transfer and the consequent conservation of energy in channels with segmented baffles. The influence of Reynolds number, baffle spacing, baffle material, and heat flux on local and average heat-transfer coefficients have been studied. Our results show that the flow must pass over three to six baffles before it becomes periodic and fully-developed. Augmentation of heat transfer was obtained with increases in Reynolds number, thermal conductivity of the baffles and decreases in baffle spacing and wall heat flux. (Author).
HEAT TRANSFER ENHANCEMENT USING ALUMINA NANOFLUID IN CIRCULAR MICRO CHANNEL
Directory of Open Access Journals (Sweden)
K. S. ARJUN
2017-01-01
Full Text Available In this study, thermal and flow behavior models for circular microchannel using water and its nanofluids with alumina as a coolant fluid in single phase flow have been developed. A finite volume-based CFD technique is used and models are solved by using Fluent Solver. The 2D axis symmetric geometry with structured mesh and 100 x 18 nodes are used for single phase flow with Al2O3 nanoparticles of 23 nm average diameter. Viscous laminar and standard k-ε models are used to predict the steady temperature in laminar and turbulent zone. The heat transfer enhancement upto 83% in laminar and turbulent zones are obtained with the Re ranging from 5 to 11980 and particle volume concentration from 0 to 5%. Even though the pressure drop increases with increase in Re, it is comparatively less compared to the corresponding decrease in temperature. The increase in temperature depends on Re and Pe; but the temperature distribution is found to be independent of radial position even for very low Pe. Comparison with analytical results both in laminar and turbulent zone is provided to justify the assumptions introduced in the models and very close agreement is observed statistically. Nusselt number can well predict the analytical data.
LARGE EDDY SIMULATION OF FREE SURFACE TURBULENT CHANNEL FLOW WITH HEAT TRANSFER
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
In this paper, the Large Eddy Simulation (LES) was used to study the free-surface turbulent channel flow with passive heat transfer. The three-dimensional filtered incompressible Navier-Stokes equations and energy equation were numerically solved with dynamic Subgrid Scale (SGS) models for modeling turbulent stresses and heat flux. To compare the turbulent behavior of the free-surface and two-walled channel flows, the LES of two-walled turbulent channel flow was performed. The statistical quantities and flow structures of the free-surface turbulence with heat transfer in the vicinity of the free-surface were investigated. The results are also in good agreement with theoretical analysis and available results by Direct Numerical Simulation (DNS).
Modelling of Phase Change Heat Transfer System for Micro-channel and Chaos Simulation
Institute of Scientific and Technical Information of China (English)
LUO Xiao-Ping; CUI Z. F.
2008-01-01
The dynamic properties for the micro-channel phase change heat transfer system axe studied by theoretical method combined with experiment. Liquid-vapour interface dynamic systems are obtained by introducing disjoining pressure produced by three phase molecular interactions and Lie algebra analysis. Experiments for 0.6 mm×2 mm rectangular micro-channel are carried out to obtain the pressure time serials. Power spectrum density analysis for these serials shows that the system is in chaotic state if the frequency is above 7.39 Hz. The result indicates that the high heat transfer performance of the micro channel phase change system may re/ate to the characteristics of chaos. The chaos attractor is drawn by the simulation of the obtained differential dynamic system under the conditions of our experiment.
Heat transfer performance of Al2O3/water nanofluids in a mini channel heat sink.
Dominic, A; Sarangan, J; Suresh, S; Sai, Monica
2014-03-01
The high density heat removal in electronic packaging is a challenging task of modern days. Finding compact, energy efficient and cost effective methods of heat removal is being the interest of researchers. In the present work, mini channel with forced convective heat transfer in simultaneously developing regime is investigated as the heat transfer coefficient is inversely proportional to hydraulic diameter. Mini channel heat sink is made from the aluminium plate of 30 mm square with 8 mm thickness. It has 15 mini channel of 0.9 mm width, 1.3 mm height and 0.9 mm of pitch. DI water and water based 0.1% and 0.2% volume fractions of Al2O3/water nanofluids are used as coolant. The flow rates of the coolants are maintained in such a way that it is simultaneously developing. Reynolds number is varied from 400 to 1600 and heat input is varied from 40 W to 70 W. The results showed that heat transfer coefficient is more than the heat transfer coefficient of fully developed flow. Also the heat transfer is more for nanofluids compared to DI water.
Forced Convection Heat Transfer in Plate Channels Filled with Packed Beds or Sintered Porous Media
Institute of Scientific and Technical Information of China (English)
姜培学; 李勐; 任泽霈
2002-01-01
In the present work, forced convection heat transfer in plate channels filled with metallic or non-metallic particles (packed beds) or sintered porous media is simulated numerically using a thermal non-equilibrium model. The numerical simulation results are compared with experimental data. The difference between convection heat transfer in packed beds and in sintered porous media and the effects of the boundary condition assumptions are investigated. The results show that the numerical simulation of convection heat transfer of air or water in packed beds using the local thermal non-equilibrium model and the variable porosity model agrees well with the experimental data. The convection heat transfer coefficient in sintered porous media is much higher than that in packed beds. In the numerical simulation of convection heat transfer in sintered porous media, the boundary conditions on the wall should be that the particle temperatures are equal to the fluid temperature.
Enhanced MicroChannel Heat Transfer in Macro-Geometry using Conventional Fabrication Approach
Ooi, KT; Goh, AL
2016-09-01
This paper presents studies on passive, single-phase, enhanced microchannel heat transfer in conventionally sized geometry. The intention is to allow economical, simple and readily available conventional fabrication techniques to be used for fabricating macro-scale heat exchangers with microchannel heat transfer capability. A concentric annular gap between a 20 mm diameter channel and an 19.4 mm diameter insert forms a microchannel where heat transfer occurs. Results show that the heat transfer coefficient of more than 50 kW/m·K can be obtained for Re≈4,000, at hydraulic diameter of 0.6 mm. The pressure drop values of the system are kept below 3.3 bars. The present study re-confirms the feasibility of fabricating macro-heat exchangers with microchannel heat transfer capability.
Heat transfer and pressure drop in an annular channel with downflow
Dolan, F. X.; Crowley, C. J.; Qureshi, Z. H.
The onset of a flow instability (OFI) determines the minimum flow rate for cooling in the flow channels of a nuclear fuel assembly. A test facility was constructed with full-scale models (length and diameter) of annular flow channels incorporating many instruments to measure heat transfer and pressure drop with downflow in the annulus. Tests were performed both with and without axial centering ribs at prototypical values of pressure, flow rate and uniform wall heat flux. The axial ribs have the effect of subdividing the annulus into quadrants, so the problem becomes one of parallel channel flow, unlike previous experiments in tubes (upflow and downflow). Other tests were performed to determine the effects if any of asymmetric and non-uniform circumferential wall heating, operating pressure level and dissolved gas concentration. Data from the tests are compared with models for channel heat transfer and pressure drop profiles in several regimes of wall heating from single-phase forced convection through partially and fully developed nucleate boiling. Minimum stable flow rates were experimentally determined as a function of wall heat flux and heat distribution and compared with the model for the transition to fully developed boiling which is a key criterion in determining the OFI condition in the channel. The heat transfer results in the channel without ribs are in excellent agreement with predictions from a computer model of the flow in the annulus and with empirical correlations developed from similar tests. The test results with centering ribs show that geometrical variations between the channels can lead to differences in subchannel behavior which can make the effect of the ribs and the geometry an important factor when assessing the power level at which the fuel assembly (and the reactor) can be operated to prevent overheating in the event of a loss-of-coolant-accident (LOCA).
The technology of heat transfer enhancement in channels by means of flow pulsations
Directory of Open Access Journals (Sweden)
Tsynaeva Anna
2016-01-01
Full Text Available The rate and efficiency of curing of concrete can boost when used intense heat. The work is dedicated to the development and research of technologies of intensification of heat transfer in channels by pulsations. The study was conducted by means of numerical methods based on mass and momentum conservation equations (Navier-Stokes with software Code Saturne. Verification of implemented methods and software was performed. The research of heat transfer enhancement for semicircle-shaped channel exposed to low-frequency pulsations was performed. The pulsation frequency of the flow during the study was in a range of 0…10 Hz. A significant (up to 4 times increase of turbulent kinetic energy with implementing pulsations was detected. Flow pulsations with frequency of 10 Hz results in 1.21 times increase of heat transfer coefficient.
Measurements of mixed convective heat transfer to low temperature helium in a horizontal channel
Yeroshenko, V. M.; Kuznetsov, Y. V.; Shevchenko, O. A.; Hendricks, R. C.; Daney, D. E.
1979-01-01
A horizontal 2.85 m long, 19 mm i.d. stainless steel heated circular channel was employed to measure coefficients of heat transfer to low temperature helium flow. Experimental parameters range from 6.5 to 15 K, from 0.12 to 0.3 MPa at heat fluxes up to 1000 W/m square and Reynolds numbers from 9,000 to 20,000. A significantly nonuniform distribution of heat transfer coefficients over the tube periphery is observed. Difference between temperatures on the upper and lower surfaces of the stainless steel channel wall was found to reach 9 K. It was noted that the highest temperature on the wall outer surface is displaced from its uppermost point. Measurements of local flow temperatures revealed vortical structure of the flow. The displacement of the point with the highest temperature is attributable to the effect of vortices. The relationships for calculating local and averaged coefficients of heat transfer are proposed.
Heat transfer including radiation and slag particles evolution in MHD channel-I
Energy Technology Data Exchange (ETDEWEB)
Im, K H; Ahluwalia, R K
1980-01-01
Accurate estimates of convective and radiative heat transfer in the magnetohydrodynamic channel are provided. Calculations performed for a base load-size channel indicate that heat transfer by gas radiation almost equals that by convection for smooth walls, and amounts to 70% as much as the convective heat transfer for rough walls. Carbon dioxide, water vapor, and potassium atoms are the principal participating gases. The evolution of slag particles by homogeneous nucleation and condensation is also investigated. The particle-size spectrum so computed is later utilized to analyze the radiation enhancement by slag particles in the MHD diffuser. The impact of the slag particle spectrum on the selection of a workable and design of an efficient seed collection system is discussed.
The effect of the magnetic field on heat transfer in a slotted channel
Energy Technology Data Exchange (ETDEWEB)
Evtushenko, I.; Kirillov, I.; Sidorenkov, S. [D.V. Efremov Scientific Research Institute of Electrophysical Apparatus, St. Petersburg (Russian Federation)] [and others
1994-12-31
The results of numerical and experimental studies of the liquid metal heat transfer in the slotted channel with transverse magnetic field are presented. Theoretical predictions were prepared by both Efremov Institute and Argonne National Laboratory. The heat transfer test was conducted at ALEX facility jointly between ANL and Efremov Institute. The test section consisted of the two slotted geometry (b/a=10) parts - with and without {open_quotes}anchor links{close_quotes}. The Hartmann numbers (M) up to 1050 and Interaction parameters (N) up to 2000, based on the half-width of the short wall (7 mm) were achieved. The heat flux to the top wall was up to 9 x 10{sup 4} W/m{sup 2}. The test results showed the improvement of heat transfer in the straight channel at low and moderate N. The Nusselt number at small N (around 120) was up to 3 times higher than in the turbulent flow at the same Peclet number. Qualitative correlations between the heat transfer results and velocity fluctuation data show that the generation of large velocity fluctuation in the side layer of the heated wall is the main reason for the heat transfer improvement, high average velocity in the side layer is of the less effect on the heat transfer. At high N the velocity fluctuations are suppressed and consequently the Nusselt number at high N is smaller than at the corresponding turbulent flow.
Experimental study of natural convective heat transfer in a vertical hexagonal sub channel
Tandian, Nathanael P.; Umar, Efrizon; Hardianto, Toto; Febriyanto, Catur
2012-06-01
The development of new practices in nuclear reactor safety aspects and optimization of recent nuclear reactors, including the APWR and the PHWR reactors, needs a knowledge on natural convective heat transfer within sub-channels formed among several nuclear fuel rods or heat exchanger tubes. Unfortunately, the currently available empirical correlation equations for such heat transfer modes are limited and researches on convective heat transfer within a bundle of vertical cylinders (especially within the natural convection modes) are scarcely done. Although boundary layers around the heat exchanger cylinders or fuel rods may be dominated by their entry regions, most of available convection correlation equations are for fully developed boundary layers. Recently, an experimental study on natural convective heat transfer in a subchannel formed by several heated parallel cylinders that arranged in a hexagonal configuration has been being done. The study seeks for a new convection correlation for the natural convective heat transfer in the sub-channel formed among the hexagonal vertical cylinders. A new convective heat transfer correlation equation has been obtained from the study and compared to several similar equations in literatures.
Heat Transfer Characteristics of Wavy-Wall Channels in Micropolar Fluids
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Forced convection flow through a sinusoidally curved converging-diverging channel in micropolar fluids has been investigated numerically. A simple coordinate transformation is employed to transform the complex wavy-wall channel to a parallel-plate channel, and the cubic spline alternating-direction implicit method is then used to solve the flow patterns and heat transfer characteristics. The effects of the wavy geometry, vortex viscosity parameter and Reynolds number on skin-friction coefficient and Nusselt number have been examined in detail. Results show that the flow through a sinusoidally curved converging-diverging channel forms a strong forward flow and a reticular vortex within each wave for larger Reynolds number and wavy amplitudes. The heat transfer rate of a micropolar fluid is smaller than that of a Newtonian fluid, but the skin friction of a micropolar fluid is larger than that of a Newtonian fluid. Moreover, both Reynolds number and wavy amplitude tend to enhance the total heat transfer rate, irrespective of whether the fluids are Newtonian fluids or micropolar fluids.
The effect of magnetic field on instabilities of heat transfer from an obstacle in a channel
Energy Technology Data Exchange (ETDEWEB)
Rashidi, S.; Esfahani, J.A., E-mail: abolfazl@um.ac.ir
2015-10-01
This paper presents forced convective heat transfer in a channel with a built-in square obstacle. The governing equations with the boundary conditions are solved using a finite volume method. The computations were done for a fixed blockage ratio (S=1/8) at Pr=0.71, and Reynolds (Re) and Stuart (N) numbers ranging from 1 to 250 and 0 to 10, respectively. The results are presented to show the effect of the channel walls and streamwise magnetic field at different Reynolds numbers on forced convection heat transfer from a square cylinder. A correlation is obtained for Nusselt number, in which the effect of a magnetic field is taken into account. The obtained results revealed that the existence of channel walls decreases the effects of magnetic field on Nusselt number. It also showed that by increasing Stuart number the thickness of thermal boundary layer increases and the convective heat transfer decreases. - Highlights: • The magnetic field is used to control the instabilities of heat transfer. • The thickness of thermal boundary layer increases by increasing Stuart number. • Unsteadiness in temperature field increases with increase in Reynolds number. • Time-averaged Nusselt number decreases with increase in Stuart number. • The Lorentz forces are much denser near the surface of the obstacle.
Radiative transfer theory at satellite-borne SSM/I channels and remote sensing data analysis
Institute of Scientific and Technical Information of China (English)
金亚秋
1997-01-01
Vector radiative transfer (VRT) at the SSM/I channels (from 19 to 85 GHz) for multilayer of dis crete scatterers as a model of snowpack/vegetation canopy is developed. Using the physical optics approximation, the scattering, extinction coefficients and phase function of VRT equation for vegetation canopy are derived The dense medium VRT is applied to the snow-layer. Numerical solutions of two coupled VRT equations simulate scattering and emission signature from snowpack/vegetation canopy at SSM/I channels. Numerical results are applied to simulation and analysis of the SSM/I observations over China’s northeast forest and pasture areas in Naqu, Tibet
Institute of Scientific and Technical Information of China (English)
F M Abbasi; A Alsaedi; T Hayat
2014-01-01
The present investigation addresses the simultaneous effects of heat and mass transfer in the mixed convection peristaltic flow of viscous fluid in an asymmetric channel. The channel walls exhibit the convective boundary conditions. In addition, the effects due to Soret and Dufour are taken into consideration. Resulting problems are solved for the series solutions. Numerical values of heat and mass transfer rates are displayed and studied. Results indicate that the concentration and temperature of the fluid increase whereas the mass transfer rate at the wall decreases with increase of the mass transfer Biot number. Furthermore, it is observed that the temperature decreases with the increase of the heat transfer Biot number.
MHD non-Newtonian micropolar fluid flow and heat transfer in channel with stretching walls
Institute of Scientific and Technical Information of China (English)
M. ASHRAF; N. JAMEEL; K. ALI
2013-01-01
A study is presented for magnetohydrodynamics (MHD) flow and heat trans-fer characteristics of a viscous incompressible electrically conducting micropolar fluid in a channel with stretching walls. The micropolar model introduced by Eringen is used to describe the working fluid. The transformed self similar ordinary differential equations together with the associated boundary conditions are solved numerically by an algorithm based on quasi-linearization and multilevel discretization. The effects of some physical parameters on the flow and heat transfer are discussed and presented through tables and graphs. The present investigations may be beneficial in the flow and thermal control of polymeric processing.
Liquid metal MHD and heat transfer in a tokamak blanket slotted coolant channel
Energy Technology Data Exchange (ETDEWEB)
Reed, C.B.; Hua, T.Q.; Black, D.B. [Argonne National Lab., Chicago, IL (United States); Kirillov, I.R.; Sidorenkov, S.I.; Shapiro, A.M.; Evtushenko, I.A. [D. V. Efremov Scientific Research Inst. of Electrophysical Apparatus, St. Petersburg (Russian Federation). MHD-Machines Lab.
1993-12-31
A liquid metal MHD (Magnetohydrodynamic)/heat transfer test was conducted at the ALEX (Argonne Liquid Metal Experiment) facility of ANL (Argonne National Laboratory), jointly between ANL and NIIEFA (Efremov Institute). The test section was a rectangular slotted channel geometry (meaning the channel has a high aspect ratio, in this case 10:1, and the long side is parallel to the applied magnetic field). Isothermal and heat transfer data were collected. A heat flux of {approximately}9 W/cm{sup 2} was applied to the top horizontal surface (the long side) of the test section. Hartmann Numbers to 1050 (2 Tesla), interaction parameters to 9 {times} 10{sup 3}, Peclet numbers of 10--200, based on the half-width of the small dimension (7mm), and velocities of 1--75 cm/sec. were achieved. The working fluid was NaK (sodium potassium eutectic). All four interior walls were bare, 300-series stainless steel, conducting walls.
Liquid metal MHD and heat transfer in a tokamak blanket slotted coolant channel
Reed, C. B.; Hua, T. Q.; Black, D. B.; Kirillov, I. R.; Sidorenkov, S. I.; Shapiro, A. M.; Evtushenko, I. A.
A liquid metal MHD (Magnetohydrodynamic)/heat transfer test was conducted at the ALEX (Argonne Liquid Metal Experiment) facility of ANL (Argonne National Laboratory), jointly between ANL and NIIEFA (Efremov Institute). The test section was a rectangular slotted channel geometry (meaning the channel has a high aspect ratio, in this case 10:1, and the long side is parallel to the applied magnetic field). Isothermal and heat transfer data were collected. A heat flux of approximately 9 W/sq cm was applied to the top horizontal surface (the long side) of the test section. Hartmann Numbers to 1050 (2 Tesla), interaction parameters to 9 x 10(exp 3), Peclet numbers of 10-200, based on the half-width of the small dimension (7 mm), and velocities of 1-75 cm/sec. were achieved. The working fluid was NaK (sodium potassium eutectic). All four interior walls were bare, 300-series stainless steel, conducting walls.
Parmenter, C S; Clegg, S M; Krajnovich, D J; Lu, S
1997-08-05
The state-to-state transfer of rotational and vibrational energy has been studied for S1 glyoxal (CHOCHO) in collisions with D2, N2, CO and C2H4 using crossed molecular beams. A laser is used to pump glyoxal seeded in He to its S1 zero point level with zero angular momentum about its top axis (K' = 0). The inelastic scattering to each of at least 26 S1 glyoxal rotational and rovibrational levels is monitored by dispersed S1-S0 fluorescence. Various collision partners are chosen to investigate the relative influences of reduced mass and the collision pair interaction potential on the competition among the energy transfer channels. When the data are combined with that obtained previously from other collision partners whose masses range from 2 to 84 amu, it is seen that the channel competition is controlled primarily by the kinematics of the collisional interaction. Variations in the intermolecular potential play strictly a secondary role.
Heat Transfer on Steady MHD rotating flow through porous medium in a parallel plate channel
Directory of Open Access Journals (Sweden)
Dr. G. Prabhakara Rao,
2015-04-01
Full Text Available We discussed the combined effects of radiative heat transfer and a transverse magnetic field on steady rotating flow of an electrically conducting optically thin fluid through a porous medium in a parallel plate channel and non-uniform temperatures at the walls. The analytical solutions are obtained from coupled nonlinear partial differential equations for the problem. The computational results are discussed quantitatively with the aid of the dimensionless parameters entering in the solution.
AN INVESTIGATION OF TURBULENT HEAT TRANSFER IN CHANNEL FLOWS BY LARGE EDDY SIMULATION
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Large Eddy Simulation (LES) of fully developed turbulent channel flow with heat transfer was performed to investigate the effects of the Reynolds number on the turbulence behavior. In the present study, the bottom wall of the channel was cooled and the top wall was heated. The Reynolds numbers, based on the central mean-velocity and the half-width of the channel, were chosen as 4000, 6000, 104 and 2×104, and the Prandtl number as 1.0. To validate our calculations, the present results were compared with available data obtained by Direct Numerical Simulation (DNS), which proves to be in good agreement with each other. To reveal the effects of the Reynolds number, some typical quantities, including the velocity fluctuations, temperature fluctuation, heat fluxes and turbulent Prandtl number, were studied.
Augmentation of heat transfer in a bubble agitated vertical rectangular channel
Mitra, Asish; Dutta, Tapas Kumar; Ghosh, Dibyendu Narayan
2012-04-01
This paper presents the results of an experimental study of convective heat transfer between three parallel vertical plates symmetrically spaced with and without bubble agitation to ascertain the degree of augmentation of the heat transfer coefficients due to agitation. The centre plate was electrically heated, while the other side plates were water-cooled forming two successive parallel vertical rectangular channels of dimensions 20 cm × 3.5 cm × 35 cm (length W, gap L, height H) each. At the bottom of the hot and cold plates air spargers were fitted. Water/ethylene glycol (100%) was used to fill the channels. The superficial gas velocity ranged from 0.0016 to 0.01 m/s. Top, bottom and sides of the channels were open to the water/ethylene glycol in the chamber which is the novel aspect of this study. Experimental data have been correlated as under: Natural convective heat transfer: Nu = 0.60 Gr 0.29, r = 0.96, σ = 0.186, 1.17 E6 E-2 < ( ReFrPr 2) < 1.36 E2.
Convection heat transfer from discrete heat sources in a liquid cooled rectangular channel
Energy Technology Data Exchange (ETDEWEB)
Bhowmik, H. [Department of Mechanical Engineering, Dhaka University of Engineering and Technology, Gazipur 1700 (Bangladesh); Tso, C.P. [Faculty of Engineering and Technology, Multimedia University, Jalan Ayer Keroh Lama, 75450 Melaka (Malaysia); Tou, K.W.; Tan, F.L. [School of Mechanical and Production Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)
2005-11-01
Steady-state experiments are performed to study general convective heat transfer from an in-line four simulated electronic chips in a vertical rectangular channel using water as the working fluid. The experimental data covers a wide range for laminar flow under natural, mixed and forced convection conditions with Reynolds number based on channel hydraulic diameter ranging from 40 to 2220 and Reynolds number based on heat source length ranging from 50 to 2775, respectively. The heat flux ranges from 0.1W/cm{sup 2} to 0.6W/cm{sup 2}. The inlet water temperature is at 24{sup o}C. The effect of heat fluxes, flow rates and geometrical parameters such as chip number are investigated. The experimental results indicate that the heat transfer coefficient is strongly affected by Reynolds number and fully-developed values of heat transfer coefficient are reached before the first chip. Empirical correlations are developed for relations using Nusselt number, Reynolds number and Grashof number, based on channel hydraulic diameter. (author)
The evaluation of steam-water heat transfer in vertical channel using Trac code
Energy Technology Data Exchange (ETDEWEB)
Sang Won, Lee; Han Gon, Kim; Byong Sup, Kim; Seung, Jong [Korea Electric Power Co., Taejon (Korea, Republic of)
2001-07-01
The safety injection system(SIS) of the Korean Next Generation Reactor (KNGR) injects water into the reactor vessel directly for the effective usage of ECC water. The injection location is 83 inches higher than cold leg centerline. Due to this geometrical characteristics, during late reflood phase in large break LOCA, complicate thermal-hydraulic phenomena different from existing cold-leg injection plant could be occurred. Among these phenomena, the steam-water heat transfer is evaluated in this paper. We have selected TRAC code for the evaluation tool because it can handle the reactor vessel in three-dimensional coordinates and is has been validated using UPTF experiments. For this evaluation, we performed steam-water interaction experiments in vertical rectangular channel. The experiments have been performed for co-current and counter-current flow, various steam velocity, various water flow rate. Water is injected from the top of the channel as a thin film. Steam is injected from the top or the bottom of channel. All the experiments are performed in the condition of atmospheric pressure and that void fraction is ranged from 0.9 to 0.95. Therefore, it can be treated as annular-mist flow regime. TRAC model has been developed for the simulation of these experiments. As a result of simulation, it can be concluded that TRAC code predicts heat transfer coefficients as much as 10 times compared to experimental results. In order to correct these differences, we modified the heat transfer correlation for annular-mist flow in TRAC code. This modified correlation can be used heat transfer in the downcomer only. We will perform the larger break LOCA sensitivity analyses for the effect of heat transfer in the downcomer. (authors)
Forced Convective Heat Transfer in a Plate Channel Filled with Solid Particles
Institute of Scientific and Technical Information of China (English)
Pei－XueJiang; Ze－PeiRen; 等
1996-01-01
A numerical study of fluid flow and convective heat transfer in a plate channel filled with solid(metallic)perticles is presented in this paper,The study uses the thermal equilibrium model and a newly developed numerical model which does not assume idealized local thermal equilibrium between the solid particles and the fluid.The numerical simulation results are compared with the experimental data in reference[2].The paper investigates the effects of the assumption of local thermal equilibrium versus non-thermal equilibrium,the thermal conductivity of the solid particles and the particle diameter on convective heat transfer.For the conditions studied.the convective heat transfer and the temperature filed assuming local thermal equilibrium are much different from that for the non-thermal equilibrium assumption when the difference between the solid and fluid thermal conductivities is large,The relative values of the thermal conductivities of the solid particles and the fluid also have a profound effect on the temperature distribution in the channel.The pressure drop decreases as the particle diameter increases and the convective heat transfer coefficient may decrease of increase as the particle diameter increasws depending on the values of ε，λs，λf,λd,αu，ρu.
Makinde, O. D.; Chinyoka, T.
2010-12-01
This present study consists of a numerical investigation of transient heat transfer in channel flow of an electrically conducting variable viscosity Boussinesq fluid in the presence of a magnetic field and thermal radiation. The temperature dependent nature of viscosity is assumed to follow an exponentially model and the system exchanges heat with the ambient following Newton's law of cooling. The governing nonlinear equations of momentum and energy transport are solved numerically using a semi-implicit finite difference method. Solutions are presented in graphical form and given in terms of fluid velocity, fluid temperature, skin friction and heat transfer rate for various parametric values. Our results reveal that combined effect of thermal radiation, magnetic field, viscosity variation and convective cooling have significant impact in controlling the rate of heat transfer in the boundary layer region.
Proton transfer in the K-channel analog of B-type Cytochrome c oxidase from Thermus thermophilus.
Woelke, Anna Lena; Wagner, Anke; Galstyan, Gegham; Meyer, Tim; Knapp, Ernst-Walter
2014-11-04
A key enzyme in aerobic metabolism is cytochrome c oxidase (CcO), which catalyzes the reduction of molecular oxygen to water in the mitochondrial and bacterial membranes. Substrate electrons and protons are taken up from different sides of the membrane and protons are pumped across the membrane, thereby generating an electrochemical gradient. The well-studied A-type CcO uses two different entry channels for protons: the D-channel for all pumped and two consumed protons, and the K-channel for the other two consumed protons. In contrast, the B-type CcO uses only a single proton input channel for all consumed and pumped protons. It has the same location as the A-type K-channel (and thus is named the K-channel analog) without sharing any significant sequence homology. In this study, we performed molecular-dynamics simulations and electrostatic calculations to characterize the K-channel analog in terms of its energetic requirements and functionalities. The function of Glu-15B as a proton sink at the channel entrance is demonstrated by its rotational movement out of the channel when it is deprotonated and by its high pKA value when it points inside the channel. Tyr-244 in the middle of the channel is identified as the valve that ensures unidirectional proton transfer, as it moves inside the hydrogen-bond gap of the K-channel analog only while being deprotonated. The electrostatic energy landscape was calculated for all proton-transfer steps in the K-channel analog, which functions via proton-hole transfer. Overall, the K-channel analog has a very stable geometry without large energy barriers.
Heat transfer performance of a novel double-layer mini-channel heat sink
Tang, Biao; Zhou, Rui; Bai, Pengfei; Fu, Ting; Lu, Longsheng; Zhou, Guofu
2017-03-01
High pressure drop and significant non-uniformity in temperature distribution along the streamwise direction are still challenges to the design of mini-channel heat sink. High density mini-channel arrays with high liquid-wall contact area are usually pursued in a conventional single-layer design of heat sink, which also inevitably brings high pressure drop. A novel double-layer structured heat sink is proposed in this paper. Four heat sinks with various designs in mini-channel density and flow direction were fabricated and studied experimentally on the heat transfer performance. The single factor of heat load does not show obvious effect on the overall thermal resistance of the heat sinks. On the other hand, slight decrease in thermal resistance was found with the increase in heat load at high flow rates. Moreover, a computational fluid dynamics modeling work was conducted. The results indicate that the parallel cross-flow field regulated by the double-layer structure enhances the heat exchange in both horizontal and vertical directions and consequently gives an uniform temperature distribution and high heat transfer efficiency.
MHD two-layered unsteady fluid flow and heat transfer through a horizontal channel between
Directory of Open Access Journals (Sweden)
Raju T. Linga
2014-02-01
Full Text Available An unsteady magnetohydrodynamic (MHD two-layered fluids flow and heat transfer in a horizontal channel between two parallel plates in the presence of an applied magnetic and electric field is investigated, when the whole system is rotated about an axis perpendicular to the flow. The flow is driven by a constant uniform pressure gradient in the channel bounded by two parallel insulating plates, when both fluids are considered as electrically conducting, incompressible with variable properties, viz. different viscosities, thermal and electrical conductivities. The transport properties of the two fluids are taken to be constant and the bounding plates are maintained at constant and equal temperatures. The governing partial differential equations are then reduced to the ordinary linear differential equations using two-term series. Closed form solutions for primary and secondary velocity, also temperature distributions are obtained in both the fluid regions of the channel. Profiles of these solutions are plotted to discuss the effects of the flow and heat transfer characteristics, and their dependence on the governing parameters involved, such as the Hartmann number, rotation parameter, ratios of the viscosities, heights, electrical and thermal conductivities
Simulation of Transport Channel in China's Middle Route South-to-North Water Transfer Project
Institute of Scientific and Technical Information of China (English)
FANG Shenguang; WEI Jiahua; WU Baosheng; SHANG Yizi
2009-01-01
The unsteady flow in the Middle Route South-to-North Water Transfer Channel was simulated numerically using an implicit solution procedure for the Saint Venant equations. An equivalent roughness was used to simulate the effect of many transfer structures on the water levels in the main channel. Various gate operating and control methods were analyzed to study the response to disturbances produced by varying the flow rates through the Tianjin outlet. The results show that when the inflow at the head changes in the same way as the sum of the flow rates through all the outlets, the transition time and the fluctuation of the water levels using the timed gate operation method are less than when using the simultaneous gate operation method, but the variations of the gate openings and flow rates through each control gate are much larger. The flow disturbances produced by the Tianjin outlet can be rectified within several channel sections and the transition time can be greatly shortened by allowing the water levels immediately upstream of the control gates to vary within proscribed ranges, rather than being held constant.
Numerical heat transfer in a rectangular channel with mounted obstacles on upper and lower walls
Energy Technology Data Exchange (ETDEWEB)
Korichi, Abdelkader [Centre Universitaire de Medea, Quartier Ain D' heb Medea 26000 (Algeria); Oufer, Lounes [Universite des Sciences et de la Technologie Houari Boumediene, Faculte de Genie Mecanique et de Genie des Procedes, Departement de Genie des Procedes, B.P. 32, El-Alia, Bab-Ezzouar, Algiers (Algeria)
2005-07-01
A numerical investigation of convective heat transfer between a fluid and three physical obstacles (blocks) mounted on the lower wall (2 blocks) and on the upper wall (1 block) of a rectangular channel was conducted. Laminar flow of the fluid circulating through the channel was assumed. The effect of the Reynolds number, block spacing and dimensions and solid to fluid thermal conductivity ratio were studied. A uniform heat flux through the blocks was assumed. The results showed that transition from steady to unsteady flows occurred at lower values of the Reynolds number when an obstacle is placed on the upper wall of the channel. The isotherms around the blocks were presented and the heat transfer evaluated through the Nusselt number. As expected, the results obtained showed that as the value of the Reynolds number was increased, the heat removed from the obstacles increased sensibly with a maximum heat removal around the obstacle corners. Moreover, the temperature difference between the three obstacles decreased as the Reynolds number was increased. Some disagreement in the results was observed when compared with those reported in the literature. (authors)
Directory of Open Access Journals (Sweden)
Syed Tauseef Mohyud-Din
2015-12-01
Full Text Available This article is dedicated to analyzing the heat transfer in the flow of water-based nanofluids in a channel with non-parallel stretchable walls. The magnetohydrodynamic (MHD nature of the flow is considered. Equations governing the flow are transformed into a system of nonlinear ordinary differential equations. The said system is solved by employing two different techniques, the variational iteration method (VIM and the Runge-Kutta-Fehlberg method (RKF. The influence of the emerging parameters on the velocity and temperature profiles is highlighted with the help of graphs coupled with comprehensive discussions. A comparison with the already existing solutions is also made, which are the special cases of the current problem. It is observed that the temperature profile decreases with an increase in the nanoparticle volume fraction. Furthermore, a magnetic field can be used to control the possible separation caused by the backflows in the case of diverging channels. The effects of parameters on the skin friction coefficient and Nusselt number are also presented using graphical aid. The nanoparticle volume fraction helps to reduce the temperature of the channel and to enhance the rate of heat transfer at the wall.
Laminar Flow and Heat Transfer Characteristics in Jackets of Triangular Flow Channels
Institute of Scientific and Technical Information of China (English)
王翠华; 刘胜举; 吴剑华; 李雅侠
2013-01-01
Laminar flow and heat transfer characteristics of jacketed vessel with triangular flow channels were numerically studied under hydrodynamically and thermally fully developed conditions. Constant heat flux at the heated wall was assumed. The numerical program code in terms of vorticity, stream function, axial velocity com-ponent and energy equations was written based on a finite volume method. Based on the numerical results, the flow and temperature field were given, and the effects of Dean and Prandtl numbers on flow and heat transfer were ex-amined, and the correlations of flow resistance and mean Nusselt number were developed for the jacket. The results show that the structure of secondary flow is steady two vortices in the investigated range of dimensionless curvature ratio and Reynolds number. Two peaks of local Nusselt number increase significantly with Prandtl and Dean num-ber increasing, but the local Nusselt numbers near two ends and at the center of the heated wall increase only slightly. The center and two ends of heated wall are the poor positions for heat transfer in the jacket. Compared with the outer half coil jacket at the same area of heated wall, curvature radius, Reynolds number and Prandtl number, the jacket of triangular flow channel has lower flow resistance and less mean Nusselt number.
Institute of Scientific and Technical Information of China (English)
Jingchun Min; Bingqiang Zhang
2014-01-01
Numerical calculations were conducted to simulate the flow and mass transfer in narrow membrane channels with and without flow disturbers. The channel consists of an impermeable solid wall and a membrane surface with a spacing of 2.0 mm. The flow disturbers studied include rectangular winglets, which are often used as lon-gitudinal vortex generators to enhance heat transfer in heat exchanger applications, as wel as square prism, tri-angular prism, and circular cylinder, which are used here to mimic the traditional spacer filaments for comparison of their abilities in enhancing the convective mass transfer near the membrane surface to al eviate the concentration polarization. The disturber performance was evaluated in terms of concentration polarization factor versus consumed pumping power, with a larger factor meaning a more serious concentration polarization. Calculations were carried out for NaCl solution flow with Reynolds numbers ranging from 400 to 1000. The results show that the traditional flow disturbers can considerably reduce the concentration polarization but cause a substantial pressure drop, while the rectangular winglets can effectively reduce the concentration polarization with a much less pressure drop penalty. The rectangular winglets were optimized in geometry under equal pumping power condition.
Turbulent heat-and-mass transfer in channel flow at transcritical temperature conditions
Kim, Kukjin; Scalo, Carlo; Hickey, Jean-Pierre
2016-11-01
Turbulent heat and mass transfer at transcritical thermodynamic conditions is studied in turbulent channel flow using the high-fidelity DNS for solution to the compressible Navier-Stokes equations in the conservative form closed with the Peng-Robinson state equation. To isolate the real fluid effects on turbulent heat transfer, the bulk pressure is maintained at supercritical pb = 1 . 1pc and the isothermal walls are set to ΔT / 2 above and below the local pseudo-boiling temperature Tpb of the fluid (R-134a) where ΔT is 5K, 10K, and 20K. This setup allows the flow to reach a statistically-steady state while capturing the highest thermodynamic gradients, thus allowing a detailed study on thermodynamics of transcritical turbulent heat transfer. All thermodynamic and turbulent scales are fully resolved which is shown through a careful grid convergence analysis. The time-averaged density and compressibility factor are highly dependent on the temperature field and their large near-wall gradient causes thermodynamically-induced peaks in the RMS quantities resulting in strong turbulent mixing. The ejection of heavy pseudo-liquid blobs by near-wall turbulent structures into the channel core leads to a third RMS peak which is not observable in ideal gas simulations.
Heat Transfer in MHD Mixed Convection Flow of a Ferrofluid along a Vertical Channel.
Gul, Aaiza; Khan, Ilyas; Shafie, Sharidan; Khalid, Asma; Khan, Arshad
2015-01-01
This study investigated heat transfer in magnetohydrodynamic (MHD) mixed convection flow of ferrofluid along a vertical channel. The channel with non-uniform wall temperatures was taken in a vertical direction with transverse magnetic field. Water with nanoparticles of magnetite (Fe3O4) was selected as a conventional base fluid. In addition, non-magnetic (Al2O3) aluminium oxide nanoparticles were also used. Comparison between magnetic and magnetite nanoparticles were also conducted. Fluid motion was originated due to buoyancy force together with applied pressure gradient. The problem was modelled in terms of partial differential equations with physical boundary conditions. Analytical solutions were obtained for velocity and temperature. Graphical results were plotted and discussed. It was found that temperature and velocity of ferrofluids depend strongly on viscosity and thermal conductivity together with magnetic field. The results of the present study when compared concurred with published work.
Finite analytic numerical solution of heat transfer and flow past a square channel cavity
Chen, C.-J.; Obasih, K.
1982-01-01
A numerical solution of flow and heat transfer characteristics is obtained by the finite analytic method for a two dimensional laminar channel flow over a two-dimensional square cavity. The finite analytic method utilizes the local analytic solution in a small element of the problem region to form the algebraic equation relating an interior nodal value with its surrounding nodal values. Stable and rapidly converged solutions were obtained for Reynolds numbers ranging to 1000 and Prandtl number to 10. Streamfunction, vorticity and temperature profiles are solved. Local and mean Nusselt number are given. It is found that the separation streamlines between the cavity and channel flow are concave into the cavity at low Reynolds number and convex at high Reynolds number (Re greater than 100) and for square cavity the mean Nusselt number may be approximately correlated with Peclet number as Nu(m) = 0.365 Pe exp 0.2.
Heat Transfer in MHD Mixed Convection Flow of a Ferrofluid along a Vertical Channel.
Directory of Open Access Journals (Sweden)
Aaiza Gul
Full Text Available This study investigated heat transfer in magnetohydrodynamic (MHD mixed convection flow of ferrofluid along a vertical channel. The channel with non-uniform wall temperatures was taken in a vertical direction with transverse magnetic field. Water with nanoparticles of magnetite (Fe3O4 was selected as a conventional base fluid. In addition, non-magnetic (Al2O3 aluminium oxide nanoparticles were also used. Comparison between magnetic and magnetite nanoparticles were also conducted. Fluid motion was originated due to buoyancy force together with applied pressure gradient. The problem was modelled in terms of partial differential equations with physical boundary conditions. Analytical solutions were obtained for velocity and temperature. Graphical results were plotted and discussed. It was found that temperature and velocity of ferrofluids depend strongly on viscosity and thermal conductivity together with magnetic field. The results of the present study when compared concurred with published work.
Analysis of glucose and insulin mass transfer in a novel 2-channel bioartificial pancreas.
Moussy, Y; Moussy, F
1995-01-01
This paper introduces a newly developed 2-channel bioartificial pancreas for the treatment of type I diabetes. In this device, insulin secreting cells (islets of Langerhans) are placed between 2 semi-permeable membranes that form a flat rectangular chamber. One side of the chamber is in contact with blood from an artery and the other side with blood from a vein. In addition to the diffusive transfer of glucose and insulin, the pressure difference between the artery and the vein creates an ultrafiltration flux through the islet chamber. This diffusion and ultrafiltration flux carries glucose from the artery to the islets, and insulin from the islets to the vein. The bioartificial pancreas has a compact geometry and the blood channels were designed to prevent blood clotting. The predicted insulin release in response to a square-wave and a triangular-wave glucose stimulation is given for the bioartificial pancreas of dimensions necessary for implantation in diabetic patients.
Surface velocity divergence model of air/water interfacial gas transfer in open-channel flows
Sanjou, M.; Nezu, I.; Okamoto, T.
2017-04-01
Air/water interfacial gas transfer through a free surface plays a significant role in preserving and restoring water quality in creeks and rivers. However, direct measurements of the gas transfer velocity and reaeration coefficient are still difficult, and therefore a reliable prediction model needs to be developed. Varying systematically the bulk-mean velocity and water depth, laboratory flume experiments were conducted and we measured surface velocities and dissolved oxygen (DO) concentrations in open-channel flows to reveal the relationship between DO transfer velocity and surface divergence (SD). Horizontal particle image velocimetry measurements provide the time-variations of surface velocity divergence. Positive and negative regions of surface velocity divergence are transferred downstream in time, as occurs in boil phenomenon on natural river free-surfaces. The result implies that interfacial gas transfer is related to bottom-situated turbulence motion and vertical mass transfer. The original SD model focuses mainly on small-scale viscous motion, and this model strongly depends on the water depth. Therefore, we modify the SD model theoretically to accommodate the effects of the water depth on gas transfer, introducing a non-dimensional parameter that includes contributions of depth-scale large-vortex motion, such as secondary currents, to surface renewal events related to DO transport. The modified SD model proved effective and reasonable without any dependence on the bulk mean velocity and water depth, and has a larger coefficient of determination than the original SD model. Furthermore, modeling of friction velocity with the Reynolds number improves the practicality of a new formula that is expected to be used in studies of natural rivers.
Experimental Study of Heat Transfer in the Steam Thermal Siphon Tube Channel
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Ulchiekov Mikhail A.
2016-01-01
Full Text Available The results of experimental studies of heat transfer into the thermo-syphon tube with different thermal loads are represented. Are examined two types of liquid as the working fluid. The values of temperatures in the steam channel of thermo-syphon tube are registered and the dependences of the coefficients of heat exchange on the power of heating element are obtained. The influence of thermal load and properties of liquid on the intensity of the processes of evaporation and condensation of working fluid in the thermo-syphon installation are established.
Numerical investigation of turbulent flow and heat transfer in channel with ribs
DEFF Research Database (Denmark)
Myllerup, Lisbeth; Larsen, Poul Scheel
1999-01-01
The performance of three different low-Reynolds number turbulence models has been explored for the benchmark test of fully developed (periodic) flow in a ribbed plane channel. Results are presented for two values of the Reynolds number (based on mean velocity and hydraulic diameter), Re = 37......,200 and Re = 12,600, for which experimental data are available for the flow field and heat transfer, respectively. Comparison with experimental data includes the Nusselt number distribution along ribbed surface and profiles of mean velocity....
Energy Technology Data Exchange (ETDEWEB)
Korichi, Abdelkader [Centre Universitaire de Medea, Quartier Ain D' heb, Medea 26000 (Algeria)], E-mail: a_korichi@hotmail.com; Oufer, Lounes [Universite des Sciences et de la Technologie Houari Boumediene, Faculte de Genie Mecanique et de Genie des Procedes, Departement de Genie Chimique et de Cryogenie, Laboratoire des Phenomenes de Transfert, BP 32, El-Alia, Bab-Ezzouar, Alger (Algeria)], E-mail: lounesoufer@yahoo.com
2007-10-15
A numerical investigation is conducted in a rectangular channel with heated obstacles mounted alternatively on the upper and lower walls. Time-dependent two dimensional laminar flow with constant thermophysical properties is assumed for air at three values of the Reynolds number (50, 500 and 1000). A detailed analysis is carried out to investigate flow pattern and Nusselt number. Streamwise periodic contraction-expansion of the cross-section induces bifurcation from steady to unsteady flow. In the unsteady state, a self-sustained periodic oscillatory flow occurs. It is also found that a travelling wave generated by the vortex shedding contributes mainly to heat transfer enhancement.
Heat Transfer to MHD Oscillatory Viscoelastic Flow in a Channel Filled with Porous Medium
Directory of Open Access Journals (Sweden)
Rita Choudhury
2012-01-01
Full Text Available The combined effect of a transverse magnetic field and radiative heat transfer on unsteady flow of a conducting optically thin viscoelastic fluid through a channel filled with saturated porous medium and nonuniform walls temperature has been discussed. It is assumed that the fluid has small electrical conductivity and the electromagnetic force produced is very small. Closed-form analytical solutions are constructed for the problem. The effects of the radiation and the magnetic field parameters on velocity profile and shear stress for different values of the viscoelastic parameter with the combination of the other flow parameters are illustrated graphically, and physical aspects of the problem are discussed.
Li, Changping
2014-11-10
In this report, we propose a fast numerical solution for the steady state radiative transfer equation in order to calculate the path loss due to light absorption and scattering in various type of underwater channels. In the proposed scheme, we apply a direct non-uniform method to discretize the angular space and an upwind type finite difference method to discretize the spatial space. A Gauss-Seidel iterative method is then applied to solve the fully discretized system of linear equations. The accuracy and efficiency of the proposed scheme is validated by Monte Carlo simulations.
Directory of Open Access Journals (Sweden)
Mr. Sanjay V. Barad,
2014-04-01
Full Text Available In this paper The Thermal behaviour of Micro channel heat sink were investigated used Al2o3-water base nanoluid. The model have been solved by ANSYS fluent 14.5 solver. The Dimension of each rectangular channel is 215m width, 821m depth and 4.48cm length. The Reynolds number range from 200 to 400 for power input 100 w. The high thermal conductivity of nanoparticles is shown to enhance the single phase heat transfer coefficient, especially for laminar flow. Higher heat transfer coefficient were achieved mostly in entrances region of micro channels. The enhancement was weaker in fully developed region.
Hydrogen bonding: a channel for protons to transfer through acid-base pairs.
Wu, Liang; Huang, Chuanhui; Woo, Jung-Je; Wu, Dan; Yun, Sung-Hyun; Seo, Seok-Jun; Xu, Tongwen; Moon, Seung-Hyeon
2009-09-10
Different from H(3)O(+) transport as in the vehicle mechanism, protons find another channel to transfer through the poorly hydrophilic interlayers in a hydrated multiphase membrane. This membrane was prepared from poly(phthalazinone ether sulfone kentone) (SPPESK) and H(+)-form perfluorosulfonic resin (FSP), and poorly hydrophilic electrostatically interacted acid-base pairs constitute the interlayer between two hydrophilic phases (FSP and SPPESK). By hydrogen bonds forming and breaking between acid-base pairs and water molecules, protons transport directly through these poorly hydrophilic zones. The multiphase membrane, due to this unique transfer mechanism, exhibits better electrochemical performances during fuel cell tests than those of pure FSP and Nafion-112 membranes: 0.09-0.12 S cm(-1) of proton conductivity at 25 degrees C and 990 mW cm(-2) of the maximum power density at a current density of 2600 mA cm(-2) and a cell voltage of 0.38 V.
Energy Technology Data Exchange (ETDEWEB)
Hellgartner, Stefanie Christine
2015-11-13
In this work, the N=40 subshell closure is investigated with two complementary methods using a radioactive {sup 72}Zn ISOLDE beam: One- and two-neutron transfer reactions and multiple Coulomb excitation. In the one-neutron transfer reaction, two new levels of {sup 73}Zn were discovered. The two-neutron transfer channel allowed to study the differential cross section of the ground state and the 2{sup +}{sub 1} state of {sup 74}Zn. In the Coulomb excitation experiment, the measured B(E2) values and quadrupole moments of {sup 72}Zn showed that the yrast states 0{sup +}{sub 1}, 2{sup +}{sub 1} and 4{sup +}{sub 1} are moderately collective. Contrary, the 0{sup +}{sub 2} state has a different structure, since it features a stronger closed N=40 configuration compared to the ground state.
Institute of Scientific and Technical Information of China (English)
唐新宜; 朱冬生
2012-01-01
Experimental and numerical investigations have been conducted to study turbulent flow of water and heat transfer characteristics in a rectangular channel with discontinuous crossed ribs and grooves.The tests investigated the overall heat transfer performance and friction factor in ribbed and ribbed-grooved channels with rib angle of 30°.The experimental results show that the overall thermo-hydraulic performance for ribbed-grooved channel is increased by 10%-13.6% when compared to ribbed channel.The investigation on the effects of different rib angles and rib pitches on heat transfer characteristics and friction factor in ribbed-grooved channel was carried out using Fluent with SST（shear-stress transport） k-ω turbulence model.The numerical results indicate that the case for rib angle of 45° shows the best overall thermo-hydraulic performance,about 18%-36% higher than the case for rib angle of 0°.In addition,the flow patterns and local heat transfer characteristics for ribbed and ribbed-grooved channels based on the numerical simulation were also analyzed to reveal the mechanism of heat transfer enhancement.
Enhance heat transfer in the channel with V-shaped wavy lower plate using liquid nanofluids
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Azher M. Abed
2015-03-01
Full Text Available The heat transfer and flow characteristics in corrugated with V-shape lower plate using nanofluids are numerically studied. The computations are performed on uniform heat flux over a range of Reynolds number (Re 8000–20,000. The governing equations are numerically solved in the domain by a finite volume method (FVM using the k–ε standard turbulent model. Studies are carried out for different types of nanoparticles Al2O3,CuO, SiO2 and ZnO with different volume fractions in the range of 0–4%. Three different types of base fluid (water, glycerin, ethylene glycol are also examined. Results indicated that the average Nusselt number for nanofluids is greater than that of the base liquid. The SiO2 nanofluid yields the best heat transfer enhancement among all other type of nanofluids. Heat transfer enhancement increase with increases the volumetric concentration, but it is accompanied by increasing pressure drop values. Moreover, the average Nusselt number increases with an increase in Reynolds number and volume concentration. The SiO2–glycerin nanofluid has the highest Nusselt number compared with other base fluids. The present study shows that these V-shaped wavy channels have advantages by using nanofluids and thus serve as promising candidates for incorporation into efficient heat transfer devices.
Mixed convection heat transfer from confined tandem square cylinders in a horizontal channel
Huang, Zhu
2013-11-01
This paper presents a numerical study on the two-dimensional laminar mixed convective flow and heat transfer around two identical isothermal square cylinders arranged in tandem and confined in a channel. The spacing between the cylinders is fixed with four widths of the cylinder and the blockage ratio and the Prandtl number are fixed at 0.1 and 0.7 respectively. The mixed convective flow and heat transfer is simulated by high accuracy multidomain pseudospectral method. The Reynolds number (Re) is studied in the range 80 ≤ Re ≤ 150, the Richardson number (Ri) demonstrating the influence of thermal buoyancy ranges from 0 to 1. Numerical results reveal that, with the thermal buoyancy effect, the mixed convective flow sheds vortex behind the cylinders and keeps periodic oscillating. The variations of characteristic quantities related to flow and heat transfer processes, such as the overall drag and lift coefficients and the Nusselt numbers, are presented and discussed. Furthermore, the influence of thermal buoyancy on the fluid flow and heat transfer are discussed and analysed. © 2013 Elsevier Ltd. All rights reserved.
A note on the flow and heat transfer enhancement in a channel with built-in winglet pair
Energy Technology Data Exchange (ETDEWEB)
Hiravennavar, S.R. [Department of Aerospace Engineering, IIT Madras, Chennai 600036 (India)]. E-mail: sadashiv_h@yahoo.co.in; Tulapurkara, E.G. [Department of Aerospace Engineering, IIT Madras, Chennai 600036 (India)]. E-mail: egt@ae.iitm.ac.in; Biswas, G. [Department of Mechanical Engineering, IIT Kanpur, Kanpur 208016 (India)]. E-mail: gtm@iitk.ac.in
2007-04-15
Counter rotating longitudinal vortices produced by winglet in a channel are known to enhance heat transfer. In the present investigation the flow structure and heat-transfer enhancement by a winglet pair of non-zero thickness has been studied. A delta winglet pair type vortex generator is placed in a hydrodynamically developed and thermally developing laminar channel flow. Computations are done by solving the unsteady, three-dimensional, incompressible Navier-Strokes equations and energy equation using a modified Marker-and-Cell (MAC) method. The flow structure is complex and consists of main, corner and induced vortices. It is observed that as compared to a channel without winglets, the heat transfer is enhanced by 33% when single winglet is used and by 67% when a winglet pair is employed. Effects of thickness of the winglets and Reynolds number on the heat transfer augmentation are presented.
Heat transfer of copper/water nanofluid flow through converging-diverging channel
Institute of Scientific and Technical Information of China (English)
Mohamed Rafik SARI; Mohamed KEZZAR; Rachid ADJABI
2016-01-01
The main objective of this work is to investigate analytically the steady nanofluid flow and heat transfer characteristics between nonparallel plane walls. Using appropriate transformations for the velocity and temperature, the basic nonlinear partial differential equations are reduced to the ordinary differential equations. Then, these equations have been solved analytically and numerically for some values of the governing parameters, Reynolds number, Re, channel half angle, α, Prandtl number, Pr, and Eckert number, Ec, using Adomian decomposition method and the Runge-Kutta method with mathematic package. Analytical and numerical results are searched for the skin friction coefficient, Nusselt number and the velocity and temperature profiles. It is found on one hand that the Nusselt number increases as Eckert number or channel half-angle increases, but it decreases as Reynolds number increases. On the other hand, it is also found that the presence of Cu nanoparticles in a water base fluid enhances heat transfer between nonparallel plane walls and in consequence the Nusselt number increases with the increase of nanoparticles volume fraction. Finally, an excellent agreement between analytical results and those obtained by numerical Runge-Kutta method is highly noticed.
Fiévet, Bruno; Pommier, Julien; Voiseux, Claire; Bailly du Bois, Pascal; Laguionie, Philippe; Cossonnet, Catherine; Solier, Luc
2013-06-18
Controlled amounts of liquid tritium are discharged as tritiated water (HTO) by the nuclear industry into the English Channel. Because the isotopic discrimination between 3H and H is small, organically bound tritium (OBT) and HTO should show the same T/H ratio under steady-state conditions. We report data collected from the environment in the English Channel. Tritium concentrations measured in seawater HTO, as well as in biota HTO and OBT, confirm that tritium transfers from HTO to OBT result in conservation of the T/H ratio (ca. 1 × 10(-16)). The kinetics of the turnover of tritium between seawater HTO, biota HTO, and OBT was investigated. HTO in two algae and a mollusk is shown to exchange rapidly with seawater HTO. However, the overall tritium turnover between HTO and the whole-organism OBT is a slow process with a tritium biological half-life on the order of months. Nonsteady-state conditions exist where there are sharp changes in seawater HTO. As a consequence, for kinetic reasons, the T/H ratio in OBT may deviate transiently from that observed in HTO of samples from the marine ecosystem. Dynamic modeling is thus more realistic for predicting tritium transfers to biota OBT under nonsteady-state conditions.
On the dissipation and dispersion of entropy waves in heat transferring channel flows
Fattahi, A.; Hosseinalipour, S. M.; Karimi, N.
2017-08-01
This paper investigates the hydrodynamic and heat transfer effects on the dissipation and dispersion of entropy waves in non-reactive flows. These waves, as advected density inhomogeneities downstream of unsteady flames, may decay partially or totally before reaching the exit nozzle, where they are converted into sound. Attenuation of entropy waves dominates the significance of the subsequent acoustic noise generation. Yet, the extent of this decay process is currently a matter of contention and the pertinent mechanisms are still largely unexplored. To resolve this issue, a numerical study is carried out by compressible large eddy simulation of the wave advection in a channel subject to convective and adiabatic thermal boundary conditions. The dispersion, dissipation, and spatial correlation of the wave are evaluated by post-processing of the numerical results. This includes application of the classical coherence function as well as development of nonlinear quantitative measures of wave dissipation and dispersion. The analyses reveal that the high frequency components of the entropy wave are always strongly damped. The survival of the low frequency components heavily depends on the turbulence intensity and thermal boundary conditions of the channel. In general, high turbulence intensities and particularly heat transfer intensify the decay and destruction of the spatial coherence of entropy waves. In some cases, they can even result in the complete annihilation of the wave. The current work can therefore resolve the controversies arising over the previous studies of entropy waves with different thermal boundary conditions.
DIRECT NUMERICAL SIMULATION OF TURBULENT HEAT TRANSFER IN A WALL-NORMAL ROTATING CHANNEL FLOW
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
Direct Nmerical Simulation (DNS) of turbulent heat transfer in a wall-normal rotating channel flow has been carried out for the rotation number Nτ from 0 to 0.1, the Reynolds number 194 based on the friction velocity of non-rotating case and the half-height of the channel, and the Prandtl number 1. The objective of this study is to reveal the effects of rotation on the characteristics of turbulent flow and heat transfer. Based on the present calculated results, two typical rotation regimes are identified. When 0＜Nτ＜0.06, turbulence and thermal statistics correlated with the spanwise velocity fluctuation are enhanced since the shear rate of spanwise mean flow induced by Coriolis force increases; however, the other statistics are suppressed. When Nτ＞0.06, turbulence and thermal statistics are suppressed significantly because the Coriolis force effect plays as a dominated role in the rotating flow. Remarkable change of the direction of near-wall streak structures based on the velocity and temperature fluctuations is identified.
Directory of Open Access Journals (Sweden)
Dingcheng Yang
2015-01-01
Full Text Available An optimal resource allocation strategy for MIMO relay system is considered in simultaneous wireless information and energy transfer network, where two users with multiple antennas communicate with each other assisted by an energy harvesting MIMO relay that gathers energy from the received signal by applying time switching scheme and forwards the received signal by using the harvesting energy. It is focused on the precoder design and resource allocation strategies for the system to allocate the resources among the nodes in decode-and-forward (DF mode. Specifically, optimal precoder design and energy transfer strategy in MIMO relay channel are firstly proposed. Then, we formulate the resource allocation optimization problem. The closed-form solutions for the time and power allocation are derived. It is revealed that the solution can flexibly allocate the resource for the MIMO relay channel to maximize the sum rate of the system. Simulation results demonstrated that the performance of the proposed algorithm outperforms the traditional fixed method.
Fustinoni, D.; Gramazio, P.; Vitali, L.; Niro, A.
2017-01-01
In this paper we present new experimental results on local heat transfer characteristics of a forced air-flow through a 12-mm-height, rectangular channel of 1:10 aspect ratio, with square-cross-section ribs mounted onto the lower surface. Data are collected on a completely redesigned test section. Specifically, the electric heater is made of very thin copper tracks, in direct contact with the air flow and covering at 97.5% the channel lower surface to guarantee a very uniform heat flux. The copper tracks are laminated onto a 2-mm thick board of FR-4 glass epoxy to provide negligible heat conduction inside the plate and heat losses from its sides. Finally, the channel walls are in XPS and, into the upper one, a double glazing consisting of two 120 mm x 120 mm Germanium windows is mounted to allow optical access to the IR camera and to reduce local heat dispersions. Data here presented refer to convection over 4 mm x 2 mm ribs in transverse configuration for Reynolds numbers, based on the duct hydraulic diameter, ranging between 700 and 8000. Preliminary tests show how the new apparatus has significantly improved the quality, the ease and the quickness of the measurements.
V, Sudarev A.; V, Sudarev B.; A, Suryaninov A.
2012-05-01
The introduction of new structural materials and technologies contributes to the efficiency increase for the compact IPMs used in various branches of engineering. Use of a driving high-temperature (TIT600K), regenerative (the regeneration ratio is E>85%) micro gas turbine engine μGTE, major components which are made of structural ceramics, allows not only to maintain the effective efficiency at ηe=26-30%, but, also, sharply reduce the material consumption rate for the micro source as a whole. Application of the laser prototyping technique to manufacture the air heater, which is a part of μGTE, increases the IPM compactness. Miniaturization of the air heater, manufactured by the structural ceramics laser fusion, can significantly reduce the hydraulic diameter (dh<=1.0 mm) of the channels, designed to transport the working media inside it. Reducing dh leads to a significant increase in the hydraulic resistance of the micro channels. The associated increase in the energy consumption for μGTE's own needs is compensated by increasing the TIT, E, and heat transfer coefficients in micro channels, and by eliminating the need in cooling for high temperature IPM components.
Heat transfer in a porous saturated wavy channel with asymmetric convective boundary conditions
Institute of Scientific and Technical Information of China (English)
Q Hussain; S Asghar; T Hayat; A Alsaedi
2015-01-01
The viscous flow in a wavy channel with convective boundary conditions is investigated. The channel is filled with a porous viscous fluid. Two cases of equal and different external convection coefficients on the walls are taken into account. Effect of viscous dissipation is also considered. The governing equations are derived employing long wavelength and low Reynolds number approximations. Exact closed form solutions are obtained for the simplified equations. Important physical features for peristaltic flow caused by the wavy wave are pumping, trapping and heat transfer rate at the channel walls. These are discussed one by one in depth and detail through graphical illustrations. Special attention has been given to the effects of convective boundary conditions. The results show that for Bi1≠Bi2, there exists a critical value of Brinkman number Brc at which the temperatures of both the walls become equal. And, for Bi1>Bi2 and Br>Brc, the temperature of the cold wall exceeds the temperature of hot wall.
Salama, Amgad
2014-08-25
Numerical simulation of flow and heat transfer in two adjacent channels is conducted with one of the channels partially blocked. This system simulates typical channels of a material testing reactor. The blockage is assumed due to the buckling of one of the channel plates inward along its width. The blockage ratio considered in this work is defined as the ratio between the cross-sectional area of the blocked and the unblocked channel. In this work, we consider a blockage ratio of approximately 40%. However, the blockage is different along the width of the channel, ranging from 0% at the end of the channel to 90% in the middle. The channel walls are sandwiching volumetric heat sources that vary spatially as chopped cosine functions. Interesting patterns are highlighted and investigated. The reduction in the flow area of one channel results in the flow redistributing among the two channels according to the changes in their hydraulic conductivities. The results of the numerical simulations show that the maximum wall temperature in the blocked channel is well below the boiling temperature at the operating pressure.
Mansoor, Mohammad M.
2012-02-01
A 3D-conjugate numerical investigation was conducted to predict heat transfer characteristics in a rectangular cross-sectional micro-channel employing simultaneously developing single-phase flows. The numerical code was validated by comparison with previous experimental and numerical results for the same micro-channel dimensions and classical correlations based on conventional sized channels. High heat fluxes up to 130W/cm 2 were applied to investigate micro-channel thermal characteristics. The entire computational domain was discretized using a 120×160×100 grid for the micro-channel with an aspect ratio of (α=4.56) and examined for Reynolds numbers in the laminar range (Re 500-2000) using FLUENT. De-ionized water served as the cooling fluid while the micro-channel substrate used was made of copper. Validation results were found to be in good agreement with previous experimental and numerical data [1] with an average deviation of less than 4.2%. As the applied heat flux increased, an increase in heat transfer coefficient values was observed. Also, the Reynolds number required for transition from single-phase fluid to two-phase was found to increase. A correlation is proposed for the results of average Nusselt numbers for the heat transfer characteristics in micro-channels with simultaneously developing, single-phase flows. © 2011 Elsevier Ltd.
Describing one- and two-neutron halos in effective field theory
Indian Academy of Sciences (India)
Daniel R Phillips
2014-11-01
In this paper, the recent work our group has undertaken on effective field theory (EFT) analyses of experimental data pertaining to one- and two-neutron halo nuclei is discussed. The cases of 19C and 8Li (one-neutron halos) and 22C (two-neutron halo) are considered. For 19C and 8Li electromagnetic processes, such as Coulomb dissociation and radiative capture are considered. In the 22C system the way in which the measured matter radius can be used to derive constraints on the two-neutron separation energy of this very neutron-rich system is shown. In each case the Halo EFT’s ability to correlate different experimental observables with one another, in a modelindependent manner, and up to an accuracy that is determined by the separation of scales in the halo system is shown.
Two-neutron overlap functions for {sup 6}He from a microscopic structure model.
Energy Technology Data Exchange (ETDEWEB)
Brida, I.; Nunes, F. M. (Physics); (Michigan State Univ.)
2010-12-01
A fully antisymmetrized microscopic model is developed for light two-neutron halo nuclei using a hyper-spherical basis to describe halo regions. The many-body wavefunction is optimized variationally. The model is applied to {sup 6}He bound by semi realistic Minnesota nucleon-nucleon forces. The two-neutron separation energy and the radius of the halo are reproduced in agreement with experiment. Antisymmetrization effects between {sup 4}He and halo neutrons are found to be crucial for binding of {sup 6}He. We also properly extract two-neutron overlap functions and find that there is a significant increase of 30%-70% in their normalization due to microscopic effects as compared to the results of three-body models.
Two-neutron overlap functions for {sup 6}He from a microscopic structure model
Energy Technology Data Exchange (ETDEWEB)
Brida, I., E-mail: brida@anl.go [NSCL and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Nunes, F.M. [NSCL and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
2010-12-01
A fully antisymmetrized microscopic model is developed for light two-neutron halo nuclei using a hyper-spherical basis to describe halo regions. The many-body wavefunction is optimized variationally. The model is applied to {sup 6}He bound by semi realistic Minnesota nucleon-nucleon forces. The two-neutron separation energy and the radius of the halo are reproduced in agreement with experiment. Antisymmetrization effects between {sup 4}He and halo neutrons are found to be crucial for binding of {sup 6}He. We also properly extract two-neutron overlap functions and find that there is a significant increase of 30%-70% in their normalization due to microscopic effects as compared to the results of three-body models.
Directory of Open Access Journals (Sweden)
Ali Najah Al-Shamani
2015-03-01
Full Text Available Numerical study of heat transfer due to turbulent flow of nanofluids through rib–groove channel have been investigated. The continuity, momentum and energy equations are solved by the finite volume method (FVM. Four different rib–groove shapes have been examined. Four different types of nanoparticles, Al2O3, CuO, SiO2, and ZnO with different volumes fractions in the range of 1–4% and different nanoparticle diameter in the range of 25–70 nm, have been also studied. The computations are performed under constant temperature over a range of Reynolds number (Re 10,000–40,000. Results indicate that the Trapezoidal with increasing height in the flow direction rib–trapezoidal groove has the best heat transfer rate and high Nusselt number. It is also found that the SiO2 – nanofluid has the highest value of Nusselt number in comparison with the other type of nanofluids. The Nusselt number increases as the volume fraction increases and it decreases as the nanoparticle diameter increases. The present study shows that these Trapezoidal rib–groove using nanofluids have the potential to dramatically increase heat transfer characteristics and thus can be good candidates for the development of efficient heat exchanger device.
Large-eddy simulation of high-Schmidt number mass transfer in a turbulent channel flow
Calmet, Isabelle; Magnaudet, Jacques
1997-02-01
Mass transfer through the solid boundary of a turbulent channel flow is analyzed by means of large-eddy simulation (LES) for Schmidt numbers Sc=1, 100, and 200. For that purpose the subgrid stresses and fluxes are closed using the Dynamic Mixed Model proposed by Zang et al. [Phys. Fluids A 5, 3186 (1993)]. At each Schmidt number the mass transfer coefficient given by the LES is found to be in very good quantitative agreement with that measured in the experiments. At high Schmidt number this coefficient behaves like Sc-2/3, as predicted by standard theory and observed in most experiments. The main statistical characteristics of the fluctuating concentration field are analyzed in connection with the well-documented statistics of the turbulent motions. It is observed that concentration fluctuations have a significant intensity throughout the channel at Sc=1 while they are negligible out of the wall region at Sc=200. The maximum intensity of these fluctuations depends on both the Schmidt and Reynolds numbers and is especially influenced by the intensity of the velocity fluctuations present in the buffer layer of the concentration field. At Sc=1, strong similarities are observed between the various terms contributing to the turbulent kinetic energy budget and their counterpart in the budget of the variance of concentration fluctuations. At high Schmidt number, the latter budget is much more influenced by the small turbulent structures subsisting in the viscous sublayer. The instantaneous correlation between the spatial characteristics of the concentration field and those of the velocity field is clearly demonstrated by the presence of low- and high-concentration streaks close to the wall. The geometrical characteristics of these structures are found to be highly Sc dependent. In particular their spanwise wavelength is identical to that of the streamwise velocity streaks at Sc=1 while it is reduced by half at Sc=200. Analysis of the co-spectra between concentration and
Larsson, Richard; Rayer, Peter; Saunders, Roger; Bell, William; Booton, Anna; Buehler, Stefan A.; Eriksson, Patrick; John, Viju
2015-04-01
Channels 19-22 of the Special Sensor Microwave Imager/Sounder (SSMIS) on the DMSP satellite are simulated using a diverse atmospheric temperature profile dataset. These channels all measure the absorption spectra of the main isotope of molecular oxygen, and have pass-bands that are close in frequency to the center frequencies of four of the spectral lines. As a consequence, the channels measure high up in the atmosphere. The sensitivity of some channels even peak above the present upper levels of numerical weather prediction models at 80 km. The high altitude of the measurements in turn means that the molecular oxygen spectroscopy is noticeably affected by the Zeeman effect; this splits a line into frequency-separated polarized components as a function of the external magnetic field. The simulations have been performed using both ARTS and RTTOV as forward radiative transfer simulators. ARTS uses a line-by-line approach to radiative transfer. For the Zeeman effect calculations, ARTS can read line data and 3D magnetism directly from databases and then performs the splitting and polarization for each finite layer to calculate polarized absorption that is input to the radiative transfer equation. RTTOV uses a fast approach to radiative transfer, pre-calculating scalar effective transmission predictors for a set of atmospheric scenarios for each channel. For the Zeeman effect calculations, an altitude independent magnetic field is required as input for the layered transmission for the radiative transfer equation. Our results show that the differences between the models are small compared to sensor noise for all channels. The mean difference between models is larger for the lower altitude channels 21 and 22, but the standard deviation is small between the models. The mean simulated brightness temperatures of ARTS are closer to SSMIS than the RTTOV values, but it is not possible to tell which model is more accurate as temperature errors in the profiles are expected to be
Mohebbi, Rasul; Heidari, Hanif
The aim of this paper is investigating the forced convection heat transfer in a channel with transverse rectangular cavities using the lattice Boltzmann method (LBM) which is not available in the literature yet. The effects of the Reynolds number (100-400), cavity aspect ratio (AR=0.25, 0.5, 1.0), distance of cavities from each other (S‧=0,2,4,6) in fixed depth of cavity (A‧=0.5) on the velocity and temperature profiles are studied. Moreover, the flow patterns such as deflection and re-circulation zone inside the cavities are obtained. The local and averaged Nusselt numbers on the channel walls are achieved. The results show that the channel with cavities achieves heat transfer enhancements relative to the smooth channel. For the constant cavity aspect ratio, the maximum value of averaged Nusselt number in the channel is obtained in the case of S‧=2. Heat transfer to the working fluids increases significantly by increasing the aspect ratio. The existed results are used to ascertain the validity of the numerical code and excellent agreement between results was found.
Institute of Scientific and Technical Information of China (English)
Jingchun Min; Bingqiang Zhang
2015-01-01
Numerical calculations were conducted to simulate the flow and mass transfer in narrow membrane channels equipped with delta winglets, which are often used as longitudinal vortex generators to enhance heat transfer in heat exchanger applications. The channel consists of an impermeable solid wall and a membrane. The delta winglets are attached to the solid wal surface to enhance the mass transfer near the membrane surface and sup-press the concentration polarization. The winglet performance was evaluated in terms of concentration polariza-tion factor versus consumed pumping power. Calculations were implemented for NaCl solution flow in a membrane channel having a height of 2.0 mm for Reynolds numbers ranging from 400 to 1000. The delta wing-lets were optimized under equal pumping power condition, and the results of optimization suggest winglet height of 5/6 of the channel height, aspect ratio of 2.0, attack angle of 30°, and a winglet interval equal to the chan-nel height. The optimal delta winglets were compared with the optimal rectangular winglets we found previous-ly, and it is shown that the rectangular winglets yield a somewhat better performance than the delta winglets. © 2015 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Al rights reserved.
Directory of Open Access Journals (Sweden)
Al Mubarak Ali A.
2013-01-01
Full Text Available An experimental investigation has been carried out to study the heat transfer characteristics in a channel with heated target plate inclined at an angle cooled by single array of equally spaced centered impinging jets for three different jet Reynolds numbers (Re=9300, 14400 and 18800. Air ejected from an array of orifices impinges on the heated target surface The target plate forms the leading edge of a gas turbine blade cooled by jet impingement technique. The work includes the effect of jet Reynolds numbers and feed channel aspect ratios (H/d = 5, 7, 9 where H=2.5, 3.5, 4.5 cm and d=0.5 cm on the heat transfer characteristics for a given orifice jet plate configuration with equally spaced centered holes with outflow exiting in both directions (with inclined heated target surface. In general, It has been observed that, H/d=9 gives the maximum heat transfer over the entire length of the target surface as compared to all feed channel aspect ratios. H/d=9 gives 3% more heat transfer from the target surface as compared to H/d=5 (for Re=14400. Also, it has been observed that the magnitude of the averaged local Nusselt number increases with an increase in the jet Reynolds number for all the feed channel aspect ratios studied.
Lewandowska, Monika; Malinowski, Leszek
2016-01-01
The data resulting from the thermal-hydraulic test of the ITER TF CICC are used to determine the flow partition and the overall effective heat transfer coefficient (hBC) between bundle and central channel in a direct way, i.e. by analysis of the heat transfer between both flow channels, based on the mass and energy balance equations and the readings of thermometers located inside the cable. In cases without a local heat source in the considered cable segment the obtained hBC values were consistent with those obtained in earlier studies by analysis of experimental data using indirect methods. It was also observed that the transverse heat transfer was strongly enhanced in a cable segment heated from outside. This phenomenon results from the mass transfer from the bundle region to the central channel. The experimental hBC data obtained for the case without a heat source in the considered segment were also compared with those calculated using various heat transfer correlations.
Institute of Scientific and Technical Information of China (English)
M.M.RASHIDI; A.HOSSEINI; I.POP; S.KUMAR; N.FREIDOONIMEHR
2014-01-01
The main purpose of this study is to survey numerically comparison of two-phase and single phase of heat transfer and flow field of copper-water nanofluid in a wavy channel. The computational fluid dynamics (CFD) prediction is used for heat transfer and flow prediction of the single phase and three different two-phase models (mixture, volume of fluid (VOF), and Eulerian). The heat transfer coefficient, temperature, and velocity distributions are investigated. The results show that the differences between the temperature field in the single phase and two-phase models are greater than those in the hydrodynamic field. Also, it is found that the heat transfer coefficient predicted by the single phase model is enhanced by increasing the volume fraction of nanoparticles for all Reynolds numbers; while for the two-phase models, when the Reynolds number is low, increasing the volume fraction of nanoparticles will enhance the heat transfer coefficient in the front and the middle of the wavy channel, but gradually decrease along the wavy channel.
Two-neutron knockout from neutron-deficient $^{34}$Ar, $^{30}$S, and $^{26}$Si
Yoneda, K; Brown, B A; Campbell, C M; Cook, J M; Cottle, P D; Davies, A D; Dinca, D C; Gade, A; Glasmacher, T; Hansen, P G; Hoagland, T; Kemper, K W; Lecouey, J L; Müller, W F; Obertelli, A; Reynolds, R R; Terry, J R; Tostevin, J A; Zwahlen, H
2006-01-01
Two-neutron knockout reactions from nuclei in the proximity of the proton dripline have been studied using intermediate-energy beams of neutron-deficient $^{34}$Ar, $^{30}$S, and $^{26}$Si. The inclusive cross sections, and also the partial cross sections for the population of individual bound final states of the $^{32}$Ar, $^{28}$S and $^{24}$Si knockout residues, have been determined using the combination of particle and $\\gamma$-ray spectroscopy. Similar to the two-proton knockout mechanism on the neutron-rich side of the nuclear chart, these two-neutron removal reactions from already neutron-deficient nuclei are also shown to be consistent with a direct reaction mechanism.
The effect of heating direction on flow boiling heat transfer of R134a in micro-channels
Xu, Mingchen; Jia, Li; Dang, Chao; Peng, Qi
2017-04-01
This paper presents effects of heating directions on heat transfer performance of R134a flow boiling in micro- channel heat sink. The heat sink has 30 parallel rectangular channels with cross-sectional dimensions of 500μm width 500μm depth and 30mm length. The experimental operation condition ranges of the heat flux and the mass flux were 13.48 to 82.25 W/cm2 and 373.3 to 1244.4 kg/m2s respectively. The vapor quality ranged from 0.07 to 0.93. The heat transfer coefficients of top heating and bottom heating both were up to 25 kW/m2 K. Two dominate transfer mechanisms of nucleate boiling and convection boiling were observed according to boiling curves. The experimental results indicated that the heat transfer coefficient of bottom heating was 13.9% higher than top heating in low heat flux, while in high heat flux, the heat transfer coefficient of bottom heating was 9.9%.higher than the top heating, because bubbles were harder to divorce the heating wall. And a modified correlation was provided to predict heat transfer of top heating.
Directory of Open Access Journals (Sweden)
Prasad Kerehalli
2015-01-01
Full Text Available An analysis is carried out to study the effects of temperature-dependent transport properties on the fully developed free and forced MHD convection flow in a vertical channel. In this model, viscous and Ohmic dissipation terms are also included. The governing nonlinear equations (in non-dimensional form are solved numerically by a second order finite difference scheme. A parametric study is performed in order to illustrate the interactive influences of the model parameters; namely, the magnetic parameter, the variable viscosity parameter, the mixed convection parameter, the variable thermal conductivity parameter, the Brinkmann number and the Eckert number. The velocity field, the temperature field, the skin friction and the Nusselt number are evaluated for several sets of values of these parameters. For some special cases, the obtained numerical results are compared with the available results in the literature: Good agreement is found. Of all the parameters, the variable thermo-physical transport property has the strongest effect on the drag, heat transfer characteristics, the stream-wise velocity, and the temperature field.
Two neutrons halos: from {sup 11}Li to {sup 22}C
Energy Technology Data Exchange (ETDEWEB)
Frederico, T. [Instituto Tecnologico de Aeronautica (ITA/CTA), Sao Jose dos Campos, SP (Brazil)
2012-07-01
Full text: The universal aspects of weakly-bound neutron-rich light nuclei will be discussed qualitatively and quantitatively, considering the cases where large two-neutron halos are formed. The low-energy properties of light halo nuclei with two and three-body structures (one- and two-neutron halos) dominated by s-wave two-body interactions will be addressed in respect to halo size and charge radii. We focus on the Borromean cases of {sup 11}Li and the recently discovered {sup 22}C. Due to the large size of the two-neutron halos in respect to the nuclear interaction range, the general properties associated with the halo neutrons tail are model independent. These halo properties obey scaling laws which are functions mainly dominated by the neutron-neutron and neutron-core scattering lengths, with an additional short-range scale that parameterizes the physics of the 2n-core system at the nuclear interaction range. The essential physics supporting the model independence of the scaling laws is the Thomas-Efimov phenomena, and the scaling laws for the s-wave two-neutron halos appears in practice as limit-cycles calculated in a renormalized zero-range three-body model. The different radii and charge radius of the Borromean 2n-core systems with s-wave interactions are determined by scaling laws calculated within the three-body model. For example, the charge radius of {sup 11}Li is in perfect agreement with data, despite the simplicity of the model. The possibility of these nuclei present s-wave near-threshold resonances are also discussed. These aspects were recently reviewed in Ref.1. [1] T. Frederico, A. Delfino, L. Tomio, M. T. Yamashita, Prog. Part. Nucl. Phys. 67 (2012) 939. (author)
Energy Technology Data Exchange (ETDEWEB)
Malvandi, A., E-mail: amirmalvandi@aut.ac.ir [Department of Mechanical Engineering, Amirkabir University of Technology (Tehran Polytechnic), 424 Hafez Avenue, Tehran (Iran, Islamic Republic of); Ganji, D.D., E-mail: ddg_davood@yahoo.com [Mechanical Engineering Department, Babol Noshirvani University of Technology, Babol (Iran, Islamic Republic of)
2014-08-01
The present study is a theoretical investigation of the laminar flow and convective heat transfer of water/alumina nanofluid inside a parallel-plate channel in the presence of a uniform magnetic field. A modified two-component, four-equation, nonhomogeneous equilibrium model was employed for the alumina/water nanofluid, which fully accounted for the effect of the nanoparticle volume fraction distribution. The no-slip condition of the fluid–solid interface is abandoned in favor of a slip condition which appropriately represents the non-equilibrium region near the interface at micro/nano channels. The results obtained indicated that nanoparticles move from the heated walls (nanoparticles depletion) toward the core region of the channel (nanoparticles accumulation) and construct a non-uniform nanoparticles distribution. Moreover, in the presence of the magnetic field, the near wall velocity gradients increase, enhancing the slip velocity and thus the heat transfer rate and pressure drop increase. - Highlights: • Force convection of alumina/water nanofluid inside a parallel-plate channel. • Magnetic field effects on nanoparticles' migration. • Effects of Brownian motion and thermophoresis diffusivities on nanoparticle migration. • Different mechanisms of heat transfer rate based on nanoparticles' diameter.
Institute of Scientific and Technical Information of China (English)
肖军; 叶沿林; 游海波; 杨再宏; 曹中鑫; 江栋兴; 郑涛; 华辉; 李智焕; 葛俞成; 李湘庆; 楼建玲; 李阔昂; 李奇特; 乔锐; 陈瑞九
2012-01-01
A neutron detector array was used in a breakup reaction experiment at RIKEN with an 82.5 MeV/u SHe beam impinging on the CH2 and C targets. The array was calibrated using the cosmic ray, the 7 ray from the 6He+Pb reaction and the mono-energetic neutrons from the 7Li(p, n)TBe(g.s.+0.43 MeV) reaction. The position resolution, timing resolution and neutron de- tection efficiency were obtained accordingly. Cross-talk rejection conditions were developed based on analysis of the data taken from the 7Li(p, n)TBe(g.s.+0.43 MeV) test experiment, and finally a preliminary two-neutron correlation function for the SHe breakup reaction was investigated.
Measuring oxygen isotopes beyond the neutron dripline: Two-neutron emission and radioactivity
Kohley, Zach
2013-10-01
The availability of rare isotope beams has made it possible to extend nuclear structure measurements to nuclei far away from stability. Drastic changes in the structure, properties, and available decay-modes of these exotic isotopes have been observed in comparison to their stable counterparts. The oxygen isotopic chain has been particularly interesting with observations of new shell closures at N = 14 and N = 16. The MoNA-LISA/Sweeper setup at the National Superconducting Cyclotron Laboratory at Michigan State University has allowed for studies of the oxygen isotopes to be extended beyond the neutron dripline. Recently, the 26O ground state was observed for the first time and shown to be unbound by less than 200 keV. The low energy ground state of the two-neutron unbound 26O opened the possibility for the discovery of two-neutron radioactivity. A new technique was developed to measure the lifetimes of neutron unbound nuclei in the picosecond range. This technique was applied to the 26O decay and a half-life of 4.5-1. 5 + 1 . 1 (stat.) +/-3 (sys.) ps was extracted. This corresponds to 26O having a finite lifetime at an 82% confidence level and, thus, suggests the possibility of two-neutron radioactivity. Supported by the National Science Foundation, under Grant No. PHY-1102511.
Energy Technology Data Exchange (ETDEWEB)
Islam, M.S.; Monde, Masanori [Saga Univ. (Japan); Hino, Ryutaro; Haga, Katsuhiro; Sudo, Yukio
1997-07-01
Frictional pressure drop and heat transfer performance in a very narrow rectangular channel having one-sided constant heat flux and repeated-ribs for turbulent flow have been investigated experimentally, and their experimental correlations were obtained using the least square method. The rib pitch-to-height ratios(p/k) were 10 and 20 while holding the rib height constant at 0.2mm, the Reynolds number(Re) from 2,414 to 98,458 under different channel heights of 1.2mm, 2.97mm, and 3.24mm, the rib height-to-channel equivalent diameter(k/De) of 0.03, 0.04, and 0.09 respectively. The results show that the rib-roughened surface augments heat transfer 2-3 times higher than that of the smooth surface with the expense of 2.8-4 times higher frictional pressure drop under Re=5000-10{sup 5}, p/k=10, and H=1.2mm. Experimental results obtained by channel height, H=1.2mm shows a little bit higher heat transfer and friction factor performance than the higher channel height, H=3.24mm. The effect of fin and consequently higher turbulence intensity are responsible for producing higher heat transfer rates. The obtained correlations could be used to design the cooling passages between the target plates to remove high heat flux up to 12MW/m{sup 2} generated at target plates in a high-intensity proton accelerator system. (author). 54 refs.
Institute of Scientific and Technical Information of China (English)
Wenquan TAO; Junmei WU
2008-01-01
3-D numerical simulations were presented for laminar flow and heat transfer characteristics in a rectangular channel with vortex generators. The effects of Reynolds number (from 800 to 3 000), the attack angle of vortex generator (from 15° to 90°) and the shape of vortex generator were examined. The numerical results were analyzed based on the field synergy principle. It is found that the inherent mechanism of the heat transfer enhancement by longitudinal vortex can be explained by the field synergy principle, that is, the second flow generated by vortex generators results in the reduction of the intersection angle between the velocity and fluid temperature gradient. The longitudinal vortex improves the field synergy of the large downstream region of longitudinal vortex generator (LVG) and the region near (LVG); however, transverse vortex only improves the syn-ergy of the region near vortex generator. Thus, longitudinal vortex can enhance the integral heat transfer of the flow field, while transverse vortex can only enhance the local heat transfer. The synergy angle decreases with the increase of Reynolds number for the channel with LVG to differ from the result obtained from the plain channel, and the triangle winglet performs better than the rectanglar one under the same surface area condition.
Rheology of the Cu-H2O nanofluid in porous channel with heat transfer: Multiple solutions
Raza, J.; Rohni, A. M.; Omar, Z.; Awais, M.
2017-02-01
Dynamics of nanofluid comprising a base fluid (water) with copper (Cu) nanoparticles have been considered in channel with porous walls under magnetic field influence. The channel walls are considered to be permeable in order to analyze the wall mass transfer phenomenon. Relevant mathematical modelling has been performed and the derived PDEs are converted into coupled nonlinear ODEs by using suitable transformations. Computations have been made numerically by employing the shooting technique. It is noted that multiple solutions occur for the variation of suction Reynolds number, solid volume fraction and magnetic parameters which are interpreted in detail.
Energy Technology Data Exchange (ETDEWEB)
Boukadida, N. [Faculte des Sciences, Dept. of Physics, Monastir (Tunisia); Ben Nasrallah, S. [Ecole Nationale d' Ingenieurs de Monastir, Dept. of Energetics (Tunisia)
2001-01-01
A detailed numerical analysis concerning the mechanism of heat and mass transfer during water evaporation in a two dimensional steady laminar flow of dry air or air-vapor mixture in a horizontal channel is studied. The gas is considered as absorbing, emitting and non-scattering medium with variable thermophysical properties. The results show the effect of different state variables on the coefficients of heat and mass transfer and the domain where the analogy between the heat and mass transfer is valid. They also show the effect of the thermal radiation on the ratio between Sherwood and Nusselt numbers. The comparison between the present results and those obtained in previous published studies [32-34] features to a satisfactory agreement. (authors)
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Han, Sol; Choi, Seok Min; Sohn, Ho-Seong; Cho, Hyung Hee [Yonsei Univ., Seoul (Korea, Republic of)
2017-03-15
The present study investigated the effect of the rib arrangement and a guide vane for enhancing internal cooling of the blade. Two types of rib arrangements were used in the first and second passage in parallel. Aspect ratio of the channel was 5 and a fixed Reynolds number based on hydraulic diameter was 10,000. The attack angle of rib was 60°, rib pitch-to-height ratio (p/e) was 10, and the rib height-to-hydraulic-diameter ratio (e/D{sub n}) was 0.075. The effect of an interaction between Dean vortices and the secondary vortices from the first passage was observed. Overall, the attack angle of rib in the first passage was dominant factor to heat transfer and flow patterns in turning region. Also, the channel with a guide vane showed enhanced heat transfer at the tip surface with reducing flow separation and recirculation.
Energy Technology Data Exchange (ETDEWEB)
Hibbs, R.; Chen, Y.; Nikitopoulos, D. [Louisiana State Univ., Baton Rouge, LA (United States)] [and others
1995-10-01
The effect of vortex generators on the mass (heat) transfer from the ribbed passage of a two pass turbine blade coolant channel is investigated with the intent of optimizing the vortex generator geometry so that significant enhancements in mass/heat transfer can be achieved. In the experimental configuration considered, ribs are mounted on two opposite walls; all four walls along each pass are active and have mass transfer from their surfaces but the ribs are non-participating. Mass transfer measurements, in the form of Sherwood number ratios, are made along the centerline and in selected inter-rib modules. Results are presented for Reynolds number in the range of 5,000 to 40,000, pitch to rib height ratios of 10.5 and 21, and vortex generator-rib spacing to rib height ratios of 0.55, and 1.5. Centerline and spanwise averaged Sherwood number ratios are presented along with contours of the Sherwood number ratios. Results indicate that the vortex generators induce substantial increases in the local mass transfer rates, particularly along the side walls, and modest increases in the average mass transfer rates. The vortex generators have the effect of making the inter-rib profiles along the ribbed walls more uniform. Along the side walls, horse-shoe vortices that characterize the vortex generator wake are associated with significant mass transfer enhancements. The wake effects and the levels of enhancement decrease somewhat with increasing Reynolds number and decreasing pitch.
Galvan, Manuel de Jesus
In the past years, hydrocarbon fuels have been the focus of attention as the interest in developing reusable, high-performing liquid rocket engines has grown. Liquid methane (LCH4) has been of particular interest because of the cost, handling, and storage advantages that it presents when compared to currently used propellants. Deep space exploration requires thrusters that can operate reliably during long-duration missions. One of the challenges in the development of a reliable engine has been providing adequate combustion chamber cooling to prevent engine failure. Regenerative (regen) cooling has presented itself as an appealing option because it provides improved cooling and engine efficiency over other types of cooling, such as film or dump cooling. Due to limited availability of experimental sub-critical liquid methane cooling data for pressure-fed regen engine design, there has been an interest in studying the heat transfer characteristics of the propellant. For this reason, recent experimental studies at the Center for Space Exploration Technology Research (cSETR) at the University of Texas at El Paso (UTEP) have focused on investigating the heat transfer characteristics of sub-critical CH4 flowing through smooth sub-scale cooling channels. In addition to investigating smooth channels, the cSETR has conducted experiments to investigate the effects of internal longitudinal fins on the heat transfer of methane. To conduct the experiments, the cSETR developed a conduction-based thermal concentrator known as the High Heat Flux Test Facility (HHFTF) in which the channels are heated. In this study, a smooth channel and three channels with longitudinal fins all with cross sectional geometries of 3.2 mm x 3.2 mm were tested. The Nusselt numbers ranged from 70 and 510, and Reynolds numbers were between 50,000 and 128,000. Sub-cooled film-boiling phenomena were discovered in the data pertaining to the smooth and two finned channels. Sub-cooled film-boiling was not
Taghavi Fadaki, S. S.; Amanifard, N.; Deylami, H. M.; Dolati, F.
2017-02-01
In the present study, a new design of collecting electrodes is studied for performing a higher performance in EHD phenomena in a smooth channel. The effect of the electric field on the heat transfer enhancement and swirling flow patterns for a new design of multiple collectors in a smooth channel is numerically investigated with 2-D approach. In this regard, the corona device configuration comprises a single fixed emitting wire situated at the centerline of the channel and different grounded electrode arrangements which are in two types of wire and plate. The results indicate that the multi-collector arrangements cause significant changes in the flow pattern, heat transfer coefficient and friction factor. Furthermore, it is found that the thermal enhancement factor has remarkable growth, and EHD efficiency for two types of wire and plate collectors is notable. Besides, as an outstanding result, the electrohydrodynamic phenomenon has a negative effect on the heat transfer enhancement depending upon the values of Reynolds number and applied electric potential.
Kamajaya, Ketut; Umar, Efrizon; Sudjatmi, K. S.
2012-06-01
This study focused on natural convection heat transfer using a vertical rectangular sub-channel and water as the coolant fluid. To conduct this study has been made pipe heaters are equipped with thermocouples. Each heater is equipped with five thermocouples along the heating pipes. The diameter of each heater is 2.54 cm and 45 cm in length. The distance between the central heating and the pitch is 29.5 cm. Test equipment is equipped with a primary cooling system, a secondary cooling system and a heat exchanger. The purpose of this study is to obtain new empirical correlations equations of the vertical rectangular sub-channel, especially for the natural convection heat transfer within a bundle of vertical cylinders rectangular arrangement sub-channels. The empirical correlation equation can support the thermo-hydraulic analysis of research nuclear reactors that utilize cylindrical fuel rods, and also can be used in designing of baffle-free vertical shell and tube heat exchangers. The results of this study that the empirical correlation equations of natural convection heat transfer coefficients with rectangular arrangement is Nu = 6.3357 (Ra.Dh/x)0.0740.
Flow Boiling Heat Transfer in Two-Phase Micro Channel Heat Sink at Low Water Mass Flux
Kuznetsov, Vladimir V.; Shamirzaev, Alisher S.
2009-08-01
Boiling heat transfer at water flow with low mass flux in heat sink which contained rectangular microchannels was studied. The stainless steel heat sink contained ten parallel microchannels with a size of 640 × 2050 μm in cross-section with typical wall roughness of 10-15 μm. The local flow boiling heat transfer coefficients were measured at mass velocity of 17 and 51 kg/m2s, heat flux on 30 to 150 kW/m2 and vapor quality of up to 0.8 at pressure in the channels closed to atmospheric one. It was observed that Kandlikar nucleate boiling correlation is in good agreement with the experimental data at mass flow velocity of 85 kg/m2s. At smaller mass flux the Kandlikar model and Zhang, Hibiki and Mishima model demonstrate incorrect trend of heat transfer coefficients variation with vapor quality.
Calculation of the drag and heat transfer from a sphere in the gas flow in a cylindrical channel
Simakov, N. N.
2016-09-01
A numerical experiment on the simulation of heat transfer from a sphere to a gas flow in a cylindrical channel in the Stokes and transient flow regimes has been described. Radial and axial profiles of the gas temperature and the dependences of drag coefficient C d of the body and Nusselt number Nu on Reynolds number Re have been calculated and analyzed. The problem of the influence of the early drag crisis for a sphere on its heat transfer to the gas flow has been considered. The estimation of this phenomenon has shown that the early drag crisis of the sphere in a strongly turbulent flow causes a reduction in heat transfer from the sphere to the gas by three to six times (in approximately the same proportion as for its drag coefficient).
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Muhammad Zubair Akbar
2016-04-01
Full Text Available The paper presents the numerical study of heat and mass transfer analysis in a viscous unsteady MHD nanofluid flow through a channel with porous walls and medium in the presence of metallic nanoparticles. The two cases for effective thermal conductivity are discussed in the analysis through H-C model. The impacts of the governing parameters on the flow, heat and mass transfer aspects of the issue are talked about. Under the patronage of small values of permeable Reynolds number and relaxation/contraction parameter, we locate that, when wall contraction is together with suction, flow turning is encouraged close to the wall where the boundary layer is shaped. On the other hand, when the wall relaxation is coupled with injection, the flow adjacent to the porous walls decreased. The outcome of the exploration may be beneficial for applications of biotechnology. Numerical solutions for the velocity, heat and mass transfer rate at the boundary are obtained and analyzed.
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Ning Wang
2014-06-01
Full Text Available Supercritical convective heat transfer characteristics of hydrocarbon fuel play a fundamental role in the active cooling technology of scramjet. In this paper, a 2D-axisymmetric numerical study of supercritical heat transfer of RP3 flowing inside the cooling channels of scramjet has been conducted. The main thermophysical properties of RP3, including density, specific heat, and thermal conductivity, are obtained from experimental data, while viscosity is evaluated from a commercial code with a ten-species surrogate. Effects of heat flux, mass flow rate, and inlet temperature on supercritical heat transfer processes have been investigated. Results indicate that when the wall temperature rises above the pseudocritical temperature of RP3, heat transfer coefficient decreases as a result of drastic decrease of the specific heat. The conventional heat transfer correlations, that is, Gnielinski formula, are no longer proper for the supercritical heat transfer of RP3. The modified Jackson and Hall formula, which was proposed for supercritical CO2 and water, gives good prediction except when the wall temperature is near or higher than the pseudocritical temperature.
Ghasemian, M.; Najafian Ashrafi, Z.; Goharkhah, M.; Ashjaee, M.
2015-05-01
Laminar forced convection heat transfer of water based Fe3O4 ferrofluid in a mini channel in the presence of constant and alternating magnetic fields is studied numerically. The hot ferrofluid flows into the 20 mm (l)×2 mm (h) mini channel with isothermal top and bottom cold surfaces and is subjected to a transverse non-uniform magnetic field produced by current carrying wires. Two-phase mixture model is implemented and the governing equations are solved using the finite volume approach. Primarily, the effects of the constant magnetic field location and intensity on the convective heat transfer are investigated. Simulation results show that the heat transfer is enhanced due to the disruption of the thermal boundary layer. However, this effect is more pronounced when the magnetic field source is placed in the fully developed region. In the next section, an alternating magnetic field with frequencies ranging from 0 to 10 Hz is imposed to the ferrofluid at different Reynolds numbers of Re=10, 25 and 50. A 16.48% heat transfer enhancement is obtained with a constant magnetic field at Re=25 and magnetic field intensity, Mn=1.07×108. This value is increased up to 27.72% by applying an alternating magnetic field with the same intensity at f=4 Hz. Results also indicate that the heat transfer enhancement due to the magnetic field is more significant at lower Reynolds numbers. The optimum frequency for heat transfer enhancement has been obtained for all the cases which shows that it has an increasing trend with the Reynolds number.
Indirect DNS Covert Channel based on Base 16 Matrix for Stealth Short Message Transfer
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Md Asri Ngadi
2011-11-01
Full Text Available Covert Channel are the methods to conceal a message in the volatile medium carrier such as radio signal and network packets. Until now, covert channels based on the packet length produce abnormal packet length when the length of the message is long. Abnormal packet length, especially in the normal network will expose the covert channels to network security perimeter. Therefore, it motivates the study to propose a new method based on reference matrix to hide the secret message in DNS request. Normal DNS request packet was collected from the campus network. The proposed packets length covert channel was compared with normal DNS request packets. The study found that the new purpose covert channels produce normal DNS packet length according to the campus network.
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Herman, C.; Kang, E. [Dept. of Mechanical Engineering, Johns Hopkins Univ., Baltimore, MD (United States)
2001-01-01
An experimental study was conducted of incompressible, moderate Reynolds number flow of air over heated rectangular blocks in a two-dimensional, horizontal channel. Holographic interferometry combined with high-speed cinematography was used to visualize the unsteady temperature fields in self- sustained oscillatory flow. Experiments were conducted in the laminar, transitional and turbulent flow regimes for Reynolds numbers in the range from Re = 520 to Re = 6600. Interferometric measurements were obtained in the thermally and fluiddynamically periodically fully developed flow region on the ninth heated block. Flow oscillations were first observed between Re = 1054 and Re = 1318. The period of oscillations, wavelength and propagation speed of the Tollmien-Schlichting waves in the main channel were measured at two characteristic flow velocities, Re = 1580 and Re = 2370. For these Reynolds numbers it was observed that two to three waves span one geometric periodicity length. At Re = 1580 the dominant oscillation frequency was found to be around 26 Hz and at Re = 2370 the frequency distribution formed a band around 125 Hz. Results regarding heat transfer and pressure drop are presented as a function of the Reynolds number, in terms of the block-average Nusselt number and the local Nusselt number as well as the friction factor. Measurements of the local Nusselt number together with visual observations indicate that the lateral mixing caused by flow instabilities is most pronounced along the upstream vertical wall of the heated block in the groove region, and it is accompanied by high heat transfer coefficients. At Reynolds numbers beyond the onset of oscillations the heat transfer in the grooved channel exceeds the performance of the reference geometry, the asymmetrically heated parallel plate channel. (orig.)
Herman, C.; Kang, E.
An experimental study was conducted of incompressible, moderate Reynolds number flow of air over heated rectangular blocks in a two-dimensional, horizontal channel. Holographic interferometry combined with high-speed cinematography was used to visualize the unsteady temperature fields in self- sustained oscillatory flow. Experiments were conducted in the laminar, transitional and turbulent flow regimes for Reynolds numbers in the range from Re=520 to Re=6600. Interferometric measurements were obtained in the thermally and fluiddynamically periodically fully developed flow region on the ninth heated block. Flow oscillations were first observed between Re=1054 and Re=1318. The period of oscillations, wavelength and propagation speed of the Tollmien-Schlichting waves in the main channel were measured at two characteristic flow velocities, Re=1580 and Re=2370. For these Reynolds numbers it was observed that two to three waves span one geometric periodicity length. At Re=1580 the dominant oscillation frequency was found to be around 26Hz and at Re=2370 the frequency distribution formed a band around 125Hz. Results regarding heat transfer and pressure drop are presented as a function of the Reynolds number, in terms of the block-average Nusselt number and the local Nusselt number as well as the friction factor. Measurements of the local Nusselt number together with visual observations indicate that the lateral mixing caused by flow instabilities is most pronounced along the upstream vertical wall of the heated block in the groove region, and it is accompanied by high heat transfer coefficients. At Reynolds numbers beyond the onset of oscillations the heat transfer in the grooved channel exceeds the performance of the reference geometry, the asymmetrically heated parallel plate channel.
Heat transfer in a compact heat exchanger containing rectangular channels and using helium gas
Olson, D. A.
1991-01-01
Development of a National Aerospace Plane (NASP), which will fly at hypersonic speeds, require novel cooling techniques to manage the anticipated high heat fluxes on various components. A compact heat exchanger was constructed consisting of 12 parallel, rectangular channels in a flat piece of commercially pure nickel. The channel specimen was radiatively heated on the top side at heat fluxes of up to 77 W/sq cm, insulated on the back side, and cooled with helium gas flowing in the channels at 3.5 to 7.0 MPa and Reynolds numbers of 1400 to 28,000. The measured friction factor was lower than that of the accepted correlation for fully developed turbulent flow, although the uncertainty was high due to uncertainty in the channel height and a high ratio of dynamic pressure to pressure drop. The measured Nusselt number, when modified to account for differences in fluid properties between the wall and the cooling fluid, agreed with past correlations for fully developed turbulent flow in channels. Flow nonuniformity from channel-to-channel was as high as 12 pct above and 19 pct below the mean flow.
Shi, Xiaojun; Gao, Jianmin; Xu, Liang; Li, Fajin
2013-11-01
Using steam as working fluid to replace compressed air is a promising cooling technology for internal cooling passages of blades and vanes. The local heat transfer characteristics and the thermal performance of steam flow in wide aspect ratio channels ( W/ H = 2) with different angled ribs on two opposite walls have been experimentally investigated in this paper. The averaged Nusselt number ratios and the friction factor ratios of steam and air in four ribbed channels were also measured under the same test conditions for comparison. The Reynolds number range is 6,000-70,000. The rib angles are 90°, 60°, 45°, and 30°, respectively. The rib height to hydraulic diameter ratio is 0.047. The pitch-to-rib height ratio is 10. The results show that the Nusselt number ratios of steam are 1.19-1.32 times greater than those of air over the range of Reynolds numbers studied. For wide aspect ratio channels using steam as the coolant, the 60° angled ribs has the best heat transfer performance and is recommended for cooling design.
Robust quantum state transfer via topologically protected edge channels in dipolar arrays
Dlaska, C.; Vermersch, B.; Zoller, P.
2017-03-01
We show how to realise quantum state transfer between distant qubits using the chiral edge states of a two-dimensional topological spin system. Our implementation based on Rydberg atoms allows to realise the quantum state transfer protocol in state-of-the-art experimental setups. In particular, we show how to adapt the standard state transfer protocol to make it robust against dispersive and disorder effects.
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Nili-Ahmadabadi M.
2012-01-01
Full Text Available This paper will present the results of the experimental investigation of heat transfer in a non-annular channel between rotor and stator similar to a real generator. Numerous experiments and numerical studies have examined flow and heat transfer characteristics of a fluid in an annulus with a rotating inner cylinder. In the current study, turbulent flow region and heat transfer characteristics have been studied in the air gap between the rotor and stator of a generator. The test rig has been built in a way which shows a very good agreement with the geometry of a real generator. The boundary condition supplies a non-homogenous heat flux through the passing air channel. The experimental devices and data acquisition method are carefully described in the paper. Surface-mounted thermocouples are located on the both stator and rotor surfaces and one slip ring transfers the collected temperature from rotor to the instrument display. The rotational speed of rotor is fixed at three under: 300rpm, 900 rpm and 1500 rpm. Based on these speeds and hydraulic diameter of the air gap, the Reynolds number has been considered in the range: 4000
Nouri-Borujerdi, Ali; Moazezi, Arash
2017-07-01
The current study investigates the conjugate heat transfer characteristics for laminar flow in backward facing step channel. All of the channel walls are insulated except the lower thick wall under a constant temperature. The upper wall includes a insulated obstacle perpendicular to flow direction. The effect of obstacle height and location on the fluid flow and heat transfer are numerically explored for the Reynolds number in the range of 10 ≤ Re ≤ 300. Incompressible Navier-Stokes and thermal energy equations are solved simultaneously in fluid region by the upwind compact finite difference scheme based on flux-difference splitting in conjunction with artificial compressibility method. In the thick wall, the energy equation is obtained by Laplace equation. A multi-block approach is used to perform parallel computing to reduce the CPU time. Each block is modeled separately by sharing boundary conditions with neighbors. The developed program for modeling was written in FORTRAN language with OpenMP API. The obtained results showed that using of the multi-block parallel computing method is a simple robust scheme with high performance and high-order accurate. Moreover, the obtained results demonstrated that the increment of Reynolds number and obstacle height as well as decrement of horizontal distance between the obstacle and the step improve the heat transfer.
Léguillon, R.; Nishio, K.; Hirose, K.; Makii, H.; Nishinaka, I.; Orlandi, R.; Tsukada, K.; Smallcombe, J.; Chiba, S.; Aritomo, Y.; Ohtsuki, T.; Tatsuzawa, R.; Takaki, N.; Tamura, N.; Goto, S.; Tsekhanovich, I.; Petrache, C. M.; Andreyev, A. N.
2016-10-01
It is shown that the multinucleon transfer reactions is a powerful tool to study fission of exotic neutron-rich actinide nuclei, which cannot be accessed by particle-capture or heavy-ion fusion reactions. In this work, multinucleon transfer channels of the 18O + 232Th reaction are used to study fission of fourteen nuclei 231,232,233,234Th, 232,233,234,235,236Pa, and 234,235,236,237,238U. Identification of fissioning nuclei and of their excitation energy is performed on an event-by-event basis, through the measurement of outgoing ejectile particle in coincidence with fission fragments. Fission fragment mass distributions are measured for each transfer channel, in selected bins of excitation energy. In particular, the mass distributions of 231,234Th and 234,235,236Pa are measured for the first time. Predominantly asymmetric fission is observed at low excitation energies for all studied cases, with a gradual increase of the symmetric mode towards higher excitation energy. The experimental distributions are found to be in general agreement with predictions of the fluctuation-dissipation model.
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R. Léguillon
2016-10-01
Full Text Available It is shown that the multinucleon transfer reactions is a powerful tool to study fission of exotic neutron-rich actinide nuclei, which cannot be accessed by particle-capture or heavy-ion fusion reactions. In this work, multinucleon transfer channels of the 18O+232Th reaction are used to study fission of fourteen nuclei 231,232,233,234Th, 232,233,234,235,236Pa, and 234,235,236,237,238U. Identification of fissioning nuclei and of their excitation energy is performed on an event-by-event basis, through the measurement of outgoing ejectile particle in coincidence with fission fragments. Fission fragment mass distributions are measured for each transfer channel, in selected bins of excitation energy. In particular, the mass distributions of 231,234Th and 234,235,236Pa are measured for the first time. Predominantly asymmetric fission is observed at low excitation energies for all studied cases, with a gradual increase of the symmetric mode towards higher excitation energy. The experimental distributions are found to be in general agreement with predictions of the fluctuation–dissipation model.
Heat and mass transfer in a vertical channel under heat-gravitational convection conditions
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Petrichenko Michail
2016-01-01
Full Text Available Heat-gravitational motion of an air flow in a vertical channel with one-sided heating in an area with low Reynolds number is stated in Boussinesq approximation. Hydraulic variables field in a heat-gravitational motion is modeled with the application of ANSYS-FLUENT. It is converted to average velocity and temperature values in a cross section of the channel. The value of an average velocity is determined by rate of heat supply in a barotropic flow with a polytropic coefficient n
Misra, J C; Rath, H J
2010-01-01
Of concern in the paper is a study of steady incompressible viscoelastic and electrically conducting fluid flow and heat transfer in a parallel plate channel with stretching walls in the presence of a magnetic field applied externally. The flow is considered to be governed by Walter's liquid B fluid. The problem is solved by developing a suitable numerical method. The results are found to be in good agrement with those of earlier investigations reported in existing scientific literatures. The study reveals that a back flow occurs near the central line of the channel due to the stretching walls and further that this flow reversal can be stopped by applying a strong external magnetic field. The study also shows that with the increase in the strength of the magnetic field, the fluid velocity decreases but the temperature increases. Thus the study bears potential applications in the study of the haemodynamic flow of blood in the cardiovascular system when subjected to an external magnetic field.
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Ahmed W. Mustava
2013-04-01
Full Text Available The effect of a semi-circular cylinders in a two dimensional channel on heat transfer by forced convection from two heat sources with a constant temperature has been studied numerically. Each channel contains two heat sources; one on the upper surface of the channel and the other on the lower surface of the channel. There is semi-circular cylinder under the source in upper surface and there is semi-circular cylinder above the source in lower surface. The location of the second heat source with its semi-cylinder has been changed and keeps the first source with its semi- cylinder at the same location. The flow and temperature field are studied numerically with different values of Reynolds numbers and for different spacing between the centers of the semi-cylinders. The laminar flow field is analyzed numerically by solving the steady forms of the two-dimensional incompressible Navier- Stokes and energy equations. The Cartesian velocity components and pressure on a collocated (non-staggered grid are used as dependent variables in the momentum equations, which discretized by finite volume method, body fitted coordinates are used to represent the complex channel geometry accurately, and grid generation technique based on elliptic partial differential equations is employed. SIMPLE algorithm is used to adjust the velocity field to satisfy the conservation of mass. The range of Reynolds number is (Re= 100 – 800 and the range of the spacing between the semi-cylinders is(1-4 and the Prandtl number is 0.7.The results showed that increasing the spacing between the semi-cylinders increases the average of Nusselt number of the first heat source for all Reynolds numbers. As well as the results show that the best case among the cases studied to enhance the heat transfer is when the second heat source and its semi-cylinder located on at the distance (S=1.5 from the first half of the cylinder and the Reynolds number is greater than (Re ≥ 400 because of the
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Yasmin Asia
2016-01-01
Full Text Available The unsteady laminar incompressible flow and heat transfer characteristics of an electrically conducting micropolar fluid in a porous channel with expanding or contracting walls is investigated. The relevant partial differential equations have been reduced to ordinary ones. The reduced system of ordinary differential equations (ODEs has been solved numerically by lower-upper (LU triangular factorization or Gaussian elimination and successive over relaxation (SOR method. The effects of some physical parameters such as magnetic parameter, micropolar parameters, wall expansion ratio, permeability Reynolds number and Prandtl number on the velocity, microrotation, temperature and the shear and couple stresses are discussed.
Samarin, V. V.
2016-05-01
The time-dependent Schrödinger equation and the coupled channel approach based on the method of perturbed stationary two-center states are used to describe nucleon transfers and fusion in low-energy nuclear reactions. Results of the cross sections calculation for the formation of the 198Au and fusion in the 6He+197Au reaction and for the formation of the 65Zn in 6He+64Zn reaction agree satisfactorily with the experimental data near the barrier. The Feynman's continual integrals calculations for a few-body systems were used for the proposal of the new form of the shell model mean field for helium isotopes.
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Hemant Poonia
2015-06-01
Full Text Available In this paper the effects of Hall current on MHD free convection flow in a vertical rotating channel filled with porous medium have been studied. A uniform magnetic field is applied in the direction normal to the plates. The entire system rotates about an axis normal to the planes of the plates with uniform angular velocity ' . The temperature of one of the plates varies periodically and the temperature difference of the plates is high enough to induce radiative heat transfer. The effects of various parameters on the velocity and temperature field are shown graphically. Also the results on Skin Frication and Nusselt Number are shown in tables.
Effect of rib angle on local heat/mass transfer distribution in a two-pass rib-roughened channel
Chandra, P. R.; Han, J. C.; Lau, S. C.
1987-01-01
The naphthalene sublimation technique is used to investigate the heat transfer characteristics of turbulent air flow in a two-pass channel. A test section that resembles the internal cooling passages of gas turbine airfoils is employed. The local Sherwood numbers on the ribbed walls were found to be 1.5-6.5 times those for a fully developed flow in a smooth square duct. Depending on the rib angle-of-attack and the Reynolds number, the average ribbed-wall Sherwood numbers were 2.5-3.5 times higher than the fully developed values.
Energy Technology Data Exchange (ETDEWEB)
Abbas, Z.; Naveed, M., E-mail: rana.m.naveed@gmail.com [Department of Mathematics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Sajid, M. [Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad 44000 (Pakistan)
2015-10-15
In this paper, effects of Hall currents and nonlinear radiative heat transfer in a viscous fluid passing through a semi-porous curved channel coiled in a circle of radius R are analyzed. A curvilinear coordinate system is used to develop the mathematical model of the considered problem in the form partial differential equations. Similarity solutions of the governing boundary value problems are obtained numerically using shooting method. The results are also validated with the well-known finite difference technique known as the Keller-Box method. The analysis of the involved pertinent parameters on the velocity and temperature distributions is presented through graphs and tables.
CSIR Research Space (South Africa)
Scheepers, G
2006-01-01
Full Text Available Conference on Computational and Applied Mechanics SACAM06 Cape Town, 16-18 January 2006 SACAM EXPERIMENTAL AND NUMERICAL STUDY OF NEAR BLEED HOLE HEAT TRANSFER ENHANCEMENT IN INTERNAL TURBINE BLADE COOLING CHANNELS Scheepers G*, Morris RM, Visser JA....5×104, while the hole suction ratio in terms of Reynolds number was varied from 0 to 5. 1. Introduction With the ever increasing demand for higher thermal efficiency, modern jet turbine blades are exposed to temperatures which comprehensively exceed...
Boltenko, E. A.
2016-10-01
The results of the experimental study of the heat-transfer crisis on heat-release surfaces of annular channels with swirl and transit flow are presented. The experiments were carried out using electric heated annular channels with one and (or) two heat-release surfaces. For the organization of transit flow on a convex heat-release surface, four longitudinal ribs were installed uniformly at its perimeter. Swirl flow was realized using a capillary wound tightly (without gaps) on the ribs. The ratio between swirl and transit flows in the annular gap was varied by applying longitudinal ribs of different height. The experiments were carried out using a closed-type circulatory system. The experimental data were obtained in a wide range of regime parameters. Both water heated to the temperature less than the saturation temperature and water-steam mixture were fed at the inlet of the channels. For the measurement of the temperature of the heat-release surfaces, chromel-copel thermocouples were used. It was shown that the presence of swirl flow on a convex heatrelease surface led to a significant decrease in critical heat flows (CHF) compared to a smooth surface. To increase CHF, it was proposed to use the interaction of swirl flows of the heat carrier. The second swirl flow was transit flow, i.e., swirl flow with the step equal to infinity. It was shown that CHF values for a channel with swirl and transit flow in all the studied range of regime parameters was higher than CHF values for both a smooth annular channel and a channel with swirl. The empirical ratios describing the dependence of CHF on convex and concave heat-release surfaces of annular channels with swirl and transit flow on the geometrical characteristics of channels and the regime parameters were obtained. The experiments were carried out at the pressure p = 3.0-16.0 MPa and the mass velocity ρw = 250-3000 kg/(m2s).
Czarske, Jueurgen W; Koukourakis, Nektarios; Buettner, Lars
2016-01-01
Multimode fibers are attractive for a variety of applications such as internet data transfer, data center hubs, micromanipulation, optogenetics and other biomedical applications. A major hurdle for imaging through multimode fibers is the occurring scrambling, resulting in a randomization of light. Recently, clear imaging has been successfully accomplished using wavefront shaping, but the spatial information was transferred synchronously only. We demonstrate asynchronous information transmission using individual phase conjugations by employing only one spatial light modulator with multiple windows. Our findings pave the way towards individual signal transfer inside strongly scattering media.
Constraints on two-neutron separation energy in the Borromean $^{22}$C nucleus
Yamashita, M T; Frederico, T; Tomio, L
2011-01-01
The recently extracted matter radius of carbon isotope $^{22}$C allows us to estimate the mean-square distance of a halo neutron with respect to the center-of-mass of this nucleus. By considering this information, we suggest an energy region for an experimental investigation of the unbound $^{21}$C virtual state. Our analysis, in a renormalized zero-ranged three-body model, also indicates that the two-neutron separation energy in $^{22}$C is expected to be found below $\\sim$0.4~MeV, where the $^{22}$C is approximated by a Borromean configuration with a pointlike $^{20}$C and two $s$-wave halo neutrons. A virtual-state energy of $^{21}$C close to zero, would make the $^{22}$C, within Borromean nuclei configurations, the most promising candidate to present an excited bound Efimov state or a continuum three-body resonance.
Experimental and Computational Studies of Turbulent Mass Transfer in a Mixing Channel
DEFF Research Database (Denmark)
Hjertager, Lene Kristin; Hjertager, Bjørn H.; Solberg, Tron
2008-01-01
Experiments are carried out for passive mixing in order to obtain local mean and turbulent velocities and concentrations. The mixing takes place in a square channel with two inlets separated by a block. A combined PIV/PLIF technique is used to obtain instantaneous velocity and concentration fields....... Three different flow cases are studied. The 2D numerical predictions of the mixing channel show that none of the k- ε turbulence models tested is suitable for the flow cases studied here. The turbulent Schmidt number is reduced to obtain a better agreement between measured and predicted mean...
Directory of Open Access Journals (Sweden)
Cieśliński Janusz T.
2016-09-01
Full Text Available This study is focused on experimental investigation of selected type of brazed plate heat exchanger (PHEx. The Wilson plot approach was applied in order to estimate heat transfer coefficients for the PHEx passages. The main aim of the paper was to experimentally check ability of several correlations published in the literature to predict heat transfer coefficients by comparison experimentally obtained data with appropriate predictions. The results obtained revealed that Hausen and Dittus-Boelter correlations underestimated heat transfer coefficient for the tested PHEx by an order of magnitude. The Aspen Plate code overestimated heat transfer coefficient by about 50%, while Muley-Manglik correlation overestimated it from 1% to 25%, dependent on the value of Reynolds number and hot or cold liquid side.
Cieśliński, Janusz T.; Fiuk, Artur; Typiński, Krzysztof; Siemieńczuk, Bartłomiej
2016-09-01
This study is focused on experimental investigation of selected type of brazed plate heat exchanger (PHEx). The Wilson plot approach was applied in order to estimate heat transfer coefficients for the PHEx passages. The main aim of the paper was to experimentally check ability of several correlations published in the literature to predict heat transfer coefficients by comparison experimentally obtained data with appropriate predictions. The results obtained revealed that Hausen and Dittus-Boelter correlations underestimated heat transfer coefficient for the tested PHEx by an order of magnitude. The Aspen Plate code overestimated heat transfer coefficient by about 50%, while Muley-Manglik correlation overestimated it from 1% to 25%, dependent on the value of Reynolds number and hot or cold liquid side.
Experimental and Computational Studies of Turbulent Mass Transfer in a Mixing Channel
DEFF Research Database (Denmark)
Hjertager, Lene Kristin; Hjertager, Bjørn H.; Solberg, Tron
2008-01-01
Experiments are carried out for passive mixing in order to obtain local mean and turbulent velocities and concentrations. The mixing takes place in a square channel with two inlets separated by a block. A combined PIV/PLIF technique is used to obtain instantaneous velocity and concentration field...
Experiments and CFD Modelling of Turbulent Mass Transfer in a Mixing Channel
DEFF Research Database (Denmark)
Hjertager Osenbroch, Lene Kristin; Hjertager, Bjørn H.; Solberg, Tron
2006-01-01
Experiments are carried out for passive mixing in order to obtain local mean and turbulent velocities and concentrations. The mixing takes place in a square channel with two inlets separated by a block. A combined PIV/PLIF technique is used to obtain instantaneous velocity and concentration field...
Analytical solutions of heat transfer for laminar flow in rectangular channels
Rybiński, Witold; Mikielewicz, Jarosław
2014-12-01
The paper presents two analytical solutions namely for Fanning friction factor and for Nusselt number of fully developed laminar fluid flow in straight mini channels with rectangular cross-section. This type of channels is common in mini- and microchannel heat exchangers. Analytical formulae, both for velocity and temperature profiles, were obtained in the explicit form of two terms. The first term is an asymptotic solution of laminar flow between parallel plates. The second one is a rapidly convergent series. This series becomes zero as the cross-section aspect ratio goes to infinity. This clear mathematical form is also inherited by the formulae for friction factor and Nusselt number. As the boundary conditions for velocity and temperature profiles no-slip and peripherally constant temperature with axially constant heat flux were assumed (H1 type). The velocity profile is assumed to be independent of the temperature profile. The assumption of constant temperature at the channel's perimeter is related to the asymptotic case of channel's wall thermal resistance: infinite in the axial direction and zero in the peripheral one. It represents typical conditions in a minichannel heat exchanger made of metal.
Tripathi, Dharmendra; Bég, O Anwar
2012-08-01
Magnetohydrodynamic peristaltic flows arise in controlled magnetic drug targeting, hybrid haemodynamic pumps and biomagnetic phenomena interacting with the human digestive system. Motivated by the objective of improving an understanding of the complex fluid dynamics in such flows, we consider in the present article the transient magneto-fluid flow and heat transfer through a finite length channel by peristaltic pumping. Reynolds number is small enough and the wavelength to diameter ratio is large enough to negate inertial effects. Analytical solutions for temperature field, axial velocity, transverse velocity, pressure gradient, local wall shear stress, volume flowrate and averaged volume flowrate are obtained. The effects of the transverse magnetic field, Grashof number and thermal conductivity on the flow patterns induced by peristaltic waves (sinusoidal propagation along the length of channel) are studied using graphical plots. The present study identifies that greater pressure is required to propel the magneto-fluid by peristaltic pumping in comparison to a non-conducting Newtonian fluid, whereas, a lower pressure is required if heat transfer is effective. The analytical solutions further provide an important benchmark for future numerical simulations.
Deev, V. I.; Kharitonov, V. S.; Churkin, A. N.
2017-02-01
Experimental data on heat transfer to supercritical pressure water presented at ISSCWR-5, 6, and 7 international symposiums—which took place in 2011-2015 in Canada, China, and Finland—and data printed in recent periodical scientific publications were analyzed. Results of experiments with annular channels and three- and four-rod bundles of heating elements positioned in square or triangular grids were examined. Methodology used for round pipes was applied at generalization of experimental data and establishing of correlations suitable for engineering analysis of heat exchange coefficient in conditions of strongly changing water properties in the near-critical pressure region. Empiric formulas describing normal heat transfer to supercritical pressure water mowing in annular channels and rod bundles were obtained. As compared to existing recommendations, suggested correlations are distinguished by specified dependency of heat exchange coefficient on density of heat flux and mass flow velocity of water near pseudo-critical temperature. Differences between computed values of heat exchange coefficient and experimental data usually do not exceed ±25%. Detailed statistical analysis of deviations between computed and experimental results at different states of supercritical pressure water flow was carried out. Peculiarities of deteriorated heat exchange were considered and their existence boundaries were defined. Experimental results obtained for these regimes were generalized using criteria by J.D. Jackson that take the influence of thermal acceleration and Archimedes forces on heat exchange processes into account. Satisfactory agreement between experimental data on heat exchange at flowing of water in annular channels and rod bundles and data for round pipes was shown.
MHD copper-water nanofluid flow and heat transfer through convergent-divergent channel
Energy Technology Data Exchange (ETDEWEB)
Azimi, Mohammadreza; Riazi, Rouzbeh [Faculty of New Sciences and TechnologiesUniversity of Tehran, Tehran (Iran, Islamic Republic of)
2016-10-15
This work is focused on the analytical solution of a nanofluid consisting of pure water with copper nanoparticle steady flow through convergent-divergent channel. The velocity and temperature distributions are determined by a novel method called Reconstruction of variational iteration method (RVIM). The effects of angle of the channel, Reynolds and Hartmann numbers on the nanofluid flow are then investigated. The influences of solid volume fraction and Eckert number upon the temperature distribution are discussed. Based on the achieved results, Nusselt number enhances with increment of solid volume fraction of nanoparticles, Reynolds and Eckert numbers. Also the fourth order Runge-Kutta method, which is one of the most relevant numerical techniques, is used to investigate the validity and accuracy of RVIM and good agreement is observed between the solutions obtained from RVIM and some known numerical results.
Directory of Open Access Journals (Sweden)
A. Daniyel Raj
2015-03-01
Full Text Available During many decades, continuous device performance improvement has been made possible only through device scaling. But presently, due to aggressive scaling at the sub-micron or nanometer region, the conventional planner silicon technology is suffering from the fundamental physical limits. Such imposed limits on further downscaling of silicon planner technology have lead to alternative device technology like Silicon-On-Insulator (SOI technology. Due-to some of its inherent advantages, the Silicon-On-Insulator (SOI technology has reduced the Short-channel-effects (SCEs and thus increased transistor scalability. Till now, intense research interests have been paid in practical fabrication and theoretical modeling of SOI MOSFETs but a little attention has been paid to understand the circuit level performance improvement with nano-scale SOI MOSFETs. The circuit level performance analysis of SOI MOSFET is highly essential to understand the impact of SOI technology on next level VLSI circuit and chip design and for doing so device compact models are high on demand. In such scenario, under present research, a physics based compact device model of SOI MOSFET has been developed. At the first phase of the compact model development, a physics based threshold voltage model has been developed by solving 2-D Poisson’s equation at the channel region and at the second phase, a current-voltage model has been developed with drift-diffusion analysis. Different SCEs, valid at nano-scale, are effectively incorporated in threshold voltage and Current-Voltage model. At the third phase, using the compact model, the Voltage Transfer Characteristics (VTC for a nano-scale SOI CMOS inverter has been derived with graphical analysis. The impacts of different device parameters e.g.; channel length and channel doping concentration on VTC has been investigated through simulation and the results have been analyzed.
de Godoy, C M; Cukierman, S
2001-09-01
Proton conductance (g(H)) in single SS stereoisomers of dioxolane-linked gramicidin A (gA) channels were measured in different phospholipid bilayers at different HCl concentrations. In particular, measurements were obtained in bilayers made of 1,2-diphytanoyl 3-phosphocholine (DiPhPC) or its ethylated derivative 1,2-diphytanoyl 3-ethyl-phosphocholine (et-DiPhPC,). The difference between these phospholipids is that in et-DiPhPC one of the phosphate oxygens is covalently linked to an ethyl group and cannot be protonated. In relatively dilute acid solutions, g(H) in DiPhPC is significantly higher than in et-DiPhPC. At high acid concentrations, g(H) is the same in both diphytanoyl bilayers. Such differences in g(H) can be accounted for by surface charge effects at the membrane/solution interfaces. In the linear portion of the log g(H)-log [H] relationship, g(H) values in diphytanoyl bilayers were significantly larger (approximately 10-fold) than in neutral glyceryl monooleate (GMO) membranes. The slopes of the linear log-log relationships between g(H) and [H] in diphytanoyl and GMO bilayers are essentially the same (approximately 0.76). This slope is significantly lower than the slope of the log-log plot of proton conductivity versus proton concentration in aqueous solutions (approximately 1.00). Because the chemical composition of the membrane-channel/solution interface is strikingly different in GMO and diphytanoyl bilayers, the reduced slope in g(H)-[HCl] relationships may be a characteristic of proton transfer in the water wire inside the SS channel. Values of g(H) in diphytanoyl bilayers were also significantly larger than in membranes made of the more common biological phospholipids 1-palmitoyl 2-oleoyl phosphocholine (POPC) or 1-palmitoyl 2-oleoyl phosphoethanolamine (POPE). These differences, however, cannot be accounted for by different surface charge effects or by different internal dipole potentials. On the other hand, maximum g(H) measured in the SS channel
On computations for thermal radiation in MHD channel flow with heat and mass transfer.
Hayat, T; Awais, M; Alsaedi, A; Safdar, Ambreen
2014-01-01
This study examines the simultaneous effects of heat and mass transfer on the three-dimensional boundary layer flow of viscous fluid between two infinite parallel plates. Magnetohydrodynamic (MHD) and thermal radiation effects are present. The governing problems are first modeled and then solved by homotopy analysis method (HAM). Influence of several embedded parameters on the velocity, concentration and temperature fields are described.
Directory of Open Access Journals (Sweden)
Taymaz Imdat
2015-01-01
Full Text Available The Lattice Boltzmann Method is applied to computationally investigate the laminar flow and heat transfer of an incompressible fluid with constant material properties in a two-dimensional channel with a built-in bluff body. In this study, a triangular prism is taken as the bluff body. Not only the momentum transport, but also the energy transport is modeled by the Lattice Boltzmann Method. A uniform lattice structure with a single time relaxation rule is used. For obtaining a higher flexibility on the computational grid, interpolation methods are applied, where the information is transferred from the lattice structure to the computational grid by Lagrange interpolation. The flow is investigated for different Reynolds numbers, while keeping the Prandtl number at the constant value of 0.7. The results show how the presence of a triangular prism effects the flow and heat transfer patterns for the steady-state and unsteady-periodic flow regimes. As an assessment of the accuracy of the developed Lattice Boltzmann code, the results are compared with those obtained by a commercial Computational Fluid Dynamics code. It is observed that the present Lattice Boltzmann code delivers results that are of similar accuracy to the well-established Computational Fluid Dynamics code, with much smaller computational time for the prediction of the unsteady phenomena.
Indian Academy of Sciences (India)
ANUJ K SHUKLA; ANUPAM DEWAN
2016-06-01
A computational study was carried out for the heat transfer augmentation in a three-dimensional square channel fitted with different types of ribs. The standard k–e model and its two variants (RNG and realizable) were used for turbulence modeling. The predictions were compared with available experimental andcomputational results. Three rib configurations were used in the present study: 90° continuous attached ribs, 60° V-shaped broken attached thick and thin ribs. It was observed that the maximum heat transfer occurs at the normalized rib spacing (p/e) = 10 in the case of 90° attached ribs. The effects of the blockage ratio and rib thickness were investigated for 60° V-shaped broken ribs with Re = 10,000–30,000 and p/e = 10. It was observed that the average Nusselt number decreases with an increase in the Reynolds number for almost all configurations studied in the present study. For the 60° V-shaped broken ribs, increasing the blockage ratio had an adverse effect on the heat transfer. It was also observed that thin ribs perform better than thick ribs.
Energy Technology Data Exchange (ETDEWEB)
Hajipour, Mastaneh; Dehkordi, Asghar Molaei [Department of Chemical and Petroleum Engineering, Sharif University of Technology, P. O. Box 11155-9465, Tehran (Iran, Islamic Republic of)
2012-05-15
In this article, mixed-convective heat transfer of nano-fluids in a vertical channel partially filled with highly porous medium was studied. In the porous region, the Brinkman-Forchheimer extended Darcy model was used to describe the fluid flow pattern. Different viscous dissipation models were also applied to account for viscous heating. At the porous medium-fluid interface, interfacial coupling conditions for the fluid velocity and temperature were used to derive the analytical solution using a two-parameter perturbation method. The model used for the nano-fluids incorporates the effects of Brownian motion and thermophoresis. With constant wall temperature, velocity and temperature profiles and expressions for the Nusselt number values were obtained for fully-developed fluid flow. In addition, a numerical analysis was conducted using finite-difference method to compare the obtained results. Finally, a parametric study was conducted to investigate the influences of various parameters on the fluid flow pattern and heat-transfer performance. The predicted results clearly indicate that the presence of nano-particles in the base fluid enhances the heat-transfer process significantly. (authors)
Heat transfer to MHD oscillatory dusty fluid flow in a channel filled with a porous medium
Indian Academy of Sciences (India)
Om Prakash; O D Makinde; Devendra Kumar; Y K Dwivedi
2015-06-01
In this paper, we examine the combined effects of thermal radiation, buoyancy force and magnetic field on oscillatory flow of a conducting optically thin dusty fluid through a vertical channel filled with a saturated porous medium. The governing partial differential equations are obtained and solved analytically by variable separable method. Numerical results depicting the effects of various embedded parameters like radiation number, Hartmann number and Grashof number on dusty fluid velocity profiles, temperature profiles, Nusselt number and skin friction coefficient are presented graphically and discussed qualitatively.
Institute of Scientific and Technical Information of China (English)
Sohail Nadeem; Safia Akram
2011-01-01
In the present paper we discuss the magnetohydrodynamic (MHD) peristaltic flow of a hyperbolic tangent fluid model in a vertical asymmetric channel under a zero Reynolds number and long wavelength approximation. Exact solution of the temperature equation in the absence of dissipation term has been computed and the analytical expression for stream function and axial pressure gradient are established. The flow is analyzed in a wave frame of reference moving with the velocity of wave. The expression for pressure rise has been computed numerically. The physical features of pertinent parameters are analyzed by plotting graphs and discussed in detail.
Heat Transfer from Water Flowing Through a Chilled-Bed Open Channel
1990-05-01
suggest NUD = ReD Pr (Cf/2) (9) 1.07 + 12.7 (Pr 213 - I) FCf/2 where C/2 = (2.236 In ReD- 4.639)- 2 . Sieder and Tate’s (1936) correlation is NUD = 0.027...York: Pergamon Press. Sieder , E.N. and G.E. Tate (1936) Heat transfer and pressure drop of liquids in tubes. Industrial and Engineering Chemistry, 28
Directory of Open Access Journals (Sweden)
Mikielewicz Dariusz
2016-06-01
Full Text Available In the paper presented are the results of calculations using authors own model to predict heat transfer coefficient during flow boiling of carbon dioxide. The experimental data from various researches were collected. Calculations were conducted for a full range of quality variation and a wide range of mass velocity. The aim of the study was to test the sensitivity of the in-house model. The results show the importance of taking into account the surface tension as the parameter exhibiting its importance in case of the flow in minichannels as well as the influence of reduced pressure. The calculations were accomplished to test the sensitivity of the heat transfer model with respect to selection of the appropriate two-phase flow multiplier, which is one of the elements of the heat transfer model. For that purpose correlations due to Müller-Steinhagen and Heck as well as the one due to Friedel were considered. Obtained results show a good consistency with experimental results, however the selection of two-phase flow multiplier does not significantly influence the consistency of calculations.
Analytical solutions of heat transfer for laminar flow in rectangular channels
Directory of Open Access Journals (Sweden)
Rybiński Witold
2014-12-01
Full Text Available The paper presents two analytical solutions namely for Fanning friction factor and for Nusselt number of fully developed laminar fluid flow in straight mini channels with rectangular cross-section. This type of channels is common in mini- and microchannel heat exchangers. Analytical formulae, both for velocity and temperature profiles, were obtained in the explicit form of two terms. The first term is an asymptotic solution of laminar flow between parallel plates. The second one is a rapidly convergent series. This series becomes zero as the cross-section aspect ratio goes to infinity. This clear mathematical form is also inherited by the formulae for friction factor and Nusselt number. As the boundary conditions for velocity and temperature profiles no-slip and peripherally constant temperature with axially constant heat flux were assumed (H1 type. The velocity profile is assumed to be independent of the temperature profile. The assumption of constant temperature at the channel’s perimeter is related to the asymptotic case of channel’s wall thermal resistance: infinite in the axial direction and zero in the peripheral one. It represents typical conditions in a minichannel heat exchanger made of metal.
Three-body model for the two-neutron decay of $^{16}$Be
Lovell, A E; Thompson, I J
2016-01-01
While diproton decay was first theorized in 1960 and first measured in 2002, it was first observed only in 2012. The measurement of $^{14}$Be in coincidence with two neutrons suggests that $^{16}$Be does decay through the simultaneous emission of two strongly correlated neutrons. In this work, we construct a full three-body model of $^{16}$Be (as $^{14}$Be + n + n) in order to investigate its configuration in the continuum and in particular the structure of its ground state. In order to describe the three-body system, effective n-$^{14}$Be potentials were constructed, constrained by the experimental information on $^{15}$Be. The hyperspherical R-matrix method was used to solve the three-body scattering problem, and the resonance energy of $^{16}$Be was extracted from a phase shift analysis. In order to reproduce the experimental resonance energy of $^{16}$Be within this three-body model, a three-body interaction was needed. For extracting the width of the ground state of $^{16}$Be, we use the full width at ha...
Natural Convection Heat and Mass Transfer from Falling Films in Vertical Channels
Buck, Gregory Allen
1990-01-01
In the design of solar collector/regenerators for use in open cycle absorption refrigeration (OCAR) units, the problem of predicting evaporation rates and solution temperatures is of paramount importance in determining overall cycle performance. This transport of heat and mass is dominated by natural convection with buoyant forces primarily generated as a result of film heating by the solar flux, but aided by the evaporation of water (the lighter species) into the rising moist air stream. In order to better understand the mechanism of these combined buoyant interactions, the governing equations for natural convection flow in a vertical channel bounded by a heated falling film (simulating a glazed collector/regenerator) were solved using several different finite difference techniques. The numerical results were validated against existing experimental and numerical results for simplified boundary conditions. The appropriate nondimensionalization for the falling film boundary condition was established, ostensibly for the first time, and a parametric study for an air-water vapor mixture has been presented. Curve fits to the numerical results were determined for engineering design applications. To further confirm the validity of the numerical solutions, an experimental apparatus was constructed using electric resistance heat to simulate the constant heat flux of the solar source. Water was introduced at the top of this heated vertical surface at various flow rates and under various supplied heat fluxes, and a natural convection channel flow generated between the heated falling film and a parallel, plexiglass surface. Film temperatures and moist air velocity profiles were measured at various streamwise (vertical) locations for comparison with the numerical results. In general, measured film temperatures were 15 to 20 percent lower than the predicted values, but came to within 3 percent of the predictions when experimental uncertainty was incorporated into the numerical
Directory of Open Access Journals (Sweden)
HongWei Ma
2014-10-01
Full Text Available The surface effect is becoming apparently significant as the miniaturization of fluidic devices. In the micro/nanochannel fluidics, the electrode surface effects have the same important influence on the current signals as the channel surface effects. In this paper, when aqueous solution are driven with non-continuous DC electric field force, the characteristics of current signals of the fluid transferring through microfluidic channel are systematically studied. Six modes of current signal are summarized, and some new significant phenomena are found, e.g. there exists a critical voltage at which the steady current value equals to zero; the absolute value of the steady current decreases at first, however, it increases with the external voltage greater than the critical voltage as the electrode area ratio of cathode and anode is 10 and 20; the critical voltage increases with the enhancing of electrode area ratio of cathode and anode and solution pH, while it decreases with the raising of ion concentration. Finally, the microscopic mechanism of the electrode surface charge effects is discussed preliminarily. The rules will be helpful for detecting and manipulating single biomolecules in the micro/nanofluidic chips and biosensors.
Infrared light irradiation diminishes effective charge transfer in slow sodium channel gating system
Plakhova, Vera B.; Bagraev, Nikolai T.; Klyachkin, Leonid E.; Malyarenko, Anna M.; Romanov, Vladimir V.; Krylov, Boris V.
2001-02-01
Effects of infrared light irradiation (IR) on cultured dorsal root ganglia cells were studied by the whole-cell patch-clamp technique. The IR field is demonstrated to diminish the effective charge transfer in the activation system from 6.2 +-0.6 to 4.5 +-0.4 in units of electron charge per e-fold change in membrane potential. The effects was blocked with ouabain. Our data is the first indication that sodium pump might be the molecular sensor of infrared irradiation in animal kingdom.
Energy Technology Data Exchange (ETDEWEB)
Akram, Safia, E-mail: safia_akram@yahoo.com [Department of Basic Sciences, MCS, National University of Sciences and Technology, Rawalpindi 46000 (Pakistan); Nadeem, S.; Hussain, Anwar [Department of Mathematics, Quaid-i-Azam University, Islamabad 45320 (Pakistan)
2014-08-01
In the present analysis we discussed the influence of heat and mass transfer on the peristaltic flow of a Bingham in an inclined magnetic field and channel with different wave forms. The governing two dimensional equations of momentum, heat and mass transfer are simplified under the assumptions of long wavelength and low Reynolds number approximation. The exact solutions of momentum, heat and mass transfer are calculated. Finally, graphical behaviors of various physical parameters are also discussed through the graphical behavior of pressure rise, pressure gradient, temperature concentration and stream functions. - Highlights: • Combine effects of heat and mass transfer on peristaltic flow problem is discussed. • Effects of inclined magnetic field and channel on new fluid model are discussed. • Effects of different wave forms are also discussed in the present flow problem.
Han, J. C.; Chandra, P. R.; Lau, S. C.
1988-01-01
The napthalene sublimation technique was employed to study the detailed mass transfer distributions around the sharp 180 deg turns in a two-pass, square, smooth channel and in an identical channel with two rib-roughened opposite walls. Experiments conducted for Reynolds numbers of 15,000, 30,000, and 60,000 indicate that the Sherwood numbers on the top, outer, and inner walls around the turn in the rib-roughened channel are higher than the corresponding Sherwood numbers around the turn in the smooth channel. Sherwood numbers after the sharp turn are found to be higher than those before the turn for both the smooth and the ribbed channels.
Institute of Scientific and Technical Information of China (English)
K. Ramesh; M. Devakar
2015-01-01
The intention of this investigation is to study the effects of heat transfer and inclined magnetic field on the peristaltic flow of Williamson fluid in an asymmetric channel through porous medium. The governing two-dimensional equations are simplified under the assumption of long wavelength approximation. The simplified equations are solved for the stream function, temperature, and axial pressure gradient by using a regular perturbation method. The expression for pressure rise is computed numerically. The profiles of velocity, pressure gradient, temperature, heat transfer coefficient and stream function are sketched and interpreted for various embedded parameters and also the behavior of stream function for various wave forms is discussed through graphs. It is observed that the peristaltic velocity increases from porous medium to non-porous medium, the magnetic effects have increasing effect on the temperature, and the size of the trapped bolus decreases with the increasing of magnetic effects while the trend is reversed with the increasing of Darcy number. Moreover, limiting solutions of our problem are in close agreement with the corresponding results of the Newtonian fluid model.
Heat transfer characteristics of supercritical water in different shape channels%不同通道内超临界水流动换热特性
Institute of Scientific and Technical Information of China (English)
宋明强; 周涛; 陈柏旭; 黄彦平; 夏榜样
2015-01-01
以具有不同当量直径的矩形、圆形、三角形、环形等管道为研究对象，利用ANSYS CFX分别计算在定质量流量和定流体速度条件下，超临界水在不同通道内的流动换热特性。发现在定质量流量条件下，圆形通道换热特性最优，且小当量直径促进流体换热；在定入口流速条件下，环形通道换热特性最优，小当量直径管道促进亚临界流体换热，大当量直径管道促进超临界流体换热。%Background: Supercritical water reactor (SCWR) is the only one that uses light water as a coolant among all fourth generation nuclear reactors.Purpose: This study aims to investigate the characteristics of supercritical water heat transfer in various pipelines.Methods: The models of rectangular, triangular, circle and annular channels are employed, with equivalent diameters of 2 mm, 3 mm and 5 mm for each of them. Based on these models, heat transfer charactersistics of supercritical water in different shape channels at certain mass flow and fluid velocity were calculatedvia ANSYS CFX.Results: There are two situations for the same equivalent diameter: in the condition of constant mass flow rate, the heat transfer property of circle channel outperforms other three types of channels, and the smaller equivalent diameter channels, the better of the heat transfer. In constant fluid velocity condition, the heat transfer property of annular channel presents best performance over others, and the smaller equivalent diameter channels, the better of the heat transfer in subcritical condition whilst the bigger equivalent diameter channels, the better of the heat transfer in supercritical condition.Conclusion: Compared with the experimental results, the model can provide a certain reference for the design of supercritical water reactor.
Khanwale, Makrand A.; Khadamkar, Hrushikesh P.; Mathpati, Channamallikarjun S.
2015-11-01
Physics of development of flow structures around the drop rising with solute transfer is highly influenced by the interfacial behaviour and is remarkably different than a particle rising under the same conditions. We report on the use of simultaneous particle image velocimetry-planar laser induced fluorescence technique to measure scalar and velocity fields around a drop rising in a quiescent liquid channel. The selected continuous phase is glycerol, and the drop consists of a mixture of toluene, acetone, and a dye rhodamine-6G, with acetone working as a interfacial tension depressant. The drop lies in the spherical region with Eötvös number, Eo = 1.95, Morton number, M = 78.20 and the particle Reynolds number being, Rep = 0.053. With Rep approaching that of creeping flow, we analyse the effect of interfacial instabilities solely, contrary to other investigations [M. Wegener et al., "Impact of Marangoni instabilities on the fluid dynamic behaviour of organic droplets," Int. J. Heat Mass Transfer 52, 2543-2551 (2009); S. Burghoff and E. Y. Kenig, "A CFD model for mass transfer and interfacial phenomena on single droplets," AIChE J. 52, 4071-4078 (2006); J. Wang et al., "Numerical simulation of the Marangoni effect on transient mass transfer from single moving deformable drops," AIChE J. 57, 2670-2683 (2011); R. F. Engberg, M. Wegener, and E. Y. Kenig, "The impact of Marangoni convection on fluid dynamics and mass transfer at deformable single rising droplets—A numerical study," Chem. Eng. Sci. 116, 208-222 (2014)] which account for turbulence as well as interfacial instabilities with Rep in the turbulent range. The velocity and concentration fields obtained are subjected to scale-wise energy decomposition using continuous wavelet transform. Scale-wise probability distribution functions of wavelet coefficients are calculated to check intermittent non-Gaussian behaviour for simultaneous velocity and scalar statistics. Multi-fractal singularity spectra for scalar
Wiles, E.; Green, A. N.; Watkeys, M. K.; Jokat, W.
2017-09-01
Sediment delivery to the abyssal regions of the oceans is an integral process in the source to sink cycle of material derived from adjacent continents and islands. The Zambezi River, the largest in southern Africa, delivers vast amounts of material to the inner continental shelf of central Mozambique. The aim of this contribution is to better constrain sediment transport pathways to the abyssal plains using the latest, regional, high-resolution multibeam bathymetry data available, taking into account the effects of bottom water circulation, antecedent basin morphology and sea-level change. Results show that sediment transport and delivery to the abyssal plains is partitioned into three distinct domains; southern, central and northern. Sediment partitioning is primarily controlled by changes in continental shelf and shelf-break morphology under the influence of a clockwise rotating shelf circulation system. However, changes in sea-level have an overarching control on sediment delivery to particular domains. During highstand conditions, such as today, limited sediment delivery to the submarine Zambezi Valley and Channel is proposed, with increased sediment delivery to the deepwater basin being envisaged during regression and lowstand conditions. However, there is a pronounced along-strike variation in sediment transport during the sea-level cycle due to changes in the width, depth and orientation of the shelf. This combination of features outlines a sequence stratigraphic concept not generally considered in the strike-aligned shelf-slope-abyssal continuum.
Wu, Wenjia; Li, Yifan; Chen, Pingping; Liu, Jindun; Wang, Jingtao; Zhang, Haoqin
2016-01-13
Herein, nanocomposite membranes are fabricated based on functionalized graphene oxides (FGOs) and sulfonated poly(ether ether ketone) (SPEEK), followed by being impregnated with imidazole-type ionic liquid (IL). The functional groups (acidic group or basic group) on FGOs generate strong interfacial interactions with SPEEK chains and then adjust their motion and stacking. As a result, the nanocomposite membranes possess tunable interfacial domains as determined by its free volume characteristic, which provides regulated location for IL storage. The stored ILs act as hopping sites for water-free proton conduction along the FGO-constructed interfacial channels. The microstructure at SPEEK-FGO interface governs the IL uptake and distribution in nanocomposite membrane. Different from GO and vinyl imidazole functionalized GO (VGO), the presence of acidic (-SO3H) groups confers the p-styrenesulfonic acid functionalized GO (SGO) incorporated nanocomposite membrane loose interface and strong electrostatic attraction with imidazole-type IL, imparting an enhanced IL uptake and anhydrous proton conductivity. Nanocomposite membrane containing 7.5% SGO attains the maximum IL uptake of 73.7% and hence the anhydrous conductivity of 21.9 mS cm(-1) at 150 °C, more than 30 times that of SPEEK control membrane (0.69 mS cm(-1)). In addition, SGOs generate electrostatic attractions to the ILs confined within SGO-SPEEK interface, affording the nanocomposite membrane enhanced IL retention ability.
Directory of Open Access Journals (Sweden)
M.A. Ahmed
2015-09-01
Full Text Available In this paper, convective heat transfer of SiO2–water nanofluid flow in channels with different shapes is numerically and experimentally studied over Reynolds number ranges of 400–4000. Three different channels such as trapezoidal, sinusoidal and straight were fabricated and tested. The SiO2–water nanofluid with different volume fractions of 0%, 0.5% and 1.0% were prepared and examined. All physical properties of nanofluid which are required to evaluate the flow and thermal characteristics have been measured. In the numerical aspect of the current work, the governing equations are discretized by using the collocated finite volume method and solved iteratively by using the SIMPLE algorithm. In addition, the low Reynolds number k–ε model of Launder and Sharma is employed to compute the turbulent non-isothermal flow in the present study. The results showed that the average Nusselt number and the heat transfer enhancement increase as the nanoparticles volume fraction increases, however, at the expense of increasing pressure drop. Furthermore, the trapezoidal-corrugated channel has the highest heat transfer enhancement followed by the sinusoidal-corrugated channel and straight channel. The numerical results are compared with the corresponding experimental data, and the results are in a good agreement.
小通道内的冷凝换热模型分析%Analysis of Condensation Heat Transfer Model in Small Channels
Institute of Scientific and Technical Information of China (English)
胡灿; 李敏霞; 马一太; 付兴
2012-01-01
目前国内外对于大通道内的冷凝换热研究较多,而对小通道内的冷凝换热研究较少,小通道内重力、切应力、表面张力的相互作用与大通道不同,导致小通道内的冷凝换热机理不同于大通道,因此大通道内的冷凝换热模型不能很好地预测小通道内的冷凝换热,而小通道内冷凝换热的研究对设计和优化紧凑型换热器具有重要意义.总结9种小通道内的冷凝换热预测模型,并根据1 1个独立研究机构的测试结果,收集6种工质(R134a,R32,R22,R123,R410A,R1234yf)的1183个小通道内的冷凝换热试验数据点.比较各模型的预测结果和数据点发现,各预测模型并不是适用于小通道内所有工质和工况的预测,应根据工质和工况选择合适的模型.GARIMELLA的预测模型对R134a、R32、R22、R1234yf的数据点的预测误差很小,而KOYAMA的预测模型适用范围比较广,大部分工况下误差也是可接受的.%There are many researches about condensation heat transfer in macro-channels, but the studies of condensation heat transfer in small channels is limited available,and the interaction of gravity,shear stress and surface tension in small channels is different with macro-channels, result that the mechanism of condensation heat transfer in small channels is different with macro-channels, therefore condensation heat transfer prediction model of macro-channels can not predict heat transfer coefficients of small channels very well. While, the research of condensation heat transfer in small channels is significance for designing and optimizing compact heat exchanger. Nine condensation heat transfer prediction models of small channels are addressed, and a database is setup by collecting 1 183 condensation heat transfer data points of small channels which involves six types of refrigerants(R134a, R32, R22, R123, R410A, R1234yf )from 11 independent research groups. On basis of the comparison between the prediction
Bielert, E; ten Kate, H
2012-01-01
For a future luminosity upgrade of CERN’s Large Hadron Collider, a drastically improved heat removal in the inner triplet quadrupole magnets is required. One of the necessary improvements involves the cable insulation. A porous all-polyimide insulation scheme has been proposed recently. Essentially the insulation features a network of micro channels filled with superfluid helium that significantly increases the heat transfer through the insulation layer. A three dimensional Finite Element model required to simulate and study the enhanced heat transfer through the micro channels is presented here. The thermal coupling between heated cable and helium as well as the heat flux through the micro-channels are investigated. The model is validated by comparison of results with published measured data. Finally a sensitivity analysis is performed concerning the stability of the cables in magnet windings.
Bourgin, D.; Courtin, S.; Haas, F.; Stefanini, A. M.; Montagnoli, G.; Goasduff, A.; Montanari, D.; Corradi, L.; Fioretto, E.; Huiming, J.; Scarlassara, F.; Rowley, N.; Szilner, S.; Mijatović, T.
2014-10-01
Background: The nuclear structure of colliding nuclei is known to influence the fusion process. Couplings of the relative motion to nuclear shape deformations and vibrations lead to an enhancement of the sub-barrier fusion cross section in comparison with the predictions of one-dimensional barrier penetration models. This enhancement is explained by coupled-channels calculations including these couplings. The sub-barrier fusion cross section is also affected by nucleon transfer channels between the colliding nuclei. Purpose: The aim of the present experiment is to investigate the influence of the projectile and target nuclear structures on the fusion cross sections in the Ca40+Ni58 and Ca40+Ni64 systems. Methods: The experimental and theoretical fusion excitation functions as well as the barrier distributions were compared for these two systems. Coupled-channels calculations were performed using the ccfull code. Results: Good agreement was found between the measured and calculated fusion cross sections for the Ca40+Ni58 system. The situation is different for the Ca40+Ni64 system where the coupled-channels calculations with no nucleon transfer clearly underestimate the fusion cross sections below the Coulomb barrier. The fusion excitation function was, however, well reproduced at low and high energies by including the coupling to the neutron pair-transfer channel in the calculations. Conclusions: The nuclear structure of the colliding nuclei influences the fusion cross sections below the Coulomb barrier for both Ca40+Ni58,64 systems. Moreover, we highlighted the effect of the neutron pair-transfer channel on the fusion cross sections in Ca40+Ni64.
Directory of Open Access Journals (Sweden)
Sidra Aman
2017-01-01
Full Text Available Applications of carbon nanotubes, single walls carbon nanotubes (SWCNTs and multiple walls carbon nanotubes (MWCNTs in thermal engineering have recently attracted significant attention. However, most of the studies on CNTs are either experimental or numerical and the lack of analytical studies limits further developments in CNTs research particularly in channel flows. In this work, an analytical investigation is performed on heat transfer analysis of SWCNTs and MWCNTs for mixed convection Poiseuille flow of a Casson fluid along a vertical channel. These CNTs are suspended in three different types of base fluids (Water, Kerosene and engine Oil. Xue [Phys. B Condens. Matter 368, 302–307 (2005] model has been used for effective thermal conductivity of CNTs. A uniform magnetic field is applied in a transverse direction to the flow as magnetic field induces enhancement in the thermal conductivity of nanofluid. The problem is modelled by using the constitutive equations of Casson fluid in order to characterize the non-Newtonian fluid behavior. Using appropriate non-dimensional variables, the governing equations are transformed into the non-dimensional form, and the perturbation method is utilized to solve the governing equations with some physical conditions. Velocity and temperature solutions are obtained and discussed graphically. Expressions for skin friction and Nusselt number are also evaluated in tabular form. Effects of different parameters such as Casson parameter, radiation parameter and volume fraction are observed on the velocity and temperature profiles. It is found that velocity is reduced under influence of the exterior magnetic field. The temperature of single wall CNTs is found greater than MWCNTs for all the three base fluids. Increase in volume fraction leads to a decrease in velocity of the fluid as the nanofluid become more viscous by adding CNTs.
Aman, Sidra; Khan, Ilyas; Ismail, Zulkhibri; Salleh, Mohd Zuki; Alshomrani, Ali Saleh; Alghamdi, Metib Said
2017-01-01
Applications of carbon nanotubes, single walls carbon nanotubes (SWCNTs) and multiple walls carbon nanotubes (MWCNTs) in thermal engineering have recently attracted significant attention. However, most of the studies on CNTs are either experimental or numerical and the lack of analytical studies limits further developments in CNTs research particularly in channel flows. In this work, an analytical investigation is performed on heat transfer analysis of SWCNTs and MWCNTs for mixed convection Poiseuille flow of a Casson fluid along a vertical channel. These CNTs are suspended in three different types of base fluids (Water, Kerosene and engine Oil). Xue [Phys. B Condens. Matter 368, 302-307 (2005)] model has been used for effective thermal conductivity of CNTs. A uniform magnetic field is applied in a transverse direction to the flow as magnetic field induces enhancement in the thermal conductivity of nanofluid. The problem is modelled by using the constitutive equations of Casson fluid in order to characterize the non-Newtonian fluid behavior. Using appropriate non-dimensional variables, the governing equations are transformed into the non-dimensional form, and the perturbation method is utilized to solve the governing equations with some physical conditions. Velocity and temperature solutions are obtained and discussed graphically. Expressions for skin friction and Nusselt number are also evaluated in tabular form. Effects of different parameters such as Casson parameter, radiation parameter and volume fraction are observed on the velocity and temperature profiles. It is found that velocity is reduced under influence of the exterior magnetic field. The temperature of single wall CNTs is found greater than MWCNTs for all the three base fluids. Increase in volume fraction leads to a decrease in velocity of the fluid as the nanofluid become more viscous by adding CNTs.
E1 strength function for two-neutron halo nuclei in an analytical three-body approach
Energy Technology Data Exchange (ETDEWEB)
Pushkin, A. [SENTEF, Department of Physics, University of Bergen (Norway); Jonson, B.; Zhukov, M.V. [Department of Physics, Chalmers University of Technology and University of Gothenburg, S - 412 96 Goeteborg (Sweden)
1996-08-01
An analytical expression for the E1 strength function for two-neutron halo nuclei is derived in a three-body model. Yukawa type wavefunctions for the ground state and three-body plane waves for the final state were used. The expression reproduces the shape and the position of the maximum of the experimental strength function for {sup 11}Li well. It is shown that the exact expression can be approximated over a large energy range with a simple function by introducing an effective two-neutron separation energy. This provides a theoretical approach for quick estimates of the E1 strength function for two-body halo nuclei. (author). Letter-to-the-editor.
Lin, Meng-Kai; Nakayama, Yasuo; Zhuang, Ying-Jie; Su, Kai-Jun; Wang, Chin-Yung; Pi, Tun-Wen; Metz, Sebastian; Papadopoulos, Theodoros A.; Chiang, T.-C.; Ishii, Hisao; Tang, S.-J.
2017-02-01
Organic molecules with a permanent electric dipole moment have been widely used as a template for further growth of molecular layers in device structures. Key properties of the resulting organic films such as energy level alignment (ELA), work function, and injection/collection barrier are linked to the magnitude and direction of the dipole moment at the interface. Using angle-resolved photoemission spectroscopy (ARPES), we have systematically investigated the coverage-dependent work function and spectral line shapes of occupied molecular energy states (MESs) of chloroaluminium-phthalocyanine (ClAlPc) grown on Ag(111). We demonstrate that the dipole orientation of the first ClAlPc layer can be controlled by adjusting the deposition rate and postannealing conditions, and we find that the ELA at the interface differs by ˜0.4 eV between the Cl up and down configurations of the adsorbed ClAlPc molecules. These observations are rationalized by density functional theory (DFT) calculations based on a realistic model of the ClAlPc/Ag(111) interface, which reveal that the different orientations of the ClAlPc dipole layer lead to different charge-transfer channels between the adsorbed ClAlPc and Ag(111) substrate. Our findings provide a useful framework toward method development for ELA tuning.
Nazari, Saman; Toghraie, Davood
2017-03-01
This study has compared the convection heat transfer of Water-based fluid flow with that of Water-Copper oxide (CuO) nanofluid in a sinusoidal channel with a porous medium. The heat flux in the lower and upper walls has been assumed constant, and the flow has been assumed to be two-dimensional, steady, laminar, and incompressible. The governing equations include equations of continuity, momentum, and energy. The assumption of thermal equilibrium has been considered between the porous medium and the fluid. The effects of the parameters, Reynolds number and Darcy number on the thermal performance of the channel, have been investigated. The results of this study show that the presence of a porous medium in a channel, as well as adding nanoparticles to the base fluid, increases the Nusselt number and the convection heat transfer coefficient. Also the results show that As the Reynolds number increases, the temperature gradient increases. In addition, changes in this parameter are greater in the throat of the flow than in convex regions due to changes in the channel geometry. In addition, porous regions reduce the temperature difference, which in turn increases the convective heat transfer coefficient.
Shit, G. C.; Mondal, A.; Sinha, A.; Kundu, P. K.
2016-11-01
A mathematical model has been developed for studying the electro-osmotic flow and heat transfer of bio-fluids in a micro-channel in the presence of Joule heating effects. The flow of bio-fluid is governed by the non-Newtonian power-law fluid model. The effects of thermal radiation and velocity slip condition have been examined in the case of hydrophobic channel. The Poisson-Boltzmann equation governing the electrical double layer field and a body force generated by the applied electric potential field are taken into consideration. The results presented here pertain to the case where the height of the channel is much greater than the thickness of electrical double layer comprising the Stern and diffuse layers. The expressions for flow characteristics such as velocity, temperature, shear stress and Nusselt number have been derived analytically under the purview of the present model. The results estimated on the basis of the data available in the existing scientific literatures are presented graphically. The effects of thermal radiation have an important bearing on the therapeutic procedure of hyperthermia, particularly in understanding the heat transfer in micro-channel in the presence of electric potential. The dimensionless Joule heating parameter has a reducing impact on Nusselt number for both pseudo-plastic and dilatant fluids, nevertheless its impact on Nusselt number is more pronounced for dilatant fluid. Furthermore, the effect of viscous dissipation has a significant role in controlling heat transfer and should not be neglected.
Han, J. C.; Chandra, P. R.
1987-01-01
The heat transfer characteristics of turbulent air flow in a multipass channel were studied via the naphthalene sublimation technique. The naphthalene-coated test section, consisting of two straight, square channels joined by a 180 deg turn, resembled the internal cooling passages of gas turbine airfoils. The top and bottom surfaces of the test channel were roughened by rib turbulators. The rib height-to-hydraulic diameter ratio (e/D) were 0.063 and 0.094, and the rib pitch-to-height ratio (P/e) were 10 and 20. The local heat/mass transfer coefficients on the roughened top wall and on the smooth divider and side walls of the test channel were determined for three Reynolds numbers of 15, 30, and 60, thousand, and for three angles of attack (alpha) of 90, 60, and 45 deg. Results showed that the local Sherwood numbers on the ribbed walls were 1.5 to 6.5 times those for a fully developed flow in a smooth square duct. The average ribbed-wall Sherwood numbers were 2.5 to 3.5 times higher than the fully developed values, depending on the rib angle of attack and the Reynolds number. The results also indicated that, before the turn, the heat/mass transfer coefficients in the cases of alpha = 60 and 45 deg were higher than those in the case of alpha=90 deg. However, after the turn, the heat/mass transfer coefficients in the oblique-rib cases were lower than those in the transverse rib case. Correlations for the average Sherwood number ratios for individual channel surfaces and for the overall Sherwood number ratios are reported. Correlations for the fully developed friction factors and for the loss coefficients are also provided.
Directory of Open Access Journals (Sweden)
Anwar Ilmar Ramadhan
2015-03-01
Full Text Available Safety is a major concern in the design, operation and development of a nuclear reactor. One aspect of nuclear reactor safety factor is thermal-hydraulics aspect. In a PWR-type nuclear power plant has been used lighter fluid coolant is water or H2O. In this research, using nanofluid Al2O3-Water with volume fraction of (1%, (2% and also (3%, used as a cooling fluid in a nuclear reactor core with sub channel PWR fuel element rectangular arrangement. This research was carried out modeling of fuel elements are arranged rectangular, then performed numerical simulations using Computational Fluid Dynamics (CFD code. In order to obtain the characteristic pattern of flow velocity of each fluid, the fluid temperature distribution along the cylinder wall temperature distribution of the fuel element. Then analyzed the heat transfer in a nuclear reactor core with sub channel PWR fuel element rectangular arrangement, including heat transfer coefficient, Nusselt number (Nu, as well as heat transfer correlations. Heat transfer correlation for nanofluid Al2O3-Water (1%, (2% and also (3% proved to core of PWR nuclear reactor fuel element sub channel rectangular arrangement with the Reynolds number (Re is stretched, namely: 404 096
African Journals Online (AJOL)
“Chemistry Department, Kenyatta University, P. 0. Box 43844 ... harvester (X) [L 2] in a manner consistent with the following Forster equation for long range energy transfer [3-7]. .... sensitive foods, chemical reactors and essences. Recently we ...
Energy Technology Data Exchange (ETDEWEB)
Saboya, Sergio Mourao [Centro Tecnico Aeroespacial, Sao Jose dos Campos, SP (Brazil). Inst. Tecnologico de Aeronautica; Saboya, Francisco Eduardo Mourao [Universidade Federal Fluminense, Niteroi, RJ (Brazil)]. E-mails: saboya@mec.ita.cta.br; fsaboya@mec.uff.br
2000-07-01
Finned absorber solar collectors are devices in which plates (fins) are fixed perpendicularly to the absorber plate. The purpose of these fins is to cause the so called 'cavity effect', lowering the collector losses. This paper studies the heat transfer that occurs in the collector channel. This analysis is done using the efficiency of the collector, which is calculated solving the system of equations that govern the collector thermal behavior, and the computation of the convection heat transfer between the fluid flowing in the channel and the absorber plate. This analysis allows the calculation of design parameters such as mass flow rate and exit bulk temperature of the fluid. (author)
Hot-electron real-space transfer and longitudinal transport in dual AlGaN/AlN/{AlGaN/GaN} channels
Šermukšnis, E.; Liberis, J.; Matulionis, A.; Avrutin, V.; Ferreyra, R.; Özgür, Ü.; Morkoç, H.
2015-03-01
Real-space transfer of hot electrons is studied in dual-channel GaN-based heterostructure operated at or near plasmon-optical phonon resonance in order to attain a high electron drift velocity at high current densities. For this study, pulsed electric field is applied in the channel plane of a nominally undoped Al0.3Ga0.7N/AlN/{Al0.15Ga0.85N/GaN} structure with a composite channel of Al0.15Ga0.85N/GaN, where the electrons with a sheet density of 1.4 × 1013 cm-2, estimated from the Hall effect measurements, are confined. The equilibrium electrons are situated predominantly in the Al0.15Ga0.85N layer as confirmed by capacitance-voltage experiment and Schrödinger-Poisson modelling. The main peak of the electron density per unit volume decreases as more electrons occupy the GaN layer at high electric fields. The associated decrease in the plasma frequency induces the plasmon-assisted decay of non-equilibrium optical phonons (hot phonons) confirmed by the decrease in the measured hot-phonon lifetime from 0.95 ps at low electric fields down below 200 fs at fields of E \\gt 4 kV cm-1 as the plasmon-optical phonon resonance is approached. The onset of real-space transfer is resolved from microwave noise measurements: this source of noise dominates for E \\gt 8 kV cm-1. In this range of fields, the longitudinal current exceeds the values measured for a mono channel reference Al0.3Ga0.7N/AlN/GaN structure. The results are explained in terms of the ultrafast decay of hot phonons and reduced alloy scattering caused by the real-space transfer in the composite channel.
Murat Kuscu; Alper Kiraz; Akan, Ozgur B.
2015-01-01
Fluorescent Molecules as Transceiver Nanoantennas: The First Practical and High-Rate Information Transfer over a Nanoscale Communication Channel based on FRET Murat Kuscu1, Alper Kiraz2 & Ozgur B. Akan1 1Next-generation andWireless Communications Laboratory (NWCL), Department of Electrical and Electronics Engineering, Koc University, Istanbul, 34450, Turkey, 2Optofluidics and Nano-Optics Research Laboratory, Department of Physics, Koc University, Istanbul, 34450, Turke...
Directory of Open Access Journals (Sweden)
Shinji Kuriyama
2015-08-01
Full Text Available In the very high temperature reactor (VHTR, which is a next generation nuclear reactor system, ceramics are used as a fuel coating material and graphite is used as a core structural material. Even if a depressurization accident occurs and the reactor power goes up instantly, the temperature of the core will change only slowly. This is because the thermal capacity of the core is so high. Therefore, the VHTR system can passively remove the decay heat of the core by natural convection and radiation from the surface of the reactor pressure vessel. The objectives of this study are to investigate the heat transfer characteristics of natural convection of a one-side heated vertical channel with inserted porous materials of high porosity and also to develop the passive cooling system for the VHTR. An experiment was carried out using a one-side heated vertical rectangular channel. To obtain the heat transfer and fluid flow characteristics of the vertical channel with inserted porous material, we have also carried out a numerical analysis using a commercial Computational Fluid Dynamics (CFD code. This paper describes the thermal performances of the one-side heated vertical rectangular channel with an inserted copper wire of high porosity.
Energy Technology Data Exchange (ETDEWEB)
Vitaly Osmachkin [Russian Research Center ' Kurchatov Institute' 1, Kurchatov sq, Moscow 123182 (Russian Federation)
2005-07-01
Full text of publication follows: The influence of power transient, changes of flow rate, inlet temperatures or pressure in cores of nuclear reactors on heat transfer and burnout conditions in channels depend on rate of such violations. Non-uniform distribution of the heat flux is also important factor for heat transfer and development of crisis phenomenon. Such effects may be significant for NPPs safety. But they have not yet generally accepted interpretation. Steady state approach is often recommended for use in calculations. In the paper a review of experimental observed so-called non-equilibrium effects is presented. The effects of space and time factors are displaying due delay in reformation turbulence intensity, velocity, temperatures or void fraction profiles, water film flow on the surface of heated channels. For estimation of such effect different methods are used. Modern computer codes based on two or three fluids approaches are considered as most effective. But simple and clear correlations may light up the mechanics of effects on heat transfer and improve general understanding of scale and significance of the transient events. In the paper the simplified methods for assessment the influence of lags in the development of distributions of parameters of flow, the relaxation of temporal or space violations are considered. They are compared with more sophisticated approaches. Velocities of disturbance fronts moving along the channels are discussed also. (author)
Mabood, Fazle; Khan, Waqar A; Ismail, Ahmad Izani Md
2013-01-01
In this article, an approximate analytical solution of flow and heat transfer for a viscoelastic fluid in an axisymmetric channel with porous wall is presented. The solution is obtained through the use of a powerful method known as Optimal Homotopy Asymptotic Method (OHAM). We obtained the approximate analytical solution for dimensionless velocity and temperature for various parameters. The influence and effect of different parameters on dimensionless velocity, temperature, friction factor, and rate of heat transfer are presented graphically. We also compared our solution with those obtained by other methods and it is found that OHAM solution is better than the other methods considered. This shows that OHAM is reliable for use to solve strongly nonlinear problems in heat transfer phenomena.
Directory of Open Access Journals (Sweden)
Khilap Singh
2016-01-01
Full Text Available The effects of chemical reaction on heat and mass transfer flow of a micropolar fluid in a permeable channel with heat generation and thermal radiation is studied. The Rosseland approximations are used to describe the radiative heat flux in the energy equation. The model contains nonlinear coupled partial differential equations which have been transformed into ordinary differential equation by using the similarity variables. The relevant nonlinear equations have been solved by Runge-Kutta-Fehlberg fourth fifth-order method with shooting technique. The physical significance of interesting parameters on the flow and heat transfer characteristics as well as the local skin friction coefficient, wall couple stress, and the heat transfer rate are thoroughly examined.
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.
Protocol channels as a new design alternative of covert channels
Wendzel, Steffen
2008-01-01
Covert channel techniques are used by attackers to transfer hidden data. There are two main categories of covert channels: timing channels and storage channels. This paper introduces a third category called protocol channels. A protocol channel switches one of at least two protocols to send a bit combination to a destination while sent packets include no hidden information themselves.
Linga Raju, T.; Neela Rao, B.
2016-08-01
The paper aims to analyze the heat transfer aspects of a two-layered fluid flow in a horizontal channel under the action of an applied magnetic and electric fields, when the whole system is rotated about an axis perpendicular to the flow. The flow is driven by a common constant pressure gradient in the channel bounded by two parallel porous insulating plates, one being stationary and the other one oscillatory. The fluids in the two regions are considered electrically conducting, and are assumed to be incompressible with variable properties, namely, different densities, viscosities, thermal and electrical conductivities. The transport properties of the two fluids are taken to be constant and the bounding plates are maintained at constant and equal temperature. The governing partial differential equations are then reduced to the ordinary linear differential equations by using a two-term series. The temperature distributions in both fluid regions of the channel are derived analytically. The results are presented graphically to discuss the effect on the heat transfer characteristics and their dependence on the governing parameters, i.e., the Hartmann number, Taylor number, porous parameter, and ratios of the viscosities, heights, electrical and thermal conductivities. It is observed that, as the Coriolis forces become stronger, i.e., as the Taylor number increases, the temperature decreases in the two fluid regions. It is also seen that an increase in porous parameter diminishes the temperature distribution in both the regions.
Nucleate boiling heat transfer in vertical rectangular mini-channel%竖直矩形细通道内的水沸腾换热特性
Institute of Scientific and Technical Information of China (English)
常威; 张树生; 程林; 郭雷
2012-01-01
以宽度为1.0mm和0.1mm的竖直矩形细通道内的沸腾换热特性为研究对象,运用数值模拟的方法探索气泡生成、长大和脱离的过程,通过几何重构和界面追踪的方法获取相界面移动和变化对系统内压差以及平均表面换热系数的影响.计算中考虑重力、表面张力和壁面黏性的作用.研究结果表明:通道宽度的不同对气泡生长方式和气泡形态产生很大影响,且核态沸腾换热系数随着细通道宽度的减小而增大;表面张力在细通道沸腾换热过程中所起的作用明显增大,证明细通道有强化换热的作用;由于数值计算中进行了理想化假设,导致数值模拟的沸腾传热系数比现有细通道沸腾传热实验传热系数普遍偏高.%In order to study the characteristics of boiling two-phase heat transfer in vertical rectangular mini-channels with width of 1.0 mm and 0.1 mm, a numerical simulation was conducted to explore the course of bubble generation, growing up and departure from the wall. Gravity, surface tension and the wall adhesion were taken into consideration, the effect caused by the interface movement on the system pressure difference and the average surface heat transfer coefficient was also discussed by using the geometry reconstruction and interface tracking method. The results show that the variation of channel width has great influence on the course of bubble growth and motion. As the channel size decreases, the nucleate boiling heat transfer coefficient increases obviously, proving that the mini-channel can enhance the heat transfer. However, due to some idealized assumptions, the boiling heat transfer coefficient of the numerical simulation is higher than the existing experimental value.
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Min Du
2012-11-01
Full Text Available Intra-Body Communication (IBC, which modulates ionic currents over the human body as the communication medium, offers a low power and reliable signal transmission method for information exchange across the body. This paper first briefly reviews the quasi-static electromagnetic (EM field modeling for a galvanic-type IBC human limb operating below 1 MHz and obtains the corresponding transfer function with correction factor using minimum mean square error (MMSE technique. Then, the IBC channel characteristics are studied through the comparison between theoretical calculations via this transfer function and experimental measurements in both frequency domain and time domain. High pass characteristics are obtained in the channel gain analysis versus different transmission distances. In addition, harmonic distortions are analyzed in both baseband and passband transmissions for square input waves. The experimental results are consistent with the calculation results from the transfer function with correction factor. Furthermore, we also explore both theoretical and simulation results for the bit-error-rate (BER performance of several common modulation schemes in the IBC system with a carrier frequency of 500 kHz. It is found that the theoretical results are in good agreement with the simulation results.
Chen, Xi Mei; Mak, Peng Un; Pun, Sio Hang; Gao, Yue Ming; Lam, Chan-Tong; Vai, Mang I.; Du, Min
2012-01-01
Intra-Body Communication (IBC), which modulates ionic currents over the human body as the communication medium, offers a low power and reliable signal transmission method for information exchange across the body. This paper first briefly reviews the quasi-static electromagnetic (EM) field modeling for a galvanic-type IBC human limb operating below 1 MHz and obtains the corresponding transfer function with correction factor using minimum mean square error (MMSE) technique. Then, the IBC channel characteristics are studied through the comparison between theoretical calculations via this transfer function and experimental measurements in both frequency domain and time domain. High pass characteristics are obtained in the channel gain analysis versus different transmission distances. In addition, harmonic distortions are analyzed in both baseband and passband transmissions for square input waves. The experimental results are consistent with the calculation results from the transfer function with correction factor. Furthermore, we also explore both theoretical and simulation results for the bit-error-rate (BER) performance of several common modulation schemes in the IBC system with a carrier frequency of 500 kHz. It is found that the theoretical results are in good agreement with the simulation results. PMID:23443387
Komov, A. T.; Varava, A. N.; Dedov, A. V.; Zakharenkov, A. V.; Boltenko, É. A.
2017-01-01
The present work is a continuation of experimental investigations conducted at the Moscow Power Engineering Institute (MPEI) on heat-transfer intensification. Brief descriptions of the working section and structure of intensifiers are given and their basic geometric parameters are enumerated. New systematized experimental data on the coefficients of hydraulic resistance and heat transfer in the regime of single-phase convection are given in an extended range of regime parameters and geometric characteristics of the intensifiers. Considerable increase in the heat-transfer coefficient as a function of the geometric characteristics of the intensifier has been established experimentally. The values of the relative fin height, at which these are the maxima of heat transfer and hydraulic resistance, have been established. Calculated dependences for the coefficient of hydraulic resistance and heat transfer have been obtained.
Komov, A. T.; Varava, A. V.; Zakharenkov, A. V.; Dedov, A. V.; Boltenko, E. A.; Agishev, B. Y.
2016-10-01
The work is a continuation of the experimental studies on the enhancement of heat transfer in the fuel assembly on the experimental stand in National Research University "Moscow Power Engineering Institute". The description of the experimental setup, construction and main geometrical parameters of intensifier are presented. The new experimental data on the pressure loss and heat transfer coefficient using an edge enhancer - twisted wire single-phase convection mode are presented. In the research, the range mode parameters and geometric characteristics of the intensifier were extended. The relation of the coefficients of hydraulic resistance and the Nusselt number of steps twist twisted wire was found, the effect of the ribs on the heat transfer coefficient was shown. It is found that for any twist pitch ranging from 20 to 100 mm corresponds to a maximum heat transfer rib height H = 0,35. An increase in the heat transfer coefficient in the convex heating surface was experimentally obtained.
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Toshio Suzuki
2016-02-01
Full Text Available The formation of two-neutron “halo”, a low-density far-extended surface of weakly-bound two neutrons, is described using the neutron–neutron (nn interaction fixed at the low-energy nn scattering limit. This method is tested for loosely-bound two neutrons in 24O, where a good agreement with experimental data is found. It is applied to halo neutrons in 22C in two ways: with the 20C core being closed or correlated (due to excitations from the closed core. This nn interaction is shown to be strong enough to produce a two-neutron halo in both cases, locating 22C on the drip line, while 21C remains unbound. A unique relation between the two neutron separation energy, S2n, and the radius of neutron halo is presented. New predictions for S2n and the radius of neutron halo are given for 22C. The appearance of Efimov states is also discussed.
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Nabil T. M. Eldabe
2014-01-01
Full Text Available This paper is devoted to the study of the peristaltic motion of non-Newtonian fluid with heat and mass transfer through a porous medium in the channel under the effect of magnetic field. A modified Casson non-Newtonian constitutive model is employed for the transport fluid. A perturbation series’ method of solution of the stream function is discussed. The effects of various parameters of interest such as the magnetic parameter, Casson parameter, and permeability parameter on the velocity, pressure rise, temperature, and concentration are discussed and illustrated graphically through a set of figures.
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Syed Tauseef Mohyud-Din
2016-01-01
Full Text Available The combined effects of heat transfer and chemical reaction are studied for the flow through a semi-infinite asymmetric channel with orthogonally deformable porous walls. The similarity transforms have been used to reduce the conservation laws to a corresponding system of nonlinear ordinary differential equations. The resulting equations are solved, both analytically and numerically, by using Homotopy Analysis Method (HAM and the fourth-order Runge-Kutta (RK-4 method, respectively. The convergence of the analytical solution is assured through the so-called total squared residual error analysis. The optimal values of auxiliary parameters are obtained by minimizing the total squared residual error.
Energy Technology Data Exchange (ETDEWEB)
Fang, Chin [SLAC National Accelerator Lab., Menlo Park, CA (United States); Corttrell, R. A. [SLAC National Accelerator Lab., Menlo Park, CA (United States)
2015-05-06
This Technical Note provides an overview of high-performance parallel Big Data transfers with and without encryption for data in-transit over multiple network channels. It shows that with the parallel approach, it is feasible to carry out high-performance parallel "encrypted" Big Data transfers without serious impact to throughput. But other impacts, e.g. the energy-consumption part should be investigated. It also explains our rationales of using a statistics-based approach for gaining understanding from test results and for improving the system. The presentation is of high-level nature. Nevertheless, at the end we will pose some questions and identify potentially fruitful directions for future work.
Experimental study of dryout heat transfer in rectangular channel%矩形通道干涸点传热特性试验研究
Institute of Scientific and Technical Information of China (English)
李虹波; 陈炳德; 赵华; 熊万玉
2012-01-01
The experiment of dryout heat transfer in rectangular channel has been carried out on the basic experimental loop of flow & heat transfer at NPIC. The results of the experimental study of thermal-hydraulic parameters on characteristics of dryout heat transfer in rectangular channel show that; (1) The dryout heat flux, wall temperature and heat transfer coefficient decrease, while the dryout quality increases with the increase of inlet quality; (2) The dryout heat flux, wall temperature and heat transfer coefficient increase, while the dryout quality decreases with the increase of mass flow velocity; (3) The dryout heat flux, quality, wall temperature and heat transfer coefficient increase with the increase of system pressure. Comparing the experimental data with empirical correlations, it finds out that these correlations are appropriate for the situations of middle-high pressure and low-middle mass flow velocity, and deviate seriously in low pressure and high mass flow velocity cases. Based on the Gutajellade correlation, and considering the effects of the dimension of rectangular channel and inlet enthalpy on heat transfer, a new correlation for dryout in rectangular channel is developed, which correlates the experimental data quite well.%在中国核动力研究设计院流动传热基础试验平台上进行了矩形通道干涸点传热试验.通过对各种热工水力参数的试验研究,得出结论:(1)随着进口含汽率的增加,干涸点热流密度减小,含汽率增加,壁面温度降低,传热系数减小；(2)随着质量流速的增大,干涸点热流密度增大,含汽率减小,壁面温度升高,传热系数增大；(3)随着系统压力的升高,干涸点热流密度增大,含汽率增加,壁面温度升高,传热系数增大.由试验数据与现有经验关系式的比较,发现这些关系式适合中高压、中低质量流速工况,而对低压、高质量流速工况存在较大的偏差.在古塔杰拉奇关系式的基础上,引
Kuscu, Murat; Kiraz, Alper; Akan, Ozgur B.
2015-01-01
Nanocommunications via Förster Resonance Energy Transfer (FRET) is a promising means of realising collaboration between photoactive nanomachines to implement advanced nanotechnology applications. The method is based on exchange of energy levels between fluorescent molecules by the FRET phenomenon which intrinsically provides a virtual nanocommunication link. In this work, further to the extensive theoretical studies, we demonstrate the first information transfer through a FRET-based nanocommunication channel. We implement a digital communication system combining macroscale transceiver instruments and a bulk solution of fluorophore nanoantennas. The performance of the FRET-based Multiple-Input and Multiple-Output (MIMO) nanocommunication channel between closely located mobile nanoantennas in the sample solution is evaluated in terms of Signal-to-Noise Ratio (SNR) and Bit Error Rate (BER) obtained for the transmission rates of 50 kbps, 150 kbps and 250 kbps. The results of the performance evaluation are very promising for the development of high-rate and reliable molecular communication networks at nanoscale.
Shao, Dongguo; Yang, Haidong; Xiao, Yi; Liu, Biyu
2014-01-01
A new method is proposed based on the finite difference method (FDM), differential evolution algorithm and Markov Chain Monte Carlo (MCMC) simulation to identify water quality model parameters of an open channel in a long distance water transfer project. Firstly, this parameter identification problem is considered as a Bayesian estimation problem and the forward numerical model is solved by FDM, and the posterior probability density function of the parameters is deduced. Then these parameters are estimated using a sampling method with differential evolution algorithm and MCMC simulation. Finally this proposed method is compared with FDM-MCMC by a twin experiment. The results show that the proposed method can be used to identify water quality model parameters of an open channel in a long distance water transfer project under different scenarios better with fewer iterations, higher reliability and anti-noise capability compared with FDM-MCMC. Therefore, it provides a new idea and method to solve the traceability problem in sudden water pollution accidents.
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Calisir Tamer
2015-01-01
Full Text Available Thermal control of electronic components is a continuously emerging problem as power loads keep increasing. The present study is mainly focused on experimental and numerical investigation of impinging jet cooling of 18 (3 × 6 array flash mounted electronic components under a constant heat flux condition inside a rectangular channel in which air, following impingement, is forced to exit in a single direction along the channel formed by the jet orifice plate and impingement plate. Copper blocks represent heat dissipating electronic components. Inlet flow velocities to the channel were measured by using a Laser Doppler Anemometer (LDA system. Flow field observations were performed using a Particle Image Velocimetry (PIV and thermocouples were used for temperature measurements. Experiments and simulations were conducted for Re = 4000 – 8000 at fixed value of H = 10 × Dh. Flow field results were presented and heat transfer results were interpreted using the flow measurement observations. Numerical results were validated with experimental data and it was observed that the results are in agreement with the experiments.
Transfer reactions at the neutron dripline with triton target
Borge, M J G; Fynbo, H O U; Gomez Camacho, J; Johansen, J; Johansson, H T; Jonson, B; Krücken, R; Kurcewicz, J; Martel, I; Moro, A; Mücher, D; Nilsson, T; Nyman, G; Raabe, R; Randisi, G; Riisager, K; Sambi, S; Sanchez-Benitez, AM; Tengblad, O
2012-01-01
Two-neutron transfer to $^{9}$Li will populate the ground state of $^{11}$Li as well as low-lying resonances in a way that is complementary to studies of these states performed at higher beam energies. We aim at detecting the charged particles from the transfer reactions as well as neutrons coming from the decay of possible $^{11}$Li resonances.
Transfer reactions at the neutron dripline with triton target
Two-neutron transfer to $^{9}$Li will populate the ground state of $^{11}$Li as well as low-lying resonances in a way that is complementary to studies of these states performed at higher beam energies. We aim at detecting the charged particles from the transfer reactions as well as neutrons coming from the decay of possible $^{11}$Li resonances.
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J.C. Misra
2016-03-01
Full Text Available In the present paper, the problem of oscillatory MHD flow of blood in a porous arteriole in presence of chemical reaction and an external magnetic field has been investigated. Heat and mass transfer during arterial blood flow are also studied. A mathematical model is developed and analyzed by using appropriate mathematical techniques. Expressions for the velocity profile, volumetric flow rate, wall shear stress and rates of heat and mass transfer have been obtained. Variations of the said quantities with different parameters are computed by using MATHEMATICA software. The quantitative estimates are presented through graphs and table.
Ryzhenkov, V.; Ivashchenko, V.; Vinuesa, R.; Mullyadzhanov, R.
2016-10-01
We use the open-source code nek5000 to assess the accuracy of high-order spectral element large-eddy simulations (LES) of a turbulent channel flow depending on the spatial resolution compared to the direct numerical simulation (DNS). The Reynolds number Re = 6800 is considered based on the bulk velocity and half-width of the channel. The filtered governing equations are closed with the dynamic Smagorinsky model for subgrid stresses and heat flux. The results show very good agreement between LES and DNS for time-averaged velocity and temperature profiles and their fluctuations. Even the coarse LES grid which contains around 30 times less points than the DNS one provided predictions of the friction velocity within 2.0% accuracy interval.
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Gaëlle Gonzalez
Full Text Available Cell microparticles (MPs released in the extracellular milieu can embark plasma membrane and intracellular components which are specific of their cellular origin, and transfer them to target cells. The MP-mediated, cell-to-cell transfer of three human membrane glycoproteins of different degrees of complexity was investigated in the present study, using a CHO cell model system. We first tested the delivery of CAR and CD46, two monospanins which act as adenovirus receptors, to target CHO cells. CHO cells lack CAR and CD46, high affinity receptors for human adenovirus serotype 5 (HAdV5, and serotype 35 (HAdV35, respectively. We found that MPs derived from CHO cells (MP-donor cells constitutively expressing CAR (MP-CAR or CD46 (MP-CD46 were able to transfer CAR and CD46 to target CHO cells, and conferred selective permissiveness to HAdV5 and HAdV35. In addition, target CHO cells incubated with MP-CD46 acquired the CD46-associated function in complement regulation. We also explored the MP-mediated delivery of a dodecaspanin membrane glycoprotein, the CFTR to target CHO cells. CFTR functions as a chloride channel in human cells and is implicated in the genetic disease cystic fibrosis. Target CHO cells incubated with MPs produced by CHO cells constitutively expressing GFP-tagged CFTR (MP-GFP-CFTR were found to gain a new cellular function, the chloride channel activity associated to CFTR. Time-course analysis of the appearance of GFP-CFTR in target cells suggested that MPs could achieve the delivery of CFTR to target cells via two mechanisms: the transfer of mature, membrane-inserted CFTR glycoprotein, and the transfer of CFTR-encoding mRNA. These results confirmed that cell-derived MPs represent a new class of promising therapeutic vehicles for the delivery of bioactive macromolecules, proteins or mRNAs, the latter exerting the desired therapeutic effect in target cells via de novo synthesis of their encoded proteins.
Vajravelu, K.; Sreenadh, S.; Dhananjaya, S.; Lakshminarayana, P.
2016-08-01
In this paper, the influence of heat transfer on the peristaltic flow of a conducting Phan-Thien-Tanner fluid in an asymmetric channel with porous medium is studied. The coupled nonlinear governing differential equations are solved by a perturbation technique. The expressions for the temperature field, the stream function, the axial velocity, and the pressure gradient are obtained. The effects of the various physical parameters such as the magnetic parameter M, the permeability parameter σ, the Brinkman number Br and the Weissenberg number We on the pumping phenomenon are analyzed through graphs and the results are discussed in detail. It is observed that the velocity and the pressure are decreased with increasing the magnetic parameter M whereas the effect of the parameter M on the temperature field is quite the opposite.
Uwanta, Ime Jimmy; Usman, Halima
2014-01-01
The present paper investigates the combined effects of Soret and Dufour on free convective heat and mass transfer on the unsteady one-dimensional boundary layer flow over a vertical channel in the presence of viscous dissipation and constant suction. The governing partial differential equations are solved numerically using the implicit Crank-Nicolson method. The velocity, temperature, and concentration distributions are discussed numerically and presented through graphs. Numerical values of the skin-friction coefficient, Nusselt number, and Sherwood number at the plate are discussed numerically for various values of physical parameters and are presented through tables. It has been observed that the velocity and temperature increase with the increase in the viscous dissipation parameter and Dufour number, while an increase in Soret number causes a reduction in temperature and a rise in the velocity and concentration.
Role of transfer reactions in heavy-ion collisions at the Coulomb barrier
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Pollarolo Giovanni
2011-10-01
Full Text Available One and two neutron transfer reactions are discussed in the semiclassical formalism. The twoneutrons transfer cross sections are calculated in the successive approximation. Comparisons with new experimental data below the Coulomb barrier are discussed in term of transfer probabilities as a function of the distance of closest approach for Coulomb scattering.
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R. N. Barik
2013-09-01
Full Text Available An analysis is made to study the effects of diffusion-thermo and chemical reaction on fully developed laminar MHD flow of electrically conducting viscous incompressible fluid in a vertical channel formed by two vertical parallel plates was taken into consideration with uniform temperature and concentration. The analytical solution by Laplace transform technique of partial differential equations is used to obtain the expressions for the velocity, temperature and concentration. It is interesting to note that during the course of computation, the transient solution at large time coincides with steady state solution derived separately and the diffusion-thermo effect creates an anomalous situation in temperature and velocity profiles for small Prandtl numbers. The study is restricted to only destructive reaction and non-conducting case cannot be derived as a particular case still it is quite interesting and more realistic than the earlier one.
Harlow, George E.; Flores, Kennet E.; Marschall, Horst R.
2016-08-01
Jadeitites in serpentinite mélanges are the product of crystallization from and/or metasomatism by aqueous fluids that transfer components from and within a subduction channel-the slab-mantle interaction volume-into discrete rock units, most commonly found within the serpentinized or serpentinizing portion of the channel or the overlying mantle rocks at high pressure (1 to > 2 GPa). Two serpentinite mélanges on either side of the Motagua fault system (MFS) of the Guatemala Suture Zone contain evidence of this process. Whole rock compositional analyses are reported here from 86 samples including jadeitites and the related rocks: omphacitites, albitites and mica rocks. The predominance of a single phase in most of these rocks is reflected in the major element compositions and aspects of the trace elements, such as REE abundances tracking Ca in clinopyroxene. Relative to N-MORB all samples show relative enrichments in the high field strength elements (HFSE) Hf, Zr, U, Th, and the LILE Ba and Cs, contrasted by depletions in K and in some cases Pb or Sr. Most jadeitites are also depleted in the highly compatible elements Cr, Sc and Ni despite their occurrence in serpentinite mélange; however, some omphacitite samples show the opposite. Trace elements in these jadeitite samples show a strong similarity with GLOSS (globally subducted oceanic sediment) and other terrigenous sediments in terms of their trace-element patterns, but are offset to lower abundances. Jadeitites thus incorporate a strong trace-element signature derived from sediments mixed with that from fluid derived from altered oceanic crust. Enrichment in the HFSE argues for mobility of these elements in aqueous fluids at high P/T conditions in the subduction channel and a remarkable lack of fractionation that might otherwise be expected from dissolution and fluid transport.
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Xiaolei Yu
2014-10-01
Full Text Available Accurate inversion of land surface geo/biophysical variables from remote sensing data for earth observation applications is an essential and challenging topic for the global change research. Land surface temperature (LST is one of the key parameters in the physics of earth surface processes from local to global scales. The importance of LST is being increasingly recognized and there is a strong interest in developing methodologies to measure LST from the space. Landsat 8 Thermal Infrared Sensor (TIRS is the newest thermal infrared sensor for the Landsat project, providing two adjacent thermal bands, which has a great benefit for the LST inversion. In this paper, we compared three different approaches for LST inversion from TIRS, including the radiative transfer equation-based method, the split-window algorithm and the single channel method. Four selected energy balance monitoring sites from the Surface Radiation Budget Network (SURFRAD were used for validation, combining with the MODIS 8 day emissivity product. For the investigated sites and scenes, results show that the LST inverted from the radiative transfer equation-based method using band 10 has the highest accuracy with RMSE lower than 1 K, while the SW algorithm has moderate accuracy and the SC method has the lowest accuracy.
Energy Technology Data Exchange (ETDEWEB)
Akram, Safia, E-mail: safia_akram@yahoo.com [Department of Humanities and Basic Sciences, Military College of Signals, National University of Sciences and Technology, Rawalpindi 46000 (Pakistan); Department of Mathematics, Quaid-i-Azam University 45320, Islamabad 44000 (Pakistan); Nadeem, S. [Department of Mathematics, Quaid-i-Azam University 45320, Islamabad 44000 (Pakistan)
2013-02-15
We discuss the peristaltic motion of a two dimensional Jeffrey fluid in an asymmetric channel under the effects of induced magnetic field and heat transfer. The problem is simplified by using long wave length and low Reynolds approximations. Exact and closed form Adomian solutions are presented. Expressions for the velocity, stream function, magnetic force function, temperature, pressure gradient and pressure rise are computed. The results of pertinent parameters are discussed. Finally, the trapping phenomena for different wave shapes are discussed. It is observed that the pressure rise for sinusoidal wave is less than trapezoidal wave and greater than triangular in a Jeffrey fluid. - Highlights: Black-Right-Pointing-Pointer The effects of induced magnetic field and heat transfer in peristaltic motion of a two dimensional Jeffrey fluid are discussed. Black-Right-Pointing-Pointer In this paper exact and closed form Adomian solutions are presented. Black-Right-Pointing-Pointer Different wave shapes are considered to observe the behavior of pressure rise and trapping phenomena.
Neutron transfer reactions in the fp-shell region
Energy Technology Data Exchange (ETDEWEB)
Mahgoub, Mahmoud
2008-06-26
Neutron transfer reactions were used to study the stability of the magic number N=28 near {sup 56}Ni. On one hand the one-neutron pickup (d,p) reaction was used for precision spectroscopy of single-particle levels in {sup 55}Fe. On the other hand we investigated the two-neutron transfer mechanism into {sup 56}Ni using the pickup reaction {sup 58}Ni((vector)p,t){sup 56}Ni. In addition the reliability of inverse kinematics reactions at low energy to study exotic nuclei was tested by the neutron transfer reactions t({sup 40}Ar,p){sup 42}Ar and d({sup 54}Fe,p){sup 55}Fe using tritium and deuterium targets, respectively, and by comparing the results with those of the normal kinematics reactions. The experimental data, differential cross-section and analyzing powers, are compared to DWBA and coupled channel calculations utilizing the code CHUCK3. By performing the single-neutron stripping reaction ((vector)d,p) on {sup 54}Fe the 1f{sub 7/2} shell in the ground state configuration was found to be partly broken. The instability of the 1f{sub 7/2} shell and the magic number N=28 was confirmed once by observing a number of levels with J{sup {pi}} = 7/2{sup -} at low excitation energies, which should not be populated if {sup 54}Fe has a closed 1f{sub 7/2} shell, and also by comparing our high precision experimental data with a large scale shell model calculation using the ANTOINE code [5]. Calculations including a partly broken 1f{sub 7/2} shell show better agreement with the experiment. The instability of the 1f{sub 7/2} shell was confirmed also by performing the two-neutron pick-up reaction ((vector)p,t) on {sup 58}Ni to study {sup 56}Ni, where a considerable improvement in the DWBA calculation was observed after considering 1f{sub 7/2} as a broken shell. To prove the reliability of inverse kinematics transfer reactions at low energies ({proportional_to} 2 AMeV), the aforementioned single-neutron transfer reaction (d,p) was repeated using a beam of {sup 54}Fe ions and a
Li, Changping
2015-07-22
In this letter, we propose a fast numerical solution for the steady state radiative transfer equation based on the approach in [1] in order to calculate the optical path loss of light propagation suffering from attenuation due to the absorption and scattering in various water types. We apply an optimal non-uniform method to discretize the angular space and an upwind type finite difference method to discretize the spatial space. A Gauss-Seidel iterative method is then applied to solve the fully discretized system of linear equations. Finally, we extend the resulting radiance in 2-dimensional to 3-dimensional by the azimuthal symmetric assumption to compute the received optical power under the given receiver aperture and field of view. The accuracy and efficiency of the proposed scheme are validated by uniform RTE solver and Monte Carlo simulations.
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Song, YoungShin; Lee, Chang-Soo [Chungnam National University, Daejeon (Korea, Republic of)
2014-10-15
A microfluidic method for the in situ production of monodispersed alginate hydrogels using biocompatible polymer gelation by crosslinker mass transfer is described. Gelation of the hydrogel was achieved in situ by the dispersed calcium ion in the microfluidic device. The capillary number (Ca) and the flow rate of the disperse phase which are important operating parameters mainly influenced the formation of three distinctive flow regions, such as dripping, jetting, and unstable dripping. Under the formation of dripping region, monodispersed alginate hydrogels having a narrow size distribution (C.V=2.71%) were produced in the microfluidic device and the size of the hydrogels, ranging from 30 to 60 µm, could be easily controlled by varying the flow rate, viscosity, and interfacial tension. This simple microfluidic method for the production of monodisperse alginate hydrogels shows strong potential for use in delivery systems of foods, cosmetics, inks, and drugs, and spherical alginate hydrogels which have biocompatibility will be applied to cell transplantation.
Energy Technology Data Exchange (ETDEWEB)
Sridharan, Kumar; Anderson, Mark; Allen, Todd; Corradini, Michael
2012-01-30
on Cr-carbide on the graphite surface. Ni-electroplating dramatically reduced corrosion of alloys, although some diffusion of Fe and Cr were observed occur through the Ni plating. A pyrolytic carbon and SiC (PyC/SiC) CVD coating was also investigated and found to be effective in mitigating corrosion. The KCl-MgCl2 molten salt was less corrosive than FLiNaK fluoride salts for corrosion tests performed at 850oC. Cr dissolution in the molten chloride salt was still observed and consequently Ni-201 and Hastelloy N exhibited the least depth of attack. Grain-boundary engineering (GBE) of Incoloy 800H improved the corrosion resistance (as measured by weight loss and maximum depth of attack) by nearly 50% as compared to the as-received Incoloy 800H sample. Because Cr dissolution is an important mechanism of corrosion, molten salt electrochemistry experiments were initiated. These experiments were performed using anodic stripping voltammetry (ASV). Using this technique, the reduction potential of Cr was determined against a Pt quasi-reference electrode as well as against a Ni(II)-Ni reference electrode in molten FLiNaK at 650 oC. The integrated current increased linearly with Cr-content in the salt, providing for a direct assessment of the Cr concentration in a given salt of unknown Cr concentration. To study heat transfer mechanisms in these molten salts over the forced and mixed convection regimes, a forced convective loop was constructed to measure heat transfer coefficients, friction factors and corrosion rates in different diameter tubes in a vertical up flow configuration in the laminar flow regime. Equipment and instrumentation for the forced convective loop was designed, constructed, and tested. These include a high temperature centrifugal pump, mass flow meter, and differential pressure sensing capabilities to an uncertainty of < 2 Pa. The heat transfer coefficient for the KCl-MgCl2 salt was measured in two different diameter channels (0.083 and 0.370Ã). In the 0
Energy Technology Data Exchange (ETDEWEB)
Ortiz-Rodriguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.; Solis Sanches, L. O.; Miranda, R. Castaneda; Cervantes Viramontes, J. M. [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica. Av. Ramon Lopez Velarde 801. Col. Centro Zacatecas, Zac (Mexico); Vega-Carrillo, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica. Av. Ramon Lopez Velarde 801. Col. Centro Zacatecas, Zac., Mexico. and Unidad Academica de Estudios Nucleares. C. Cip (Mexico)
2013-07-03
In this work the performance of two neutron spectrum unfolding codes based on iterative procedures and artificial neural networks is evaluated. The first one code based on traditional iterative procedures and called Neutron spectrometry and dosimetry from the Universidad Autonoma de Zacatecas (NSDUAZ) use the SPUNIT iterative algorithm and was designed to unfold neutron spectrum and calculate 15 dosimetric quantities and 7 IAEA survey meters. The main feature of this code is the automated selection of the initial guess spectrum trough a compendium of neutron spectrum compiled by the IAEA. The second one code known as Neutron spectrometry and dosimetry with artificial neural networks (NDSann) is a code designed using neural nets technology. The artificial intelligence approach of neural net does not solve mathematical equations. By using the knowledge stored at synaptic weights on a neural net properly trained, the code is capable to unfold neutron spectrum and to simultaneously calculate 15 dosimetric quantities, needing as entrance data, only the rate counts measured with a Bonner spheres system. Similarities of both NSDUAZ and NSDann codes are: they follow the same easy and intuitive user's philosophy and were designed in a graphical interface under the LabVIEW programming environment. Both codes unfold the neutron spectrum expressed in 60 energy bins, calculate 15 dosimetric quantities and generate a full report in HTML format. Differences of these codes are: NSDUAZ code was designed using classical iterative approaches and needs an initial guess spectrum in order to initiate the iterative procedure. In NSDUAZ, a programming routine was designed to calculate 7 IAEA instrument survey meters using the fluence-dose conversion coefficients. NSDann code use artificial neural networks for solving the ill-conditioned equation system of neutron spectrometry problem through synaptic weights of a properly trained neural network. Contrary to iterative procedures, in
Institute of Scientific and Technical Information of China (English)
白超; 韩勇军; 伊寅; 史小锋; 郭兆元; 封启玺
2016-01-01
为研究水下航行器小通道内的蒸汽换热特性，对采用矩形通道设计的冷凝通道进行实验研究，分析不同蒸汽入口温度对通道换热特性的影响。实验结果表明：矩形小通道具有较好的冷凝换热效果，通道总平均换热量、热流密度以及通道出口冷凝液温度均随通道入口蒸汽温度升高而升高。但总传热系数和蒸汽侧换热系数随通道入口蒸汽温度升高而降低。最后在实验数据基础上，将实验值与仿真值进行对比分析，修正仿真模型，确定过热蒸汽冷凝成水的过程中相变点位置，为后续闭式循环动力系统壳体冷凝器的设计提供依据和参考。%In order to study the characteristics of steam heat transfer in a small channel of the underwater vehicle. This article researched the experimental investigation of the condensation heart transfer in small channels, and analyzed the different steam inlet temperatures on heat transfer characteristics of channels. The experimental results show that the small rectangular channel has good condensing heat transfer effect, the channel overall average heat transfer, heat flux and export condensate temperature were increased with the channel inlet steam temperature become high, but the total heat transfer coefficient and steam side heat transfer coefficient were decreasedwith the channel inlet steam temperature were increased. Finally, the paper compared the experimental value and simulation analysison the basis of experimental data, and verified the simulation model, and the superheated steam condensation water was determined in the process of phase transformation point location, being provided for the design of power system shell condenser of the subsequent closed cycle power system shell condenser.
Directory of Open Access Journals (Sweden)
Mohammad J Hossain
Full Text Available To investigate the molecular basis of the emergence of Aeromonas hydrophila responsible for an epidemic outbreak of motile aeromonad septicemia of catfish in the Southeastern United States, we sequenced 11 A. hydrophila isolates that includes five reference and six recent epidemic isolates. Comparative genomics revealed that recent epidemic A. hydrophila isolates are highly clonal, whereas reference isolates are greatly diverse. We identified 55 epidemic-associated genetic regions with 313 predicted genes that are present in epidemic isolates but absent from reference isolates and 35% of these regions are located within genomic islands, suggesting their acquisition through lateral gene transfer. The epidemic-associated regions encode predicted prophage elements, pathogenicity islands, metabolic islands, fitness islands and genes of unknown functions, and 34 of the genes encoded in these regions were predicted as virulence factors. We found two pilus biogenesis gene clusters encoded within predicted pathogenicity islands. A functional metabolic island that encodes a complete pathway for myo-inositol catabolism was evident by the ability of epidemic A. hydrophila isolates to use myo-inositol as a sole carbon source. Testing of A. hydrophila field isolates found a consistent correlation between myo-inositol utilization as a sole carbon source and the presence of an epidemic-specific genetic marker. All epidemic isolates and one reference isolate shared a novel O-antigen cluster. Altogether we identified four different O-antigen biosynthesis gene clusters within the 11 sequenced A. hydrophila genomes. Our study reveals new insights into the evolutionary changes that have resulted in the emergence of recent epidemic A. hydrophila strains.
Energy Technology Data Exchange (ETDEWEB)
Costa, Romarly F. da [Instituto de Física “Gleb Wataghin,” Universidade Estadual de Campinas, 13083-859 Campinas, São Paulo (Brazil); Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-580 Santo André, São Paulo (Brazil); Oliveira, Eliane M. de; Lima, Marco A. P. [Instituto de Física “Gleb Wataghin,” Universidade Estadual de Campinas, 13083-859 Campinas, São Paulo (Brazil); Bettega, Márcio H. F. [Departamento de Física, Universidade Federal do Paraná, CP 19044, 81531-990 Curitiba, Paraná (Brazil); Varella, Márcio T. do N. [Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970 São Paulo, São Paulo (Brazil); Jones, Darryl B. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide SA 5001 (Australia); Brunger, Michael J. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide SA 5001 (Australia); Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur (Malaysia); Blanco, Francisco [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid, Ciudad Universitaria, 2840 Madrid (Spain); Colmenares, Rafael [Hospital Ramón y Cajal, 28034 Madrid (Spain); and others
2015-03-14
We report theoretical and experimental total cross sections for electron scattering by phenol (C{sub 6}H{sub 5}OH). The experimental data were obtained with an apparatus based in Madrid and the calculated cross sections with two different methodologies, the independent atom method with screening corrected additivity rule (IAM-SCAR), and the Schwinger multichannel method with pseudopotentials (SMCPP). The SMCPP method in the N{sub open}-channel coupling scheme, at the static-exchange-plus-polarization approximation, is employed to calculate the scattering amplitudes at impact energies ranging from 5.0 eV to 50 eV. We discuss the multichannel coupling effects in the calculated cross sections, in particular how the number of excited states included in the open-channel space impacts upon the convergence of the elastic cross sections at higher collision energies. The IAM-SCAR approach was also used to obtain the elastic differential cross sections (DCSs) and for correcting the experimental total cross sections for the so-called forward angle scattering effect. We found a very good agreement between our SMCPP theoretical differential, integral, and momentum transfer cross sections and experimental data for benzene (a molecule differing from phenol by replacing a hydrogen atom in benzene with a hydroxyl group). Although some discrepancies were found for lower energies, the agreement between the SMCPP data and the DCSs obtained with the IAM-SCAR method improves, as expected, as the impact energy increases. We also have a good agreement among the present SMCPP calculated total cross section (which includes elastic, 32 inelastic electronic excitation processes and ionization contributions, the latter estimated with the binary-encounter-Bethe model), the IAM-SCAR total cross section, and the experimental data when the latter is corrected for the forward angle scattering effect [Fuss et al., Phys. Rev. A 88, 042702 (2013)].
da Costa, Romarly F; de Oliveira, Eliane M; Bettega, Márcio H F; Varella, Márcio T do N; Jones, Darryl B; Brunger, Michael J; Blanco, Francisco; Colmenares, Rafael; Limão-Vieira, Paulo; García, Gustavo; Lima, Marco A P
2015-03-14
We report theoretical and experimental total cross sections for electron scattering by phenol (C6H5OH). The experimental data were obtained with an apparatus based in Madrid and the calculated cross sections with two different methodologies, the independent atom method with screening corrected additivity rule (IAM-SCAR), and the Schwinger multichannel method with pseudopotentials (SMCPP). The SMCPP method in the Nopen-channel coupling scheme, at the static-exchange-plus-polarization approximation, is employed to calculate the scattering amplitudes at impact energies ranging from 5.0 eV to 50 eV. We discuss the multichannel coupling effects in the calculated cross sections, in particular how the number of excited states included in the open-channel space impacts upon the convergence of the elastic cross sections at higher collision energies. The IAM-SCAR approach was also used to obtain the elastic differential cross sections (DCSs) and for correcting the experimental total cross sections for the so-called forward angle scattering effect. We found a very good agreement between our SMCPP theoretical differential, integral, and momentum transfer cross sections and experimental data for benzene (a molecule differing from phenol by replacing a hydrogen atom in benzene with a hydroxyl group). Although some discrepancies were found for lower energies, the agreement between the SMCPP data and the DCSs obtained with the IAM-SCAR method improves, as expected, as the impact energy increases. We also have a good agreement among the present SMCPP calculated total cross section (which includes elastic, 32 inelastic electronic excitation processes and ionization contributions, the latter estimated with the binary-encounter-Bethe model), the IAM-SCAR total cross section, and the experimental data when the latter is corrected for the forward angle scattering effect [Fuss et al., Phys. Rev. A 88, 042702 (2013)].
Directory of Open Access Journals (Sweden)
. Dr. S. Rawat
2014-01-01
Full Text Available A mathematical model is presented for the steady, two-dimensional magneto-convection heat transfer of a two-phase, electrically-conducting, particle-suspension in a channel containing a non-Darcian porous medium intercalated between two parallel plates, in the presence of a transverse magnetic field. The channel walls are assumed to be isothermal but at different temperatures. The governing equations for the one-dimensional steady flow are formulated following Marble (1970 and extended to include the influence of Darcian porous drag, Forcheimmer quadratic drag, buoyancy effects, Lorentz body force (hydromagnetic retardation force and particle-phase viscous stresses. Special boundary conditions for the particle-phase wall conditions are implemented. The governing coupled, non-linear differential equations are reduced from an (x,y coordinate system to a one-dimensional (y coordinate system. A series of transformations is then employed to non-dimensionalize the model in terms of a single independent variable, , yielding a quartet of coupled ordinary differential equations which are solved numerically using the finite element method, under appropriate transformed boundary conditions. The influence of for example Grashof free convection number (Gr, Hartmann hydromagnetic number (Ha, inverse Stokes number (Skm, Darcy number (Da, Forcheimmer number (Fs,particle loading parameter (PL, buoyancy parameter (B on the fluid-phase velocity and particle-phase velocity are presented graphically. A number of special cases of the transformed model are also studied. The mathematical model finds applications in solar collector devices, electronic fabrication, jet nozzle flows, industrial materials processing transport phenomena, MHD energy generator systems etc.
Institute of Scientific and Technical Information of China (English)
李隆键; 陈欢; 吴治娟
2012-01-01
The three dimensional physical model and mathematical model of turbulent flow and heat transfer in the channel of honeycombed plate heat exchanger were established, and the corresponding flow field and temperature field was numerically simulated. The heat transfer and pressure drop characteristics of the channel were investigated under different Reynolds number. The computed results showed that both the heat transfer coefficient and pressure drop of the channel were obviously increased along with Reynolds number. On the other hand the characteristics of heat transfer and pressure drop of the channel were compared with that of the parallel plate channels. At last, the mechanism of the heat transfer enhancement was analyzed according to fields synergy principle.%建立了蜂窝板换热器湍流流动的物理数学模型,并应用数值分析方法模拟了蜂窝板换热器的三维流动传热过程；分析了不同雷诺数下通道内流动阻力和换热性能及其随雷诺数的变化规律,并与相同当量直径的平行平板通道的流动换热性能进行了对比.结果表明,蜂窝板换热器在换热系数提高的同时流动阻力也增大了,在雷诺数Re=3000～15000的范围内,其传热努塞尔数比平行平板增大了0.93～2.12倍,阻力系数增大了2.24～2.35倍.最后从场协同理论的角度分析了蜂窝板强化传热的机理.
Shi, Weixiu; Pan, Lisheng
2017-02-01
Using ethanol or acetone as the working fluid, the performance of starting up and heat transfer of closed-loop plate oscillating heat pipe with parallel channels (POHP-PC) were experimentally investigated by varying filling ratio, inclination, working fluids and heating power. The performance of the tested pulsating heat pipe was mainly evaluated by thermal resistance and wall temperature. Heating copper block and cold water bath were adopted in the experimental investigations. It was found that oscillating heat pipe with filling ratio of 50% started up earlier than that with 70% when heating input was 159.4 W, however, it has similar starting up performance with filling ratio of 50% as compared to 70% on the condition of heat input of 205.4 W. And heat pipe with filling ratio of 10% could not start up but directly transit to dry burning. A reasonable filling ratio range of 35%‒70% was needed in order to achieve better performance, and there are different optimal filling ratios with different heating inputs - the more heating input, the higher optimal filling ratio, and vice versa. However, the dry burning appeared easily with low filling ratio, especially at very low filling ratio, such as 10%. And higher filling ratio, such as 70%, resulted in higher heat transfer ( dry burning ) limit. With filling ratio of 70% and inclination of 75°, oscillating heat pipe with acetone started up with heating input of just 24W, but for ethanol, it needed to be achieved 68 W, Furthermore, the start time with acetone was similar as compared to that with ethanol. For steady operating state, the heating input with acetone was about 80 W, but it transited to dry burning state when heating input was greater than 160 W. However, for ethanol, the heating input was in vicinity of 160 W. Furthermore, thermal resistance with acetone was lower than that with ethanol at the same heating input of 120 W.
Burmester, Mike; Munilla, Jorge; Ortiz, Andrés; Caballero-Gil, Pino
2017-07-04
The National Strategy for Global Supply Chain Security published in 2012 by the White House identifies two primary goals for strengthening global supply chains: first, to promote the efficient and secure movement of goods, and second to foster a resilient supply chain. The Internet of Things (IoT), and in particular Radio Frequency Identification (RFID) technology, can be used to realize these goals. For product identification, tracking and real-time awareness, RFID tags are attached to goods. As tagged goods move along the supply chain from the suppliers to the manufacturers, and then on to the retailers until eventually they reach the customers, two major security challenges can be identified: (I) to protect the shipment of goods that are controlled by potentially untrusted carriers; and (II) to secure the transfer of ownership at each stage of the chain. For the former, grouping proofs in which the tags of the scanned goods generate a proof of "simulatenous" presence can be employed, while for the latter, ownership transfer protocols (OTP) are used. This paper describes enhanced security solutions for both challenges. We first extend earlier work on grouping proofs and group codes to capture resilient group scanning with untrusted readers; then, we describe a modified version of a recently published OTP based on channels with positive secrecy capacity adapted to be implemented on common RFID systems in the supply chain. The proposed solutions take into account the limitations of low cost tags employed in the supply chain, which are only required to generate pseudorandom numbers and compute one-way hash functions.
Institute of Scientific and Technical Information of China (English)
王国顺; 杨晨
2014-01-01
The development of network economy makes consumer channels gradually present diversification trend, and the channel migration about the offline channel to online channel becomes inevitable. The coordination of physical retail and internet retail will be the future model of retail enterprises. In the process of multi-channel choice and migration, the consumer trust transfer has been a hot topic recently. Based on multi-channel environment, this paper attempts to employ Nicosia model and TRA theory to analyze the factors of the formation of consumer online trust, the relationship between the consumer trust transfer and channel migration, as well as a set of guidelines for retail enterprises to achieve the channel coordination.%网络经济的发展导致了消费渠道的多样化，线下消费和线上消费相互转化，实体零售和网络零售的协同成为零售企业未来发展的趋势。从多渠道背景出发，结合Nicosia模型和TRA理论，分析了消费者在线信任的构成要素，提出了消费者信任转移路径模型和消费者渠道迁徙路径模型，通过分析消费者信任转移和渠道迁徙行为之间存在相关关系，提出了零售企业实现渠道协同的建议。
Afrand, Masoud; Karimipour, Arash; Nadooshan, Afshin Ahmadi; Akbari, Mohammad
2016-10-01
Simulation of forced convection of FMWNT-water (functionalized multi-walled carbon nano-tubes) nano-fluid in a micro-channel under a magnetic field in slip flow regime is performed. The micro-channel wall is divided into two portions. The micro-channel entrance is insulated while the rest of length of the micro-channel has constant temperature (TC). Moreover, the micro-channel domain is exposed to a magnetic field with constant strength of B0. High temperature nano-fluid (TH) enters the micro-channel and exposed to its cold walls. Slip velocity boundary condition along the walls of the micro-channel is considered. Governing equations are numerically solved using FORTRAN computer code based on the SIMPLE algorithm. Results are presented as the velocity, temperature, and Nusselt number profiles. Greater Reynolds number, Hartmann number, and volume fraction related to more heat transfer rate; however, the effects of Ha and ϕ are more noteworthy at higher Re.
Institute of Scientific and Technical Information of China (English)
曹浩然; 黄荣华; 孟宪超; 黎俊亨
2015-01-01
以聚变堆包层第一壁内流道作为研究对象，设计了以空气为介质的包层第一壁U型流道换热性能实验台架。通过测量第一壁流道沿流动方向的温度和压力分布，研究了在不同管径和雷诺数下，温度、流速和弯头形状等因素对第一壁流道换热性能的影响，并与数值模拟结果进行了对比分析。实验结果表明：30mm×30mm最大的U型方管可以在不增加流动阻力的情况下，提高流体与管壁之间换热强度23％，并且通过弯头处渐缩的优化改进可进一步提高换热强度15％，数值分析结果与之也较符合。本研究表明通过改变包层第一壁流道的形状和尺寸可以有效提高第一壁流道的换热性能。%A set of apparatus of the U‐shape flow channels with air as coolant was designed to study the flow channels in the first‐wall of fusion reactor blanket .The temperature distributions of the flow channels in the first‐wall were measured along the flowing direction ,and the impacts of flow channel diameter ,Reynolds number ,temperature ,inlet velocity and corner shape on heat transfer perform‐ance of the first wall were investigated by comparing the measured data with numerical simulation re‐sults .The experiment results show that the largest U‐shape flow channel with 30 mm × 30 mm square cross‐section could increase performance of heat transfer between coolant and flow channel wall by 23% without the increasing coolant flow resistance ,the modified flow channel design with the conver‐ging flow area could further enhance the heat transfer by almost 15% ,with which the numerical simu‐lation results agree well .Research results show that the heat transfer performance of flow channels could be efficiently increased by modifying the size and shape .
Energy Technology Data Exchange (ETDEWEB)
Sridharan, Kumar; Anderson, Mark; Allen, Todd; Corradini, Michael
2012-01-30
on Cr-carbide on the graphite surface. Ni-electroplating dramatically reduced corrosion of alloys, although some diffusion of Fe and Cr were observed occur through the Ni plating. A pyrolytic carbon and SiC (PyC/SiC) CVD coating was also investigated and found to be effective in mitigating corrosion. The KCl-MgCl2 molten salt was less corrosive than FLiNaK fluoride salts for corrosion tests performed at 850oC. Cr dissolution in the molten chloride salt was still observed and consequently Ni-201 and Hastelloy N exhibited the least depth of attack. Grain-boundary engineering (GBE) of Incoloy 800H improved the corrosion resistance (as measured by weight loss and maximum depth of attack) by nearly 50% as compared to the as-received Incoloy 800H sample. Because Cr dissolution is an important mechanism of corrosion, molten salt electrochemistry experiments were initiated. These experiments were performed using anodic stripping voltammetry (ASV). Using this technique, the reduction potential of Cr was determined against a Pt quasi-reference electrode as well as against a Ni(II)-Ni reference electrode in molten FLiNaK at 650 oC. The integrated current increased linearly with Cr-content in the salt, providing for a direct assessment of the Cr concentration in a given salt of unknown Cr concentration. To study heat transfer mechanisms in these molten salts over the forced and mixed convection regimes, a forced convective loop was constructed to measure heat transfer coefficients, friction factors and corrosion rates in different diameter tubes in a vertical up flow configuration in the laminar flow regime. Equipment and instrumentation for the forced convective loop was designed, constructed, and tested. These include a high temperature centrifugal pump, mass flow meter, and differential pressure sensing capabilities to an uncertainty of < 2 Pa. The heat transfer coefficient for the KCl-MgCl2 salt was measured in two different diameter channels (0.083 and 0.370Ã). In the 0
Research of the Trust Transfer on Consumer's Online Payment Channel%消费者网购支付渠道信任转移研究
Institute of Scientific and Technical Information of China (English)
李宝库; 高玉平; 倪元元
2016-01-01
Based on the theory of TAM and trust transfer,the paper builds the conceptual model of payment channel which transferred from traditional internet payment to mobile internet payment,and analyzes how the factors of TAM model and user perception affect consumer's usage intention of mobile payment,and then the model is performed by empirical research. The results reveal online payment not only directly influence mobile payment initial trust, but also indirectly affect the mobile payment initial trust through structural security and perceived usefulness. Perceived usefulness,structural security and personal innovation has a positive effect on initial trust. But the perceived ease of use and convenience have little effects on the mobile payment initial trust.%基于TAM理论和信任转移理论，构建消费者网购支付渠道信任由传统互联网转移至移动互联网，以及该信任转移过程中各个因素对消费者移动支付使用意愿影响的概念模型，并采用结构方程对模型进行检验。结果表明：消费者对传统互联网支付信任不仅直接影响其对移动支付的初始信任，而且通过移动支付的结构性保障、感知有用性间接影响其对移动支付的初始信任；感知有用性、结构性保障和个人创新性均与移动支付初始信任有正相关关系；而移动支付的便捷性和消费者对移动支付的感知易用性对移动支付初始信任的假设没有得到实证支持。
Institute of Scientific and Technical Information of China (English)
穆祥鹏; 陈文学; 郭晓晨; 崔巍
2013-01-01
In northern China at high latitudes there are some long-distance water transfer channel projects which are mostly planed or built in the last century. Due to the economic conditions at that time, these channel projects were designed without considering for winter time and only transfer water under non-ice condition. However with the development of economy, it is urgent to transfer water in winter in order to al-leviate the shortage of water presently. But constrained by the structure form, the freezing resistance abili-ties of these channels are poor, which are not suitable for transferring water under ice cover. Instead install-ing thermal insulation covers for channels can prevent water from freezing. This method not only can solve the shortage of water in winter, but also can save the engineering transformation investment, which has great economic benefits and social benefits. In this paper the heat loss process of water in channels with thermal insulation covers is analyzed theoretically. Then a one-dimensional ice-hydraulics mathematical mod-el of channel with thermal insulation covers is established and the heat loss process of water is simulated. The influences of insulation cover thickness, flow rate and outflow temperature from water source on water transfer in winter are analyzed. Finally, on the basis of the above researches, the water transfer feasibility is demonstrated for channels with thermal insulation cover in winter and the safe schemes of water transfer are put forward. The study results have some reference value for water transfer safety and engineering trans-formation for channel project in winter.%中国北方高纬度地区有一些渠道工程，因其建设年代早，受规划之初经济条件限制，未考虑冰期运行，仅在非冰期输水。随着经济发展，目前亟需实现冬季输水。但是受结构上的限制，这些渠道抗冰冻能力差，无法采取冰盖下输水或冰水二相流输水，通过加设保温
Institute of Scientific and Technical Information of China (English)
江乐新; 李雅瑾; 江劲松
2013-01-01
In order to study how to design heat conduction channel of solar thermal component with better heat transfer performance, the prototype of solar thermal component were simplified as different physical models with four types of heat conduction channels, i. e. single circle flow channel, single rectangle flow channel, five circles flow channel, five rectangles flow channel. The material section, flow section and areas for heat transfer are the same for all the types. Taking the distilled water of 20 X. as the flowing working substance, the heat transfer performance of four types of heat conduction channels was simulated numerically by using FLUENT and the average exit temperature and the wall heat transfer rate of the heat conduction channel were analyzed. It was found that the best type was the five rectangles flow channel, compared to the other three channels, the temperature difference between inlet and outlet and the wall heat transfer rate improved by 7. 5% , 2. 6% , 4. 3% and 55. 4% , 17. 0% , 23. 3% respectively. The numerical simulation results were similar to the experimental results, and the average value of their relative error was 2% , providing a theoretical basis for section type's design and research of heat conduction channel.%为了研究如何设计导热流道能使光热组件具有更好的传热性能,对光热组件的实体模型进行简化处理,并建立了包含单圆形流道、单矩形流道、五圆形流道、五矩形流道的4种截面型式导热流道的物理模型,且它们的材料截面积、流量截面积和传热面积均相等.以20℃蒸馏水为流动工质,借助FLUENT分别对4种不同型式的导热流道的传热性能展开数值模拟研究,分析了导热流道的出口平均温度和壁面导热速率,发现五矩形流道的效果最好,相比于单圆形、单矩形、五圆形的进出口温差和壁面导热速率分别提高了7.5％、2.6％、4.3％和55.4％、17.0％、23.3％.模拟结果与
Institute of Scientific and Technical Information of China (English)
李菊先; 马俊青; 刘长垠; 侯丽娜
2012-01-01
According to the design technology standard of South-to-North Water Transfer Project main channel, the construction of water pipeline crossing the main channel will not occupy the water head of main channel. Based on the relationship among the bottom elevations of water pipeline and main channel, and the design water line, pipeline bridge upon the channel and the inverted siphon under the bottom of channel have been considered. After the comprehensive analysis and comparison on technology.economy, and construction etc,the inverted siphon under the bottom of channel with the protective box culvert outside has been used for the construction of water pipeline when crossing the main channel.%根据南水北调总干渠总体设计技术规定:输水管道穿越总干渠,其穿越建筑物不占用总干渠水头.为满足总体设计要求,根据输水管道管底高程、总干渠渠底高程及设计水位的相互关系,考虑了渠上管道桥和渠底倒虹吸两种穿越方案,通过技术、经济、施工等综合分析比较,确定输水管道穿总干渠建筑物型式为渠底倒虹吸,倒虹吸管外加防护箱涵.
We propose to use fast-timing and spectroscopy to study five nuclei including the doubly magic $^{132}$Sn and its four neighbours: two-neutron hole $^{130}$Sn, one-neutron hole $^{131}$Sn, one-neutron particle $^{133}$Sn and two-neutron particle $^{134}$Sn. There is an increasing interest in these nuclei since they serve to test nuclear models using state-of-the-art interactions and many body approaches, and they provide information relevant to deduce single particle states. In addition properties of these nuclei are very important to model the astrophysical $\\textit{r-process}$. The present ISOLDE facility provides unique capabilities to study these Sn nuclei populated in the $\\beta$-decay of In isomers, produced from a UCx target unit equipped with neutron converter and ionized with RILIS, capable of selective isomer ionization. The increased production yields for $^{132}$In are estimated to be 200 larger than in the previous work done at OSIRIS. We will use the recently commissioned Isolde Decay Station (I...
Manning, Robert M.
2004-01-01
The systems engineering description of a wideband communications channel is provided which is based upon the fundamental propagation aspects of the problem. In particular, the well known time variant description of a channel is formulated from the basic multiple scattering processes that occur in a random propagation medium. Such a connection is required if optimal processing methods are to be applied to mitigate the deleterious random fading and multipathing of the channel. An example is given which demonstrates how the effective bandwidth of the channel is diminished due to atmospheric propagation impairments.
Technology Transfer Issues and a New Technology Transfer Model
Choi, Hee Jun
2009-01-01
The following are major issues that should be considered for efficient and effective technology transfer: conceptions of technology, technological activity and transfer, communication channels, factors affecting transfer, and models of transfer. In particular, a well-developed model of technology transfer could be used as a framework for…
Institute of Scientific and Technical Information of China (English)
张强; 王良璧
2014-01-01
用数值模拟方法研究了在矩形通道底壁安装矩形涡产生器对(RWP)时纵向涡对层流换热的影响。在雷诺数变化范围为500~7000,通道底壁安装RWP和不安装RWP两种情况下,比较了流体流动和换热性能。同时对涡产生器的高度和攻角对表面换热性能的影响也做了研究。结果表明：通道的底壁安装 RWP 可以显著提高换热性,雷诺数越大,换热性越强。随着涡产生器高度的增大,换热性增强,但阻力系数会急剧增加。当攻角为29°时,强化换热效果是最强的。%A numerical simulation is performed to investigate the effect of longitudinal vortices on the heat transfer enhancement of the laminar flow in a rectangle duct mounted with rectangular winglet pair (RWP)on the bottom wall.Reynolds number is defined in two times of channel height ranges from 500 to 7 000.The comparison of the fluid flow and heat transfer characteristics with RWP or without RWP is made.The effect of the height of vortex generator pair and its at-tack angle on heat transfer performance of channel surface is investigated.The results show that the case with RWP on the bottom wall of the channel can significantly enhance heat transfer.The larger Reynolds number is,the stronger heat transfer enhancement is.With increasing height of RWP,heat transfer is enhanced,but drag coefficient is sharply increased.The heat transfer en-hancement is the strongest when the angle of attack is 2 9 deg.
Institute of Scientific and Technical Information of China (English)
毕成; 唐桂华; 陶文铨
2012-01-01
结合对流传热场协同原理分析了微酒窝通道、圆柱面凹槽通道及低肋通道强化传热特点,研究发现酒窝与圆柱面凹槽强化传热主要原因为：1）增加近壁区流体扰动,促进酒窝或凹槽内部流体与主流之间的传热;2）酒窝与凹槽均可扩展传热面积,进而提高总传热量。与低肋通道相比,酒窝与圆柱面凹槽仅对其附近流体的流动产生影响,而对主流流体的流动影响较小,进而阻力增加较少。提出传热量单元性能参数PEC_A作为评价指标,酒窝通道综合性能参数略高于圆柱面凹槽通道,而远高于低肋通道。%According to the field synergy principle,the convective heat transfer characteristics in micro-channels with dimples,cylindrical grooves and low fins are numerically studied,and the reasons of the enhanced heat transfer in the dimple and cylindrical channels are in two ways：1）increasing the turbulence of fluid near the wall and enhancing heat transfer between the main stream and the fluid inside the dimples or cylindrical grooves;2）dimples and grooves can extend more surface for the total heat transfer.Compared with low fins,only the fluids inside or near dimples and grooves are influenced and dimples or grooves do not have much impact on the main stream such that more flow resistance can be avoided.We proposed a parameter PEC_a as the evaluation coefficient,and the results show that the PEC_A of the dimple channel is slightly higher than that of the cylindrical channel,but much higher than that of the low fin channel.
Kohley, Z; Lunderberg, E; DeYoung, P A; Attanayake, H; Bauman, T; Bazin, D; Brown, B A; Christian, G; Divaratne, D; Grimes, S M; Haagsma, A; Finck, J E; Frank, N; Luther, B; Mosby, S; Nagi, T; Peaslee, G F; Peters, W A; Schiller, A; Smith, J K; Snyder, J; Strongman, M J; Thoennessen, M; Volya, A
2012-01-01
The two-neutron unbound ground state resonances of $^{26}$O and $^{16}$Be were populated using one-proton knockout reactions from $^{27}$F and $^{17}$B beams. A coincidence measurement of 3-body system (fragment + n + n) allowed for the decay energy of the unbound nuclei to be reconstructed. A low energy resonance, $<$ 200 keV, was observed for the first time in the $^{24}$O + n + n system and assigned to the ground state of $^{26}$O. The $^{16}$Be ground state resonance was observed at 1.35 MeV. The 3-body correlations of the $^{14}$Be + n + n system were compared to simulations of a phase-space, sequential, and dineutron decay. The strong correlations in the n-n system from the experimental data could only be reproduced by the dineutron decay simulation providing the first evidence for a dineutron-like decay.
Institute of Scientific and Technical Information of China (English)
孟现珂; 孙中宁; 周平; 徐广展
2012-01-01
The water-cooled pebble bed reactor core is the porous channels stacked with spherical fuel elements, having evident effect on enhancing heat transfer. Owing to the variability and randomness characteristics of it's interstice, pebble bed channels have a very complex heat transfer situation and have little correlative research. In order to research the heat transfer characters of pebble bed channels with internal heat source, electromagnetic induction heating method was adopted for overall heating the pebble bed which was composed of 8 mm diameter steel balls, and the internal heat transfer characteristics were researched. By comparing and analyzing the experimental data, the rule of power distribution and heat transfer coefficient with heat flux density, inlet temperature and working fluid' s Re were got. According to the experimental data fitting, the dimensionless average heat transfer coefficient correlation criteria was got. The fitting results are good agreement with the experimental results within difference.%球床水冷反应堆的堆芯为球形燃料元件堆积成的多孔通道,具有显著的强化换热作用.球床通道内的孔隙因具有多变性、随机性的特点,换热情况非常复杂,相关研究较少.为了研究含内热源球床通道内的换热特性,本文用直径为8 mm碳钢球堆积形成球床,以蒸馏水为工质,采用电磁感应加热方式对球床进行整体加热,研究球床通道内部的换热特性.通过对实验数据进行分析,得到了球床通道内部的功率分布和换热系数随热流密度、工质Re的变化规律,根据实验数据拟合得到了球床通道内平均换热系数的无量纲准则关联式,拟合结果与实验结果的相对偏差在12％以内,符合良好.
Institute of Scientific and Technical Information of China (English)
陈冲; 高璞珍; 谭思超; 余志庭; 陈先兵
2015-01-01
为了研究竖直窄矩形通道内环状流的流动传热特性，建立了窄矩形通道内环状流的数学物理模型，并进行了实验验证。通过数值求解环状流的数学物理模型得到了环状流区域的压降梯度、沸腾传热系数和液膜内的速度分布。结果表明窄矩形通道内的环状流模型能够很好地预测环状流区域的压降梯度和沸腾传热系数，而且环状流液膜内速度在法向的分布是非线性的，在层流边界层区速度梯度较大。热通量和窄矩形通道的尺寸对液膜的流速有很大影响，随热通量的增加和窄矩形通道尺寸的减小液膜的流速逐渐增加，然而质量流速对液膜流速的影响较小，而且随质量流速的增加液膜的速度逐渐减小。%A mathematical model of annular flow in vertical rectangular narrow channel was developed and experimental verification was performed in order to study flow and heat transfer characteristics of annular flow in vertical rectangular narrow channel. Through numerically solving the mathematical model, pressure gradient, boiling heat transfer and liquid film velocity profile in the annular flow region were obtained. The present model could well predict pressure gradient and boiling heat transfer. The liquid film velocity profile of annular flow in the normal direction was not linear, and liquid film velocity gradient was large in the laminar boundary layer. Rectangular narrow channel size and heat flux had significant effect on liquid film velocity profile. Liquid film velocity increased with increasing heat flux and decreased with increasing channel size. The effect of mass flow rate on liquid film velocity was smaller than the effect of heat flux and channel size, and liquid film velocity decreased with increasing mass flow rate.
Energy Technology Data Exchange (ETDEWEB)
Fang, Chin [SLAC National Accelerator Lab., Menlo Park, CA (United States)
2015-02-07
This Technical Note describes how the Zettar team came up with a data transfer cluster design that convincingly proved the feasibility of using high-density servers for high-performance Big Data transfers. It then outlines the tests, operations, and observations that address a potential over-heating concern regarding the use of Non-Volatile Memory Host Controller Interface Specification (NVMHCI aka NVM Express or NVMe) Gen 3 PCIe SSD cards in high-density servers. Finally, it points out the possibility of developing a new generation of high-performance Science DMZ data transfer system for the data-intensive research community and commercial enterprises.
Institute of Scientific and Technical Information of China (English)
李彩霞; 王斯民; 胡鹏睿
2012-01-01
采用数值仿真的方法,模拟了矩形微通道内层流流动换热过程,使用的工质为去离子水.模拟结果揭示了以下结论:矩形微通道侧面的面积热阻会显著随流速而变化,在整体范围内,面积热阻会随流速的增加而减小,且减小的幅度会越来越小.微通道内流体流速的设置还因考虑到泵的承受能力,若流速过高,对泵性能的要求也会提高,因此流速的设置要综合考虑面积热阻和泵的性能.微通道的横截面积尺寸对微通道性能的影响不大.当微通道长宽比为1时,阻力系数最小.%The process of laminar flow and heat transfer inside the rectangular micro channel unit was numerically stimulated with the deionized water as working fluid. The result proves that the speed of flow has the influence on the area thermal resistance of the rectangular micro channel. As the speed of flow increases, the area thermal resistance of the rectangular micro channel reduces; when the speed of flow further increases, the temperature difference and the area thermal resistance reduce slowly. Increasing the speed of flow requests the higher performance for pump output, therefore the design of the flow speed in the micro channel should consider the area thermal resistance and the performance of pump. The cross area size of micro channel has a little influence on the micro channel performance. When the ratio of length to breadth of micro channel is 1, the resistance coefficient is the least.
Energy Technology Data Exchange (ETDEWEB)
You, Byunghyun; Jeong, Yong Hoon [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)
2014-05-15
A fuel assembly had hexagonal structure adjacent to 6 fuel assemblies, which influence to the target fuel assembly due to elimination of duct. For calculating the influence, 6 additional channels were generated between the adjacent fuel assemblies and cross flow model was applied to the channels. The adjacent fuel assemblies were analyzed and the results were used in the additional channel as boundary condition of the target fuel assembly. To design the specifications of duct-less assembly, modified or brand-new thermal-hydraulic methodology is needed which is using MATRA-LMR and CFD codes in this study. The MATRA-LMR is a sub-channel analysis code for LMR that has been developed in Korea Atomic Energy Research Institute. It is designed to analyze a fuel assembly with wire-wrap and duct structure. However, the duct-less core is not able to be analyzed by the MATRA-LMR which doesn't consider cross flow between the fuel assemblies and effect of grid spacer. The code need improvement by editing source code to eliminate effect of duct and analyze pressure drop and mixing between the sub-channels caused by grid spacer and cross flow between the fuel assemblies. To validate reformed pressure drop model and cross flow model in MATRA-LMR, CFD analysis is performed. For verifying the results of CFD, LMR subchannel experimental data is benchmarked which is done by ORNL. The verified CFD for thermalhydraulic analysis calculated pressure drop and mixing caused by grid spacer and cross flow between fuel assemblies.
Alami nia, Amin; Campo, Antonio
2016-12-01
In the present study, the heat transfer enhancement of a bundle of flush-mounted ribbons placed on the floor of a rectangular duct was investigated experimentally. The flush-mounted ribbons act as heat sources and the cooling happens with air. The air flow was three-dimensional, steady, viscous and incompressible under both laminar and turbulent conditions (500 ≤ {Re}_{{Dh }} ≤ 4500). The hydrodynamics and heat transfer behavior of the air flow was studied by means of an active method with application of corona wind. The state of the art of this work revolves around an experimental investigation of an electrohydrodynamics (EHD) active method and heat transfer enhancement from the surfaces of the flush-mounted ribbons. Due to the intricacies of the required experiment, a special apparatus needed to be designed and constructed. The aim of this work is application of EHD active method for convective heat transfer enhancement. In this method the different arrangement of wire electrodes has been achieved. The results show that in same Reynolds numbers and voltages of wires, the heat transfer enhancement was increase in arrangement 1 than other 4 arrangements.
Analysis of Gaseous Slip Flow and Heat Transfer in Micro Rectangular Channels%微矩形槽道内的气体滑移流动和传热分析
Institute of Scientific and Technical Information of China (English)
肖睿; 辛明道; 朱恂
2001-01-01
This article present the theoretical analysis of gas flow and heat transfer in micro rectangular channels in the regime of velocity-slip and temperature-jump. The model is built on the assumption that the bottom wall of the channel is in uniform heat flux while the other three walls are adiabatic, and that the flow and heat transfer is of the hydraulic and thermal fully developed laminar flow of the incompressible fluid. Analytic solutions of the cross-section distributions of both the velocity and temperature are obtained.The friction and heat transfer performances are discussed. The agreement between analytic solutions and experimental results existed shows that in a definite extension of Knudsen number the traditional Navier-Stoks equations and energy equations with the boundary conditions of slip velocity and temperature jump can describe the gaseous flow and heat transfer mechanisms in micro rectangular channels.%分析了微矩形槽道内的不可压缩气体在速度滑移和温度跳跃区的流动和传热过程。在分析模型中，假定矩形槽道底面定热流加热，其余三面绝热，流动和换热均为充分发展，且处于滑移流动区。给出了截面上速度分布和温度分布的分析解，讨论了阻力特性和换热特性，并与实验结果作了比较。二者的吻合程度表明，在一定的Knudsen数范围内，传统的Navier-Stokes方程和能量方程在考虑了速度滑移和温度跳跃影响后可以描述微矩形槽道内的气体流动和传热过程。
Vanasse, Jared
2016-01-01
Using halo effective field theory (EFT), an expansion in $R_{core}/R_{halo}$, where $R_{core}$ is the radius of the core and $R_{halo}$ the radius of the halo nucleus, we calculate the charge and neutron form factors of the two-neutron halo nuclei $^{11}$Li, $^{14}$Be, and $^{22}$C to next-to-leading-order (NLO) by treating them as an effective three-body system. From the form factors we extract the point charge and point matter radii, inter-neutron distance, and neutron opening angle. Agreement is found with existing experimental extractions. Results are given for the point charge and point matter radii for arbitrary neutron core scattering effective range, $\\rho_{cn}$, that can be used for predictions once $\\rho_{cn}$ is measured. Estimates for $\\rho_{cn}$ are also used to make NLO predictions. Finally, our point charge radii are compared to other halo-EFT predictions, and setting the core mass equal to the neutron mass our point charge radius is found to agree with an analytical prediction in the unitary l...
Ameri, A. A.; Rigby, D. L.; Steinthorsson, E.; Gaugler, Raymond (Technical Monitor)
2002-01-01
The Low Reynolds number version of the Stress-omega model and the two equation k-omega model of Wilcox were used for the calculation of turbulent heat transfer in a 180 degree turn simulating an internal coolant passage. The Stress-omega model was chosen for its robustness. The turbulent thermal fluxes were calculated by modifying and using the Generalized Gradient Diffusion Hypothesis. The results showed that using this Reynolds Stress model allowed better prediction of heat transfer compared to the k-omega two equation model. This improvement however required a finer grid and commensurately more CPU time.
Turbulent heat transfer of liquid metal inside the sub-channels of reactor core%液态金属在堆芯子通道内的湍流换热
Institute of Scientific and Technical Information of China (English)
葛志浩; 彭勇升; 吕逸君; 邓维平; 赵平辉
2015-01-01
采用 Speziale-Sarkar-Gatski (SSG)雷诺应力模型对液态金属在堆芯子通道内的流动、传热过程进行计算流体动力学(Computational Fluid Dynamics, CFD)模拟，研究雷诺数(Re)、分子普朗特数(Pr)、格拉晓夫数(Gr)、节径比(P/D)等无量纲参数对湍流换热的影响。比较无量纲对流换热系数(Nu)可以看出，CFD 预测值与实验值及经验关系式符合得较好。对各种不同无量纲参数下的计算结果进行分析发现：在 P/D 和 Re 数相同条件下，三角形子通道的壁面温度分布比方形更均匀，换热情况更好；提高 Re 数，增大 P/D，选用 Pr 数大的冷却剂，可有效改善温度和换热的周向分布不均情况；在 Re 数大于10000的条件下，浮力对液态金属换热的影响可忽略不计。%Background: Liquid metal has been proposed as the coolant of the fourth generation nuclear reactor and the accelerator driven sub-critical system. Due to its low molecular Prandtl number (Pr), liquid metal differs from other coolants like water or gas in heat transfer. Purpose: This study aims to investigate the character of heat transfer of liquid metal inside the reactor core. Methods: Speziale-Sarkar-Gatski (SSG) Reynolds stress model was applied to the Computational Fluid Dynamics (CFD) prediction of liquid metal flow and heat transfer inside the sub-channels of the reactor core. Effect of different dimensionless parameters, e.g. Reynolds number (Re), Pr, Grashof number (Gr) and pitch-to-diameter ratio (P/D) on the turbulent heat transfer calculated results was investigated. Results: The dimensionless convective heat transfer coefficient (Nu), predicted by the CFD method, agrees well with the experimental data and the empirical relations. Conclusion: Based on the analysis of various dimensionless parameters, it is found that the heat exchange performs better in triangular fuel assembly sub-channels than that in square sub-channels, under the same
An analytical channel thermal noise model for deep-submicron MOSFETs with short channel effects
Jeon, Jongwook; Lee, Jong Duk; Park, Byung-Gook; Shin, Hyungcheol
2007-07-01
In this work, an analytical channel thermal noise model for short channel MOSFETs is derived. The transfer function of the noise was derived by following the Tsividis' method. The proposed model takes into account the channel length modulation, velocity saturation, and carrier heating effects in the gradual channel region. Modeling results show good agreements with the measured noise data.
Hayat, T.; Farooq, S.; Alsaedi, A.; Ahmad, B.
2016-08-01
The purpose of present investigation is to study the Hall and MHD effects on peristaltic flow of Carreau-Yasuda fluid in a convectively curved configuration. Thermal radiation, Soret and Dufour effects are also accounted. The channel walls comprised the no slip and compliant properties. Constitutive equations for mass, momentum, energy and concentration are first modeled in view of considered assumptions and then simplified under long wavelength and low Reynolds number approximation. Solution of the resulting system of equations is carried out via a regular perturbation technique. Physical behaviors of velocity, temperature, concentration and streamlines are discussed with the help of graphical representation.
Institute of Scientific and Technical Information of China (English)
郑志皋; 陶乐仁; 黄理浩
2014-01-01
A single-side heating apparatus is set up to study the flow boiling and heat transfer in vertical narrow rectangular channel,experiment research on flow boiling and heat transfer characteristics in a vertical narrow rectangular channel with the section of 250mm ×5 mm is carried out.According to the experimental analysis:(1 )With the increase of dryness,the local heat transfer coefficient firstly increases then decreases ,there is a maximum,which is saturated nucleate boiling region ,the steam quality is close to zero,also it is close to the onset of boiling.Accordingly flow mode of fluid is from single phase,bubble,slug, churn to annular flow.(2)For flow boiling heat transfer,nuclear boiling heat transfer is significantly affected by heat flux,but liquid film evaporation is nearly not.So it is assumed that heat transfer is caused by the change of heat flux.(3 )The change of inlet temperature has influence on single-phase flow heat transfer coefficient,but flow boiling heat transfer coefficient has great re-lationship with flow pattern and generated bubbles,and not inlet temperature.%建立单面加热垂直矩形窄通道流动沸腾换热试验装置，针对截面250mm ×3．5mm的窄缝通道，对水流动沸腾换热特性进行试验研究。通过试验分析可知：（1）随着干度的增加，局部换热系数先增加后减小，有一个最大值，此时处于饱和核沸腾区域，其蒸汽干度也接近于0，同时也接近于沸腾起始点。相应地流体从单相流-泡状-块状流-搅拌-环状流转变。（2）在流动沸腾换热中，热流密度对核态沸腾换热有明显影响，而对流动沸腾液膜蒸发的影响甚小，所以可以认为由热流密度的变化而引起的换热变化，主要表现在核态沸腾。（3）入口温度的变化对单相流动的换热系数有影响，而沸腾换热系数与流型及汽泡的产生及扰动有极大关系，入口温度对流动沸腾局部换热系数基本没有影响。
Institute of Scientific and Technical Information of China (English)
李虹波; 陈炳德; 熊万玉
2011-01-01
在流动传热基础试验平台上进行了矩形通道干涸后过渡沸腾传热试验.对过渡沸腾的传热特性进行分析;对进口含汽率、质量流速、系统压力等各热工水力参数对过渡沸腾传热的影响进行试验研究.结果表明:干涸后过渡沸腾是一个不稳定的传热过程,壁面温度发生明显的脉动,过渡沸腾会引起质量流速和流道进出口压降等流动参数的脉动;进口含汽率的增加会导致过渡沸腾热流密度减小,壁面温度升高,传热系数减小;质量流速的增大或者系统压力的升高均会导致过渡沸腾热流密度增大,壁面温度降低,传热系数增大.%The experiment of post-dryout transition boiling heat transfer in rectangular channel has been carried out on the basic experimental loop of flow and heat transfer. The characteristics of the transition boiling heat transfer is analyzed. The effects of thermal-hydraulic parameters such as inlet quality,mass flow velocity,and system pressure on the characteristics of post-dryout transition boiling heat transfer are experimentally researched. The results show that the post-dryout transition boiling is unstable,wall temperature oscillates fiercely,and the mass flow velocity and pressure drop oscillate as also; the post-dryout transition boiling heat flux and heat transfer coefficient are decreased,but the wall temperature is increased with the increasing of inlet quality; and the post-dryout transition boiling heat flux and heat transfer coefficient are increased,but the wall temperature is decreased with the increasing of mass flow velocity or system press.
Lavanya, B.
2017-07-01
The present paper analyses a solution for the transient free flow on a viscous and incompressible fluid between two vertical walls as a result of heta and mass transfer. The perturbation technique ahs been used to find the solutions for the velocity and temperature fields by solving the governing partial differential equations. The temperature of the one plate is assumed to be fluctuating. The effcets of the various parametrs entering into the problem, on the velocity and the temprature are depivted graphically. The impact of various parameters (Da, Rv, Pr, R and S) on velocity and temperature fields are shown graphically. The expressions for skin friction at both walls are also obtained.
Institute of Scientific and Technical Information of China (English)
高维和; 黄沛; 牛志勇
2009-01-01
在网络时代,电子商务企业专注于产品销售,而将生产外包.凭借着贴近市场的网络优势,它们拥有不能完全契约化的产品创新的专有信息,面临着如何选择合适的渠道组织模式,防止信息的攫取和误用.文中表明,电子商务企业是否进行创新性投资和制造商最后生产产品的质量相关,网络销售商传递信息时,制造商机会主义行为动机取决于自身销售能力和相应投资的规模,并提出如何规避信息传递的机会主义风险,提升渠道价值的相应措施.%More and more e-commerce corporations specialize in product end-marketing and outsourcing production in network times. And taking advantage of Internet, they can promptly find the innovation information of product firstly that cannot be contracted. However, they will face how to choose suitable channel organization in order to prevent the misappropriation of the information. The paper explains whether e-commerce corporations invest to innovate decided by the quality of the product that producer presents. And the motivation of producer's opportunism related with sales ability and investment scale. We also analyze the mechanism in the choice of channel though the perspective of information transferring. And finally we suggest the measures of how to avoid opportunism and increase the channel value.
LAMINAR FLOW AND HEAT TRANSFER IN MICRO－ANNULAR CHANNEL IN SLIP FLOW REGIME%滑移流区内微环缝槽道中的层流流动与换热
Institute of Scientific and Technical Information of China (English)
朱恂; 辛明道
2001-01-01
In this article, the momentum and energy equations with the boundary conditions of slip velocity and temperature jump are solved for the hydraulic and thermalfully developed laminar flow of the incompressible fluid in micro-annular channel. A theoretical analysis is conducted for flow and heat transfer characteristics in this micro channel on the condition of one wall heated alonewith uniform heat flux and two walls heated with different heat flux in slipflow regime. The influences of the Kn number, the ratio of inner diameter toouter diameter and the heat flux ratio on the flow and heat transfercharacteristics are discussed, respectively. The results show that the frictioncoefficient and Nusselt number in the micro-annular channel are smaller thanthat in the macrochannel, and decrease with the increase of Kn number.%本文针对微环缝槽道采用速度滑移和温度跳跃边界条件求解了不可压缩气体的N-S方程和能量方程，理论分析了微环缝槽道在单侧或双侧不同热流密度加热条件下的流动与层流换热特性，讨论了Kn数、内外径比对流动阻力及换热特性的影响。结果表明：滑移流区微环缝通道内的流阻和Nusselt数明显低于连续流区；且随着Kn数的增加，流阻和Nusselt数均减小；但其随内外径比r*的变化趋势与连续流区相似。
Datta, S.; Jones, W. L.; Ebrahimi, H.; Chen, R.; Payne, V.; Kroodsma, R.
2014-12-01
The first step in radiometric inter-calibration is to ascertain the self-consistency and reasonableness of the observed brightness temperature (Tb) for each individual sensor involved. One of the widely used approaches is to compare the observed Tb with a simulated Tb using a forward radiative transfer model (RTM) and input geophysical parameters at the geographic location and time of the observation. In this study we intend to test the sensitivity of the RTM to uncertainties in the input geophysical parameters as well as to the underlying physical assumptions of gaseous absorption and surface emission in the RTM. SAPHIR, a cross track scanner onboard Indo-French Megha-Tropique Satellite, gives us a unique opportunity of studying 6 dual band 183 GHz channels at an inclined orbit over the Tropics for the first time. We will also perform the same sensitivity analysis using the Advance Technology Microwave Sounder (ATMS) 23 GHz and five 183 GHz channels. Preliminary analysis comparing GDAS and an independent retrieved profile show some sensitivity of the RTM to the input data. An extended analysis of this work using different input geophysical parameters will be presented. Two different absorption models, the Rosenkranz and the MonoRTM will be tested to analyze the sensitivity of the RTM to spectroscopic assumptions in each model. Also for the 23.8 GHz channel, the sensitivity of the RTM to the surface emissivity model will be checked. Finally the impact of these sensitivities on radiometric inter-calibration of radiometers at sounding frequencies will be assessed.
Institute of Scientific and Technical Information of China (English)
曾文良; 张正国
2012-01-01
对并流多通道进出口(MPC)轴流管壳式换热器壳程传热性能进行数值模拟,分别研究了管排数N,Re,不同开孔率的挡板对壳程进口段的局部传热系数分布、局部平均Nu的分布、换热器的平均Nu等特性的影响.结果表明:在无挡板条件下,随着N的减小,壳程传热系数分布不均现象得到有效的遏制,N=7时基本上无传热死区.挡板的存在,不但使得进口段的局部传热系数分布更加均匀,而且能够提高换热器的整体传热Nu.不同参数的挡板之间,挡板1的作用最为明显,可以使得Nu提高10％-12％.%Shell-side heat transfer performances of inlet and outlet of longitudinal flow shell-and-tube heat exchanger with multi-parallel-channel (MPC) were numerically simulated. The influences of baffle on the local heat transfer coefficient distribution of inlet region, local-mean Nu distributions, and mean Nu of heat exchanger were investigated with pipe-line-number, N, Re and different punching ratio, respectively. The results reveal that with the decreasing of N, the non-uniformity of local heat transfer coefficient is effectively improved and there is not any heat transfer skip area when N =7. It also shows that fluid-distribution-baffles ( FDBs) can not only effectively improve the local heat transfer coefficient distribution of inlet region but also enhance the global Nu of heat exchanger. The comparison of different FDBs shows that FDB of No. 1 has the best performance and can enhance Nu by 10%-12%.
Institute of Scientific and Technical Information of China (English)
白超; 韩勇军; 伊寅; 史小锋; 郭兆元; 封启玺; 路骏
2016-01-01
针对水下航行器用冷凝器的结构特性和使用环境，建立冷凝器中小通道内蒸汽冷凝换热过程的焓值模型，对流换热系数模型和压力模型。根据4种不同的换热系数计算式，求解对应关系式下的焓值、温度、压力和干度仿真值，并结合实验数据进行对比分析，得到在单相区采用 D-B关联式，在两相区采用 A-R关联式，计算的结果误差最小。并以此为基础，对小通道的截面尺寸进行计算分析，计算结果表明：当通道截面宽度为6 mm时，小通道具有较好的流动换热能力，为水下航行器的工程设计提供重要参考。%According to the underwater environment and use structural characteristics of the condenser of underwater vehicle, the paper develops the the model of enthalpy, the model of convective heat transfer coefficient and the model of pressure. Based on the four kinds of formula of heat transfer coefficient, the paper solves the simulation value of the enthalpy, temperature, pressure and dry degree, and compared them with the experimental data. The results show that using the D-B correlation in the single-phase region and using A-R correlation in two-phase region, the simulation results is most consistent with experimental data. And based on this, this paper calculates and analyzes the cross section size of the small channel. The results show that when the width is 6 mm, the small channel has a good flow and heat transfer capability, and provide an important reference for the engineering design of underwater vehicle.
Liu, Gaisheng; Zheng, C.; Gorelick, S.M.
2007-01-01
This paper evaluates the dual-domain mass transfer (DDMT) model to represent transport processes when small-scale high-conductivity (K) preferential flow paths (PFPs) are present in a homogenous porous media matrix. The effects of PFPs upon solute transport were examined through detailed numerical experiments involving different realizations of PFP networks, PFP/matrix conductivity contrasts varying from 10:1 to 200:1, different magnitudes of effective conductivities, and a range of molecular diffusion coefficients. Results suggest that the DDMT model can reproduce both the near-source peak and the downstream low-concentration spreading observed in the embedded dendritic network when there are large conductivity contrasts between high-K PFPs and the low-K matrix. The accuracy of the DDMT model is also affected by the geometry of PFP networks and by the relative significance of the diffusion process in the network-matrix system. Copyright 2007 by the American Geophysical Union.
Mishima, A.; Nasu, K.
1989-03-01
The one-dimensional extended Peierls-Hubbard model with half-filled-band electrons is studied in order to clarify the lattice relaxation path of the photogenerated charge-transfer excitation in halogen-bridged mixed-valence metal complexes. The ground and excited states are calculated within mean-field theory for electrons and the adiabatic approximation for phonons. It is concluded that the main origin of the photoinduced absorption is a distant pair of the hole-polaron and the electron-polaron. This distant pair is created not from the ground state of the self-trapped exciton (STE), but from the excited states of the STE through their autodissociation. This is consistent with the experiment on the excitation energy dependence of the photoinduced absorption yield.
Yamashita, M. T.; Marques de Carvalho, R. S.; Frederico, T.; Tomio, Lauro
2012-08-01
Relevant to experimental investigations on the 22C properties, we are correcting numerical results presented in [M.T. Yamashita, R.S. Marques de Carvalho, T. Frederico, L. Tomio, Phys. Lett. B 697 (2011) 90], updating our estimate for the two-neutron separation energy, and adding the charge radius prediction for this halo nucleus with respect to 20C: √{ - } ≳ 0.9 fm.
Institute of Scientific and Technical Information of China (English)
汪洋; 罗新奎; 王小军; 杨祺; 张文瑞
2016-01-01
微尺度高效换热器具有结构紧凑、热阻小、换热系数大等特点。以A/B混合制冷剂为工质，对其密度、饱和蒸气压、表面张力和黏度进行了计算并拟合出标准差在1%内的相应的物性温度曲线，并对其在-45、20、60℃入口温度下在1.1/1.2 mm尺寸的矩形微通道内的换热特性进行了实验研究，在给定400 W外热流下，不同入口温度有效换热热流密度都在50000 W/m2左右，入口温度越高，平均换热系数越大。%Microscale high efficiency heat exchanger has the character of compact structure,low thermal resistance and high heat transfer coefficient. The density,saturated pressure,surface tension and viscosity of the refrigerant mixed with A and B were calculated and curve fitting of physical properties to temperature with the standard deviation under 1 percent were established. The heat transfer characteristics in a rectangle micro channel with the size of 1.1 mm/1.2 mm at the inlet temperature of-45,20 and 60℃the external heat flux density of 400 W is studied,the different working condi-tion has the same effective heat exchange heat flux density while the average heat transfer coefficient grows with the inlet temperature.
Piégay, Hervé; Moulin, Bertrand; Hupp, Cliff R.
2017-02-01
When and whence does wood enter large mountain alluvial rivers? How stable through time are characteristics and quantities of wood deposited in a reach? These simple questions related to the complex practice of wood budgeting are explored on the Isère River in France. We hypothesise that (i) the wood originates from the riparian zone all along the alluvial reach and that (ii) the characters and quantity of wood in the reach can vary through time according to flood occurrence and provenance. In order to validate these hypotheses, two complementary approaches were performed: (i) wood pieces were surveyed along 190 km river length and taxonomy, in-channel wood macromorphology, and dendrochemistry were used to infer wood origin (local vs. upstream, respective subbasin contributions) and transport conditions; (ii) wood movement was monitored using both tracking techniques in specific sampling plots and with an experiment orchestrated using wood placement coupled with a significant artificial flood. Surveys were done over a period of 3 years so as to include two distinct sampling events to explore wood deposition and mobilisation within a channel network under different flood conditions. One of the subbasins, the Arly River, underwent a 1-in-30-year flood in 2004, allowing us to assess its effect on in-channel wood quantity and characteristics. Results confirm that wood is primarily introduced by erosion from river banks but they are not always as close as expected from the sites of deposition. Temporal variability of wood introduced, deposited, and transferred downstream is also significant in terms of abundance and origin as shown by dendrochemical and macromorphological signatures. The types of wood observed along the channel length changes through time. Large flood signature can be detected from wood characteristics and uplands make a slight contribution. But in average, wood characteristics do not change much (no significant difference between years and tributaries
The lifting scheme of 4-channel orthogonal wavelet transforms
Institute of Scientific and Technical Information of China (English)
PENG Lizhong; CHU Xiaoyong
2006-01-01
The 4-channel smooth wavelets with linear phase and orthogonality are designed from the 2-channel orthogonal wavelets with high transfer vanishing moments. Reversely, for simple lifting scheme of such 4-channel orthogonal wavelet transforms, a new 2-channel orthogonal wavelet associated with this 4-channel wavelet is constructed. The new 2-channel wavelet has at least the same number of vanishing moments as the associated 4-channel one. Finally, by combining the two such 2-channel wavelet systems, the lifting scheme of 4-channel orthogonal wavelet transform, which has simple structure and is easy to apply, is presented.
Institute of Scientific and Technical Information of China (English)
唐凌虹; 谭思超; 高璞珍
2014-01-01
In this study , the effects of three types of longitudinal vortex generator (LVG) configurations on the flow and heat transfer characteristics in a rectangular channel were investigated and analyzed by field synergy principle .The results show that the temperature of plate fuel assembly can be decreased and the critical heat flux (CHF) of the reactor will be increased .Compared by the performance evaluation parameter ,JF factor ,the results indicate that “common flow up”combined with ellipse pole configura-tion can bring about more enhancement of heat transfer at a modest expense of the addi-tional pressure-loss .%对渐缩式纵向涡发生器与椭圆支柱共同作用下矩形通道内的流动换热性能进行了研究，与渐缩式纵向涡发生器、渐扩式纵向涡发生器和光通道的流动换热性能进行了对比，并利用场协同原理对其换热机理进行了分析。结果表明：纵向涡发生器可增强换热，有利于降低加热板的表面温度，从而提高反应堆堆芯的C H F值。采用JF因子对各矩形通道的综合流动换热性能进行了比较，结果表明，渐缩式纵向涡发生器与椭圆支柱组合结构能以较小的阻力代价得到较大的换热效果，是一种理想的强化换热方式。
Martinac, Boris
Living cells are exposed to a variety of mechanical stimuli acting throughout the biosphere. The range of the stimuli extends from thermal molecular agitation to potentially destructive cell swelling caused by osmotic pressure gradients. Cellular membranes present a major target for these stimuli. To detect mechanical forces acting upon them cell membranes are equipped with mechanosensitive (MS) ion channels. Functioning as molecular mechanoelectrical transducers of mechanical forces into electrical and/or chemical intracellular signals these channels play a critical role in the physiology of mechanotransduction. Studies of prokaryotic MS channels and recent work on MS channels of eukaryotes have significantly increased our understanding of their gating mechanism, physiological functions, and evolutionary origins as well as their role in the pathology of disease.
Ogata, Kazuyuki; Furumoto, Takenori; Matsumoto, Takuma; Yahiro, Masanobu
2012-01-01
The breakup cross section (BUX) of 22C by 12C at 250 MeV/nucleon is evaluated by the continuum-discretized coupled-channels method incorporating the cluster-orbital shell model (COSM) wave functions. Contributions of the low-lying 0+_2 and 2+_1 resonances predicted by COSM to the BUX are investigated. The 2+_1 resonance gives a narrow peak in the BUX, as in usual resonant reactions, whereas the 0+_2 resonant cross section has a peculiar shape due to the coupling to the nonresonant continuum, i.e., the Fano effect. By changing the scattering angle of 22C after the breakup, a variety of shapes of the 0+_2 resonant cross sections is obtained. Mechanism of the appearance of the sizable Fano effect in the breakup of 22C is discussed.
Badikyan, Karen
2016-01-01
The possibility of channeling the low-energy relativistic positrons around separate crystallographic axes with coaxial symmetry of negative ions in some types of crystals is shown. The process of annihilation of positrons with electrons of medium was studied in detail.
Institute of Scientific and Technical Information of China (English)
Alice Yang
2009-01-01
@@ "Brands" and "Channels" are the two most important things in Ku-Hai Chen's eyes when doing business with Main-land China. Ku-Hai Chen, Executive Director of the International Trade Institute of Taiwan External Trade Development Council (TAITRA), flies frequently between Chinese Taipei and Mainland China, and was in Beijing earlier this month for his seminar.
FMCG companies specific distribution channels
Directory of Open Access Journals (Sweden)
Ioana Barin
2009-12-01
Full Text Available Distribution includes all activities undertaken by the producer, alone or in cooperation, since the end of the final finished products or services until they are in possession of consumers. The distribution consists of the following major components: distribution channels or marketing channels, which together form a distribution network; logistics o rphysical distribution. In order to effective achieve, distribution of goods requires an amount of activities and operational processes related to transit of goods from producer to consumer, the best conditions, using existing distribution channels and logistics system. One of the essential functions of a distribution is performing acts of sale, through which, with the actual movement of goods, their change of ownership takes place, that the successive transfer of ownership from producer to consumer. This is an itinerary in the economic cycle of goods, called the distribution channel.
Channel Power in Multi-Channel Environments
M.G. Dekimpe (Marnik); B. Skiera (Bernd)
2004-01-01
textabstractIn the literature, little attention has been paid to instances where companies add an Internet channel to their direct channel portfolio. However, actively managing multiple sales channels requires knowing the customers’ channel preferences and the resulting channel power. Two key compon
Channel Power in Multi-Channel Environments
M.G. Dekimpe (Marnik); B. Skiera (Bernd)
2004-01-01
textabstractIn the literature, little attention has been paid to instances where companies add an Internet channel to their direct channel portfolio. However, actively managing multiple sales channels requires knowing the customers’ channel preferences and the resulting channel power. Two key
Energy Technology Data Exchange (ETDEWEB)
Al Omari, S.A.B. [UAE University, Mechanical Engineering Department, Al Ain (United Arab Emirates)
2012-10-15
Enhancement in the heat removal from hot water co-flowing in a mini-channel in a direct contact manner with two liquid metals, gallium and mercury, is investigated numerically. Results show that the liquid metals lead to superior heat removal from hot water co-flowing in the channel as compared to the case when only water flows in the channel. Moreover, it is found that gallium yields higher heat removal from water than mercury by about 15 %. This percentage, representing the superiority of gallium over mercury increases to about 20 % under conditions when the mass flow rate of both the liquid metal and the co-flowing water are doubled. The results reported showed numerical mesh independence. However, the results show much dependence on the spatial discretization scheme adopted where it is found that first order upwind scheme yields somewhat over predicted heat exchange rates in the channel, as compared with the case when a second order scheme is used. It is found further that the channel efficiency in removing heat from the water is remarkable in the first half of the overall channel length where in general the heat removed in the first 10 mm of the channel length is found to be about 70 % of the total heat removed. This percentage is a bit less than that when only water flows in the channel. (orig.)
In, Visarath; Longhini, Patrick; Kho, Andy; Neff, Joseph D.; Leung, Daniel; Liu, Norman; Meadows, Brian K.; Gordon, Frank; Bulsara, Adi R.; Palacios, Antonio
2012-12-01
The nonlinear channelizer is an integrated circuit made up of large parallel arrays of analog nonlinear oscillators, which, collectively, serve as a broad-spectrum analyzer with the ability to receive complex signals containing multiple frequencies and instantaneously lock-on or respond to a received signal in a few oscillation cycles. The concept is based on the generation of internal oscillations in coupled nonlinear systems that do not normally oscillate in the absence of coupling. In particular, the system consists of unidirectionally coupled bistable nonlinear elements, where the frequency and other dynamical characteristics of the emergent oscillations depend on the system's internal parameters and the received signal. These properties and characteristics are being employed to develop a system capable of locking onto any arbitrary input radio frequency signal. The system is efficient by eliminating the need for high-speed, high-accuracy analog-to-digital converters, and compact by making use of nonlinear coupled systems to act as a channelizer (frequency binning and channeling), a low noise amplifier, and a frequency down-converter in a single step which, in turn, will reduce the size, weight, power, and cost of the entire communication system. This paper covers the theory, numerical simulations, and some engineering details that validate the concept at the frequency band of 1-4 GHz.
Selective permeability of gap junction channels.
Goldberg, Gary S; Valiunas, Virginijus; Brink, Peter R
2004-03-23
Gap junctions mediate the transfer of small cytoplasmic molecules between adjacent cells. A family of gap junction proteins exist that form channels with unique properties, and differ in their ability to mediate the transfer of specific molecules. Mutations in a number of individual gap junction proteins, called connexins, cause specific human diseases. Therefore, it is important to understand how gap junctions selectively move molecules between cells. Rules that dictate the ability of a molecule to travel through gap junction channels are complex. In addition to molecular weight and size, the ability of a solute to transverse these channels depends on its net charge, shape, and interactions with specific connexins that constitute gap junctions in particular cells. This review presents some data and interpretations pertaining to mechanisms that govern the differential transfer of signals through gap junction channels.
Technology and technology transfer: some basic issues
Shamsavari, Ali; Adikibi, Owen; Taha, Yasser
2002-01-01
This paper addresses various issues relating to technology and transfer of technology such as technology and society, technology and science, channels and models of technology transfer, the role of multinational companies in transfer of technology, etc. The ultimate objective is to pose the question of relevance of some existing models and ideas like technological independence in an increasingly globalised world economy.
Quantum teleportation without classical channel
Al Amri, M.; Li, Zheng-Hong; Zubairy, M. Suhail
2016-11-01
For the first time, we show how quantum teleportation can be achieved without the assistance of classical channels. Our protocol does not need any pre-established entangled photon pairs beforehand. Just by utilizing quantum Zeno effect and couterfactual communication idea, we can achieve two goals; entangling a photon and an atom and also disentangling them by non-local interaction. Information is completely transferred from atom to photon with controllable disentanglement processes. More importantly, there is no need to confirm teleportation results via classical channels.
Sivakumar, A.; Alagumurthi, N.; Senthilvelan, T.
2016-07-01
The microchannels are device used to remove high heat fluxes from smaller area. In this experimental research work the heat transfer performance of nanofluids of Al2O3/water and CuO/water were compared. The important character of such fluids is the enhanced thermal conductivity, in comparison with base fluid without considerable alteration in physical and chemical properties. The effect of forced convective heat transfer coefficient was calculated using serpentine shaped microchannel heat exchanger. Furthermore we calculated the forced convective heat transfer coefficient of the nanofluids using theoretical correlations in order to compare the results with the experimental data. The heat transfer coefficient for different particle concentration and temperature were analysed using forced convection heat transfer using nanofluids. The findings indicate considerable enhancement in convective heat transfer coefficient of the nanofluids as compared to the basefluid. The results also shows that CuO/water nanofluid has increased heat transfer coefficient compared with Al2O3/water and base fluids. Moreover the experimental results indicate there is increased forced convective heat transfer coefficient with the increase in nano particle concentration.
Investigating Knowledge Transfer Mechanisms for Oil Rigs
DEFF Research Database (Denmark)
Vianello, Giovanna; Ahmed, Saeema
2009-01-01
It is widely recognized, both in industry and academia, that clear strategies in knowledge transfer positively influence the success of a firm. A firm should support the transfer of knowledge by standardizing communication channels within and across departments, based upon personalization......, codification or a combination of these two strategies. The characteristics of the business influence the choice of communication channels used for knowledge transfer. This paper presents a case study exploring the transfer of knowledge within and across projects, specifically the transfer of service knowledge...... in the case of complex machinery. The strategies used for knowledge transfer were analysed and compared with the expected transfer mechanisms, similarities and differences were investigated and are described. A family of four identical rigs for offshore drilling was the selected case. The transfer...
Radionuclide transfer. Radionuklid Transfer
Energy Technology Data Exchange (ETDEWEB)
Gerber, G.B.
1993-01-01
The research project described here had the aim to obtain further information on the transfer of nuclides during pregnancy and lactation. The tests were carried out in mini-pigs and rats receiving unchanging doses of radionuclides with the food. The following findings were revealed for the elements examined: Fe, Se, Cs and Zn were characterized by very high transfer levels in the mother, infant and foetus. A substantial uptake by the mother alone was observed for Co, Ag and Mn. The uptake by the foetus and infant here was 1 to 10 times lower. A preferential concentration in certain tissues was seen for Sr and Tc; the thyroid levels of Tc were about equally high in mothers and infants, while Sr showed less accumulation in the maternal bone. The lanthanide group of substances (Ce, Eu and Gd as well as Y and Ru) were only taken up to a very limited extent. The uptake of the examined radionuclides (Fe, Co, Ag, Ce) with the food ingested was found here to be ten times greater in rats as compared to mini-pigs. This showed that great caution must be observed, if the behaviour of radionuclides in man is extrapolated from relevant data obtained in rodents. (orig./MG)
Theoretical postulation of PLC channel model
Directory of Open Access Journals (Sweden)
Alexandru Ionuţ Chiuţă
2009-05-01
Full Text Available The objective of this document is to supply atheoretical basis for modelling the communicationlinks over powerlines. A comprehensive summary oftransmission properties and the noise scenario onpublic mains supply when used for data transmissionare given.Different PLC models - PLC channel, noise inPLC channel, coupling units, filters and conditioningdevices – will be created and they will be used tosimulate the PLC channel.PLC applications will have to work at veryunusual channels, solely designed for optimalelectrical power transportation, completelydisregarding signal transmission at high frequencies.It is shown that the typical properties aredescribed by transfer functions and noise scenariostypical for access and inhouse networks. The generaltransfer function for different channel types is derivedand, since an emulation system should reproducetypical classes of channels rather than singlemeasurements, the transfer function is concretisedwith reference channels. These are later serving asbasis for development of channel simulators andchannel emulators. Special attention is paid tomodelling of aperiodic impulsive noise since PLCsystems are reacting very sensitive to them and thisclass of noise has been insufficiently considered so far.
Comparison of proton irradiated P-channel and N-channel CCDs
Energy Technology Data Exchange (ETDEWEB)
Gow, Jason P.D., E-mail: j.p.d.gow@open.ac.uk [e2v Centre for Electronic Imaging, Planetary and Space Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Murray, Neil J.; Holland, Andrew D. [e2v Centre for Electronic Imaging, Planetary and Space Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Burt, David; Pool, Peter J. [e2v Technologies plc, 106 Waterhouse Lance, Chelmsford, Essex CM1 2QU (United Kingdom)
2012-09-11
Charge transfer inefficiency and dark current effects are compared for e2v Technologies plc p-channel and n-channel CCDs, both irradiated with protons. The p-channel devices, prior to their irradiation, exhibited twice the dark current and considerable worse charge transfer inefficiency (CTI) than a typical n-channel. The radiation induced increase in dark current was found to be comparable with n-channel CCDs, and its temperature dependence suggest that the divacancy is the dominant source of thermally generated dark current pre- and post-irradiation. The factor of improvement in tolerance to radiation induced CTI varied by between 15 and 25 for serial CTI and 8 and 3 for parallel CTI, between -70 Degree-Sign C and -110 Degree-Sign C, respectively.
Two-Neutron Alignment in 127Xe
Chakraborty, S.; Sharma, H. P.; Tiwary, S. S.; Majumder, C.; Prajapati, P. K.; Rai, S.; Popli, P.; Singh, M.; Bhattacharjee, S. S.; Singh, R. P.; Muralithar, S.; Banerjee, P.; Ganguly, S.; Kumar, S.; Kumar, A.; Palit, R.
2017-08-01
High spin states in 127Xe have been investigated via 9Be induced fusion-evaporation reaction at 48 MeV. Spin and parity of excited states up to ˜ {47/2} have been confirmed from angular correlation and linear polarization results. Rotational alignment of the second pair of h 11/2 neutrons has been observed at ω ˜ 0.44 MeV; beyond that, the band is associated with ν[ h 11/2]3 configuration. The alignment phenomena has been discussed in comparison with the neighboring 125,129Xe.
Investigating Knowledge Transfer Mechanisms for Oil Rigs
DEFF Research Database (Denmark)
Vianello, Giovanna; Ahmed, Saeema
2009-01-01
of lessons learnt from one rig to the next, and the actual situation emerged. Various approaches for transferring knowledge were elicited and analysed with regard to the types of knowledge that were transferred and the context in which they were used. This study indicates factors that should be considered......It is widely recognized, both in industry and academia, that clear strategies in knowledge transfer positively influence the success of a firm. A firm should support the transfer of knowledge by standardizing communication channels within and across departments, based upon personalization......, codification or a combination of these two strategies. The characteristics of the business influence the choice of communication channels used for knowledge transfer. This paper presents a case study exploring the transfer of knowledge within and across projects, specifically the transfer of service knowledge...
DEFF Research Database (Denmark)
Nielsen, Søren Bo
2014-01-01
Against a background of rather mixed evidence about transfer pricing practices in multinational enterprises (MNEs) and varying attitudes on the part of tax authorities, this paper explores how multiple aims in transfer pricing can be pursued across four different transfer pricing regimes. A MNE h...
Kasper, Gabriele
1992-01-01
Attempting to clarify the concept of pragmatic transfer, this article proposes as a basic distinction Leech/Thomas' dichotomy of sociopragmatics versus pragmalinguistics, presenting evidence for transfer at both levels. Issues discussed include pragmatic universals in speech act realization, conditions for pragmatic transfer, communicative…
Flavonoid regulation of EAG1 channels
Carlson, Anne E.; Brelidze, Tinatin I.
2013-01-01
The voltage-gated, K+-selective ether á go-go 1 (EAG1) channel is expressed throughout the brain where it is thought to regulate neuronal excitability. Besides its normal physiological role in the brain, EAG1 is abnormally expressed in several cancer cell types and promotes tumor progression. Like all other channels in the KCNH family, EAG1 channels have a large intracellular carboxy-terminal region that shares structural similarity with cyclic nucleotide–binding homology domains (CNBHDs). EAG1 channels, however, are not regulated by the direct binding of cyclic nucleotides and have no known endogenous ligands. In a screen of biological metabolites, we have now identified four flavonoids as potentiators of EAG1 channels: fisetin, quercetin, luteolin, and kaempferol. These four flavonoids shifted the voltage dependence of activation toward more hyperpolarizing potentials and slowed channel deactivation. All four flavonoids regulated channel gating with half-maximal concentrations of 2–8 µM. The potentiation of gating did not require the amino-terminal or post-CNBHD regions of EAG1 channels. However, in fluorescence resonance energy transfer and anisotropy-based binding assays, flavonoids bound to the purified CNBHD of EAG1 channels. The CNBHD of KCNH channels contains an intrinsic ligand, a conserved stretch of residues that occupy the cyclic nucleotide–binding pocket. Mutations of the intrinsic ligand in EAG1 (Y699A) potentiated gating similar to flavonoids, and flavonoids did not further potentiate EAG1-Y699A channels. Furthermore, the Y699A mutant CNBHD bound to flavonoids with higher affinity than wild-type CNBHD. These results suggest that the flavonoids identified here potentiated EAG1 channels by binding to the CNBHD, possibly by displacing their intrinsic ligand. EAG1 channels should be considered as a possible target for the physiological effects of flavonoids. PMID:23440277
Optimization of bandwidth of communication channels of corporate networks
Directory of Open Access Journals (Sweden)
G. I. Bondarenko
2014-09-01
Full Text Available Introduction. This article contains overview of the organization of communication between applications on the corporate network. It is stated that the main digital channel (channel B - 64 kbit/s and the primary digital channel (channel E1 the digital stream - 2048 kbit/s are used as the main channels in corporate networks. Problem areas of the functioning of the corporate network are identified. There are the rent of communication channels, which is growing rapidly with increasing the quality and speed of data transmission, and optimal use of bandwidth of communication channels. Setting of task. Optimal use of transmission channels bandwidth and minimizing the rent cost of channels is possible in two ways - the use of compression techniques of voice and video information and the application of variable structure of channels by using various-speed transmission channels. Differential pulse code modulation, adaptive differential pulse code modulation are the modern methods of speech signals processing. Organization of various-speed channels is performed in the structure of the BCC (for speech signals or PCR (for video. Suggestions for optimizing the structure of the channel signals. Proposed method of various-speed channels formation by using the channel intervals appropriate BCC (octets in the structure of signals E1 as envelopes containing various-speed channels. Channels can be selected for synchronization procedure CRC to simplify recognition of channels in the structure of E1. In this case, the minimal speed in the channel is 4 kbit/s. Conclusions. The proposed structure of envelopes is based on octet channel intervals of standard group signal of the primary group plesiochronous hierarchy E1 when transferring various-speed digital signals maximum allows to use the bandwidth at a fixed structure of channel interval, it makes possible to agree on the structure of the various-speed signals with the existing in communication networks.
Institute of Scientific and Technical Information of China (English)
张光磊; 刘善仕; 申红艳
2011-01-01
在全球化竞争时代，企业如何提高研发团队的创新绩效是一个重要的研究议题。尽管部分理论研究者已经认识到知识转移在组织结构对创新绩效的影响中具有重要的作用，但检验这三者之间关系的经验研究迄今还不多见。知识转移渠道被认为是知识接受者与发送者之间进行转移的媒介与路径。本研究将组织结构、知识转移渠道、研发团队创新绩效整合在一个理论模型中对77家高新技术企业458个研发团队进行了实证研究。研究结果表明：知识转移渠道在集权程度、反馈速度与团队创新绩效的关系之间具有部分中介效用；在部门整合能力与团队创新绩效之间具有完全的中%In this global competition world, how to improve R＆D team＇s innovation performance is a significant issue for a company. Some researchers have realized that knowledge Transfer, in an organizational structure, acts an important role in innovation performance, nevertheless there are few empirical studies bout the relationship between the three factors. Channels of knowledge Transfer is considered to be the conversion media and path between knowledge receivers and transmitters. This paper integrate organizational structure, knowledge Transfer Channels and R＆D innovation performance into one theoretical model to make a positive study. It reveals that channels of knowledge Transfer are partially effective between centralization, feeding - back speed and team innovation performance, and are completely media effective between section - integration power and team innovation performance. This paper, at the time of theoretical study, also provides some beneficial inspiration for innovation practice of R＆D team.
Genetic algorithm optimization for finned channel performance
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Compared to a smooth channel, a finned channel provides a higher heat transfer coefficient; increasing the fin height enhances the heat transfer. However, this heat transfer enhancement is associated with an increase in the pressure drop. This leads to an increased pumping power requirement so that one may seek an optimum design for such systems. The main goal of this paper is to define the exact location and size of fins in such a way that a minimal pressure drop coincides with an optimal heat transfer based on the genetic algorithm. Each fin arrangement is considered a solution to the problem(an individual for genetic algorithm). An initial population is generated randomly at the first step. Then the algorithm has been searched among these solutions and made new solutions iteratively by its functions to find an optimum design as reported in this article.
Microlayer during boiling in narrow slot channels
Diev, Mikhail D.; Leontiev, Alexander I.
1997-01-01
An international space station Alpha will have a two-phase thermal control system. Boiling of a liquid ammonia will be a process of heat collection in evaporative heat exchangers. Unfortunately, only little data is available for boiling heat transfer in microgravity. Geometries of boiling channels working good in normal gravity are not appropriate in microgravity, and special means should be worked out to avoid some undesired events. From this point of view, the narrow slot channels may be assumed as a promising geometry for microgravity operation. During boiling in narrow slots, the vapor bubbles are flattened between the channel walls. The vapor phase and the channel wall are separated by a thin liquid film which is known as a microlayer. The paper presents the experimental results compared to the theoretical analysis, the paper also shows the narrow slot channels as a perspective configuration for microgravity applications.
Role of neutron transfer processes on the 6Li+120Sn and 7Li+119Sn fusion reactions
Directory of Open Access Journals (Sweden)
Fisichella M.
2015-01-01
Full Text Available The results concerning the study of 6Li+120Sn and 7Li+119Sn systems are presented. These two sistems are characterised by very similar structures of the interacting nuclei and by different Q-value for one-and two- neutron transfer. Our aim is to disentangle the possible effects due to the different n-transfer Q-values, at sub-barriers energies, by comparing the two fusion excitation function. In these experiments the fusion cross section has been measured by using a stack activation technique. No particular differences in the two fusion excitation functions have been observed.
Energy Technology Data Exchange (ETDEWEB)
Lizcano C, D
2003-07-01
In recent experiments, the fusion of the exotic radioactive nucleus {sup 6} He with {sup 209} Bi has been studied for the first time at energies above and below the Coulomb barrier. A considerable enhancement in the fusion was observed, which implies a reduction of about 25% in the nominal fusion barrier. Some previous theoretical works suggest that this striking effect may be caused by the coupling to neutron transfer channels with a positive Q-value which would lead to a neutron flow and the consequent formation of a neck between the projectile and the target. Later, in the current work, we ran two new experiments on the same reaction using the FN Tandem Van de Graaff (10 MV) accelerator and the dual superconducting TwinSol system, both of them belonging to the University of Notre Dame, USA. This time, the purpose was to study one- and two-neutron transfer and the {sup 6} He projectile breakup at laboratory energies of 14.7, 16.2, 17.9, 19.0 and 22.5 MeV. A strong group of {sup 4} He was observed (with an effective Q-value about .5 MeV) whose integrated cross section results exceptionally high, exceeding the fusion cross section both above and below the barrier. The simultaneously measured elastic scattering angular distribution required high total cross sections so that this yield is confirmed. Preliminary coupled channels calculations sing the computer program called Fresco developed at the University of Surrey (England) suggested that the reaction mechanisms may be better described as a direct nuclear breakup and two-neutron transfer to unbound states in {sup 211} Bi. These calculations predicted also an enhancement in the fusion cross section below the barrier due to the transfer and breakup channel coupling, which strongly suggests that this channel is the 'doorway state' that explains the fusion barrier reduction observed in previous experiments. It was found that the {sup 4} He group fully dominates the total reaction cross section at the
Institute of Scientific and Technical Information of China (English)
徐晓冉; 张锁龙; 王存明
2013-01-01
焊接型板式传热器的紧凑性好、质量轻、传热性能好、初始成本低等优越性已越来越被人们所认识，因此人们纷纷对板式传热器内流动状态和传热机理展开研究。鉴于此，本文运用数值模拟软件 Fluent 对全焊接翅片板式传热器双流道进行模拟，在此基础上又进行了实验研究及实验数据与数值模拟的对比分析，得出不同结构参数和操作参数下翅片的传热系数和压力降，并分析翅片高度和翅片间距对翅片传热性能与流动阻力的影响。结果表明：①固定冷侧的入口速度和温度，热侧的传热系数和压降随之热侧入口速度增加而增大；②板间距一定时，翅片高度并非越高传热性能越好；③翅片间距越小，传热性能越好。%Compacted size,light weight,good heat transfer performances,and low operating costs have made welded plate heat exchanger increasingly recognized in the industry. Fluid flow and heat transfer in plate heat exchangers have been widely studied. The numerical simulation of double channel’s flow field plate heat exchanger was presented in this paper using software. The fin heat transfer coefficient and pressure drop were obtained at different structural and operational parameters. The influences of fin height and fin spacing on heat transfer performance and flow resistance were also analyzed. The results showed the following:the velocity and temperature on the fixed cold side,heat transfer coefficient and pressure drop on the hot side increased with the hot side inlet velocity;at fixed plate spacing,the heat transfer performance was not in proportion with fin height;heat transfer performance was better at smaller fin spacing.
Institute of Scientific and Technical Information of China (English)
王彦红; 李素芬; 东明
2015-01-01
为了深入理解再生冷却过程中碳氢燃料的超临界湍流传热特性，以正癸烷为研究对象，对其在非对称受热（上壁面外侧加热）方形通道内的流动传热进行了数值研究。在数值方法可靠性得到充分验证的基础上，详细探讨了进口温度和压力等运行参数对通道上壁面和侧壁面内侧平均壁温和平均努塞尔数分布的影响。计算结果表明：在运行压力接近临界压力且主流温度处于拟临界温度附近的综合条件下，流体热物性剧烈变化导致的类膜态沸腾效应，引起了上壁面内侧显著的传热恶化现象。同时，不平衡压差诱发的通道截面速度场异常分布，进一步影响了上壁面内侧近壁区域流体的换热性能。另外，类膜态沸腾效应致使上壁面热流更多地传递到侧壁面，导致侧壁面平均努塞尔数大幅增大，相比于正常换热的最大增幅约为50%。%In order to deeply understand the supercritical turbulent heat transfer characteristics of hydrocar⁃bon fuel in the regenerative cooling process,numerical study on flow and heat transfer of n-decane in a square channel with asymmetric heating imposed on the top exterior channel surface was conducted. After the reliability of the numerical methods was fully validated,effects of two operating parameters,including the inlet temperature and pressure,on the distribution of averaged wall temperature and averaged Nusselt number of the top and side in⁃ternal channel surfaces,have been discussed in detail. Results indicate that under the compositive conditions of the operational pressure being close to the critical pressure and the bulk fluid temperature being in the vicinity of the pseudo-critical temperature,a pseudo-film boiling effect occurs due to the drastic fluid thermophysical prop⁃erties variations,and thus leads to a significant heat transfer deterioration phenomenon at the top internal wall. Si
Energy Technology Data Exchange (ETDEWEB)
Na, Jonggeol; Jung, Ikhwan; Kshetrimayum, Krishnadash S.; Park, Seongho; Park, Chansaem; Han, Chonghun [Seoul National University, Seoul (Korea, Republic of)
2014-12-15
Driven by both environmental and economic reasons, the development of small to medium scale GTL(gas-to-liquid) process for offshore applications and for utilizing other stranded or associated gas has recently been studied increasingly. Microchannel GTL reactors have been preferred over the conventional GTL reactors for such applications, due to its compactness, and additional advantages of small heat and mass transfer distance desired for high heat transfer performance and reactor conversion. In this work, multi-microchannel reactor was simulated by using commercial CFD code, ANSYS FLUENT, to study the geometric effect of the microchannels on the heat transfer phenomena. A heat generation curve was first calculated by modeling a Fischer-Tropsch reaction in a single-microchannel reactor model using Matlab-ASPEN integration platform. The calculated heat generation curve was implemented to the CFD model. Four design variables based on the microchannel geometry namely coolant channel width, coolant channel height, coolant channel to process channel distance, and coolant channel to coolant channel distance, were selected for calculating three dependent variables namely, heat flux, maximum temperature of coolant channel, and maximum temperature of process channel. The simulation results were visualized to understand the effects of the design variables on the dependent variables. Heat flux and maximum temperature of cooling channel and process channel were found to be increasing when coolant channel width and height were decreased. Coolant channel to process channel distance was found to have no effect on the heat transfer phenomena. Finally, total heat flux was found to be increasing and maximum coolant channel temperature to be decreasing when coolant channel to coolant channel distance was decreased. Using the qualitative trend revealed from the present study, an appropriate process channel and coolant channel geometry along with the distance between the adjacent
Pätzold, Matthias
2011-01-01
Providing a comprehensive overview of the modelling, analysis and simulation of mobile radio channels, this book gives a detailed understanding of fundamental issues and examines state-of-the-art techniques in mobile radio channel modelling. It analyses several mobile fading channels, including terrestrial and satellite flat-fading channels, various types of wideband channels and advanced MIMO channels, providing a fundamental understanding of the issues currently being investigated in the field. Important classes of narrowband, wideband, and space-time wireless channels are explored in deta
Energy Technology Data Exchange (ETDEWEB)
Olson, Marvin
2016-01-12
A method, system, and apparatus for installing channel nuts includes a shank, a handle formed on a first end of a shank, and an end piece with a threaded shaft configured to receive a channel nut formed on the second end of the shaft. The tool can be used to insert or remove a channel nut in a channel framing system and then removed from the channel nut.
Heat Transfer Phenomena in Supercritical Water Nuclear Reactors
Energy Technology Data Exchange (ETDEWEB)
Mark H. Anderson; MichaelL. Corradini; Riccardo Bonazza; Jeremy R. Licht
2007-10-03
A supercritical water heat transfer facility has been built at the University of Wisconsin to study heat transfer in ancircular and square annular flow channel. A series of integral heat transfer measurements has been carried out over a wide range of heat flux, mas velocity and bulk water temperatures at a pressure of 25 MPa. The circular annular test section geometry is a 1.07 cm diameter heater rod within a 4.29 diameter flow channel.
Mixed convection in a baffled grooved channel
Indian Academy of Sciences (India)
Aayush K Sharma; Pallab S Mahapatra; Nirmal K Manna; Koushik Ghosh
2015-05-01
In the present numerical work, flow structure and heat transfer characteristics are investigated in a baffled grooved channel, differentially heated from the sides. The baffle is placed vertically downward from the top wall of grooved channel geometry, with the motive of diverting outside forced flow towards the inside of the square cavity. In-house CFD code based on finite volume method has been used to solve the 2D equations of continuity, momentum and energy. The effect of change in baffle position and height is investigated in the range of Richardson numbers 0.1 to 10. For the present study, external flow from both left and right of the grooved channel are considered. A remarkable enhancement of heat transfer is observed in presence of baffle. The study has also pointed out that for optimal performance, the position and height of the baffle need to be adjusted depending on the direction of external flow.
DEFF Research Database (Denmark)
Rohde, Carsten; Rossing, Christian Plesner
trade internally as the units have to decide what prices should be paid for such inter-unit transfers. One important challenge is to uncover the consequences that different transfer prices have on the willingness in the organizational units to coordinate activities and trade internally. At the same time...
Grimpe, Christoph; Hussinger, Katrin
2008-01-01
Literature has identified formal and informal channels in university technology transfer. While formal technology transfer typically involves a legal contract on a patent or on collaborative research activities, informal transfer channels refer to personal contacts and hence to the tacit dimension of knowledge transfer. Research is, however, scarce regarding the interaction of formal and informal transfer mechanisms. In this paper, we analyze whether these activities are mutually reinforcing,...
Directory of Open Access Journals (Sweden)
Dirk Morschett, Dr.,
2005-01-01
Full Text Available Multi-channel retailing entails the parallel use by retailing enterprises of several sales channels. The results of an online buyer survey which has been conducted to investigate the impact of multi-channel retailing (i.e. the use of several retail channels by one retail company on consumer behaviour show that the frequently expressed concern that the application of multi-channel systems in retailing would be associated with cannibalization effects, has proven unfounded. Indeed, the appropriate degree of similarity, consistency, integration and agreement achieves the exact opposite. Different channels create different advantages for consumers. Therefore the total benefit an enterprise which has a multi-channel system can offer to its consumers is larger, the greater the number of available channels. The use of multi-channel systems is associated with additional purchases in the different channels. Such systems are thus superior to those offering only one sales channel to their customers. Furthermore, multi-channel systems with integrated channels are superior to those in which the channels are essentially autonomous and independent of one another. In integrated systems, consumers can achieve synergy effects in the use of sales-channel systems. Accordingly, when appropriately formulated, multi-channel systems in retailing impact positively on consumers. They use the channels more frequently, buy more from them and there is a positive customer-loyalty impact. Multi-channel systems are strategic options for achieving customer loyalty, exploiting customer potential and for winning new customers. They are thus well suited for approaching differing and varied target groups.
"Transfer Shock" or "Transfer Ecstasy?"
Nickens, John M.
The alleged characteristic drop in grade point average (GPA) of transfer students and the subsequent rise in GPA was investigated in this study. No statistically significant difference was found in first term junior year GPA between junior college transfers and native Florida State University students after the variance accounted for by the…
Quantum channels and memory effects
Caruso, Filippo; Giovannetti, Vittorio; Lupo, Cosmo; Mancini, Stefano
2014-10-01
Any physical process can be represented as a quantum channel mapping an initial state to a final state. Hence it can be characterized from the point of view of communication theory, i.e., in terms of its ability to transfer information. Quantum information provides a theoretical framework and the proper mathematical tools to accomplish this. In this context the notion of codes and communication capacities have been introduced by generalizing them from the classical Shannon theory of information transmission and error correction. The underlying assumption of this approach is to consider the channel not as acting on a single system, but on sequences of systems, which, when properly initialized allow one to overcome the noisy effects induced by the physical process under consideration. While most of the work produced so far has been focused on the case in which a given channel transformation acts identically and independently on the various elements of the sequence (memoryless configuration in jargon), correlated error models appear to be a more realistic way to approach the problem. A slightly different, yet conceptually related, notion of correlated errors applies to a single quantum system which evolves continuously in time under the influence of an external disturbance which acts on it in a non-Markovian fashion. This leads to the study of memory effects in quantum channels: a fertile ground where interesting novel phenomena emerge at the intersection of quantum information theory and other branches of physics. A survey is taken of the field of quantum channels theory while also embracing these specific and complex settings.
Hadamard quantum broadcast channels
Wang, Qingle; Das, Siddhartha; Wilde, Mark M.
2017-10-01
We consider three different communication tasks for quantum broadcast channels, and we determine the capacity region of a Hadamard broadcast channel for these various tasks. We define a Hadamard broadcast channel to be such that the channel from the sender to one of the receivers is entanglement-breaking and the channel from the sender to the other receiver is complementary to this one. As such, this channel is a quantum generalization of a degraded broadcast channel, which is well known in classical information theory. The first communication task we consider is classical communication to both receivers, the second is quantum communication to the stronger receiver and classical communication to other, and the third is entanglement-assisted classical communication to the stronger receiver and unassisted classical communication to the other. The structure of a Hadamard broadcast channel plays a critical role in our analysis: The channel to the weaker receiver can be simulated by performing a measurement channel on the stronger receiver's system, followed by a preparation channel. As such, we can incorporate the classical output of the measurement channel as an auxiliary variable and solve all three of the above capacities for Hadamard broadcast channels, in this way avoiding known difficulties associated with quantum auxiliary variables.
Cold plate with combined inclined impingement and ribbed channels
Energy Technology Data Exchange (ETDEWEB)
Parida, Pritish R.
2015-12-22
Heat transfer devices and methods for making the same that include a first enclosure having at least one inlet port; a second enclosure having a bottom plate and one or more dividing walls to establish channels, at least one internal surface of each channel having rib structures to create turbulence in a fluid flow; and a jet plate connecting the first enclosure and the second enclosure having impinging jets that convey fluid from the first enclosure to the channels, said impinging jets being set at an angular deviation from normal to cause local acceleration of fluid and to increase a local heat transfer rate.
Flow dynamics and concentration polarisation in spacer-filled channels
DEFF Research Database (Denmark)
Lipnizki, Jens; Jonsson, Gunnar Eigil
2002-01-01
The key to developing highly efficient spiral-wound modules is the improvement of the mass transfer mechanisms. In this study a study of the mass transfer has been carried out using a flat test cell with six permeate outlets and a rectangular feed channel. Using this experimental set-up, it has b...
USACE Navigation Channels 2012
California Department of Resources — This dataset represents both San Francisco and Los Angeles District navigation channel lines. All San Francisco District channel lines were digitized from CAD files...
DEFF Research Database (Denmark)
Gale, A.S.; Surlyk, Finn; Anderskouv, Kresten
2013-01-01
. Within this channel were smaller erosional structures (hardgrounds, and locally have a basal fill of granular phosphorite. The entire channel system was progressively infilled by chalk, as demonstrated by the expanded succession...
Burnout and distribution of liquid between the flow core and wall films in narrow slot channels
Boltenko, E. A.; Shpakovskii, A. A.
2010-03-01
Previous works on studying distribution of liquid between the flow core and wall films in narrow slot channels are briefly reviewed. Interrelation between mass transfer processes and burnout is shown. A procedure for calculating burnout on convex and concave heat-transfer surfaces in narrow slot channels is presented.
Eeg Transfer Entropy Tracks Changes in Information Transfer on the Onset of Vision
Madulara, M. D.; Francisco, P. A. B.; Nawang, S.; Arogancia, D. C.; Cellucci, C. J.; Rapp, P. E.; Albano, A. M.
We investigate the pairwise mutual information and transfer entropy of ten-channel, free-running electroencephalographs measured from thirteen subjects under two behavioral conditions: eyes open resting and eyes closed resting. Mutual information measures nonlinear correlations; transfer entropy determines the directionality of information transfer. For all channel pairs, mutual information is generally lower with eyes open compared to eyes closed indicating that EEG signals at different scalp sites become more dissimilar as the visual system is engaged. On the other hand, transfer entropy increases on average by almost two-fold when the eyes are opened. The largest one-way transfer entropies are to and from the Oz site consistent with the involvement of the occipital lobe in vision. The largest net transfer entropies are from F3 and F4 to almost all the other scalp sites.
Quantum Multiple Access Channel
Institute of Scientific and Technical Information of China (English)
侯广; 黄民信; 张永德
2002-01-01
We consider the transmission of classical information over a quantum channel by many senders, which is a generalization of the two-sender case. The channel capacity region is shown to be a convex hull bound by the yon Neumann entropy and the conditional yon Neumann entropies. The result allows a reasonable distribution of channel capacity over the senders.
Baluška, František; Mancuso, Stefano
2013-01-01
In his recent opus magnum review paper published in the October issue of Physiology Reviews, Rainer Hedrich summarized the field of plant ion channels.1 He started from the earliest electric recordings initiated by Charles Darwin of carnivorous Dionaea muscipula,1,2 known as Venus flytrap, and covered the topic extensively up to the most recent discoveries on Shaker-type potassium channels, anion channels of SLAC/SLAH families, and ligand-activated channels of glutamate receptor-like type (GLR) and cyclic nucleotide-gated channels (CNGC).1 PMID:23221742
Charged and Neutral Particles Channeling Phenomena Channeling 2008
Dabagov, Sultan B.; Palumbo, Luigi
2010-04-01
On the discovery of coherent Bremsstrahlung in a single crystal at the Frascati National Laboratories / C. Barbiellini, G. P. Murtas and S. B. Dabagov -- Advances in coherent Bremsstrahlung and LPM-effect studies (to the lOOth anniversary from the birth of L. D. Landau) / N. F. Shul'ga -- Spectra of radiation and created particles at intermediate energy in oriented crystal taking into account energy loss / V. N. Baier and V. M. Katkov -- The coherent Bremsstrahlung beam at MAX-lab facility / K. Fissum ... [et al.] -- Radiation from thin, structured targets (CERN NA63) / A. Dizdar -- Hard incoherent radiation in thick crystals / N. F. Shul'ga, V. V. Syshchenko and A. I. Tarnovsky -- Coherent Bremsstrahlung in periodically deformed crystals with a complex base / A. R. Mkrtchyan, A. A. Saharian and V. V. Parazian -- Induction of coherent x-ray Bremsstrahlung in crystals under the influence of acoustic waves / A. R. Mkrtchyan and V. V. Parazian -- Coherent processes in bent single crystals / V. A. Maisheev -- Experimental and theoretical investigation of complete transfer phenomenon for media with various heat exchange coefficients / A. R. Mkrtchyan, A. E. Movsisyan and V. R. Kocharyan -- Coherent pair production in crystals / A. R. Mkrtchyan, A. A. Saharian and V. V. Parazian -- Negative particle planar and axial channeling and channeling collimation / R. A. Carrigan, Jr. -- CERN crystal-based collimation in modern hadron colliders / W. Scandale -- Studies and application of bent crystals for beam steering at 70 GeV IHEP accelerator / A. G. Afonin ... [et al.] -- Crystal collimation studies at the Tevatron (T-980) / N. V. Mokhov ... [et al.] -- Fabrication of crystals for channeling of particles in accellerators / A. Mazzolari ... [et al.] -- New possibilities to facilitate collimation of both positively and negatively charged particle beams by crystals / V. Guidi, A. Mazzolari and V. V. Tikhomirov -- Increase of probability of particle capture into the channeling
Design of joint source/channel coders
1991-01-01
The need to transmit large amounts of data over a band limited channel has led to the development of various data compression schemes. Many of these schemes function by attempting to remove redundancy from the data stream. An unwanted side effect of this approach is to make the information transfer process more vulnerable to channel noise. Efforts at protecting against errors involve the reinsertion of redundancy and an increase in bandwidth requirements. The papers presented within this document attempt to deal with these problems from a number of different approaches.
Surface vacancy channels through ion channeling
Energy Technology Data Exchange (ETDEWEB)
Redinger, Alex; Standop, Sebastian; Michely, Thomas [II. Physikalisches Institut, Universitaet Koeln, Zuelpicher Strasse 77, 50937 Koeln (Germany); Rosandi, Yudi; Urbassek, Herbert M. [Fachbereich Physik, Technische Universitaet Kaiserslautern, Erwin-Schroedinger-Strasse, D-67663 Kaiserslautern (Germany)
2009-07-01
Damage patterns of single ion impacts on Pt(111) have been studied by scanning tunneling microscopy (STM) and molecular dynamics simulations (MD). Low temperature experiments, where surface diffusion is absent, have been performed for argon and xenon ions with energies between 1 keV and 15 keV at an angle of incidence of 86 {sup circle} measured with respect to the surface normal. Ions hitting preexisting illuminated step edges penetrate into the crystal and are guided in open crystallographic directions, one or more layers underneath the surface (subsurface channeling). In the case of argon channeling the resulting surface damage consists of adatom and vacancy pairs aligned in ion beam direction. After xenon channeling thin surface vacancy trenches along the ion trajectories - surface vacancy channels - are observed. They result from very efficient sputtering and adatom production along the ion trajectory. This phenomena is well reproduced in molecular dynamics simulations of single ion impacts at 0 K. The damage patterns of Argon and Xenon impacts can be traced back to the different energy losses of the particles in the channel. Channeling distances exceeding 1000 A for 15 keV xenon impacts are observed.
Quantum biological channel modeling and capacity calculation.
Djordjevic, Ivan B
2012-12-10
Quantum mechanics has an important role in photosynthesis, magnetoreception, and evolution. There were many attempts in an effort to explain the structure of genetic code and transfer of information from DNA to protein by using the concepts of quantum mechanics. The existing biological quantum channel models are not sufficiently general to incorporate all relevant contributions responsible for imperfect protein synthesis. Moreover, the problem of determination of quantum biological channel capacity is still an open problem. To solve these problems, we construct the operator-sum representation of biological channel based on codon basekets (basis vectors), and determine the quantum channel model suitable for study of the quantum biological channel capacity and beyond. The transcription process, DNA point mutations, insertions, deletions, and translation are interpreted as the quantum noise processes. The various types of quantum errors are classified into several broad categories: (i) storage errors that occur in DNA itself as it represents an imperfect storage of genetic information, (ii) replication errors introduced during DNA replication process, (iii) transcription errors introduced during DNA to mRNA transcription, and (iv) translation errors introduced during the translation process. By using this model, we determine the biological quantum channel capacity and compare it against corresponding classical biological channel capacity. We demonstrate that the quantum biological channel capacity is higher than the classical one, for a coherent quantum channel model, suggesting that quantum effects have an important role in biological systems. The proposed model is of crucial importance towards future study of quantum DNA error correction, developing quantum mechanical model of aging, developing the quantum mechanical models for tumors/cancer, and study of intracellular dynamics in general.
Quantum Biological Channel Modeling and Capacity Calculation
Directory of Open Access Journals (Sweden)
Ivan B. Djordjevic
2012-12-01
Full Text Available Quantum mechanics has an important role in photosynthesis, magnetoreception, and evolution. There were many attempts in an effort to explain the structure of genetic code and transfer of information from DNA to protein by using the concepts of quantum mechanics. The existing biological quantum channel models are not sufficiently general to incorporate all relevant contributions responsible for imperfect protein synthesis. Moreover, the problem of determination of quantum biological channel capacity is still an open problem. To solve these problems, we construct the operator-sum representation of biological channel based on codon basekets (basis vectors, and determine the quantum channel model suitable for study of the quantum biological channel capacity and beyond. The transcription process, DNA point mutations, insertions, deletions, and translation are interpreted as the quantum noise processes. The various types of quantum errors are classified into several broad categories: (i storage errors that occur in DNA itself as it represents an imperfect storage of genetic information, (ii replication errors introduced during DNA replication process, (iii transcription errors introduced during DNA to mRNA transcription, and (iv translation errors introduced during the translation process. By using this model, we determine the biological quantum channel capacity and compare it against corresponding classical biological channel capacity. We demonstrate that the quantum biological channel capacity is higher than the classical one, for a coherent quantum channel model, suggesting that quantum effects have an important role in biological systems. The proposed model is of crucial importance towards future study of quantum DNA error correction, developing quantum mechanical model of aging, developing the quantum mechanical models for tumors/cancer, and study of intracellular dynamics in general.
Smith, Nanette R.
1995-01-01
The objective of this summer's work was to attempt to enhance Technology Application Group (TAG) ability to measure the outcomes of its efforts to transfer NASA technology. By reviewing existing literature, by explaining the economic principles involved in evaluating the economic impact of technology transfer, and by investigating the LaRC processes our William & Mary team has been able to lead this important discussion. In reviewing the existing literature, we identified many of the metrics that are currently being used in the area of technology transfer. Learning about the LaRC technology transfer processes and the metrics currently used to track the transfer process enabled us to compare other R&D facilities to LaRC. We discuss and diagram impacts of technology transfer in the short run and the long run. Significantly, it serves as the basis for analysis and provides guidance in thinking about what the measurement objectives ought to be. By focusing on the SBIR Program, valuable information regarding the strengths and weaknesses of this LaRC program are to be gained. A survey was developed to ask probing questions regarding SBIR contractors' experience with the program. Specifically we are interested in finding out whether the SBIR Program is accomplishing its mission, if the SBIR companies are providing the needed innovations specified by NASA and to what extent those innovations have led to commercial success. We also developed a survey to ask COTR's, who are NASA employees acting as technical advisors to the SBIR contractors, the same type of questions, evaluating the successes and problems with the SBIR Program as they see it. This survey was developed to be implemented interactively on computer. It is our hope that the statistical and econometric studies that can be done on the data collected from all of these sources will provide insight regarding the direction to take in developing systematic evaluations of programs like the SBIR Program so that they can
sprotocols
2014-01-01
### Method: Blastocyst transfer is usually performed 24 hours after aggregation when the morulae have become expanded blastocysts and on the same day as injection. A little time is given between injection and transfer to allow blastocysts to re-expand. **The Recipient** Careful selection of the recipient is most important as the pups are the end result of a lot of hard work. Two strains of mice are used:RB Swiss and (CBA*C57BL6/J)f1. RB Swiss are quiet and make excellent mothers ...
Holman, J P
2010-01-01
As one of the most popular heat transfer texts, Jack Holman's "Heat Transfer" is noted for its clarity, accessible approach, and inclusion of many examples and problem sets. The new tenth edition retains the straight-forward, to-the-point writing style while covering both analytical and empirical approaches to the subject. Throughout the book, emphasis is placed on physical understanding while, at the same time, relying on meaningful experimental data in those situations that do not permit a simple analytical solution. New examples and templates provide students with updated resources for computer-numerical solutions.
2003-01-01
sim present Simulation Presentation Interactive Media Element This IME is used in the Computer Communications and Networks class offered in the Graduate School of Operations and Information Sciences. This introductory computer networking course provides the theory and principles of networking and communications protocols. This IME is used to help students understand data transfer options. CS3502 Computer Communications and Networks
Reinhart, T.
2006-01-01
On the eve of the Iraq war, fears were expressed in different circles that under the cover of war, Israel may attempt a transfer of Palestinians in the “seam line” area of the northern West Bank (Kalkilya, Tulkarem). Last week, the army produced a scene from this scenario. On April 2 at 3 AM, a larg
Directory of Open Access Journals (Sweden)
Sheikhzadeh Ghanbarali
2016-01-01
Full Text Available In this study, thermo-physical and geometrical parameters affecting entropy generation of nanofluid turbulent flow such as the volume fraction, Reynolds number and diameter of the channel and micro-channel with circular cross section under constant flux are examined analytically. Water is used as a base fluid of nanofluid with nanoparticles of Ag, Cu, CuO and TiO2. The study is conducted for Reynolds numbers of 20000, 40000 and 100000, volume fractions of 0, 0.01, 0.02, 0.03 and 0.04, channel diameters of 2, 4, 6 and 8 cm and micro-channel diameters of 20, 40, 60 and 80 micrometers. Based on the results, the most of the generated entropy in channel is due to heat transfer, and also, with increasing the diameter of the channel, Bejan number increases. The contribution of entropy generation due to heat transfer in the micro-channel is very poor and the major contribution of entropy generation is due to friction. The maximum amount of entropy generation in channel belongs to nanofluids with Ag, Cu, CuO and TiO2 nanoparticles, respectively, while in the micro-channel this behavior is reversed; and the minimum entropy generation happens in nanofluids with Ag, Cu, CuO and TiO2 nanoparticles, respectively. In channel and micro-channel, for all nanofluids except for the water-TiO2, with increasing volume fraction of nanoparticles, the entropy generation decreases. In channel and micro-channel, the total entropy generation increases as Reynolds number augments.
Institute of Scientific and Technical Information of China (English)
孙慧琳
2015-01-01
基于新产品研发团队这一临时性组织情境，探讨团队断裂带对新产品研发团队创新绩效的影响，尤其是团队快速信任和知识转移渠道在其中的情境机制。通过选取本土企业内98个新产品研发团队的团队领导-团队成员配对样本，运用层级回归分析对假设进行验证。研究结果发现，团队断裂带与新产品研发团队创新绩效之间存在倒“U”字型关系，团队快速信任和知识转移渠道均显著调节这一非线性关系。即在团队快速信任水平越高或知识转移渠道越丰富的情况下，团队断裂带与新产品研发团队创新绩效之间的倒“U”字型关系越不明显。%Based on the organizational context of new product development (NPD)teams,this paper aims to explore the curvilinear relationship between team faultlines and team innovation performance,especially the moderating roles of swift trust and knowledge transfer channel.U-sing the hierarchical linear regression,we tested hypothetical model by means of 98 dyad samples of the leaders and their subordinates from local firms'NPD teams.Results of the analyses suggest that team faultlines have a reversed U shape impact on NPD teams'innovation performance.In addition,both swift trust and knowledge transfer channel serve as the conditional variables and moderate the reversed U shape relationship between team faultlines and team innovation perform-ance.
Institute of Scientific and Technical Information of China (English)
张钧波; 张敏
2014-01-01
This paper studies power-law non-Newtonian fluid where the shearing stress accords with the Ostwald-de Waele relational formula.It aims to solve the problem of the apparent viscosity changing with the shearing rates and the calculation which is different from Newtonian fluid.Cell-based central method is used for the non-linear viscosity coefficient discretization.It adopts FVM for flow and heat transfer numerical simulation of fully developed laminar in eccentric annular channel.The calculation results show that the power-law factor has a great impact on the fluid flow,but the impact on the heat transfer is influenced by the eccentricity .The eccentric-ity of annular channel can lead to the asymmetrical distribution of circumferential temperature and velocity.%以剪切应力符合Ostwald-de Waele关系式的幂律非牛顿流体为研究对象。针对幂律非牛顿流体的表观黏度随剪切速率变化且计算过程有别于牛顿流体的问题，运用基元中心法对非线性粘性系数进行离散。采用有限体积法对幂律非牛顿流体在偏心圆环管中的充分发展层流流动和传热进行数值计算。计算结果表明流体的幂律因子对流动的影响较大，但对传热的影响受到到偏心率的影响。流道偏心会引起圆环通道内速度和温度的周向分布不均匀，且偏心程度越严重，周向分布不均匀性越强烈。
Heat transfer enhancement using tip and junction vortices
Gentry, Mark Cecil
1998-10-01
Single-phase convective heat transfer can be enhanced by modifying the heat transfer surface to passively generate streamwise vortices. The swirling flow of the vortices modifies the temperature field, thinning the thermal boundary layer and increasing surface convection. Tip vortices generated by delta wings and junction vortices generated by hemispherical protuberances were studied in laminar flat-plate and developing channel flows. Local and average convective measurements were obtained, and the structure of the vortices was studied using quantitative flow visualization and vortex strength measurements. The pressure drop penalty associated with the heat transfer enhancement was also investigated. Tip vortices generated by delta wings enhanced local convection by as much as 300% over a flat-plate boundary layer flow. Vortex strength increased with Reynolds number based on chord length, wing aspect ratio, and wing angle of attack. As the vortices were advected downstream, they decayed because of viscous interactions. In the developing channel flow, tip vortices produced a significant local heat transfer enhancement on both sides of the channel. The largest spatially averaged heat transfer enhancement was 55%; it was accompanied by a 100% increase in the pressure drop relative to the same channel flow with no delta-wing vortex generator. Junction vortices created by hemispherical surface protuberances provided local heat transfer enhancements as large as 250%. Vortex strength increased with an increasing ratio of hemisphere radius to local boundary layer thickness on a flat plate. In the developing channel flows, heat transfer enhancements were observed on both sides of the channel. The largest spatially averaged heat transfer enhancement was 50%; it was accompanied by a 90% pressure drop penalty relative to the same channel flow with no hemispherical vortex generator. This research is important in compact heat exchanger design. Enhancing heat transfer can lead to
Yard, J; Devetak, I; Yard, Jon; Hayden, Patrick; Devetak, Igor
2006-01-01
We analyze quantum broadcast channels, which are quantum channels with a single sender and many receivers. Focusing on channels with two receivers for simplicity, we generalize a number of results from the network Shannon theory literature which give the rates at which two senders can receive a common message, while a personalized one is sent to one of them. Our first collection of results applies to channels with a classical input and quantum outputs. The second class of theorems we prove concern sending a common classical message over a quantum broadcast channel, while sending quantum information to one of the receivers. The third group of results we obtain concern communication over an isometry, giving the rates at quantum information can be sent to one receiver, while common quantum information is sent to both, in the sense that tripartite GHZ entanglement is established. For each scenario, we provide an additivity proof for an appropriate class of channels, yielding single-letter characterizations of the...
DEFF Research Database (Denmark)
Klausen, Thomas Kjær
of volume perturbations evolution have developed system of channels and transporters to tightly control volume homeostasis. In the past decades evidence has been mounting, that the importance of these volume regulated channels and transporters are not restricted to the defense of cellular volume...... but are also essential for a number of physiological processes such as proliferation, controlled cell death, migration and endocrinology. The thesis have been focusing on two Channels, namely the swelling activated Cl- channel (ICl, swell) and the transient receptor potential Vanilloid (TRPV4) channel. I: Cl......- serves a multitude of functions in the mammalian cell, regulating the membrane potential (Em), cell volume, protein activity and the driving force for facilitated transporters giving Cl- and Cl- channels a major potential of regulating cellular function. These functions include control of the cell cycle...
Valverde, Miguel A; Cantero-Recasens, Gerard; Garcia-Elias, Anna; Jung, Carole; Carreras-Sureda, Amado; Vicente, Rubén
2011-09-23
Ion channels are specialized transmembrane proteins that permit the passive flow of ions following their electrochemical gradients. In the airways, ion channels participate in the production of epithelium-based hydroelectrolytic secretions and in the control of intracellular Ca(2+) levels that will ultimately activate almost all lung cells, either resident or circulating. Thus, ion channels have been the center of many studies aiming to understand asthma pathophysiological mechanisms or to identify therapeutic targets for better control of the disease. In this minireview, we focus on molecular, genetic, and animal model studies associating ion channels with asthma.
Bowen, G
2002-01-01
In classical information theory the capacity of a noisy communication channel cannot be increased by the use of feedback. In quantum information theory the no-cloning theorem means that noiseless copying and feedback of quantum information cannot be achieved. In this paper, quantum feedback is defined as the unlimited use of a noiseless quantum channel from receiver to sender. Given such quantum feedback, it is shown to provide no increase in the entanglement-assisted capacities of a noisy quantum channel, in direct analogy to the classical case. It is also shown that in various cases of non-assisted capacities, feedback can increase the capacity of many quantum channels.
Directory of Open Access Journals (Sweden)
Swarna Bais
2016-12-01
Full Text Available Praziquantel (PZQ is effectively the only drug currently available for treatment and control of schistosomiasis, a disease affecting hundreds of millions of people worldwide. Many anthelmintics, likely including PZQ, target ion channels, membrane protein complexes essential for normal functioning of the neuromusculature and other tissues. Despite this fact, only a few classes of parasitic helminth ion channels have been assessed for their pharmacological properties or for their roles in parasite physiology. One such overlooked group of ion channels is the transient receptor potential (TRP channel superfamily. TRP channels share a common core structure, but are widely diverse in their activation mechanisms and ion selectivity. They are critical to transducing sensory signals, responding to a wide range of external stimuli. They are also involved in other functions, such as regulating intracellular calcium and organellar ion homeostasis and trafficking. Here, we review current literature on parasitic helminth TRP channels, focusing on those in schistosomes. We discuss the likely roles of these channels in sensory and locomotor activity, including the possible significance of a class of TRP channels (TRPV that is absent in schistosomes. We also focus on evidence indicating that at least one schistosome TRP channel (SmTRPA has atypical, TRPV1-like pharmacological sensitivities that could potentially be exploited for future therapeutic targeting.
DEFF Research Database (Denmark)
Stott, Jennifer B; Jepps, Thomas Andrew; Greenwood, Iain A
2014-01-01
identified as being crucial mediators of this process in a variety of smooth muscle. Recently, KV7 channels have been shown to be involved in the pathogenesis of hypertension, as well as being implicated in other smooth muscle disorders, providing a new and inviting target for smooth muscle disorders.......Potassium channels are key regulators of smooth muscle tone, with increases in activity resulting in hyperpolarisation of the cell membrane, which acts to oppose vasoconstriction. Several potassium channels exist within smooth muscle, but the KV7 family of voltage-gated potassium channels have been...
Institute of Scientific and Technical Information of China (English)
符建; 何赛灵; 肖三水; 仇霪; 何建军
2001-01-01
A theoretical analysis is presented for a channel drop tunnelling structure composed of a horizontal input channel, a vertical output channel and a multi-mode cavity in a photonic crystal. Criteria for a complete transfer are derived for applications of wavelength division demultiplexing. The analytical results are verified with a numerical simulation using a finite difference time domain method. The vertical channel dropping tunnelling system makes the demultiplexing device much more compact, as compared to the conventional parallel channel dropping system.
Roberts, Roland Blaine
1994-01-01
The Rochester RMS was used to measure excitation functions for 180^circ sub -barrier one- and two-neutron pickup reactions for E _{rm lab} final states were not identified. The RMS technique was chosen for its self-normalizing property which makes obtaining absolute cross sections straightforward. The distorted-wave Born-approximation (DWBA) computer code scPTOLEMY was used to obtain quantal predictions of the one-neutron pickup yields. The calculations were performed for several final states and summed (using the appropriate spectroscopic factors) to estimate the total quasi-elastic transfer yield. P scTOLEMY over-predicted the yield in each system by a factor of 2-3. Since DWBA calculations for heavy-ion reactions are known to have difficulty reproducing experimentally measured yields within a factor of two, this discrepancy is not surprising. Although the absolute yields were not reproduced by the calculations, the shape of the excitation function is well reproduced. No calculations were performed for two-neutron transfer due to the lack of reliable spectroscopic factors. The transfer probabilities are obtained directly from these measurements. Distances of closest approach were calculated using a proximity potential. The slopes of transfer probability vs distance of closest approach are in good agreement with the predictions obtained from semi-classical theory using binding energies, indicating the absence of a "slope anomaly." This is consistent with the prediction that diffractive effects, which may distort the measured slope, are minimized at backward angles and sub-barrier energies--the precise conditions under which these measurements were performed. Angle-integrated transfer cross sections were derived from the measured transfer probabilities by assuming the ions follow Rutherford trajectories. These derived yields are consistent with the hypothesis that fusion enhancements in previously measured fusion yields for the ^ {32}S + ^{98,100} Mo systems are
Energy Technology Data Exchange (ETDEWEB)
Bauer, H.
1998-12-31
The scattering system {sup 162}Dy {yields} {sup 116}Sn has been examined at energies in the vicinity of the Coulomb barrier using the Heidelberg-Darmstadt Crystal Ball spectrometer combined with 5 Germanium-CLUSTER detectors. In order to study pairing correlations as a function of angular momentum cold events were selected in the 2n stripping channel by identifying and suppressing the dominant hot part of the transfer with the Crystal Ball. The CLUSTER detectors with their high {gamma}-efficiency were used to identify the transfer channel and to resolve individual final states. Cross sections for the population of individual yrast states in a cold transfer reaction have been measured for the first time indicating the strong influence of higher transfer multipolarities. At small surface distances Coulomb-nuclear interferences were found to be responsible for the stronger decline of the population of higher yrast states in the transfer channel as compared to the Coulex channel. As a preparatory study for 2n transfer measurements between high spin yrast states in the backbending region of deformed nuclei the Coulomb excitation process in the crossing region of two bands in {sup 162}Dy has been analyzed. The gross properties of the measured population probabilities could be interpreted in a simple band mixing model. (orig.)
Taback, I.
1979-01-01
The vulnerability of electronic equipment to carbon fibers is studied. The effectiveness of interfaces, such as filters, doors, window screens, and cabinets, which affect the concentration, exposure, or deposition of carbon fibers on both (internal and external) sides of the interface is examined. The transfer function of multilayer aluminum mesh, wet and dry, polyurethane foam, and window screen are determined as a function of air velocity. FIlters installed in typical traffic control boxes and air conditioners are also considered.
Multichannel transfer function with dimensionality reduction
Kim, Han Suk
2010-01-17
The design of transfer functions for volume rendering is a difficult task. This is particularly true for multi-channel data sets, where multiple data values exist for each voxel. In this paper, we propose a new method for transfer function design. Our new method provides a framework to combine multiple approaches and pushes the boundary of gradient-based transfer functions to multiple channels, while still keeping the dimensionality of transfer functions to a manageable level, i.e., a maximum of three dimensions, which can be displayed visually in a straightforward way. Our approach utilizes channel intensity, gradient, curvature and texture properties of each voxel. The high-dimensional data of the domain is reduced by applying recently developed nonlinear dimensionality reduction algorithms. In this paper, we used Isomap as well as a traditional algorithm, Principle Component Analysis (PCA). Our results show that these dimensionality reduction algorithms significantly improve the transfer function design process without compromising visualization accuracy. In this publication we report on the impact of the dimensionality reduction algorithms on transfer function design for confocal microscopy data.
A linearization of quantum channels
Crowder, Tanner
2015-06-01
Because the quantum channels form a compact, convex set, we can express any quantum channel as a convex combination of extremal channels. We give a Euclidean representation for the channels whose inverses are also valid channels; these are a subset of the extreme points. They form a compact, connected Lie group, and we calculate its Lie algebra. Lastly, we calculate a maximal torus for the group and provide a constructive approach to decomposing any invertible channel into a product of elementary channels.
Restrepo-Angulo, Iván; De Vizcaya-Ruiz, Andrea; Camacho, Javier
2010-08-01
Ion channels play essential roles in human physiology and toxicology. Cardiac contraction, neural transmission, temperature sensing, insulin release, regulation of apoptosis, cellular pH and oxidative stress, as well as detection of active compounds from chilli, are some of the processes in which ion channels have an important role. Regulation of ion channels by several chemicals including those found in air, water and soil represents an interesting potential link between environmental pollution and human diseases; for instance, de novo expression of ion channels in response to exposure to carcinogens is being considered as a potential tool for cancer diagnosis and therapy. Non-specific binding of several drugs to ion channels is responsible for a huge number of undesirable side-effects, and testing guidelines for several drugs now require ion channel screening for pharmaceutical safety. Animal toxins targeting human ion channels have serious effects on the population and have also provided a remarkable tool to study the molecular structure and function of ion channels. In this review, we will summarize the participation of ion channels in biological processes extensively used in toxicological studies, including cardiac function, apoptosis and cell proliferation. Major findings on the adverse effects of drugs on ion channels as well as the regulation of these proteins by different chemicals, including some pesticides, are also reviewed. Association of ion channels and toxicology in several biological processes strongly suggests these proteins to be excellent candidates to follow the toxic effects of xenobiotics, and as potential early indicators of life-threatening situations including chronic degenerative diseases.
A High Performance Micro Channel Interface for Real-Time Industrial Image Processing
Thomas H. Drayer; Joseph G. Tront; Richard W. Conners
1995-01-01
Data collection and transfer devices are critical to the performance of any machine vision system. The interface described in this paper collects image data from a color line scan camera and transfers the data obtained into the system memory of a Micro Channel-based host computer. A maximum data transfer rate of 20 Mbytes/sec can be achieved using the DMA capabilities...
Experimental study of two-phase water flow in vertical thin rectangular channels
Wright, Christopher T.; O'Brien, James E.; Anderson, Elgin A.
2001-11-01
An experimental heat transfer study of two-phase water flow in vertical thin rectangular channels with side vents is conducted. A multiple, heated channel configuration with up- and down-flow conditions is investigated. Parallel heated and unheated flow channels test the effects of cross flow on the onset of nucleate boiling (ONB) and critical heat flux (CHF). The test apparatus provides pressure and substrate temperature data and visual data of the boiling regimes and side-vent flow patterns. The objectives are to determine the two-phase, heat and mass transfer characteristics between adjacent channels as permitted by side-vent cross flow. These data will help develop ONB and CHF correlations for flow geometries typical of plate-type nuclear reactors and heat exchangers. Fundamentally, the data shows how the geometry, flow conditions, and channel configurations affect the heat transfer characteristics of interior channel flows, essential in understanding the ONB and CHF phenomena.
Generalized channeled polarimetry.
Alenin, Andrey S; Tyo, J Scott
2014-05-01
Channeled polarimeters measure polarization by modulating the measured intensity in order to create polarization-dependent channels that can be demodulated to reveal the desired polarization information. A number of channeled systems have been described in the past, but their proposed designs often unintentionally sacrifice optimality for ease of algebraic reconstruction. To obtain more optimal systems, a generalized treatment of channeled polarimeters is required. This paper describes methods that enable handling of multi-domain modulations and reconstruction of polarization information using linear algebra. We make practical choices regarding use of either Fourier or direct channels to make these methods more immediately useful. Employing the introduced concepts to optimize existing systems often results in superficial system changes, like changing the order, orientation, thickness, or spacing of polarization elements. For the two examples we consider, we were able to reduce noise in the reconstruction to 34.1% and 57.9% of the original design values.
Athermalized channeled spectropolarimeter enhancement.
Energy Technology Data Exchange (ETDEWEB)
Jones, Julia Craven; Way, Brandyn Michael; Mercier, Jeffrey Alan; Hunt, Jeffery P.
2013-09-01
Channeled spectropolarimetry can measure the complete polarization state of light as a function of wavelength. Typically, a channeled spectropolarimeter uses high order retarders made of uniaxial crystal to amplitude modulate the measured spectrum with the spectrally-dependent Stokes polarization information. A primary limitation of conventional channeled spectropolarimeters is related to the thermal variability of the retarders. Thermal variation often forces frequent system recalibration, particularly for field deployed systems. However, implementing thermally stable retarders, made of biaxial crystal, results in an athermal channeled spectropolarimeter that relieves the need for frequent recalibration. This report presents experimental results for an anthermalized channeled spectropolarimeter prototype produced using potassium titanyl phosphate. The results of this prototype are compared to the current thermal stabilization state of the art. Finally, the application of the technique to the thermal infrared is studied, and the athermalization concept is applied to an infrared imaging spectropolarimeter design.
Cardiac potassium channel subtypes
DEFF Research Database (Denmark)
Schmitt, Nicole; Grunnet, Morten; Olesen, Søren-Peter
2014-01-01
that they could constitute targets for new pharmacological treatment of atrial fibrillation. The interplay between the different K(+) channel subtypes in both atria and ventricle is dynamic, and a significant up- and downregulation occurs in disease states such as atrial fibrillation or heart failure......About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K(+) channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K(+) channels...... drive the late repolarization of the ventricle with some redundancy, and in atria this repolarization reserve is supplemented by the fairly atrial-specific KV1.5, Kir3, KCa, and K2P channels. The role of the latter two subtypes in atria is currently being clarified, and several findings indicate...
Turbulent mixed convection in asymmetrically heated vertical channel
Directory of Open Access Journals (Sweden)
Mokni Ameni
2012-01-01
Full Text Available In this paper an investigation of mixed convection from vertical heated channel is undertaken. The aim is to explore the heat transfer obtained by adding a forced flow, issued from a flat nozzle located in the entry section of a channel, to the up-going fluid along its walls. Forced and free convection are combined studied in order to increase the cooling requirements. The study deals with both symmetrically and asymmetrically heated channel. The Reynolds number based on the nozzle width and the jet velocity is assumed to be 3 103 and 2.104; whereas, the Rayleigh number based on the channel length and the wall temperature difference varies from 2.57 1010 to 5.15 1012. The heating asymmetry effect on the flow development including the mean velocity and temperature the local Nusselt number, the mass flow rate and heat transfer are examined.
EVALUATION OF STAGE-DISCHARGE RELATIONSHIP IN COMPOUND CHANNELS
Institute of Scientific and Technical Information of China (English)
MOHAGHEGH A; KOUCHAKZADEH S
2008-01-01
Experimental results were compared with the computed results obtained from the nine most well-known methods for computation of discharge in a compound channel. The results demonstrate a high accuracy of the divided channel method with the horizontal division lines, while the length of division line is included within the calculation of the wetted perimeter. In addition, as relative depth increases, the results of the all methods converge to each other and also in case of steeper slopes in lower relative depths, more agreements between different calculated methods and experimental results were observed. Furthermore, the results show the effects of the maximum momentum transfer on the horizontal interface between the main channel and flood plains, while further angular distance from the horizontal interface toward the vertical interface between main channel and flood plains causes gradual decrease of momentum transfer effects.
Institute of Scientific and Technical Information of China (English)
王伟晗; 王清成; 陈亚平
2013-01-01
通过对倾斜角35°首尾相连的三分螺旋折流板换热器的数值模拟，展示了其壳侧通道内流体在典型切面上的流场和流线分布，以及典型切面上典型直线的流动和换热参数分布，并与性能测试结果进行了对比。结果表明，数值模拟结果与实验结果是吻合的。螺旋折流板形成的近似螺旋通道，使换热器壳侧流体受离心力和向心力共同作用形成了迪恩涡二次流，且在每个螺旋周期内都存在；二次流增强了主流区域流体与靠近壁面流体的掺混，使得壳侧典型切面上中心线和折流板外缘直线的轴向速度较大；除主流中心区域外，壳侧流体在二次流的作用下具有均匀的湍流动能；二次流所在区域内，壳侧同心柱面内典型直线上换热系数相差不大，但由于二次流能使其附近区域传热面上的流体得到不断卷吸掺混，由此强化传热。%Using the numerical simulation of end to end tube-and-shell heat exchangers with trisection helical baffles with 35°inclined angle, this research demonstrated the distribution of the flow field and streamline on the typical sections of fluid in the shell side channel, as well as the distribution of flow and heat transfer parameters of typical straight lines on the typical sections. The results showed that the approximate spiral channel composed by helical baffles impelled the Dean vortex secondary flow formed by the combined effect of centrifugal and centripetal force, and the Dean vortex secondary flow existed in each spiral cycle. the secondary flow enhanced the mixing of fluid in mainstream region and fluid near the wall, resulting a larger axial velocity of the centerline and the outer edge straight line on the typical sections. Other than the mainstream center region, the shell side fluid had uniform turbulent kinetic energy in the role of secondary flow. The heat transfer coefficient on the concentric cylindrical surface
DNS of turbulent channel flow subject to oscillatory heat flux
Directory of Open Access Journals (Sweden)
Bukhvostova Anastasia
2014-01-01
Full Text Available In this paper we study the heat transfer in a turbulent channel flow, which is periodically heated through its walls. We consider the flow of air and water vapor using direct numerical simulation. We consider the fluid as a compressible Newtonian gas. We focus on the heat transfer properties of the system, e.g., the temperature difference between the walls and the Nusselt number. We consider the dependence of these quantities on the frequency of the applied heat flux. We observe that the mean temperature difference is quite insensitive to the frequency and that the amplitude of its oscillations is such that its value multiplied by the square root of frequency is approximately constant. Next we add droplets to the channel, which can undergo phase transitions. The heat transfer properties of the channel in the case with droplets are found to increase by more than a factor of two, compared to the situation without droplets.
Data Transfer Throughput Research Over Mobile Networks
Directory of Open Access Journals (Sweden)
Karolis Žvinys
2013-05-01
Full Text Available This work analyses communication channel settings of UMTS technology, which are related with a data transfer throughput. The paper describes the measurement equipment that is suitable for measuring parameters of a mobile network channel. Besides, it analyses the suitability of this equipment and issue of parameter values that are associated with data throughput. Further, the study includes the selection of the most specific parameters, which are crucial for data speed. Using these parameters, models were developed for prediction of data transfer throughput. To build the model, the linear and nonlinear forecasting methods were used. The linear prediction was made by using linear regression, nonlinear — neural networks. Using the linear prediction model, 77.83% forecast accuracy was achieved, while the accuracy of forecasted nonlinear transmission rate amounted to 76.19%. The accuracy of prediction models was obtained using eight parameters of the communication channel. Finally, the paper presents the data throughput prediction models that allow predicting data speed with the help of channel parameters presented by a standard terminal. The list of these channel parameters is derived from five UE‘s of different manufacturers. The expected most accurate data transfer rate can be predicted using a set of parameters issued by Nokia device.Article in Lithuanian
Jorge, Kubie; Thomas, Grassie
2012-01-01
A core task of engineers is to analyse energy related problems. The analytical treatment is usually based on principles of thermodynamics, fluid mechanics and heat transfer, but is increasingly being handled computationally.This unique resource presents a practical textbook, written for both undergraduates and professionals, with a series of over 60 computer workbooks on an accompanying CD.The book emphasizes how complex problems can be deconstructed into a series of simple steps. All thermophysical property computations are illustrated using diagrams within text and on the compani
Directory of Open Access Journals (Sweden)
Don Kulasiri
2005-01-01
model drying porous materials. Coupled partial differential equations governing the moisture and heat transfer can be solved using numerical techniques, and in this paper we solve them analytically in a setting suitable for industrial drying situations. We discuss the nature of the solutions using the physical properties of Pinus radiata. It is shown that the temperature gradients play a significant role in deciding the moisture profiles within the material when thickness is large and that models based only on moisture potential gradients may not be sufficient to explain the drying phenomena in moist porous materials.
Endwall convective heat transfer for bluff bodies
DEFF Research Database (Denmark)
Wang, Lei; Salewski, Mirko; Sundén, Bengt
2012-01-01
The endwall heat transfer characteristics of forced flow past bluff bodies have been investigated using liquid crystal thermography (LCT). The bluff body is placed in a rectangular channel with both its ends attached to the endwalls. The Reynolds number varies from 50,000 to 100,000. In this study...
Transfer reactions as a doorway to fusion
Energy Technology Data Exchange (ETDEWEB)
Gomes, P.R.S.; Maciel, A.M.M.; Anjos, R.M.; Moraes, S.B.; Liguori Neto, R.; Cabezas, R.; Muri, C.; Santos, G.M. [Instituto de Fisica, Universidade Federal Fluminense, Av. Litoranea s/n, Gragoata, Niteroi, RJ, 24210-340 (Brazil); Liang, J.F. [Nuclear Physics Laboratory, University of Washington, Seattle, WA 98195 (United States)
1997-10-01
This paper discusses the role played by transfer reactions on the sub-barrier fusion enhancement. A semiclassical formalism is used to derive the transfer form factors, that are used in coupled-channel calculations. It is shown that transfer reactions that take place at small distances may be an important doorway to fusion. The relation between this formalism and the long-range absorptive fusion potential is also discussed. Results of calculations for the {sup 16}O+{sup A}Sm, {sup 32}S+{sup 100}Mo and {sup 16}O+{sup 59}Co systems are presented. (author)
Interactive Joint Transfer of Energy and Information
DEFF Research Database (Denmark)
Popovski, Petar; Fouladgar, A. M.; Simeone, Osvaldo
2013-01-01
In some communication networks, such as passive RFID systems, the energy used to transfer information between a sender and a recipient can be reused for successive communication tasks. In fact, from known results in physics, any system that exchanges information via the transfer of given physical...... key design insights. Index Terms— Two-way channel, interactive communication, energy transfer, energy harvesting....... resources, such as radio waves, particles and qubits, can conceivably reuse, at least part, of the received resources. This paper aims at illustrating some of the new challenges that arise in the design of communication networks in which the signals exchanged by the nodes carry both information and energy...
Interface studies of the MOS-structure by transfer-admittance measurements
Koomen, Jan
1974-01-01
The transfer-admittance of n- and p-channel MOS transistors has been measured under the condition of a uniform channel. These MOS transistors all showed a measurable “slow interface state drift” <0·1–0·2 V. The transfer-susceptance has been found to show a significant peak value in moderate inversio
Computation over Mismatched Channels
Karamchandani, Nikhil; Diggavi, Suhas
2012-01-01
We consider the problem of distributed computation of a target function over a multiple-access channel. If the target and channel functions are matched (i.e., compute the same function), significant performance gains can be obtained by jointly designing the computation and communication tasks. However, in most situations there is mismatch between these two functions. In this work, we analyze the impact of this mismatch on the performance gains achievable with joint computation and communication designs over separation-based designs. We show that for most pairs of target and channel functions there is no such gain, and separation of computation and communication is optimal.
Energy Technology Data Exchange (ETDEWEB)
Nicklaus, Dennis J. [Fermilab
2013-10-13
We have developed an Erlang language implementation of the Channel Access protocol. Included are low-level functions for encoding and decoding Channel Access protocol network packets as well as higher level functions for monitoring or setting EPICS process variables. This provides access to EPICS process variables for the Fermilab Acnet control system via our Erlang-based front-end architecture without having to interface to C/C++ programs and libraries. Erlang is a functional programming language originally developed for real-time telecommunications applications. Its network programming features and list management functions make it particularly well-suited for the task of managing multiple Channel Access circuits and PV monitors.
Channel Choice: A Literature Review
DEFF Research Database (Denmark)
Østergaard Madsen, Christian; Kræmmergaard, Pernille
2015-01-01
The channel choice branch of e-government studies citizens’ and businesses’ choice of channels for interacting with government, and how government organizations can integrate channels and migrate users towards the most cost-efficient channels. In spite of the valuable contributions offered no sys...... no systematic overview exist of channel choice. We present a literature review of channel choice studies in government to citizen context identifying authors, countries, methods, concepts, units of analysis, and theories, and offer suggestionsfor future studies....
Salwan, Nitish; Singh, Sandeep; Arora, Suket; Singh, Amarpreet
2013-01-01
This paper presents an overview of different concepts regarding covert channels. It discusses the various classifications and the detailing of various fields used to manipulate for the covert channel execution.Different evaluation criterias are presented for measuring the strength of covert channels. The defenses and prevention schemes for this covert channel will also be discussed. This paper also discuss about an advanced timing channel i.e.Temperature Based Covert Channel.
Limits of mass-transfer in parallel plate dialyzers
Kolev, Spas D.; Linden, van der Willem E.
1992-01-01
The absolute limits of mass transfer across the membrane in a parallel-plate dialyser set by the flow pattern in both channels were determined on the basis of a mathematical model assuming axially dispersed plug flow. The lower limit corresponds to the case of mass transfer under laminar flow condit
Hydrogen Bonds in Excited State Proton Transfer
Horke, D. A.; Watts, H. M.; Smith, A. D.; Jager, E.; Springate, E.; Alexander, O.; Cacho, C.; Chapman, R. T.; Minns, R. S.
2016-10-01
Hydrogen bonding interactions between biological chromophores and their surrounding protein and solvent environment significantly affect the photochemical pathways of the chromophore and its biological function. A common first step in the dynamics of these systems is excited state proton transfer between the noncovalently bound molecules, which stabilizes the system against dissociation and principally alters relaxation pathways. Despite such fundamental importance, studying excited state proton transfer across a hydrogen bond has proven difficult, leaving uncertainties about the mechanism. Through time-resolved photoelectron imaging measurements, we demonstrate how the addition of a single hydrogen bond and the opening of an excited state proton transfer channel dramatically changes the outcome of a photochemical reaction, from rapid dissociation in the isolated chromophore to efficient stabilization and ground state recovery in the hydrogen bonded case, and uncover the mechanism of excited state proton transfer at a hydrogen bond, which follows sequential hydrogen and charge transfer processes.
Cooperative gating between ion channels.
Choi, Kee-Hyun
2014-01-01
Cooperative gating between ion channels, i.e. the gating of one channel directly coupled to the gating of neighboring channels, has been observed in diverse channel types at the single-channel level. Positively coupled gating could enhance channel-mediated signaling while negative coupling may effectively reduce channel gating noise. Indeed, the physiological significance of cooperative channel gating in signal transduction has been recognized in several in vivo studies. Moreover, coupled gating of ion channels was reported to be associated with some human disease states. In this review, physiological roles for channel cooperativity and channel clustering observed in vitro and in vivo are introduced, and stimulation-induced channel clustering and direct channel cross linking are suggested as the physical mechanisms of channel assembly. Along with physical clustering, several molecular mechanisms proposed as the molecular basis for functional coupling of neighboring channels are covered: permeant ions as a channel coupling mediator, concerted channel activation through the membrane, and allosteric mechanisms. Also, single-channel analysis methods for cooperative gating such as the binomial analysis, the variance analysis, the conditional dwell time density analysis, and the maximum likelihood fitting analysis are reviewed and discussed.
Thermodynamics of Flow Boiling Heat Transfer
Collado, F. J.
2003-05-01
Convective boiling in sub-cooled water flowing through a heated channel is essential in many engineering applications where high heat flux needs to be accommodated. It has been customary to represent the heat transfer by the boiling curve, which shows the heat flux versus the wall-minus-saturation temperature difference. However it is a rather complicated problem, and recent revisions of two-phase flow and heat transfer note that calculated values of boiling heat transfer coefficients present many uncertainties. Quite recently, the author has shown that the average thermal gap in the heated channel (the wall temperature minus the average temperature of the coolant) was tightly connected with the thermodynamic efficiency of a theoretical reversible engine placed in this thermal gap. In this work, whereas this correlation is checked again with data taken by General Electric (task III) for water at high pressure, a possible connection between this wall efficiency and the reversible-work theorem is explored.
Real-time Covert Communications Channel for Audio Signals
Directory of Open Access Journals (Sweden)
Ashraf Seleym
2012-09-01
Full Text Available Covert communications channel is considered as a type of secure communications that creates capability to transfer information between entities while hiding the contents of the channel. Multimedia data hiding techniques can be used to establish a covert channel for secret communications within a media carrier. In this paper, a high-rate covert communications channel is developed to exploit an audio stream as a carrier signal using multiple embedding in the Quantization Index Modulation framework. The proposed approach uses multi quantization vectors to increase data transmission rate. The embedding algorithms consider the embedding process as a communications problem, that it uses structured scheme of Multiple Trellis-Coded Quantization jointed with Multiple Trellis-Coded Modulation. Using convolution codes based trellis coding returns a real-time communications, because it can be continuously encoded and decoded. The proposed approach exhibits a high channel capacity due to the increase in data embedding rate without severely increasing in embedding distortion.
Iowa State University GIS Support and Research Facility — This draft dataset consists of all ditches or channelized pieces of stream that could be identified using three input datasets; namely the1:24,000 National...
2011-03-24
Communications ....................................... 2 1.3 Steganography and Covert Channels .......................................................... 3...Internet Relay Chat ..................................................................................... 7 2.2 Steganography ...13 2.2.2 Encrypted Steganographic Systems .............................................. 15 2.2.3 Text-Based Steganography
Mclyman, W. T.
1981-01-01
Transformer transmits power and digital data across rotating interface. Array has many parallel data channels, each with potential l megabaud data rate. Ferrite-cored transformers are spaced along rotor; airgap between them reduces crosstalk.
Calcium channel blocker poisoning
Directory of Open Access Journals (Sweden)
Miran Brvar
2005-04-01
Full Text Available Background: Calcium channel blockers act at L-type calcium channels in cardiac and vascular smooth muscles by preventing calcium influx into cells with resultant decrease in vascular tone and cardiac inotropy, chronotropy and dromotropy. Poisoning with calcium channel blockers results in reduced cardiac output, bradycardia, atrioventricular block, hypotension and shock. The findings of hypotension and bradycardia should suggest poisoning with calcium channel blockers.Conclusions: Treatment includes immediate gastric lavage and whole-bowel irrigation in case of ingestion of sustainedrelease products. All patients should receive an activated charcoal orally. Specific treatment includes calcium, glucagone and insulin, which proved especially useful in shocked patients. Supportive care including the use of catecholamines is not always effective. In the setting of failure of pharmacological therapy transvenous pacing, balloon pump and cardiopulmonary by-pass may be necessary.
DEFF Research Database (Denmark)
Klausen, Thomas Kjær
- serves a multitude of functions in the mammalian cell, regulating the membrane potential (Em), cell volume, protein activity and the driving force for facilitated transporters giving Cl- and Cl- channels a major potential of regulating cellular function. These functions include control of the cell cycle...... of volume perturbations evolution have developed system of channels and transporters to tightly control volume homeostasis. In the past decades evidence has been mounting, that the importance of these volume regulated channels and transporters are not restricted to the defense of cellular volume......, controlled cell death and cellular migration. Volume regulatory mechanisms has long been in focus for regulating cellular proliferation and my thesis work have been focusing on the role of Cl- channels in proliferation with specific emphasis on ICl, swell. Pharmacological blockage of the ubiquitously...
Authentication over Noisy Channels
Lai, Lifeng; Poor, H Vincent
2008-01-01
In this work, message authentication over noisy channels is studied. The model developed in this paper is the authentication theory counterpart of Wyner's wiretap channel model. Two types of opponent attacks, namely impersonation attacks and substitution attacks, are investigated for both single message and multiple message authentication scenarios. For each scenario, information theoretic lower and upper bounds on the opponent's success probability are derived. Remarkably, in both scenarios, lower and upper bounds are shown to match, and hence the fundamental limit of message authentication over noisy channels is fully characterized. The opponent's success probability is further shown to be smaller than that derived in the classic authentication model in which the channel is assumed to be noiseless. These results rely on a proposed novel authentication scheme in which key information is used to provide simultaneous protection again both types of attacks.
Djordjevic, Ivan; Vasic, Bane
2010-01-01
This unique book provides a coherent and comprehensive introduction to the fundamentals of optical communications, signal processing and coding for optical channels. It is the first to integrate the fundamentals of coding theory and optical communication.
DEFF Research Database (Denmark)
Wanitchakool, Podchanart; Ousingsawat, Jiraporn; Sirianant, Lalida
2016-01-01
, and cystic fibrosis transmembrane conductance regulator (CFTR) in cellular apoptosis. LRRC8A-E has been identified as a volume-regulated anion channel expressed in many cell types. It was shown to be required for regulatory and apoptotic volume decrease (RVD, AVD) in cultured cell lines. Its presence also......(-) channels or as regulators of other apoptotic Cl(-) channels, such as LRRC8. CFTR has been known for its proapoptotic effects for some time, and this effect may be based on glutathione release from the cell and increase in cytosolic reactive oxygen species (ROS). Although we find that CFTR is activated...... by cell swelling, it is possible that CFTR serves RVD/AVD through accumulation of ROS and activation of independent membrane channels such as ANO6. Thus activation of ANO6 will support cell shrinkage and induce additional apoptotic events, such as membrane phospholipid scrambling....
Martinac, Boris
2008-01-01
All living cells are able to detect and translate environmental stimuli into biologically meaningful signals. Sensations of touch, hearing, sight, taste, smell or pain are essential to the survival of all living organisms. The importance of sensory input for the existence of life thus justifies the effort made to understand its molecular origins. Sensing with Ion Channels focuses on ion channels as key molecules enabling biological systems to sense and process the physical and chemical stimuli that act upon cells in their living environment. Its aim is to serve as a reference to ion channel specialists and as a source of new information to non specialists who want to learn about the structural and functional diversity of ion channels and their role in sensory physiology.
Energy Technology Data Exchange (ETDEWEB)
Lee, Ju Chul; Park, Sang Hu; Son, Chang Min; Min, June Kee; Ha, Man Yeong [Pusan National University, Busan (Korea, Republic of); Cho, Jong Rae [Korea Maritime University, Busan (Korea, Republic of)
2015-09-15
In industrial fields of machine and aerospace, cooling systems consisting of channels are widely used to increase energy efficiency and prevent system overheat. In cooling channels, a reduced pressure drop, an enhanced heat transfer, and a short channel length are considered key design requirements for optimizing the total volume and weight of a system. In this work, we improved heat transfer efficiency by using milli-scale wavy structures inside the channel. By optimizing the inner structures through computational fluid dynamics analysis and Taguchi method, the Nusselt number increased by approximately 11.7% with a similar pressure drop compared with that of a normal channel for a Reynolds number of 1000.
Institute of Scientific and Technical Information of China (English)
Ya-ping ZHANG; Hao ZHANG; Dayue Darrel DUAN
2013-01-01
Vascular remodeling of cerebral arterioles,including proliferation,migration,and apoptosis of vascular smooth muscle cells (VSMCs),is the major cause of changes in the cross-sectional area and diameter of the arteries and sudden interruption of blood flow or hemorrhage in the brain,ie,stroke.Accumulating evidence strongly supports an important role for chloride (Clˉ) channels in vascular remodeling and stroke.At least three Clˉ channel genes are expressed in VSMCs:1) the TMEM16A (or Ano1),which may encode the calcium-activated Clˉ channels (CACCs); 2) the CLC-3 Clˉ channel and Clˉ/H+ antiporter,which is closely related to the volume-regulated Clˉ channels (VRCCs); and 3) the cystic fibrosis transmembrane conductance regulator (CFTR),which encodes the PKA-and PKC-activated Clˉ channels.Activation of the CACCs by agonist-induced increase in intracellular Ca2+ causes membrane depolarization,vasoconstriction,and inhibition of VSMC proliferation.Activation of VRCCs by cell volume increase or membrane stretch promotes the production of reactive oxygen species,induces proliferation and inhibits apoptosis of VSMCs.Activation of CFTR inhibits oxidative stress and may prevent the development of hypertension.In addition,Clˉ current mediated by gammaaminobutyric acid (GABA) receptor has also been implicated a role in ischemic neuron death.This review focuses on the functional roles of Clˉ channels in the development of stroke and provides a perspective on the future directions for research and the potential to develop Clˉ channels as new targets for the prevention and treatment of stroke.
Experimental Investigation on Heat Transfer Enhancement in Composite Porous Media
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The method of composite porous media with mini-longitudinal channels at the surface and with beads packing between plates was put foward to improve the integated performance of flow and heat transfer in porous media. The experimental results in the corresponding porous media were reported and analyzed. The experiments indicate that with proper matching of the particle diameter dp, the mini-channel width w, the channel depth d and the distance between plates δr the heat transfer in the composite porois media is enhanced and flow resistence reduced compared with those of no mini-longitudinal channels at the surface. So this is an effective method to improve the integrated performance of flow and heat transfer in porous media.
Understanding heat transfer in 2D channel flows including recirculation
Dirkse, M.H.; Loon, van W.K.P.; Stigter, J.D.; Bot, G.P.A.
2007-01-01
Inviscid, irrotational two-dimensional flows can be modelled using the Schwarz¿Christoffel integral. Although bounded flows including boundary layer separation and recirculation are not irrotational, a model is presented that uses the Schwarz¿Christoffel integral to model these flows. The model sepa
Energy Efficient Beam Transfer Channels for High Energy Particle Accelerators
Gardlowski, Philipp; Ondreka, David
2016-01-01
conducting (NC) magnets or high current pulsed (HCP) magnets are an economic solution. For high repetition rates above 1.0 Hz, superconducting Cos(N) (SC) magnets or superferric (SF) magnets are more attractive; at least if they are operated in DC mode and if no dynamic losses occur in the cryogenic system. Unfortunately, a range between these values exist, in which no...
1986-01-01
This book is based on a series of lectures for a course on ionic channels held in Santiago, Chile, on November 17-20, 1984. It is intended as a tutorial guide on the properties, function, modulation, and reconstitution of ionic channels, and it should be accessible to graduate students taking their first steps in this field. In the presentation there has been a deliberate emphasis on the spe cific methodologies used toward the understanding of the workings and function of channels. Thus, in the first section, we learn to "read" single channel records: how to interpret them in the theoretical frame of kinetic models, which information can be extracted from gating currents in re lation to the closing and opening processes, and how ion transport through an open channel can be explained in terms of fluctuating energy barriers. The importance of assessing unequivocally the origin and purity of mem brane preparations and the use of membrane vesicles and optical tech niques in the stUGY of ionic channels a...
Nihei, Kurt T.; Yi, Weidong; Myer, Larry R.; Cook, Neville G. W.; Schoenberg, Michael
1999-03-01
The properties of guided waves which propagate between two parallel fractures are examined. Plane wave analysis is used to obtain a dispersion equation for the velocities of fracture channel waves. Analysis of this equation demonstrates that parallel fractures form an elastic waveguide that supports two symmetric and two antisymmetric dispersive Rayleigh channel waves, each with particle motions and velocities that are sensitive to the normal and tangential stiffnesses of the fractures. These fracture channel waves degenerate to shear waves when the fracture stiffnesses are large, to Rayleigh waves and Rayleigh-Lamb plate waves when the fracture stiffnesses are low, and to fracture interface waves when the fractures are either very closely spaced or widely separated. For intermediate fracture stiffnesses typical of fractured rock masses, fracture channel waves are dispersive and exhibit moderate to strong localization of guided wave energy between the fractures. The existence of these waves is examined using laboratory acoustic measurements on a fractured marble plate. This experiment confirms the distinct particle motion of the fundamental antisymmetric fracture channel wave (A0 mode) and demonstrates the ease with which a fracture channel wave can be generated and detected.
Non-Markovianity and reservoir memory of quantum channels: a quantum information theory perspective.
Bylicka, B; Chruściński, D; Maniscalco, S
2014-07-21
Quantum technologies rely on the ability to coherently transfer information encoded in quantum states along quantum channels. Decoherence induced by the environment sets limits on the efficiency of any quantum-enhanced protocol. Generally, the longer a quantum channel is the worse its capacity is. We show that for non-Markovian quantum channels this is not always true: surprisingly the capacity of a longer channel can be greater than of a shorter one. We introduce a general theoretical framework linking non-Markovianity to the capacities of quantum channels and demonstrate how harnessing non-Markovianity may improve the efficiency of quantum information processing and communication.
Non-Markovianity and reservoir memory of quantum channels: a quantum information theory perspective
Bylicka, B.; Chruściński, D.; Maniscalco, S.
2014-01-01
Quantum technologies rely on the ability to coherently transfer information encoded in quantum states along quantum channels. Decoherence induced by the environment sets limits on the efficiency of any quantum-enhanced protocol. Generally, the longer a quantum channel is the worse its capacity is. We show that for non-Markovian quantum channels this is not always true: surprisingly the capacity of a longer channel can be greater than of a shorter one. We introduce a general theoretical framework linking non-Markovianity to the capacities of quantum channels and demonstrate how harnessing non-Markovianity may improve the efficiency of quantum information processing and communication. PMID:25043763
Influence of radiation heat transfer during a severe accident
Energy Technology Data Exchange (ETDEWEB)
Cazares R, R. I.; Epinosa P, G.; Varela H, J. R.; Vazquez R, A. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco No. 186, Col. Vicentina, 09340 Ciudad de Mexico (Mexico); Polo L, M. A., E-mail: ricardo-cazares@hotmail.com [Comision Nacional de Seguridad Nuclear y Salvaguardias, Dr. Barragan No. 779, Col. Narvarte, 03020 Ciudad de Mexico (Mexico)
2016-09-15
The aim of this work is to determine the influence of the radiation heat transfer on an average fuel channel during a severe accident of a BWR nuclear power plant. The analysis considers the radiation heat transfer in a participating medium, where the gases inside the system participate in the radiation heat transfer. We consider the steam-water mixture as an isothermal gray gas, and the boundaries of the system as a gray diffuse isothermal surface for the clad and refractory surfaces for the rest, and consider the average fuel channel as an enclosure system. During a severe accident, generation and diffusion of hydrogen begin at high temperature range (1,273 to 2,100 K), and the fuel rod cladding oxidation, but the hydrogen generated do not participate in the radiation heat transfer because it does not have any radiation properties. The heat transfer process in the fuel assembly is considered with a reduced order model, and from this, the convection and the radiation heat transfer is introduced in the system. In this paper, a system with and without the radiation heat transfer term was calculated and analyzed in order to obtain the influence of the radiation heat transfer on the average fuel channel. We show the behavior of radiation heat transfer effects on the temporal evolution of the hydrogen concentration and temperature profiles in a fuel assembly, where a stream of steam is flowing. Finally, this study is a practical complement for more accurate modeling of a severe accident analysis. (Author)
Conductance of Ion Channels - Theory vs. Experiment
Pohorille, Andrew; Wilson, Michael; Mijajlovic, Milan
2013-01-01
Transmembrane ion channels mediate a number of essential physiological processes in a cell ranging from regulating osmotic pressure to transmission of neural signals. Kinetics and selectivity of ion transport is of critical importance to a cell and, not surprisingly, it is a subject of numerous experimental and theoretical studies. In this presentation we will analyze in detail computer simulations of two simple channels from fungi - antiamoebin and trichotoxin. Each of these channels is made of an alpha-helical bundle of small, nongenomically synthesized peptides containing a number of rare amino acids and exhibits strong antimicrobial activity. We will focus on calculating ionic conductance defined as the ratio of ionic current through the channel to applied voltage. From molecular dynamics simulations, conductance can be calculated in at least two ways, each involving different approximations. Specifically, the current, given as the number of charges transferred through the channel per unit of time, can be obtained from the number of events in which ions cross the channel during the simulation. This method works well for large currents (high conductance values and/or applied voltages). If the number of crossing events is small, reliable estimates of current are difficult to achieve. Alternatively, conductance can be estimated assuming that ion transport can be well approximated as diffusion in the external potential given by the free energy profile. Then, the current can be calculated by solving the one-dimensional diffusion equation in this external potential and applied voltage (the generalized Nernst-Planck equation). To do so three ingredients are needed: the free energy profile, the position-dependent diffusion coefficient and the diffusive flux of ions into the channel. All these quantities can be obtained from molecular dynamics simulations. An important advantage of this method is that it can be used equally well to estimating large and small currents
Advanced Concepts for Underwater Acoustic Channel Modeling
Etter, P. C.; Haas, C. H.; Ramani, D. V.
2014-12-01
This paper examines nearshore underwater-acoustic channel modeling concepts and compares channel-state information requirements against existing modeling capabilities. This process defines a subset of candidate acoustic models suitable for simulating signal propagation in underwater communications. Underwater-acoustic communications find many practical applications in coastal oceanography, and networking is the enabling technology for these applications. Such networks can be formed by establishing two-way acoustic links between autonomous underwater vehicles and moored oceanographic sensors. These networks can be connected to a surface unit for further data transfer to ships, satellites, or shore stations via a radio-frequency link. This configuration establishes an interactive environment in which researchers can extract real-time data from multiple, but distant, underwater instruments. After evaluating the obtained data, control messages can be sent back to individual instruments to adapt the networks to changing situations. Underwater networks can also be used to increase the operating ranges of autonomous underwater vehicles by hopping the control and data messages through networks that cover large areas. A model of the ocean medium between acoustic sources and receivers is called a channel model. In an oceanic channel, characteristics of the acoustic signals change as they travel from transmitters to receivers. These characteristics depend upon the acoustic frequency, the distances between sources and receivers, the paths followed by the signals, and the prevailing ocean environment in the vicinity of the paths. Properties of the received signals can be derived from those of the transmitted signals using these channel models. This study concludes that ray-theory models are best suited to the simulation of acoustic signal propagation in oceanic channels and identifies 33 such models that are eligible candidates.
Pool spacing in forest channels
David R. Montgomery; John M. Buffington; Richard D. Smith; Kevin M. Schmidt; George Pess
1995-01-01
Field surveys of stream channels in forested mountain drainage basins in southeast Alaska and Washington reveal that pool spacing depends on large woody debris (LWD) loading and channel type, slope, and width. Mean pool spacing in pool-riffle, plane-bed, and forced pool-riffle channels systematically decreases from greater than 13 channel widths per pool to less than 1...
Institute of Scientific and Technical Information of China (English)
欧龙姣; 阴继翔; 武广剑; 杨宇伟; 阴勇光
2016-01-01
采用 Fluent软件,对基管相同的圆翅片管和5种椭圆翅片管用稳态RNGκ-ε模型进行三维数值模拟,5种椭圆翅片管Afin ,Amin ,De ,Per ,β分别与圆翅片(Cir )有相同的翅片面积、最小截面面积、翅片当量直径、翅片周长和翅化比.通过对不同雷诺数(Re)下流场及翅片表面局部努塞尔数(Nu)的分析比较,得到翅片管通道内流体流动及换热的特征,并提供了圆翅片管和5种椭圆翅片管的综合换热性能Nu/f 的结果.研究表明,圆翅片Cir的Nu大于椭圆翅片Afin ,De ,Per ,β,但小于椭圆翅片Amin .圆翅片的阻力系数f大于椭圆翅片Afin ,Per ,β的f ,且小于椭圆翅片Amin的f.椭圆翅片De 在Re 较小(Re≤8000)时与圆翅片Cir的f的差值较小,在Re较大(Re>8000)时与圆翅片Cir基本相同.椭圆翅片Amin的综合换热效果最好.%The three dimensional numerical simulation of circular finned tube and 5 kinds of elliptical fin tube is performed with the steady state RNGκ-εmodel by the Fluent software.The base pipes of the cir-cular finned tube and five elliptical finned tubes are same.Fluid field and local Nusselt number on fin surface are analyzed and compared for different Reynolds numbers (Re)to obtain fluid flow and heat transfer characteristics in the channel of annular finned tube,and the result of comprehensive heat trans-fer coefficient (Nu/f)on a circular finned tube and 5 elliptical finned tubes is also provided.The results show that the Nu of circular fin is biggest among elliptical fin Afin ,elliptical fin De ,elliptical fin Per and elliptical finβ,but it is smaller than elliptical fin Amin .The flow resistance coefficient of circular fin is biggest among elliptical fin Afin ,elliptical fin Per and elliptical finβ,but it is smaller than elliptical fin Amin .The results of Thermal Resistance is contrary to Nusselts.The difference of flow resistance coeffi-cient between elliptical fin De,and the circular fin is small when the
Calcium channels and migraine.
Pietrobon, Daniela
2013-07-01
Missense mutations in CACNA1A, the gene that encodes the pore-forming α1 subunit of human voltage-gated Ca(V)2.1 (P/Q-type) calcium channels, cause a rare form of migraine with aura (familial hemiplegic migraine type 1: FHM1). Migraine is a common disabling brain disorder whose key manifestations are recurrent attacks of unilateral headache that may be preceded by transient neurological aura symptoms. This review, first, briefly summarizes current understanding of the pathophysiological mechanisms that are believed to underlie migraine headache, migraine aura and the onset of a migraine attack, and briefly describes the localization and function of neuronal Ca(V)2.1 channels in the brain regions that have been implicated in migraine pathogenesis. Then, the review describes and discusses i) the functional consequences of FHM1 mutations on the biophysical properties of recombinant human Ca(V)2.1 channels and native Ca(V)2.1 channels in neurons of knockin mouse models carrying the mild R192Q or severe S218L mutations in the orthologous gene, and ii) the functional consequences of these mutations on neurophysiological processes in the cerebral cortex and trigeminovascular system thought to be involved in the pathophysiology of migraine, and the insights into migraine mechanisms obtained from the functional analysis of these processes in FHM1 knockin mice. This article is part of a Special Issue entitled: Calcium channels. Copyright © 2012 Elsevier B.V. All rights reserved.
MEMS in microfluidic channels.
Energy Technology Data Exchange (ETDEWEB)
Ashby, Carol Iris Hill; Okandan, Murat; Michalske, Terry A.; Sounart, Thomas L.; Matzke, Carolyn M.
2004-03-01
Microelectromechanical systems (MEMS) comprise a new class of devices that include various forms of sensors and actuators. Recent studies have shown that microscale cantilever structures are able to detect a wide range of chemicals, biomolecules or even single bacterial cells. In this approach, cantilever deflection replaces optical fluorescence detection thereby eliminating complex chemical tagging steps that are difficult to achieve with chip-based architectures. A key challenge to utilizing this new detection scheme is the incorporation of functionalized MEMS structures within complex microfluidic channel architectures. The ability to accomplish this integration is currently limited by the processing approaches used to seal lids on pre-etched microfluidic channels. This report describes Sandia's first construction of MEMS instrumented microfluidic chips, which were fabricated by combining our leading capabilities in MEMS processing with our low-temperature photolithographic method for fabricating microfluidic channels. We have explored in-situ cantilevers and other similar passive MEMS devices as a new approach to directly sense fluid transport, and have successfully monitored local flow rates and viscosities within microfluidic channels. Actuated MEMS structures have also been incorporated into microfluidic channels, and the electrical requirements for actuation in liquids have been quantified with an elegant theory. Electrostatic actuation in water has been accomplished, and a novel technique for monitoring local electrical conductivities has been invented.
Channel Identification Machines
Directory of Open Access Journals (Sweden)
Aurel A. Lazar
2012-01-01
Full Text Available We present a formal methodology for identifying a channel in a system consisting of a communication channel in cascade with an asynchronous sampler. The channel is modeled as a multidimensional filter, while models of asynchronous samplers are taken from neuroscience and communications and include integrate-and-fire neurons, asynchronous sigma/delta modulators and general oscillators in cascade with zero-crossing detectors. We devise channel identification algorithms that recover a projection of the filter(s onto a space of input signals loss-free for both scalar and vector-valued test signals. The test signals are modeled as elements of a reproducing kernel Hilbert space (RKHS with a Dirichlet kernel. Under appropriate limiting conditions on the bandwidth and the order of the test signal space, the filter projection converges to the impulse response of the filter. We show that our results hold for a wide class of RKHSs, including the space of finite-energy bandlimited signals. We also extend our channel identification results to noisy circuits.
Channelization of plumes beneath ice shelves
Dallaston, M. C.
2015-11-11
© 2015 Cambridge University Press. We study a simplified model of ice-ocean interaction beneath a floating ice shelf, and investigate the possibility for channels to form in the ice shelf base due to spatial variations in conditions at the grounding line. The model combines an extensional thin-film description of viscous ice flow in the shelf, with melting at its base driven by a turbulent ocean plume. Small transverse perturbations to the one-dimensional steady state are considered, driven either by ice thickness or subglacial discharge variations across the grounding line. Either forcing leads to the growth of channels downstream, with melting driven by locally enhanced ocean velocities, and thus heat transfer. Narrow channels are smoothed out due to turbulent mixing in the ocean plume, leading to a preferred wavelength for channel growth. In the absence of perturbations at the grounding line, linear stability analysis suggests that the one-dimensional state is stable to initial perturbations, chiefly due to the background ice advection.
Programmable Electrowetting with Channels and Droplets
Directory of Open Access Journals (Sweden)
Ananda Banerjee
2015-01-01
Full Text Available In this work, we demonstrate continuous and discrete functions in a digital microfluidic platform in a programmed manner. Digital microfluidics is gaining popularity in biological and biomedical applications due to its ability to manipulate discrete droplet volumes (nL–pL, which significantly reduces the need for a costly and precious biological and physiological sample volume and, thus, diagnostic time. Despite the importance of discrete droplet volume handling, the ability of continuous microfluidics to process larger sample volumes at a higher throughput cannot be easily reproduced by merely using droplets. To bridge this gap, in this work, parallel channels are formed and programmed to split into multiple droplets, while droplets are programmed to be split from one channel, transferred and merged into another channel. This programmable handling of channels and droplets combines the continuous and digital paradigms of microfluidics, showing the potential for a wider range of microfluidic functions to enable applications ranging from clinical diagnostics in resource-limited environments, to rapid system prototyping, to high throughput pharmaceutical applications.
Directory of Open Access Journals (Sweden)
Di Zhang
2014-04-01
Full Text Available Modern gas turbine blade is operating at high temperature which requires abundant cooling. Considering both heat transfer rate and pumping power for internal passages, developing efficient cooling passages is of great importance. Ribbed channel has been proved as effective heat transfer enhancement technology for considerable heat transfer characteristics; however, the pressure loss is impressive. Dimple and protrusion are frequently considered as new heat transfer augmentation tools for their low friction loss in recent years. Numerical simulations are adopted to investigate the thermal performance of rectangular channel with compound heat transfer enhancement structures with ribs, dimples, and protrusions. Among all configurations, the nondimensional dimple/protrusion depths are 0.2. The results present the flow structures of all channel configurations. The Nu/Nu0 distributions of channel section are discussed for each case. The pressure penalty f/f0 and the thermal performance TP are also considered as important parameters for heat transfer enhancement. It can be concluded that the optimal structure of the compound heat transfer enhancement structure is rib + protrusion (D = 6 mm + dimple (D = 15 mm.
Secure quantum signatures using insecure quantum channels
Amiri, Ryan; Wallden, Petros; Kent, Adrian; Andersson, Erika
2016-03-01
Digital signatures are widely used in modern communication to guarantee authenticity and transferability of messages. The security of currently used classical schemes relies on computational assumptions. We present a quantum signature scheme that does not require trusted quantum channels. We prove that it is unconditionally secure against the most general coherent attacks, and show that it requires the transmission of significantly fewer quantum states than previous schemes. We also show that the quantum channel noise threshold for our scheme is less strict than for distilling a secure key using quantum key distribution. This shows that "direct" quantum signature schemes can be preferable to signature schemes relying on secret shared keys generated using quantum key distribution.
Multiplexing technique for computer communications via satellite channels
Binder, R.
1975-01-01
Multiplexing scheme combines technique of dynamic allocation with conventional time-division multiplexing. Scheme is designed to expedite short-duration interactive or priority traffic and to delay large data transfers; as result, each node has effective capacity of almost total channel capacity when other nodes have light traffic loads.
Covert Channels in SIP for VoIP Signalling
Mazurczyk, Wojciech; Szczypiorski, Krzysztof
In this paper, we evaluate available steganographic techniques for SIP (Session Initiation Protocol) that can be used for creating covert channels during signaling phase of VoIP (Voice over IP) call. Apart from characterizing existing steganographic methods we provide new insights by introducing new techniques. We also estimate amount of data that can be transferred in signalling messages for typical IP telephony call.
Covert Channels in SIP for VoIP signalling
Mazurczyk, Wojciech
2008-01-01
In this paper, we evaluate available steganographic techniques for SIP (Session Initiation Protocol) that can be used for creating covert channels during signaling phase of VoIP (Voice over IP) call. Apart from characterizing existing steganographic methods we provide new insights by introducing new techniques. We also estimate amount of data that can be transferred in signalling messages for typical IP telephony call.
Dequantization Via Quantum Channels
Andersson, Andreas
2016-10-01
For a unital completely positive map {Φ} ("quantum channel") governing the time propagation of a quantum system, the Stinespring representation gives an enlarged system evolving unitarily. We argue that the Stinespring representations of each power {Φ^m} of the single map together encode the structure of the original quantum channel and provide an interaction-dependent model for the bath. The same bath model gives a "classical limit" at infinite time {mto∞} in the form of a noncommutative "manifold" determined by the channel. In this way, a simplified analysis of the system can be performed by making the large- m approximation. These constructions are based on a noncommutative generalization of Berezin quantization. The latter is shown to involve very fundamental aspects of quantum-information theory, which are thereby put in a completely new light.
Hosur, Pavan; Roberts, Daniel A; Yoshida, Beni
2015-01-01
We study chaos and scrambling in unitary channels by considering their entanglement properties as states. Using out-of-time-order correlation functions to diagnose chaos, we characterize the ability of a channel to process quantum information. We show that the generic decay of such correlators implies that any input subsystem must have near vanishing mutual information with almost all partitions of the output. Additionally, we propose the negativity of the tripartite information of the channel as a general diagnostic of scrambling. This measures the delocalization of information and is closely related to the decay of out-of-time-order correlators. We back up our results with numerics in two non-integrable models and analytic results in a perfect tensor network model of chaotic time evolution. These results show that the butterfly effect in quantum systems implies the information-theoretic definition of scrambling.
Energy Technology Data Exchange (ETDEWEB)
Hosur, Pavan; Qi, Xiao-Liang [Department of Physics, Stanford University,476 Lomita Mall, Stanford, California 94305 (United States); Roberts, Daniel A. [Center for Theoretical Physics and Department of Physics, Massachusetts Institute of Technology,77 Massachusetts Ave, Cambridge, Massachusetts 02139 (United States); Yoshida, Beni [Perimeter Institute for Theoretical Physics,31 Caroline Street North, Waterloo, Ontario N2L 2Y5 (Canada); Walter Burke Institute for Theoretical Physics, California Institute of Technology,1200 E California Blvd, Pasadena CA 91125 (United States)
2016-02-01
We study chaos and scrambling in unitary channels by considering their entanglement properties as states. Using out-of-time-order correlation functions to diagnose chaos, we characterize the ability of a channel to process quantum information. We show that the generic decay of such correlators implies that any input subsystem must have near vanishing mutual information with almost all partitions of the output. Additionally, we propose the negativity of the tripartite information of the channel as a general diagnostic of scrambling. This measures the delocalization of information and is closely related to the decay of out-of-time-order correlators. We back up our results with numerics in two non-integrable models and analytic results in a perfect tensor network model of chaotic time evolution. These results show that the butterfly effect in quantum systems implies the information-theoretic definition of scrambling.
Julius, David
2013-01-01
Nociception is the process whereby primary afferent nerve fibers of the somatosensory system detect noxious stimuli. Pungent irritants from pepper, mint, and mustard plants have served as powerful pharmacological tools for identifying molecules and mechanisms underlying this initial step of pain sensation. These natural products have revealed three members of the transient receptor potential (TRP) ion channel family--TRPV1, TRPM8, and TRPA1--as molecular detectors of thermal and chemical stimuli that activate sensory neurons to produce acute or persistent pain. Analysis of TRP channel function and expression has validated the existence of nociceptors as a specialized group of somatosensory neurons devoted to the detection of noxious stimuli. These studies are also providing insight into the coding logic of nociception and how specification of nociceptor subtypes underlies behavioral discrimination of noxious thermal, chemical, and mechanical stimuli. Biophysical and pharmacological characterization of these channels has provided the intellectual and technical foundation for developing new classes of analgesic drugs.
Automatic cross-talk removal from multi-channel data
Allen, B; Ottewill, A; Allen, Bruce; Hua, Wensheng; Ottewill, Adrian
1999-01-01
A technique is described for removing interference from a signal of interest ("channel 1") which is one of a set of N time-domain instrumental signals ("channels 1 to N"). We assume that channel 1 is a linear combination of "true" signal plus noise, and that the "true" signal is not correlated with the noise. We also assume that part of this noise is produced, in a poorly-understood way, by the environment, and that the environment is monitored by channels 2 to N. Finally, we assume that the contribution of channel n to channel 1 is described by an (unknown!) linear transfer function R_n(t-t'). Our technique estimates the R_i and provides a way to subtract the environmental contamination from channel 1, giving an estimate of the "true" signal which minimizes its variance. It also provides some insights into how the environment is contaminating the signal of interest. The method is illustrated with data from a prototype interferometric gravitational-wave detector, in which the channel of interest (differential...
BLIND CHANNEL ESTIMATION IN DELAY DIVERSITY FOR FREQUENCY SELECTIVE CHANNELS
Institute of Scientific and Technical Information of China (English)
Zhao Zheng; Jia Ying; Yin Qinye
2003-01-01
Delay diversity is an effective transmit diversity technique to combat adverse ef-fects of fading. Thus far, previous work in delay diversity assumed that perfect estimates ofcurrent channel fading conditions are available at the receiver and training symbols are requiredto estimate the channel from the transmitter to the receiver. However, increasing the number ofthe antennas increases the required training interval and reduces the available time within whichdata may be transmitted. Learning the channel coefficients becomes increasingly difficult for thefrequency selective channels. In this paper, with the subspace method and the delay character ofdelay diversity, a channel estimation method is proposed, which does not use training symbols. Itaddresses the transmit diversity for a frequency selective channel from a single carrier perspectivein the form of a simple equivalent fiat fading model. Monte Carlo simulations give the perfor-mance of channel estimation and the performance comparison of our channel-estimation-baseddetector with decision feedback equalization, which uses the perfect channel information.
K(v)7 channels: function, pharmacology and channel modulators.
Dalby-Brown, William; Hansen, Henrik H; Korsgaard, Mads P G; Mirza, Naheed; Olesen, Søren-P
2006-01-01
K(v)7 channels are unique among K(+) channels, since four out of the five channel subtypes have well-documented roles in the development of human diseases. They have distinct physiological functions in the heart and in the nervous system, which can be ascribed to their voltage-gating properties. The K(v)7 channels also lend themselves to pharmacological modulation, and synthetic openers as well as blockers of the channels, regulating neuronal excitability, have existed even before the K(v)7 channels were identified by cloning. In the present review we give an account on the focused efforts to develop selective modulators, openers as well as blockers, of the K(v)7 channel subtypes, which have been undertaken during recent years, along with a discussion of the K(v)7 ion channel physiology and therapeutic indications for modulators of the neuronal K(v)7 channels.
Ionic Channels in Thunderclouds
Losseva, T. V.; Fomenko, A. S.; Nemtchinov, I. V.
2007-12-01
We proceed to study the formation and propagation of ionic channels in thunderclouds in the framework of the model of the corona discharge wave propagation (Fomenko A.S., Losseva T.V., Nemtchinov I.V. The corona discharge waves in thunderclouds and formation of ionic channels // 2004 Fall Meeting. EOS Trans. AGU. 2004. V. 85. ¹ 47. Suppl. Abstract AE23A-0835.). In this model we proposed a hypothesis that the structure of a thundercloud becomes nonuniform due to corona discharge on the drops and ice particles and formation of ionic channels with higher conductivity than the surrounding air. When the onset strength of corona discharge becomes smaller than the electric field strength the corona discharge increases concentrations of ions in a small part of the cloud (a hot spot). An additional charge at opposite ends of the hot spot forms due to polarization process. The increased electric field initiates corona discharge in other parts of the cloud on ice particles and water drops with smaller sizes. The corona discharge front moves as a wave with the velocity of the order of ion drift and formes a highly conductive channel. We model this non-stationary problem with Poisson equation which is solved simultaneously with a simplified set of kinetic equations for ions, small charged particles and electrons (at high electric fields), including ionization due to electronic impact, attachment and formation of positive ions. By applying 3D numerical simulations we obtain the parameters of formed ionic channels with respect to onset electric fields both from large particles (in hot spot) and from small particles (surrounding hot spot), microscopic currents from particles with different sizes and the external electric field in the cloud. The interaction of ionic channels is also investigated. This work was supported by Russian Foundation of Basic Research (Project No 07-05-00998-à).
Search for proton emission in {sup 54}Ni and multi-nucleon transfer reactions in the actinide region
Energy Technology Data Exchange (ETDEWEB)
Geibel, Kerstin
2012-06-15
The first part of the thesis presents the investigation of fusion-evaporation reactions in order to verify one-proton emission from the isomeric 10{sup +} state in the proton rich nucleus {sup 54}Ni. Between the years 2006 and 2009 a series of experimental studies were performed at the Tandem accelerator in the Institut fuer Kernphysik (IKP), University of Cologne. These experiments used fusion-evaporation reactions to populate {sup 54}Ni via the two-neutron-evaporation channel of the compound nucleus {sup 56}Ni. The cross section for the population of the ground state of {sup 54}Ni was predicted to be in orders of microbarn. This required special care with respect to the sensitivity of the experimental setup, which consisted of a double-sided silicon-strip detector (DSSSD), a neutron-detector array and HPGe detectors. In two experiments the excitation functions of the reactions ({sup 32}S+{sup 24}Mg) and ({sup 28}Si+{sup 28}Si) were determined to find the optimal experimental conditions for the population of {sup 54}Ni. A final experiment employed a {sup 28}Si beam at an energy of 70 MeV, impinging on a {sup 28}Si target. With a complex analysis it is possible to obtain a background-free energy spectrum of the DSSSD. An upper cross section limit for the population of the 10{sup +} state in {sup 54}Ni is established at σ({sup 54}Ni(10{sup +})) ≤ (13.9 ± 7.8) nbarn. In the second part of the thesis the population of actinide nuclei by multi-nucleon transfer reactions is investigated. Two experiments, performed in 2007 and 2008 at the CLARA-PRISMA setup at the Laboratori Nazionali di Legnaro, are analyzed with respect to the target-like reaction products. In both experiments {sup 238}U was used as target. A {sup 70}Zn beam with 460 MeV and a {sup 136}Xe beam with 926 MeV, respectively, impinged on the target, inducing transfer reactions. Kinematic correlations between the reaction partners are used to obtain information on the unobserved target-like reaction
Communicating Under Channel Uncertainty
Warsi, Naqueeb; Shah, Tapan
2010-01-01
For a single transmit and receive antenna system, a new constellation design is proposed to combat errors in the phase estimate of the channel coefficient. The proposed constellation is a combination of PSK and PAM constellations, where PSK is used to provide protection against phase errors, while PAM is used to increase the transmission rate using the knowledge of the magnitude of the channel coefficient. The performance of the proposed constellation is shown to be significantly better than the widely used QAM in terms of probability of error. The proposed strategy can also be extended to systems using multiple transmit and receive antennas.
Riahi-Madvar, Hossien; Ayyoubzadeh, Seyed Ali; Namin, Masoud Montazeri; Seifi, Akram
2011-01-01
Flow in compound channels with overbank flows becomes more complex because of shear interactions between flows in main channel and flood plains, lateral momentum transfer and secondary flows. Compound channels have interesting applications in flood control, civil engineering and environmental management. Because it is difficult to obtain sufficiently accurate and comprehensive understandings of flow in natural compound rivers, the developed models of flow in overbank flows have many uncertain...
Characterisation of K+ Channels in Human Fetoplacental Vascular Smooth Muscle Cells
Brereton, Melissa F.; Mark Wareing; Rebecca L Jones; Greenwood, Susan L.
2013-01-01
Adequate blood flow through placental chorionic plate resistance arteries (CPAs) is necessary for oxygen and nutrient transfer to the fetus and a successful pregnancy. In non-placental vascular smooth muscle cells (SMCs), K(+) channels regulate contraction, vascular tone and blood flow. Previous studies showed that K(+) channel modulators alter CPA tone, but did not distinguish between effects on K(+) channels in endothelial cells and SMCs. In this study, we developed a preparation of freshly...
Energy Technology Data Exchange (ETDEWEB)
Basmajian, V.V.
1986-01-28
This patent describes a heat transfer apparatus which consists of: heat exchanging means for orientation in the earth below ground substantially vertically, having a hollow conduit of length from top to bottom much greater than the span across the hollow conduit orthogonal to its length with a top, bottom and an intermediate portion contiguous and communicating with the top and bottom portions for allowing thermally conductive fluid to flow freely between the top, intermediate and bottom portions for immersion in thermally conductive fluid in the region around the heat exchanging means for increasing the heat flow between the latter and earth when inserted into a substantially vertical borehole in the earth with the top portion above the bottom portion. The heat exchanger consists of heat exchanging conduit means in the intermediate portion for carrying refrigerant. The heat exchanging conduit consisting of tubes of thermally conductive material for carrying the refrigerant and extending along the length of the hollow conduit for a tube length that is less than the length of the hollow conduit. The hollow conduit is formed with port means between the top and the plurality of tubes for allowing the thermally conductive fluid to pass in a flow path embracing the tubes, the bottom portion, an outer channel around the hollow conduit and the port means.
Zhao, Ying-xiao; Zhang, Yue; Fan, Li-jie; Li, Wei-xing; Chen, Zeng-ping
2014-09-01
An optical fiber control and transmission module is designed and realized based on Virtex-7 field programmable gata array (FPGA), which can be applied in multi-channel broadband digital receivers. The module consists of sampling data transfer submodule and multi-channel synchronous sampling control submodule. The sampling data transmission in 4× fiber link channel is realized with the self-defined transfer protocol. The measured maximum data rate is 4.97 Gbyte/s. By connecting coherent clocks to the transmitter and receiver endpoints and using the self-defined transfer protocol, multi-channel sampling control signals transferred in optical fibers can be received synchronously by each analog-to-digital converter (ADC) with high accuracy and strong anti-interference ability. The module designed in this paper has certain reference value in increasing the transmission bandwidth and the synchronous sampling accuracy of multi-channel broadband digital receivers.
Developments in relativistic channeling
Energy Technology Data Exchange (ETDEWEB)
Carrigan, R.A. Jr.
1996-10-01
The possibility of using channeling as a tool for high energy accelerator applications and particle physics has now been extensively investigated. Bent crystals have been used for accelerator extraction and for particle deflection. Applications as accelerating devices have been discussed but have not yet been tried. 61 refs., 1 fig.
DEFF Research Database (Denmark)
the manual channel. Not surprisingly, most papers deal with non-manuals on the face. Once again, the papers at this workshop clearly identify the potentials of even closer cooperation between sign linguists and sign language engineers, and we think it is events like this that contribute a lot to a better...
Eisenhut, Michael; Wallace, Helen
2011-04-01
Most physical illness in vertebrates involves inflammation. Inflammation causes disease by fluid shifts across cell membranes and cell layers, changes in muscle function and generation of pain. These disease processes can be explained by changes in numbers or function of ion channels. Changes in ion channels have been detected in diarrhoeal illnesses, pyelonephritis, allergy, acute lung injury and systemic inflammatory response syndromes involving septic shock. The key role played by changes in ion transport is directly evident in inflammation-induced pain. Expression or function of all major categories of ion channels like sodium, chloride, calcium, potassium, transient receptor potential, purinergic receptor and acid-sensing ion channels can be influenced by cyto- and chemokines, prostaglandins, leukotrienes, histamine, ATP, reactive oxygen species and protons released in inflammation. Key pathways in this interaction are cyclic nucleotide, phosphoinositide and mitogen-activated protein kinase-mediated signalling, direct modification by reactive oxygen species like nitric oxide, ATP or protons and disruption of the cytoskeleton. Therapeutic interventions to modulate the adverse and overlapping effects of the numerous different inflammatory mediators on each ion transport system need to target adversely affected ion transport systems directly and locally.
Directory of Open Access Journals (Sweden)
Enrique eBalderas
2015-03-01
Full Text Available Since its discovery in a glioma cell line 15 years ago, mitochondrial BKCa channel (mitoBKCa has been studied in brain cells and cardiomyocytes sharing general biophysical properties such as high K+ conductance (~300 pS, voltage-dependency and Ca2+-sensitivity. Main advances in deciphering the molecular composition of mitoBKCa have included establishing that it is encoded by the Kcnma1 gene, that a C-terminal splice insert confers mitoBKCa ability to be targeted to cardiac mitochondria, and evidence for its potential coassembly with β subunits. Notoriously, β1 subunit directly interacts with cytochrome c oxidase and mitoBKCa can be modulated by substrates of the respiratory chain. mitoBKCa channel has a central role in protecting the heart from ischemia, where pharmacological activation of the channel impacts the generation of reactive oxygen species and mitochondrial Ca2+ preventing cell death likely by impeding uncontrolled opening of the mitochondrial transition pore. Supporting this view, inhibition of mitoBKCa with Iberiotoxin, enhances cytochrome c release from glioma mitochondria. Many tantalizing questions remain. Some of them are: how is mitoBKCa coupled to the respiratory chain? Does mitoBKCa play non-conduction roles in mitochondria physiology? Which are the functional partners of mitoBKCa? What are the roles of mitoBKCa in other cell types? Answers to these questions are essential to define the impact of mitoBKCa channel in mitochondria biology and disease.
Intermittency and exotic channels
Bialas, A
1994-01-01
It is pointed out that accurate measurements of short-range two-particle correlations in like-charge K\\pi and in \\pi^ 0\\pi^ 0 channels should be very helpful in determining the origin of the \\lq\\lq intermittency\\rq\\rq\\ phenomenon observed recently for the like-charge pion pairs.
Frank Huysmans; Jos de Haan
2010-01-01
Original title: Alle kanalen staan open. The rapid changes taking place in the media landscape in the Netherlands - characterised by digitisation and convergence of media technologies - raise the question of how the Dutch are dealing with the many new opportunities that have opened up. All channels
Chemistry in Microfluidic Channels
Chia, Matthew C.; Sweeney, Christina M.; Odom, Teri W.
2011-01-01
General chemistry introduces principles such as acid-base chemistry, mixing, and precipitation that are usually demonstrated in bulk solutions. In this laboratory experiment, we describe how chemical reactions can be performed in a microfluidic channel to show advanced concepts such as laminar fluid flow and controlled precipitation. Three sets of…
DEFF Research Database (Denmark)
Pedersen, Stine Falsig; Owsianik, Grzegorz; Nilius, Bernd
2005-01-01
to a plethora of data on the roles of TRPs in a variety of tissues and species, including mammals, insects, and yeast. The present review summarizes the most pertinent recent evidence regarding the structural and functional properties of TRP channels, focusing on the regulation and physiology of mammalian TRPs....
Technology transfer by multinationals
Kostyantyn Zuzik
2003-01-01
The paper analyses the issue of technology transfer by multinational corporations. The following questions are explored: (a) world market of technologies, the role of MNCs (b) Choice of the technology transfer mode, Dunning's OLI-theory as a factor of the choice of the mode of transfer (c) measurement and profitability of technology transfer (d) transfer of technology through partnerships, JVs, alliances and through M&As (e) aspects of technology transfer by services multinationals. Paper uti...
Technology transfer by multinationals
2003-01-01
The paper analyses the issue of technology transfer by multinational corporations. The following questions are explored: (a) world market of technologies, the role of MNCs (b) Choice of the technology transfer mode, Dunning's OLI-theory as a factor of the choice of the mode of transfer (c) measurement and profitability of technology transfer (d) transfer of technology through partnerships, JVs, alliances and through M&As (e) aspects of technology transfer by services multinationals. Paper uti...
The gLite File Transfer Service
Badino, Paolo; Casey, J; Frohner, A; Kunszt, Peter Z; McCance, G
2006-01-01
In this paper we describe the architecture and implementation of the gLite File Transfer Service (FTS) and list the most basic deployment scenarios. The FTS is addressing the need to manage massive wide-area data transfers on dedicated network channels while allowing the involved sites and users to manage their policies. The FTS manages the transfers in a robust way, allowing for an optimized high throughput between storage systems. The FTS can be used to perform the LHC Tier-0 to Tier-1 data transfer as well as the Tier-1 to Tier-2 data distribution and collection. The storage system peculiarities can be taken into account by fine-tuning the parameters of the FTS managing a particular channel. All the manageability related features as well as the interaction with other components that form part of the overall service are described as well. The FTS is also extensible so that particular user groups or experiment frameworks can customize its behavior both for pre- and post-transfer tasks. The FTS has been desig...
Experimental study of natural circulation flow instability in rectangular channels
Energy Technology Data Exchange (ETDEWEB)
Zhou, Tao; Qi, Shi; Song, Mingqiang [North China Electric Power Univ., Beijing (China). School of Nuclear Science and Engineering; Passive Nuclear Safety Technology, Beijing (China). Beijing Key Lab.; Xiao, Zejun [Nuclear, Reactor Thermal Hydraulics Technology, Chengdu (China). CNNC Key Lab.
2017-05-15
Experiments of natural circulation flow instability were conducted in rectangular channels with 5 mm and 10 mm wide gaps. Results for different heating powers were obtained. The results showed that the flow will tend to be instable with the growing of heating power. The oscillation period of pressure D-value and volume flow are the same, but their phase positions are opposite. They both can be described by trigonometric functions. The existence of edge position and secondary flow will strengthen the disturbance of fluid flow in rectangle channels, which contributes to heat transfer. The disturbance of bubble and fluid will be strengthened, especially in the saturated boiling section, which make it possible for the mixing flow. The results also showed that the resistance in 5 mm channel is bigger than that in 10 mm channel, it is less likely to form stable natural circulation in the subcooled region.
[Advances in the study of virtual channels of cochlear implant].
Zhu, Ziyan; Guan, Tian; Ye, Datian
2009-12-01
This paper discusses virtual channels of cochlear implant, which is produced by simultaneous or sequential activation of adjacent cochlear implant electrodes. Virtual channels create and transfer more available spectral pitch information with the limited number of fixed electrodes, which can be recognized as pitch percepts intermediate to those produced by each electrode separately. This technique not only utilizes the interaction of electrodes but also increases the number of place-pitch steps available to cochlear implant listeners. Virtual channels could be used to realize speech recognition in noisy environment, in enjoying music, and in understanding Chinese language. The study of virtual channels would significantly enhance the traditional cochlear implant therapy and benefit people suffering severe to profound hearing loss.
A New Covert Channel over Cellular Voice Channel in Smartphones
Aloraini, Bushra; Johnson, Daryl; Stackpole, Bill; Mishra, Sumita
2015-01-01
Investigating network covert channels in smartphones has become increasingly important as smartphones have recently replaced the role of traditional computers. Smartphones are subject to traditional computer network covert channel techniques. Smartphones also introduce new sets of covert channel techniques as they add more capabilities and multiple network connections. This work presents a new network covert channel in smartphones. The research studies the ability to leak information from the...
Structural dynamics of potassium-channel gating revealed by single-molecule FRET.
Wang, Shizhen; Vafabakhsh, Reza; Borschel, William F; Ha, Taekjip; Nichols, Colin G
2016-01-01
Crystallography has provided invaluable insights regarding ion-channel selectivity and gating, but to advance understanding to a new level, dynamic views of channel structures within membranes are essential. We labeled tetrameric KirBac1.1 potassium channels with single donor and acceptor fluorophores at different sites and then examined structural dynamics within lipid membranes by single-molecule fluorescence resonance energy transfer (FRET). We found that the extracellular region is structurally rigid in both closed and open states, whereas the N-terminal slide helix undergoes marked conformational fluctuations. The cytoplasmic C-terminal domain fluctuates between two major structural states, both of which become less dynamic and move away from the pore axis and away from the membrane in closed channels. Our results reveal mobile and rigid conformations of functionally relevant KirBac1.1 channel motifs, implying similar dynamics for similar motifs in eukaryotic Kir channels and in cation channels in general.
Biased Brownian motion in narrow channels with asymmetry and anisotropy
To, Kiwing; Peng, Zheng
2016-11-01
We study Brownian motion of a single millimeter size bead confined in a quasi-two-dimensional horizontal channel with built-in anisotropy and asymmetry. Channel asymmetry is implemented by ratchet walls while anisotropy is introduced using a channel base that is grooved along the channel axis so that a bead can acquire a horizontal impulse perpendicular to the longitudinal direction when it collides with the base. When energy is injected to the channel by vertical vibration, the combination of asymmetric walls and anisotropic base induces an effective force which drives the bead into biased diffusive motion along the channel axis with diffusivity and drift velocity increase with vibration strength. The magnitude of this driving force, which can be measured in experiments of tilted channel, is found to be consistent to those obtained from dynamic mobility and position probability distribution measurements. These results are explained by a simple collision model that suggests the random kinetic energies transfer between different translational degrees of freedom may be turned into useful work in the presence of asymmetry and anisotropy.
Rapid Fabrication Techniques for Liquid Rocket Channel Wall Nozzles
Gradl, Paul R.
2016-01-01
The functions of a regeneratively-cooled nozzle are to (1) expand combustion gases to increase exhaust gas velocity while, (2) maintaining adequate wall temperatures to prevent structural failure, and (3) transfer heat from the hot gases to the coolant fluid to promote injector performance and stability. Regeneratively-cooled nozzles are grouped into two categories: tube-wall nozzles and channel wall nozzles. A channel wall nozzle is designed with an internal liner containing a series of integral coolant channels that are closed out with an external jacket. Manifolds are attached at each end of the nozzle to distribute coolant to and away from the channels. A variety of manufacturing techniques have been explored for channel wall nozzles, including state of the art laser-welded closeouts and pressure-assisted braze closeouts. This paper discusses techniques that NASA MSFC is evaluating for rapid fabrication of channel wall nozzles that address liner fabrication, slotting techniques and liner closeout techniques. Techniques being evaluated for liner fabrication include large-scale additive manufacturing of freeform-deposition structures to create the liner blanks. Abrasive water jet milling is being evaluated for cutting the complex coolant channel geometries. Techniques being considered for rapid closeout of the slotted liners include freeform deposition, explosive bonding and Cold Spray. Each of these techniques, development work and results are discussed in further detail in this paper.
Knowledge transfer and university patents in Mexico
María Guadalupe Calderón-Martínez; José García-Quevedo
2013-01-01
Purpose The aim of this paper is to examine the factors that influence the ability of Mexican public universities to generate patents. Academic patents are deserving of increasing interest as channels for the transfer of knowledge from universities to firms. Design/methodology/approach A review of the international literature on the main factors that explain the production of patents was undertaken. On the basis of this information, a database for 80 Mexican universities was built and a mod...
Quantum state transfer via Bloch oscillations.
Tamascelli, Dario; Olivares, Stefano; Rossotti, Stefano; Osellame, Roberto; Paris, Matteo G A
2016-05-18
The realization of reliable quantum channels, able to transfer a quantum state with high fidelity, is a fundamental step in the construction of scalable quantum devices. In this paper we describe a transmission scheme based on the genuinely quantum effect known as Bloch oscillations. The proposed protocol makes it possible to carry a quantum state over different distances with a minimal engineering of the transmission medium and can be implemented and verified on current quantum technology hardware.
Monaural and binaural subjective modulation transfer functions in simple reverberation
DEFF Research Database (Denmark)
2008-01-01
The envelope of a signal is filtered by the transmission channel through which it passes. The amount of reduction for a given envelope, or modulation, frequency has been called the modulation transfer function (MTF) and can be derived from the impulse response of the transmission channel [Schroeder......, M.R. (1981) Modulation transfer-functions: Definition and measurement, Acustica, 49, 179-182]. The envelope of a speech signal is critical for intelligibility, and the speech transmission index (STI) predicts the intelligibility of speech through a given transmission channel based on its MTF...... [Houtgast, T. and Steeneken, H.J.M. (1973) Modulation transfer-function in room acoustics as a predictor of speech intelligibility, Acustica, 28, 66-73]. In the present study, the results of intensity modulation detection experiments with broad-band noise carriers are reported in monaural and binaural...
Digital communications over fading channels
Beltz, Nathan E.; Robertson, R. Clark
2004-01-01
In this report, the probabilities of bit error for the most commonly used digital modulation techniques are analyzed. Analytic solutions are developed for the probability of bit error when the signal is affected by the most commonly encountered impairment to system performance for a wireless channel, the transmission of the signal over a fading channel. In this report, the effect of a slow, flat Ricean fading channel on communications systems performance is examined. Since channel fading ...
Radar channel balancing with commutation
Energy Technology Data Exchange (ETDEWEB)
Doerry, Armin Walter
2014-02-01
When multiple channels are employed in a pulse-Doppler radar, achieving and maintaining balance between the channels is problematic. In some circumstances the channels may be commutated to achieve adequate balance. Commutation is the switching, trading, toggling, or multiplexing of the channels between signal paths. Commutation allows modulating the imbalance energy away from the balanced energy in Doppler, where it can be mitigated with filtering.
Energy Technology Data Exchange (ETDEWEB)
Aritomi, Masanori; Takemoto, Takatoshi [Tokyo Institute of Technology, Tokyo (Japan); Chiang, Jing-Hsien [Japan NUS Corp. Ltd., Toyko (Japan)] [and others
1995-09-01
A concept of natural circulation BWRs such as the SBWR has been proposed and seems to be promising in that the primary cooling system can be simplified. The authors have been investigating thermo-hydraulic instabilities which may appear during the start-up in natural circulation BWRs. In our previous works, geysering was investigated in parallel boiling channels for both natural and forced circulations, and its driving mechanism and the effect of system pressure on geysering occurrence were made clear. In this paper, geysering is investigated in a vertical column and a U-shaped vertical column heated in the lower parts. It is clarified from the results that the occurrence mechanism of geysering and the dependence of system pressure on geysering occurrence coincide between parallel boiling channels in circulation systems and vertical columns in non-circulation systems.
``Just Another Distribution Channel?''
Lemstra, Wolter; de Leeuw, Gerd-Jan; van de Kar, Els; Brand, Paul
The telecommunications-centric business model of mobile operators is under attack due to technological convergence in the communication and content industries. This has resulted in a plethora of academic contributions on the design of new business models and service platform architectures. However, a discussion of the challenges that operators are facing in adopting these models is lacking. We assess these challenges by considering the mobile network as part of the value system of the content industry. We will argue that from the perspective of a content provider the mobile network is ‘just another’ distribution channel. Strategic options available for the mobile communication operators are to deliver an excellent distribution channel for content delivery or to move upwards in the value chain by becoming a content aggregator. To become a mobile content aggregator operators will have to develop or acquire complementary resources and capabilities. Whether this strategic option is sustainable remains open.
Heimburg, Thomas
2010-01-01
The interpretation electrical phenomena in biomembranes is usually based on the assumption that the experimentally found discrete ion conduction events are due to a particular class of proteins called ion channels while the lipid membrane is considered being an inert electrical insulator. The particular protein structure is thought to be related to ion specificity, specific recognition of drugs by receptors and to macroscopic phenomena as nerve pulse propagation. However, lipid membranes in their chain melting regime are known to be highly permeable to ions, water and small molecules, and are therefore not always inert. In voltage-clamp experiments one finds quantized conduction events through protein-free membranes in their melting regime similar to or even undistinguishable from those attributed to proteins. This constitutes a conceptual problem for the interpretation of electrophysiological data obtained from biological membrane preparations. Here, we review the experimental evidence for lipid ion channels...
DMT of weighted Parallel Channels: Application to Broadcast Channel
Mroueh, Lina; Othman, Ghaya Rekaya-Ben; Belfiore, Jean-Claude
2008-01-01
In a broadcast channel with random packet arrival and transmission queues, the stability of the system is achieved by maximizing a weighted sum rate capacity with suitable weights that depend on the queue size. The weighted sum rate capacity using Dirty Paper Coding (DPC) and Zero Forcing (ZF) is asymptotically equivalent to the weighted sum capacity over parallel single-channels. In this paper, we study the Diversity Multiplexing Tradeoff (DMT) of the fading broadcast channel under a fixed weighted sum rate capacity constraint. The DMT of both identical and different parallel weighted MISO channels is first derived. Finally, we deduce the DMT of a broadcast channel using DPC and ZF precoders.
Transfer Readiness Pilot Study.
Scott-Skillman, Thelma; And Others
The California Community Colleges (CCC) has implemented a prototype model for determining student transfer readiness as a primary means of assessing community college transfer effectiveness. This report provides definitions of transfer readiness and guidelines for colleges participating in the CCC transfer readiness study. First, a memorandum from…
DEFF Research Database (Denmark)
Bateman, I.J.; Brouwer, R.; Ferrini, S.
We develop and test guidance principles for benefits transfers. These argue that when transferring across relatively similar sites, simple mean value transfers are to be preferred but that when sites are relatively dissimilar then value function transfers will yield lower errors. The paper also...
On partially entanglement breaking channels
Chruscinski, D; Chruscinski, Dariusz; Kossakowski, Andrzej
2005-01-01
Using well known duality between quantum maps and states of composite systems we introduce the notion of Schmidt number of a quantum channel. It enables one to define classes of quantum channels which partially break quantum entanglement. These classes generalize the well known class of entanglement breaking channels.
Elam, Jeffrey W.; Lee, Seon W.; Wang, Hsien -Hau; Pellin, Michael J.; Byrum, Karen; Frisch, Henry J.
2015-09-22
A method and system for providing a micro-channel plate detector. An anodized aluminum oxide membrane is provided and includes a plurality of nanopores which have an Al coating and a thin layer of an emissive oxide material responsive to incident radiation, thereby providing a plurality of radiation sensitive channels for the micro-channel plate detector.
Energy Technology Data Exchange (ETDEWEB)
Doyle, Barney Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Corona, Aldo [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Nguyen, Anh [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2014-09-01
A MS Excel program has been written that calculates accidental, or unintentional, ion channeling in cubic bcc, fcc and diamond lattice crystals or polycrystalline materials. This becomes an important issue when simulating the creation by energetic neutrons of point displacement damage and extended defects using beams of ions. All of the tables and graphs in the three Ion Beam Analysis Handbooks that previously had to be manually looked up and read from were programed into Excel in handy lookup tables, or parameterized, for the case of the graphs, using rather simple exponential functions with different powers of the argument. The program then offers an extremely convenient way to calculate axial and planar half-angles and minimum yield or dechanneling probabilities, effects on half-angles of amorphous overlayers, accidental channeling probabilities for randomly oriented crystals or crystallites, and finally a way to automatically generate stereographic projections of axial and planar channeling half-angles. The program can generate these projections and calculate these probabilities for
Barron, Randall F
2016-01-01
Cryogenic Heat Transfer, Second Edition continues to address specific heat transfer problems that occur in the cryogenic temperature range where there are distinct differences from conventional heat transfer problems. This updated version examines the use of computer-aided design in cryogenic engineering and emphasizes commonly used computer programs to address modern cryogenic heat transfer problems. It introduces additional topics in cryogenic heat transfer that include latent heat expressions; lumped-capacity transient heat transfer; thermal stresses; Laplace transform solutions; oscillating flow heat transfer, and computer-aided heat exchanger design. It also includes new examples and homework problems throughout the book, and provides ample references for further study.
Studies of multimodal gating of the sodium channel.
Keynes, Richard D
2002-01-01
Chandler and Meves found that in squid axons perfused with NaF a small flow of Na+ ions persisted in the inactivated state, and that the Na+ channel therefore has more than one open state. Studies by Correa and Bezanilla on single patches in squid axons showed that such steady currents arose from reopening of the channel at a relatively low frequency. Currents with comparable properties are generated in mammalian brain cells and elsewhere. The existence of a third mode of gating was established by Patlak and Ortiz when they showed that in frog muscle fibres there were occasionally quite large bursts of late openings. Again, similar behaviour has been observed in other types of muscle and in brain cells. It is suggested that the voltage gating of all ionic channels involves a screw-helical mechanism, operating in steps each transferring unit charge. For segment S4 in domain IV of Na+ channels, three charges have to be transferred to reach the initial open state, and a fourth for fast inactivation to take place. The single late openings in the inactivated steady state may be explained by the transfer of a fifth charge in IVS4, while the larger bursts of reopening involve a modulation of the mechanism of fast inactivation.
Investigation of the unbound 21C nucleus via transfer reaction
Directory of Open Access Journals (Sweden)
Fukui Tokuro
2014-03-01
Full Text Available The cross section of the transfer reaction 20C(d,p21C at 30.0 MeV is investigated. The continuum-discretized coupled-channels method (CDCC is used in order to obtain the final state wave function. The smoothing procedure of the transition matrix and the channel-coupling effect on the cross section are discussed.