Secondary Distributions Research Articles

Improved calculation of displacements per atom cross section in solids by gamma and electron irradiation

Several authors had estimated the displacements per atom cross sections under different approximations and models, including most of the main gamma- and electron-material interaction processes. These previous works used numerical approximation formulas which are applicable for limited energy ranges. We proposed the Monte Carlo assisted Classical Method (MCCM), which relates the established theories about atom displacements to the electron and positron secondary fluence distributions calculated from the Monte Carlo simulation. In this study the MCCM procedure is adapted in order to estimate the displacements per atom cross sections for gamma and electron irradiation. The results obtained through this procedure are compared with previous theoretical calculations. An improvement in about 10–90% for the gamma irradiation induced dpa cross section is observed in our results on regard to the previous evaluations for the studied incident energies. On the other hand, the dpa cross section values produced by irradiation with electrons are improved by our calculations in about 5–50% when compared with the theoretical approximations. When thin samples are irradiated with electrons, more precise results are obtained through the MCCM (in about 20–70%) with respect to the previous studies.

Measurement of the b-jet nuclear modification factors in PbPb collisions at sNN=2.76 TeV with CMS

Modification to jets in high-energy heavy-ion collisions is expected to depend on the flavor of the fragmenting parton. To disentangle this flavor dependence, jets associated to heavy quarks are identified in pp and PbPb collisions. Jets are first tagged by their secondary vertices and the contribution from bottom quarks is extracted using template fits to their secondary vertex mass distributions. In this talk, the b-jet nuclear modification factors are presented in the range of 80 < jet p T < 250 GeV / c , using the full 2011 PbPb and 2013 pp data collected at s N N = 2.76 TeV .

Numerical Simulation of the Primary, Secondary and Tertiary Potential Distribution on Porous Cathode in a Flow-through Packed Bed Reactor. Influence of Thickness, Concentration and Hydrodynamics in Porous Media

Packed bed electrodes can be used for electrochemical recovery of heavy metals from a variety of industrial and laboratory model solutions. The packed bed electrode forms a porous flow-through (Figure 1) configuration providing large surface area usually depleting the concentration of several metal ions below 0.1 ppm. For design porpoises of these electrodes, it is necessary to study the influence of geometry (cathode thickness), flow rate and concentration on potential distribution.Numerical simulations of primary, secondary and tertiary current distributions on the porous cathode of a packed bed electrochemical reactor (Figure 1) were calculated. For primary and secondary current distribution, Laplace equations with its respective boundary conditions (constant potential for primary current distribution and charge transfer kinetics described by a Tafel approximation in secondary current distribution) were evaluated using the finite element method. For tertiary current distribution, the influence of hydrodynamics was taken in account, considering Navier-Stokes model with Brinkman extension for porous media. Once Brinkman equations was solved and local velocity distributions were obtained, local mass transfer coefficients were evaluated by means of following relationship: Kma=cvb where Km is local mass transport coefficient, a is the specific area, v is local velocity, c and b are empirical constants taken from literature. The effects of flow rate, ion concentration, matrix conductivity and thicknes on the distribution of current on porous cathode are analyzed. Results of current distribution obtained by Nava et. al 2008 [1] enable comparisons with the simulations.

Simulation of Current Distribution Under Turbulent Flow Conditions in a Laboratory Filter-Press Flow Cell

A theoretical analysis of primary, secondary and tertiary current distributions along a planar nickel electrode in a laboratory filter-press flow cell has been carried out using the reduction of Fe(CN)6 3 − ions in a sodium carbonate electrolyte as a model reaction system. The primary current distribution decreased at the inlet and outlet of the cell and became uniform away from the entrance and exit. The secondary current distribution predominated throughout the electrode; edge effects appearing only at the corners of the cell. The tertiary current distribution presented higher edge effects compared to those experienced under secondary current distribution due to jet flow at the inlet of the cell. The limiting current density incorporated numerically calculated local flow velocities under turbulent flow which were simulated by solving the Reynolds averaged Navier-Stokes (RANS) equation, expressed in terms of turbulent viscosity and a standard turbulence model.

Secondary hadron distributions in a two component model

Inclusive charged hadron cross sections, $d\ensuremath{\sigma}/d\ensuremath{\eta}$, and the mean transverse momenta, $⟨{p}_{T}⟩$, are considered within the two component model, which combines the powerlike and the exponential terms in ${p}_{T}$. The observed dependences of the spectra shape on energy and the event multiplicity qualitatively agree with that expected from the Regge theory with the perturbative QCD Pomeron. Finally, the dependences observed are used to make predictions on the mean transverse momenta, $⟨{p}_{T}⟩$, as function of multiplicity at LHC energies, which are tested on available experimental data.

Robust optimization of supply chain network design in fuzzy decision system

This paper presents a new robust optimization method for supply chain network design problem by employing variable possibility distributions. Due to the variability of market conditions and demands, there exist some impreciseness and ambiguousness in developing procurement and distribution plans. The proposed optimization method incorporates the uncertainties encountered in the manufacturing industry. The main motivation for building this optimization model is to make tools available for producers to develop robust supply chain network design. The modeling approach selected is a fuzzy value-at-risk (VaR) optimization model, in which the uncertain demands and transportation costs are characterized by variable possibility distributions. The variable possibility distributions are obtained by using the method of possibility critical value reduction to the secondary possibility distributions of uncertain demands and costs. We also discuss the equivalent parametric representation of credibility constraints and VaR objective function. Furthermore, we take the advantage of structural characteristics of the equivalent optimization model to design a parameter-based domain decomposition method. Using the proposed method, the original optimization problem is decomposed to two equivalent mixed-integer parametric programming sub-models so that we can solve the original optimization problem indirectly by solving its sub-models. Finally, we present an application example about a food processing company with four suppliers, five plants, five distribution centers and five customer zones. We formulate our application example as parametric optimization models and conduct our numerical experiments in the cases when the input data (demands and costs) are deterministic, have fixed possibility distributions and have variable possibility distributions. Experimental results show that our parametric optimization method can provide an effective and flexible way for decision makers to design a supply chain network.

Three Dimensional Sound Field Reproduction using Multiple Circular Loudspeaker Arrays: Functional Analysis Guided Approach

Three dimensional sound field reproduction based on higher order Ambisonics requires the placement of loudspeakers on a sphere that surrounds the target reproduction region. The deployment of a spherical array is not trivial especially for implementation in real rooms where the placement flexibility is highly desirable. This paper proposes a design of multiple circular loudspeaker arrays for reproducing three dimensional sound fields originating from a limited region of interest. We apply a functional analysis framework to formulate the sound field reproduction problem in a closed form. Secondary source distributions and target sound fields are modeled as two Hilbert spaces and mapped by an integral operator and its adjoint operator, from which a self-adjoint operator is constructed and the singular value decomposition is applied to represent source distributions and sound fields with two sets of interrelated singular functions. We derive the solutions for a circular secondary source arrangement and propose the design of placing multiple circular loudspeaker arrays only over the limited region of interest. Such a design allows for non-spherical and non-uniform loudspeaker placement and thus provides a flexible array arrangement. The reproduction accuracy of the proposed method is verified through numerical simulations.

Generation of an [formula omitted] Covariance Matrix by Monte Carlo Sampling of the Phonon Frequency Spectrum

Formats and procedures are currently established for representing covariances in the ENDF library for many reaction types. However, no standard exists for thermal neutron inelastic scattering cross section covariance data. These cross sections depend on the material's dynamic structure factor, or S(α,β). The structure factor is a function of the phonon density of states (DOS). Published ENDF thermal neutron scattering libraries are commonly produced by modeling codes, such as NJOY/LEAPR, which utilize the DOS as the fundamental input and directly output the S(α,β) matrix. To calculate covariances for the computed S(α,β) data, information about uncertainties in the DOS is required. The DOS may be viewed as a probability distribution function of available atomic vibrational energy states in a solid. In this work, density functional theory and lattice dynamics in the harmonic approximation were used to simulate the structure of silicon dioxide (α-quartz) to produce the DOS. A range for the variation in the partial DOS for silicon in α-quartz was established based on limits of variation in the crystal lattice parameters. Uncertainty in an experimentally derived DOS may also be incorporated with the same methodology. A description of possible variation in the DOS allowed Monte Carlo generation of a set of perturbed DOS spectra which were sampled to produce the S(α,β) covariance matrix for scattering with silicon in α-quartz. With appropriate sensitivity matrices, it is shown that the S(α,β) covariance matrix can be propagated to generate covariance matrices for integrated cross sections, secondary energy distributions, and coupled energy-angle distributions.

Chronoamperometric In Situ Measurement of the Specific Conductivity of a Thin Film on the Disc Electrode Surface

A new method to measure both the total resistance and the specific conductivity of a thin film (for the current flow in the normal direction) is proposed [1].It is assumed that the film has been deposited on the surface of a disc electrode (in static or rotating conditions). A relatively small diameter of the disc is preferable to ensure the maximal uniformity of the film along the surface. The thickness of the film, Lf, should be sufficiently small compared to the disc radius, ro, but it should cover the surface in a uniform manner. The conductivity properties of the deposited material may be isotropic or anisotropic (different in the normal and tangential directions).The primary and secondary distributions of the electric potential and the current after a small-amplitude potential step have been analyzed for such a film-coated electrode in contact with an electrolyte solution, CE and RE being located sufficiently far from the disc electrode (WE). The three-dimensional (3D) character of these distributions inside the solution has been taken into account.Analytical expressions have been derived for the overall short-time resistance of the system, Rtot, with taking into account the contributions of both the solution and the film. Due to the 3D effect this quantity for the primary distribution is not equal to the sum of the short-time resistances of these components of the system, Rs for solution and Rf for the film. Analytical formulas have been deduced, allowing one to calculate immediately the film resistance, Rf, on the basis of measured values of Rtot and Rs. Then, the specific conductivity of the film, kf, is found from relation: kf = Lf / Rf pro 2.Both parameters of the film may be determined by this method for a set of electrode potential values, see Fig.1 for a poly(titanocene-propyl-pyrrole) film.The merits of this procedure to determine the high-frequency transport parameters are: 1) film deposition at a small surface area (but still macroscopic) substrate; 2) no lower restriction for the film thickness (except for their uniformity); 3) in situ measurements inside the conventional cell; 4) non-destructive procedure (film may be used for further texts); 5) simple data treatment; 6) weak effects of local film's imperfections, etc.Support of RFFI (projects 09-03-01172 and 10-08-00847) is acknowledged.Fig. 1 Dependence of the specific conductivity of the poly(titanocene-propyl-pyrrole) film on the potential.[1]. M.A. Vorotyntsev, D.V. Konev / Electrochim. Acta 56 (2011) 9105– 9112

Numerical simulation of the primary, secondary and tertiary current distributions on the cathode of a rotating cylinder electrode cell. Influence of using plates and a concentric cylinder as counter electrodes

Numerical simulations of primary, secondary and tertiary current distributions on the cathode of a rotating cylinder electrode (RCE) cell, using four-plate, six-plate, and a concentric cylinder as counter electrodes, were calculated using the finite element method. Copper electrodeposition from an acidic sulfate electrolyte is used as a test system. Charge transfer kinetics is described by a Tafel approximation while mass transport is considered using a Nernstian diffusion layer expression. The importance of using plates and concentric counter electrodes on RCE cathode is demonstrated. The effects of applied current density and electrode rotation speed on the distribution of current on RCE cathode are analyzed. Electrodeposition experiments with copper enable comparisons with the simulations.

Heat Transfer Aspects on Rotating MHD Two-phase Convective Flow through an Inclined Channel in the Presence of Electric Field

Steady, laminar, inc ompressible and fully developed fluid flow of two immiscible electrically conducting fluids between two infinite inclined parallel plates has been studied when the two plates are maintained at different constant temperaturesand . A constant magnetic field B 0is applied transverse to the plates and a constant electric field E0is applied across the channel. The whole system is rotated at an angular velocity about an axis perpendicular to the channel plates. The transport properties of the two fluids are taken to be constant. Approximate solutions for temperature, primary and secondary velocity distributions are obtained using regular perturbation method because the resulting equations are coupled and non-linear.It is observed that in the short circuit case (E = 0), as rotation increases both the primary velocity and temperature distribution decrease where as secondary velocity oscillates. It is also observed that for the open circuit case ( = ±1)as the rotation increases the secondary velocity becomes oscillatory. In case of = �1, the increasing rotation tends to accelerate the primary velocity, but in case of positive E, it accelerates the primary velocity in the opposite direction. For t he open circuit case (E = ±1), as the rotation increases the temperature decreases for small values of rotation and increases for large rotation.

Finite element and network electrical simulation of rotating magnetofluid flow in nonlinear porous media with inclined magnetic field and hall currents

A mathematical model is presented for viscous hydromagnetic flow through a hybrid non-Darcy porous media rotating generator. The system is simulated as steady, incompressible flow through a nonlinear porous regime intercalated between parallel plates of the generator in a rotating frame of reference in the presence of a strong, inclined magnetic field A pressure gradient term is included which is a function of the longitudinal coordinate. The general equations for rotating viscous magnetohydrodynamic flow are presented and neglecting convective acceleration effects, the two-dimensional viscous flow equations are derived incorporating current density components, porous media drag effects, Lorentz drag force components and Hall current effects. Using an appropriate group of dimensionless variables, the momentum equations for primary and secondary flow are rendered nondimensional and shown to be controlled by six physical parameters-Hartmann number (Ha), Hall current parameter (Nh), Darcy number (Da), Forchheimer number (Fs), Ekman number (Ek) and dimensionless pressure gradient parameter (Np), in addition to one geometric parameter-the orientation of the applied magnetic field (? ). Several special cases are extracted from the general model, including the non-porous case studied earlier by Ghosh and Pop (2006). A numerical solution is presented to the nonlinear coupled ordinary differential equations using both the Network Simulation Method and Finite Element Method, achieving excellent agreement. Additionally very good agreement is also obtained with the earlier analytical solutions of Ghosh and Pop (2006). for selected Ha, Ek and Nh values. We examine in detail the effects of magnetic field, rotation, Hall current, bulk porous matrix drag, second order porous impedance, pressure gradient and magnetic field inclination on primary and secondary velocity distributions and also frictional shear stresses at the plates. Primary velocity is seen to decrease with an increase in Hall current parameter (Nh) with the converse observed for the secondary velocity.

Impact of microstructural evolutions during thermal aging of Alloy 625 on its monotonic mechanical properties

Alloy 625 is widely used for petrochemical, marine and aerospace applications owing to its outstanding corrosion and mechanical properties at high temperatures. However, this alloy is prone to complex microstructure evolutions above 500 ∘ C that may impact its mechanical properties. In this study, the impact of its microstructure evolutions occurring upon thermal aging on the monotonic mechanical properties has been studied. Thermal exposures of up to ∼2000 hours in the 550 ∘ C – 900 ∘ C temperature range have been investigated. TTT diagrams of the δ and γ′′ phases were established based on high resolution scanning electron microscopy observations. The evolutions of secondary carbides distributions were also followed. It has been observed a steep increase of the room temperature micro-hardness after overagings performed at 650 ∘ C and 700 ∘ C due to the precipitation of the γ′′ phase. Moreover, it is clearly demonstrated a strengthening effect of the δ phase observed after long term thermal exposures at temperatures in excess of 700 ∘ C. Finally, the impact of a thermal aging in the γ′′ precipitation domain on the tensile properties was evaluated from room temperature up to 800 ∘ C. It is shown that the loss of high temperature ductility is not correlated to the precipitation of grain boundary secondary carbides.

Influence of the patient size on secondary doses delivered in light ion beams

*Secondary radiation exposure of patients in light ion therapy is of concern due to possible normal tissue damage and risk of induction of secondary cancers. Neutrons, protons and heavier ions are generated by nuclear inelastic interactions of primary ions both in the beam line and in the patient. The patient is exposed to a complex radiation field and secondary doses can be deposited in normal tissues both close to and relatively far from the treated volume. The energy distribution of secondary particles and secondary doses delivered to different organs were studied by the MC code SHIELD-HIT10 using the anthropomorphic phantoms representing a 10-year-old child (CHILD-HIT) and an adult male (ADAM-HIT). Brain tumor irradiations were simulated with approximated scanned beams of 1 H, 7 Li and 12 C ions. The influence of patient size on the secondary dose distributions were studied using the same target definition and irradiation geometry with a lateral beam. For the scanned beams, the secondary organ absorbed doses normalized per absorbed dose to the treated volume (brain tumor) were in the range 1 nGy/Gy - 0.1 mGy/Gy and the absorbed doses in the CHILD-HIT phantom were higher than in ADAM-HIT by up to a factor of 5, depending on organ.

Electron-induced double ionization of isolated water molecules

Theoretical doubly differential and total cross sections for electron-induced double ionization of oriented water molecules are reported here. The calculations are performed within the first Born approximation by describing the initial molecular state by means of single-center wave functions. Furthermore, the incident (scattered) electron is described by a plane wave while a Coulomb wave function is used for modeling the two secondary ejected electrons. The contribution of each final state to the double-ionization process is analyzed, namely, in considering target electrons ejected either from similar or from different molecular subshells. Thus, secondary electron energetic distributions as well as total cross sections are reported for particular target configurations, pointing out orientation effects in the double-ionization process.

Current density distribution and gas volume fraction in the gap of lantern blade electrodes

Electrochemical processes involving gas evolution at appreciable rates have been optimized in their design for the sake of reduced energy consumption. The present investigation was conducted in view to reducing the energy demand of a pilot process for electrolytic reduction of hematite particles to iron metal; attention was paid at the design of the lantern blade anodes where oxygen evolution occurs. An experimental cell consisting on two facing anodes and two remote cathodes has been designed and used for investigation of the gas behavior and current density distribution at the anode blades. The model for prediction of secondary distributions was validated by measurement of the currents at the segmented anodes and the effects of the average current density and the anode gap could be observed. The model was finally applied to the pilot cell for iron production; as expected, larger gaps allow more uniform current distributions at the anode, however without reducing the cell voltage. In contrast, blade lengths in the order of 10–15×10−3m only would allow visible reduction in the cell voltage.

Influence of Purge Flow Injection Angle on the Aerothermal Performance of a Rotor Blade Cascade

This paper is focused on the influence of stator-rotor purge flow injection angle on the aerodynamic and thermal performance of a rotor blade cascade. Tests were performed in a seven-blade cascade of a high-pressure gas turbine rotor at low Mach number (Ma2is = 0.3) under different blowing conditions. A number of fins were installed inside the upstream slot to simulate the effect of rotation on the seal flow exiting the gap in a linear cascade environment. The resulting coolant flow is ejected with the correct angle in the tangential direction. Purge flow injection angle and blowing conditions were changed in order to identify the best configuration in terms of end wall thermal protection and secondary flows reduction. The 3D flow field was surveyed by traversing a five-hole miniaturized pressure probe in a downstream plane. Secondary flow velocities, loss coefficient, and vorticity distributions are presented for the most significant test conditions. Film cooling effectiveness distributions on the platform were obtained by thermochromic liquid crystals (TLC) technique. Results show that purge flow injection angle has an impact on secondary flows development and, thus, on the end wall thermal protection, especially at high injection rates. Passage vortex is enhanced by a negative injection angle, which simulates the real counter rotating purge flow direction.

Purge flow and interface gap geometry influence on the aero-thermal performance of a rotor blade cascade

This paper is focused on the influence of the geometry of an interface seal gap on the aerodynamic and thermal performance of a rotor blade cascade. Tests are performed in a seven-blade cascade of a gas turbine high-pressure subsonic rotor at low Mach number (Ma2is=0.3). To simulate some of the effects of rotation on the seal flow exiting the gap on a linear cascade environment, a number of fins are installed inside the slot, providing the coolant flow with an injection angle in the tangential direction. Tests are carried out at variable blowing conditions and different gap widths. Moreover, the influence of a radial misalignment between stator and rotor platforms is also investigated for variable injection conditions. The 3D flow field is surveyed by traversing a 5-hole miniaturized pressure probe in a downstream plane. Secondary flows velocities, loss coefficient and vorticity distributions are presented for the most relevant test conditions. Film cooling effectiveness distributions on the platform are obtained by Thermochromic Liquid Crystals technique. Results show that engine purge flow injection conditions have to be reproduced in the wind tunnel as close as possible, in order to get the correct blade aero-thermal performance.

Numerical simulation of current distribution along the boron-doped diamond anode of a filter-press-type FM01-LC reactor during the oxidation of water

This work shows a theoretical analysis of primary and secondary current distributions along a boron-doped diamond (BDD) anode of a filter-press-type FM01-LC reactor. Hydroxyl radical formation via water discharge was used as a test system. Microelectrolysis studies confirm that hydroxyl radicals are formed at potentials between 2.3V⩽E⩽2.75V vs. SHE and that at higher potentials oxygen evolution reaction (OER) occurs. Primary current distribution is more uniform away from the curved corners of the cell, originated by the spacer between electrodes; however, the current distribution values at the corners and near to them, differ with a magnitude order of 1×10−5; hence, primary current distribution at BDD anode in the FM01-LC reactor can be considered uniform. Secondary current distribution at different over potential values of 1.7, 1.9 and 2.15V, respectively, did not show border effects. Attenuation of secondary current distribution is associated to kinetic parameters of water discharge on BDD and appropriate cell design. The importance of secondary current distribution for the production of hydroxyl radicals on BDD anode, to avoid OER, is discussed.

High sensitivity sputter neutral mass spectrometry – Sputtering of neutral mixed clusters from gold–aluminum alloys

We have used the surface sensitivity of laser sputter neutral mass spectrometry to make measurements of clusters sputtered from AuAl alloys surfaces with high dynamic range. Polycrystalline AuAl4 and Au4Al were bombarded with 15keV Ar+ at 60° incidence, and the resulting secondary neutral yield distributions were measured using laser postionization mass spectrometry. Neutral clusters containing up to 28 atoms were observed and exhibited an odd–even variation in signal dependent on the stability of the photoion. Clusters sputtered from Au4Al were gold rich compared to the substrate and the yield of neutral clusters containing n atoms, Yn, was found to follow a power in n, i.e. Yn∝n−δ, where the exponent δ was approximately 3.4.