Results 1 - 10 of 1755
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[en] Samples of (TIGaSe2)1-x(TIInSe2)x solid solutions are synthesized. The frequency dependences (2*10''1-10''6 Hz) of components of the total complex impedance are studied by the impedance spectroscopy technique and relaxation processes are investigated depending on the composition of the (TIGaSe2)1-x(TIInSe2)x solid solution in the solubility region (x=0-0.3). Corresponding diagrams on the (Z-Z') complex plane are analyzed using the equivalent substitution circuit method. An anomaly in the temperature dependence of the electrical conductivity, which manifests itself in an abrupt increase in the conductivity, is found for the studied (TIGaSe2)1-x (TIInSe2)x solid solution at 300K. This peculiarity is associated with the phase transition into the superionic state after 0.25 MGy gamma irradiation.
[en] One of the important tasks in the design activities is to accurately predict the pressure losses and flow distribution in the reactor. This task can be challenging especially when facing configurations with no empirical correlations available in the literature. An example of such challenges encountered in the design activity is a region in the flow path which undergoes a sudden contraction followed by a double expansion. In this paper, with the aim of estimating the appropriate orifice size corresponding to the targeted pressure drop, the flow in the above mentioned region is investigated numerically and representative results are presented. In this work, CFD analyses were conducted to develop a correlation for pressure loss coefficient for fluid experiencing a sudden contraction followed by two expansions. Sensitivity tests were also conducted to identify the proper turbulence model and to achieve a grid independent solution.
[en] A conserved current solid-on-solid model with conservative noise on a 3D Sierpinski tetrahedron substrate is studied. The interface width W grows as tβ, with β = 0.0396 ± 0.0009, and becomes saturated as Lα, with α = 0.195±0.005, where L is the system size. The dynamic exponent z ≈ 4.92 is estimated from the relation z = α/β. These values satisfy a scaling relation α+z = 2zrw, where zrw is the random walk exponent of the fractal substrate. Our results are consistent with the values estimated from a fractional Langevin equation with a conservative noise.
[en] A numerically efficient force distribution method for actuator saturation avoidance is proposed, which is applicable to two different types of the mechanisms with two degrees of actuator redundancy, parallel mechanism (PM) and cable-driven parallel mechanism (CDPM). The proposed method searches the optimal force solutions based on their geometric interpretation. Each actuator force with two degrees of actuator redundancy is expressed as a plane equation with respect to two intermediate variables. Thus, the optimal forces are found by searching for both the intersections between force planes and the common intersection points among those force planes. The proposed method for each of PM and CDPM is described. Then for two different exemplary mechanisms, the 2T 2R -type 4- DOF CDPM with six actuation cables and for the 2T1R -type planar 3- DOF PM with five active joints, comparative simulations moving along the spiral trajectory are conducted, employing three different methods, the proposed method and the other two typical off-line methods, the interior point method and the linear matrix inequality method. It is confirmed from those simulation results that the computational efficiency of the proposed method in finding their desired optimal force solutions is superior to the ones of the other two typical offline optimal searching methods and also sufficiently fast enough in real time applications.
[en] Using the impedance spectroscopy methods the charge transfer in solid solution (TlGaSe2)1-x(TlInS2)x in the frequency range of 20-10''6 Hz before and after γ-irradiation with a dose of 0.25 MGy have been investigated. The relaxation character of dielectric constant dispersion and dielectric loss nature are established. The frequency dependence of the dielectric loss tangent (tgδ) in solid solution crystals (TlGaSe2)1-x(TlInS2)x is due not by only the relaxation polarization, but also by through conduction. The response rate is fp=10''3 Hs and the duration of the relaxation period is τ=10''-3s. It is found that the regularity σ∼ f''S (0,1 ≤S≤1,0) indicating on electric conduction on localized states takes place in frequency range 10''5 - 5·10''5 Hz for the electric conduction. The further frequency increase leads to the increase of ionic conductivity and to the system transition in the superionic state.
[en] It has been recognized that radioiodine is potentially one of the most hazardous fission products that can be released from the fuel of nuclear reactors during a severe accident. According to the thermodynamic calculations and various experiments under the severe accident condition, the iodine released from the fuel would be primarily in its reduced state as cesium iodide (CsI) in the containment. Iodide, which is one of the major iodine species if the CsI solution is dissolved in cooling water, is easily diffused into the gas phase after being oxidized into gaseous I2 by gamma irradiation. The range of their conditions is close to those anticipated in the case of a severe accident. The modeling effect has also been pursued to predict the iodine chemistry behavior under severe accident conditions. The empirical models are practically used in the severe accident codes, such as IODE, ASTEC, IMPAR, etc., when modeling the iodine species with a limited set of reactions and the typical codes adapted in the mechanistic approach are INSPECT (IodiNe SPECiation and Transport) developed in AEAT, which has been integrated with some changes into MELCOR 1.8.5 and the LIRIC model (Library of Iodine reactions in containment) developed at AECL. Although there are many experimental results and correlations to estimate the volatile iodine in an aqueous phase, but there are significant differences between iodine models due to the uncertainties on the boundary conditions, such as the pH solution, occur if not controlled. A new empirical model is proposed to estimate the volatile iodine in an aqueous phase according to the pH and irradiation dose rate in the pool. The model was evaluated by comparison with available experimental results and these comparisons showed that the volatile iodine can be predicted at various initial pH levels for the 10-3 M to 10-4 CsI solution with good agreement.
[en] This paper investigates cylindrically symmetric distribution of an anisotropic fluid under the expansion-free condition, which requires the existence of a vacuum cavity within the fluid distribution. We have discussed two families of solutions that further provide two exact models in each family. Some of these solutions satisfy the Darmois junction condition while some show the presence of a thin shell on both boundary surfaces. We also formulate a relation between the Weyl tensor and energy density. (author)
[en] This paper reports a methodology for preparing close-packed two dimensional gold nanoprism films and hexagonal nanoplate films at a hexane/water interface. By controlling the concentration of linker molecules in the hexane layer and the temperature of the colloid solution, highly ordered close-packed nanoplate arrays can be fabricated. These films were investigated to compare their corresponding surface enhanced Raman scattering (SERS) efficiencies. It was demonstrated that the Au nanoprism films resulted in a stronger SERS enhancement than the Au hexagonal nanoplate films. The difference in the SERS enhancement is attributed to the film array difference, demonstrating that Au nanoprism films have a higher line contact density than their Au hexagonal analogues
[en] The kinematic shear viscosity of aqueous electrolyte solutions has been studied. The temperature dependence of this parameter is shown to be described by an exponential formula at T < Td and a formula of the argon-like type at T > Td , where Td is the temperature of the dipole ordering, in the whole considered concentration interval. Main attention is focused on the peculiarities in the temperature and concentration dependences of the shear viscosity in the argon-like interval. It is shown that the root-like concentration dependence can appear, only if the Debye theory of dilute electrolyte solutions is applicable. Beyond its validity domain, the series expansion of the kinematic shear viscosity in the concentration parameter should have an analytical character. The latter behavior is inherent in the concentration dependence of the shear viscosity in the majority of experiments. The error of reproducing the experimental data did not exceed the experimental one, i.e. it was smaller than 4-5%
[en] The adequate formation efficiency of the [Cu2+, Ni2+---(Gly-Gly-His . 3H+)]-1 complex in the gas phase MS spectra reflects what is also observed in the solution phase absorption spectra. The C-CO2 bond is found to be the weakest bond of the [(Cu2+, Ni2+---Gly-Gly-His) - 3H+]-1 complex in our low energy CID-MS/MS spectra. The structure of the [(Cu2+, Ni2+---Gly-Gly-His) - 3H+]-1 complex in the gas phase was assumed to maintain the planar structure it held in the solution phase on the basis of the analysis of the MS and MS/MS spectra. Mass spectrometry (MS) is a very useful means by which to study the interactions of metal cation-biomolecule complexes in the gas phase. The analysis of the fragmentation patterns of metal cationized peptides produced under electrospray ionization (ESI)-MS can provide complementary information for peptide sequencing when the fragmentation of the protonated peptide is insufficient. The specific interactions in metal ion-peptide systems have been studied to develop practical sensors for the detection and quantification of metal ions