Determination of separated region in a curved tube

The formation of atherosclerosis in a curved aorta is closely related to the existence of separated vortex region. This paper deals with the steady laminar motion of an incompressible Newtonian fluid through a curved tube with circular cross-section whose curvature is small and whose curvature gradient is not too large. Using the momentum integral method and the approximation of quasi-constant curvature, an equation which determines the location of separation and reattachment is derived. From this equation the earliest point of separation and the corresponding critical Reynolds number are obtained, and the relation between the position of separation and reattachment and Reynolds number R_e for different azimuthal angle are revealed. It is concluded that the separation first emerges at the position whose curvature gradient has the maximum absolute value. With increasing R_e, the separation region extends in the direction of mainstream, azimuthal angle and radius vector, and then forms a three-dimensional separated vortex, which gradually enlarges in all three directions with the increase of Reynolds number. The theoretical results also very clearly demonstrate the following striking experimental fact: if a symmetrical curved tube exhibits a separated vortex at the outside of the upstream, then it must have another one symmetrically placed at the inside of its downstream.     

Validating a GIS-based multi-criteria method for potential road identification

This paper investigated the validation of a multi-criteria method for identifying potential roads, and demonstrated the capability of analyzing GPS vehicle tracking data for identifying vehicle movement patterns and potential roads. The multi-criteria method was evaluated by comparing the predictions to the site visit results on 34 selected road segments meeting different criteria levels. Results show that locations meeting higher criteria levels have higher possibilities to be roads: an approximately 91% possibility of road existence for the locations meeting all five criteria; 55% for the locations meeting four criteria; and 14% for those meeting criteria level two or three. This approach provides an opportunity for land managers to update existing GIS roads map, or identify newly formed roads that may need either rehabilitation or inclusion into the roads maintenance program.     

Accurate Higher-Order Analytical Approximate Solutions to Large-Amplitude Oscillating Systems with a General Non-Rational Restoring Force

A new approximate analytical approach for accurate higher-order nonlinear solutions of oscillations with large amplitude is presented in this paper. The oscillatory system is subjected to a non-rational restoring force. This approach is built upon linearization of the governing dynamic equation associated with the method of harmonic balance. Unlike the classical harmonic balance method, simple linear algebraic equations instead of nonlinear algebraic equations are obtained upon linearization prior to harmonic balancing. This approach also explores large parameter regions beyond the classical perturbation methods which in principle are confined to problems with small parameters. It has significant contribution as there exist many nonlinear problems without small parameters. Through some examples in this paper, we establish the general approximate analytical formulas for the exact period and periodic solution which are valid for small as well as large amplitudes of oscillation.     

Mechanical and electrochemical properties of platinum coating by double glow plasma on titanium alloy substrate

In this paper, a platinum coating was deposited on titanium alloy substrate by a double glow plasma. Phase and microstructure of platinum coating were examined by X-ray diffraction and scanning electron microscopy, respectively. The microhardness of the coating was estimated by nanoindentation instrument. The adhesive force between the coating and the substrate was performed with scratch tester. The electrochemical behavior of the platinum coating in 3.5 wt % sodium chloride solution was investigated by potentiodynamic polarization. The results indicated that an adherent platinum coating could be successfully obtained on titanium alloy substrates. Compared with the titanium alloy substrate, the platinum coating had a relative low corrosion current density and high corrosion potential. It indicated that the platinum coating had a better corrosion resistance than the titanium alloy substrate.     

Study on the “Tin-Ene” reaction of α-bromoacetophenone and metallic tin with aldehydes

β-hydroxy ketones were obtained in good yields by the “tin-ene” reactions of α-bromoacetophenone and metallic tin with aldehydes.     

IRMPD Action Spectroscopy of Alkali Metal Cation–Cytosine Complexes: Effects of Alkali Metal Cation Size on Gas Phase Conformation

The gas-phase structures of alkali metal cation-cytosine complexes generated by electrospray ionization are probed via infrared multiple photon dissociation (IRMPD) action spectroscopy and theoretical calculations. IRMPD action spectra of five alkali metal cation–cytosine complexes exhibit both similar and distinctive spectral features over the range of ~1000–1900 cm^-1. The IRMPD spectra of the Li⁺(cytosine), Na⁺(cytosine), and K⁺(cytosine) complexes are relatively simple but exhibit changes in the shape and shifts in the positions of several bands that correlate with the size of the alkali metal cation. The IRMPD spectra of the Rb⁺(cytosine) and Cs⁺(cytosine) complexes are much richer as distinctive new IR bands are observed, and the positions of several bands continue to shift in relation to the size of the metal cation. The measured IRMPD spectra are compared to linear IR spectra of stable low-energy tautomeric conformations calculated at the B3LYP/def2-TZVPPD level of theory to identify the conformations accessed in the experiments. These comparisons suggest that the evolution in the features in the IRMPD action spectra with the size of the metal cation, and the appearance of new bands for the larger metal cations, are the result of the variations in the intensities at which these complexes can be generated and the strength of the alkali metal cation-cytosine binding interaction, not the presence of multiple tautomeric conformations. Only a single tautomeric conformation is accessed for all five alkali metal cation–cytosine complexes, where the alkali metal cation binds to the O2 and N3 atoms of the canonical amino-oxo tautomer of cytosine, M⁺(C₁).

Single-Ion Conduction and Electrochemical Characteristics of Poly (Oxyethylene)/ Lithium Methoxy Oligo(Oxyethylene) Sulfate Blend

Abstract

The ion conduction of a blend of poly(oxyethylene) (PEO) and lithium methoxy oligo(oxyethylene) sulfate (SAL₈) and its electrochemical characteristics were studied. The maximum ambient conductivity of the blend reaches 1.2 × 10^?6 S/cm. The blend exhibits single-ion conduction, excellent mechanical performance, and electrochemical stability. A battery of Li/PEO + SAL₈/Li_1+xV₃O₈ has a constant discharge capacity at different discharge current densities up to a certain voltage, while the discharge capacity of Li/P (MEO_16-AM) + LiClO₄/Li_1+xV₃O₈ decreases with an increase of the discharge current density.     

Determination of Hypochlorite via Fluorescence Change from Blue to Green Based on 4-(1 H-imidazo [4,5-f] [1,10]-phenanthrolin-2-yl) Benzaldehyde Oxime

The new design strategy will provide the possibility for preparing a dynamic sensor by employing the inhibition of C?=?N isomerization. In this work, the functional probe 4-(1 H-imidazo [4,5-f] [1,10]-phenanthrolin-2-yl) benzaldehyde oxime (compound 4) has been synthesized and such molecule gives rise to blue emission. Due to the incorporation of hypochlorite, the oxime group can be oxidized to the structure of aldehyde. As a result, the molecular motif exhibits sharp emission change from blue to green due to the addition of hypochlorite with enough sensitivity and selectivity (detection limit?=?53 nM, linear range 0.5-8.0 µM). It has also been used for monitoring ClO^? by employing solution color change and the absorption signal difference could effectively rule out the effects of interference species. To our knowledge, it will be the first case of a highly selective hypochlorite sensor derived from oxime isomerization reaction based on phenanthroline backbone.

     

Subcomponent self-assembly of circular helical Dy6(L)6 and bipyramid Dy12(L)8 architectures directed via second-order template effects

In situ metal-templated (hydrazone) condensation also called subcomponent self-assembly of 4,6-dihydrazino-pyrimidine, o-vanillin and dysprosium ions resulted in the formation of discrete hexa- or dodecanuclear metallosupramolecular Dy₆(L)₆ or Dy₁₂(L)₈ aggregates resulting from second-order template effects of the base and the lanthanide counterions used in these processes. XRD analysis revealed unique circular helical or tetragonal bipyramid architectures in which the bis(hydrazone) ligand L adopts different conformations and shows remarkable differences in its mode of metal coordination. While a molecule of trimethylamine acts as a secondary template that fills the void of the Dy₆(L)₆ assembly, sodium ions take on this role for the formation of heterobimetallic Dy₁₂(L)₈ by occupying vacant coordination sites, thus demonstrating that these processes can be steered in different directions upon subtle changes of reaction conditions. Furthermore, Dy₆(L)₆ shows an interesting spin-relaxation energy barrier of 435 K, which is amongst the largest values within multinuclear lanthanide single-molecular magnets.

Subcomponent self-assembly gave access to Dy₁₂(L)₈ and Dy₆(L)₆ architectures via second-order template effects. The Dy₆(L)₆ assembly behaves as a single-molecule magnet exhibiting a high anisotropy barrier and butterfly-shaped magnetic hysteresis.     

Development of a 3D Eulerian/Lagrangian Aircraft Icing Simulation Solver Based on OpenFOAM

A 3D icing simulation code is developed in the open-source CFD toolbox OpenFOAM. A hybrid Cartesian/body-fitted meshing method is used to generate high-quality meshes around complex ice shapes. Steady-state 3D Reynolds-averaged Navier-Stokes (RANS) equations are solved to provide the ensemble-averaged flow around the airfoil. Considering the multi-scale nature of droplet size distribution, and more importantly, to represent the less uniform nature of the Super-cooled Large Droplets (SLD), two droplet tracking methods are realized: the Eulerian method is used to track the small-size droplets (below 50 μm) for the sake of efficiency; the Lagrangian method with random sampling is used to track the large droplets (above 50 μm); the heat transfer of the surface overflow is solved on a virtual surface mesh; the ice accumulation is estimated via the Myers model; finally, the final ice shape is predicted by time marching. Limited by the availability of experimental data, validations are performed on 3D simulations of 2D geometries using the Eulerian and Lagrangian methods, respectively. The code proves to be feasible and accurate enough in predicting ice shapes. Finally, an icing simulation result of the M6 wing is presented to illustrate the full 3D capability.