Spectral density analysis of the interface in stratified oil-water flows

In this work the wavy interface of stratified oil-water flows was investigated using wire conductance probes. The experiments were carried out in a 38mm ID acrylic pipe using water and oil (Exxsol D140 oil: ρ=830kgm, μ=0.0055kgms) as test fluids. High-speed imaging revealed that almost two-dimensional interfacial waves develop at the inlet junction for input oil-to-water flow rate ratios different from one. Downstream the inlet section, however, the interface has a complex three dimensional structure with very small amplitude contributions. The structure of such interfaces can be properly investigated from the power spectrum of the conductance probe signal. A rigorous and detailed methodology is presented for estimating the power spectrum of the interface signal that is based on the Wiener-Khinchine theorem and makes extensive use of a Fast Fourier Transform (FFT) algorithm. Interface spectra were studied at two locations, close to the inlet of the test section and at 7m downstream. The results showed that the waves at the inlet have a unique peak frequency of about 19Hz and that, at the downstream location, this frequency is still present but has a smaller significance compared to that caused by the mechanical vibrations of the set up. This frequency was independent of the flow rates and could be a characteristic of the pair of the test fluids used rather than of the flow. © 2014 The Authors

Collateral, Renegotiation and the Value of Diffusely Held Debt

Debt with many creditors is analyzed in a continuous-time pricing model of the levered firm. We specifically allow for debtor opportunism vis-a-vis a non-coordinated group of creditors, in form of repeated strategic renegotiation offers and default threats. We show that the creditors' initial entitlement to non-collateralized assets will be expropriated through exchange offers. Exchange offers successively increase the level of collateral until all assets are fully collateralized. The ex ante optimal debt contract is neither fully collateralized nor without any collateral. Diffusely held debt allows for a larger debt capacity and bears lower credit risk premia than privately held debt. We derive simple closed-form solutions for the value of equity and defaultable bonds. Numerical estimates show that the bond valuation is very sensitive to the correct specification of the debt renegotiation model.

Reorganization Law and Dilution Threats in Different Financial Systems

In a market-based financial system, credit is held by dispersed creditors, and out-of-court renegotiation of debt is more likely to fail because of hold-out problems; in a bank-based system, out-of-court renegotiation stands good chances to succeed. Since out-of-court renegotiation is a substitute for court-supervised reorganization, the design of a reorganization law cannot abstract from the financial system. Chapter 11-style renegotiation is shown to benefit public debt firms and to be harmful for private debt firms; the overall effect depends on the financial system, but is likely to be positive only in a market-based system. The case for a reorganization law is weakened if dilution threats like exit consents are taken into account: such a law is then in most cases undesirable. Legislation, however, which jointly introduces a reorganization law while facilitating the use of dilution threats will improve welfare in a market-based system, but reduce welfare in a bank-based system. Thus, the paper indentifies a new determinant in the debate over optimal bankruptcy codes, which is how easily dilution threats can be deployed.Workouts;reorganization law;Chapter 11;financial systems;dilution threats;exit consents;hold-in effect

Collateral, Renegotiation and the Value of Diffusely Held Debt

Debt with many creditors is analyzed in a continuous-time pricing model of the levered firm. We specifically allow for debtor opportunism vis-a-vis a non-coordinated group of creditors, in form of repeated strategic renegotiation offers and default threats. We show that the creditors' initial entitlement to non-collateralized assets will be expropriated through exchange offers. Exchange offers successively increase the level of collateral until all assets are fully collateralized. The ex ante optimal debt contract is neither fully collateralized nor without any collateral. Diffusely held debt allows for a larger debt capacity and bears lower credit risk premia than privately held debt. We derive simple closed-form solutions for the value of equity and defaultable bonds. Numerical estimates show that the bond valuation is very sensitive to the correct specification of the debt renegotiation model.Debt reorganization;multiple creditors

Unusual Kondo physics in a Co impurity atom embedded in noble-metal chains

We analyze the conduction bands of the one dimensional noble-metal chains that contain a Co magnetic impurity by means of ab initio calculations. We compare the results obtained for Cu and Ag pure chains, as well as O doped Cu, Ag and Au chains with those previously found for Au pure chains. We find similar results in the case of Cu and Au hosts, whereas for Ag chains a different behavior is obtained. Differences and similarities among the different systems are analyzed by comparing the electronic structure of the three noble-metal hosts. The d-orbitals of Cu chains at the Fermi level have the same symmetry as in the case of Au chains. These orbitals hybridize with the corresponding ones of the Co impurity, giving rise to the possibility of exhibiting a two-channel Kondo physics.Comment: Accepted in IEEE Trans. Magn. - April 201

Structure and energetics of ammonia clusters (NH3)n (n=3-20) investigated using a rigid-polarizable model derived from ab initio calculations

An analytical model has been developed to describe the interaction between rigid ammonia molecules including the explicit description of induction. The parameters of the model potential were chosen by fitting high quality ab initio data obtained using second-order Moller-Plesset (MP2) perturbation theory and extended basis sets. The description of polarization effects is introduced by using a noniterative form of the "charge on spring model", the latter accounting for more than 95% of the dipole induction energy and of the increased molecular dipole. Putative global minima for (NH3)(n) (n = 3-20) have been optimized using this new model, the structure and energetics of the clusters with n = 3-5 being found in good agreement with previous ab initio results including electronic correlation. Results for larger species have been compared with previous structural studies where only nonpolarizable models were employed. Our model predicts larger binding energies for any cluster size than previous analytical surfaces, the results often suggesting a reorganization of the relative energy ranking and a different structure for the global minimum

Non-uniqueness of ergodic measures with full Hausdorff dimension on a Gatzouras-Lalley carpet

In this note, we show that on certain Gatzouras-Lalley carpet, there exist more than one ergodic measures with full Hausdorff dimension. This gives a negative answer to a conjecture of Gatzouras and Peres

Arl13b interferes with α-tubulin acetylation

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