Degradation of cellulosic insulation in power transformers: a SEC–MALLS study of artificially aged transformer papers

The molecular weight distributions of artificially aged transformer papers were studied using SEC–MALLS with 0.5 % DMAc/LiCl as solvent, providing chain length distributions and averages. The slow dissolution and presence of non-cellulosic contaminants tend in some cases to introduce errors in the DP_w estimates, and a modified data processing procedure was developed to correct for extraneous scattering. Data were compared to the intrinsic viscosities obtained in 0.5 M Cuen and the ‘viscosimetric DP’ calculated thereof according to ISO 5351. DP_visc was 2–3 times lower than the weight average DP (DP_w), but closer to or slightly above the number average DP (DP_n) obtained by SEC–MALLS in the case of pure cellulose. Ageing of transformer papers were in some cases associated with changes in the polydispersity (DP_w/DP_n). The apparent degradation rate (defined as δ(1/DP)/δt) gradually decreased with time, resulting in a tendency for a ‘level-off’ DP in the range 200–300 for DP_visc and DP_n, and roughly 1,000 for DP_w.     

Qualitative analysis of the anisotropic two-body problem under Seeliger's potential

In this paper we study the two-body problem that describes the motion of two-point masses in an anisotropic space under the influence of the Seeliger potential. We will show that the set of initial conditions leading to collisions and ejections has positive measure and study the capture and escape solutions in the positive-energy case using the infinity manifold. We will also apply the Melnikov method to show that the flow on the zero-energy manifold of another potential which is the sum of the classical Keplerian potential and the anisotropic Seeliger's potential perturbation is chaotic.     

Density and tails of unimodal convolution semigroups

We give sharp bounds for the isotropic unimodal probability convolution semigroups when their Lévy–Khintchine exponent has Matuszewska indices strictly between 0 and 2.     

An interactive approach for Bi-attribute multi-item auctions

The advances in the technological infrastructure and in the Internet led electronic auctions to become popular. With online sites, people buy/sell inexpensive products/services through auctions. In this paper, we develop an interactive approach that provides aid to both the buyer and the bidders in a bi-attribute, multi-item auction environment. Our approach is applicable for both reverse and forward auctions. We test our approach for underlying linear preference functions of the buyer. We also adapt it as a heuristic for the case the buyer has a nonlinear preference function. The test results show that our approach works well.     

Photoluminescence of Turkish purple jade (turkiyenite)

The purple-colored unique gem material is only found in the Harmanc?k (Bursa) region of the western Anatolia (Turkey). Therefore, it is specially called “Turkish purple jade or turkiyenite” on the worldwide gem market. Even though its jadeite implication is the principal constituent, the material cannot be considered as a single jadeite mineral since other implications are quartz, orthoclase, epidote, chloritoid and phlogopite minerals.Even if the analytical methods are used to characterize and identify the Turkish purple jade samples in detail, the luminescence spectra, especially photoluminescence features regarding to composite mineral implications of the material are important because of the existence the numerous characteristic broad and intensive luminescence bands in the samples. We can state that the UV-irradiation luminescence centers as photoluminescence (PL) are due to the overall signals in the Turkish purple jade samples. Accordingly, the distinctive photoluminescence peaks at 743, 717, 698, 484, 465 and 442 nm in PL-2D (counter diagram and sections) and PL-3D (sequence spectra) ranging between 300 and 900 nm of wavelengths, and between 220 and 340 K of temperatures are observed.Finally, photoluminescence features of the heterogeneous-structured material cannot be simply attributed to any chemical impurities, since the jade mass has numerous heterogeneous mineral constituents instead of a single jadeite mineral. Six different mineral implications and chemical impurities in the material composition display complex and individual all kind of luminescence features. Therefore, photoluminescence as well as radioluminescence, cathodoluminescence and thermoluminescence spectra provide positive identification regarding to the provenance (geographic origin) of the original Turkish purple jade (turkiyenite).     

On the Cauchy problem for a model equation for shallow water waves of moderate amplitude

We prove the local well-posedness for a nonlinear equation modeling the evolution of the free surface for waves of moderate amplitude in the shallow water regime.