Electroacoustic and Behavioural Evaluation of Hearing Aid Digital Signal Processing Features

Modern digital hearing aids provide an array of features to improve the user listening experience. As the features become more advanced and interdependent, it becomes increasingly necessary to develop accurate and cost-effective methods to evaluate their performance. Subjective experiments are an accurate method to determine hearing aid performance but they come with a high monetary and time cost. Four studies that develop and evaluate electroacoustic hearing aid feature evaluation techniques are presented. The first study applies a recent speech quality metric to two bilateral wireless hearing aids with various features enabled in a variety of environmental conditions. The study shows that accurate speech quality predictions are made with a reduced version of the original metric, and that a portion of the original metric does not perform well when applied to a novel subjective speech quality rating database. The second study presents a reference free (non-intrusive) electroacoustic speech quality metric developed specifically for hearing aid applications and compares its performance to a recent intrusive metric. The non-intrusive metric offers the advantage of eliminating the need for a shaped reference signal and can be used in real time applications but requires a sacrifice in prediction accuracy. The third study investigates the digital noise reduction performance of seven recent hearing aid models. An electroacoustic measurement system is presented that allows the noise and speech signals to be separated from hearing aid recordings. It is shown how this can be used to investigate digital noise reduction performance through the application of speech quality and speech intelligibility measures. It is also shown how the system can be used to quantify digital noise reduction attack times. The fourth study presents a turntable-based system to investigate hearing aid directionality performance. Two methods to extract the signal of interest are described. Polar plots are presented for a number of hearing aid models from recordings generated in both the free-field and from a head-and-torso simulator. It is expected that the proposed electroacoustic techniques will assist Audiologists and hearing researchers in choosing, benchmarking, and fine-tuning hearing aid features

Stable and Efficient Electronic Business Networks: Key Players and the Dilemma of Peripheral Firms

This paper studies a spatial model of electronic business network formation where firms build links based on a cost-benefit analysis. Benefits result from directly and indirectly connected firms in terms of knowledge flows, which are heterogeneous: a 'key-player' (e.g. a firm providing an exchange platform in a business- to-business network) provides a higher level of knowledge flows than 'peripheral' firms (e.g. tier 3 suppliers in a vertically differentiated industry). For intermediate cost values of link formation, stable and efficient network structures comprise only a subset of the total set of firms, excluding peripheral firms which are most distantly located to the key player. When link formation implies a certain degree of network congestion, the stable and efficient network size is smaller than in a model with bilateral decisions upon link formation between two firms

Stable and Efficient Electronic Business Networks: Key Players and the Dilemma of Peripheral Firms

This paper studies a spatial model of electronic business network formation where firms build links based on a cost-benefit analysis. Benefits result from directly and indirectly connected firms in terms of knowledge flows, which are heterogeneous: a 'key-player' (e.g. a firm providing an exchange platform in a business- to-business network) provides a higher level of knowledge flows than 'peripheral' firms (e.g. tier 3 suppliers in a vertically differentiated industry). For intermediate cost values of link formation, stable and efficient network structures comprise only a subset of the total set of firms, excluding peripheral firms which are most distantly located to the key player. When link formation implies a certain degree of network congestion, the stable and efficient network size is smaller than in a model with bilateral decisions upon link formation between two firms

Stau-catalyzed 6^6Li Production in Big-Bang Nucleosynthesis

If the gravitino mass is in the region from a few GeV to a few 10's GeV, the scalar lepton X such as stau is most likely the next lightest supersymmetry particle. The negatively charged and long-lived X^- may form a Coulomb bound state (A X) with a nucleus A and may affect the big-bang nucleosynthesis through catalyzed fusion process. We calculate a production cross section of Li6 from the catalyzed fusion (He4 X^-) + d \to Li6 + X^- by solving the Schr\"{o}dinger equation exactly for three-body system of He4, d, and X. We utilize the state-of-the-art coupled-channel method, which is known to be very accurate to describe other three-body systems in nuclear and atomic reactions. The importance of the use of appropriate nuclear potential and the exact treatment of the quantum tunneling in the fusion process are emphasized. We find that the astrophysical S-factor at the Gamow peak corresponding to T=10 keV is 0.038 MeV barn. This leads to the Li6 abundance from the catalyzed process as Li6|_{CBBN}\simeq 4.3\times 10^{-11} (D/2.8\times 10^{-5}) ([n_{X^-}/s]/10^{-16}) in the limit of long lifetime of X. Particle physics implication of this result is also discussed.Comment: 16 pages, 7 figure

Charge Form Factor and Cluster Structure of 6^6Li Nucleus

The charge form factor of ${}^6$Li nucleus is considered on the basis of its cluster structure. The charge density of ${}^6$Li is presented as a superposition of two terms. One of them is a folded density and the second one is a sum of ${}^4$He and the deuteron densities. Using the available experimental data for ${}^4$He and deuteron charge form factors, a good agreement of the calculations within the suggested scheme is obtained with the experimental data for the charge form factor of ${}^6$Li, including those in the region of large transferred momenta.Comment: 12 pages 5 figure

Metastable Se6 as a ligand for Ag+: from isolated molecular to polymeric 1D and 2D structures

Attempts to prepare the hitherto unknown Se6 2+ cation by the reaction of elemental selenium and Ag[A] ([A]- = [Sb(OTeF5)6]-, [Al(OC(CF3)3)4]-) in SO2 led to the formation of [(OSO)Ag(Se6)Ag(OSO)][Sb(OTeF5)6]2 1 and [(OSO)2Ag(Se6)Ag(OSO)2][Al(OC(CF3)3)4]2 2a. 1 could only be prepared by using bromine as co-oxidant, however, bulk 2b (2a with loss of SO2) was accessible from Ag[Al(OC(CF3)3)4] and grey Se in SO2 (chem. analysis). The reactions of Ag[MF6] (M= As, Sb) and elemental selenium led to crystals of 1/∞{[Ag(Se6)]∞[Ag2(SbF6)3]∞} 3 and {1/∞[Ag(Se6)Ag]∞}[AsF6]2 4. Pure bulk 4 was best prepared by the reaction of Se4[AsF6]2, silver metal and elemental selenium. Attempts to prepare bulk 1 and 3 were unsuccessful. 1–4 were characterized by single-crystal X-ray structure determinations, 2b and 4 additionally by chemical analysis and 4 also by X-ray powder diffraction, FT-Raman and FT-IR pectroscopy. Application of the PRESTO III sequence allowed for the first time 109Ag MAS NMR investigations of 4 as well as AgF, AgF2, AgMF6 and {1/∞[Ag(I2)]∞}[MF6] (M= As, Sb). Compounds 1 and 2a/b, with the very large counter ions, contain isolated [Ag(Se6)Ag]2+ heterocubane units consisting of a Se6 molecule bicapped by two silver cations (local D3d sym). 3 and 4, with the smaller anions, contain close packed stacked arrays of Se6 rings with Ag+ residing in octahedral holes. Each Ag+ ion coordinates to three selenium atoms of each adjacent Se6 ring. 4 contains [Ag(Se6)+]∞ stacks additionally linked by Ag(2)+ into a two dimensional network. 3 features a remarkable 3-dimensional [Ag2(SbF6)3]- anion held together by strong Sb–F … Ag contacts between the component Ag+ and [SbF6]- ions. The hexagonal channels formed by the [Ag2(SbF6)3]- anions are filled by stacks of [Ag(Se6)+]∞ cations. Overall 1–4 are new members of the rare class of metal complexes of neutral main group elemental clusters, in which the main group element is positively polarized due to coordination to a metal ion. Notably, 1 to 4 include the commonly metastable Se6 molecule as a ligand. The structure, bonding and thermodynamics of 1 to 4 were investigated with the help of quantum chemical calculations (PBE0/TZVPP and (RI-)MP2/TZVPP, in part including COSMO solvation) and Born–Fajans–Haber-cycle calculations. From an analysis of all the available data it appears that the formation of the usually metastable Se6 molecule from grey selenium is thermodynamically driven by the coordination to the Ag+ ions

Duopolistic Competition between Independent and Collaborative Business-to-Business Marketplaces

This paper studies imperfect price competition between two intermediaries in an electronic business-to-business matching market with indirect network externalities. The intermediaries differ with regard to their ownership structure: an independent third party incumbent marketplace competes with a challenging collaborative buy-side consortium marketplace in terms of attracting buying and selling firms. When firms can register exclusively with at most one intermediary, the incumbent is only able to deter entry if the number of firms taking ownership in the consortium is sufficiently small. Otherwise, the consortium can successfully enter and monopolize the market. When agents can multi-home, i.e. they register simultaneously with both intermediaries, the consortium can always enter while both intermediaries stay in the market with positive profitsB2B e-commerce, intermediation, network externalities, matching