This paper shows a novel method to characterize wind turbine power performance directly from high-frequency fluctuating measurements. In particular, we show how to evaluate the dynamic response of the wind turbine system on fluctuating wind speed in the range of seconds. The method is based on the stochastic differential equations known as the Langevin equations of diffusive Markov processes. Thus, the fluctuating wind turbine power output is decomposed into two functions: (i) the relaxation, which describes the deterministic dynamic response of the wind turbine to its desired operation state, and (ii) the stochastic force (noise), which is an intrinsic feature of the system of wind power conversion. As a main result, we show that independently of the turbulence intensity of the wind, the characteristic of the wind turbine power performance is properly reconstructed. This characteristic is given by their fixed points (steady states) from the deterministic dynamic relaxation conditioned for given wind speed values. The method to estimate these coefficients directly from the data is presented and applied to numerical model data, as well as to real-world measured power output data. The method is universal and is not only more accurate than the current standard procedure of ensemble averaging (IEC-61400-12) but it also allows a faster and robust estimation of wind turbines' power curves. Copyright (C) 2007 John Wiley & Sons, Ltd.

The structure of plasma-sprayed hydroxyapatites possesses a variety of partially dehydrated hydroxyapatite structures. Nuclear magnetic resonance, IR spectroscopy, and X-ray diffraction have been used to analyze the structure of partially dehydrated hydroxyapatites. The oxyhydroxyapatites are prepared from crystalline hydroxyapatite by thermal treatment in air. The obtained results enable an advanced phase analysis of plasma-sprayed hydroxyapatite layers.

Regardless of the applied plasma-spraying conditions, plasma-spraying results in thermal decomposition of the hydroxy/apatite raw material. However, total thermal decomposition into tetracalcium phosphate and tricalcium phosphate is only obtained for extreme spraying conditions. For usual conditions the structure of the hydroxy/apatite is characterized by a partial loss of hydroxy groups in the channels of the apatite structure, leading to the formation of volatile water and oxide ions.

Aluminum doped zinc oxide (ZnO:Al) films which can be used as transparent electrodes or heating layers have been deposited by the low cost spray pyrolysis technique. Undoped and Al-doped ZnO films deposited using various preparation conditions and on different substrates (soda lime glass, quartz glass and crystalline quartz, respectively) have been studied. The effect of substrate type, temperature, deposition time and doping concentration on ZnO:Al thin layers have been investigated by analysing the optical and structural properties of the films. A substrate temperature of 770 K allows the preparation of nanosized ZnO:Al crystals with preferred [002] orientation. Films with optical transmission T>85% and a adjustable resistivity ρ between 2 and 100 Ω cm have been obtained. The resistivity value of the films can be adjusted by tuning suitable processing parameters. The feasibility of the spray pyrolysis technique for the preparation of thin semiconducting ZnO:Al films on conventional soda lime glass substrates is demonstrated.

Various probe ions have been employed to improve the performance of Yb-doped laser glasses. Lanthanide ions similar to the Yb3+, e.g. Nd3+, EU3+ and Gd3+, are sensitive to their site surroundings and that is why they are useful for obtaining the structural information needed to tailor the laser host matrix. A new promising laser glass based on these investigations has been developed. We assume that the favorable laser properties of this glass can be explained by formation of [Yb(PO4)3]-clusters which are nearly isolated from the main part of the network. The electron-phonon coupling in optimized fluoride phosphate glasses with tetrahedral anions may efficiently depopulate the terminal laser level.

Mg0.5Ti2(PO4)3 has been prepared by a sol-gel technique and structure determination has been carried out by Rietveld refinement. It belongs to the NASICON-type structure, space group R3̄c, and is characterized by a low thermal expansion coefficient of 3.7 × 10−6K−1.

Ionic conductivity of some glasses with a relative high content of Na2O in the ternary system Na2ONb2O5P2O5 has been measured using a complex impedance technique. The maximum of the ionic conductivity was found for the composition 55.6 mol% Na2O; 15.3 mol% Nb2O5; 29.1 mol% P2O5 reaching a value of 1.35 × 10−3Scm at 300°C with an activation energy of 0.54 eV, quite similar with that of NASIGLAS, which is up to now the best glassy material in regard of the sodium ion conducting properties. A decisive advantage of the described composition is the occurence of glass formation at a significantly lower temperature.

ChemInformVolume 20, Issue 17 Reviews ChemInform Abstract: 31P and 29Si NMR Investigations of the Structure of NASICON-Compounds C. JAEGER, C. JAEGER Sekt. Phys., Friedrich-Schiller-Univ., DDR-6900 JenaSearch for more papers by this authorG. SCHELER, G. SCHELER Sekt. Phys., Friedrich-Schiller-Univ., DDR-6900 JenaSearch for more papers by this authorS. BARTH, S. BARTH Sekt. Phys., Friedrich-Schiller-Univ., DDR-6900 JenaSearch for more papers by this authorA. FELTZ, A. FELTZ Sekt. Phys., Friedrich-Schiller-Univ., DDR-6900 JenaSearch for more papers by this author C. JAEGER, C. JAEGER Sekt. Phys., Friedrich-Schiller-Univ., DDR-6900 JenaSearch for more papers by this authorG. SCHELER, G. SCHELER Sekt. Phys., Friedrich-Schiller-Univ., DDR-6900 JenaSearch for more papers by this authorS. BARTH, S. BARTH Sekt. Phys., Friedrich-Schiller-Univ., DDR-6900 JenaSearch for more papers by this authorA. FELTZ, A. FELTZ Sekt. Phys., Friedrich-Schiller-Univ., DDR-6900 JenaSearch for more papers by this author First published: April 25, 1989 https://doi.org/10.1002/chin.198917341Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume20, Issue17April 25, 1989 RelatedInformation

The solid solution Na1+xZr2 (PO4)3-x(SiO4)x has been investigated by 23Na NMR. The parameters of the quadrupole of the Na(1) positions in NaZr2(PO4)3 are νq=1.2±0.1 MHz and η=0.04±0.04. Those for the Na(1) and Na(2) sites in Na4Zr2(SiO4)3 are found to be Na(1): νq=1.04±0.1 MHz, η=0.84±0.7; Na(2): νq=0.87±0.05 MHz, η=0.53+0.4 with an intensity ratio for the lines of approximately 1:3, as expected. The random substitution of phosphorus atoms on their lattice sites by silicon atoms for increasing x leads to a distribution of the parameters of the quadrupole tensors. Increasing substitution strongly affects the asymmetry of the electric field gradient.

Die Verbindungen Na3MgZr(PO4)3 und Na3MnZr(PO4)3 kristallisieren in der NASICON-Struktur (Raumgruppe R3̄c — D3d6) mit den Gitterkonstanten a0 = (890,7 ± 0,6) pm, c0 = (2222±4) pm bzw. a0 = 900,0 pm, c0 = 2239,3 pm. Modellrechnungen zur Intensität der Pulverdiffraktogramme und 31P-MAS-NMR-Messungen belegen eine ungeordnete Verteilung der ZrIV- und MgII- bzw. MnII-Atome auf den Oktaederplätzen, wobei sich die Na+-Ionen auf einen NaI-Platz und drei NaII-Plätze etwa gleich verteilen. Die Verbindungen schmelzen inkongruent bei 1075 °C bzw. 1025 °C. Die Mangan-Verbindung hat bei 300 °C eine etwa um den Faktor 3 grössere Leitfähigkeit. Insgesamt ist die Na+-Ionenleitfähigkeit bei 300 °C um etwa drei Grössenordnungen geringer als für Na3Zr2(SiO4)2(PO4), was auf den unregelmässigen Aufbau der beiden Verbindungen zurückgeführt wird.

For investigation of phase relations in the NASICON system some compositions of the general formula Na4Zr2−xSi3O12 −2x were prepared by sol-gel technique and the usual method of sintering the oxide mixtures. DTA measurements indicate that unannealed samples in this series must contain a glassy phase. By means of X-ray analysis of a sample of the composition Na4ZrSi3O10 it was clearly shown that this sample does not exist as a definite compound, but must be regarded as a composite material consisting of the well known compound Na4Zr2(SiO4)3 and a glassy phase of the composition Na4Si3O8. This result was proved by high resolution 29Si-magic angle spinning (MAS)-NMR measurements which allow the simultaneous registration of both crystalline and glassy phases and the determination of the relative Si-content of the phases with high accuracy. In this manner the glass composition in the sample was estimated for 1.98 Na2O·3SiO2.

AbstractBoth the title compounds crystallize in the hexagonal space group R3c with Z = 6 and they are isostructural with Na1+xZr2(PO4)3‐x(SiO4)x (NASICON).

The original NASICON system Na 1+χ Zr 2 (SiO 4 ) χ (PO 4 ) 3-χ was investigated by 29 Si and 31 P NMR. With increasing χ a continuous down-field shift of the single resonance lines was observed both in 29 Si and 31 P NMR. The linewidth shows a maximum around χ = 1.5. Both effects are explained by a change in the net atomic charge q Zr of zirconium caused by the substitution of phosphorus by silicon. In Na 4 Zr 2 (SiO 4 ) 3 q Zr was estimated to be 1.32 from the NMR data.

Up to four fixed resonances are observed in the title system independent of the composition: NaZr2(PO4)3 (y≲0.5), Na3Zr1.5(PO4)3 (y0), Na4P2O7 (y0) and a fourth line which we are so far unable to interpret in structural terms. The 31P chemical shift parameters of Na3Zr1.5(PO4)3 are: δ = −11.9±0.3 ppm, Δσ = 64±2 ppm and η = 0.52±0.05.

It is proved by 31P-NMR that the mixed crystals of the series Na1+2xMgxZr2−x(PO4)3 are composed of five introduced basic structures NaZr2(PO4)3, Na2MgZr(PO4)3, Na3MgZr(PO4)3, Na4Mg1.5Zr0.5(PO4)3 and Na5Mg2(PO4)3 (x ≦ 1). The Mg2+- and Zr4+-ions are statistically distributed. No amorphous minor constituents can be found. The region of this series of mixed crystals is already broken up for x > 1, whereas the theoretical limit is x = 1.5. For x > 1 monophosphates are formed partially with Na+ and Mg2+ in the second coordination sphere of phosphorus. Mit Hilfe der 31P-NMR wird gezeigt, daß die Mischkristalle der Verbindungsreihe Na1+2xMgxZr2−x(PO4)3, für x ≦ 1 aus den fünf Basisstrukturen NaZr2(PO4)3, Na2Mg0,5Zr1,5(PO4)3, Na3MgZr(PO4)3, Na4Mg1,5Zr0,5(PO4)3, und Na5Mg2(PO4)3, aufgebaut sind. Die Ionen Mg2+ und Zr4+ sind im Netzwerk statistisch verteilt. Es werden keine amorphen Nebenphasen gefunden. Der Misch-kristallbereich wird bereits bei Werten x > 1 durchbrochen, obwohl die theoretische Grenze bei x = 1,5 liegt. Für Werte x > 1 bilden sich zum Teil Monophosphate mit Na+ und Mg2+ in der zweiten Koordinationsphäre des Phosphors.

Preparation, X-ray pattern, thermal and conductivity behaviour of the compounds Na3MnZr(PO4)3 and Na3MgZr(PO4)3 are reported. Na3ZnZr(PO4)3 could not be obtained at comparable conditions. The conductivity of the two compounds is about two orders of magnitude smaller than for NASICON.