金属在高温状态下复折射率的确定

本文采用FTIR光谱辐射计测量了金属Zr,Mo在高温状态下的辐射,通过基于Frsnel函数的优化算法,得到了Zr,Mo在红外波段的复折射率n-jx,实部n的最大估计误差约为6%,x(消光系数)的最大估计误差约为5%.高温的测量采用了实验室的专利紫外光子测温法.     

Plasma for special applications

Summary The large development of industrial plasma techniques is due to new understanding of chemical concepts of reactive gases excited by electron impact. In this way, it is possible to obtain larger operational facilities of the processes, i.e.: the elimination of wet treatment and flexibility of tools. Therefore, many engineers agree on the widespread application of these technologies.The numerous advantages of plasma techniques are realized by two different concepts according to the equilibrium of the reactive systems (atmospheric system with gas temperature = electronic temperature) or non-equilibrium systems (rotational temperature = translational temperature = 500° K — vibrational temperature = 500° K — vibrational temperature >3,100° K — electronic temperature > 1 to 2 eV).For the high pressure torch, both the thermal and chemical properties of the plasma mixture are employed at the same moment which lead to high temperature reactions, high kinetic rates, and short residence times. These tools are used today for extractive metallurgy, oil treatment, plasma spray, optical fibers, and production of high purity materials. We have chosen to present them through the example of silicon refining by a RF plasma torch. The multiphase extractive process controls the efficiency of the treatment. At the liquid-plasma interface the evaporation of the impurities is measured by emission spectroscopy with an optical fiber (K, Na, Mg). The working parameters of the system [plasma gas composition (O₂, H₂, Ar), Rf-power source, speed of the treatment] can be adjusted by such measures. The photovoltaic efficiency of the materials has been determined in correlation with the spectroscopic measurements.For the low pressure plasma reactor, the chemical properties are studied by measuring the vibrational level of the excited molecular species. For instance, reactive levels of vibrational states increase the kinetic rate by a factor of 10⁴ to 10⁶ with a gas temperature approaching room temperature. In this way, a large number of industrial applications has been developed with a glow discharge reactor and a corona discharge reactor essentially for surface treatment such as etching, grafting, polymerization, nitriding, deposition etc. We have chosen to explain the nitriding process of metals and silicon in order to point out the role of vibrational species and particularly, those of the NH molecules. These results are correlated with the evolution of the hardness of the material and the conversion rate of the reactive molecule.

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Plasma für spezielle Anwendungen

Zusammenfassung Die starke Entwicklung industrieller Plasmaverfahren ist auf neue chemische Konzepte der Anregung von reaktiven Gasen durch Elektronenstöße zurückzuführen. So wird es möglich, die Durchführung des Prozesses besser zu steuern, d. h. eine nasse Behandlung zu vermeiden und flexibler zu sein. Entsprechend bevorzugen viele Ingenieure diese Verfahren.Die Vorteile der Plasmaverfahren kann man in verschiedenen Systemen realisieren, nämlich in reaktiven Systemen im thermischen Gleichgewicht (atmosphärischer Druck, wobei Gastemperatur und Elektronentemperatur gleich sind) oder in Systemen, die nicht im thermischen Gleichgewicht sind (Rotationstemperatur Elektronentemperatur oder Rotationstemperatur = Translationstemperatur = 500 K, Vibrationstemperatur >3100 K, Elektronentemperatur >1–2 eV).Im Falle eines bei hohem Druck betriebenen Plasmabrenners bewerkstelligen die thermischen und die chemischen Eigenschaften des Plasmas eine Reaktion bei hoher Temperatur, hohe Reaktionskonstanten und kurze Aufenthaltszeiten. Diese Verfahren werden heute eingesetzt in der extraktiven Metallurgie, in der Behandlung von Ölen, in der Plasmaspritztechnik und für die Herstellung von optischen Fasern und Reinststoffen. Sie werden in diesem Beitrag anhand der Darstellung von hochreinem Silicium in einem Hochfrequenzplasmareaktor besprochen. Die Ausbeute der Behandlung wird über einen vielphasigen Extraktionsprozeß gesteuert. Die Verflüchtigung von Verunreinigungen (K, Mg, Na) im Grenzbereich zwischen Flüssigphase und Plasma wird mit Hilfe von optischen Fasern emissionsspektrometrisch gemessen. Die Betriebsparameter des Systems und Zusammensetzung des Plasmagases (O₂, H₂, Ar), Hochfrequenzleistung, Reaktionsgeschwindigkeit werden hierüber gesteuert. Die photovoltaischen Eigenschaften des hergestellten Siliciums wurden untersucht und ihre Korrelation mit den spektroskopisch gemessenen Größen überprüft.Im Fall von Plasmareaktoren bei niedrigem Druck sind die chemischen Eigenschaften von den Vibrationsniveaus der angeregten Moleküle abhängig. Zum Beispiel nimmt die Reaktionsgeschwindigkeit bei einer Gastemperatur, die in der Nähe der Umgebungstemperatur liegt, infolge reaktiver Vibrationsniveaus um einen Faktor 10⁴ bis 10⁶ zu. Zahlreiche industrielle Anwendungen von Glimmentladungen oder Coronarentladungen wurden dementsprechend entwickelt, hauptsächlich für Oberflächenbehandlungen wie Ätzen, Implantieren, Polymerisieren, Nitrieren oder Beschichten. Anhand der Nitrierung von Metallen und von Silicium wird der Einfluß des Vibrationsniveaus, insbesondere von NH-Molekülen besprochen. Die Ergebnisse stehen in Zusammenhang mit der Härte des Materials sowie der Reaktionsrate des reaktiven Moleküls.

     

Chemical modification of coumarin dimer and HIV-1 integrase inhibitory activity

A systematic series of chemically modified coumarin dimmers has been synthesized and tested for their inhibitory activity against HIV-1 integrase. We observed that modified coumarin dimmers containing hydrophobic moiety on the linker display potent inhibitory activities.     

Lamb wave reflection at the free edge of a plate

This study concentrates on the reflection of Lamb waves at the free end of a plate. The conversion phenomena are examined in detail over a large frequency range and the energy conversion coefficients are obtained by three different ways: theoretically, numerically (finite element method) and experimentally. The experimental energy determination is obtained from the measurement of the plate normal displacements, by mean of a laser interferometer. All results are in relatively good agreement and the energy balance between incident and reflected waves is discussed in each case.     

Isotopic study of post-anthesis foliar incorporation of sulphur and nitrogen in wheat

Nitrogen (N) and sulphur (S) supplies have a strong influence on the quality and quantity of wheat storage proteins, which play an important role in the bread-making process. In order to relate the incorporation and distribution of foliar N and S fertilisers at the post-anthesis stage to the quality of wheat, 15N and 34S isotopes were used as tracers. The incorporation of these tracers in different plant parts (leaves, stems, ears) and in each storage protein fraction (gliadins, HMW and LMW glutenin subunits) was determined by isotopic ratio mass spectrometry coupled with an elemental analyser (EA-IRMS). By this means, the true recovery coefficient of N and S (TRCNfertiliser and TRCSfertiliser) and the N and S derived from fertilisers (Ndff and Sdff) could be determined. The TRCNfertiliser and TRCSfertiliser values of the different plant parts provide evidence of the applied N and S assimilation and translocation from wheat leaves to the seeds. The determination of Ndff and Sdff incorporated into storage proteins shows the efficiency and the influence of N and S incorporation into each storage protein fraction. Moreover, a favourable stage for fertiliser application can be determined by the TRCNfertiliser values in the grain and in the whole plant. The fertilisers enriched in stable isotope used in the culture techniques can be a means of understanding the effectiveness of fertilisers in the expression of wheat quality.     

Micromechanical modeling of packing and size effects in particulate composites

This paper is devoted to the introduction of packing and size effects in micromechanical predictions of the overall elastic moduli of particulate composite materials. Whereas micromechanical models derived from the classical ‘point approach’ are known to be unable to model such effects, it is shown that the so-called ‘morphologically representative pattern-based approach’ (MRP-based approach) offers new means of taking some geometrical parameters into account such as the mean distance between nearest-neighbor particles or their size, so as to predict the dependence of the overall moduli on these parameters, at least in a relative way. Moreover, when internal lengths, such as the thickness of interphase shells of coated particles, are introduced, absolute size effects can be predicted as well. Illustrative applications are reported in view of comparisons between such new treatments and the predictions of some classical models which are shown to coincide with the ones derived from MRP-based models in definite limiting cases only.     

An Interferometric Optical Technique for In-Situ Measurement of Fiber Diameter

The diameter distribution of fibers plays an important role in the performance of many fiberglass products. The fiberglass industry, however, currently lacks the advanced instrumentation necessary for performing on-line fiber diameter measurements. Enhanced measurement capabilities would provide manufacturers and researchers a tool to improve fiberizing methods, production efficiency, and overall fiberglass product performance. This paper describes the size measurement of moving glass fibers using the Phase Doppler Anemometry technique. Simulation results are presented and validated experimentally. Theoretical modeling uses the mathematical solution for a tilted circular cylinder interacting with focused Laser beams. Experimental laboratory studies have been also conducted to evaluate the factors not included in the theoretical models.     

Three-and two-dimensional calculations for the interface anisotropy dependence of magnetic properties of exchange-spring Nd2Fe(14)B/α-Fe multilayers with out-of-plane easy axes

Hysteresis loops,energy products and magnetic moment distributions of perpendicularly oriented Nd2Fe(14)B/α-Fe exchange-spring multilayers are studied systematically based on both three-dimensional(3D)and one-dimensional(1D)micromagnetic methods,focused on the influence of the interface anisotropy.The calculated results are carefully compared with each other.The interface anisotropy effect is very palpable on the nucleation,pinning and coercive fields when the soft layer is very thin.However,as the soft layer thickness increases,the pinning and coercive fields are almost unchanged with the increment of interface anisotropy though the nucleation field still monotonically rises.Negative interface anisotropy decreases the maximum energy products and increases slightly the angles between the magnetization and applied field.The magnetic moment distributions in the thickness direction at various applied fields demonstrate a progress of three-step magnetic reversal,i.e.,nucleation,evolution and irreversible motion of the domain wall.The above results calculated by two models are in good agreement with each other.Moreover,the in-plane magnetic moment orientations based on two models are different.The 3D calculation shows a progress of generation and disappearance of vortex state,however,the magnetization orientations within the film plane calculated by the 1D model are coherent.Simulation results suggest that negative interface anisotropy is necessarily avoided experimentally.