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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 177-196 
    ISSN: 1573-4862
    Keywords: Interfaces ; ultrasonics ; partial contact ; quasi-static
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A quasi-static model for the ultrasonic transmission and reflection at imperfect interfaces is developed. The interface is represented by a distributed spring, determined by the change in static compliance of the medium with respect to one with a perfect interface, and a distributed mass, representing excess mass at the interface. Comparison of the model predictions to exact solutions for two simple cases illustrates its accuracy at low frequencies. The spring stiffnesses can be derived from existing solutions for the elastic displacement of materials containing cracks and inclusions under static load. Results for a variety of cases are reviewed. Applications of the model to study the characteristics of partially contacting surfaces in several problem areas of current interest are discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4862
    Keywords: Beam propagation ; bimetallic weld ; Gauss-Hermite beam model ; finite element method ; ultrasonics ; anisotropic medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract In this paper, predictions of two models for the propagation of ultrasonic beams through a two-dimensional, bimetallic weld geometry are compared. The finite element method can predict beam propagation through quite general geometry with high accuracy. This model, however, requires significant computational time. On the other hand, the approximate Gauss-Hermite model offers considerably greater computational speed, but has lower accuracy in certain regions and cannot treat the most general geometries and inhomogeneities in material properties. This paper compares the performances of the two models for the case of the two-dimensional, bimetallic weld consisting of multiple layers, some of which have anisotropic properties. It is found that the results of the two models are in good agreement in the vicinity of the central ray, and that the deviation increases as one moves away from the axis. Also, as the beam propagates through multiple interfaces, the accuracy of the Gauss-Hermite solution decreases.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of nondestructive evaluation 4 (1984), S. 107-123 
    ISSN: 1573-4862
    Keywords: ultrasonics ; transducers ; focusing ; refractior ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A scalar theory of the propagation of Gaussian ultrasonic beams through lenses and interfaces is presented. For radiation into a fluid, the Fresnel approximation is employed to derive the laws of propagation of Guassian beams (previously employed in the analysis of coherent optical systems). These are then generalized to situations commonly found in nondestructive evaluation by treating the effects of propagation through lenses and through curved interfaces at oblique incidence. A numerical example illustrates the ease with which insight into diffraction phenomena for complex geometries can be gained by this approach. The limitations imposed on the theory by aberrations and the scalar assumption are discussed, and the relationship of the Gaussian theory to the radiation of piston transducers is explored.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1871-4528
    Keywords: partitioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Zusammenfassung Der Einfluss des Genotypes von Pfropfreis und Unterlage auf das Wachstum und den Ertrag von Kartoffelpflanzen, die durch Pfropfungen zwischen einer spät reifenden, einer frühen und einer frühen Hauptanbausorte (Tab. 1) hergestellt wurden, wurde in grossen Töpfen (30 cm Durchmesser) an Hand aufeinanderfolgender Ernten in wöchentlichen oder 2-wöchentlichen Abständen untersucht. Beim Mitteln der Ergebnisse aus den 9 aufeinander folgenden Ernten zeigte es sich (Tab. 2), dass das Wachstum der spät reifenden Sorte Cara durch die Pfropfung nur wenig vermindert wurde, und dass bei den Pfropfungen zwischen der Sorte Cara und der früh reifenden Sorte Pentland Javelin das Pfropfreis auf die meisten Wachstumserscheinungen den dominierenden Einfluss ausübte. In ähnlicher Weise dominierte das Pfropfreis über der Unterlege bei Pfropfungen zwischen der Sorte Cara und der frühen Hauptanbausorte Pentland Dell, obgleich alle Knollen an der Unterlage erzeugt wurden (Tab. 3). Die Unterlagen von Pentland Dell tendierten jedoch, verglichen mit denen von Cara, zur Einschränkung des Spitzenwachstums. Dieser Unterschied im Einfluss wurde bestätigt, indem die Änderungen der wichtigsten Leistungen des Pfropfreises (Abbildungen 2a–6a) und der Unterlage (Abbildungen 2b–6b) dargestellt wurden, wie das Trockengewicht der Spitze, das Trockengewicht der Wurzeln, das Trockengewicht der Knollen, das Gesamttrockengewicht und der Prozentsatz der gesamten Trockenmasse in den Knollen, Bei der Schlussernte, die 13 Wochen nach dem Umsetzen der Pflanzen in grosse Töpfe durchgeführt wurde, zeigte es sich, dass die Pfropfreiser von Pentland Javelin abgestorben (Tab. 4) und diejenigen von Pentland Dell teilweise senescent waren (Tab. 5). Insgesamt ergaben die Pflanzen von Cara auf Cara die grössten Knollenerträge und die grösste Gesamttrockenmasse. Ein Versuch in Feldparzellen mit Pfropfungen zwischen den Sorten Cara und Pentland Dell ergab eine weitere Bestätigung der oben genannten Ergebnisse mit der Ausnahme, dass Messungen der Bodenbedeckung (Tab. 6) ergaben, dass die Unterlage anfänglich fast ebenso viel Einfluss auf das Spitzenwachstum ausübt wie das Pfropfreis; Pfropfreiser oder Unterlagen von Pentland Dell verzögern das Spitzenwachstum in gleicher Weise wie diejenigen von Cara. Der Einfluss des Pfropfreises vergrösserte sich dejoch fortlaufend, so dass bei zwei Ernten, die nach 13 und 16 Wochen nach dem Auspflanzen ins Feld durchgeführt wurden, der Einfluss des Pfropfreises dominant über dem der Unterlage wurde (Tab. 7). Pflanzen von Cara auf Cara lieferten wieder die höchste Gesamttrockenmasse und bei der Schlussernte waren die Pflanzen mit Cara Pfropfreisern noch grün und im Wachstum während diejenigen mit Pentland Dell Pfropfreisern senescent geworden waren.
    Abstract: Résumé L'influence du génotype du greffon et du porte-greffe sur la croissance et le rendement de pieds de pommes de terre produits par greffage entre variété tardive, précoce et demi-précoce est étudiée en grands pots (30 cm de diamètre) par arrachages échelonnés à une ou deux semaines d'intervalle. Les moyennes effectuées à partir des résultats des neuf arrachages montrent (tableau 2) que la croissance de la variété la plus tardive Cara n'est que légèrement ralentie par un greffage et que dans le cas de greffes entre Cara et la variété plus précoce Pentland Dell le greffon a l'influence la plus importante sur la plupart des différents aspects de la croissance. De façon semblable, dans le cas de greffes entre Cara et la variété précoce Pentland Dell le greffon domine sur le porte-greffe alors même que les tubercules sont formés sur le porte-greffe (tableau 3). Toutefois, les porte-greffes de Pentland Dell ont tendance à diminuer le développement de la partie aérienne par rapport à ceux de Cara. Cette différence est en effet confirmée si l'on figure graphiquement les principaux effets du greffon (figures 2a–6a) et du porte-greffe (figures 2b–6b) sur le poids sec de la partie aérienne, le poids sec des racines, le poids sec des tubercules, le poids sec total et le pourcentage de matière sèche totale dans les tubercules. Une récolte finale, effectuée 13 semaines après le transfert des plantes en grands pots, montre que les greffons de Pentland Javelin sont morts (tableau 4) et que ceux de Pentland Dell sont partiellement sénescents (tableau 5). Les pieds de Cara sur Cara produisent les meilleurs rendements en tubercules et en matière sèche totale. Une expérimentation en parcelles au champ, avec des greffes entre Cara et Pentland Dell confirme les conclusions précédentes à l'exception des mesures de couvertures du sol (tableau 6) qui montrent que le portegreffe a au moins autant d'effet que le greffon sur la croissance de la partie aérienne. Les greffons ou les porte-greffes de Pentland Dell retardent la croissance de la partie aérienne à un degré équivalent à ceux de Cara. Malgré tout, l'influence du greffon augmente progressivement, si bien que pour les deux récoltes effectuées 13 et 16 semaines après la plantation au champ, l'effet du greffon est plus important que celui du portegreffe (tableau 7). Encore une fois, les plantes de Cara sur Cara produisent la matière sèche totale la plus élevée et, à la récolte finale, les plantes avec greffon de Cara sont encore vertes et en croissance, tandis que celles avec greffon Pentland Dell deviennent sénescentes.
    Notes: Summary The effect of stock and scion genotype on the growth and yield of potato plants was tested in large pots. In grafts between an early and a late-maturing cultivar the scion genotype had the dominant influence on most aspects of the growth. The stock had less influence, but stocks of cv. Pentland Dell (early main crop) supported less vigorous growth than those of cv. Cara (late main crop). Similar results were obtained in field plots lightly infested with potato cyst nematode. Ground cover measurements showed that compared with Cara, scions and stocks of Pentland Dell initially retarded growth to a similar degree but that later in the growing season the scion had a greater effect than the stock. The scion had a greater influence on the partitioning of assimilates and on haulm weight than the stock, but both the stock and the scion influenced final tuber yields.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of aquatic ecosystem stress and recovery 4 (1995), S. 231-238 
    ISSN: 1573-5141
    Keywords: sediment toxicity ; sediment spiking ; chironomid ; fluoranthene ; partitioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The bioavailability of fluoranthene (as a model toxicant) in freshwater sediment tests with Chironomus riparius was investigated in relation to the partitioning of the chemical between water and sediment. Effects on survival and successful development of newly hatched larvae through to adult emergence were measured over a range of sediment concentrations. Radiolabelled fluoranthene was employed to enable sediment, aqueous and tissue concentrations to be determined. A significant effect on emergence was obtained at a measured sediment concentration of 80 mg kg-1 (dry weight). The measured concentration in the overlying water was 88 μg l-1. Although effects at 170 mg kg-1 (dry weight) were more severe, the measured concentration in the overlying water was similar (89 μg l-1), probably reflecting the approach towards the solubility limit. Bioaccumulation of fluoranthene, determined by analysis of emerging adults, was approximately proportional to the sediment concentration. Although the aqueous phase concentration appeared to be the principal factor controlling bioavailability, the increasing toxicity, when water concentrations had reached a plateau, suggested that other mechanisms may also be involved. Different sediment spiking procedures resulted in broadly similar partitioning of the chemical between the sediment and the overlying water. There were only minor differences in toxicity between the procedures, two of which allowed the carrier solvent used for spiking to be eliminated before addition of the test organisms. It was concluded that, for most purposes, all four procedures were equally acceptable, and by retaining a flexible approach, even for standardised regulatory tests, spiking procedures may be tailored to the physico-chemical properties of the test material.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of aquatic ecosystem stress and recovery 4 (1973), S. 231-238 
    ISSN: 1573-5141
    Keywords: sediment toxicity ; sediment spiking ; chironomid ; fluoranthene ; partitioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The bioavailability of fluoranthene (as a model toxicant) in freshwater sediment tests with Chironomus riparius was investigated in relation to the partitioning of the chemical between water and sediment. Effects on survival and successful development of newly hatched larvae through to adult emergence were measured over a range of sediment concentrations. Radiolabelled fluoranthene was employed to enable sediment, aqueous and tissue concentrations to be determined. A significant effect on emergence was obtained at a measured sediment concentration of 80 mg kg-1 (dry weight). The measured concentration in the overlying water was 88 μg l-1. Although effects at 170 mg kg-1 (dry weight) were more severe, the measured concentration in the overlying water was similar (89 μg l-1), probably reflecting the approach towards the solubility limit. Bioaccumulation of fluoranthene, determined by analysis of emerging adults, was approximately proportional to the sediment concentration. Although the aqueous phase concentration appeared to be the principal factor controlling bioavailability, the increasing toxicity, when water concentrations had reached a plateau, suggested that other mechanisms may also be involved. Different sediment spiking procedures resulted in broadly similar partitioning of the chemical between the sediment and the overlying water. There were only minor differences in toxicity between the procedures, two of which allowed the carrier solvent used for spiking to be eliminated before addition of the test organisms. It was concluded that, for most purposes, all four procedures were equally acceptable, and by retaining a flexible approach, even for standardised regulatory tests, spiking procedures may be tailored to the physico-chemical properties of the test material.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 16 (1984), S. 867-878 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of OH reactions with furan (k1), thiophene (k2), and tetrahydrothiophene (k3), have been investigated over the temperature range 254-425 K. OH radicals were produced by flash photolysis of water vapor at λ 〉 165 nm and detected by timeresolved resonance fluorescence spectroscopy. The following Arrhenius expressions adequately describe the measured rate constants as a function of temperature (units are cm3 molecule-1 S-1): k1 = (1.33 ± 0.29) × 10-11 exp[(333 ± 67)/T], k2 = (3.20 ± 0.70) × 10-12 exp[(325 ± 71)/T], k3 = (1.13 ± 0.35) × 10-11 exp[(166 ± 97)/T]. The results are compared with previous investigations and their implications regarding reaction mechanisms and atmospheric residence times are discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 16 (1984), S. 1623-1636 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of OH reactions with 1-4 carbon aliphatic thiols have been investigated over the temperature range 252-430 K. OH radicals were produced by flash photolysis of water vapor at λ 〉 165 nm and detected by time-resolved resonance fluorescence spectroscopy. All thiols investigated react with OH at nearly the same rate; k(298 K) = 3.2-4.6 × 10-11 cm3 molecule-1 s-1, -Eact = 0.6-1.0 kcal/mol, A = 0.6-1.2 × 10-11 cm3 molecule-1 s-1. CH3SH and CH3SD react with OH at identical rates over the entire temperature range investigated. We conclude that the dominant reaction pathway is addition to the sulfur atom.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 17 (1985), S. 1281-1297 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Absolute rate coefficients for the reaction of OH with HCl (k1) have been measured as a function of temperature over the range 240-1055 K. OH was produced by flash photolysis of H2O at λ 〉 165 nm, 266 nm laser photolysis of O3/H2O mixtures, or 266 nm laser photolysis of H2O2. OH was monitored by time-resolved resonance fluorescenceor pulsed laser-induced fluorescence. In many experiments the HCl concentration was measured in situ in the slow flow reactor by UV photometry. Over the temperature range 240-363 K the following Arrhenius expression is an adequate representation of the data: k1 = (2.4 ± 0.2) × 10-12 exp[-(327 ± 28)/T]cm3 molecule-1 s-1. Over the wider temperature range 240-1055 K, the temperature dependence of k1 deviates from the Arrhenius form, but is adequately described by the expression k1 = 4.5 × 10-17 T1.65 exp(112/T) cm3 molecule-1 s-1. The error in a calculated rate coefficient at any temperature is 20%.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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