bluuebunny/crossref_metadata_2025 huggingface dataset:
Tip shape reconstruction of the probes for shear‐force and near‐field microscopes
Authors: Chuklanov A. P. , Bukharaev A. A.
Published: March 2006

This work is devoted to reconstructing the tip apex of the probes for shear‐force and scanning near‐field optical microscopes. The lateral resolution of these microscopes strongly depends on the tip radius of the corresponding probes. The transmission electron microscope (TEM) is used for estimating the tip radius as a rule. However, it is rather difficult to use TEM in the routine experiments. We present the method for determination of the tip shape using the special test samples. Two types of tips have been used: the homemade electrochemically etched W microwires and the commercial fiber probes. The estimation of the tip radius was made from the tip apex, which was extracted by our deconvolution method from the corresponding experimental images obtained on a shear‐force microscope. Additional TEM experiments allowed us to compare the results obtained by these two independent methods. Correlation was investigated between the scanning near‐field optical microscopy (SNOM) lateral resolution and the reconstructed tip apex of the fiber probe used in the corresponding experiment. Copyright © 2006 John Wiley & Sons, Ltd.
Study of X‐ray absorption near‐edge structure with a photoemission electron microscope
Authors: Zhang Zengming , Ding Zejun , Yoshikawa Hideki , Shimizu Ryuichi
Published: March 2006

The contribution to total electron yield (TEY) from all emitted electrons consisting of photoelectrons, Auger electrons, their inelastic‐scattering background and secondary electrons that are excited by X rays with energies near the Ag L3 edge was calculated by a Monte Carlo simulation method that describes electron scattering processes in solids as well as the secondary electron cascade production. The simulated TEYs at different energies are very close to the experimental values, and the ratio of TEYs at the X‐ray energies of 3370 and 3340 eV also agrees with the measured one. The secondary electrons contribute ∼65% to all emitted electrons; while ∼30% is due to the widely distributed energy‐loss background for inelastic scattered electrons. X‐ray absorption near‐edge structure (XANES) spectrum in TEYs simulated on the basis of a Monte Carlo method reproduces the measured spectrum with considerable success. Copyright © 2006 John Wiley & Sons, Ltd.
Angle‐resolved XPS study of thin oxides after wet cleaning on Si0.8 Ge0.2 substrates
Authors: Martinez E. , Abbadie A. , Renault O. , Cayrefourcq I. , Quiais‐Marthon S.
Published: March 2006

One challenge in the downscaling of complementary metal‐oxide semiconductors (CMOSs) is surface cleaning without the use of strong chemical and mechanical forces, which might damage the patterns.1, 2 We present in this paper the chemical surface properties of wafers after different types of wet cleaning of single wafers, using notably the advanced additive technologies: HF‐O3‐based or SC1‐like‐based cleaning. Angle‐resolved X‐ray photoelectron spectroscopy was used to analyse the chemical oxide composition and thickness, as well as the interface structure. On both Si and Si0.8Ge0.2 substrates, less contamination and a better oxide quality were obtained with the addition of H2O2 in SC1‐like solutions. On Si0.8Ge0.2 substrates, the oxide was mainly composed of silicon oxide. Germanium was located at the interfacial layer. Copyright © 2006 John Wiley & Sons, Ltd.
Combined AES and TOF‐SIMS analysis of a thermally treated Ag/Ti/Al metallization system
Authors: Scheithauer U. , Treichler R.
Published: March 2006

Both Auger electron spectroscopy (AES) and time‐of‐flight secondary ion mass spectroscopy (TOF‐SIMS) were applied to study a three‐layer backside metallization stack that was thermally treated up to temperatures above the normal process temperature. In addition to conventional sputter depth profiling, we applied a more sophisticated sample preparation method—in situ low angle cross sectioning. This way the depth scale was enlarged approximately by a factor of 20, and therefore transferred to lateral dimensions. This allows a more detailed AES analysis of the metallization system using mappings of elemental distributions. The TOF‐SIMS depth profiles were recorded as a function of the lateral geometric coordinates and in depth as a function of the sputter ion dose. This way it was possible to analyse the three‐dimensional sample composition. Copyright © 2006 John Wiley & Sons, Ltd.
Oxidation of PbSnTe solid solutions and of PbSn alloys
Authors: Berchenko N. N. , Nikiforov A. Yu. , Fadeyev S. V.
Published: March 2006

Composition of oxide and oxide–semiconductor interface in binary chalcogenide solid solutions of PbTeSnTe and PbSn alloys was analyzed by method of equilibrium condensed phase diagrams and experimentally studied by X‐ray diffractometry (XRD), Raman spectroscopy, and Auger electron spectroscopy (AES). In accordance with the PbSnTeO equilibrium phase diagram, thermal oxidation of both PbSnTe and PbSn compounds proceeds with the initial preferential oxidation of tin to SnO2. Tin oxide dominates the composition of the growing oxide layer and prevents PbTe and Pb from oxidizing to PbTeO3 and PbO, respectively. Formation of SnO2 is followed by tellurium precipitation at the oxide–semiconductor interface. Two other oxide phases, PbSnO3 and Pb2SnO4, predicted by both PbSnTeO and PbSnO equilibrium phase diagrams were observed only in the thermally annealed PbSnTe solid solution. Copyright © 2006 John Wiley & Sons, Ltd.
Microstructure of kaolin spheres produced by a gel‐casting process with a biopolymer additive
Authors: Chumnanklang Rung‐Arun , Jaroenworaluck Angkhana , Panyathanmaporn Thammarat , Supothina Sitthisuntorn
Published: March 2006

Over the past few years due to increased environmental awareness, there has been great interest in improving ceramic processing to reduce the use of organic solvent and synthetic binders. This work is focused on a gel‐casting process using a biopolymer that is environmentally friendly, easy to burn out and inexpensive. Starch was employed as a binder and kaolin clay was used as the starting material. To fabricate kaolin spheres, aqueous kaolin slurry was mixed with a starch solution. A small volume of the kaolin‐starch solution was added to a vegetable oil at high temperature. The starch then formed a strong, cross‐linked gel and immobilized the clay powders into the desired spherical shape. The kaolin spheres were then dried and sintered at different temperatures for 1 h. The phases present in the spheres was identified by X‐ray diffraction (XRD) analysis. The microstructure and dimensions of the kaolin spheres were examined using a field emission scanning electron microscope (FE‐SEM) in conjunction with energy dispersive spectrometry (EDS). An image analysis technique was used to identify the pore volume of the spheres. Copyright © 2006 John Wiley & Sons, Ltd.
Effective energy loss function of silver derived from reflection electron energy loss spectra
Authors: Zhang Z. M. , Ding Z. J. , Li H. M. , Tőkési K. , Varga D. , Tóth J.
Published: March 2006

The electron inelastic scattering in silver is studied both experimentally and theoretically. The reflection electron energy loss spectroscopy (REELS) spectra were measured using the ESA‐31. It is shown that the surface excitation is enhanced with decreasing primary energy. For the higher resolution spectra with the narrower energy distribution of elastically scattered electrons, the Tougaard's recursive formula describes inelastic scattering cross section from the measured energy loss spectrum as well as the extended Landau approach. At low primary energies, the differential inverse inelastic mean free path (DIIMFP) for low loss energies extracted by Tougaard's recursive method is smaller than that by the extended Landau approach. The latter method is better for measured REELS spectra with a large full width at half maximum (FWHM) of elastic peak (e.g. for a CMA). The effective energy loss function (EELF) has been derived from these experiments based on the extended Landau approach. The Monte Carlo simulated REELS spectra with the derived EELF agree well with the experimental spectra. Copyright © 2006 John Wiley & Sons, Ltd.
Probing the electronic structure of NiX, (X = B, S, P) catalysts with XPS
Authors: Diplas S. , Jørgensen S. , Taftø J. , Tønnessen T. , Knutsen T. , Lehrmann J. , Våland T. , Abel M.‐L. , Watts J. F.
Published: March 2006

Amorphous films of NiB, NiP and NiS were produced by electrodeposition on pure polycrystalline Ni. The films were studied with X‐ray photoelectron spectroscopy (XPS). Changes in the Auger parameter (AP), peak energy shifts and changes in the Ni 2p shake up satellite intensity and energy were used to probe the electronic changes occurring upon alloying Ni with P, S and B. It is suggested that the Ni sites experience a higher electron density in the alloys than in the pure element and this could be the reason for the increased catalytic activity. Copyright © 2006 John Wiley & Sons, Ltd.
Intrinsic and extrinsic contributions to plasmon excitations in electron emission processes
Authors: Gervasoni J. L. , Kövér L.
Published: March 2006

In this work, we study in detail the process of excitation of bulk and surface plasmons during the emission of electrons in the proximity of a solid surface. We take into account the effects due to electron transport (extrinsic contributions) and residual hole (intrinsic contributions).

We use the dielectric response theory and the specular reflection model. The results obtained for Al metal illustrate that, depending on the distance from the surface, the separation of extrinsic and intrinsic contributions could be ambiguous because of interference effects between the photoelectron and the photohole present in both processes. Copyright © 2006 John Wiley & Sons, Ltd.
Finite Integer Computations: An Algebraic Foundation for Their Correctness
Authors: Glesner Sabine
Published: March 2006

Even though computations on finite integer representations are as old as computers themselves, there is one problem that has been inexcusably neglected: integer computations in programming languages do not operate on the ring [inline-graphic not available: see fulltext] of integer numbers but only on finite subsets of it. Changing the size of integer representations may change the results of operations performed on them in unexpected ways. In particular, increasing the representation size of intermediate results during computation may lead to incorrect final results. In this paper, we develop an algebraic foundation for integer arithmetic under changing representation sizes and, in particular, a criterion for safely replacing one finite integer arithmetic by another. This safety criterion has also been verified in the theorem prover Isabelle/HOL. Based on this formal development, we not only reveal and explain an inconsistency in the Java Card integer arithmetic but also propose an optimization for Java Card integer expressions and their safe transformation into Java Card bytecode. We also discuss the application of this safety criterion to constant folding, a standard compiler optimization, for Java and C compilers.
An exploratory retrospective study of people suffering from hypersensitivity illnesses who attend medical or classical homeopathic treatment
Authors: Kimby C.K. , Henningsen Inge , Fønnebø Vinjar , Launsø L.
Published: March 2006

The objective of this study is to describe patients who had treatment for hypersensitivity illnesses by general practitioners (GPs) or classical homeopaths (CHs) and the patients’ self-reported effectiveness of the treatment received. The data stems from an exploratory retrospective study amongst 88 Danish patients (response rate 58%) suffering from hypersensitivity illnesses, who chose treatment from one of six GPs or one of 10 CHs who participated in the project. The patients themselves selected their treatment. The GPs or the CHs considered that the patient's treatment was complete or that the patient was in a situation of current ‘maintenance treatment’. The patients’ primary reason for consulting the GP or the CH was that they were suffering from hypersensitivity illnesses.

No significant difference was found between the two groups of patients in relation to age, education and duration of hypersensitivity symptoms. The CH patients were more likely to be employed in teaching, research, health care or the social sector compared to GP patients. The two groups of patients were similar in respect of their health at the start of the treatment, 57% of the patients who consulted a CH experienced an improvement of their state of health compared to 24% of the GP patients. Both groups of patients experienced an improvement of their psychological health after treatment. Logistic regression analysis showed that the GP or CH was the only significant effect variable. The results are based on the patients’ retrospective, self-reported effectiveness of the treatments.
Associations between somatic cell counts at calving or prior to drying-off and future somatic cell counts, in the remaining or subsequent lactation
Authors: Whist Anne C , Østerås Olav
Published: March 2006

Composite milk somatic cell counts (CMSCC) from four separate datasets, containing 3338, 350, 1408 and 1404 herds, were used. All herds were enrolled in the Norwegian Dairy Herd Recording System (NDHRS). The aim was to investigate associations between CMSCC at calving or prior to drying-off and future CMSCC in the remaining or subsequent lactation. CMSCC was determined using Fossomatic 5000® cell counters (Foss Electric, Hillerød, Denmark) according to IDF recommendations (International Dairy Federation, 1984) and a natural logarithmic transformation of the CMSCC data (lnCMSCC) was performed. Results obtained were arranged according to parity and lactation stage and regression models and general linear mixed models were applied, the latter model to account for clustering between herds. The best associations between CMSCC at calving or prior to drying-off and future CMSCC in the remaining or subsequent lactation were found by using at least two CMSCC test days after calving or prior to drying-off. The geometric mean of the second and third or the first three CMSCC test days explained 50% of the variation in future CMSCC in first parity cows. This information was accessible at 151 days in milk (DIM) in bimonthly tested herds, and at 87 DIM for monthly tested herds. There was not a large difference using two or three single consecutive weighted CMSCC test days compared with the geometric mean of two or three CMSCC test days. Our findings indicate the need of using at least two CMSCC test days and, if only one CMSCC test day is used, it should be obtained after 14 d post-calving or preferably after 30 DIM.
Economic impacts of reduced milk production associated with papillomatous digital dermatitis in dairy cows in the USA
Authors: Losinger Willard C
Published: March 2006

The goal of this study was to measure the economic impacts of reduced milk production associated with papillomatous digital dermatitis (PDD) in dairy cows in the USA, and of specific risk factors for PDD, in 1996. The method applied was an economic-welfare analysis of producer and consumer surplus, with the GUM Workbench used to analyse uncertainties in the measurements. Reduced milk production associated with PDD was found to reduce consumer surplus by $750 million±$580 million, and to increase the economic surplus of producers by $560 million±$470 million, with a net economic loss of $190 million±$130 million. An examination of the economic effects of specific epidemiologic risk factors for PDD showed that having dairy cows that were not born on the operation had important economic consequences associated with the disease, as did the type of land to which dairy cows had access during the winter months and the type of flooring on which cows walked. Washing hoof-trimming equipment between cows was an important biosecurity measure that was associated with reduced PDD. The epidemiologic model used also implicated hoof trimmers who trimmed cattle hooves on other operations as having an important economic impact associated with this disease, although this finding may have been erroneous.
Evaluation of microbial diversity during the manufacture of Fior di Latte di Agerola, a traditional raw milk pasta-filata cheese of the Naples area
Authors: Coppola Salvatore , Fusco Vincenzina , Andolfi Rosamaria , Aponte Maria , Blaiotta Giuseppe , Ercolini Danilo , Moschetti Giancarlo
Published: March 2006

Microbial diversity of the raw milk for the production of Fior di Latte di Agerola and its changes during cheesemaking were studied. Viable counts showed that at the end of curd ripening, loads of lactic acid bacteria, both mesophilic and thermophilic rods and cocci, higher than those commonly evidenced in similar cheeses produced by using natural or commercial starters, were detected. Identification of 272 isolates, supported by molecular diagnostic aids, evidenced representative cultures of a high number of bacterial taxa of interest as participating in the process, although most of the isolates belonged to Lactococcus lactis and Lactobacillus helveticus species. RAPD-PCR and REA-PFGE biotyping were performed for the isolates of the above species and it was shown that most of the strains isolated from the raw milk occurred during the whole cheesemaking process, and an active role of these strains in the fermentation was supposed. The results offer further proof of the importance of the raw milk as source of technologically interesting strains of lactic acid bacteria capable of driving the fermentation of traditional cheeses.
Dry matter intake precalving in cows offered fresh and conserved pasture
Authors: Roche John R
Published: March 2006

Maintaining dry matter intake (DMI) during the last 2 weeks of gestation is difficult, and a failure to do so is reported to have negative implications on postcalving DMI (Grummer, 1995) and subsequent milk production (Bertics et al. 1992). DMI at the end of gestation, but excluding the last 1–2 d before parturition, can decrease by up to 30% (Lodge et al. 1975; Bertics et al. 1992; Dewhurst et al. 2000). The extent of the decline varies and may be influenced by a number of factors, such as level of feeding precalving (Lodge et al. 1975; Murphy, 1999; Dewhurst et al. 2000) or amount of non-structural carbohydrates in the precalving diet (Coppock et al. 1972; Forbes, 1995). Most studies were undertaken with cows receiving total mixed ration (TMR) or conserved forage and concentrates. However, this may have been one of the reasons for the witnessed depression. Increasing the proportion of rapidly fermentable carbohydrates or alternatively decreasing the fibre concentration in the precalving diet appears to exacerbate this decline (Coppock et al. 1972; Minor et al. 1998). Research suggests that ruminants may actively select against concentrates as plasma oestrogen concentrations increase, such as happens in the weeks preceding parturition (Forbes, 1995). When hay was offered ad libitum, increasing concentrations of oestrogen (up to 400 μg infused intravenously) had no effect. However, when a complete pelleted diet was offered, a 90-μg infusion caused a lower feed intake, followed by a significant increase after treatment was stopped. The lack of depression in precalving DMI reported by Coppock et al. (1972) and Vazquez-Anon et al. (1994) when forage was the principal component of the diet, supports this.
Comparative sequence analysis of spa gene of Staphylococcus aureus isolated from bovine mastitis: characterization of an unusual spa gene variant
Authors: El-Sayed Amr , Alber Jörg , Lämmler Christoph , Abdulmawjood Amir , Zschöck Michael , Hugo Castañeda V.
Published: March 2006

The protein A encoding gene spa of four Staphylococcus aureus strains isolated from bovine clinical mastitis was amplified by PCR and sequenced. The four strains were selected after an initial screening of spa gene of 41 strains isolated from mastitic cows and were subjected to detailed investigations. According to the sequencing results the spa gene of three strains (M1, M2, M3) appeared with gene segments encoding five (E, D, A, B and C) and four (E, A, B and C) IgG binding domains for two (M1, M3) and one (M2) strain, respectively and with gene segments encoding four, two and two repeats of the octapeptide Xr-repeats for the strains M1, M2 and M3, respectively. For the remaining Staph. aureus strain (M4) gene segments encoding IgG binding domains E, D and A and a new domain BC with a size of 219 bp could be observed. The BC domain appears, with a deletion of a 123 bp segment from the border region between both domains, as fused domain of both previously characterized domains. The Xr-region of this strain had 11 octapeptide repeats.
Effects of graded levels of duodenal infusions of leucine on mammary uptake and output in lactating dairy cows
Authors: Rulquin Henri , Pisulewski Pawel M
Published: March 2006

Four multiparous Holstein cows, each equipped with a duodenal cannula and an ultrasonic mammary blood flow probe, were assigned to a 4×4 Latin square to measure the effects of duodenal infusions of Leu (0, 40, 80 and 120 g/d) on lactational responses and mammary metabolism of nutrients. Cows were fed a diet of 67·0% corn silage, 5·3% grass hay, 14·2% peas, 7·8% maize starch, 1·0% each of molasses, urea, and sodium bicarbonate and 2·4% minerals and vitamins. Requirements of the remaining 9 essential amino acids were met by infusing into the duodenum 323 g/d of a mixture of amino acids including, Ile, Val, Met, Lys, Trp, Phe, His, Thr, Arg, Tyr and Glu. Milk protein content and yield were highest with 40 g/d of Leu and then progressively declined. Milk fat content and yield were significantly decreased over the entire range of Leu infusions. Arterial concentrations of Leu increased linearly and corresponding mammary arterio-venous differences increased to a plateau with 80 g/d of Leu. As Leu infusions increased, extraction rates of Leu decreased linearly, whereas those of Ile, Val, Lys, Arg, Thr and Tyr were significantly increased. Leu was taken up by the mammary gland according to milk output with 0 and 40 g/d of Leu infused and then largely in excess. Based on responses of protein yield and mammary uptake to milk output ratio, Leu concentration in total amino acids absorbed in the small intestine needs to be close to 8·9% for optimal milk protein synthesis.
Quadrupole correlations governing the pattern of jet noise
Authors: Ribner H. S.
Published: March 2006

The effects of convection and refraction dominate the heart-shaped pattern of jet noise. These can be corrected out to yield the small ‘basic directivity’ of the eddy noise generators. The observed quasi-ellipsoidal pattern was predicted by Ribner (1963, 1964) in a variant of the Lighthill theory postulating isotropic turbulence superposed on a mean shear flow. This had the feature of dealing with the joint effects of the quadrupoles without displaying them individually. The present paper reformulates the theory so as to calculate the relative contributions of the different quadrupole self and cross-correlations to the sound emitted in a given direction. Some minor errors are corrected.

Of the thirty-six possible quadrupole correlations only nine yield distinct non-vanishing contributions to the axisymmetric noise pattern of a round jet. The correlations contribute either cos4θ, cos2θ sin2θ or sin4θ directional patterns, where θ is the angle with the jet axis. A separation into parts called ‘self noise’ (from turbulence alone) and ‘shear noise’ (jointly from turbulence and mean flow) may be made.

The nine self-noise patterns combine as
$A\; cos^4\theta(1)+A\; cos^2sin^2\theta(\frac{7}{8}+\frac{7}{8}+\frac{1}{8}+\frac{1}{8})+A sin^2 \theta (\frac {12}{32} & + & \frac{12}{32}+\frac{7}{32}+\frac{1}{32})\\
& = & A(cos^2\theta+sin^\theta)^2 = A;$
this is uniform in all directions as it must be, arising from isotropic turbulence. The two non-vanishing shear-noise correlation patterns combine as
$B\;cos^4\theta (1) + B\;cos^2\theta sin^2\theta(\frac{1}{2})=B(cos^2\theta+sin^2\theta)^2 = A;$

The overall ‘basic’ pattern (self noise plus shear noise) thus has the form A + B(cos2θ + cos4θ)/2; this is a slight change from the previous result. The dimensional constants A and B are of comparable magnitude; the pattern in any plane through the jet axis thus resembles an ellipse of modest eccentricity.

Frequency spectra are also discussed, following the earlier work. Since the self noise depends quadratically on turbulent velocity components and the shear noise only linearly, there is a relative shift of the self noise to higher frequencies. This in conjunction with refraction figures in the explanation of the deeper pitch of jet noise radiated at small angles to the axis.

Finally, the predictions are shown to be compatible with recent experimental results.
On the motion established by a constant energy explosion followed by an expanding piston
Authors: Goldsworthy F. A.
Published: March 2006

The paper examines the influence of a piston motion on the gaseous motion set up by an explosion. This is a problem of relevance not only to explosions in which the remnants of the original explosive are present, but also by the application of the hypersonic similarity law, to the steady flow at high Mach number past a blunt-nosed object with increasing thickness. In the vicinity of the piston perturbation theory breaks down and matching techniques have to be employed. A solution is given in terms of a small parameter which essentially depends on the ratio of the speed of the piston to that of the shock. Some particular cases are discussed in which the piston motion plays a similar role to the counter pressure of the undisturbed gas.
Some calculations of gravity wave resistance in an inviscid stratified fluid
Authors: Mackinnon R. F. , Mulley R. , Warren F. W. G.
Published: March 2006

A disk moves edgewise in a vertical plane with a sufficiently small constant velocity in a uniformly stratified inviscid fluid under gravity. The resultant hydrodynamic thrust on the disk is estimated. Configurations of some associated phase surfaces are shown. A transient Green's function is presented for the case when the Boussinesq approximation is not made, and also for an analogous case of inertial waves in a rotating fluid.
The interaction region in the boundary layer of a shock tube
Authors: Ban S. D. , Kuerti G.
Published: March 2006

Velocity and temperature boundary layers developed on a plane wall by ideal shock-tube flow are considered for weak shock and expansion waves. Analytically, the boundary layer consists of three regions, bounded by (1) expansion-wave head, (2) diaphragm location, (3) contact discontinuity, (4) shock. The flow fields (1, 2) and (3, 4) are, essentially, known. In the interaction region (2, 3), these flow fields merge, the governing equations are ‘singular parabolic’ and admit boundary conditions usually associated with elliptic equations. It is convenient to replace the weak expansion wave in the main flow by a line discontinuity. A consistent linearization scheme can now be devised to obtain the solution in the three regions. In (2, 3), the resulting linear singular parabolic equations for the first-order solutions are solved successfully by an iterative finite difference method, normally applied to elliptic equations.
Diffraction of a plane shock by an analytic blunt body
Authors: Moran John P. , Van Moorhem William K.
Published: March 2006

A study is made of the transient flow which results from the impingement of a plane shock on a blunt body. The analysis is based on Taylor-series expansions in the space and time variables of the flow properties and of the shape of the reflected shock. Coefficients of the series are determined numerically so as to satisfy the exact equations of motion and shock jump conditions. Convergence problems are ameliorated by recasting the series into continued fractions. While the analysis does not treat the transition from regular to Mach reflexion, it remains valid for all time in the subsonic region of the flow if the incident shock is sufficiently strong. In any case, it is accurate enough where it is valid to be useful for evaluation of more conventional numerical methods.
Mixed convection from a sphere at small Reynolds and Grashof numbers
Authors: Hieber C. A. , Gebhart B.
Published: March 2006

Consideration is given to the effects of gravity which arise when a heated sphere, maintained at a steady uniform temperature, is located in a vertical uniform stream. Restricting analysis to a medium of unit Prandtl number (σ), the method of matched asymptotic expansions is employed in obtaining solutions for the velocity, temperature and pressure fields in the limit: G = o(R2), R ↓ 0 (G and R being, respectively, the Grashof and Reynolds numbers). Based on these results, conjectures are formed about the corresponding pure natural convection problem.
Distant side-walls cause slow amplitude modulation of cellular convection
Authors: Segel Lee A.
Published: March 2006

The effect of vertical boundaries on convection in a shallow layer of fluid heated from below is considered. By means of a multiple-scale perturbation analysis, results for horizontally unbounded layers are modified so that they ‘fit in’ to a rectangular region. The critical Rayleigh number and critical wave-number are determined. Motion is predicted to have the form of finite ‘rolls’ whose axes are parallel to the shorter sides of the dish. Aspects of the non-linear development and stability of this motion are studied. The general question of convective pattern selection in a bounded layer is discussed in the light of available theoretical and experimental results.
Some electrically driven flows in magnetohydrodynamics Part 3. The asymptotic theory for flow between circular electrodes
Authors: Hunt J. C. R. , Stewartson K.
Published: March 2006

In this, the third, part we present a complete asymptotic analysis of the distribution of velocity and electric potential in an electrically conducting liquid between two circular electrodes of finite diameter, 2b, when a current is passed between them. The electrodes are set opposite to each other in insulating planes, a distance 2aapart, and a magnetic field is applied perpendicular to these planes.

The asymptotic solution is obtained under the restriction that the Hartmann numberMsatisfies both the conditionsM[Gt ] 1 andM½l[Gt ] 1, wherel=b/a. It enables us to calculate the distribution of velocity and electrical potential throughout the flow field, and provides an expansion for the resistanceRbetween the electrodes in descending powers ofM½l, which is correct provided terms of orderM−1and (lM½)−3are neglected. Comparison of the theoretical results with experiment shows good agreement in the measurements ofRand in the direct probe measurements of electrical potential within the fluid. This is one of the first experiments in which direct probe measurements of an MHD flow, as well as external measurements, have provided such a satisfactory confirmation of the theory. Direct measurements of the velocity, by means of a Pitot tube as in part 2, or by means of a hot-film anemometer undertaken by Malcolm (1968), agree less well with the theory.
A laboratory model of the wind-driven ocean circulation
Authors: Beardsley R. C.
Published: March 2006

A simple laboratory model for the wind-driven ocean circulation is re-studied experimentally and theoretically. Introduced by Pedlosky & Greenspan (1967), the model consists of a rotating cylinder with sloping bottom, the fluid inside being driven by the steady relative rotation of the cylinder's lid. A linear theory is developed to illustrate the modification in the interior and Stewartson boundary layers caused by variation of the bottom slope from 0 to O(1); Stommel's (1948) model is obtained when the bottom slope tan α [Lt ] E¼, and the Munk & Carrier (1950) model is obtained for E¼ [Lt ] tan α [Lt ] 1 (E is the Ekman number). Measurements of the interior cross-contour ‘Sverdrup’ velocity agree well with theory when the Ekman-layer Reynolds number RE is ≈ 1 or less. The western boundarylayer azimuthal velocity agrees reasonably well with theory, although the observed variation with depth and bottom slope were not predicted. The western boundary layer shows downstream intensification when RE is increased from ≈ 1 until topographic Rossby waves appear in the transition region between western boundary layer and interior. The motion becomes unstable when a critical value of RE is reached, independent of the bottom slope, and a low-frequency two-dimensional flow oscillation is observed. A brief comparison is made with previous wind-driven ocean circulation studies.
Real space-time Green's functions applied to plate vibration induced by turbulent flow
Authors: Crighton D. G. , Williams J. E. Ffowcs
Published: March 2006

The paper describes calculations of the statistical properties of turbulence-induced plate vibration, the computational scheme making no reference to Fourier synthesis. The problem considered is that of a local turbulent field acting on an infinite thin elastic plate, and the statistics of the response field are described at large distances from the forcing region. Effects of mechanical dissipation in the plate are examined, along with a discussion of the relevance of the results to problems involving plates of finite extent.
Magnetohydrodynamic flow between rotating coaxial disks
Authors: Stephenson C. J.
Published: March 2006

This is a study of the magnetohydrodynamic flow of an incompressible viscous fluid between coaxial disks, with a uniform axial magnetic field B. The fluid has density ρ, viseosity η and electrical conductivity σ. The flow is assumed to be steady, and to be similar in the sense that the radial and tangential components of velocity increase linearly with radial distance from the axis of rotation. Most of the work is concerned with disks which are electrical insulators, one of which rotates while the other remains stationary. The imposed conditions can then be represented by the Reynolds number R = ρΩad2/η and the Hartmann number M2 = σB2d2/η, where Ωa is the angular velocity of the rotating disk and d is the gap between the disks. Asymptotic solutions are given for R [Lt ] M2, and numerical solutions are obtained for values of R and M2 up to 512. Experimental measurements are presented which are in general agreement with the theoretical flows, and the results for small values of the Hartmann number provide the first known experimental support for the purely hydrodynamic solutions in the range 100 < R < 800.
Anisotropic surface waves under a vertical magnetic force
Authors: Shercliff J. A.
Published: March 2006

A conducting liquid with a free surface is subjected to a vertical magnetic force due to imposed, horizontal, magnetic and current fields in the liquid. Because the current field is modified differently by differently oriented surface waves, the propagation of gravity waves becomes strongly anisotropic. The cases of shallow and deep fluid are explored. The group velocity shows features that are reminiscent of magnetoacoustic waves. The need for stability of the surface sets limits on the magnetic force which may be imposed. The feasibility of experiments is discussed and the effect of ohmic damping and surface tension is found to be relatively unimportant under suitably chosen conditions.
The effect of horizontal gradients on thermohaline convection
Authors: Thorpe S. A. , Hutt P. K. , Soulsby R.
Published: March 2006

When the vertical boundaries of a container of stratified brine solution are heated, cells are observed to form in the brine with a layered structure. An explanation of this phenomenon has been given in terms of the successive growth of cells from the top and bottom of the container. An alternative explanation is given here which is based on an examination of the stability of the fluid layer in the neighbourhood of the vertical boundaries, a layer in which there exist horizontal gradients in both temperature and salinity, and the explanation is subjected to comparison with a carefully controlled laboratory experiment. The theoretical description is fairly general and it seems possible that the effects of horizontal gradients of salinity and temperature, which approximately compensate each other so as to leave no horizontal density gradient, may be important in the ocean, as suggested by Stern (1967).
Non-linear theory of unstable plane Poiseuille flow
Authors: Dowell E. H.
Published: March 2006

A theoretical study of plane Poiseuille flow is made using the full non-linear Navier-Stokes equations. The mathematical technique employed is to use a Fourier decomposition in the streamwise spatial variable, a Galerkin expansion in the lateral variable and numerical integration with respect to time. By retaining the non-linear terms, the limit cycle oscillations of an unstable (in a linear sense) flow are obtained. A brief investigation of the possibility of instability due to large (non-linear) disturbances is also made. The results are negative for the cases examined. Comparisons with results previously obtained by others from linear theory illustrate the accuracy and efficacy of the method.
On higher-order wave theory for submerged two-dimensional bodies
Authors: Salvesen Nils
Published: March 2006

The importance of non-linear free-surface effects on potential flow past two-dimensional submerged bodies is investigated by the use of higher-order perturbation theory. A consistent second-order solution for general body shapes is derived. A comparison between experimental data and theory is presented for the free-surface waves and for the wave resistance of a foil-shaped body. The agreement is good in general for the second-order theory, while the linear theory is shown to be inadequate for predicting the wave drag at the relatively small submergence treated here. It is also shown, by including the third-order freesurface effects, how the solution to the general wave theory breaks down at low speeds.
Axisymmetric turbulent mass transfer in a circular tube
Authors: Quarmby Alan , Anand R. K.
Published: March 2006

Solutions of the diffusion equation are obtained for mass transfer in a fully developed turbulent flow in a plain circular tube in two axisymmetric situations. The cases studied are a point source positioned at the centre of the tube and a ring source in the tube wall in which there is a uniform mass flux along a short length of the tube. The purpose of the work is to establish the correctness of the descriptions of the velocity profile and radial eddy diffusivities of mass and momentum in order to provide a firm base from which consideration of the non-axisymmetric situation could proceed.

The turbulent velocity profile is deduced from a two-part model based on a sublayer profile and the Von Kármán similarity hypothesis. The radial eddy diffusivity of momentum is described by an expression due to Reichardt and Van Driest and from this the radial eddy diffusivity of mass as a function of radius is obtained by use of a ratio which takes account of fluid properties and the value of the radial eddy diffusivity.

The analysis is substantiated by experiments carried out with nitrous oxide, Schmidt number = 0·77, for Reynolds numbers from 20,000 to 130,000. The concentration profiles measured at several axial positions downstream from the source are in good agreement with the analytical solutions in both cases. Direct measurements of the eddy diffusivity of mass and momentum were obtained as added confirmation and also gave good agreement with the theory.
Non-axisymmetric turbulent mass transfer in a circular tube
Authors: Quarmby Alan , Anand R. K.
Published: March 2006

Theory and experiment are presented for mass transfer into a fully developed turbulent flow in a plain circular tube in two non-axisymmetric cases. The cases studied are a diametral line source and a discontinuous ring source, in which there is a uniform mass flux over rectangular areas of the tube wall. A comparison is made between the concentration profiles predicted by the solutions of the diffusion equation and experiments using nitrous oxide, Schmidt number S = 0·77, as a tracer gas in air. The range of experiments covers Reynolds numbers R from 20,000 to 120,000.

In the analysis, the assumption is made that the tangential and radial eddy diffusivities of mass are equal at a point. The radial diffusivity of mass, which is a function of radial position, is related to the radial eddy diffusivity of momentum by a ratio, which takes account of fluid properties and the value of the radial eddy diffusivity of momentum. The satisfactory agreement between analysis and experiment establishes the correctness of this assumption. Further confirmation was obtained by direct evaluation of the tangential eddy diffusivity of mass from the measured concentration profiles.
Visualization of transition
Authors: Wortmann F. X.
Published: March 2006

In an experimental study the development of transition downstream of Görtler vortices was investigated. With the tellurium method it was possible to distinguish beyond the Görtler vortices to successive instability modes. The first deforms the vortex pattern in a steady way and produces between each vortex pair boundary-layer profiles with two points of inflexion. When this has been established another instability mode starts, consisting of regular three-dimensional oscillations. By detailed flow visualization a nearly complete picture of the different flow patterns can be obtained.
Separation and magnetohydrodynamics
Authors: Buckmaster John
Published: March 2006

This paper is an investigation of MHD boundary layers in a transverse magnetic field when the magnetic Reynolds number (Rm) is small. The main purpose is to understand something about the suppression of separation by a strong magnetic field, with particular emphasis on the behaviour near a rear stagnation point. Given anO(1) inviscid flow it is shown that there is a critical value ofN, the interaction parameter, to completely suppress separation. This value is one half that proposed by Leibovich (1967), a discrepancy that is due to the non-regularity of the boundary-layer equations at a rear stagnation point, a possibility that Leibovich did not consider in his solution. Model linear equations suggest the true role of Leibovich's solution. The possibility of a viscous wake leaving the rear stagnation point is considered and it is suggested that one doesnotarise from vorticity generated in the boundary layer.
Reacting flow as an example of a boundary layer under singular external conditions
Authors: Conti Raul , Van Dyke Milton
Published: March 2006

An inviscid flow with infinite gradients at the wall poses a problem for the accompanying boundary layer that is fundamentally different from the conventional one of bounded gradients. It turns out that in both cases the external gradients do not affect the first-order boundary layer, but the unbounded gradients generate second-order corrections that are of a lower order in Reynolds number than the conventional ones. The present singularity in stagnation-point reacting flow is of an algebraic type, and the boundary-layer corrections that it generates are proportional to non-integral powers of the Reynolds number, with exponents that vanish with the rate of reaction. The present example clarifies such matters as the matching of boundary layer and singular inviscid flow, the structure and decay of the new corrections, and their ranking in comparison with the conventional second-order effects. Numerical computations illustrate the problem and give quantitative results in a few selected cases.
The drag on a cloud of spherical particles in low Reynolds number flow
Authors: Tam Christopher K. W.
Published: March 2006

A formula for the drag exerted on a cloud of spherical particles of a given particle size distribution in low Reynolds number flow is derived. It is found that the drag experienced by a particle depends only on the first three moments of the distribution function. A treatment of viscous interaction betweenNparticles to the lowest order is carried out systematically. By appealing to the concept of ‘randomness’ of the particle cloud, equations describing the averaged properties of the fluid motion are derived. The averages are formed over a statistical ensemble of particle configurations. These mean flow equations so obtained are in a form resembling a generalized version of Darcy's empirical equation for the motion of fluid in a porous medium. The physical meaning of these equations is discussed.
Vortex shedding from slender cones at low Reynolds numbers
Authors: Gaster M.
Published: March 2006

Water-tunnel experiments on two cones of taper ratio 36:1 and 18:1 have shown that the frequency of vortex shedding is controlled by the local diameter and has a value which is slightly lower than that on a parallel cylinder of the same size. The shedding process is modulated by a low-frequency oscillation which has a frequency dependent only on U2/v and is independent of any physical dimension of the model. A mathematical analogue of the wake, which helps to explain these features of the flow, has been constructed. The pattern of vortices in the wake of a cone suggested by this model is in reasonable agreement with the photographic evidence.
Note on the swimming deceleration of a dolphin
Authors: Niiler P. P. , White H. J.
Published: March 2006

A series of decelerative swimming motions of a dolphin were recorded underwater showing that the animal decelerated more rapidly than could be accounted for by frictional drag. The theory of swimming slender bodies was used to calculate the mean thrust on the dolphin produced by the observed motions. It is shown that the dolphin is decelerating by producing a swimming thrust opposite to the direction of swimming.
On the non-linear Lamb-Taylor instability
Authors: Nayfeh Ali Hasan
Published: March 2006

A non-linear analysis of the inviscid stability of the common surface of two superposed fluids is presented. One of the fluids is a liquid layer with finite thickness having one surface adjacent to a solid boundary whereas the second surface is in contact with a semi-infinite gas of negligible density. The system is accelerated by a force normal to the interface and directed from the liquid to the gas. A second-order expansion is obtained using the method of multiple time scales. It is found that standing as well as travelling disturbances with wave-numbers greater than

$K^{\prime}_c = k_c[1+\frac{3}{8}a^2k^2_c + \frac{51}{512}a^4k^4_c]^{\frac{1}{2}}$

where a is the disturbance amplitude and kc is the linear cut-off wave-number, oscillate and are stable. However, the frequency in the case of standing waves and the wave velocity in the case of travelling waves are amplitude dependent. Below this cut-off wave-number disturbances grow in amplitude. The cut-off wave-number is independent of the layer thickness although decreasing the layer thickness decreases the growth rate. Although standing waves can be obtained by the superposition of travelling waves in the linear case, this is not true in the non-linear case because the amplitude dependences of the wave speed and frequency are different. A mechanism is proposed to explain the overstability behaviour observed by Emmons, Chang & Watson (1960).
Existence and uniqueness of normal shock waves in gas-particle mixtures
Authors: Schubert Barbara Schmitt-Von
Published: March 2006

A mixture of a gas and small solid particles is considered which, far upstream, is in a constant equilibrium state, and moves with a constant velocity. The existence of shock waves is investigated in the four possible cases, namely for frozen flow, for two kinds of partly frozen flow, and for equilibrium flow. It is shown that, in all these cases, compressive shocks may exist, if the upstream velocity exceeds the velocity of sound appropriate to the type of flow. Rarefaction shocks are impossible in each case. Moreover, it is shown that the downstream values of the flow parameters are determined uniquely, and the direction of their change is given. Only rather general assumptions concerning the behaviour of the gas are needed. The paper takes into account the influence of the finite particle volume fraction unlike most previous papers on the topic.