bluuebunny/crossref_metadata_2025_split huggingface dataset:
Periodic Wake Behind a Circular Cylinder at Low Reynolds Numbers
Authors: Hussain A K M F , Ramjee V 
Published: July 2016

SummaryThe effects of free-stream turbulence and of sinusoidal free-stream pulsations of controlled frequencies and amplitudes on the periodic wake of a circular cylinder are investigated experimentally by employing hot-wire and smoke visualisation techniques. In addition, the effects of cylinder yaw and mild favourable and adverse pressure gradients on the vortex shedding mechanism have been explored.The data relating frequency to mean velocity follow Berger’s relation; this relation is uninfluenced by free-stream turbulence intensities up to 8 per cent. As the longitudinal turbulence intensity increases from 0.3 to 8 per cent, the downstream distance Lp behind the cylinder over which the hot-wire signal is periodic decreases progressively, indicating that the otherwise steady periodic wake interacts non-linearly with the three-dimensional free-stream turbulence and undergoes either transition or rapid diffusion by turbulence, depending on both the Reynolds number and the turbulence intensity. For a given turbulence intensity, Lp decreases also with increasing Reynolds number.The shedding frequency behind a yawed cylinder does not vary as the cosine of the yaw angle ϕ for ϕ < 50°; the signal switches intermittently between periodic and irregular form as the yaw is increased from 0 to 70°. Mild pressure gradients (favourable as well as adverse) do not affect the shedding frequency; this is confirmed by smoke visualisation, which also shows that the pressure gradient changes the longitudinal vortex spacing downstream; the measured frequency is that determined by the local Reynolds number corresponding to the Berger relation.Sinusoidal streamwise pulsations of controlled frequencies, and of amplitudes up to 10 per cent of free-stream velocity, have no effect on the natural shedding frequency; this is confirmed by smoke visualisation of the cylinder wake. However, the wake signal is amplitude-modulated at a frequency equal to the difference between the pulsation frequency and the natural shedding frequency corresponding to the free-stream mean velocity. The vortices are diffused faster in the presence of pulsation. When the pulsation amplitude is increased beyond 20 per cent, the hot-wire signal frequency in the wake equals the driving frequency; the frequency in the wake centre is also that of the pulsation. The effect of free-stream pulsation on the periodic wake is different from that due to longitudinal or transverse cylinder vibration, when lock-in has been observed.It appears that free-stream disturbances – random or periodic – cannot account for the “Tritton jump”.
A Simulation of a Supersonic Intake on a Hybrid Computer
Authors: Colbourne D.E. 
Published: July 2016

SummaryA simulation of the steady-state and dynamic performance of a supersonic powerplant intake is described. A lumped-parameter form of the equations of motion for a compressible fluid is developed. The resulting equations, together with steady-state characteristics, are used to model the performance of a two-dimensional supersonic intake. The model is implemented on the NGTE hybrid computer. The performance, both steady-state and transient, of the resulting real-time simulation has been investigated. Step and frequency responses at two high Mach number flight conditions have been examined and compared with test data. The favourable comparisons obtained demonstrate the validity of the chosen technique.
The Development of Intermittent Turbulence on a Swept Attachment Line Including the Effects of Compressibility
Authors: Poll D.I.A. 
Published: July 2016

SummaryA model of the boundary layer transition process at an infinite swept attachment line under incompressible flow conditions and in the presence of a gross upstream disturbance is developed. The approach adopted is based upon the spot concepts of Emmons which are well established for transition on a flat plate. An extension to compressible flow situations is made by means of a simple transformation which reduces the process to an equivalent incompressible form. A new criterion for predicting the onset of attachment-line transition is proposed.
On the Application of Linearized Theory to Multi-Element Aerofoils Part I: Tandem Flat Plate Aerofoils
Authors: Watt G.D. , Parkinson G.V. 
Published: July 2016

SummaryA linearized two-dimensional incompressible potential flow theory for two-element uncambered tandem aerofoil sections is developed. It leads to formulas for lift and moment which can be calculated rapidly on a programmable hand calculator, and which reduce, when the two aerofoil elements come together, to the familiar thin-aerofoil formulas for an aerofoil with a simple flap. The theory is shown to give lift and moment predictions which are in good agreement with predictions of numerical potential flow theory.
The Measurement of High Speed Air Velocity and Temperature using Sound Wave Photography
Authors: Elliott D. E. 
Published: July 2016

SummaryA transient sound wave is generated by discharging a spark in an air stream, the velocity and temperature of which are required. After a time interval of about 25 microseconds a shadowgraph photograph of the sound wave is taken; a second photograph is obtained after a further known time interval of the same order. The two exposures, both on the same negative, show the propagation of the sound wave in the air stream and from this the Mach number, the true velocity, the local velocity of sound, and hence the temperature, can be calculated.Using this method, measurements of Mach numbers of the order of 0·5 gave values between 98 per cent, and 100 per cent, of those calculated from pressure measurements. Typical examples of the sound wave photographs are shown. With further development along the lines indicated in the paper greater accuracy should be possible. The local speed of sound was measured to an estimated accuracy of ±1·5 per cent.Since only a very short time interval is needed to obtain the photographs, the method appears promising for investigating explosions of brief duration, or dealing with flows of pulsating character.
Note on a Null Method for the Direct Measurement of Pressure Coefficients
Authors: Tanner L. H. 
Published: July 2016

SummaryValues of the pressure coefficient Cp between +1 and -1 can be measured directly in incompressible flow by comparison with the known pressures on a circular cylinder placed in the tunnel working section. The development of the method and the apparatus required are described. The method gives more consistent and accurate readings than can easily be obtained with normal manometer measurements, particularly when the pressure differences are small and the tunnel speed not very steady. Since the coefficients depend on Reynolds number only, less precise measurement and control of tunnel speed are required, unless, the coefficients to be measured are subject to critical scale effects. Possible ways of extending the range of coefficients which can be measured are suggested.
Non-Propagating Cracks in Vee- Notched Specimens Subject to Fatigue Loading
Authors: Frost N. E. 
Published: July 2016

SummaryReversed direct stress and rotating bending fatigue tests have been carried out on Vee-notched specimens of aluminium alloy, nickel chromium steel and mild steel.Diagrams are presented showing the relationship between the geometric stress concentration factor Kt and the strength reduction factor Kt. It was found that non-propagating cracks formed in the roots of the sharper notches. These cracks formed at or above some critical value of Kt, the value depending on the specimen material. Below the critical value of Kt, cracks did not form unless the applied nominal stress exceeded that at the fatigue limit, and a crack, once formed, continued to propagate until the specimen failed. Above the critical value of Kt, non-propagating cracks formed at nominal stresses less than the fatigue limit, the stress having to be increased to the latter value in order to propagate the crack. This critical value of Kt coincided with the maximum Kf value realised. It would appear that Kf equals Kt up to a certain value of Kt; there is then a transition where Kt reaches a maximum at the critical value of Kt. Increasing the value of Kt above the critical value causes no further increase and may tend to decrease the value of Kt.The conclusions drawn apply only when the fatigue stresses are completely reversed, i.e. the mean load is zero.
Effect of Higher-Harmonic Deflection Components on the Creep Buckling of Columns
Authors: Patel Sharad A. , Kempner Joseph 
Published: July 2016

SummaryThe influence of higher-harmonic deflection components on the creep-buckling characteristics of an idealised H-section column is investigated. The creep properties of the material of the column are defined by a simple power-function creep law. The results show that higher-harmonic deflection components reduce the column lifetime significantly only when their initial amplitudes, as well as the initial amplitude of the first harmonic component, are very large. Furthermore, it is shown that second-harmonic components have a much smaller effect on the column behaviour than do third-harmonic components.
Maximum Ranges of Intercontinental Missiles
Authors: Lawden Derek F. 
Published: July 2016

SummaryThe thrust magnitude programme of a rocket missile being supposed specified, the problem is solved of programming the thrust direction to achieve maximum range on the Earth's surface. Earth curvature and rotation, and variation of gravity with height are taken into account, but air resistance is neglected. Motion is assumed to take place in the Equatorial plane. Tables are included from which the optimal trajectories of missiles may be computed when two design parameters are known and these tables are used to assess the advantage to be gained at extreme ranges by firing in the sense of the Earth's rotation rather than against it.
Moments and Deflections of a Simply-Supported Beam Grillage
Authors: Ellington J. P. , McCallion H. 
Published: July 2016

Summary:By using the methods of the Calculus of Finite Differences, expressions are obtained for the nodal moments and deflections of a simply-supported grillage, subjected to a loading constant along one set of beams and having a sinusoidal variation along the other set of beams. A simple example verifies the expressions and illustrates their use.
Variably Reinforced Circular Holes in Stressed Plates
Authors: Hicks Raymond 
Published: July 2016

Summary
Expressions are obtained for the radial, tangential, and shear stresses
in an infinite plate containing a variably reinforced circular hole. The
variation in the cross-sectional area of the reinforcement is chosen so that
the maximum tensile resistance of the reinforcement occurs at points around
the hole where the stresses in the plate tend to be high. It is shown that
when the reinforcement has a given weight, the effect of varying its cross
section is to reduce the stress concentration in the plate.
The following particular applied stress systems are considered:—

(i)
Uniform tension or compression in one direction.

(ii)
Uniform shear.

(iii)
Unequal principal stresses.

For the particular cases of uniform end loading and unequal applied
stresses in the ratio 2:1, data have been obtained which enable the designer
to determine the stress distribution in plates with reinforcements having a
reasonably wide range of practical dimensions.
Some inequalities for (a + b)p and (a + b)p + (a − b)p
Authors: Jameson G. J. O. 
Published: July 2016

We start from two simple identities:For any p > 0 and 0 ≥ b ≥ a, now letCan we formulate statements about Gp(a, b) that generalise (1) and (2)? We cannot hope for equalities, but perhaps we can establish inequalities which somehow reproduce (1) when p = 1 and (2) when p = 2. For (1), this might mean an inequality of the form Apap ≤ Gp (a, b) ≤ Bpap for certain constants Ap and Bp, and for (2) a similar statement with ap replaced by ap + bp. However, these are not the only possibilities, as we shall see.
A fresh look at Euler's limit formula for the gamma function
Authors: Jameson G. J. O. 
Published: July 2016

Consider the problem of defining a continuous function f(x) which agrees with factorials at integers. There are many possible ways to do this. In fact, such a function can be constructed by taking any continuous definition of f(x) on [0,1] with f(0) = f(1) = 1 (such as f(x) = 1), and then extending the definition to all x > 1 by the formula f(x + 1) = (x + 1)f(x). This construction was discussed by David Fowler in [1] and [2]. For example, the choice f(x) = ½x(x − 1) + 1 results in a function that is differentiable everywhere, including at integers.However, this approach had already been overtaken in 1729, when Euler obtained the conclusive solution to the problem by defining what we now call the gamma function. Among all the possible functions that reproduce factorials, this is the ‘right’ one, in the sense that it is the only one satisfying a certain smoothness condition which we will specify below. Admittedly, Euler didn't know this. It is known as the Bohr-Mollerup theorem, and was only proved nearly two centuries later.First, a remark on notation: the notation Γ (x) for the gamma function, introduced by Legendre, is such that Γ (n) is actually (n − 1)! instead of n!. Though this might seem a little perverse, it does result in some formulae becoming slightly neater. Some writers, including Fowler, write x! for Γ (x + 1), and refer to this as the ‘factorial function’. However, the notation Γ (x) is very firmly entrenched, and I will adhere to it here.
The influence of plasma shielding effect on laser-ablated copper samples: a focus on signal-to-background ratio and plasma expansion
Authors: Pishdast M. , Eslami Majd A. , Kavosh Tehrani M. 
Published: July 2016

AbstractThe influence of plasma shielding effect induced by ambient gas pressure and laser intensity on the laser-produced Cu plasma parameters, signal-to-background ratio (S/B) and expansion are experimentally and numerically investigated. A Q-switched Nd:YAG laser at 1064 nm at various intensities ranging from 2 to 7.1 GW/cm2 intensity (40–150 mJ) is used to produce Cu plasma in air, argon (Ar), helium (He), and neon (Ne) ambient gas at various pressures ranging from 5 to 1000 mbar. Laser-induced breakdown spectroscopy reveals that spectral radiation, S/B, electron temperature, number density, and front edge velocity of the plasma have an increasing trend up to a certain value of laser intensity and gas pressure. Afterwards, a saturation trend is achieved, which is attributed to the shielding and self-regulation effect. The numerical modeling of the laser-produced Cu plasma in the presence of air at atmospheric pressure is carried out using the MULTI radiation hydrodynamics code. We have shown that the feature of plasma shielding effect observed in the experiments can be reproduced using a continuum hydrodynamics model. Laser intensity at about 3.5 GW/cm2 is found to produce the highest S/B at 1000 mbar air. He, Ne, air, and Ar show the best S/B, respectively and the best S/B is found for air, Ar, He, and Ne at 10, 5, 10, and 20 mbar, respectively. The expansion of plasma plume is studied using a simple and effective technique based on probe laser absorption and scattering method. The plasma plume expansion through He, Ne, air, and Ar at 1000 mbar pressure has the highest velocity, respectively. The simulated results of strong shock wave model and Rankine–Hugoniot jump condition are fitted to the experimental data, which are then used to estimate the values of the ablation parameters.
Investigation of ionization speed in field ionization with laser–plasma interaction
Authors: Tian Y. , Jin X. , Yan W. , Gu X. , Yu J. , Li J. , Li B. 
Published: July 2016

AbstractThe effects of target density and laser intensity on ionization speed are studied in this paper by 1D3V particle-in-cell simulations, where the field ionization of single atom is involved basing Ammosov-Delone-Krainov model in the form of Penetrante and Bardsley. To consider the ionization speed, the evolution of plasma density for the helium target, particularly, the ion density change rate near the target front surface, are discussed. The results show that not only the laser intensity, but also the target density will affect field ionization and further affect the plasma formation. This work will be helpful for further understanding of plasma formation in intense laser pulse. Also, it may be benefit for the setup of initial parameters before the simulation of laser–plasma interaction.
Marriage patterns and residential behaviour among Norwegian women in Amsterdam, 1621–1720
Authors: SOMMERSETH HILDE L. , EKAMPER PETER , SOGNER SØLVI 
Published: July 2016

AbstractUsing marriage banns registers from the Amsterdam City Archives, this study identifies the demographic and spatial behaviour of Norwegian female immigrants to Amsterdam, a city that witnessed rapid economic and population growth during the seventeenth century. The article approaches the topic by making: (1) an ethnic distinction between mixed Norwegian/non-Norwegian unions and homogeneous all-Norwegian unions, as well as (2) a distinction by husband's occupation in these unions, whether at sea or on land. Like all women in Amsterdam, Norwegian women experienced a general pressure in the marriage market around 1675, though a somewhat lower pressure for homogeneous unions with sailors. Occupation may explain the residential pattern, suggesting that work defined neighbourhoods more than ethnicity.
Orthogonal photoswitching in a multifunctional molecular system
Authors: Lerch Michael M. , Hansen Mickel J. , Velema Willem A. , Szymanski Wiktor , Feringa Ben L. 
Published: July 2016

AbstractThe wavelength-selective, reversible photocontrol over various molecular processes in parallel remains an unsolved challenge. Overlapping ultraviolet-visible spectra of frequently employed photoswitches have prevented the development of orthogonally responsive systems, analogous to those that rely on wavelength-selective cleavage of photo-removable protecting groups. Here we report the orthogonal and reversible control of two distinct types of photoswitches in one solution, that is, a donor–acceptor Stenhouse adduct (DASA) and an azobenzene. The control is achieved by using three different wavelengths of irradiation and a thermal relaxation process. The reported combination tolerates a broad variety of differently substituted photoswitches. The presented system is also extended to an intramolecular combination of photoresponsive units. A model application for an intramolecular combination of switches is presented, in which the DASA component acts as a phase-transfer tag, while the azobenzene moiety independently controls the binding to α-cyclodextrin.
Underwater microscopy for in situ studies of benthic ecosystems
Authors: Mullen Andrew D. , Treibitz Tali , Roberts Paul L. D. , Kelly Emily L. A. , Horwitz Rael , Smith Jennifer E. , Jaffe Jules S. 
Published: July 2016

AbstractMicroscopic-scale processes significantly influence benthic marine ecosystems such as coral reefs and kelp forests. Due to the ocean’s complex and dynamic nature, it is most informative to study these processes in the natural environment yet it is inherently difficult. Here we present a system capable of non-invasively imaging seafloor environments and organisms in situ at nearly micrometre resolution. We overcome the challenges of underwater microscopy through the use of a long working distance microscopic objective, an electrically tunable lens and focused reflectance illumination. The diver-deployed instrument permits studies of both spatial and temporal processes such as the algal colonization and overgrowth of bleaching corals, as well as coral polyp behaviour and interspecific competition. By enabling in situ observations at previously unattainable scales, this instrument can provide important new insights into micro-scale processes in benthic ecosystems that shape observed patterns at much larger scales.
Monitoring G protein-coupled receptor and β-arrestin trafficking in live cells using enhanced bystander BRET
Authors: Namkung Yoon , Le Gouill Christian , Lukashova Viktoria , Kobayashi Hiroyuki , Hogue Mireille , Khoury Etienne , Song Mideum , Bouvier Michel , Laporte Stéphane A. 
Published: July 2016

AbstractEndocytosis and intracellular trafficking of receptors are pivotal to maintain physiological functions and drug action; however, robust quantitative approaches are lacking to study such processes in live cells. Here we present new bioluminescence resonance energy transfer (BRET) sensors to quantitatively monitor G protein-coupled receptors (GPCRs) and β-arrestin trafficking. These sensors are based on bystander BRET and use the naturally interacting chromophores luciferase (RLuc) and green fluorescent protein (rGFP) fromRenilla. The versatility and robustness of this approach are exemplified by anchoring rGFP at the plasma membrane or in endosomes to generate high dynamic spectrometric BRET signals on ligand-promoted recruitment or sequestration of RLuc-tagged proteins to, or from, specific cell compartments, as well as sensitive subcellular BRET imaging for protein translocation visualization. These sensors are scalable to high-throughput formats and allow quantitative pharmacological studies of GPCR trafficking in real time, in live cells, revealing ligand-dependent biased trafficking of receptor/β-arrestin complexes.
Hydrogen peroxide, nitric oxide and UV RESISTANCE LOCUS8 interact to mediate UV-B-induced anthocyanin biosynthesis in radish sprouts
Authors: Wu Qi , Su Nana , Zhang Xiaoyan , Liu Yuanyuan , Cui Jin , Liang Yongchao 
Published: July 2016

AbstractThe cross talk among hydrogen peroxide (H2O2), nitric oxide (NO) and UV RESISTANCE LOCUS8 (UVR8) in UV-B-induced anthocyanin accumulation in the hypocotyls of radish sprouts was investigated. The results showed that UV-B irradiation significantly increased the anthocyanin accumulation and the expression of UVR8, and a similar trend appeared in radish sprouts subjected to cadmium, chilling and salt stresses regardless of light source. However, these responses disappeared under dark exposure. These results suggest that abiotic stress-induced anthocyanin accumulation and UVR8 expression were light-dependent. Moreover, abiotic stresses all enhanced the production of H2O2 and exogenous H2O2 addition significantly increased the anthocyanin concentration and UVR8 transcription, while these increases were severely inhibited by addition of dimethylthiourea (DMTU, a chemical trap for H2O2). It seems to suggest that H2O2 played an important role in the anthocyanin biosynthesis. Furthermore, addition of 0.5 mM sodium nitroprusside (SNP, a NO-releasing compound) substantially induced the anthocyanin accumulation, and H2O2-induced anthocyanin accumulation and UVR8 expression were significantly suppressed by co-treatment with 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl (PTIO, a NO scavenger), which was parallel with the expression of anthocyanin biosynthesis-related transcription factors and structural genes. All these results demonstrate that both H2O2 and NO are involved in UV-B-induced anthocyanin accumulation, and there is a crosstalk between them as well as a classical UVR8 pathway.