bluuebunny/crossref_metadata_2025 huggingface dataset:
Global electricity demand, generation, grid system, and renewable energy polices: a review
Authors: Hasanuzzaman M. , Zubir Ummu Salamah , Ilham Nur Iqtiyani , Seng Che Hang
Published: July 2016

The rising concerns on the impacts of greenhouse gas (GHG) emissions and global warming have forced the world to search for alternative clean and green energy resources. Renewable energy is one of the most sustainable forms of energy, and is an increasingly popular replacement to fossil fuels. In line with this, the world has witnessed tremendous growth in renewable energy technologies as well as unprecedented adoption of renewable‐based electricity generation in the past few decades. This review paper focuses on the global energy demand, power generation, electricity production, electrical grid system as well as current global polices to move forward for renewable energy‐based power generation. This work compiles the latest literature (i.e., journal articles, conference proceedings, reports, etc.) on global energy demand, power generation, electrical grid system as well as current global polices related to renewable energy. From the review, it is found that renewable energy is one of the potential resources to fulfill the future energy demand with mitigating GHG emissions and global warming. It is also found that many polices has been implementing globally to promote renewable energy‐based power generation. WIREs Energy Environ 2017, 6:e222. doi: 10.1002/wene.222

This article is categorized under:

Energy Infrastructure > Climate and Environment

Energy and Climate > Climate and Environment

Energy Policy and Planning > Economics and Policy
Does Intraoperative Systematic Bacterial Sampling During Complete Cytoreductive Surgery (CRS) with Hyperthermic Intraoperative Peritoneal Chemotherapy (HIPEC) Influence Postoperative Treatment? A New Predictive Factor for Postoperative Abdominal Infectious Complications
Authors: Dazza Marie , Schwarz Lilian , Coget Julien , Frebourg Noelle , Wood Gregory , Huet Emmanuel , Bridoux Valérie , Veber Benoit , Tuech Jean‐Jacques
Published: July 2016

Background

Cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) is an emerging curative treatment option for patients with peritoneal carcinomatosis. It has a long‐term survival benefit but is associated with high rates of morbidity, ranging from 12 % to 65 %, mainly due to infectious complications. We sought to evaluate the clinical relevance of routine intraoperative bacteriological sampling following CRS/HIPEC.

Study design

Between November 2010 and December 2014, every patients receiving CRS/HIPEC were included. Three samples were routinely collected from standardized locations for intraperitoneal rinsing liquid bacteriological analysis (RLBA) after completion of HIPEC. The clinical and surgical features, bacteriological results, and short‐term outcomes were retrospectively reviewed.

Results

The overall mortality and morbidity rates were 5 and 45 %, respectively. Among the 75 included patients, 40 % (n = 30) had at least one positive bacterial culture. Risk factors for a positive culture were colorectal resection (adjusted hazard ratio [HR] = 3.072, 95 % CI 1.843–8.004; p = 0.009) and blood loss >1000 mL (HR = 4.272, 95 % CI 1.080–18.141; p = 0.031). Among 26 (35 %) patients with abdominal infectious complications, 13 (17 %) experienced isolated complications. A positive RLBA result was independently associated with abdominal infectious complications (HR = 5.108, 95 % CI 1.220–16.336; p = 0.024) and isolated abdominal infectious complications (HR = 4.199, 95 % CI 1.064–15.961; p = 0.04).

Conclusions

Forty percent of the RLBA samples obtained following CRS/HIPEC tested positive for bacteria. Bacterial sampling of rinsing liquid should be systematically performed. An aggressive and immediate antibiotic strategy needs to be evaluated.
Gallstones and Bariatric Surgery: To Treat or Not to Treat?
Authors: Morais Marina , Faria Gil , Preto John , Costa‐Maia José
Published: July 2016

Background

Obesity and rapid weight loss after bariatric surgery are risk factors for gallstone disease.

Objectives

The present study sought to evaluate the feasibility of selective concomitant cholecystectomy only in patients with symptomatic disease and study risk factors for the development of symptomatic gallstones after bariatric surgery.

Methods

Between January 2010 and December 2012, 734 consecutive patients presenting to our institution underwent bariatric surgery. From these, 81 patients were excluded due to prior or concurrent cholecystectomy. The remaining 653 patients with in situ gallbladder were followed for 12 months and were clinically screened for symptomatic or complicated cholelithiasis. Clinical and demographic characteristics were compared at baseline and 12 months after surgery.

Results

Of the 653 patients with in situ gallbladder, only 24 (3.3 %) developed symptomatic gallstones and only nine presented complicated disease. None of the patients with asymptomatic disease at the time of surgery progressed to symptomatic or complicated disease. Patients who developed symptomatic disease were not significantly different, although there was a trend toward longer obesity evolution, lower insulin levels, and lower hepatic enzymes level. A multivariate regression analysis revealed that patients with gastric sleeve were more likely to develop symptomatic gallstones.

Conclusions

Although further studies are required, the management of gallstones in morbidly obese patients should not be different from normal‐weight patients. Therefore, performing a laparoscopic cholecystectomy only in symptomatic patients is an effective approach and asymptomatic gallstones should not be treated at the time of bariatric surgery.
Ultrasonographic Evaluation of Neural Tube Defects at 11–14 Weeks
Authors: Batra Meenu
Published: July 2016

Fetal neural tube defects are the second most common serious fetal birth defects. In fetuses with open spina bifida there is leakage of cerebrospinal fluid into the amniotic cavity which causes hypertension in the subarachnoid space leading to caudal displacement of the brain. The cranial signs (lemon and banana) are detectable during the second trimester scan. In the first trimester, there are alterations in the appearance of the posterior brain at 11–13 weeks. In fetuses with open spina bifida, the posterior shift of the brain is evident from the first trimester, resulting in compression of the fourth ventricle and alteration of the normal intracranial translucency. In the midsagittal view of the face, if the fourth ventricle is not visible, it should arouse the suspicion of the possibility of an underlying open spina bifida and hence, a detailed examination of the fetal spine should be performed. Also, because of the posterior shift of the brain, the brainstem (BS) appears relatively enlarged and shifted backwards. The BS to brainstem to occipital bone distance (BSOB) [BS/BSOB] ratio is increased and it is usually more than one. At 11–13-week scan, the midsagittal view of the face is the standard view obtained in every fetus and it is feasible to visualize the posterior region of brain in this view. Suspicious cases should undergo a detailed assessment of the spine, especially on transvaginal scan followed by targeted examination of the spine at 16–18 weeks.
Outcomes of General Anesthesia and Conscious Sedation in Endovascular Treatment for Stroke
Authors: Just Caroline , Rizek Philippe , Tryphonopoulos Peter , Pelz David , Arango Miguel
Published: July 2016

Background Recent studies have strongly indicated the benefits of endovascular therapy for acute ischemic stroke, but what remains a continued debate is the role for general anaesthesia versus conscious sedation (CS) for such procedures. Retrospective studies have found poorer neurological outcomes in patients who underwent general anesthesia (GA); however, some have revealed worse baseline stroke severity in these patients.Methods This study is a retrospective cohort study aimed at comparing mortality and morbidity of GA versus CS in patients treated with endovascular intervention in acute ischemic stroke. Chi-square and t-test analyses were used. Results Patients in the GA (n=42) group were more likely to be deceased than those in the CS (n=67) group at hospital discharge, 3 months, and 6 months poststroke onset. Morbidity, as defined by modified Rankin Score, was significantly greater in the GA group at hospital discharge, and a similar trend was seen in morbidity at 3 months postdischarge. Conclusion General anesthesia for endovascular intervention in acute ischemic stroke was associated with increased mortality and poorer neurological incomes compared with conscious sedation. In our study, age, gender, history of hypertension, history of diabetes, and baseline National Institute of Health Stroke Scale were not significantly different between the groups. Although the need for a randomized, prospective study on this topic is clear, our study represents further corroboration of the safety and efficacy of conscious sedation in these procedures.
Roots, Schottky semigroups, and a proof of Bandt’s conjecture
Authors: CALEGARI DANNY , KOCH SARAH , WALKER ALDEN
Published: July 2016

In 1985, Barnsley and Harrington defined a ‘Mandelbrot Set’${\mathcal{M}}$for pairs of similarities: this is the set of complex numbers$z$with$0<|z|<1$for which the limit set of the semigroup generated by the similarities$$\begin{eqnarray}x\mapsto zx\quad \text{and}\quad x\mapsto z(x-1)+1\end{eqnarray}$$is connected. Equivalently,${\mathcal{M}}$is the closure of the set of roots of polynomials with coefficients in$\{-1,0,1\}$. Barnsley and Harrington already noted the (numerically apparent) existence of infinitely many small ‘holes’ in${\mathcal{M}}$, and conjectured that these holes were genuine. These holes are very interesting, since they are ‘exotic’ components of the space of (2-generator) Schottky semigroups. The existence of at least one hole was rigorously confirmed by Bandt in 2002, and he conjectured that the interior points are dense away from the real axis. We introduce the technique oftrapsto construct and certify interior points of${\mathcal{M}}$, and use them to prove Bandt’s conjecture. Furthermore, our techniques let us certify the existence of infinitely many holes in${\mathcal{M}}$.
Costs and Mortality Associated With Multidrug-Resistant Healthcare-Associated Acinetobacter Infections
Authors: Nelson Richard E. , Schweizer Marin L. , Perencevich Eli N. , Nelson Scott D. , Khader Karim , Chiang Hsiu-Yin , Chorazy Margaret L. , Blevins Amy , Ward Melissa A. , Samore Matthew H.
Published: July 2016

BACKGROUND

Our objective was to estimate the per-infection and cumulative mortality and cost burden of multidrug-resistant (MDR) Acinetobacter healthcare-associated infections (HAIs) in the United States using data from published studies.

METHODS

We identified studies that estimated the excess cost, length of stay (LOS), or mortality attributable to MDR Acinetobacter HAIs. We generated estimates of the cost per HAI using 3 methods: (1) overall cost estimates, (2) multiplying LOS estimates by a cost per inpatient-day ($4,350) from the payer perspective, and (3) multiplying LOS estimates by a cost per inpatient-day from the hospital ($2,030) perspective. We deflated our estimates for time-dependent bias using an adjustment factor derived from studies that estimated attributable LOS using both time-fixed methods and either multistate models (70.4% decrease) or matching patients with and without HAIs using the timing of infection (47.4% decrease). Finally, we used the incidence rate of MDR Acinetobacter HAIs to generate cumulative incidence, cost, and mortality associated with these infections.

RESULTS

Our estimates of the cost per infection were $129,917 (method 1), $72,025 (method 2), and $33,510 (method 3). The pooled relative risk of mortality was 4.51 (95% CI, 1.10–32.65), which yielded a mortality rate of 10.6% (95% CI, 2.5%–29.4%). With an incidence rate of 0.141 (95% CI, 0.136–0.161) per 1,000 patient-days at risk, we estimated an annual cumulative incidence of 12,524 (95% CI, 11,509–13,625) in the United States.

CONCLUSION

The estimates presented here are relevant to understanding the expenditures and lives that could be saved by preventing MDR Acinetobacter HAIs.

Infect Control Hosp Epidemiol 2016;1–7
Reynolds stress distribution and turbulence generated secondary flow in the turbulent three-dimensional wall jet
Authors: Namgyal L. , Hall J. W.
Published: July 2016

The lateral half-width of the turbulent three-dimensional wall jet is typically five to eight times larger than the vertical half-width normal to the wall. Although the reason for this behaviour is not fully understood, it is caused by mean secondary flows that develop in the jet due to the presence of the wall. The origin of the secondary flow has been associated previously with both vorticity reorientation and also gradients in the Reynolds stresses, although this has not been directly quantified as yet. The present investigation focuses on a wall jet formed using a circular contoured nozzle with exit Reynolds number of 250 000. Stereoscopic particle image velocimetry measurements are used herein to measure the three-component velocity, thereby allowing access to the full Reynolds stress tensor that contributes to the secondary flow in a turbulent three-dimensional wall jet. Throughout the jet, the Reynolds normal stress ($\overline{u^{2}}$) makes the largest contribution to the Reynolds stress field whereas Reynolds shear stress ($\overline{vw}$) is found to be negligible when compared with other stresses. In particular, the differences in the Reynolds normal stresses ($\overline{v^{2}}-\overline{w^{2}}$) are found to be significantly larger than $\overline{vw}$; these terms are important for the generation of turbulence secondary flow in the wall jet. Above all, the differences in the Reynolds normal stresses are oriented to reinforce the near-wall streamwise vorticity, and thus contribute to the large lateral growth of this flow. The contours of the turbulent kinetic budget indicate that the turbulent energy budget obtained on the jet centreline is different from that obtained off of the jet centreline.
Acoustic receptivity simulations of flow past a flat plate with elliptic leading edge
Authors: Shahriari Nima , Bodony Daniel J. , Hanifi Ardeshir , Henningson Dan S.
Published: July 2016

We present results of numerical simulations of leading-edge acoustic receptivity for acoustic waves impinging on the leading edge of a finite-thickness flat plate. We use both compressible and incompressible flow solvers fitted with high-order high-accuracy numerical methods and independent methods of estimating the receptivity coefficient. The results show that the level of acoustic receptivity in the existing literature appears to be one order of magnitude too high. Our review of previous numerical simulations and experiments clearly identifies some contradictory trends. In the limit of an infinitely thin flat plate, our results are consistent with asymptotic theory and numerical simulations.
ILLUSORY MODELS OF PEANO ARITHMETIC
Authors: KIKUCHI MAKOTO , KURAHASHI TAISHI
Published: July 2016

By using a provability predicate of PA, we define ThmPA(M) as the set of theorems of PA in a modelMof PA. We say a modelMof PA is (1) illusory if ThmPA(M) ⊈ ThmPA(ℕ), (2) heterodox if ThmPA(M) ⊈ TA, (3) sane ifM⊨ ConPA, and insane if it is not sane, (4) maximally sane if it is sane and ThmPA(M) ⊆ ThmPA(N) implies ThmPA(M) = ThmPA(N) for every sane modelNof PA. We firstly show thatMis heterodox if and only if it is illusory, and that ThmPA(M) ∩ TA ≠ ThmPA(ℕ) for any illusory modelM. Then we show that there exists a maximally sane model, every maximally sane model satisfies ¬ConPA+ConPA, and there exists a sane model of ¬ConPA+ConPAwhich is not maximally sane. We define that an insane model is (5) illusory by nature if its every initial segment being a nonstandard model of PA is illusory, and (6) going insane suddenly if its every initial segment being a sane model of PA is not illusory. We show that there exists a model of PA which is illusory by nature, and we prove the existence of a model of PA which is going insane suddenly.
Control Reversal Effects on Swept-Back Wings
Authors: Templeton Haydn
Published: July 2016

Aileron reversal effects on swept-back wings in general and elevon reversal effects on tailless swept-back wings in particular are discussed on a non-mathematical basis, attention being confined to the orthodox flap type of control. The main purpose of the paper is to convey in the simplest terms possible a clear physical picture of the conditions producing loss of control power, emphasis being naturally laid upon the part played by structural wing distortion. Certain qualitative features relating to the two phenomena are also discussed. As a general introduction to the discussion on aileron reversal effects, the definition of “aileron power” in relation to the actual dynamic condition of rolling is described at some length. For elevon reversal effects on tailless aircraft the effect of wing flexibility on both “elevon power” and on trim in steady symmetric flight is considered.

With the descriptive treatment adopted the analysis is of necessity broad and general but is designed to appeal to those not too familiar with the subject. The results of certain calculations on a hypothetical wing, which may be of interest, are included. A mathematical analysis for the quantitative estimation of both aileron and elevon reversal effects is given in the Appendix.
The Measurement of Gas Turbine Combustion Efficiency by Gas Analysis
Authors: Richards L. J. , Street J. C.
Published: July 2016

Following a brief discussion of various methods of measuring combustion efficiency in gas turbine chambers, the superiority in accuracy of applied gas analysis is stated. Factors leading to inefficiencies in combustion are outlined and the exhaust constituents requiring measurement are deduced. The chief difficulty in the past in the application of gas analysis methods to combustion efficiency determination has been the time consumed in actual analysis of samples; at Thornton Research Centre means of overcoming this difficulty have been investigated and several rapid and accurate analytical techniques have been developed and used successfully. These techniques are described, together with other promising methods at present under development. The broad requirements of obtaining exhaust gas samples for analysis are discussed and typical sampling systems described; precautions necessary in applying these systems are given. Formulse for the calculation of combustion efficiency from analytical results, together with any assumptions made, are given in the text and their derivation explained in an Appendix. The techniques described have been developed primarily for use in conjunction with rig testing of aircraft gas turbine combustion chambers; the broader application—for instance, to engine testing—of the principles involved are considered briefly.
Surging of Axial Compressors
Authors: Pearson H. , Bowmer T.
Published: July 2016

It is fairly generally known that if, at any fixed speed of a compressor, either axial or centrifugal, the flow is reduced by throttling the outlet, then a point is eventually reached at which a complete breakdown of the air flow occurs and in most cases an actual flow reversal through the compressor takes place. Sometimes this phenomenon is gradual, taking the form of a sort of burbling, but more generally it takes the form of a sudden “ bang ” associated with a violent shake of the whole foundation of the bed on which the compressor is mounted. In most centrifugal compressors the flow reversal which takes place stops rapidly, the performance recovers, and a second “ surge ” occurs if the throttling is not reduced. The frequency of these individual surges varies greatly according to the degree of throttling and many other conditions; it may be only one isolated occurrence, in which case it would be concluded that the working point was just, but only just on the surge point, or it may take the form of a rapid series of thuds indicating that the working point is beyond the surge. In all cases of centrifugal compressors known to the authors reduction of the throttling will restore the compressor to its normal performance.
Strain Measurement by X-ray Diffraction Methods
Authors: Greenough G. B.
Published: July 2016

Many papers have been written on the measurement of strain by X-ray diffraction methods and on the interpretation of these strains in terms of stresses. Whereas, during the past few years, the experimental methods of determining the strains have. remained largely unchanged, research has shown that the older techniques for calculating stresses from strains are not always valid.

In this paper an attempt is made to describe some of the principles of strain measurement by X-ray diffraction methods to those who are unfamiliar with the methods. The types of stress and strain systems which may exist in polycrystalline metals are then considered, particular attention being paid to the effect of the elastic and plastic anisotropy of the individual crystals. Some indication is given as to how the earlier methods of interpreting X-ray strain measurements should be modified, but no rigid routine method is proposed for use in a general case.
Approximate Calculation of the Laminar Boundary Layer
Authors: Thwaites B.
Published: July 2016

The steady two-dimensional flow of viscous incompressible fluid in the boundary layer along a solid boundary, which is governed by Prandtl's approximation to the full equations of motion, presents a problem which in general is as intractable as any in applied mathematics. The problem, however, has such an immediate and necessary application that approximate methods of varying accuracy which go beyond the formal processes of expansions in series and so on, have been devised for the rapid calculation of the principal characteristics of the laminar boundary-layer, the variation of pressure along the surface being known. Such methods usually represent approximately the boundary-layer velocity distribution at any point by one of a known family of distributions whose spacing along the surface is determined by some means, often by the use of Kármán's momentum equation.
The Steady Circulatory Flow about a Circular Cylinder with Uniformly Distributed Suction at the Surface
Authors: Preston J. H.
Published: July 2016

Summary and Conclusions

Exact solutions for the steady circulatory flow about a circular cylinder with suction applied at its surface have been obtained for the following cases: —

(a)

the cylinder at rest and a circulation at infinity,

(b)

the cylinder rotating and zero circulation at infinity,

(c)

the cylinder rotating in either direction with a circulation at infinity,

provided that, in general, the suction velocity is greater than a certain limiting value.

There is a particular case of (c) when the circulation at the cylinder equals that at infinity in magnitude and direction, for which the circulation is constant at all radii, for all values of R—presumably for blowing as well as suction.

The addition of a uniform stream parallel to the cylinder axis does not affect the circulatory motion, and the solution for the combined flow, which is exact, has some practical interest in that it demonstrates that the boundary layer on a long, circular, rotating boss can be kept thin and that the circulatory motion outside the boundary layer can be prevented by the suitable application of suction before starting the rotation.

The flow (a) is important in connection with the withdrawal of the Thwaites flap. The existence of steady state solutions, coupled with the arguments of Section 5.2, make it appear highly probable that a wing employing this device will retain its lift indefinitely, when the flap is withdrawn.

For high rates of suction flow, the flows exhibit the characteristics of boundary layer flows, in that the vorticity is confined to a narrow annulus enveloping the cylinder and the velocity distribution near the wall tends to the well-known asymptotic distribution of Griffith and Meredith.

It would be interesting to investigate these flows experimentally and to examine the stability of the laminar flow under suction conditions.

The analysis throughout is simple and expressions are obtained for the velocity distribution, the stresses, the vorticity and the torque, and so on.
The whirling of a spinning top
Authors: Morris J.
Published: July 2016

This paper has been compiled because of the applicability of the treatment of the stability of the motion of the common spinning top to the problem of the whirling of rotating shafts, carrying loads of appreciable moments of inertia. This problem is assuming renewed interest and importance, especially in the drives of contra-propeller systems and the more recent high speed prime movers.
The linearised theory of conical fields in supersonic flow, with applications to plane aerofoils
Authors: Goldstein S. , Ward G. N.
Published: July 2016

In many important problems of supersonic flow, either for the whole field of flow or a part of it, the velocity components are constant on straight lines through a fixed point. Such velocity fields are called conical fields. In the usual theory of the linearised perturbations of a steady supersonic flow, the velocity is assumed to differ only slightly from a uniform undisturbed velocity, and in the defining equations and boundary conditions all non-linear terms in the components of the perturbation velocity (and their space derivatives) are neglected. In this paper the equations of linearised supersonic conical fields, and their general solution, are set out both for the region inside and for the region outside the Mach cone of the origin in the conical field. The results are applied to flow past plane triangular aerofoils with straight edges downstream of the vertex (of which there are six cases), to flow past those plane aerofoils of more extended shape and finite span for which the solution may be obtained by combining a finite number of conical fields, and to the problem of plane triangular vanes in semi-infinite free jets. In the applications, the velocity fields are determined in considerable detail, but a main purpose in setting them out was to exhibit the mathematical methods used and the physical considerations that enter in determining the mathematical solutions.
The properties of crossed flexure pivots, and the influence of the point at which the strips cross
Authors: Wittrick W. H.
Published: July 2016

Summmary

It is shown that the rotational stiffness of a crossed flexure pivot varies considerably when subjected to an applied force. The type of variation can be radically changed simply by moving the point at which the strips cross. The relation between torque and rotation for a given applied force is not exactly linear and the extent of the non-linearity is determined by taking into account the small movements of the centre of rotation of the pivot. Finally, for design purposes, an analysis of the maximum stresses in the strips is given.

Crossed flexure pivots, of the type shown in Fig. 1, are extensively used in aeronautical research equipment to replace knife edges or ball bearings. Perhaps the most frequent use is for the fulcrum of the balance arm in a wind tunnel balance. Here, a null-point method of reading is almost invariably used, so that the prime considerations influencing the design of a flexure pivot for such a purpose are (a) that the applied loads should not cause instability of the pivot, and (b) that the rotational stiffness should be small enough to give adequate sensitivity.
The Anti-Symmetric Vibrations of Aircraft
Authors: Traill-Nash R. W.
Published: July 2016

It is assumed that pure anti-symmetric vibrations of an aircraft can exist, involving fuselage torsion but excluding fuselage bending. With this assumption, which in most cases is a reasonable approximation, the eigenvalue equations for anti-symmetric vibrations of a complete aircraft are derived in a very general form. The “lumped mass” approximation to the continuous mass distribution is used and sub-matrices are associated with properties of relatively simple branches of the system. The final eigenvalue equations are expressed in terms of these sub-matrices so that in a numerical application the physical system as such is considered only in relation to properties of the simple branches. It is assumed initially that the aircraft wing and tail have flexural axes of the conventional type, but the treatment is generalised to cover swept and cranked wing aircraft.
Beams on Cross-Girders with Clamped Ends
Authors: Klitchieff J.M.
Published: July 2016

In a previous paper it was assumed that the cross-girders are freely supported at their ends. In practice these ends can often be considered as clamped (“ built-in ”), for example, a span of continuous bottom-girders of a ship between two transverse bulkheads.

In the following discussion it is assumed that the ends of the cross-girders are clamped, conditions at the ends of the main beams remaining arbitrary, as in Ref. 1.
A Note on Supersonic Wing Integral Equations in Unsteady Flow
Authors: Miles John W.
Published: July 2016

The integral equations for the pressure distribution on an oscillating thin wing having a prescribed velocity distribution in a supersonic flow are developed.
The Theory of Aerofoils in Unsteady Motion
Authors: Radok J. R. M.
Published: July 2016

The theory of aerofoils in unsteady flow, which has made substantial progress in the last decade due largely to the ground work of Küssner and his co-workers, is presented here in a form suitable for application in aeroelastic problems, particularly those concerned with the dynamic loads on aircraft arising from gusts.

Exact expressions are given for the aerodynamic lift and moment for an oscillating aerofoil as well as for the case of arbitrary motion through disturbed air. The expressions for the latter case involve two special functions, generally referred to as Wagner and Küssner functions. Exact values of these functions are tabulated together with useful approximations. The problem of a wing-tail combination is discussed and a method of solution indicated. The bibliography at the end of the paper lists the most important publications in this field.
Note on Mr. Mair's Paper
Authors: Holder D. W. , North R. J.
Published: July 2016

The scheme for taking a pair of photographs of opposite sensitivity for each flow is a useful one in certain problems, but is unsuitable for use in a routine experiment (in which several hundred photographs may be required) because of the additional labour and expense involved. This is particularly so because, apart from resolving any ambiguity which may occur in regions of intense density gradient, the second photograph usually will not give much additional information about the flow. Moreover, the scheme does not overcome the other difficulties associated with the use of an apparatus having inadequate range. The most serious of these is that the apparatus is unable to differentiate between the strengths of density gradients when they exceed the value which deflects the image of the light source completely on to, or away from, the knife edge. Photographs illustrating this effect are reproduced in Ref. 1; the use of inadequate range (i.e. too much sensitivity) is a common fault in wind-tunnel photographs.
The Dust Problem in Hot-Wire Anemometry
Authors: Collis D. C.
Published: July 2016

Experimental work is described showing that a major cause of changes in the calibrations of hot-wire anemometers consists in the precipitation of dust on the upstream surface of the wire during use. A simple means of cleaning the air in closed-circuit wind tunnels is described. The rate of change of calibration due to dust was reduced in the Manchester University Fluid Motion Laboratory by at least a factor of 15, by adequate cleaning of the air and by minimising the amount of interchange between the tunnel air and the atmosphere. It is concluded that where accurate results are required from hot wires used in a wind tunnel, the tunnel should be designed to be dust-free.
Buckling of Oblique Plates with Clamped Edges under Uniform Compression
Authors: Wittrick W. H.
Published: July 2016

The problem of the buckling of flat oblique plates (i.e.in the shape of parallelograms) with all edges clamped under a uniform system of stress is considered. An energy method of calculating the critical stresses is developed and applied to the particular case of a clamped oblique plate under uniform compression parallel to two of the sides. Numerical values for the buckling stress coefficient are obtained for plates having acute angles of 60° and 45°, and side ratios varying between 3/5 and 5/3.
Flow Changes in Gases in which Mass and Impulse are Conserved
Authors: Dawson L. G.
Published: July 2016

This note discusses changes in the state of a gas flowing in a duct of constant area. In the past, changes, such as normal shock waves, combustion and other phenomena, which are defined by the equations of energy, conservation of momentum and mass flow, have each been treated on their merits. In this note a method is developed whereby all phenomena governed by these three equations can be solved by a single general method. The method rests on the derivation of a parameter which is unaltered in value by the change, in all cases where the total temperature is constant. A shock wave is an example of such a discontinuity. In problems of heat addition or extraction, the parameter changes its value only because of the change in total temperature. The change in total temperature may be calculated from the known quantity of heat added or extracted.

The parameters derived are useful in showing how problems of this type should be attacked analytically. With oblique waves it is easy to derive a relation between the normal velocities before and after the wave, and it is probable that this relationship has not been published before.
Compressor-Turbine Matching of Two-Spool Turbo-props
Authors: Morley A. W.
Published: July 2016

The problem of the best division of pressure ratio between the two spools is investigated by means of simplified expressions for component characteristics. It is found that a unique position of the L.P. compressor operating line (i.e. maximum L.P. flexibility) is obtained when the H.P. compressor operating line is vertical. This arrangement requires a low pressure ratio on the H.P. spool and gives an engine whose power is sensitive to air intake temperature changes, so that the H.P. rotor tends to overspeed at sea level and surge at high altitude. Checks by standard methods show that the algebraic approach is useful for understanding the two-spool matching problem.
Oil Damped Free Vibration with Particular Reference to Systems having Nearly-Equal Natural Frequencies
Authors: Bishop R. E. D. , Johnson D. C.
Published: July 2016

This paper concerns the free vibration of linear systems which are subject to damping. The general theory for a system having n degrees of freedom is recalled and illustrated by means of a simple example. Using an analytical method, the approximate theory for small damping is derived, showing the nature of the entrainment of the principal modes; the results are found to confirm those of Southwell (who uses a physical argument) and they are illustrated by an example. The approximate theory is shown to need modification when there are two nearly-equal natural frequencies and the appropriate corrections are found. The analysis is made somewhat complicated by the existence of two criteria of “ smallness ” instead of one; these are the difference between the close natural frequencies and the amount of the damping.
The Shock Pattern of a Wing-Body Combination, Far from the Flight Path
Authors: Walkden F.
Published: July 2016

The position and strength of the front shock wave at large distances from a wing-body combination, are deduced from the linear theory for the combination, using a method developed by Whitham. The combination consists of a body of revolution and a wing which has thickness and is lifting. The effects of interference between the flow over the body and the flow over the wing are included. In any direction the flow far from the wing-body combination is equivalent to the flow past a body of revolution determined from the configuration of the combination. The modified formulae for unsteady flow are given and some results are evaluated for the combination of a body of revolution and a delta wing with subsonic leading edges.
The Vibrations of a Thin-Walled Stiffened Cylinder in an Acoustic Field
Authors: Foxwell J. H. , Franklin R. E.
Published: July 2016

When a vibrating structure encloses a volume of fluid, the acoustic effects within this volume modify considerably the response characteristics of the structure, provided that the cylinder is vibrating in radial modes only. Measurements made of the displacement caused by a particular sound wave are of the same order as the values predicted. The calculation of the response of the cylinder to an acoustic wave also yields the sound field inside the cylinder and, again, the results are in general agreement with practical experience.
Notes on Thin Wing Theory at Low Supersonic Speeds
Authors: Hancock G. J.
Published: July 2016

On the basis of the linearised theory, the integral relationship for the incidence distribution in terms of the velocity potential is established for wings with subsonic leading edges. Some analytical problems are analysed. A simple general numerical method is given for this design problem which compares favourably with exact linear theories. In Part II, to be published, a further numerical method is developed, for calculating the loading onanyspecified thin wing with subsonic leading edges, which again agrees favourably with exact linear theory. Both of these numerical techniques can be easily accommodated on desk calculating machines.
Note on the Forces that Act near the Centre and the Tips of a Swept-Back Wing
Authors: Hurley D. G.
Published: July 2016

The momentum equation is used to calculate the drag that acts near the tip of a semi-infinite swept-forward wing of constant chord that is at zero incidence to a uniform stream of incompressible, inviscid fluid. The drag is given as a function of wing section and angle of sweep and is shown to be unaffected by shaping the tip. The results may be used to calculate the drag that acts near die centre and the thrusts that act near the tips of a swept-back wing, provided that its aspect ratio is sufficiently great for the regions where the different forces act to be separated. Some results due to Neumark and to Küchemann and Weber suggest that this will be so provided that the aspect ratio is greater than about two. The results are combined with some due to these authors to estimate the spanwise extent of the forces. It is found that this extent decreases as the angle of sweep is increased and that it depends quite markedly on the wing section.
On the Buckling of Certain Optimum Plate Structures with Linearly Varying Thickness
Authors: Mansfield E. H.
Published: July 2016

This paper is concerned with the buckling under uniform longitudinal compression of a variety of structures composed of plates whose thickness tapers linearly to zero across the section. Such structures include the angle of Fig. 1, the strut of cruciform section of Fig. 2 and the simply-supported strip of Fig. 3. For given cross-sectional area and overall dimensions (e.g. length of arm) the sections with linearly varying thickness achieve a greater buckling load (assuming that local buckling, rather than Euler buckling, is the criterion) than sections with any other smooth variation of thickness. These particular sections are therefore optimum sections and, even if they may not be used in practice, provide a convenient yardstick for purposes of comparison. The buckling loads are considerably greater than those for the corresponding “constant thickness” sections.
Notes on Thin Wing Theory at Low Supersonic Speeds
Authors: Hancock G. J.
Published: July 2016

The main advantage of the method presented in Part I of this paper is the generality with regard to the shape of the wing plan form. This is a welcome innovation in the field of supersonic wing theory, where methods of solution of the usual lifting problem are restricted to a limited number of wing shapes. Most of the lifting characteristics of wings are now known at supersonic speeds, but the range of wings with curved subsonic leading and trailing edges needs further investigations. Therefore it seems that the extension of the design problem to include these lifting problems is a useful addition to the extensive literature on the subject.
Theoretical and Experimental Studies of Stall Propagation in Rows of Axial Flow Compressor Blades
Authors: Wood M. D.
Published: July 2016

The paper concerns a phenomenon which occurs in rows of closely spaced blades, as in an axial flow compressor, when the flow around the blades approaches the stalling condition. Patches of stalled flow can propagate along the blade row, thus causing cyclic variations in the lift on individual blades. Under certain conditions this cyclic loading can lead to large blade stresses, and ultimately to blade failure.
The Design of an Annular Entry to a Circular Duct
Authors: Gibbings J. C.
Published: July 2016

This report describes the design of an annular entry for the axisymmetric flow into a circular duct, shaped so that the wall velocity gradients are favourable to the development of the boundary layer flow. As a first step the accelerating flow around a two-dimensional 90° duct bend with favourable gradients was obtained. This shape was modified and the axisymmetric flow pattern through it obtained by a combination of electrical analogue and relaxation methods and then checked by experiment. The favourable gradients were retained in the axisymmetric flow.
Struts with Linearly Varying Axial Loading
Authors: Przemieniecki J. S.
Published: July 2016

Analytical solutions for the deflections and bending moments are derived for elastic struts with linearly varying axial loading applied either (a) along the undeformed straight strut axis or (b) at the strut axis in the deflected position. The instability of struts with various end conditions is discussed and the stability criteria are given as a series of curves relating the maximum compressive axial load with the maximum distributed loading. Furthermore, explicit formulae for the deflections and bending moment distributions have been compiled for several typical cases of lateral loading combined with the axial loading of the type (a), which is of some practical importance in aircraft structures. A numerical example is included to show the practical application of the general analysis to a typical strut problem.
Some Simple Transformation Functions for Square and Triangular Holes with Rounded Corners
Authors: Wittrick W. H.
Published: July 2016

Transformation functions, in the form of three-term polynomials, are derived for the conformal mapping of the region outside a square or an equilateral triangle, having rounded corners with varying and controllable degrees of curvature, on to the region outside the unit circle.
Reattachment of a Two-Dimensional, Incompressible Jet to an Adjacent Flat Plate
Authors: Bourque C. , Newman B. G.
Published: July 2016

As part of a general investigation into Coanda effect, a study has been made of the reattachment of a two-dimensional, incompressible, turbulent jet to an adjacent, inclined, flat plate. The jet separates from the boundaries at the slot lips and reattaches to the plate downstream, a phenomenon which is associated with the lowering of the pressure between the jet and the plate accompanying the entrainment of fluid there. It is found that the flow becomes independent of both the length of the plate and the Reynolds number when these parameters are sufficiently large: the flow, scaled with respect to the width of the slot, is then uniquely determined by the plate inclination. Two approximate theories are developed for the mean pressure within the separation bubble, the position of reattachment and the increase in volume flow from the slot: the agreement with experiment is fairly satisfactory. These theories are a development of Dodds's analysis for the reattachment of a jet to a plate offset from, and parallel to, the axis of the slot and, for the purpose of comparison, a limited study is also made of this flow.
The Stability of the Short-Period Motion of an Airframe Having Non-Linear Normal Force and Pitching Moment Curves
Authors: Christopher P. A. T.
Published: July 2016

The analysis of the stability of second-order non-linear systems by Poincare's method of singular points in the phase plane is briefly presented and used to determine stability criteria for the short-period motion of an airframe having non-linear normal force and pitching moment curves. These results are then compared with those obtained by the application of quasilinear stability theory.
The Design of Wing Plan Forms for Transonic Speeds
Authors: Lock R. C.
Published: July 2016

A method is suggested for designing the shape of the plan form of an unwarped swept-back wing so as to control the magnitude of the singularity that occurs in the chordwise loading distribution at the leading edge. At a Mach number of unity it is possible to do this simply and directly by an approximate application of linearised lifting-surface theory. Details are given of three families of wing plan forms, of varying sweep and aspect ratio, in all of which the strength of the leading-edge singularity is held constant near the wing tips, behind the Mach line from the root trailing edge. The local chordwise load distributions have been calculated in detail for several of these wings and it is found that in all cases the loading curves become effectively independent of spanwise position over that part of the span for which the singularity is constant.
Theoretical Pressure Distribution at Zero Lift at Supersonic Speeds for Slender Delta Wings having Fuselages of Circular Cross Section
Authors: Lock R. C.
Published: July 2016

A method is developed for calculating the pressure distribution at zero lift for a class of slender configurations consisting of a wing of delta type plan form combined with a body of revolution of the same overall length. Slender-body and slender-wing theory are combined to take into account the interference between the wing and the fuselage. An expression is found for the pressure at a general point on the wing or fuselage, although some numerical integration is still needed. This expression is simplified to obtain algebraic formulae for the pressure at the wing-fuselage junction and along the top of the fuselage. A further simplification is possible when the fuselage radius is small compared with the local wing semi-span. A particular example is considered consisting of a “Newby” wing with a parabolic fuselage; pressure distributions and drag curves are calculated.
The Elastic Stress Concentration Factors in Shouldered Shafts
Authors: Allison I. M.
Published: July 2016

The photoelastic “stress freezing” technique has been employed to evaluate the elastic stress concentration factors associated with the fillet blend radius in a number of shouldered shafts. The full range of practical sizes of blend radius and depth of shoulder has been examined. Comprehensive results for the shaft subjected to torsion, pure bending and axial load are given in this (Part I) and in two subsequent papers (Parts II and III).

The accuracy of the graphs of stress concentration factors is better than six per cent. Comparison has been made with the existing theoretical and experimental results for each mode of loading. The results of an investigation into die limiting value of the stress concentration factor (for a particular shoulder radius) as the depth of the shoulder is increased to infinity are included in Part III.