bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measured Amplitude Variations of the 19.8 kHz Field of NPM Near Its Antipode
Authors: Snyder F. P. , Bickel J. E. 
Published: November 2015

Measurements of the field intensity of VLF transmissions from NPM at 19.8 kHz were made at four fixed ground sites located in Bechuanaland, Mrica, during July and August 1963. The sites were in the vicinity of the antipode of the transmitter in Hawaii. Each site employed both a vertical whip and a vertical, rotating loop antenna.The data indicate that a standing‐wave interference pattern is present in the antipodal region most of the time. During local sunrise and sunset, such a pattern appears to be absent and the signal appears to be received primarily from one general direction. Oscillations of 1‐ to 2‐hr periods in the diurnal amplitude data are explained as being due to interference of signals arriving from various directions, with phase changes associated with changes of the terminator position along the paths.The difference between east‐to‐west (E‐W) and west‐to‐east (W‐E) attenuation rates for the first waveguide mode is examined. A value of about 0.6 dBfMm is consistent with the observations.
Electromagnetic Scattering by Thin Inhomogeneous Circular Cylinders
Authors: Taylor Clayborne D. 
Published: November 2015

The general problem of electromagnetic wave scattering by thin inhomogeneous circular cylinders is completely formulated. An integral equation for the induced axial current distribution is derived and solved for an incident plane wave of arbitrary direction of propagation. A knowledge of this induced current allows the determination of the scattered fields as well as the scattering cross section.For convenience the conductivity is only considered to vary axially. Numerical results are presented for the induced axial current and scattering cross section. An important application of this work is in missile vulnerability studies. To this end numerical results are presented for a missile having an ionized exhaust trail. The conductivity of the exhaust trail is considered to taper exponentially along its axis.
Propagation in Nonuniform Slightly Gyrotropic Media
Authors: Gross Stanley H. 
Published: November 2015

A previous paper, part I, presented the basic theory of propagation in nonuniform gyrotropic media in terms of an E and H mode representation. The representation results in a type of coupling that is independent of the rate of variation in the medium and thereby permits the study of regions with strong inhomogeneities along the gyrotropic axis. The coupling between modes arises due to the deviation of the gyromagnetic parameter Y =ωc/ω from zero and infinite values.Part I provided solutions for models with Y > 1. In this presentation, details will be given for the Y < 1 case which is pertinent for propagation in the ionosphere at medium and higher frequencies. An iterative expansion procedure is employed, as previously, and some general properties are deduced from the solutions. The analysis is applied to the evaluation of the far field radiated by an electric current element exterior to a parabolic electron density layer. These results are applicable to the study of propagation through an ionospheric layer or an ionospheric irregularity.
Full‐Wave Solutions in Terms of Coupled Vacuum Modes
Authors: Walsh Edward J. 
Published: November 2015

Various definitions of wave modes can be used to decompose the field of electromagnetic waves in a stratified magnetoionic medium. Magnetoionic modes corresponding to a homogeneous medium of the local characteristics are a very common, though arbitrary choice. They are not necessarily practical for computation or interpretation in all situations.This paper deals with Poeverlein's modes which have the characteristics of waves propagating in vacuum. His modes represent the waves that would be obtained in an extremely narrow vacuum gap introduced at the point under consideration. The formalism is demonstrated and compared with conventional coupled‐wave theory in the simple ease of vertical propagation in a horizontally stratified isotropic medium.The numerical solution of the general vacuum‐mode wave equations is discussed for oblique incidence on a horizontally stratified, anisotropic medium with arbitrary orientation of the magnetic field. Particular attention is paid to the problem of numerical swamping. A method is developed for dealing with the swamping phenomenon, which emphasizes the physical aspects of this computational problem.2Computations were made on a realistic ionospheric model at 16 kHz. The results obtained are compared with other authors results for the same profile.
On Digital Computer Solutions of Fredholm Integral Equations of the First and Second Kind Occurring in Antenna Theory
Authors: Harrison Charles W. , Taylor Clayborne D. , O'Donnell Edward E. , Aronson Eugene A. 
Published: November 2015

An open‐ended iterative technique is presented for solving a Fredholm integral equation of the second kind having a singular kernel, using a digital computer. To ascertain the accuracy of the solution, the original equation is recast analytically into a Fredholm integral equation of the first kind. The unknown function is then obtained by expanding it into a series of orthogonal functions and determining the unknown coefficients by inverting the infinite matrix (truncated at the desired order) using machine methods. The numerical results obtained from the two procedures are in complete agreement. This implies that a definitive solution of the integral equation is obtained.The problem chosen for solution in this paper arises in connection with the determination of the current distribution along a perfectly conducting open‐ended cylindrical tube that is sufficiently thin so that the phase change of the plane wave exciting electromagnetic field across its diameter may be neglected. A solution for the current that converges is obtained because the structure is driven by the field along its entire length—not at some discrete point by a slice generator, as is the case in the usual theoretical model of the linear transmitting antenna. Curves for the current distribution along the structure for parallel incidence of the electric field are given. Also, the radar cross sections of several tubes for the same field orientation are determined.
Response of Transmission Lines in Proximity to a Cylindrical Scatterer
Authors: Harrison Charles W. 
Published: November 2015

A wire is run very close to the surface of a highly conducting cylinder and parallel to its axis. The cylinder is longer and of much larger radius than the wire. Arbitrary values of impedance are connected between the ends of the wire and the cylinder. One objective of this study is to develop formulas for the currents in the load impedances when the transmission line formed by the wire and its image is driven by the nonuniform field consisting of the superposition of the incident plane‐wave field and the backscattered field from the cylinder.A second objective is to obtain formulas for the load currents in the terminating impedances of a transmission‐line loop oriented parallel to and in the near‐zone field of the cylinder. Coupling to the image two‐wire line is taken into account.Since the theory depends fundamentally on the field very close to an unloaded cylindrical receiving antenna of moderate diameter, a portion of the paper is devoted to a short‐cut procedure for obtaining expressions for this field which satisfy the boundary conditions.A brief tabulation of integral values required in the theory is supplied.
Wavelength Dependence of Microwave Propagation Far Beyond the Radio Horizon
Authors: Eklund Folke , Wickerts Sture 
Published: November 2015

The wavelength dependence of microwave propagation far beyond the radio horizon is studied experimentally and theoretically. The experiments made over a 259‐km path at 1000 MHz and 3000 MHz with scaled antennas give as a main result a wavelength dependence of actually received power relative to received power in free space ranging from λ−1 to λ−3. The exponent of the wavelength dependence is found to be correlated to the level of received signal power.Calculations are made of received signal power under the assumption that the tropospheric refractive index field of the common volume is of a turbulent structure, where the variations obey the −5/3 spectral law. There are also locally sharp boundaries within the common volume, which act as reflecting facets.A meteorological reasoning leads to the conclusion that there is a connection between the intensity of the turbulence and the refractive index gradient through the reflecting facets. Based on this, we get a relation between the exponent of the wavelength dependence and the level of received signal power.As a main result, reflections in the facets at 1000 MHz play a dominating role while at 3000 MHz, turbulent scatter is the most important propagation mechanism.Finally, theoretical and experimental results are compared and a comparatively good agreement is found.
Horizon Focusing Effects Observed on Ionospherically Reflected Radio Waves
Authors: Humphrey L. C. 
Published: November 2015

The focusing gain parameters associated with radio waves reflected obliquely from the ionosphere as derived theoretically are compared with experimental observations. The description of the field in the neighborhood of the caustic depends on the shape of the ionosphere with respect to the earth. For an ionosphere concentric with the earth and a surface location transmitter it is convenient to describe the focusing gain in terms of the evaluation angle of arrival. For a tilted ionosphere, or for an elevated transmitter in which the caustic is elevated above the earth's surface, it is convenient to describe the field as a function of the distance behind the cusp, and above the caustic surface.Experimental observations indicate both situations may exist in nature. The concentric ionosphere is termed the normal situation, and a gain inversely proportional to the approximate cube of the elevation angle was indicated by the experimental data as opposed to a straight inverse relationship by geometric optics. The effect of a distorted ionosphere was evidenced by strong focusing gain at positive elevation angles. It is hypothesized that an increase in curvature of the ionosphere can result in the observed gains which would be consistent with the theory. The required curvature has been observed on other experimental programs.
A Numerical Study of VLF Mode Structure and Polarization Below an Anisotropic Ionosphere
Authors: Pappert Richard A. 
Published: November 2015

The cylindrical waveguide problem with a diffuse, anisotropic upper boundary is rigorously formulated using a conformal transformation. This will allow us to demonstrate the adequacy of an ad hoc method used in a previous paper for simultaneously treating earth curvature and ionospheric
effects.Weakly attenuated components of the mode spectrum associated with easterly propagation below a highly anisotropic ionosphere are developed numerically in the frequency range from 10–30 kHz. Also, the field strength distributions in the guide are presented. It is shown that modes of the earth detached variety, unlike the usual quasi‐TM or quasi‐TE modes, can contain comparable amounts of vertical and horizontal polarization. The numerical results also suggest that at the high end of the frequency spectrum considered, modes which are principally TE may be of importance in the mode sum.
Density Tapering of Circular Aperture Array Antennas
Authors: Redlien Henry W. 
Published: November 2015

The evaluation of the performance of density‐tapered arrays may be made in simple terms and based on the simple concept of dividing the total input power into a “design” component and a “hash” component of radiation. The design component is the nominal directive radiation pattern that would result from the continuous aperture excitation of the array; the hash component is the wide‐angle radiation that results from the gaps in the aperture excitation required in density tapering.The parameters evaluated include antenna gain, number of active and inactive (dummy) elements, and the level of hash radiation. Density tapering is compared with amplitude tapering, and formulas are summarized for convenient reference. Examples of particular low side‐lobe taper functions have been computed, and the results are tabulated.
Admittance of Infinite and Finite Cylindrical Metallic
Authors: Andersen J. Bach 
Published: November 2015

A monopole antenna excited by a coaxial line is studied in detail. The mathematical model of the excitation is a magnetic ring current the radius of which may be larger than the radius of the cylinder. First a study is made of the waves guided by and radiated from an infinite cylinder. Numerical results for the current and the conductance are given. The conductance decreases when the gap width increases.The standing‐wave antenna is treated with an assumed effective gap at the antenna ends. A solution of the antenna problem is found by superimposing the multiply reflected waves. In the solution, the effect of the gap and the antenna end separates. Accurate values for the gap admittance and the end admittance are derived from experimental values obtained by Hartig.
Antenna Radiation Properties in Presence of Anisotropic Plasmas
Authors: Bachynski M.P. , Gibbs B. W. 
Published: November 2015

An extensive quantitative experimental investigation was conducted on the influence of a magnetic field on the radiation from a horn antenna situated behind a layer or sheath of plasma. The magnetic field direction in the experiments was along the principal direction of radiation of the antenna which is normal to the layer of plasma.The experimental results were compared with theory based on the reciprocity theorem. For the left circularly polarized wave radiation pattern, propagation effects at off‐normal incidence corresponding to the condition for which the ordinary wave mode switches to the extraordinary wave mode as the electron density passes through the critical density are shown to be of importance. For the right circularly polarized wave mode, significant departures in the measured radiation pattern from the theoretical occur in the region of the electron cyclotron frequency and below. Satisfactory correspondence between theory and experiment is found for values of the electron cyclotron frequency that are greater than the wave frequency.
Is waveform worth it? A comparison of LiDAR approaches for vegetation and landscape characterization
Authors: Anderson Karen , Hancock Steven , Disney Mathias , Gaston Kevin J. 
Published: November 2015

Light Detection and Ranging (LiDAR) systems are frequently used in ecological studies to measure vegetation canopy structure. Waveform LiDAR systems offer new capabilities for vegetation modelling by measuring the time‐varying signal of the laser pulse as it illuminates different elements of the canopy, providing an opportunity to describe the 3D structure of vegetation canopies more fully. This article provides a comparison between waveform airborne laser scanning (ALS) data and discrete return ALS data, using terrestrial laser scanning (TLS) data as an independent validation. With reference to two urban landscape typologies, we demonstrate that discrete return ALS data provided more biased and less consistent measurements of woodland canopy height (in a 100% tree covered plot, height underestimation bias = 0.82 m; sd = 1.78 m) than waveform ALS data (height overestimation bias = −0.65 m; sd = 1.45 m). The same biases were found in suburban data (in a plot consisting of 100% hard targets e.g. roads and pavements), but discrete return ALS were more consistent here than waveform data (sd = 0.57 m compared to waveform sd = 0.76 m). Discrete return ALS data performed poorly in describing the canopy understorey, compared to waveform data. Our results also highlighted errors in discrete return ALS intensity, which were not present with waveform data. Waveform ALS data therefore offer an improved method for measuring the three‐dimensional structure of vegetation systems, but carry a higher data processing cost. New toolkits for analysing waveform data will expedite future analysis and allow ecologists to exploit the information content of waveform LiDAR.
Effect of Chelate Ring Size in Iron(II) Isothiocyanato Complexes with Tetradentate Tripyridyl‐alkylamine Ligands on Spin Crossover Properties
Authors: Leibold Michael , Kisslinger Sandra , Heinemann Frank W. , Hampel Frank , Ichiyanagi Yuko , Klein Michael , Homenya Patrick , Renz Franz , Toftlund Hans , Brehm Georg , Schneider Siegfried , Reiher Markus , Schindler Siegfried 
Published: November 2015

Abstract Iron(II) complexes of the type [Fe(L)(NCS)2] with tetradentate ligands L are well known to show spin crossover properties. However, this behavior is quite sensitive in regard to small changes of the ligand system. Starting from the thoroughly investigated complex [Fe(tmpa)(NCS)2] [tmpa = tris(2‐pyridylmethyl)amine, also abbreviated as tpa in the literature] we modified the ligand by increasing systematically the chelate ring sizes from 5 to 6 thus obtaining complexes [Fe(pmea)(NCS)2], [Fe(pmap)(NCS)2], and [Fe(tepa)(NCS)2] [pmea = N,N‐bis[(2‐pyridyl)methyl]‐2‐(2‐pyridyl)ethylamine, pmap = N,N‐bis[2‐(2‐pyridyl)ethyl]‐(2‐pyridyl)methylamine, and tepa = tris[2‐(2‐pyridyl)ethyl]amine]. All complexes were structurally characterized and spin crossover properties were investigated using Mößbauer spectroscopy, magnetic measurements, and IR/Raman analyses. The results demonstrated that only the iron complexes with tmpa and pmea showed spin crossover properties, whereas the complexes with the ligands pmap and tepa only formed high spin complexes. Furthermore, DFT calculations supported these findings demonstrating again the strong influence of ligand environment. Herein the effect of increasing the chelate ring sizes in iron(II) isothiocyanato complexes with tetradentate tripyridyl‐alkylamine ligands is clearly demonstrated.
Guidelines: the do’s, don’ts and don’t knows of feedback for clinical education
Authors: Lefroy Janet , Watling Chris , Teunissen Pim W. , Brand Paul 
Published: November 2015

Introduction The guidelines offered in this paper aim to amalgamate the literature on formative feedback into practical Do’s, Don’ts and Don’t Knows for individual clinical supervisors and for the institutions that support clinical learning.
Methods The authors built consensus by an iterative process. Do’s and Don’ts were proposed based on authors’ individual teaching experience and awareness of the literature, and the amalgamated set of guidelines were then refined by all authors and the evidence was summarized for each guideline. Don’t Knows were identified as being important questions to this international group of educators which if answered would change practice. The criteria for inclusion of evidence for these guidelines were not those of a systematic review, so indicators of strength of these recommendations were developed which combine the evidence with the authors’ consensus.
Results A set of 32 Do and Don’t guidelines with the important Don’t Knows was compiled along with a summary of the evidence for each. These are divided into guidelines for the individual clinical supervisor giving feedback to their trainee (recommendations about both the process and the content of feedback) and guidelines for the learning culture (what elements of learning culture support the exchange of meaningful feedback, and what elements constrain it?)
Conclusion Feedback is not easy to get right, but it is essential to learning in medicine, and there is a wealth of evidence supporting the Do’s and warning against the Don’ts. Further research into the critical Don’t Knows of feedback is required.
Heterotopic Pregnancy with an Intrauterine Twin Gestation and Ruptured Tubal Pregnancy: An Unusual Presentation
Authors: Bagchi Sipra , Aggarwal Abhinav , Gupta Ashish Kumar , Aggarwal Aakriti Kapoor , Sachdeva Primal , Pandit Abhinav 
Published: November 2015

AbstractHeterotopic pregnancy is diagnosed as coexistent presence of fetuses at two or more implantation sites. Its incidence is very rare with presence of live intrauterine twins being even rarer. Diagnosis in such cases is difficult with ultrasound being the investigation of choice. Management is primarily surgical. It is a clinical entity which is becoming even more common with widespread use of assisted reproductive techniques. A 20-year-old primigravida with 10 weeks of gestation presented with sudden onset pain on right side of abdomen. She had history of treatment for infertility for 1 year.
Ultrasound revealed live intrauterine twin pregnancy with a heterogeneous lesion in right adnexal region and peritoneal free fluid. In concordance with clinical findings a diagnosis of heterotopic pregnancy with ruptured ectopic was made. Patient was managed through emergency laparotomy without disturbing the intrauterine twin gestation. Higher incidence of heterotopic pregnancy has been observed in patients undergoing assisted reproductive techniques and therefore warrant regular and detailed examination and follow up to avoid complications like ruptured ectopic pregnancy.
Functional Outcomes of Burn Patients with or without Rehabilitation in Mainland China
Authors: Tang Dan , Li-Tsang Cecilia W.P. , Au Ricky K.C. , Li Kui-cheng , Yi Xian-feng , Liao Lin-rong , Cao Hai-yan , Feng Ya-nan , Liu Chuan-shun 
Published: November 2015

Background/Objective To evaluate the functional outcomes of moderate to severe burn patients with and without rehabilitation in terms of self-care performance and quality of life (QOL). Methods Fifty-five patients with total burn surface area of 30% or more were divided into two groups: rehabilitation and conventional care groups. The rehabilitation group underwent comprehensive rehabilitation interventions (e.g., occupational therapy, physiotherapy, and patient and family education) in addition to standard clinical interventions received by the conventional care group. The outcomes included self-care performance (Modified Barthel Index [MBI]), QOL (World Health Organization Quality of Life-BREF), pain and itchiness (Visual Analogue Scale [VAS]), quality of sleep, and mental health (Self-Rating Depression Scale [SDS] and Self-Rating Anxiety Scale) measured before and 3 months after the intervention. Results After the intervention, significant improvements were found in MBI, all dimensions of QOL, pain, and SDS in the rehabilitation group (all p < .05). In the conventional care group, significant improvements were found only in MBI (p < .001), the physical health dimension of QOL (p < .01), and pain (p < .001). Group comparisons showed that the rehabilitation group achieved significantly better outcomes after the intervention in MBI (p < .001), VAS score of itching (p = .009), and the physical health (p = .002), psychological health (p = .021), and social relationships dimensions of QOL (p < .001). Conclusion Patients with moderate to severe burn injuries can benefit from rehabilitation interventions in terms of physical health, mental health, performance of daily living, and QOL.