1,683 research outputs found
Phase modulating with odd and even finite power series of a modulating signal
Method and apparatus is presented for producing a phase-modulated waveform having a high degree of linearity between the modulating signal and the phase of the modulated carrier signal. Two signals representing finite odd and even power series transformations of the modulating signal are produced and multiplied with two quadrature components of the input carrier signal, respectively. One of the multiplied signals is subtracted from the other and the resulting signal is hard-limited to produce a phase-modulated output signal. The means for producing the two signals representing the odd and even power series of the modulating signal includes means for varying the coefficients of the two power series. By means of an existing computer program, the coefficients of the two power series are selected such that there is an extremely high degree of linearity between the modulating signal and the phase of the modulated carrier signal
Wide deviation phase modulator
Modulator produces phase-modulated waveform having high modulating linearity. Technique is inherently wideband with respect to carrier frequency and can operate over decade carrier frequency range without adjustments. Circuit performance is both mathematically predictable and highly reproducible
An analysis of the effects of secondary reflections on dual-frequency reflectometers
The error-producing mechanism involving secondary reflections in a dual-frequency, distance measuring reflectometer is examined analytically. Equations defining the phase, and hence distance, error are derived. The error-reducing potential of frequency-sweeping is demonstrated. It is shown that a single spurious return can be completely nullified by optimizing the sweep width
Transnational reflections on transnational research projects on men, boys and gender relations
This article reflects on the research project, ‘Engaging South African and Finnish youth towards new traditions of non-violence, equality and social well-being’, funded by the Finnish and South African national research councils, in the context of wider debates on research, projects and transnational processes. The project is located within a broader analysis of research projects and projectization (the reduction of research to separate projects), and the increasing tendencies for research to be framed within and as projects, with their own specific temporal and organizational characteristics. This approach is developed further in terms of different understandings of research across borders: international, comparative, multinational and transnational. Special attention is given to differences between research projects that are in the Europe and the EU, and projects that are between the global North and the global South. The theoretical, political and practical challenges of the North-South research project are discussed
The complexity of dominating set reconfiguration
Suppose that we are given two dominating sets and of a graph
whose cardinalities are at most a given threshold . Then, we are asked
whether there exists a sequence of dominating sets of between and
such that each dominating set in the sequence is of cardinality at most
and can be obtained from the previous one by either adding or deleting
exactly one vertex. This problem is known to be PSPACE-complete in general. In
this paper, we study the complexity of this decision problem from the viewpoint
of graph classes. We first prove that the problem remains PSPACE-complete even
for planar graphs, bounded bandwidth graphs, split graphs, and bipartite
graphs. We then give a general scheme to construct linear-time algorithms and
show that the problem can be solved in linear time for cographs, trees, and
interval graphs. Furthermore, for these tractable cases, we can obtain a
desired sequence such that the number of additions and deletions is bounded by
, where is the number of vertices in the input graph
Progressive Star Bursts and High Velocities in the Infrared Luminous, Colliding Galaxy Arp 118
In this paper we demonstrate for the first time the connection between the
spatial and temporal progression of star formation and the changing locations
of the very dense regions in the gas of a massive disk galaxy (NGC 1144) in the
aftermath of its collision with a massive elliptical (NGC 1143). These two
galaxies form the combined object Arp 118, a collisional ring galaxy system.
The results of 3D, time-dependent, numerical simulations of the behavior of the
gas, stars, and dark matter of a disk galaxy and the stars and dark matter in
an elliptical during a collision are compared with multiwavelength observations
of Arp 118. The collision that took place approximately 22 Myr ago generated a
strong, non-linear density wave in the stars and gas in the disk of NGC 1144,
causing the gas to became clumped on a large scale. This wave produced a series
of superstarclusters along arcs and rings that emanate from the central point
of impact in the disk. The locations of these star forming regions match those
of the regions of increased gas density predicted the time sequence of models.
The models also predict the large velocity gradients observed across the disk
of NGC 1144. These are due to the rapid radial outflow of gas coupled to large
azimuthal velocities in the expanding ring, caused by the impact of the massive
intruder.Comment: 12 pages in document, and 8 figures (figures are separate from the
document's file); Submitted to Astrophysical Journal Letter
An investigation of the existence of a surface water layer on aircraft radomes during simulated flight in heavy precipitation
An experiment to investigate the electromagnetic attenuation effects of an impacting water spray on an aircraft weather radome was conducted in Langley's 4 X 7 m. wind tunnel equipped with a water spray system. Results indicate no significant liquid water film formed at the stagnation point of the radome under the test conditions. However, a water sheath was observed standing away from the radome surface, which could possibly have significant attenuation properties of its own. Due to the lack of fidelity in modeling both the natural environment with the tunnel apparatus and the water sheath, it is recommended that further studies be undertaken to better define the water distribution in the vicinity of the radome and measure its effect on weather radar performance
The 24 GHz measurements of 2.2 lambda conical horn antennas illuminating a conducting sheet
Monostatic reflection-coefficient magnitude, absolute value of Gamma, measurements occurring between a radiating horn and a metal reflecting plate are presented for a family of three 2.2 lambda diameter conical horn antennas. The three horns have different aperture phase deviations: 6 deg, 22.5 deg, and 125 deg. Measurements of the magnitude of absolute value of Gamma as a function of horn-plate separation (d) extend from an effective antenna aperture short (d = O) to beyond the far-field boundary (d = 2D(sup 2)/lambda, where D is the antenna diameter). Measurement data are presented with various physical environments for each of the horns. Measured scalar data are compared with theoretical data from two models, a numerical model for a circular waveguide aperture in a ground plane and a scalar diffraction theory model. This work was conducted in support of the development effort for a spaceborne multifrequency microwave reflectometer designed to accurately determine the distance from a space vehicle's surface to a reflecting plasma boundary. The metal reflecting plate was used to simulate the RF reflectivity of a critically dense plasma. The resulting configuration, a ground plane mounted aperture facing a reflecting plane in close proximity, produces a strong interaction between the ground plane and the reflecting plate, especially at integral half-wavelength separations. The transition coefficient is characterized by large amplitude variations
Token Jumping in minor-closed classes
Given two -independent sets and of a graph , one can ask if it
is possible to transform the one into the other in such a way that, at any
step, we replace one vertex of the current independent set by another while
keeping the property of being independent. Deciding this problem, known as the
Token Jumping (TJ) reconfiguration problem, is PSPACE-complete even on planar
graphs. Ito et al. proved in 2014 that the problem is FPT parameterized by
if the input graph is -free.
We prove that the result of Ito et al. can be extended to any
-free graphs. In other words, if is a -free
graph, then it is possible to decide in FPT-time if can be transformed into
. As a by product, the TJ-reconfiguration problem is FPT in many well-known
classes of graphs such as any minor-free class
Integrable System Constructed out of Two Interacting Superconformal Fields
We describe how it is possible to introduce the interaction between
superconformal fields of the same conformal dimensions. In the classical case
such construction can be used to the construction of the Hirota - Satsuma
equation. We construct supersymmetric Poisson tensor for such fields, which
generates a new class of Hamiltonin systems. We found Lax representation for
one of equation in this class by supersymmetrization Lax operator responsible
for Hirota - Satsuma equation. Interestingly our supersymmetric equation is not
reducible to classical Hirota - Satsuma equation. We show that our generalized
system is reduced to the one of the supersymmetric KDV equation (a=4) but in
this limit integrals of motion are not reduced to integrals of motion of the
supersymmetric KdV equation.Comment: 15 pages,late
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