1,124 research outputs found
A biomimetic antenna in the shape of a bat’s ear
This letter presents a novel antenna that physically
resembles the ear of a bat. The device consists of a circular ground
plane with a central monopole element. An equilateral triangular
conducting plate is curved around the ground so that the base of
the triangle is electrically connected to the perimeter of the circle
and is of the same length. The input characteristic is similar to the
monopole above ground, providing there are a sufficient number of
modes in the triangular plate at the frequency of interest. Certain
frequencies yield a high gain and a radiation pattern with low side
lobes
An historical study of school health education in Massachusetts from the colonial period to the first world war
Thesis (Ed.D.)--Boston Universit
Efficient automotive electromagnetic modelling
The Transmission Line Modelling (TLM) method is applied to the electromagnetic modelling
of vehicles. Implications of increasing frequencies in computer models of electromagnetic
compatibility (EMC) studies are discussed. Efficient algorithms and resource management
strategies are developed With a view to producing accurate results m a realistic computational
run time.
Theoretical aspects covered are: (1) the development and accuracy of the TLM method; (2) an improved Partial Huygens' surface for plane wave excitation; (3) an evaluation of high-performance local and global absorbing boundary conditions. Implementation aspects of TLM addressed include: (1) the effects of arithmetic precision on link line voltage and stub impedance calculations; (2) the development of an object-oriented computer code using the Object Modelling Technique; (3) methods for estimating and managing the memory requirement and run lime of simulations.
It is shown that by optimizing algorithms and carefully managing resources, sufficient improvement
can be made to allow relatively sophisticated models to be run on a modest desktop computer
Accuracy of harmonic analysis techniques for direction of arrival estimation using time modulated arrays
This paper presents a comparison between two direction of arrival (DoA) estimation methods using time modulated linear arrays (TMLAs). The first method uses a two element array and numerically derives the signal DoA by using the ratio of the
two harmonics created by array. The second method makes use of a greater number of elements and known steering angles of the array sidebands. Results of a numerical simulation are presented which detail the accuracy in direction finding when using the two
techniques while the array is subject to environmental conditions such as noise and coherent signal interference. It is shown that whilst the second method requires a greater number of elements,
it has greater immunity to noise and multipaths
Acoustical direction finding with time-modulated arrays
Time-Modulated Linear Arrays (TMLAs) offer useful efficiency savings over conventional phased arrays when applied in parameter estimation applications. The present paper considers the application of TMLAs to acoustic systems and proposes an algorithm for efficiently deriving the arrival angle of a signal. The proposed technique is applied in the frequency domain, where the signal and harmonic content is captured. Using a weighted average method on harmonic amplitudes and their respective main beam angles, it is possible to determine an estimate for the signal’s direction of arrival. The method is demonstrated and evaluated using results from both numerical and practical implementations and performance data is provided. The use of Micro-Electromechanical Systems (MEMS) sensors allows time-modulation techniques to be applied at ultrasonic frequencies. Theoretical predictions for an array of five isotropic elements with half-wavelength spacing and 1000 data samples suggest an accuracy of ±1∘ within an angular range of approximately ±50∘ . In experiments of a 40 kHz five-element microphone array, a Direction of Arrival (DoA) estimation within ±2.5∘ of the target signal is readily achieved inside a ±45∘ range using a single switched input stage and a simple hardware setup
A method for forming distributed beams in time modulated planar arrays
The sidebands which originate in time modulated arrays can be used for numerous applications, including multipath signal separation and directional power transfer. In the present paper, a method of simultaneously producing a series of beams that are steered towards unique two-dimensional directions is presented by developing the theory of time-modulated linear arrays to time-modulated planar arrays. A planar array is modelled as two linear arrays on orthogonal axes and the binomial and Dolph-Chebyshev time-weighting distributions are applied to a 5 × 5 element array. The output of the array is shown in both the time and frequency domains
The UEFA Champions League: maintaining the status quo?
Purpose -
The purpose of the paper was to examine the competitive balance of the UEFA Champions League group stages. There are numerous financial and commercial benefits to clubs that participate in this competition. The current paper examines if the seeding system operated by UEFA is hindering some lower ranked teams from qualification and thus the associated benefits.
Design/Methodology/Approach -
Data was collected for all UEFA Champions League group stages between1999/2000 and 2013/2014. Data analysis techniques included Herfindahl-Hirschman Index (HHI) to examine competitive balance and one way ANOVAs to examine the impact of the current seeding system on club performance.
Findings -
The findings suggest that there are flaws in the ranking and seeding system used by UEFA as results show that the competition is competitively imbalanced at the group stage. Additionally, clubs that are continually placed in the highest seeding pot historically tend to accumulate more points and finish in a higher position in the group thus giving them a better opportunity to progress further in the competition.
Research Limitations/Implications -
The study has implications for both the clubs competing in the Champions League, who will be affected by the seeding system and UEFA themselves when considering the sporting integrity of their flagship competition.
Originality/Value -
To our knowledge this is the first paper of its kind to examine competitive balance in this competition and the paper contributes new knowledge that extends the research undertaken in the field previously.</p
Radiation characteristics of a conical monopole antenna with a partially corrugated ground plane.
In order to preserve broadband performance, the conical monopole antenna is ideally mounted on a semi-infinite ground plane. Practical finite ground planes can introduce unwanted effects in the radiation patterns such as significant back lobes. Periodic surfaces such as rotationally symmetric corrugated structures have been proven capable of improving the radiation characteristics of a variety of antennas. In this paper, the radiation patterns of a conical antenna with a PEC reflector are initially presented. The PEC reflector is then replaced with a partially corrugated reflector surface. The effects of the partially corrugated reflector on the radiation patterns and electric field distribution along the reflector surface are investigated. The simulation results reveal that the radiation patterns of a conical antenna with a partially corrugated reflector are more stable over a wide frequency band than that for the PEC reflector
A study on the effect of a metallic ring worn on human fingers using a simple scannable block hand phantom
A simple geometrical representation of a human hand has been constructed which allow a metallic
ring to be placed on the finger. The electric field magnitude within an isolated finger is measured and compared
with the cases when the ring is worn. The ring has been found to significantly alter the electric field magnitude
within the finger at 1800 MHz. This effect can also be found within the adjacent fingers at both 900 MHz and
1800 MHz
Performance metrics for the prediction of link and path availability in VANETs
In this paper metrics are produced which may be used for performance enhancement in Vehicular ad-hoc networks (VANETs) protocols. The method described makes use of the concept of link availability estimates which are produced on an individual link basis and which may be combined by multiplication to produce a quality metric for the whole route. The technique is discussed in the context of the Ad hoc On-demand Distance Vector (AODV) routing method
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