156,452 research outputs found
Doherty, O J, 414863
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/382077Surname: DOHERTY. Given Name(s) or Initials: O J. Military Service Number or Last Known Location: 414863. Missing, Wounded and Prisoner of War Enquiry Card Index Number: 54109.212550
Item: [2016.0049.14370] "Doherty, O J, 414863
Amplificador Doherty e antena combinadora
No full textThe conventional Doherty architecture is commonly used in wireless transmitters
for its ability to boost the average efficiency of a traditional single-ended
class B amplifier. It consists of two parallel single-ended amplifying branches
(named carrier and peaking amplifiers) which are linked, at the output, through
a /4 combiner. This output combiner commonly has a significant impact on
the overall bandwidth, as it is usually built from a transmission line structure
with tuned dimensions. Other non-conventional combining structures could be
designed, targeting a wider bandwidth, contributing to an overall increase of
the Doherty amplifier’s bandwidth. Being this an high relevance research topic
for the development of high efficient and broadband amplifiers, it is highly desirable
to have a laboratory setup that implements a Doherty power amplifier
to which distinct output combiner structures can be connected and tested. In
that sense, the design of two single-ended amplifiers (the carrier and the peaking)
was performed in a circuit simulator (ADS, from Keysight) together with
the input power divider that compose the Doherty architecture. The Doherty
amplifier main board was designed to incorporate the carrier and peaking amplifiers,
and also the power splitter at the input, and it was prepared so that
it could be connected to any desired combiner to be tested. A traditional Doherty
power combiner was designed and both boards (Doherty amplifier and
the combiner) were produced, connected and tested in the RF laboratory. The
measured amplifier presented the typical caractheristics of a Doherty amplifier
with nearly 75% of drain efficiency at full-power, and nearly 50% at the
output back-off level. In addition, a second combiner unit was designed with
two purposes. The first was to demonstrate the operation of the designed
Doherty amplifier with a distinct output combiner, showing that, as intended
in this work, it is suited to test multiple combiner structures. The second objective
was to serve as preliminary test to evaluate the possibility of merging
the output combiner with the antenna element. Taking advantage of the electromagnetic
coupling between antennas, this second combiner structure uses
two antenna elements that were tuned to simultaneously behave as output
combiner of the Doherty amplifier and a radiating element.A arquitetura Doherty convencional é tipicamente utilizada em transmissores
sem fios pela sua capacidade de aumentar a eficiência média de um tradicional
amplificador em classe B. O amplificador Doherty consiste em dois
amplificadores em paralelo (chamados de amplificadores carrier e peaking)
que são ligados, na saída, através de um combinador de /4. Este combinador
de saída geralmente tem um impacto significativo na largura de banda
do amplificador, pois é tipicamente construído a partir de uma estrutura de
linhas de transmissão com dimensões ajustadas para uma frequência. Outras
estruturas de combinadores não convencionais podem ser projetadas,
visando uma largura de banda maior, contribuindo para um aumento geral
da largura de banda do amplificador Doherty. Sendo este um tópico de investigação
de elevada relevância para o desenvolvimento de amplificadores
de alta eficiência e largura de banda, seria interessante ter um setup de laboratório
que implemente um amplificador de potência Doherty para o qual
estruturas combinadoras distintas possam ser ligadas à saída do amplificador
e testadas. Nesse sentido, o projeto de dois amplificadores (carrier e
peaking) foi realizado num simulador de circuitos (ADS, da Keysight) junto
com o divisor de potência de entrada que compõe a arquitetura Doherty. A
placa principal do amplificador Doherty foi projetada para incorporar os amplificadores
carrier e peaking, e também o divisor de potência na entrada, e foi
preparada de modo que pudesse ser ligada a qualquer combinador desejado
a ser testado. Um combinador de potência Doherty tradicional foi projetado
e ambas as placas (amplificador Doherty e o combinador) foram produzidas,
soldadas e testadas no laboratório de RF. O amplificador medido apresentou
as características típicas de um amplificador Doherty com aproximadamente
75% de eficiência de dreno na potência máxima e aproximadamente 50% no
ponto de output back-off. Além disso, foi projetado um segundo combinador
com dois objetivos. O primeiro foi demonstrar o funcionamento do amplificador
Doherty projetado com um combinador de saída distinto, mostrando que,
como pretendido neste trabalho, o amplificador desenhado é adequado para
testar múltiplas estruturas combinadoras. O segundo objetivo foi servir como
teste preliminar para avaliar a possibilidade de fundir o combinador de saída
com a antena. Aproveitando o acoplamento eletromagnético entre antenas,
esta segunda estrutura combinadora utiliza duas antenas que foram projetadas
para se comportarem simultaneamente como combinador de saída do
amplificador Doherty e como elemento radiante.Mestrado em Engenharia Eletrónica e Telecomunicaçõe
GCM simulations of the Indian Ocean dipole influence on East African rainfall: present and future.
No full textSix coupled GCMs are assessed in terms of their ability to simulate observed characteristics of East African rainfall, the Indian Ocean dipole and their temporal correlation. Model results are then used to analyze the future behaviour of rainfall and the DMI. All models simulate reasonably well the spatial distribution and variability of annual and seasonal rainfall over the 1961–1990 period. Model simulation of observed DMI characteristics is less consistent with observations, however, five models reproduce similar correlations to those observed between the DMI and East African short rains (SON). In the future, there are no clear inter-model patterns of rainfall or DMI behaviour. In this sample of models four (two) out of six simulate modest increases (decreases) in annual rainfall by the 2080s. For SON, three of the six models indicate a trend towards increasingly positive phase of the DMI, two indicate a decrease and one shows no substantial change
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
O. A. C. Review Volume XIV Issue 8, May 1902
No full textThis issue begins with an article regarding post-graduation employment and the value of a diploma from the Ontario Agricultural College. Agricultural articles pertain to the entomology of parasites in Canada and the value of rural improvement to the farm. Professor Doherty contributed an article on travelling to the Rockies. The Personals column contains alumni news. While the Locals column provides campus humour. .After College - whatIn the shadow of the RockiesCanada`s parasitesThe practical value of beautifying country homesEditorialAthleticsLocalsPersonalsadvertisin
Transmissor de comunicações móveis híbrido Doherty-outphasing
No full textO elevado crescimento da indústria de telecomunicações móveis tem apresentado
alguns desafios, nomeadamente no que diz respeito à utilização de recursos. Por um
lado, pretendem-se sistemas capazes de proporcionar elevadas taxas de transmissão,
contudo sacrificando o menos possível a largura de banda ocupada. Por outro,
pretendem-se sistemas eficientes do ponto de vista do consumo energético.
O tipo de modulação usada atualmente nos sinais de comunicações móveis, aumentam
de facto, a taxa de transmissão para a mesma largura de banda. No entanto, estas
modulações têm um PAPR elevado, o que causa uma enorme perda de eficiência nos
amplificadores de potência. Acresce a isso o facto de que o PA é a maior fonte de nãolinearidade
do sistema, tendo isso impacto tanto na ocupação espetral como na
qualidade da receção do sinal. É, portanto, extremamente importante e desejável, que
o amplificador de potência seja o mais linear e eficiente possível.
O amplificador Doherty, assim como o amplificador Outphasing são duas soluções que
conseguem de alguma forma dar resposta a estas questões, sendo o amplificador
Doherty o mais usado atualmente em estações base. No entanto, ambos têm as suas
vantagens e desvantagens. Foi no sentido de juntar o melhor que cada uma das
arquiteturas oferece, que começaram a surgir os híbridos Doherty-Outphasing, e que
têm sido alvo de interesse e investigação nos últimos anos.
Nesta Dissertação, foi feito um estudo destes amplificadores e híbridos, assim como a
implementação e caracterização de um transmissor híbrido Doherty-Outphasing, onde
se comprovou que, de facto, um híbrido proporciona uma melhor eficiência. O
transmissor implementado apresentou uma PAE medida superior a 50% numa gama de
8dB de PBO, PAE máxima de 70% e uma potência máxima de saída de 25WThe high growth of the mobile telecommunications industry has presented some
challenges, particularly regarding the use of resources. On the one hand, it is intended
systems capable of providing high transmission rates yet sacrificing as little as possible
the occupied bandwidth. On the other hand, energy-efficient systems are requirable.
The type of modulation currently used in mobile communication signals actually
increases the transmission rate to the same bandwidth. However, they have a high
PAPR, which causes a huge loss of efficiency in power amplifiers. In addition, the PA is
the largest source of nonlinearity in the system, affecting both spectral occupancy and
signal reception quality. It is therefore extremely important and desirable that the
power amplifier be as linear and efficient as possible.
The Doherty amplifier as well as the Outphasing amplifier are two solutions that
somehow manage to answer these questions, being the Doherty amplifier the most
commonly used in base stations. However, both have their advantages and
disadvantages. It was with the goal of bringing together the best that each of the
architectures offers, that led to the emergence of the Doherty-Outphasing hybrids, and
which have been the subject of interest and research in recent years.
In this dissertation, a study of these amplifiers and hybrids was done, as well as the
implementation and characterization of a hybrid transmitter Doherty-Outphasing,
where it was proven that in fact, a hybrid provides a better efficiency. The implemented
transmitter had a measured PAE greater than 50% in a range of 8dB of PBO, maximum
PAE of 70% and a maximum output power of 25WMestrado em Engenharia Eletrónica e Telecomunicaçõe
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Disseny d'un amplificador Doherty
No full textEs tracta de dissenyar i muntar un amplificador de dos vies amb modulació de carrega (Doherty), a una banda propera las 2 GHz. Pel rist tecnologic del TFC, pot ser que s'acabi a nivell de simulació i muntatge del circuit imprés, o de a nivelll de mesures totals. Requereix polaritzar transistors en classe AB, B i C (per definir, simular amb ADS i fer els circuits impressos microstrip
Characterization of the structural response of a lithiated SiO<sub>2</sub> / Si interface: A reactive molecular dynamics study
No full textWe report the results of a computational study regarding the mechanical properties of a lithiated Si/SiO2 interface using reactive molecular dynamics. The study is motivated by an intended application of SiO2-coated Sinanotubes as fibers in structural batteries with a fiber-reinforced composite architecture while serving as anodes. According to the results, main failure properties due to partly irreversible bond breakage during mechanical deformation are identified, indicating agreement with bond energy/bond order based estimates. Microscopic failure properties are also identified and interpreted in view of the observed processes of bonding degradation. In particular, the effect of Li distribution on the shear deformation response is evaluated as significant.Applied Mechanic
Disseny d'un amplificador Doherty
No full textEs tracta de dissenyar i muntar un amplificador de dos vies amb modulació de carrega (Doherty), a una banda propera las 2 GHz. Pel rist tecnologic del TFC, pot ser que s'acabi a nivell de simulació i muntatge del circuit imprés, o de a nivelll de mesures totals. Requereix polaritzar transistors en classe AB, B i C (per definir, simular amb ADS i fer els circuits impressos microstrip
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