10,232 research outputs found
Mary Louis Doherty papers
No full textMary Louis Doherty (1896-1995) was an expatriate American and journalist who lived in Mexico most of her life, working for Mexican government officials as well as private institutions and individuals. She corresponded with Katherine Anne Porter after they met in Mexico City in 1921. Doherty and Porter lived together in Mexico City in 1931 and in Washington, D. C., in 1944. She served as one of the models for the character of Laura in Porter's short story, "Flowering Judas." The Doherty collection consists of correspondence, biographical materials, publications, legal documents, and photographs. Letters from Porter comprise a portion of the correspondence
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Through the Lens of Color: An Interview with Gareth Doherty, Author of Paradoxes of Green: Landscapes of a City-State
No full textThis interview by Mark Tirpak with Gareth Doherty of Harvard University Graduate School of Design, focuses on his Paradoxes of Green: Landscapes of a City-State (University of California Press, 2017). With Paradoxes of Green (2017) and via the interview, Doherty recounts some of the findings of his ethnographic fieldwork in the Kingdom of Bahrain and describes tensions arising from differing conceptions of what ‘green’ means or signifies within this growing and predominantly arid region. An argument that Doherty makes in Paradoxes of Green (2017) is that color and form are interlinked, and that color deserves deeper consideration by policy-makers and other formal shapers of cities. The interview draws from Paradoxes of Green (2017) to discuss some of Doherty’s findings as well as his latest work on the intersections between landscape architecture and anthropology.Version of Recor
Through the Lens of Color: An Interview with Gareth Doherty, Author of Paradoxes of Green: Landscapes of a City-State
No full textThis interview by Mark Tirpak with Gareth Doherty of Harvard University Graduate School of Design, focuses on his Paradoxes of Green: Landscapes of a City-State (University of California Press, 2017). With Paradoxes of Green (2017) and via the interview, Doherty recounts some of the findings of his ethnographic fieldwork in the Kingdom of Bahrain and describes tensions arising from differing conceptions of what ‘green’ means or signifies within this growing and predominantly arid region. An argument that Doherty makes in Paradoxes of Green (2017) is that color and form are interlinked, and that color deserves deeper consideration by policy-makers and other formal shapers of cities. The interview draws from Paradoxes of Green (2017) to discuss some of Doherty’s findings as well as his latest work on the intersections between landscape architecture and anthropology
Helping children think: Gaze aversion and teaching
No full textLooking away from an interlocutor's face during demanding cognitive activity can help adults answer challenging arithmetic and verbal-reasoning questions (Glenberg, Schroeder, & Robertson, 1998). However, such `gaze aversion' (GA) is poorly applied by 5-year-old school children (Doherty-Sneddon, Bruce, Bonner, Longbotham, & Doyle, 2002). In Experiment 1 we trained ten 5-year-old children to use GA while thinking about answers to questions. This trained group performed significantly better on challenging questions compared with 10 controls given no GA training. In Experiment 2 we found significant and monotonic age-related increments in spontaneous use of GA across three cohorts of ten 5-year-old school children (mean ages: 5;02, 5;06 and 5;08). Teaching and encouraging GA during challenging cognitive activity promises to be invaluable in promoting learning, particularly during early primary years
Wideband Digital Intensive Doherty Concepts
No full textMany applications require wide bandwidth transmitters, but unfortunately, they usually have way less than 50% average drain efficiency for their modulated signals. This low efficiency is a significant drawback in all wireless applications, both for battery power devices and base stations. The Doherty radio frequency (RF) power amplifier architecture is widely used to enhance the average efficiency for modulated signals in base stations. Its popularity is due to its relatively cheap and simple hardware and its suitability to handle high-power wideband modulated signals. However, even Doherty amplifiers often have less than 50% average efficiency and are restricted in their RF bandwidth.This thesis reviews recent research on the Doherty power amplifier (DPA) topology and discusses possible power and bandwidth efficiency improvements. In the second part of the thesis, another topology is introduced, which also provides Doherty-like behavior. That topology is called a Pseudo Doherty Load Modulated Balanced Amplifier (PD-LMBA). The performance of PD-LMBA is compared with “conventional” DPAs. Circuit design examples of DPA and PD-LMBA are given. The thesis concludes with a PD-LMBA prototype design, which appears to be very promising in its wideband performance.Electrical Engineering | Microelectronic
A Wideband Two-Way Digital Doherty Transmitter in 40nm CMOS
No full textA 40nm CMOS wideband digital Cartesian push-pull inverted Doherty operating in class-E is presented. Wideband Doherty operation is achieved over a 1.9-to-3GHz frequency band, using an off-chip power combining network. The fully digital transmitter (DTX) provides 25.3dBm peak power with a drain/DTX line-up efficiency (DE/SE) of 58.7%/44.9%, respectively, at 2.4GHz. When operated with a 160MHz 256-QAM OFDM signal, it achieves 46.1%/32.7% average DE/SE, with an ACLR and EVM better than −40.6dBc and −33.9dB, respectively, using a simple memory-less digital pre-distortion (DPD).Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic
Evaluation of Doherty Amplifier Implementations
No full textThesis (MScIng)--Stellenbosch University, 2008.ENGLISH ABSTRACT: Modern communication systems demand efficient, linear power amplifiers. The amplifiers are
often operated in the backed-off power levels at which linear amplifiers such as class B amplifier
are particularly inefficient. The Doherty amplifier provides an improvement as it increases efficiency
at backed of power levels. Doherty amplifiers consists of two amplifiers, a carrier amplifier
and a peaking amplifier, of which the output is combined in a novel way. Implementation of
the Doherty amplifier with transistors is not ideal. One of the main problems is the insufficient
current production of the peaking amplifier at peak envelope power (PEP) if it is implemented
as a class C amplifier. A suggested solution to this problem is a bias adaption system that
controls the peaking amplifier gate voltage dynamically depending on the input power levels.
The design and evaluation of such a adaptive Doherty amplifier is the main goal of this thesis.
A classical Doherty amplifier with and an uneven Doherty amplifier with unequal power division
between the carrier and peaking amplifiers are also evaluated and compared with the adaptive
Doherty amplifier.
The amplifiers are designed using a 10 W LDMOS FET device, the MRF282. The adaptive
Doherty amplifier and the uneven Doherty amplifier show significant improvements in efficiency
and output power over the even Doherty amplifier. At PEP the adaptive Doherty delivers 42.4
dBm at 39.75 % power added efficiency (PAE), the uneven Doherty amplifier 41.9 dBm at 40.75
% PAE and the even Doherty amplifier 40.8 dBm at 38.6 % PAE. At 3dB backed-off input power
the adaptive Doherty amplifier has an efficiency of 34.3%, compared to 34.9 5% for the uneven
Doherty amplifier and 29.75 % for the even Doherty amplifier.AFRIKAANSE OPSOMMING: Moderne kommunikasie stelsels vereis effektiewe, linieêre drywing versterkers. Die versterkers
word dikwels in laer drywings vlakke bedryf waar linieêre versterkers soos ’n klas B versterker
besondere lae effektiwiteit het. Die Doherty versterker bied ’n uitweg omdat dit verbeterde
effektiwiteit by lae drywings vlakke bied. ’n Doherty versterker bestaan uit twee versterkers, die
hoof versterker en die aanvullende versterker, waarvan die uittrees met ’n spesiale kombinasie
netwerk bymekaar gevoeg word. Die implementasie van Doherty versterkers met transistors is
nie ideaal nie. Een van die hoof probleme is die onvoldoende stroom wat deur die aanvullings
versterker gebied word by piek omhulsel drywing (POD). ’n Oplossing vir die probleem is om ’n
aanpassings sisteem te gebruik wat die aanvullende versterker se hekspanning dinamies beheer
afhangende van die intree drywings vlakke. Die ontwerp en evaluasie van so ’n aanpassings
Doherty versterker is die hoof doel van hierdie tesis. ’n Klassieke Doherty versterke met gelyke
drywings verdeling en ’n ongelyke Doherty versterker wat gebruik maak van ongelyke drywings
verdeling tussen die hoof-en aanvullende versterkers is ook gevalueer en vergelyk met die aanpassings
Doherty versterker.
Die versterkers was ontwerp met ’n 10 W LDMOS FET, die MRF282. Die aanpassings Doherty
versterker en die ongelyke Doherty versterker het aanmerklike verbeteringe in effektiwiteit en
uittree drywing gebring in vergelyking met die ewe Doherty versterker. By POD het die aanpassings
versterker 42.4 dBm teen 39.75 % drywing toegevoegde effektiwiteit (DTE) gelewer, die
ongelyke Doherty versterker 41.9 dBm teen 40.75 % DTE, en die ewe Doherty versterker 40.8
dBm teen 38.6 DTE. By ’n intree drywingsvlak 3 dB laer as POD het die aanpassings Doherty
versterker ’n effektiwiteit van 34.3 % getoon, in vergelyking met die onewe Doherty versterker
se 34.9 % en die ewe Doherty versterker se 29.75 % DTE
Swearing in of William C. Doherty, circa 1960s
No full textSwearing in of William C. Doherty. Doherty served as president of the National Association of Letter Carriers from 1941 to 1962. Pictured with AFL-CIO President, George Meany and President of the United States, Lyndon B. Johnson. Circa 1960s
The AB-C Doherty power amplifier. part I: theory
No full textIn this article, the complete theoretical analysis of a Doherty amplifier employing a Class AB bias condition for the Main and a Class C one for the Auxiliary devices, respectively, is presented. Starting from the simplified model of an active device, the analysis of the AB-C Doherty behavior is carried out as a function of the input signal. In particular, the proposed approach is based on the analysis of the output drain current waveforms generated by the two active devices, while assuming a Tuned Load configuration (i.e., short circuit condition) for higher harmonic terminations. A closed form formulation is derived in order to directly design an AB-C Doherty amplifier, while fully understanding the basis of its physical behavior. Finally, which Doherty parameters can be chosen by the designer or have to be implicitly fixed are discussed and clarifie
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