Chemical Mechanical Polishing Optimization for 4H-SiC

Scratch free surfaces are required for substrates used in epitaxial growth. Silicon carbide (SiC) is a substrate material that is used in the epitaxial growth of SiC, GaN, and InGaN electronic devices. Preliminary chemical mechanical polishing (CMP) studies of 1 3/8 4H-SiC wafers were performed in an attempt to identify the polishing parameter values that result in a maximum material removal rate and thus reduce substrate polishing time. Previous studies reported increased material removal rates associated with increasing polishing temperature, slurry pH, pressure, and polishing pad speed. In the current study, the effects of temperature, slurry pH, polishing pressure, and polishing pad speed were examined independently while keeping other polishing parameters constant. Material removal rates were determined using pre and post-polish wafer mass measurements. Photographs at specific wafer locations were obtained before and after each polishing period and compared to calculated removal rates. The current study indicated that different temperatures affect the removal rate by changing pad fiber dynamic shear modulus and not by altering the chemical reaction rate between the polishing slurry and wafer surface atoms. Also, in contradiction to other studies, a decrease in material removal was observed for increasing slurry pH levels. Increased applied pressure resulted in higher removal rates and unwanted polishing pad damage. Higher pad rotational speeds produced non-linear increases in material removal rates and appeared to have the greatest impact on material removal rates. High pressures and rotational speeds introduced variability and randomness in the calculated removal rates

The Lantern, 2012-2013

• How They Run • What Was Said in Boston • On the Last Day of the Month • An Angel Tries to Surprise Humans • I Wonder if God Modeled Boys After Books • Marred with Modern Scars • Feather Bed • Ode to a Pen • Objet Petit A • Breaking News: Grownups Fear Return of Disco • Neuroscience • New Document • We Were Stars, and the Sky was Our Grass • About a Man • Trojan • An Ode • Yr Body Sour • That Lake in Jamaica • Live While Chiefs are Still Fighting • Lament for Mathematics • The Robert Frost House • People Fell in Love on Me • Sunday Review • Looks Silly in Tiny Desk Chairs • Two Years Later • Better Than Nothing • Istanbul • Packs of Cigarettes • Sonnet • Outside King of Steaks • Obstinance • Coffee Grinds • Autumn Equinox • Homecoming • Oh, San Francisco • Slide: A Beginning • Slowly Last Summer • Of Dogs and Men • Letters Not Sent • Before the Race • The Little Things • Tarpon Springs • Payment for Rebellion • Wednesday • When is President\u27s Day? • Heartless Parallels and Perpendiculars • Railway • Presto Agitato • Easier Said Than Done • Waves • Four White Women • Rope • Alter Ego Self Portrait • Pebbles • Coney Island • Guanjuanto • Growth • Evolve • Winter Blackout • Honeybee • Frames • Wanderlust • Guiding Light 1 • Frick\u27s Lock • The Ones That Never Leave • In Memoriam: Rachel Blunthttps://digitalcommons.ursinus.edu/lantern/1179/thumbnail.jp

The Lantern, 2011-2012

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Is technology optimism justified? A discussion towards a comprehensive narrative

This paper is based on a discussion developed by one of the thematic working groups at the Biennial International Workshop Advances in Energy Studies (BIWAES) 2017 hold in Naples, Italy. The topic was the role of technology in energy transition and global problems. Owing to the heterogeneity of the participants in the working group, different viewpoints were put together, leading to some shared conclusions. In particular, the role played by the different narratives used in discussing the role of technology in facing global problems was pointed out as the origin of cognitive dissonance. The presented reflections address some conceptual weaknesses in the current debate on technology and global issues, framed in global policies that appear incapable to obtain tangible results. The technology optimism seems, in fact, to be based on the elusive use of both the concepts of technology and sustainability, that are put together for narrative purposes without an explicit conceptual assessment. On one hand, the factual role of technology and its beneficiary are almost never clearly addressed in the debate. On the other hand, the fact that any new technology will serve the cause of sustainability is not questioned whatsoever, without taking into account the social, political and ethical framework in which technology is supposed to be operated

A review of non-destructive testing techniques for the in-situ investigation of fretting fatigue cracks

© 2020 The Authors Fretting fatigue can significantly reduce the life of components, leading to unexpected in-service failures. This phenomenon has been studied for over a century, with significant progress being made during the past decade. There are various methods that have been used to study fretting fatigue cracks in order to gain a greater understanding of the effects of fretting fatigue. Destructive methods are traditionally used to observe fretting fatigue cracks. Although useful in determining crack location, crack length, crack propagation modes, crack path and shape, it is not efficient or reliable for time based measurements. Non-destructive testing has developed in recent years and now in-situ monitoring can be used during testing in order to increase the understanding of fretting fatigue. This paper presents a review of non-destructive testing techniques used in-situ during fretting fatigue testing, which are compared in order to conclude the suitability of each technique. Recent developments in non-destructive techniques that could be also applied for fretting fatigue tests are also discussed, as well as recommendations for future research made

Negative Conductance Load Modulation RF Power Amplifier

The number of mobile wireless devices on the market has increased substantially over the last decade. The frequency spectrum has become crowded due to the number of devices demanding radio traffic and new modulation schemes have been developed to accommodate the number of users. These new modulation schemes have caused very poor efficiencies in power amplifiers for wireless transmission systems due to high peak-to-average power ratios (PAPR). This thesis first presents the issue with classical power amplifiers in modern modulation systems. A brief overview of current attempts to mitigate this issue is provided. A new RF power amplifier topology is then presented with supporting simulations. The presented amplifier topology utilizes the concept of negative conductance and load modulation. The amplifier operates in two stages, a low power stage and a high power stage. A negative conductance amplifier is utilized during peak power transmission to modulate the load presented to the input amplifier. This topology is shown to greatly improve the power added efficiency of power amplifiers in systems with high PAPR

Acceptability and prescribing adherence to revised antiemetic guidelines in paediatric patients receiving chemotherapy.

The objective of this poster presentation is to assess adherence to and acceptability of revised antiemetic prescribing guidelines implemented 20091 and evaluation of use of the patient-specific antiemetic record. Case notes, prescription and administration charts were reviewed retrospectively for 20 patients receiving chemotherapy during April 2011. Prescribing of chemotherapy and antiemetics over the previous 12 months was recorded and adherence to guidelines assessed. Recently implemented patient sickness diary cards completed by patients/carers on each cycle of chemotherapy were evaluated. Prescribers' views and awareness of the guidelines were gathered from a specifically designed self-administered questionnaire. Outcomes from the study were presented at a multidisciplinary meeting where changes in practice were agreed. Of the 20 patients (11 oncology; 9 haematology), 13 were male and ranged from 6 months to 19 years old. Five patients had received chemotherapy for longer than 12 months. Prescribing adhered to the guidelines greater than 70% of the time in eight patients, between 30–70% of the time in 10 patients and less than 30% of the time in two patients. Non-adherence trends were: unclear documentation of patients receiving prechemotherapy antiemetics, ondansetron continued longer than 24 h postchemotherapy to prevent acute nausea and vomiting, metoclopramide started concomitantly with ondansetron for prevention of delayed nausea and vomiting and lorazepam not being administered immediately post an acute emetic episode. Non-adherence was justified when there was a previous adverse reaction to an antiemetic or when emesis continued despite appropriate management and/or confounding circumstances such as parenteral nutrition. Omissions from the guidelines were use of aprepitant in teenagers receiving cisplatin-based regimens, emetogenic risk of clofarabine and intrathecal cytarabine and guidance on evaluating emetogenic risk for investigational medicinal products such as chimeric 14.18/CHO monoclonal antibody (antiGD2). Five patients returned completed Patient Sickness Diary Cards. Excluding one patient with low-grade glioma and pre-existing vomiting prior to chemotherapy who experienced 13 vomits over a 5 day reporting period, only three vomits were noted over a total of 36 days reported but 22 patient days (61%) were recorded as nauseated. 17 out of 35 (49%) prescriber questionnaires were returned. Prescribers reported awareness of the guidelines and considered them helpful. The patient specific antiemetic record was not used, and there was multidisciplinary agreement that working practices be reviewed to facilitate accessibility. The revised guidelines are mostly adhered to and the results have informed where adjustments and additional information are required. The patient diary card and the patient specific antiemetic record were considered useful in the individualisation of treatment and are to be integrated into working practices and used for continuous quality monitoring