170,989 research outputs found
EBM: A Quantitative Usability Model for Video Games
No full textFull text is available to authenticated members of The University of Auckland only.Usability is an important aspect of video games, because an unusable system can prevent a player from enjoying a game. This thesis presents a quantitative model to measure game control usability of platform video games, called EBM. It is based on the hypoth- esis that the e ort required to play a game is a good indicator of the game's usability. EBM produces a score called \EBM score", which estimates game control usability. It is calculated by combining the contributing factors of e ort, such as duration and intu- itiveness measures. The duration and intuitiveness measures of each game function are combined through a weighted average, weighted by each game function's relative function usage. Then the EBM score is calculated by a weighted sum of the overall duration and intuitiveness measures, using factor weights. EBM was validated by measuring the correlation between EBM scores and SUS scores for a total of 33 control schemes for 7 di erent platform games (5 schemes for 5 games, and 4 schemes for 2 games). Two di erent tests were conducted to validate di erent aspects of the model. The rst test investigated EBM's capability of estimating game control usability of di erent control schemes from the same game. The second test investigated EBM's capability of estimating game control usability of di erent control schemes from di erent games. For each control scheme 3 measurements were taken from 3 di erent participants. The correlations between the EBM scores and SUS scores of the 5 control schemes correlated signi cantly for each of the 7 games. Furthermore, the overall correlation between the EBM and SUS scores of all 33 control schemes across the 7 games was signi cant. Next, Controller Designer was developed to automate the calculation of EBM scores. It is based on EBM, and is used to support developers in designing control schemes. The tool was evaluated based on its usability and e ectiveness in helping the developers design a usable control scheme. The evaluation process involved using a set of interview questions to measure the e ectiveness of Controller Designer, and a SUS questionnaire to measure the usability of Controller Designer. The preliminary results showed that the tool contains problems that still need to be resolved before the tool can be useful
Ethics, EBM, and hospital management
No full textMatters of hospital management do not figure prominently on the medical ethics agenda. However, management decisions that have to be taken in the area of hospital care are in fact riddled with ethical questions and do have significant impact on patients, staff members, and the community being served. In this decision making process evidence based medicine (EBM) plays an increasingly important role as a tool for rationalising as well as rationing health care resources. In this article, ethical issues of hospital management and the role of EBM will be explored, with particular reference to disease management programs, diagnosis related groups, and clinical pathways as recent developments in the German health care system
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
ADDITIVE MANUFACTURING OF PURE COPPER USING ELECTRON BEAM MELTING (EBM)
No full textPure copper (Cu) has the properties of high optical reflectivity and surface tarnishing as well as excellent thermal and electrical conductivity. Accordingly, laser-based additive manufacturing (AM) techniques confront various difficulties to produce thismaterial. In contrast, the electron beam melting (EBM) process is paving to become an excellent method to manufacture AM parts from such materials. This is since theelectron beam is not influenced by the optical reflectivity of the material. Furthermore, EBM works under vacuum that can protect the powder material from oxidization. In addition, the high working temperature and preheating process for each layer canensure a uniform heat input and a much lower cooling rate. Hence, the EBM processcan significantly prevent the parts from delamination failure caused by residual stress. Accordingly, this research work is intended to investigate the EBM processability and geometrical freedom/accuracy of EBM made copper components. The 99.95% pure Cu powder with a particle size range of 45-100μm are used to produce samples. All the samples are built with a certain layer thickness of 50μm with altering parameters, including the processing temperature, line offset, focus offset, beamspeed, and beam current. It is found that the processing temperature of 500°C leadsto low density and severe lateral melting/sintering. Accordingly, the temperature is lowered to 450°C, 400°C, 350°C, and 310°C to control the excessive lateral melting. Since dense parts could only be produced above 400°C, this work focuses on developing 400°C processing temperature with different line offset, focus offset, beamspeed, and beam current. However, it is observed that the processing window of the EBM process is rather narrow, too high or too low energy input could both result in a porous part with severe distortion. After many experimental optimizations runs, the combination of the optimum parameters is reached which can deliver parts with over 99% density and a good geometrical stability. After optimization, the benchmark partsare designed and manufactured according to electrical and thermal applications (using the optimum parameters). Afterwards, the corresponding geometrical freedomand accuracy of the copper components made by EBM is assessed and discussed.Ren koppar (Cu) har egenskaper som hög optisk reflektivitet och ytans anlöning samt utmärkt termisk och elektrisk ledningsförmåga. Följaktligen möter laserbaserad additiv tillverkning (additive manufacturing, AM) olika svårigheter när det gäller att producera detta material. Däremot är elektronstrålesmältning ("electron beam melting", EBM) på väg att bli en utmärktmetod för att tillverka AM-delar av sådana material. Detta beror på att elektronstrålen inte påverkas av materialets optiska reflektivitet. Dessutom arbetar EBM under vakuum som kan skydda pulvermaterialet från oxidering. Dessutom kan den höga arbetstemperaturen och förvärmningsprocessen för varje lager säkerställa en jämn värmetillförsel och en mycket lägre kylningshastighet. EBM-processen kan därför i hög grad förhindra att delamineringsfel orsakade av restspänningar uppstår. Syftet med detta forskningsarbete är därför att undersöka EBM-processbarheten och den geometriska friheten/precisionen hos EBM tillverkade kopparkomponenter. Det 99,95 % rena Cu-pulvret med ett partikelstorleksområde på 45-100 μm används för att producera prover. Alla prover är byggda med en viss tjocklek på 50 μm med ändrade parametrar, inklusive bearbetningstemperatur, linjeförskjutning, fokusförskjutning, strålhastighet och strålström. Det har visat sig att bearbetningstemperaturen på 500°C leder till låg densitet och allvarlig lateral smältning/sintring. Följaktligen sänks temperaturen till 450°C, 400°C, 350°C och 310°C för att kontrollera den överdrivna laterala smältningen. Eftersom täta delar endast kunde produceras över 400°C, fokuserar detta arbete på att utveckla 400°C bearbetningstemperatur med olika linjeförskjutning, fokusförskjutning, strålhastighet och strålström. Det observeras dock att bearbetningsfönstret för EBMprocessen är ganska smalt, för hög eller för låg energitillförsel kan båda resultera i en porösdel med allvarlig förvrängning. Efter många experimentella optimeringskörningar uppnås kombinationen av de optimala parametrarna som kan leverera delar med över 99% densitet och en god geometrisk stabilitet. Efter optimering designas och tillverkas benchmarkdelarna i enlighet med elektriska och termiska applikationer (med optimala parametrar). Därefter bedöms och diskuteras motsvarande geometriska frihet och noggrannhet hos kopparkomponenterna tillverkade av EBM
Microstructures of electron beam melted (EBM) biomaterial Ti-6Al-4V
No full textTi-6Al-4V alloy is an attractive biomaterial. The current work evaluates the microstructures of
the solid and net-shape Ti-6Al-4V alloy produced by Electron Beam Melting (EBM) system
using SEM/EDX and optical microscope. The microstructures are influenced by the cooling rate,
processing parameters of the EBM system and re-heating of the existing layer during the melting
of subsequent layers. Layer structure and columnar grains have been observed, with growing
direction parallel to the built direction. The interior of these grains consists of alternating α / β
phases. The β phase in the colonies resembles rod shape embedded in the α platelet. Along the
grain boundaries more or less continuous α layers were observed. In comparison to solid
samples uneven surfaces and pores were seen in the net shape structure. Microhardness
evaluation of the EBM produced alloys was also carried out and compared with conventionally
produced alloys
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
Kritische Bewertung von RCTs nach einem EBM-Grundkurs im dritten Studienjahr im Vergleich zur Expertenbewertung
No full textIntroduction: An essential aim of courses in evidence-based medicine (EBM) is to improve the skills for reading and interpreting medical literature adequately. Regarding the conceptual framework, it is important to consider different educational levels.Aim: Our primary aim was to investigate the applicability of different instruments for the assessment of methodological study quality by 3rd grade students after short courses in EBM. Our secondary outcomes were agreement with expert assessments and student's knowledge and competences.Methods: We conducted four short courses in EBM of 90 minutes each for health care management and medical students focused on critical appraisal of the literature. At the end, the students assessed five publications about randomized controlled trials (RCTs) using five different instruments; the results were compared to expert assessments.Results: In total, 167 students participated in our EBM courses. Students' assessments showed a non-systematic over- and underestimation of risk of bias compared to expert assessments with no clear direction. Agreement with expert assessments ranged between 66% to over 80%. Across RCTs, evidence was found that the choice of instrument had an impact on agreement rates between expert and student assessments (p=0.0158). Three RCTs showed an influence of the instrument on the agreement rate (p<0.05 each). Discussion: Our results contrast sharply with those of many other comparable evaluations. Reasons may be a lack of students' motivation due to the compulsory courses, and the comparison to a reference standard in addition to self-ratings causing objectivity.Conclusion: Undergraduates should become familiar with the principles of EBM, including research methods, and the reading of scientific papers as soon as possible. For a deeper understanding, clinical experience seems to be an indispensable precondition. Based on our results, we would recommend an integration of lectures about EBM and critical appraisal at least twice during studies and with greater intensity shortly before graduation.Einleitung: Ein wesentliches Ziel von Kursen in evidenzbasierter Medizin (EBM) ist die Verbesserung von Fähigkeiten für adäquates Lesen und Interpretieren medizinischer Fachliteratur. Hinsichtlich der Konzeption ist es wichtig, unterschiedliche Ausbildungsgrade zu berücksichtigen.Ziel: Primäres Ziel war die Untersuchung der Anwendbarkeit verschiedener Instrumente zur Bewertung der methodischen Qualität von publizierten Studien durch Studenten im dritten Studienjahr nach einem Kurzlehrgang in EBM. Sekundäre Ziele waren Übereinstimmung mit Experten-Bewertungen sowie Kenntnisse und Kompetenzen der Studenten.Methoden: Vier Veranstaltungen zur EBM von jeweils 90 Minuten wurden für Medizinmanagement- und Medizinstudenten mit dem Fokus auf die kritische Bewertung von Literatur in Hinblick auf ein Bias-Risiko durchgeführt. Am Ende bewerteten die Studenten fünf Publikationen über randomisierte klinische Studien (RCTs) mit fünf verschiedenen Instrumenten; die Ergebnisse wurden mit Bewertungen von Experten verglichen.Ergebnisse: Insgesamt nahmen 167 Studenten an den EBM-Kursen teil. Im Vergleich zu den Experten-Bewertungen zeigten die Bewertungen der Studenten eine nicht systematische Über- und Unterschätzung des Bias-Risikos ohne erkennbare Richtung. Die Übereinstimmung mit den Experten-Bewertungen reichte von 66% bis über 80%. Für die RCTs zeigte sich, dass die Auswahl des Instruments einen Einfluss auf die Übereinstimmungsrate zwischen studentischen und Experten-Bewertungen hatte (p=0,0158). Bei drei RCTs konnte ein Einfluss des Instruments auf die Übereinstimmungsrate festgestellt werden (jeweils p<0,05).Diskussion: Die Ergebnisse stehen in starkem Widerspruch zu denen vieler anderer, vergleichbarer Erhebungen. Gründe können in der mangelnden Motivation der Studenten für die Pflichtveranstaltung liegen. Es ist aber auch möglich, dass der Vergleich mit einem Referenzstandard als Ergänzung zu Selbstauskünften zu Objektivität führte.Schlussfolgerung: Nicht graduierte Studenten sollten mit den Prinzipien der EBM so früh wie möglich vertraut gemacht werden, ebenso mit Forschungsmethoden und der Lektüre von wissenschaftlichen Publikationen. Für ein tieferes Verständnis scheint klinische Erfahrung eine unverzichtbare Voraussetzung zu sein. Auf der Basis unserer Ergebnisse empfehlen wir, Veranstaltungen zur EBM und kritischen Bewertung mindestens zweimal im Studienverlauf und mit größerer Intensität kurz vor dem Abschluss durchzuführen
Continuous Reduced-Order Dynamic Model Based on Energy Balancing for Inductive Power Transfer Systems
No full textResonant circuits are commonly used in inductive power transfer (IPT) systems for the charging of electric vehicles because of the high power efficiency. Transient behaviors of the resonant circuits, which play a significant role in the design and analysis of IPT systems, are cumbersome to model analytically because of the high-order. This article develops a reduced-order continuous dynamic model based on the energy interactions among the resonant tanks. By applying the proposed energy balancing method (EBM), the order of the dynamic model is reduced to half of the number of the passive components in the resonant circuits. To show the accuracy of the EBM, the dynamics of a series-series (SS) compensated IPT system are modeled using Laplace phasor transformation (LPT) and EBM separately and the results are compared. The order of the EBM is found to be one-fourth of that of the LPT method. The sensitivity of the EBM to the switching frequency is discussed when the zero voltage switching turn-on operation is attained. Besides, to prove the advantage of reducing the order of the dynamic model, model predictive controls (MPCs) based on EBM and LPT are developed. The transient performances of the MPC controllers are simulated and the control inputs are applied to an experimental setup. Finally, experiments are conducted to verify the accuracy of the proposed EBM under zero and nonzero conditions and the effectiveness of the developed MPC controller.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.DC systems, Energy conversion & Storag
How can we teach EBM in clinical practice? : an analysis of barriers to implementation of on-the-job EBM teaching and learning
No full textIntroduction: Evidence-based medicine (EBM) improves the quality of health care. Courses on how to teach EBM in practice are available, but knowledge does not automatically imply its application in teaching. We aimed to identify and compare barriers and facilitators for teaching EBM in clinical practice in various European countries. Methods: A questionnaire was constructed listing potential barriers and facilitators for EBM teaching in clinical practice. Answers were reported on a 7-point Likert scale ranging from not at all being a barrier to being an insurmountable barrier. Results: The questionnaire was completed by 120 clinical EBM teachers from 11 countries. Lack of time was the strongest barrier for teaching EBM in practice (median 5). Moderate barriers were the lack of requirements for EBM skills and a pyramid hierarchy in health care management structure (median 4). In Germany, Hungary and Poland, reading and understanding articles in English was a higher barrier than in the other countries. Conclusion: Incorporation of teaching EBM in practice faces several barriers to implementation. Teaching EBM in clinical settings is most successful where EBM principles are culturally embedded and form part and parcel of everyday clinical decisions and medical practice
Isothermal Oxidation Behavior of EBM-Additive Manufactured Alloy 718
No full textOxidation of Alloy 718 manufactured by electron beam melting (EBM) process has been undertaken in ambient air at 650, 700, and 800 degrees C for up to 168 h. At 800 degrees C, a continuous external chromia oxide enriched in (Cr, Ti, Mn, Ni) and an internal oxide that was branched structure of alumina formed, whereas at 650 and 700 degrees C, a continuous, thin and protective chromia layer was detected. The oxidation kinetics of the exposed EBM Alloy 718 followed the parabolic rate law with an effective activation energy of similar to 248 +/- 22 kJ/mol in good agreement with values in the literature for conventionally processed chromia-forming Ni-based superalloys. The oxide scale formed on the surface perpendicular to the build direction was slightly thicker, and more adherent compared to the scale formed on the surface along the build direction, attributed to the varied grain texture in the two directions of the EBM-manufactured specimens. The increased oxygen diffusion and high Cr depletion found on the surface along the build direction were attributed to the fine grains and formation of vacancies/voids along this grain orientation.</p
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