170,235 research outputs found
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
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
Investigation of the structure and the crystallization behavior of precursor-derived Si-C-N and Si-B-C-N ceramics with X-ray and neutron diffraction
No full textDie atomare Nahordnung und die mittelreiweitige Struktur amorpher Si-C-N- und Si-B-C-N-Keramiken wurde mit Röntgen- und Neutronenbeugung untersucht. Ein Vergleich der Strukturfaktoren S(Q) von Si-C-N-Keramiken, die sich in ihrer chemischen Zusammensetzung unterscheiden, mit den S(q) von amorphem Kohlenstoff und amorphem Si3N4, hat gezeigt, dass die S(q) der Keramiken ein gewichtetes Mittel dieser beiden S(q) darstellen. Die amorphen Si-C-N-Keramiken setzen sich also zuammen aus einer amorphen graphitartigen Phase und amorphem Si3N4 und die partiellen S(q) für diese beiden Phasen konnten mit der so genannten Konzentrations-Kontrast-Variation gewonnen werden. Die partiellen S(q) der amorphen Kohlenstoffphase in den Si-C-N-Keramiken wurden mit einem Strukturmodell für amorphen Kohlenstoff simuliert. Diese Simulation hat ergeben, dass die atomare Anordnung der amorphen Kohlenstoffphase in Si-C-N-Keramiken innerhalb der Kohlenstoffebenen der Ordnung in amorphem Kohlenstoff entspricht, die Ordnung zwischen den Ebenen jedoch weniger ausgeprägt ist. Bei einer detailierten Untersuchung der Parrkorrelationsfunktion von Si-B-C-N-Keramiken wurden zusätzliche B-N-Bindungen gefunden, wobei die Boratome in einer hexagonalen Struktur eingebaut sind. Die B-N-Bindungen in der amorphen BN-C Phase erstrecken sich im Gegensatz zu den C-C Bindungen nur über einen beschränkten Bereich. Die Kleinwinkelbeugung zeigt ebenfalls eine Separation in zwei amorphe Phasen. Kristallistion beginnt bei den Si-C-N-Keramiken je nach Kohlenstoffgehalt bei 1200-1400°C. Man findet Reflexe von a- und b-Si3N4 und SiC. Zwischen 1400-1500°C findet eine Zersetzung der Si3N4-Phase in SiC und Stickstoff statt. Im Gegensatz zu den Si-C-N-Keramiken sind in den Si-B-C-N-Keramiken bei 1400°C nur SiC Nanokristallite mit einer Größe von etwa 2nm vorhanden. Ab 1700°C entsteht krist. Si3N4. Hochtemperaturstabile Si-B-C-N-Keramiken zeigen nicht die erwartete Reaktion von Si3N4 mit Kohlenstoff bei etwa 1480°C.The atomic short-range order and the medium range structure of amorphous Si-C-N and Si-B-C-N ceramics was investigated by X-ray and neutron scattering. Comparison of the structure factors S(q) of Si-C-N ceramics which differ in chemical composition with those of amorphous carbon and amorphous silicon nitride revealed that the S(q) of the ceramics are a weighted average of these two S(q). So the amorphous Si-C-N ceramics consist of an amorphous graphite like phase and of amorphous silicon nitride and the partial S(q) for these two phases could be derived by the so called concentration contrast variation method. The partial S(q) of the amorphous carbon phase in Si-C-N ceramics were simulated with a structure model for amorphous carbon. The simulation showed that the atomic arrangement of the amorphous carbon phase in Si-C-N ceramics in the layers is equal to amorphous carbon, but the order between the layers is less pronounced. A detailed investigation of the pair correlation functions of Si-B-C-N ceramics revealed additional B-N bonds where the boron atoms are incorporated in a hexagonal structure. The B-N bonds in the amorphous BN-C phase exist only within a restricted correlation range in contrast to the C-C bonds. Small angle scattering also shows the separation in two amorphous phases. Crystallisation in Si-C-N ceramics starts at 1200-1400°C depending on their carbon content. Reflections from alpha- and beta-silicon nitride and SiC are observed. Between 1400°C and 1500°C the silicon nitride phase decomposes into SiC and nitrogen. In contrast to the Si-C-N ceramics, only SiC nanocrystallites with a size of about 2nm were found in the Si-B-C-N ceramics after annealing at 1400°C. At 1700°C crystalline silicon nitride is formed. High-temperature stable Si-B-C-N ceramics do not show the expected reaction of silicon nitride with carbon at about 1480°C
Thermochemie und Konstitution von Si-(B-)C-N Precursorkeramiken
No full textIn the present work the phase equilibria and phase reactions of Si-C-N and Si-B-C-N precursor-derived ceramics were studied by means of the CALPHAD method combined with experimental studies: e. g. DTA/TG, XRD, HRTEM and SEM. Thermodynamic calculations of different types of phase diagrams, phase fraction diagrams and phase composition diagrams in regard to the reaction behavior of Si-C-N and Si-B-C-N ceramics were carried out using software such as THERMO-CALC. Consistent Scheil's reaction schemes for the systems Si-C-N and Si-B-C-N are presented. The thermal degradation of precursor-derived Si-C-N ceramics has been characterized quantitatively by taking into account the endothermic phase reactions Si3N4+3C = 3SiC+2N2 and Si3N4 = 3Si+2N2. Because of the first reaction the thermal stability of the Si-C-N ceramics is limited to about 1550°C. The results of the thermodynamic calculations are in good agreement with the experimental results and describe very well quantitatively the high temperature behavior of the ceramics. The incorporation of boron in Si-C-N ceramics can increase the thermal stability up to 2000°C. Both effects, i. e. (1) decreased carbon activity and (2) encapsulation effect cause the high temperature stability of Si-B-C-N ceramics. A model for the phase formation was developed which can describe qualitatively the dependence of thermal stability on material composition. The thermal expansion behavior and the thermal diffusivity of some precursor-derived amorphous Si-C-N and Si-B-C-N ceramics were studied applying differential dilatometry and the laser flash method, respectively. No glass transition was detected for these amorphous ceramic materials. The thermal expansion coefficients of these ceramics are comparable with those of crystallized Si3N4. The thermal conductivities of these ceramics are much lower than those of crystallized Si3N4 and SiC. In addition, phase reactions of polymer-precursors of the system Si-C-N-H and resulting compositions were also calculated by the CALPHAD method.In der vorliegenden Arbeit wurde die Konstitution von Keramiken der Systeme Si-C-N und Si-B-C-N umfassend untersucht. Hierzu wurden thermodynamische Berechnungen (CALPHAD-Methode) mit experimentellen Untersuchungen (DTA/TG, XRD, REM, TEM) kombiniert. Es wurden verschiedenartige Phasendiagramme und Phasenmengendiagramme für die Systeme Si-C-N und Si-B-C-N berechnet. Aus den berechneten Phasendiagrammen wurden die Scheil-Reaktionsschemata der Systeme Si-C-N und Si-B-C-N entwickelt. Das Hochtemperaturverhalten der Si-C-N-Precursorkeramiken wurde quantitativ unter Berücksichtigung der zwei wichtigen Reaktionen Si3N4+3C=3SiC+2N2 und Si3N4=3Si+2N2 charakterisiert. Die CALPHAD- Simulationsrechnungen stimmen mit den experimentellen Ergebnissen gut überein. Ein Modell für die quantitative Beschreibung der Hochtemperaturstabilität der Si-B-C-N-Precursorkeramiken wurde vorgeschlagen. Beide hierfür angenommenen Effekte (1) geringere Kohlenstoffaktivität und (2) Einkapseleffekt führen zur Hochtemperaturstabilisierung der Si-B-C-N Keramiken. Für die Phasenbildung der Si-(B-)C-N-Precursorkeramiken wurde ein Modell entwickelt, das qualitativ die thermische Stabilität in Abhängigkeit von der Zusammensetzung des Materials beschreiben kann. Es wurden noch die thermophysikalischen Eigenschaften der amorphen Si-C-N- und Si-B-C-N-Precursorkeramiken mit der Differenzdilatometrie und der Laser-Flash-Methode untersucht. Die thermischen Ausdehnungskoeffizienten der Keramiken sind mit denen von kristallisiertem Si3N4 vergleichbar. Die amorphen Precursorkeramiken weisen keine Glastransformation auf und sind daher trotz der glasartigen Struktur der Si3+y/4CyN4-y-Phase im Sinne der Definition keine Gläser. Die Wärmeleitfähigkeiten sind viel niedriger als die von kristallisiertem Si3N4 und SiC. Zum näheren Verständnis der bei der Thermolyse ablaufenden Kondensationsmechanismen wurden außerdem in dieser Arbeit die Phasengleichgewichte im System Si-C-N-H berechnet
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Verformung und bruchmechanische Eigenschaften von Si-C-N-Precursorkeramiken
No full textThis thesis deals with the investigation of the deformation and fracture mechanical properties of precursor-derived (PDC) Si-C-N ceramics. The materials were synthesized from a liquid poly(ureamethylvinyl)silazane precursor. In order to access the intrinsic mechanical behavior of the materials, fully dense defect-free PDC specimens devoid of process induced extrinsic features were fabricated using a special casting and crosslinking process and controlled thermolysis procedures. The investigations were performed on a range of Si-C-N-(H) PDC with progressively varying material structures from hydrogenated amorphous to phase-separated nanocrystalline microstructures, from which the influence of material structure on the mechanical behavior was analyzed.
The crack-tip fracture toughness (KI0) of the materials were evaluated using the novel crack opening displacement (COD) method. The estimated KI0 values ranged from 0.6 to 1.2 MPa m1/2. The variation in KI0 was well correlated with the structural evolution in the materials, effected by the progressive stripping of the one-fold coordinated hydrogen in the amorphous materials leading to increased network connectivity, and the nucleation and growth of turbostratic graphite (TG) and nanocrystalline SiC in the phase-separated materials. The net change in the resistance to fracture in these materials was effected by the change in the average fracture surface energy and crack deflection toughening. Crack deflection observed even in the amorphous materials revealed the presence of structural and compositional inhomogeneities. To further understand the cause and effect of crack deflection in terms of crack tip damage mechanisms, roughness analysis of fracture surfaces was carried out using the fractal approach. The analysis revealed self-affine scaling up to a correlation length of around 50 nm and a self-affine roughness exponent (ζ) of 0.8 ± 0.1 in all the materials, the latter in agreement with the universal roughness exponent conjectured in literature. However, no correlation was observed between the observed roughness exponents and the fracture toughness of the corresponding materials. Examination of the crack opening near the crack tip by high resolution AFM imaging revealed no persistent damage cavities along the crack, concluding that the fracture in the investigated Si-C-N ceramics proceeded in a brittle manner in the resolvable length scales, at crack velocities employed in the present experiments.
The deformation behavior of the present Si-C-N ceramics under contact loading conditions was investigated using spherical as well as sharp (Vickers and Berkovich) indentation experiments. The elastic moduli and nanoindentation hardness evaluated from the analysis of the nanoindentation load-displacement curves correlated well with the evolution of material resistance to elastic and plastic deformation, commensurate with the structural and microstructural evolution in the materials. Analysis of the elastic and plastic deformation work quantities derived from the load-unload cycle in the Berkovich nanoindentation enabled the discrimination of the different plastic deformation characteristics of the amorphous and phase segregated materials. The equi-proportional variation of elastic and plastic deformation in the amorphous Si-C-N materials identical to vitreous silica indicated the anomalous character of plastic deformation in these materials that induced appreciable strain hardening under progressive densification. This was manifested in the load-dependant increase in hardness. The contrasting variation of plastic deformation work in the phase-separated materials indicated the emergence of an additional plastic deformation mechanism in these materials, that proceeded by a shear deformation promoted by the TG-phase. The anomalous densification behavior in amorphous Si-C-N materials also led to a load dependence of the strain rate sensitivity (m), also observed in vitreous silica, and controlled the evolution of indentation size effect (ISE). The magnitude and direction of ISE was determined by the relative dominance of the two concurrent effects, namely strain hardening and indentation creep deformation. The evolution of strain rate sensitivity in the range of investigated materials showed good agreement with the cluster model, which relates the increase in the number density of isolated regions in the microstructure to a corresponding increase in m. The non-densifying shear mode of plastic deformation in phase-separated materials led to a decrease in the strain hardening capability, increase in m and increased vulnerability to ISE.In der vorliegenden Dissertation wird die Untersuchung der Verformung und der bruchmechanischen Eigenschaften von Si-C-N-Precursorkeramiken (precursor-derived ceramics, PDC) beschrieben. Die Hauptziele der vorliegenden Arbeit waren (i) die intrinsischen mechanischen Eigenschaften der Si-C-N-Precursorkeramiken zu bestimmen und (ii) die me¬chanischen Eigenschaften dann mit der Struktur der Materialien, die bei der mehrstufigen Phasenbildung während der Precursor-zu-Keramik Umwandlung entsteht, zu korrelieren. Mit dieser Ziele wurden völlig dichte defektfreie keramische Proben mit Strukturen, vom organisch amorphen bis zum anorganisch nano-kristallinen Zustand durch thermische Vernetzung und temperaturkontrollierte Thermolyse eines flüssigen Poly(ureamethylvinyl)silazan-Precursorpolymers hergestellt. Strukturelle Veränderungen der amorphen Probenmaterialien wurden durch die fortschreitende Entfernung des Wasserstoffs im Verlauf der Thermolyse und die damit einhergehende kontinuierliche Zunahme der Strukturver¬dichtung festgestellt. Die Be¬seitigung des Wasserstoffs führte bei 1200°C zu einer Phasenausscheidung durch Überführung des überschüssigen freien Kohlenstoffs in eine turbostrati¬sche Graphitphase (TG-Phase) und bei 1300°C zur Keimbildung von nano-kri¬stallinem SiC (n-SiC).
Für die bruchmechanische Charakterisierung diente als Bewertungskriterium die Bruchzähigkeit an der Rissspitze („crack-tip toughness“, kritischer Spannungsin¬tensitätsfaktor an der Rissspitze, KI0), wozu eine neu entwickelte Rissöffnungspro¬fil-Methode (crack-opening displacement, COD) eingesetzt wurde. In Abhängigkeit vom Umwandlungs¬grad der Materialien wurden KI0-Werte von 0.6 bis 1,2 MPam1/2 ermittelt. Die Zunahme des Bruchwiderstandes der amorphen Materialien kann auf die zu¬nehmende Vernetzung durch die kontinuierliche Entfernung des Wasserstoffs zu¬rückgeführt werden. Durch die daraus resultierende Erhöhung des Vernetzungsgrades wurde auch die nanoskalige Rissablenkung in amorphen Materialien erhöht. Andererseits steuerten die Pfade mit niedrigerer Oberflächenenergie im Gefüge, die auf die Separierung der TG-Phase zurückzuführen sind, die Mikromechanik der Riss¬ausbreitung in phasengetrennten Materialien. Die Netto-Änderung des Bruchwiderstandes in diesen Materialien erfolgte sowohl durch die Änderung der durchschnittlichen Bruch¬oberflächenenergie als auch durch eine Zunahme der Rissablenkung. Die Rauhigkeit der Bruchoberflächen wurde mit der fraktalen Annäherung analysiert. Die Fraktal¬analyse ergab eine Korrelationslänge (ξ) von ca. 50 nm und einen Rauhigkeitsexponent (ζ) von 0.8 ± 0.1 in allen Materialien. Dieser Wert stimmt mit dem Universalrauhigkeitsexponent, der, nach Bouchaud et al. bei 0.8 liegt, überein. Es wurde jedoch keine Wechselwirkung zwischen den ermittelten Rauhigkeitsexponenten und der Bruchzähigkeit der entsprechenden Materialien festgestellt. Die Prüfung der Rissöffnung in der Nähe der Rissspitze ließ keine Beschädigungs¬kavitäten entlang des Bruches erkennen. Daraus ist zu schließen, dass der Bruch in den untersuchten Si-C-N-Keramiken soweit mit den gegebenen Abbil¬dungstechniken erkennbar als reiner Sprödbruch verlief.
Das elastische und plastische Verformungsverhalten der untersuchten Si-C-N-Keramiken unter Kontaktbelastungsbedingungen wurde durch Eindruckexperimente untersucht. Die Elas¬tizitätsmodule und Härte, die sich aus der Nanoindentation-Last-Eindrucktiefe Kurven ergaben, stimmten mit dem Materialwiderstand gegen die elastische und plastische Verformung der jeweiligen Materialien überein. Die equiproportionale Änderung der Eindrucksarbeit der elastischen und plasti¬schen Verformung in amorphen Materialien zeigte den anomalen Charakter der plastischen Verformung, die bei der Materialverdichtung stattfand. Der Materialverdichtung führte in den amorphen Materialien zu einer Kaltverfesti¬gung. Die Größe der Kaltverfestigung sowohl von der angewandten Belastung als auch von der Belastungsrate abhängt. Die entgegen¬gesetzte Entwicklung der Verformungsarbeit in den phasengetrennten Materia¬lien zeigte das Auftreten einer zusätzlichen Form von plastischer Verformung, die durch die Scherverformung der TG-Phase gefördert wurde. Die Kapazität der phasen¬getrennten Materialien für die Verfestigung war niedriger als bei den amorphen Materialien. Die beiden Modi der plastischen Verformung beein¬flussten auch die Lastabhängigkeit der Härte (indentation size effect, ISE). Das Ausmaß der ISE scheint durch die relative Dominanz von Eindruck-Kriechverformung und Fähigkeit zur Kaltverfestigung bestimmt zu werden. Die Änderung der Dehnraten¬empfindlichkeit der untersuchten Si-C-N-Materialien stimmte mit dem sogenannten „cluster model“ des Materialflusses überein. Der entgegengesetzte Einfluss der Belastung auf die Dehnratenempfindlichkeit der amorphen und phasengetrennten Materialien verdeutlicht wiederum deres unterschiedlich wirksamen Verformungsmechanismen
IGF-1 and PDGF-bb Suppress IL-1β-Induced Cartilage Degradation through Down-Regulation of NF-κB Signaling: Involvement of Src/PI-3K/AKT Pathway
No full textInterleukin-1β (IL-1β) is a pro-inflammatory cytokine that plays a key role in the pathogenesis of osteoarthritis (OA). Growth factors (GFs) capable of antagonizing the catabolic actions of cytokines may have therapeutic potential in the treatment of OA. Herein, we investigated the potential synergistic effects of insulin-like growth factor (IGF-1) and platelet-derived growth factor (PDGF-bb) on different mechanisms participating in IL-1β-induced activation of nuclear transcription factor-κB (NF-κB) and apoptosis in chondrocytes.Primary chondrocytes were treated with IL-1β to induce dedifferentiation and co-treated with either IGF-1 or/and PDGF-bb and evaluated by immunoblotting and electron microscopy.Pretreatment of chondrocytes with IGF-1 or/and PDGF-bb suppressed IL-1β-induced NF-κB activation via inhibition of IκB-α kinase. Inhibition of IκB-α kinase by GFs led to the suppression of IκB-α phosphorylation and degradation, p65 nuclear translocation and NF-κB-regulated gene products involved in inflammation and cartilage degradation (COX-2, MMPs) and apoptosis (caspase-3). GFs or BMS-345541 (specific inhibitor of the IKK) reversed the IL-1β-induced down-regulation of collagen type II, cartilage specific proteoglycans, β1-integrin, Shc, activated MAPKinase, Sox-9 and up-regulation of active caspase-3. Furthermore, the inhibitory effects of IGF-1 or/and PDGF-bb on IL-1β-induced NF-κB activation were sensitive to inhibitors of Src (PP1), PI-3K (wortmannin) and Akt (SH-5), suggesting that the pathway consisting of non-receptor tyrosine kinase (Src), phosphatidylinositol 3-kinase and protein kinase B must be involved in IL-1β signaling.The results presented suggest that IGF-1 and PDGF-bb are potent inhibitors of IL-1β-mediated activation of NF-κB and apoptosis in chondrocytes, may be mediated in part through suppression of Src/PI-3K/AKT pathway, which may contribute to their anti-inflammatory effects
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
A 0.12mm<sup>2</sup> Wien-Bridge Temperature Sensor with 0.1°C (3σ) Inaccuracy from -40°C to 180°C
No full text Resistor-based temperature sensors can achieve much higher resolution and energy efficiency than conventional BJT-based sensors [1], but they typically occupy more area (> 0.25 mm 2 ) and have lower operating temperatures (le 125 {circ} {C}) [2]-[4]. This work describes a 0.12mm 2 resistor-based sensor that uses a Wien-bridge (WB) filter to achieve 0.1 {circ} {C} (3 sigma) inaccuracy from - 40 {circ} {C} to 180 {circ} {C}. Compared to a state-of-the-art WB sensor [4], it occupies 6 × less area and achieves comparable relative accuracy over a 76% wider operating range. Session 10.3 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 InstrumentationMicroelectronic
A ±25A Versatile Shunt-Based Current Sensor with 10kHz Bandwidth and ±0.25% Gain Error from -40°C to 85°C Using 2-Current Calibration
No full textAccurate current sensing is critical in many industrial applications, such as battery management and motor control. Precise shunt-based current sensors have been reported with gain errors of less than 1% over the industrial temperature range (-40°C to 85°C) [1]–[4]. However, since they are intended for coulomb counting, their bandwidth is limited to a few tens of Hz, making them unsuitable for battery impedance or motor-current sensing. This paper presents a current sensor with a wide (10kHz) bandwidth and a tunable temperature compensation scheme (TCS), which allows it to be flexibly used with different types of shunts while maintaining high accuracy. A low-cost room-temperature calibration scheme is proposed to optimize gain flatness over temperature by exploiting the shunt's self-heating at large currents. Over the industrial temperature range and a ±25A current range, it achieves state-of-the-art gain error (±0.25%) with both low-cost PCB and stable metal-alloy shunts.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 InstrumentationMicroelectronic
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