439 research outputs found
A review on graphene and graphene composites for application in electromagnetic shielding
No full text<p>This document is an author version of review paper ragarding new shielding materials. <span>To design an EMI shielding product, a compromise must be achieved between the electromagnetic shielding efficiency, the thickness of shielding materials, durability, mechanical strength, reduced volume and weight, and elasticity. Due to its ability to block EMWs, flexibility, lightweight, and chemical resistivity, graphene has been identified as a promising candidate material for efficient EMI shielding. Herein, we reviewed the studies that investigated various graphene-based composites as potential EMI shielding materials, with a focus on the composites based on graphene and silver nanowires due to their high EMI shielding efficiency, low production price, and favorable mechanical properties. </span></p>
PENGARUH MODEL PEMBELAJARAN BU EMI TERHADAP PRESTASI MENULIS CERKAK SISWA KELAS IX DI SMP NEGERI 1 BAURENO KABUPATEN BOJONEGORO
No full textWe know that writing skills in literature learning are skills that cannot be considered easy. Because this skill will certainly require a person's ability to be able to express ideas, ideas, thoughts and feelings so that they can become a work of art. Even other people can understand and feel the benefits of the work. So the learning outcomes that have been achieved by a school, whether high or low or good or bad, will really depend on the learning process. In particular, what learning experiences have been experienced and learned by the student. Because after all, experience is the best teacher. The author, as a Javanese language teacher, is fully aware that there are many students and students with different characteristics. Characteristics, abilities, knowledge, understanding, and so on in an effort to practice the material presented are certainly different. The aim of this research is to find out whether the BU EMI Model can improve the Cerkak writing achievement of class IX students at SMP Negeri 1 Baureno, Bojonegoro Regency. In this way, the Javanese language teaching and learning process is more effective and provides optimal results for students. Data resulting from the practical application of learning innovation at the first meeting, students seemed reluctant to write personal experiences into a Cerkak. Most likely this is because students generally feel they are not used to writing Cerkak and therefore find it difficult. That kind of thinking needs to be dismissed by using innovative learning models. Then the author tried to use the BU EMI Model. It turned out that class IX students became more enthusiastic. This can certainly increase students' grades in learning Cerkak Writing. In the end, this can also improve student achievement in learning Cerkak Writing. Cerkak is difficult. Such thinking needs to be pushed aside by using innovative models. Then the author uses this EMI BU Model. It turned out that class IX students became more enthusiastic. This certainly can increase student scores in Writing Cerkak. In the end it can also increase student achievement in learning Cerkak Writing
A High-Linearity and Low-EMI Multilevel Class-D Amplifier
No full textThis article presents a Class-D audio amplifier for automotive applications. Low electromagnetic interference (EMI) and, hence, smaller LC filter size are obtained by employing a fully differential multilevel output stage switching at 4.2 MHz. A modulation scheme with minimal switching activity at zero input reduces idle power, which is further assisted by a gate-charge reuse scheme. It also achieves high linearity due to the high loop gain realized by a third-order feedback loop with a bandwidth of 800 kHz. The prototype, fabricated in a 180-nm high-voltage BCD process, achieves a minimum THD+N of -107.8 dB/-102 dB and a peak efficiency of 91%/87% with 8- and 4-Ω loads, respectively, while drawing 7-mA quiescent current from a 14.4-V supply. The prototype meets the CISPR 25 Class 5 EMI standard with a 5.7-dB margin using an LC filter with a cutoff frequency of 580 kHz.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 InstrumentationElectrical Engineering, Mathematics and Computer ScienceMicroelectronic
Twinning for graphene-based composites in EMI shielding
No full textInternational audienceIn the era of intensive development of microelectronics, energy, and car industries along with Radio-Frequency (RF) telecommunications, the pollution caused by Electromagnetic Waves (EWs) is ever-present. EW interferences (Electromagnetic Interference-EMI) exhibit perturbation and negative impact on devices and systems including those used in everyday life as well as on the specialized, sensitive, and sophisticated instruments used in research laboratories. EMI could cause untrusted signals and RF noise. To prevent these issues, materials able to block or absorb the radiated EWs are urgently required. The GrInShield project is focused on developing new graphene-based shielding nano-materials and increasing researchers' expertise in EMI shielding measuring, protective materials, and possibilities to bring these new products to the market. INTRODUCTION: The GrInShield project uses graphene oxide (GO) obtained by Hummers' reaction and electrochemical exfoliation of graphite [1,2]. We have analysed the factors that affect the shielding efficiency of materials [3] and studied the reaction conditions that lead to obtaining graphene with different sizes and oxygen content [4]. RESULTS AND DISCUSSION: The GrInShield project aims to produce composites of GO with silver nanowires (AgNWs) to develop GO-AgNW composites for EMI shielding applications. To achieve these goals, the project gathers experts from the chemistry of nanomaterials, and polymer processing, along with specialists for near-field microscopy tools and radiofrequency (RF) characterization of materials. CONCLUSIONS: The GrInShield project is developing new nanomaterials for EMI shielding based on carbon nanomaterials, metallic nanomaterials, and polymers. The fabrication of low-cost, sustainable, eco-friendly, durable EMI shielding material should be achieved
Twinning for graphene-based composites in EMI shielding
No full textIn the era of intensive development of microelectronics, energy, and car industries along with Radio-Frequency (RF) telecommunications, the pollution caused by Electromagnetic Waves (EWs) is ever-present. EW interferences (Electromagnetic Interference-EMI) exhibit perturbation and negative impact on devices and systems including those used in everyday life as well as on the specialized, sensitive, and sophisticated instruments used in research laboratories. EMI could cause untrusted signals and RF noise. To prevent these issues, materials able to block or absorb the radiated EWs are urgently required. The GrInShield project is focused on developing new graphene-based shielding nano-materials and increasing researchers' expertise in EMI shielding measuring, protective materials, and possibilities to bring these new products to the market. INTRODUCTION: The GrInShield project uses graphene oxide (GO) obtained by Hummers' reaction and electrochemical exfoliation of graphite [1,2]. We have analysed the factors that affect the shielding efficiency of materials [3] and studied the reaction conditions that lead to obtaining graphene with different sizes and oxygen content [4]. RESULTS AND DISCUSSION: The GrInShield project aims to produce composites of GO with silver nanowires (AgNWs) to develop GO-AgNW composites for EMI shielding applications. To achieve these goals, the project gathers experts from the chemistry of nanomaterials, and polymer processing, along with specialists for near-field microscopy tools and radiofrequency (RF) characterization of materials. CONCLUSIONS: The GrInShield project is developing new nanomaterials for EMI shielding based on carbon nanomaterials, metallic nanomaterials, and polymers. The fabrication of low-cost, sustainable, eco-friendly, durable EMI shielding material should be achieved.Supplementary Issue - ExcellMater Conference 2024Innovative biomaterials for novel medical devices conference : AbstractsAvailable on-line at the Journal web address: [https://www.ache.org.rs/HI/
Conducted EMI in Inverters with SiC Transistors
No full textConducted EMI in Inverters with SiC Transistors Electromagnetic Interference (EMI) is the main side effect accompanied with the fast voltage and current switching transients in power electronics applications. Compliance of the Electromagnetic Compatibility (EMC) standard is prescribed for any power electronics product before entering the market. In recent years, the new emerged wide band-gap transistor technology Silicon Carbide (SiC) exhibits great potential to replace Silicon (Si) as the dominant transistor because of its superior qualities (e.g. faster switching, higher blocking voltage and higher operating temperature). However, these advances come at the cost of increased EMI resulting from the SiC transistor’s faster switching speed and higher switching frequencies. In the past, a large variety of EMI suppression approaches have been developed for motor drive systems. However, most of them serve the conventional Si power devices (e.g. IGBT) based motor drive systems. As the result, exploration of corresponding EMI emission mechanism and new suppression approaches is critical. The desired EMC investigations should cover the following features of the SiC power devices based drive systems. \u95 The differences with the Si power devices based motor drive systems and the causes of the differences. \u95 The common EMC analysis and reduction techniques that can be used for both SiC and Si devices based motor drive systems. \u95 The approaches that improve the EMC performance for SiC devices based motor drive systems. In this thesis, with conventional Si IGBTs as the reference, systematic investigations are presented on variable speed drive systems using the latest SiC JFET as the power devices. Main achievements of this thesis are summarized as follows. System equivalent circuit modeling method for EMC performance evaluation This modeling method is used for evaluating the noise suppressing performance on varies noise propagation paths of the drive system. Additionally, by introducing the actual noise source emission instead of using idealized noise source (e.g pure square waveforms) emission, improved noise level prediction is achieved. The method is based on curve-fitting of the impedance-frequency characteristics measured on the leads of individual components and between different portions of the system. Various sub-circuits of the system are modeled as RCL composed equivalent circuits in order to represent details within the conducted frequency range. The model development procedure is presented in Chapter 3. Current transfer ratio measurements are used to verify the model. In addition, the model is also applied in Chapter 5 and 6. Chapter 5 utilizes the model to predict the noise emission levels of the SiC JFETs and Si IGBTs based motor drives respectively. Chapter 6 utilizes the model to predict the filter insertion losses. This method is applicable for both SiC and Si based motor drive systems. Characterization and cancellation of EMI filter parasitics to improve high frequency filtering performance This study explores the parasitics cancellation techniques for EMI filters with three-dimensional spatial layout that utilizes multi-layer PCB technology and employs surface mount technology (SMT) components. The employed SMT components are named x-dimensional (x-dim) components that have the same height (x=14mm) and double sided SMT electrical terminations. In addition to positioning the employed x-dimensional SMT components in the 2D plane, the components are able to be placed in a third dimension by being stacked onto more PCB layers. This extends the conventional parasitic cancellation techniques to three dimensions. Chapter 4 discusses and implements the 3D cancellation techniques in a LC filter for motor drives. The techniques enhance the filter performance especially in the high frequency range, which is critical to handle the increased EMI due to SiC fast switching speed. Comparison and identification of noise emission difference between Si IGBTs and SiC JFETs based motor drives This study compares and identifies the causes of the EMI noise emission differences between Si IGBT and SiC JFET based motor drives. In Chapter 5, two inverter prototypes – with Si IGBTs and SiC JFETs as the power transistors respectively are compared under the same power level and using the same layout. The gate drivers are designed to fully exploit the switching speed for the two types of devices at turn-on transition and to provide the same driving condition at turn-off transition. Their switching waveforms are compared under the inductive switching test condition, using one inverter leg consisting of two switches. The caused EMI level differences are clarified by Fourier analysis transformed from the time-domain measurements. In the system level, their EMI noise levels are compared under unfiltered, C filtered and LC filtered conditions. In order to identify the causes of the noise level differences, the two inverters are operated in the CM testing mode, in which the three top and bottom semiconductors are switched on or off simultaneously at a fixed 50% duty ratio. Hence the maximized CM and DM wave shapes are achieved. Improve EMI filter to accommodate SiC JFETs in motor drives In the second part of Chapter 5, the EMI filter design for SiC JFET motor drive system is improved based on the presence of different noise emissions from the Si IGBT and SiC JFET source. An equivalent circuit model is delivered to predict the noise spectrum emitted from the SiC source and stands as the basis for improving the EMI filter design. The proposed EMI method effectively suppress the increased high frequency noise resulted from the SiC faster switching dv/dts and di/dts. The modeled results agree well with the experiments. Suppression at SiC noise source due to substrate capacitive coupling Two methods to suppress the noise emission due to capacitive coupling are proposed in Chapter 6. One is to use separated substrate, the other one is to use the broadband modeling. Comparing two inverters that use the conventional heat sink and insulated metal substrate (IMS), the emitted noise levels are significantly different due to the different capacitive coupling magnitude. The first part of the Chapter proposes to use separated substrates. The second part presents a broadband modeling procedure to identify the most effective filter design to suppress the capacitive coupling. Both methods effectively suppress the noise emission to comply with the IEC61800-3-C2 standard. How EMI emission is affected by the capacitive coupling is identified.Electrical Power ProcessingElectrical Engineering, Mathematics and Computer Scienc
Hybrid Polyaniline/rGO/AgNWs Composites for High-Performance EMI Shielding
No full textAs electronic devices and wireless systems continue to expand rapidly, electromagnetic interference (EMI) has become a pressing issue, impacting both the functionality of electronic components and human well-being. Conductive polymer composites have gathered attention for EMI shielding due to their lightweight nature, mechanical flexibility, and ability to overcome the drawbacks of traditional metallic and carbon-based materials. Among the most promising fillers, reduced graphene oxide (rGO) and silver nanowires (AgNWs) stand out, offering high electrical conductivity, low percolation thresholds, and uniform dispersion within polymer matrices. In this study, novel polyaniline-based composite materials for electro- magnetic interference (EMI) shielding were developed by incorporating reduced graphene oxide (rGO), silver nanowires (AgNWs), and their hybrid (rGO/AgNWs) into a polymer matrix. To obtain flexible films with enhanced mechanical properties, the synthesized composites were incorporated into a polycaprolactone matrix. Morphology of prepared films was examined using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), while molecular structure was analyzed by FTIR and Raman spectroscopy. Electrical properties relevant to EMI shielding were evaluated using a Vector Network Analyzer (VNA). The PANI/rGO/AgNWs composite is anticipated to exhibit excellent EMI shielding performance due to uniform filler dispersion and the conductive pathways formed by metallic nanowires within the PANI matrix. This results in enhanced electrical conductivity and effective shielding, even at low filler content and minimal thickness, demonstrating strong potential for practical electromagnetic protection applications.Twenty-sixth annual conference on material science (YUCOMAT 2025), Herceg Novi, Montenegro, 1-5 September 2025
A critical genre based approach to teaching academic writing in a tertiary EFL context in Indonesia.
No full textDeposited with permission of the author. © 2005 Dr. Emi EmiliaThis thesis reports on the effectiveness of using a genre-based approach in teaching academic English writing to studnet teachers who were learning English as a foreign language in a state university
Systematic Design of EMI-Resilient Negative-Feedback Amplifiers
No full textThe information transfer capacity of negative-feedback amplifiers, and electronic circuits in general, is limited by three fundamental limitations being noise, bandwidth, and signal power. Electromagnetic Interference (EMI) is not a fundamental limitation, but it also hampers the information transfer. EMI may have such detrimental effects that malfunctioning of the electronic circuit occurs. This may result in loss of information, or worse, possibly dangerous situations. That is a reason why susceptibility to EMI is regulated by law. The ratio of the intended signal and the errors, the Signal-to-Error ratio (SER) can be regarded as a figure of merit of the signal handling performance of an amplifier for a given input signal and electromagnetic environment. EMI from out-of-band signals, i.e., signals with a frequency (much) higher than the bandwidth of the amplifier, may result in a DC shift and detection of the, in-band, low frequency envelope variations (envelope or `AM' detection) of the high frequency interference, caused by even-order nonlinearities in the active devices used. Specifically envelope detection may severely hamper the SER, since this will often be a signal in the pass band, while DC-shifts may not be in the pass band. This work focuses on reducing the errors introduced by the fundamental limitations and EMI in negative-feedback amplifiers. A systematic design approach for application specific negative-feedback amplifiers with specified SER is proposed in this work. It enables the designer to calculate noise, bandwidth, EMI, and the required bias parameters of the transistors used in application specific amplifiers in order to meet the SER requirements.micro-electronicsElectrical Engineering, Mathematics and Computer Scienc
The invisible artist: Arrangers in popular music (1950-2000): Their contribution and techniques
No full textThis thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University.This thesis is based on the research conducted by the author for the series,
Richard Niles' History of Pop Arranging, seven thirty-minute documentary
programmes for BBC Radio 2, researched, written and presented by the author and
broadcast in 2003. It also draws on interviews conducted by the author (and other
research) between 2002 and 2007 both for the radio series and for this thesis and on
the author's experience as a professional arranger in popular music working with
many of the genre's significant recording artists including Paul McCartney, Ray
Charles, Cher, Tina Turner, Westlife, Tears For Fears, Dusty Springfield, James
Brown, Pet Shop Boys, Kylie Minogue and producers including Trevor Hom, Steve
Lipson, Steve Mac and Steve Anderson.
It will be argued that the role of the arranger in popular music has often been
undervalued and that during a critical period of popular music history (1950-2000)
arrangers played a significant part in the evolution of musical content. This thesis is,
to the best of the author's knowledge, the first time (apart from the above mentioned
documentary) the subject has ever been examined. The arranger is "invisible" because musical arrangers are often un-credited on
record liner notes or in books or articles concerning popular music. A considerable
amount of research has been necessary to determine who wrote many of the
arrangements considered herein. Motown's Berry Gordy purposely kept the names of
musicians and arrangers off the records because he feared others might 'poach' the
trademark 'Motown Sound'. Other record labels considered the job of the arranger to
be reminiscent of an earlier era, diluting the Rock 'n' Roll image of emotion and
spontanaeity they wished to promote. Some producers and recording artists disliked
sharing credit for their work. Motown arranger David Van dePitte told the author that
arranging was "thankless and anonymous - a very service-oriented profession where
others often take credit for what you've done." Arranging has therefore remained an
intrinsically unseen art created by 'invisible' artists. By analyzing many recordings,
revealing the techniques and concepts they have used in their work to create popular
records, arrangers and their art will be made more 'visible'
- …
