3,275 research outputs found
LC compensators for power factor correction of nonlinear loads
No full textThis material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. Copyright @ 2004 IEEEA method is presented for finding the optimum fixed LC compensator for power factor correction of nonlinear loads where both source voltage and load current harmonics are present. The LC combination is selected because pure capacitive capacitors alone would not sufficiently correct the power factor. Optimization minimizes the transmission loss, maximizes the power factor, and maximizes the efficiency. The performance of the obtained compensator is discussed by means of numerical examples
LC compensators based on transmission loss minimization for nonlinear loads
No full textThis material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. Copyright @ 2004 IEEEThis paper presents a method employing the penalty function search algorithm to determine the LC compensator value for the optimal power factor correction in nonsinusoidal systems. The objective of the proposed method is to minimize the transmission loss while the power factor and efficiency are taken as constraints and utilized in order to solve the multiobjective optimization problem by transforming it into a single objective one. Examples show that the load nonlinearity can have a significant impact on optimal compensator sizes
Cost-effective applications of power factor correction for nonlinear loads
No full textThis material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. Copyright @ 2005 IEEEThe objective of this paper is to propose a new approach for designing passive LC compensators by using the penalty function method as an optimization tool. The performance of the cost-effective passive LC compensator for a constant load depends on the appropriate inductor and capacitor selection. Several design methods are reviewed and a novel design methodology is proposed in this paper. By using the proposed method, the designer can quickly find appropriate parameter values to meet the desired circuit performance. Simulated results show that an appropriate combination of the inductor and capacitor selected by the proposed method can meet the desired power-quality requirement. Different cases of design examples are shown in this paper to verify the performance of the proposed design methodology
A 155W −95.6 dB THD+N GaN-based Class-D Audio Amplifier With LC Filter Nonlinearity Compensation
No full textSilicon MOSFETs-based medium-power (< 50W) Class-D amplifiers (CDAs) switching in the MHz range have gained popularity in recent years, which achieves better linearity thanks to a higher loop gain in the audio band while enabling the use of LC filters with higher cut-off frequencies. However, for high-power (>100 W) CDAs, such switching frequency and high load current could lead to significant power loss. Furthermore, in the presence of a large current and voltage applied to the load, the linearity of the system can quickly degrade due to LC filter component voltage/current dependency. Without any LC filter nonlinearity compensation technique, LC components with high voltage/current rating must be used to reach high system linearity, which are often expensive and bulky. This paper presents a CDA using a GaN-based output stage to achieve high switching frequency and good efficiency simultaneously, and an integrated controller implemented in a 180nm CMOS technology to compensate for the LC filter nonlinearity. Switching at 1.8 MHz, the CDA can deliver a maximum of 155W from a 50V supply into a load with a peak efficiency of 91.7%. It achieves a peak THD+N of −95.6 dB (0.0017%) while allowing the use of cheaper and smaller nonlinear LC components.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 Components, Technology and MaterialsMicroelectronic
A - 121.5-dB THD Class-D Audio Amplifier With 49-dB LC Filter Nonlinearity Suppression
No full textClass-D audio amplifiers produce electromagnetic interference (EMI), which often needs to be suppressed by an external LC filter. However, due to component nonlinearity, this filter can itself cause significant distortion. This article presents a class-D amplifier that suppresses LC filter nonlinearity by 49 dB and is robust to ±30% variations in its cutoff frequency. This is achieved by a dual-loop architecture, in which an inner loop provides stability, while an outer loop provides the high gain needed to suppress the LC filter and output-stage nonlinearity. A prototype, implemented in a 180-nm BCD process, achieves -121.5-dB total harmonic distortion (THD) and -107.1-dB THD+N, which is maintained to within 3 dB even as the LC filter cutoff frequency is varied from 62 to 106 kHz. It can deliver a maximum of 21 W into a 4-Ω load with 87% efficiency and 12 W into an 8-Ω load with 91% efficiency, measured at 10% THD. 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
Mutual coupling between parasitic elements of split ring resonator on antenna
No full textThe parasitic elements on antenna have become an important issue in improving the antenna performance in various wireless devices. These elements are mostly used as radiator and resonator in antenna. However, an investigation of the mutual coupling between parasitic elements is rare to be found in metamaterial resonator antenna studies. From this unusual approach, this paper presents the new mutual coupling structure of parasitic elements with the split ring resonator (SRR) on antenna. The suggested antenna consists of two rectangular SRRs and conventional monopole antenna. These resonators play the role of the parasitic element in antenna. In order to operate these SRRs, linear monopole antenna is used as an active antenna which can provide the time-varying magnetic field with normal direction. In metamaterial technology, a negative effective permeability can be generated at resonant frequency via periodic arrangement of these SRRs which are electrically small LC resonant elements with a high quality factor. Fundamentally, mutual coupling phenomenon has been observed between adjacent resonators, so that the antenna with two resonators has the same effect on parasitic elements, too. In this study, the coupling coefficient between two parasitic element resonators on antenna is obtained from scattering parameter simulation results. On the basis of the electromagnetic field characteristics and the result of antenna parameter, this study will be exquisite from the previous studies of antennas that utilize the SRR
Dang Laboratory Hosts Computational Biologist Studying Pancreatic Tumor Microenvironment
No full textHien T. Dang, PhD, and Yotsawat Pomyen, PhD, first began collaborating in 2016 while they were both working at the National Cancer Institute’s Laboratory of Human Carcinogenesis (LHC). In 2024, Dr. Pomyen again joined forces with Dr. Dang–this time in her laboratory at Jefferson, where he has been working as a Fulbright Thai Visiting Scholar (see sidebar).
Dr. Pomyen, a computational biologist, specializes in primary liver cancer research and is a member of Thailand’s Initiative on Gene Expression Research–Liver Cancer (TIGER-LC). His academic background includes a Master of Science in Bioinformatics from King Mongkut’s University of Technology Thonburi, as well as a Master of Science in Modern Epidemiology and a Doctor of Philosophy (PhD) in Biostatistics & Bioinformatics from Imperial College London.
As a computational biologist, Dr. Pomyen’s expertise lies at the intersection of mathematics, biology and computer science: “With my background in bioinformatics and biostatistics, I am able to utilize, modify and manipulate any statistical and mathematical methods and combine them with a high-performance computing (HPC) facility to solve biological problems,” he says.
In addition to liver cancer, he has studied tumors of the breast, lung and bile ducts–and his computational methods can be applied to any type of cancer. While working in the Dang Lab, Dr. Pomyen has been focusing on pancreatic cancer, which often spreads to the liver, lungs or lymph nodes.
Using data from the Jefferson Molecular Profiling of Pancreatic Cancer Program, he is performing spatial transcriptome analyses in the tumor microenvironment. This work supports three key goals: understanding how normal cells and cancer cells communicate with each other; studying the specific signals they send to or exchange with each other; and identifying changes in these cellular behaviors that occur in response to existing cancer treatments.
“By applying advanced statistical methods to huge quantities of data, we can start to identify biomarkers that might help us diagnose pancreatic cancer much sooner,” he says. “In addition, we want to support development of highly targeted therapies so patients can be treated more effectively and with fewer side effects and less risk of the pancreatic cancer spreading to other organs.”
“This is the beginning of a blossoming research collaboration that will not only help us understand the biology of pancreatic cancer but also the diverse risk factors associated with pancreatic cancer,” said Dr. Dang. For more information about the Dang Laboratory, visit jefferson.edu/danglab.
The Fulbright Thai Visiting Scholar Program
Each year, the Thailand-United States Educational Foundation (Fulbright Thailand) offers up to three grants to mid-career Thai national scholars in a variety of fields to lecture, pursue research or undertake special academic-related projects in the United States.
Yotsawat Pomyen, PhD, a research scientist in the Translational Research Unit of Chulabhorn Research Institute in Bangkok, developed a proposal in collaboration with Hien T. Dang, PhD, J. Wallace Davis and Gail G. Davis Chair in Surgery and Vice Chair for Research at Jefferson.
The proposal was selected, and Dr. Pomyen began his tenure as Thai Visiting Scholar and Foster Fellow in the Dang Laboratory at Jefferson in September 2024. He is expected to return to Thailand in February 2025, with aspirations for continued collaboration with Dr. Dang
Multichannel LC ADC: to Record Atrial Electrograms
No full textBiosignals such as electoencephalogram (EEG), electrocorticogram (ECoG), atrial electrogram (AEG) etc. are being recorded from multiple channels simultaneously to improve the spatial resolution of the signals. Conventional multichannel synchronous Analog-to-Digital Converters (ADCs) are used to convert the analog continuous time signals into discrete digital values. Several biosignals have a sparsity in time domain as they have fast-rising peaks in between periods of low activity. Use of conventional synchronous ADCs for conversion of such signals is not an efficient approach as their operation is constant, irrespectiveof the activity of the input signals. Asynchronous ADCs such as level-crossing (LC) ADCs exploit the sparsity of biosignals and thus their operation is activity-dependent. However, multichannel configurations of LC ADCs do not yet exist. This problem is investigated in this work and a new ADC architecture is presented that can combine synchronous sampling with level-crossing quantisation method while converting input signals from several channels simultaneously. The synchronous LC ADC presented in this work achieves 3.37 times reduction in quantisation steps and 6 times reduction in number of output bits generated during conversion of AEG signals as compared to conventional synchronous ADCs. The problem in existing LC ADCs of data overhead in adaptive resolution technique is solved through a novel method named split resolution technique which is also presented in this work.Electrical Engineerin
Using LC/MS/MS to determine matrine, oxymatrine, ferulic acid, mangiferin, and glycyrrhizin in the Chinese medicinal preparations Shiau-feng-saan and Dang-guei-nian-tong-tang
No full textWe have developed a simple, rapid, selective, and reproducible method for the quality control of traditional Chinese medicinal preparations. In this study, we used LC/MS/MS to simultaneously identify and quantify five marker compounds - matrine, oxymatrine, ferulic acid, mangiferin, and glycyrrhizin - in preparations of Shiau-feng-saan and Dang-guei-nian-tong-tang. The calibration curves for the five marker compounds were linear over the concentration range 50-2500 ng/mL (R-2 > 0.9971). The matrix effect was minimized and the recoveries of the five marker compounds were > 90% at a concentration of 1 mu g/mL. Our experimental data reveal that significant differences exist between samples obtained from different sources. (c) 2005 Elsevier B.V. All rights reserved
Practical considerations regarding power factor for nonlinear loads
No full textThis material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. Copyright @ 2004 IEEEThe choice of LC compensator may be constrained by the availability of manufacturers units. To account for this, the capacitor values are chosen from among standard values and for each value the transmission losses is minimized, or power factor is maximized, or transmission efficiency is maximized. The global minimum or maximum is obtained by scanning all local minims or maxims. The performance of the obtained compensator is discussed by means of numerical examples
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