89 research outputs found

    A Compact Electromagnetic Vibration Harvesting System with High Performance Interface Electronics

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    A compact vibration-based electromagnetic (EM) energy harvesting system utilizing high performance interface electronics, has been presented. The energy harvester module consists of an AA-battery sized cylinder tube with an external coil winding, a fixed magnet at the bottom of the tube, and a free magnet inside. The transducer is able to operate at low external vibration frequencies between 9.5 and 12 Hz. The generated AC voltage is converted to DC using a custom rectifier circuit that utilizes a gate cross coupled (GCC) input stage. This decreases the effective threshold voltage of the utilized diodes, while increasing the DC output power delivered to the load. The autonomous system, composed of an EM energy harvester module and a 0.35 mu m CMOS IC, delivers 11.6 mu W power to a 41 mu A load at an external vibration frequency of 12 Hz. The volume of the total system is 4.5 cm(3), and the overall system power density is 2.6 mu W/cm(3)

    A closed core microfluxgate sensor with cascaded planar FeNi rings

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    In this paper, we present a new microfabricated fluxgate sensor structure using cascaded planar rings as the ferromagnetic core. The planar ring structures provide closed magnetic excitation loops enabling uniform core saturation with relatively small excitation magnetic field. The magnetic excitation is provided with a rod passing through the ring cores. Planar coils placed under the edges of the core are used as sensing elements. By using this structure, fluxgate sensors having a closed core configuration are realized with a developed microfabrication process in a very small area (<0.1 mm(2)) with reduced number of via connections. The ferromagnetic rings are realized with a standard FeNi (iron nickel) electroplating process. The main advantage of this structure is the possibility to arrange the linear operation range of the sensor by only changing the number of ring cores, without affecting the excitation mechanism. This is demonstrated by simulations and microfabricated prototypes having 18 and 12 ring cores with +/- 300 mu T and +/- 550 mu T linear operation ranges, respectively. A maximum linear operation range of +/- 2 mT is achieved with a larger size, 4-ring core. This is the widest linear operation range achieved with the microfabricated fluxgate type sensors, without using a feedback loop, to the best of our knowledge. (C) 2010 Elsevier B.V. All rights reserved

    Reconfigurable nested ring-split ring transmitarray unit cell employing the element rotation method by microfluidics

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    A continuously tunable, circularly polarized X-band microfluidic transmitarray unit cell employing the element rotation method is designed and fabricated. The unit cell comprises a double layer nested ring-split ring structure realized as microfluidic channels embedded in Polydimethylsiloxane (PDMS) using soft lithography techniques. Conductive regions of the rings are formed by injecting a liquid metal (an alloy of Ga, In, and Sn), whereas the split region is air. Movement of the liquid metal together with the split around the ring provides 360° linear phase shift range in the transmitted field through the unit cell. A circularly polarized unit cell is designed to operate at 8.8 GHz, satisfying the necessary phase shifting conditions provided by the element rotation method. Unit cell prototypes are fabricated and the proposed concept is verified by the measurements using waveguide simulator method, within the frequency range of 8-10 GHz. The agreement between the simulation and measurement results is satisfactory, illustrating the viability of the approach to be used in reconfigurable antennas and antenna arrays. © 2015 IEEE

    Design of a Gd-DOTA-Phthalocyanine Conjugate Combining MRI Contrast Imaging and Photosensitization Properties as a Potential Molecular Theranostic

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    Cataloged from PDF version of article.The design and synthesis of a phthalocyanine - Gd-DOTA conjugate is presented to open the way to novel molecular theranostics, combining the properties of MRI contrast imaging with photodynamic therapy. The rational design of the conjugate integrates isomeric purity of the phthalocyanine core substitution, suitable biocompatibility with the use of polyoxo water-solubilizing substituents, and a convergent synthetic strategy ended by the use of click chemistry to graft the Gd-DOTA moiety to the phthalocyanine. Photophysical and photochemical properties, contrast imaging experiments and preliminary in vitro investigations proved that such a combination is relevant and lead to a new type of potential theranostic agent

    Micro fluxgate sensor with cascaded planar ring cores

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    In this paper, we present a new microfabricated fluxgate sensor structure having cascaded planar rings as the ferromagnetic core. A circular magnetic excitation is provided with a rod passing through the FeNi rings as a sewing thread. Planar coils placed under the edges of the core are used as sensing elements. The sensing coils and the excitation rod are made of AlSi, and the planar FeNi ferromagnetic core is electroplated in between the excitation rod metallization. The sensor with 18 cascaded cores has 623 mu V/mT sensitivity and +/- 300 mu T linear operation range for a sinusoidal current excitation at 1 MHz with 170 mA peak

    Factors Associated with Hemorrhagic Transformation in Infarctions Involving the Posterior Circulation System

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    PubMed ID: 31138479Backgrounds and Purpose: Hemorrhagic transformation (HT) following stroke of the posterior circulation is a rare occurrence, and its risk factors remain relatively unknown. This study aimed at examining the rate of HT and its risk factors in patients enduring acute ischemic stroke in the territories of the vertebral, basilar, and posterior-cerebral arteries. Materials and Methods: A total of 217 consecutive patients the risk factors for ischemic stroke were recorded and comprehensive biochemical, cardiac assessments, and neuroimaging were performed. National Institutes of Health Stroke Scale (NIHSS) scores were calculated for each patient. Those with HT as documented with neuroimaging based on the European Cooperative Acute Stroke Study criteria and potential risk factors were assessed. Results: There were 217 participants with a mean age of 67.33 ± 12.44 years. Among 17 patients (7.8%) developing HT, 8 (47%) had parenchymal hematoma, and 9(53.5%) had hemorrhagic infarction. Cardioembolism was the most frequent etiological factor both in the overall group (31.0%) as well as in those with HT (41.2%). Factors that emerged as significant predictors of HT included high systolic (odds ratio [OR] 1.14; 95% confidence interval [CI] 1.08-1.20; P< .001) and diastolic blood pressure (P= .001) on the day of admission and the infarction volume of greater than or equal to 3.60 ± 3.29 cm³(OR 1.00, 95% CI 1.00-1.01; P< .001). While NIHSS scores were not significantly different on Day 1, HT patients had higher NIHSS scores at Day 10(OR 1.22; 95% CI 1.09-1.36; P< .001), and this difference was also reflected in mRS at the end of the 3 month period. Conclusion: HT is a rare complication of the infarction of the posterior circulation that is associated with increased morbidity and mortality. Identification of predictive factors for HT in patients with the acute infarction of the posterior circulation may facilitate patient selection for thrombolytic treatment. © 2019 Elsevier Inc

    An Electromagnetic Micro-Power Generator for Low Frequency Vibrations with Tunable Resonance

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    This paper presents an electromagnetic (EM) micro-power generator with tunable resonance frequency which can harvest energy from low frequency environmental vibrations. The reported power generator up-converts low frequency environmental vibrations before mechanical-to-electrical energy conversion by utilizing two diaphragms with different resonance frequencies. Power is generated through electromagnetic induction by a magnet attached to the low frequency diaphragm, and a 50 turn, 2.1 Omega coil, and a magnetic piece on the high frequency diaphragm. Both of the diaphragms are fixed to a common frame via rubber springs, which makes the resonance frequency of each diaphragm tunable. The fabricated prototype generates 5.2 mV and 3.21 mu W RMS power by up-converting 13 Hz, 7.5 mm peak-to-peak vibrations to 200 Hz. Tunability of the resonance frequency is experimentally verified by operating the same device at 2-30 Hz external vibrations
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