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Sample records for voltage-activated proton currents

  1. Dextromethorphan inhibition of voltage-gated proton currents in BV2 microglial cells.

    Science.gov (United States)

    Song, Jin-Ho; Yeh, Jay Z

    2012-05-10

    Dextromethorphan, an antitussive drug, has a neuroprotective property as evidenced by its inhibition of microglial production of pro-inflammatory cytokines and reactive oxygen species. The microglial activation requires NADPH oxidase activity, which is sustained by voltage-gated proton channels in microglia as they dissipate an intracellular acid buildup. In the present study, we examined the effect of dextromethorphan on proton currents in microglial BV2 cells. Dextromethorphan reversibly inhibited proton currents with an IC(50) value of 51.7 μM at an intracellular/extracellular pH gradient of 5.5/7.3. Dextromethorphan did not change the reversal potential or the voltage dependence of the gating. Dextrorphan and 3-hydroxymorphinan, major metabolites of dextromethorphan, and dextromethorphan methiodide were ineffective in inhibiting proton currents. The results indicate that dextromethorphan inhibition of proton currents would suppress NADPH oxidase activity and, eventually, microglial activation. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  2. Antipsychotics, chlorpromazine and haloperidol inhibit voltage-gated proton currents in BV2 microglial cells.

    Science.gov (United States)

    Shin, Hyewon; Song, Jin-Ho

    2014-09-05

    Microglial dysfunction and neuroinflammation are thought to contribute to the pathogenesis of schizophrenia. Some antipsychotic drugs have anti-inflammatory activity and can reduce the secretion of pro-inflammatory cytokines and reactive oxygen species from activated microglial cells. Voltage-gated proton channels on the microglial cells participate in the generation of reactive oxygen species and neuronal toxicity by supporting NADPH oxidase activity. In the present study, we examined the effects of two typical antipsychotics, chlorpromazine and haloperidol, on proton currents in microglial BV2 cells using the whole-cell patch clamp method. Chlorpromazine and haloperidol potently inhibited proton currents with IC50 values of 2.2 μM and 8.4 μM, respectively. Chlorpromazine and haloperidol are weak bases that can increase the intracellular pH, whereby they reduce the proton gradient and affect channel gating. Although the drugs caused a marginal positive shift of the activation voltage, they did not change the reversal potential. This suggested that proton current inhibition was not due to an alteration of the intracellular pH. Chlorpromazine and haloperidol are strong blockers of dopamine receptors. While dopamine itself did not affect proton currents, it also did not alter proton current inhibition by the two antipsychotics, indicating dopamine receptors are not likely to mediate the proton current inhibition. Given that proton channels are important for the production of reactive oxygen species and possibly pro-inflammatory cytokines, the anti-inflammatory and antipsychotic activities of chlorpromazine and haloperidol may be partly derived from their ability to inhibit microglial proton currents. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Molecular mechanism of voltage sensing in voltage-gated proton channels

    Science.gov (United States)

    Rebolledo, Santiago; Perez, Marta E.

    2013-01-01

    Voltage-gated proton (Hv) channels play an essential role in phagocytic cells by generating a hyperpolarizing proton current that electrically compensates for the depolarizing current generated by the NADPH oxidase during the respiratory burst, thereby ensuring a sustained production of reactive oxygen species by the NADPH oxidase in phagocytes to neutralize engulfed bacteria. Despite the importance of the voltage-dependent Hv current, it is at present unclear which residues in Hv channels are responsible for the voltage activation. Here we show that individual neutralizations of three charged residues in the fourth transmembrane domain, S4, all reduce the voltage dependence of activation. In addition, we show that the middle S4 charged residue moves from a position accessible from the cytosolic solution to a position accessible from the extracellular solution, suggesting that this residue moves across most of the membrane electric field during voltage activation of Hv channels. Our results show for the first time that the charge movement of these three S4 charges accounts for almost all of the measured gating charge in Hv channels. PMID:23401575

  4. Voltage-gated proton channel is expressed on phagosomes

    International Nuclear Information System (INIS)

    Okochi, Yoshifumi; Sasaki, Mari; Iwasaki, Hirohide; Okamura, Yasushi

    2009-01-01

    Voltage-gated proton channel has been suggested to help NADPH oxidase activity during respiratory burst of phagocytes through its activities of compensating charge imbalance and regulation of pH. In phagocytes, robust production of reactive oxygen species occurs in closed membrane compartments, which are called phagosomes. However, direct evidence for the presence of voltage-gated proton channels in phagosome has been lacking. In this study, the expression of voltage-gated proton channels was studied by Western blot with the antibody specific to the voltage-sensor domain protein, VSOP/Hv1, that has recently been identified as the molecular correlate for the voltage-gated proton channel. Phagosomal membranes of neutrophils contain VSOP/Hv1 in accordance with subunits of NADPH oxidases, gp91, p22, p47 and p67. Superoxide anion production upon PMA activation was significantly reduced in neutrophils from VSOP/Hv1 knockout mice. These are consistent with the idea that voltage-gated proton channels help NADPH oxidase in phagocytes to produce reactive oxygen species.

  5. Irradiation of optically activated SI-GaAs high-voltage switches with low and high energy protons

    CERN Document Server

    Bertolucci, Ennio; Mettivier, G; Russo, P; Bisogni, M G; Bottigli, U; Fantacci, M E; Stefanini, A; Cola, A; Quaranta, F; Vasanelli, L; Stefanini, G

    1999-01-01

    Semi-Insulating Gallium Arsenide (SI-GaAs) devices have been tested for radiation hardness with 3-4 MeV or 24 GeV proton beams. These devices can be operated in dc mode as optically activated electrical switches up to 1 kV. Both single switches (vertical Schottky diodes) and multiple (8) switches (planar devices) have been studied, by analyzing their current-voltage (I-V) reverse characteristics in the dark and under red light illumination, both before and after irradiation. We propose to use them in the system of high-voltage (-600 V) switches for the microstrip gas chambers for the CMS experiment at CERN. Low energy protons (3-4 MeV) were used in order to produce a surface damage below the Schottky contact: their fluence (up to 2.6*10/sup 15/ p/cm/sup 2/) gives a high-dose irradiation. The high energy proton irradiation (energy: 24 GeV, fluence: 1.1*10/sup 14/ p/cm/sup 2/) reproduced a ten years long proton exposure of the devices in CMS experiment conditions. For low energy irradiation, limited changes of ...

  6. Voltage and pH sensing by the voltage-gated proton channel, HV1.

    Science.gov (United States)

    DeCoursey, Thomas E

    2018-04-01

    Voltage-gated proton channels are unique ion channels, membrane proteins that allow protons but no other ions to cross cell membranes. They are found in diverse species, from unicellular marine life to humans. In all cells, their function requires that they open and conduct current only under certain conditions, typically when the electrochemical gradient for protons is outwards. Consequently, these proteins behave like rectifiers, conducting protons out of cells. Their activity has electrical consequences and also changes the pH on both sides of the membrane. Here we summarize what is known about the way these proteins sense the membrane potential and the pH inside and outside the cell. Currently, it is hypothesized that membrane potential is sensed by permanently charged arginines (with very high p K a ) within the protein, which results in parts of the protein moving to produce a conduction pathway. The mechanism of pH sensing appears to involve titratable side chains of particular amino acids. For this purpose their p K a needs to be within the operational pH range. We propose a 'counter-charge' model for pH sensing in which electrostatic interactions within the protein are selectively disrupted by protonation of internally or externally accessible groups. © 2018 The Author.

  7. Voltage and pH sensing by the voltage-gated proton channel, HV1

    Science.gov (United States)

    2018-01-01

    Voltage-gated proton channels are unique ion channels, membrane proteins that allow protons but no other ions to cross cell membranes. They are found in diverse species, from unicellular marine life to humans. In all cells, their function requires that they open and conduct current only under certain conditions, typically when the electrochemical gradient for protons is outwards. Consequently, these proteins behave like rectifiers, conducting protons out of cells. Their activity has electrical consequences and also changes the pH on both sides of the membrane. Here we summarize what is known about the way these proteins sense the membrane potential and the pH inside and outside the cell. Currently, it is hypothesized that membrane potential is sensed by permanently charged arginines (with very high pKa) within the protein, which results in parts of the protein moving to produce a conduction pathway. The mechanism of pH sensing appears to involve titratable side chains of particular amino acids. For this purpose their pKa needs to be within the operational pH range. We propose a ‘counter-charge’ model for pH sensing in which electrostatic interactions within the protein are selectively disrupted by protonation of internally or externally accessible groups. PMID:29643227

  8. Investigation of the double exponential in the current-voltage characteristics of silicon solar cells. [proton irradiation effects on ATS 1 cells

    Science.gov (United States)

    Wolf, M.; Noel, G. T.; Stirn, R. J.

    1977-01-01

    Difficulties in relating observed current-voltage characteristics of individual silicon solar cells to their physical and material parameters were underscored by the unexpected large changes in the current-voltage characteristics telemetered back from solar cells on the ATS-1 spacecraft during their first year in synchronous orbit. Depletion region recombination was studied in cells exhibiting a clear double-exponential dark characteristic by subjecting the cells to proton irradiation. A significant change in the saturation current, an effect included in the Sah, Noyce, Shockley formulation of diode current resulting from recombination in the depletion region, was caused by the introduction of shallow levels in the depletion region by the proton irradiation. This saturation current is not attributable only to diffusion current from outside the depletion region and only its temperature dependence can clarify its origin. The current associated with the introduction of deep-lying levels did not change significantly in these experiments.

  9. Voltage Dependence of a Neuromodulator-Activated Ionic Current123

    Science.gov (United States)

    2016-01-01

    Abstract The neuromodulatory inward current (IMI) generated by crab Cancer borealis stomatogastric ganglion neurons is an inward current whose voltage dependence has been shown to be crucial in the activation of oscillatory activity of the pyloric network of this system. It has been previously shown that IMI loses its voltage dependence in conditions of low extracellular calcium, but that this effect appears to be regulated by intracellular calmodulin. Voltage dependence is only rarely regulated by intracellular signaling mechanisms. Here we address the hypothesis that the voltage dependence of IMI is mediated by intracellular signaling pathways activated by extracellular calcium. We demonstrate that calmodulin inhibitors and a ryanodine antagonist can reduce IMI voltage dependence in normal Ca2+, but that, in conditions of low Ca2+, calmodulin activators do not restore IMI voltage dependence. Further, we show evidence that CaMKII alters IMI voltage dependence. These results suggest that calmodulin is necessary but not sufficient for IMI voltage dependence. We therefore hypothesize that the Ca2+/calmodulin requirement for IMI voltage dependence is due to an active sensing of extracellular calcium by a GPCR family calcium-sensing receptor (CaSR) and that the reduction in IMI voltage dependence by a calmodulin inhibitor is due to CaSR endocytosis. Supporting this, preincubation with an endocytosis inhibitor prevented W7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride)-induced loss of IMI voltage dependence, and a CaSR antagonist reduced IMI voltage dependence. Additionally, myosin light chain kinase, which is known to act downstream of the CaSR, seems to play a role in regulating IMI voltage dependence. Finally, a Gβγ-subunit inhibitor also affects IMI voltage dependence, in support of the hypothesis that this process is regulated by a G-protein-coupled CaSR. PMID:27257619

  10. Activation of acid-sensing ion channels by localized proton transient reveals their role in proton signaling.

    Science.gov (United States)

    Zeng, Wei-Zheng; Liu, Di-Shi; Liu, Lu; She, Liang; Wu, Long-Jun; Xu, Tian-Le

    2015-09-15

    Extracellular transients of pH alterations likely mediate signal transduction in the nervous system. Neuronal acid-sensing ion channels (ASICs) act as sensors for extracellular protons, but the mechanism underlying ASIC activation remains largely unknown. Here, we show that, following activation of a light-activated proton pump, Archaerhodopsin-3 (Arch), proton transients induced ASIC currents in both neurons and HEK293T cells co-expressing ASIC1a channels. Using chimera proteins that bridge Arch and ASIC1a by a glycine/serine linker, we found that successful coupling occurred within 15 nm distance. Furthermore, two-cell sniffer patch recording revealed that regulated release of protons through either Arch or voltage-gated proton channel Hv1 activated neighbouring cells expressing ASIC1a channels. Finally, computational modelling predicted the peak proton concentration at the intercellular interface to be at pH 6.7, which is acidic enough to activate ASICs in vivo. Our results highlight the pathophysiological role of proton signalling in the nervous system.

  11. Radiation effects on the current-voltage and capacitance-voltage characteristics of advanced p-n junction diodes surrounded by shallow trench isolation

    International Nuclear Information System (INIS)

    Poyai, A.; Simoen, E.; Claeys, C.; Hayama, K.; Kobayashi, K.; Ohyama, H.

    2002-01-01

    This paper investigates the impact of 20 MeV proton irradiation on the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of different geometry n + -p-well junction diodes surrounded by shallow trench isolation and processed in a 0.18 μm CMOS technology. From I-V characteristics, a higher current damage coefficient was found for the bulk than for the peripheral component. The radiation-induced boron de-activation resulted in a lowering of the p-well doping, which has been derived from high-frequency C-V measurements. This was confirmed by deep level transient spectroscopy (DLTS) analysis, revealing the presence of interstitial boron related radiation defects. As will be demonstrated for the bulk leakage-current damage coefficient, the electric field enhanced generation rate of charge carriers and the radiation-induced boron de-activation should be accounted for properly

  12. New digital reference current generation for shunt active power filter under distorted voltage conditions

    Energy Technology Data Exchange (ETDEWEB)

    Abdusalam, Mohamed; Karimi, Shahram; Saadate, Shahrokh [Groupe de Recherche en Electrotechnique et Electronique de Nancy (GREEN), CNRS UMR 7037 (France); Poure, Philippe [Laboratoire d' Instrumentation Electronique de Nancy (LIEN), EA 3440, Universite Henri Poincare - Nancy Universite, B.P. 239, 54506 Vandoeuvre les Nancy Cedex (France)

    2009-05-15

    In this paper, a new reference current computation method suitable for shunt active power filter control under distorted voltage conditions is proposed. The active power filter control is based on the use of self-tuning filters (STF) for the reference current generation and on a modulated hysteresis current controller. This active filter is intended for harmonic compensation of a diode rectifier feeding a RL load under distorted voltage conditions. The study of the active filter control is divided in two parts. The first one deals with the harmonic isolator which generates the harmonic reference currents and is experimentally implemented in a DS1104 card of a DSPACE prototyping system. The second part focuses on the generation of the switching pattern of the inverter by using a modulated hysteresis current controller, implemented in an analogue card. The use of STF instead of classical extraction filters allows extracting directly the voltage and current fundamental components in the {alpha}-{beta} axis without phase locked loop (PLL). The performances are good even under distorted voltage conditions. First, the effectiveness of the new proposed method is mathematically studied and verified by computer simulation. Then, experimental results are presented using a DSPACE system associated with the analogue current controller for a real shunt active power filter. (author)

  13. Real-Time Microscopic Monitoring of Flow, Voltage and Current in the Proton Exchange Membrane Water Electrolyzer.

    Science.gov (United States)

    Lee, Chi-Yuan; Li, Shih-Chun; Chen, Chia-Hung; Huang, Yen-Ting; Wang, Yu-Syuan

    2018-03-15

    Looking for alternative energy sources has been an inevitable trend since the oil crisis, and close attentioned has been paid to hydrogen energy. The proton exchange membrane (PEM) water electrolyzer is characterized by high energy efficiency, high yield, simple system and low operating temperature. The electrolyzer generates hydrogen from water free of any carbon sources (provided the electrons come from renewable sources such as solar and wind), so it is very clean and completely satisfies the environmental requirement. However, in long-term operation of the PEM water electrolyzer, the membrane material durability, catalyst corrosion and nonuniformity of local flow, voltage and current in the electrolyzer can influence the overall performance. It is difficult to measure the internal physical parameters of the PEM water electrolyzer, and the physical parameters are interrelated. Therefore, this study uses micro-electro-mechanical systems (MEMS) technology to develop a flexible integrated microsensor; internal multiple physical information is extracted to determine the optimal working parameters for the PEM water electrolyzer. The real operational data of local flow, voltage and current in the PEM water electrolyzer are measured simultaneously by the flexible integrated microsensor, so as to enhance the performance of the PEM water electrolyzer and to prolong the service life.

  14. Low Voltage Current Mode Switched-Current-Mirror Mixer

    Directory of Open Access Journals (Sweden)

    Chunhua Wang

    2009-09-01

    Full Text Available A new CMOS active mixer topology can operate at 1 V supply voltage by use of SCM (switched currentmirror. Such current-mode mixer requires less voltage headroom with good linearization. Mixing is achieved with four improved current mirrors, which are alternatively activated. For ideal switching, the operation is equivalent to a conventional active mixer. This paper analyzes the performance of the SCM mixer, in comparison with the conventional mixer, demonstrating competitive performance at a lower supply voltage. Moreover, the new mixer’s die, without any passive components, is very small, and the conversion gain is easy to adjust. An experimental prototype was designed and simulated in standard chartered 0.18μm RF CMOS Process with Spectre in Cadence Design Systems. Experimental results show satisfactory mixer performance at 2.4 GHz.

  15. Sodium and Proton Effects on Inward Proton Transport through Na/K Pumps

    Science.gov (United States)

    Mitchell, Travis J.; Zugarramurdi, Camila; Olivera, J. Fernando; Gatto, Craig; Artigas, Pablo

    2014-01-01

    The Na/K pump hydrolyzes ATP to export three intracellular Na (Nai) as it imports two extracellular K (Ko) across animal plasma membranes. Within the protein, two ion-binding sites (sites I and II) can reciprocally bind Na or K, but a third site (site III) exclusively binds Na in a voltage-dependent fashion. In the absence of Nao and Ko, the pump passively imports protons, generating an inward current (IH). To elucidate the mechanisms of IH, we used voltage-clamp techniques to investigate the [H]o, [Na]o, and voltage dependence of IH in Na/K pumps from ventricular myocytes and in ouabain-resistant pumps expressed in Xenopus oocytes. Lowering pHo revealed that Ho both activates IH (in a voltage-dependent manner) and inhibits it (in a voltage-independent manner) by binding to different sites. Nao effects depend on pHo; at pHo where no Ho inhibition is observed, Nao inhibits IH at all concentrations, but when applied at pHo that inhibits pump-mediated current, low [Na]o activates IH and high [Na]o inhibits it. Our results demonstrate that IH is a property inherent to Na/K pumps, not linked to the oocyte expression environment, explains differences in the characteristics of IH previously reported in the literature, and supports a model in which 1), protons leak through site III; 2), binding of two Na or two protons to sites I and II inhibits proton transport; and 3), pumps with mixed Na/proton occupancy of sites I and II remain permeable to protons. PMID:24940773

  16. Identification of an HV 1 voltage-gated proton channel in insects.

    Science.gov (United States)

    Chaves, Gustavo; Derst, Christian; Franzen, Arne; Mashimo, Yuta; Machida, Ryuichiro; Musset, Boris

    2016-04-01

    The voltage-gated proton channel 1 (HV 1) is an important component of the cellular proton extrusion machinery and is essential for charge compensation during the respiratory burst of phagocytes. HV 1 has been identified in a wide range of eukaryotes throughout the animal kingdom, with the exception of insects. Therefore, it has been proposed that insects do not possess an HV 1 channel. In the present study, we report the existence of an HV 1-type proton channel in insects. We searched insect transcriptome shotgun assembly (TSA) sequence databases and found putative HV 1 orthologues in various polyneopteran insects. To confirm that these putative HV 1 orthologues were functional channels, we studied the HV 1 channel of Nicoletia phytophila (NpHV 1), an insect of the Zygentoma order, in more detail. NpHV 1 comprises 239 amino acids and is 33% identical to the human voltage-gated proton channel 1. Patch clamp measurements in a heterologous expression system showed proton selectivity, as well as pH- and voltage-dependent gating. Interestingly, NpHV 1 shows slightly enhanced pH-dependent gating compared to the human channel. Mutations in the first transmembrane segment at position 66 (Asp66), the presumed selectivity filter, lead to a loss of proton-selective conduction, confirming the importance of this aspartate residue in voltage-gated proton channels. Nucleotide sequence data have been deposited in the GenBank database under accession number KT780722. © 2016 Federation of European Biochemical Societies.

  17. Current-current interaction picture for proton-proton scattering

    International Nuclear Information System (INIS)

    Clarke, D.J.; Lo, S.Y.

    1979-01-01

    The authors propose that color current - color current interaction is reponsible for small angle elastic proton proton scattering at asymptotic energy. Excellent fits are obtained for all data above 12 GeV/c which covers twelve orders of magnitude

  18. Novel dimeric bis(7)-tacrine proton-dependently inhibits NMDA-activated currents

    International Nuclear Information System (INIS)

    Luo, Jialie; Li, Wenming; Liu, Yuwei; Zhang, Wei; Fu, Hongjun; Lee, Nelson T.K.; Yu, Hua; Pang, Yuanping; Huang, Pingbo; Xia, Jun; Li, Zhi-Wang; Li, Chaoying; Han, Yifan

    2007-01-01

    Bis(7)-tacrine has been shown to prevent glutamate-induced neuronal apoptosis by blocking NMDA receptors. However, the characteristics of the inhibition have not been fully elucidated. In this study, we further characterize the features of bis(7)-tacrine inhibition of NMDA-activated current in cultured rat hippocampal neurons. The results show that with the increase of extracellular pH, the inhibitory effect decreases dramatically. At pH 8.0, the concentration-response curve of bis(7)-tacrine is shifted rightwards with the IC 50 value increased from 0.19 ± 0.03 μM to 0.41 ± 0.04 μM. In addition, bis(7)-tacrine shifts the proton inhibition curve rightwards. Furthermore, the inhibitory effect of bis(7)-tacrine is not altered by the presence of the NMDA receptor proton sensor shield spermidine. These results indicate that bis(7)-tacrine inhibits NMDA-activated current in a pH-dependent manner by sensitizing NMDA receptors to proton inhibition, rendering it potentially beneficial therapeutic effects under acidic conditions associated with stroke and ischemia

  19. Tungsten oxide proton conducting films for low-voltage transparent oxide-based thin-film transistors

    International Nuclear Information System (INIS)

    Zhang, Hongliang; Wan, Qing; Wan, Changjin; Wu, Guodong; Zhu, Liqiang

    2013-01-01

    Tungsten oxide (WO x ) electrolyte films deposited by reactive magnetron sputtering showed a high room temperature proton conductivity of 1.38 × 10 −4 S/cm with a relative humidity of 60%. Low-voltage transparent W-doped indium-zinc-oxide thin-film transistors gated by WO x -based electrolytes were self-assembled on glass substrates by one mask diffraction method. Enhancement mode operation with a large current on/off ratio of 4.7 × 10 6 , a low subthreshold swing of 108 mV/decade, and a high field-effect mobility 42.6 cm 2 /V s was realized. Our results demonstrated that WO x -based proton conducting films were promising gate dielectric candidates for portable low-voltage oxide-based devices.

  20. Voltage-sensing domain of voltage-gated proton channel Hv1 shares mechanism of block with pore domains.

    Science.gov (United States)

    Hong, Liang; Pathak, Medha M; Kim, Iris H; Ta, Dennis; Tombola, Francesco

    2013-01-23

    Voltage-gated sodium, potassium, and calcium channels are made of a pore domain (PD) controlled by four voltage-sensing domains (VSDs). The PD contains the ion permeation pathway and the activation gate located on the intracellular side of the membrane. A large number of small molecules are known to inhibit the PD by acting as open channel blockers. The voltage-gated proton channel Hv1 is made of two VSDs and lacks the PD. The location of the activation gate in the VSD is unknown and open channel blockers for VSDs have not yet been identified. Here, we describe a class of small molecules which act as open channel blockers on the Hv1 VSD and find that a highly conserved phenylalanine in the charge transfer center of the VSD plays a key role in blocker binding. We then use one of the blockers to show that Hv1 contains two intracellular and allosterically coupled gates. Copyright © 2013 Elsevier Inc. All rights reserved.

  1. Method of controlling illumination device based on current-voltage model

    DEFF Research Database (Denmark)

    2013-01-01

    The present invention relates to an illumination device comprising a number of LEDs, means for receiving an input signal, means for generating an activation signal for at least one of the LEDs based on the input signal. The illumination device comprises further means for obtaining the voltage...... and the colorimetric properties of said light emitted by LED. The present invention relates also to a method of controlling and a meted of calibrating such illumination device....... across and current through the LED and the means for generating the activation signal is adapted to generate the activating signal based on the voltage, the current and a current- voltage model related to LED. The current-voltage model defines a relationship between the current, the voltage...

  2. Two distinct voltage-sensing domains control voltage sensitivity and kinetics of current activation in CaV1.1 calcium channels.

    Science.gov (United States)

    Tuluc, Petronel; Benedetti, Bruno; Coste de Bagneaux, Pierre; Grabner, Manfred; Flucher, Bernhard E

    2016-06-01

    Alternative splicing of the skeletal muscle CaV1.1 voltage-gated calcium channel gives rise to two channel variants with very different gating properties. The currents of both channels activate slowly; however, insertion of exon 29 in the adult splice variant CaV1.1a causes an ∼30-mV right shift in the voltage dependence of activation. Existing evidence suggests that the S3-S4 linker in repeat IV (containing exon 29) regulates voltage sensitivity in this voltage-sensing domain (VSD) by modulating interactions between the adjacent transmembrane segments IVS3 and IVS4. However, activation kinetics are thought to be determined by corresponding structures in repeat I. Here, we use patch-clamp analysis of dysgenic (CaV1.1 null) myotubes reconstituted with CaV1.1 mutants and chimeras to identify the specific roles of these regions in regulating channel gating properties. Using site-directed mutagenesis, we demonstrate that the structure and/or hydrophobicity of the IVS3-S4 linker is critical for regulating voltage sensitivity in the IV VSD, but by itself cannot modulate voltage sensitivity in the I VSD. Swapping sequence domains between the I and the IV VSDs reveals that IVS4 plus the IVS3-S4 linker is sufficient to confer CaV1.1a-like voltage dependence to the I VSD and that the IS3-S4 linker plus IS4 is sufficient to transfer CaV1.1e-like voltage dependence to the IV VSD. Any mismatch of transmembrane helices S3 and S4 from the I and IV VSDs causes a right shift of voltage sensitivity, indicating that regulation of voltage sensitivity by the IVS3-S4 linker requires specific interaction of IVS4 with its corresponding IVS3 segment. In contrast, slow current kinetics are perturbed by any heterologous sequences inserted into the I VSD and cannot be transferred by moving VSD I sequences to VSD IV. Thus, CaV1.1 calcium channels are organized in a modular manner, and control of voltage sensitivity and activation kinetics is accomplished by specific molecular mechanisms

  3. Comparative study of microcontroller controlled four-wire voltage and current source shunt active power filters

    Energy Technology Data Exchange (ETDEWEB)

    Pettersson, S.

    2009-07-01

    During the past two decades, active power filters have increasingly grown their popularity as a viable method for improving electric power quality. The main reasons for this have been the advent of fast self-commutating solid-state devices, the progression of digital technology and the improved sensor technology. Four-wire active power filters provide an efficient solution for improving the quality of supply in grounded three-phase systems or three-phase systems with neutral conductors, which are commonly used for powering residential, office and public buildings. Four-wire active power filters are applicable in compensating current harmonics, reactive power, neutral current and load phase imbalance.This thesis presents a comparative study of microcontroller controlled four-wire voltage and current source shunt active power filters. The study includes two voltage source topologies and a current source topology with two different dc-link energy storage structures, which are compared on the basis of their filtering properties, filtering performance and efficiency. The obtained results are used for determining the suitability of current source technology for four-wire active power filtering and finding the most viable four-wire shunt active power filter topology. One commonly recognized disadvantage of the current source active power filter has always been the bulky dc-link inductor. To reduce the size of the dc-link inductor, an alternative dc-link structure for current source active power filters was introduced in the late 80's. The hybrid energy storage consists of both inductive and capacitive energy storage elements, two diodes and two controllable semiconductor switching devices. Since the capacitive element is used as a main storage unit, the inductance of the dc-link inductor can be considerably reduced. However, the original dc current control method proposed is not able to utilize the full potential of the hybrid energy storage and the inductance

  4. Voltage-Gated Proton Channels: Molecular Biology, Physiology, and Pathophysiology of the HV Family

    Science.gov (United States)

    2013-01-01

    Voltage-gated proton channels (HV) are unique, in part because the ion they conduct is unique. HV channels are perfectly selective for protons and have a very small unitary conductance, both arguably manifestations of the extremely low H+ concentration in physiological solutions. They open with membrane depolarization, but their voltage dependence is strongly regulated by the pH gradient across the membrane (ΔpH), with the result that in most species they normally conduct only outward current. The HV channel protein is strikingly similar to the voltage-sensing domain (VSD, the first four membrane-spanning segments) of voltage-gated K+ and Na+ channels. In higher species, HV channels exist as dimers in which each protomer has its own conduction pathway, yet gating is cooperative. HV channels are phylogenetically diverse, distributed from humans to unicellular marine life, and perhaps even plants. Correspondingly, HV functions vary widely as well, from promoting calcification in coccolithophores and triggering bioluminescent flashes in dinoflagellates to facilitating killing bacteria, airway pH regulation, basophil histamine release, sperm maturation, and B lymphocyte responses in humans. Recent evidence that hHV1 may exacerbate breast cancer metastasis and cerebral damage from ischemic stroke highlights the rapidly expanding recognition of the clinical importance of hHV1. PMID:23589829

  5. Current and Voltage Conveyors in Current- and Voltage-Mode Precision Full-Wave Rectifiers

    Directory of Open Access Journals (Sweden)

    J. Koton

    2011-04-01

    Full Text Available In this paper new versatile precision full-wave rectifiers using current and/or voltage conveyors as active elements and two diodes are presented. The performance of these circuit solutions is analysed and compared to the opamp based precision rectifier. To analyze the behavior of the functional blocks, the frequency dependent RMS error and DC transient value are evaluated for different values of input voltage amplitudes. Furthermore, experimental results are given that show the feasibilities of the conveyor based rectifiers superior to the corresponding operational amplifier based topology.

  6. Proton and non-proton activation of ASIC channels.

    Directory of Open Access Journals (Sweden)

    Ivan Gautschi

    Full Text Available The Acid-Sensing Ion Channels (ASIC exhibit a fast desensitizing current when activated by pH values below 7.0. By contrast, non-proton ligands are able to trigger sustained ASIC currents at physiological pHs. To analyze the functional basis of the ASIC desensitizing and sustained currents, we have used ASIC1a and ASIC2a mutants with a cysteine in the pore vestibule for covalent binding of different sulfhydryl reagents. We found that ASIC1a and ASIC2a exhibit two distinct currents, a proton-induced desensitizing current and a sustained current triggered by sulfhydryl reagents. These currents differ in their pH dependency, their sensitivity to the sulfhydryl reagents, their ionic selectivity and their relative magnitude. We propose a model for ASIC1 and ASIC2 activity where the channels can function in two distinct modes, a desensitizing mode and a sustained mode depending on the activating ligands. The pore vestibule of the channel represents a functional site for binding non-proton ligands to activate ASIC1 and ASIC2 at neutral pH and to prevent channel desensitization.

  7. Proton and non-proton activation of ASIC channels.

    Science.gov (United States)

    Gautschi, Ivan; van Bemmelen, Miguel Xavier; Schild, Laurent

    2017-01-01

    The Acid-Sensing Ion Channels (ASIC) exhibit a fast desensitizing current when activated by pH values below 7.0. By contrast, non-proton ligands are able to trigger sustained ASIC currents at physiological pHs. To analyze the functional basis of the ASIC desensitizing and sustained currents, we have used ASIC1a and ASIC2a mutants with a cysteine in the pore vestibule for covalent binding of different sulfhydryl reagents. We found that ASIC1a and ASIC2a exhibit two distinct currents, a proton-induced desensitizing current and a sustained current triggered by sulfhydryl reagents. These currents differ in their pH dependency, their sensitivity to the sulfhydryl reagents, their ionic selectivity and their relative magnitude. We propose a model for ASIC1 and ASIC2 activity where the channels can function in two distinct modes, a desensitizing mode and a sustained mode depending on the activating ligands. The pore vestibule of the channel represents a functional site for binding non-proton ligands to activate ASIC1 and ASIC2 at neutral pH and to prevent channel desensitization.

  8. Mitigation of Voltage and Current Harmonics in Grid-Connected Microgrids

    DEFF Research Database (Denmark)

    Savaghebi, Mehdi; Guerrero, Josep M.; Jalilian, Alireza

    2012-01-01

    In this paper, a control approach is proposed for selective compensation of main voltage and current harmonics in grid-connected microgrids. Two modes of compensation are considered, i.e. voltage and current compensation modes. In the case that sensitive loads are connected to the point of common...... coupling (PCC), voltage compensation mode is activated in order to provide a high voltage quality at PCC. Otherwise, grid current harmonics are mitigated (current compensation mode) in order to avoid excessive harmonic supply by the grid. In both modes, harmonic compensation is achieved through proper...... control of distributed generators (DGs) interface converters. The compensation effort of each harmonic is shared considering the corresponding current harmonic supplied by the DGs. The control system of each DG comprises harmonic compensator, power controllers, voltage and current controllers and virtual...

  9. Protonic/electronic hybrid oxide transistor gated by chitosan and its full-swing low voltage inverter applications

    Energy Technology Data Exchange (ETDEWEB)

    Chao, Jin Yu [Shanxi Province Key Laboratory High Gravity Chemical Engineering, North University of China, Taiyuan 030051 (China); Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Zhu, Li Qiang, E-mail: lqzhu@nimte.ac.cn; Xiao, Hui [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Yuan, Zhi Guo, E-mail: ncityzg@163.com [Shanxi Province Key Laboratory High Gravity Chemical Engineering, North University of China, Taiyuan 030051 (China)

    2015-12-21

    Modulation of charge carrier density in condensed materials based on ionic/electronic interaction has attracted much attention. Here, protonic/electronic hybrid indium-zinc-oxide (IZO) transistors gated by chitosan based electrolyte were obtained. The chitosan-based electrolyte illustrates a high proton conductivity and an extremely strong proton gating behavior. The transistor illustrates good electrical performances at a low operating voltage of ∼1.0 V such as on/off ratio of ∼3 × 10{sup 7}, subthreshold swing of ∼65 mV/dec, threshold voltage of ∼0.3 V, and mobility of ∼7 cm{sup 2}/V s. Good positive gate bias stress stabilities are obtained. Furthermore, a low voltage driven resistor-loaded inverter was built by using an IZO transistor in series with a load resistor, exhibiting a linear relationship between the voltage gain and the supplied voltage. The inverter is also used for decreasing noises of input signals. The protonic/electronic hybrid IZO transistors have potential applications in biochemical sensors and portable electronics.

  10. Grid-Current-Feedback Active Damping for LCL Resonance in Grid-Connected Voltage-Source Converters

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Blaabjerg, Frede; Loh, Poh Chiang

    2016-01-01

    This paper investigates active damping of LCL-filter resonance in a grid-connected voltage-source converter with only grid-current feedback control. Basic analysis in the s-domain shows that the proposed damping technique with a negative high-pass filter along its damping path is equivalent...... of phase-lag, in turn, helps to shrink the region of nonminimum-phase behavior caused by negative virtual resistance inserted unintentionally by most digitally implemented active damping techniques. The presented high-pass-filtered active damping technique with a single grid-current feedback loop is thus...

  11. Flexible Compensation of Voltage and Current Unbalance and Harmonics in Microgrids

    Directory of Open Access Journals (Sweden)

    Seyyed Yousef Mousazadeh Mousavi

    2017-10-01

    Full Text Available In recent years, the harmonics and unbalance problems endanger the voltage and current quality of power systems, due to increasing usage of nonlinear and unbalanced loads. Use of Distributed Generation (DG-interfacing inverters is proposed for voltage or current compensation. In this paper, a flexible control method is proposed to compensate voltage and current unbalance and harmonics using the distributed generation (DG-interfacing inverters. This method is applicable to both grid-connected and islanded Microgrids (MGs. In the proposed method, not only the proper control of active and reactive powers can be achieved, but also there is flexibility in compensating the voltage or current quality problems at DG terminals or Points of Common Coupling (PCCs. This control strategy consists of active and reactive power controllers and a voltage/current quality-improvement block. The controller is designed in a stationary (αβ frame. An extensive simulation study has been performed and the results demonstrate the effectiveness of the proposed control scheme. Depending on the compensation modes, the harmonics and unbalance compensation of DG output current, MG-injected current to the grid, as well as PCC and DG voltages, can be achieved in grid-connected operation of MG while in the islanded operation, and the PCC and DG voltages compensation can be obtained through the proposed control scheme.

  12. Non-contact current and voltage sensor

    Science.gov (United States)

    Carpenter, Gary D; El-Essawy, Wael; Ferreira, Alexandre Peixoto; Keller, Thomas Walter; Rubio, Juan C; Schappert, Michael A

    2014-03-25

    A detachable current and voltage sensor provides an isolated and convenient device to measure current passing through a conductor such as an AC branch circuit wire, as well as providing an indication of an electrostatic potential on the wire, which can be used to indicate the phase of the voltage on the wire, and optionally a magnitude of the voltage. The device includes a housing that contains the current and voltage sensors, which may be a ferrite cylinder with a hall effect sensor disposed in a gap along the circumference to measure current, or alternative a winding provided through the cylinder along its axis and a capacitive plate or wire disposed adjacent to, or within, the ferrite cylinder to provide the indication of the voltage.

  13. Influence of current limitation on voltage stability with voltage sourced converter HVDC

    DEFF Research Database (Denmark)

    Zeni, Lorenzo; Jóhannsson, Hjörtur; Hansen, Anca Daniela

    2013-01-01

    A first study of voltage stability with relevant amount of Voltage Sourced Converter based High Voltage Direct Current (VSC-HVDC) transmission is presented, with particular focus on the converters’ behaviour when reaching their rated current. The detrimental effect of entering the current...

  14. Proton conducting sodium alginate electrolyte laterally coupled low-voltage oxide-based transistors

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yang Hui; Wan, Qing, E-mail: wanqing@nju.edu.cn [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Qiang Zhu, Li, E-mail: lqzhu@nimte.ac.cn [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Shi, Yi [School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China)

    2014-03-31

    Solution-processed sodium alginate electrolyte film shows a high proton conductivity of ∼5.5 × 10{sup −3} S/cm and a high lateral electric-double-layer (EDL) capacitance of ∼2.0 μF/cm{sup 2} at room temperature with a relative humidity of 57%. Low-voltage in-plane-gate indium-zinc-oxide-based EDL transistors laterally gated by sodium alginate electrolytes are fabricated on glass substrates. The field-effect mobility, current ON/OFF ratio, and subthreshold swing of such EDL transistors are estimated to be 4.2 cm{sup 2} V{sup −1} s{sup −1}, 2.8 × 10{sup 6}, and 130 mV/decade, respectively. At last, a low-voltage driven resistor-load inverter is also demonstrated. Such in-plane-gate EDL transistors have potential applications in portable electronics and low-cost biosensors.

  15. Proton-irradiation technology for high-frequency high-current silicon welding diode manufacturing

    Science.gov (United States)

    Lagov, P. B.; Drenin, A. S.; Zinoviev, M. A.

    2017-05-01

    Different proton irradiation regimes were tested to provide more than 20 kHz-frequency, soft reverse recovery “snap-less” behavior, low forward voltage drop and leakage current for 50 mm diameter 7 kA/400 V welding diode Al/Si/Mo structure. Silicon diode with such parameters is very suitable for high frequency resistance welding machines of new generation for robotic welding.

  16. Proton current measurements using the prompt gamma ray diagnostic technique

    International Nuclear Information System (INIS)

    Leeper, R.J.; Burns, E.J.T.; Johnson, D.J.; McMurtry, W.M.

    1981-01-01

    Prompt gamma ray signals from the nuclear reaction 7 Li(p,γ) 8 Be have been used to make time resolved proton current measurements. In these measurements, the proton beam was allowed to strike cylindrical thick lithium metal targets. The time integrated proton current was measured using gamma activation of copper via the reaction 63 Cu(γ,n) 62 Cu(β+). The positron activity of the copper sample was easily measured using coincidence counting techniques. The number of 62 Cu atoms produced per proton incident on a thick Li metal target was determined with separate calibration runs performed on the Sandia 2.5 MeV Van de Graaff accelerator. The time history of the prompt gamma production was measured using six EGG NPM-54 scintillator photomultiplier combinations shielded by 96.5 cm of concrete and 5.1 cm of Pb. The use of six scintillator photomultiplier combinations was necessary to increase the statistical precision of the data. The normalization of the prompt gamma time history data with the total time integrated proton-current measurement yielded the absolute time resolved proton current on target. Data from runs performed on the Sandia Proto I accelerator will be presented

  17. Active damping of LLCL-filter resonance based on LC-trap voltage and capacitor current feedback

    DEFF Research Database (Denmark)

    Huang, Min; Wang, Xiongfei; Loh, Poh Chiang

    2015-01-01

    . In this paper, different feedback coefficients like the proportional, derivative, integral, high pass and low pass feedback coefficients of the filter capacitor current and the LC-trap circuit voltage are investigated for damping the filter resonance. Active damping methods are analyzed by using the concept...

  18. Current-voltage characteristics of C70 solid near Meyer-Neldel temperature

    Science.gov (United States)

    Onishi, Koichi; Sezaimaru, Kouki; Nakashima, Fumihiro; Sun, Yong; Kirimoto, Kenta; Sakaino, Masamichi; Kanemitsu, Shigeru

    2017-06-01

    The current-voltage characteristics of the C70 solid with hexagonal closed-packed structures were measured in the temperature range of 250-450 K. The current-voltage characteristics can be described as a temporary expedient by a cubic polynomial of the voltage, i = a v 3 + b v 2 + c v + d . Moreover, the Meyer-Neldel temperature of the C70 solid was confirmed to be 310 K, at which a linear relationship between the current and voltage was observed. Also, at temperatures below the Meyer-Neldel temperature, the current increases with increasing voltage. On the other hand, at temperatures above the Meyer-Neldel temperature a negative differential conductivity effect was observed at high voltage side. The negative differential conductivity was related to the electric field and temperature effects on the mobility of charge carrier, which involve two variations in the carrier concentration and the activation energy for carrier hopping transport.

  19. Proton-irradiation technology for high-frequency high-current silicon welding diode manufacturing

    International Nuclear Information System (INIS)

    Lagov, P B; Drenin, A S; Zinoviev, M A

    2017-01-01

    Different proton irradiation regimes were tested to provide more than 20 kHz-frequency, soft reverse recovery “snap-less” behavior, low forward voltage drop and leakage current for 50 mm diameter 7 kA/400 V welding diode Al/Si/Mo structure. Silicon diode with such parameters is very suitable for high frequency resistance welding machines of new generation for robotic welding. (paper)

  20. Investigation of the double exponential in the current-voltage characteristics of silicon solar cells

    Science.gov (United States)

    Wolf, M.; Noel, G. T.; Stirn, R. J.

    1976-01-01

    A theoretical analysis is presented of certain peculiarities of the current-voltage characteristics of silicon solar cells, involving high values of the empirical constant A in the diode equation for a p-n junction. An attempt was made in a lab experiment to demonstrate that the saturation current which is associated with the exponential term qV/A2kT of the I-V characteristic, with A2 roughly equal to 2, originates in the space charge region and that it can be increased, as observed on ATS-1 cells, by the introduction of additional defects through low energy proton irradiation. It was shown that the proton irradiation introduces defects into the space charge region which give rise to a recombination current from this region, although the I-V characteristic is, in this case, dominated by an exponential term which has A = 1.

  1. Ring current proton decay by charge exchange

    Science.gov (United States)

    Smith, P. H.; Hoffman, R. A.; Fritz, T.

    1975-01-01

    Explorer 45 measurements during the recovery phase of a moderate magnetic storm have confirmed that the charge exchange decay mechanism can account for the decay of the storm-time proton ring current. Data from the moderate magnetic storm of 24 February 1972 was selected for study since a symmetrical ring current had developed and effects due to asymmetric ring current losses could be eliminated. It was found that after the initial rapid decay of the proton flux, the equatorially mirroring protons in the energy range 5 to 30 keV decayed throughout the L-value range of 3.5 to 5.0 at the charge exchange decay rate calculated by Liemohn. After several days of decay, the proton fluxes reached a lower limit where an apparent equilibrium was maintained, between weak particle source mechanisms and the loss mechanisms, until fresh protons were injected into the ring current region during substorms. While other proton loss mechanisms may also be operating, the results indicate that charge exchange can entirely account for the storm-time proton ring current decay, and that this mechanism must be considered in all studies involving the loss of proton ring current particles.

  2. Insulation Resistance and Leakage Currents in Low-Voltage Ceramic Capacitors with Cracks

    Science.gov (United States)

    Teverovsky, Alexander A.

    2016-01-01

    Measurement of insulation resistance (IR) in multilayer ceramic capacitors (MLCCs) is considered a screening technique that ensures the dielectric is defect-free. This work analyzes the effectiveness of this technique for revealing cracks in ceramic capacitors. It is shown that absorption currents prevail over the intrinsic leakage currents during standard IR measurements at room temperature. Absorption currents, and consequently IR, have a weak temperature dependence, increase linearly with voltage (before saturation), and are not sensitive to the presence of mechanical defects. In contrary, intrinsic leakage currents increase super-linearly with voltage and exponentially with temperature (activation energy is in the range from 0.6 eV to 1.1 eV). Leakage currents associated with the presence of cracks have a weaker dependence on temperature and voltage compared to the intrinsic leakage currents. For this reason, intrinsic leakage currents prevail at high temperatures and voltages, thus masking the presence of defects.

  3. Low-voltage protonic/electronic hybrid indium zinc oxide synaptic transistors on paper substrates

    International Nuclear Information System (INIS)

    Wu, Guodong; Wan, Changjin; Wan, Qing; Zhou, Jumei; Zhu, Liqiang

    2014-01-01

    Low-voltage (1.5 V) indium zinc oxide (IZO)-based electric-double-layer (EDL) thin-film transistors (TFTs) gated by nanogranular proton conducting SiO 2 electrolyte films are fabricated on paper substrates. Both enhancement-mode and depletion-mode operation are obtained by tuning the thickness of the IZO channel layer. Furthermore, such flexible IZO protonic/electronic hybrid EDL TFTs can be used as artificial synapses, and synaptic stimulation response and short-term synaptic plasticity function are demonstrated. The protonic/electronic hybrid EDL TFTs on paper substrates proposed here are promising for low-power flexible paper electronics, artificial synapses and bioelectronics. (paper)

  4. Flexible Compensation of Voltage and Current Unbalance and Harmonics in Microgrids

    DEFF Research Database (Denmark)

    Mousazadeh, Seyyed Yousef; Jalilian, Alireza; Savaghebi, Mehdi

    2017-01-01

    In recent years, the harmonics and unbalance problem endanger the voltage and current quality of power systems due to increasing usage of nonlinear and unbalance loads. Using DG interfacing inverters is proposed for voltage or current compensation. In this paper, a flexible control method...... is proposed to compensate voltage and current unbalance and harmonics using the Distributed Generation (DG) interfacing inverters. This method is applicable to both grid-connected and islanded microgrids. In the proposed method, not only the proper control of active and reactive powers can be achieved......) frame. An extensive simulation study has been performed and the results demonstrate the effectiveness of the proposed control scheme. The results show that depending on the compensation mode, the harmonics and unbalance compensation of DGs’ output current, MG’s injected current to the grid as well...

  5. Dynamic range of low-voltage cascode current mirrors

    DEFF Research Database (Denmark)

    Bruun, Erik; Shah, Peter Jivan

    1995-01-01

    Low-voltage cascode current mirrors are reviewed with respect to the design limitations imposed if all transistors in the mirror are required to operate in the saturation region. It is found that both a lower limit and an upper limit exist for the cascode transistor bias voltage. Further, the use....... The proposed configuration has the advantage of simplicity combined with a complete elimination of the need for fixed bias voltages or bias currents in the current mirror. A disadvantage is that it requires a higher input voltage to the current mirror...

  6. Fault Ride-through Capability Enhancement of Voltage Source Converter-High Voltage Direct Current Systems with Bridge Type Fault Current Limiters

    Directory of Open Access Journals (Sweden)

    Md Shafiul Alam

    2017-11-01

    Full Text Available This paper proposes the use of bridge type fault current limiters (BFCLs as a potential solution to reduce the impact of fault disturbance on voltage source converter-based high voltage DC (VSC-HVDC systems. Since VSC-HVDC systems are vulnerable to faults, it is essential to enhance the fault ride-through (FRT capability with auxiliary control devices like BFCLs. BFCL controllers have been developed to limit the fault current during the inception of system disturbances. Real and reactive power controllers for the VSC-HVDC have been developed based on current control mode. DC link voltage control has been achieved by a feedback mechanism such that net power exchange with DC link capacitor is zero. A grid-connected VSC-HVDC system and a wind farm integrated VSC-HVDC system along with the proposed BFCL and associated controllers have been implemented in a real time digital simulator (RTDS. Symmetrical three phase as well as different types of unsymmetrical faults have been applied in the systems in order to show the effectiveness of the proposed BFCL solution. DC link voltage fluctuation, machine speed and active power oscillation have been greatly suppressed with the proposed BFCL. Another significant feature of this work is that the performance of the proposed BFCL in VSC-HVDC systems is compared to that of series dynamic braking resistor (SDBR. Comparative results show that the proposed BFCL is superior over SDBR in limiting fault current as well as improving system fault ride through (FRT capability.

  7. Measurements of the Backstreaming Proton IONS in the Self-Magnetic Pinch (SMP) Diode Utilizing Copper Activation Technique

    Science.gov (United States)

    Mazarakis, Michael; Cuneo, Michael; Fournier, Sean; Johnston, Mark; Kiefer, Mark; Leckbee, Joshua; Simpson, Sean; Renk, Timothy; Webb, Timothy; Bennett, Nichelle

    2016-10-01

    The results presented here were obtained with an SMP diode mounted at the front high voltage end of the 8-10-MV RITS Self-Magnetically Insulated Transmission Line (MITL) voltage adder. Our experiments had two objectives: first, to measure the contribution of the back-streaming proton currents emitted from the anode target, and second, to evaluate the energy of those ions and hence the actual Anode-Cathode (A-K) gap voltage. The accelerating voltage quoted in the literature is estimated utilizing para-potential flow theories. Thus, it is interesting to have another independent measurement of the A-K voltage. We have measured the back-streaming protons emitted from the anode and propagating through a hollow cathode tip for various diode configurations and different techniques of target cleaning treatment, namely, heating at very high temperatures with DC and pulsed current, with RF plasma cleaning, and with both plasma cleaning and heating. We have also evaluated the A-K gap voltage by energy filtering techniques. Sandia is operated by Sandia Corporation, a subsidiary of Lockheed Martin Company, for the US DOE NNSA under Contract No. DE-AC04-94AL85000.

  8. Voltage- and current-activated metal–insulator transition in VO2-based electrical switches: a lifetime operation analysis

    Directory of Open Access Journals (Sweden)

    Aurelian Crunteanu, Julien Givernaud, Jonathan Leroy, David Mardivirin, Corinne Champeaux, Jean-Christophe Orlianges, Alain Catherinot and Pierre Blondy

    2010-01-01

    Full Text Available Vanadium dioxide is an intensively studied material that undergoes a temperature-induced metal–insulator phase transition accompanied by a large change in electrical resistivity. Electrical switches based on this material show promising properties in terms of speed and broadband operation. The exploration of the failure behavior and reliability of such devices is very important in view of their integration in practical electronic circuits. We performed systematic lifetime investigations of two-terminal switches based on the electrical activation of the metal–insulator transition in VO2 thin films. The devices were integrated in coplanar microwave waveguides (CPWs in series configuration. We detected the evolution of a 10 GHz microwave signal transmitted through the CPW, modulated by the activation of the VO2 switches in both voltage- and current-controlled modes. We demonstrated enhanced lifetime operation of current-controlled VO2-based switching (more than 260 million cycles without failure compared with the voltage-activated mode (breakdown at around 16 million activation cycles. The evolution of the electrical self-oscillations of a VO2-based switch induced in the current-operated mode is a subtle indicator of the material properties modification and can be used to monitor its behavior under various external stresses in sensor applications.

  9. Development of a 130-mA, 75-kV high voltage column for high-intensity dc proton injectors

    International Nuclear Information System (INIS)

    Sherman, J.; Arvin, A.; Hansborough, L.; Hodgkins, D.; Meyer, E.; Schneider, J.D.; Stevens, R.R. Jr.; Zaugg, T.

    1997-01-01

    A reliable high-voltage (HV) column has been developed for dc proton injectors with applications to high-intensity cw linacs. The HV column is coupled with a microwave-driven plasma generator to produce a 75-keV, 110-mA dc proton beam. Typical proton fraction from this source is 85--90%, requiring the HV column and accelerating electrodes to operate with a 130-mA hydrogen-ion beam current. A glow-discharge, which was caused by the ion source axial magnetic field, was initially observed in the HV column. This problem was solved by scaling the electron production processes, the magnetic field, and the HV column pressure into a favorable regime. A subsequent 168 hour reliability run on the 75-keV injector showed that the ion source (plasma generator and HV column) has >98% beam availability

  10. Voltage Sensing in Membranes: From Macroscopic Currents to Molecular Motions.

    Science.gov (United States)

    Freites, J Alfredo; Tobias, Douglas J

    2015-06-01

    Voltage-sensing domains (VSDs) are integral membrane protein units that sense changes in membrane electric potential, and through the resulting conformational changes, regulate a specific function. VSDs confer voltage-sensitivity to a large superfamily of membrane proteins that includes voltage-gated Na[Formula: see text], K[Formula: see text], Ca[Formula: see text] ,and H[Formula: see text] selective channels, hyperpolarization-activated cyclic nucleotide-gated channels, and voltage-sensing phosphatases. VSDs consist of four transmembrane segments (termed S1 through S4). Their most salient structural feature is the highly conserved positions for charged residues in their sequences. S4 exhibits at least three conserved triplet repeats composed of one basic residue (mostly arginine) followed by two hydrophobic residues. These S4 basic side chains participate in a state-dependent internal salt-bridge network with at least four acidic residues in S1-S3. The signature of voltage-dependent activation in electrophysiology experiments is a transient current (termed gating or sensing current) upon a change in applied membrane potential as the basic side chains in S4 move across the membrane electric field. Thus, the unique structural features of the VSD architecture allow for competing requirements: maintaining a series of stable transmembrane conformations, while allowing charge motion, as briefly reviewed here.

  11. Associating ground magnetometer observations with current or voltage generators

    DEFF Research Database (Denmark)

    Hartinger, M. D.; Xu, Z.; Clauer, C. R.

    2017-01-01

    A circuit analogy for magnetosphere-ionosphere current systems has two extremes for driversof ionospheric currents: ionospheric elec tric fields/voltages constant while current/conductivity vary—the“voltage generator”—and current constant while electric field/conductivity vary—the “current generator.......”Statistical studies of ground magnetometer observations associated with dayside Transient High LatitudeCurrent Systems (THLCS) driven by similar mechanisms find contradictory results using this paradigm:some studies associate THLCS with voltage generators, others with current generators. We argue that mostof...... these two assumptions substantially alter expectations for magnetic perturbations associatedwith either a current or a voltage generator. Our results demonstrate that before interpreting groundmagnetometer observations of THLCS in the context of current/voltage generators, the location...

  12. Voltage sensitivity of M2 muscarinic receptors underlies the delayed rectifier-like activation of ACh-gated K(+) current by choline in feline atrial myocytes.

    Science.gov (United States)

    Navarro-Polanco, Ricardo A; Aréchiga-Figueroa, Iván A; Salazar-Fajardo, Pedro D; Benavides-Haro, Dora E; Rodríguez-Elías, Julio C; Sachse, Frank B; Tristani-Firouzi, Martin; Sánchez-Chapula, José A; Moreno-Galindo, Eloy G

    2013-09-01

    Choline (Ch) is a precursor and metabolite of the neurotransmitter acetylcholine (ACh). In canine and guinea pig atrial myocytes, Ch was shown to activate an outward K(+) current in a delayed rectifier fashion. This current has been suggested to modulate cardiac electrical activity and to play a role in atrial fibrillation pathophysiology. However, the exact nature and identity of this current has not been convincingly established. We recently described the unique ligand- and voltage-dependent properties of muscarinic activation of ACh-activated K(+) current (IKACh) and showed that, in contrast to ACh, pilocarpine induces a current with delayed rectifier-like properties with membrane depolarization. Here, we tested the hypothesis that Ch activates IKACh in feline atrial myocytes in a voltage-dependent manner similar to pilocarpine. Single-channel recordings, biophysical profiles, specific pharmacological inhibition and computational data indicate that the current activated by Ch is IKACh. Moreover, we show that membrane depolarization increases the potency and efficacy of IKACh activation by Ch and thus gives the appearance of a delayed rectifier activating K(+) current at depolarized potentials. Our findings support the emerging concept that IKACh modulation is both voltage- and ligand-specific and reinforce the importance of these properties in understanding cardiac physiology.

  13. High-voltage, high-current, solid-state closing switch

    Science.gov (United States)

    Focia, Ronald Jeffrey

    2017-08-22

    A high-voltage, high-current, solid-state closing switch uses a field-effect transistor (e.g., a MOSFET) to trigger a high-voltage stack of thyristors. The switch can have a high hold-off voltage, high current carrying capacity, and high time-rate-of-change of current, di/dt. The fast closing switch can be used in pulsed power applications.

  14. Dual-harmonic auto voltage control for the rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

    Directory of Open Access Journals (Sweden)

    Fumihiko Tamura

    2008-07-01

    Full Text Available The dual-harmonic operation, in which the accelerating cavities are driven by the superposition of the fundamental and the second harmonic rf voltage, is useful for acceleration of the ultrahigh intensity proton beam in the rapid cycling synchrotron (RCS of Japan Proton Accelerator Research Complex (J-PARC. However, the precise and fast voltage control of the harmonics is necessary to realize the dual-harmonic acceleration. We developed the dual-harmonic auto voltage control system for the J-PARC RCS. We describe details of the design and the implementation. Various tests of the system are performed with the RCS rf system. Also, a preliminary beam test has been done. We report the test results.

  15. Universal Voltage Conveyor and Current Conveyor in Fast Full-Wave Rectifier

    Directory of Open Access Journals (Sweden)

    Josef Burian

    2012-12-01

    Full Text Available This paper deals about the design of a fast voltage-mode full-wave rectifier, where universal voltage conveyor and second-generation current conveyor are used as active elements. Thanks to the active elements, the input and output impedance of the non-linear circuit is infinitely high respectively zero in theory. For the rectification only two diodes and three resistors are required as passive elements. The performance of the circuit is shown on experimental measurement results showing the dynamic range, time response, frequency dependent DC transient value and RMS error for different values of input voltage amplitudes.

  16. Progress On Neutrino-Proton Neutral-Current Scattering In MicroBooNE

    Energy Technology Data Exchange (ETDEWEB)

    Pate, Stephen [New Mexico State U.

    2017-01-16

    The MicroBooNE Experiment at the Fermi National Accelerator Laboratory, an 89-ton active mass liquid argon time projection chamber, affords a unique opportunity to observe low-$Q^2$ neutral-current neutrino-proton scattering events. Neutral-current neutrino-proton scattering at $Q^2 < 1$ GeV$^2$ is dominated by the proton's axial form factor, which can be written as a combination of contributions from the up, down, and strange quarks: $G_A(Q^2) = \\frac{1}{2}[-G_A^u(Q^2)+G_A^d(Q^2)+G_A^s(Q^2)]$. The contribution from up and down quarks has been established in past charged-current measurements. The contribution from strange quarks at low $Q^2$ remains unmeasured; this is of great interest since the strange quark contribution to the proton spin can be determined from the low-$Q^2$ behavior: $\\Delta S = G_A^s(Q^2=0)$. MicroBooNE began operating in the Booster Neutrino Beam in October 2015. I will present the status in observing isolated proton tracks in the MicroBooNE detector as a signature for neutral-current neutrino-proton events. The sensitivity of the MicroBooNE experiment for measuring the strange quark contribution to the proton spin will be discussed.

  17. Voltage harmonics mitigation through hybrid active power filer

    International Nuclear Information System (INIS)

    Sahito, A.A.; Tunio, S.M.; Khizer, A.N.

    2016-01-01

    Fast dynamic response, high efficiency, low cost and small size of power electronic converters have exponentially increased their use in modern power system which resulted in harmonically distorted voltage and currents. Voltage harmonics mainly caused by current harmonics are more dangerous as performance and expected operating life of other power system equipment are affected by harmonically distorted supply voltage. Electronic filter circuits are used to improve system power quality by mitigating adverse effects of harmonics. Hybrid filters having advantages of both passive and active filters are preferred to resolve the problem of harmonics efficiently and avoiding any chance of resonance. In this paper, a three phase three wire network is considered to supply an adjustable speed drive represented by a resistive load connected across a three phase bridge rectifier. Simulation of the considered system shows THD (Total Harmonic Distortion) of 18.91 and 7.61 percentage in supply current and voltage respectively. A HAPF (Hybrid Active Power Filter) is proposed to reduce these THD values below 5 percentage as recommended by IEEE Standard-519. P-Q theorem is used to calculate required parameters for proposed filter, which is implemented through hysteresis control. Simulation results confirm the effectiveness of the designed filter as THD for both current and voltage have reduced below allowable limit of 5 percentage. (author)

  18. Voltage Harmonics Mitigation through Hybrid Active Power Filter

    Directory of Open Access Journals (Sweden)

    Anwer Ali Sahito

    2016-01-01

    Full Text Available Fast dynamic response, high efficiency, low cost and small size of power electronic converters have exponentially increased their use in modern power system which resulted in harmonically distorted voltage and currents. Voltage harmonics mainly caused by current harmonics are more dangerous as performance and expected operating life of other power system equipment are affected by harmonically distorted supply voltage. Electronic filter circuits are used to improve system power quality by mitigating adverse effects of harmonics. Hybrid filters having advantages of both passive and active filters are preferred to resolve the problem of harmonics efficiently and avoiding any chance of resonance. In this paper, a three phase three wire network is considered to supply an adjustable speed drive represented by a resistive load connected across a three phase bridge rectifier. Simulation of the considered system shows THD (Total Harmonic Distortion of 18.91 and 7.61% in supply current and voltage respectively. A HAPF (Hybrid Active Power Filter is proposed to reduce these THD values below 5% as recommended by IEEE Standard-519. P-Q theorem is used to calculate required parameters for proposed filter, which is implemented through hysteresis control. Simulation results confirm the effectiveness of the designed filter as THD for both current and voltage have reduced below allowable limit of 5%.

  19. Analysis and design of grid-current-feedback active damping for LCL resonance in grid-connected voltage source converters

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Blaabjerg, Frede; Loh, Poh Chiang

    2014-01-01

    This paper investigates the active damping of LCL-filter resonance within single-loop grid current control of grid-connected voltage source converters. First, the basic analysis in the continuous s-domain reveals that the grid-current-feedback active damping forms a virtual impedance across...... in a digital control system. The instability induced by the negative virtual resistance, which is commonly experienced in the feedback-type active damping, can thus be avoided. A systematic design method of the highpass filter is also proposed by the help of root locus analysis in the discrete z-domain. Lastly...

  20. Pado, a fluorescent protein with proton channel activity can optically monitor membrane potential, intracellular pH, and map gap junctions.

    Science.gov (United States)

    Kang, Bok Eum; Baker, Bradley J

    2016-04-04

    An in silico search strategy was developed to identify potential voltage-sensing domains (VSD) for the development of genetically encoded voltage indicators (GEVIs). Using a conserved charge distribution in the S2 α-helix, a single in silico search yielded most voltage-sensing proteins including voltage-gated potassium channels, voltage-gated calcium channels, voltage-gated sodium channels, voltage-gated proton channels, and voltage-sensing phosphatases from organisms ranging from mammals to bacteria and plants. A GEVI utilizing the VSD from a voltage-gated proton channel identified from that search was able to optically report changes in membrane potential. In addition this sensor was capable of manipulating the internal pH while simultaneously reporting that change optically since it maintains the voltage-gated proton channel activity of the VSD. Biophysical characterization of this GEVI, Pado, demonstrated that the voltage-dependent signal was distinct from the pH-dependent signal and was dependent on the movement of the S4 α-helix. Further investigation into the mechanism of the voltage-dependent optical signal revealed that inhibiting the dimerization of the fluorescent protein greatly reduced the optical signal. Dimerization of the FP thereby enabled the movement of the S4 α-helix to mediate a fluorescent response.

  1. AC Voltage Control of DC/DC Converters Based on Modular Multilevel Converters in Multi-Terminal High-Voltage Direct Current Transmission Systems

    Directory of Open Access Journals (Sweden)

    Rui Li

    2016-12-01

    Full Text Available The AC voltage control of a DC/DC converter based on the modular multilevel converter (MMC is considered under normal operation and during a local DC fault. By actively setting the AC voltage according to the two DC voltages of the DC/DC converter, the modulation index can be near unity, and the DC voltage is effectively utilized to output higher AC voltage. This significantly decreases submodule (SM capacitance and conduction losses of the DC/DC converter, yielding reduced capital cost, volume, and higher efficiency. Additionally, the AC voltage is limited in the controllable range of both the MMCs in the DC/DC converter; thus, over-modulation and uncontrolled currents are actively avoided. The AC voltage control of the DC/DC converter during local DC faults, i.e., standby operation, is also proposed, where only the MMC connected on the faulty cable is blocked, while the other MMC remains operational with zero AC voltage output. Thus, the capacitor voltages can be regulated at the rated value and the decrease of the SM capacitor voltages after the blocking of the DC/DC converter is avoided. Moreover, the fault can still be isolated as quickly as the conventional approach, where both MMCs are blocked and the DC/DC converter is not exposed to the risk of overcurrent. The proposed AC voltage control strategy is assessed in a three-terminal high-voltage direct current (HVDC system incorporating a DC/DC converter, and the simulation results confirm its feasibility.

  2. Possible influence of the voltage dependence of the Josephson tunneling current I(V,psi) on the corresponding current-voltage characteristic

    International Nuclear Information System (INIS)

    Hahlbohm, H.D.; Luebbig, H.; Luther, H.

    1975-01-01

    Analog computer calculations of the current-voltage characteristic involving the voltage dependence of the amplitudes of the tunneling current equation explicitly, for the case of a current driven tunneling junction at different temperatures are reported on. These studies are based upon the adiabatic representation of the current-phase relation. The influence of retarding effects is not included. Therefore the computational results can lead to practical consequences at best in the range near the transition temperature. (Auth.)

  3. Current-voltage characteristics of porous-silicon structures

    International Nuclear Information System (INIS)

    Diligenti, A.; Nannini, A.; Pennelli, G.; Pieri, F.; Fuso, F.; Allegrini, M.

    1996-01-01

    I-V DC characteristics have been measured on metal/porous-silicon structures. In particular, the measurements on metal/free-standing porous-silicon film/metal devices confirmed the result, already obtained, that the metal/porous-silicon interface plays a crucial role in the transport of any device. Four-contacts measurements on free-standing layers showed that the current linearly depends on the voltage and that the conduction process is thermally activated, the activation energy depending on the porous silicon film production parameters. Finally, annealing experiments performed in order to improve the conduction of rectifying contacts, are described

  4. Thermal instability and current-voltage scaling in superconducting fault current limiters

    Energy Technology Data Exchange (ETDEWEB)

    Zeimetz, B [Department of Materials Science and Metallurgy, Cambridge University, Pembroke Street, Cambridge CB1 3QZ (United Kingdom); Tadinada, K [Department of Engineering, Cambridge University, Trumpington Road, Cambridge CB2 1PZ (United Kingdom); Eves, D E [Department of Engineering, Cambridge University, Trumpington Road, Cambridge CB2 1PZ (United Kingdom); Coombs, T A [Department of Engineering, Cambridge University, Trumpington Road, Cambridge CB2 1PZ (United Kingdom); Evetts, J E [Department of Materials Science and Metallurgy, Cambridge University, Pembroke Street, Cambridge CB1 3QZ (United Kingdom); Campbell, A M [Department of Engineering, Cambridge University, Trumpington Road, Cambridge CB2 1PZ (United Kingdom)

    2004-04-01

    We have developed a computer model for the simulation of resistive superconducting fault current limiters in three dimensions. The program calculates the electromagnetic and thermal response of a superconductor to a time-dependent overload voltage, with different possible cooling conditions for the surfaces, and locally variable superconducting and thermal properties. We find that the cryogen boil-off parameters critically influence the stability of a limiter. The recovery time after a fault increases strongly with thickness. Above a critical thickness, the temperature is unstable even for a small applied AC voltage. The maximum voltage and maximum current during a short fault are correlated by a simple exponential law.

  5. KCNE5 induces time- and voltage-dependent modulation of the KCNQ1 current

    DEFF Research Database (Denmark)

    Angelo, Kamilla; Jespersen, Thomas; Grunnet, Morten

    2002-01-01

    The function of the KCNE5 (KCNE1-like) protein has not previously been described. Here we show that KCNE5 induces both a time- and voltage-dependent modulation of the KCNQ1 current. Interaction of the KCNQ1 channel with KCNE5 shifted the voltage activation curve of KCNQ1 by more than 140 mV in th...... the I(Ks) current in certain parts of the mammalian heart....

  6. Electron-beam-induced-current and active secondary-electron voltage-contrast with aberration-corrected electron probes

    Energy Technology Data Exchange (ETDEWEB)

    Han, Myung-Geun, E-mail: mghan@bnl.gov [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Garlow, Joseph A. [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Materials Science and Engineering Department, Stony Brook University, Stony Brook, NY 11794 (United States); Marshall, Matthew S.J.; Tiano, Amanda L. [Department of Chemistry, Stony Brook University, Stony Brook, NY 11974 (United States); Wong, Stanislaus S. [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Department of Chemistry, Stony Brook University, Stony Brook, NY 11974 (United States); Cheong, Sang-Wook [Department of Physics and Astronomy, Rutgers Center for Emergent Materials, Rutgers University, Piscataway, NJ 08854 (United States); Walker, Frederick J.; Ahn, Charles H. [Department of Applied Physics and Center for Research on Interface Structures and Phenomena, Yale University, New Haven, CT 06520 (United States); Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT 06520 (United States); Zhu, Yimei [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2017-05-15

    Highlights: • Electron-beam-induced-current (EBIC) and active secondary-electron voltage-contrast (SE-VC) are demonstrated in STEM mode combined with in situ electrical biasing in a TEM. • Electrostatic potential maps in ferroelectric thin films, multiferroic nanowires, and single crystals obtained by off-axis electron holography were compared with EBIC and SE-VC data. • Simultaneous EBIC and active SE-VC performed with atomic resolution STEM are demonstrated. - Abstract: The ability to map out electrostatic potentials in materials is critical for the development and the design of nanoscale electronic and spintronic devices in modern industry. Electron holography has been an important tool for revealing electric and magnetic field distributions in microelectronics and magnetic-based memory devices, however, its utility is hindered by several practical constraints, such as charging artifacts and limitations in sensitivity and in field of view. In this article, we report electron-beam-induced-current (EBIC) and secondary-electron voltage-contrast (SE-VC) with an aberration-corrected electron probe in a transmission electron microscope (TEM), as complementary techniques to electron holography, to measure electric fields and surface potentials, respectively. These two techniques were applied to ferroelectric thin films, multiferroic nanowires, and single crystals. Electrostatic potential maps obtained by off-axis electron holography were compared with EBIC and SE-VC to show that these techniques can be used as a complementary approach to validate quantitative results obtained from electron holography analysis.

  7. Current-voltage-temperature characteristics of DNA origami

    Energy Technology Data Exchange (ETDEWEB)

    Bellido, Edson P; Bobadilla, Alfredo D; Rangel, Norma L; Seminario, Jorge M [Department of Chemical Engineering, Texas A and M University, College Station, TX 77843 (United States); Zhong Hong; Norton, Michael L [Department of Chemistry, Marshall University, Huntington, WV 25755 (United States); Sinitskii, Alexander [Department of Chemistry, Rice University, Houston, TX 77005 (United States)

    2009-04-29

    The temperature dependences of the current-voltage characteristics of a sample of triangular DNA origami deposited in a 100 nm gap between platinum electrodes are measured using a probe station. Below 240 K, the sample shows high impedance, similar to that of the substrate. Near room temperature the current shows exponential behavior with respect to the inverse of temperature. Sweep times of 1 s do not yield a steady state; however sweep times of 450 s for the bias voltage secure a steady state. The thermionic emission and hopping conduction models yield similar barriers of {approx}0.7 eV at low voltages. For high voltages, the hopping conduction mechanism yields a barrier of 0.9 eV and the thermionic emission yields 1.1 eV. The experimental data set suggests that the dominant conduction mechanism is hopping in the range 280-320 K. The results are consistent with theoretical and experimental estimates of the barrier for related molecules.

  8. Current-voltage-temperature characteristics of DNA origami

    International Nuclear Information System (INIS)

    Bellido, Edson P; Bobadilla, Alfredo D; Rangel, Norma L; Seminario, Jorge M; Zhong Hong; Norton, Michael L; Sinitskii, Alexander

    2009-01-01

    The temperature dependences of the current-voltage characteristics of a sample of triangular DNA origami deposited in a 100 nm gap between platinum electrodes are measured using a probe station. Below 240 K, the sample shows high impedance, similar to that of the substrate. Near room temperature the current shows exponential behavior with respect to the inverse of temperature. Sweep times of 1 s do not yield a steady state; however sweep times of 450 s for the bias voltage secure a steady state. The thermionic emission and hopping conduction models yield similar barriers of ∼0.7 eV at low voltages. For high voltages, the hopping conduction mechanism yields a barrier of 0.9 eV and the thermionic emission yields 1.1 eV. The experimental data set suggests that the dominant conduction mechanism is hopping in the range 280-320 K. The results are consistent with theoretical and experimental estimates of the barrier for related molecules.

  9. DC-Voltage Fluctuation Elimination Through a DC-Capacitor Current Control for DFIG Converters Under Unbalanced Grid Voltage Conditions

    DEFF Research Database (Denmark)

    Liu, Changjin; Xu, Dehong; Zhu, Nan

    2013-01-01

    Unbalanced grid voltage causes a large second-order harmonic current in the dc-link capacitors as well as dc-voltage fluctuation, which potentially will degrade the lifespan and reliability of the capacitors in voltage source converters. This paper proposes a novel dc-capacitor current control...... method for a grid-side converter (GSC) to eliminate the negative impact of unbalanced grid voltage on the dc-capacitors. In this method, a dc-capacitor current control loop, where a negative-sequence resonant controller is used to increase the loop gain, is added to the conventional GSC current control...... loop. The rejection capability to the unbalanced grid voltage and the stability of the proposed control system are discussed. The second-order harmonic current in the dc capacitor as well as dc-voltage fluctuation is very well eliminated. Hence, the dc capacitors will be more reliable under unbalanced...

  10. Optical sensors for the measurement of electric current and voltage

    Energy Technology Data Exchange (ETDEWEB)

    Rutgers, W R; Hulshof, H J.M.; Laurensse, I J; van der Wey, A H

    1987-01-01

    Optical sensors for the measurement of electrical current and voltage were developed for application in electric power systems. The current sensor, based on the Faraday effect in a monomode glass fiber, and the voltage sensor, based on the transverse Pockels effect in a crystal, are demonstrated in wide-band (10 MHz) interference-free measurements of pulsed currents and impulse voltages.

  11. Modulation of voltage-gated channel currents by harmaline and harmane.

    Science.gov (United States)

    Splettstoesser, Frank; Bonnet, Udo; Wiemann, Martin; Bingmann, Dieter; Büsselberg, Dietrich

    2005-01-01

    Harmala alkaloids are endogenous substances, which are involved in neurodegenerative disorders such as M. Parkinson, but some of them also have neuroprotective effects in the nervous system. While several sites of action at the cellular level (e.g. benzodiazepine receptors, 5-HT and GABA(A) receptors) have been identified, there is no report on how harmala alkaloids interact with voltage-gated membrane channels. The aim of this study was to investigate the effects of harmaline and harmane on voltage-activated calcium- (I(Ca(V))), sodium- (I(Na(V))) and potassium (I(K(V)))-channel currents, using the whole-cell patch-clamp method with cultured dorsal root ganglion neurones of 3-week-old rats. Currents were elicited by voltage steps from the holding potential to different command potentials. Harmaline and harmane reduced I(Ca(V)), I(Na(V)) and I(K(V)) concentration-dependent (10-500 microM) over the voltage range tested. I(Ca(V)) was reduced with an IC(50) of 100.6 microM for harmaline and by a significantly lower concentration of 75.8 microM (P<0.001, t-test) for harmane. The Hill coefficient was close to 1. Threshold concentration was around 10 microM for both substances. The steady state of inhibition of I(Ca(V)) by harmaline or harmane was reached within several minutes. The action was not use-dependent and at least partly reversible. It was mainly due to a reduction in the sustained calcium channel current (I(Ca(L+N))), while the transient voltage-gated calcium channel current (I(Ca(T))) was only partially affected. We conclude that harmaline and harmane are modulators of I(Ca(V)) in vitro. This might be related to their neuroprotective effects.

  12. Ultra-Low Voltage Class AB Switched Current Memory Cell

    DEFF Research Database (Denmark)

    Igor, Mucha

    1996-01-01

    This paper presents the theoretical basis for the design of class AB switched current memory cells employing floating-gate MOS transistors, suitable for ultra-low-voltage applications. To support the theoretical assumptions circuits based on these cells were designed using a CMOS process with thr......This paper presents the theoretical basis for the design of class AB switched current memory cells employing floating-gate MOS transistors, suitable for ultra-low-voltage applications. To support the theoretical assumptions circuits based on these cells were designed using a CMOS process...... with threshold voltages of 0.9V. Both hand calculations and PSPICE simulations showed that the cells designed allowed a maximum signal range better than +/-13 micoamp, with a supply voltage down to 1V and a quiescent bias current of 1 microamp, resulting in a very high current efficiency and effective power...

  13. Harmonic current interaction at a low voltage customer's installations

    NARCIS (Netherlands)

    Bhattacharyya, S.; Myrzik, J.M.A.; Kling, W.L.; Cobben, J.F.G.; Casteren, van J.

    2009-01-01

    The increased uses of power electronics and switching devices in the electricity network have changed the operational environment of the power system. These devices have nonlinear voltage-current characteristics and produce harmonic currents, and consequently distort the voltage waveform. A low

  14. Digital Realization of Capacitor-Voltage Feedback Active Damping for LCL-Filtered Grid Converters

    DEFF Research Database (Denmark)

    Xin, Zhen; Wang, Xiongfei; Loh, Poh Chiang

    2015-01-01

    The capacitor voltage of an LCL-filter can also be used for active damping, if it is fed back for synchronization. By this way, an extra current sensor can be avoided. Compared with the existing active damping techniques designed with capacitor current feedback, the capacitor voltage feedback....... To overcome their drawbacks, a new derivative method is then proposed, based on the non-ideal generalized integrator. The performance of the proposed derivative has been found to match the ideal “s” function closely. Active damping based on capacitor voltage feedback can therefore be realized accurately...

  15. Load Insensitive, Low Voltage Quadrature Oscillator Using Single Active Element

    Directory of Open Access Journals (Sweden)

    Jitendra Mohan

    2017-01-01

    Full Text Available In this paper, a load insensitive quadrature oscillator using single differential voltage dual-X second generation current conveyor operated at low voltage is proposed. The proposed circuit employs single active element, three grounded resistors and two grounded capacitors. The proposed oscillator offers two load insensitive quadrature current outputs and three quadrature voltage outputs simultaneously. Effects of non-idealities along with the effects of parasitic are further studied. The proposed circuit enjoys the feature of low active and passive sensitivities. Additionally, a resistorless realization of the proposed quadrature oscillator is also explored. Simulation results using PSPICE program on cadence tool using 90 nm Complementary Metal Oxide Semiconductor (CMOS process parameters confirm the validity and practical utility of the proposed circuit.

  16. External pH modulates EAG superfamily K+ channels through EAG-specific acidic residues in the voltage sensor

    Science.gov (United States)

    Kazmierczak, Marcin; Zhang, Xiaofei; Chen, Bihan; Mulkey, Daniel K.; Shi, Yingtang; Wagner, Paul G.; Pivaroff-Ward, Kendra; Sassic, Jessica K.; Bayliss, Douglas A.

    2013-01-01

    The Ether-a-go-go (EAG) superfamily of voltage-gated K+ channels consists of three functionally distinct gene families (Eag, Elk, and Erg) encoding a diverse set of low-threshold K+ currents that regulate excitability in neurons and muscle. Previous studies indicate that external acidification inhibits activation of three EAG superfamily K+ channels, Kv10.1 (Eag1), Kv11.1 (Erg1), and Kv12.1 (Elk1). We show here that Kv10.2, Kv12.2, and Kv12.3 are similarly inhibited by external protons, suggesting that high sensitivity to physiological pH changes is a general property of EAG superfamily channels. External acidification depolarizes the conductance–voltage (GV) curves of these channels, reducing low threshold activation. We explored the mechanism of this high pH sensitivity in Kv12.1, Kv10.2, and Kv11.1. We first examined the role of acidic voltage sensor residues that mediate divalent cation block of voltage activation in EAG superfamily channels because protons reduce the sensitivity of Kv12.1 to Zn2+. Low pH similarly reduces Mg2+ sensitivity of Kv10.1, and we found that the pH sensitivity of Kv11.1 was greatly attenuated at 1 mM Ca2+. Individual neutralizations of a pair of EAG-specific acidic residues that have previously been implicated in divalent block of diverse EAG superfamily channels greatly reduced the pH response in Kv12.1, Kv10.2, and Kv11.1. Our results therefore suggest a common mechanism for pH-sensitive voltage activation in EAG superfamily channels. The EAG-specific acidic residues may form the proton-binding site or alternatively are required to hold the voltage sensor in a pH-sensitive conformation. The high pH sensitivity of EAG superfamily channels suggests that they could contribute to pH-sensitive K+ currents observed in vivo. PMID:23712551

  17. External pH modulates EAG superfamily K+ channels through EAG-specific acidic residues in the voltage sensor.

    Science.gov (United States)

    Kazmierczak, Marcin; Zhang, Xiaofei; Chen, Bihan; Mulkey, Daniel K; Shi, Yingtang; Wagner, Paul G; Pivaroff-Ward, Kendra; Sassic, Jessica K; Bayliss, Douglas A; Jegla, Timothy

    2013-06-01

    The Ether-a-go-go (EAG) superfamily of voltage-gated K(+) channels consists of three functionally distinct gene families (Eag, Elk, and Erg) encoding a diverse set of low-threshold K(+) currents that regulate excitability in neurons and muscle. Previous studies indicate that external acidification inhibits activation of three EAG superfamily K(+) channels, Kv10.1 (Eag1), Kv11.1 (Erg1), and Kv12.1 (Elk1). We show here that Kv10.2, Kv12.2, and Kv12.3 are similarly inhibited by external protons, suggesting that high sensitivity to physiological pH changes is a general property of EAG superfamily channels. External acidification depolarizes the conductance-voltage (GV) curves of these channels, reducing low threshold activation. We explored the mechanism of this high pH sensitivity in Kv12.1, Kv10.2, and Kv11.1. We first examined the role of acidic voltage sensor residues that mediate divalent cation block of voltage activation in EAG superfamily channels because protons reduce the sensitivity of Kv12.1 to Zn(2+). Low pH similarly reduces Mg(2+) sensitivity of Kv10.1, and we found that the pH sensitivity of Kv11.1 was greatly attenuated at 1 mM Ca(2+). Individual neutralizations of a pair of EAG-specific acidic residues that have previously been implicated in divalent block of diverse EAG superfamily channels greatly reduced the pH response in Kv12.1, Kv10.2, and Kv11.1. Our results therefore suggest a common mechanism for pH-sensitive voltage activation in EAG superfamily channels. The EAG-specific acidic residues may form the proton-binding site or alternatively are required to hold the voltage sensor in a pH-sensitive conformation. The high pH sensitivity of EAG superfamily channels suggests that they could contribute to pH-sensitive K(+) currents observed in vivo.

  18. Current voltage perspective of an organic electronic device

    Science.gov (United States)

    Mukherjee, Ayash K.; Kumari, Nikita

    2018-05-01

    Nonlinearity in current (I) - voltage (V) measurement is a well-known attribute of two-terminal organic device, irrespective of the geometrical or structural arrangement of the device. Most of the existing theories that are developed for interpretation of I-V data, either focus current-voltage relationship of charge injection mechanism across the electrode-organic material interface or charge transport mechanism through the organic active material. On the contrary, both the mechanisms work in tandem charge conduction through the device. The transport mechanism is further complicated by incoherent scattering from scattering centres/charge traps that are located at the electrode-organic material interface and in the bulk of organic material. In the present communication, a collective expression has been formulated that comprises of all the transport mechanisms that are occurring at various locations of a planar organic device. The model has been fitted to experimental I-V data of Au/P3HT/Au device with excellent degree of agreement. Certain physical parameters such as the effective area of cross-section and resistance due to charge traps have been extracted from the fit.

  19. Dynamic neutral beam current and voltage control to improve beam efficacy in tokamaks

    Science.gov (United States)

    Pace, D. C.; Austin, M. E.; Bardoczi, L.; Collins, C. S.; Crowley, B.; Davis, E.; Du, X.; Ferron, J.; Grierson, B. A.; Heidbrink, W. W.; Holcomb, C. T.; McKee, G. R.; Pawley, C.; Petty, C. C.; Podestà, M.; Rauch, J.; Scoville, J. T.; Spong, D. A.; Thome, K. E.; Van Zeeland, M. A.; Varela, J.; Victor, B.

    2018-05-01

    An engineering upgrade to the neutral beam system at the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] enables time-dependent programming of the beam voltage and current. Initial application of this capability involves pre-programmed beam voltage and current injected into plasmas that are known to be susceptible to instabilities that are driven by energetic ( E ≥ 40 keV) beam ions. These instabilities, here all Alfvén eigenmodes (AEs), increase the transport of the beam ions beyond a classical expectation based on particle drifts and collisions. Injecting neutral beam power, P beam ≥ 2 MW, at reduced voltage with increased current reduces the drive for Alfvénic instabilities and results in improved ion confinement. In lower-confinement plasmas, this technique is applied to eliminate the presence of AEs across the mid-radius of the plasmas. Simulations of those plasmas indicate that the mode drive is decreased and the radial extent of the remaining modes is reduced compared to a higher beam voltage case. In higher-confinement plasmas, this technique reduces AE activity in the far edge and results in an interesting scenario of beam current drive improving as the beam voltage reduces from 80 kV to 65 kV.

  20. Simulation of forward dark current voltage characteristics of tandem solar cells

    International Nuclear Information System (INIS)

    Rubinelli, F.A.

    2012-01-01

    The transport mechanisms tailoring the shape of dark current–voltage characteristics of amorphous and microcrystalline silicon based tandem solar cell structures are explored with numerical simulations. Our input parameters were calibrated by fitting experimental current voltage curves of single and double junction structures measured under dark and illuminated conditions. At low and intermediate forward voltages the dark current–voltage characteristics show one or two regions with a current–voltage exponential dependence. The diode factor is unique in tandem cells with the same material in both intrinsic layers and two dissimilar diode factors are observed in tandem cells with different materials on the top and bottom intrinsic layers. In the exponential regions the current is controlled by recombination through gap states and by free carrier diffusion. At high forward voltages the current grows more slowly with the applied voltage. The current is influenced by the onset of electron space charge limited current (SCLC) in tandem cells where both intrinsic layers are of amorphous silicon and by series resistance of the bottom cell in tandem cells where both intrinsic layers are of microcrystalline silicon. In the micromorph cell the onset of SCLC becomes visible on the amorphous top sub-cell. The dark current also depends on the thermal generation of electron–hole (e–h) pairs present at the tunneling recombination junction. The highest dependence is observed in the tandem structure where both intrinsic layers are of microcrystalline silicon. The prediction of meaningless dark currents at low forward and reverse voltages by our code is discussed and one solution is given. - Highlights: ► Transport mechanisms shaping the dark current-voltage curves of tandem devices. ► The devices are amorphous and microcrystalline based tandem solar cells. ► Two regions with a current-voltage exponential dependence are observed. ► The tandem J-V diode factor is the

  1. Bidirectional current-voltage converters based on magnetostrictive/piezoelectric composites

    NARCIS (Netherlands)

    Jia, Y.; Or, S.W.; Chan, H.L.W.; Jiao, J.; Luo, H.; Van der Zwaag, S.

    2009-01-01

    We report a power supply-free, bidirectional electric current-voltage converter based on a coil-wound laminated composite of magnetostrictive alloy and piezoelectric crystal. An electric current applied to the coil induces a magnetic field, resulting in an electric voltage from the composite due to

  2. Current-voltage characteristics of quantum-point contacts in the closed-channel regime: Transforming the bias voltage into an energy scale

    DEFF Research Database (Denmark)

    Gloos, K.; Utko, P.; Aagesen, M.

    2006-01-01

    We investigate the I(V) characteristics (current versus bias voltage) of side-gated quantum-point contacts, defined in GaAs/AlxGa1-xAs heterostructures. These point contacts are operated in the closed-channel regime, that is, at fixed gate voltages below zero-bias pinch-off for conductance. Our....... Such a built-in energy-voltage calibration allows us to distinguish between the different contributions to the electron transport across the pinched-off contact due to thermal activation or quantum tunneling. The first involves the height of the barrier, and the latter also its length. In the model that we...

  3. Current-voltage model of LED light sources

    DEFF Research Database (Denmark)

    Beczkowski, Szymon; Munk-Nielsen, Stig

    2012-01-01

    Amplitude modulation is rarely used for dimming light-emitting diodes in polychromatic luminaires due to big color shifts caused by varying magnitude of LED driving current and nonlinear relationship between intensity of a diode and driving current. Current-voltage empirical model of light...

  4. Current-Voltage Characteristic of Nanosecond - Duration Relativistic Electron Beam

    Science.gov (United States)

    Andreev, Andrey

    2005-10-01

    The pulsed electron-beam accelerator SINUS-6 was used to measure current-voltage characteristic of nanosecond-duration thin annular relativistic electron beam accelerated in vacuum along axis of a smooth uniform metal tube immersed into strong axial magnetic field. Results of these measurements as well as results of computer simulations performed using 3D MAGIC code show that the electron-beam current dependence on the accelerating voltage at the front of the nanosecond-duration pulse is different from the analogical dependence at the flat part of the pulse. In the steady-state (flat) part of the pulse), the measured electron-beam current is close to Fedosov current [1], which is governed by the conservation law of an electron moment flow for any constant voltage. In the non steady-state part (front) of the pulse, the electron-beam current is higher that the appropriate, for a giving voltage, steady-state (Fedosov) current. [1] A. I. Fedosov, E. A. Litvinov, S. Ya. Belomytsev, and S. P. Bugaev, ``Characteristics of electron beam formed in diodes with magnetic insulation,'' Soviet Physics Journal (A translation of Izvestiya VUZ. Fizika), vol. 20, no. 10, October 1977 (April 20, 1978), pp.1367-1368.

  5. Voltage-regulating constant-current sources in a linear induction accelerator

    International Nuclear Information System (INIS)

    Zhao Juan; Cao Kefeng; Deng Jianjun; Zhu Lijun; Yang Jia; Ye Chao; Huang Bin; Cao Ningxiang; Dong Jinxuan; Zhang Jichang; Yu Zhiguo; Chen Min

    2002-01-01

    Constant-current Sources are one of key units in a linear induction accelerator. The requirements for the sources are to supply stable direct current of high power for the induction coil, be easy to computer-control and highly stable and reliable. Applying the technique of linear current source regulating in series, the primary voltage of the power transformer is regulated through an MJYS-JL-350A type three-phase alterative voltage-regulating module. The output current variation is 300-500 A when the load variation is 0.06-0.1 Ω and the voltage drop of the regulator tube is controlled within 8 V±2V when the variation of mains voltage is in ±10%. Both the current ripple and stability meet the technical requirements. The constant-current sources are controlled through an industrial controller. For each of the constant-current sources has a smallest system comprised of 8051 which is communication-controlled through a RS-485 interface, the sources can be controlled remotely

  6. Pseudo-diode based on protonic/electronic hybrid oxide transistor

    Science.gov (United States)

    Fu, Yang Ming; Liu, Yang Hui; Zhu, Li Qiang; Xiao, Hui; Song, An Ran

    2018-01-01

    Current rectification behavior has been proved to be essential in modern electronics. Here, a pseudo-diode is proposed based on protonic/electronic hybrid indium-gallium-zinc oxide electric-double-layer (EDL) transistor. The oxide EDL transistors are fabricated by using phosphorous silicate glass (PSG) based proton conducting electrolyte as gate dielectric. A diode operation mode is established on the transistor, originating from field configurable proton fluxes within the PSG electrolyte. Current rectification ratios have been modulated to values ranged between ˜4 and ˜50 000 with gate electrode biased at voltages ranged between -0.7 V and 0.1 V. Interestingly, the proposed pseudo-diode also exhibits field reconfigurable threshold voltages. When the gate is biased at -0.5 V and 0.3 V, threshold voltages are set to ˜-1.3 V and -0.55 V, respectively. The proposed pseudo-diode may find potential applications in brain-inspired platforms and low-power portable systems.

  7. Energy-dependent proton damage in silicon

    Energy Technology Data Exchange (ETDEWEB)

    Donegani, Elena Maria

    2017-09-29

    Non Ionizing Energy Loss (NIEL) in the sensor bulk is a limiting factor for the lifetime of silicon detectors. In this work, the proton-energy dependent bulkdamage is studied in n- and p-type silicon pad diodes. The samples are thin (200 μm thick), and oxygen enriched (bulk material types: MCz, standard or deepdiffused FZ). Irradiations are performed with 23 MeV, 188 MeV and 23 GeV protons; the 1 MeV neutron equivalent fluence assumes selected values in the range [0.1,3].10{sup 14} cm{sup -2}. In reverse bias, Current-Voltage (IV) and Capacitance-Voltage (CV) measurements are performed to electrically characterise the samples; in forward bias, IV and CV measurements point out the transition from lifetime to relaxationlike semiconductor after irradiation. By means of Thermally Stimulated Current (TSC) measurements, 13 bulk defects have been found after proton irradiation. Firstly, TSC spectra are analysed to obtain defect concentrations after defect filling at the conventional temperature T{sub fill} =10 K. Secondly, temperature dependent capture coefficients of bulk defects are explained, according to the multi-phonon process, from the analysis of TSC measurements at higher filling temperatures (T{sub fill}<130 K). Thirdly, a new method based on the SRH statistics and accounting for cluster-induced shift in activation energy is proposed; it allows to fully characterise bulk defects (in terms of activation energy, concentration and majority capture cross-section) and to distinguish between point- and cluster-like defects. A correlation is noted between the leakage current and the concentration of three deep defects (namely the V{sub 2}, V{sub 3} and H(220K) defects), for all the investigated bulk materials and types, and after all the considered proton energies and fluences. At least five defects are found to be responsible for the space charge, with positive contributions from the E(30K) and B{sub i}O{sub i} defects, or negative contributions from three deep

  8. Energy-dependent proton damage in silicon

    International Nuclear Information System (INIS)

    Donegani, Elena Maria

    2017-01-01

    Non Ionizing Energy Loss (NIEL) in the sensor bulk is a limiting factor for the lifetime of silicon detectors. In this work, the proton-energy dependent bulkdamage is studied in n- and p-type silicon pad diodes. The samples are thin (200 μm thick), and oxygen enriched (bulk material types: MCz, standard or deepdiffused FZ). Irradiations are performed with 23 MeV, 188 MeV and 23 GeV protons; the 1 MeV neutron equivalent fluence assumes selected values in the range [0.1,3].10 14 cm -2 . In reverse bias, Current-Voltage (IV) and Capacitance-Voltage (CV) measurements are performed to electrically characterise the samples; in forward bias, IV and CV measurements point out the transition from lifetime to relaxationlike semiconductor after irradiation. By means of Thermally Stimulated Current (TSC) measurements, 13 bulk defects have been found after proton irradiation. Firstly, TSC spectra are analysed to obtain defect concentrations after defect filling at the conventional temperature T fill =10 K. Secondly, temperature dependent capture coefficients of bulk defects are explained, according to the multi-phonon process, from the analysis of TSC measurements at higher filling temperatures (T fill <130 K). Thirdly, a new method based on the SRH statistics and accounting for cluster-induced shift in activation energy is proposed; it allows to fully characterise bulk defects (in terms of activation energy, concentration and majority capture cross-section) and to distinguish between point- and cluster-like defects. A correlation is noted between the leakage current and the concentration of three deep defects (namely the V 2 , V 3 and H(220K) defects), for all the investigated bulk materials and types, and after all the considered proton energies and fluences. At least five defects are found to be responsible for the space charge, with positive contributions from the E(30K) and B i O i defects, or negative contributions from three deep acceptors H(116K), H(140K) and H(152K).

  9. Autowaves in an active two-wire line with exponential current-voltage characteristics

    International Nuclear Information System (INIS)

    Zhuravlev, V. M.

    2006-01-01

    Nonlinear wave processes in two-wire lines containing an active element with an exponential current-voltage characteristic (CVC) similar to that of a p-n junction are investigated. These lines are models of systems that are encountered in various physical and biological applications, such as biological membranes and semiconductor devices. It is shown that such systems may operate in different modes each of which has different dispersion and dissipation properties and, as a consequence, is described by autowave processes of different types. The behavior of a system in all basic modes is analyzed. For each mode, exact solutions to relevant equations are found and their differential conservation laws and intrinsic symmetries are investigated. One of common properties of such equations is the presence of a special superposition principle that describes the discrete structure of excitations in a line that consist of individual elementary excitations. It is shown that autopulses may be generated in such systems

  10. Analysis of the current-voltage characteristics lineshapes of resonant tunneling diodes

    International Nuclear Information System (INIS)

    Rivera, P.H.; Schulz, P.A.

    1996-01-01

    It is discussed the influence of a two dimensional electron gas at the emitter-barrier interface on the current-voltage characteristics of a Ga As-Al Ga As double-barrier quantum well resonant tunneling diode. This effect is characterized by the modification of the space charge distribution along the structure. Within the framework of a self-consistent calculation we analyse the current-voltage characteristics of the tunneling diodes. This analysis permits us to infer different tunneling ways, related to the formation of confined states in the emitter region, and their signatures in the current-voltage characteristics. We show that varying the spacer layer, together with barrier heights, changes drastically the current density-voltage characteristics lineshapes. We compare our results with a variety of current-voltage characteristics lineshapes. We compare our results with a variety of current-voltage characteristics reported in the literature. The general trend of experimental lineshapes can be reproduced and interpreted with our model. The possibility of tunneling paths is predicted for a range that has not yet been explored experimentally. (author). 12 refs., 4 figs

  11. Feasibility of proton-activated implantable markers for proton range verification using PET

    Science.gov (United States)

    Cho, Jongmin; Ibbott, Geoffrey; Gillin, Michael; Gonzalez-Lepera, Carlos; Titt, Uwe; Paganetti, Harald; Kerr, Matthew; Mawlawi, Osama

    2013-11-01

    Proton beam range verification using positron emission tomography (PET) currently relies on proton activation of tissue, the products of which decay with a short half-life and necessitate an on-site PET scanner. Tissue activation is, however, negligible near the distal dose fall-off region of the proton beam range due to their high interaction energy thresholds. Therefore Monte Carlo simulation is often supplemented for comparison with measurement; however, this also may be associated with systematic and statistical uncertainties. Therefore, we sought to test the feasibility of using long-lived proton-activated external materials that are inserted or infused into the target volume for more accurate proton beam range verification that could be performed at an off-site PET scanner. We irradiated samples of ≥98% 18O-enriched water, natural Cu foils, and >97% 68Zn-enriched foils as candidate materials, along with samples of tissue-equivalent materials including 16O water, heptane (C7H16), and polycarbonate (C16H14O3)n, at four depths (ranging from 100% to 3% of center of modulation (COM) dose) along the distal fall-off of a modulated 160 MeV proton beam. Samples were irradiated either directly or after being embedded in Plastic Water® or balsa wood. We then measured the activity of the samples using PET imaging for 20 or 30 min after various delay times. Measured activities of candidate materials were up to 100 times greater than those of the tissue-equivalent materials at the four distal dose fall-off depths. The differences between candidate materials and tissue-equivalent materials became more apparent after longer delays between irradiation and PET imaging, due to the longer half-lives of the candidate materials. Furthermore, the activation of the candidate materials closely mimicked the distal dose fall-off with offsets of 1 to 2 mm. Also, signals from the foils were clearly visible compared to the background from the activated Plastic Water® and balsa wood

  12. Voltage current characteristics of type III superconductors

    International Nuclear Information System (INIS)

    Dorofejev, G.L.; Imenitov, A.B.; Klimenko, E.Y.

    1980-01-01

    An adequate description of voltage-current characteristics is important in order to understand the nature of high critical current for the electrodynamic construction of type-III superconductors and for commercial superconductor specification. Homogeneous monofilament and multifilament Nb-Ti, Nb-Zr,Nb 3 Sn wires were investigated in different ranges of magnetic field, temperature and current. The shape of the voltage-current characteristics of multifilament wires, and the parameter's dependence on temperature and magnetic field may be explained qualitatively by the longitudinal heterogeneous nature of the filaments. A method of attaining the complete specification of the wire's electro-physical properties is proposed. It includes the traditional description of a critical surface (i.e. the surface corresponding to a certain conventional effective resistivity in T,B,J-space) and a description of any increasing parameter that depends on B and T. (author)

  13. Voltage current characteristics of type III superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Dorofeiev, G L; Imenitov, A B; Klimenko, E Y [Gosudarstvennyi Komitet po Ispol' zovaniyu Atomnoi Ehnergii SSSR, Moscow. Inst. Atomnoi Ehnergii

    1980-06-01

    An adequate description of voltage-current characteristics is important in order to understand the nature of high critical current for the electrodynamic construction of type-III superconductors and for commercial superconductor specification. Homogeneous monofilament and multifilament Nb-Ti, Nb-Zr,Nb/sub 3/Sn wires were investigated in different ranges of magnetic field, temperature and current. The shape of the voltage-current characteristics of multifilament wires, and the parameter's dependence on temperature and magnetic field may be explained qualitatively by the longitudinal heterogeneous nature of the filaments. A method of attaining the complete specification of the wire's electro-physical properties is proposed. It includes the traditional description of a critical surface (i.e. the surface corresponding to a certain conventional effective resistivity in T,B,J-space) and a description of any increasing parameter that depends on B and T.

  14. Voltage-current characteristics of multiterminal HVDC-VSC for offshore wind farms

    Energy Technology Data Exchange (ETDEWEB)

    Gomis-Bellmunt, Oriol [Centre d' Innovacio Tecnologica en Convertidors Estatics i Accionaments (CITCEA-UPC), Universitat Politecnica de Catalunya UPC, Av. Diagonal, 647, Pl. 2., 08028 Barcelona (Spain); IREC Catalonia Institute for Energy Research, Barcelona (Spain); Liang, Jun; Ekanayake, Janaka; Jenkins, Nicholas [School of Engineering, Cardiff University, Queen' s Buildings, The Parade, Cardiff CF24 3AA, Wales (United Kingdom)

    2011-02-15

    Voltage-current characteristics and equilibrium points for the DC voltages of multiterminal HVDC systems using voltage source converters are discussed. The wind farm rectifiers and grid connected inverters are analyzed through their operating modes, governing equations and graphical characteristics. Using the converter equations and the HVDC grid conductance matrix the equilibrium voltages and currents are found. Case studies are presented considering wind power generation, loss of a converter and voltage sags in the AC grid. (author)

  15. Highly Accurate Derivatives for LCL-Filtered Grid Converter with Capacitor Voltage Active Damping

    DEFF Research Database (Denmark)

    Xin, Zhen; Loh, Poh Chiang; Wang, Xiongfei

    2016-01-01

    The middle capacitor voltage of an LCL-filter, if fed back for synchronization, can be used for active damping. An extra sensor for measuring the capacitor current is then avoided. Relating the capacitor voltage to existing popular damping techniques designed with capacitor current feedback would...... are then proposed, based on either second-order or non-ideal generalized integrator. Performances of these derivatives have been found to match the ideal “s” function closely. Active damping based on capacitor voltage feedback can therefore be realized accurately. Experimental results presented have verified...

  16. Current-voltage characteristic of a resonant tunneling diode under electromagnetic radiation

    Directory of Open Access Journals (Sweden)

    N Hatefi Kargan

    2013-09-01

    Full Text Available  In this paper, current-voltage characteristic of a resonant tunneling diode under electromagnetic radiation has been calculated and compared with the results when there is no electromagnetic radiation. For calculating current -voltage characteristic, it is required to calculate the transmission coefficient of electrons from the well and barrier structures of this device. For calculating the transmission coefficient of electrons at the presence of electromagnetic radiation, Finite Difference Time Domain (FDTD method has been used and when there is no electromagnetic radiation Transfer Matrix Method (TMM and finite diffirence time domain method have been used. The results show that the presence of electromagnetic radiation causes resonant states other than principal resonant state (without presence of electromagnetic radiation to appear on the transmition coefficient curve where they are in distances from the principal peak and from each other. Also, the presence of electromagnetic radiation causes peaks other than principal peak to appear on the current-voltage characteristics of the device. Under electromagnetic radiation, the number of peaks on the current-voltage curve is smaller than the number of peaks on the current-voltage transmission coefficient. This is due to the fact that current-voltage curve is the result of integration on the energy of electrons, Thus, the sharper and low height peaks on the transmission coefficient do not appear on the current-voltage characteristic curve.

  17. Enhanced current and voltage regulators for stand-alone applications

    DEFF Research Database (Denmark)

    Federico, de Bosio; Pastorelli, Michele; Antonio DeSouza Ribeiro, Luiz

    2016-01-01

    State feedback decoupling permits to achieve a better dynamic response for Voltage Source in stand-alone applications. The design of current and voltage regulators is performed in the discrete-time domain since it provides better accuracy and allows direct pole placement. As the attainable...... bandwidth of the current loop is mainly limited by computational and PWM delays, a lead compensator structure is proposed to overcome this limitation. The design of the voltage regulator is based on the Nyquist criterion, verifying to guarantee a high sensitivity peak. Discrete-time domain implementation...

  18. Parameter design and performance simulation of a 10 kV voltage compensation type active superconducting fault current limiter

    International Nuclear Information System (INIS)

    Chen, L.; Tang, Y.J.; Song, M.; Shi, J.; Ren, L.

    2013-01-01

    Highlights: •For a practical 10 kV system, the 10 kV active SFCL’s basic parameters are designed. •Under different fault conditions, the 10 kV active SFCL’s performances are simulated. •The designed 10 kV active SFCL’s engineering feasibility is discussed preliminarily. -- Abstract: Since the introduction of superconducting fault current limiter (SFCL) into electrical distribution system may be a good choice with economy and practicability, the parameter design and current-limiting characteristics of a 10 kV voltage compensation type active SFCL are studied in this paper. Firstly, the SFCL’s circuit structure and operation principle are presented. Then, taking a practical 10 kV distribution system as its application object, the SFCL’s basic parameters are designed to meet the system requirements. Further, using MATLAB, the detailed current-limiting performances of the 10 kV active SFCL are simulated under different fault conditions. The simulation results show that the active SFCL can deal well with the faults, and the parameter design’s suitability can be testified. At the end, in view of the engineering feasibility of the 10 kV active SFCL, some preliminary discussions are carried out

  19. A New Asymmetrical Current-fed Converter with Voltage Lifting

    Directory of Open Access Journals (Sweden)

    DELSHAD, M.

    2011-05-01

    Full Text Available This paper presents a new zero voltage switching current-fed DC-DC converter with high voltage gain. In this converter all switches (main and auxiliary turn on under zero voltage switching and turn off under almost zero voltage switching due to snubber capacitor. Furthermore, the voltage spike across the main switch due to leakage inductance of forward transformer is absorbed. The flyback transformer which is connected to the output in series causes to high voltage gain and less voltage stress on the power devices. Considering high efficiency and voltage gain of this converter, it is suitable for green generated systems such as fuel cells or photovoltaic systems. The presented experimental results verify the integrity of the proposed converter.

  20. Unusual Voltage-Gated Sodium Currents as Targets for Pain.

    Science.gov (United States)

    Barbosa, C; Cummins, T R

    2016-01-01

    Pain is a serious health problem that impacts the lives of many individuals. Hyperexcitability of peripheral sensory neurons contributes to both acute and chronic pain syndromes. Because voltage-gated sodium currents are crucial to the transmission of electrical signals in peripheral sensory neurons, the channels that underlie these currents are attractive targets for pain therapeutics. Sodium currents and channels in peripheral sensory neurons are complex. Multiple-channel isoforms contribute to the macroscopic currents in nociceptive sensory neurons. These different isoforms exhibit substantial variations in their kinetics and pharmacology. Furthermore, sodium current complexity is enhanced by an array of interacting proteins that can substantially modify the properties of voltage-gated sodium channels. Resurgent sodium currents, atypical currents that can enhance recovery from inactivation and neuronal firing, are increasingly being recognized as playing potentially important roles in sensory neuron hyperexcitability and pain sensations. Here we discuss unusual sodium channels and currents that have been identified in nociceptive sensory neurons, describe what is known about the molecular determinants of the complex sodium currents in these neurons. Finally, we provide an overview of therapeutic strategies to target voltage-gated sodium currents in nociceptive neurons. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Performance of unified power quality conditioner (UPQC) based on fuzzy controller for attenuating of voltage and current harmonics

    Science.gov (United States)

    Milood Almelian, Mohamad; Mohd, Izzeldin I.; Asghaiyer Omran, Mohamed; Ullah Sheikh, Usman

    2018-04-01

    Power quality-related issues such as current and voltage distortions can adversely affect home and industrial appliances. Although several conventional techniques such as the use of passive and active filters have been developed to increase power quality standards, these methods have challenges and are inadequate due to the increasing number of applications. The Unified Power Quality Conditioner (UPQC) is a modern strategy towards correcting the imperfections of voltage and load current supply. A UPQC is a combination of both series and shunt active power filters in a back-to-back manner with a common DC link capacitor. The control of the voltage of the DC link capacitor is important in achieving a desired UPQC performance. In this paper, the UPQC with a Fuzzy logic controller (FLC) was used to precisely eliminate the imperfections of voltage and current harmonics. The results of the simulation studies using MATLAB/Simulink and Simpower system programming for R-L load associated through an uncontrolled bridge rectifier was used to assess the execution process. The UPQC with FLC was simulated for a system with distorted load current and a system with distorted source voltage and load current. The outcome of the comparison of %THD in the load current and source voltage before and after using UPQC for the two cases was presented.

  2. A Hybrid, Current-Source/Voltage-Source Power Inverter Circuit

    DEFF Research Database (Denmark)

    Trzynadlowski, Andrzej M.; Patriciu, Niculina; Blaabjerg, Frede

    2001-01-01

    A combination of a large current-source inverter and a small voltage-source inverter circuits is analyzed. The resultant hybrid inverter inherits certain operating advantages from both the constituent converters. In comparison with the popular voltage-source inverter, these advantages include...... reduced switching losses, improved quality of output current waveforms, and faster dynamic response to current control commands. Description of operating principles and characteristics of the hybrid inverter is illustrated with results of experimental investigation of a laboratory model....

  3. Mitigation of Grid Current Distortion for LCL-Filtered Voltage Source Inverter with Inverter Current Feedback Control

    DEFF Research Database (Denmark)

    Xin, Zhen; Mattavelli, Paolo; Yao, WenLi

    2018-01-01

    LCL filters feature low inductance; thus, the injected grid current from an LCL-filtered Voltage Source Inverter (VSI) can be easily distorted by grid voltage harmonics. This problem is especially tough for the control system with Inverter-side Current Feedback (ICF), since the grid current...... harmonics can freely flow into the filter capacitor. In this case, because of the loss of harmonic information, traditional harmonic controllers fail to mitigate the grid current distortion. Although this problem may be avoided using the grid voltage feedforward scheme, the required differentiators may...

  4. Analytical drift-current threshold voltage model of long-channel double-gate MOSFETs

    International Nuclear Information System (INIS)

    Shih, Chun-Hsing; Wang, Jhong-Sheng

    2009-01-01

    This paper presents a new, physical threshold voltage model to solve the ambiguity in determining the threshold voltage of double-gate (DG) MOSFETs. To avoid the difficulties of the conventional 2ψ B model in nearly undoped DG MOSFETs, this study proposes to define the on–off switching based on the actual roles of the drift and diffusion components in the total drain current. The drift current strongly enhances beyond the threshold voltage, while the diffusion current plays a major role in the subthreshold. The threshold voltage is defined as the drift component that exceeds the diffusion counterpart. From the solutions of Poisson's equation, the drift and diffusion currents of DG MOSFETs are separately formulated to derive the analytical expressions of the threshold voltage and associated threshold current. This model provides a comprehensive description of the switching behavior of DG MOSFET devices, and offers a physical onset threshold current to determine the threshold voltage in practical extraction

  5. Dynamic voltage-current characteristics for a water jet plasma arc

    International Nuclear Information System (INIS)

    Yang Jiaxiang; Lan Sheng; Xu Zuoming

    2008-01-01

    A virtual instrument technology is used to measure arc current, arc voltage, dynamic V-I characteristics, and nonlinear conductance for a cone-shaped water jet plasma arc under ac voltage. Experimental results show that ac arc discharge mainly happens in water vapor evaporated from water when heated. However, due to water's cooling effect and its conductance, arc conductance, reignition voltage, extinguish voltage, and current zero time are very different from those for ac arc discharge in gas work fluid. These can be valuable to further studies on mechanism and characteristics of plasma ac discharge in water, and even in gas work fluid

  6. Depletion voltage studies on n-in-n MCz silicon diodes after irradiation with 70 MeV protons

    CERN Document Server

    Holmkvist, William

    2014-01-01

    Silicon detectors is the main component in the pixel detectors in the ATLAS experiment at CERN in order to detect the particles and recreate their tracks after a proton-proton collision. One criteria on these detectors is to be able to operate in the high radiation field close to the particle collision. The usual behavior of the silicon detectors is that they get type inverted and an increase in the depletion voltage can be seen after exposed to significant amounts of radiation. In contrast n-type Magnetic Czochralski (MCz) silicon doesn’t follow FZ silicons pattern of getting type inverted when it comes to high energy particle irradiation, in the range of GeV. However it was observed that MCz silicon diodes that had been irradiated with 23 MeV protons followed the FZ silicon behavior and did type invert. The aim of the project is to find out how the depletion voltage of MCz silicon changes after being irradiated by 70 MeV at fluencies of 1E13, 1E14 and 5E14 neq/cm2, to give a further insight of at what en...

  7. Electronic Current Transducer (ECT) for high voltage dc lines

    Science.gov (United States)

    Houston, J. M.; Peters, P. H., Jr.; Summerayes, H. R., Jr.; Carlson, G. J.; Itani, A. M.

    1980-02-01

    The development of a bipolar electronic current transducer (ECT) for measuring the current in a high voltage dc (HVDC) power line at line potential is discussed. The design and construction of a free standing ECT for use on a 400 kV line having a nominal line current of 2000 A is described. Line current is measured by a 0.0001 ohm shunt whose voltage output is sampled by a 14 bit digital data link. The high voltage interface between line and ground is traversed by optical fibers which carry digital light signals as far as 300 m to a control room where the digital signal is converted back to an analog representation of the shunt voltage. Two redundant electronic and optical data links are used in the prototype. Power to operate digital and optical electronics and temperature controlling heaters at the line is supplied by a resistively and capacitively graded 10 stage cascade of ferrite core transformers located inside the hollow, SF6 filled, porcelain support insulator. The cascade is driven by a silicon controlled rectifier inverter which supplies about 100 W of power at 30 kHz.

  8. Classification of methods for measuring current-voltage characteristics of semiconductor devices

    Directory of Open Access Journals (Sweden)

    Iermolenko Ia. O.

    2014-06-01

    Full Text Available It is shown that computer systems for measuring current-voltage characteristics are very important for semiconductor devices production. The main criteria of efficiency of such systems are defined. It is shown that efficiency of such systems significantly depends on the methods for measuring current-voltage characteristics of semiconductor devices. The aim of this work is to analyze existing methods for measuring current-voltage characteristics of semiconductor devices and to create the classification of these methods in order to specify the most effective solutions in terms of defined criteria. To achieve this aim, the most common classifications of methods for measuring current-voltage characteristics of semiconductor devices and their main disadvantages are considered. Automated and manual, continuous, pulse, mixed, isothermal and isodynamic methods for measuring current-voltage characteristics are analyzed. As a result of the analysis and generalization of existing methods the next classification criteria are defined: the level of automation, the form of measurement signals, the condition of semiconductor device during the measurements, and the use of mathematical processing of the measurement results. With the use of these criteria the classification scheme of methods for measuring current-voltage characteristics of semiconductor devices is composed and the most effective methods are specified.

  9. Oscillation of Critical Current by Gate Voltage in Cooper Pair Transistor

    International Nuclear Information System (INIS)

    Kim, N.; Cheong, Y.; Song, W.

    2010-01-01

    We measured the critical current of a Cooper pair transistor consisting of two Josephson junctions and a gate electrode. The Cooper pair transistors were fabricated by using electron-beam lithography and double-angle evaporation technique. The Gate voltage dependence of critical current was measured by observing voltage jumps at various gate voltages while sweeping bias current. The observed oscillation was 2e-periodic, which shows the Cooper pair transistor had low level of quasiparticle poisoning.

  10. Beyond voltage-gated ion channels: Voltage-operated membrane proteins and cellular processes.

    Science.gov (United States)

    Zhang, Jianping; Chen, Xingjuan; Xue, Yucong; Gamper, Nikita; Zhang, Xuan

    2018-04-18

    Voltage-gated ion channels were believed to be the only voltage-sensitive proteins in excitable (and some non-excitable) cells for a long time. Emerging evidence indicates that the voltage-operated model is shared by some other transmembrane proteins expressed in both excitable and non-excitable cells. In this review, we summarize current knowledge about voltage-operated proteins, which are not classic voltage-gated ion channels as well as the voltage-dependent processes in cells for which single voltage-sensitive proteins have yet to be identified. Particularly, we will focus on the following. (1) Voltage-sensitive phosphoinositide phosphatases (VSP) with four transmembrane segments homologous to the voltage sensor domain (VSD) of voltage-gated ion channels; VSPs are the first family of proteins, other than the voltage-gated ion channels, for which there is sufficient evidence for the existence of the VSD domain; (2) Voltage-gated proton channels comprising of a single voltage-sensing domain and lacking an identified pore domain; (3) G protein coupled receptors (GPCRs) that mediate the depolarization-evoked potentiation of Ca 2+ mobilization; (4) Plasma membrane (PM) depolarization-induced but Ca 2+ -independent exocytosis in neurons. (5) Voltage-dependent metabolism of phosphatidylinositol 4,5-bisphosphate (PtdIns[4,5]P 2 , PIP 2 ) in the PM. These recent discoveries expand our understanding of voltage-operated processes within cellular membranes. © 2018 Wiley Periodicals, Inc.

  11. Gate modulation of proton transport in a nanopore.

    Science.gov (United States)

    Mei, Lanju; Yeh, Li-Hsien; Qian, Shizhi

    2016-03-14

    Proton transport in confined spaces plays a crucial role in many biological processes as well as in modern technological applications, such as fuel cells. To achieve active control of proton conductance, we investigate for the first time the gate modulation of proton transport in a pH-regulated nanopore by a multi-ion model. The model takes into account surface protonation/deprotonation reactions, surface curvature, electroosmotic flow, Stern layer, and electric double layer overlap. The proposed model is validated by good agreement with the existing experimental data on nanopore conductance with and without a gate voltage. The results show that the modulation of proton transport in a nanopore depends on the concentration of the background salt and solution pH. Without background salt, the gated nanopore exhibits an interesting ambipolar conductance behavior when pH is close to the isoelectric point of the dielectric pore material, and the net ionic and proton conductance can be actively regulated with a gate voltage as low as 1 V. The higher the background salt concentration, the lower is the performance of the gate control on the proton transport.

  12. Measurement and statistical analysis of single-molecule current-voltage characteristics, transition voltage spectroscopy, and tunneling barrier height.

    Science.gov (United States)

    Guo, Shaoyin; Hihath, Joshua; Díez-Pérez, Ismael; Tao, Nongjian

    2011-11-30

    We report on the measurement and statistical study of thousands of current-voltage characteristics and transition voltage spectra (TVS) of single-molecule junctions with different contact geometries that are rapidly acquired using a new break junction method at room temperature. This capability allows one to obtain current-voltage, conductance voltage, and transition voltage histograms, thus adding a new dimension to the previous conductance histogram analysis at a fixed low-bias voltage for single molecules. This method confirms the low-bias conductance values of alkanedithiols and biphenyldithiol reported in literature. However, at high biases the current shows large nonlinearity and asymmetry, and TVS allows for the determination of a critically important parameter, the tunneling barrier height or energy level alignment between the molecule and the electrodes of single-molecule junctions. The energy level alignment is found to depend on the molecule and also on the contact geometry, revealing the role of contact geometry in both the contact resistance and energy level alignment of a molecular junction. Detailed statistical analysis further reveals that, despite the dependence of the energy level alignment on contact geometry, the variation in single-molecule conductance is primarily due to contact resistance rather than variations in the energy level alignment.

  13. Protonic charge defect structures in floating water bridges observed as Zundel and Eigen solvation arrangements

    Science.gov (United States)

    Teschke, Omar; de Castro, Jose Roberto; Valente Filho, Juracyr Ferraz; Soares, David Mendez

    2017-10-01

    Protonic arrangements were detected in water bridge structures using confocal Raman microscopy, and the spectra show two formed structures. The measured Raman spectra were modified using the voltage applied to the bridge structure, which changed the proportion of these two species. Initially, for a 6.3 kV applied voltage, there was a measurable increase in the bridge current above the Ohmic contribution and the observed Raman spectrum of this new injected specie corresponded to the computed spectrum for the Zundel protonic arrangement. As the voltage further increases a contribution from the Eigen proton solvation specie is added to the measured spectrum.

  14. Two coupled Josephson junctions: dc voltage controlled by biharmonic current

    International Nuclear Information System (INIS)

    Machura, L; Spiechowicz, J; Kostur, M; Łuczka, J

    2012-01-01

    We study transport properties of two Josephson junctions coupled by an external shunt resistance. One of the junctions (say, the first) is driven by an unbiased ac current consisting of two harmonics. The device can rectify the ac current yielding a dc voltage across the first junction. For some values of coupling strength, controlled by an external shunt resistance, a dc voltage across the second junction can be generated. By variation of system parameters such as the relative phase or frequency of two harmonics, one can conveniently manipulate both voltages with high efficiency, e.g. changing the dc voltages across the first and second junctions from positive to negative values and vice versa. (paper)

  15. Design of a New Acceleration System for High-Current Pulsed Proton Beams from an ECR Source

    Science.gov (United States)

    Cooper, Andrew L.; Pogrebnyak, Ivan; Surbrook, Jason T.; Kelly, Keegan J.; Carlin, Bret P.; Champagne, Arthur E.; Clegg, Thomas B.

    2014-03-01

    A primary objective for accelerators at TUNL's Laboratory for Experimental Nuclear Astrophysics (LENA) is to maximize target beam intensity to ensure a high rate of nuclear events during each experiment. Average proton target currents of several mA are needed from LENA's electron cyclotron resonance (ECR) ion source because nuclear cross sections decrease substantially at energies of interest tube structures; and provide better heat dissipation by using deionized water to provide the current drain needed to establish the accelerating tube's voltage gradient. Details of beam optical modeling calculations, proposed accelerating tube design, and initial beam pulsing tests will be described. Work supported in part by USDOE Office of HE and Nuclear Physics.

  16. In-situ monitoring of internal local temperature and voltage of proton exchange membrane fuel cells.

    Science.gov (United States)

    Lee, Chi-Yuan; Fan, Wei-Yuan; Hsieh, Wei-Jung

    2010-01-01

    The distribution of temperature and voltage of a fuel cell are key factors that influence performance. Conventional sensors are normally large, and are also useful only for making external measurements of fuel cells. Centimeter-scale sensors for making invasive measurements are frequently unable to accurately measure the interior changes of a fuel cell. This work focuses mainly on fabricating flexible multi-functional microsensors (for temperature and voltage) to measure variations in the local temperature and voltage of proton exchange membrane fuel cells (PEMFC) that are based on micro-electro-mechanical systems (MEMS). The power density at 0.5 V without a sensor is 450 mW/cm(2), and that with a sensor is 426 mW/cm(2). Since the reaction area of a fuel cell with a sensor is approximately 12% smaller than that without a sensor, but the performance of the former is only 5% worse.

  17. Low-cost wireless voltage & current grid monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Hines, Jacqueline [SenSanna Inc., Arnold, MD (United States)

    2016-12-31

    This report describes the development and demonstration of a novel low-cost wireless power distribution line monitoring system. This system measures voltage, current, and relative phase on power lines of up to 35 kV-class. The line units operate without any batteries, and without harvesting energy from the power line. Thus, data on grid condition is provided even in outage conditions, when line current is zero. This enhances worker safety by detecting the presence of voltage and current that may appear from stray sources on nominally isolated lines. Availability of low-cost power line monitoring systems will enable widespread monitoring of the distribution grid. Real-time data on local grid operating conditions will enable grid operators to optimize grid operation, implement grid automation, and understand the impact of solar and other distributed sources on grid stability. The latter will enable utilities to implement eneygy storage and control systems to enable greater penetration of solar into the grid.

  18. Balanced Current Control Strategy for Current Source Rectifier Stage of Indirect Matrix Converter under Unbalanced Grid Voltage Conditions

    Directory of Open Access Journals (Sweden)

    Yeongsu Bak

    2016-12-01

    Full Text Available This paper proposes a balanced current control strategy for the current source rectifier (CSR stage of an indirect matrix converter (IMC under unbalanced grid voltage conditions. If the three-phase grid connected to the voltage source inverter (VSI of the IMC has unbalanced voltage conditions, it affects the currents of the CSR stage and VSI stage, and the currents are distorted. Above all, the distorted currents of the CSR stage cause instability in the overall system, which can affect the life span of the system. Therefore, in this paper, a control strategy for balanced currents in the CSR stage is proposed. To achieve balanced currents in the CSR stage, the VSI stage should receive DC power without ripple components from the CSR stage. This is implemented by controlling the currents in the VSI stage. Therefore, the proposed control strategy decouples the positive and negative phase-sequence components existing in the unbalanced voltages and currents of the VSI stage. Using the proposed control strategy under unbalanced grid voltage conditions, the stability and life span of the overall system can be improved. The effectiveness of the proposed control strategy is verified by simulation and experimental results.

  19. Performance enhancement of the single-phase series active filter by employing the load voltage waveform reconstruction and line current sampling delay reduction methods

    DEFF Research Database (Denmark)

    Senturk, O.S.; Hava, A.M.

    2011-01-01

    This paper proposes the waveform reconstruction method (WRM), which is utilized in the single-phase series active filter's (SAF's) control algorithm, in order to extract the load harmonic voltage component of voltage harmonic type single-phase diode rectifier loads. Employing WRM and the line...... current sampling delay reduction method, a single-phase SAF compensated system provides higher harmonic isolation performance and higher stability margins compared to the system using conventional synchronous-reference-frame-based methods. The analytical, simulation, and experimental studies of a 2.5 k...

  20. Current-Voltage Characteristics of Quasi-One-Dimensional Superconductors

    DEFF Research Database (Denmark)

    Vodolazov, D.Y.; Peeters, F.M.; Piraux, L.

    2003-01-01

    The current-voltage (I-V) characteristics of quasi-one-dimensional superconductors were discussed. The I-V characteristics exhibited an unusual S behavior. The dynamics of superconducting condensate and the existence of two different critical currents resulted in such an unusual behavior....

  1. Branching in current-voltage characteristics of intrinsic Josephson junctions

    International Nuclear Information System (INIS)

    Shukrinov, Yu M; Mahfouzi, F

    2007-01-01

    We study branching in the current-voltage characteristics of the intrinsic Josephson junctions of high-temperature superconductors in the framework of the capacitively coupled Josephson junction model with diffusion current. A system of dynamical equations for the gauge-invariant phase differences between superconducting layers for a stack of ten intrinsic junctions has been numerically solved. We have obtained a total branch structure in the current-voltage characteristics. We demonstrate the existence of a 'breakpoint region' on the current-voltage characteristics and explain it as a result of resonance between Josephson and plasma oscillations. The effect of the boundary conditions is investigated. The existence of two outermost branches and correspondingly two breakpoint regions for the periodic boundary conditions is shown. One branch, which is observed only at periodic boundary conditions, corresponds to the propagating of the plasma mode. The second one corresponds to the situation when the charge oscillations on the superconducting layers are absent, excluding the breakpoint. A time dependence of the charge oscillations at breakpoints is presented

  2. Photocontrol of Voltage-Gated Ion Channel Activity by Azobenzene Trimethylammonium Bromide in Neonatal Rat Cardiomyocytes.

    Directory of Open Access Journals (Sweden)

    Sheyda R Frolova

    Full Text Available The ability of azobenzene trimethylammonium bromide (azoTAB to sensitize cardiac tissue excitability to light was recently reported. The dark, thermally relaxed trans- isomer of azoTAB suppressed spontaneous activity and excitation propagation speed, whereas the cis- isomer had no detectable effect on the electrical properties of cardiomyocyte monolayers. As the membrane potential of cardiac cells is mainly controlled by activity of voltage-gated ion channels, this study examined whether the sensitization effect of azoTAB was exerted primarily via the modulation of voltage-gated ion channel activity. The effects of trans- and cis- isomers of azoTAB on voltage-dependent sodium (INav, calcium (ICav, and potassium (IKv currents in isolated neonatal rat cardiomyocytes were investigated using the whole-cell patch-clamp technique. The experiments showed that azoTAB modulated ion currents, causing suppression of sodium (Na+ and calcium (Ca2+ currents and potentiation of net potassium (K+ currents. This finding confirms that azoTAB-effect on cardiac tissue excitability do indeed result from modulation of voltage-gated ion channels responsible for action potential.

  3. Grid-Voltage-Feedforward Active Damping for Grid-Connected Inverter with LCL Filter

    DEFF Research Database (Denmark)

    Lu, Minghui; Wang, Xiongfei; Blaabjerg, Frede

    2016-01-01

    For the grid-connected voltage source inverters, the feedforward scheme of grid voltage is commonly adopted to mitigate the current distortion caused by grid background voltages harmonics. This paper investigates the grid-voltage-feedforward active damping for grid connected inverter with LCL...... filter. It reveals that proportional feedforward control can not only fulfill the mitigation of grid disturbance, but also offer damping effects on the LCL filter resonance. Digital delays are intrinsic to digital controlled inverters; with these delays, the feedforward control can be equivalent...

  4. Current source converter based D-STATCOM for voltage sag mitigation

    Directory of Open Access Journals (Sweden)

    Singh Moirangthem Deben

    2015-01-01

    Full Text Available This paper presents a novel method of realizing one of the custom power controllers, the distribution static synchronous compensator (D-STATCOM using current source converter (CSC topology. Almost all the custom power controllers such as dynamic voltage restorer (DVR, unified power quality conditioner (UPQC including D-STATCOM are generally designed and implemented by using voltage source converters (VSC and not much research publications with CSC based approach has been reported over the last one decade. Since the D-STATCOM is a current injection device, its performance can be improved when realized by a current-source converter which can generate a controllable current directly at its output terminals and offers many advantageous features. In this paper, an attempt has been made to study the performance of a CSC based D-STATCOM suitable for use in the power distribution system in order to mitigate voltage sag and improve power quality. The proposed model uses a three leg CSC whose switching strategy is based on sinusoidal pulse width modulation (SPWM. The model has been simulated in the Matlab/Simulink environment. The results of the simulation runs under steady state and dynamic load perturbation provide excellent voltage and current waveforms that support the justification of the proposed model.

  5. High Voltage Coil Current Sensor for DC-DC Converters Employing DDCC

    Directory of Open Access Journals (Sweden)

    M. Drinovsky

    2015-12-01

    Full Text Available Current sensor is an integral part of every switching converter. It is used for over-current protection, regulation and in case of multiphase converters for balancing. A new high voltage current sensor for coil-based current sensing in DC-DC converters is presented. The sensor employs DDCC with high voltage input stage and gain trimming. The circuit has been simulated and implemented in 0.35 um BCD technology as part of a multiphase DC-DC converter where its function has been verified. The circuit is able to sustain common mode voltage on the input up to 40 V, it occupies 0.387*0.345 mm2 and consumes 3.2 mW typically.

  6. High Voltage, Fast-Switching Module for Active Control of Magnetic Fields and Edge Plasma Currents

    Science.gov (United States)

    Ziemba, Timothy; Miller, Kenneth; Prager, James; Slobodov, Ilia

    2016-10-01

    Fast, reliable, real-time control of plasma is critical to the success of magnetic fusion science. High voltage and current supplies are needed to mitigate instabilities in all experiments as well as disruption events in large scale tokamaks for steady-state operation. Silicon carbide (SiC) MOSFETs offer many advantages over IGBTs including lower drive energy requirements, lower conduction and switching losses, and higher switching frequency capabilities; however, these devices are limited to 1.2-1.7 kV devices. As fusion enters the long-pulse and burning plasma eras, efficiency of power switching will be important. Eagle Harbor Technologies (EHT), Inc. developing a high voltage SiC MOSFET module that operates at 10 kV. This switch module utilizes EHT gate drive technology, which has demonstrated the ability to increase SiC MOSFET switching efficiency. The module will allow more rapid development of high voltage switching power supplies at lower cost necessary for the next generation of fast plasma feedback and control. EHT is partnering with the High Beta Tokamak group at Columbia to develop detailed high voltage module specifications, to ensure that the final product meets the needs of the fusion science community.

  7. In-situ Monitoring of Internal Local Temperature and Voltage of Proton Exchange Membrane Fuel Cells

    Directory of Open Access Journals (Sweden)

    Chi-Yuan Lee

    2010-06-01

    Full Text Available The distribution of temperature and voltage of a fuel cell are key factors that influence performance. Conventional sensors are normally large, and are also useful only for making external measurements of fuel cells. Centimeter-scale sensors for making invasive measurements are frequently unable to accurately measure the interior changes of a fuel cell. This work focuses mainly on fabricating flexible multi-functional microsensors (for temperature and voltage to measure variations in the local temperature and voltage of proton exchange membrane fuel cells (PEMFC that are based on micro-electro-mechanical systems (MEMS. The power density at 0.5 V without a sensor is 450 mW/cm2, and that with a sensor is 426 mW/cm2. Since the reaction area of a fuel cell with a sensor is approximately 12% smaller than that without a sensor, but the performance of the former is only 5% worse.

  8. Exploring dark current voltage characteristics of micromorph silicon tandem cells with computer simulations

    NARCIS (Netherlands)

    Sturiale, A.; Li, H. B. T.; Rath, J.K.; Schropp, R.E.I.; Rubinelli, F.A.

    2009-01-01

    The transport mechanisms controlling the forward dark current-voltage characteristic of the silicon micromorph tandem solar cell were investigated with numerical modeling techniques. The dark current-voltage characteristics of the micromorph tandem structure at forward voltages show three regions:

  9. Potential well measurements in spherical electrostatic-inertial plasma confinement (SEIC) using a collimated proton detector

    International Nuclear Information System (INIS)

    Miley, G.H.; Nadler, J.H.; Gu, Y.B.

    1992-01-01

    A collimated proton detector has been developed for spatially resolved proton measurement in SEIC deuterium fusion experiments. The results are used to infer the potential well depth and well dynamics during SEIC operation. The SEIC operates as follows: ions enter the cathode-grid and are decelerated due to the presence of the positive space charge in the center created by the high ion density there. Since the fusion cross-section is ion-velocity dependent, the greater the height of the positive potential, the lower is the fusion reaction rate in that region. This source profile is determined by the collimated proton measurement. Analysis of the observed proton energy and parametric dependence on voltage current indicates that beam-background fusion predominantly occurs (for a typical 12-mA cathode current, 30-kV cathode voltage in a 4-mTorr D, background). Computer simulations suggest that for these parameters, a positive space charge potential of magnitude about 1/2 of the applied voltage forms inside the cathode. These results establish the first measurement of a positive potential well structure inside an ion injected SEIC device. The dynamics of the well profile with changing injected current is described along with a description of the technique used for unfolding the proton data

  10. Voltage current characteristics of type III superconductors

    Science.gov (United States)

    Dorofejev, G. L.; Imenitov, A. B.; Klimenko, E. Yu.

    1980-06-01

    An adequate description of voltage-current characteristics is important in order to understand the nature of high critical current for the electrodynamic construction of type-III superconductors and for commercial superconductor specification. Homogenious monofilament and multifilament Nb-Ti, Nb-Zr, Nb 3Sn wires were investigated in different ranges of magnetic field, temperature and current. The longitudinal electric field for homogenious wires may be described by E=J ρnexp- T c/T 0+ T/T 0+ B/B 0+ J/J 0, where To, Bo, Jo are the increasing parameters, which depend weakly on B and T, of the electric field. The shape of the voltage-current characteristics of multifilament wires, and the parameter's dependence on temperature and magnetic field may be explained qualitatively by the longitudinal heterogeneous nature of the filaments. A method of attaining the complete specification of the wire's electro-physical properties is proposed. It includes the traditional description of a critical surface (ie the surface corresponding to a certain conventional effective resistivity in T, B, J - space) and a description of any increasing parameter that depends on B and T.

  11. Doping of 6H-SiC pn structures by proton irradiation

    International Nuclear Information System (INIS)

    Strel'chuk, Anatoly M.; Lebedev, Alexandre A.; Kozlovski, Vitali V.; Savkina, Natali S.; Davydov, Denis V.; Solov'ev, Viktor V.; Rastegaeva, Marina G.

    1999-01-01

    The influence of proton irradiation on current-voltage characteristics, N d - N a values and parameters of deep centres in 6H-SiC pn structures grown by sublimation epitaxy has been studied. The irradiation was carried out with 8 MeV protons in the range of doses from 10 14 to 10 16 cm -2 . Irradiation with a dose of 3.6x10 14 cm -2 leaves the voltage drop at high forward currents (10 A/cm 2 ) practically unchanged. For higher irradiation dose of 1.8x10 15 cm -2 , the forward voltage drop and the degree of compensation in the samples increased ; partial annealing of the radiation defects and partial recovery of the electrical parameters occurred after annealing at T∼400-800 K. Irradiation with a dose of 5.4x10 15 cm -2 resulted in very high resistance in forward biased pn structures which remained high even after heating to 500 deg. C. It is suggested that proton irradiation causes decreasing of the lifetime and formation of an i- or an additional p-layer

  12. A micro-power LDO with piecewise voltage foldback current limit protection

    International Nuclear Information System (INIS)

    Wei Hailong; Liu Youbao; Guo Zhongjie; Liao Xue

    2012-01-01

    To achieve a constant current limit, low power consumption and high driving capability, a micro-power LDO with a piecewise voltage-foldback current-limit circuit is presented. The current-limit threshold is dynamically adjusted to achieve a maximum driving capability and lower quiescent current of only 300 nA. To increase the loop stability of the proposed LDO, a high impedance transconductance buffer under a micro quiescent current is designed for splitting the pole that exists at the gate of the pass transistor to the dominant pole, and a zero is designed for the purpose of the second pole phase compensation. The proposed LDO is fabricated in a BiCMOS process. The measurement results show that the short-circuit current of the LDO is 190 mA, the constant limit current under a high drop-out voltage is 440 mA, and the maximum load current under a low drop-out voltage is up to 800 mA. In addition, the quiescent current of the LDO is only 7 μA, the load regulation is about 0.56% on full scale, the line regulation is about 0.012%/V, the PSRR at 120 Hz is 58 dB and the drop-out voltage is only 70 mV when the load current is 250 mA. (semiconductor integrated circuits)

  13. Surge currents and voltages at the low voltage power mains during lightning strike to a GSM tower

    Energy Technology Data Exchange (ETDEWEB)

    Markowska, Renata [Bialystok Technical University (Poland)], E-mail: remark@pb.edu.pl

    2007-07-01

    The paper presents the results of numerical calculations of lightning surge currents and voltages in the low voltage power mains system connected to a free standing GSM base station. Direct lightning strike to GSM tower was studied. The analysis concerned the current that flows to the transformer station through AC power mains, the potential difference between the grounding systems of the GSM and the transformer stations and the voltage differences between phase and PE conductors of the power mains underground cable at both the GSM and the transformer sides. The calculations were performed using a numerical program based on the electromagnetic field theory and the method of moments. (author)

  14. Josephson tunneling current in the presence of a time-dependent voltage

    International Nuclear Information System (INIS)

    Harris, R.E.

    1975-01-01

    The expression for the current through a small Josephson tunnel junction in the presence of a time-dependent voltage is presented. Four terms appear: the usual sine, cosine, and quasiparticle terms, and a reactive part of the quasiparticle current. The latter is displayed graphically as a function of both energy and temperature. It is shown that in the limit of zero dc voltage and small ac voltage, the Josephson device behaves linearly. Interpretation of the in- and out-of-phase components of the current in this linear limit is given to provide physical insight into some of the details of the general expression. Finally, the tunneling current in the linear limit is shown for thin tunneling barriers to be proportional to the current in a single superconductor in the presence of an electromagnetic field

  15. A grid-voltage-sensorless resistive active power filter with series LC-filter

    DEFF Research Database (Denmark)

    Bai, Haofeng; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    Voltage-sensorless control has been investigated for Voltage Source Inverters (VSIs) for many years due to the reduced system cost and potentially improved system reliability. The VSI based Resistive Active Power Filters (R-APFs) are now widely used to prevent the harmonic resonance in power...... distribution network, for which the voltage sensors are needed in order to obtain the current reference. In this paper a grid-voltage-sensorless control strategy is proposed for the R-APF with series LC-filter. Unlike the traditional resistance emulation method, this proposed control method re...

  16. A Grid-Voltage-Sensorless Resistive Active Power Filter with Series LC-Filter

    DEFF Research Database (Denmark)

    Bai, Haofeng; Wang, Xiongfei; Blaabjerg, Frede

    2018-01-01

    Voltage-sensorless control has been investigated for Voltage Source Inverters (VSIs) for many years due to the reduced system cost and potentially improved system reliability. The VSI based Resistive Active Power Filters (R-APFs) are now widely used to prevent the harmonic resonance in power...... distribution network, for which the voltage sensors are needed in order to obtain the current reference. In this paper a grid-voltage-sensorless control strategy is proposed for the R-APF with series LC-filter. Unlike the traditional resistance emulation method, this proposed control method re...

  17. LASL high-current proton storage rings

    International Nuclear Information System (INIS)

    Lawrence, G.P.; Cooper, R.K.; Hudgings, D.W.; Spalek, G.; Jason, A.J.; Higgins, E.F.; Gillis, R.E.

    1980-01-01

    The Proton Storage Ring at LAMPF is a high-current accumulator designed to convert long 800-MeV linac pulses into very short high-intensity proton bunches ideally suited to driving a pulsed polyenergetic neutron source. The Ring, authorized for construction at $19 million, will operate in a short-bunch high-frequency mode for fast neutron physics and a long-bunch low-frequency mode for thermal neutron-scattering programs. Unique features of the project include charge-changing injection with initial conversion from H - to H 0 , a high repetition rate fast-risetime extraction kicker, and high-frequency and first-harmonic bunching system

  18. Current-Voltage Characteristics of Bi-dithiolbenzene in Parallel Arrangement

    International Nuclear Information System (INIS)

    Boudjella, Aissa

    2011-01-01

    The low voltage conductance of interacting two 1,4-dithiolbenzene (DTB) molecules is investigated. The simulation results show that the electron transport can be controlled either by changing the Fermi level position E f or modifying its inter-molecular spacing d. Molecular assembly system with close interaction between DTB units, affects significantly the conductance. In addition, the position of the Fermi plays an important role in determining the current flow. Moreover, it is important to note that E f affects not only the threshold voltage V th , but also the saturation voltage V sat . When E f approaches the LUMO energy level, V th decreases, while V sat increases. To conclude, the threshold voltage and the saturation voltage depend on the Fermi level position and the inter-molecular spacing.

  19. Calcium determination in bone by proton activation analysis. Progress report

    International Nuclear Information System (INIS)

    Wilson, R.; Adelstein, S.

    1974-01-01

    The incidence of post-menopausal osteoporosis in almost epidemic proportions makes the early diagnosis and development of effective therapy a matter of considerable concern. Current status of the project is reviewed and new applications of calcium determination by in vivo proton activation analysis are discussed. The proton activation method promises to give precise and reproducible measurements of calcium content for a single vertebra or several vertebrae in vivo. By controlling the number and energy of protons incident on a vertebra and by accurately detecting the number of 2.17 MeV gamma rays emitted, one may determine the 40Ca content. The proton technique offers advantages by directly measuring calcium in a very well-defined region. On-going studies by the construction of a lead shield for in vivo counting and for the analysis of the results are also given

  20. Current-voltage curves of gold quantum point contacts revisited

    DEFF Research Database (Denmark)

    Hansen, K.; Nielsen, S K.; Brandbyge, Mads

    2000-01-01

    We present measurements of current-voltage (I-V) curves on gold quantum point contacts (QPCs) with a conductance up to 4 G(0) (G(0) = 2e(2)/h is the conductance quantum) and voltages up to 2 V. The QPCs are formed between the gold tip of a scanning tunneling microscope and a Au(110) surface under...

  1. Silicon/HfO2 interface: Effects of proton irradiation

    International Nuclear Information System (INIS)

    Maurya, Savita; Radhakrishna, M.

    2015-01-01

    Substrate oxide interfaces are of paramount importance in deciding the quality of the semiconductor devices. In this work we have studied how 200 keV proton irradiation affects the interface of a 13 nm thick, atomic layer deposited hafnium dioxide on silicon substrate. Pre- and post-irradiation electrical measurements are used to quantify the effect of proton irradiation for varying electrode geometries. Proton irradiation introduces positive charge in the oxide and at the interface of Si/HfO 2 interface. The gate current is not very much affected under positive injection since the induced positive charge is compensated by the injected electrons. Current voltage characteristics under negative bias get affected by the proton irradiation

  2. Lifetime test on a high-performance dc microwave proton source

    International Nuclear Information System (INIS)

    Sherman, J.D.; Hodgkins, D.J.; Lara, P.D.; Schneider, J.D.; Stevens, R.R. Jr.

    1995-01-01

    Powerful CW proton linear accelerators (100 mA at 0.5--1 GeV) are being proposed for spallation neutron source applications.These production accelerators require high availability and reliability. A microwave proton source, which has already demonstrated several key beam requirements, was operated for one week (170 hours) in a dc mode to test the reliability and lifetime of its plasma generator. The source was operated with 570 W of microwave (2.45 GHz) discharge power and with a 47-kV extraction voltage. This choice of operating parameters gave a proton current density of 250-mA/cm 2 at 83% proton fraction, which is sufficient for a conservative dc injector design. The beam current was 60--65 mA over most of the week, and was sufficiently focused for RFQ injection. Total beam availability, defined as 47-keV beam-on time divided by elapsed time, was 96.2%. Spark downs in the high voltage column and a gas flow control problem caused all the downtime; no plasma generator failures were observed

  3. Nonlinear current-voltage behavior in PZT thin films

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Mi; Zhang, Weikang; Zhang, Zebin; Li, Shida; Zhang, Ping; Lan, Kuibo [Tianjin University, School of Electrical and Information Engineering, Tianjin (China)

    2017-05-15

    In this paper, Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} (PZT) thin films were prepared by sol-gel synthesis and characterized by X-ray diffraction, field emission scanning electron microscopy and current-voltage measurements. Here, we demonstrate that in addition to the outstanding ferroelectric and dielectric properties, the PZT films also have remarkably nonlinear current-voltage characteristics. Considering the contact of semi-conductive grains in the PZT films, a double Schottky barrier (DSB) model may be responsible for such phenomena. The test results show that with the decrease of annealing temperature and the increase of the film thickness, the threshold voltages (V{sub th}) increase obviously. The maximum V{sub th} value of 60.95 V and the minimum value of 6.9 V in our experiments were obtained from the five-layered samples annealed at 600 C and the two-layered samples annealed at 700 C, respectively. As a result, PZT thin film may lead to efficient switching and sensing devices. (orig.)

  4. Current and Voltage Mode Multiphase Sinusoidal Oscillators Using CBTAs

    Directory of Open Access Journals (Sweden)

    M. Sagbas

    2013-04-01

    Full Text Available Current-mode (CM and voltage-mode (VM multiphase sinusoidal oscillator (MSO structures using current backward transconductance amplifier (CBTA are proposed. The proposed oscillators can generate n current or voltage signals (n being even or odd equally spaced in phase. n+1 CBTAs, n grounded capacitors and a grounded resistor are used for nth-state oscillator. The oscillation frequency can be independently controlled through transconductance (gm of the CBTAs which are adjustable via their bias currents. The effects caused by the non-ideality of the CBTA on the oscillation frequency and condition have been analyzed. The performance of the proposed circuits is demonstrated on third-stage and fifth-stage MSOs by using PSPICE simulations based on the 0.25 µm TSMC level-7 CMOS technology parameters.

  5. ASIC-like, proton-activated currents in rat hippocampal neurons.

    Science.gov (United States)

    Baron, Anne; Waldmann, Rainer; Lazdunski, Michel

    2002-03-01

    The expression of mRNA for acid sensing ion channels (ASIC) subunits ASIC1a, ASIC2a and ASIC2b has been reported in hippocampal neurons, but the presence of functional hippocampal ASIC channels was never assessed. We report here the first characterization of ASIC-like currents in rat hippocampal neurons in primary culture. An extracellular pH drop induces a transient Na(+) current followed by a sustained non-selective cation current. This current is highly sensitive to pH with an activation threshold around pH 6.9 and a pH(0.5) of 6.2. About half of the total peak current is inhibited by the spider toxin PcTX1, which is specific for homomeric ASIC1a channels. The remaining PcTX1-resistant ASIC-like current is increased by 300 microM Zn(2+) and, whereas not fully activated at pH 5, it shows a pH(0.5) of 6.0 between pH 7.4 and 5. We have previously shown that Zn(2+) is a co-activator of ASIC2a-containing channels. Thus, the hippocampal transient ASIC-like current appears to be generated by a mixture of homomeric ASIC1a channels and ASIC2a-containing channels, probably heteromeric ASIC1a+2a channels. The sustained non-selective current suggests the involvement of ASIC2b-containing heteromeric channels. Activation of the hippocampal ASIC-like current by a pH drop to 6.9 or 6.6 induces a transient depolarization which itself triggers an initial action potential (AP) followed by a sustained depolarization and trains of APs. Zn(2+) increases the acid sensitivity of ASIC channels, and consequently neuronal excitability. It is probably an important co-activator of ASIC channels in the central nervous system.

  6. Development of an intelligent high-voltage direct-current power supply for nuclear detectors

    International Nuclear Information System (INIS)

    Zhao Xiuliang

    1997-01-01

    The operation and performances of a new type direct-current high-voltage power supply are described. The power supply with intelligent feature is controlled by a single-chip microcomputer (8031), and various kinds of output voltage can be preset. The output-voltage is monitored and regulated by the single-chip microcomputer and displayed by LED. The output voltage is stable when the load current is within the allowable limits

  7. A common pathway for charge transport through voltage-sensing domains.

    Science.gov (United States)

    Chanda, Baron; Bezanilla, Francisco

    2008-02-07

    Voltage-gated ion channels derive their voltage sensitivity from the movement of specific charged residues in response to a change in transmembrane potential. Several studies on mechanisms of voltage sensing in ion channels support the idea that these gating charges move through a well-defined permeation pathway. This gating pathway in a voltage-gated ion channel can also be mutated to transport free cations, including protons. The recent discovery of proton channels with sequence homology to the voltage-sensing domains suggests that evolution has perhaps exploited the same gating pathway to generate a bona fide voltage-dependent proton transporter. Here we will discuss implications of these findings on the mechanisms underlying charge (and ion) transport by voltage-sensing domains.

  8. Characterizations of Proton-irradiated wide bandgap semiconductor devices

    International Nuclear Information System (INIS)

    Kim, J. H.; Kim, H. R.; Ahn, J. H.

    2008-04-01

    Current-voltages were compared before and after proton irradiation. As expected from simulation results, 5keV protons severely damaged the transistors' performance compared to 25MeV protons. Also, the effects of both lower and higher fluencies were compared. Source-Drain currents were dramatically decreased under higher fluency. At the highest dose of 2x10 16 protons/cm 2 there was a decrease of 43% in IDS and a 29% decrease in gm. The data is consistent with the introduction of defect centers in the HEMT structure by the high energy protons leading to a reduction in carrier concentration and mobility in the 2- dimensional electron gas channel due to the extremely thin 2DEG and the high displacement threshold energy, AlGaN/GaN HEMT has great potential for applications in earth orbit

  9. Thyristor current-pulse generator for betatron electromagnet with independent low-voltage supply

    International Nuclear Information System (INIS)

    Baginskii, B.A.; Makarevich, V.N.; Shtein, M.M.

    1989-01-01

    A thyristor generator is described that produces unipolar current pulses in the winding of a betatron electromagnet. The voltage on the electro-magnet is increased and the shape of the current pulses is improved by use of an intermediate inductive storage device. The current pulses have a duration of 11 msec, an amplitude of 190 A, and a repetition frequency of 50 Hz. The maximum magnetic-field energy is 450 J, the voltage on the electromagnet winding is 1.5 kV, and the supply voltage is 27 V

  10. A dulal-functional medium voltage level DVR to limit downstream fault currents

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Li, Yun Wei; Vilathgamuwa, D. Mahinda

    2007-01-01

    on the other parallel feeders connected to PCC. Furthermore, if not controlled properly, the DVR might also contribute to this PCC voltage sag in the process of compensating the missing voltage, thus further worsening the fault situation. To limit the flow of large line currents, and therefore restore the PCC...... situations. Controlling the DVR as a virtual inductor would also ensure zero real power absorption during the DVR compensation and thus minimize the stress in the dc link. Finally, the proposed fault current limiting algorithm has been tested in Matlab/Simulink simulation and experimentally on a medium......The dynamic voltage restorer (DVR) is a modern custom power device used in power distribution networks to protect consumers from sudden sags (and swells) in grid voltage. Implemented at medium voltage level, the DVR can be used to protect a group of medium voltage or low voltage consumers. However...

  11. An overview of current experiments in search of proton decay

    International Nuclear Information System (INIS)

    Goldhaber, M.; Sulak, L.R.

    1981-01-01

    Detectors being used in current experiments dedicated to the search for proton decay, fall into two classes, totally active water Cherenkov detectors with light collected by phototubes, and sampling calorimeters with particle ionization tracked by gas tube arrays. An example of each type is considered in detail, the features of other detectors in the two classes are pointed out and compared with those of the same type. (U.K.)

  12. Current integrator using the voltage to frequency converter

    International Nuclear Information System (INIS)

    Ukai, K.; Gomi, K.

    1975-01-01

    A current integrator using the Voltage to Frequency Converter has been constructed to measure the beam intensity of the 1.3 GeV Electron Synchrotron at the INS. This integrator ranges the current 10 -7 to 10 -11 amperes and has been calibrated by the extracted electron beam and constant current sources. The accuracy of this integrator agrees with the previous integrator within 1%. (auth.)

  13. High Order Voltage and Current Harmonic Mitigation Using the Modular Multilevel Converter STATCOM

    NARCIS (Netherlands)

    Kontos, E.; Tsolaridis, Georgios; Teodorescu, Remus; Bauer, P.

    2017-01-01

    Due to the increase of power electronic-based loads, the maintenance of high power quality poses a challenge in modern power systems. To limit the total harmonic distortion in the line voltage and currents at the point of the common coupling (PCC), active power filters are commonly employed. This

  14. Cathode fall model and current-voltage characteristics of field emission driven direct current microplasmas

    Energy Technology Data Exchange (ETDEWEB)

    Venkattraman, Ayyaswamy [Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036 (India)

    2013-11-15

    The post-breakdown characteristics of field emission driven microplasma are studied theoretically and numerically. A cathode fall model assuming a linearly varying electric field is used to obtain equations governing the operation of steady state field emission driven microplasmas. The results obtained from the model by solving these equations are compared with particle-in-cell with Monte Carlo collisions simulation results for parameters including the plasma potential, cathode fall thickness, ion number density in the cathode fall, and current density vs voltage curves. The model shows good overall agreement with the simulations but results in slightly overpredicted values for the plasma potential and the cathode fall thickness attributed to the assumed electric field profile. The current density vs voltage curves obtained show an arc region characterized by negative slope as well as an abnormal glow discharge characterized by a positive slope in gaps as small as 10 μm operating at atmospheric pressure. The model also retrieves the traditional macroscale current vs voltage theory in the absence of field emission.

  15. Cathode fall model and current-voltage characteristics of field emission driven direct current microplasmas

    International Nuclear Information System (INIS)

    Venkattraman, Ayyaswamy

    2013-01-01

    The post-breakdown characteristics of field emission driven microplasma are studied theoretically and numerically. A cathode fall model assuming a linearly varying electric field is used to obtain equations governing the operation of steady state field emission driven microplasmas. The results obtained from the model by solving these equations are compared with particle-in-cell with Monte Carlo collisions simulation results for parameters including the plasma potential, cathode fall thickness, ion number density in the cathode fall, and current density vs voltage curves. The model shows good overall agreement with the simulations but results in slightly overpredicted values for the plasma potential and the cathode fall thickness attributed to the assumed electric field profile. The current density vs voltage curves obtained show an arc region characterized by negative slope as well as an abnormal glow discharge characterized by a positive slope in gaps as small as 10 μm operating at atmospheric pressure. The model also retrieves the traditional macroscale current vs voltage theory in the absence of field emission

  16. PV source based high voltage gain current fed converter

    Science.gov (United States)

    Saha, Soumya; Poddar, Sahityika; Chimonyo, Kudzai B.; Arunkumar, G.; Elangovan, D.

    2017-11-01

    This work involves designing and simulation of a PV source based high voltage gain, current fed converter. It deals with an isolated DC-DC converter which utilizes boost converter topology. The proposed converter is capable of high voltage gain and above all have very high efficiency levels as proved by the simulation results. The project intends to produce an output of 800 V dc from a 48 V dc input. The simulation results obtained from PSIM application interface were used to analyze the performance of the proposed converter. Transformer used in the circuit steps up the voltage as well as to provide electrical isolation between the low voltage and high voltage side. Since the converter involves high switching frequency of 100 kHz, ultrafast recovery diodes are employed in the circuitry. The major application of the project is for future modeling of solar powered electric hybrid cars.

  17. Features of current-voltage characteristic of nonequilibrium trench MOS barrier Schottky diode

    Science.gov (United States)

    Mamedov, R. K.; Aslanova, A. R.

    2018-06-01

    The trench MOS barrier Schottky diodes (TMBS diode) under the influence of the voltage drop of the additional electric field (AEF) appearing in the near-contact region of the semiconductor are in a nonequilibrium state and their closed external circuit flows currents in the absence of an external voltage. When an external voltage is applied to the TMBS diode, the current transmission is described by the thermionic emission theory with a specific feature. Both forward and reverse I-V characteristics of the TMBS diode consist of two parts. In the initial first part of the forward I-V characteristic there are no forward currents, but reverse saturation currents flow, in its subsequent second part the currents increase exponentially with the voltage. In the initial first part of the reverse I-V characteristic, the currents increase in an abrupt way and in the subsequent second part the saturation currents flow under the action of the image force. The mathematical expressions for forward and reverse I-V characteristic of the TMBS diode and also narrow or nanostructure Schottky diode are proposed, which are in good agreement with the results of experimental and calculated I-V characteristics.

  18. Dimerization of the voltage-sensing phosphatase controls its voltage-sensing and catalytic activity.

    Science.gov (United States)

    Rayaprolu, Vamseedhar; Royal, Perrine; Stengel, Karen; Sandoz, Guillaume; Kohout, Susy C

    2018-05-07

    Multimerization is a key characteristic of most voltage-sensing proteins. The main exception was thought to be the Ciona intestinalis voltage-sensing phosphatase (Ci-VSP). In this study, we show that multimerization is also critical for Ci-VSP function. Using coimmunoprecipitation and single-molecule pull-down, we find that Ci-VSP stoichiometry is flexible. It exists as both monomers and dimers, with dimers favored at higher concentrations. We show strong dimerization via the voltage-sensing domain (VSD) and weak dimerization via the phosphatase domain. Using voltage-clamp fluorometry, we also find that VSDs cooperate to lower the voltage dependence of activation, thus favoring the activation of Ci-VSP. Finally, using activity assays, we find that dimerization alters Ci-VSP substrate specificity such that only dimeric Ci-VSP is able to dephosphorylate the 3-phosphate from PI(3,4,5)P 3 or PI(3,4)P 2 Our results indicate that dimerization plays a significant role in Ci-VSP function. © 2018 Rayaprolu et al.

  19. Effects of gamma irradiation on voltage-dependant NA+ and K+ currents in N1E-115 cells

    International Nuclear Information System (INIS)

    Diserbo, M.; Barbier, M.; Quignard, J.F.

    1998-01-01

    Effects of 15 Gy gamma irradiation on voltage-dependent Na + and K + currents in differentiated N1E-115 cells are studied by using whole cell recording. Only, we observed an activation of Na + currents at a lower threshold. (authors)

  20. Direct-current proton-beam measurements at Los Alamos

    International Nuclear Information System (INIS)

    Sherman, J.; Stevens, R.R.; Schneider, J.D.; Zaugg, T.

    1994-01-01

    Recently, a CW proton accelerator complex was moved from Chalk River Laboratories (CRL) to Los Alamos National Laboratory. This includes a 50-keV dc proton injector with a single-solenoid low-energy beam transport system (LEBT) and a CW 1.25-MeV, 267-MHz radiofrequency quadrupole (RFQ). The move was completed after CRL had achieved 55-mA CW operation at 1.25 MeV using 250-kW klystrode tubes to power the RFQ. These accelerator components are prototypes for the front end of a CW linac required for an accelerator-driven transmutation linac, and they provide early confirmation of some CW accelerator components. The injector (ion source and LEBT) and emittance measuring unit are installed and operational at Los Alamos. The dc microwave ion source has been operated routinely at 50-keV, 75-mA hydrogen-ion current. This ion source has demonstrated very good discharge and H 2 gas efficiencies, and sufficient reliability to complete CW RFQ measurements at CRL. Proton fraction of 75% has been measured with 550-W discharge power. This high proton fraction removes the need for an analyzing magnet. Proton LEBT emittance measurements completed at Los Alamos suggest that improved transmission through the RFQ may be achieved by increasing the solenoid focusing current. Status of the final CW RFQ operation at CRL and the installation of the RFQ at Los Alamos is given

  1. Realization of Nth-Order Voltage Transfer Function using Current Conveyors CCII

    Directory of Open Access Journals (Sweden)

    K. Vrba

    1997-06-01

    Full Text Available A universal method for the realization of arbitrary voltage transfer function in canonic form is presented. A voltage-controlled current-source using a plus-type second-generation current conveyor is here applied as the basic building element. Filters designed according to this method have a high input impedance and low sensitivity to variations of circuit parameters. All passive elements are grounded.

  2. High-temperature performance of MoS{sub 2} thin-film transistors: Direct current and pulse current-voltage characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, C.; Samnakay, R.; Balandin, A. A., E-mail: balandin@ee.ucr.edu [Nano-Device Laboratory (NDL), Department of Electrical Engineering, Bourns College of Engineering, University of California—Riverside, Riverside, California 92521 (United States); Phonon Optimized Engineered Materials (POEM) Center, Materials Science and Engineering Program, University of California—Riverside, Riverside, California 92521 (United States); Rumyantsev, S. L. [Department of Electrical, Computer, and Systems Engineering, Center for Integrated Electronics, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation); Shur, M. S. [Department of Electrical, Computer, and Systems Engineering, Center for Integrated Electronics, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2015-02-14

    We report on fabrication of MoS{sub 2} thin-film transistors (TFTs) and experimental investigations of their high-temperature current-voltage characteristics. The measurements show that MoS{sub 2} devices remain functional to temperatures of at least as high as 500 K. The temperature increase results in decreased threshold voltage and mobility. The comparison of the direct current (DC) and pulse measurements shows that the direct current sub-linear and super-linear output characteristics of MoS{sub 2} thin-films devices result from the Joule heating and the interplay of the threshold voltage and mobility temperature dependences. At temperatures above 450 K, a kink in the drain current occurs at zero gate voltage irrespective of the threshold voltage value. This intriguing phenomenon, referred to as a “memory step,” was attributed to the slow relaxation processes in thin films similar to those in graphene and electron glasses. The fabricated MoS{sub 2} thin-film transistors demonstrated stable operation after two months of aging. The obtained results suggest new applications for MoS{sub 2} thin-film transistors in extreme-temperature electronics and sensors.

  3. Voltage Balancing Method on Expert System for 51-Level MMC in High Voltage Direct Current Transmission

    Directory of Open Access Journals (Sweden)

    Yong Chen

    2016-01-01

    Full Text Available The Modular Multilevel Converters (MMC have been a spotlight for the high voltage and high power transmission systems. In the VSC-HVDC (High Voltage Direct Current based on Voltage Source Converter transmission system, the energy of DC link is stored in the distributed capacitors, and the difference of capacitors in parameters and charge rates causes capacitor voltage balance which affects the safety and stability of HVDC system. A method of MMC based on the expert system for reducing the frequency of the submodules (SMs of the IGBT switching frequency is proposed. Firstly, MMC with 51 levels for HVDC is designed. Secondly, the nearest level control (NLC for 51-level MMC is introduced. Thirdly, a modified capacitor voltage balancing method based on expert system for MMC-based HVDC transmission system is proposed. Finally, a simulation platform for 51-level Modular Multilevel Converter is constructed by using MATLAB/SIMULINK. The results indicate that the strategy proposed reduces the switching frequency on the premise of keeping submodule voltage basically identical, which greatly reduces the power losses for MMC-HVDC system.

  4. Voltage stability in low voltage microgrids in aspects of active and reactive power demand

    Directory of Open Access Journals (Sweden)

    Parol Mirosław

    2016-03-01

    Full Text Available Low voltage microgrids are autonomous subsystems, in which generation, storage and power and electrical energy consumption appear. In the paper the main attention has been paid to the voltage stability issue in low voltage microgrid for different variants of its operation. In the introduction a notion of microgrid has been presented, and also the issue of influence of active and reactive power balance on node voltage level has been described. Then description of voltage stability issue has been presented. The conditions of voltage stability and indicators used to determine voltage stability margin in the microgrid have been described. Description of the low voltage test microgrid, as well as research methodology along with definition of considered variants of its operation have been presented further. The results of exemplary calculations carried out for the daily changes in node load of the active and reactive power, i.e. the voltage and the voltage stability margin indexes in nodes have been presented. Furthermore, the changes of voltage stability margin indexes depending on the variant of the microgrid operation have been presented. Summary and formulation of conclusions related to the issue of voltage stability in microgrids have been included at the end of the paper.

  5. Low voltage stress-induced leakage current and traps in ultrathin oxide (1.2 2.5 nm) after constant voltage stresses

    Science.gov (United States)

    Petit, C.; Zander, D.

    2007-10-01

    It has been shown that the low voltage gate current in ultrathin oxide metal-oxide-semiconductor devices is very sensitive to electrical stresses. Therefore, it can be used as a reliability monitor when the oxide thickness becomes too small for traditional electrical measurements to be used. In this work, we present a study on n-MOSCAP devices at negative gate bias in the direct tunneling (DT) regime. If the low voltage stress-induced leakage current (LVSILC) depends strongly on the low sense voltages, it also depends strongly on the stress voltage magnitude. We show that two LVSILC peaks appear as a function of the sense voltage in the LVSILC region and that their magnitude, one compared to the other, depends strongly on the stress voltage magnitude. One is larger than the other at low stress voltage and smaller at high stress voltage. From our experimental results, different conduction mechanisms are analyzed. To explain LVSILC variations, we propose a model of the conduction through the ultrathin gate oxide based on two distinctly different trap-assisted tunneling mechanisms: inelastic of gate electron (INE) and trap-assisted electron (ETAT).

  6. High-voltage direct-current circuit breakers

    International Nuclear Information System (INIS)

    Yoshioka, Y.; Hirasawa, K.

    1991-01-01

    This paper reports that in 1954 the first high-voltage direct-current (HVDC) transmission system was put into operation between Gotland and the mainland of Sweden. Its system voltage and capacity were 100 kV and 20 MW, respectively. Since then many HVDC transmission systems have been planned, constructed, or commissioned in more than 30 places worldwide, and their total capacity is close to 40 GW. Most systems commissioned to date are two-terminal schemes, and HVDC breakers are not yet used in the high-potential main circuit of those systems, because the system is expected to perform well using only converter/inverter control even at a fault stage of the transmission line. However, even in a two-terminal scheme there are not a few merits in using an HVDC breaker when the system has two parallel transmission lines, that is, when it is a double-circuit system

  7. Voltage-Controlled Square/Triangular Wave Generator with Current Conveyors and Switching Diodes

    Directory of Open Access Journals (Sweden)

    Martin Janecek

    2012-12-01

    Full Text Available A novel relaxation oscillator based on integrating the diode-switched currents and Schmitt trigger is presented. It is derived from a known circuit with operational amplifiers where these active elements were replaced by current conveyors. The circuit employs only grounded resistances and capacitance and is suitable for high frequency square and triangular signal generation. Its frequency can be linearly and accurately controlled by voltage that is applied to a high-impedance input. Computer simulation with a model of a manufactured conveyor prototype verifies theoretic assumptions.

  8. Subcell Light Current-Voltage Characterization of Irradiated Multijunction Solar Cell

    Directory of Open Access Journals (Sweden)

    Walker Don

    2017-01-01

    Full Text Available The degradation of individual subcell J-V parameters, such as short circuit current, open circuit voltage, fill factor, and power of a GaInP/GaInAs/Ge triple junction solar cell by 1 MeV electrons were derived utilizing the spectral reciprocity relation between electroluminescence and external quantum efficiency. After exposure to a fluence of 1 × 1015 1 MeV electrons, it was observed that up to 67% of the voltage loss is from the middle, GaInAs subcell. Also, the dark saturation current of the Ge and GaInAs subcells increased but a simultaneous decrease in ideality factor caused a reduction of the open circuit voltage. The reduced ideality factor further indicates a change in the primary recombination mechanism.

  9. Application of active electrode compensation to perform continuous voltage-clamp recordings with sharp microelectrodes.

    Science.gov (United States)

    Gómez-González, J F; Destexhe, A; Bal, T

    2014-10-01

    Electrophysiological recordings of single neurons in brain tissues are very common in neuroscience. Glass microelectrodes filled with an electrolyte are used to impale the cell membrane in order to record the membrane potential or to inject current. Their high resistance induces a high voltage drop when passing current and it is essential to correct the voltage measurements. In particular, for voltage clamping, the traditional alternatives are two-electrode voltage-clamp technique or discontinuous single electrode voltage-clamp (dSEVC). Nevertheless, it is generally difficult to impale two electrodes in a same neuron and the switching frequency is limited to low frequencies in the case of dSEVC. We present a novel fully computer-implemented alternative to perform continuous voltage-clamp recordings with a single sharp-electrode. To reach such voltage-clamp recordings, we combine an active electrode compensation algorithm (AEC) with a digital controller (AECVC). We applied two types of control-systems: a linear controller (proportional plus integrative controller) and a model-based controller (optimal control). We compared the performance of the two methods to dSEVC using a dynamic model cell and experiments in brain slices. The AECVC method provides an entirely digital method to perform continuous recording and smooth switching between voltage-clamp, current clamp or dynamic-clamp configurations without introducing artifacts.

  10. Impact of irradiations by protons with different energies on silicon sensors

    International Nuclear Information System (INIS)

    Neubueser, Coralie

    2013-06-01

    In the frame of the CMS tracker upgrade campaign the radiation damage of oxygenrich n-type silicon pad diodes induced by 23 MeV and 23 GeV protons was investigated. The diodes were manufactured by Hamamatsu Photonics. After irradiation with 1 MeV neutron equivalent fluences between 1 x 10 11 cm -2 and 1.5 x 10 15 cm -2 , the sensors were electrically characterized by means of capacitance-voltage (CV) and current-voltage (IV) measurements. Current pulses recorded by the Transient Current Technique (TCT) and Charge Collection Efficiency (CCE) measurements show a dependence of the bulk damage on the proton energy. At a fluence of Φ eq ∼3 x 10 14 cm -2 oxygen-rich n-type diodes demonstrate clear Space Charge Sign Inversion (SCSI) after 23 MeV proton irradiation. This effect does not appear after the irradiation with 23 GeV protons. Moreover, RD50 pad diodes were irradiated with 23 MeV protons, electrically characterized and compared to results obtained after 23 GeV irradiations. Our previous observation on the energy dependence of the radiation damage could be confirmed. In order to get a deeper understanding of the differences of the radiation induced defects, the Deep Level Transient Spectroscopy (DLTS) and Thermally Stimulated Current Technique (TSC) were utilized. Defects with impact on the space charge could be identified and characterized and it was possible to find some hints for the reason of the SCSI after 23 MeV proton irradiation. Moreover, a dependence on the oxygen concentration of the sensors could be observed.

  11. H∞ Robust Current Control for DFIG Based Wind Turbine subject to Grid Voltage Distortions

    DEFF Research Database (Denmark)

    Wang, Yun; Wu, Qiuwei; Gong, Wenming

    2016-01-01

    This paper proposes an H∞ robust current controller for doubly fed induction generator (DFIG) based wind turbines (WTs) subject to grid voltage distortions. The controller is to mitigate the impact of the grid voltage distortions on rotor currents with DFIG parameter perturbation. The grid voltage...... distortions considered include asymmetric voltage dips and grid background harmonics. An uncertain DFIG model is developed with uncertain factors originating from distorted stator voltage, and changed generator parameters due to the flux saturation effect, the skin effect, etc. Weighting functions...... are designed to efficiently track the unbalanced current components and the 5th and 7th background harmonics. The robust stability (RS) and robust performance (RP) of the proposed controller are verified by the structured singular value µ. The performance of the H∞ robust current controller was demonstrated...

  12. Non-contact current and voltage sensor having detachable housing incorporating multiple ferrite cylinder portions

    Science.gov (United States)

    Carpenter, Gary D.; El-Essawy, Wael; Ferreira, Alexandre Peixoto; Keller, Thomas Walter; Rubio, Juan C.; Schappert, Michael A.

    2016-04-26

    A detachable current and voltage sensor provides an isolated and convenient device to measure current passing through a conductor such as an AC branch circuit wire, as well as providing an indication of an electrostatic potential on the wire, which can be used to indicate the phase of the voltage on the wire, and optionally a magnitude of the voltage. The device includes a housing formed from two portions that mechanically close around the wire and that contain the current and voltage sensors. The current sensor is a ferrite cylinder formed from at least three portions that form the cylinder when the sensor is closed around the wire with a hall effect sensor disposed in a gap between two of the ferrite portions along the circumference to measure current. A capacitive plate or wire is disposed adjacent to, or within, the ferrite cylinder to provide the indication of the voltage.

  13. Observation of dark pulses in 10 nm thick YBCO nanostrips presenting hysteretic current voltage characteristics

    Science.gov (United States)

    Ejrnaes, M.; Parlato, L.; Arpaia, R.; Bauch, T.; Lombardi, F.; Cristiano, R.; Tafuri, F.; Pepe, G. P.

    2017-12-01

    We have fabricated several 10 nm thick and 65 nm wide YBa2Cu3O7-δ (YBCO) nanostrips. The nanostrips with the highest critical current densities are characterized by hysteretic current voltage characteristics (IVCs) with a direct bistable switch from the zero-voltage to the finite voltage state. The presence of hysteretic IVCs allowed the observation of dark pulses due to fluctuations phenomena. The key role of the bistable behavior is its ability to transform a small disturbance (e.g. an intrinsic fluctuation) into a measurable transient signal, i.e. a dark pulse. On the contrary, in devices characterized by lower critical current density values, the IVCs are non-hysteretic and dark pulses have not been observed. To investigate the physical origin of the dark pulses, we have measured the bias current dependence of the dark pulse rate: the observed exponential increase with the bias current is compatible with mechanisms based on thermal activation of magnetic vortices in the nanostrip. We believe that the successful amplification of small fluctuation events into measurable signals in nanostrips of ultrathin YBCO is a milestone for further investigation of YBCO nanostrips for superconducting nanostrip single photon detectors and other quantum detectors for operation at higher temperatures.

  14. High energy proton irradiation effects on SiC Schottky rectifiers

    International Nuclear Information System (INIS)

    Nigam, S.; Kim, Jihyun; Ren, F.; Chung, G.Y.; MacMillan, M.F.; Dwivedi, R.; Fogarty, T.N.; Wilkins, R.; Allums, K.K.; Abernathy, C.R.; Pearton, S.J.; Williams, J.R.

    2002-01-01

    4H-SiC Schottky rectifiers with dielectric overlap edge termination were exposed to 40 MeV protons at fluences from 5x10 7 -5x10 9 cm -2 . The reverse breakdown voltage decreased from ∼500 V in unirradiated devices to ∼-450 V after the highest proton dose. The reverse leakage current at -250 V was approximately doubled under these conditions. The forward current at -2 V decreased by ∼1% (fluence of 5x10 7 cm -2 ) to ∼42% (fluence of 5x10 9 cm -2 ), while the current at lower biases was increased due to the introduction of defect centers. The ideality factor, on-state resistance, and forward turn-on voltage showed modest increases for fluences of ≤5x10 8 cm -2 , but were more strongly affected (increase of 40%-75%) at the highest dose employed

  15. Differences between signal currents for both polarities of applied voltages on cavity ionization chambers

    International Nuclear Information System (INIS)

    Takata, N.

    2000-01-01

    It is necessary to obtain precise values of signal currents for the measurement of exposure rates for gamma rays with cavity ionization chambers. Signal currents are usually expected to have the same absolute values for both polarities of applied voltages. In the case of cylindrical cavity ionization chambers, volume recombination loss of ion pairs depends on the polarity of the applied voltage. This is because the values of mobility are different for positive and negative ions. It was found, however, that values of signal currents from a cylindrical ionization chamber change slightly more with a negative than with a positive applied voltage, even after being corrected for volume recombination loss. Moreover, absolute values of saturation currents, which are obtained by extrapolation of correction of initial recombination and diffusion loss, were larger for the negative than for the positive applied voltage. It is known from an experiment with parallel plate ionization chambers that when negative voltage is applied to the repeller electrode, the saturated signal current decreases with an increase in the applied voltage. This is because secondary electrons are accelerated and the stopping power of air for these electrons decreases. When positive voltage is applied, the reverse is true. The effects of acceleration and deceleration of secondary electrons by the electric field thus seem to cause a tendency opposite to the experimental results on the signal currents from cylindrical ionization chambers. The experimental results for the cylindrical ionization chamber can be explained as follows. When negative voltage is applied, secondary electrons are attracted to the central (collecting) electrode. Consequently, the path length of the trajectories of these secondary electrons in the ionization volume increases and signal current increases. The energy gain from the electric field by secondary electrons which stop in the ionization chamber also contributes to the

  16. On-line monitoring of base current and forward emitter current gain of the voltage regulator's serial pnp transistor in a radiation environment

    Directory of Open Access Journals (Sweden)

    Vukić Vladimir Đ.

    2012-01-01

    Full Text Available A method of on-line monitoring of the low-dropout voltage regulator's operation in a radiation environment is developed in this paper. The method had to enable detection of the circuit's degradation during exploitation, without terminating its operation in an ionizing radiation field. Moreover, it had to enable automatic measurement and data collection, as well as the detection of any considerable degradation, well before the monitored voltage regulator's malfunction. The principal parameters of the voltage regulator's operation that were monitored were the serial pnp transistor's base current and the forward emitter current gain. These parameters were procured indirectly, from the data on the voltage regulator's load and quiescent currents. Since the internal consumption current in moderately and heavily loaded devices was used, the quiescent current of a negligibly loaded voltage regulator of the same type served as a reference. Results acquired by on-line monitoring demonstrated marked agreement with the results acquired from examinations of the voltage regulator's maximum output current and minimum dropout voltage in a radiation environment. The results were particularly consistent in tests with heavily loaded devices. Results obtained for moderately loaded voltage regulators and the risks accompanying the application of the presented method, were also analyzed.

  17. Theory of passive proton conductance in lipid bilayers.

    Science.gov (United States)

    Nagle, J F

    1987-10-01

    The large permeability of lipid bilayers to protons compared to other small ions calls for a special proton transport mechanism. At the present time, only mechanisms involving transient hydrogen-bonded chains of water can account for the experimental result that the conductance is nearly independent of pH. Three models involving transient hydrogen-bonded chains are discussed, including an outline of the kinetic calculations that lead to predictions of current versus voltage drop and current versus pH differences. These calculations can be compared to experiment to determine which, if any, of these models pertains to lipid bilayers.

  18. Correlation of proton irradiation induced threshold voltage shifts to deep level traps in AlGaN/GaN heterostructures

    Science.gov (United States)

    Zhang, Z.; Cardwell, D.; Sasikumar, A.; Kyle, E. C. H.; Chen, J.; Zhang, E. X.; Fleetwood, D. M.; Schrimpf, R. D.; Speck, J. S.; Arehart, A. R.; Ringel, S. A.

    2016-04-01

    The impact of proton irradiation on the threshold voltage (VT) of AlGaN/GaN heterostructures is systematically investigated to enhance the understanding of a primary component of the degradation of irradiated high electron mobility transistors. The value of VT was found to increase monotonically as a function of 1.8 MeV proton fluence in a sub-linear manner reaching 0.63 V at a fluence of 1 × 1014 cm-2. Silvaco Atlas simulations of VT shifts caused by GaN buffer traps using experimentally measured introduction rates, and energy levels closely match the experimental results. Different buffer designs lead to different VT dependences on proton irradiation, confirming that deep, acceptor-like defects in the GaN buffer are primarily responsible for the observed VT shifts. The proton irradiation induced VT shifts are found to depend on the barrier thickness in a linear fashion; thus, scaling the barrier thickness could be an effective way to reduce such degradation.

  19. WE-D-BRB-03: Current State of Volumetric Image Guidance for Proton Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Hua, C. [St. Jude Children’s Research Hospital (United States)

    2016-06-15

    The goal of this session is to review the physics of proton therapy, treatment planning techniques, and the use of volumetric imaging in proton therapy. The course material covers the physics of proton interaction with matter and physical characteristics of clinical proton beams. It will provide information on proton delivery systems and beam delivery techniques for double scattering (DS), uniform scanning (US), and pencil beam scanning (PBS). The session covers the treatment planning strategies used in DS, US, and PBS for various anatomical sites, methods to address uncertainties in proton therapy and uncertainty mitigation to generate robust treatment plans. It introduces the audience to the current status of image guided proton therapy and clinical applications of CBCT for proton therapy. It outlines the importance of volumetric imaging in proton therapy. Learning Objectives: Gain knowledge in proton therapy physics, and treatment planning for proton therapy including intensity modulated proton therapy. The current state of volumetric image guidance equipment in proton therapy. Clinical applications of CBCT and its advantage over orthogonal imaging for proton therapy. B. Teo, B.K Teo had received travel funds from IBA in 2015.

  20. WE-D-BRB-03: Current State of Volumetric Image Guidance for Proton Therapy

    International Nuclear Information System (INIS)

    Hua, C.

    2016-01-01

    The goal of this session is to review the physics of proton therapy, treatment planning techniques, and the use of volumetric imaging in proton therapy. The course material covers the physics of proton interaction with matter and physical characteristics of clinical proton beams. It will provide information on proton delivery systems and beam delivery techniques for double scattering (DS), uniform scanning (US), and pencil beam scanning (PBS). The session covers the treatment planning strategies used in DS, US, and PBS for various anatomical sites, methods to address uncertainties in proton therapy and uncertainty mitigation to generate robust treatment plans. It introduces the audience to the current status of image guided proton therapy and clinical applications of CBCT for proton therapy. It outlines the importance of volumetric imaging in proton therapy. Learning Objectives: Gain knowledge in proton therapy physics, and treatment planning for proton therapy including intensity modulated proton therapy. The current state of volumetric image guidance equipment in proton therapy. Clinical applications of CBCT and its advantage over orthogonal imaging for proton therapy. B. Teo, B.K Teo had received travel funds from IBA in 2015.

  1. Rotor current transient analysis of DFIG-based wind turbines during symmetrical voltage faults

    International Nuclear Information System (INIS)

    Ling, Yu; Cai, Xu; Wang, Ningbo

    2013-01-01

    Highlights: • We theoretically analyze the rotor fault current of DFIG based on space vector. • The presented analysis is simple, easy to understand. • The analysis highlights the accuracy of the expression of the rotor fault currents. • The expression can be widely used to analyze the different levels of voltage symmetrical fault. • Simulation results show the accuracy of the expression of the rotor currents. - Abstract: The impact of grid voltage fault on doubly fed induction generators (DFIGs), especially rotor currents, has received much attention. So, in this paper, the rotor currents of based-DFIG wind turbines are considered in a generalized way, which can be widely used to analyze the cases under different levels of voltage symmetrical faults. A direct method based on space vector is proposed to obtain an accurate expression of rotor currents as a function of time for symmetrical voltage faults in the power system. The presented theoretical analysis is simple and easy to understand and especially highlights the accuracy of the expression. Finally, the comparable simulations evaluate this analysis and show that the expression of the rotor currents is sufficient to calculate the maximum fault current, DC and AC components, and especially helps to understand the causes of the problem and as a result, contributes to adapt reasonable approaches to enhance the fault ride through (FRT) capability of DFIG wind turbines during a voltage fault

  2. Current and voltage distribution in the diffuse vacuum arc

    NARCIS (Netherlands)

    Schellekens, H.; Schram, D.C.

    1985-01-01

    On the basis of extensive measurements, a model is developed for the diffuse plasma of the high-current vacuum arc. The model shows that the current constriction and the voltage distribution in the diffuse vacuum arc prior to anode-spot formation are caused by the pressure source to which the

  3. Proton channel HVCN1 is required for effector functions of mouse eosinophils

    Science.gov (United States)

    2013-01-01

    Background Proton currents are required for optimal respiratory burst in phagocytes. Recently, HVCN1 was identified as the molecule required for the voltage-gated proton channel activity associated with the respiratory burst in neutrophils. Although there are similarities between eosinophils and neutrophils regarding their mechanism for respiratory burst, the role of proton channels in eosinophil functions has not been fully understood. Results In the present study, we first identified the expression of the proton channel HVCN1 in mouse eosinophils. Furthermore, using HVCN1-deficient eosinophils, we demonstrated important cell-specific effector functions for HVCN1. Similar to HVCN1-deficient neutrophils, HVCN1-deficient eosinophils produced significantly less reactive oxygen species (ROS) upon phorbol myristate acetate (PMA) stimulation compared with WT eosinophils. In contrast to HVCN1-deficient neutrophils, HVCN1-deficient eosinophils did not show impaired calcium mobilization or migration ability compared with wild-type (WT) cells. Uniquely, HVCN1-deficient eosinophils underwent significantly increased cell death induced by PMA stimulation compared with WT eosinophils. The increased cell death was dependent on NADPH oxidase activation, and correlated with the failure of HVCN1-deficient cells to maintain membrane polarization and intracellular pH in the physiological range upon activation. Conclusions Eosinophils require proton channel HVCN1 for optimal ROS generation and prevention of activation-induced cell death. PMID:23705768

  4. High-voltage-activated calcium current subtypes in mouse DRG neurons adapt in a subpopulation-specific manner after nerve injury.

    Science.gov (United States)

    Murali, Swetha S; Napier, Ian A; Mohammadi, Sarasa A; Alewood, Paul F; Lewis, Richard J; Christie, MacDonald J

    2015-03-01

    Changes in ion channel function and expression are characteristic of neuropathic pain. Voltage-gated calcium channels (VGCCs) are integral for neurotransmission and membrane excitability, but relatively little is known about changes in their expression after nerve injury. In this study, we investigate whether peripheral nerve ligation is followed by changes in the density and proportion of high-voltage-activated (HVA) VGCC current subtypes in dorsal root ganglion (DRG) neurons, the contribution of presynaptic N-type calcium channels in evoked excitatory postsynaptic currents (EPSCs) recorded from dorsal horn neurons in the spinal cord, and the changes in expression of mRNA encoding VGCC subunits in DRG neurons. Using C57BL/6 mice [8- to 11-wk-old males (n = 91)] for partial sciatic nerve ligation or sham surgery, we performed whole cell patch-clamp recordings on isolated DRG neurons and dorsal horn neurons and measured the expression of all VGCC subunits with RT-PCR in DRG neurons. After nerve injury, the density of P/Q-type current was reduced overall in DRG neurons. There was an increase in the percentage of N-type and a decrease in that of P/Q-type current in medium- to large-diameter neurons. No changes were found in the contribution of presynaptic N-type calcium channels in evoked EPSCs recorded from dorsal horn neurons. The α2δ-1 subunit was upregulated by 1.7-fold and γ-3, γ-2, and β-4 subunits were all downregulated 1.7-fold in injured neurons compared with sham-operated neurons. This comprehensive characterization of HVA VGCC subtypes in mouse DRG neurons after nerve injury revealed changes in N- and P/Q-type current proportions only in medium- to large-diameter neurons. Copyright © 2015 the American Physiological Society.

  5. Electronic voltage and current transformers testing device.

    Science.gov (United States)

    Pan, Feng; Chen, Ruimin; Xiao, Yong; Sun, Weiming

    2012-01-01

    A method for testing electronic instrument transformers is described, including electronic voltage and current transformers (EVTs, ECTs) with both analog and digital outputs. A testing device prototype is developed. It is based on digital signal processing of the signals that are measured at the secondary outputs of the tested transformer and the reference transformer when the same excitation signal is fed to their primaries. The test that estimates the performance of the prototype has been carried out at the National Centre for High Voltage Measurement and the prototype is approved for testing transformers with precision class up to 0.2 at the industrial frequency (50 Hz or 60 Hz). The device is suitable for on-site testing due to its high accuracy, simple structure and low-cost hardware.

  6. Depression of voltage-activated Ca2+ release in skeletal muscle by activation of a voltage-sensing phosphatase.

    Science.gov (United States)

    Berthier, Christine; Kutchukian, Candice; Bouvard, Clément; Okamura, Yasushi; Jacquemond, Vincent

    2015-04-01

    Phosphoinositides act as signaling molecules in numerous cellular transduction processes, and phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) regulates the function of several types of plasma membrane ion channels. We investigated the potential role of PtdIns(4,5)P2 in Ca(2+) homeostasis and excitation-contraction (E-C) coupling of mouse muscle fibers using in vivo expression of the voltage-sensing phosphatases (VSPs) Ciona intestinalis VSP (Ci-VSP) or Danio rerio VSP (Dr-VSP). Confocal images of enhanced green fluorescent protein-tagged Dr-VSP revealed a banded pattern consistent with VSP localization within the transverse tubule membrane. Rhod-2 Ca(2+) transients generated by 0.5-s-long voltage-clamp depolarizing pulses sufficient to elicit Ca(2+) release from the sarcoplasmic reticulum (SR) but below the range at which VSPs are activated were unaffected by the presence of the VSPs. However, in Ci-VSP-expressing fibers challenged by 5-s-long depolarizing pulses, the Ca(2+) level late in the pulse (3 s after initiation) was significantly lower at 120 mV than at 20 mV. Furthermore, Ci-VSP-expressing fibers showed a reversible depression of Ca(2+) release during trains, with the peak Ca(2+) transient being reduced by ∼30% after the application of 10 200-ms-long pulses to 100 mV. A similar depression was observed in Dr-VSP-expressing fibers. Cav1.1 Ca(2+) channel-mediated current was unaffected by Ci-VSP activation. In fibers expressing Ci-VSP and a pleckstrin homology domain fused with monomeric red fluorescent protein (PLCδ1PH-mRFP), depolarizing pulses elicited transient changes in mRFP fluorescence consistent with release of transverse tubule-bound PLCδ1PH domain into the cytosol; the voltage sensitivity of these changes was consistent with that of Ci-VSP activation, and recovery occurred with a time constant in the 10-s range. Our results indicate that the PtdIns(4,5)P2 level is tightly maintained in the transverse tubule membrane of the muscle fibers

  7. Mapping return currents in laser-generated Z-pinch plasmas using proton deflectometry

    International Nuclear Information System (INIS)

    Manuel, M. J.-E.; Sinenian, N.; Seguin, F. H.; Li, C. K.; Frenje, J. A.; Rinderknecht, H. G.; Casey, D. T.; Zylstra, A. B.; Petrasso, R. D.; Beg, F. N.

    2012-01-01

    Dynamic return currents and electromagnetic field structure in laser-generated Z-pinch plasmas have been measured using proton deflectometry. Experiments were modeled to accurately interpret deflections observed in proton radiographs. Current flow is shown to begin on axis and migrate outwards with the expanding coronal plasma. Magnetic field strengths of ∼1 T are generated by currents that increase from ∼2 kA to ∼7 kA over the course of the laser pulse. Proton deflectometry has been demonstrated to be a practical alternative to other magnetic field diagnostics for these types of plasmas.

  8. Impact of irradiations by protons with different energies on silicon sensors

    Energy Technology Data Exchange (ETDEWEB)

    Neubueser, Coralie

    2013-06-15

    In the frame of the CMS tracker upgrade campaign the radiation damage of oxygenrich n-type silicon pad diodes induced by 23 MeV and 23 GeV protons was investigated. The diodes were manufactured by Hamamatsu Photonics. After irradiation with 1 MeV neutron equivalent fluences between 1 x 10{sup 11} cm{sup -2} and 1.5 x 10{sup 15} cm{sup -2}, the sensors were electrically characterized by means of capacitance-voltage (CV) and current-voltage (IV) measurements. Current pulses recorded by the Transient Current Technique (TCT) and Charge Collection Efficiency (CCE) measurements show a dependence of the bulk damage on the proton energy. At a fluence of {Phi}{sub eq}{approx}3 x 10{sup 14} cm{sup -2} oxygen-rich n-type diodes demonstrate clear Space Charge Sign Inversion (SCSI) after 23 MeV proton irradiation. This effect does not appear after the irradiation with 23 GeV protons. Moreover, RD50 pad diodes were irradiated with 23 MeV protons, electrically characterized and compared to results obtained after 23 GeV irradiations. Our previous observation on the energy dependence of the radiation damage could be confirmed. In order to get a deeper understanding of the differences of the radiation induced defects, the Deep Level Transient Spectroscopy (DLTS) and Thermally Stimulated Current Technique (TSC) were utilized. Defects with impact on the space charge could be identified and characterized and it was possible to find some hints for the reason of the SCSI after 23 MeV proton irradiation. Moreover, a dependence on the oxygen concentration of the sensors could be observed.

  9. Control algorithms based on the active and non-active currents for a UPQC without series transformers

    OpenAIRE

    Correa Monteiro, Luis Fernando; Aredes, Mauricio; Pinto, J. G.; Exposto, Bruno; Afonso, João L.

    2016-01-01

    This study presents control algorithms for a new unified power quality conditioner (UPQC) without the series transformers that are frequently used to make the insertion of the series converter of the UPQC between the power supply and the load. The behaviour of the proposed UPQC is evaluated in presence of voltage imbalances, as well as under non-sinusoidal voltage-and current conditions. The presented algorithms derive from the concepts involving the active and non-active currents, together w...

  10. Mitigation of grid-current distortion for LCL-filtered grid-connected voltage-source inverter with inverter-side current control

    DEFF Research Database (Denmark)

    Xin, Zhen; Mattavelli, Paolo; Yao, WenLi

    2017-01-01

    Due to the low inductance of an LCL-filter, the grid current generated by an LCL-filtered Voltage Source Inverter (VSI) is sensitive to low-order grid-voltage harmonics. This issue is especially tough for the control system with Inverter Current Feedback (ICF), because the grid-current harmonics...... can freely flow into the filter capacitor without control. To cope with this issue, this paper develops an approach for the ICF control system to suppress the grid-current harmonics without adding extra sensors. The proposed method applies harmonic controllers and feedforward scheme simultaneously...

  11. The current-voltage relation of a pore and its asymptotic behavior in a Nernst-Planck model

    Directory of Open Access Journals (Sweden)

    Marius Birlea

    2012-08-01

    Full Text Available A model for current-voltage nonlinearity and asymmetry is a good starting point for explaining the electrical behavior of the nanopores in synthetic or biological membranes. Using a Nernst-Planck model, we found three behaviors for the current density in a membrane's pore as a function of voltage: a quasi-ohmic, slow rising linear current at low voltages, a nonlinear current at intermediate voltages, and a non-ohmic, fast rising linear current at large voltages. The slope of the quasi-ohmic current depends mainly on the height of energy barrier inside the pore, w, through an exponential term, ew. The magnitude of the non-ohmic linear current is controlled by the potential energy gradient at the pore entrance, w/r. The current-voltage relation is asymmetric if the ion's potential energy inside the pore has an asymmetric triangular profile. The model has only two assumed parameters, the energy barrier height, w, and the relative size of the entrance region of the pore, r, which is a useful feature for fitting and interpreting experimental data.

  12. Non-contact current and voltage sensing method using a clamshell housing and a ferrite cylinder

    Science.gov (United States)

    Carpenter, Gary D.; El-Essawy, Wael; Ferreira, Alexandre Peixoto; Keller, Thomas Walter; Rubio, Juan C.; Schappert, Michael

    2016-04-26

    A method of measurement using a detachable current and voltage sensor provides an isolated and convenient technique for to measuring current passing through a conductor such as an AC branch circuit wire, as well as providing an indication of an electrostatic potential on the wire, which can be used to indicate the phase of the voltage on the wire, and optionally a magnitude of the voltage. The device includes a housing that contains the current and voltage sensors, which may be a ferrite cylinder with a hall effect sensor disposed in a gap along the circumference to measure current, or alternative a winding provided through the cylinder along its axis and a capacitive plate or wire disposed adjacent to, or within, the ferrite cylinder to provide the indication of the voltage.

  13. Improved detection of electrical activity with a voltage probe based on a voltage-sensing phosphatase.

    Science.gov (United States)

    Tsutsui, Hidekazu; Jinno, Yuka; Tomita, Akiko; Niino, Yusuke; Yamada, Yoshiyuki; Mikoshiba, Katsuhiko; Miyawaki, Atsushi; Okamura, Yasushi

    2013-09-15

      One of the most awaited techniques in modern physiology is the sensitive detection of spatiotemporal electrical activity in a complex network of excitable cells. The use of genetically encoded voltage probes has been expected to enable such analysis. However, in spite of recent progress, existing probes still suffer from low signal amplitude and/or kinetics too slow to detect fast electrical activity. Here, we have developed an improved voltage probe named Mermaid2, which is based on the voltage-sensor domain of the voltage-sensing phosphatase from Ciona intestinalis and Förster energy transfer between a pair of fluorescent proteins. In mammalian cells, Mermaid2 permits ratiometric readouts of fractional changes of more than 50% over a physiologically relevant voltage range with fast kinetics, and it was used to follow a train of action potentials at frequencies of up to 150 Hz. Mermaid2 was also able to detect single action potentials and subthreshold voltage responses in hippocampal neurons in vitro, in addition to cortical electrical activity evoked by sound stimuli in single trials in living mice.

  14. Mechanism of formation of subnanosecond current front in high-voltage pulse open discharge

    Science.gov (United States)

    Schweigert, I. V.; Alexandrov, A. L.; Zakrevsky, Dm. E.; Bokhan, P. A.

    2014-11-01

    The mechanism of subnanosecond current front rise observed previously in the experiment in high-voltage pulse open discharge in helium is studied in kinetic particle-in-cell simulations. The Boltzmann equations for electrons, ions, and fast atoms are solved self-consistently with the Poisson equations for the electrical potential. The partial contributions to the secondary electron emission from the ions, fast atoms, photons, and electrons, bombarding the electrode, are calculated. In simulations, as in the experiment, the discharge glows between two symmetrical cathodes and the anode grid in the midplane at P =6 Torr and the applied voltage of 20 kV. The electron avalanche development is considered for two experimental situations during the last stage of breakdown: (i) with constant voltage and (ii) with decreasing voltage. For case (i), the subnanosecond current front rise is set by photons from the collisional excitation transfer reactions. For the case (ii), the energetic electrons swamp the cathode during voltage drop and provide the secondary electron emission for the subnanosecond current rise, observed in the experiment.

  15. High current proton linear accelerators and nuclear power

    International Nuclear Information System (INIS)

    Tunnicliffe, P.R.; Chidley, B.G.; Fraser, J.S.

    1976-01-01

    This paper outlines a possible role that high-current proton linear accelerators might play as ''electrical breeders'' in the forthcoming nuclear-power economy. A high-power beam of intermediate energy protons delivered to an actinide-element target surrounded by a blanket of fertile material may produce fissile material at a competitive cost. Criteria for technical performance and, in a Canadian context, for costs are given and the major problem areas outlined not only for the accelerator and its associated rf power source but also for the target assembly. (author)

  16. Use of multi-functional flexible micro-sensors for in situ measurement of temperature, voltage and fuel flow in a proton exchange membrane fuel cell.

    Science.gov (United States)

    Lee, Chi-Yuan; Chan, Pin-Cheng; Lee, Chung-Ju

    2010-01-01

    Temperature, voltage and fuel flow distribution all contribute considerably to fuel cell performance. Conventional methods cannot accurately determine parameter changes inside a fuel cell. This investigation developed flexible and multi-functional micro sensors on a 40 μm-thick stainless steel foil substrate by using micro-electro-mechanical systems (MEMS) and embedded them in a proton exchange membrane fuel cell (PEMFC) to measure the temperature, voltage and flow. Users can monitor and control in situ the temperature, voltage and fuel flow distribution in the cell. Thereby, both fuel cell performance and lifetime can be increased.

  17. Characteristics of output voltage and current of integrated nanogenerators

    KAUST Repository

    Yang, Rusen; Qin, Yong; Li, Cheng; Dai, Liming; Wang, Zhong Lin

    2009-01-01

    three criteria: Schottky behavior test, switching-polarity tests, and linear superposition of current and voltage tests. The 11 tests can effectively rule out the system artifacts, whose sign does not change with the switching measurement polarity

  18. The current status of proton therapy in the world, the European Union and Slovakia

    International Nuclear Information System (INIS)

    Ruzicka, J.

    2011-01-01

    Proton therapy is considered to be very promising cancer treatment modality, and therefore many countries of the world are trying to (regardless of the high investment costs) to build their own atomic centre (or other proton centres if they operate already some). Proton therapy allows better control of therapeutic doses of radiation to which the patient is exposed. Proton irradiation of the tumor can kill more cancer cells while minimizing damage of healthy tissue. Currently there is about 33 facilities in operation in the world where proton therapy can be carried out. Proton therapy complex with new, highly sophisticated equipment is also being constructed in Slovakia - in The Central Military Hospital in Ruzomberok. The project is in its final stage of implementation. The paper describes the current status of proton therapy in the world, the European Union (EU) and Slovakia. In conclusion principally new Proton therapy unit complex built in Slovakia with similar facilities currently existing in EU countries (old 15 member states) is compared (especially from technical and medical aspects). (author)

  19. Ultra Low Voltage Class AB Switched Current Memory Cells Based on Floating Gate Transistors

    DEFF Research Database (Denmark)

    Mucha, Igor

    1999-01-01

    current memory cells were designed using a CMOS process with threshold voltages V-T0n = \\V-T0p\\ = 0.9 V for the n- and p-channel devices. Both hand calculations and PSPICE simulations showed that the designed example switched current memory cell allowed a maximum signal range better than +/-18 mu......A proposal for a class AB switched current memory cell, suitable for ultra-low-voltage applications is presented. The proposal employs transistors with floating gates, allowing to build analog building blocks for ultralow supply voltage operation also in CMOS processes with high threshold voltages....... This paper presents the theoretical basis for the design of "floating-gate'' switched current memory cells by giving a detailed description and analysis of the most important impacts degrading the performance of the cells. To support the theoretical assumptions circuits based on "floating-gate'' switched...

  20. Construction and validation of a homology model of the human voltage-gated proton channel hHV1.

    Science.gov (United States)

    Kulleperuma, Kethika; Smith, Susan M E; Morgan, Deri; Musset, Boris; Holyoake, John; Chakrabarti, Nilmadhab; Cherny, Vladimir V; DeCoursey, Thomas E; Pomès, Régis

    2013-04-01

    The topological similarity of voltage-gated proton channels (H(V)1s) to the voltage-sensing domain (VSD) of other voltage-gated ion channels raises the central question of whether H(V)1s have a similar structure. We present the construction and validation of a homology model of the human H(V)1 (hH(V)1). Multiple structural alignment was used to construct structural models of the open (proton-conducting) state of hH(V)1 by exploiting the homology of hH(V)1 with VSDs of K(+) and Na(+) channels of known three-dimensional structure. The comparative assessment of structural stability of the homology models and their VSD templates was performed using massively repeated molecular dynamics simulations in which the proteins were allowed to relax from their initial conformation in an explicit membrane mimetic. The analysis of structural deviations from the initial conformation based on up to 125 repeats of 100-ns simulations for each system reveals structural features consistently retained in the homology models and leads to a consensus structural model for hH(V)1 in which well-defined external and internal salt-bridge networks stabilize the open state. The structural and electrostatic properties of this open-state model are compatible with proton translocation and offer an explanation for the reversal of charge selectivity in neutral mutants of Asp(112). Furthermore, these structural properties are consistent with experimental accessibility data, providing a valuable basis for further structural and functional studies of hH(V)1. Each Arg residue in the S4 helix of hH(V)1 was replaced by His to test accessibility using Zn(2+) as a probe. The two outermost Arg residues in S4 were accessible to external solution, whereas the innermost one was accessible only to the internal solution. Both modeling and experimental data indicate that in the open state, Arg(211), the third Arg residue in the S4 helix in hH(V)1, remains accessible to the internal solution and is located near the

  1. Correlation of proton irradiation induced threshold voltage shifts to deep level traps in AlGaN/GaN heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z.; Cardwell, D.; Sasikumar, A.; Arehart, A. R.; Ringel, S. A., E-mail: ringel.5@osu.edu [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Kyle, E. C. H.; Speck, J. S. [Department of Materials, University of California, Santa Barbara, California 93106-5050 (United States); Chen, J.; Zhang, E. X.; Fleetwood, D. M.; Schrimpf, R. D. [Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee 37235 (United States)

    2016-04-28

    The impact of proton irradiation on the threshold voltage (V{sub T}) of AlGaN/GaN heterostructures is systematically investigated to enhance the understanding of a primary component of the degradation of irradiated high electron mobility transistors. The value of V{sub T} was found to increase monotonically as a function of 1.8 MeV proton fluence in a sub-linear manner reaching 0.63 V at a fluence of 1 × 10{sup 14} cm{sup −2}. Silvaco Atlas simulations of V{sub T} shifts caused by GaN buffer traps using experimentally measured introduction rates, and energy levels closely match the experimental results. Different buffer designs lead to different V{sub T} dependences on proton irradiation, confirming that deep, acceptor-like defects in the GaN buffer are primarily responsible for the observed V{sub T} shifts. The proton irradiation induced V{sub T} shifts are found to depend on the barrier thickness in a linear fashion; thus, scaling the barrier thickness could be an effective way to reduce such degradation.

  2. Correlation of proton irradiation induced threshold voltage shifts to deep level traps in AlGaN/GaN heterostructures

    International Nuclear Information System (INIS)

    Zhang, Z.; Cardwell, D.; Sasikumar, A.; Arehart, A. R.; Ringel, S. A.; Kyle, E. C. H.; Speck, J. S.; Chen, J.; Zhang, E. X.; Fleetwood, D. M.; Schrimpf, R. D.

    2016-01-01

    The impact of proton irradiation on the threshold voltage (V T ) of AlGaN/GaN heterostructures is systematically investigated to enhance the understanding of a primary component of the degradation of irradiated high electron mobility transistors. The value of V T was found to increase monotonically as a function of 1.8 MeV proton fluence in a sub-linear manner reaching 0.63 V at a fluence of 1 × 10 14  cm −2 . Silvaco Atlas simulations of V T shifts caused by GaN buffer traps using experimentally measured introduction rates, and energy levels closely match the experimental results. Different buffer designs lead to different V T dependences on proton irradiation, confirming that deep, acceptor-like defects in the GaN buffer are primarily responsible for the observed V T shifts. The proton irradiation induced V T shifts are found to depend on the barrier thickness in a linear fashion; thus, scaling the barrier thickness could be an effective way to reduce such degradation.

  3. Transient voltage response of a superconducting strip to a supercritical current pulse

    International Nuclear Information System (INIS)

    Attekum, P.M.Th.M. van; Wouters, M.C.H.M.; Wolter, J.; Horstman, R.E.

    1981-01-01

    A superconductor subject to a supercritical current pulse displays a delay time between the onset of the current pulse and the onset of the corresponding voltage response. From the onset of the voltage response it takes a second (transient) time to reach the stationary state. It is shown that the transient time can be explained with inhomogeneities in the strip which give rise to a distribution of delay times. The transient time is thus not related to a characteristic time in the superconductor. For small supercritical currents also heating effects show up. (author)

  4. Performance evaluation of wideband bio-impedance spectroscopy using constant voltage source and constant current source

    International Nuclear Information System (INIS)

    Mohamadou, Youssoufa; Oh, Tong In; Wi, Hun; Sohal, Harsh; Farooq, Adnan; Woo, Eung Je; McEwan, Alistair Lee

    2012-01-01

    Current sources are widely used in bio-impedance spectroscopy (BIS) measurement systems to maximize current injection for increased signal to noise while keeping within medical safety specifications. High-performance current sources based on the Howland current pump with optimized impedance converters are able to minimize stray capacitance of the cables and setup. This approach is limited at high frequencies primarily due to the deteriorated output impedance of the constant current source when situated in a real measurement system. For this reason, voltage sources have been suggested, but they require a current sensing resistor, and the SNR reduces at low impedance loads due to the lower current required to maintain constant voltage. In this paper, we compare the performance of a current source-based BIS and a voltage source-based BIS, which use common components. The current source BIS is based on a Howland current pump and generalized impedance converters to maintain a high output impedance of more than 1 MΩ at 2 MHz. The voltage source BIS is based on voltage division between an internal current sensing resistor (R s ) and an external sample. To maintain high SNR, R s is varied so that the source voltage is divided more or less equally. In order to calibrate the systems, we measured the transfer function of the BIS systems with several known resistor and capacitor loads. From this we may estimate the resistance and capacitance of biological tissues using the least-squares method to minimize error between the measured transimpedance excluding the system transfer function and that from an impedance model. When tested on realistic loads including discrete resistors and capacitors, and saline and agar phantoms, the voltage source-based BIS system had a wider bandwidth of 10 Hz to 2.2 MHz with less than 1% deviation from the expected spectra compared to more than 10% with the current source. The voltage source also showed an SNR of at least 60 dB up to 2.2 MHz

  5. Modified SOGI based shunt active power filter to tackle various grid voltage abnormalities

    Directory of Open Access Journals (Sweden)

    Kalpeshkumar Patil

    2017-10-01

    Full Text Available Shunt Active Power Filters (SAPF have been effectively used to compensate the harmonics generated by the non-linear loads. The SAPF’s performance depends on the accurate generation of reference current, which is dependent greatly on the template of supply voltage. When the grid voltage (or its template is characterized by different abnormalities like presence of harmonics, imbalance, dc-offset etc., some of the conventional techniques of frequency estimation may fail to correctly estimate the frequency. This ultimately affects the reference current generation and hence, the SAPF operation, ultimately leading to high distortion of the grid currents. The paper presents modified dual second-order generalized integrator (MDSOGI based SAPF to ensure effective compensation of harmonics, even when the grid voltage is characterized by all the abnormalities mentioned above. It is highlighted with one case that when the sensed voltage is having dc-offset, DSOGI-SAPF results into the source current with THD, dc-offset and harmonic with values 5.82%, 0.8% and 4.5%, respectively. For the same case, the proposed technique yields grid current which is free of dc-offset and 2nd harmonic and has THD = 3.57%. The dynamic performance of the MDSOGI-SAPF is validated and its superior performance over DSOGI-SAPF is illustrated even with experimental results.

  6. Gaas Displacement Damage Dosimeter Based on Diode Dark Currents

    Directory of Open Access Journals (Sweden)

    Warner Jeffrey H.

    2017-01-01

    Full Text Available GaAs diode dark currents are correlated over a very large proton energy range as a function of displacement damage dose (DDD. The linearity of the dark current increase with DDD over a wide range of applied voltage bias deems this device an excellent candidate for a displacement damage dosimeter. Additional proton testing performed in situ enabled error estimate determination to within 10% for simulated space use.

  7. Voltage-dependent inward currents in smooth muscle cells of skeletal muscle arterioles

    Science.gov (United States)

    Shirokov, Roman E.

    2018-01-01

    Voltage-dependent inward currents responsible for the depolarizing phase of action potentials were characterized in smooth muscle cells of 4th order arterioles in mouse skeletal muscle. Currents through L-type Ca2+ channels were expected to be dominant; however, action potentials were not eliminated in nominally Ca2+-free bathing solution or by addition of L-type Ca2+ channel blocker nifedipine (10 μM). Instead, Na+ channel blocker tetrodotoxin (TTX, 1 μM) reduced the maximal velocity of the upstroke at low, but not at normal (2 mM), Ca2+ in the bath. The magnitude of TTX-sensitive currents recorded with 140 mM Na+ was about 20 pA/pF. TTX-sensitive currents decreased five-fold when Ca2+ increased from 2 to 10 mM. The currents reduced three-fold in the presence of 10 mM caffeine, but remained unaltered by 1 mM of isobutylmethylxanthine (IBMX). In addition to L-type Ca2+ currents (15 pA/pF in 20 mM Ca2+), we also found Ca2+ currents that are resistant to 10 μM nifedipine (5 pA/pF in 20 mM Ca2+). Based on their biophysical properties, these Ca2+ currents are likely to be through voltage-gated T-type Ca2+ channels. Our results suggest that Na+ and at least two types (T- and L-) of Ca2+ voltage-gated channels contribute to depolarization of smooth muscle cells in skeletal muscle arterioles. Voltage-gated Na+ channels appear to be under a tight control by Ca2+ signaling. PMID:29694371

  8. Coordinated Voltage Control of Active Distribution Network

    Directory of Open Access Journals (Sweden)

    Xie Jiang

    2016-01-01

    Full Text Available This paper presents a centralized coordinated voltage control method for active distribution network to solve off-limit problem of voltage after incorporation of distributed generation (DG. The proposed method consists of two parts, it coordinated primal-dual interior point method-based voltage regulation schemes of DG reactive powers and capacitors with centralized on-load tap changer (OLTC controlling method which utilizes system’s maximum and minimum voltages, to improve the qualified rate of voltage and reduce the operation numbers of OLTC. The proposed coordination has considered the cost of capacitors. The method is tested using a radial edited IEEE-33 nodes distribution network which is modelled using MATLAB.

  9. A Novel Programmable CMOS Fuzzifiers Using Voltage-to-Current Converter Circuit

    Directory of Open Access Journals (Sweden)

    K. P. Abdulla

    2012-01-01

    Full Text Available This paper presents a new voltage-input, current-output programmable membership function generator circuit (MFC using CMOS technology. It employs a voltage-to-current converter to provide the required current bias for the membership function circuit. The proposed MFC has several advantageous features. This MFC can be reconfigured to perform triangular, trapezoidal, S-shape, Z-Shape, and Gaussian membership forms. This membership function can be programmed in terms of its width, slope, and its center locations in its universe of discourses. The easily adjustable characteristics of the proposed circuit and its accuracy make it suitable for embedded system and industrial control applications. The proposed MFC is designed using the spice software, and simulation results are obtained.

  10. Study on model current predictive control method of PV grid- connected inverters systems with voltage sag

    Science.gov (United States)

    Jin, N.; Yang, F.; Shang, S. Y.; Tao, T.; Liu, J. S.

    2016-08-01

    According to the limitations of the LVRT technology of traditional photovoltaic inverter existed, this paper proposes a low voltage ride through (LVRT) control method based on model current predictive control (MCPC). This method can effectively improve the photovoltaic inverter output characteristics and response speed. The MCPC method of photovoltaic grid-connected inverter designed, the sum of the absolute value of the predictive current and the given current error is adopted as the cost function with the model predictive control method. According to the MCPC, the optimal space voltage vector is selected. Photovoltaic inverter has achieved automatically switches of priority active or reactive power control of two control modes according to the different operating states, which effectively improve the inverter capability of LVRT. The simulation and experimental results proves that the proposed method is correct and effective.

  11. Voltage and Current Regulators Design of Power Converters in Islanded Microgrids based on State Feedback Decoupling

    DEFF Research Database (Denmark)

    Federico, de Bosio; de Sousa Ribeiro, Luiz Antonio; Freijedo Fernandez, Francisco Daniel

    2016-01-01

    In stand-alone microgrids based on voltage source inverters state feedback coupling between the capacitor voltage and inductor current degrades significantly the dynamics performance of voltage and current regulators. The decoupling of the controlled states is proposed, considering the limitations...

  12. Proof of principle study of the use of a CMOS active pixel sensor for proton radiography.

    Science.gov (United States)

    Seco, Joao; Depauw, Nicolas

    2011-02-01

    Proof of principle study of the use of a CMOS active pixel sensor (APS) in producing proton radiographic images using the proton beam at the Massachusetts General Hospital (MGH). A CMOS APS, previously tested for use in s-ray radiation therapy applications, was used for proton beam radiographic imaging at the MGH. Two different setups were used as a proof of principle that CMOS can be used as proton imaging device: (i) a pen with two metal screws to assess spatial resolution of the CMOS and (ii) a phantom with lung tissue, bone tissue, and water to assess tissue contrast of the CMOS. The sensor was then traversed by a double scattered monoenergetic proton beam at 117 MeV, and the energy deposition inside the detector was recorded to assess its energy response. Conventional x-ray images with similar setup at voltages of 70 kVp and proton images using commercial Gafchromic EBT 2 and Kodak X-Omat V films were also taken for comparison purposes. Images were successfully acquired and compared to x-ray kVp and proton EBT2/X-Omat film images. The spatial resolution of the CMOS detector image is subjectively comparable to the EBT2 and Kodak X-Omat V film images obtained at the same object-detector distance. X-rays have apparent higher spatial resolution than the CMOS. However, further studies with different commercial films using proton beam irradiation demonstrate that the distance of the detector to the object is important to the amount of proton scatter contributing to the proton image. Proton images obtained with films at different distances from the source indicate that proton scatter significantly affects the CMOS image quality. Proton radiographic images were successfully acquired at MGH using a CMOS active pixel sensor detector. The CMOS demonstrated spatial resolution subjectively comparable to films at the same object-detector distance. Further work will be done in order to establish the spatial and energy resolution of the CMOS detector for protons. The

  13. Application in low level counting of corona counters operating in voltage or current pulse recording modes

    International Nuclear Information System (INIS)

    Oravec, J.; Usacev, S.; Duka-Zojomi, A.; Sitar, B.; Benovic, D.; Holy, K.

    1977-01-01

    The advantages of current or voltage modes of recording are discussed. It appears that the current mode is more advantageous in measurements of rare events caused by highly ionizing particles on a high background of weakly ionizing particles. A 2.3 litre multiwire corona counter was used for the determination of 226 Ra content in drinking water. The 226 Ra content was estimated by measuring 222 Rn activity. The minimum measurable activity of the system was 0.07 pCi/l of water. (author)

  14. A 1.8 V LDO voltage regulator with foldback current limit and thermal protection

    International Nuclear Information System (INIS)

    Liu Zhiming; Fu Zhongqian; Huang Lu; Xi Tianzuo

    2009-01-01

    This paper introduces the design of a l.8 V low dropout voltage regulator (LDO) and a foldback current limit circuit which limits the output current to 3 mA when load over-current occurs. The LDO was implemented in a 0.18 μm CMOS technology. The measured result reveals that the LDO's power supply rejection (PSR) is about -58 dB and -54 dB at 20 Hz and 1 kHz respectively, the response time is 4 μs and the quiescent current is 20 μA. The designed LDO regulator can work with a supply voltage down to 2.0 V with a drop-out voltage of 200 mV at a maximum load current of 240 mA. (semiconductor integrated circuits)

  15. Tunneling effects in the current-voltage characteristics of high-efficiency GaAs solar cells

    Science.gov (United States)

    Kachare, R.; Anspaugh, B. E.; Garlick, G. F. J.

    1988-01-01

    Evidence is that tunneling via states in the forbidden gap is the dominant source of excess current in the dark current-voltage (I-V) characteristics of high-efficiency DMCVD grown Al(x)Ga(1-x)As/GaAs(x is equal to or greater than 0.85) solar cells. The dark forward and reverse I-V measurements were made on several solar cells, for the first time, at temperatures between 193 and 301 K. Low-voltage reverse-bias I-V data of a number of cells give a thermal activation energy for excess current of 0.026 + or - 0.005 eV, which corresponds to the carbon impurity in GaAs. However, other energy levels between 0.02 eV and 0.04 eV were observed in some cells which may correspond to impurity levels introduced by Cu, Si, Ge, or Cd. The forward-bias excess current is mainly due to carrier tunneling between localized levels created in the space-charge layer by impurities such as carbon, which are incorporated during the solar cell growth process. A model is suggested to explain the results.

  16. Hysteretic current-voltage characteristics in RF-sputtered nanocrystalline TiO2 thin films

    International Nuclear Information System (INIS)

    Villafuerte, Manuel; Juarez, Gabriel; Heluani, Silvia P. de; Comedi, David

    2007-01-01

    We have measured the current-voltage characteristics at room temperature of a nanocrystalline TiO 2 thin film fabricated by reactive RF-sputtering deposition and sandwiched between ITO (indium-tin-oxide)-buffered glass substrate and an indium top electrode. The I-V characteristics are ohmic for low voltages and become non-linear, hysteretic and asymmetric as the voltage is increased. The system is shown to be well represented by two distinct resistance states in the non-ohmic region. Current transient evolutions were also measured for constant voltage excitations. The resistance is stable in time for voltages in the ohmic regime. In contrast, for voltages in the non-ohmic regime, the resistance has a small variation for a short period of time (order of tens seconds) and then increases with time. For those transients, long characteristic times (on the order of tens of minutes up to hours) were found. The behavior of the system is discussed on the basis of experimental results reported in the literature for similar systems and existing models for electric-field induced resistive switching

  17. Current-voltage characteristics of carbon nanotubes with substitutional nitrogen

    DEFF Research Database (Denmark)

    Kaun, C.C.; Larade, B.; Mehrez, H.

    2002-01-01

    unit cell generates a metallic transport behavior. Nonlinear I-V characteristics set in at high bias and a negative differential resistance region is observed for the doped tubes. These behaviors can be well understood from the alignment/mis-alignment of the current carrying bands in the nanotube leads......We report ab initio analysis of current-voltage (I-V) characteristics of carbon nanotubes with nitrogen substitution doping. For zigzag semiconducting tubes, doping with a single N impurity increases current flow and, for small radii tubes, narrows the current gap. Doping a N impurity per nanotube...

  18. Flexible Power Regulation and Current-limited Control of Grid-connected Inverter under Unbalanced Grid Voltage Faults

    DEFF Research Database (Denmark)

    Guo, Xiaoqiang; Liu, Wenzhao; Lu, Zhigang

    2017-01-01

    The grid-connected inverters may experience excessive current stress in case of unbalanced grid voltage Fault Ride Through (FRT), which significantly affects the reliability of the power supply system. In order to solve the problem, the inherent mechanisms of the excessive current phenomenon...... with the conventional FRT solutions are discussed. The quantitative analysis of three phase current peak values are conducted and a novel current-limited control strategy is proposed to achieve the flexible active and reactive power regulation and successful FRT in a safe current operation area with the aim...

  19. Annealing enhancement effect by light illumination on proton irradiated Cu(In, Ga)Se2 thin-film solar cells

    International Nuclear Information System (INIS)

    Kawakita, Shirou; Imaizumi, Mitsuru; Matsuda, Sumio; Yamaguchi, Masafumi; Kushiya, Katsumi; Ohshima, Takeshi; Itoh, Hisayoshi

    2002-01-01

    In this paper, we investigated the high radiation tolerance of copper indium gallium di-selenide (CIGS) thin-film solar cells by conducting in situ measurements of short circuit current and open circuit voltage of CIGS thin-film solar cells during and after proton irradiation under short circuit condition. We found that the annealing rate of proton-induced defects in CIGS thin-film solar cells under light illumination with an AM0 solar simulator is higher than that under dark conditions. The activation energy of proton-induced defects in the CIGS thin-film solar cells with (without) light illumination is 0.80 eV (0.92 eV), which implies on enhanced defect annealing rate in CIGS thin-film solar cells due to minority-carrier injection. (author)

  20. Current-voltage characteristics of bulk heterojunction organic solar cells: connection between light and dark curves

    Energy Technology Data Exchange (ETDEWEB)

    Boix, Pablo P.; Guerrero, Antonio; Garcia-Belmonte, Germa; Bisquert, Juan [Photovoltaic and Optoelectronic Devices Group, Departament de Fisica, Universitat Jaume I, ES-12071 Castello (Spain); Marchesi, Luis F. [Laboratorio Interdisciplinar de, Eletroquimica e Ceramica (LIEC), Universidade Federal de Sao Carlos (Brazil); Photovoltaic and Optoelectronic Devices Group, Departament de Fisica, Universitat Jaume I, ES-12071 Castello (Spain)

    2011-11-15

    A connection is established between recombination and series resistances extracted from impedance spectroscopy and current-voltage curves of polythiophene:fullerene organic solar cells. Recombination is shown to depend exclusively on the (Fermi level) voltage, which allows construction of the current-voltage characteristics in any required conditions based on a restricted set of measurements. The analysis highlights carrier recombination current as the determining mechanism of organic solar cell performance. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Variable speed wind turbine generator system with current controlled voltage source inverter

    International Nuclear Information System (INIS)

    Muyeen, S.M.; Al-Durra, Ahmed; Tamura, J.

    2011-01-01

    highlights: → Current controlled voltage source inverter scheme for wind power application. → Low voltage ride through of wind farm. → Variable speed wind turbine driven permanent magnet synchronous generator-operation and control. -- Abstract: The present popular trend of wind power generation is to use variable speed wind turbine (VSWT) driving a doubly fed induction generator (DFIG), wound field synchronous generator (WFSG) or permanent magnet synchronous generator (PMSG). Among them, stability analyses of DFIG type of VSWT have already been reported in many literatures. However, transient stability and low voltage ride through (LVRT) characteristics analyses for synchronous generator type of VSWT is not sufficient enough. This paper focuses on detailed LVRT characteristic analysis of variable speed wind turbine driving a PMSG (VSWT-PMSG) with current controlled voltage source inverter (CC-VSI). Modeling and suitable control strategies for overall system are developed to augment the low voltage ride through capability of variable speed wind generator, considering recent wind farm grid code. Both symmetrical and unsymmetrical faults are analyzed as network disturbances in this paper. The permanent fault due to unsuccessful reclosing of circuit breakers is taken into consideration, which is a salient feature of this study. Moreover, the dynamic characteristic is analyzed using real wind speed data measured in Hokkaido Island, Japan. The proposed control scheme is simulated by using the standard power system simulation package PSCAD/EMTDC and results are verified by comparing that of voltage controlled voltage source inverter scheme available in power system literature.

  2. Variable speed wind turbine generator system with current controlled voltage source inverter

    Energy Technology Data Exchange (ETDEWEB)

    Muyeen, S.M., E-mail: muyeen0809@yahoo.co [Dept. of Electrical Engineering, Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Al-Durra, Ahmed [Dept. of Electrical Engineering, The Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Tamura, J. [Dept. of EEE, Kitami Institute of Technology, 165 Koen-cho, Kitami 090-8507 (Japan)

    2011-07-15

    highlights: {yields} Current controlled voltage source inverter scheme for wind power application. {yields} Low voltage ride through of wind farm. {yields} Variable speed wind turbine driven permanent magnet synchronous generator-operation and control. -- Abstract: The present popular trend of wind power generation is to use variable speed wind turbine (VSWT) driving a doubly fed induction generator (DFIG), wound field synchronous generator (WFSG) or permanent magnet synchronous generator (PMSG). Among them, stability analyses of DFIG type of VSWT have already been reported in many literatures. However, transient stability and low voltage ride through (LVRT) characteristics analyses for synchronous generator type of VSWT is not sufficient enough. This paper focuses on detailed LVRT characteristic analysis of variable speed wind turbine driving a PMSG (VSWT-PMSG) with current controlled voltage source inverter (CC-VSI). Modeling and suitable control strategies for overall system are developed to augment the low voltage ride through capability of variable speed wind generator, considering recent wind farm grid code. Both symmetrical and unsymmetrical faults are analyzed as network disturbances in this paper. The permanent fault due to unsuccessful reclosing of circuit breakers is taken into consideration, which is a salient feature of this study. Moreover, the dynamic characteristic is analyzed using real wind speed data measured in Hokkaido Island, Japan. The proposed control scheme is simulated by using the standard power system simulation package PSCAD/EMTDC and results are verified by comparing that of voltage controlled voltage source inverter scheme available in power system literature.

  3. Implementation of an active instructional design for teaching the concepts of current, voltage and resistance

    Science.gov (United States)

    Orlaineta-Agüero, S.; Del Sol-Fernández, S.; Sánchez-Guzmán, D.; García-Salcedo, R.

    2017-01-01

    In the present work we show the implementation of a learning sequence based on an active learning methodology for teaching Physics, this proposal tends to promote a better learning in high school students with the use of a comic book and it combines the use of different low-cost experimental activities for teaching the electrical concepts of Current, Resistance and Voltage. We consider that this kind of strategy can be easily extrapolated to higher-education levels like Engineering-college/university level and other disciplines of Science. To evaluate this proposal, we used some conceptual questions from the Electric Circuits Concept Evaluation survey developed by Sokoloff and the results from this survey was analysed with the Normalized Conceptual Gain proposed by Hake and the Concentration Factor that was proposed by Bao and Redish, to identify the effectiveness of the methodology and the models that the students presented after and before the instruction, respectively. We found that this methodology was more effective than only the implementation of traditional lectures, we consider that these results cannot be generalized but gave us the opportunity to view many important approaches in Physics Education; finally, we will continue to apply the same experiment with more students, in the same and upper levels of education, to confirm and validate the effectiveness of this methodology proposal.

  4. A 1.8 V LDO voltage regulator with foldback current limit and thermal protection

    Energy Technology Data Exchange (ETDEWEB)

    Liu Zhiming; Fu Zhongqian; Huang Lu; Xi Tianzuo, E-mail: zml1985@mail.ustc.edu.c [Department of Electronic Science and Technology, University of Science and Technology of China, Hefei 230027 (China)

    2009-08-15

    This paper introduces the design of a l.8 V low dropout voltage regulator (LDO) and a foldback current limit circuit which limits the output current to 3 mA when load over-current occurs. The LDO was implemented in a 0.18 {mu}m CMOS technology. The measured result reveals that the LDO's power supply rejection (PSR) is about -58 dB and -54 dB at 20 Hz and 1 kHz respectively, the response time is 4 {mu}s and the quiescent current is 20 {mu}A. The designed LDO regulator can work with a supply voltage down to 2.0 V with a drop-out voltage of 200 mV at a maximum load current of 240 mA. (semiconductor integrated circuits)

  5. Leakage Currents in Low-Voltage PME and BME Ceramic Capacitors

    Science.gov (United States)

    Teverovsky, Alexander

    2015-01-01

    Introduction of BME capacitors to high-reliability electronics as a replacement for PME capacitors requires better understanding of changes in performance and reliability of MLCCs to set justified screening and qualification requirements. In this work, absorption and leakage currents in various lots of commercial and military grade X7R MLCCs rated to 100V and less have been measured to reveal difference in behavior of PME and BME capacitors in a wide range of voltages and temperatures. Degradation of leakage currents and failures in virgin capacitors and capacitors with introduced cracks has been studied at different voltages and temperatures during step stress highly accelerated life testing. Mechanisms of charge absorption, conduction and degradation have been discussed and a failure model in capacitors with defects suggested.

  6. Simulation and investigation of SiPM’s leakage currents at low voltages

    International Nuclear Information System (INIS)

    Parygin, P P; Popova, E V; Grachev, V M

    2017-01-01

    Technology Computer-Aided Design (TCAD) allows us to use computers in order to develop semiconductor processing technologies and devices and optimize them. Within a framework of a study of silicon photomultipliers (SiPM) a simulation of these devices has been made. The simulation was performed for the irradiated SiPMs and current-voltage characteristics were obtained for the modeled devices. Investigation of current-voltage curve below breakdown with regard to the simulated structure was performed. Obtained curves are presented. (paper)

  7. Enhanced Decoupled Double Synchronous Reference Frame Current Controller for Unbalanced Grid-Voltage Conditions

    DEFF Research Database (Denmark)

    Reyes, M.; Rodriguez, Pedro; Vazquez, S.

    2012-01-01

    . In these codes, the injection of positive- and negative-sequence current components becomes necessary for fulfilling, among others, the low-voltage ride-through requirements during balanced and unbalanced grid faults. However, the performance of classical dq current controllers, applied to power converters......, under unbalanced grid-voltage conditions is highly deficient, due to the unavoidable appearance of current oscillations. This paper analyzes the performance of the double synchronous reference frame controller and improves its structure by adding a decoupling network for estimating and compensating...

  8. On proton events of different solar activity cycles

    International Nuclear Information System (INIS)

    Sattarov, I.; Sherdanov, Ch.; Sattarov, B.

    1997-01-01

    In solar activity cycle N21 and N22 the latitude distribution of the proton large flares and sunspot groups is being studied. It was found that higher proton activity of cycle N22 is connected with its higher latitude sunspot activity (author)

  9. ELECTROMECHANICAL TRANSIENT PROCESSES DURING SUPPLY VOLTAGE CHANGING IN THE SYSTEM OF POLYMER INSULATION COVERING OF THE CURRENT-CARRYING CORE OF ULTRA HIGH VOLTAGE CABLES

    Directory of Open Access Journals (Sweden)

    V. M. Zolotaryov

    2018-04-01

    Full Text Available Aim. The article is devoted to the analysis of the electromechanical transient processes in a system of three frequency-controlled electric drives based on asynchronous motors that control current-carrying core motion, as well as to the study of the effect of such processes on the modes applying three-layer polymer insulation to the current-carrying core. Technique. The study was conducted based on the concepts of electromechanics, electromagnetic field theory, mathematical physics, mathematical modeling. Results. A mathematical model has been developed to analyze transients in an electromechanical system consisting of three frequency-controlled electric drives providing current-carrying core motion of ultra-high voltage cables in an inclined extrusion line. The coordination of the electromechanical parameters of the system drives has been carried out and the permissible changes in the supply voltage at the limiting mass while moving current-carrying core of ultra-high voltage cables with applied polymer insulation have been estimated. Scientific novelty. For the first time it is determined that with the limiting mass of the current-carrying core, the electromechanical system allows to stabilize the current-carrying core speed with the required accuracy at short-term decreases in the supply voltage by no more than 27 % of its amplitude value. It is also shown that this system is resistant to short-term increases in voltage by 32 % for 0.2 s. Practical significance. Using the developed model, it is possible to calculate the change in the configuration and speed of the slack current-carrying core when applying polymer insulation, depending on the specific mass of the current-carrying core per unit length, its tension at the bottom, the torque of the traction motor and the supply voltage to achieve stable operation of the system and accurate working of the set parameters.

  10. Comparison between voltage by turn measured on different tokamaks operating in hybrid wave current drive regime

    International Nuclear Information System (INIS)

    Briffod, G.; Hoang, G.T.

    1987-06-01

    On a tokamak in a current drive operation with a hybrid wave, the R.F. current is estimated from the voltage drop by plasma turn generated by R.F. power application. This estimated current is not proportional to the injected power. There still exists in the plasma an electric field corresponding to the current part produced by induction. The role evaluation of this parameter on the current drive efficiency is important. In this report the relation voltage-R.F. current is studied on Petula and results on the voltage evolution by turn on different machines are compared [fr

  11. Production of fast switching power thyristors by proton irradiation

    International Nuclear Information System (INIS)

    Sawko, D.C.; Bartko, J.

    1983-01-01

    There are several techniques currently employed by various manufacturers in the fabrication of fast switching power thyristors. Gold doping and irradiation by electron beams are among the more common ones. In all cases, the fast switching capability results from a reduction of the minority carrier lifetime of the host material by the introduction of carrier traps or recombination centers. However, accompanying this beneficial reduction in switching speed is a deleterious increase in forward voltage drop which also results from the introduction of carrier traps. Methods which minimize the voltage drop increase as the switching speed is reduced are highly desirable. One such method would achieve this by introducing the traps or recombination centers into well defined narrow regions where they will be more effective in reducing the switching speed than in increasing the forward voltage drop. Because the proton range-energy relationship in materials is relatively well defined and the lifetime reducing displacements occur near the end of their ranges, the lifetime in silicon can be reduced where desired by the precise control of proton energy. Dual energy proton beams from a tandem Van de Graaff accelerator were used in the experiments to determine whether proton beam irradiations offer advantages over other techniques. This was the subject of the present work. The results indicate that this is the preferred technique for reproducibly and rapidly processing fast switching thyristors with superior characteristics. The experimental procedure is discussed and comparisons are made with electron and neutron irradiated thyristors

  12. Active control of flying capacitor currents in multilevel voltage-source inverters

    Czech Academy of Sciences Publication Activity Database

    Kokeš, Petr; Semerád, Radko

    2013-01-01

    Roč. 58, č. 4 (2013), s. 393-410 ISSN 0001-7043 Institutional support: RVO:61388998 Keywords : voltage source inverter (VSI) * multilevel inverter * flying capacitor Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  13. Activity of Palythoa caribaeorum Venom on Voltage-Gated Ion Channels in Mammalian Superior Cervical Ganglion Neurons.

    Science.gov (United States)

    Lazcano-Pérez, Fernando; Castro, Héctor; Arenas, Isabel; García, David E; González-Muñoz, Ricardo; Arreguín-Espinosa, Roberto

    2016-05-05

    The Zoanthids are an order of cnidarians whose venoms and toxins have been poorly studied. Palythoa caribaeorum is a zoanthid commonly found around the Mexican coastline. In this study, we tested the activity of P. caribaeorum venom on voltage-gated sodium channel (NaV1.7), voltage-gated calcium channel (CaV2.2), the A-type transient outward (IA) and delayed rectifier (IDR) currents of KV channels of the superior cervical ganglion (SCG) neurons of the rat. These results showed that the venom reversibly delays the inactivation process of voltage-gated sodium channels and inhibits voltage-gated calcium and potassium channels in this mammalian model. The compounds responsible for these effects seem to be low molecular weight peptides. Together, these results provide evidence for the potential use of zoanthids as a novel source of cnidarian toxins active on voltage-gated ion channels.

  14. Electrical Power Supply to Offshore Oil Installations by High Voltage Direct Current Transmission

    Energy Technology Data Exchange (ETDEWEB)

    Myhre, Joergen Chr.

    2001-07-01

    This study was initiated to investigate if it could be feasible to supply offshore oil installations in the North Sea with electrical power from land. A prestudy of alternative converter topologies indicated that the most promising solution would be to investigate a conventional system with reduced synchronous compensator rating. The study starts with a summary of the state of power supply to offshore installations today, and a short review of classical HVDC transmission. It goes on to analyse how a passive network without sources influences the inverter. The transmission, with its current controlled rectifier and large inductance, is simulated as a current source. Under these circumstances the analysis shows that the network frequency has to adapt in order to keep the active and reactive power balance until the controllers are able to react. The concept of firing angle for a thyristor is limited in a system with variable frequency, the actual control parameter is the firing delay time. Sensitivity analysis showed some astonishing consequences. The frequency rises both by an increase in the active and in the reactive load. The voltage falls by an increase in the active load, but rises by an increase in the inductive load. Two different control principles for the system of inverter, synchronous compensator and load are defined. The first takes the reference for the firing delay time from the fundamental voltage at the point of common coupling. The second takes the reference for the firing delay time from the simulated EMF of the synchronous compensator. Of these, the second is the more stable and should be chosen as the basis for a possible control system. Two simulation tools are applied. The first is a quasi-phasor model running on Matlab with Simulink. The other is a time domain model in KREAN. The time domain model is primarily used for the verification of the quasi-phasor model, and shows that quasi-phasors is still a valuable tool for making a quick analysis

  15. Voltage dependence of a stochastic model of activation of an alpha helical S4 sensor in a K channel membrane

    Science.gov (United States)

    Vaccaro, S. R.

    2011-09-01

    The voltage dependence of the ionic and gating currents of a K channel is dependent on the activation barriers of a voltage sensor with a potential function which may be derived from the principal electrostatic forces on an S4 segment in an inhomogeneous dielectric medium. By variation of the parameters of a voltage-sensing domain model, consistent with x-ray structures and biophysical data, the lowest frequency of the survival probability of each stationary state derived from a solution of the Smoluchowski equation provides a good fit to the voltage dependence of the slowest time constant of the ionic current in a depolarized membrane, and the gating current exhibits a rising phase that precedes an exponential relaxation. For each depolarizing potential, the calculated time dependence of the survival probabilities of the closed states of an alpha helical S4 sensor are in accord with an empirical model of the ionic and gating currents recorded during the activation process.

  16. Achievable peak electrode voltage reduction by neurostimulators using descending staircase currents to deliver charge.

    Science.gov (United States)

    Halpern, Mark

    2011-01-01

    This paper considers the achievable reduction in peak voltage across two driving terminals of an RC circuit when delivering charge using a stepped current waveform, comprising a chosen number of steps of equal duration, compared with using a constant current over the total duration. This work has application to the design of neurostimulators giving reduced peak electrode voltage when delivering a given electric charge over a given time duration. Exact solutions for the greatest possible peak voltage reduction using two and three steps are given. Furthermore, it is shown that the achievable peak voltage reduction, for any given number of steps is identical for simple series RC circuits and parallel RC circuits, for appropriate different values of RC. It is conjectured that the maximum peak voltage reduction cannot be improved using a more complicated RC circuit.

  17. LED Current Balance Using a Variable Voltage Regulator with Low Dropout vDS Control

    Directory of Open Access Journals (Sweden)

    Hung-I Hsieh

    2017-02-01

    Full Text Available A cost-effective light-emitting diode (LED current balance strategy using a variable voltage regulator (VVR with low dropout vDS control is proposed. This can regulate the multiple metal-oxide-semiconductor field-effect transistors (MOSFETs of the linear current regulators (LCR, maintaining low dropout vDS on the flat vGS-characteristic curves and making all drain currents almost the same. Simple group LCRs respectively loaded with a string LED are employed to implement the theme. The voltage VVdc from a VVR is synthesized by a string LED voltage NvD, source voltage vR, and a specified low dropout vDS = VQ. The VVdc updates instantly, through the control loop of the master LCR, which means that all slave MOSFETs have almost the same biases on their flat vGS-characteristic curves. This leads to all of the string LED currents being equal to each other, producing an almost even luminance. An experimental setup with microchip control is built to verify the estimations. Experimental results show that the luminance of all of the string LEDs are almost equal to one another, with a maximum deviation below 1% during a wide dimming range, while keeping all vDS of the MOSFETs at a low dropout voltage, as expected.

  18. Power grid current harmonics mitigation drawn on low voltage rated switching devices with effortless control

    Energy Technology Data Exchange (ETDEWEB)

    Marques, Hugo S.; Anunciada, Victor; Borges, Beatriz V. [Power Electronics Group, Instituto de Telecomunicacoes, Lisbon (Portugal); Instituto Superior Tecnico - Universidade Tecnica de Lisboa, Lisbon (Portugal)

    2010-01-15

    The great majority of the existing hybrid active power filter solutions is normally focused in 3{phi} systems and, in general, concentrates its domain of application in specific loads with deterministic behavior. Because common use grids do not exhibit these characteristics, it is mandatory to develop solutions for more generic scenarios, encouraging the use of less classical hybrid solutions. In fact, due to the widely use of switch mode converters in a great variety of consumer electronics, the problematic of mains current harmonic mitigation is no longer an exclusive matter of 3{phi} systems. The contribution of this paper is to present a shunt hybrid active power filter topology, initially conceived to work in 1{phi} domestic grids, able to operate the inverter at a voltage rate that can be lower than 10% of the mains voltage magnitude, even under nonspecific working conditions. In addition, the results shown in this paper demonstrate that this topology can, without lack of generality, be suitable to medium voltage (1{phi} or 3{phi}) systems. A new control approach for the proposed topology is discussed in this paper. The control method exhibits an extremely simple architecture requiring single point current sensing only, with no need for any kind of reference. Its practical implementation can be fulfilled by using very few, common use, operational amplifiers. The principle of operation, design criteria, simulation predictions and experimental results are presented and discussed. (author)

  19. Voltage-dependent gating in a "voltage sensor-less" ion channel.

    Directory of Open Access Journals (Sweden)

    Harley T Kurata

    2010-02-01

    Full Text Available The voltage sensitivity of voltage-gated cation channels is primarily attributed to conformational changes of a four transmembrane segment voltage-sensing domain, conserved across many levels of biological complexity. We have identified a remarkable point mutation that confers significant voltage dependence to Kir6.2, a ligand-gated channel that lacks any canonical voltage-sensing domain. Similar to voltage-dependent Kv channels, the Kir6.2[L157E] mutant exhibits time-dependent activation upon membrane depolarization, resulting in an outwardly rectifying current-voltage relationship. This voltage dependence is convergent with the intrinsic ligand-dependent gating mechanisms of Kir6.2, since increasing the membrane PIP2 content saturates Po and eliminates voltage dependence, whereas voltage activation is more dramatic when channel Po is reduced by application of ATP or poly-lysine. These experiments thus demonstrate an inherent voltage dependence of gating in a "ligand-gated" K+ channel, and thereby provide a new view of voltage-dependent gating mechanisms in ion channels. Most interestingly, the voltage- and ligand-dependent gating of Kir6.2[L157E] is highly sensitive to intracellular [K+], indicating an interaction between ion permeation and gating. While these two key features of channel function are classically dealt with separately, the results provide a framework for understanding their interaction, which is likely to be a general, if latent, feature of the superfamily of cation channels.

  20. Production of activation products in space-craft components by protons in low earth orbit

    International Nuclear Information System (INIS)

    Normand, E.; Johnson, M.L.

    1986-01-01

    A spacecraft orbiting the Earth through trapped radiation belts will be subject to an induced effect as well as to the direct irradiation by the protons and electrons of the trapped belts. This induced effect is activation of the spacecraft materials by the trapped belt protons. This activation will produce many radioisotopes having half-lives ranging from seconds to millions of years, and emitting various types of radiation. Of primary concern are radioisotopes that emit gamma rays and have half-lives of several years or less. Cross-section data sets are currently being compiled for proton-induced activation products by the Los Alamos National Laboratory. Despite uncertainties in cross-section data, it is instructive to illustrate the magnitude of activation levels and the resulting dose rates calculated in an approximate manner. A number of simplifying assumptions are made

  1. On the Distribution of Lightning Current among Interconnected Grounding Systems in Medium Voltage Grids

    Directory of Open Access Journals (Sweden)

    Guido Ala

    2018-03-01

    Full Text Available This paper presents the results of a first investigation on the effects of lightning stroke on medium voltage installations’ grounding systems, interconnected with the metal shields of the Medium Voltage (MV distribution grid cables or with bare buried copper ropes. The study enables us to evaluate the distribution of the lightning current among interconnected ground electrodes in order to estimate if the interconnection, usually created to reduce ground potential rise during a single-line-to-ground fault, can give place to dangerous situations far from the installation hit by the lightning stroke. Four different case studies of direct lightning stroke are presented and discussed: (1 two secondary substations interconnected by the cables’ shields; (2 two secondary substations interconnected by a bare buried conductor; (3 a high voltage/medium voltage station connected with a secondary substation by the medium voltage cables’ shields; (4 a high voltage/medium voltage station connected with a secondary substation by a bare buried conductor. The results of the simulations show that a higher peak-lowering action on the lighting-stroke current occurs due to the use of bare conductors as interconnection elements in comparison to the cables’ shields.

  2. Stability of high current diode under 100-nanosecond-pulse voltage

    International Nuclear Information System (INIS)

    Lai Dingguo; Qiu Aici; Zhang Yongmin; Huang Jianjun; Ren Shuqing; Yang Li

    2012-01-01

    Stability of high current diode under pulse voltage with 80 ns and 34 ns rise time was studied on the flash Ⅱ accelerator. Influence of rise time of diode voltage on startup time and cathode emission uniformity and repeatability of diode impedance was analyzed by comparing the experimental results with numerically simulated results, and the influence mechanism was discussed. The startup time of diode increases with the increasing of rise time of voltage, and the repeatability of diode impedance decreases. Discal plane cathode is prone to emit rays intensely in the center area, the time that plasma covers the surface of the cathode increases and the shielding effect has more impact on cathode emission according to the increase of rise time. Local intense emission on the cathode increases expansion speed of plasma and reduces the effective emission area. The stability of characteristic impedance of diode under a pulse voltage with slow rise time is decreased by the combined action of expansion speed of plasma and the effective emission area. (authors)

  3. Development of a Voltage Compensation Type Active SFCL and Its Application for Transient Performance Enhancement of a PMSG-Based Wind Turbine System

    Directory of Open Access Journals (Sweden)

    Lei Chen

    2017-01-01

    Full Text Available Considering the rapid development of high temperature superconducting (HTS materials, superconducting power applications have attracted more and more attention in the power industry, particularly for electrical systems including renewable energy. This paper conducts experimental tests on a voltage compensation type active superconducting fault current limiter (SFCL prototype and explores the SFCL’s application in a permanent-magnet synchronous generator- (PMSG- based wind turbine system. The SFCL prototype is composed of a three-phase air-core superconducting transformer and a voltage source converter (VSC integrated with supercapacitor energy storage. According to the commissioning test and the current-limiting test, the SFCL prototype can automatically suppress the fault current and offer a highly controlled compensation voltage in series with the 132 V electrical test system. To expand the application of the active SFCL in a 10 kW class PMSG-based wind turbine system, digital simulations under different fault cases are performed in MATLAB/Simulink. From the demonstrated simulation results, using the active SFCL can help to maintain the power balance, mitigate the voltage-current fluctuation, and improve the wind energy efficiency. The active SFCL can be regarded as a feasible solution to assist the PMSG-based wind turbine system to achieve low-voltage ride-through (LVRT operation.

  4. Grid Voltage Modulated Control of Grid-Connected Voltage Source Inverters under Unbalanced Grid Conditions

    DEFF Research Database (Denmark)

    Li, Mingshen; Gui, Yonghao; Quintero, Juan Carlos Vasquez

    2017-01-01

    In this paper, an improved grid voltage modulated control (GVM) with power compensation is proposed for grid-connected voltage inverters when the grid voltage is unbalanced. The objective of the proposed control is to remove the power ripple and to improve current quality. Three power compensation...... objectives are selected to eliminate the negative sequence components of currents. The modified GVM method is designed to obtain two separate second-order systems for not only the fast convergence rate of the instantaneous active and reactive powers but also the robust performance. In addition, this method...

  5. Activity of Palythoa caribaeorum Venom on Voltage-Gated Ion Channels in Mammalian Superior Cervical Ganglion Neurons

    Directory of Open Access Journals (Sweden)

    Fernando Lazcano-Pérez

    2016-05-01

    Full Text Available The Zoanthids are an order of cnidarians whose venoms and toxins have been poorly studied. Palythoa caribaeorum is a zoanthid commonly found around the Mexican coastline. In this study, we tested the activity of P. caribaeorum venom on voltage-gated sodium channel (NaV1.7, voltage-gated calcium channel (CaV2.2, the A-type transient outward (IA and delayed rectifier (IDR currents of KV channels of the superior cervical ganglion (SCG neurons of the rat. These results showed that the venom reversibly delays the inactivation process of voltage-gated sodium channels and inhibits voltage-gated calcium and potassium channels in this mammalian model. The compounds responsible for these effects seem to be low molecular weight peptides. Together, these results provide evidence for the potential use of zoanthids as a novel source of cnidarian toxins active on voltage-gated ion channels.

  6. Dark Current And Voltage Measurements Of Metal-Organic-Semiconductor (M-Or-S) Diode

    International Nuclear Information System (INIS)

    Adianto

    1996-01-01

    . Some Metal-Organic-Semiconductor (M-Or-S) thin film diodes, constructed with an organic polymer (polymerized toluene) as an active component has been successfully fabricated. The thin film M-Or-S diodes were fabricated on an n-type silicon with resistivity of 250-500 Ocm and p type silicon with resistivity of 10-20 Ocm as a substrate with polymerized toluene used as insulator. When deposited on silicon wafers with electrode of evaporated Ni on the n-type silicon and evaporated Au as the electrode on the polymerized toluene film, the electronic devices of Metal-Organic- Semiconductor (M-Or-S) type can be produced with one of its characteristics is that their light sensitivity. A plasma ion deposition system was constructed and used to deposit organic monomeric substance (toluene) that functioned as an isolator between semiconductor and the evaporated metal electrodes. The current-voltage measurements for different configurations of M-Or-S devices were carried out to determine the current-voltage (1-V) characteristics for M-Or-S devices with different materials and thicknesses. In addition to the 1-V measurement mentioned before, 1-V measurements of the devices were also carried out by using a curve tracer oscilloscope, and the picture of the effective parameters of each of the device could be taken by using a polaroid camera. Since the devices are very sensitive to light, the devices were all tested in a black-box which was covered by a black cloth to make sure that there was no light coming through. The experimental results for p- and n-type silicon substrates showed that an M-Or-S diode with n-type gave a higher breakdown voltage than that p- type silicon. In addition, the reverse bias breakdown voltage increased as the thickness of the thin film increased in the range of 50 -2500 V/μm

  7. A voltage control method for an active capacitive DC-link module with series-connected circuit

    DEFF Research Database (Denmark)

    Wang, Haoran; Wang, Huai; Blaabjerg, Frede

    2017-01-01

    Many efforts have been made to improve the performance of power electronic systems with active capacitive DC-link module in terms of power density as well as reliability. One of the attractive solution is an active capacitive DC-link with the series-connected circuit because of handling small......-rated power. However, in the existing control method of this circuit, the DC-link current of the backward-stage or forward-stage need to be sensed for extracting the ripple components, which limits the flexibility of the active DC-link module. Thus, in this paper, a voltage control method of an active...... capacitive DC-link module is proposed. Current sensor at the DC-link will be cancel from the circuit. The controller of the series-connected circuit requires internal voltage signals of the DC-link module only, making it possible to be fully independent without any additional connection to the main circuit...

  8. Current-voltage characteristic of a Josephson junction with randomly distributed Abrikosov vortices

    International Nuclear Information System (INIS)

    Fistul, M.V.; Giuliani, G.F.

    1997-01-01

    We have developed a theory of the current-voltage characteristic of a Josephson junction in the presence of randomly distributed, pinned misaligned Abrikosov vortices oriented perpendicularly to the junction plane. Under these conditions the Josephson phase difference var-phi acquires an interesting stochastic dependence on the position in the plane of the junction. In this situation it is possible to define an average critical current which is determined by the spatial correlations of this function. Due to the inhomogeneity, we find that for finite voltage bias the electromagnetic waves propagating in the junction display a broad spectrum of wavelengths. This is at variance with the situation encountered in homogeneous junctions. The amplitude of these modes is found to decrease as the bias is increased. We predict that the presence of these excitations is directly related to a remarkable feature in the current-voltage characteristic. The dependence of the position and the magnitude of this feature on the vortex concentration has been determined. copyright 1997 The American Physical Society

  9. Currents and voltages in the MFTF coils during the formation of a normal zone

    International Nuclear Information System (INIS)

    Owen, E.W.

    1980-08-01

    Expressions are obtained for the currents and voltages in a pair of inductively coupled superconducting coils under two conditions: formation of a normal zone and during a change in the level of the current in one coil. A dump resistor of low resistance and a detector bridge is connected across each coil. Calculated results are given for the MFTF coils. The circuit equations during formation of a normal zone are nonlinear and time-varying, consequently, only a series solution is possible. The conditions during a change in current are more easily found. After the transient has died away, the voltages in the coil associated with the changing source are all self-inductive, while the voltages in the other coil are all mutually inductive

  10. Calculation of DC Arc Plasma Torch Voltage- Current Characteristics Based on Steebeck Model

    International Nuclear Information System (INIS)

    Gnedenko, V.G.; Ivanov, A.A.; Pereslavtsev, A.V.; Tresviatsky, S.S.

    2006-01-01

    The work is devoted to the problem of the determination of plasma torches parameters and power sources parameters (working voltage and current of plasma torch) at the predesigning stage. The sequence of calculation of voltage-current characteristics of DC arc plasma torch is proposed. It is shown that the simple Steenbeck model of arc discharge in cylindrical channel makes it possible to carry out this calculation. The results of the calculation are confirmed by the experiments

  11. Theory of magnetospheric hydromagnetic waves excited by energetic ring-current protons

    International Nuclear Information System (INIS)

    Chen, Liu; Hasegawa, Akira.

    1987-06-01

    A general theoretical formulation, allowing finite ion Larmor radii, general magnetic field geometries and plasma equilibria, has been developed to investigate excitations of magnetohydrodynamic (MHD) Alfven waves within the earth's magnetosphere by the storm-time energetic ring-current protons. In particular, it is found that for adiabatically injected protons, various predicted instability properties are consistent with satellite observations. 8 refs

  12. Functional diversity of potassium channel voltage-sensing domains.

    Science.gov (United States)

    Islas, León D

    2016-01-01

    Voltage-gated potassium channels or Kv's are membrane proteins with fundamental physiological roles. They are composed of 2 main functional protein domains, the pore domain, which regulates ion permeation, and the voltage-sensing domain, which is in charge of sensing voltage and undergoing a conformational change that is later transduced into pore opening. The voltage-sensing domain or VSD is a highly conserved structural motif found in all voltage-gated ion channels and can also exist as an independent feature, giving rise to voltage sensitive enzymes and also sustaining proton fluxes in proton-permeable channels. In spite of the structural conservation of VSDs in potassium channels, there are several differences in the details of VSD function found across variants of Kvs. These differences are mainly reflected in variations in the electrostatic energy needed to open different potassium channels. In turn, the differences in detailed VSD functioning among voltage-gated potassium channels might have physiological consequences that have not been explored and which might reflect evolutionary adaptations to the different roles played by Kv channels in cell physiology.

  13. Mechanism of pH-dependent activation of the sodium-proton antiporter NhaA

    Science.gov (United States)

    Huang, Yandong; Chen, Wei; Dotson, David L.; Beckstein, Oliver; Shen, Jana

    2016-10-01

    Escherichia coli NhaA is a prototype sodium-proton antiporter, which has been extensively characterized by X-ray crystallography, biochemical and biophysical experiments. However, the identities of proton carriers and details of pH-regulated mechanism remain controversial. Here we report constant pH molecular dynamics data, which reveal that NhaA activation involves a net charge switch of a pH sensor at the entrance of the cytoplasmic funnel and opening of a hydrophobic gate at the end of the funnel. The latter is triggered by charging of Asp164, the first proton carrier. The second proton carrier Lys300 forms a salt bridge with Asp163 in the inactive state, and releases a proton when a sodium ion binds Asp163. These data reconcile current models and illustrate the power of state-of-the-art molecular dynamics simulations in providing atomic details of proton-coupled transport across membrane which is challenging to elucidate by experimental techniques.

  14. A Novel Sliding Mode Control Technique for Indirect Current Controlled Active Power Filter

    Directory of Open Access Journals (Sweden)

    Juntao Fei

    2012-01-01

    Full Text Available A novel sliding mode control (SMC method for indirect current controlled three-phase parallel active power filter is presented in this paper. There are two designed closed loops in the system: one is the DC voltage controlling loop and the other is the reference current tracking loop. The first loop with a PI regulator is used to control the DC voltage approximating to the given voltage of capacitor, and the output of PI regulator through a low-pass filter is applied as the input of the power supply reference currents. The second loop implements the tracking of the reference currents using integral sliding mode controller, which can improve the harmonic treating performance. Compared with the direct current control technique, it is convenient to be implemented with digital signal processing system because of simpler system structure and better harmonic treating property. Simulation results verify that the generated reference currents have the same amplitude with the load currents, demonstrating the superior harmonic compensating effects with the proposed shunt active power filter compared with the hysteresis method.

  15. Proton exchange membrane fuel cells

    CERN Document Server

    Qi, Zhigang

    2013-01-01

    Preface Proton Exchange Membrane Fuel CellsFuel CellsTypes of Fuel CellsAdvantages of Fuel CellsProton Exchange Membrane Fuel CellsMembraneCatalystCatalyst LayerGas Diffusion MediumMicroporous LayerMembrane Electrode AssemblyPlateSingle CellStackSystemCell Voltage Monitoring Module (CVM)Fuel Supply Module (FSM)Air Supply Module (ASM)Exhaust Management Module (EMM)Heat Management Module (HMM)Water Management Module (WMM)Internal Power Supply Module (IPM)Power Conditioning Module (PCM)Communications Module (COM)Controls Module (CM)SummaryThermodynamics and KineticsTheoretical EfficiencyVoltagePo

  16. Influence of coupling parameter on current-voltage characteristics of intrinsic Josephson junctions in high-T c superconductors

    International Nuclear Information System (INIS)

    Shukrinov, Yu.M.; Mahfouzi, F.

    2006-01-01

    We study the current-voltage characteristics of intrinsic Josephson junctions in high-T c superconductors by numerical calculations and in framework of capacitively coupled Josephson junctions model we obtain the total number of branches. The influence of the coupling parameter α on the current-voltage characteristics at fixed parameter β (β 2 1/β c , where β c is McCumber parameter) and the influence of α on β-dependence of the current-voltage characteristics are investigated. We obtain the α-dependence of the branch's slopes and branch's endpoints. The presented results show new features of the coupling effect on the scheme of hysteresis jumps in current-voltage characteristics of intrinsic Josephson junctions in high-T c superconductors

  17. Cross Voltage Control with Inner Hysteresis Current Control for Multi-output Boost Converter

    DEFF Research Database (Denmark)

    Nami, Alireza; Zare, Firuz; Blaabjerg, Frede

    2009-01-01

    Multi-output boost (MOB) converter is a novel DC-DC converter unlike the regular boost converter, has the ability to share its total output voltage and to have different series output voltage from a given duty cycle for low and high power applications. In this paper, discrete voltage control...... with inner hysteresis current control loop has been proposed to keep the simplicity of the control law for the double-output MOB converter, which can be implemented by a combination of analogue and logical ICs or simple microcontroller to constrain the output voltages of MOB converter at their reference...... voltages against variation in load or input voltage. The salient features of the proposed control strategy are simplicity of implementation and ease to extend to multiple outputs in the MOB converter. Simulation and experimental results are presented to show the validity of control strategy....

  18. Current voltage characteristics of composite superconductors with high contact resistance

    International Nuclear Information System (INIS)

    Akhmetov, A.A.; Baev, V.P.

    1984-01-01

    An experimental study has been made of current-voltage characteristics of composite superconductors with contact resistance between superconducting filaments and normal metal with high electrical conductivity. It is shown that stable resistive states exist in such conductors over a wide range of currents. The presence of resistive states is interpreted in terms of the resistive domain concept. The minimum and maximum currents of resistive states are found to be dependent on the electrical resistance of normal metal and magnetic field. (author)

  19. The effect of random dopant fluctuation on threshold voltage and drain current variation in junctionless nanotransistors

    International Nuclear Information System (INIS)

    Rezapour, Arash; Rezapour, Pegah

    2015-01-01

    We investigate the effect of dopant random fluctuation on threshold voltage and drain current variation in a two-gate nanoscale transistor. We used a quantum-corrected technology computer aided design simulation to run the simulation (10000 randomizations). With this simulation, we could study the effects of varying the dimensions (length and width), and thicknesses of oxide and dopant factors of a transistor on the threshold voltage and drain current in subthreshold region (off) and overthreshold (on). It was found that in the subthreshold region the variability of the drain current and threshold voltage is relatively fixed while in the overthreshold region the variability of the threshold voltage and drain current decreases remarkably, despite the slight reduction of gate voltage diffusion (compared with that of the subthreshold). These results have been interpreted by using previously reported models for threshold current variability, load displacement, and simple analytical calculations. Scaling analysis shows that the variability of the characteristics of this semiconductor increases as the effects of the short channel increases. Therefore, with a slight increase of length and a reduction of width, oxide thickness, and dopant factor, we could correct the effect of the short channel. (paper)

  20. Method and system for a gas tube switch-based voltage source high voltage direct current transmission system

    Science.gov (United States)

    She, Xu; Chokhawala, Rahul Shantilal; Zhou, Rui; Zhang, Di; Sommerer, Timothy John; Bray, James William

    2016-12-13

    A voltage source converter based high-voltage direct-current (HVDC) transmission system includes a voltage source converter (VSC)-based power converter channel. The VSC-based power converter channel includes an AC-DC converter and a DC-AC inverter electrically coupled to the AC-DC converter. The AC-DC converter and a DC-AC inverter include at least one gas tube switching device coupled in electrical anti-parallel with a respective gas tube diode. The VSC-based power converter channel includes a commutating circuit communicatively coupled to one or more of the at least one gas tube switching devices. The commutating circuit is configured to "switch on" a respective one of the one or more gas tube switching devices during a first portion of an operational cycle and "switch off" the respective one of the one or more gas tube switching devices during a second portion of the operational cycle.

  1. A Smart Voltage and Current Monitoring System for Three Phase Inverters Using an Android Smartphone Application.

    Science.gov (United States)

    Mnati, Mohannad Jabbar; Van den Bossche, Alex; Chisab, Raad Farhood

    2017-04-15

    In this paper, a new smart voltage and current monitoring system (SVCMS) technique is proposed. It monitors a three phase electrical system using an Arduino platform as a microcontroller to read the voltage and current from sensors and then wirelessly send the measured data to monitor the results using a new Android application. The integrated SVCMS design uses an Arduino Nano V3.0 as the microcontroller to measure the results from three voltage and three current sensors and then send this data, after calculation, to the Android smartphone device of an end user using Bluetooth HC-05. The Arduino Nano V3.0 controller and Bluetooth HC-05 are a cheap microcontroller and wireless device, respectively. The new Android smartphone application that monitors the voltage and current measurements uses the open source MIT App Inventor 2 software. It allows for monitoring some elementary fundamental voltage power quality properties. An effort has been made to investigate what is possible using available off-the-shelf components and open source software.

  2. Module Five: Relationships of Current, Voltage, and Resistance; Basic Electricity and Electronics Individualized Learning System.

    Science.gov (United States)

    Bureau of Naval Personnel, Washington, DC.

    This module covers the relationships between current and voltage; resistance in a series circuit; how to determine the values of current, voltage, resistance, and power in resistive series circuits; the effects of source internal resistance; and an introduction to the troubleshooting of series circuits. This module is divided into five lessons:…

  3. A fast high-voltage current-peak detection system for the ALICE transition radiation detector

    Energy Technology Data Exchange (ETDEWEB)

    Verclas, Robert [Physikalisches Institut, Ruprecht-Karls-Universitaet Heidelberg (Germany); Collaboration: ALICE-Collaboration

    2016-07-01

    During LHC operation in run 1, the gaseous detectors of ALICE occasionally experienced simultaneous trips in their high voltage which affected the majority of the high voltage channels. These trips are caused by large anode currents in the detector and are potentially related to LHC machine operations. We developed and installed a fast current-peak detection system for the ALICE Transition Radiation Detector. This system is based on FPGA technology and monitors 144 out 522 high voltage channels minimally invasively at a maximum readout rate of 2 MHz. It is an integral part of the LHC beam monitoring system. We report on the latest status.

  4. High Voltage Gain Dual Active Bridge Converter with an Extended Operation Range for Renewable Energy Systems

    DEFF Research Database (Denmark)

    Zhang, Zhe; Tomas Manez, Kevin; Yudi, Xiao

    2018-01-01

    Bridge (P2DAB) converter, i.e. low-voltage (LV) side parallel and high-voltage (HV) side series, is proposed to achieve high voltage gain and low current stress over switching devices and transformer windings. Given the unmodified P2DAB power stage, by regulating the phase-shift angle between......Developing bidirectional dc-dc converters has become a critical research topic and gains more and more attention in recent years due to the extensive applications of smart grids with energy storages, hybrid and electrical vehicles and dc microgrids. In this paper, a Partial Parallel Dual Active...... the paralleled active bridges, the power equations and voltage gain are then modified, and therefore the operation range can be extended effectively. The operating principles of the proposed converter and its power characteristics under various operation modes are studied, and the design constraints...

  5. A high voltage ratio and low ripple interleaved DC-DC converter for fuel cell applications.

    Science.gov (United States)

    Chang, Long-Yi; Chao, Kuei-Hsiang; Chang, Tsang-Chih

    2012-01-01

    This paper proposes a high voltage ratio and low ripple interleaved boost DC-DC converter, which can be used to reduce the output voltage ripple. This converter transfers the low DC voltage of fuel cell to high DC voltage in DC link. The structure of the converter is parallel with two voltage-doubler boost converters by interleaving their output voltages to reduce the voltage ripple ratio. Besides, it can lower the current stress for the switches and inductors in the system. First, the PSIM software was used to establish a proton exchange membrane fuel cell and a converter circuit model. The simulated and measured results of the fuel cell output characteristic curve are made to verify the correctness of the established simulation model. In addition, some experimental results are made to validate the effectiveness in improving output voltage ripple of the proposed high voltage ratio interleaved boost DC-DC converters.

  6. Specific expression of the human voltage-gated proton channel Hv1 in highly metastatic breast cancer cells, promotes tumor progression and metastasis

    International Nuclear Information System (INIS)

    Wang, Yifan; Li, Shu Jie; Pan, Juncheng; Che, Yongzhe; Yin, Jian; Zhao, Qing

    2011-01-01

    Highlights: → Hv1 is specifically expressed in highly metastatic human breast tumor tissues. → Hv1 regulates breast cancer cytosolic pH. → Hv1 acidifies extracellular milieu. → Hv1 exacerbates the migratory ability of metastatic cells. -- Abstract: The newly discovered human voltage-gated proton channel Hv1 is essential for proton transfer, which contains a voltage sensor domain (VSD) without a pore domain. We report here for the first time that Hv1 is specifically expressed in the highly metastatic human breast tumor tissues, but not in poorly metastatic breast cancer tissues, detected by immunohistochemistry. Meanwhile, real-time RT-PCR and immunocytochemistry showed that the expression levels of Hv1 have significant differences among breast cancer cell lines, MCF-7, MDA-MB-231, MDA-MB-468, MDA-MB-453, T-47D and SK-BR-3, in which Hv1 is expressed at a high level in highly metastatic human breast cancer cell line MDA-MB-231, but at a very low level in poorly metastatic human breast cancer cell line MCF-7. Inhibition of Hv1 expression in the highly metastatic MDA-MB-231 cells by small interfering RNA (siRNA) significantly decreases the invasion and migration of the cells. The intracellular pH of MDA-MB-231 cells down-regulated Hv1 expression by siRNA is obviously decreased compared with MDA-MB-231 with the scrambled siRNA. The expression of matrix metalloproteinase-2 and gelatinase activity in MDA-MB-231 cells suppressed Hv1 by siRNA were reduced. Our results strongly suggest that Hv1 regulates breast cancer intracellular pH and exacerbates the migratory ability of metastatic cells.

  7. Electrochemical H-D isotope effect at metal-perovskite proton conductor interfaces

    DEFF Research Database (Denmark)

    Kek, D.; Bonanos, N.

    1999-01-01

    The H-D isotope effect on the electrode kinetics of a metal-proton conductor interface has been investigated. The current-voltage behaviour depends on the nature of the electrode (Ni, Ag), the atmosphere (H(2), D(2)), the partial pressures of the gases, and the temperature. The isotope effect was...

  8. High-voltage integrated linear regulator with current sinking capabilities for portable ultrasound scanners

    DEFF Research Database (Denmark)

    Pausas, Guifre Vendrell; Llimos Muntal, Pere; Jørgensen, Ivan Harald Holger

    2017-01-01

    This paper presents a high-voltage integrated regulator capable of sinking current for driving pulse-triggered level shifters in drivers for ultrasound applications. The regulator utilizes a new topology with a feedback loop and a current sinking circuit to satisfy the requirements of the portable....... The proposed design has been implemented in high-voltage 0.18 μm process whithin an area of 0.11 mm2 and it is suitable for system-on-chip integration due to its low component count and the fully integrated design....

  9. Current-voltage relation for thin tunnel barriers: Parabolic barrier model

    DEFF Research Database (Denmark)

    Hansen, Kim; Brandbyge, Mads

    2004-01-01

    We derive a simple analytic result for the current-voltage curve for tunneling of electrons through a thin uniform insulating layer modeled by a parabolic barrier. Our model, which goes beyond the Wentzel–Kramers–Brillouin approximation, is applicable also in the limit of highly transparant...

  10. Activation of 45-MeV proton irradiation and proton-induced neutron irradiation in polymers

    International Nuclear Information System (INIS)

    Ra, Se-Jin; Kim, Kye-Ryung; Jung, Myung-Hwan; Yang, Tae-Keon

    2010-01-01

    During beam irradiation experiments with more than a few MeV energetic protons, the sample activation problem can be very severe because it causes many kinds of additional problems for the post-processing of the samples, such as time loss, inconvenience of sample handling, personal radiation safety, etc. The most serious problem is that immediate treatment of the sample is impossible in some experiments, such as nano-particle synthesizing. To solve these problems, we studied why the samples are activated and how the level of the activation can be reduced. It is known that the main reasons of activation are nuclear reactions with elements of the target material by primary protons and secondary produced neutrons. Even though the irradiation conditions are same, the level of the activation can be different depending on the target materials. For the nanoparticle synthesizing experiments, the target materials can be defined as the container and the sample itself. The reduction of the activation from the container is easier than the reduction from the sample. Therefore, we tried to reduce the activation level by changing the container materials. In this paper, the results are displayed for some candidate container materials, such as polymethyl methacrylate, polystyrene, Glass, etc., with 45-MeV and 10-nA proton beams. As a result, PS is the most suitable material for the container because of its relatively low level of the activation by protons. Also the contribution of secondary produced neutrons to the activation is negligible.

  11. Gas stream analysis using voltage-current time differential operation of electrochemical sensors

    Science.gov (United States)

    Woo, Leta Yar-Li; Glass, Robert Scott; Fitzpatrick, Joseph Jay; Wang, Gangqiang; Henderson, Brett Tamatea; Lourdhusamy, Anthoniraj; Steppan, James John; Allmendinger, Klaus Karl

    2018-01-02

    A method for analysis of a gas stream. The method includes identifying an affected region of an affected waveform signal corresponding to at least one characteristic of the gas stream. The method also includes calculating a voltage-current time differential between the affected region of the affected waveform signal and a corresponding region of an original waveform signal. The affected region and the corresponding region of the waveform signals have a sensitivity specific to the at least one characteristic of the gas stream. The method also includes generating a value for the at least one characteristic of the gas stream based on the calculated voltage-current time differential.

  12. Effect of localized states on the current-voltage characteristics of metal-semiconductor contacts with thin interfacial layer

    Science.gov (United States)

    Chattopadhyay, P.

    1994-10-01

    The role of discrete localized states on the current-voltage characteristics of metal-semiconductor contact is examined. It is seen that, because of these localized states, the logarithmic current vs voltage characteristics become nonlinear. Such nonlinearity is found sensitive to the temperature, and the energy and density of the localized states. The predicted temperature dependence of barrier height and the current-voltage characteristics are in agreement with the experimental results of Aboelfotoh [ Phys. Rev. B39, 5070 (1989)].

  13. Current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization

    International Nuclear Information System (INIS)

    Stoyanov, D G

    2007-01-01

    The balances of particles and charges in the volume of parallel-plane ionization chamber are considered. Differential equations describing the distribution of current densities in the chamber volume are obtained. As a result of the differential equations solution an analytical form of the current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization in the volume is obtained

  14. Current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization

    Energy Technology Data Exchange (ETDEWEB)

    Stoyanov, D G [Faculty of Engineering and Pedagogy in Sliven, Technical University of Sofia, 59, Bourgasko Shaussee Blvd, 8800 Sliven (Bulgaria)

    2007-08-15

    The balances of particles and charges in the volume of parallel-plane ionization chamber are considered. Differential equations describing the distribution of current densities in the chamber volume are obtained. As a result of the differential equations solution an analytical form of the current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization in the volume is obtained.

  15. SOGI-based capacitor voltage feedback active damping in LCL-filtered grid converters

    DEFF Research Database (Denmark)

    Xin, Zhen; Wang, Xiongfei; Loh, Poh Chiang

    2015-01-01

    The capacitor voltage feedback active damping control is an attractive way to suppress LCL-filter resonance especially for the systems where the capacitor voltage is used for grid synchronization, since no extra sensors are added. The derivative is the core of the capacitor voltage feedback active...... derivative is more suited for capacitor voltage feedback active damping control. Experimental results validate the effectiveness of the proposed method....

  16. Modelling chloride penetration in concrete using electrical voltage and current approaches

    Directory of Open Access Journals (Sweden)

    Juan Lizarazo-Marriaga

    2011-03-01

    Full Text Available This paper reports a research programme aimed at giving a better understanding of the phenomena involved in the chloride penetration in cement-based materials. The general approach used was to solve the Nernst-Planck equation numerically for two physical ideal states that define the possible conditions under which chlorides will move through concrete. These conditions are named in this paper as voltage control and current control. For each condition, experiments and simulations were carried out in order to establish the importance of electrical variables such as voltage and current in modelling chloride transport in concrete. The results of experiments and simulations showed that if those electrical variables are included as key parameters in the modelling of chloride penetration through concrete, a better understanding of this complex phenomenon can be obtained.

  17. CURRENT-VOLTAGE CURVES FOR TREATING EFFLUENT CONTAINING HEDP: DETERMINATION OF THE LIMITING CURRENT

    Directory of Open Access Journals (Sweden)

    T. Scarazzato

    2015-12-01

    Full Text Available Abstract Membrane separation techniques have been explored for treating industrial effluents to allow water reuse and component recovery. In an electrodialysis system, concentration polarization causes undesirable alterations in the ionic transportation mechanism. The graphic construction of the current voltage curve is proposed for establishing the value of the limiting current density applied to the cell. The aim of this work was to determine the limiting current density in an electrodialysis bench stack, the function of which was the treatment of an electroplating effluent containing HEDP. For this, a system with five compartments was used with a working solution simulating the rinse waters of HEDP-based baths. The results demonstrated correlation between the regions defined by theory and the experimental data.

  18. Two ways to model voltage-current curves of adiabatic MgB2 wires

    International Nuclear Information System (INIS)

    Stenvall, A; Korpela, A; Lehtonen, J; Mikkonen, R

    2007-01-01

    Usually overheating of the sample destroys attempts to measure voltage-current curves of conduction cooled high critical current MgB 2 wires at low temperatures. Typically, when a quench occurs a wire burns out due to massive heat generation and negligible cooling. It has also been suggested that high n values measured with MgB 2 wires and coils are not an intrinsic property of the material but arise due to heating during the voltage-current measurement. In addition, quite recently low n values for MgB 2 wires have been reported. In order to find out the real properties of MgB 2 an efficient computational model is required to simulate the voltage-current measurement. In this paper we go back to basics and consider two models to couple electromagnetic and thermal phenomena. In the first model the magnetization losses are computed according to the critical state model and the flux creep losses are considered separately. In the second model the superconductor resistivity is described by the widely used power law. Then the coupled current diffusion and heat conduction equations are solved with the finite element method. In order to compare the models, example runs are carried out with an adiabatic slab. Both models produce a similar significant temperature rise near the critical current which leads to fictitiously high n values

  19. Microwave proton source development for a high-current linac injector

    International Nuclear Information System (INIS)

    Sherman, J.; Bolme, G.; Geisik, C.

    1995-01-01

    Powerful CW proton linear accelerators (100-mA at 0.5--1.0 GeV) are being proposed for spallation neutron-source applications. A 75-keV, 110-mA dc proton injector using a microwave ion source is being tested for these applications. It has achieved 80-keV, 110-mA hydrogen-ion-beam operation. Video and dc beam-current toroid diagnostics are operational, and an EPICS control system is also operational on the 75-keV injector. A technical base development program has also been carried out on a 50-keV injector obtained from Chalk River Laboratories, and it includes low-energy beam transport studies, ion source lifetime tests, and proton-fraction enhancement studies. Technical base results and the present status of the 75-keV injector will be presented

  20. The Glycolytic Metabolite, Fructose-1,6-bisphosphate, Blocks Epileptiform Bursts by Attenuating Voltage-Activated Calcium Currents in Hippocampal Slices

    Directory of Open Access Journals (Sweden)

    Li-Rong Shao

    2018-06-01

    Full Text Available Manipulation of metabolic pathways (e.g., ketogenic diet (KD, glycolytic inhibition alters neural excitability and represents a novel strategy for treatment of drug-refractory seizures. We have previously shown that inhibition of glycolysis suppresses epileptiform activity in hippocampal slices. In the present study, we aimed to examine the role of a “branching” metabolic pathway stemming off glycolysis (i.e., the pentose-phosphate pathway, PPP in regulating seizure activity, by using a potent PPP stimulator and glycolytic intermediate, fructose-1,6-bisphosphate (F1,6BP. Employing electrophysiological approaches, we investigated the action of F1,6BP on epileptiform population bursts, intrinsic neuronal firing, glutamatergic and GABAergic synaptic transmission and voltage-activated calcium currents (ICa in the CA3 area of hippocampal slices. Bath application of F1,6BP (2.5–5 mM blocked epileptiform population bursts induced in Mg2+-free medium containing 4-aminopyridine, in ~2/3 of the slices. The blockade occurred relatively rapidly (~4 min, suggesting an extracellular mechanism. However, F1,6BP did not block spontaneous intrinsic firing of the CA3 neurons (when synaptic transmission was eliminated with DNQX, AP-5 and SR95531, nor did it significantly reduce AMPA or NMDA receptor-mediated excitatory postsynaptic currents (EPSCAMPA and EPSCNMDA. In contrast, F1,6BP caused moderate reduction (~50% in GABAA receptor-mediated current, suggesting it affects excitatory and inhibitory synapses differently. Finally and unexpectedly, F1,6BP consistently attenuated ICa by ~40% without altering channel activation or inactivation kinetics, which may explain its anticonvulsant action, at least in this in vitro seizure model. Consistent with these results, epileptiform population bursts in CA3 were readily blocked by the nonspecific Ca2+ channel blocker, CdCl2 (20 μM, suggesting that these bursts are calcium dependent. Altogether, these data

  1. A novel transient rotor current control scheme of a doubly-fed induction generator equipped with superconducting magnetic energy storage for voltage and frequency support

    Science.gov (United States)

    Shen, Yang-Wu; Ke, De-Ping; Sun, Yuan-Zhang; Daniel, Kirschen; Wang, Yi-Shen; Hu, Yuan-Chao

    2015-07-01

    A novel transient rotor current control scheme is proposed in this paper for a doubly-fed induction generator (DFIG) equipped with a superconducting magnetic energy storage (SMES) device to enhance its transient voltage and frequency support capacity during grid faults. The SMES connected to the DC-link capacitor of the DFIG is controlled to regulate the transient dc-link voltage so that the whole capacity of the grid side converter (GSC) is dedicated to injecting reactive power to the grid for the transient voltage support. However, the rotor-side converter (RSC) has different control tasks for different periods of the grid fault. Firstly, for Period I, the RSC injects the demagnetizing current to ensure the controllability of the rotor voltage. Then, since the dc stator flux degenerates rapidly in Period II, the required demagnetizing current is low in Period II and the RSC uses the spare capacity to additionally generate the reactive (priority) and active current so that the transient voltage capability is corroborated and the DFIG also positively responds to the system frequency dynamic at the earliest time. Finally, a small amount of demagnetizing current is provided after the fault clearance. Most of the RSC capacity is used to inject the active current to further support the frequency recovery of the system. Simulations are carried out on a simple power system with a wind farm. Comparisons with other commonly used control methods are performed to validate the proposed control method. Project supported by the National Natural Science Foundation of China (Grant No. 51307124) and the Major Program of the National Natural Science Foundation of China (Grant No. 51190105).

  2. Bio-Inspired Carbon Monoxide Sensors with Voltage-Activated Sensitivity

    KAUST Repository

    Savagatrup, Suchol

    2017-09-27

    Carbon monoxide (CO) outcompetes oxygen when binding to the iron center of hemeproteins, leading to a reduction in blood oxygen level and acute poisoning. Harvesting the strong specific interaction between CO and the iron porphyrin provides a highly selective and customizable sensor. We report the development of chemiresistive sensors with voltage-activated sensitivity for the detection of CO comprising iron porphyrin and functionalized single-walled carbon nanotubes (F-SWCNTs). Modulation of the gate voltage offers a predicted extra dimension for sensing. Specifically, the sensors show a significant increase in sensitivity toward CO when negative gate voltage is applied. The dosimetric sensors are selective to ppm levels of CO and functional in air. UV/Vis spectroscopy, differential pulse voltammetry, and density functional theory reveal that the in situ reduction of FeIII to FeII enhances the interaction between the F-SWCNTs and CO. Our results illustrate a new mode of sensors wherein redox active recognition units are voltage-activated to give enhanced and highly specific responses.

  3. A Self-Biased Active Voltage Doubler for Energy Harvesting Systems

    KAUST Repository

    Tayyab, Umais

    2017-12-03

    An active voltage doubler utilizing a single supply op-amp for energy harvesting system is presented. The proposed doubler is used for rectification process to achieve both acceptably high power conversion efficiency (PCE) and large rectified DC voltage. The incorporated op-amp is self-biased, meaning no external supply is needed but rather it uses part of the harvested energy for its biasing. The proposed active doubler achieves maximum power conversion efficiency (PCE) of 61.7% for a 200 Hz sinusoidal input of 0.8 V for a 20 K load resistor. This efficiency is 2 times more when compared with the passive voltage doubler. The rectified DC voltage is almost 2 times more than conventional passive doubler. The relation between PCE and the load resistor is also presented. The proposed active voltage doubler is designed and simulated in LF 0.15 μm CMOS process technology using Cadence virtuoso tool.

  4. Radio frequency glow discharge source with integrated voltage and current probes used for evaluation of discharge parameters

    International Nuclear Information System (INIS)

    Wilken, L.; Hoffmann, V.; Wetzig, K.

    2006-01-01

    A radio frequency (rf) Grimm-type glow discharge source for the chemical analysis of solid samples, with integrated voltage and current probes, was developed. All elements of a plasma equivalent circuit are determined from the measured current-voltage characteristics. The procedure is based on the independent evaluation of the ion current and electron current region. The physical meaning of the parameters is investigated by comparisons with measurements from dc glow discharges. We found that the reduced rf current of the powered electrode is comparable to the reduced current in dc discharges. A formula is developed that corrects the reduced current due to gas heating. The sheath thickness at the powered rf electrode is evaluated and is between 75 and 1100 μm. The voltage of the bulk plasma is in the range 2-15 V, and the resistance is between 30 and 400 Ω. The bulk plasma consumes about 3% of the total power, and the reduced voltage is comparable to the reduced electrical field in the positive column of direct current discharges. The sheath voltage at the grounded electrode is in the range 25-100 V, the capacities are between 10 and 400 pF, and the resistances are in the range 100 Ω-5000 Ω. We also found invariants for the evaluated sheath parameters

  5. Cathode voltage and discharge current oscillations in HiPIMS

    Czech Academy of Sciences Publication Activity Database

    Klein, P.; Hnilica, J.; Hubička, Zdeněk; Čada, Martin; Šlapanská, M.; Zemánek, M.; Vašina, P.

    2017-01-01

    Roč. 26, č. 5 (2017), s. 1-12, č. článku 055015. ISSN 0963-0252 R&D Projects: GA ČR(CZ) GA15-00863S Institutional support: RVO:68378271 Keywords : HiPIMS * voltage and current oscillations * spokes Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 3.302, year: 2016

  6. An Annotated Bibliography of High-Voltage Direct-Current Transmission and Flexible AC Transmission (FACTS) Devices, 1991-1993.

    Energy Technology Data Exchange (ETDEWEB)

    Litzenberger, Wayne; Lava, Val

    1994-08-01

    References are contained for HVDC systems, converter stations and components, overhead transmission lines, cable transmission, system design and operations, simulation of high voltage direct current systems, high-voltage direct current installations, and flexible AC transmission system (FACTS).

  7. Ca(2+) currents and voltage responses in Type I and Type II hair cells of the chick embryo semicircular canal.

    Science.gov (United States)

    Masetto, Sergio; Zampini, Valeria; Zucca, Giampiero; Valli, Paolo

    2005-11-01

    Type I and Type II hair cells, and Type II hair cells located in different zones of the semicircular canal crista, express different patterns of voltage-dependent K channels, each one specifically shaping the hair cell receptor potential. We report here that, close to hatching, chicken embryo semicircular canal Type I and Type II hair cells express a similar voltage-dependent L-type calcium current (I(Ca)), whose main features are: activation above -60 mV, fast activation kinetics, and scarce inactivation. I(Ca) should be already active at rest in Zone 1 Type II hair cells, whose resting membrane potential was on average slightly less negative than -60 mV. Conversely, I(Ca) would not be active at rest in Type II hair cells from Zone 2 and 3, nor in Type I hair cells, since their resting membrane potential was significantly more negative than -60 mV. However, even small depolarising currents would activate I(Ca) steadily in Zone 2 and 3 Type II hair cells, but not in Type I hair cells because of the robust repolarising action of their specific array of K(+) currents. The implications of the present findings in the afferent discharge are discussed.

  8. Photonic characterization of capacitance-voltage characteristics in MOS capacitors and current-voltage characteristics in MOSFETs

    International Nuclear Information System (INIS)

    Kim, H. C.; Kim, H. T.; Cho, S. D.; Song, S. J.; Kim, Y. C.; Kim, S. K.; Chi, S. S.; Kim, D. J.; Kim, D. M.

    2002-01-01

    Based on the photonic high-frequency capacitance-voltage (HF-CV) response of MOS capacitors, a new characterization method is reported for the analysis of interface states in MOS systems. An optical source with a photonic energy less than the silicon band-gap energy (hv g ) is employed for the photonic HF-CV characterization of interface states distributed in the photoresponsive energy band (E C - hv t C ). If a uniform distribution of trap levels is assumed, the density of interface states (D it ) in the photoresponsive energy band of MOS capacitors, characterized by the new photonic HF-CV method, was observed to be D it = 1 ∼ 5 x 10 11 eV -1 cm -2 . Photonic current-voltage characteristics (I D - V GS , V DS ) of MOSFETs, which are under control of the photoconductive and the photovoltaic effects, are also investigated under optical illumination

  9. Nonlinear current-voltage characteristics of WO3-x nano-/micro-rods

    Science.gov (United States)

    Shen, Zhenguang; Peng, Zhijian; Zhao, Zengying; Fu, Xiuli

    2018-04-01

    A series of crystalline tungsten oxide nano-/micro-rods with different compositions of WO3, WO2.90, W19O55 (WO2.89) and W18O49 (WO2.72) but identical morphology feature were first prepared. Then, various nanoscaled electrical devices were fabricated from them by micro-fabrication through a focused ion beam technique. Interestingly, the devices from the oxygen-deficient WO3-x display significantly nonlinear current-voltage characteristics. The calculated nonlinear coefficients of the WO2.90, WO2.83, and WO2.72 varistors are 2.52, 3.32 and 4.91, respectively. The breakdown voltage of the WO2.90, WO2.83, and WO2.72 varistors are 1.93, 1.28 and 0.93 V, respectively. Such WO3-x nano-varistors might be promising for low-voltage electrical/electronic devices.

  10. Macroscopic quantum effects in the zero voltage state of the current biased Josephson junction

    International Nuclear Information System (INIS)

    Clarke, J.; Devoret, M.H.; Martinis, J.; Esteve, D.

    1985-05-01

    When a weak microwave current is applied to a current-biased Josephson tunnel junction in the thermal limit the escape rate from the zero voltage state is enhanced when the microwave frequency is near the plasma frequency of the junction. The resonance curve is markedly asymmetric because of the anharmonic properties of the potential well: this behavior is well explained by a computer simulation using a resistively shunted junction model. This phenomenon of resonant activation enables one to make in situ measurements of the capacitance and resistance shunting the junction, including contributions from the complex impedance presented by the current leads. For the relatively large area junctions studied in these experiments, the external capacitive loading was relatively unimportant, but the damping was entirely dominated by the external resistance

  11. Voltage-controlled Enzymes: The new Janus Bifrons

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Villalba-Galea

    2012-09-01

    Full Text Available The Ciona intestinalis voltage sensitive phosphatase, Ci-VSP, was the first Voltage-controlled Enzyme (VEnz proven to be under direct command of the membrane potential. The discovery of Ci-VSP conjugated voltage sensitivity and enzymatic activity in a single protein. These two facets of Ci-VSP activity have provided a unique model for studying how membrane potential is sensed by proteins and a novel mechanism for control of enzymatic activity. These facets make Ci-VSP a fascinating and versatile enzyme.Ci-VSP has a voltage sensing domain (VSD that resembles those found in voltage-gated channels (VGC. The VSD resides in the N-terminus and is formed by four putative trans-membrane segments. The fourth segment contains charged residues which are likely involved in voltage sensing. Ci-VSP produces sensing currents in response to changes in potential, within a defined range of voltages. Sensing currents are analogous to gating currents in VGC. As known, these latter proteins contain four VSDs which are entangled in a complex interaction with the pore domain –the effector domain in VGC. This complexity makes studying the basis of voltage sensing in VGC a difficult enterprise. In contrast, Ci-VSP is thought to be monomeric and its catalytic domain –the VSP’s effector domain– can be cleaved off without disrupting the basic electrical functioning of the VSD. For these reasons, VSPs are considered a great model for studying the activity of a VSD in isolation. Finally, VSPs are also phosphoinositide phosphatases. Phosphoinositides are signaling lipids found in eukaryotes and are involved in many processes, including modulation of VGC activity and regulation of cell proliferation. Understanding VSPs as VEnz has been the center of attention in recent years and several reviews has been dedicated to this area. Thus, this review will be focused instead on the other face of this true Janus Bifrons and recapitulate what is known about VSPs as electrically

  12. High-current proton accelerators-meson factories

    International Nuclear Information System (INIS)

    Dmitrievskij, V.P.

    1979-01-01

    A possibility of usage of accelerators of neutron as well as meson factories is considered. Parameters of linear and cyclic accelerators are given, which are employed as meson factories and as base for developing intense neutron generators. It is emphasized that the principal aim of developing neutron generators on the base of high current proton accelerators is production of intense neutron fluxes with a present energy spectrum. Production of tens-and-hundreds milliampere currents at the energy of 800-1000 MeV is considered at present for two types of accelerating facilities viz. linear accelerators under continuous operating conditions and cyclotrons with strong focusing. Quantitative evaluations of developing high-efficiency linear and cyclic accelerators are considered. The basic parameters of an ccelerating complex are given, viz. linear accelerator-injector and 800 MeV isochronous cyclotron. The main problems associated with their realization are listed [ru

  13. Mitigation of Grid-Current Distortion for LCL-Filtered Voltage-Source Inverter with Inverter-Current Feedback Control

    DEFF Research Database (Denmark)

    Xin, Zhen; Mattavelli, Paolo; Yao, WenLi

    2018-01-01

    harmonics can freely flow into the filter capacitor. In this case, because of the loss of harmonic information, traditional harmonic controllers fail to mitigate the grid current distortion. Although this problem may be avoided using the grid voltage feedforward scheme, the required differentiators may...

  14. The Effect of Current-Limiting Reactors on the Tripping of Short Circuits in High-Voltage Electrical Equipment

    International Nuclear Information System (INIS)

    Volkov, M. S.; Gusev, Yu. P.; Monakov, Yu. V.; Cho, Gvan Chun

    2016-01-01

    The insertion of current-limiting reactors into electrical equipment operating at a voltage of 110 and 220 kV produces a change in the parameters of the transient recovery voltages at the contacts of the circuit breakers for disconnecting short circuits, which could be the reason for the increase in the duration of the short circuit, damage to the electrical equipment and losses in the power system. The results of mathematical modeling of the transients, caused by tripping of the short circuit in a reactive electric power transmission line are presented, and data are given on the negative effect of a current-limiting resistor on the rate of increase and peak value of the transient recovery voltages. Methods of ensuring the standard requirements imposed on the parameters of the transient recovery voltages when using current-limiting reactors in the high-voltage electrical equipment of power plants and substations are proposed and analyzed

  15. The dynamic current-voltage characteristic as a powerful tool to analyze fast phenomena in plasma

    International Nuclear Information System (INIS)

    Ivan, L. M.; Mihai-Plugaru, M.; Amarandei, G.; Aflori, M.; Dimitriu, D. G.

    2006-01-01

    The static current-voltage characteristic of an electrode immersed in plasma is obtained by slowly increasing and subsequently decreasing the potential on the electrode with respect to the plasma potential or the ground. This characteristic can give us important information about the phenomena that take place in front of the electrode. Current jumps can be evidenced which were often associated with an hysteresis effect, regions with S-type or N-type negative differential resistance, etc. The method is always used when we investigate the appearance of complex space charge configurations (CSCC) in front of an electrode immersed in plasma. However, to investigate the dynamics of such structures or other fast phenomena (like instabilities) which take place in plasma devices with frequencies of tenth, hundred kHz or more, complex investigation techniques must be used. One of the most efficient methods to investigate fast phenomena in plasma devices is the dynamic current-voltage characteristic. This is obtained by recording the time series of the current collected by the electrode when the voltage applied on it is very fast modified (most likely increased) by using a signal generator. In this way, very fast oscillations of the current can be recorded and new phenomena can be evidenced. We used this technique to study the phenomena which take place at the onset of electrostatic instabilities in Q-machine plasma, namely the potential relaxation instability (PRI) and the electrostatic ion-cyclotron instability (EICI). The obtained experimental results prove that the negative differential resistance region in the static current-voltage characteristic is the result of a nonlinear dynamics of a CSCC in form of a double layer (DL) which takes place just before the onset of the instabilities. In the case of the PRI we emphasized current jumps related with the DL appearance, which are not present in the static current-voltage characteristic at high plasma density. (authors)

  16. Current-voltage curve of sodium channels and concentration dependence of sodium permeability in frog skin

    DEFF Research Database (Denmark)

    Fuchs, W; Larsen, Erik Hviid; Lindemann, B

    1977-01-01

    1. The inward facing membranes of in vitro frog skin epithelium were depolarized with solutions of high K concentration. The electrical properties of the epithelium are then expected to be governed by the outward facing, Na-selective membrane.2. In this state, the transepithelial voltage (V...... was recorded. This procedure was repeated after blocking the Na channels with amiloride to obtain the current-voltage curve of transmembrane and paracellular shunt pathways. The current-voltage curve of the Na channels was computed by subtracting the shunt current from the total current.4. The instantaneous I...... of the inward facing membranes but reflects the true behaviour of P(Na).6. The steady-state P(Na) at a given (Na)(o) is smaller than the transient P(Na) observed right after a stepwise increase of (Na)(o) to this value. The time constant of P(Na)-relaxation is in the order of seconds.7. In conclusion, Na...

  17. Research of the voltage and current stabilization processes by using the silicon field-effect transistor

    International Nuclear Information System (INIS)

    Karimov, A.V.; Yodgorova, D.M.; Kamanov, B.M.; Giyasova, F.A.; Yakudov, A.A.

    2012-01-01

    The silicon field-effect transistors were investigated to use in circuits for stabilization of current and voltage. As in gallium arsenide field-effect transistors, in silicon field-effect transistors with p-n-junction a new mechanism of saturation of the drain current is experimentally found out due to both transverse and longitudinal compression of channel by additional resistance between the source and the gate of the transistor. The criteria for evaluating the coefficients of stabilization of transient current suppressors and voltage stabilizator based on the field-effect transistor are considered. (authors)

  18. Contamination of current-clamp measurement of neuron capacitance by voltage-dependent phenomena

    Science.gov (United States)

    White, William E.

    2013-01-01

    Measuring neuron capacitance is important for morphological description, conductance characterization, and neuron modeling. One method to estimate capacitance is to inject current pulses into a neuron and fit the resulting changes in membrane potential with multiple exponentials; if the neuron is purely passive, the amplitude and time constant of the slowest exponential give neuron capacitance (Major G, Evans JD, Jack JJ. Biophys J 65: 423–449, 1993). Golowasch et al. (Golowasch J, Thomas G, Taylor AL, Patel A, Pineda A, Khalil C, Nadim F. J Neurophysiol 102: 2161–2175, 2009) have shown that this is the best method for measuring the capacitance of nonisopotential (i.e., most) neurons. However, prior work has not tested for, or examined how much error would be introduced by, slow voltage-dependent phenomena possibly present at the membrane potentials typically used in such work. We investigated this issue in lobster (Panulirus interruptus) stomatogastric neurons by performing current clamp-based capacitance measurements at multiple membrane potentials. A slow, voltage-dependent phenomenon consistent with residual voltage-dependent conductances was present at all tested membrane potentials (−95 to −35 mV). This phenomenon was the slowest component of the neuron's voltage response, and failure to recognize and exclude it would lead to capacitance overestimates of several hundredfold. Most methods of estimating capacitance depend on the absence of voltage-dependent phenomena. Our demonstration that such phenomena make nonnegligible contributions to neuron responses even at well-hyperpolarized membrane potentials highlights the critical importance of checking for such phenomena in all work measuring neuron capacitance. We show here how to identify such phenomena and minimize their contaminating influence. PMID:23576698

  19. Study of current-voltage characteristics in PbTe(Ga) alloys at low temperatures

    International Nuclear Information System (INIS)

    Akimov, B.A.; Albul, A.V.; Bogdanov, E.V.

    1992-01-01

    Results of determining current-voltage characteristics in PbTe(Ga) monocrystals of n- and p-types of conductivity in strong electric fields E ≤ 2 x 10 3 V/Cm at 4.2-77 K are presented. It was established that at helium and nitrogen temperatures, the current-voltage characteristics of PbTe(Ga) alloys, high-ohmic state of which was realized in helium, differed qualitatively from ones, typical for unalloyed PbTe. The superlinear dependence, observed in the fields, beginning from E ≥ 1 V/cm, is explained in the framework of concepts of strong electric field effect on conductivity of impurity states

  20. Microscopic origin of gating current fluctuations in a potassium channel voltage sensor.

    Science.gov (United States)

    Freites, J Alfredo; Schow, Eric V; White, Stephen H; Tobias, Douglas J

    2012-06-06

    Voltage-dependent ion channels open and close in response to changes in membrane electrical potential due to the motion of their voltage-sensing domains (VSDs). VSD charge displacements within the membrane electric field are observed in electrophysiology experiments as gating currents preceding ionic conduction. The elementary charge motions that give rise to the gating current cannot be observed directly, but appear as discrete current pulses that generate fluctuations in gating current measurements. Here we report direct observation of gating-charge displacements in an atomistic molecular dynamics simulation of the isolated VSD from the KvAP channel in a hydrated lipid bilayer on the timescale (10-μs) expected for elementary gating charge transitions. The results reveal that gating-charge displacements are associated with the water-catalyzed rearrangement of salt bridges between the S4 arginines and a set of conserved acidic side chains on the S1-S3 transmembrane segments in the hydrated interior of the VSD. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  1. Suppressing voltage transients in high voltage power supplies

    International Nuclear Information System (INIS)

    Lickel, K.F.; Stonebank, R.

    1979-01-01

    A high voltage power supply for an X-ray tubes includes voltage adjusting means, a high voltage transformer, switch means connected to make and interrupt the primary current of the transformer, and over-voltage suppression means to suppress the voltage transient produced when the current is switched on. In order to reduce the power losses in the suppression means, an impedance is connected in the transformer primary circuit on operation of the switch means and is subsequently short-circuited by a switch controlled by a timer after a period which is automatically adjusted to the duration of the transient overvoltage. (U.K.)

  2. Expression, Purification and Reconstitution of the Voltage Sensing Domain from Ci-VSP

    Science.gov (United States)

    Li, Qufei; Jogini, Vishwanath; Wanderling, Sherry; Cortes, D. Marien; Perozo, Eduardo

    2013-01-01

    The voltage-sensing domain (VSD) is the common scaffold responsible for the functional behavior of voltage gated ion channels, voltage sensitive enzymes and proton channels. Because of the position of the voltage dependence of the available VSD structures, at present, they all represent the activated state of the sensor. Yet, in the absence of a consensus resting state structure, the mechanistic details of voltage sensing remain controversial. The voltage dependence of the VSD from Ci-VSP (Ci-VSD) is dramatically right shifted, so that at 0 mV It presumably populates the putative resting state. Appropriate biochemical methods are an essential prerequisite to generate sufficient amounts of Ci-VSD protein for high-resolution structural studies. Here, we present a simple and robust protocol for the Escherichia coli expression of eukaryotic Ci-VSD at milligram levels. The protein is pure, homogeneous, mono-disperse and well folded after solubilization in Anzergent 3-14 at the analyzed concentration (~ 0.3 mg/mL). Ci-VSD can be reconstituted into liposomes of various compositions and initial site-directed spin labeling and EPR spectroscopic measurements indicate its first transmembrane segment folds into an α-helix, in agreement to the homologous region of other VSDs. Based on current results and enhanced relaxation EPR spectroscopy measurement, Ci-VSD reconstitutes essentially randomly in proteo-liposomes, precluding straightforward application of transmembrane voltages in combination with spectroscopic methods. Nevertheless, the present results represent an initial step that makes the resting state of a VSD accessible to a variety of biophysical and structural approaches, including X-ray crystallography, spectroscopic methods and electrophysiology in lipid bilayers. PMID:22989304

  3. Plug-and-Play Voltage/Current Stabilization DC Microgrid Clusters with Grid-Forming/Feeding Converters

    DEFF Research Database (Denmark)

    Han, Renke; Tucci, Michele; Martinelli, Andrea

    2018-01-01

    In this paper, we propose a new decentralized control scheme for Microgrid (MG) clusters, given by the interconnection of atomic dc MGs, each composed by grid-forming and grid-feeding converters. In particular, we develop a new Plug-and-Play (PnP) voltage/current controller for each MG in order...... to achieve simultaneous voltage support and current feeding function with local references. The coefficients of each stabilizing controller are characterized by explicit inequalities, which are related only to local electrical parameters of the MG. With the proposed controller, each MG can plug...

  4. High voltage power supplies for ITER RF heating and current drive systems

    International Nuclear Information System (INIS)

    Gassmann, T.; Arambhadiya, B.; Beaumont, B.; Baruah, U.K.; Bonicelli, T.; Darbos, C.; Purohit, D.; Decamps, H.; Albajar, F.; Gandini, F.; Henderson, M.; Kazarian, F.; Lamalle, P.U.; Omori, T.; Parmar, D.; Patel, A.; Rathi, D.; Singh, N.P.

    2011-01-01

    The RF heating and current drive (H and CD) systems to be installed for the ITER fusion machine are the electron cyclotron (EC), ion cyclotron (IC) and, although not in the first phase of the project, lower hybrid (LH). These systems require high voltage, high current power supplies (HVPS) in CW operation. These HVPS should deliver around 50 MW electrical power to each of the RF H and CD systems with stringent requirements in terms of accuracy, voltage ripple, response time, turn off time and fault energy. The PSM (Pulse Step Modulation) technology has demonstrated over the past 20 years its ability to fulfill these requirements in many industrial facilities and other fusion reactors and has therefore been chosen as reference design for the IC and EC HVPS systems. This paper describes the technical specifications, including interfaces, the resulting constraints on the design, the conceptual design proposed for ITER EC and IC HVPS systems and the current status.

  5. Sensing charges of the Ciona intestinalis voltage-sensing phosphatase.

    Science.gov (United States)

    Villalba-Galea, Carlos A; Frezza, Ludivine; Sandtner, Walter; Bezanilla, Francisco

    2013-11-01

    Voltage control over enzymatic activity in voltage-sensitive phosphatases (VSPs) is conferred by a voltage-sensing domain (VSD) located in the N terminus. These VSDs are constituted by four putative transmembrane segments (S1 to S4) resembling those found in voltage-gated ion channels. The putative fourth segment (S4) of the VSD contains positive residues that likely function as voltage-sensing elements. To study in detail how these residues sense the plasma membrane potential, we have focused on five arginines in the S4 segment of the Ciona intestinalis VSP (Ci-VSP). After implementing a histidine scan, here we show that four arginine-to-histidine mutants, namely R223H to R232H, mediate voltage-dependent proton translocation across the membrane, indicating that these residues transit through the hydrophobic core of Ci-VSP as a function of the membrane potential. These observations indicate that the charges carried by these residues are sensing charges. Furthermore, our results also show that the electrical field in VSPs is focused in a narrow hydrophobic region that separates the extracellular and intracellular space and constitutes the energy barrier for charge crossing.

  6. Development of a prototype solid state fault current limiting and interrupting device for low voltage distribution networks.

    OpenAIRE

    Ahmed, M.; Putrus, G. A.; Ran, L.; Penlington, R.

    2006-01-01

    This paper describes the development of a solid-state Fault Current Limiting and Interrupting Device (FCLID) suitable for low voltage distribution networks. The main components of the FCLID are a bidirectional semiconductor switch that can disrupt the short-circuit current, and a voltage clamping element that helps in controlling the current and absorbing the inductive energy stored in the network during current interruption. Using a hysteresis type control algorithm, the short-circuit curren...

  7. Active interrogation using energetic protons

    International Nuclear Information System (INIS)

    Morris, Christopher L.; Chung, Kiwhan; Greene, Steven J.; Hogan, Gary E.; Makela, Mark; Mariam, Fesseha; Milner, Edward C.; Murray, Matthew; Saunders, Alexander; Spaulding, Randy; Wang, Zhehui; Waters, Laurie; Wysocki, Frederick

    2010-01-01

    Energetic proton beams provide an attractive alternative when compared to electromagnetic and neutron beams for active interrogation of nuclear threats because they have large fission cross sections, long mean free paths and high penetration, and they can be manipulated with magnetic optics. We have measured time-dependent cross sections and neutron yields for delayed neutrons and gamma rays using 800 MeV and 4 GeV proton beams with a set of bare and shielded targets. The results show significant signals from both unshielded and shielded nuclear materials. Measurements of neutron energies yield suggest a signature unique to fissile material. Results are presented in this paper.

  8. MAGY: An innovative high voltage-low current power supply for gyrotron

    International Nuclear Information System (INIS)

    Siravo, Ugo; Alex, Juergen; Bader, Michael; Carpita, Mauro; Fasel, Damien; Gavin, Serge; Perez, Albert

    2011-01-01

    From the electrical point of view, the body and the anode of high power gyrotrons behave as capacitive loads. A highly dynamic power supply is, therefore, hard to achieve. The MAGY concept (Modulator for the Anode of a triode type GYrotron) embodies an innovative solution to manage the capacitive current ensuring a very low ripple on the output voltage. It consists of a series of independent, bi-directional and regulated DC sources. Compared to existing topologies, this solution requires a smaller number of power modules. It avoids internal high frequency modulation and simultaneously offers high resolution of the output voltage and a wide range of operating scenarios.

  9. A novel current mode controller for a static compensator utilizing Goertzel algorithm to mitigate voltage sags

    International Nuclear Information System (INIS)

    Najafi, E.; Yatim, A.H.M.

    2011-01-01

    Research highlights: → We proposed a new current control method for STATCOM. → The current control method maintains a fixed switching frequency. → It also produces fewer harmonics compared to conventional hysteresis method. → A new voltage dip (sag) detection method was used in STATCOM. → The control method can mitigate voltage sag in each phase separately. -- Abstract: Static compensator (STATCOM) has been widely proposed for power quality and network stability improvement. It is easily connected in parallel to the electric network and has many advantages for electrical grids. It can improve network stability; power factor, power transfer rating and can avoid some disturbances such as sags and swells. Most of STATCOM controllers are based on voltage controllers that are based on balanced d-q transform. However, they are not thorough solutions for network disturbances since in most cases single-phase disturbances occur in electrical networks that cannot be avoided by the conventional controllers. Voltage mode controllers are also not capable of responding fast enough to the changes expected of a network system. This paper proposes a new current mode controller to overcome the mentioned problem. The approach uses a fixed frequency current controller to maintain voltage levels in voltage sags (dips). This approach is also simple and can be easily implemented by digitally. It has superior performance over conventional methods in terms of harmonic reduction in STATCOM output current. Another important factor for STATCOM effectiveness in sag mitigation is its sag detection method. This paper also introduces a new sag detection method based on Goertzel algorithm which is both effective and simple for practical applications. The simulation results presented illustrate the superiority of the proposed controller and sag detection algorithm to be utilized in the STATCOM.

  10. Calcium current activation kinetics in isolated pyramidal neurones of the Ca1 region of the mature guinea-pig hippocampus.

    Science.gov (United States)

    Kay, A R; Wong, R K

    1987-11-01

    1. Neurones were isolated from the CA1 region of the guinea-pig hippocampus and subjected to the whole-cell mode of voltage clamping, to determine the kinetics of voltage-gated Ca2+ channel activation. 2. Isolated neurones had an abbreviated morphology, having lost most of the distal dendritic tree during the isolation procedure. The electrical compactness of the cells facilitates voltage clamp analysis. 3. Block of sodium and potassium currents revealed a persistent current activated on depolarization above -40 mV, which inactivated slowly when the intracellular medium contained EGTA. The current was blocked by Co2+ and Cd2+, augmented by increases in Ca2+ and could be carried by Ba2+, suggesting that the current is borne by Ca2+. 4. Steady-state activation of the Ca2+ current was found to be well described by the Boltzman equation raised to the second power. 5. The open channel's current-voltage (I-V) relationship rectified in the inward direction and was consistent with the constant-field equation. 6. The kinetics of Ca2+ current onset followed m2 kinetics throughout the range of its activation. Tail current kinetics were in accord with this model. A detailed Hodgkin-Huxley model was derived, defining the activation of this current. 7. The kinetics of the currents observed in this regionally and morphologically defined class of neurones were consistent with the existence of a single kinetic class of channels.

  11. ISAC target operation with high proton currents

    CERN Document Server

    Dombsky, M; Schmor, P; Lane, M

    2003-01-01

    The TRIUMF-ISAC facility target stations were designed for ISOL target irradiations with up to 100 mu A proton beam currents. Since beginning operation in 1998, ISAC irradiation currents have progressively increased from initial values of approx 1 mu A to present levels of up to 40 mu A on refractory metal foil targets. In addition, refractory carbide targets have operated at currents of up to 15 mu A for extended periods. The 1-40 mu A operational regime is achieved by tailoring each target to the thermal requirements dictated by material properties such as beam power deposition, thermal conductivity and maximum operating temperature of the target material. The number of heat shields on each target can be varied in order to match the effective emissivity of the target surface for the required radiative power dissipation. Targets of different thickness, surface area and volume have been investigated to study the effect of diffusion and effusion delays on the yield of radioisotopes. For yields of short-lived p...

  12. Induction of divalent cation permeability by heterologous expression of a voltage sensor domain.

    Science.gov (United States)

    Arima, Hiroki; Tsutsui, Hidekazu; Sakamoto, Ayako; Yoshida, Manabu; Okamura, Yasushi

    2018-01-06

    The voltage sensor domain (VSD) is a protein domain that confers sensitivity to membrane potential in voltage-gated ion channels as well as the voltage-sensing phosphatase. Although VSDs have long been considered to function as regulatory units acting on adjacent effectors, recent studies have revealed the existence of direct ion permeation paths in some mutated VSDs and in the voltage-gated proton channel. In this study, we show that calcium currents are evoked upon membrane hyperpolarization in cells expressing a VSD derived from an ascidian voltage-gated ion channel superfamily. Unlike the previously reported omega-pore in the Shaker K + channel and rNav1.4, mutations are not required. From electrophysiological experiments in heterologous expression systems, we found that the conductance is directly mediated by the VSD itself and is carried by both monovalent and divalent cations. This is the first report of divalent cation permeation through a VSD-like structure. Copyright © 2018 Elsevier B.V. All rights reserved.

  13. Current-Voltage Characteristics of DC Discharge in Micro Gas Jet Injected into Vacuum Environment

    International Nuclear Information System (INIS)

    Matra, K; Furuta, H; Hatta, A

    2013-01-01

    A current-voltage characteristic of direct current (DC) gas discharge operated in a micro gas jet injected into a secondary electron microscope (SEM) chamber is presented. Ar gas was injected through a 30 μm orifice gas nozzle (OGN) and was evacuated by an additional pump to keep the high vacuum environment. Gas discharges were ignited between the OGN as anode and a counter electrode of Si wafer. The discharge was self-pulsating in most of the cases while it was stable at lower pressure, larger gap length, and larger time averaged current. The self-pulsating discharge was oscillated by the RC circuit consisting of a stray capacitor and a large ballast resistor. The real time plots of voltage and current during the pulsating was investigated using a discharge model.

  14. Investigation of the Effects of Facility Background Pressure on the Performance and Voltage-Current Characteristics of the High Voltage Hall Accelerator

    Science.gov (United States)

    Kamhawi, Hani; Huang, Wensheng; Haag, Thomas; Spektor, Rostislav

    2014-01-01

    The National Aeronautics and Space Administration (NASA) Science Mission Directorate In-Space Propulsion Technology office is sponsoring NASA Glenn Research Center to develop a 4 kW-class Hall thruster propulsion system for implementation in NASA science missions. A study was conducted to assess the impact of varying the facility background pressure on the High Voltage Hall Accelerator (HiVHAc) thruster performance and voltage-current characteristics. This present study evaluated the HiVHAc thruster performance in the lowest attainable background pressure condition at NASA GRC Vacuum Facility 5 to best simulate space-like conditions. Additional tests were performed at selected thruster operating conditions to investigate and elucidate the underlying physics that change during thruster operation at elevated facility background pressure. Tests were performed at background pressure conditions that are three and ten times higher than the lowest realized background pressure. Results indicated that the thruster discharge specific impulse and efficiency increased with elevated facility background pressure. The voltage-current profiles indicated a narrower stable operating region with increased background pressure. Experimental observations of the thruster operation indicated that increasing the facility background pressure shifted the ionization and acceleration zones upstream towards the thruster's anode. Future tests of the HiVHAc thruster are planned at background pressure conditions that are expected to be two to three times lower than what was achieved during this test campaign. These tests will not only assess the impact of reduced facility background pressure on thruster performance, voltage-current characteristics, and plume properties; but will also attempt to quantify the magnitude of the ionization and acceleration zones upstream shifting as a function of increased background pressure.

  15. Input-current-shaper based on a modified SEPIC converter with low voltage stress

    DEFF Research Database (Denmark)

    Petersen, Lars

    2001-01-01

    The boost topology is often the designer's first choice when dealing with PFC front-ends. This topology is well documented in the literature and has obvious advantages like continuous input current and low voltage- and current-stress compared to other PFC topologies. The PFC SEPIC converter also...

  16. Current-voltage hysteresis and dielectric properties of PVA coated MWCNT film

    Science.gov (United States)

    Das, Amit Kumar; Meikap, Ajit Kumar

    2017-12-01

    In this work, we have prepared polyvinyl alcohol (PVA) coated multiwall carbon nanotube (MWCNT) film by an in situ chemical oxidative preparation technique. The thermogravimetric analysis clearly explains the thermal degradation of pure polymer and polymer nanocomposite film. We have studied the AC electrical transport properties and current-voltage (I-V) characteristic of PVA-MWCNT composites within the temperature range 300 ≤ T ≤ 423 K and frequency range 150 Hz ≤ f ≤ 2 MHz. It is observed that the dielectric constant of the composite film increases significantly. The frequency variation of AC conductivity follows the power law ( ωS ) and a sharp transition from small polaron tunneling to correlated barrier hopping model is found. The imaginary part of electric modulus shows non-Debye type asymmetric behaviour. The impedance spectroscopy shows the negative temperature coefficient of resistance of the composite film. Nyquist plot of the composite film at different temperatures is established from impedance measurement. The current-voltage characteristic (under ± 20 V) shows hysteresis behaviour and field dependent resistance. We simulate the experimentally observed current density-electric field data with the established theory.

  17. Current-voltage hysteresis and dielectric properties of PVA coated MWCNT film

    Science.gov (United States)

    Das, Amit Kumar; Meikap, Ajit Kumar

    2018-06-01

    In this work, we have prepared polyvinyl alcohol (PVA) coated multiwall carbon nanotube (MWCNT) film by an in situ chemical oxidative preparation technique. The thermogravimetric analysis clearly explains the thermal degradation of pure polymer and polymer nanocomposite film. We have studied the AC electrical transport properties and current-voltage (I-V) characteristic of PVA-MWCNT composites within the temperature range 300 ≤ T ≤ 423 K and frequency range 150 Hz ≤ f ≤ 2 MHz. It is observed that the dielectric constant of the composite film increases significantly. The frequency variation of AC conductivity follows the power law ( ωS ) and a sharp transition from small polaron tunneling to correlated barrier hopping model is found. The imaginary part of electric modulus shows non-Debye type asymmetric behaviour. The impedance spectroscopy shows the negative temperature coefficient of resistance of the composite film. Nyquist plot of the composite film at different temperatures is established from impedance measurement. The current-voltage characteristic (under ± 20 V) shows hysteresis behaviour and field dependent resistance. We simulate the experimentally observed current density-electric field data with the established theory.

  18. Integrated Three-Voltage-Booster DC-DC Converter to Achieve High Voltage Gain with Leakage-Energy Recycling for PV or Fuel-Cell Power Systems

    Directory of Open Access Journals (Sweden)

    Chih-Lung Shen

    2015-09-01

    Full Text Available In this paper, an integrated three-voltage-booster DC-DC (direct current to direct current converter is proposed to achieve high voltage gain for renewable-energy generation systems. The proposed converter integrates three voltage-boosters into one power stage, which is composed of an active switch, a coupled-inductor, five diodes, and five capacitors. As compared with conventional high step-up converters, it has a lower component count. In addition, the features of leakage-energy recycling and switching loss reduction can be accomplished for conversion efficiency improvement. While the active switch is turned off, the converter can inherently clamp the voltage across power switch and suppress voltage spikes. Moreover, the reverse-recovery currents of all diodes can be alleviated by leakage inductance. A 200 W prototype operating at 100 kHz switching frequency with 36 V input and 400 V output is implemented to verify the theoretical analysis and to demonstrate the feasibility of the proposed high step-up DC-DC converter.

  19. Large conductance Ca2+-activated K+ (BK channel: Activation by Ca2+ and voltage

    Directory of Open Access Journals (Sweden)

    RAMÓN LATORRE

    2006-01-01

    Full Text Available Large conductance Ca2+-activated K+ (BK channels belong to the S4 superfamily of K+ channels that include voltage-dependent K+ (Kv channels characterized by having six (S1-S6 transmembrane domains and a positively charged S4 domain. As Kv channels, BK channels contain a S4 domain, but they have an extra (S0 transmembrane domain that leads to an external NH2-terminus. The BK channel is activated by internal Ca2+, and using chimeric channels and mutagenesis, three distinct Ca2+-dependent regulatory mechanisms with different divalent cation selectivity have been identified in its large COOH-terminus. Two of these putative Ca2+-binding domains activate the BK channel when cytoplasmic Ca2+ reaches micromolar concentrations, and a low Ca2+ affinity mechanism may be involved in the physiological regulation by Mg2+. The presence in the BK channel of multiple Ca2+-binding sites explains the huge Ca2+ concentration range (0.1 μM-100 μM in which the divalent cation influences channel gating. BK channels are also voltage-dependent, and all the experimental evidence points toward the S4 domain as the domain in charge of sensing the voltage. Calcium can open BK channels when all the voltage sensors are in their resting configuration, and voltage is able to activate channels in the complete absence of Ca2+. Therefore, Ca2+ and voltage act independently to enhance channel opening, and this behavior can be explained using a two-tiered allosteric gating mechanism.

  20. Effect of electric and magnetic fields on current-voltage characteristics of a lyotropic liquid crystal

    International Nuclear Information System (INIS)

    Minasyants, M.Kh.; Badalyan, G. G.; Shahinian, A. A.

    1997-01-01

    The effect of electric and magnetic fields on current-voltage characteristics is studied for the lamellar phase in the lyotropic liquid-crystal sodium pentadecylsulfonate (SPDS)-water and lecithin-water systems. It has been found that the current-voltage characteristics of both systems have hysteresis. In the case of ionogenic SPDS, the hysteresis is formed due to ion current caused by the spatial reorientation of domains consisting of parallel lamellar fragments; in the case of lecithin, whose molecules contain dipoles, the hysteresis is formed due to the spatial reorientation of domains caused by the interaction of the resultant dipole moment of the domains with the electric field. It is shown that the introduction into lamellae of cetylpyridine bromide, which has an intrinsic magnetic moment, changes the resultant magnetic moment of domains and, thus, also the hysteresis loop of the current-voltage characteristic. The systems studied show the 'memory' effect with respect to both the electric and magnetic fields. Field-induced processes of domain reorientation were recorded by the method of small-angle x-ray scattering

  1. Calculation of current-voltage characteristics of electron-capture detectors

    International Nuclear Information System (INIS)

    Hinneburg, D.; Grosse, H.J.; Leonhardt, J.; Popp, P.

    1983-01-01

    Starting from the law of conservation of charge a stationary one-dimensional non-linear differential equation system is derived, which is applied to the direct-current mode of an electron-capture detector with parallel electrode plates. The theory takes into account space-charge, recombination, and inhomogeneous ionization and it deals with three kinds of charge carriers with different mobilities (positive and negative ions, electrons). Terms due to diffusion and gas-flow losses are excluded. The equations so constructed were programmed to get a means of calculating the charge and field distributions and the current-voltage characteristics as functions of various parameters of the detectors, the attaching gas and the ionization. For two cases the results are given. (author)

  2. Cavity Voltage Phase Modulation MD

    CERN Document Server

    Mastoridis, Themistoklis; Molendijk, John; Timko, Helga; CERN. Geneva. ATS Department

    2016-01-01

    The LHC RF/LLRF system is currently configured for extremely stable RF voltage to minimize transient beam loading effects. The present scheme cannot be extended beyond nominal beam current since the demanded power would exceed the peak klystron power and lead to saturation. A new scheme has therefore been proposed: for beam currents above nominal (and possibly earlier), the cavity phase modulation by the beam will not be corrected (transient beam loading), but the strong RF feedback and One-Turn Delay feedback will still be active for loop and beam stability in physics. To achieve this, the voltage set point will be adapted for each bunch. The goal of this MD was to test a new algorithm that would adjust the voltage set point to achieve the cavity phase modulation that would minimize klystron forward power.

  3. Influence of process parameters on threshold voltage and leakage current in 18nm NMOS device

    Science.gov (United States)

    Atan, Norani Binti; Ahmad, Ibrahim Bin; Majlis, Burhanuddin Bin Yeop; Fauzi, Izzati Binti Ahmad

    2015-04-01

    The process parameters are very crucial factor in the development of transistors. There are many process parameters that influenced in the development of the transistors. In this research, we investigate the effects of the process parameters variation on response characteristics such as threshold voltage (VTH) and sub-threshold leakage current (IOFF) in 18nm NMOS device. The technique to identify semiconductor process parameters whose variability would impact most on the device characteristic is realized through the process by using Taguchi robust design method. This paper presents the process parameters that influenced in threshold voltage (VTH) and sub-threshold leakage current (IOFF) which includes the Halo Implantation, Compensation Implantation, Adjustment Threshold voltage Implantation and Source/Drain Implantation. The design, fabrication and characterization of 18nm HfO2/TiSi2 NMOS device is simulated and performed via a tool called Virtual Wafer Fabrication (VWF) Silvaco TCAD Tool known as ATHENA and ATLAS simulators. These two simulators were combined with Taguchi L9 Orthogonal method to aid in the design and the optimization of the process parameters to achieve the optimum average of threshold voltage (VTH) and sub-threshold leakage current, (IOFF) in 18nm device. Results from this research were obtained; where Halo Implantation dose was identified as one of the process parameter that has the strongest effect on the response characteristics. Whereby the Compensation Implantation dose was identified as an adjustment factor to get the nominal values of threshold voltage VTH, and sub-threshold leakage current, IOFF for 18nm NMOS devices equal to 0.302849 volts and 1.9123×10-16 A/μm respectively. The design values are referred to ITRS 2011 prediction.

  4. Experimental and theoretical studies of a high temperature cesium-barium tacitron, with application to low voltage-high current inversion

    International Nuclear Information System (INIS)

    Murray, C.S.; El-Genk, M.S.

    1994-02-01

    A low voltage/high current switch refer-red as ''Cs-Ba tacitron'' is studied for use as a dc to ac inverter in high temperature and/or ionizing radiation environments. The operational characteristics of the Cs-Ba tacitron as a switch were investigated experimentally in three modes: (a) breakdown mode, (b) I-V mode, and (c) current modulation mode. Operation parameters measured include switching frequencies up to 20 kHz, hold-off voltages up to 200 V, current densities in excess of 15 A/CM 2 , switch power density of 1 kW/cm 2 , and a switching efficiency in excess of 90 % at collector voltages greater than 30 V. Also, if the discharge current is circuit limited to a value below the maximum thermal emission current density, the voltage drop is constant and below 3 V

  5. Comment on: "Current-voltage characteristics and zero-resistance state in 2DEG"

    OpenAIRE

    Cheremisin, M. V.

    2003-01-01

    We demonstrate that N(S)-shape current-voltage characteristics proposed to explain zero-resistance state in Corbino(Hall bar) geometry 2DEG (cond-mat/0302063, cond-mat/0303530) cannot account essential features of radiation-induced magnetoresistance oscillations experiments.

  6. Status report on the Los Alamos proton storage ring

    International Nuclear Information System (INIS)

    Colton, E.; Neuffer, D.; Thiessen, H.A.

    1988-01-01

    The proton storage ring currently operates at an average current of 30 μA corresponding to 1.25 /times/ 10 13 protons per pulse (ppp) at a repetition rate of 15 Hz. The design operating current for the machine is 100 μA. We are limited to running at the reduced yield because of beam losses during the accumulation period. These losses are understood and arise mainly from emittance growths during the injection and multiple scattering in the stripping foil during the storage. During beam studies we have succeeded in accumulating in excess of 3.7 /times/ 10 13 ppp. We have also observed a coherent transverse instability at high charge levels. The signature for the instability is rapid coherent growth of the transverse beam size followed by a loss of beam in the machine. The threshold for the instability depends most strongly upon rf voltage and beam size. 3 refs., 1 fig., 1 tab

  7. Evaluation of the Induced Activity in Air by the External Proton Beam in the Target Room of the Proton Accelerator Facility of Proton Engineering Frontier Project

    International Nuclear Information System (INIS)

    Lee, Cheol Woo; Lee, Young Ouk; Cho, Young Sik; Ahn, So Hyun

    2007-01-01

    One of the radiological concerns is the worker's exposure level and the concentration of the radionuclides in the air after shutdown, for the safety analysis on the proton accelerator facility. Although, the primary radiation source is the protons accelerated up to design value, all of the radio-nuclide is produced from the secondary neutron and photon induced reaction in air. Because, the protons don't penetrate the acceleration equipment like the DTL tank wall or BTL wall, secondary neutrons or photons are only in the air in the accelerator tunnel building because of the short range of the proton in the materials. But, for the case of the target rooms, external proton beams are occasionally used in the various experiments. When these external proton beams travel through air from the end of the beam transport line to the target, they interact directly with air and produce activation products from the proton induced reaction. The external proton beam will be used in the target rooms in the accelerator facility of the Proton Accelerator Frontier Project (PEFP). In this study, interaction characteristics of the external proton beam with air and induced activity in air from the direct interaction of the proton beam were evaluated

  8. Device for monitoring cell voltage

    Science.gov (United States)

    Doepke, Matthias [Garbsen, DE; Eisermann, Henning [Edermissen, DE

    2012-08-21

    A device for monitoring a rechargeable battery having a number of electrically connected cells includes at least one current interruption switch for interrupting current flowing through at least one associated cell and a plurality of monitoring units for detecting cell voltage. Each monitoring unit is associated with a single cell and includes a reference voltage unit for producing a defined reference threshold voltage and a voltage comparison unit for comparing the reference threshold voltage with a partial cell voltage of the associated cell. The reference voltage unit is electrically supplied from the cell voltage of the associated cell. The voltage comparison unit is coupled to the at least one current interruption switch for interrupting the current of at least the current flowing through the associated cell, with a defined minimum difference between the reference threshold voltage and the partial cell voltage.

  9. COAXIAL DISK SHUNT FOR MEASURING IN THE HEAVY-CURRENT CHAIN OF HIGH-VOLTAGE GENERATOR OF STORM DISCHARGES OF IMPULSES OF CURRENT OF ARTIFICIAL LIGHTNING WITH THE INTEGRAL OF ACTION TO 15•106 J/OHM

    Directory of Open Access Journals (Sweden)

    M. I. Baranov

    2017-10-01

    Full Text Available Purpose. Description of construction and basic technical descriptions developed and created in Research & Design Institute «Molniya» National Technical University «Kharkiv Polytechnic Institute» high-voltage heavy-current coaxial disk shunt of type of SC-300M2, allowing reliably to measure the peak-temporal parameters (PTP of impulses of current of artificial lightning in wide peak and temporal ranges with the integral of their action to 15·106 J/Ohm. Methodology. Electrophysics bases of high-voltage impulsive technique, scientific and technical bases of development and creation of high-voltage heavy-current impulsive electrical equipment, including the powerful generators of current of lightning (GCL, and also measuring methods in bit chains powerful high-voltage GCL AVP large impulsive currents of micro- and millisecond temporal ranges. Results. Offered and described new construction of measuring high-voltage heavy-current shunt, containing a measuring round disk from stainless steel easily soiled a 12Х18Н10Т thickness 2 mm and external diameter 80 mm. Experimental a way impulsive active resistance of RS≈0,08 mOhm of the indicated measuring disk and on his basis a calculation coefficient transformation is found of SS of coaxial disk shunt of type of SC-300M2, numeral equal in the concerted mode of operations of his coaxial cable line (CCL SS≈2/RS≈25·103 A/V. It is rotined that it is expedient to use this value SS for measuring in the heavy-current bit chain of GCL ATP impulsive A- and repeated impulsive D- component of current of artificial lightning, and also ATP of aperiodic impulse of current of artificial lightning of temporal form 10 μc/350 μc. It is set that taking into account application in the end CCL of shunt of a co-ordinate divizor of voltage with two output coaxial sockets 1:1 (for SSA≈25·103 A/V and 1:2 (SSC≈12,5·103 A/V at measuring of ATP intermediate B-, protracted C- and shortened protracted C

  10. Biased low differential input impedance current receiver/converter device and method for low noise readout from voltage-controlled detectors

    Science.gov (United States)

    Degtiarenko, Pavel V [Williamsburg, VA; Popov, Vladimir E [Newport News, VA

    2011-03-22

    A first stage electronic system for receiving charge or current from voltage-controlled sensors or detectors that includes a low input impedance current receiver/converter device (for example, a transimpedance amplifier), which is directly coupled to the sensor output, a source of bias voltage, and the device's power supply (or supplies), which use the biased voltage point as a baseline.

  11. Thermal domains in inhomogeneous current-carrying superconductors. Current-voltage characteriscs and dynamics of domain formation after current jumps

    International Nuclear Information System (INIS)

    Bezuglyj, A.I.; Shklovskij, V.A.

    1984-01-01

    The static and dynamic behavior of thermal domains in inhomogeneous superconducting films, where the inhomogeneity behaves like a portion of the film with a reduced critical current, have been studied theoretically within the framework of the phenomenological approach, using the heat balance equation and the dependence of the superconductor critical current on temperature. Depending on the size of the inhomogeneity (local or extended) and on the relative values of parameters of the homogeneous and inhomogeneous regions, different types of current-voltage characteristics are obtained. The nonstationary problem of thermal domain formation near the inhomogeneity after a current jump has been solved, and the domain boundary (kink) dynamics at a distance from the inhomogeneity has been analyzed. A combination of the results allows one to describe the whole process of normal phase formation and its spread throughout the superconducting film

  12. Comparison of pad detectors produced on different silicon materials after irradiation with neutrons, protons and pions

    International Nuclear Information System (INIS)

    Kramberger, G.; Cindro, V.; Dolenc, I.; Mandic, I.; Mikuz, M.; Zavrtanik, M.

    2010-01-01

    A set of 44 pad detectors produced on p- and n-type MCz and Fz wafers was irradiated with 23 GeV protons, 200 MeV pions and reactor neutrons up to the equivalent fluences of Φ eq =3x10 15 cm -2 . The evolution of the full depletion voltage and the leakage current were monitored during short- and long-term annealing. At selected representative annealing steps, charge collection measurements were performed for all samples with LHC speed electronics. Measurements of full depletion voltage, leakage current and charge collection efficiency were compared for different irradiation particles and silicon materials.

  13. Comparison of pad detectors produced on different silicon materials after irradiation with neutrons, protons and pions

    Energy Technology Data Exchange (ETDEWEB)

    Kramberger, G., E-mail: Gregor.Kramberger@ijs.s [Jozef Stefan Institute and Department of Physics, University of Ljubljana, SI-1000 Ljubljana (Slovenia); Cindro, V.; Dolenc, I.; Mandic, I.; Mikuz, M.; Zavrtanik, M. [Jozef Stefan Institute and Department of Physics, University of Ljubljana, SI-1000 Ljubljana (Slovenia)

    2010-01-01

    A set of 44 pad detectors produced on p- and n-type MCz and Fz wafers was irradiated with 23 GeV protons, 200 MeV pions and reactor neutrons up to the equivalent fluences of PHI{sub eq}=3x10{sup 15}cm{sup -2}. The evolution of the full depletion voltage and the leakage current were monitored during short- and long-term annealing. At selected representative annealing steps, charge collection measurements were performed for all samples with LHC speed electronics. Measurements of full depletion voltage, leakage current and charge collection efficiency were compared for different irradiation particles and silicon materials.

  14. Glow-to-arc transition events in H2-Ar direct current pulsed plasma: Automated measurement of current and voltage

    International Nuclear Information System (INIS)

    Mendes, Luciano A.; Rodrigues, Jhonatam C.; Mafra, Marcio

    2012-01-01

    The glow-to-arc transition phenomena (arcing) observed in plasma reactors used in materials processing was studied through the arcs characteristic current and voltage waveforms. In order to capture these arcs signals, a LABVIEW based automated instrumentation system (ARCVIEW) was developed, including the integration of an oscilloscope equipped with proper current and voltage probes. The system also allows capturing the process parameters at the arc occurrence moments, which were used to map the arcs events conditions. Experiments in H 2 -Ar DC pulsed plasma returned signals data from 215 arcs events, which were analyzed through software routines. According to the results, an anti-arcing system should react in the time order of few microseconds to prevent most of the damage caused by the undesired arcing phenomena.

  15. Results of the 2015 testbeam of a 180 nm AMS High-Voltage CMOS sensor prototype

    CERN Document Server

    Benoit, M.

    2016-07-21

    Active pixel sensors based on the High-Voltage CMOS technology are being investigated as a viable option for the future pixel tracker of the ATLAS experiment at the High-Luminosity LHC. This paper reports on the testbeam measurements performed at the H8 beamline of the CERN Super Proton Synchrotron on a High-Voltage CMOS sensor prototype produced in 180 nm AMS technology. Results in terms of tracking efficiency and timing performance, for different threshold and bias conditions, are shown.

  16. Proton and gamma -Rays Irradiation-Induced Dark Current Random Telegraph Signal in a 0.18-mu{{m}} CMOS Image Sensor

    Science.gov (United States)

    Martin, E.; Nuns, T.; Virmontois, C.; David, J.-P.; Gilard, O.

    2013-08-01

    The dark current random telegraph signal (RTS) behavior has been studied in a five-transistor-per-pixel (5T) pinned photodiode 0.18-μm COTS active pixel sensor (APS). Several devices, irradiated using protons and gamma rays, have been studied in order to assess the ionizing and displacement damage effects. The influence of the proton energy, fluence, ionizing dose and applied bias during irradiation on the number of RTS pixels, the number of discrete levels, maximum transition amplitude, and mean switching time constants is investigated.

  17. Spectrum Analyzer Application for the Proton Synchrotron Wall Current Monitors

    CERN Document Server

    Limpens, Rik

    The Proton Synchrotron (PS) is a key component in CERN's accelerator complex, where it usually accelerates either protons or heavy ions. The new acquisition system for the PS ring wall current monitors has been installed to be able to perform higher frequency measurements of a beam bunch. This is an important improvement, since the oscillating signals are related to losses of a beam bunch. The main goal of this project is to develop a LabVIEW application running on a Real-Time target to perform continuous and triggered spectral acquisition of a PS beam bunch and to provide a data visualization and analysis tool for the operators and users of the machine.

  18. The Design of Operational Amplifier for Low Voltage and Low Current Sound Energy Harvesting System

    Science.gov (United States)

    Fang, Liew Hui; Rahim, Rosemizi Bin Abd; Isa, Muzamir; Idris Syed Hassan, Syed; Ismail, Baharuddin Bin

    2018-03-01

    The objective of this paper is to design a combination of an operational amplifier (op-amp) with a rectifier used in an alternate current (ac) to direct current (dc) power conversion. The op-amp was designed to specifically work at low voltage and low current for a sound energy harvesting system. The goal of the op-amp design with adjustable gain was to control output voltage based on the objectives of the experiment conducted. The op-amp was designed for minimum power dissipation performance, with the means of increasing the output current when receiving a large amount of load. The harvesting circuits which designed further improved the power output efficiency by shortening the fully charged time needed by a supercapacitor bank. It can fulfil the long-time power demands for low power device. Typically, a small amount of energy sources were converted to electricity and stored in the supercapacitor bank, which was built by 10 pieces of capacitors with 0.22 F each, arranged in parallel connection. The highest capacitance was chosen based on the characteristic that have the longest discharging time to support the applications of a supercapacitor bank. Testing results show that the op-amp can boost the low input ac voltage (∼3.89 V) to high output dc voltage (5.0 V) with output current of 30 mA and stored the electrical energy in a big supercapacitor bank having a total of 2.2 F, effectively. The measured results agree well with the calculated results.

  19. Simulations of plasma heating caused by the coalescence of multiple current loops in a proton-boron fusion plasma

    International Nuclear Information System (INIS)

    Haruki, T.; Yousefi, H. R.; Sakai, J.-I.

    2010-01-01

    Two dimensional particle-in-cell simulations of a dense plasma focus were performed to investigate a plasma heating process caused by the coalescence of multiple current loops in a proton-boron-electron plasma. Recently, it was reported that the electric field produced during the coalescence of two current loops in a proton-boron-electron plasma heats up all plasma species; proton-boron nuclear fusion may therefore be achievable using a dense plasma focus device. Based on this work, the coalescence process for four and eight current loops was investigated. It was found that the return current plays an important role in both the current pinch and the plasma heating. The coalescence of four current loops led to the breakup of the return current from the pinched plasma, resulting in plasma heating. For the coalescence of eight current loops, the plasma was confined by the pinch but the plasma heating was smaller than the two and four loop cases. Therefore the heating associated with current loop coalescence depends on the number of initial current loops. These results are useful for understanding the coalescence of multiple current loops in a proton-boron-electron plasma.

  20. The effects of electron and proton radiation on GaSb infrared solar cells

    Science.gov (United States)

    Gruenbaum, P. E.; Avery, J. E.; Fraas, L. M.

    1991-01-01

    Gallium antimonide (GaSb) infrared solar cells were exposed to 1 MeV electrons and protons up to fluences of 1 times 10(exp 15) cm (-2) and 1 times 10(exp 12) cm (-2) respectively. In between exposures, current voltage and spectral response curves were taken. The GaSb cells were found to degrade slightly less than typical GaAs cells under electron irradiation, and calculations from spectral response curves showed that the damage coefficient for the minority carrier diffusion length was 3.5 times 10(exp 8). The cells degraded faster than GaAs cells under proton irradiation. However, researchers expect the top cell and coverglass to protect the GaSb cell from most damaging protons. Some annealing of proton damage was observed at low temperatures (80 to 160 C).

  1. NO involvement in the inhibition of ghrelin on voltage-dependent potassium currents in rat hippocampal cells.

    Science.gov (United States)

    Lu, Yong; Dang, Shaokang; Wang, Xu; Zhang, Junli; Zhang, Lin; Su, Qian; Zhang, Huiping; Lin, Tianwei; Zhang, Xiaoxiao; Zhang, Yurong; Sun, Hongli; Zhu, Zhongliang; Li, Hui

    2018-01-01

    Ghrelin is a peptide hormone that plays an important role in promoting appetite, regulating distribution and rate of use of energy, cognition, and mood disorders, but the relevant neural mechanisms of these function are still not clear. In this study, we examined the effect of ghrelin on voltage-dependent potassium (K + ) currents in hippocampal cells of 1-3 days SD rats by whole-cell patch-clamp technique, and discussed whether NO was involved in this process. The results showed that ghrelin significantly inhibited the voltage-dependent K + currents in hippocampal cells, and the inhibitory effect was more significant when l-arginine was co-administered. In contrast, N-nitro- l-arginine methyl ester increased the ghrelin inhibited K + currents and attenuated the inhibitory effect of ghrelin. While d-arginine (D-AA) showed no significant impact on the ghrelin-induced decrease in K + current. These results show that ghrelin may play a physiological role by inhibiting hippocampal voltage dependent K + currents, and the NO pathway may be involved in this process. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Regulation of KV channel voltage-dependent activation by transmembrane β subunits

    Directory of Open Access Journals (Sweden)

    Xiaohui eSun

    2012-04-01

    Full Text Available Voltage-activated K+ (KV channels are important for shaping action potentials and maintaining resting membrane potential in excitable cells. KV channels contain a central pore-gate domain (PGD surrounded by four voltage-sensing domains (VSD. The VSDs will change conformation in response to alterations of the membrane potential thereby inducing the opening of the PGD. Many KV channels are heteromeric protein complexes containing auxiliary β subunits. These β subunits modulate channel expression and activity to increase functional diversity and render tissue specific phenotypes. This review focuses on the KV β subunits that contain transmembrane (TM segments including the KCNE family and the β subunits of large conductance, Ca2+- and voltage-activated K+ (BK channels. These TM β subunits affect the voltage-dependent activation of KV α subunits. Experimental and computational studies have described the structural location of these β subunits in the channel complexes and the biophysical effects on VSD activation, PGD opening and VSD-PGD coupling. These results reveal some common characteristics and mechanistic insights into KV channel modulation by TM β subunits.

  3. Interaction of a dinoflagellate neurotoxin with voltage-activated ion channels in a marine diatom.

    Science.gov (United States)

    Kitchen, Sheila A; Bourdelais, Andrea J; Taylor, Alison R

    2018-01-01

    The potent neurotoxins produced by the harmful algal bloom species Karenia brevis are activators of sodium voltage-gated channels (VGC) in animals, resulting in altered channel kinetics and membrane hyperexcitability. Recent biophysical and genomic evidence supports widespread presence of homologous sodium (Na + ) and calcium (Ca 2+ ) permeable VGCs in unicellular algae, including marine phytoplankton. We therefore hypothesized that VGCs of these phytoplankton may be an allelopathic target for waterborne neurotoxins produced by K. brevis blooms that could lead to ion channel dysfunction and disruption of signaling in a similar manner to animal Na + VGCs. We examined the interaction of brevetoxin-3 (PbTx-3), a K. brevis neurotoxin, with the Na + /Ca 2+ VGC of the non-toxic diatom Odontella sinensi s using electrophysiology. Single electrode current- and voltage- clamp recordings from O. sinensis in the presence of PbTx-3 were used to examine the toxin's effect on voltage gated Na + /Ca 2+ currents. In silico analysis was used to identify the putative PbTx binding site in the diatoms. We identified Na + /Ca 2+ VCG homologs from the transcriptomes and genomes of 12 diatoms, including three transcripts from O. sinensis and aligned them with site-5 of Na + VGCs, previously identified as the PbTx binding site in animals. Up to 1 µM PbTx had no effect on diatom resting membrane potential or membrane excitability. The kinetics of fast inward Na + /Ca 2+ currents that underlie diatom action potentials were also unaffected. However, the peak inward current was inhibited by 33%, delayed outward current was inhibited by 25%, and reversal potential of the currents shifted positive, indicating a change in permeability of the underlying channels. Sequence analysis showed a lack of conservation of the PbTx binding site in diatom VGC homologs, many of which share molecular features more similar to single-domain bacterial Na + /Ca 2+ VGCs than the 4-domain eukaryote channels

  4. Proton activation analysis at the Harvard Cyclotron Laboratory

    International Nuclear Information System (INIS)

    Sisterson, J.M.; Koehler, A.M.

    1984-01-01

    High-energy proton activation analysis (PAA), a simple non-destructive technique, has been developed for use as an adjunct to neutron activation analysis. Potential advantages of protons include the ability to achieve very precise localization of the activation volume over a pre-determined depth in the target. To demonstrate the versatility of PAA, results are reported on the measurement of the whole body calcium content in animals and on the determination of the Ca/P molar ratio in small quantities (<50 mg) of chemical and biological samples. The animal experiments demonstrate the ability to achieve a uniform irradiation over a large volume and utilizes large NaI crystals with a special chamber for uniform combined detection efficiency, where the Ca/P molar ratio determination requires a Ge/Li detector and analysis of the resulting gamma ray spectrum. The feasibility is being assessed of using proton beam activation of the eye to measure blood flow in the rabbit choroid, based on earlier work where it was used to measure blood in mouse skeletal tissue. 6 references, 7 figures, 4 tables

  5. A sensorless control method for capacitor voltage balance and circulating current suppression of modular multilevel converter

    DEFF Research Database (Denmark)

    Liu, Hui; Ma, Ke; Loh, Poh Chiang

    2015-01-01

    There are several problems in the Modular Multilevel Converter (MMC), such as the appearance of circulating current, capacitor voltage unbalance and the requirement for a high number of sensors. All these problems will decrease the reliability and raise the cost/uncertainty of using MMC solutions....... As a result, a sensorless control method is proposed in this paper, which targets to improve the performances of MMC in respect to the above mentioned disadvantages: To decrease the cost and simplify the physical implementation, a state observer is proposed and designed to estimate both the capacitor voltages...... and the circulating currents in order to replace the high numbers of sensors. Furthermore, a control method combining the circulating current suppression and the capacitor voltage balancing is conducted based on the proposed state observer. It is concluded that the proposed state observer and control method can...

  6. A Circulating Current Suppression Method for Parallel Connected Voltage-Source-Inverters (VSI) with Common DC and AC Buses

    DEFF Research Database (Denmark)

    Wei, Baoze; Guerrero, Josep M.; Quintero, Juan Carlos Vasquez

    2016-01-01

    This paper describes a theoretical with experiment study on a control strategy for the parallel operation of threephase voltage source inverters (VSI), to be applied to uninterruptible power systems (UPS). A circulating current suppression strategy for parallel VSIs is proposed in this paper based...... on circulating current control loops used to modify the reference currents by compensating the error currents among parallel inverters. Both of the cross and zero-sequence circulating currents are considered. The proposed method is coordinated together with droop and virtual impedance control. In this paper......, droop control is used to generate the reference voltage of each inverter, and the virtual impedance is used to fix the output impedance of the inverters. In addition, a secondary control is used in order to recover the voltage deviation caused by the virtual impedance. And the auxiliary current control...

  7. Inward rectifier potassium current IKir promotes intrinsic pacemaker activity of thalamocortical neurons.

    Science.gov (United States)

    Amarillo, Yimy; Tissone, Angela I; Mato, Germán; Nadal, Marcela S

    2018-06-01

    Slow repetitive burst firing by hyperpolarized thalamocortical (TC) neurons correlates with global slow rhythms (rectifier potassium current I Kir induces repetitive burst firing at slow and delta frequency bands. We demonstrate this in mouse TC neurons in brain slices by manipulating the Kir maximum conductance with dynamic clamp. We also performed a thorough theoretical analysis that explains how the unique properties of I Kir enable this current to induce slow periodic bursting in TC neurons. We describe a new ionic mechanism based on the voltage- and time-dependent interaction of I Kir and hyperpolarization-activated cationic current I h that endows TC neurons with the ability to oscillate spontaneously at very low frequencies, even below 0.5 Hz. Bifurcation analysis of conductance-based models of increasing complexity demonstrates that I Kir induces bistability of the membrane potential at the same time that it induces sustained oscillations in combination with I h and increases the robustness of low threshold-activated calcium current I T -mediated oscillations. NEW & NOTEWORTHY The strong inwardly rectifying potassium current I Kir of thalamocortical neurons displays a region of negative slope conductance in the current-voltage relationship that generates potassium currents activated by hyperpolarization. Bifurcation analysis shows that I Kir induces bistability of the membrane potential; generates sustained subthreshold oscillations by interacting with the hyperpolarization-activated cationic current I h ; and increases the robustness of oscillations mediated by the low threshold-activated calcium current I T . Upregulation of I Kir in thalamocortical neurons induces repetitive burst firing at slow and delta frequency bands (<4 Hz).

  8. High current, high energy proton beams accelerated by a sub-nanosecond laser

    Czech Academy of Sciences Publication Activity Database

    Margarone, Daniele; Krása, Josef; Picciotto, A.; Torrisi, L.; Láska, Leoš; Velyhan, Andriy; Prokůpek, Jan; Ryc, L.; Parys, P.; Ullschmied, Jiří; Rus, Bedřich

    2011-01-01

    Roč. 653, č. 1 (2011), s. 159-163 ISSN 0168-9002 R&D Projects: GA ČR(CZ) GAP205/11/1165; GA AV ČR IAA100100715; GA MŠk(CZ) 7E09092 EU Projects: European Commission(XE) 212105 - ELI-PP Institutional research plan: CEZ:AV0Z10100523; CEZ:AV0Z20430508 Keywords : laser-acceleration * proton beam * high ion current * time -of-flight * proton energy distribution Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.207, year: 2011

  9. Optimal conditions for high current proton irradiations at the university of Wisconsin's ion beam laboratory

    International Nuclear Information System (INIS)

    Wetteland, C. J.; Field, K. G.; Gerczak, T. J.; Eiden, T. J.; Maier, B. R.; Albakri, O.; Sridharan, K.; Allen, T. R.

    2013-01-01

    The National Electrostatics Corporation's (NEC) Toroidal Volume Ion Source (TORVIS) source is known for exceptionally high proton currents with minimal service downtime as compared to traditional sputter sources. It has been possible to obtain over 150μA of proton current from the source, with over 70μA on the target stage. However, beam fluxes above ∼1×10 17 /m2-s may have many undesirable effects, especially for insulators. This may include high temperature gradients at the surface, sputtering, surface discharge, cracking or even disintegration of the sample. A series of experiments were conducted to examine the role of high current fluxes in a suite of ceramics and insulating materials. Results will show the optimal proton irradiation conditions and target mounting strategies needed to minimize unwanted macro-scale damage, while developing a procedure for conducting preliminary radiation experiments.

  10. Bupivacaine inhibits large conductance, voltage- and Ca2+- activated K+ channels in human umbilical artery smooth muscle cells

    Science.gov (United States)

    Martín, Pedro; Enrique, Nicolás; Palomo, Ana R. Roldán; Rebolledo, Alejandro; Milesi, Veronica

    2012-01-01

    Bupivacaine is a local anesthetic compound belonging to the amino amide group. Its anesthetic effect is commonly related to its inhibitory effect on voltage-gated sodium channels. However, several studies have shown that this drug can also inhibit voltage-operated K+ channels by a different blocking mechanism. This could explain the observed contractile effects of bupivacaine on blood vessels. Up to now, there were no previous reports in the literature about bupivacaine effects on large conductance voltage- and Ca2+-activated K+ channels (BKCa). Using the patch-clamp technique, it is shown that bupivacaine inhibits single-channel and whole-cell K+ currents carried by BKCa channels in smooth muscle cells isolated from human umbilical artery (HUA). At the single-channel level bupivacaine produced, in a concentration- and voltage-dependent manner (IC50 324 µM at +80 mV), a reduction of single-channel current amplitude and induced a flickery mode of the open channel state. Bupivacaine (300 µM) can also block whole-cell K+ currents (~45% blockage) in which, under our working conditions, BKCa is the main component. This study presents a new inhibitory effect of bupivacaine on an ion channel involved in different cell functions. Hence, the inhibitory effect of bupivacaine on BKCa channel activity could affect different physiological functions where these channels are involved. Since bupivacaine is commonly used during labor and delivery, its effects on umbilical arteries, where this channel is highly expressed, should be taken into account. PMID:22688134

  11. The Studies of a Vacuum Gap Breakdown after High-Current Arc Interruption with Increasing the Voltage

    Science.gov (United States)

    Schneider, A. V.; Popov, S. A.; Batrakov, A. V.; Dubrovskaya, E. L.; Lavrinovich, V. A.

    2017-12-01

    Vacuum-gap breakdown has been studied after high-current arc interruption with a subsequent increase in the transient recovery voltage across a gap. The effects of factors, such as the rate of the rise in the transient voltage, the potential of the shield that surrounds a discharge gap, and the arc burning time, have been determined. It has been revealed that opening the contacts earlier leads to the formation of an anode spot, which is the source of electrode material vapors into the discharge gap after current zero moment. Under the conditions of increasing voltage, this fact results in the breakdown. Too late opening leads to the breakdown of a short gap due to the high electric fields.

  12. Low Noise Bias Current/Voltage References Based on Floating-Gate MOS Transistors

    DEFF Research Database (Denmark)

    Igor, Mucha

    1997-01-01

    The exploitation of floating-gate MOS transistors as reference current and voltage sources is investigated. Test structures of common source and common drain floating-gate devices have been implemented in a commercially available 0.8 micron double-poly CMOS process. The measurements performed...

  13. Four-point probe measurements using current probes with voltage feedback to measure electric potentials

    Science.gov (United States)

    Lüpke, Felix; Cuma, David; Korte, Stefan; Cherepanov, Vasily; Voigtländer, Bert

    2018-02-01

    We present a four-point probe resistance measurement technique which uses four equivalent current measuring units, resulting in minimal hardware requirements and corresponding sources of noise. Local sample potentials are measured by a software feedback loop which adjusts the corresponding tip voltage such that no current flows to the sample. The resulting tip voltage is then equivalent to the sample potential at the tip position. We implement this measurement method into a multi-tip scanning tunneling microscope setup such that potentials can also be measured in tunneling contact, allowing in principle truly non-invasive four-probe measurements. The resulting measurement capabilities are demonstrated for \

  14. Hyperpolarization-activated current (I(h)) in vestibular calyx terminals: characterization and role in shaping postsynaptic events.

    Science.gov (United States)

    Meredith, Frances L; Benke, Tim A; Rennie, Katherine J

    2012-12-01

    Calyx afferent terminals engulf the basolateral region of type I vestibular hair cells, and synaptic transmission across the vestibular type I hair cell/calyx is not well understood. Calyces express several ionic conductances, which may shape postsynaptic potentials. These include previously described tetrodotoxin-sensitive inward Na(+) currents, voltage-dependent outward K(+) currents and a K(Ca) current. Here, we characterize an inwardly rectifying conductance in gerbil semicircular canal calyx terminals (postnatal days 3-45), sensitive to voltage and to cyclic nucleotides. Using whole-cell patch clamp, we recorded from isolated calyx terminals still attached to their type I hair cells. A slowly activating, noninactivating current (I(h)) was seen with hyperpolarizing voltage steps negative to the resting potential. External Cs(+) (1-5 mM) and ZD7288 (100 μM) blocked the inward current by 97 and 83 %, respectively, confirming that I(h) was carried by hyperpolarization-activated, cyclic nucleotide gated channels. Mean half-activation voltage of I(h) was -123 mV, which shifted to -114 mV in the presence of cAMP. Activation of I(h) was well described with a third order exponential fit to the current (mean time constant of activation, τ, was 190 ms at -139 mV). Activation speeded up significantly (τ=136 and 127 ms, respectively) when intracellular cAMP and cGMP were present, suggesting that in vivo I(h) could be subject to efferent modulation via cyclic nucleotide-dependent mechanisms. In current clamp, hyperpolarizing current steps produced a time-dependent depolarizing sag followed by either a rebound afterdepolarization or an action potential. Spontaneous excitatory postsynaptic potentials (EPSPs) became larger and wider when I(h) was blocked with ZD7288. In a three-dimensional mathematical model of the calyx terminal based on Hodgkin-Huxley type ionic conductances, removal of I(h) similarly increased the EPSP, whereas cAMP slightly decreased simulated EPSP size

  15. "Water-in-salt" electrolytes enable the use of cost-effective aluminum current collectors for aqueous high-voltage batteries.

    Science.gov (United States)

    Kühnel, R-S; Reber, D; Remhof, A; Figi, R; Bleiner, D; Battaglia, C

    2016-08-16

    The extended electrochemical stability window offered by highly concentrated electrolytes allows the operation of aqueous batteries at voltages significantly above the thermodynamic stability limit of water, at which the stability of the current collector potentially limits the cell voltage. Here we report the observation of suppressed anodic dissolution of aluminum in "water-in-salt" electrolytes enabling roll-to-roll electrode fabrication for high-voltage aqueous lithium-ion batteries on cost-effective light-weight aluminum current collectors using established lithium-ion battery technology.

  16. E-beam high voltage switching power supply

    Science.gov (United States)

    Shimer, Daniel W.; Lange, Arnold C.

    1997-01-01

    A high power, solid state power supply is described for producing a controllable, constant high voltage output under varying and arcing loads suitable for powering an electron beam gun or other ion source. The present power supply is most useful for outputs in a range of about 100-400 kW or more. The power supply is comprised of a plurality of discrete switching type dc-dc converter modules, each comprising a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, and an output rectifier for producing a dc voltage at the output of each module. The inputs to the converter modules are fed from a common dc rectifier/filter and are linked together in parallel through decoupling networks to suppress high frequency input interactions. The outputs of the converter modules are linked together in series and connected to the input of the transmission line to the load through a decoupling and line matching network. The dc-dc converter modules are phase activated such that for n modules, each module is activated equally 360.degree./n out of phase with respect to a successive module. The phased activation of the converter modules, combined with the square current waveforms out of the step up transformers, allows the power supply to operate with greatly reduced output capacitance values which minimizes the stored energy available for discharge into an electron beam gun or the like during arcing. The present power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle using simulated voltage feedback signals and voltage feedback loops. Circuitry is also provided for sensing incipient arc currents reflected at the output of the power supply and for simultaneously decoupling the power supply circuitry from the arcing load.

  17. E-beam high voltage switching power supply

    International Nuclear Information System (INIS)

    Shimer, D.W.; Lange, A.C.

    1997-01-01

    A high power, solid state power supply is described for producing a controllable, constant high voltage output under varying and arcing loads suitable for powering an electron beam gun or other ion source. The present power supply is most useful for outputs in a range of about 100-400 kW or more. The power supply is comprised of a plurality of discrete switching type dc-dc converter modules, each comprising a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, and an output rectifier for producing a dc voltage at the output of each module. The inputs to the converter modules are fed from a common dc rectifier/filter and are linked together in parallel through decoupling networks to suppress high frequency input interactions. The outputs of the converter modules are linked together in series and connected to the input of the transmission line to the load through a decoupling and line matching network. The dc-dc converter modules are phase activated such that for n modules, each module is activated equally 360 degree/n out of phase with respect to a successive module. The phased activation of the converter modules, combined with the square current waveforms out of the step up transformers, allows the power supply to operate with greatly reduced output capacitance values which minimizes the stored energy available for discharge into an electron beam gun or the like during arcing. The present power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle using simulated voltage feedback signals and voltage feedback loops. Circuitry is also provided for sensing incipient arc currents reflected at the output of the power supply and for simultaneously decoupling the power supply circuitry from the arcing load. 7 figs

  18. A current-mode voltage regulator with an embedded sub-threshold reference for a passive UHF RFID transponder

    Energy Technology Data Exchange (ETDEWEB)

    Liu Zhongqi [Department of Electronic Engineering, Tsinghua University, Beijing 100084 (China); Zhang Chun; Li Yongming; Wang Zhihua, E-mail: liu-zq04@mails.tsinghua.edu.c [Institute of Microelectronics, Tsinghua University, Beijing 100084 (China)

    2010-06-15

    This paper presents a current-mode voltage regulator for a passive UHF RFID transponder. The passive tag power is extracted from RF energy through the RF-to-DC rectifier. Due to huge variations of the incoming RF power, the rectifier output voltage should be regulated to achieve a stable power supply. By accurately controlling the current flowing into the load with an embedded sub-threshold reference, the regulated voltage varies in a range of 1-1.3 V from -20 to 80 {sup 0}C, and a bandwidth of about 100 kHz is achieved for a fast power recovery. The circuit is fabricated in UMC 0.18 {mu}m mixed-mode CMOS technology, and the current consumption is only 1 {mu}A. (semiconductor integrated circuits)

  19. A current-mode voltage regulator with an embedded sub-threshold reference for a passive UHF RFID transponder

    International Nuclear Information System (INIS)

    Liu Zhongqi; Zhang Chun; Li Yongming; Wang Zhihua

    2010-01-01

    This paper presents a current-mode voltage regulator for a passive UHF RFID transponder. The passive tag power is extracted from RF energy through the RF-to-DC rectifier. Due to huge variations of the incoming RF power, the rectifier output voltage should be regulated to achieve a stable power supply. By accurately controlling the current flowing into the load with an embedded sub-threshold reference, the regulated voltage varies in a range of 1-1.3 V from -20 to 80 0 C, and a bandwidth of about 100 kHz is achieved for a fast power recovery. The circuit is fabricated in UMC 0.18 μm mixed-mode CMOS technology, and the current consumption is only 1 μA. (semiconductor integrated circuits)

  20. High-performance feedback-type active damping of LCL-filtered voltage source converters

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Blaabjerg, Frede; Loh, Poh Chiang

    2015-01-01

    a generalized impedance-based model of grid current control with feedback-type active damping. Then, a controller design method based on the z-domain root contours and frequency-domain passivity theorem is proposed. It not only allows a co-design of the grid current controller and damping controller......Active damping of LCL-filter resonance based on single-state feedback control is widely used with voltage source converters. Its robustness against grid impedance variation has always been a major concern with its controller design. To deal with this issue, this paper begins by developing......, but ensures also a robust stabilization against the grid parameters variations. For illustration, the approach is applied to design three single-state feedback-damping schemes, and their damping robustness are compared under both inductive and resonant grid impedances. Experimental results validate...

  1. Common-Mode Voltage Reduction of Three-to-Five Phase Indirect Matrix Converters with Zero-Current Vector Modulation

    DEFF Research Database (Denmark)

    Zhang, Guanguan; Yang, Jian; Yang, Yongheng

    2017-01-01

    In order to reduce the Common-Mode Voltage (CMV) in three-to-five phase indirect matrix converters, three improved Space Vector Pulse Width Modulation (SVPWM) methods are proposed and discussed. The improved modulation schemes are achieved by reorganizing zero vectors from the inversion stage......) in the inversion stage, which results in a large amount of third-order harmonics in output currents. In addition, the method that utilizes two adjacent active current vectors (ACVs) and the method that uses two non-adjacent ACVs in the rectification stage have the same CMV peak value. By contrast, the latter...... achieves a lower Total Harmonic Distortion (THD) level of the output currents. Simulation results verify the effectiveness of the proposed methods....

  2. Mechanism of Estradiol-Induced Block of Voltage-Gated K+ Currents in Rat Medial Preoptic Neurons

    Science.gov (United States)

    Druzin, Michael; Malinina, Evgenya; Grimsholm, Ola; Johansson, Staffan

    2011-01-01

    The present study was conducted to characterize possible rapid effects of 17-β-estradiol on voltage-gated K+ channels in preoptic neurons and, in particular, to identify the mechanisms by which 17-β-estradiol affects the K+ channels. Whole-cell currents from dissociated rat preoptic neurons were studied by perforated-patch recording. 17-β-estradiol rapidly (within seconds) and reversibly reduced the K+ currents, showing an EC50 value of 9.7 µM. The effect was slightly voltage dependent, but independent of external Ca2+, and not sensitive to an estrogen-receptor blocker. Although 17-α-estradiol also significantly reduced the K+ currents, membrane-impermeant forms of estradiol did not reduce the K+ currents and other estrogens, testosterone and cholesterol were considerably less effective. The reduction induced by estradiol was overlapping with that of the KV-2-channel blocker r-stromatoxin-1. The time course of K+ current in 17-β-estradiol, with a time-dependent inhibition and a slight dependence on external K+, suggested an open-channel block mechanism. The properties of block were predicted from a computational model where 17-β-estradiol binds to open K+ channels. It was concluded that 17-β-estradiol rapidly reduces voltage-gated K+ currents in a way consistent with an open-channel block mechanism. This suggests a new mechanism for steroid action on ion channels. PMID:21625454

  3. Effect of high-voltage impulse current on the structure and function of rabbit heart

    Directory of Open Access Journals (Sweden)

    Xin-ping XU

    2011-06-01

    Full Text Available Objective To explore the effect of high-voltage impulse current(HVIC on the structure and function of rabbit heart.Methods Sixty healthy male rabbits were involved in present study and divided into 6 groups randomly(n=10.The rabbits were then shocked using a high-voltage pulse generator with current intensity of 0,50,100,150,250 and 500mA(pulse width 100μs,duration 5s respectively.The heart rate and electrocardiogram(ECG of rabbits were detected before and 0,1,3,7,14 and 28 days after the electric shock.Moreover,the myocardial tissue of rabbits was obtained immediately and 28 days after shock to observe the pathological changes.Results Immediately after electric shock of 50 to 500mA,the heart rate of rabbit increased by different degree,and the ECG showed arrhythmia,myocardial ischemia,atrial fibrillation and atrioventricular block,and the changes recovered gradually one day later.The pathological observation showed cell swelling,separation of myofibril and sarcoplasmic condensation of Purkinje fibers immediately after electric shock of 50 to 500mA,and the changes recovered 28 days after shock.The cardiac injuries aggravated with the increasing of current intensity,especially when it exceeded 150mA,and the recovery time prolonged.Conclusion High-voltage impulse current may induce recoverable injuries on heart structure and function,and the damage effect shows a correlation with the current intensity.

  4. Exploration of genetically encoded voltage indicators based on a chimeric voltage sensing domain

    Directory of Open Access Journals (Sweden)

    Yukiko eMishina

    2014-09-01

    Full Text Available Deciphering how the brain generates cognitive function from patterns of electrical signals is one of the ultimate challenges in neuroscience. To this end, it would be highly desirable to monitor the activities of very large numbers of neurons while an animal engages in complex behaviours. Optical imaging of electrical activity using genetically encoded voltage indicators (GEVIs has the potential to meet this challenge. Currently prevalent GEVIs are based on the voltage-sensitive fluorescent protein (VSFP prototypical design or on the voltage dependent state transitions of microbial opsins.We recently introduced a new VSFP design in which the voltage-sensing domain (VSD is sandwiched between a FRET pair of fluorescent proteins (termed VSFP-Butterflies and also demonstrated a series of chimeric VSD in which portions of the VSD of Ciona intestinalis voltage-sensitive phosphatase (Ci-VSP are substituted by homologous portions of a voltage-gated potassium channel subunit. These chimeric VSD had faster sensing kinetics than that of the native Ci-VSD. Here, we describe a new set of VSFPs that combine chimeric VSD with the Butterfly structure. We show that these chimeric VSFP-Butterflies can report membrane voltage oscillations of up to 200 Hz in cultured cells and report sensory evoked cortical population responses in living mice. This class of GEVIs may be suitable for imaging of brain rhythms in behaving mammalians.

  5. Exploration of genetically encoded voltage indicators based on a chimeric voltage sensing domain.

    Science.gov (United States)

    Mishina, Yukiko; Mutoh, Hiroki; Song, Chenchen; Knöpfel, Thomas

    2014-01-01

    Deciphering how the brain generates cognitive function from patterns of electrical signals is one of the ultimate challenges in neuroscience. To this end, it would be highly desirable to monitor the activities of very large numbers of neurons while an animal engages in complex behaviors. Optical imaging of electrical activity using genetically encoded voltage indicators (GEVIs) has the potential to meet this challenge. Currently prevalent GEVIs are based on the voltage-sensitive fluorescent protein (VSFP) prototypical design or on the voltage-dependent state transitions of microbial opsins. We recently introduced a new VSFP design in which the voltage-sensing domain (VSD) is sandwiched between a fluorescence resonance energy transfer pair of fluorescent proteins (termed VSFP-Butterflies) and also demonstrated a series of chimeric VSD in which portions of the VSD of Ciona intestinalis voltage-sensitive phosphatase are substituted by homologous portions of a voltage-gated potassium channel subunit. These chimeric VSD had faster sensing kinetics than that of the native Ci-VSD. Here, we describe a new set of VSFPs that combine chimeric VSD with the Butterfly structure. We show that these chimeric VSFP-Butterflies can report membrane voltage oscillations of up to 200 Hz in cultured cells and report sensory evoked cortical population responses in living mice. This class of GEVIs may be suitable for imaging of brain rhythms in behaving mammalians.

  6. A Circulating-Current Suppression Method for Parallel-Connected Voltage-Source Inverters With Common DC and AC Buses

    DEFF Research Database (Denmark)

    Wei, Baoze; Guerrero, Josep M.; Quintero, Juan Carlos Vasquez

    2017-01-01

    This paper presents a theoretical study with experimental validation of a circulating-current suppression method for parallel operation of three-phase voltage source inverters (VSI), which may be suitable for modular parallel uninterruptible power supply systems or hybrid AC/DC microgrid applicat......This paper presents a theoretical study with experimental validation of a circulating-current suppression method for parallel operation of three-phase voltage source inverters (VSI), which may be suitable for modular parallel uninterruptible power supply systems or hybrid AC/DC microgrid......, and added into the conventional droop plus virtual impedance control. In the control architecture, the reference voltages of the inverters are generated by the primary control loop which consists of a droop control and a virtual impedance. The secondary control is used to compensate the voltage drop...

  7. Multiple current peaks in room-temperature atmospheric pressure homogenous dielectric barrier discharge plasma excited by high-voltage tunable nanosecond pulse in air

    Energy Technology Data Exchange (ETDEWEB)

    Yang, De-Zheng; Wang, Wen-Chun; Zhang, Shuai; Tang, Kai; Liu, Zhi-jie; Wang, Sen [Key Lab of Materials Modification, Dalian University of Technology, Ministry of Education, Dalian 116024 (China)

    2013-05-13

    Room temperature homogenous dielectric barrier discharge plasma with high instantaneous energy efficiency is acquired by using nanosecond pulse voltage with 20-200 ns tunable pulse width. Increasing the voltage pulse width can lead to the generation of regular and stable multiple current peaks in each discharge sequence. When the voltage pulse width is 200 ns, more than 5 organized current peaks can be observed under 26 kV peak voltage. Investigation also shows that the organized multiple current peaks only appear in homogenous discharge mode. When the discharge is filament mode, organized multiple current peaks are replaced by chaotic filament current peaks.

  8. The Hv1 proton channel responds to mechanical stimuli.

    Science.gov (United States)

    Pathak, Medha M; Tran, Truc; Hong, Liang; Joós, Béla; Morris, Catherine E; Tombola, Francesco

    2016-11-01

    The voltage-gated proton channel, Hv1, is expressed in tissues throughout the body and plays important roles in pH homeostasis and regulation of NADPH oxidase. Hv1 operates in membrane compartments that experience strong mechanical forces under physiological or pathological conditions. In microglia, for example, Hv1 activity is potentiated by cell swelling and causes an increase in brain damage after stroke. The channel complex consists of two proton-permeable voltage-sensing domains (VSDs) linked by a cytoplasmic coiled-coil domain. Here, we report that these VSDs directly respond to mechanical stimuli. We find that membrane stretch facilitates Hv1 channel opening by increasing the rate of activation and shifting the steady-state activation curve to less depolarized potentials. In the presence of a transmembrane pH gradient, membrane stretch alone opens the channel without the need for strong depolarizations. The effect of membrane stretch persists for several minutes after the mechanical stimulus is turned off, suggesting that the channel switches to a "facilitated" mode in which opening occurs more readily and then slowly reverts to the normal mode observed in the absence of membrane stretch. Conductance simulations with a six-state model recapitulate all the features of the channel's response to mechanical stimulation. Hv1 mechanosensitivity thus provides a mechanistic link between channel activation in microglia and brain damage after stroke. © 2016 Pathak et al.

  9. Comparison of short-lived medical isotopes activation by laser thin target induced protons and conventional cyclotron proton beams

    Science.gov (United States)

    Murray, Joseph; Dudnikova, Galina; Liu, Tung-Chang; Papadopoulos, Dennis; Sagdeev, Roald; Su, J. J.; UMD MicroPET Team

    2014-10-01

    Production diagnostic or therapeutic nuclear medicines are either by nuclear reactors or by ion accelerators. In general, diagnostic nuclear radioisotopes have a very short half-life varying from tens of minutes for PET tracers and few hours for SPECT tracers. Thus supplies of PET and SPECT radiotracers are limited by regional production facilities. For example 18F-fluorodeoxyglucose (FDG) is the most desired tracer for positron emission tomography because its 110 minutes half-life is sufficient long for transport from production facilities to nearby users. From nuclear activation to completing image taking must be done within 4 hours. Decentralized production of diagnostic radioisotopes will be idea to make high specific activity radiotracers available to researches and clinicians. 11 C, 13 N, 15 O and 18 F can be produced in the energy range from 10-20 MeV by protons. Protons of energies up to tens of MeV generated by intense laser interacting with hydrogen containing targets have been demonstrated by many groups in the past decade. We use 2D PIC code for proton acceleration, Geant4 Monte Carlo code for nuclei activation to compare the yields and specific activities of short-lived isotopes produced by cyclotron proton beams and laser driven protons.

  10. Frequency-Controlled Current-Fed Resonant Converter with No Input Ripple Current

    Directory of Open Access Journals (Sweden)

    Bor-Ren Lin

    2018-02-01

    Full Text Available This paper studies a frequency-controlled current-fed resonant circuit. The adopted direct current (DC-to-DC converter contains two boost circuits and a resonant circuit on the primary side. First, two boost circuits are connected in parallel to achieve voltage step-up and reduce input ripple current by using interleaved pulse-width modulation. Therefore, the size and current rating of boost inductors are decreased in the proposed converter. Second, the boost voltage is connected to the resonant circuit to realize the mechanism of the zero-voltage switching of all active switches and zero-current switching of all diodes. Two boost circuits and a resonant circuit use the same power devices in order to lessen the switch counts. The voltage doubler topology is adopted on the secondary side (high-voltage side. Therefore, the voltage rating of diodes on the high-voltage side is clamped at output voltage. The feasibility of the studied circuit is confirmed by the experimental tests with a 1 kW prototype circuit.

  11. Flexible operation of parallel grid-connecting converters under unbalanced grid voltage

    DEFF Research Database (Denmark)

    Lu, Jinghang; Savaghebi, Mehdi; Guerrero, Josep M.

    2017-01-01

    -link voltage ripple, and overloading. Moreover, under grid voltage unbalance, the active power delivery ability is decreased due to the converter's current rating limitation. In this paper, a thorough study on the current limitation of the grid-connecting converter under grid voltage unbalance is conducted....... In addition, based on the principle that total output active power should be oscillation free, a coordinated control strategy is proposed for the parallel grid-connecting converters. The case study has been conducted to demonstrate the effectiveness of this proposed control strategy....

  12. Correlation of the antimicrobial activity of salicylaldehydes with broadening of the NMR signal of the hydroxyl proton. Possible involvement of proton exchange processes in the antimicrobial activity.

    Science.gov (United States)

    Elo, Hannu; Kuure, Matti; Pelttari, Eila

    2015-03-06

    Certain substituted salicylaldehydes are potent antibacterial and antifungal agents and some of them merit consideration as potential chemotherapeutic agents against Candida infections, but their mechanism of action has remained obscure. We report here a distinct correlation between broadening of the NMR signal of the hydroxyl proton of salicylaldehydes and their activity against several types of bacteria and fungi. When proton NMR spectra of the compounds were determined using hexadeuterodimethylsulfoxide as solvent and the height of the OH proton signal was measured, using the signal of the aldehyde proton as an internal standard, it was discovered that a prerequisite of potent antimicrobial activity is that the proton signal is either unobservable or relatively very low, i.e. that it is extremely broadened. Thus, none of the congeners whose OH proton signal was high were potent antimicrobial agents. Some congeners that gave a very low OH signal were, however, essentially inactive against the microbes, indicating that although drastic broadening of the OH signal appears to be a prerequisite, also other (so far unknown) factors are needed for high antimicrobial activity. Because broadening of the hydroxyl proton signal is related to the speed of the proton exchange process(es) involving that proton, proton exchange may be involved in the mechanism of action of the compounds. Further studies are needed to analyze the relative importance of different factors (such as electronic effects, strength of the internal hydrogen bond, co-planarity of the ring and the formyl group) that determine the rates of those processes. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  13. Current-voltage characteristics of carbon nanostructured field emitters in different power supply modes

    Science.gov (United States)

    Popov, E. O.; Kolosko, A. G.; Filippov, S. V.; Romanov, P. A.; Terukov, E. I.; Shchegolkov, A. V.; Tkachev, A. G.

    2017-12-01

    We received and compared the current-voltage characteristics of large-area field emitters based on nanocomposites with graphene and nanotubes. The characteristics were measured in two high voltage scanning modes: the "slow" and the "fast". Correlation between two types of hysteresis observed in these regimes was determined. Conditions for transition from "reverse" hysteresis to the "direct" one were experimentally defined. Analysis of the eight-shaped hysteresis was provided with calculation of the effective emission parameters. The phenomenological model of adsorption-desorption processes in the field emission system was proposed.

  14. Monitoring of the submerged arc welding process using current and voltage transducers

    International Nuclear Information System (INIS)

    Barrera, G.; Velez, M.; Espinosa, M.A.; Santos, O.; Barrera, E.; Gomez, G.

    1996-01-01

    Welding by fusion is one of the most used techniques to join materials in the manufacture industry. given the increase in applications of this welding process and the demand of more quality in the welding deposits, these welding processes are good candidates for the improvement of their instrumentation and control. Any improvement in the control technique will have a positive effect in the quality and productivity of the welding process. Some of the most significant variables in the submerged arc welding process are: current, voltage and torch speed. For the instrumentation of this research work, two transducers were designed, one for CD current monitoring and one for CD voltage monitoring of the welding machine. The design of both transducers includes an isolation amplifier. Graphical programming and the concept of virtual instrumentation were the main tools used for the design of the data acquisition system and the signal processing task. (Author) 9 refs

  15. Method and apparatus for remote tube crevice detection by current and voltage probe resistance measurement

    Science.gov (United States)

    Kikta, Thomas J.; Mitchell, Ronald D.

    1992-01-01

    A method and apparatus for determining the extent of contact between an electrically conducting tube and an electrically conductive tubesheet surrounding the tube, based upon the electrical resistance of the tube and tubesheet. A constant current source is applied to the interior of the electrically conducting tube by probes and a voltmeter is connected between other probes to measure the voltage at the point of current injection, which is inversely proportional to the amount of contact between the tube and tubesheet. Namely, the higher the voltage measured by the voltmeter, the less contact between the tube and tubesheet.

  16. A novel concept of fault current limiter based on saturable core in high voltage DC transmission system

    Science.gov (United States)

    Yuan, Jiaxin; Zhou, Hang; Gan, Pengcheng; Zhong, Yongheng; Gao, Yanhui; Muramatsu, Kazuhiro; Du, Zhiye; Chen, Baichao

    2018-05-01

    To develop mechanical circuit breaker in high voltage direct current (HVDC) system, a fault current limiter is required. Traditional method to limit DC fault current is to use superconducting technology or power electronic devices, which is quite difficult to be brought to practical use under high voltage circumstances. In this paper, a novel concept of high voltage DC transmission system fault current limiter (DCSFCL) based on saturable core was proposed. In the DCSFCL, the permanent magnets (PM) are added on both up and down side of the core to generate reverse magnetic flux that offset the magnetic flux generated by DC current and make the DC winding present a variable inductance to the DC system. In normal state, DCSFCL works as a smoothing reactor and its inductance is within the scope of the design requirements. When a fault occurs, the inductance of DCSFCL rises immediately and limits the steepness of the fault current. Magnetic field simulations were carried out, showing that compared with conventional smoothing reactor, DCSFCL can decrease the high steepness of DC fault current by 17% in less than 10ms, which verifies the feasibility and effectiveness of this method.

  17. Water Electrolysis at Different Current - Voltage Regimes

    International Nuclear Information System (INIS)

    Kleperis, J.; Blums, J.; Vanags, M.

    2007-01-01

    Full text: Electrochemical impedance and volt-amperic methods were used to compare an efficiency of water electrolysis for different materials and different electrode configurations. Two and three electrode measurements were made, using standard calomel reference electrode. Non-standard capacitative electrolysis was analyzed in special cell made from cylindrical steel electrodes. Volt-amperic measurements from - 15V to +15V DC didn't indicated the presence of oxidation - reduction reactions when distilled water was used as electrolyte. Impedance measurements showed unusual frequency behavior when the AC voltage increased till 0.5V. Different nickel and carbon electrodes (plate, porous and textile - type) were used to learn classical Faraday electrolysis in strong alkali solutions. Flying increase of current was indicator of the presence of electrolysis, and characteristic potential was used differ between materials accordingly they effectiveness for usage in an electrolyser device. (Aithors)

  18. Proton-air and proton-proton cross sections

    Directory of Open Access Journals (Sweden)

    Ulrich Ralf

    2013-06-01

    Full Text Available Different attempts to measure hadronic cross sections with cosmic ray data are reviewed. The major results are compared to each other and the differences in the corresponding analyses are discussed. Besides some important differences, it is crucial to see that all analyses are based on the same fundamental relation of longitudinal air shower development to the observed fluctuation of experimental observables. Furthermore, the relation of the measured proton-air to the more fundamental proton-proton cross section is discussed. The current global picture combines hadronic proton-proton cross section data from accelerator and cosmic ray measurements and indicates a good consistency with predictions of models up to the highest energies.

  19. Proton gradients and proton-dependent transport processes in the chloroplast

    Directory of Open Access Journals (Sweden)

    Ricarda eHöhner

    2016-02-01

    Full Text Available Proton gradients are fundamental to chloroplast function. Across thylakoid membranes, the light induced proton gradient is essential for ATP synthesis. As a result of proton pumping into the thylakoid lumen, an alkaline stromal pH develops, which is required for full activation of pH-dependent Calvin Benson cycle enzymes. This implies that a pH gradient between the cytosol (pH 7 and the stroma (pH 8 is established upon illumination. To maintain this pH gradient chloroplasts actively extrude protons. More than 30 years ago it was already established that these proton fluxes are electrically counterbalanced by Mg2+, K+ or Cl- fluxes, but only recently the first transport systems that regulate the pH gradient were identified. Notably several (Na+,K+/H+ antiporter systems where identified, that play a role in pH gradient regulation, ion homeostasis, osmoregulation, or coupling of secondary active transport. The established pH gradients are important to drive uptake of essential ions and solutes, but not many transporters involved have been identified to date. In this mini review we summarize the current status in the field and the open questions that need to be addressed in order to understand how pH gradients are maintained, how this is interconnected with other transport processes and what this means for chloroplast function.

  20. Current-voltage characteristics of dendrimer light-emitting diodes

    International Nuclear Information System (INIS)

    Stevenson, S G; Samuel, I D W; Staton, S V; Knights, K A; Burn, P L; Williams, J H T; Walker, Alison B

    2010-01-01

    We have investigated current-voltage (I-V) characteristics of unipolar and bipolar organic diodes that use phosphorescent dendrimers as the emissive organic layer. Through simulation of the measured I-V characteristics we were able to determine the device parameters for each device structure studied, leading to a better understanding of injection and transport behaviour in these devices. It was found that the common practice of assuming injection barriers are equal to the difference between bare electrode work functions and molecular orbital levels is unsuitable for the devices considered here, particularly for gold contacts. The studies confirm that different aromatic units in the dendrons can give significant differences in the charge transporting properties of the dendrimers.

  1. Current-voltage characteristics of dendrimer light-emitting diodes

    Science.gov (United States)

    Stevenson, S. G.; Samuel, I. D. W.; Staton, S. V.; Knights, K. A.; Burn, P. L.; Williams, J. H. T.; Walker, Alison B.

    2010-09-01

    We have investigated current-voltage (I-V) characteristics of unipolar and bipolar organic diodes that use phosphorescent dendrimers as the emissive organic layer. Through simulation of the measured I-V characteristics we were able to determine the device parameters for each device structure studied, leading to a better understanding of injection and transport behaviour in these devices. It was found that the common practice of assuming injection barriers are equal to the difference between bare electrode work functions and molecular orbital levels is unsuitable for the devices considered here, particularly for gold contacts. The studies confirm that different aromatic units in the dendrons can give significant differences in the charge transporting properties of the dendrimers.

  2. Current-voltage characteristics of dendrimer light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Stevenson, S G; Samuel, I D W [Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS (United Kingdom); Staton, S V; Knights, K A; Burn, P L [Department of Chemistry, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA (United Kingdom); Williams, J H T; Walker, Alison B, E-mail: a.b.walker@bath.ac.u [Department of Physics, University of Bath, Bath, BA2 7AY (United Kingdom)

    2010-09-29

    We have investigated current-voltage (I-V) characteristics of unipolar and bipolar organic diodes that use phosphorescent dendrimers as the emissive organic layer. Through simulation of the measured I-V characteristics we were able to determine the device parameters for each device structure studied, leading to a better understanding of injection and transport behaviour in these devices. It was found that the common practice of assuming injection barriers are equal to the difference between bare electrode work functions and molecular orbital levels is unsuitable for the devices considered here, particularly for gold contacts. The studies confirm that different aromatic units in the dendrons can give significant differences in the charge transporting properties of the dendrimers.

  3. Electrooptic Methods for Measurement of Small DC Currents at High Voltage Level

    DEFF Research Database (Denmark)

    Tønnesen, Ole; Beatty, Neville; Skilbreid, Asbjørn Ottar

    1989-01-01

    collectors are connected via resistors RA and RB to the protective side of the voltage to be measured and the emitters to the negative side. The currents flowing in to the bases of the transistors are independently controlled by the light levels following on the two photodiodes PDA, PDB....

  4. Impact of proton irradiation on deep level states in n-GaN

    International Nuclear Information System (INIS)

    Zhang, Z.; Arehart, A. R.; Cinkilic, E.; Ringel, S. A.; Chen, J.; Zhang, E. X.; Fleetwood, D. M.; Schrimpf, R. D.; McSkimming, B.; Speck, J. S.

    2013-01-01

    Deep levels in 1.8 MeV proton irradiated n-type GaN were systematically characterized using deep level transient spectroscopies and deep level optical spectroscopies. The impacts of proton irradiation on the introduction and evolution of those deep states were revealed as a function of proton fluences up to 1.1 × 10 13 cm −2 . The proton irradiation introduced two traps with activation energies of E C - 0.13 eV and 0.16 eV, and a monotonic increase in the concentration for most of the pre-existing traps, though the increase rates were different for each trap, suggesting different physical sources and/or configurations for these states. Through lighted capacitance voltage measurements, the deep levels at E C - 1.25 eV, 2.50 eV, and 3.25 eV were identified as being the source of systematic carrier removal in proton-damaged n-GaN as a function of proton fluence

  5. 16 CFR Figures 1 and 2 to Part 1204 - Suggested Instrumentation for Current Monitoring Device and High Voltage Facility

    Science.gov (United States)

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Suggested Instrumentation for Current Monitoring Device and High Voltage Facility 1 Figures 1 and 2 to Part 1204 Commercial Practices CONSUMER... Instrumentation for Current Monitoring Device and High Voltage Facility EC03OC91.008 ...

  6. Interactions Between Indirect DC-Voltage Estimation and Circulating Current Controllers of MMC-Based HVDC Transmission Systems

    DEFF Research Database (Denmark)

    Wickramasinghe, Harith R.; Konstantinou, Georgios; Pou, Josep

    2018-01-01

    Estimation-based indirect dc-voltage control in MMCs interacts with circulating current control methods. This paper proposes an estimation-based indirect dc-voltage control method for MMC-HVDC systems and analyzes its performance compared to alternative estimations. The interactions between......-state and transient performance is demonstrated using a benchmark MMC-HVDC transmission system, implemented in a real-time digital simulator. The results verify the theoretical evaluations and illustrate the operation and performance of the proposed indirect dc-voltage control method....

  7. Featuring of transient tunneling current by voltage pulse and application to an electrochemical biosensor

    Science.gov (United States)

    Yun, Jun Yeon; Lee, Won Cheol; Choi, Seong Wook; Park, Young June

    2018-03-01

    We suggest a voltage pulse method for detecting the transient tunneling current component (faradaic current component) in a metal/redox-active monolayer/electrolyte system. After applying the pulse to the metal electrode, the capacitive current prevails; therefore, it is difficult to extract the tunneling current, which carries information on the biochemical reactions occurring between the biomarkers in the electrolyte and the self-assembled monolayer (SAM) as the probe peptide system. Instead of waiting until the capacitive current diminishes, and thereby, the tunneling current also decreases, we try to extract the tunneling current in an early stage of the pulse. The method is based on the observation that the capacitive current becomes symmetrized in the positive and negative pulses after introducing the SAM on the metal electrode. When the energy level of the redox molecule is higher than the Fermi level of the metal under zero-bias condition, the tunneling current in the negative pulse can be extracted by subtracting the capacitive current obtained from the positive pulse, where the tunneling current is neglected. The experiment conducted for detecting trypsin as a biomarker shows that the method enhances the sensitivity and the specific-to-nonspecific ratio of the sensor device in the case of the nonspecific protein-abundant electrolyte solution, as evinced by cyclic voltammetry measurements in comparison.

  8. Activation cross-section measurements of some proton induced reactions on Ni, Co and Mo for proton activation analysis (PAA) purposes

    International Nuclear Information System (INIS)

    Alharbi, A.A.; Alzahrani, J.; Azzam, A.; Nuclear Research Center, Cairo

    2011-01-01

    The experimental proton induced reaction cross sections on some elements of the Havar alloy were measured using the activation method and the well established stacked-foil technique combined with high resolution gamma-ray spectroscopy. They included the reactions nat Ni(p,x) 57 Ni, nat Co(p,x) 58(m+g) Co and nat Mo(p,x) 94g,95g,96(m+g) Tc, the aim being to obtain reliable data in the proton energy range up to 26 MeV for some important reactions to be used in the proton activation analysis of steel or other alloys. Irradiations were performed using the CS-30 Cyclotron at KFSH and RC, Riyadh, Saudi Arabia. The activity measurements were carried out in PNU laboratories, Riyadh, Saudi Arabia. The experimental excitation functions for the investigated reactions were constructed and compared with the performed computed theoretical nuclear model calculations using two different codes: ALICE-IPPE and TALYS. A comparison between our measured cross-section values and the available published data is also presented, with a view to checking the consistency of the reported experimental work from various laboratories.

  9. Low-Cost Open-Source Voltage and Current Monitor for Gas Metal Arc Weld 3D Printing

    Directory of Open Access Journals (Sweden)

    A. Pinar

    2015-01-01

    Full Text Available Arduino open-source microcontrollers are well known in sensor applications for scientific equipment and for controlling RepRap 3D printers. Recently low-cost open-source gas metal arc weld (GMAW RepRap 3D printers have been developed. The entry-level welders used have minimal controls and therefore lack any real-time measurement of welder voltage or current. The preliminary work on process optimization of GMAW 3D printers requires a low-cost sensor and data logger system to measure welder current and voltage. This paper reports on the development of a low-cost open-source power measurement sensor system based on Arduino architecture. The sensor system was designed, built, and tested with two entry-level MIG welders. The full bill of materials and open source designs are provided. Voltage and current were measured while making stepwise adjustments to the manual voltage setting on the welder. Three conditions were tested while welding with steel and aluminum wire on steel substrates to assess the role of electrode material, shield gas, and welding velocity. The results showed that the open source sensor circuit performed as designed and could be constructed for <$100 in components representing a significant potential value through lateral scaling and replication in the 3D printing community.

  10. Constant voltage and constant current control implementation for electric vehicles (evs) wireless charger

    Science.gov (United States)

    Tampubolon, Marojahan; Pamungkas, Laskar; Hsieh, Yao Ching; Chiu, Huang Jen

    2018-04-01

    This paper presents the implementation of Constant Voltage (CV) and Constant Current (CC) control for a wireless charger system. A battery charging system needs these control modes to ensure the safety of the battery and the effectiveness of the charging system. Here, the wireless charger system does not employ any post-regulator stage to control the output voltage and output current of the charger. But, it uses a variable frequency control incorporated with a conventional PI control. As a result, the size and the weight of the system are reduced. This paper discusses the brief review of the SS-WPT, control strategy and implementation of the CV and CC control. Experimental hardware with 2kW output power has been performed and tested. The results show that the proposed CV and CC control method works well with the system.

  11. Proton production, neutralisation and reduction in a floating water bridge

    International Nuclear Information System (INIS)

    Sammer, Martina; Wexler, Adam D; Kuntke, Philipp; Stanulewicz, Natalia; Lankmayr, Ernst; Woisetschläger, Jakob; Fuchs, Elmar C; Wiltsche, Helmar

    2015-01-01

    This work reports on proton production, transport, reduction and neutralization in floating aqueous bridges under the application of a high dc voltage (‘floating water bridge’). Recently possible mechanisms for proton transfer through the bridge were suggested. In this work we visualize and describe the production of protons in the anolyte and their neutralization in the catholyte. Apart from that, protons are reduced to hydrogen due to electrolysis. Microbubbles are detached instantly, due to the electrohydrodynamic flow at the electrode surface. No larger, visible bubbles are formed and the system degasses through the bridge due to its higher local temperature. A detailed analysis of trace elements originating from beaker material, anode or the atmosphere is presented, showing that their influence on the overall conduction compared to the contribution of protons is negligible. Finally, an electrochemical rationale of high voltage electrolysis of low ionic strength solutions is presented. (paper)

  12. Proton production, neutralisation and reduction in a floating water bridge

    Science.gov (United States)

    Sammer, Martina; Wexler, Adam D.; Kuntke, Philipp; Wiltsche, Helmar; Stanulewicz, Natalia; Lankmayr, Ernst; Woisetschläger, Jakob; Fuchs, Elmar C.

    2015-10-01

    This work reports on proton production, transport, reduction and neutralization in floating aqueous bridges under the application of a high dc voltage (‘floating water bridge’). Recently possible mechanisms for proton transfer through the bridge were suggested. In this work we visualize and describe the production of protons in the anolyte and their neutralization in the catholyte. Apart from that, protons are reduced to hydrogen due to electrolysis. Microbubbles are detached instantly, due to the electrohydrodynamic flow at the electrode surface. No larger, visible bubbles are formed and the system degasses through the bridge due to its higher local temperature. A detailed analysis of trace elements originating from beaker material, anode or the atmosphere is presented, showing that their influence on the overall conduction compared to the contribution of protons is negligible. Finally, an electrochemical rationale of high voltage electrolysis of low ionic strength solutions is presented.

  13. Voltage-Dependent Gating of hERG Potassium Channels

    Science.gov (United States)

    Cheng, Yen May; Claydon, Tom W.

    2012-01-01

    The mechanisms by which voltage-gated channels sense changes in membrane voltage and energetically couple this with opening of the ion conducting pore has been the source of significant interest. In voltage-gated potassium (Kv) channels, much of our knowledge in this area comes from Shaker-type channels, for which voltage-dependent gating is quite rapid. In these channels, activation and deactivation are associated with rapid reconfiguration of the voltage-sensing domain unit that is electromechanically coupled, via the S4–S5 linker helix, to the rate-limiting opening of an intracellular pore gate. However, fast voltage-dependent gating kinetics are not typical of all Kv channels, such as Kv11.1 (human ether-à-go-go related gene, hERG), which activates and deactivates very slowly. Compared to Shaker channels, our understanding of the mechanisms underlying slow hERG gating is much poorer. Here, we present a comparative review of the structure–function relationships underlying activation and deactivation gating in Shaker and hERG channels, with a focus on the roles of the voltage-sensing domain and the S4–S5 linker that couples voltage sensor movements to the pore. Measurements of gating current kinetics and fluorimetric analysis of voltage sensor movement are consistent with models suggesting that the hERG activation pathway contains a voltage independent step, which limits voltage sensor transitions. Constraints upon hERG voltage sensor movement may result from loose packing of the S4 helices and additional intra-voltage sensor counter-charge interactions. More recent data suggest that key amino acid differences in the hERG voltage-sensing unit and S4–S5 linker, relative to fast activating Shaker-type Kv channels, may also contribute to the increased stability of the resting state of the voltage sensor. PMID:22586397

  14. Dual Regulation of Voltage-Sensitive Ion Channels by PIP2

    Directory of Open Access Journals (Sweden)

    Aldo A Rodríguez Menchaca

    2012-09-01

    Full Text Available Over the past 16 years, there has been an impressive number of ion channels shown to be sensitive to the major phosphoinositide in the plasma membrane, phosphatidilinositol 4,5-bisphosphate (PIP2. Among them are voltage-gated channels, which are crucial for both neuronal and cardiac excitability. Voltage-gated calcium (Cav channels were shown to be regulated bidirectionally by PIP2. On one hand, PIP2 stabilized their activity by reducing current rundown but on the other hand it produced a voltage-dependent inhibition by shifting the activation curve to more positive voltages. For voltage-gated potassium (Kv channels PIP2 was first shown to prevent N-type inactivation. Careful examination of the effects of PIP2 on the activation mechanism of Kv1.2 has shown a similar bidirectional regulation as in the Cav channels. The two effects could be distinguished kinetically, in terms of their sensitivities to PIP2 and by distinct molecular determinants. The rightward shift of the Kv1.2 voltage dependence implicated basic residues in the S4-S5 linker and was consistent with stabilization of the inactive state of the voltage sensor. A third type of a voltage-gated ion channel modulated by PIP2 is the hyperpolarization-activated cyclic nucleotide-gated (HCN channel. PIP2 has been shown to enhance the opening of HCN channels by shifting their voltage-dependent activation toward depolarized potentials. The sea urchin HCN channel, SpIH, showed again a PIP2-mediated bidirectional effect but in reverse order than the depolarization-activated Cav and Kv channels: a voltage-dependent potentiation, like the mammalian HCN channels, but also an inhibition of the cGMP-induced current activation. Just like the Kv1.2 channels, distinct molecular determinants underlied the PIP2 dual effects on SpIH channels. The dual regulation of these very different ion channels, all of which are voltage dependent, points to conserved mechanisms of regulation of these channels by PIP2.

  15. Effect of cytosolic pH on inward currents reveals structural characteristics of the proton transport cycle in the influenza A protein M2 in cell-free membrane patches of Xenopus oocytes.

    Directory of Open Access Journals (Sweden)

    Mattia L DiFrancesco

    Full Text Available Transport activity through the mutant D44A of the M2 proton channel from influenza virus A was measured in excised inside-out macro-patches of Xenopus laevis oocytes at cytosolic pH values of 5.5, 7.5 and 8.2. The current-voltage relationships reveal some peculiarities: 1. "Transinhibition", i.e., instead of an increase of unidirectional outward current with increasing cytosolic H(+ concentration, a decrease of unidirectional inward current was found. 2. Strong inward rectification. 3. Exponential rise of current with negative potentials. In order to interpret these findings in molecular terms, different kinetic models have been tested. The transinhibition basically results from a strong binding of H(+ to a site in the pore, presumably His37. This assumption alone already provides inward rectification and exponential rise of the IV curves. However, it results in poor global fits of the IV curves, i.e., good fits were only obtained for cytosolic pH of 8.2, but not for 7.5. Assuming an additional transport step as e.g. caused by a constriction zone at Val27 resulted in a negligible improvement. In contrast, good global fits for cytosolic pH of 7.5 and 8.2 were immediately obtained with a cyclic model. A "recycling step" implies that the protein undergoes conformational changes (assigned to Trp41 and Val27 during transport which have to be reset before the next proton can be transported. The global fit failed at the low currents at pHcyt = 5.5, as expected from the interference of putative transport of other ions besides H(+. Alternatively, a regulatory effect of acidic cytosolic pH may be assumed which strongly modifies the rate constants of the transport cycle.

  16. A uniform laminar air plasma plume with large volume excited by an alternating current voltage

    Science.gov (United States)

    Li, Xuechen; Bao, Wenting; Chu, Jingdi; Zhang, Panpan; Jia, Pengying

    2015-12-01

    Using a plasma jet composed of two needle electrodes, a laminar plasma plume with large volume is generated in air through an alternating current voltage excitation. Based on high-speed photography, a train of filaments is observed to propagate periodically away from their birth place along the gas flow. The laminar plume is in fact a temporal superposition of the arched filament train. The filament consists of a negative glow near the real time cathode, a positive column near the real time anode, and a Faraday dark space between them. It has been found that the propagation velocity of the filament increases with increasing the gas flow rate. Furthermore, the filament lifetime tends to follow a normal distribution (Gaussian distribution). The most probable lifetime decreases with increasing the gas flow rate or decreasing the averaged peak voltage. Results also indicate that the real time peak current decreases and the real time peak voltage increases with the propagation of the filament along the gas flow. The voltage-current curve indicates that, in every discharge cycle, the filament evolves from a Townsend discharge to a glow one and then the discharge quenches. Characteristic regions including a negative glow, a Faraday dark space, and a positive column can be discerned from the discharge filament. Furthermore, the plasma parameters such as the electron density, the vibrational temperature and the gas temperature are investigated based on the optical spectrum emitted from the laminar plume.

  17. Characterizing proton-activated materials to develop PET-mediated proton range verification markers

    Science.gov (United States)

    Cho, Jongmin; Ibbott, Geoffrey S.; Kerr, Matthew D.; Amos, Richard A.; Stingo, Francesco C.; Marom, Edith M.; Truong, Mylene T.; Palacio, Diana M.; Betancourt, Sonia L.; Erasmus, Jeremy J.; DeGroot, Patricia M.; Carter, Brett W.; Gladish, Gregory W.; Sabloff, Bradley S.; Benveniste, Marcelo F.; Godoy, Myrna C.; Patil, Shekhar; Sorensen, James; Mawlawi, Osama R.

    2016-06-01

    Conventional proton beam range verification using positron emission tomography (PET) relies on tissue activation alone and therefore requires particle therapy PET whose installation can represent a large financial burden for many centers. Previously, we showed the feasibility of developing patient implantable markers using high proton cross-section materials (18O, Cu, and 68Zn) for in vivo proton range verification using conventional PET scanners. In this technical note, we characterize those materials to test their usability in more clinically relevant conditions. Two phantoms made of low-density balsa wood (~0.1 g cm-3) and beef (~1.0 g cm-3) were embedded with Cu or 68Zn foils of several volumes (10-50 mm3). The metal foils were positioned at several depths in the dose fall-off region, which had been determined from our previous study. The phantoms were then irradiated with different proton doses (1-5 Gy). After irradiation, the phantoms with the embedded foils were moved to a diagnostic PET scanner and imaged. The acquired data were reconstructed with 20-40 min of scan time using various delay times (30-150 min) to determine the maximum contrast-to-noise ratio. The resultant PET/computed tomography (CT) fusion images of the activated foils were then examined and the foils’ PET signal strength/visibility was scored on a 5 point scale by 13 radiologists experienced in nuclear medicine. For both phantoms, the visibility of activated foils increased in proportion to the foil volume, dose, and PET scan time. A linear model was constructed with visibility scores as the response variable and all other factors (marker material, phantom material, dose, and PET scan time) as covariates. Using the linear model, volumes of foils that provided adequate visibility (score 3) were determined for each dose and PET scan time. The foil volumes that were determined will be used as a guideline in developing practical implantable markers.

  18. Special features of the current-voltage characteristics of short superconducting bridges

    International Nuclear Information System (INIS)

    Zhilinskii, S.; Latyshev, Y.; Nad', F.

    1981-01-01

    A study was made of variable-thickness superconducting bridges made of tin and indium. The current-voltage characteristics were determined for these bridges as a function of their length and width. The characteristics exhibited a linear region as well as an inflection. The temperature of the appearance of such an inflection depended on the length of the bridge but was independent of the bridge material

  19. Zero-Sequence Voltage Modulation Strategy for Multiparallel Converters Circulating Current Suppression

    DEFF Research Database (Denmark)

    Zhu, Rongwu; Liserre, Marco; Chen, Zhe

    2017-01-01

    A zero-sequence circulating current (ZSCC) is typically generated among the multiparallel converters that share the common dc link and ac side without isolated transformers under the space vector modulation (SVM), due to the injected third-order zero-sequence voltage (ZSV). This paper analyzes SVM...... references and filter inductances. The simulation and experimental results based on the parallel converters clearly verify the effectiveness of the proposed control....

  20. A Novel Modulation Function-Based Control of Modular Multilevel Converters for High Voltage Direct Current Transmission Systems

    Directory of Open Access Journals (Sweden)

    Majid Mehrasa

    2016-10-01

    Full Text Available In this paper, a novel modulation function-based method including analyses of the modulation index and phase is proposed for operation of modular multilevel converters (MMCs in high voltage direct current (HVDC transmission systems. The proposed modulation function-based control technique is developed based on thorough and precise analyses of all MMC voltages and currents in the a-b-c reference frame in which the alternating current (AC-side voltage is the first target to be obtained. Using the AC-side voltage, the combination of the MMC upper and lower arm voltages is achieved as the main structure of the proposed modulation function. The main contribution of this paper is to obtain two very simple new modulation functions to control MMC performance in different operating conditions. The features of the modulation function-based control technique are as follows: (1 this control technique is very simple and can be easily achieved in a-b-c reference frame without the need of using Park transformation; and (2 in addition, the inherent properties of the MMC model are considered in the proposed control technique. Considering these properties leads to constructing a control technique that is robust against MMC parameters changes and also is a very good tracking method for the components of MMC input currents. These features lead to improving the operation of MMC significantly, which can act as a rectifier in the HVDC structure. The simulation studies are conducted through MATLAB/SIMULINK software, and the results obtained verify the effectiveness of the proposed modulation function-based control technique.

  1. Guest Editorial: Flexible Operation and Control for Medium Voltage Direct-Current (MVDC) Grid

    DEFF Research Database (Denmark)

    Li, Yong; Guerrero, Josep M.; Siano, Pierluigi

    2017-01-01

    We appreciate very much the support from the IET Power Electronics editorial board for this Special Issue on ‘Flexible Operation and Control for Medium Voltage Direct-Current (MVDC) Grid’. In this final version for publication, 15 papers have been selected for this Special Issue. Three papers...... relate to the topology of MVDC converter, four papers relate to the control of MVDC converter, four papers relate to the introduction of application fields of MVDC grid, and four papers relate to the semiconductor power device and drives towards the application in the medium- and high-voltage DC grid....

  2. The voltage-gated proton channel Hv1 is expressed in pancreatic islet β-cells and regulates insulin secretion

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Qing [Department of Biophysics, School of Physics Science, The Key Laboratory of Bioactive Materials, Ministry of Education, Nankai University, Tianjin 300071 (China); Che, Yongzhe [School of Medicine, Nankai University, Tianjin 300071 (China); Li, Qiang; Zhang, Shangrong [Department of Biophysics, School of Physics Science, The Key Laboratory of Bioactive Materials, Ministry of Education, Nankai University, Tianjin 300071 (China); Gao, Ying-Tang [Key Laboratory of Artificial Cell, Third Central Clinical College of Tianjin Medical University, Tianjin 300170 (China); Wang, Yifan; Wang, Xudong; Xi, Wang; Zuo, Weiyan [Department of Biophysics, School of Physics Science, The Key Laboratory of Bioactive Materials, Ministry of Education, Nankai University, Tianjin 300071 (China); Li, Shu Jie, E-mail: shujieli@nankai.edu.cn [Department of Biophysics, School of Physics Science, The Key Laboratory of Bioactive Materials, Ministry of Education, Nankai University, Tianjin 300071 (China)

    2015-12-25

    The voltage-gated proton channel Hv1 is a potent acid extruder that participates in the extrusion of the intracellular acid. Here, we showed for the first time, Hv1 is highly expressed in mouse and human pancreatic islet β-cells, as well as β-cell lines. Imaging studies demonstrated that Hv1 resides in insulin-containing granules in β-cells. Knockdown of Hv1 with RNA interference significantly reduces glucose- and K{sup +}-induced insulin secretion in isolated islets and INS-1 (832/13) β-cells and has an impairment on glucose- and K{sup +}-induced intracellular Ca{sup 2+} homeostasis. Our data demonstrated that the expression of Hv1 in pancreatic islet β-cells regulates insulin secretion through regulating Ca{sup 2+} homeostasis.

  3. Ion diode performance on a positive polarity inductive voltage adder with layered magnetically insulated transmission line flow

    International Nuclear Information System (INIS)

    Hinshelwood, D. D.; Schumer, J. W.; Allen, R. J.; Commisso, R. J.; Jackson, S. L.; Murphy, D. P.; Phipps, D.; Swanekamp, S. B.; Weber, B. V.; Ottinger, P. F.; Apruzese, J. P.; Cooperstein, G.; Young, F. C.

    2011-01-01

    A pinch-reflex ion diode is fielded on the pulsed-power machine Mercury (R. J. Allen, et al., 15th IEEE Intl. Pulsed Power Conf., Monterey, CA, 2005, p. 339), which has an inductive voltage adder (IVA) architecture and a magnetically insulated transmission line (MITL). Mercury is operated in positive polarity resulting in layered MITL flow as emitted electrons are born at a different potential in each of the adder cavities. The usual method for estimating the voltage by measuring the bound current in the cathode and anode of the MITL is not accurate with layered flow, and the interaction of the MITL flow with a pinched-beam ion diode load has not been studied previously. Other methods for determining the diode voltage are applied, ion diode performance is experimentally characterized and evaluated, and circuit and particle-in-cell (PIC) simulations are performed. Results indicate that the ion diode couples efficiently to the machine operating at a diode voltage of about 3.5 MV and a total current of about 325 kA, with an ion current of about 70 kA of which about 60 kA is proton current. It is also found that the layered flow impedance of the MITL is about half the vacuum impedance.

  4. Voltage-Mode All-Pass Filters Including Minimum Component Count Circuits

    Directory of Open Access Journals (Sweden)

    Sudhanshu Maheshwari

    2007-01-01

    Full Text Available This paper presents two new first-order voltage-mode all-pass filters using a single-current differencing buffered amplifier and four passive components. Each circuit is compatible to a current-controlled current differencing buffered amplifier with only two passive elements, thus resulting in two more circuits, which employ a capacitor, a resistor, and an active element, thus using a minimum of active and passive component counts. The proposed circuits possess low output impedance, and hence can be easily cascaded for voltage-mode systems. PSPICE simulation results are given to confirm the theory.

  5. Effect of selected factors on the current flow and voltage loss at ...

    African Journals Online (AJOL)

    In this paper, laboratory scale study was conducted to investigate the current flow and voltage loss at the electrodes in the electrochemical treatment of a tropical laterite. Three different tests using calcium chloride (CC) as anolyte and sodium chloride (SC) as catholyte (NC); SC as anolyte and Phosphoric acid (PA) as ...

  6. On-line Monitoring Device for High-voltage Switch Cabinet Partial Discharge Based on Pulse Current Method

    Science.gov (United States)

    Y Tao, S.; Zhang, X. Z.; Cai, H. W.; Li, P.; Feng, Y.; Zhang, T. C.; Li, J.; Wang, W. S.; Zhang, X. K.

    2017-12-01

    The pulse current method for partial discharge detection is generally applied in type testing and other off-line tests of electrical equipment at delivery. After intensive analysis of the present situation and existing problems of partial discharge detection in switch cabinets, this paper designed the circuit principle and signal extraction method for partial discharge on-line detection based on a high-voltage presence indicating systems (VPIS), established a high voltage switch cabinet partial discharge on-line detection circuit based on the pulse current method, developed background software integrated with real-time monitoring, judging and analyzing functions, carried out a real discharge simulation test on a real-type partial discharge defect simulation platform of a 10KV switch cabinet, and verified the sensitivity and validity of the high-voltage switch cabinet partial discharge on-line monitoring device based on the pulse current method. The study presented in this paper is of great significance for switch cabinet maintenance and theoretical study on pulse current method on-line detection, and has provided a good implementation method for partial discharge on-line monitoring devices for 10KV distribution network equipment.

  7. On the energy dependence of the relative contributions ionospheric and solar sources of the ring current protons

    International Nuclear Information System (INIS)

    Kovtyukh, A.

    2007-01-01

    The energy dependence of a fraction of ring current protons of i onospheric origin is calculated using the AMPTE/CCE data for a typical magnetic storm (D st = -120 nT). It is shown that at L = 6-7 (L is the Mcllwain parameter) this fraction monotonically decreases from ∼83 to 25-30% with an increase in proton energy from 5 to 315 keV and is 30-40% at energy 40-50 keV corresponding to the maximum of proton energy density at L 6-7. It is evident that the core of the ring current (L = 3.7-4.7) is enriched by solar protons with E∼10-200 keV during storm main phase (the maximum effect is achieved at E∼20-50 keV). (author)

  8. Latest Diagnostic Electronics Development for the PROSCAN Proton Accelerator

    International Nuclear Information System (INIS)

    Duperrex, P.A.; Frei, U.; Gamma, G.; Mueller, U.; Rezzonico, L.

    2004-01-01

    New VME-based diagnostic electronics are being developed for PROSCAN, a proton accelerator for medical application presently under construction at PSI. One new development is a VME-based multi-channel logarithmic amplifier for converting current to voltage (LogIV). The LogIV boards are used for measuring current from the multiple wire (harp) profile monitors. The LogIV calibration method, current dependant bandwidth and temperature stability are presented. Another development is a BPM front end, based on the newest digital receiver techniques. Features of this new system are the remote control of the preamplifier stage and the continuous monitoring of each individual signal overall gain. Characteristics of the developed prototype are given

  9. Effects of tetracaine on voltage-activated calcium sparks in frog intact skeletal muscle fibers.

    Science.gov (United States)

    Hollingworth, Stephen; Chandler, W Knox; Baylor, Stephen M

    2006-03-01

    The properties of Ca(2+) sparks in frog intact skeletal muscle fibers depolarized with 13 mM [K(+)] Ringer's are well described by a computational model with a Ca(2+) source flux of amplitude 2.5 pA (units of current) and duration 4.6 ms (18 degrees C; Model 2 of Baylor et al., 2002). This result, in combination with the values of single-channel Ca(2+) current reported for ryanodine receptors (RyRs) in bilayers under physiological ion conditions, 0.5 pA (Kettlun et al., 2003) to 2 pA (Tinker et al., 1993), suggests that 1-5 RyR Ca(2+) release channels open during a voltage-activated Ca(2+) spark in an intact fiber. To distinguish between one and greater than one channel per spark, sparks were measured in 8 mM [K(+)] Ringer's in the absence and presence of tetracaine, an inhibitor of RyR channel openings in bilayers. The most prominent effect of 75-100 microM tetracaine was an approximately sixfold reduction in spark frequency. The remaining sparks showed significant reductions in the mean values of peak amplitude, decay time constant, full duration at half maximum (FDHM), full width at half maximum (FWHM), and mass, but not in the mean value of rise time. Spark properties in tetracaine were simulated with an updated spark model that differed in minor ways from our previous model. The simulations show that (a) the properties of sparks in tetracaine are those expected if tetracaine reduces the number of active RyR Ca(2+) channels per spark, and (b) the single-channel Ca(2+) current of an RyR channel is normal voltage-activated sparks (i.e., in the absence of tetracaine) are produced by two or more active RyR Ca(2+) channels. The question of how the activation of multiple RyRs is coordinated is discussed.

  10. An accelerated beam-plasma neutron/proton source and early application of a fusion plasma

    International Nuclear Information System (INIS)

    Ohnishi, M.; Yoshikawa, K.; Yamamoto, Y.; Hoshino, C.; Masuda, K.; Miley, G.; Jurczyk, B.; Stubbers, R.; Gu, Y.

    1999-01-01

    We measured the number of the neutrons and protons produced by D-D reactions in an accelerated beam-plasma fusion and curried out the numerical simulations. The linear dependence of the neutron yield on a discharge current indicates that the fusion reactions occur between the background gas and the fast particles. i.e. charge exchanged neutrals and accelerated ions. The neutron yield divided by (fusion cross section x ion current x neutral gas pressure) still possesses the dependence of the 1.2 power of discharge voltage. which shows the fusion reactions are affected by the electrostatic potential built-up in the center. The measured proton birth profiles suggest the existence of a double potential well, which is supported by the numerical simulations. (author)

  11. Coordinated Voltage Control of Distributed PV Inverters for Voltage Regulation in Low Voltage Distribution Networks

    DEFF Research Database (Denmark)

    Nainar, Karthikeyan; Pokhrel, Basanta Raj; Pillai, Jayakrishnan Radhakrishna

    2017-01-01

    This paper reviews and analyzes the existing voltage control methods of distributed solar PV inverters to improve the voltage regulation and thereby the hosting capacity of a low-voltage distribution network. A novel coordinated voltage control method is proposed based on voltage sensitivity...... optimization. The proposed method is used to calculate the voltage bands and droop settings of PV inverters at each node by the supervisory controller. The local controller of each PV inverter implements the volt/var control and if necessary, the active power curtailment as per the received settings and based...... on measured local voltages. The advantage of the proposed method is that the calculated reactive power and active power droop settings enable fair contribution of the PV inverters at each node to the voltage regulation. Simulation studies are conducted using DigSilent Power factory software on a simplified...

  12. The effect of applied control strategy on the current-voltage correlation of a solid oxide fuel cell stack during dynamic operation

    Science.gov (United States)

    Szmyd, Janusz S.; Komatsu, Yosuke; Brus, Grzegorz; Ghigliazza, Francesco; Kimijima, Shinji; Ściążko, Anna

    2014-09-01

    This paper discusses the transient characteristics of the planar type SOFC cell stack, of which the standard output is 300 W. The transient response of the voltage to the manipulation of an electric current was investigated. The effects of the response and of the operating condition determined by the operating temperature of the stack were studied by mapping a current-voltage (I-V) correlation. The current-based fuel control (CBFC) was adopted for keeping the fuel utilization factor at constant while the value of the electric current was ramped at the constant rate. The present experimental study shows that the transient characteristics of the cell voltage are determined by primarily the operating temperature caused by the manipulation of the current. Particularly, the slope of the I-V curve and the overshoot found on the voltage was remarkably influenced by the operating temperature. The different values of the fuel utilization factor influence the height of the settled voltages. The CBFC has significance in determining the slope of the I-V characteristic, but the different values ofthe fuel utilization factor does not affect the slope as the operating temperature does. The CBFC essentially does not alter the amplitude of the overshoot on the voltage response, since this is dominated by the operating temperature and its change is caused by manipulating the current.

  13. The effect of applied control strategy on the current-voltage correlation of a solid oxide fuel cell stack during dynamic operation

    Directory of Open Access Journals (Sweden)

    Szmyd Janusz S.

    2014-09-01

    Full Text Available This paper discusses the transient characteristics of the planar type SOFC cell stack, of which the standard output is 300 W. The transient response of the voltage to the manipulation of an electric current was investigated. The effects of the response and of the operating condition determined by the operating temperature of the stack were studied by mapping a current-voltage (I-V correlation. The current-based fuel control (CBFC was adopted for keeping the fuel utilization factor at constant while the value of the electric current was ramped at the constant rate. The present experimental study shows that the transient characteristics of the cell voltage are determined by primarily the operating temperature caused by the manipulation of the current. Particularly, the slope of the I-V curve and the overshoot found on the voltage was remarkably influenced by the operating temperature. The different values of the fuel utilization factor influence the height of the settled voltages. The CBFC has significance in determining the slope of the I-V characteristic, but the different values ofthe fuel utilization factor does not affect the slope as the operating temperature does. The CBFC essentially does not alter the amplitude of the overshoot on the voltage response, since this is dominated by the operating temperature and its change is caused by manipulating the current.

  14. The Effect of Image Potential on the Current-Voltage Characteristics of a Ferritin-layer

    Directory of Open Access Journals (Sweden)

    Eunjung Bang

    2010-11-01

    Full Text Available Considering for the concept of power storage systems, such as those used to supply power to microelectronic devices, ferritins have aroused a lot of interests for applications in bioelectrochemical devices. And electron transfer rates from the proteins to electrode surface are key determinants of overall performance and efficiency of the ferritin-based devices. Here we have investigated the electron transport mechanism of ferritin layer which was immobilized on an Au electrode. The current-voltage (I-V curves are obtained by a conductive atomic force microscope (c-AFM as a function of contact area between AFM tip and the ferritin layer. In the low voltage region, I-V curves are affected by both Fowler-Nordheim tunneling and image force. On the other hand, the experimental results are consistent with a Simmons model in a high voltage region, indicating that, as the voltage increases, the image potential has a dominant effect on the electron transport mechanism. These results are attributed to the film-like character of the ferritin layer, which generates an image potential to lower the barrier height in proportion to the voltage increment.

  15. Voltage-dependent gating of hERG potassium channels

    Directory of Open Access Journals (Sweden)

    Yen May eCheng

    2012-05-01

    Full Text Available The mechanisms by which voltage-gated channels sense changes in membrane voltage and energetically couple this with opening of the ion conducting pore has been the source of significant interest. In voltage-gated potassium (Kv channels, much of our knowledge in this area comes from Shaker-type channels, for which voltage-dependent gating is quite rapid. In these channels, activation and deactivation are associated with rapid reconfiguration of the voltage-sensing domain unit that is electromechanically coupled, via the S4-S5 linker helix, to the rate-limiting opening of an intracellular pore gate. However, fast voltage-dependent gating kinetics are not typical of all Kv channels, such as Kv11.1 (human ether-a-go-go related gene, hERG, which activates and deactivates very slowly. Compared to Shaker channels, our understanding of the mechanisms underlying slow hERG gating is much poorer. Here, we present a comparative review of the structure-function relationships underlying voltage-dependent gating in Shaker and hERG channels, with a focus on the roles of the voltage sensing domain and the S4-S5 linker that couples voltage sensor movements to the pore. Measurements of gating current kinetics and fluorimetric analysis of voltage sensor movement are consistent with models suggesting that the hERG activation pathway contains a voltage independent step, which limits voltage sensor transitions. Constraints upon hERG voltage sensor movement may result from loose packing of the S4 helices and additional intra-voltage sensor counter charge interactions. More recent data suggest that key amino acid differences in the hERG voltage sensing unit and S4-S5 linker, relative to fast activating Shaker-type Kv channels, may also contribute to the increased stability of the resting state of the voltage sensor.

  16. A Low Input Current and Wide Conversion Ratio Buck Regulator with 75% Efficiency for High-Voltage Triboelectric Nanogenerators

    Science.gov (United States)

    Luo, Li-Chuan; Bao, De-Chun; Yu, Wu-Qi; Zhang, Zhao-Hua; Ren, Tian-Ling

    2016-01-01

    It is meaningful to research the Triboelectric Nanogenerators (TENG), which can create electricity anywhere and anytime. There are many researches on the structures and materials of TENG to explain the phenomenon that the maximum voltage is stable and the current is increasing. The output voltage of the TENG is high about 180-400 V, and the output current is small about 39 μA, which the electronic devices directly integration of TENG with Li-ion batteries will result in huge energy loss due to the ultrahigh TENG impedance. A novel interface circuit with the high-voltage buck regulator for TENG is introduced firstly in this paper. The interface circuit can transfer the output signal of the TENG into the signal fit to a lithium ion battery. Through the circuit of the buck regulator, the average output voltage is about 4.0 V and the average output current is about 1.12 mA. Further, the reliability and availability for the lithium ion battery and the circuit are discussed. The interface circuit is simulated using the Cadence software and verified through PCB experiment. The buck regulator can achieve 75% efficiency for the High-Voltage TENG. This will lead to a research hot and industrialization applications.

  17. Design and construction of constant voltage and current regulated source with proper characteristics to be used in electronics laboratory designs

    International Nuclear Information System (INIS)

    Peon A, R.

    1978-01-01

    A regulated direct current feeding source was designed for the Nuclear Energy National Institute Electronics Labortory, with the following characteristics: a) voltage input 105-130V a.c. 50-60 Hz; b) voltage output 0.40 V d.c.; c) output current 0-2 Amp d.c.; d) load regulation 0.001%; e) line regulation 0.001%; f) ripple and noise 200 μ Vpp; g) temperature interval 3-60 0 C; h) stability 0.5%; i) output impedance as voltage source 0.01 ohms; j) transient response 50 μ seg. Besides of operating normally, that is as voltage source or current-source through the front controls, the source can be used and interconnected with one or other compatible sources (autoseries, autoparallel and programmed reference). The source will cost 70,000 pesos approximately. (author)

  18. Structural activation calculations due to proton beam loss in the APT accelerator design

    International Nuclear Information System (INIS)

    Lee, S. K.; Beard, C. A.; Wilson, W. B.; Daemen, L. L.; Liska, D. J.; Waters, L. S.; Adams, M. L.

    1995-01-01

    For the new, high-power accelerators currently being designed, the amount of activation of the accelerator structure has become an important issue. To quantify this activation, a methodology was utilized that coupled transport and depletion codes to obtain dose rate estimates at several locations near the accelerator. This research focused on the 20 and 100 MeV sections of the Bridge-Coupled Drift Tube Linear Accelerator. The peak dose rate was found to be approximately 6 mR/hr in the 100 MeV section near the quadrupoles at a 25-cm radius for an assumed beam loss of 1 nA/m. It was determined that the activation was dominated by the proton interactions and subsequent spallation product generation, as opposed to the presence of the generated neutrons. The worst contributors were the spallation products created by proton bombardment of iron, and the worst component was the beam pipe, which consists mostly of iron. No definitive conclusions about the feasibility of hands-on maintenance can be determined, as the design is still not finalized

  19. Structural activation calculations due to proton beam loss in the APT accelerator design

    International Nuclear Information System (INIS)

    Lee, S.K.; Beard, C.A.; Wilson, W.B.; Daemen, L.L.; Liska, D.J.; Waters, L.S.; Adams, M.L.

    1994-01-01

    For the new, high-power accelerators currently being designed, the amount of activation of the accelerator structure has become an important issue. To quantify this activation, a methodology was utilized that coupled transport and depletion codes to obtain dose rate estimates at several locations near the accelerator. This research focused on the 20 and 100 MeV sections of the Bridge-Coupled Drift Tube Linear Accelerator. The peak dose rate was found to be approximately 6 mR/hr in the 100 MeV section near the quadrupoles at a 25-cm radius for an assumed beam loss of 1 nA/m. It was determined that the activation was dominated by the proton interactions and subsequent spallation product generation, as opposed to the presence of the generated neutrons. The worst contributors were the spallation products created by proton bombardment of iron, and the worst component was the beam pipe, which consists mostly of iron. No definitive conclusions about the feasibility of hands-on maintenance can be determined, as the design is still not finalized

  20. Current-voltage relationship in the auroral particle acceleration region

    Directory of Open Access Journals (Sweden)

    M. Morooka

    2004-11-01

    Full Text Available The current-voltage relationship in the auroral particle acceleration region has been studied statistically by the Akebono (EXOS-D satellite in terms of the charge carriers of the upward field-aligned current. The Akebono satellite often observed field-aligned currents which were significantly larger than the model value predicted by Knight (1973. We compared the upward field-aligned current estimated by three different methods, and found that low-energy electrons often play an important role as additional current carriers, together with the high-energy primary electrons which are expected from Knight's relation. Such additional currents have been observed especially at high and middle altitudes of the particle acceleration region. Some particular features of electron distribution functions, such as "cylindrical distribution functions" and "electron conics", have often been observed coinciding with the additional currents. They indicated time variability of the particle acceleration region. Therefore, we have concluded that the low-energy electrons within the "forbidden" region of electron phase space in the stationary model often contribute to charge carriers of the current because of the rapid time variability of the particle acceleration region. "Cylindrical distribution functions" are expected to be found below the time-varying potential difference. We statistically examined the locations of "cylindrical distribution function", and found that their altitudes are related to the location where the additional currents have been observed. This result is consistent with the idea that the low-energy electrons can also carry significant current when the acceleration region changes in time.

  1. Do protons decay

    International Nuclear Information System (INIS)

    Litchfield, P.J.

    1984-09-01

    The experimental status of proton decay is reviewed after the Leipzig International conference, July 1984. A brief comparative description of the currently active experiments is given. From the overall samples of contained events it can be concluded that the experiments are working well and broadly agree with each other. The candidates for proton decay from each experiment are examined. Although several experiments report candidates at a higher rate than expected from background calculations, the validity of these calculations is still open to doubt. (author)

  2. Coordinated control for low voltage ride-through of a PMSG-based wind power plant

    Directory of Open Access Journals (Sweden)

    Khagendra Thapa

    2016-01-01

    Full Text Available Wind turbine generators should be kept connected to a power grid, while supporting the voltage recovery in the case of a grid fault to meet low voltage ride-through requirement in some grid codes. This paper proposes a coordinated control scheme that prevents the increase in the DC-link voltage by reducing the active power in the machine side converter of permanent magnet synchronous generators (PMSGs in proportion to the voltage dip at the terminal of PMSGs. The proposed scheme changes the current priorities from the active current to the reactive current to inject more reactive power for a severe fault depending on the voltage dip. In addition, the grid-side converter operates in a voltage control mode with the slope, which is the ratio of reactive current capability to the voltage tolerance around a rated value. Moreover, during the fault, the slope is changed depending on the voltage dip to inject more reactive current. The performance of the proposed scheme is validated for a wind power plant consisting of 20 units of 5-MW PMSGs using an EMTP-RV simulator. The results demonstrate that the scheme enables the PMSGs not only to survive during the fault, but also to provide a dynamic reactive power support.

  3. Symmetric voltage-controlled variable resistance

    Science.gov (United States)

    Vanelli, J. C.

    1978-01-01

    Feedback network makes resistance of field-effect transistor (FET) same for current flowing in either direction. It combines control voltage with source and load voltages to give symmetric current/voltage characteristics. Since circuit produces same magnitude output voltage for current flowing in either direction, it introduces no offset in presense of altering polarity signals. It is therefore ideal for sensor and effector circuits in servocontrol systems.

  4. Proton conduction in biopolymer exopolysaccharide succinoglycan

    Energy Technology Data Exchange (ETDEWEB)

    Kweon, Jin Jung [Department of Physics, Korea University, Seoul 136-713 (Korea, Republic of); National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 (United States); Lee, Kyu Won; Kim, Hyojung; Lee, Cheol Eui, E-mail: rscel@korea.ac.kr [Department of Physics, Korea University, Seoul 136-713 (Korea, Republic of); Jung, Seunho [Department of Bioscience and Biotechnology and UBITA, Konkuk University, Seoul 143-701 (Korea, Republic of); Kwon, Chanho [Naraebio Research Laboratories, 177 Dangha-ri, Bongdam-eup, Hawseong-si 445-892 (Korea, Republic of)

    2014-07-07

    Protonic currents play a vital role in electrical signalling in living systems. It has been suggested that succinoglycan plays a specific role in alfalfa root nodule development, presumably acting as the signaling molecules. In this regard, charge transport and proton dynamics in the biopolymer exopolysaccharide succinoglycan have been studied by means of electrical measurements and nuclear magnetic resonance (NMR) spectroscopy. In particular, a dielectric dispersion in the system has revealed that the electrical conduction is protonic rather electronic. Besides, our laboratory- and rotating-frame {sup 1}H NMR measurements have elucidated the nature of the protonic conduction, activation of the protonic motion being associated with a glass transition.

  5. Mechanisms of Gain Control by Voltage-Gated Channels in Intrinsically-Firing Neurons

    Science.gov (United States)

    Patel, Ameera X.; Burdakov, Denis

    2015-01-01

    Gain modulation is a key feature of neural information processing, but underlying mechanisms remain unclear. In single neurons, gain can be measured as the slope of the current-frequency (input-output) relationship over any given range of inputs. While much work has focused on the control of basal firing rates and spike rate adaptation, gain control has been relatively unstudied. Of the limited studies on gain control, some have examined the roles of synaptic noise and passive somatic currents, but the roles of voltage-gated channels present ubiquitously in neurons have been less explored. Here, we systematically examined the relationship between gain and voltage-gated ion channels in a conductance-based, tonically-active, model neuron. Changes in expression (conductance density) of voltage-gated channels increased (Ca2+ channel), reduced (K+ channels), or produced little effect (h-type channel) on gain. We found that the gain-controlling ability of channels increased exponentially with the steepness of their activation within the dynamic voltage window (voltage range associated with firing). For depolarization-activated channels, this produced a greater channel current per action potential at higher firing rates. This allowed these channels to modulate gain by contributing to firing preferentially at states of higher excitation. A finer analysis of the current-voltage relationship during tonic firing identified narrow voltage windows at which the gain-modulating channels exerted their effects. As a proof of concept, we show that h-type channels can be tuned to modulate gain by changing the steepness of their activation within the dynamic voltage window. These results show how the impact of an ion channel on gain can be predicted from the relationship between channel kinetics and the membrane potential during firing. This is potentially relevant to understanding input-output scaling in a wide class of neurons found throughout the brain and other nervous systems

  6. Stray voltage mitigation

    Energy Technology Data Exchange (ETDEWEB)

    Jamali, B.; Piercy, R.; Dick, P. [Kinetrics Inc., Toronto, ON (Canada). Transmission and Distribution Technologies

    2008-04-09

    This report discussed issues related to farm stray voltage and evaluated mitigation strategies and costs for limiting voltage to farms. A 3-phase, 3-wire system with no neutral ground was used throughout North America before the 1930s. Transformers were connected phase to phase without any electrical connection between the primary and secondary sides of the transformers. Distribution voltage levels were then increased and multi-grounded neutral wires were added. The earth now forms a parallel return path for the neutral current that allows part of the neutral current to flow continuously through the earth. The arrangement is responsible for causing stray voltage. Stray voltage causes uneven milk production, increased incidences of mastitis, and can create a reluctance to drink water amongst cows when stray voltages are present. Off-farm sources of stray voltage include phase unbalances, undersized neutral wire, and high resistance splices on the neutral wire. Mitigation strategies for reducing stray voltage include phase balancing; conversion from single to 3-phase; increasing distribution voltage levels, and changing pole configurations. 22 refs., 5 tabs., 13 figs.

  7. A new high-voltage level-shifting circuit for half-bridge power ICs

    International Nuclear Information System (INIS)

    Kong Moufu; Chen Xingbi

    2013-01-01

    In order to reduce the chip area and improve the reliability of HVICs, a new high-voltage level-shifting circuit with an integrated low-voltage power supply, two PMOS active resistors and a current mirror is proposed. The integrated low-voltage power supply not only provides energy for the level-shifting circuit and the logic circuit, but also provides voltage signals for the gates and sources of the PMOS active resistors to ensure that they are normally-on. The normally-on PMOS transistors do not, therefore, need to be fabricated in the depletion process. The current mirror ensures that the level-shifting circuit has a constant current, which can reduce the process error of the high-voltage devices of the circuit. Moreover, an improved RS trigger is also proposed to improve the reliability of the circuit. The proposed level-shifting circuit is analyzed and confirmed by simulation with MEDICI, and the simulation results show that the function is achieved well. (semiconductor integrated circuits)

  8. Investigation of leakage current and breakdown voltage in irradiated double-sided 3D silicon sensors

    International Nuclear Information System (INIS)

    Betta, G.-F. Dalla; Mendicino, R.; Povoli, M.; Sultan, D.M.S.; Ayllon, N.; Hoeferkamp, M.; McDuff, H.; Seidel, S.; Boscardin, M.; Zorzi, N.; Mattiazzo, S.

    2016-01-01

    We report on an experimental study aimed at gaining deeper insight into the leakage current and breakdown voltage of irradiated double-sided 3D silicon sensors from FBK, so as to improve both the design and the fabrication technology for use at future hadron colliders such as the High Luminosity LHC. Several 3D diode samples of different technologies and layout are considered, as well as several irradiations with different particle types. While the leakage current follows the expected linear trend with radiation fluence, the breakdown voltage is found to depend on both the bulk damage and the surface damage, and its values can vary significantly with sensor geometry and process details.

  9. C-terminus-mediated voltage gating of Arabidopsis guard cell anion channel QUAC1.

    Science.gov (United States)

    Mumm, Patrick; Imes, Dennis; Martinoia, Enrico; Al-Rasheid, Khaled A S; Geiger, Dietmar; Marten, Irene; Hedrich, Rainer

    2013-09-01

    Anion transporters in plants play a fundamental role in volume regulation and signaling. Currently, two plasma membrane-located anion channel families—SLAC/SLAH and ALMT—are known. Among the ALMT family, the root-expressed ALuminium-activated Malate Transporter 1 was identified by comparison of aluminum-tolerant and Al(3+)-sensitive wheat cultivars and was subsequently shown to mediate voltage-independent malate currents. In contrast, ALMT12/QUAC1 (QUickly activating Anion Channel1) is expressed in guard cells transporting malate in an Al(3+)-insensitive and highly voltage-dependent manner. So far, no information is available about the structure and mechanism of voltage-dependent gating with the QUAC1 channel protein. Here, we analyzed gating of QUAC1-type currents in the plasma membrane of guard cells and QUAC1-expressing oocytes revealing similar voltage dependencies and activation–deactivation kinetics. In the heterologous expression system, QUAC1 was electrophysiologically characterized at increasing extra- and intracellular malate concentrations. Thereby, malate additively stimulated the voltage-dependent QUAC1 activity. In search of structural determinants of the gating process, we could not identify transmembrane domains common for voltage-sensitive channels. However, site-directed mutations and deletions at the C-terminus of QUAC1 resulted in altered voltage-dependent channel activity. Interestingly, the replacement of a single glutamate residue, which is conserved in ALMT channels from different clades, by an alanine disrupted QUAC1 activity. Together with C- and N-terminal tagging, these results indicate that the cytosolic C-terminus is involved in the voltage-dependent gating mechanism of QUAC1.

  10. Wide Operating Voltage Range Fuel Cell Battery Charger

    DEFF Research Database (Denmark)

    Hernandez Botella, Juan Carlos; Mira Albert, Maria del Carmen; Sen, Gokhan

    2014-01-01

    DC-DC converters for fuel cell applications require wide voltage range operation due to the unique fuel cell characteristic curve. Primary parallel isolated boost converter (PPIBC) is a boost derived topology for low voltage high current applications reaching an efficiency figure up to 98...... by two the converter input-to-output voltage gain. This allows covering the conditions when the fuel cell stack operates in the activation region (maximum output voltage) and increases the degrees of freedom for converter optimization. The transition between operating modes is studied because represents...

  11. Characteristics of output voltage and current of integrated nanogenerators

    KAUST Repository

    Yang, Rusen

    2009-01-01

    Owing to the anisotropic property and small output signals of the piezoelectric nanogenerators (NGs) and the influence of the measurement system and environment, identification of the true signal generated by the NG is critical. We have developed three criteria: Schottky behavior test, switching-polarity tests, and linear superposition of current and voltage tests. The 11 tests can effectively rule out the system artifacts, whose sign does not change with the switching measurement polarity, and random signals, which might change signs but cannot consistently add up or cancel out under designed connection configurations. This study establishes the standards for designing and scale up of integrated nanogenerators. © 2009 American Institute of Physics.

  12. Peculiarities on voltage - current characteristics of HTS tapes at overloading conditions cooled by liquid nitrogen

    International Nuclear Information System (INIS)

    Vysotsky, V S; Fetisov, S S; Sytnikov, V E

    2008-01-01

    Electro - technical devices are considered as the most prospective use for high temperature superconductors. For such devices the overload currents due to faults in grids are the operational reality. In these cases the fault currents may forcibly go to superconductors being sometimes dozens times more than the critical currents of HTS. Overloads are the working modes for fault current limiters also. To understand the behavior of HTS devices at overloads it is important to study voltage-current characteristics (VCC) of basic HTS tapes in real cooling conditions. The knowledge of VCC permits to model and to simulate properly HTS devices behavior at overloads. We performed the study of VCC of several HTS tapes at currents several times more than their critical ones. Both, 1-G and 2-G tapes were tested. There were found peculiarities or 'spikes' on VCC at rising currents that vanished at decaying currents. It was shown that such peculiarities are determined by the change of cooling conditions from the convective heat exchange to the nucleate boiling. Nucleate boiling activation and development times were determined. Their dependencies on heat release were measured. The data obtained can be used in simulation of heating of real superconducting devices at overload conditions

  13. Oxygen sensor using proton-conductor thick-film operative at room temperature. Puroton dodentai atsumaku wo mochiita joon sadogata sanso sensor

    Energy Technology Data Exchange (ETDEWEB)

    Miura, Norio; Yoshida, Nobuaki; Matayoshi, Naoko; Shimizu, Yoichi; Yamazoe, Noboru; Kuwata, Shigeki [Kyushu Univ., Fukuoka, (Japan) Niihama National College of Tech., Ehime, (Japan)

    1989-10-01

    An amperometric solid-state oxygen sensor using a proton-conductor thick-film was examined as a miniaturized and intelligent oxygen sensor operative at room temperature. The good-conditioned proton-conductor film of about 10{mu}m in thickness without holes was formed on a porous alumina substrate by spin-coating the paste containing antimonic acid and a polyvinyl alcohol binder. Using this material, the thick-film oxygen sensor was made. A limiting current, controlled by oxygen permeation through the gas-diffusion layer, was observed when an external voltage was over 1.4V. The limiting current increased linearly with an increase in oxygen partial pressure up to 1.0 atm at an external voltage of 1.6V. The 90% response time for increasing oxygen partial pressure was about 40 seconds at 30 centigrade. Moreover, it was found that the sensor could also respond to dissolved oxygen in water at room temperature. With a sensor using a hydrophobic gas-diffusion layer containing a polystyrene binder, the limiting current was linear to the dissolved oxygen concentration up to 20ppm. 15 refs., 5 figs.

  14. High voltage distribution scheme for large size GEM detector

    International Nuclear Information System (INIS)

    Saini, J.; Kumar, A.; Dubey, A.K.; Negi, V.S.; Chattopadhyay, S.

    2016-01-01

    Gas Electron Multiplier (GEM) detectors will be used for Muon tracking in the Compressed Baryonic Matter (CBM) experiment at the Facility for Anti-proton Ion Research (FAIR) at Darmstadt, Germany. The sizes of the detector modules in the Muon chambers are of the order of 1 metre x 0.5 metre. For construction of these chambers, three GEM foils are used per chamber. These foils are made by two layered 50μm thin kapton foil. Each GEM foil has millions of holes on it. In such a large scale manufacturing of the foils, even after stringent quality controls, some of the holes may still have defects or defects might develop over the time with operating conditions. These defects may result in short-circuit of the entire GEM foil. A short even in a single hole will make entire foil un-usable. To reduce such occurrences, high voltage (HV) segmentation within the foils has been introduced. These segments are powered either by individual HV supply per segment or through an active HV distribution to manage such a large number of segments across the foil. Individual supplies apart from being costly, are highly complex to implement. Additionally, CBM will have high intensity of particles bombarding on the detector causing the change of resistive chain current feeding the GEM detector with the variation in the intensity. This leads to voltage fluctuations across the foil resulting in the gain variation with the particle intensity. Hence, a low cost active HV distribution is designed to take care of the above discussed issues

  15. Active Power Filter DC Bus Voltage Piecewise Reaching Law Variable Structure Control

    OpenAIRE

    Liu, Baolian; Ding, Zujun; Zhao, Huanyu; Jin, Defei

    2014-01-01

    The DC bus voltage stability control is one key technology to ensure that Active Power Filter (APF) operates stably. The external disturbances such as power grid and load fluctuation and the system parameters changing may affect the stability of APF DC bus voltage and the normal operation of APF. The mathematical model of DC bus voltage is established according to power balance principle and a DC bus voltage piecewise reaching law variable structure control algorithm is proposed to solve the ...

  16. Analytical Model for Voltage-Dependent Photo and Dark Currents in Bulk Heterojunction Organic Solar Cells

    Directory of Open Access Journals (Sweden)

    Mesbahus Saleheen

    2016-05-01

    Full Text Available A physics-based explicit mathematical model for the external voltage-dependent forward dark current in bulk heterojunction (BHJ organic solar cells is developed by considering Shockley-Read-Hall (SRH recombination and solving the continuity equations for both electrons and holes. An analytical model for the external voltage-dependent photocurrent in BHJ organic solar cells is also proposed by incorporating exponential photon absorption, dissociation efficiency of bound electron-hole pairs (EHPs, carrier trapping, and carrier drift and diffusion in the photon absorption layer. Modified Braun’s model is used to compute the electric field-dependent dissociation efficiency of the bound EHPs. The overall net current is calculated considering the actual solar spectrum. The mathematical models are verified by comparing the model calculations with various published experimental results. We analyze the effects of the contact properties, blend compositions, charge carrier transport properties (carrier mobility and lifetime, and cell design on the current-voltage characteristics. The power conversion efficiency of BHJ organic solar cells mostly depends on electron transport properties of the acceptor layer. The results of this paper indicate that improvement of charge carrier transport (both mobility and lifetime and dissociation of bound EHPs in organic blend are critically important to increase the power conversion efficiency of the BHJ solar cells.

  17. Protonic transistors from thin reflecting films

    Energy Technology Data Exchange (ETDEWEB)

    Ordinario, David D.; Phan, Long; Jocson, Jonah-Micah [Department of Chemical Engineering and Materials Science, University of California, Irvine, California 92697 (United States); Nguyen, Tam [Department of Chemistry, University of California, Irvine, California 92697 (United States); Gorodetsky, Alon A., E-mail: alon.gorodetsky@uci.edu [Department of Chemical Engineering and Materials Science, University of California, Irvine, California 92697 (United States); Department of Chemistry, University of California, Irvine, California 92697 (United States)

    2015-01-01

    Ionic transistors from organic and biological materials hold great promise for bioelectronics applications. Thus, much research effort has focused on optimizing the performance of these devices. Herein, we experimentally validate a straightforward strategy for enhancing the high to low current ratios of protein-based protonic transistors. Upon reducing the thickness of the transistors’ active layers, we increase their high to low current ratios 2-fold while leaving the other figures of merit unchanged. The measured ratio of 3.3 is comparable to the best values found for analogous devices. These findings underscore the importance of the active layer geometry for optimum protonic transistor functionality.

  18. Voltage-current characteristics of a pin-plate system with different plate configurations

    International Nuclear Information System (INIS)

    Feng, Zhuangbo; Long, Zhengwei

    2013-01-01

    In this paper, the voltage-current (V-I) characteristics of a pin-plate system with four types of collection plate configurations are studied experimentally. The collection plates consider a single metal plate, a metal plate with a fly ash cake layer, a metal plate with a clean filter media and a metal plate with a dirty filter media. The results show that the clean filter media has no obvious effect on the V-I characteristics. But the dirty filter media reduces the current density because of its high resistance. The thick fly ash cake layer increase current density because of the anti-corona effect but the increment is not very obvious.

  19. The effect of activation rate on left atrial bipolar voltage in patients with paroxysmal atrial fibrillation.

    Science.gov (United States)

    Williams, Steven E; Linton, Nick; O'Neill, Louisa; Harrison, James; Whitaker, John; Mukherjee, Rahul; Rinaldi, Christopher A; Gill, Jaswinder; Niederer, Steven; Wright, Matthew; O'Neill, Mark

    2017-09-01

    Bipolar voltage is used during electroanatomic mapping to define abnormal myocardium, but the effect of activation rate on bipolar voltage is not known. We hypothesized that bipolar voltage may change in response to activation rate. By examining corresponding unipolar signals we sought to determine the mechanisms of such changes. LA extrastimulus mapping was performed during CS pacing in 10 patients undergoing first time paroxysmal atrial fibrillation ablation. Bipolar and unipolar electrograms were recorded using a PentaRay catheter (4-4-4 spacing) and indifferent IVC electrode, respectively. An S1S2 pacing protocol was delivered with extrastimulus coupling interval reducing from 350 to 200 milliseconds. At each recording site (119 ± 37 per LA), bipolar peak-to-peak voltage, unipolar peak to peak voltage and activation delay between unipole pairs was measured. Four patterns of bipolar voltage/extrastimulus coupling interval curves were seen: voltage attenuation with plateau voltage >1 mV (48 ± 15%) or voltage unaffected by coupling interval with plateau voltage >1 mV (17 ± 10%) or voltage attenuation were associated with significantly greater unipolar voltage attenuation at low (25 ± 28 mV/s vs. 9 ± 11 mV/s) and high (23 ± 29 mV/s vs. 6 ± 12 mV/s) plateau voltage sites (P voltage attenuation (P = 0.026). Bipolar electrogram voltage is dependent on activation rate at a significant proportion of sites. Changes in unipolar voltage and timing underlie these effects. These observations have important implications for use of voltage mapping to delineate abnormal atrial substrate. © 2017 The Authors. Journal of Cardiovascular Electrophysiology published by Wiley Periodicals, Inc.

  20. Non-canonical spectral decomposition of random functions of the traction voltage and current in electric transportation systems

    Directory of Open Access Journals (Sweden)

    N.A. Kostin

    2015-03-01

    Full Text Available The paper proposes the non-canonical spectral decomposition of random functions of the traction voltages and currents. This decomposition is adapted for the electric transportation systems. The numerical representation is carried out for the random function of voltage on the pantograph of electric locomotives VL8 and DE1.

  1. Luminescence evolution from alumina ceramic surface before flashover under direct and alternating current voltage in vacuum

    Energy Technology Data Exchange (ETDEWEB)

    Su, Guo-Qiang; Wang, Yi-Bo; Song, Bai-Peng; Mu, Hai-Bao, E-mail: haibaomu@xjtu.edu.cn, E-mail: gjzhang@xjtu.edu.cn; Zhang, Guan-Jun, E-mail: haibaomu@xjtu.edu.cn, E-mail: gjzhang@xjtu.edu.cn [State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Li, Feng; Wang, Meng [Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China)

    2016-06-15

    The luminescence evolution phenomena from alumina ceramic surface in vacuum under high voltage of direct and alternating current are reported, with the voltage covering a large range from far below to close to the flashover voltage. Its time resolved and spatial distributed behaviors are examined by a photon counting system and an electron-multiplying charge-coupled device (EMCCD) together with a digital camera, respectively. The luminescence before flashover exhibits two stages as voltage increasing, i.e., under a relative low voltage (Stage A), the luminescence is ascribed to radiative recombination of hetero-charges injected into the sample surface layer by Schottky effect; under a higher voltage (Stage B), a stable secondary electron emission process, resulting from the Fowler-Nordheim emission at the cathode triple junction (CTJ), is responsible for the luminescence. Spectrum analysis implies that inner secondary electrons within the surface layer of alumina generated during the SSEE process also participate in the luminescence of Stage B. A comprehensive interpretation of the flashover process is formulated, which might promote a better understanding of flashover issue in vacuum.

  2. A Transformerless Hybrid Active Filter Capable of Complying with Harmonic Guidelines for Medium-Voltage Motor Drives

    Science.gov (United States)

    Kondo, Ryota; Akagi, Hirofumi

    This paper presents a transformerless hybrid active filter that is integrated into medium-voltage adjustable-speed motor drives for fans, pumps, and compressors without regenerative braking. The authors have designed and constructed a three-phase experimental system rated at 400V and 15kW, which is a downscaled model from a feasible 6.6-kV 1-MW motor drive system. This system consists of the hybrid filter connecting a passive filter tuned to the 7th harmonic filter in series with an active filter that is based on a three-level diode-clamped PWM converter, as well as an adjustable-speed motor drive in which a diode rectifier is used as the front end. The hybrid filter is installed on the ac side of the diode rectifier with no line-frequency transformer. The downscaled system has been exclusively tested so as to confirm the overall compensating performance of the hybrid filter and the filtering performance of a switching-ripple filter for mitigating switching-ripple voltages produced by the active filter. Experimental results verify that the hybrid filter achieves harmonic compensation of the source current in all the operating regions from no-load to the rated-load conditions, and that the switching-ripple filter reduces the switching-ripple voltages as expected.

  3. Magnetosphere-ionosphere coupling currents in Jupiter's middle magnetosphere: effect of magnetosphere-ionosphere decoupling by field-aligned auroral voltages

    Directory of Open Access Journals (Sweden)

    J. D. Nichols

    2005-03-01

    Full Text Available We consider the effect of field-aligned voltages on the magnetosphere-ionosphere coupling current system associated with the breakdown of rigid corotation of equatorial plasma in Jupiter's middle magnetosphere. Previous analyses have assumed perfect mapping of the electric field and flow along equipotential field lines between the equatorial plane and the ionosphere, whereas it has been shown that substantial field-aligned voltages must exist to drive the field-aligned currents associated with the main auroral oval. The effect of these field-aligned voltages is to decouple the flow of the equatorial and ionospheric plasma, such that their angular velocities are in general different from each other. In this paper we self-consistently include the field-aligned voltages in computing the plasma flows and currents in the system. A third order differential equation is derived for the ionospheric plasma angular velocity, and a power series solution obtained which reduces to previous solutions in the limit that the field-aligned voltage is small. Results are obtained to second order in the power series, and are compared to the original zeroth order results with no parallel voltage. We find that for system parameters appropriate to Jupiter the effect of the field-aligned voltages on the solutions is small, thus validating the results of previously-published analyses.

  4. Verification of the short-circuit current making capability of high-voltage switching devices

    NARCIS (Netherlands)

    Smeets, R.P.P.; Linden, van der W.A.

    2001-01-01

    Switching-in of short-circuit current leads to pre-arcing in the switching device. Pre-arcing affects the ability of switchgear to close and latch. In three-phase systems, making is associated with transient voltage phenomena that may have a significant impact on the duration of the pre-arcing

  5. Singularities of current-voltage characteristics of GaAs films fabricated by pulsed ions ablation

    International Nuclear Information System (INIS)

    Kabyshev, A.V.; Konusov, F.V.; Lozhnikov, S.N.; Remnev, G.E.; Saltymakov, M.S.

    2009-01-01

    A singularities and advantages of the optical, photoelectric and electrical properties of GaAs in comparison with other available materials for electronics, for example, silicon allow to manufacture on it base the devices having an advanced characteristics. The GaAs for electronics, obtained from the dense ablation plasma, possess some preferences as compared to material manufactured by traditional methods of vacuum deposition. The electrical characteristics of GaAs produced by chemical deposition were extensively studied. Purpose of this work is investigation the current-voltage characteristics of thin films of GaAs, deposited on polycrystalline corundum (polycor) from plasma forming the power ions bunch and determination of the thermal vacuum annealing effect on photoelectric and electrical properties of films. Peculiarities of optical, photoelectric and current-voltage characteristics of films obtained by ions ablation are determined by deposition conditions and resistance of initial target GaAs. The transitions between the states with low- and high conduction were revealed directly after deposition in films having the optical properties similar to amorphous materials and/or after annealing in films with properties similar to initial target GaAs. Behavior of current-voltage characteristics at vacuum annealing correlates with Schottky barrier height and photosensitivity and is accompanies of the transport mechanism change. The stable properties of films are formed at its dark conduction 10 -10 -10 -8 s and after annealing at T an =600-700 K. (authors)

  6. Voltage Dependence of Supercapacitor Capacitance

    Directory of Open Access Journals (Sweden)

    Szewczyk Arkadiusz

    2016-09-01

    Full Text Available Electronic Double-Layer Capacitors (EDLC, called Supercapacitors (SC, are electronic devices that are capable to store a relatively high amount of energy in a small volume comparing to other types of capacitors. They are composed of an activated carbon layer and electrolyte solution. The charge is stored on electrodes, forming the Helmholtz layer, and in electrolyte. The capacitance of supercapacitor is voltage- dependent. We propose an experimental method, based on monitoring of charging and discharging a supercapacitor, which enables to evaluate the charge in an SC structure as well as the Capacitance-Voltage (C-V dependence. The measurement setup, method and experimental results of charging/discharging commercially available supercapacitors in various voltage and current conditions are presented. The total charge stored in an SC structure is proportional to the square of voltage at SC electrodes while the charge on electrodes increases linearly with the voltage on SC electrodes. The Helmholtz capacitance increases linearly with the voltage bias while a sublinear increase of total capacitance was found. The voltage on SC increases after the discharge of electrodes due to diffusion of charges from the electrolyte to the electrodes. We have found that the recovery voltage value is linearly proportional to the initial bias voltage value.

  7. Testing and analysis of tube voltage and tube current in the radiation generator for mammography

    International Nuclear Information System (INIS)

    Jung, Hong Ryang; Hong, Dong Hee; Han, Beom Hui

    2014-01-01

    Breast shooting performance management and quality control of the generator is applied to the amount of current IEC(International Electrotechnical Commission) 60601-2-45 tube voltage and tube current are based on standards that were proposed in the analysis of the test results were as follows. Tube voltage according to the value of the standard deviation by year of manufacture from 2001 to 2010 as a 42-3.15 showed the most significant, according to the year of manufacture by tube amperage value of the standard deviation to 6.38 in the pre-2000 showed the most significant , manufactured after 2011 the standard deviation of the devices, the PAE(Percent Average Error) was relatively low. This latest generation device was manufactured in the breast of the tube voltage and tube diagnosed shooting the correct amount of current to maintain the performance that can be seen. The results of this study as the basis for radiography diagnosed breast caused by using the device's performance and maintain quality control, so the current Food and Drug Administration 'about the safety of diagnostic radiation generator rule' specified in the test cycle during three years of self-inspection radiation on a radiation generating device ensure safety and performance of the device using a coherent X-ray(constancy) by two ultimately able to keep the radiation dose to the public to reduce the expected effect is expected

  8. Beam forming system modernization at the MMF linac proton injector

    CERN Document Server

    Derbilov, V I; Nikulin, E S; Frolov, O T

    2001-01-01

    The isolation improvements of the beam forming system (BFS) of the MMF linac proton injector ion source are reported. The mean beam current and,accordingly, BFS electrode heating were increased when the MMF linac has began to operate regularly in long beam sessions with 50 Hz pulse repetition rate. That is why the BFS electrode high-voltage isolation that was made previously as two consequently and rigidly glued solid cylinder insulators has lost mechanical and electric durability. The substitution of large (160 mm) diameter cylinder insulator for four small diameter (20 mm) tubular rods has improved vacuum conditions in the space of beam forming and has allowed to operate without failures when beam currents being up to 250 mA and extraction and focusing voltage being up to 25 and 40 kV respectively. Moreover,the construction provides the opportunity of electrode axial move. The insulators are free from electrode thermal expansion mechanical efforts in a transverse direction.

  9. Functional model of a high-current high-voltage superconducting switches

    International Nuclear Information System (INIS)

    Menke, Kh.; Shishov, Yu.A.

    1977-01-01

    Considered are problems of superconducting switches (SS) for energy extraction from magnets at a current of several kiloamperes and a voltage of several kilovolts with a time for transition to the normal state of <0.5 ms. SS is made of a wire of 0.5 mm diameter containing 19 strands of Nb-Ti alloy of 65 μm diameter. The wire matrix was etched out, 19 wires of 4.5 m length were braided together. On each of three groups of wires a heater wire of constantan of 0.12 mm diameter and 6 m length was wound. A second heater intended for slow heating during current feeding into the magnet, is wound over the braid. The wires and heaters are parallel connected and impregnated by an epoxy compound. The following main parameters were obtained in SS testing: critical current of 920 A, resistance in the normal state of 2.5 Ohm, and minimum delay time of 0.2 ms at a nominal current of 0.8 of the critical one

  10. High intensity proton linac activities at Los Alamos

    International Nuclear Information System (INIS)

    Rusnak, B.; Chan, K.C.; Campbell, B.

    1998-01-01

    High-current proton linear accelerators offer an attractive alternative for generating the intense neutron fluxes needed for transmutations technologies, tritium production and neutron science. To achieve the fluxes required for tritium production, a 100-mA, 1700-MeV cw proton accelerator is being designed that uses superconducting cavities for the high-energy portion of the linac, from 211 to 1,700 MeV. The development work supporting the linac design effort is focused on three areas: superconducting cavity performance for medium-beta cavities at 700 MHz, high power rf coupler development, and cryomodule design. An overview of the progress in these three areas is presented

  11. Mathematical model of voltage-current characteristics of Bi(2223)/Ag magnets under an external magnetic field

    CERN Document Server

    Pitel, J; Lehtonen, J; Kovács, P

    2002-01-01

    We have developed a mathematical model, which enables us to predict the voltage-current V(I) characteristics of a solenoidal high-temperature superconductor (HTS) magnet subjected to an external magnetic field parallel to the magnet axis. The model takes into account the anisotropy in the critical current-magnetic field (I sub c (B)) characteristic and the n-value of Bi(2223)Ag multifilamentary tape at 20 K. From the power law between the electric field and the ratio of the operating and critical currents, the voltage on the magnet terminals is calculated by integrating the contributions of individual turns. The critical current of each turn, at given values of operating current and external magnetic field, is obtained by simple linear interpolation between the two suitable points of the I sub c (B) characteristic, which corresponds to the angle alpha between the vector of the resulting magnetic flux density and the broad tape face. In fact, the model is valid for any value and orientation of external magneti...

  12. Proton induction linacs as high-intensity neutron sources

    International Nuclear Information System (INIS)

    Keefe, D.; Hoyer, E.

    1981-01-01

    Proton induction linacs are explored as high intensity neutron sources. The induction linac - concept, properties, experience with electrons, and possibilities - and its limitations for accelerating ions are reviewed. A number of proton induction linac designs are examined with the LIACEP program and general conclusions are given. Results suggest that a proton induction accelerator of the lowest voltage, consistent with good neutron flux, is preferred and could well be cost competitive with the usual rf linac/storage ring designs. (orig.)

  13. A high-current, high-voltage power supply with special output current waveform for APS injector synchrotron dipole magnets

    International Nuclear Information System (INIS)

    Fathizadeh, M.; Despe, O.D.; McGhee, D.G.; Mills, F.E.; Turner, L.R.

    1991-01-01

    This paper describes a high-voltage, high-current power supply for the injector synchrotron dipole magnets at APS. In order to reset the dipole magnets in each cycle two different current waveforms are suggested. The first current waveform consists of three sections, namely: dc-reset, linear ramp, and recovery sections where injection is done ''on the fly''. The second current waveform consists of six different sections, dc-reset, transition to injection level, injection flat level, parabolic, linear ramp and recovery sections. The effect of such waveforms on the beam is discussed and the power supply limitations to follow such waveforms are given. The power supply limitations are due to the power components and control loops. The reference for the current loop is generated by a DAC which is discussed

  14. Research of Measurement Circuits for High Voltage Current Transformer Based on Rogowski Coils

    Directory of Open Access Journals (Sweden)

    Yan Bing

    2014-02-01

    Full Text Available The electronic current transformer plays an irreplaceable position in the field of relay protection and current measurement of the power system. Rogowski coils are used as sensor parts, and in order to improve the measurement accuracy and reliability, the circuits at the high voltage system are introduced and improved in this paper, including the analog integral element, the filtering circuit and the phase shift circuit. Simulations results proved the reliability and accuracy of the improved circuits.

  15. Multielement proton activation analysis: application to airborne particulate matter

    International Nuclear Information System (INIS)

    Priest, P.; Devillers, M.; Desaedeleer, G.

    1980-01-01

    Proton activation analysis in the range of 25 to 30 MeV proton energies allows the determination of Na, Mg, Ca, Ti, Fe, Zn, As, Sr, Sn and Pb in airborne particles collected by 4 to 7 stage impactors. Under normal, not limitative irradiation and counting conditions, the determination is accurate for samples collected from 1 to 10 m 3 of air in rural atmospheres

  16. Realisations of single-resistance-controlled quadrature oscillators using a generalised current follower transconductance amplifier and a unity-gain voltage-follower

    OpenAIRE

    Herencsár, Norbert; Vrba, Kamil; Koton, Jaroslav; Lahiri, Abhirup

    2010-01-01

    This article presents realisations of single-resistance-controlled-oscillators (SRCOs) using the recently proposed modern active building block (ABB), namely the generalised current follower transconductance amplifier (GCFTA) and unity-gain voltage-follower (UGVF). The SRCO is made using reduced number of components: one GCFTA and one UGVF as the ABBs, two resistors and two grounded capacitors. The circuit offers the advantage of non-interactive control of condition of oscillation and frequen...

  17. Five-Level Active-Neutral-Point-Clamped DC/DC Converter for Medium-Voltage DC Grids

    DEFF Research Database (Denmark)

    Liu, Dong; Deng, Fujin; Chen, Zhe

    2017-01-01

    This paper proposes a five-level active-neutralpoint- clamped (5L-ANPC) dc/dc converter for applications in medium voltage dc (MVDC) grids. A modulation strategy is proposed for the 5L-ANPC dc/dc converter to generate multilevel voltage waveforms, which can effectively reduce voltage change rate dv...... effectively eliminate high voltage leaps caused by the dead time effect. In addition, a capacitor voltage control strategy is proposed for the 5L-ANPC dc/dc converter to ensure the balanced flying capacitor voltage and desired five-level voltage waveforms. Finally, simulation and experimental studies...

  18. Generic inertia emulation controller for multi-terminal voltage-source-converter high voltage direct current systems

    DEFF Research Database (Denmark)

    Zhu, Jiebei; Guerrero, Josep M.; Hung, William

    2014-01-01

    A generic Inertia Emulation Controller (INEC) scheme for Multi-Terminal Voltage-Source-Converter based HVDC (VSC-MTDC) systems is proposed and presented in this paper. The proposed INEC can be incorporated in any Grid-side Voltage-Source-Converter (GVSC) station, allowing the MTDC terminal...

  19. Voltage clamp methods for the study of membrane currents and SR Ca2+ release in adult skeletal muscle fibres

    Science.gov (United States)

    Hernández-Ochoa, Erick O.; Schneider, Martin F.

    2012-01-01

    Skeletal muscle excitation-contraction (E-C)1 coupling is a process composed of multiple sequential stages, by which an action potential triggers sarcoplasmic reticulum (SR)2 Ca2+ release and subsequent contractile activation. The various steps in the E-C coupling process in skeletal muscle can be studied using different techniques. The simultaneous recordings of sarcolemmal electrical signals and the accompanying elevation in myoplasmic Ca2+, due to depolarization-initiated SR Ca2+ release in skeletal muscle fibres, have been useful to obtain a better understanding of muscle function. In studying the origin and mechanism of voltage dependency of E-C coupling a variety of different techniques have been used to control the voltage in adult skeletal fibres. Pioneering work in muscles isolated from amphibians or crustaceans used microelectrodes or ‘high resistance gap’ techniques to manipulate the voltage in the muscle fibres. The development of the patch clamp technique and its variant, the whole-cell clamp configuration that facilitates the manipulation of the intracellular environment, allowed the use of the voltage clamp techniques in different cell types, including skeletal muscle fibres. The aim of this article is to present an historical perspective of the voltage clamp methods used to study skeletal muscle E-C coupling as well as to describe the current status of using the whole-cell patch clamp technique in studies in which the electrical and Ca2+ signalling properties of mouse skeletal muscle membranes are being investigated. PMID:22306655

  20. A differential low-voltage high gain current-mode integrated RF receiver front-end

    Energy Technology Data Exchange (ETDEWEB)

    Wang Chunhua; Ma Minglin; Sun Jingru; Du Sichun; Guo Xiaorong; He Haizhen, E-mail: wch1227164@sina.com [School of Information Science and Technology, Hunan University, Changsha 410082 (China)

    2011-02-15

    A differential low-voltage high gain current-mode integrated RF front end for an 802.11b WLAN is proposed. It contains a differential transconductance low noise amplifier (G{sub m}-LNA) and a differential current-mode down converted mixer. The single terminal of the G{sub m}-LNA contains just one MOS transistor, two capacitors and two inductors. The gate-source shunt capacitors, C{sub x1} and C{sub x2}, can not only reduce the effects of gate-source C{sub gs} on resonance frequency and input-matching impedance, but they also enable the gate inductance L{sub g1,2} to be selected at a very small value. The current-mode mixer is composed of four switched current mirrors. Adjusting the ratio of the drain channel sizes of the switched current mirrors can increase the gain of the mixer and accordingly increase the gain of RF receiver front-end. The RF front-end operates under 1 V supply voltage. The receiver RFIC was fabricated using a chartered 0.18 {mu}m CMOS process. The integrated RF receiver front-end has a measured power conversion gain of 17.48 dB and an input referred third-order intercept point (IIP3) of -7.02 dBm. The total noise figure is 4.5 dB and the power is only 14 mW by post-simulations. (semiconductor integrated circuits)

  1. High Current, Low Voltage Power Converter [20kA, 6V] LHC Converter Prototype

    CERN Document Server

    Jørgensen, H E; Dupaquier, A; Fernqvist, G

    1998-01-01

    The superconducting LHC accelerator requires high currents (~12.5kA) and relatively low voltages (~10 V) for its magnets. The need to install the power converters underground is the driving force for reduced volume and high efficiency. Moreover, the LHC machine will require a very high level of performance from the power converters, particularly in terms of DC stability, dynamic response and also in matters of EMC. To meet these requirements soft-switching techniques will be used. This paper describes the development of a [20kA,6V] power converter intended as a stable high-current source for D CCT calibration and an evaluation prototype for the future LHC converters. The converter is made with a modular concept with five current sources [4kA,6V] in parallel. The 4kA sources are built as plu g-in modules: a diode rectifier on the AC mains with a damped L-C passive filter, a Zero Voltage Switching inverter working at 20 kHz and an output stage (high frequency transformers, Schottky rectifi ers and output filter...

  2. Optimal conditions for high current proton irradiations at the university of Wisconsin's ion beam laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Wetteland, C. J.; Field, K. G.; Gerczak, T. J. [Materials Science Program, University of Wisconsin, Madison, WI 53706 (United States); Eiden, T. J.; Maier, B. R.; Albakri, O.; Sridharan, K.; Allen, T. R. [Department of Engineering Physics, University of Wisconsin, Madison, WI 53706 (United States)

    2013-04-19

    The National Electrostatics Corporation's (NEC) Toroidal Volume Ion Source (TORVIS) source is known for exceptionally high proton currents with minimal service downtime as compared to traditional sputter sources. It has been possible to obtain over 150{mu}A of proton current from the source, with over 70{mu}A on the target stage. However, beam fluxes above {approx}1 Multiplication-Sign 10{sup 17}/m2-s may have many undesirable effects, especially for insulators. This may include high temperature gradients at the surface, sputtering, surface discharge, cracking or even disintegration of the sample. A series of experiments were conducted to examine the role of high current fluxes in a suite of ceramics and insulating materials. Results will show the optimal proton irradiation conditions and target mounting strategies needed to minimize unwanted macro-scale damage, while developing a procedure for conducting preliminary radiation experiments.

  3. Low Voltage Ride-Through of Two-Stage Grid-Connected Photovoltaic Systems Through the Inherent Linear Power-Voltage Characteristic

    DEFF Research Database (Denmark)

    Yang, Yongheng; Sangwongwanich, Ariya; Liu, Hongpeng

    2017-01-01

    In this paper, a cost-effective control scheme for two-stage grid-connected PhotoVoltaic (PV) systems in Low Voltage Ride-Through (LVRT) operation is proposed. In the case of LVRT, the active power injection by PV panels should be limited to prevent from inverter over-current and also energy...... aggregation at the dc-link, which will challenge the dc-link capacitor lifetime if remains uncontrolled. At the same time, reactive currents should be injected upon any demand imposed by the system operators. In the proposed scheme, the two objectives can be feasibly achieved. The active power is regulated...... point tracking controller without significant hardware or software modifications. In this way, the PV system will not operate at the maximum power point, whereas the inverter will not face any over-current challenge but can provide reactive power support in response to the grid voltage fault...

  4. Determination of the cathode fall voltage in fluorescent lamps by measurement of the operating voltage

    International Nuclear Information System (INIS)

    Hilscher, A.

    2002-01-01

    A new method for the determination of the cathode fall voltage of fluorescent lamps is shown. The cathode fall voltage can be determined by measurement of the lamp operating voltage at constant lamp wall temperature, constant discharge current and variation of the electrode heating current. Commercial lamps, which do not need to be specially prepared, can be used for the measurement. The results show good correlation to other measurements of the cathode fall voltage at various discharge currents by means of capacitive coupling. The measured values of the cathode fall voltage are used for determining the minimum, target and maximum setting of the sum of the squares of the pin currents of one electrode (the so-called SOS value) as a function of the discharge current in fluorescent lamp dimming. (author)

  5. Low energy current accumulator for high-energy proton rings

    International Nuclear Information System (INIS)

    Month, M.

    1977-01-01

    Building current in high-energy p-p colliding beam machines is most appropriately done in a low-energy (small circumference) current accumulator. Three significant factors favor such a procedure: First, large rings tend to be susceptible to unstable longitudinal density oscillations. These can be avoided by pumping up the beam in the accumulator. When the current stack is injected into the storage ring, potentially harmful instability is essentially neutralized. Second, high-field magnets characteristic of future high energy proton rings are designed with superconducting coils within the iron magnetic shield. This means coil construction and placement errors propagate rapidly within the beam aperture. An intermediate ''stacking ring'' allows the minimum use of the superconducting ring aperture. Finally, the coils are vulnerable to radiation heating and possible magnet quenching. By minimizing beam manipulaion in the superconducting environment and using only the central portion of the beam aperture, coil vulnerability can be put at a minimum

  6. Effect of temperature on current voltage characteristics in ZnO/CdS/CuGaSe2 single crystal solar cells

    International Nuclear Information System (INIS)

    Saad, M.; Kassis, A.

    2005-03-01

    Current voltage characteristics of Zn O/CdS/CuGaSe 2 single crystal solar cells, which have gone through repetitive annealing treatment and have been measured at different values of temperature and illumination intensity, were analyzed using the two-diode equation. The analysis revealed that current transport in these cells is governed by two competing transport mechanisms relating strongly to interface states and that both mechanisms are thermally and light activated. These two mechanisms are interface recombination and tunneling enhanced interface recombination. The activation energy values of the saturation current density in both mechanisms were calculated from the temperature dependence of the parameters describing each of them. It was found that these values depend on temperature and illumination intensity. Furthermore, the behavior of the photovoltaic parameters could be explained relying on the results of the analysis. (Authors)

  7. Inrush Transient Current Analysis and Suppression of Photovoltaic Grid-Connected Inverters During Voltage Sag

    DEFF Research Database (Denmark)

    Li, Zhongyu; Zhao, Rende; Xin, Zhen

    2016-01-01

    The Inrush Transient Current (ITC) in the output of the photovoltaic grid-connected inverters is usually generated when grid voltage sag occurs, which can trigger the protection of the grid-connected inverters, and even destroy the semiconductor switches. Then, the grid-connected inverters...

  8. Improvement of proton source based on cylindrical inertial electrostatic confinement fusion with ion source

    International Nuclear Information System (INIS)

    Yamauchi, Kunihito; Ohura, Sonoe; Tashiro, Atsushi; Watanabe, Masato; Okino, Akitoshi; Kohno, Toshiyuki; Hotta, Eiki; Yuura, Morimasa

    2005-01-01

    Inertial Electrostatic Confinement Fusion (IECF) device is a compact fusion proton/neutron source with an extremely simple configuration, high controllability, and hence high safety. Therefore, it has been studied for practical use as a portable neutron/proton source for various applications such as landmine detection and medical positron emission tomography. However, some problems remain for the practical use, and the most critical one is the insufficiency of absolute neutron/proton yields. In this study, a new IECF device was designed and tested to obtain high neutron/proton yields. The key features of the new device are the cylindrical electrode configuration in consideration of better electrostatic confinement of ions and extraction of protons, and an integrated ion source that consists of sixteen ferrite magnets and biasing the grid anode. To investigate the performance characteristics of the device and the effect of the ion source, three kinds of experimental setup were used for comparison. At first, the device was operated with the basic setup. Then a cusp magnetic field was applied by using ferrite magnets, and the grid anode was negatively biased. As a result, it was confirmed that the ion source works effectively. At the same voltage and current, the obtained neutron production rate was about one order of magnitude higher than that of the conventional spherical IECF device. The maximum neutron production rate of 6.8x10 9 n/s was obtained at a pulsed discharge of -70 kV and 10 A with an anode bias voltage of -1.0 kV. (author)

  9. DC-bus voltage control of grid-connected voltage source converter by using space vector modulated direct power control under unbalanced network conditions

    DEFF Research Database (Denmark)

    Xiao, Lei; Huang, Shoudao; Lu, Kaiyuan

    2013-01-01

    Unbalanced grid voltage will cause large dc-bus voltage ripple and introduce high harmonic current components on the grid side. This will severely threaten the safety of the grid-connected voltage source converter (VSC) and consequently, affect the healthy operation condition of the load. In this......Unbalanced grid voltage will cause large dc-bus voltage ripple and introduce high harmonic current components on the grid side. This will severely threaten the safety of the grid-connected voltage source converter (VSC) and consequently, affect the healthy operation condition of the load....... In this study, a new proportional-integral-resonant (PI-RES) controller-based, space vector modulated direct power control topology is proposed to suppress the dc-bus voltage ripple and in the same time, controlling effectively the instantaneous power of the VSC. A special ac reactive power reference component...... is introduced in the controller, which is necessary in order to reduce the dc-bus voltage ripple and active power harmonics at the same time. The proposed control topology is implemented in the lab. Simulation and experimental results are provided to validate its performance and the analysis presented...

  10. Design of a power amplifier for the LAMPF proton storage ring transverse damper system

    International Nuclear Information System (INIS)

    Lunsford, J.S.

    1981-01-01

    A power amplifier has been designed to drive the 50-Ω stripline deflection structures in the transverse active damper of the Los Alamos 800-MeV Proton Storage Ring (PSR). The unit will provide 600-V peak-to-peak with a dc-to-100-MHz bandwidth. Other important characteristics include < 40-ns delay time, 50-dB voltage gain, and 4-ns risetime with < 5% overshoot and ringing. Because of the current-drive properties of the amplifier, two amplifiers could be combined to provide over 1000-V peak-to-peak into 50 Ω, with very little bandwidth degradation. Components in the power amplifier that represent new designs are a 20-tube distributed-amplifier output stage; a driver stage, using VMOS FET and bipolar transistors; a high-voltage probe, with good dc stability and 150-MHz bandwidth; a transient suppressor circuit, using PIN diodes to protect the transistorized drivers from tube arcing; a nonlinear amplifier to compensate for the nonlinear characteristics of the distributed amplifier; and a first-fail indicator circuit to aid in locating the prime causes of equipment failures

  11. Cavity Voltage Phase Modulation MD blocks 3 and 4

    CERN Document Server

    Mastoridis, T; Butterworth, A; Molendijk, J; Tuckmantel, J

    2013-01-01

    The LHC RF/LLRF system is currently setup for extremely stable RF voltage to minimize transient beam loading effects. The present scheme cannot be extended beyond nominal beam current since the demanded power would push the klystrons to saturation. For beam currents above nominal (and possibly earlier), the cavity phase modulation by the beam (transient beam loading) will not be corrected, but the strong RF feedback and One-Turn Delay feedback will still be active for RF loop and beam stability in physics. To achieve this, the voltage set point should be adapted for each bunch. The goal of these MDs was to test thefirmware version of an iterative algorithm that adjusts the voltage set point to achieve the optimal phase modulation for klystron forward power considerations.

  12. Proposal and Development of a High Voltage Variable Frequency Alternating Current Power System for Hybrid Electric Aircraft

    Science.gov (United States)

    Sadey, David J.; Taylor, Linda M.; Beach, Raymond F.

    2017-01-01

    The development of ultra-efficient commercial vehicles and the transition to low-carbon emission propulsion are seen as strategic thrust paths within NASA Aeronautics. A critical enabler to these paths comes in the form of hybrid electric propulsion systems. For megawatt-class systems, the best power system topology for these hybrid electric propulsion systems is debatable. Current proposals within NASA and the Aero community suggest using a combination of alternating current (AC) and direct current (DC) for power generation, transmission, and distribution. This paper proposes an alternative to the current thought model through the use of a primarily high voltage AC power system, supported by the Convergent Aeronautics Solutions (CAS) Project. This system relies heavily on the use of doubly-fed induction machines (DFIMs), which provide high power densities, minimal power conversion, and variable speed operation. The paper presents background on the activity along with the system architecture, development status, and preliminary results.

  13. Current-voltage characteristics of individual conducting polymer nanotubes and nanowires

    Institute of Scientific and Technical Information of China (English)

    Long Yun-ze; Yin Zhi-Hua; Li Meng-Meng; Gu Chang-Zhi; Duvail Jean-Luc; Jin Ai-zi; Wan Mei-xiang

    2009-01-01

    We report the current-voltage (Ⅰ-Ⅴ) characteristics of individual polypyrrole nanotubes and poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires in a temperature range from 300 K to 2 K. Considering the complex structures of such quasi-one-dimensional systems with an array of ordered conductive regions separated by disordered barriers, we use the extended fluctuation-induced tunneling (FIT) and thermal excitation model (Kaiser expression) to fit the temperature and electric-field dependent Ⅰ-Ⅴ curves. It is found that the Ⅰ-Ⅴ data measured at higher temperatures or higher voltages can be well fitted by the Kaiser expression. However, the low-temperature data around the zero bias clearly deviate from those obtained from this model. The deviation (or zero-bias conductance suppression)could be possibly ascribed to the occurrence of the Coulomb-gap in the density of states near the Femi level and/or the enhancement of electron-electron interaction resulting from nanosize effects, which have been revealed in the previous studies on low-temperature electronic transport in conducting polymer films, pellets and nanostructures. In addition,similar Ⅰ-Ⅴ characteristics and deviation are also observed in an isolated K0.27MnO2 nanowire.

  14. A Comparative Study of Voltage, Peak Current and Dual Current Mode Control Methods for Noninverting Buck-Boost Converter

    Directory of Open Access Journals (Sweden)

    M. Č. Bošković

    2016-06-01

    Full Text Available This paper presents a comparison of voltage mode control (VMC and two current mode control (CMC methods of noninverting buck-boost converter. The converter control-to-output transfer function, line-to-output transfer function and the output impedance are obtained for all methods by averaging converter equations over one switching period and applying small-signal linearization. The obtained results are required for the design procedure of feedback compensator to keep a system stable and robust. A comparative study of VMC, peak current mode control (PCMC and dual-current mode control (DCMC is performed. Performance evaluation of the closed-loop system with obtained compensator between these methods is performed via numerical simulations.

  15. Autonomous Voltage Oscillations in a Direct Methanol Fuel Cell

    International Nuclear Information System (INIS)

    Nogueira, Jéssica A.; Peña Arias, Ivonne K.; Hanke-Rauschenbach, Richard; Vidakovic-Koch, Tanja; Varela, Hamilton; Sundmacher, Kai

    2016-01-01

    Proton exchange membrane fuel cells fed with H_2/CO mixtures at the anode have a considerably lower performance than fuel cells fed with pure hydrogen. However, when operated in an autonomous oscillatory regime, the overall voltage loss decreases due to a self-cleaning mechanism. Another molecule, also widely used as feed in the fuel cell and susceptible to kinetic instabilities, is methanol. To the best of our knowledge, there are no reports on autonomous voltage oscillations in the direct methanol fuel cell (DMFC). The purpose of this work was to explore if such instabilities also occur in the DMFC system. Initially, half-cell experiments with a gas diffusion electrode were performed. Then, a DMFC was operated under current control and studied by means of electrochemical impedance spectroscopy. The half-cell measurements revealed that the induction period for oscillations depends on the mass transfer conditions, where on stagnant electrode the induction time was shorter than in the case of forced convection. The DMFC showed also autonomous voltage oscillations above a certain threshold current. The results obtained by electrochemical impedance spectroscopy give evidence of a negative differential resistance in the fuel cell, hitherto not described in the literature, which can be related to the appearance of oscillations during galvanostatic methanol electro-oxidation. These results open the possibility to evaluate the performance of low-temperature fuel cells fed with carbon-containing fuels under oscillatory operating conditions.

  16. Enzyme domain affects the movement of the voltage sensor in ascidian and zebrafish voltage-sensing phosphatases.

    Science.gov (United States)

    Hossain, Md Israil; Iwasaki, Hirohide; Okochi, Yoshifumi; Chahine, Mohamed; Higashijima, Shinichi; Nagayama, Kuniaki; Okamura, Yasushi

    2008-06-27

    The ascidian voltage-sensing phosphatase (Ci-VSP) consists of the voltage sensor domain (VSD) and a cytoplasmic phosphatase region that has significant homology to the phosphatase and tensin homolog deleted on chromosome TEN (PTEN). The phosphatase activity of Ci-VSP is modified by the conformational change of the VSD. In many proteins, two protein modules are bidirectionally coupled, but it is unknown whether the phosphatase domain could affect the movement of the VSD in VSP. We addressed this issue by whole-cell patch recording of gating currents from a teleost VSP (Dr-VSP) cloned from Danio rerio expressed in tsA201 cells. Replacement of a critical cysteine residue, in the phosphatase active center of Dr-VSP, by serine sharpened both ON- and OFF-gating currents. Similar changes were produced by treatment with phosphatase inhibitors, pervanadate and orthovanadate, that constitutively bind to cysteine in the active catalytic center of phosphatases. The distinct kinetics of gating currents dependent on enzyme activity were not because of altered phosphatidylinositol 4,5-bisphosphate levels, because the kinetics of gating current did not change by depletion of phosphatidylinositol 4,5-bisphosphate, as reported by coexpressed KCNQ2/3 channels. These results indicate that the movement of the VSD is influenced by the enzymatic state of the cytoplasmic domain, providing an important clue for understanding mechanisms of coupling between the VSD and its effector.

  17. Electrochemical mass-flow control of hydrogen using a fullerene-based proton conductor

    International Nuclear Information System (INIS)

    Maruyama, Ryuichiro

    2002-01-01

    A membrane electrode assembly (MEA) was fabricated using proton conductive hydrogensulfated fullerenol (C 60 (OSO 3 H) n (OH) n ). Rate-controlled mass flow of hydrogen was performed by applying voltage to both electrodes of the MEA without humidification. The amount of the electrochemically transported hydrogen through the MEA increased as the applied current increased, obeying Faraday's law. Residual gas analysis of the transported hydrogen showed that the transported hydrogen contains trace amounts of water less than 1%

  18. Molecular and functional differences in voltage-activated sodium currents between GABA projection neurons and dopamine neurons in the substantia nigra

    OpenAIRE

    Ding, Shengyuan; Wei, Wei; Zhou, Fu-Ming

    2011-01-01

    GABA projection neurons (GABA neurons) in the substantia nigra pars reticulata (SNr) and dopamine projection neurons (DA neurons) in substantia nigra pars compacta (SNc) have strikingly different firing properties. SNc DA neurons fire low-frequency, long-duration spikes, whereas SNr GABA neurons fire high-frequency, short-duration spikes. Since voltage-activated sodium (NaV) channels are critical to spike generation, the different firing properties raise the possibility that, compared with DA...

  19. An improved low-voltage ride-through performance of DFIG based wind plant using stator dynamic composite fault current limiter.

    Science.gov (United States)

    Gayen, P K; Chatterjee, D; Goswami, S K

    2016-05-01

    In this paper, an enhanced low-voltage ride-through (LVRT) performance of a grid connected doubly fed induction generator (DFIG) has been presented with the usage of stator dynamic composite fault current limiter (SDCFCL). This protection circuit comprises of a suitable series resistor-inductor combination and parallel bidirectional semiconductor switch. The SDCFCL facilitates double benefits such as reduction of rotor induced open circuit voltage due to increased value of stator total inductance and concurrent increase of rotor impedance. Both effects will limit rotor circuit over current and over voltage situation more secured way in comparison to the conventional scheme like the dynamic rotor current limiter (RCL) during any type of fault situation. The proposed concept is validated through the simulation study of the grid integrated 2.0MW DFIG. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

  20. Current-voltage analysis of the record-efficiency CuGaSe2 solar cell: Application of the current separation method and the interface recombination model

    International Nuclear Information System (INIS)

    Saad, M.; Kasis, A.

    2011-01-01

    Current-voltage (j-V) characteristics of the record-efficiency CuGaSe 2 solar cell measured under several illumination levels are analyzed using a two-diode equation for a more accurate description of cell behavior. The contribution of each diode to the total cell j-V characteristic under illumination was estimated using the current separation method presented recently. This is performed in an effort to identify the distinctive features of this record-efficiency cell which have led to the up-to-date highest open circuit voltage of V o c = 946 mV and fill factor of FF = 66.5% for CuGaSe 2 solar cells. Furthermore, the interface recombination component of the cell current under illumination is quantitatively discussed applying the interface recombination model presented earlier. (author)

  1. Proton-recoil proportional-counter array for neutron-image construction

    International Nuclear Information System (INIS)

    Fink, C.L.; Eichholz, J.J.; DeVolpi, A.

    1984-01-01

    The fuel-motion measurement capability of the fast-neutron hodoscope has been upgraded by the addition of a 360-detector proton-recoil proportional-counter array, which detects high-energy fission neutrons. The current sensitive amplifier/discriminator module for each detector fits into a 12.7 by 12.7 by 102 mm package and cost less than $100 per module. It has a 50 ns rise time, a noise level of 100 nA, and a deadtime per event of 200 ns. Provision has been provided for the independent adjustment of the input current versus discriminator voltage for each module. The new proportional-counters cost approximately $400 each. Each detector has been tested to have the same gain versus voltage response. A space-charge model relating count-rate changes to space-charge effects has also been developed. The new detector array has been operational for approximately two years and has become the main detector system in fuel-motion analysis. It has significantly improved the linearity, stability, count-rate capability, and setup ease of the hodoscope

  2. High voltage systems

    International Nuclear Information System (INIS)

    Martin, M.

    1991-01-01

    Industrial processes usually require electrical power. This power is used to drive motors, to heat materials, or in electrochemical processes. Often the power requirements of a plant require the electric power to be delivered at high voltage. In this paper high voltage is considered any voltage over 600 V. This voltage could be as high as 138,000 V for some very large facilities. The characteristics of this voltage and the enormous amounts of power being transmitted necessitate special safety considerations. Safety must be considered during the four activities associated with a high voltage electrical system. These activities are: Design; Installation; Operation; and Maintenance

  3. Transformer-based asymmetrical embedded Z-source neutral point clamped inverters with continuous input current and enhanced voltage boost capability

    DEFF Research Database (Denmark)

    Mo, W.; Loh, Poh Chiang; Blaabjerg, Frede

    2013-01-01

    Z-source Neutral Point Clamped (NPC) inverters were introduced to integrate both the advantages of Z-source inverters and NPC inverters. However, traditional Z-source inverters suffer from high voltage stress and chopping input current. This paper proposes six types transformer-based impedance-so......-source NPC inverters which have enhanced voltage boost capability and continuous input current by utilizing of transformer and embedded dc source configuration. Experimental results are presented to verify the theory validation....

  4. Power-MOSFET Voltage Regulator

    Science.gov (United States)

    Miller, W. N.; Gray, O. E.

    1982-01-01

    Ninety-six parallel MOSFET devices with two-stage feedback circuit form a high-current dc voltage regulator that also acts as fully-on solid-state switch when fuel-cell out-put falls below regulated voltage. Ripple voltage is less than 20 mV, transient recovery time is less than 50 ms. Parallel MOSFET's act as high-current dc regulator and switch. Regulator can be used wherever large direct currents must be controlled. Can be applied to inverters, industrial furnaces photovoltaic solar generators, dc motors, and electric autos.

  5. Transformer current sensor for superconducting magnetic coils

    Science.gov (United States)

    Shen, S.S.; Wilson, C.T.

    1985-04-16

    The present invention is a current transformer for operating currents larger than 2kA (two kiloamps) that is capable of detecting a millivolt level resistive voltage in the presence of a large inductive voltage. Specifically, the present invention includes substantially cylindrical primary turns arranged to carry a primary current and substantially cylindrical secondary turns arranged coaxially with and only partially within the primary turns, the secondary turns including an active winding and a dummy winding, the active and dummy windings being coaxial, longitudinally separated and arranged to mutually cancel voltages excited by commonly experienced magnetic fields, the active winding but not the dummy winding being arranged within the primary turns.

  6. Active current control in wind power plants during grid faults

    DEFF Research Database (Denmark)

    Martinez, Jorge; Kjær, Phillip C.; Rodriguez, Pedro

    2010-01-01

    Modern wind power plants are required and designed to ride through faults in electrical networks, subject to fault clearing. Wind turbine fault current contribution is required from most countries with a high amount of wind power penetration. In order to comply with such grid code requirements......, wind turbines usually have solutions that enable the turbines to control the generation of reactive power during faults. This paper addresses the importance of using an optimal injection of active current during faults in order to fulfil these grid codes. This is of relevant importance for severe...... faults, causing low voltages at the point of common coupling. As a consequence, a new wind turbine current controller for operation during faults is proposed. It is shown that to achieve the maximum transfer of reactive current at the point of common coupling, a strategy for optimal setting of the active...

  7. Instability of Wind Turbine Converters during Current Injection to Low Voltage Grid Faults and PLL Frequency Based Stability Solution

    DEFF Research Database (Denmark)

    Göksu, Ömer; Teodorescu, Remus; Bak, Claus Leth

    2014-01-01

    In recent grid codes for wind power integration, wind turbines are required to stay connected during grid faults even when the grid voltage drops down to zero; and also to inject reactive current in proportion to the voltage drop. However, a physical fact, instability of grid-connected converters...... during current injection to very low (close to zero) voltage faults, has been omitted, i.e., failed to be noticed in the previous wind power studies and grid code revisions. In this paper, the instability of grid side converters of wind turbines defined as loss of synchronism (LOS), where the wind...... turbines lose synchronism with the grid fundamental frequency (e.g., 50 Hz) during very deep voltage sags, is explored with its theory, analyzed and a novel stability solution based on PLL frequency is proposed; and both are verified with power system simulations and by experiments on a grid...

  8. Measurements of fusion-protons anisotropy around the pinch axis within high-current PF-1000 experiments

    Energy Technology Data Exchange (ETDEWEB)

    Sadowski, M.J. [The Andrzej Soltan Institute for Nuclear Studies - IPJ, 05-400 Otwock-Swierk (Poland)] [Institute of Plasma Physics and Laser Microfusion - IPPLM, 01-497 Warsaw (Poland); Malinowska, A.; Malinowski, K.; Czaus, K.; Kwiatkowski, R.; Skladnik-Sadowska, E.; Zebrowski, J. [The Andrzej Soltan Institute for Nuclear Studies - IPJ, 05-400 Otwock-Swierk (Poland); Karpinski, L.; Paduch, M.; Scholz, M.; Stepniewski, W. [Institute of Plasma Physics and Laser Microfusion - IPPLM, 01-497 Warsaw (Poland)

    2011-07-01

    The paper describes measurements of fast protons produced by D-D fusion reactions during high-current discharges within the PF-1000 facility operated with the deuterium filling at 27 kV, 480 kJ. The measurements were performed by means of a set of pinhole-cameras equipped with PM-355 track detectors shielded by 80-{mu}m-thick Al-filters, which eliminated fast primary deuterons and protons of lower energy (< 3 MeV). Those cameras were placed at different angles around the pinch axis. The obtained proton images showed a distinct angular anisotropy, which was explained by an influence of local magnetic fields connected with a filamentary structure of the plasma column during the fast proton (and neutron) emission. The paper shows that in addition to measurements of a fusion neutron anisotropy it is reasonable to study also an anisotropy of fusion protons (originated from the second branch of the D-D reactions), as well as other charged fusion products. This document is composed of a paper followed by a poster

  9. 14 MeV proton activation analysis

    International Nuclear Information System (INIS)

    Constantinescu, B.; Ivanov, E.; Plostinaru, D.; Popa-Nemoiu, A.; Pascovichi, G.

    1985-01-01

    A fast nuclear nondestructive method for protein analysis using the 14 MeV proton activation has been developed. The total nitrogen content was measured through the reaction: 14 N (p,n) 14 O, (Tsub(1/2)=71 s). The 14 O activity was detected by means of its characteristic 2.312 MeV gamma-ray line with a NaI(Tl) detector. For a fast determination of a large number of samples a mechanized sistem reacting a rate of one sample per minute has been developed. The laboratory electronics comprises a multichannel analyser, a PDP computer and an electronic module comtroller. Comparison of the results obtained by the method described and the classical Kjeldal technique for samples of various cereal grains (soya bean seads, wheat, barley and corn) showed good correlation. A problem of the analysis of the whole protein region on corn and soya-bean seads, where this region is thicker (0,2 - 2 mm), is mentioned. In this case flour was proposed to be used to obtain a protein homogeneous sample and the irradiaton dose for a sample was about 33,000 Gy, mainly (99%) from protons (27 s x 100 nA x 14 MeV)

  10. LED-Based High-Voltage Lines Warning System

    Directory of Open Access Journals (Sweden)

    Eldar MUSA

    2013-04-01

    Full Text Available LED-based system, running with the current of high-voltage lines and converting the current flowing through the line into the light by using a toroid transformer, has been developed. The transformer’s primary winding is constituted by the high voltage power line. Toroidal core consists of two equal parts and the secondary windings are evenly placed on these two parts. The system is mounted on the high-voltage lines as a clamp. The secondary winding ends are connected in series by the connector on the clamp. LEDs are supplied by the voltage at the ends of secondary. Current flowing through highvoltage transmission lines is converted to voltage by the toroidal transformer and the light emitting LEDs are supplied with this voltage. The theory of the conversion of the current flowing through the line into the light is given. The system, running with the current of the line and converting the current into the light, has been developed. System has many application areas such as warning high voltage lines (warning winches to not hinder the high-voltage lines when working under the lines, warning planes to not touch the high-voltage lines, remote measurement of high-voltage line currents, and local illumination of the line area

  11. Direct model-based predictive control scheme without cost function for voltage source inverters with reduced common-mode voltage

    Science.gov (United States)

    Kim, Jae-Chang; Moon, Sung-Ki; Kwak, Sangshin

    2018-04-01

    This paper presents a direct model-based predictive control scheme for voltage source inverters (VSIs) with reduced common-mode voltages (CMVs). The developed method directly finds optimal vectors without using repetitive calculation of a cost function. To adjust output currents with the CMVs in the range of -Vdc/6 to +Vdc/6, the developed method uses voltage vectors, as finite control resources, excluding zero voltage vectors which produce the CMVs in the VSI within ±Vdc/2. In a model-based predictive control (MPC), not using zero voltage vectors increases the output current ripples and the current errors. To alleviate these problems, the developed method uses two non-zero voltage vectors in one sampling step. In addition, the voltage vectors scheduled to be used are directly selected at every sampling step once the developed method calculates the future reference voltage vector, saving the efforts of repeatedly calculating the cost function. And the two non-zero voltage vectors are optimally allocated to make the output current approach the reference current as close as possible. Thus, low CMV, rapid current-following capability and sufficient output current ripple performance are attained by the developed method. The results of a simulation and an experiment verify the effectiveness of the developed method.

  12. CCE measurements and annealing studies on proton-irradiated p-type MCz silicon diodes

    CERN Document Server

    Hoedlmoser, H; Köhler, M; Nordlund, H

    2007-01-01

    Magnetic Czochralski (MCz) silicon has recently been investigated for the development of radiation tolerant detectors for future high-luminosity HEP experiments. A study of p-type MCz Silicon diodes irradiated with protons up to a fluence of has been performed by means of Charge Collection Efficiency (CCE) measurements as well as standard CV/IV characterizations. The changes of CCE, full depletion voltage and leakage current as a function of fluence are reported. A subsequent annealing study of the irradiated detectors shows an increase in effective doping concentration and a decrease in the leakage current, whereas the CCE remains basically unchanged. Two different series of detectors have been compared differing in the implantation dose of p-spray isolation as well as effective doping concentration (Neff) of the p-type bulk presumably due to a difference in thermal donor (TD) activation during processing. The series with the higher concentration of TDs shows a delayed reverse annealing of Neff after irradia...

  13. High voltage dc-dc converter with dynamic voltage regulation and decoupling during load-generated arcs

    Science.gov (United States)

    Shimer, Daniel W.; Lange, Arnold C.

    1995-01-01

    A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules.

  14. High voltage dc--dc converter with dynamic voltage regulation and decoupling during load-generated arcs

    Science.gov (United States)

    Shimer, D.W.; Lange, A.C.

    1995-05-23

    A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules. 5 Figs.

  15. Improving the voltage quality of an inverter via by-passing the harmonic current components

    DEFF Research Database (Denmark)

    Zhong, Qing-Chang; Blaabjerg, Frede; Guerrero, Josep M.

    2012-01-01

    In this paper, a control strategy is proposed to improve the total harmonic distortion (THD) of the output voltage of an inverter. The physical interpretation of the control strategy is to connect shunt resonant filters at harmonic frequencies to the output so that the harmonic current components...

  16. Current and future applications of protons in medical imaging and treatment

    Energy Technology Data Exchange (ETDEWEB)

    Schulte, Reinhard W. [Loma Linda University Medical Center, CA (United States). Dept. of Radiation Medicine

    2011-07-01

    Protons have a more than 50-year history of applications in medical therapy and more recently also in imaging. Therapy with protons became possible after proton accelerators capable of accelerating protons to energies higher than 150 MeV had been built during the 1940s in a few places around the world. Proton radiography experiments started at the Harvard Cyclotron in the early 1960s. Physicist Allan Cormack, who shared the Nobel Prize for laying the foundation of computed tomography together with Sir Godfrey Hounsfield in 1979, suggested that protons can be used for tomographic imaging for the first time in 1963. Proton CT requires a rotating proton gantry, which did not become available until 1991, at our institution. The interest in proton CT has been renewed due to the fact that exact proton treatment planning is only possible with accurate knowledge of the relative proton stopping power distribution (with respect to water) of the patient, which is best derived by using protons for imaging. Early attempts to do proton CT were hampered by the lack of high-resolution particle trackers, fast data acquisition electronics, and sufficient computing power. Also, efficient proton CT reconstruction algorithms had to be developed that can handle reconstruction based on a large number of proton histories, taking into account the non-straight probabilistic paths of multiply scattered protons. Most of these challenges have been or are about to be solved with the help of high-energy and particle physicists, computer science engineers, and applied mathematicians. In this talk, I will give an update on the development of proton CT for applications in proton therapy. This is an update from a talk I gave at the Annual Brazilian Physics Meeting in 2001, when I first suggested that physicists should contribute to the development of modern proton CT. Brazilian physicists have provided many valuable ideas and discussions for this exciting development. (author)

  17. Current and future applications of protons in medical imaging and treatment

    International Nuclear Information System (INIS)

    Schulte, Reinhard W.

    2011-01-01

    Protons have a more than 50-year history of applications in medical therapy and more recently also in imaging. Therapy with protons became possible after proton accelerators capable of accelerating protons to energies higher than 150 MeV had been built during the 1940s in a few places around the world. Proton radiography experiments started at the Harvard Cyclotron in the early 1960s. Physicist Allan Cormack, who shared the Nobel Prize for laying the foundation of computed tomography together with Sir Godfrey Hounsfield in 1979, suggested that protons can be used for tomographic imaging for the first time in 1963. Proton CT requires a rotating proton gantry, which did not become available until 1991, at our institution. The interest in proton CT has been renewed due to the fact that exact proton treatment planning is only possible with accurate knowledge of the relative proton stopping power distribution (with respect to water) of the patient, which is best derived by using protons for imaging. Early attempts to do proton CT were hampered by the lack of high-resolution particle trackers, fast data acquisition electronics, and sufficient computing power. Also, efficient proton CT reconstruction algorithms had to be developed that can handle reconstruction based on a large number of proton histories, taking into account the non-straight probabilistic paths of multiply scattered protons. Most of these challenges have been or are about to be solved with the help of high-energy and particle physicists, computer science engineers, and applied mathematicians. In this talk, I will give an update on the development of proton CT for applications in proton therapy. This is an update from a talk I gave at the Annual Brazilian Physics Meeting in 2001, when I first suggested that physicists should contribute to the development of modern proton CT. Brazilian physicists have provided many valuable ideas and discussions for this exciting development. (author)

  18. Development of Multi-Functional Voltage Restore System

    Science.gov (United States)

    Suzuki, Satoshi; Ueda, Yoshinobu; Koganezawa, Takehisa; Ogihara, Yoshinori; Mori, Kenjiro; Fukazu, Naoaki

    Recently, with the dawn of the electric deregulation, the installation of distributed generation with power electronics device has grown. This current causes a greater concern of power quality, primarily voltage disturbance for power companies, and their interest in power quality is peaking. Utilities are also interested in keeping their customers satisfied, as well as keeping them on-line and creating more revenue for the utility. As a countermeasure against the above surroundings, a variety type of devices based on power electronics has been developed to protect customers' load from power line voltage disturbance. One of them is the series type voltage restore. The series device is an active device, designed to provide a pure sinusoidal load voltage at all times, correcting voltage disturbance. Series type device compensates for voltage anomalies by inserting the ‘missing’ voltage onto the line through insertion transformer and inverter. This paper shows the setting guideline of target level to compensate voltage disturbance, that is, voltage dip, voltage harmonics, voltage imbalance and voltage flicker, and the design approach of the prototype of series voltage restores to accomplish the required compensation level. The prototype system gives satisfactory compensation performance through evaluation tests, which confirm the validity and effectiveness of the system.

  19. A proton-activated, outwardly rectifying chloride channel in human umbilical vein endothelial cells

    International Nuclear Information System (INIS)

    Ma Zhiyong; Zhang Wei; Chen Liang; Wang Rong; Kan Xiaohong; Sun Guizhen; Liu Chunxi; Li Li; Zhang Yun

    2008-01-01

    Extracellular acidic pH-activated chloride channel I Cl,acid , has been characterized in HEK 293 cells and mammalian cardiac myocytes. This study was designed to characterize I Cl,acid in human umbilical vein endothelial cells(HUVECs). The activation and deactivation of the current rapidly and repeatedly follows the change of the extracellular solution at pH 4.3, with the threshold pH 5.3. In addition, at very positive potentials, the current displays a time-dependent facilitation. pH-response relationship for I Cl,acid revealed that EC 50 is pH 4.764 with a threshold pH value of pH 5.3 and nH of 14.545. The current can be blocked by the Cl - channel inhibitor DIDS (100 μM). In summary, for the first time we report the presence of proton-activated, outwardly rectifying chloride channel in HUVECs. Because an acidic environment can develop in local myocardium under pathological conditions such as myocardial ischemia, I Cl,acid would play a role in regulation of EC function under these pathological conditions

  20. Bimodal voltage dependence of TRPA1: mutations of a key pore helix residue reveal strong intrinsic voltage-dependent inactivation.

    Science.gov (United States)

    Wan, Xia; Lu, Yungang; Chen, Xueqin; Xiong, Jian; Zhou, Yuanda; Li, Ping; Xia, Bingqing; Li, Min; Zhu, Michael X; Gao, Zhaobing

    2014-07-01

    Transient receptor potential A1 (TRPA1) is implicated in somatosensory processing and pathological pain sensation. Although not strictly voltage-gated, ionic currents of TRPA1 typically rectify outwardly, indicating channel activation at depolarized membrane potentials. However, some reports also showed TRPA1 inactivation at high positive potentials, implicating voltage-dependent inactivation. Here we report a conserved leucine residue, L906, in the putative pore helix, which strongly impacts the voltage dependency of TRPA1. Mutation of the leucine to cysteine (L906C) converted the channel from outward to inward rectification independent of divalent cations and irrespective to stimulation by allyl isothiocyanate. The mutant, but not the wild-type channel, displayed exclusively voltage-dependent inactivation at positive potentials. The L906C mutation also exhibited reduced sensitivity to inhibition by TRPA1 blockers, HC030031 and ruthenium red. Further mutagenesis of the leucine to all natural amino acids individually revealed that most substitutions at L906 (15/19) resulted in inward rectification, with exceptions of three amino acids that dramatically reduced channel activity and one, methionine, which mimicked the wild-type channel. Our data are plausibly explained by a bimodal gating model involving both voltage-dependent activation and inactivation of TRPA1. We propose that the key pore helix residue, L906, plays an essential role in responding to the voltage-dependent gating.