Optimization of direct current-enhanced radiofrequency ablation: an ex vivo study.

PubMed

Tanaka, Toshihiro; Isfort, Peter; Bruners, Philipp; Penzkofer, Tobias; Kichikawa, Kimihiko; Schmitz-Rode, Thomas; Mahnken, Andreas H

2010-10-01

The purpose of this study was to investigate the optimal setting for radiofrequency (RF) ablation combined with direct electrical current (DC) ablation in ex vivo bovine liver. An electrical circuit combining a commercially available RF ablation system with DC was developed. The negative electrode of a rectifier that provides DC was connected to a 3-cm multitined expandable RF probe. A 100-mH inductor was used to prevent electrical leakage from the RF generator. DC was applied for 15 min and followed by RF ablation in freshly excised bovine livers. Electric current was measured by an ammeter. Coagulation volume, ablation duration, and mean amperage were assessed for various DC voltages (no DC, 2.2, 4.5, and 9.0 V) and different RF ablation protocols (stepwise increase from 40 to 80 W, 40 W fixed, and 80 W fixed). Results were compared using Kruskal-Wallis and Mann-Whitney U test. Applying DC with 4.5 or 9.0 V, in combination with 40 W fixed or a stepwise increase of RF energy, resulted in significantly increased zone of ablation size compared with 2.2 V or no DC (P = 0.009). At 4.5 V DC, the stepwise increase of RF energy resulted in the same necrosis size as a 40 W fixed protocol (26.6 +/- 3.9 vs. 26.5 +/- 4.0 ml), but ablation duration was significantly decreased (296 +/- 85 s vs. 423 +/- 104 s; P = 0.028). Mean amperage was significantly lower at 4.5 V compared with 9.0 V (P = 0.028). Combining a stepwise increase of RF energy with a DC voltage of 4.5 V is most appropriate to increase coagulation volume and to minimize procedure time.

Optimization of Direct Current-Enhanced Radiofrequency Ablation: An Ex Vivo Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, Toshihiro, E-mail: toshihir@bf6.so-net.ne.jp; Isfort, Peter; Bruners, Philipp

2010-10-15

The purpose of this study was to investigate the optimal setting for radiofrequency (RF) ablation combined with direct electrical current (DC) ablation in ex vivo bovine liver. An electrical circuit combining a commercially available RF ablation system with DC was developed. The negative electrode of a rectifier that provides DC was connected to a 3-cm multitined expandable RF probe. A 100-mH inductor was used to prevent electrical leakage from the RF generator. DC was applied for 15 min and followed by RF ablation in freshly excised bovine livers. Electric current was measured by an ammeter. Coagulation volume, ablation duration, andmore » mean amperage were assessed for various DC voltages (no DC, 2.2, 4.5, and 9.0 V) and different RF ablation protocols (stepwise increase from 40 to 80 W, 40 W fixed, and 80 W fixed). Results were compared using Kruskal-Wallis and Mann-Whitney U test. Applying DC with 4.5 or 9.0 V, in combination with 40 W fixed or a stepwise increase of RF energy, resulted in significantly increased zone of ablation size compared with 2.2 V or no DC (P = 0.009). At 4.5 V DC, the stepwise increase of RF energy resulted in the same necrosis size as a 40 W fixed protocol (26.6 {+-} 3.9 vs. 26.5 {+-} 4.0 ml), but ablation duration was significantly decreased (296 {+-} 85 s vs. 423 {+-} 104 s; P = 0.028). Mean amperage was significantly lower at 4.5 V compared with 9.0 V (P = 0.028). Combining a stepwise increase of RF energy with a DC voltage of 4.5 V is most appropriate to increase coagulation volume and to minimize procedure time.« less

Battery charging and discharging research based on the interactive technology of smart grid and electric vehicle

NASA Astrophysics Data System (ADS)

Zhang, Mingyang

2018-06-01

To further study the bidirectional flow problem of V2G (Vehicle to Grid) charge and discharge motor, the mathematical model of AC/DC converter and bi-directional DC/DC converter was established. Then, lithium battery was chosen as the battery of electric vehicle and its mathematical model was established. In order to improve the service life of lithium battery, bidirectional DC/DC converter adopted constant current and constant voltage control strategy. In the initial stage of charging, constant current charging was adopted with current single closed loop control. After reaching a certain value, voltage was switched to constant voltage charging controlled by voltage and current. Subsequently, the V2G system simulation model was built in MATLAB/Simulink. The simulation results verified the correctness of the control strategy and showed that when charging, constant current and constant voltage charging was achieved, the grid side voltage and current were in the same phase, and the power factor was about 1. When discharging, the constant current discharge was applied, and the grid voltage and current phase difference was r. To sum up, the simulation results are correct and helpful.

Synthesis of zirconium oxynitride in air under DC electric fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morisaki, Nobuhiro; Tokunaga, Tomoharu; Sasaki, Katsuhiro

We synthesized zirconium oxynitride from yttria-stabilized zirconia (YSZ) in air by applying DC electric fields that produced a controlled electric current in the specimen. When YSZ was heated under an applied DC electric field, the electric current of the specimen steeply increased at a critical temperature, called a flash event, during flash sintering. By keeping the electric current of the specimen constant during the flash event and then holding the specimen at the critical temperature, YSZ was transformed into zirconium oxynitride under the optimal conditions of 50 V/cm, 500 mA, and 1000 °C. We confirmed that zirconium oxynitride formed using high-resolution transmission electronmore » microscopy, electron energy-loss spectroscopy, and energy-dispersive spectrometry. To convert oxides to nitrides, reducing conditions are necessary to form excess oxygen vacancies. Our technique produced the strong reducing conditions necessary to form nitrides from the oxides by delivering a controlled electric current to the specimen.« less

Theory of controlling band-width broadening in terahertz sideband generation in semiconductors by a direct current electric field

NASA Astrophysics Data System (ADS)

Liu, Houquan; Zhang, Xingchu

2017-03-01

In a semiconductor, optically excited electron-hole pairs, driven by a strong terahertz (THz) field, can recombine to create THz sidebands in the optical spectrum. The sideband spectrum exhibits a "plateau" up to a cutoff frequency of 3.17Up, where Up is the ponderomotive energy. In this letter, we predict that the bandwidth of this sideband spectrum plateau can be broadened by applying an additional direct-current (DC) electric field. We find that if applying a DC field of EDC=0.2ETHz (where EDC and ETHz are the amplitudes of the DC field and THz field, respectively), the sideband spectrum presents three plateaus with 5.8Up, 10.05Up and 16Up being the cutoff frequencies of the first, second and third plateaus, respectively. This bandwidth broadening occurs because the DC field can increase the kinetic energy that an electron-hole pair can gain from the THz field. This effect means that the bandwidth of the sideband spectrum can be controlled flexibly by changing the DC field, thereby facilitating the ultrafast electro-optical applications of THz sideband generation.

Foundations of DC plasma sources

NASA Astrophysics Data System (ADS)

Tomas Gudmundsson, Jon; Hecimovic, Ante

2017-12-01

A typical dc discharge is configured with the negative cathode at one end and a positive anode at the other end, separated by a gas filled gap, placed inside a long glass cylinder. A few hundred volts between the cathode and anode is required to maintain the discharge. The type of discharge that is formed between the two electrodes depends upon the pressure of the working gas, the nature of the working gas, the applied voltage and the geometry of the discharge. We discuss the current-voltage characteristics of the discharge as well as the distinct structure that develops in the glow discharge region. The dc glow discharge appears in the discharge current range from μA to mA at 0.5-300 Pa pressure. We discuss the various phenomena observed in the dc glow discharge, including the cathode region, the positive column, and striations. The dc glow discharge is maintained by the emission of secondary electrons from the cathode target due to the bombardment of ions. For decades, the dc glow discharge has been used as a sputter source. Then it is often operated as an obstructed abnormal glow discharge and the required applied voltage is in the range 2-5 kV. Typically, the cathode target (the material to be deposited) is connected to a negative voltage supply (dc or rf) and the substrate holder faces the target. The relatively high operating pressure, in the range from 2 to 4 Pa, high applied voltages, and the necessity to have a conductive target limit the application of dc glow discharge as a sputter source. In order to lower the discharge voltage and expand the operation pressure range, the lifetime of the electrons in target vicinity is increased through applying magnetic field, by adding permanent magnets behind the cathode target. This arrangement is coined the magnetron sputtering discharge. The various configurations of the magnetron sputtering discharge and its applications are described. Furthermore, the use of dc discharges for chemical analysis, the Penning discharge and the hollow cathode discharges and some of its applications are briefly discussed.

The decolouration of methyl orange using aluminum foam, ultrasound and direct electric current

NASA Astrophysics Data System (ADS)

Liu, C. M.; Huang, X. Y.; Zhang, H. Y.; Dai, J. D.; Ning, C. C.

2018-01-01

The decolouration of methyl orange (MO) using aluminum (Al) foam, ultrasound and direct electric current (DC) is investigated. The decolouration rate (DR) of MO using only Al foam is low because there is a passivation oxide layer on the Al foam surface. Due to the low utilization of ultrasound in MO water solution medium, the DR of MO using only ultrasonic irradiation is also poor. The DR of MO is greatly increased when Al foam, ultrasonic irradiation and DC are used together. There is good synergistic effect between Al foam, ultrasound and DC in decolouration of MO. This enhancement of DR may be related to the cavitation, cleaning of Al foam surface and water electrolysis. Due to the surface charge on wire carrying stationary current, Al foam with DC acts like a serious anodes and cathodes and makes water electrolysis giving hydrogen gas to cleavage azo bond. The DC applied on Al foam is beneficial for reductive decolouration of MO. Our results show that DC is a new way for the reductive decolouration MO in water.

Applying to the DC Opportunity Scholarship Program: How Do Parents Rate Their Children's Current Schools at Time of Application and What Do They Want in New Schools? NCEE Evaluation Brief. NCEE 2016-4003

ERIC Educational Resources Information Center

Dynarski, Mark; Betts, Julian; Feldman, Jill

2016-01-01

The DC Opportunity Scholarship Program (OSP), established in 2004, is the only federally-funded private school voucher program for low-income parents in the United States. This evaluation brief describes findings using data from more than 2,000 applicants' parents, who applied to the program from spring 2011 to spring 2013 following…

Method and system for operating an electric motor

DOEpatents

Gallegos-Lopez, Gabriel; Hiti, Silva; Perisic, Milun

2013-01-22

Methods and systems for operating an electric motor having a plurality of windings with an inverter having a plurality of switches coupled to a voltage source are provided. A first plurality of switching vectors is applied to the plurality of switches. The first plurality of switching vectors includes a first ratio of first magnitude switching vectors to second magnitude switching vectors. A direct current (DC) current associated with the voltage source is monitored during the applying of the first plurality of switching vectors to the plurality of switches. A second ratio of the first magnitude switching vectors to the second magnitude switching vectors is selected based on the monitoring of the DC current associated with the voltage source. A second plurality of switching vectors is applied to the plurality of switches. The second plurality of switching vectors includes the second ratio of the first magnitude switching vectors to the second magnitude switching vectors.

Certain applied electrical signals during EPG cause negative effects on stylet probing behaviors by adult Lygus lineolaris (Hemiptera: Miridae).

PubMed

Backus, Elaine A; Cervantes, Felix A; Godfrey, Larry; Akbar, Waseem; Clark, Thomas L; Rojas, Maria G

This study is the first to fully evaluate whether electrical signals applied to large insects during electropenetrography (EPG; also called electrical penetration graph) negatively affect insect behavior. During EPG, electrical signals are applied to plants, and thus to the gold-wire-tethered insects feeding on them. The insect completes an electrical circuit whose changes in voltage reflect the insect's stylet probing/penetration behaviors, recorded as waveform output. For nearly 50 years of EPG science, evidence has supported that there are no or negligible effects on tiny insects from applied electricity during EPG. Recently however, EPG studies of large-bodied hemipterans such as heteropterans and sharpshooter leafhoppers have been published. The wider stylet diameters of such large insects cause them to have lower inherent resistances to applied signals compared with smaller insects, conveying more electrical current. The present study asked whether such increased currents would affect insect stylet probing, by comparing Lygus lineolaris behaviors on pin-head cotton squares using an AC-DC electropenetrograph. Effects of AC or DC applied signals were separately examined in two factorial studies, each comparing four input resistor (Ri) levels (10 6 , 10 7 , 10 8 and 10 9  Ω) and four applied voltage levels (2, 60, 150 and 250 mV). Results showed that changes in both probing and non-probing behaviors were indeed caused by changing signal type, Ri level, or applied voltage. Negative effects on feeding were numerically greater overall for DC than AC applied signals, perhaps due to muscular tetany from DC; however, AC versus DC could not be statistically tested. Results strongly support the need for flexible Ri and applied voltage levels and types, to tailor instrument settings to the size and special needs of each insect subject. Our findings will facilitate further EPG studies of Lygus spp., such as host plant resistance or insecticidal assays/bioassays to assess mode of action and appropriate dosage. It is hoped that this study will also inform EPG studies of similar, large heteropterans in the future. Published by Elsevier Ltd.

Multilayer Piezoelectric Stack Actuator Characterization

NASA Technical Reports Server (NTRS)

Sherrit, Stewart; Jones, Christopher M.; Aldrich, Jack B.; Blodget, Chad; Bao, Xioaqi; Badescu, Mircea; Bar-Cohen, Yoseph

2008-01-01

Future NASA missions are increasingly seeking to use actuators for precision positioning to accuracies of the order of fractions of a nanometer. For this purpose, multilayer piezoelectric stacks are being considered as actuators for driving these precision mechanisms. In this study, sets of commercial PZT stacks were tested in various AC and DC conditions at both nominal and extreme temperatures and voltages. AC signal testing included impedance, capacitance and dielectric loss factor of each actuator as a function of the small-signal driving sinusoidal frequency, and the ambient temperature. DC signal testing includes leakage current and displacement as a function of the applied DC voltage. The applied DC voltage was increased to over eight times the manufacturers' specifications to investigate the correlation between leakage current and breakdown voltage. Resonance characterization as a function of temperature was done over a temperature range of -180C to +200C which generally exceeded the manufacturers' specifications. In order to study the lifetime performance of these stacks, five actuators from one manufacturer were driven by a 60volt, 2 kHz sine-wave for ten billion cycles. The tests were performed using a Lab-View controlled automated data acquisition system that monitored the waveform of the stack electrical current and voltage. The measurements included the displacement, impedance, capacitance and leakage current and the analysis of the experimental results will be presented.

Single-contact tunneling thermometry

DOEpatents

Maksymovych, Petro

2016-02-23

A single-contact tunneling thermometry circuit includes a tunnel junction formed between two objects. Junction temperature gradient information is determined based on a mathematical relationship between a target alternating voltage applied across the junction and the junction temperature gradient. Total voltage measured across the junction indicates the magnitude of the target alternating voltage. A thermal gradient is induced across the junction. A reference thermovoltage is measured when zero alternating voltage is applied across the junction. An increasing alternating voltage is applied while measuring a thermovoltage component and a DC rectification voltage component created by the applied alternating voltage. The target alternating voltage is reached when the thermovoltage is nullified or doubled by the DC rectification voltage depending on the sign of the reference thermovoltage. Thermoelectric current and current measurements may be utilized in place of the thermovoltage and voltage measurements. The system may be automated with a feedback loop.

Modelling ac ripple currents in HTS coated conductors

NASA Astrophysics Data System (ADS)

Xu, Zhihan; Grilli, Francesco

2015-10-01

Dc transmission using high temperature superconducting (HTS) coated conductors (CCs) offers a promising solution to the globally growing demand for effective, reliable and economic transmission of green energy up to the gigawatt level over very long distances. The credible estimation of the losses and thereby the heat dissipation involved, where ac ripples (introduced in rectification/ac-dc conversion) are viewed as a potential source of notable contribution, is highly essential for the rational design of practical HTS dc transmission cables and corresponding cryogenic systems to fulfil this demand. Here we report a targeted modelling study into the ac losses in a HTS CC subject to dc and ac ripple currents simultaneously, by solving Maxwell’s equations using the finite element method (FEM) in the commercial software package COMSOL. It is observed that the instantaneous loss exhibits only one peak per cycle in the HTS CC subject to sinusoidal ripples, given that the amplitude of the ac ripples is smaller than approximately 20% of that of the dc current. This is a distinct contrast to the usual observation of two peaks per cycle in a HTS CC subject to ac currents only. The unique mechanism is also revealed, which is directly associated with the finding that, around any local minima of the applied ac ripples, the critical state of -J c is never reached at the edges of the HTS CC, as it should be according to the Bean model. When running further into the longer term, it is discovered that the ac ripple loss of the HTS CC in full-wave rectification decays monotonically, at a speed which is found to be insensitive to the frequency of the applied ripples within our targeted situations, to a relatively low level of approximately 1.38 × 10-4 W m-1 in around 1.7 s. Comparison between this level and other typical loss contributions in a HTS dc cable implies that ac ripple currents in HTS CCs should only be considered as a minor source of dissipation in superconducting dc transmission.

Arbitrary frequency tunable radio frequency bandpass filter based on nano-patterned Permalloy coplanar waveguide (invited)

NASA Astrophysics Data System (ADS)

Wang, Tengxing; Rahman, B. M. Farid; Peng, Yujia; Xia, Tian; Wang, Guoan

2015-05-01

A well designed coplanar waveguide (CPW) based center frequency tunable bandpass filter (BPF) at 4 GHz enabled with patterned Permalloy (Py) thin film has been implemented. The operating frequency of BPF is tunable with only DC current without the use of any external magnetic field. Electromagnetic bandgap resonators structure is adopted in the BPF and thus external DC current can be applied between the input and output of the filter for tuning of Py permeability. Special configurations of resonators with multiple narrow parallel sections have been considered for larger inductance tenability; the tunability of CPW transmission lines of different widths with patterned Py thin film on the top of the signal lines is compared and measured. Py thin film patterned as bars is deposited on the top of the multiple narrow parallel sections of the designed filter. No extra area is required for the designed filter configuration. Filter is measured and results show that its center frequency could be tuned from 4 GHz to 4.02 GHz when the DC current is applied from 0 mA to 400 mA.

Does trans‐spinal and local DC polarization affect presynaptic inhibition and post‐activation depression?

PubMed Central

Kaczmarek, D.; Ristikankare, J.

2017-01-01

Key points Trans‐spinal polarization was recently introduced as a means to improve deficient spinal functions. However, only a few attempts have been made to examine the mechanisms underlying DC actions. We have now examined the effects of DC on two spinal modulatory systems, presynaptic inhibition and post‐activation depression, considering whether they might weaken exaggerated spinal reflexes and enhance excessively weakened ones.Direct current effects were evoked by using local intraspinal DC application (0.3–0.4 μA) in deeply anaesthetized rats and were compared with the effects of trans‐spinal polarization (0.8–1.0 mA).Effects of local intraspinal DC were found to be polarity dependent, as locally applied cathodal polarization enhanced presynaptic inhibition and post‐activation depression, whereas anodal polarization weakened them. In contrast, both cathodal and anodal trans‐spinal polarization facilitated them.The results suggest some common DC‐sensitive mechanisms of presynaptic inhibition and post‐activation depression, because both were facilitated or depressed by DC in parallel. Abstract Direct current (DC) polarization has been demonstrated to alleviate the effects of various deficits in the operation of the central nervous system. However, the effects of trans‐spinal DC stimulation (tsDCS) have been investigated less extensively than the effects of transcranial DC stimulation, and their cellular mechanisms have not been elucidated. The main objectives of this study were, therefore, to extend our previous analysis of DC effects on the excitability of primary afferents and synaptic transmission by examining the effects of DC on two spinal modulatory feedback systems, presynaptic inhibition and post‐activation depression, in an anaesthetized rat preparation. Other objectives were to compare the effects of locally and trans‐spinally applied DC (locDC and tsDCS). Local polarization at the sites of terminal branching of afferent fibres was found to induce polarity‐dependent actions on presynaptic inhibition and post‐activation depression, as cathodal locDC enhanced them and anodal locDC depressed them. In contrast, tsDCS modulated presynaptic inhibition and post‐activation depression in a polarity‐independent fashion because both cathodal and anodal tsDCS facilitated them. The results show that the local presynaptic actions of DC might counteract both excessively strong and excessively weak monosynaptic actions of group Ia and cutaneous afferents. However, they indicate that trans‐spinally applied DC might counteract the exaggerated spinal reflexes but have an adverse effect on pathologically weakened spinal activity by additional presynaptic weakening. The results are also relevant for the analysis of the basic properties of presynaptic inhibition and post‐activation depression because they indicate that some common DC‐sensitive mechanisms contribute to them. PMID:27891626

Comparative study of 0° X-cut and Y + 36°-cut lithium niobate high-voltage sensing

NASA Astrophysics Data System (ADS)

Patel, N.; Branch, D. W.; Schamiloglu, E.; Cular, S.

2015-08-01

A comparison study between Y + 36° and 0° X-cut lithium niobate (LiNbO3) was performed to evaluate the influence of crystal cut on the acoustic propagation to realize a piezoelectric high-voltage sensor. The acoustic time-of-flight for each crystal cut was measured when applying direct current (DC), alternating current (AC), and pulsed voltages. Results show that the voltage-induced shift in the acoustic wave propagation time scaled quadratically with voltage for DC and AC voltages applied to X-cut crystals. For the Y + 36° crystal, the voltage-induced shift scales linearly with DC voltages and quadratically with AC voltages. When applying 5 μs voltage pulses to both crystals, the voltage-induced shift scaled linearly with voltage. For the Y + 36° cut, the voltage-induced shift from applying DC voltages ranged from 10 to 54 ps and 35 to 778 ps for AC voltages at 640 V over the frequency range of 100 Hz-100 kHz. Using the same conditions as the Y + 36° cut, the 0° X-cut crystal sensed a shift of 10-273 ps for DC voltages and 189-813 ps for AC voltage application. For 5 μs voltage pulses, the 0° X-cut crystal sensed a voltage induced shift of 0.250-2 ns and the Y + 36°-cut crystal sensed a time shift of 0.115-1.6 ns. This suggests a frequency sensitive response to voltage where the influence of the crystal cut was not a significant contributor under DC, AC, or pulsed voltage conditions. The measured DC data were compared to a 1-D impedance matrix model where the predicted incremental length changed as a function of voltage. When the voltage source error was eliminated through physical modeling from the uncertainty budget, the combined uncertainty of the sensor (within a 95% confidence interval) decreased to 0.0033% using a Y + 36°-cut crystal and 0.0032% using an X-cut crystal for all the voltage conditions used in this experiment.

Comparative study of 0° X-cut and Y + 36°-cut lithium niobate high-voltage sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, N.; Department of Electrical and Computer Engineering, MSC01 1100, University of New Mexico, Albuquerque, New Mexico 87131-0001; Branch, D. W.

2015-08-15

A comparison study between Y + 36° and 0° X-cut lithium niobate (LiNbO{sub 3}) was performed to evaluate the influence of crystal cut on the acoustic propagation to realize a piezoelectric high-voltage sensor. The acoustic time-of-flight for each crystal cut was measured when applying direct current (DC), alternating current (AC), and pulsed voltages. Results show that the voltage-induced shift in the acoustic wave propagation time scaled quadratically with voltage for DC and AC voltages applied to X-cut crystals. For the Y + 36° crystal, the voltage-induced shift scales linearly with DC voltages and quadratically with AC voltages. When applying 5more » μs voltage pulses to both crystals, the voltage-induced shift scaled linearly with voltage. For the Y + 36° cut, the voltage-induced shift from applying DC voltages ranged from 10 to 54 ps and 35 to 778 ps for AC voltages at 640 V over the frequency range of 100 Hz–100 kHz. Using the same conditions as the Y + 36° cut, the 0° X-cut crystal sensed a shift of 10–273 ps for DC voltages and 189–813 ps for AC voltage application. For 5 μs voltage pulses, the 0° X-cut crystal sensed a voltage induced shift of 0.250–2 ns and the Y + 36°-cut crystal sensed a time shift of 0.115–1.6 ns. This suggests a frequency sensitive response to voltage where the influence of the crystal cut was not a significant contributor under DC, AC, or pulsed voltage conditions. The measured DC data were compared to a 1-D impedance matrix model where the predicted incremental length changed as a function of voltage. When the voltage source error was eliminated through physical modeling from the uncertainty budget, the combined uncertainty of the sensor (within a 95% confidence interval) decreased to 0.0033% using a Y + 36°-cut crystal and 0.0032% using an X-cut crystal for all the voltage conditions used in this experiment.« less

Comparative study of 0° X-cut and Y+36°-cut lithium niobate high-voltage sensing

DOE PAGES

Patel, N.; Branch, D. W.; Schamiloglu, E.; ...

2015-08-11

A comparison study between Y+36° and 0° X-cut lithium niobate (LiNbO 3) was performed to evaluate the influence of crystal cut on the acoustic propagation to realize a piezoelectric high-voltage sensor. The acoustic time-of-flight for each crystal cut was measured when applying direct current (DC), alternating current (AC), and pulsed voltages. Results show that the voltage-induced shift in the acoustic wave propagation time scaled quadratically with voltage for DC and AC voltages applied to X-cut crystals. For the Y+36° crystal, the voltage-induced shift scales linearly with DC voltages and quadratically with AC voltages. When applying 5 μs voltage pulses tomore » both crystals, the voltage-induced shift scaled linearly with voltage. For the Y+36° cut, the voltage-induced shift from applying DC voltages ranged from 10 to 54 ps and 35 to 778 ps for AC voltages at 640 V over the frequency range of 100 Hz–100 kHz. Using the same conditions as the Y+36° cut, the 0° X-cut crystal sensed a shift of 10–273 ps for DC voltages and 189–813 ps for AC voltage application. For 5 μs voltage pulses, the 0° X-cut crystal sensed a voltage induced shift of 0.250–2 ns and the Y+36°-cut crystal sensed a time shift of 0.115–1.6 ns. This suggests a frequency sensitive response to voltage where the influence of the crystal cut was not a significant contributor under DC, AC, or pulsed voltage conditions. The measured DC data were compared to a 1-D impedance matrix model where the predicted incremental length changed as a function of voltage. Furthermore, when the voltage source error was eliminated through physical modeling from the uncertainty budget, the combined uncertainty of the sensor (within a 95% confidence interval) decreased to 0.0033% using a Y + 36°-cut crystal and 0.0032% using an X-cut crystal for all the voltage conditions used in this experiment.« less

Variable-frequency inverter controls torque, speed, and braking in ac induction motors

NASA Technical Reports Server (NTRS)

Nola, F. J.

1974-01-01

Dc to ac inverter provides optimum frequency and voltage to ac induction motor, in response to different motor-load and speed requirements. Inverter varies slip frequency of motor in proportion to required torque. Inverter protects motor from high current surges, controls negative slip to apply braking, and returns energy stored in momentum of load to dc power source.

Effect of an alternating current electric field on Co(OH)2 periodic precipitation

NASA Astrophysics Data System (ADS)

Karam, Tony; Sultan, Rabih

2013-02-01

The present paper studies the effect of an alternating current (AC) electric field on Co(OH)2 Liesegang patterns. In the presence of an AC electric field, the band spacing increases with spacing number, but reaches a plateau at large spacing (or band) numbers. The band spacing increases with applied AC voltage, but to a much lesser extent than the effect of a DC electric field under the same applied voltage [see R. Sultan, R. Halabieh, Chem. Phys. Lett. 332 (2000) 331][1]. At low enough applied voltage, the band spacing increases with frequency. At higher voltages, the band spacing becomes independent of the field frequency. The effect of concentration of the inner electrolyte (Co2+), exactly opposes that observed under DC electric field; i.e., the band spacing decreases with increasing concentration. The dynamics were shown to be governed by a competitive scenario between the diffusion gradient and the alternating current electric field factor.

A new type of single-phase five-level inverter

NASA Astrophysics Data System (ADS)

Xu, Zhi; Li, Shengnan; Qin, Risheng; Zhao, Yanhang

2017-11-01

At present, Neutral Point Clamped (NPC) multilevel inverter is widely applied in new energy field. However, it has some disadvantages including low utilization rate of direct current (DC) voltage source and the unbalance of neutral potential. Therefore, a new single-phase five level inverter is proposed in this paper. It has two stage structure, the former stage is equivalent to three level DC/DC converter, and the back stage uses H bridge to realize inverter. Compared with the original central clamp type inverter, the new five level inverter can improve the utilization of DC voltage, and realize the neutral point potential balance with hysteresis comparator.

Lymphocyte Electrotaxis in vitro and in vivo

PubMed Central

Lin, Francis; Baldessari, Fabio; Gyenge, Christina Crenguta; Sato, Tohru; Chambers, Robert D.; Santiago, Juan G.; Butcher, Eugene C.

2008-01-01

Electric fields are generated in vivo in a variety of physiologic and pathologic settings, including penetrating injury to epithelial barriers. An applied electric field with strength within the physiologic range can induce directional cell migration (i.e. electrotaxis) of epithelial cells, endothelial cells, fibroblasts, and neutrophils suggesting a potential role in cell positioning during wound healing. In the present study, we investigated the ability of lymphocytes to respond to applied direct current (DC) electric fields. Using a modified transwell assay and a simple microfluidic device, we show that human peripheral blood lymphocytes migrate toward the cathode in physiologically relevant DC electric fields. Additionally, electrical stimulation activates intracellular kinase signaling pathways shared with chemotactic stimuli. Finally, video microscopic tracing of GFP-tagged immunocytes in the skin of mouse ears reveals that motile cutaneous T cells actively migrate toward the cathode of an applied DC electric field. Lymphocyte positioning within tissues can thus be manipulated by externally applied electric fields, and may be influenced by endogenous electrical potential gradients as well. PMID:18684937

Lymphocyte electrotaxis in vitro and in vivo.

PubMed

Lin, Francis; Baldessari, Fabio; Gyenge, Christina Crenguta; Sato, Tohru; Chambers, Robert D; Santiago, Juan G; Butcher, Eugene C

2008-08-15

Electric fields are generated in vivo in a variety of physiologic and pathologic settings, including penetrating injury to epithelial barriers. An applied electric field with strength within the physiologic range can induce directional cell migration (i.e., electrotaxis) of epithelial cells, endothelial cells, fibroblasts, and neutrophils suggesting a potential role in cell positioning during wound healing. In the present study, we investigated the ability of lymphocytes to respond to applied direct current (DC) electric fields. Using a modified Transwell assay and a simple microfluidic device, we show that human PBLs migrate toward the cathode in physiologically relevant DC electric fields. Additionally, electrical stimulation activates intracellular kinase signaling pathways shared with chemotactic stimuli. Finally, video microscopic tracing of GFP-tagged immunocytes in the skin of mouse ears reveals that motile cutaneous T cells actively migrate toward the cathode of an applied DC electric field. Lymphocyte positioning within tissues can thus be manipulated by externally applied electric fields, and may be influenced by endogenous electrical potential gradients as well.

Analysis and Control of Pulse-Width Modulated AC to DC Voltage Source Converters.

NASA Astrophysics Data System (ADS)

Wu, Rusong

The pulse width modulated AC to DC voltage source converter is comprehensively analyzed in the thesis. A general mathematical model of the converter is first established, which is discontinuous, time-variant and non-linear. The following three techniques are used to obtain closed form solutions: Fourier analysis, transformation of reference frame and small signal linearization. Three models, namely, a steady-state DC model, a low frequency small signal AC model and a high frequency model, are consequently developed. Finally, three solution sets, namely, the steady-state solution, various dynamic transfer functions and the high frequency harmonic components, are obtained from the three models. Two control strategies, the Phase and Amplitude Control (PAC) and a new proposed strategy, Predicted Current Control with a Fixed Switching Frequency (PCFF), are investigated. Based on the transfer functions derived from the above mentioned analysis, regulators for a closed-loop control are designed. A prototype circuit is built to experimentally verify the theoretical predictions. The analysis and experimental results show that both strategies produce nearly sinusoidal line current with unity power factor on the utility side in both rectifying and regenerating operations and concurrently provide a regulated DC output voltage on the load side. However the proposed PCFF control has a faster and improved dynamic response over the PAC control. Moreover it is also easier to be implemented. Therefore, the PCFF control is preferable to the PAC control. As an example of application, a configuration of variable DC supply under PCFF control is proposed. The quasi-optimal dynamic response obtained shows that the PWM AC to DC converter lays the foundation for building a four-quadrant, fast-dynamic system, and the PCFF control is an effective strategy for improving dynamic performances not only as applied to the AC to DC converter, but also as applied to the DC to DC chopper or other circuits.

Burner ignition system

DOEpatents

Carignan, Forest J.

1986-01-21

An electronic ignition system for a gas burner is battery operated. The battery voltage is applied through a DC-DC chopper to a step-up transformer to charge a capacitor which provides the ignition spark. The step-up transformer has a significant leakage reactance in order to limit current flow from the battery during initial charging of the capacitor. A tank circuit at the input of the transformer returns magnetizing current resulting from the leakage reactance to the primary in succeeding cycles. An SCR in the output circuit is gated through a voltage divider which senses current flow through a flame. Once the flame is sensed, further sparks are precluded. The same flame sensor enables a thermopile driven main valve actuating circuit. A safety valve in series with the main gas valve responds to a control pressure thermostatically applied through a diaphragm. The valve closes after a predetermined delay determined by a time delay orifice if the pilot gas is not ignited.

Influence of electrical fields (AC and DC) on phytoremediation of metal polluted soils with rapeseed (Brassica napus) and tobacco (Nicotiana tabacum).

PubMed

Bi, Ran; Schlaak, Michael; Siefert, Eike; Lord, Richard; Connolly, Helen

2011-04-01

The combined use of electrokinetic remediation and phytoremediation to decontaminate soil polluted with heavy metals has been demonstrated in a laboratory-scale experiment. The plants species selected were rapeseed and tobacco. Three kinds of soil were used: un-contaminated soil from forest area (S1), artificially contaminated soil with 15mgkg(-1) Cd (S2) and multi-contaminated soil with Cd, Zn and Pb from an industrial area (S3). Three treatment conditions were applied to the plants growing in the experimental vessels: control (no electrical field), alternating current electrical field (AC, 1Vcm(-1)) and direct current electrical field (DC, 1Vcm(-1)) with switching polarity every 3h. The electrical fields were applied for 30d for rapeseed and 90d for tobacco, each experiment had three replicates. After a total of 90d growth for rapeseed and of 180d for tobacco, the plants were harvested. The pH variation from anode to cathode was eliminated by switching the polarity of the DC field. The plants reacted differently under the applied electrical field. Rapeseed biomass was enhanced under the AC field and no negative effect was found under DC field. However, no enhancement of the tobacco biomass under the AC treatment was found. The DC field had a negative influence on biomass production on tobacco plants. In general, Cd content was higher in both species growing in S2 treated with AC field compared to the control. Metal uptake (Cd, Cu, Zn and Pb) per rapeseed plant shoot was enhanced by the application of AC field in all soils. Copyright © 2010 Elsevier Ltd. All rights reserved.

Two high accuracy digital integrators for Rogowski current transducers.

PubMed

Luo, Pan-dian; Li, Hong-bin; Li, Zhen-hua

2014-01-01

The Rogowski current transducers have been widely used in AC current measurement, but their accuracy is mainly subject to the analog integrators, which have typical problems such as poor long-term stability and being susceptible to environmental conditions. The digital integrators can be another choice, but they cannot obtain a stable and accurate output for the reason that the DC component in original signal can be accumulated, which will lead to output DC drift. Unknown initial conditions can also result in integral output DC offset. This paper proposes two improved digital integrators used in Rogowski current transducers instead of traditional analog integrators for high measuring accuracy. A proportional-integral-derivative (PID) feedback controller and an attenuation coefficient have been applied in improving the Al-Alaoui integrator to change its DC response and get an ideal frequency response. For the special design in the field of digital signal processing, the improved digital integrators have better performance than analog integrators. Simulation models are built for the purpose of verification and comparison. The experiments prove that the designed integrators can achieve higher accuracy than analog integrators in steady-state response, transient-state response, and temperature changing condition.

Two high accuracy digital integrators for Rogowski current transducers

NASA Astrophysics Data System (ADS)

Luo, Pan-dian; Li, Hong-bin; Li, Zhen-hua

2014-01-01

The Rogowski current transducers have been widely used in AC current measurement, but their accuracy is mainly subject to the analog integrators, which have typical problems such as poor long-term stability and being susceptible to environmental conditions. The digital integrators can be another choice, but they cannot obtain a stable and accurate output for the reason that the DC component in original signal can be accumulated, which will lead to output DC drift. Unknown initial conditions can also result in integral output DC offset. This paper proposes two improved digital integrators used in Rogowski current transducers instead of traditional analog integrators for high measuring accuracy. A proportional-integral-derivative (PID) feedback controller and an attenuation coefficient have been applied in improving the Al-Alaoui integrator to change its DC response and get an ideal frequency response. For the special design in the field of digital signal processing, the improved digital integrators have better performance than analog integrators. Simulation models are built for the purpose of verification and comparison. The experiments prove that the designed integrators can achieve higher accuracy than analog integrators in steady-state response, transient-state response, and temperature changing condition.

Novel non-equilibrium modelling of a DC electric arc in argon

NASA Astrophysics Data System (ADS)

Baeva, M.; Benilov, M. S.; Almeida, N. A.; Uhrlandt, D.

2016-06-01

A novel non-equilibrium model has been developed to describe the interplay of heat and mass transfer and electric and magnetic fields in a DC electric arc. A complete diffusion treatment of particle fluxes, a generalized form of Ohm’s law, and numerical matching of the arc plasma with the space-charge sheaths adjacent to the electrodes are applied to analyze in detail the plasma parameters and the phenomena occurring in the plasma column and the near-electrode regions of a DC arc generated in atmospheric pressure argon for current levels from 20 A up to 200 A. Results comprising electric field and potential, current density, heating of the electrodes, and effects of thermal and chemical non-equilibrium are presented and discussed. The current-voltage characteristic obtained is in fair agreement with known experimental data. It indicates a minimum for arc current of about 80 A. For all current levels, a field reversal in front of the anode accompanied by a voltage drop of (0.7-2.6) V is observed. Another field reversal is observed near the cathode for arc currents below 80 A.

A low-power high-sensitivity analog front-end for PPG sensor.

PubMed

Binghui Lin; Atef, Mohamed; Guoxing Wang

2017-07-01

This paper presents a low-power analog front-end (AFE) photoplethysmography (PPG) sensor fabricated in 0.35 μm CMOS process. The AFE amplifies the weak photocurrent from the photodiode (PD) and converts it to a strong voltage at the output. In order to decrease the power consumption, the circuits are designed in subthreshold region; so the total biasing current of the AFE is 10 μ A. Since the large input DC photocurrent is a big issue for the PPG sensing circuit, we apply a DC photocurrent rejection technique by adding a DC current-cancellation loop to reject the large DC photocurrent up to 10 μA. In addition, a pseudo resistor is used to reduce the high-pass corner frequency below 0.5 Hz and Gm-C filter is adapted to reject the out-of-band noise higher than 16 Hz. For the whole sensor, the amplifier chain can achieve a total gain of 140 dBμ and an input integrated noise current of 68.87 pA rms up to 16 Hz.

Use of solar cell in electrokinetic remediation of cadmium-contaminated soil.

PubMed

Yuan, Songhu; Zheng, Zhonghua; Chen, Jing; Lu, Xiaohua

2009-03-15

This preliminary study used a solar cell, instead of direct current (DC) power supply, to generate electric field for electrokinetic (EK) remediation of cadmium-contaminated soil. Three EK tests were conducted and compared; one was conducted on a cloudy and rainy day with solar cell, one was conducted on a sunny day with solar cell and another was conducted periodically with DC power supply. It was found that the output potential of solar cell depended on daytime and was influenced by weather conditions; the applied potential in soil was affected by the output potential and weather conditions, and the current achieved by solar cell was comparable with that achieved by DC power supply. Solar cell could be used to drive the electromigration of cadmium in contaminated soil, and removal efficiency achieved by solar cell was comparable with that achieved by DC power supply. Compared with traditional DC power supply, using solar cell as power supply for EK remediation can greatly reduce energy expenditure. This study provided an alternative to improve the EK soil remediation and expanded the use of solar cell in environmental remediation.

Magnetic characteristics and AC losses of DC type-II superconductors under oscillating magnetic fields

NASA Astrophysics Data System (ADS)

Robert, B. C.; Ruiz, H. S.

2018-07-01

Remarkable features on the magnetic moment of type-II superconducting (SC) wires of cylindrical shape, subjected to direct current conditions (DC) and transverse oscillating (AC) magnetic fields, are reported. We show how for relatively low amplitudes of the applied magnetic field, B a , the superconducting wire rapidly develops a saturation state, | {M}p| , characterizing the limits of magnetization loops that exhibit a Boolean-like behaviour. Regardless of the premagnetization state of the SC wire, we show how after two cycles of magnetic relaxation, boolean-like ±M p states can be measured during the entire period of time from which the external magnetic field B 0 ranges from 0 to ±B a , with the signs rule defined by the sign of the slope ΔB 0y (t). In addition, for the practical implementation of SC DC wires sharing the right of way with AC lines, we report that for relatively low values of magnetic field, {B}a≤slant {B}P/2, being B P the analytical value for the full penetration field in absence of transport current, I tr, the use of semi-analytical approaches for the calculation of AC losses leads to a significant underestimation of the actual contribution of the induction losses. This phenomena is particularly relevant at dimensionless fields {b}a< 1-{i}a2/3, being b a = B a /B P and, i a = I a /I c the amplitude of an AC or DC transport current, due to the local motion of flux front profiles being dominated by the occurrence of transport current. On the other hand, we have found that regardless of the nature of the transport current, either be DC or AC, when a transverse oscillating magnetic field greater than the classical limit b a = (1 - i a ) is applied to the SC wire, the difference between the obtained AC losses in both situations results to be negligible indistinctly of the approach used, semi-analytical or numerical. Thus, the actual limits from which the estimation of the AC losses can be used as an asset for the deployment of DC SC wires sharing the right of way with AC lines, against the sole use of SC wires for the transmission of AC transport current, are established.

Electrically tunable transport and high-frequency dynamics in antiferromagnetic S r3I r2O7

NASA Astrophysics Data System (ADS)

Seinige, Heidi; Williamson, Morgan; Shen, Shida; Wang, Cheng; Cao, Gang; Zhou, Jianshi; Goodenough, John B.; Tsoi, Maxim

2016-12-01

We report dc and high-frequency transport properties of antiferromagnetic S r3I r2O7 . Temperature-dependent resistivity measurements show that the activation energy of this material can be tuned by an applied dc electrical bias. The latter allows for continuous variations in the sample resistivity of as much as 50% followed by a reversible resistive switching at higher biases. Such a switching is of high interest for antiferromagnetic applications in high-speed memory devices. Interestingly, we found the switching behavior to be strongly affected by a high-frequency (microwave) current applied to the sample. The microwaves at 3-7 GHz suppress the dc switching and produce resonancelike features that we tentatively associated with the dissipationless magnonics recently predicted to occur in antiferromagnetic insulators subject to ac electric fields. We have characterized the effects of microwave irradiation on electronic transport in S r3I r2O7 as a function of microwave frequency and power, strength and direction of external magnetic field, strength and polarity of applied dc bias, and temperature. Our observations support the potential of antiferromagnetic materials for high-speed/high-frequency spintronic applications.

A novel wireless power and data transmission AC to DC converter for an implantable device.

PubMed

Liu, Jhao-Yan; Tang, Kea-Tiong

2013-01-01

This article presents a novel AC to DC converter implemented by standard CMOS technology, applied for wireless power transmission. This circuit combines the functions of the rectifier and DC to DC converter, rather than using the rectifier to convert AC to DC and then supplying the required voltage with regulator as in the transitional method. This modification can reduce the power consumption and the area of the circuit. This circuit also transfers the loading condition back to the external circuit by the load shift keying(LSK), determining if the input power is not enough or excessive, which increases the efficiency of the total system. The AC to DC converter is fabricated with the TSMC 90nm CMOS process. The circuit area is 0.071mm(2). The circuit can produce a 1V DC voltage with maximum output current of 10mA from an AC input ranging from 1.5V to 2V, at 1MHz to 10MHz.

Ultrafast strong-field photoelectron emission from biased metal surfaces: exact solution to time-dependent Schrödinger Equation

PubMed Central

Zhang, Peng; Lau, Y. Y.

2016-01-01

Laser-driven ultrafast electron emission offers the possibility of manipulation and control of coherent electron motion in ultrashort spatiotemporal scales. Here, an analytical solution is constructed for the highly nonlinear electron emission from a dc biased metal surface illuminated by a single frequency laser, by solving the time-dependent Schrödinger equation exactly. The solution is valid for arbitrary combinations of dc electric field, laser electric field, laser frequency, metal work function and Fermi level. Various emission mechanisms, such as multiphoton absorption or emission, optical or dc field emission, are all included in this single formulation. The transition between different emission processes is analyzed in detail. The time-dependent emission current reveals that intense current modulation may be possible even with a low intensity laser, by merely increasing the applied dc bias. The results provide insights into the electron pulse generation and manipulation for many novel applications based on ultrafast laser-induced electron emission. PMID:26818710

Application of sub-micrometer patterned permalloy thin film in tunable radio frequency inductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rahman, B.M. Farid; Divan, Ralu; Rosenmann, Daniel

Electrical tunable meander line inductor using coplanar waveguide structures with patterned permalloy (Py) thin film has been designed and implemented in this paper. High resistivity Si substrate is used to reduce the dielectric loss from the substrate. Inductor is implemented with a 60 nm thick Py deposited and patterned on top of the gold meander line, and Py film is patterned with dimension of 440 nm 10 lm to create the shape anisotropy field, which in turn increases the FMR frequency. Compared to a regular meanderline inductor without the application of sub-micrometer patterned Py thin film, the inductance density hasmore » been increased to 20% for the implemented inductor with patterned Py. Measured FMR frequency of the patterned Py is 4.51 GHz without the application of any external magnetic field. This has enabled the inductor application in the practical circuit boards, where the large external magnet is unavailable. Inductance tunability of the implemented inductor is demonstrated by applying a DC current. Applied DC current creates a magnetic field along the hard axis of the patterned Py thin film, which changes the magnetic moment of the thin film and thus, decreases the inductance of the line. Measured results show that the inductance density of the inductor can be varied 5% by applying 300 mA DC current, larger inductance tunability is achievable by increasing the thickness of Py film. VC 2015 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4918766]« less

Combined Effect of Alternating Current Interference and Cathodic Protection on Pitting Corrosion and Stress Corrosion Cracking Behavior of X70 Pipeline Steel in Near-Neutral pH Environment.

PubMed

Wang, Liwei; Cheng, Lianjun; Li, Junru; Zhu, Zhifu; Bai, Shuowei; Cui, Zhongyu

2018-03-22

Influence of alternating current (AC) on pitting corrosion and stress corrosion cracking (SCC) behavior of X70 pipeline steel in the near-neutral pH environment under cathodic protection (CP) was investigated. Both corrosion and SCC are inhibited by -0.775 V SCE CP without AC interference. With the superimposition of AC current (1-10 mA/cm²), the direct current (DC) potential shifts negatively under the CP of -0.775 V SCE and the cathodic DC current decreases and shifts to the anodic direction. Under the CP potential of -0.95 V SCE and -1.2 V SCE , the applied AC current promotes the cathodic reaction and leads to the positive shift of DC potential and increase of cathodic current. Local anodic dissolution occurs attributing to the generated anodic current transients in the positive half-cycle of the AC current, resulting in the initiation of corrosion pits (0.6-2 μm in diameter). AC enhances the SCC susceptibility of X70 steel under -0.775 V SCE CP, attributing to the promotion of anodic dissolution and hydrogen evolution. Even an AC current as low as 1 mA/cm² can enhance the SCC susceptibility.

Effect of vacuum arc cathode spot distribution on breaking capacity of the arc-extinguishing chamber

NASA Astrophysics Data System (ADS)

Ding, Can; Yuan, Zhao; He, Junjia

2017-10-01

A DC circuit breaker performs a key function in breaking an intermediate-frequency (IF) current since breaking a pure IF current is equivalent to breaking a very small DC with a reverse IF current. In this study, it is found that cathode spots show a ring-shaped distribution at 2000 Hz. An arc with an uneven distribution of cathode spots has been simulated. The simulation results show that the distribution of cathode spots significantly affect the microparameter distribution of arc plasma. The current distribution on the anode side differs from that on the cathode side under the total radial electric field. Specifically, the anode current distribution is both uneven and concentrated. The applied axial magnetic field, which cannot reduce the concentrated anode current distribution effectively, might increase the concentration of the anode current. Finally, the uneven distribution of cathode spots reduces the breaking capacity of the arc-extinguishing chamber.

Skid Prevention for EVs Based on the Emulation of Torque Reduction Characteristics of Separately-excited DC Motor

NASA Astrophysics Data System (ADS)

Kodama, Shinya; Hori, Yoichi

It is well-known that the separately-excited DC motor has effective torque (current) reduction characteristics in response to rapid increase in the rotational speed of the motor. These characteristics have been utilized in adhesion control of electric railway trains with separately-excited DC motor. Up to now, we have proposed a new skid prevention method for EVs, utilizing these characteristics and have made experiments with the hardware skid simulator “Motor-Generator setup”. In this paper, we applied this skid prevention control to our new vehicle “UOT CADWELL EV" equipped with BLDC motors and showed its effectiveness.

Time-dependent photon heat transport through a mesoscopic Josephson device

NASA Astrophysics Data System (ADS)

Lu, Wen-Ting; Zhao, Hong-Kang

2017-02-01

The time-oscillating photon heat current through a dc voltage biased mesoscopic Josephson Junction (MJJ) has been investigated by employing the nonequilibrium Green's function approach. The Landauer-like formula of photon heat current has been derived in both of the Fourier space and its time-oscillating versions, where Coulomb interaction, self inductance, and magnetic flux take effective roles. Nonlinear behaviors are exhibited in the photon heat current due to the quantum nature of MJJ and applied external dc voltage. The magnitude of heat current decreases with increasing the external bias voltage, and subtle oscillation structures appear as the superposition of different photon heat branches. The overall period of heat current with respect to time is not affected by Coulomb interaction, however, the magnitude and phase of it vary considerably by changing the Coulomb interaction.

Transcranial cerebellar direct current stimulation and transcutaneous spinal cord direct current stimulation as innovative tools for neuroscientists

PubMed Central

Priori, Alberto; Ciocca, Matteo; Parazzini, Marta; Vergari, Maurizio; Ferrucci, Roberta

2014-01-01

Two neuromodulatory techniques based on applying direct current (DC) non-invasively through the skin, transcranial cerebellar direct current stimulation (tDCS) and transcutaneous spinal DCS, can induce prolonged functional changes consistent with a direct influence on the human cerebellum and spinal cord. In this article we review the major experimental works on cerebellar tDCS and on spinal tDCS, and their preliminary clinical applications. Cerebellar tDCS modulates cerebellar motor cortical inhibition, gait adaptation, motor behaviour, and cognition (learning, language, memory, attention). Spinal tDCS influences the ascending and descending spinal pathways, and spinal reflex excitability. In the anaesthetised mouse, DC stimulation applied under the skin along the entire spinal cord may affect GABAergic and glutamatergic systems. Preliminary clinical studies in patients with cerebellar disorders, and in animals and patients with spinal cord injuries, have reported beneficial effects. Overall the available data show that cerebellar tDCS and spinal tDCS are two novel approaches for inducing prolonged functional changes and neuroplasticity in the human cerebellum and spinal cord, and both are new tools for experimental and clinical neuroscientists. PMID:24907311

Modularized multilevel and z-source power converter as renewable energy interface for vehicle and grid-connected applications

NASA Astrophysics Data System (ADS)

Cao, Dong

Due the energy crisis and increased oil price, renewable energy sources such as photovoltaic panel, wind turbine, or thermoelectric generation module, are used more and more widely for vehicle and grid-connected applications. However, the output of these renewable energy sources varies according to different solar radiation, wind speed, or temperature difference, a power converter interface is required for the vehicle or grid-connected applications. Thermoelectric generation (TEG) module as a renewable energy source for automotive industry is becoming very popular recently. Because of the inherent characteristics of TEG modules, a low input voltage, high input current and high voltage gain dc-dc converters are needed for the automotive load. Traditional high voltage gain dc-dc converters are not suitable for automotive application in terms of size and high temperature operation. Switched-capacitor dc-dc converters have to be used for this application. However, high voltage spike and EMI problems exist in traditional switched-capacitor dc-dc converters. Huge capacitor banks have to be utilized to reduce the voltage ripple and achieve high efficiency. A series of zero current switching (ZCS) or zero voltage switching switched-capacitor dc-dc converters have been proposed to overcome the aforementioned problems of the traditional switched-capacitor dc-dc converters. By using the proposed soft-switching strategy, high voltage spike is reduced, high EMI noise is restricted, and the huge capacitor bank is eliminated. High efficiency, high power density and high temperature switched-capacitor dc-dc converters could be made for the TEG interface in vehicle applications. Several prototypes have been made to validate the proposed circuit and confirm the circuit operation. In order to apply PV panel for grid-connected application, a low cost dc-ac inverter interface is required. From the use of transformer and safety concern, two different solutions can be implemented, non-isolated or isolated PV inverter. For the non-isolated transformer-less solution, a semi-Z-source inverter for single phase photovoltaic systems has been proposed. The proposed semi-Z-source inverter utilizes only two switching devices with doubly grounded feature. The total cost have been reduced, the safety and EMI issues caused by the high frequency ground current are solved. For the transformer isolated solution, a boost half-bridge dc-ac micro-inverter has been proposed. The proposed boost half-bridge dc-dc converter utilizes only two switching devices with zero voltage switching features which is able to reduce the total system cost and power loss.

Operating characteristic analysis of a 400 mH class HTS DC reactor in connection with a laboratory scale LCC type HVDC system

NASA Astrophysics Data System (ADS)

Kim, Sung-Kyu; Kim, Kwangmin; Park, Minwon; Yu, In-Keun; Lee, Sangjin

2015-11-01

High temperature superconducting (HTS) devices are being developed due to their advantages. Most line commutated converter based high voltage direct current (HVDC) transmission systems for long-distance transmission require large inductance of DC reactor; however, generally, copper-based reactors cause a lot of electrical losses during the system operation. This is driving researchers to develop a new type of DC reactor using HTS wire. The authors have developed a 400 mH class HTS DC reactor and a laboratory scale test-bed for line-commutated converter type HVDC system and applied the HTS DC reactor to the HVDC system to investigate their operating characteristics. The 400 mH class HTS DC reactor is designed using a toroid type magnet. The HVDC system is designed in the form of a mono-pole system with thyristor-based 12-pulse power converters. In this paper, the investigation results of the HTS DC reactor in connection with the HVDC system are described. The operating characteristics of the HTS DC reactor are analyzed under various operating conditions of the system. Through the results, applicability of an HTS DC reactor in an HVDC system is discussed in detail.

Field Trial on a Rack-mounted DC Power Supply System with 80-Ah Lithium-ion Batteries

NASA Astrophysics Data System (ADS)

Matsushima, Toshio

Using an industrial lithium-ion battery that has higher energy density than conventional valve-regulated lead-acid batteries, a rack-mounted DC-power-supply system was assembled and tested at a base transceiver station (BTS) offering actual services. A nominal output voltage and maximum output current of the system is 53.5V and 20A, respectively. An 80-Ah lithium-ion battery composed of 13 cells connected in series was applied in the system and maintained in a floating charge method. The DC-power-supply system was installed in a 19-inch power rack in the telecommunications equipment box at BTS. The characteristics of the 80Ah lithium-ion battery, specifications of the DC-power-supply system and field-test results were shown in this paper.

Center conductor diagnostic for multipactor detection in inaccessible geometries.

PubMed

Chaplin, Vernon H; Hubble, Aimee A; Clements, Kathryn A; Graves, Timothy P

2017-01-01

Electron collecting current probes are the most reliable diagnostic of multipactor and radiofrequency (RF) ionization breakdown; however, stand-alone probes can only be used in test setups where the breakdown region is physically accessible. This paper describes techniques for measuring multipactor current directly on the center conductor of a coaxial RF device (or more generally, on the signal line in any two-conductor RF system) enabling global multipactor detection with improved sensitivity compared to other common diagnostics such as phase null, third harmonic, and reflected power. The center conductor diagnostic may be AC coupled for use in systems with a low DC impedance between the center conductor and ground. The effect of DC bias on the breakdown threshold was studied: in coaxial geometry, the change in threshold was <1 dB for positive biases satisfying V DC /V RF0 <0.8, where V RF0 is the RF voltage amplitude at the unperturbed breakdown threshold. In parallel plate geometry, setting V DC /V RF0 <0.2 was necessary to avoid altering the threshold by more than 1 dB. In most cases, the center conductor diagnostic functions effectively with no bias at all-this is the preferred implementation, but biases in the range V DC =0-10V may be applied if necessary. The polarity of the detected current signal may be positive or negative depending on whether there is net electron collection or emission globally.

Effect of water on sulfur dioxide (SO2) and nitrogen oxides (NOx) removal from flue gas in a direct current corona discharge reactor

NASA Astrophysics Data System (ADS)

Yang, Jiaxiang; Chi, Xiaochun; Dong, Limin

2007-05-01

A direct current (dc) corona discharge reactor composed of needle-plate electrodes in a glass container filled with flue gas was designed. To clarify the influence of water on discharge characteristics, water was introduced in the plasma reactor as electrode where plate electrode is immersed, under the application of dc voltage. Experiment results show that (1) corona wind forming between high-voltage needle electrode and water by corona discharge enhances the cleaning efficiency of flue gas due to the existence of water and the cleaning efficiency will increase with the increase of applied dc voltage within definite range and (2) both removal efficiencies of NOx and SO2 increased in the presence of water, which reach up to 98% for SO2, and about 85% for NOx under suitable conditions. These results play an important role in flue gas cleanup research.

Electric field modulated ferromagnetism in ZnO films deposited at room temperature

NASA Astrophysics Data System (ADS)

Bu, Jianpei; Liu, Xinran; Hao, Yanming; Zhou, Guangjun; Cheng, Bin; Huang, Wei; Xie, Jihao; Zhang, Heng; Qin, Hongwei; Hu, Jifan

2018-04-01

The ZnO film deposited at room temperature, which is composed of the amorphous-phase background plus a few nanograins or nanoclusters (about 1-2 nm), exhibits room temperature ferromagnetism (FM). Such FM is found to be connected with oxygen vacancies. For the Ta/ZnO/Pt device based on the medium layer ZnO deposited at room temperature, the saturation magnetization not only is modulated between high and low resistive states by electric voltage with DC loop electric current but also increases/decreases through adjusting the magnitudes of positive/negative DC sweeping voltage. Meanwhile, the voltage-controlled conductance quantization is observed in Ta/ZnO/Pt, accompanying the voltage-controlled magnetization. However, the saturation magnetization of the Ta/ZnO/Pt device becomes smaller under positive electric voltage and returns in some extent under negative electric voltage, when the DC loop electric current is not applied.

Performance enhanced miniaturized and electrically tunable patch antenna with patterned permalloy based magneto-dielectric substrate

NASA Astrophysics Data System (ADS)

Peng, Yujia; Farid Rahman, B. M.; Wang, Xuehe; Wang, Guoan

2014-05-01

Perspective magneto-dielectric materials with high permeability are potential substrates to miniaturize the patch antenna without deteriorating its performance. Besides its high permeability at high frequency, patterned Permalloy (Py) also presents tunable permeability by applying DC current. A performance enhanced miniaturized and electrically tunable patch antenna with patterned Py thin film is first presented and developed in this paper. To suppress the magnetic loss, the Py thin film layer is consisted of an array of 2 μm × 2 μm square Py patterns between the copper patch antenna and dielectric substrate. The DC current could be applied directly on Py patterns through the copper strip lines beneath the Py patterns along the length of patch antenna. The copper strip lines are specially designed with the same width of Py patterns and the thickness much less than the skin depth at the operating frequency, which can reduce their deteriorating effects to the performance of antenna. The structure of the antenna is presented and simulated with high frequency structure simulator. The results show that compared with non-magnetic antenna, the performance of Py thin film based antenna is improved with 50% bandwidth increase from 4 MHz to 8 MHz and 1.2 dB gain enhancement from 1.16 dB to 2.36 dB. The resonant frequency of the antenna could be continuously tuned from 937 MHz to 911 MHz with the permeability of Py thin film changing from 1750 to 1 900 by applying the DC current.

Time-evolution of photon heat current through series coupled two mesoscopic Josephson junction devices

NASA Astrophysics Data System (ADS)

Lu, Wen-Ting; Zhao, Hong-Kang; Wang, Jian

2018-03-01

Photon heat current tunneling through a series coupled two mesoscopic Josephson junction (MJJ) system biased by dc voltages has been investigated by employing the nonequilibrium Green’s function approach. The time-oscillating photon heat current is contributed by the superposition of different current branches associated with the frequencies of MJJs ω j (j = 1, 2). Nonlinear behaviors are exhibited to be induced by the self-inductance, Coulomb interaction, and interference effect relating to the coherent transport of Cooper pairs in the MJJs. Time-oscillating pumping photon heat current is generated in the absence of temperature difference, while it becomes zero after time-average. The combination of ω j and Coulomb interactions in the MJJs determines the concrete heat current configuration. As the external and intrinsic frequencies ω j and ω 0 of MJJs match some specific combinations, resonant photon heat current exhibits sinusoidal behaviors with large amplitudes. Symmetric and asymmetric evolutions versus time t with respect to ω 1 t and ω 2 t are controlled by the applied dc voltages of V 1 and V 2. The dc photon heat current formula is a special case of the general time-dependent heat current formula when the bias voltages are settled to zero. The Aharonov-Bohm effect has been investigated, and versatile oscillation structures of photon heat current can be achieved by tuning the magnetic fluxes threading through separating MJJs.

Growing Neural PC-12 Cell on Crosslinked Silica Aerogels Increases Neurite Extension in the Presence of an Electric Field.

PubMed

Lynch, Kyle J; Skalli, Omar; Sabri, Firouzeh

2018-04-20

Externally applied electrical stimulation (ES) has been shown to enhance the nerve regeneration process and to influence the directionality of neurite outgrowth. In addition, the physical and chemical properties of the substrate used for nerve-cell regeneration is critical in fostering regeneration. Previously, we have shown that polyurea-crosslinked silica aerogels (PCSA) exert a positive influence on the extension of neurites by PC-12 cells, a cell-line model widely used to study neurite extension and electrical excitability. In this work, we have examined how an externally applied electric field (EF) influences the extension of neurites in PC-12 cells grown on two substrates: collagen-coated dishes versus collagen-coated crosslinked silica aerogels. The externally applied direct current (DC) bias was applied in vitro using a custom-designed chamber containing polydimethysiloxane (PDMS) embedded copper electrodes to create an electric field across the substrate for the cultured PC-12 cells. Results suggest orientation preference towards the anode, and, on average, longer neurites in the presence of the applied DC bias than with 0 V DC bias. In addition, neurite length was increased in cells grown on silica-crosslinked aerogel when compared to cells grown on regular petri-dishes. These results further support the notion that PCSA is a promising material for nerve regeneration.

Time-dependent deformation of polymer network in polymer-stabilized cholesteric liquid crystals (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lee, Kyung Min; Tondiglia, Vincent P.; Bunning, Timothy J.; White, Timothy J.

2017-02-01

Recently, we reported direct current (DC) field controllable electro-optic (EO) responses of negative dielectric anisotropy polymer stabilized cholesteric liquid crystals (PSCLCs). A potential mechanism is: Ions in the liquid crystal mixtures are trapped in/on the polymer network during the fast photopolymerization process, and the movement of ions by the application of the DC field distorts polymer network toward the negative electrode, inducing pitch variation through the cell thickness, i.e., pitch compression on the negative electrode side and pitch expansion on positive electrode side. As the DC voltage is directly applied to a target voltage, charged polymer network is deformed and the reflection band is tuned. Interestingly, the polymer network deforms further (red shift of reflection band) with time when constantly applied DC voltage, illustrating DC field induced time dependent deformation of polymer network (creep-like behavior). This time dependent reflection band changes in PSCLCs are investigated by varying the several factors, such as type and concentration of photoinitiators, liquid crystal monomer content, and curing condition (UV intensity and curing time). In addition, simple linear viscoelastic spring-dashpot models, such as 2-parameter Kelvin and 3-parameter linear models, are used to investigate the time-dependent viscoelastic behaviors of polymer networks in PSCLC.

Dynamic characteristics of corona discharge generated under rainfall condition on AC charged conductors

NASA Astrophysics Data System (ADS)

Xu, Pengfei; Zhang, Bo; Wang, Zezhong; Chen, Shuiming; He, Jinliang

2017-12-01

By synchronous measurement of corona current and the water droplet deformation process on a conductor surface, different types of corona discharge are visualized when AC voltage is applied on a line-ground electrode system. The corona characteristics are closely related to the applied voltage and water supply rate. With the increase of AC voltage, the positive Taylor cone discharge firstly appears and then disappears, replaced by the dripping and crashing discharge. Furthermore, the number of pulses in each pulse train increases with the increase of applied voltage. The mechanism of the transfer from the positive Taylor cone discharge to the dripping and crashing discharge is found to be related to the oscillation process of the water droplet. The water supply rate also has a great influence on the characteristics of corona currents. The number of positive pulse trains increases linearly when the water supply rate gets larger, leading to a higher audible noise and radio interference level from the AC corona, which is quite different from that of the DC corona. The difference between the AC and DC coronas under rainfall conditions is analyzed finally.

A grid-connected single-phase photovoltaic micro inverter

NASA Astrophysics Data System (ADS)

Wen, X. Y.; Lin, P. J.; Chen, Z. C.; Wu, L. J.; Cheng, S. Y.

2017-11-01

In this paper, the topology of a single-phase grid-connected photovoltaic (PV) micro-inverter is proposed. The PV micro-inverter consists of DC-DC stage with high voltage gain boost and DC-AC conversion stage. In the first stage, we apply the active clamp circuit and two voltage multipliers to achieve soft switching technology and high voltage gain. In addition, the flower pollination algorithm (FPA) is employed for the maximum power point tracking (MPPT) in the PV module in this stage. The second stage cascades a H-bridge inverter and LCL filter. To feed high quality sinusoidal power into the grid, the software phase lock, outer voltage loop and inner current loop control method are adopted as the control strategy. The performance of the proposed topology is tested by Matlab/Simulink. A PV module with maximum power 300W and maximum power point voltage 40V is applied as the input source. The simulation results indicate that the proposed topology and the control strategy are feasible.

Electrical Stimulation Technologies for Wound Healing

PubMed Central

Kloth, Luther C.

2014-01-01

Objective: To discuss the physiological bases for using exogenously applied electric field (EF) energy to enhance wound healing with conductive electrical stimulation (ES) devices. Approach: To describe the types of electrical currents that have been reported to enhance chronic wound-healing rate and closure. Results: Commercial ES devices that generate direct current (DC), and mono and biphasic pulsed current waveforms represent the principal ES technologies which are reported to enhance wound healing. Innovation: Wafer-thin, disposable ES technologies (wound dressings) that utilize mini or micro-batteries to deliver low-level DC for wound healing and antibacterial wound-treatment purposes are commercially available. Microfluidic wound-healing chips are currently being used with greater accuracy to investigate the EF effects on cellular electrotaxis. Conclusion: Numerous clinical trials described in subsequent sections of this issue have demonstrated that ES used adjunctively with standard wound care (SWC), enhances wound healing rate faster than SWC alone. PMID:24761348

Design and dSpace interfacing of current fed high gain dc to dc boost converter for low voltage applications

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Debraj; Das, Subhrajit; Arunkumar, G.; Elangovan, D.; Ragunath, G.

2017-11-01

In this paper a current fed interleaved DC - DC boost converter which has an isolated topology and used for high voltage step up is proposed. A basic DC to DC boost converter converts uncontrolled DC voltage into controlled DC voltage of higher magnitude. Whereas this topology has the advantages of lower input current ripple, lesser output voltage, lesser stress on switches, faster transient response, improved reliability and much lesser electromagnetic emission over the conventional DC to DC boost converter. Most important benefit of this interleaved DC to DC boost converter is much higher efficiency. The input current is divided into two paths, substantially ohmic loss (I2R) and inductor ac loss gets reduced and finally the system achieves much higher efficiency. With recent mandates on energy saving interleaved DC to DC boost converter may be used as a very powerful tool to maintain good power density keeping the input current manageable. Higher efficiency also allows higher switching frequency and as a result the topology becomes more compact and cost friendly. The proposed topology boosts 48v DC to 200 V DC. Switching frequency is 100 kHz and PSIM 9.1 Platform has been used for the simulation.

Fiber optic current monitor for high-voltage applications

DOEpatents

Renda, G.F.

1992-04-21

A current monitor which derives its power from the conductor being measured for bidirectionally measuring the magnitude of current (from DC to above 50 khz) flowing through a conductor across which a relatively high level DC voltage is applied, includes a pair of identical transmitter modules connected in opposite polarity to one another in series with the conductor being monitored, for producing from one module a first light signal having an intensity directly proportional to the magnitude of current flowing in one direction through the conductor during one period of time, and from the other module a second light signal having an intensity directly proportional to the magnitude of current flowing in the opposite direction through the conductor during another period of time, and a receiver located in a safe area remote from the high voltage area for receiving the first and second light signals, and converting the same to first and second voltage signals having levels indicative of the magnitude of current being measured at a given time. 6 figs.

Fiber optic current monitor for high-voltage applications

DOEpatents

Renda, George F.

1992-01-01

A current monitor which derives its power from the conductor being measured for bidirectionally measuring the magnitude of current (from DC to above 50 khz) flowing through a conductor across which a relatively high level DC voltage is applied, includes a pair of identical transmitter modules connected in opposite polarity to one another in series with the conductor being monitored, for producing from one module a first light signal having an intensity directly proportional to the magnitude of current flowing in one direction through the conductor during one period of time, and from the other module a second light signal having an intensity directly proportional to the magnitude of current flowing in the opposite direction through the conductor during another period of time, and a receiver located in a safe area remote from the high voltage area for receiving the first and second light signals, and converting the same to first and second voltage signals having levels indicative of the magnitude of current being measured at a given time.

Tunable features of magnetoelectric transformers.

PubMed

Dong, Shuxiang; Zhai, Junyi; Priya, Shashank; Li, Jie-Fang; Viehland, Dwight

2009-06-01

We have found that magnetostrictive FeBSiC alloy ribbons laminated with piezoelectric Pb(Zr,Ti)O(3) fiber can act as a tunable transformer when driven under resonant conditions. These composites were also found to exhibit the strongest resonant magnetoelectric voltage coefficient of 750 V/cm-Oe. The tunable features were achieved by applying small dc magnetic biases of -5

Biasing and fast degaussing circuit for magnetic materials

DOEpatents

Dress, Jr., William B.; McNeilly, David R.

1984-01-01

A dual-function circuit is provided which may be used to both magnetically bias and alternately, quickly degauss a magnetic device. The circuit may be magnetically coupled or directly connected electrically to a magnetic device, such as a magnetostrictive transducer, to magnetically bias the device by applying a d.c. current and alternately apply a selectively damped a.c. current to the device to degauss the device. The circuit is of particular value in many systems which use magnetostrictive transducers for ultrasonic transmission in different propagation modes over very short time periods.

Biasing and fast degaussing circuit for magnetic materials

DOEpatents

Dress, W.B. Jr.; McNeilly, D.R.

1983-10-04

A dual-function circuit is provided which may be used to both magnetically bias and alternately, quickly degauss a magnetic device. The circuit may be magnetically coupled or directly connected electrically to a magnetic device, such as a magnetostrictive transducer, to magnetically bias the device by applying a dc current and alternately apply a selectively damped ac current to the device to degauss the device. The circuit is of particular value in many systems which use magnetostrictive transducers for ultrasonic transmission in different propagation modes over very short time periods.

Conductive paths through polycrystalline BaTiO{sub 3}: Scanning probe microscopy study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ayvazian, Talin; Bersuker, Gennadi; Lingley, Zachary R.

2016-08-15

The microstructural features determining the leakage current through polycrystalline BaTiO{sub 3} films are investigated using Conductive Atomic Force Microscopy. Grain boundaries are found to be the dominant conductive paths compared to the conduction through the grains. Grain boundary currents are observed to reversibly rise with the increase of the applied DC voltages, indicating that the current is controlled by a field-activated charge transport process.

Effect of anode-cathode geometry on performance of the HIP-1 hot ion plasma. [magnetic mirrors

NASA Technical Reports Server (NTRS)

Lauver, M. R.

1978-01-01

Hot-ion hydrogen plasma experiments were conducted in the NASA Lewis HIP-1 magnetic mirror facility to determine how the ion temperature was influenced by the axial position of the cathode tips relative to the anodes. A steady-state EXB plasma was formed by applying a strong radially inward dc electric field near the throats of the magnetic mirrors. The dc electric field was created between hollow cathode rods inside hollow anode cylinders, both concentric with the magnetic axis. The highest ion temperatures, 900 eV, were attained when the tip of each cathode was in the same plane as the end of its anode. These temperatures were reached with 22 kV applied to the electrodes in a field of 1.1 tesla. Scaling relations were empirically determined for ion temperature and the product of ion density and neutral particle density as a function of cathode voltage, discharge current, and electrode positions. Plasma discharge current vs voltage (I-V) characteristics were determined.

Pulsed DC Electric Field–Induced Differentiation of Cortical Neural Precursor Cells

PubMed Central

Chang, Hui-Fang; Lee, Ying-Shan; Tang, Tang K.; Cheng, Ji-Yen

2016-01-01

We report the differentiation of neural stem and progenitor cells solely induced by direct current (DC) pulses stimulation. Neural stem and progenitor cells in the adult mammalian brain are promising candidates for the development of therapeutic neuroregeneration strategies. The differentiation of neural stem and progenitor cells depends on various in vivo environmental factors, such as nerve growth factor and endogenous EF. In this study, we demonstrated that the morphologic and phenotypic changes of mouse neural stem and progenitor cells (mNPCs) could be induced solely by exposure to square-wave DC pulses (magnitude 300 mV/mm at frequency of 100-Hz). The DC pulse stimulation was conducted for 48 h, and the morphologic changes of mNPCs were monitored continuously. The length of primary processes and the amount of branching significantly increased after stimulation by DC pulses for 48 h. After DC pulse treatment, the mNPCs differentiated into neurons, astrocytes, and oligodendrocytes simultaneously in stem cell maintenance medium. Our results suggest that simple DC pulse treatment could control the fate of NPCs. With further studies, DC pulses may be applied to manipulate NPC differentiation and may be used for the development of therapeutic strategies that employ NPCs to treat nervous system disorders. PMID:27352251

Pulsed Direct Current Electrospray: Enabling Systematic Analysis of Small Volume Sample by Boosting Sample Economy.

PubMed

Wei, Zhenwei; Xiong, Xingchuang; Guo, Chengan; Si, Xingyu; Zhao, Yaoyao; He, Muyi; Yang, Chengdui; Xu, Wei; Tang, Fei; Fang, Xiang; Zhang, Sichun; Zhang, Xinrong

2015-11-17

We had developed pulsed direct current electrospray ionization mass spectrometry (pulsed-dc-ESI-MS) for systematically profiling and determining components in small volume sample. Pulsed-dc-ESI utilized constant high voltage to induce the generation of single polarity pulsed electrospray remotely. This method had significantly boosted the sample economy, so as to obtain several minutes MS signal duration from merely picoliter volume sample. The elongated MS signal duration enable us to collect abundant MS(2) information on interested components in a small volume sample for systematical analysis. This method had been successfully applied for single cell metabolomics analysis. We had obtained 2-D profile of metabolites (including exact mass and MS(2) data) from single plant and mammalian cell, concerning 1034 components and 656 components for Allium cepa and HeLa cells, respectively. Further identification had found 162 compounds and 28 different modification groups of 141 saccharides in a single Allium cepa cell, indicating pulsed-dc-ESI a powerful tool for small volume sample systematical analysis.

Characterization of polymer, DNA-based, and silk thin film resistivities and of DNA-based films prepared for enhanced electrical conductivity

NASA Astrophysics Data System (ADS)

Yaney, Perry P.; Ouchen, Fahima; Grote, James G.

2009-08-01

DC resistivity studies were carried out on biopolymer films of DNA-CTMA and silk fibroin, and on selected traditional polymer films, including PMMA and APC. Films of DNA-CTMA versus molecular weight and with conductive dopants PCBM, BAYTRON P and ammonium tetrachloroplatinate are reported. The films were spin coated on glass slides configured for measurements of volume dc resistance. The measurements used the alternating polarity method to record the applied voltage-dependent current independent of charging and background currents. The Arrhenius equation plus a constant was fitted to the conductivity versus temperature data of the polymers and the non-doped DNA-based biopolymers with activation energies ranging from 0.8 to 1.4 eV.

Novel bidirectional DC-DC converters based on the three-state switching cell

NASA Astrophysics Data System (ADS)

da Silva Júnior, José Carlos; Robles Balestero, Juan Paulo; Lessa Tofoli, Fernando

2016-05-01

It is well known that there is an increasing demand for bidirectional DC-DC converters for applications that range from renewable energy sources to electric vehicles. Within this context, this work proposes novel DC-DC converter topologies that use the three-state switching cell (3SSC), whose well-known advantages over conventional existing structures are ability to operate at high current levels, while current sharing is maintained by a high frequency transformer; reduction of cost and dimensions of magnetics; improved distribution of losses, with consequent increase of global efficiency and reduction of cost associated to the need of semiconductors with lower current ratings. Three distinct topologies can be derived from the 3SSC: one DC-DC converter with reversible current characteristic able to operate in the first and second quadrants; one DC-DC converter with reversible voltage characteristic able to operate in the first and third quadrants and one DC-DC converter with reversible current and voltage characteristics able to operate in four quadrants. Only the topology with bidirectional current characteristic is analysed in detail in terms of the operating stages in both nonoverlapping and overlapping modes, while the design procedure of the power stage elements is obtained. In order to validate the theoretical assumptions, an experimental prototype is also implemented, so that relevant issues can be properly discussed.

Influences of electric current on the wettability and interfacial microstructure in Sn/Fe system

NASA Astrophysics Data System (ADS)

Shen, Ping; Gu, Yan; Yang, Nan-Nan; Zheng, Rui-Peng; Ren, Li-Hua

2015-02-01

The wettability of oxidized and clean Fe substrates by liquid Sn was investigated using a dispensed sessile drop method with and without the application of a direct current (DC) and their interfacial microstructures were compared. The initial contact angles were 107 ± 3° at 623 K when the Fe substrate was covered by an oxide film, and they did not show an appreciable decrease during isothermal dwells in the absence of DC application but progressively decreased to 42 ± 3° when a 7.5 ampere current was applied. However, in the case of the oxide film being removed by a high-vacuum pre-annealing treatment at 1073 K, the current and its polarity had a negligible effect on the wetting behavior. Nevertheless, they had a noticeable influence on the interfacial microstructure. In the absence of DC, the interface was covered by a product layer consisting of a single FeSn2 phase for the samples tested at 623 K and the FeSn2/FeSn2 grain boundaries were incompletely wetted by the Sn melt; whereas, under DC, the reaction layer was much thicker and the Sn melt wet well the FeSn2/FeSn2 grain boundaries. Moreover, a FeSn phase also formed as a result of enhanced mass transfer. The amount of the FeSn phase was larger and the grain boundary wetting of FeSn2 by liquid Sn was better for the current flowing from the molten Sn drop to the Fe substrate due to an electromigration effect.

Research and Construction of DC Energy Measurement Traceability Technology

NASA Astrophysics Data System (ADS)

Zhi, Wang; Maotao, Yang; Jing, Yang

2018-02-01

With the implementation of energy saving and emission reduction policies, DC energy metering has been widely used in many fields. In view of the lack of a DC energy measurementtraceability system, in combination with the process of downward measurement transfer in relation to the DC charger-based field calibration technology and DC energy meter and shunt calibration technologies, the paper proposed DC fast charging, high DC, small DC voltage output and measuring technologies, and built a time-based plan by converting high DC voltage into low voltage and high current into low current and then into low voltage, leaving DC energy traceable to national standards in terms of voltage, current and time and thus filling in the gap in DC energy measurement traceability.

Influence of electrically induced refraction and absorption on the measurement of spin current by pockels effect in GaAs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Houquan; She, Weilong, E-mail: shewl@mail.sysu.edu.cn

2015-03-14

The pockels effect could be utilized to measure spin current in semiconductors for linear electro-optic coefficient can be induced by spin current. When dc electric field is applied, the carriers will shift in k space, which could lead to the change of refraction and absorption coefficients. In this paper, we investigate the influence of the induced change of the refraction and absorption coefficients on the measurement of spin current by pockels effect in GaAs.

Analysis of Proportional Integral and Optimized Proportional Integral Controllers for Resistance Spot Welding System (RSWS) - A Performance Perspective

NASA Astrophysics Data System (ADS)

Rama Subbanna, S.; Suryakalavathi, M., Dr.

2017-08-01

This paper is an attempt to accomplish a performance analysis of the different control techniques on spikes reduction method applied on the medium frequency transformer based DC spot welding system. Spike reduction is an important factor to be considered while spot welding systems are concerned. During normal RSWS operation welding transformer’s magnetic core can become saturated due to the unbalanced resistances of both transformer secondary windings and different characteristics of output rectifier diodes, which causes current spikes and over-current protection switch-off of the entire system. The current control technique is a piecewise linear control technique that is inspired from the DC-DC converter control algorithms to register a novel spike reduction method in the MFDC spot welding applications. Two controllers that were used for the spike reduction portion of the overall applications involve the traditional PI controller and Optimized PI controller. Care is taken such that the current control technique would maintain a reduced spikes in the primary current of the transformer while it reduces the Total Harmonic Distortion. The performance parameter that is involved in the spikes reduction technique is the THD, Percentage of current spike reduction for both techniques. Matlab/SimulinkTM based simulation is carried out for the MFDC RSWS with KW and results are tabulated for the PI and Optimized PI controllers and a tradeoff analysis is carried out.

Current-driven non-linear magnetodynamics in exchange-biased spin valves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seinige, Heidi; Wang, Cheng; Tsoi, Maxim, E-mail: tsoi@physics.utexas.edu

2015-05-07

This work investigates the excitation of parametric resonance in exchange-biased spin valves (EBSVs). Using a mechanical point contact, high density dc and microwave currents were injected into the EBSV sample. Observing the reflected microwave power and the small rectification voltage that develops across the contact allows detecting the current-driven magnetodynamics not only in the bulk sample but originating exclusively from the small contact region. In addition to ferromagnetic resonance (FMR), parametric resonance at twice the natural FMR frequency was observed. In contrast to FMR, this non-linear resonance was excited only in the vicinity of the point contact where current densitiesmore » are high. Power-dependent measurements displayed a typical threshold-like behavior of parametric resonance and a broadening of the instability region with increasing power. Parametric resonance showed a linear shift as a function of applied dc bias which is consistent with the field-like spin-transfer torque induced by current on magnetic moments in EBSV.« less

AC/DC current ratio in a current superimposition variable flux reluctance machine

NASA Astrophysics Data System (ADS)

Kohara, Akira; Hirata, Katsuhiro; Niguchi, Noboru; Takahara, Kazuaki

2018-05-01

We have proposed a current superimposition variable flux reluctance machine for traction motors. The torque-speed characteristics of this machine can be controlled by increasing or decreasing the DC current. In this paper, we discuss an AC/DC current ratio in the current superimposition variable flux reluctance machine. The structure and control method are described, and the characteristics are computed using FEA in several AC/DC ratios.

EMERGING TECHNOLOGY SUMMARY: THEORETICAL AND EXPERIMENTAL MODELING OF MULTI-SPECIES TRANSPORT IN SOILS UNDER ELECTRIC FIELDS

EPA Science Inventory

This project investigated an innovative approach for transport of inorganic species under the influence of electric fields. This process, commonly known as electrokinetics uses low-level direct current (dc) electrical potential difference across a soil mass applied through inert...

Maximum Power Point Tracking with Dichotomy and Gradient Method for Automobile Exhaust Thermoelectric Generators

NASA Astrophysics Data System (ADS)

Fang, W.; Quan, S. H.; Xie, C. J.; Tang, X. F.; Wang, L. L.; Huang, L.

2016-03-01

In this study, a direct-current/direct-current (DC/DC) converter with maximum power point tracking (MPPT) is developed to down-convert the high voltage DC output from a thermoelectric generator to the lower voltage required to charge batteries. To improve the tracking accuracy and speed of the converter, a novel MPPT control scheme characterized by an aggregated dichotomy and gradient (ADG) method is proposed. In the first stage, the dichotomy algorithm is used as a fast search method to find the approximate region of the maximum power point. The gradient method is then applied for rapid and accurate tracking of the maximum power point. To validate the proposed MPPT method, a test bench composed of an automobile exhaust thermoelectric generator was constructed for harvesting the automotive exhaust heat energy. Steady-state and transient tracking experiments under five different load conditions were carried out using a DC/DC converter with the proposed ADG and with three traditional methods. The experimental results show that the ADG method can track the maximum power within 140 ms with a 1.1% error rate when the engine operates at 3300 rpm@71 NM, which is superior to the performance of the single dichotomy method, the single gradient method and the perturbation and observation method from the viewpoint of improved tracking accuracy and speed.

Toroidal-Core Microinductors Biased by Permanent Magnets

NASA Technical Reports Server (NTRS)

Lieneweg, Udo; Blaes, Brent

2003-01-01

The designs of microscopic toroidal-core inductors in integrated circuits of DC-to-DC voltage converters would be modified, according to a proposal, by filling the gaps in the cores with permanent magnets that would apply bias fluxes (see figure). The magnitudes and polarities of the bias fluxes would be tailored to counteract the DC fluxes generated by the DC components of the currents in the inductor windings, such that it would be possible to either reduce the sizes of the cores or increase the AC components of the currents in the cores without incurring adverse effects. Reducing the sizes of the cores could save significant amounts of space on integrated circuits because relative to other integrated-circuit components, microinductors occupy large areas - of the order of a square millimeter each. An important consideration in the design of such an inductor is preventing magnetic saturation of the core at current levels up to the maximum anticipated operating current. The requirement to prevent saturation, as well as other requirements and constraints upon the design of the core are expressed by several equations based on the traditional magnetic-circuit approximation. The equations involve the core and gap dimensions and the magnetic-property parameters of the core and magnet materials. The equations show that, other things remaining equal, as the maximum current is increased, one must increase the size of the core to prevent the flux density from rising to the saturation level. By using a permanent bias flux to oppose the flux generated by the DC component of the current, one would reduce the net DC component of flux in the core, making it possible to reduce the core size needed to prevent the total flux density (sum of DC and AC components) from rising to the saturation level. Alternatively, one could take advantage of the reduction of the net DC component of flux by increasing the allowable AC component of flux and the corresponding AC component of current. In either case, permanent-magnet material and the slant (if any) and thickness of the gap must be chosen according to the equations to obtain the required bias flux. In modifying the design of the inductor, one must ensure that the inductance is not altered. The simplest way to preserve the original value of inductance would be to leave the gap dimensions unchanged and fill the gap with a permanent- magnet material that, fortuitously, would produce just the required bias flux. A more generally applicable alternative would be to partly fill either the original gap or a slightly enlarged gap with a suitable permanent-magnet material (thereby leaving a small residual gap) so that the reluctance of the resulting magnetic circuit would yield the desired inductance.

Role of thermal heating on the voltage induced insulator-metal transition in VO2.

PubMed

Zimmers, A; Aigouy, L; Mortier, M; Sharoni, A; Wang, Siming; West, K G; Ramirez, J G; Schuller, Ivan K

2013-02-01

We show that the main mechanism for the dc voltage or dc current induced insulator-metal transition in vanadium dioxide VO(2) is due to local Joule heating and not a purely electronic effect. This "tour de force" experiment was accomplished by using the fluorescence spectra of rare-earth doped micron sized particles as local temperature sensors. As the insulator-metal transition is induced by a dc voltage or dc current, the local temperature reaches the transition temperature indicating that Joule heating plays a predominant role. This has critical implications for the understanding of the dc voltage or dc current induced insulator-metal transition and has a direct impact on applications which use dc voltage or dc current to externally drive the transition.

Influence of DC arc current on the formation of cobalt-based nanostructures

NASA Astrophysics Data System (ADS)

Orpe, P. B.; Balasubramanian, C.; Mukherjee, S.

2017-08-01

The synthesis of cobalt-based magnetic nanostructures using DC arc discharge technique with varying arc current is reported here. The structural, morphological, compositional and magnetic properties of these nanostructures were studied as a function of applied arc current. Various techniques like X-ray diffraction, transmission electron microscopy, EDAX and vibrating sample magnetometry were used to carry out this study and the results are reported here. The results clearly indicate that for a given oxygen partial pressure, an arc current of 100 A favours the formation of unreacted cobalt atomic species. Also change in arc current leads to variation in phase, diversity in morphology etc. Other property changes such as thermal changes, mechanical changes etc. are not addressed here. The magnetic characterization further indicates that the anisotropy in shape plays a crucial role in deciding the magnetic properties of the nanostructured materials. We have quantified an interesting result in our experiment, that is, for a given partial pressure, 100 A arc current results in unique variation in structural and magnetic properties as compared to other arc currents.

Nonequilibrium response of an electron-mediated charge density wave ordered material to a large dc electric field

NASA Astrophysics Data System (ADS)

Matveev, O. P.; Shvaika, A. M.; Devereaux, T. P.; Freericks, J. K.

2016-01-01

Using the Kadanoff-Baym-Keldysh formalism, we employ nonequilibrium dynamical mean-field theory to exactly solve for the nonlinear response of an electron-mediated charge-density-wave-ordered material. We examine both the dc current and the order parameter of the conduction electrons as the ordered system is driven by the electric field. Although the formalism we develop applies to all models, for concreteness, we examine the charge-density-wave phase of the Falicov-Kimball model, which displays a number of anomalous behaviors including the appearance of subgap density of states as the temperature increases. These subgap states should have a significant impact on transport properties, particularly the nonlinear response of the system to a large dc electric field.

Solid state remote power controllers for 120 VDC power systems

NASA Technical Reports Server (NTRS)

Sundberg, G. R.; Baker, D. E.

1975-01-01

Solid state remote power controllers can be applied to any dc power system up to 120 Vdc and distribute power up to 3.6 kW per hour. Devices have demonstrated total electrical efficiencies of 98.5 percent to 99.0 percent at rated load currents.

Measuring surfactant concentration in plating solutions

DOEpatents

Bonivert, William D.; Farmer, Joseph C.; Hachman, John T.

1989-01-01

An arrangement for measuring the concentration of surfactants in a electrolyte containing metal ions includes applying a DC bias voltage and a modulated voltage to a counter electrode. The phase angle between the modulated voltage and the current response to the modulated voltage at a working electrode is correlated to the surfactant concentration.

Analytical modeling of eddy-current losses caused by pulse-width-modulation switching in permanent-magnet brushless direct-current motors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, F.; Nehl, T.W.

1998-09-01

Because of their high efficiency and power density the PM brushless dc motor is a strong candidate for electric and hybrid vehicle propulsion systems. An analytical approach is developed to predict the inverter high frequency pulse width modulation (PWM) switching caused eddy-current losses in a permanent magnet brushless dc motor. The model uses polar coordinates to take curvature effects into account, and is also capable of including the space harmonic effect of the stator magnetic field and the stator lamination effect on the losses. The model was applied to an existing motor design and was verified with the finite elementmore » method. Good agreement was achieved between the two approaches. Hence, the model is expected to be very helpful in predicting PWM switching losses in permanent magnet machine design.« less

Self-oscillations in field emission nanowire mechanical resonators: a nanometric dc-ac conversion.

PubMed

Ayari, Anthony; Vincent, Pascal; Perisanu, Sorin; Choueib, May; Gouttenoire, Vincent; Bechelany, Mikhael; Cornu, David; Purcell, Stephen T

2007-08-01

We report the observation of self-oscillations in a bottom-up nanoelectromechanical system (NEMS) during field emission driven by a constant applied voltage. An electromechanical model is explored that explains the phenomenon and that can be directly used to develop integrated devices. In this first study, we have already achieved approximately 50% dc/ac (direct to alternating current) conversion. Electrical self-oscillations in NEMS open up a new path for the development of high-speed, autonomous nanoresonators and signal generators and show that field emission (FE) is a powerful tool for building new nanocomponents.

Electromagnetic Flow Meter Having a Driver Circuit Including a Current Transducer

NASA Technical Reports Server (NTRS)

Patel, Sandeep K. (Inventor); Karon, David M. (Inventor); Cushing, Vincent (Inventor)

2014-01-01

An electromagnetic flow meter (EMFM) accurately measures both the complete flow rate and the dynamically fluctuating flow rate of a fluid by applying a unipolar DC voltage to excitation coils for a predetermined period of time, measuring the electric potential at a pair of electrodes, determining a complete flow rate and independently measuring the dynamic flow rate during the "on" cycle of the DC excitation, and correcting the measurements for errors resulting from galvanic drift and other effects on the electric potential. The EMFM can also correct for effects from the excitation circuit induced during operation of the EMFM.

Characterization of Nanocrystalline Nickel-Cobalt Alloys Synthesized by Direct and Pulse Electrodeposition

NASA Astrophysics Data System (ADS)

Salehi, M.; Saidi, A.; Ahmadian, M.; Raeissi, K.

2014-01-01

Nanocrystalline Ni-Co alloys are electrodeposited by direct (DC) and pulse current (PC) in an electrolyte solution which consisted of nickel sulfate, cobalt sulfate and boric acid. Electrodeposition parameters including current density, electrolyte pH and pulse times in a single electrolyte bath were changed. XRD pattern showed that the structure of the alloys depends on Co content and the synthesis parameter and changed from single phase structure (fcc) to dual phase structure (fcc + hcp). The Co content in the deposited alloys declined from 70 at.% to 50 at.% by increasing in direct current from 70 mA/cm2 to 115 mA/cm2 and also decreased from 75 at.% to 33 at.% with decrease in pH values from 4 to 2. By applying PC the Co content changed from 76 at.% to 41 at.%. Magnetic properties measurements showed the saturation magnetization (Ms) increased with increasing the Co content. There was no significant effect on coercivity values (Hc) with change in Co content and about 40 Oe was obtained for all samples. The grain size of deposited alloys obtained between 24-58 nm and 15-21 nm by applying DC and PC, respectively.

The influence of superimposed DC current on electrical and spectroscopic characteristics of HiPIMS discharge

NASA Astrophysics Data System (ADS)

Zuo, Xiao; Chen, Rende; Liu, Jingzhou; Ke, Peiling; Wang, Aiying

2018-01-01

The electrical characteristics and spectroscopic properties have been comprehensively investigated in a DC superimposed high power impulse magnetron sputtering (DC-HiPIMS) deposition system in this paper. The influence of superimposed DC current on the variation of target and substrate current waveforms, active species and electron temperatures with pulse voltages are focused. The peak target currents in DC-HiPIMS are lower than in HiPIMS. The time scales of the two main discharge processes like ionization and gas rarefaction in DC-HiPIMS are analyzed. When the pulse voltage is higher than 600 V, the gas rarefaction effect becomes apparent. Overall, the ionization process is found to be dominant in the initial ˜100 μs during each pulse. The active species of Ar and Cr in DC-HiPIMS are higher than in HiPIMS unless that the pulse voltage reaches 900 V. However, the ionization degree in HiPIMS exceeds that in DC-HiPIMS at around 600 V. The electron temperature calculated by modified Boltzmann plot method based on corona model has a precipitous increase from 0.87 to 25.0 eV in HiPIMS, but varies mildly after the introduction of the superimposed DC current. Additionally, the current from plasma flowing to the substrate is improved when a DC current is superimposed with HiPIMS.

Grain Boundary Resistivity of Yttria-Stabilized Zirconia at 1400°C

DOE PAGES

Wang, J.; Du, A.; Yang, Di; ...

2013-01-01

Tmore » he grain size dependence of the bulk resistivity of 3 mol% yttria-stabilized zirconia at 1400°C was determined from the effect of a dc electric field E a = 18.1  V/cm on grain growth and the corresponding electric current during isothermal annealing tests. Employing the brick layer model, the present annealing test results were in accordance with extrapolations of the values obtained at lower temperature employing impedance spectroscopy and 4-point-probe dc. he combined values give that the magnitude of the grain boundary resistivity ρ b = 133  ohm-cm. he electric field across the grain boundary width was 28–43 times the applied field for the grain size and current ranges in the present annealing test.« less

Integrating DC/DC Conversion with Possible Reconfiguration within Submodule Solar Photovoltaic Systems

NASA Astrophysics Data System (ADS)

Huang, Peter Jen-Hung

This research first proposes a method to merge photovoltaic (PV) cells or PV panels within the internal components DC-DC converters. The purpose of this merged structure is to reconfigure the PV modules between series and parallel connections using high switching frequencies (hundreds of kHz). This leads to multi-levels of voltages and currents that become applied to the output filter of the converter. Further, this research introduces a concept of a switching cell that utilizes the reconfiguration of series and parallel connections in DC-DC converters. The switching occurs at high switching frequency and the switches can be integrated to be within the solar panels or in between the solar cells. The concept is generalized and applied to basic buck and boost topologies. As examples of the new types of converters: reconfigurable PV-buck and PV-boost converter topologies are presented. It is also possible to create other reconfigurable power converters: non-isolated and isolated topologies. Analysis, simulation and experimental verification for the reconfigurable PV-buck and PV-boost converters are presented extensively to illustrate proof of concept. Benefits and drawbacks of the new approach are discussed. The second part of this research proposes to utilize the internal solar cell capacitance and internal solar module wire parasitic inductances to replace the input capacitor and filter inductor in boost derived DC-DC converters for energy harvesting applications. High switching frequency (MHz) hard switched and resonant boost converters are proposed. Their analysis, simulation and experimental prototypes are presented. A specific proof-of-concept application is especially tested for foldable PV panels, which are known for their high internal wire inductance. The experimental converters successfully boost solar module voltage without adding any external input capacitance or filter inductor. Benefits and drawbacks of new proposed PV submodule integrated boost converters are discussed.

Evaluation of DC electric field distribution of PPLP specimen based on the measurement of electrical conductivity in LN2

NASA Astrophysics Data System (ADS)

Hwang, Jae-Sang; Seong, Jae-Kyu; Shin, Woo-Ju; Lee, Jong-Geon; Cho, Jeon-Wook; Ryoo, Hee-Suk; Lee, Bang-Wook

2013-11-01

High temperature superconducting (HTS) cable has been paid much attention due to its high efficiency and high current transportation capability, and it is also regarded as eco-friendly power cable for the next generation. Especially for DC HTS cable, it has more sustainable and stable properties compared to AC HTS cable due to the absence of AC loss in DC HTS cable. Recently, DC HTS cable has been investigated competitively all over the world, and one of the key components of DC HTS cable to be developed is a cable joint box considering HVDC environment. In order to achieve the optimum insulation design of the joint box, analysis of DC electric field distribution of the joint box is a fundamental process to develop DC HTS cable. Generally, AC electric field distribution depends on relative permittivity of dielectric materials but in case of DC, electrical conductivity of dielectric material is a dominant factor which determines electric field distribution. In this study, in order to evaluate DC electric field characteristics of the joint box for DC HTS cable, polypropylene laminated paper (PPLP) specimen has been prepared and its DC electric field distribution was analyzed based on the measurement of electrical conductivity of PPLP in liquid nitrogen (LN2). Electrical conductivity of PPLP in LN2 has not been reported yet but it should be measured for DC electric field analysis. The experimental works for measuring electrical conductivity of PPLP in LN2 were presented in this paper. Based on the experimental works, DC electric field distribution of PPLP specimen was fully analyzed considering the steady state and the transient state of DC. Consequently, it was possible to determine the electric field distribution characteristics considering different DC applying stages including DC switching on, DC switching off and polarity reversal conditions.

New quantum oscillations in current driven small junctions

NASA Technical Reports Server (NTRS)

Ben-Jacob, E.; Gefen, Y.

1985-01-01

The response of current-biased Josephson and normal tunnel junctions (JJs and NTJs) such as those fabricated by Voss and Webb (1981) is predicted from a quantum-mechanical description based on the observation that the response of a current-driven open system is equivalent to that of a closed system subject to an external time-dependent voltage bias. Phenomena expected include voltage oscillations with no dc voltage applied, inverse Shapiro steps of dc voltage in the presence of microwave radiation, voltage oscillation in a JJ and an NTJ coupled by a capacitance to a current-biased junction, JJ voltage oscillation frequency = I/e rather than I/2e, and different NTJ resistance than in the voltage-driven case. The effects require approximate experimental parameter values Ic = 15 nA, C = 1 fF, and T much less than 0.4 K for JJs and Ic = a few nA, C = 1 fF, and R = 3 kiloohms for 100-microV inverse Shapiro steps at 10 GHz in NTJs.

DC Motor control using motor-generator set with controlled generator field

DOEpatents

Belsterling, Charles A.; Stone, John

1982-01-01

A d.c. generator is connected in series opposed to the polarity of a d.c. power source supplying a d.c. drive motor. The generator is part of a motor-generator set, the motor of which is supplied from the power source connected to the motor. A generator field control means varies the field produced by at least one of the generator windings in order to change the effective voltage output. When the generator voltage is exactly equal to the d.c. voltage supply, no voltage is applied across the drive motor. As the field of the generator is reduced, the drive motor is supplied greater voltage until the full voltage of the d.c. power source is supplied when the generator has zero field applied. Additional voltage may be applied across the drive motor by reversing and increasing the reversed field on the generator. The drive motor may be reversed in direction from standstill by increasing the generator field so that a reverse voltage is applied across the d.c. motor.

DC-Compensated Current Transformer.

PubMed

Ripka, Pavel; Draxler, Karel; Styblíková, Renata

2016-01-20

Instrument current transformers (CTs) measure AC currents. The DC component in the measured current can saturate the transformer and cause gross error. We use fluxgate detection and digital feedback compensation of the DC flux to suppress the overall error to 0.15%. This concept can be used not only for high-end CTs with a nanocrystalline core, but it also works for low-cost CTs with FeSi cores. The method described here allows simultaneous measurements of the DC current component.

ASDTIC control and standardized interface circuits applied to buck, parallel and buck-boost dc to dc power converters

NASA Technical Reports Server (NTRS)

Schoenfeld, A. D.; Yu, Y.

1973-01-01

Versatile standardized pulse modulation nondissipatively regulated control signal processing circuits were applied to three most commonly used dc to dc power converter configurations: (1) the series switching buck-regulator, (2) the pulse modulated parallel inverter, and (3) the buck-boost converter. The unique control concept and the commonality of control functions for all switching regulators have resulted in improved static and dynamic performance and control circuit standardization. New power-circuit technology was also applied to enhance reliability and to achieve optimum weight and efficiency.

Direct electric current modifies important cellular aspects and ultrastructure features of Candida albicans yeasts: Influence of doses and polarities.

PubMed

Barbosa, Gleyce Moreno; Dos Santos, Eldio Gonçalves; Capella, Francielle Neves Carvalho; Homsani, Fortune; de Pointis Marçal, Carina; Dos Santos Valle, Roberta; de Araújo Abi-Chacra, Érika; Braga-Silva, Lys Adriana; de Oliveira Sales, Marcelo Henrique; da Silva Neto, Inácio Domingos; da Veiga, Venicio Feo; Dos Santos, André Luis Souza; Holandino, Carla

2017-02-01

Available treatments against human fungal pathogens present high levels of resistance, motivating the development of new antifungal therapies. In this context, the present work aimed to analyze direct electric current (DC) antifungal action, using an in vitro apparatus equipped with platinum electrodes. Candida albicans yeast cells were submitted to three distinct conditions of DC treatment (anodic flow-AF; electroionic flow-EIF; and cathodic flow-CF), as well as different charges, ranging from 0.03 to 2.40 C. Our results indicated C. albicans presented distinct sensibility depending on the DC intensity and polarity applied. Both the colony-forming unit assay and the cytometry flow with propidium iodide indicated a drastic reduction on cellular viability after AF treatment with 0.15 C, while CF- and EIF-treated cells stayed alive when DC doses were increased up to 2.40 C. Additionally, transmission electron microscopy revealed important ultrastructural alterations in AF-treated yeasts, including cell structure disorganization, ruptures in plasmatic membrane, and cytoplasmic rarefaction. This work emphasizes the importance of physical parameters (polarity and doses) in cellular damage, and brings new evidence for using electrotherapy to treat C. albicans pathology process. Bioelectromagnetics. 38:95-108, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

AC power generation from microbial fuel cells

NASA Astrophysics Data System (ADS)

Lobo, Fernanda Leite; Wang, Heming; Forrestal, Casey; Ren, Zhiyong Jason

2015-11-01

Microbial fuel cells (MFCs) directly convert biodegradable substrates to electricity and carry good potential for energy-positive wastewater treatment. However, the low and direct current (DC) output from MFC is not usable for general electronics except small sensors, yet commercial DC-AC converters or inverters used in solar systems cannot be directly applied to MFCs. This study presents a new DC-AC converter system for MFCs that can generate alternating voltage in any desired frequency. Results show that AC power can be easily achieved in three different frequencies tested (1, 10, 60 Hz), and no energy storage layer such as capacitors was needed. The DC-AC converter efficiency was higher than 95% when powered by either individual MFCs or simple MFC stacks. Total harmonic distortion (THD) was used to investigate the quality of the energy, and it showed that the energy could be directly usable for linear electronic loads. This study shows that through electrical conversion MFCs can be potentially used in household electronics for decentralized off-grid communities.

A galvanotaxis assay for analysis of neural precursor cell migration kinetics in an externally applied direct current electric field.

PubMed

Babona-Pilipos, Robart; Popovic, Milos R; Morshead, Cindi M

2012-10-13

The discovery of neural stem and progenitor cells (collectively termed neural precursor cells) (NPCs) in the adult mammalian brain has led to a body of research aimed at utilizing the multipotent and proliferative properties of these cells for the development of neuroregenerative strategies. A critical step for the success of such strategies is the mobilization of NPCs toward a lesion site following exogenous transplantation or to enhance the response of the endogenous precursors that are found in the periventricular region of the CNS. Accordingly, it is essential to understand the mechanisms that promote, guide, and enhance NPC migration. Our work focuses on the utilization of direct current electric fields (dcEFs) to promote and direct NPC migration - a phenomenon known as galvanotaxis. Endogenous physiological electric fields function as critical cues for cell migration during normal development and wound repair. Pharmacological disruption of the trans-neural tube potential in axolotl embryos causes severe developmental malformations(1). In the context of wound healing, the rate of repair of wounded cornea is directly correlated with the magnitude of the epithelial wound potential that arises after injury, as shown by pharmacological enhancement or disruption of this dcEF(2-3). We have demonstrated that adult subependymal NPCs undergo rapid and directed cathodal migration in vitro when exposed to an externally applied dcEF. In this protocol we describe our lab's techniques for creating a simple and effective galvanotaxis assay for high-resolution, long-term observation of directed cell body translocation (migration) on a single-cell level. This assay would be suitable for investigating the mechanisms that regulate dcEF transduction into cellular motility through the use of transgenic or knockout mice, short interfering RNA, or specific receptor agonists/antagonists.

Optimization of spin-torque switching using AC and DC pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dunn, Tom; Kamenev, Alex; Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455

2014-06-21

We explore spin-torque induced magnetic reversal in magnetic tunnel junctions using combined AC and DC spin-current pulses. We calculate the optimal pulse times and current strengths for both AC and DC pulses as well as the optimal AC signal frequency, needed to minimize the Joule heat lost during the switching process. The results of this optimization are compared against numeric simulations. Finally, we show how this optimization leads to different dynamic regimes, where switching is optimized by either a purely AC or DC spin-current, or a combination AC/DC spin-current, depending on the anisotropy energies and the spin-current polarization.

Application of Superconducting Power Cables to DC Electric Railway Systems

NASA Astrophysics Data System (ADS)

Ohsaki, Hiroyuki; Lv, Zhen; Sekino, Masaki; Tomita, Masaru

For novel design and efficient operation of next-generation DC electric railway systems, especially for their substantial energy saving, we have studied the feasibility of applying superconducting power cables to them. In this paper it is assumed that a superconducting power cable is applied to connect substations supplying electric power to trains. An analysis model line was described by an electric circuit, which was analyzed with MATLAB-Simulink. From the calculated voltages and currents of the circuit, the regenerative brake and the energy losses were estimated. In addition, assuming the heat loads of superconducting power cables and the cryogenic efficiency, the energy saving of the total system was evaluated. The results show that the introduction of superconducting power cables could achieve the improved use of regenerative brake, the loss reduction, the decreased number of substations, the reduced maintenance, etc.

Design comparison of single phase outer and inner-rotor hybrid excitation flux switching motor for hybrid electric vehicles

NASA Astrophysics Data System (ADS)

Mazlan, Mohamed Mubin Aizat; Sulaiman, Erwan; Husin, Zhafir Aizat; Othman, Syed Muhammad Naufal Syed; Khan, Faisal

2015-05-01

In hybrid excitation machines (HEMs), there are two main flux sources which are permanent magnet (PM) and field excitation coil (FEC). These HEMs have better features when compared with the interior permanent magnet synchronous machines (IPMSM) used in conventional hybrid electric vehicles (HEVs). Since all flux sources including PM, FEC and armature coils are located on the stator core, the rotor becomes a single piece structure similar with switch reluctance machine (SRM). The combined flux generated by PM and FEC established more excitation fluxes that are required to produce much higher torque of the motor. In addition, variable DC FEC can control the flux capabilities of the motor, thus the machine can be applied for high-speed motor drive system. In this paper, the comparisons of single-phase 8S-4P outer and inner rotor hybrid excitation flux switching machine (HEFSM) are presented. Initially, design procedures of the HEFSM including parts drawing, materials and conditions setting, and properties setting are explained. Flux comparisons analysis is performed to investigate the flux capabilities at various current densities. Then the flux linkages of PM with DC FEC of various DC FEC current densities are examined. Finally torque performances are analyzed at various armature and FEC current densities for both designs. As a result, the outer-rotor HEFSM has higher flux linkage of PM with DC FEC and higher average torque of approximately 10% when compared with inner-rotor HEFSM.

DC-Compensated Current Transformer †

PubMed Central

Ripka, Pavel; Draxler, Karel; Styblíková, Renata

2016-01-01

Instrument current transformers (CTs) measure AC currents. The DC component in the measured current can saturate the transformer and cause gross error. We use fluxgate detection and digital feedback compensation of the DC flux to suppress the overall error to 0.15%. This concept can be used not only for high-end CTs with a nanocrystalline core, but it also works for low-cost CTs with FeSi cores. The method described here allows simultaneous measurements of the DC current component. PMID:26805830

CHARACTERISTICS OF A FAST RISE TIME POWER SUPPLY FOR A PULSED PLASMA REACTOR FOR CHEMICAL VAPOR DESTRUCTION

EPA Science Inventory

Rotating spark gap devices for switching high-voltage direct current (dc) into a corona plasma reactor can achieve pulse rise times in the range of tens of nanoseconds. The fast rise times lead to vigorous plasma generation without sparking at instantaneous applied voltages highe...

Development of a DC propulsion system for an electric vehicle

NASA Technical Reports Server (NTRS)

Kelledes, W. L.

1984-01-01

The suitability of the Eaton automatically shifted mechanical transaxle concept for use in a near-term dc powered electric vehicle is evaluated. A prototype dc propulsion system for a passenger electric vehicle was designed, fabricated, tested, installed in a modified Mercury Lynx vehicle and track tested at the contractor's site. The system consisted of a two-axis, three-speed, automatically-shifted mechanical transaxle, 15.2 Kw rated, separately excited traction motor, and a transistorized motor controller with a single chopper providing limited armature current below motor base speed and full range field control above base speed at up to twice rated motor current. The controller utilized a microprocessor to perform motor and vehicle speed monitoring and shift sequencing by means of solenoids applying hydraulic pressure to the transaxle clutches. Bench dynamometer and track testing was performed. Track testing showed best system efficiency for steady-state cruising speeds of 65-80 Km/Hz (40-50 mph). Test results include acceleration, steady speed and SAE J227A/D cycle energy consumption, braking tests and coast down to characterize the vehicle road load.

Method to Eliminate Flux Linkage DC Component in Load Transformer for Static Transfer Switch

PubMed Central

2014-01-01

Many industrial and commercial sensitive loads are subject to the voltage sags and interruptions. The static transfer switch (STS) based on the thyristors is applied to improve the power quality and reliability. However, the transfer will result in severe inrush current in the load transformer, because of the DC component in the magnetic flux generated in the transfer process. The inrush current which is always 2~30 p.u. can cause the disoperation of relay protective devices and bring potential damage to the transformer. The way to eliminate the DC component is to transfer the related phases when the residual flux linkage of the load transformer and the prospective flux linkage of the alternate source are equal. This paper analyzes how the flux linkage of each winding in the load transformer changes in the transfer process. Based on the residual flux linkage when the preferred source is completely disconnected, the method to calculate the proper time point to close each phase of the alternate source is developed. Simulation and laboratory experiments results are presented to show the effectiveness of the transfer method. PMID:25133255

Method to eliminate flux linkage DC component in load transformer for static transfer switch.

PubMed

He, Yu; Mao, Chengxiong; Lu, Jiming; Wang, Dan; Tian, Bing

2014-01-01

Many industrial and commercial sensitive loads are subject to the voltage sags and interruptions. The static transfer switch (STS) based on the thyristors is applied to improve the power quality and reliability. However, the transfer will result in severe inrush current in the load transformer, because of the DC component in the magnetic flux generated in the transfer process. The inrush current which is always 2 ~ 30 p.u. can cause the disoperation of relay protective devices and bring potential damage to the transformer. The way to eliminate the DC component is to transfer the related phases when the residual flux linkage of the load transformer and the prospective flux linkage of the alternate source are equal. This paper analyzes how the flux linkage of each winding in the load transformer changes in the transfer process. Based on the residual flux linkage when the preferred source is completely disconnected, the method to calculate the proper time point to close each phase of the alternate source is developed. Simulation and laboratory experiments results are presented to show the effectiveness of the transfer method.

DC transport in two-dimensional electron systems under strong microwave illumination

NASA Astrophysics Data System (ADS)

Chakraborty, Shantanu

At low temperature (T) and weak magnetic field ( B), two dimensional electron systems (2DES) can exhibit strong 1/ B-periodic resistance oscillations on application of sufficiently strong microwave radiation. These oscillations are known as microwave induced resistance oscillations (MIROs), MIROs appearing near cyclotron resonance (CR) and its harmonics involve single photon processes and are called integer MIROs while the oscillations near CR subharmonics require multiphoton processes and are called fractional MIROs. Similar strong 1/B periodic resistance oscillations can occur due to strong dc current, and are known as Hall-field resistance oscillations (HIROs). Oscillations also occur for a combination of microwave radiation and strong dc current. In one prominent theory of MIROs, known as the displacement model, electrons make impurity-assisted transitions into higher or lower Landau levels by absorbing or emitting one or more (N) photons. In the presence of combined strong dc current and microwave radiation, electrons make transitions between Landau levels by absorbing or emitting photons followed by a space transition along the applied dc bias. The object of the dissertation is to explore how the different resistance oscillations area affected by strong microwave radiation when multiphoton processes are relevant. We used a coplanar waveguide (CPW) structure deposited on the sample, as opposed to simply placing the sample near the termination of a waveguide as is more the usual practice in this field. The CPW allows us to estimate the AC electric field (EAC) at the sample. In much of the work presented in this thesis we find that higher Nprocesses supersede the competing lower N processes as microwave power is increased. We show this in the presence and in the absence of a strong dc electric field. Finally, we look at the temperature evolution of fractional MIROs to compare the origin of the fractional MIROs with that of integer MIROs.

Analysis of a dc bus system with a nonlinear constant power load and its delayed feedback control.

PubMed

Konishi, Keiji; Sugitani, Yoshiki; Hara, Naoyuki

2014-02-01

This paper tackles a destabilizing problem of a direct-current (dc) bus system with constant power loads, which can be considered a fundamental problem of dc power grid networks. The present paper clarifies scenarios of the destabilization and applies the well-known delayed-feedback control to the stabilization of the destabilized bus system on the basis of nonlinear science. Further, we propose a systematic procedure for designing the delayed feedback controller. This controller can converge the bus voltage exactly on an unstable operating point without accurate information and can track it using tiny control energy even when a system parameter, such as the power consumption of the load, is slowly varied. These features demonstrate that delayed feedback control can be considered a strong candidate for solving the destabilizing problem.

A novel concept of fault current limiter based on saturable core in high voltage DC transmission system

NASA Astrophysics Data System (ADS)

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.

Avoiding the side effects of electric current pulse application to electroporated cells in disposable small volume cuvettes assures good cell survival.

PubMed

Grys, Maciej; Madeja, Zbigniew; Korohoda, Włodzimierz

2017-01-01

The harmful side effects of electroporation to cells due to local changes in pH, the appearance of toxic electrode products, temperature increase, and the heterogeneity of the electric field acting on cells in the cuvettes used for electroporation were observed and discussed in several laboratories. If cells are subjected to weak electric fields for prolonged periods, for example in experiments on cell electrophoresis or galvanotaxis the same effects are seen. In these experiments investigators managed to reduce or eliminate the harmful side effects of electric current application. For the experiments, disposable 20 μl cuvettes with two walls made of dialysis membranes were constructed and placed in a locally focused electric field at a considerable distance from the electrodes. Cuvettes were mounted into an apparatus for horizontal electrophoresis and the cells were subjected to direct current electric field (dcEF) pulses from a commercial pulse generator of exponentially declining pulses and from a custom-made generator of double and single rectangular pulses. More than 80% of the electroporated cells survived the dcEF pulses in both systems. Side effects related to electrodes were eliminated in both the flow through the dcEF and in the disposable cuvettes placed in the focused dcEFs. With a disposable cuvette system, we also confirmed the sensitization of cells to a dcEF using procaine by observing the loading of AT2 cells with calceine and using a square pulse generator, applying 50 ms single rectangular pulses. We suggest that the same methods of avoiding the side effects of electric current pulse application as in cell electrophoresis and galvanotaxis should also be used for electroporation. This conclusion was confirmed in our electroporation experiments performed in conditions assuring survival of over 80% of the electroporated cells. If the amplitude, duration, and shape of the dcEF pulse are known, then electroporation does not depend on the type of pulse generator. This knowledge of the characteristics of the pulse assures reproducibility of electroporation experiments using different equipment.

A Hybrid Constant and Oscillatory Field Ion Mobility Analyzer in Structures for Lossless Ion Manipulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prabhakaran Nair Syamala Amma, Aneesh; Hamid, Ahme

2018-02-28

Ion mobility (IM) spectrometry is becoming an important approach for analyzing molecular ions in the gas phase with applications that span a multitude of scientific areas. There are a variety of IM-based approaches that utilize either constant or oscillatory electric fields. Here, we explore the combination of constant and oscillatory fields applied in a single device to affect the separation and filtering of ions based on their mobilities. The mobility analyzer allows confining and manipulating ions utilizing a combination of radio frequency (RF), direct current (DC) fields, and traveling waves (TW) in a structures for lossless ion manipulations (SLIM) module.more » In this work, we have investigated theoretically and experimentally the concept for continuous filtering of ions based on their mobilities where ions are mobility separated and selected by a combination of TW and constant fields providing opposing forces on the ions. The SLIM module was composed of two surfaces with mirror-image arrays of electrodes and had two regions where the different TW and opposing DC fields could be applied. By appropriately choosing the DC gradient and TW parameters for the two sections, it is possible to transmit ions of a selected mobility while filtering out others. The filtering capabilities are determined by the applied DC gradient and the TW parameters, such as frequency, amplitude and the TW sequence (i.e., the duty cycle of the traveling wave). The effect of different parameters on the sensitivity and the IM resolution of the device have been investigated.« less

A Hybrid Constant and Oscillatory Field Ion Mobility Analyzer Using Structures for Lossless Ion Manipulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prabhakaran, Aneesh; Hamid, Ahmed M.; Garimella, Sandilya V. B.

Ion mobility (IM) spectrometry is becoming an important approach for analyzing molecular ions in the gas phase with applications that span a multitude of scientific areas. There are a variety of IM-based approaches that utilize either constant or oscillatory electric fields. Here, we explore the combination of constant and oscillatory fields applied in a single device to affect the separation and filtering of ions based on their mobilities. The mobility analyzer allows confining and manipulating ions utilizing a combination of radio frequency (RF), direct current (DC) fields, and traveling waves (TW) in a structures for lossless ion manipulations (SLIM) module.more » In this work, we have investigated theoretically and experimentally the concept for continuous filtering of ions based on their mobilities where ions are mobility separated and selected by a combination of TW and constant fields providing opposing forces on the ions. The SLIM module was composed of two surfaces with mirror-image arrays of electrodes and had two regions where the different TW and opposing DC fields could be applied. By appropriately choosing the DC gradient and TW parameters for the two sections, it is possible to transmit ions of a selected mobility while filtering out others. The filtering capabilities are determined by the applied DC gradient and the TW parameters, such as frequency, amplitude and the TW sequence (i.e., the duty cycle of the traveling wave). The effect of different parameters on the sensitivity and the IM resolution of the device have been investigated.« less

Electromagnetic enhancement of turbulent heat transfer.

PubMed

Kenjeres, Sasa

2008-12-01

We performed large eddy simulations (LES) of the turbulent natural convection of an electrically conductive fluid (water with 7% Na2SO4 electrolyte solution) in a moderate (4:4:1) aspect ratio enclosure heated from below and cooled from above and subjected to external nonuniformly distributed electromagnetic fields. Different configurations with permanent magnets (located under the lower thermally active wall, B_{0}=1T ) and different strengths of imposed dc electric currents ( I=0-10A ) were compared to the case of pure thermal convection in the turbulent regime, Ra=10;{7} , Pr=7 . It is demonstrated that the electromagnetic forcing of the boundary layers caused significant reorganization of flow and turbulence structures producing significant enhancement of the wall-heat transfer (up to 188% for a configuration with 35 magnets and an applied dc current of 10A ).

Characteristics of a Direct Current-driven plasma jet operated in open air

NASA Astrophysics Data System (ADS)

Li, Xuechen; Di, Cong; Jia, Pengying; Bao, Wenting

2013-09-01

A DC-driven plasma jet has been developed to generate a diffuse plasma plume by blowing argon into the ambient air. The plasma plume, showing a cup shape with a diameter of several centimeters at a higher voltage, is a pulsed discharge despite a DC voltage is applied. The pulse frequency is investigated as a function of the voltage under different gap widths and gas flow rates. Results show that plasma bullets propagate from the hollow needle to the plate electrode by spatially resolved measurement. A supposition about non-electroneutral trail of the streamer is proposed to interpret these experimental phenomena.

Sterilization by negative and positive DC plasma with a micro discharge gap at atmospheric pressure

NASA Astrophysics Data System (ADS)

Li, Hua; Jiang, Lin-Xiu; Jiang, Yong-Rong; Zhu, Jian-Min; Chen, Zhen-Cheng

2017-11-01

A new needle-to-droplet electrode structure with a micro discharge gap (2 mm) was designed to achieve direct current (DC) discharge plasma in ambient air with the aim of using the plasma to sterilize liquids. Without using noble gases or an external air flow, we succeeded in generating both a negative and positive DC plasma at atmospheric pressure. The plasma was driven by a 0 to -20,000 V, 100 W DC power supply. A stainless steel needle with a tip diameter of ˜ 50μm and a 200-μL droplet of bacteria-containing liquid served as the electrodes. At atmospheric pressure and room temperature (23∘C), utilizing the negative DC plasma, the discharge time lasted 10 s; the results showed that the higher the discharge voltage, the more efficient the sterilization effect. Conversely, when we applied a voltage of -5.5 kV, we found that the sterilization effect was more efficient for longer discharge times. Our findings demonstrate that Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) can be killed in about 30 s. Our experiments show that our sterilization method required less time and was more efficient for positive than for negative DC plasma under the same conditions.

In vitro and in vivo comparisons of constant resistance AC iontophoresis and DC iontophoresis.

PubMed

Li, S Kevin; Higuchi, William I; Zhu, Honggang; Kern, Steven E; Miller, David J; Hastings, Matthew S

2003-09-04

A previous in vitro constant electrical resistance alternating current (AC) iontophoresis study with human epidermal membrane (HEM) and a model neutral permeant has shown less inter- and intra-sample variability in iontophoretic transport relative to conventional constant direct current (DC) iontophoresis. The objectives of the present study were to address the following questions. (1) Can the skin electrical resistance be maintained at a constant level by AC in humans in vivo? (2) Are the in vitro data with HEM representative of those in vivo? (3) Does constant skin resistance AC iontophoresis have less inter- and intra-sample variability than conventional constant current DC iontophoresis in vivo? (4) What are the electrical and the barrier properties of skin during iontophoresis in vivo? In the present study, in vitro HEM experiments were carried out with the constant resistance AC and the conventional constant current DC methods using mannitol and glucose as the neutral model permeants. In vivo human experiments were performed using glucose as the permeant with a constant skin resistance AC only protocol and two conventional constant current DC methods (continuous constant current DC and constant current DC with its polarity alternated every 10 min with a 3:7 on:off duty cycle). Constant current DC iontophoresis was conducted with commercial constant current DC devices, and constant resistance AC iontophoresis was carried out by reducing and maintaining the skin resistance at a constant target value with AC supplied from a function generator. This study shows that (1) skin electrical resistance can be maintained at a constant level during AC iontophoresis in vivo; (2) HEM in vitro and human skin in vivo demonstrate similar electrical and barrier properties, and these properties are consistent with our previous findings; (3) there is general qualitative and semi-quantitative agreement between the HEM data in vitro and human skin data in vivo; and (4) constant skin resistance AC iontophoresis generally provides less inter- and intra-subject variability than conventional constant current DC.

Magneto acoustic emission apparatus for testing materials for embrittlement

NASA Technical Reports Server (NTRS)

Allison, Sidney G. (Inventor); Min, Namkung (Inventor); Yost, William T. (Inventor); Cantrell, John H. (Inventor)

1990-01-01

A method and apparatus for testing steel components for temper embrittlement uses magneto-acoustic emission to nondestructively evaluate the component. Acoustic emission signals occur more frequently at higher levels in embrittled components. A pair of electromagnets are used to create magnetic induction in the test component. Magneto-acoustic emission signals may be generated by applying an ac current to the electromagnets. The acoustic emission signals are analyzed to provide a comparison between a component known to be unembrittled and a test component. Magnetic remanence is determined by applying a dc current to the electromagnets, then turning the magnets off and observing the residual magnetic induction.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva, E.R.C. da; Filho, B.J.C.

This paper presents a PWM current clamping circuit for improving a series resonant DC link converter. This circuit is capable of reducing current peaks to about 1.2--1.4 times the DC bias current. When desired, resonant transition creates notches in the dc link current, allowing the converter`s switches to synchronize with external PWM strategy. A regulated DC current source may be obtained--by using a conventional rectifier source--to feed a DC load or a current source inverter. Phase plane approach makes ease the understanding the operation, control and design procedure of the circuit. Another topology is derived and its features compared tomore » the first circuit. Simulation results for the simplified circuit and for a three-phase induction motor driven by such inverter will be presented. Moreover, the principle is corroborated by experimental results.« less

Modeling, Development and Control of Multilevel Converters for Power System Application =

NASA Astrophysics Data System (ADS)

Vahedi, Hani

The main goal of this project is to develop a multilevel converter topology to be useful in power system applications. Although many topologies are introduced rapidly using a bunch of switches and isolated dc sources, having a single-dc-source multilevel inverter is still a matter of controversy. In fact, each isolated dc source means a bulky transformer and a rectifier that have their own losses and costs forcing the industries to avoid entering in this topic conveniently. On the other hand, multilevel inverters topologies with single-dc-source require associated controllers to regulate the dc capacitors voltages in order to have multilevel voltage waveform at the output. Thus, a complex controller would not interest investors properly. Consequently, developing a single-dc-source multilevel inverter topology along with a light and reliable voltage control is still a challenging topic to replace the 2-level inverters in the market effectively. The first effort in this project was devoted to the PUC7 inverter to design a simple and yet efficient controller. A new modelling is performed on the PUC7 inverter and it has been simplified to first order system. Afterwards, a nonlinear cascaded controller is designed and applied to regulate the capacitor voltage at 1/3 of the DC source amplitude and to generate 7 identical voltage levels at the output supplying different type of loads such as RL or rectifier harmonic ones. In next work, the PUC5 topology is proposed as a remedy to the PUC7 that requires a complicated controller to operate properly. The capacitor voltage is regulated at half of dc source amplitude to generate 5 voltage levels at the output. Although the 7-level voltage waveform is replaced by a 5-level one in PUC5 topology, it is shown that the PUC5 needs a very simple and reliable voltage balancing technique due to having some redundant switching states. Moreover, a sensor-less voltage balancing technique is designed and implemented on the PUC5 inverter successfully to work in both stand-alone and gridconnected mode of operation. Eventually, a modified configuration of the PUC5 topology is presented to work as a buck PFC rectifier. The internal performance of the rectifier is like a buck converter to generate stepped down DC voltages at the two output terminals while the grid sees a boost converter externally. As well, a decoupled voltage/current controller is designed and applied to balance the output voltages identically and synchronize the input current with grid voltage to have a PFC operation acceptably. A power balance analysis is done to show the load variation range limit. All the theoretical and simulation studies are validated by experimental results completely.

Research on resistance characteristics of YBCO tape under short-time DC large current impact

NASA Astrophysics Data System (ADS)

Zhang, Zhifeng; Yang, Jiabin; Qiu, Qingquan; Zhang, Guomin; Lin, Liangzhen

2017-06-01

Research of the resistance characteristics of YBCO tape under short-time DC large current impact is the foundation of the developing DC superconducting fault current limiter (SFCL) for voltage source converter-based high voltage direct current system (VSC-HVDC), which is one of the valid approaches to solve the problems of renewable energy integration. SFCL can limit DC short-circuit and enhance the interrupting capabilities of DC circuit breakers. In this paper, under short-time DC large current impacts, the resistance features of naked tape of YBCO tape are studied to find the resistance - temperature change rule and the maximum impact current. The influence of insulation for the resistance - temperature characteristics of YBCO tape is studied by comparison tests with naked tape and insulating tape in 77 K. The influence of operating temperature on the tape is also studied under subcooled liquid nitrogen condition. For the current impact security of YBCO tape, the critical current degradation and top temperature are analyzed and worked as judgment standards. The testing results is helpful for in developing SFCL in VSC-HVDC.

A new theoretical formulation of coupling thermo-electric breakdown in LDPE film under dc high applied fields

NASA Astrophysics Data System (ADS)

Boughariou, F.; Chouikhi, S.; Kallel, A.; Belgaroui, E.

2015-12-01

In this paper, we present a new theoretical and numerical formulation for the electrical and thermal breakdown phenomena, induced by charge packet dynamics, in low-density polyethylene (LDPE) insulating film under dc high applied field. The theoretical physical formulation is composed by the equations of bipolar charge transport as well as by the thermo-electric coupled equation associated for the first time in modeling to the bipolar transport problem. This coupled equation is resolved by the finite-element numerical model. For the first time, all bipolar transport results are obtained under non-uniform temperature distributions in the sample bulk. The principal original results show the occurring of very sudden abrupt increase in local temperature associated to a very sharp increase in external and conduction current densities appearing during the steady state. The coupling between these electrical and thermal instabilities reflects physically the local coupling between electrical conduction and thermal joule effect. The results of non-uniform temperature distributions induced by non-uniform electrical conduction current are also presented for several times. According to our formulation, the strong injection current is the principal factor of the electrical and thermal breakdown of polymer insulating material. This result is shown in this work. Our formulation is also validated experimentally.

Presynaptic and postsynaptic effects of local cathodal DC polarization within the spinal cord in anaesthetized animal preparations

PubMed Central

Bolzoni, F; Jankowska, E

2015-01-01

The present study aimed to compare presynaptic and postsynaptic actions of direct current polarization in the spinal cord, focusing on DC effects on primary afferents and motoneurons. To reduce the directly affected spinal cord region, a weak polarizing direct current (0.1–0.3 μA) was applied locally in deeply anaesthetized cats and rats; within the hindlimb motor nuclei in the caudal lumbar segments, or in the dorsal horn within the terminal projection area of low threshold skin afferents. Changes in the excitability of primary afferents activated by intraspinal stimuli (20–50 μA) were estimated using increases or decreases in compound action potentials recorded from the dorsal roots or peripheral nerves as their measure. Changes in the postsynaptic actions of the afferents were assessed from intracellularly recorded monosynaptic EPSPs in hindlimb motoneurons and monosynaptic extracellular field potentials (evoked by group Ia afferents in motor nuclei, or by low threshold cutaneous afferents in the dorsal horn). The excitability of motoneurons activated by intraspinal stimuli was assessed using intracellular records or motoneuronal discharges recorded from a ventral root or a muscle nerve. Cathodal polarization was found to affect motoneurons and afferents providing input to them to a different extent. The excitability of both was markedly increased during DC application, although post-polarization facilitation was found to involve presynaptic afferents and some of their postsynaptic actions, but only negligibly motoneurons themselves. Taken together, these results indicate that long-lasting post-polarization facilitation of spinal activity induced by locally applied cathodal current primarily reflects the facilitation of synaptic transmission. PMID:25416625

Effect of Lanthanum-Strontium Cathode Current-Collecting Layer on the Performance of Anode Supported Type Planar Solid Oxide Fuel Cells

NASA Astrophysics Data System (ADS)

Park, Sun-Young; Ji, Ho-Il; Kim, Hae-Ryoung; Yoon, Kyung Joong; Son, Ji-Won; Lee, Hae-Weon; Lee, Jong-Ho

2013-07-01

We applied screen-printed (La,Sr)CoO3 as a current-collecting layer of planar type unit-cell for lower temperature operation of SOFCs. In this study the effects of the cathode current-collecting layer on the performance of unit cell and symmetric half cell were investigated via AC and DC polarization experiments. According to our investigation, appropriately controlled current collecting layer was very effective to enhance the unit cell performance by reducing not only the ohmic resistance but also the polarization losses of SOFC cathode.

A High Efficiency Boost Converter with MPPT Scheme for Low Voltage Thermoelectric Energy Harvesting

NASA Astrophysics Data System (ADS)

Guan, Mingjie; Wang, Kunpeng; Zhu, Qingyuan; Liao, Wei-Hsin

2016-11-01

Using thermoelectric elements to harvest energy from heat has been of great interest during the last decade. This paper presents a direct current-direct current (DC-DC) boost converter with a maximum power point tracking (MPPT) scheme for low input voltage thermoelectric energy harvesting applications. Zero current switch technique is applied in the proposed MPPT scheme. Theoretical analysis on the converter circuits is explored to derive the equations for parameters needed in the design of the boost converter. Simulations and experiments are carried out to verify the theoretical analysis and equations. A prototype of the designed converter is built using discrete components and a low-power microcontroller. The results show that the designed converter can achieve a high efficiency at low input voltage. The experimental efficiency of the designed converter is compared with a commercial converter solution. It is shown that the designed converter has a higher efficiency than the commercial solution in the considered voltage range.

Technique of electrical stimulation of the vestibular analyzer under clinical conditions

NASA Technical Reports Server (NTRS)

Khechinashvili, S. N.; Zargaryan, B. M.; Karakozov, K. G.

1980-01-01

Vestibular reactions appear under the action of direct current (dc) on the labyrinth of man and animals. A decrease of the stimulation effect of dc on the extralabyrinthine nervous formations in the suggested method is achieved by the use of electric pulses with steep front and back parts, as well as by previous anesthetization of the skin in the electrode application area by means of novocain solution electrophoresis. For this purpose a pulse producer giving trapezoid pulses with smoothly changing fronts and duration was constructed. With the help of an interrupter it is possible to stop the current increase instantly, and stimulation is performed at the level of the pulse 'plateau'. To induce vestibular reactions under monopolar stimulation, it is necessary to apply the current twice as high as that with bipolar electrode position. The use of short pulses with steep front and back parts for electrode stimulation of the vestibular analyzer is considered to be inexpedient.

True random bit generators based on current time series of contact glow discharge electrolysis

NASA Astrophysics Data System (ADS)

Rojas, Andrea Espinel; Allagui, Anis; Elwakil, Ahmed S.; Alawadhi, Hussain

2018-05-01

Random bit generators (RBGs) in today's digital information and communication systems employ a high rate physical entropy sources such as electronic, photonic, or thermal time series signals. However, the proper functioning of such physical systems is bound by specific constrains that make them in some cases weak and susceptible to external attacks. In this study, we show that the electrical current time series of contact glow discharge electrolysis, which is a dc voltage-powered micro-plasma in liquids, can be used for generating random bit sequences in a wide range of high dc voltages. The current signal is quantized into a binary stream by first using a simple moving average function which makes the distribution centered around zero, and then applying logical operations which enables the binarized data to pass all tests in industry-standard randomness test suite by the National Institute of Standard Technology. Furthermore, the robustness of this RBG against power supply attacks has been examined and verified.

Single-stage three-phase boost power factor correction circuit for AC-DC converter

NASA Astrophysics Data System (ADS)

Azazi, Haitham Z.; Ahmed, Sayed M.; Lashine, Azza E.

2018-01-01

This article presents a single-stage three-phase power factor correction (PFC) circuit for AC-to-DC converter using a single-switch boost regulator, leading to improve the input power factor (PF), reducing the input current harmonics and decreasing the number of required active switches. A novel PFC control strategy which is characterised as a simple and low-cost control circuit was adopted, for achieving a good dynamic performance, unity input PF, and minimising the harmonic contents of the input current, at which it can be applied to low/medium power converters. A detailed analytical, simulation and experimental studies were therefore conducted. The effectiveness of the proposed controller algorithm is validated by the simulation results, which were carried out using MATLAB/SIMULINK environment. The proposed system is built and tested in the laboratory using DSP-DS1104 digital control board for an inductive load. The results revealed that the total harmonic distortion in the supply current was very low. Finally, a good agreement between simulation and experimental results was achieved.

Design and Development of High Voltage Direct Current (DC) Sources for the Solar Array Module Plasma Interaction Experiment

NASA Technical Reports Server (NTRS)

Bibyk, Irene K.; Wald, Lawrence W.

1995-01-01

Two programmable, high voltage DC power supplies were developed as part of the flight electronics for the Solar Array Module Plasma Interaction Experiment (SAMPIE). SAMPIE's primary objectives were to study and characterize the high voltage arcing and parasitic current losses of various solar cells and metal samples within the space plasma of low earth orbit (LEO). High voltage arcing can cause large discontinuous changes in spacecraft potential which lead to damage of the power system materials and significant Electromagnetic Interference (EMI). Parasitic currents cause a change in floating potential which lead to reduced power efficiency. These primary SAMPIE objectives were accomplished by applying artificial biases across test samples over a voltage range from -600 VDC to +300 VDC. This paper chronicles the design, final development, and test of the two programmable high voltage sources for SAMPIE. The technical challenges to the design for these power supplies included vacuum, space plasma effects, thermal protection, Shuttle vibrations and accelerations.

Using optical profilometry to characterize cell membrane roughness influenced by amyloid-beta 42 aggregates and electric fields

NASA Astrophysics Data System (ADS)

Pan, Huei-Jyuan; Wang, Ruei-Lin; Xiao, Jian-Long; Chang, Yu-Jen; Cheng, Ji-Yen; Chen, Yun-Ru; Lee, Chau-Hwang

2014-01-01

The membrane roughness of Neuro-2a neroblastoma cells is measured by using noninterferometric wide-field optical profilometry. The cells are treated with the fibril and oligomer conformers of amyloid-beta (Aβ) 42, which is a peptide of 42 amino acids related to the development of Alzheimer's disease. We find that both the Aβ42 fibrils and Aβ42 oligomers reduced the cell membrane roughness, but the effect of Aβ42 oligomers was faster and stronger than that of the fibrils. We also apply direct-current electric field (dcEF) stimulations on the cells. A dcEF of 300 mV/mm can increase the membrane roughness under the treatment of Aβ42. These results suggest that Aβ42 can decrease the membrane compliance of live neuroblastoma cells, and dcEFs may counteract this effect.

Control of plasma-liquid interaction of atmospheric DC glow discharge using liquid electrode

NASA Astrophysics Data System (ADS)

Shirai, Naoki; Aoki, Ryuta; Nito, Aihito; Aoki, Takuya; Uchida, Satoshi; Tochikubo, Fumiyoshi

2014-10-01

Atmospheric plasma in contact with liquid have a variety of interesting phenomena and applications. Previously, we investigated the fundamental characteristics of an atmospheric dc glow discharge using a liquid electrode with a miniature helium flow. We tried to control the plasma-liquid interaction by changing the plasma parameter such as gas species, liquid, and applied voltage. Sheath flow system enables another gas (N2, O2, Ar) flow to around the helium core flow. It can control the gas species around the discharge. When liquid (NaCl aq.) cathode DC discharge is generated, Na emission (588 nm) can be observed from liquid surface with increasing discharge current. Na emission strongly depends on the discharge current and liquid temperature. However, when Ar sheath flow is used, the intensity of Na becomes weak. When liquid anode DC discharge is generated, self-organized luminous pattern formation can be observed at the liquid surface. The pattern depends on existence of oxygen gas in gap. By changing the oxygen gas ratio in the gap, variety of pattern formation can be observed. The discharge in contact with liquid also can be used for synthesis of metal nanoparticles at plasma-liquid interface. Size and shape of nanoparticles depend on discharge gases. This work was supported financially in part by a Grant-in-Aid for Scientific Research on Innovative Areas (No 21110007) from MEXT, Japan.

Fundamental Study on Saving Energy for Electrified Railway System Applying High Temperature Superconductor Motor and Energy Storage System

NASA Astrophysics Data System (ADS)

Konishi, Takeshi; Nakamura, Taketsune; Amemiya, Naoyuki

Induction motor instead of dc one has been applied widely for dc electric rolling stock because of the advantage of its utility and efficiency. However, further improvement of motor characteristics will be required to realize environment-friendly dc railway system in the future. It is important to study more efficient machine applying dc electric rolling stock for next generation high performance system. On the other hand, the methods to reuse regenerative energy produced by motors effectively are also important. Therefore, we carried out fundamental study on saving energy for electrified railway system. For the first step, we introduced the energy storage system applying electric double-layer capacitors (EDLC), and its control system. And then, we tried to obtain the specification of high temperature superconductor induction/synchronous motor (HTS-ISM), which performance is similar with that of the conventional induction motors. Furthermore, we tried to evaluate an electrified railway system applying energy storage system and HTS-ISM based on simulation. We succeeded in showing the effectiveness of the introductions of energy storage system and HTS-ISM in DC electrified railway system.

Static and Dynamic Effects of Lateral Carrier Diffusion in Semiconductor Lasers

NASA Technical Reports Server (NTRS)

Li, Jian-Zhong; Cheung, Samson H.; Ning, C. Z.; Biegel, Bryan A. (Technical Monitor)

2002-01-01

Electron and hole diffusions in the plane of semiconductor quantum wells play an important part in the static and dynamic operations of semiconductor lasers. It is well known that the value of diffusion coefficients affects the threshold pumping current of a semiconductor laser. At the same time, the strength of carrier diffusion process is expected to affect the modulation bandwidth of an AC-modulated laser. It is important not only to investigate the combined DC and AC effects due to carrier diffusion, but also to separate the AC effects from that of the combined effects in order to provide design insights for high speed modulation. In this presentation, we apply a hydrodynamic model developed by the present authors recently from the semiconductor Bloch equations. The model allows microscopic calculation of the lateral carrier diffusion coefficient, which is a nonlinear function of the carrier density and plasma temperature. We first studied combined AC and DC effects of lateral carrier diffusion by studying the bandwidth dependence on diffusion coefficient at a given DC current under small signal modulation. The results show an increase of modulation bandwidth with decrease in the diffusion coefficient. We simultaneously studied the effects of nonlinearity in the diffusion coefficient. To clearly identify how much of the bandwidth increase is a result of decrease in the threshold pumping current for smaller diffusion coefficient, thus an effective increase of DC pumping, we study the bandwidth dependence on diffusion coefficient at a given relative pumping. A detailed comparison of the two cases will be presented.

Time-dependent photon heat transport through a mesoscopic Josephson device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Wen-Ting; Zhao, Hong-Kang, E-mail: zhaohonk@bit.edu.cn

The time-oscillating photon heat current through a dc voltage biased mesoscopic Josephson Junction (MJJ) has been investigated by employing the nonequilibrium Green’s function approach. The Landauer-like formula of photon heat current has been derived in both of the Fourier space and its time-oscillating versions, where Coulomb interaction, self inductance, and magnetic flux take effective roles. Nonlinear behaviors are exhibited in the photon heat current due to the quantum nature of MJJ and applied external dc voltage. The magnitude of heat current decreases with increasing the external bias voltage, and subtle oscillation structures appear as the superposition of different photon heatmore » branches. The overall period of heat current with respect to time is not affected by Coulomb interaction, however, the magnitude and phase of it vary considerably by changing the Coulomb interaction. - Highlights: • The time-oscillating photon heat current through a mesoscopic Josephson Junction has been investigated. • The Landauer-like formula of photon heat current has been derived by the nonequilibrium Green’s function approach. • Nonlinear behaviors are exhibited in the photon heat current resulting from the self inductance and Coulomb interaction. • The oscillation structure of heat current is composed of the superposition of oscillations with different periods.« less

Effects of direct current electric fields on lung cancer cell electrotaxis in a PMMA-based microfluidic device.

PubMed

Li, Yaping; Xu, Tao; Chen, Xiaomei; Lin, Shin; Cho, Michael; Sun, Dong; Yang, Mengsu

2017-03-01

Tumor metastasis is the primary cause of cancer death. Numerous studies have demonstrated the electrotactic responses of various cancer cell types, and suggested its potential implications in metastasis. In this study, we used a microfluidic device to emulate endogenous direct current electric field (dcEF) environment, and studied the electrotactic migration of non-small cell lung cancer cell lines (H460, HCC827, H1299, and H1975) and the underlying mechanisms. These cell lines exhibited greatly different response in applied dcEFs (2-6 V/cm). While H460 cells (large cell carcinoma) showed slight migration toward cathode, H1299 cells (large cell carcinoma) showed increased motility and dcEF-dependent anodal migration with cell reorientation. H1975 cells (adenocarcinoma) showed dcEF-dependent cathodal migration with increased motility, and HCC827 cells (adenocarcinoma) responded positively in migration speed and reorientation but minimally in migrating directions to dcEF. Activation of MAPK and PI3K signaling pathways was found to be associated with the realignment and directed migration of lung cancer cells. In addition, both Ca 2+ influx through activated stretch-activated calcium channels (SACCs) (but not voltage-gated calcium channels, VGCCs) and Ca 2+ release from intracellular storage were involved in lung cancer cell electrotactic responses. The results demonstrated that the microfluidic device provided a stable and controllable microenvironment for cell electrotaxis study, and revealed that the electrotactic responses of lung cancer cells were heterogeneous and cell-type dependent, and multiple signals contributed to lung cancer cells electrotaxis.

Description of bipolar charge transport in polyethylene using a fluid model with a constant mobility: model prediction

NASA Astrophysics Data System (ADS)

LeRoy, S.; Segur, P.; Teyssedre, G.; Laurent, C.

2004-01-01

We present a conduction model aimed at describing bipolar transport and space charge phenomena in low density polyethylene under dc stress. In the first part we recall the basic requirements for the description of charge transport and charge storage in disordered media with emphasis on the case of polyethylene. A quick review of available conduction models is presented and our approach is compared with these models. Then, the bases of the model are described and related assumptions are discussed. Finally, results on external current, trapped and free space charge distributions, field distribution and recombination rate are presented and discussed, considering a constant dc voltage, a step-increase of the voltage, and a polarization-depolarization protocol for the applied voltage. It is shown that the model is able to describe the general features reported for external current, electroluminescence and charge distribution in polyethylene.

Development, Demonstration, and Control of a Testbed for Multiterminal HVDC System

DOE PAGES

Li, Yalong; Shi, Xiaojie M.; Liu, Bo; ...

2016-10-21

This paper presents the development of a scaled four-terminal high-voltage direct current (HVDC) testbed, including hardware structure, communication architecture, and different control schemes. The developed testbed is capable of emulating typical operation scenarios including system start-up, power variation, line contingency, and converter station failure. Some unique scenarios are also developed and demonstrated, such as online control mode transition and station re-commission. In particular, a dc line current control is proposed, through the regulation of a converter station at one terminal. By controlling a dc line current to zero, the transmission line can be opened by using relatively low-cost HVDC disconnectsmore » with low current interrupting capability, instead of the more expensive dc circuit breaker. Utilizing the dc line current control, an automatic line current limiting scheme is developed. As a result, when a dc line is overloaded, the line current control will be automatically activated to regulate current within the allowable maximum value.« less

Oscillatory dependence of current driven domain wall motion on current pulse length

NASA Astrophysics Data System (ADS)

Thomas, Luc

2007-03-01

The motion of domain walls (DW) in magnetic nanowires driven by spin torque from spin-polarized current is of considerable interest. Most previous work has considered the effect of dc or ˜microsecond long current pulses. Here, we show that the dynamics of DWs driven by nanosecond-long current pulses is unexpectedly complex. In particular, we show that the current driven motion of a DW, confined to a pinning site in a permalloy nanowire, exhibits an oscillatory dependence on the current pulse length with a period of just a few nanoseconds [1]. This behavior can be understood within a surprisingly straightforward one dimensional analytical model of the DW's motion. When a current pulse is applied, the DW's position oscillates within the pinning potential out of phase with the DW's out-of-plane magnetization, where the latter acts like the DW's momentum. Thus, the current driven motion of the DW is akin to a harmonic oscillator, whose frequency is determined by the ``mass'' of the DW and where the restoring force is related to the slope of the pinning potential. Remarkably, when the current pulse is turned off during phases of the DW motion when it has enough momentum, the amplitude of the oscillations can be amplified such that the DW exits the pinning potential well after the pulse is turned off. This oscillatory depinning occurs for currents smaller than the dc threshold current, and, moreover, the DW moves against the electron flow, opposite to the propagation direction above the dc threshold. These effects can be further amplified by using trains of current pulses whose lengths and separations are matched to the DW's oscillation period. In this way, we have demonstrated a five fold reduction in the threshold current required to move a DW out of a pinning site, making this effect potentially important for technological applications. [1] L. Thomas, M. Hayashi, X. Jiang, R. Moriya, C. Rettner and S.S.P. Parkin, Nature 443, 197 (2006).

Ionization tube simmer current circuit

DOEpatents

Steinkraus, R.F. Jr.

1994-12-13

A highly efficient flash lamp simmer current circuit utilizes a fifty percent duty cycle square wave pulse generator to pass a current over a current limiting inductor to a full wave rectifier. The DC output of the rectifier is then passed over a voltage smoothing capacitor through a reverse current blocking diode to a flash lamp tube to sustain ionization in the tube between discharges via a small simmer current. An alternate embodiment of the circuit combines the pulse generator and inductor in the form of an FET off line square wave generator with an impedance limited step up output transformer which is then applied to the full wave rectifier as before to yield a similar simmer current. 6 figures.

Ionization tube simmer current circuit

DOEpatents

Steinkraus, Jr., Robert F.

1994-01-01

A highly efficient flash lamp simmer current circuit utilizes a fifty percent duty cycle square wave pulse generator to pass a current over a current limiting inductor to a full wave rectifier. The DC output of the rectifier is then passed over a voltage smoothing capacitor through a reverse current blocking diode to a flash lamp tube to sustain ionization in the tube between discharges via a small simmer current. An alternate embodiment of the circuit combines the pulse generator and inductor in the form of an FET off line square wave generator with an impedance limited step up output transformer which is then applied to the full wave rectifier as before to yield a similar simmer current.

Pupils' Representations of Electric Current before, during and after Instruction on DC Circuits.

ERIC Educational Resources Information Center

Psillos, D.; And Others

1987-01-01

Reported are compulsory education pupils' representations of electric current in a constructivist approach to introducing direct current (DC) circuits. Suggests that the pupils views can be modelled after an energy framework. Makes suggestions about the content, the apparatus and the experiments used in teaching DC circuits. (CW)

Analysis and Countermeasure Study on DC Bias of Main Transformer in a City

NASA Astrophysics Data System (ADS)

Wang, PengChao; Wang, Hongtao; Song, Xinpu; Gu, Jun; Liu, yong; Wu, weili

2017-07-01

According to the December 2015 Guohua Beijing thermal power transformer DC magnetic bias phenomenon, the monitoring data of 24 hours of direct current is analyzed. We find that the maximum DC current is up to 25 and is about 30s for the trend cycle, on this basis, then, of the geomagnetic storm HVDC and subway operation causes comparison of the mechanism, and make a comprehensive analysis of the thermal power plant’s geographical location, surrounding environment and electrical contact etc.. The results show that the main reason for the DC bias of Guohua thermal power transformer is the operation of the subway, and the change of the DC bias current is periodic. Finally, of Guohua thermal power transformer DC magnetic bias control method is studied, the simulation results show that the method of using neutral point with small resistance or capacitance can effectively inhibit the main transformer neutral point current.

Investigations into the use of energy storage in power system applications

NASA Astrophysics Data System (ADS)

Leung, Ka Kit

This thesis embodies research work on the design and implementation of novel fast responding battery energy storage systems, which, with sufficient capacity and rating, could remove the uncertainty in forecasting the annual peak demand. They would also benefit the day to day operation by curtailing the fastest demand variations, particularly at the daily peak periods. Energy storage that could curtail peak demands, when the most difficult operational problems occur offers a promising approach. Although AC energy cannot be stored, power electronic developments offer a fast responding interface between the AC network and DC energy stored in batteries. The attractive feature of the use of this energy storage could most effectively be located near the source of load variations, i.e. near consumers in the distribution networks. The proposed, three phase multi-purpose, Battery Energy Storage System will provide active and reactive power independent of the supply voltage with excellent power quality in terms of its waveform. Besides the above important functions applied at the distribution side of the utility, several new topologies have been developed to provide both Dynamic Voltage Regulator (DVR) and Unified Power Flow Controller (UPFC) functions for line compensation. These new topologies can provide fast and accurate control of power flow along a distribution corridor. The topologies also provide for fast damping of system oscillation due to transient or dynamic disturbances. Having demonstrated the various functions that the proposed Battery Energy Storage System can provide, the final part of the thesis investigates means of improving the performance of the proposed BESS. First, there is a need to reduce the switching losses by using soft switching instead of hard switching. A soft switching inverter using a parallel resonant dc-link (PRDCL) is proposed for use with the proposed BESS. The proposed PRDCL suppresses the dc-link voltage to zero for a very short time to allow zero voltage switching of inverter main switches without imposing excessive voltage and current stresses. Finally, in practice the battery terminal voltage fluctuates significantly as large current is being drawn or absorbed by the battery bank. When a hysteresis controller is used to control the supply line current, the ripple magnitude and frequency of the controlled current is highly dependent on the battery voltage, line inductance and the band limits of the controller. Even when these parameters are constant, the switching frequency can vary over quite a large range. A novel method is proposed to overcome this problem by controlling the dc voltage level by means of a dc-dc converter to provide a controllable voltage at the inverter dc terminal irrespective of the battery voltage variations. By proper control of the magnitude and frequency of the output of the DC-DC converter, the switching frequency can be made close to constant. A mathematical proof has been formulated and results from the simulation confirm that using the proposed technique, the frequency band has been significantly reduced and for the theoretical case, a single switching frequency is observed. The main disadvantage is the need to have an extra dc-dc converter, but this is relatively cheap and easy to obtain.

The Effects of Low Atmosphere Stunning and Deboning Time on Broiler Breast Meat Quality

USDA-ARS?s Scientific Manuscript database

A randomized complete block design with 3 replications (n = 432, 72 broilers per treatment) was used to evaluate the effects of electrical (ES) and vacuum stunning (VS) on broiler breast meat quality. Electrical stunning was performed by applying 11.5 V, <0.05 mA, AC to DC current for 3 s for each b...

Metacognitive Theory Applied: Strategic Reading Instruction in the Current Generation of Basal Readers.

ERIC Educational Resources Information Center

Schmitt, Maribeth Cassidy; Hopkins, Carol J.

A study examined the content of eight 1989 editions of the major basal reading series--those of Harcourt Brace Jovanovich; D.C. Heath and Co.; Holt Rinehart and Winston; Houghton Mifflin; Macmillan; McGraw-Hill; Scott, Foresman and Co.; and Silver Burdett and Ginn. The study determined how and the extent to which lessons and activities that…

Content of Total Phenolics, Flavan-3-Ols and Proanthocyanidins, Oxidative Stability and Antioxidant Capacity of Chocolate During Storage

PubMed Central

Komes, Draženka; Gorjanović, Stanislava; Belščak-Cvitanović, Ana; Pezo, Lato; Pastor, Ferenc; Ostojić, Sanja; Popov-Raljić, Jovanka; Sužnjević, Desanka

2016-01-01

Summary Antioxidant (AO) capacity of chocolates with 27, 44 and 75% cocoa was assessed after production and during twelve months of storage by direct current (DC) polarographic assay, based on the decrease of anodic current caused by the formation of hydroxo-perhydroxyl mercury(II) complex (HPMC) in alkaline solutions of hydrogen peroxide at potentials of mercury oxidation, and two spectrophotometric assays. Relative antioxidant capacity index (RACI) was calculated by taking the average value of the AO assay (the sample mass in all assays was identical). Oxidative stability of chocolate fat was determined by differential scanning calorimetry. Measured parameters and RACI were correlated mutually and with the content of total phenols (Folin-Ciocalteu assay), flavan-3-ols (vanillin and p-dimethylaminocinnamaldehyde assay) and proanthocyanidins (modified Bate-Smith assay). During storage, the studied functional and health-related characteristics remained unchanged. Amongst applied AO assays, the DC polarographic one, whose validity was confirmed by two-way ANOVA and F-test, correlated most significantly with oxidative stability (oxidation onset temperature and induction time). In addition, principal component analysis was applied to characterise chocolate types. PMID:27904388

Methods, systems and apparatus for adjusting duty cycle of pulse width modulated (PWM) waveforms

DOEpatents

Gallegos-Lopez, Gabriel; Kinoshita, Michael H; Ransom, Ray M; Perisic, Milun

2013-05-21

Embodiments of the present invention relate to methods, systems and apparatus for controlling operation of a multi-phase machine in a vector controlled motor drive system when the multi-phase machine operates in an overmodulation region. The disclosed embodiments provide a mechanism for adjusting a duty cycle of PWM waveforms so that the correct phase voltage command signals are applied at the angle transitions. This can reduce variations/errors in the phase voltage command signals applied to the multi-phase machine so that phase current may be properly regulated thus reducing current/torque oscillation, which can in turn improve machine efficiency and performance, as well as utilization of the DC voltage source.

Method and apparatus for using magneto-acoustic remanence to determine embrittlement

NASA Technical Reports Server (NTRS)

Allison, Sidney G. (Inventor); Namkung, Min (Inventor); Yost, William T. (Inventor); Cantrell, John H. (Inventor)

1992-01-01

A method and apparatus for testing steel components for temperature embrittlement uses magneto-acoustic emission to nondestructively evaluate the component are presented. Acoustic emission signals occur more frequently at higher levels in embrittled components. A pair of electromagnets are used to create magnetic induction in the test component. Magneto-acoustic emission signals may be generated by applying an AC current to the electromagnets. The acoustic emission signals are analyzed to provide a comparison between a component known to be unembrittled and a test component. Magnetic remanence is determined by applying a DC current to the electromagnets and then by turning the magnets off and observing the residual magnetic induction.

Direct current uninterruptible power supply method and system

DOEpatents

Sinha, Gautam

2003-12-02

A method and system are described for providing a direct current (DC) uninterruptible power supply with the method including, for example: continuously supplying fuel to a turbine; converting mechanical power from the turbine into alternating current (AC) electrical power; converting the AC electrical power to DC power within a predetermined voltage level range; supplying the DC power to a load; and maintaining a DC load voltage within the predetermined voltage level range by adjusting the amount of fuel supplied to the turbine.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhoomeeswaran, H.; Sabareesan, P., E-mail: sendtosabari@gmail.com

The article mainly focuses on the enrichment of the output power obtained from Spin torque nano-oscillator by introducing the heterogeneous structure in multilayer nanopillar device. Here we devised two homogeneous and two heterogeneous devices having NiFe and Co materials. The dynamics of the devices are governed by a famous Landu- Lifshitz -Gilbert-Solencskwei (LLGS) equation which can be solved numerically using embedded RK-4 procedure. The current density and the external magnetic field for four devices are taken as 5×l0{sup 11}A/m{sup 2} and 6×l0{sup −3} A/m respectively. The applied dc current is converted into spin polarized dc current while it passes throughmore » pinned layer. The generated spin polarized dc currents produces spin transfer torque with the free layer magnetization via spacer. Thus the magnetization of the free layer gets a sustained oscillation. The results obtained from the heterogeneous STNOs are really fascinating. The frequency of the NiFe/ Cu/NiFe and Co/Cu/NiFe devices have the same frequency but there is a tremendous change in the output power which is exactly twice that the NiFe/Cu/NiFe device. The similar behaviour is also obtained from Co/Cu/Co and NiFe/Cu/Co devices. The line width and the Q-factor of the output microwave signal are also computed. Among the four devices, the NiFe/Cu/Co heterogeneous device has low linewidth (408 MHz) and high Q-factor (4.77).« less

Temperature dependent charge transport studies across thermodynamic glass transition in P3HT:PCBM bulk heterojunction: insight from J-V and impedance spectroscopy

NASA Astrophysics Data System (ADS)

Sarkar, Atri; Rahaman, Abdulla Bin; Banerjee, Debamalya

2018-03-01

Temperature dependent charge transport properties of P3HT:PCBM bulk heterojunction are analysed by dc and ac measurements under dark conditions across a wide temperature range of 110-473 K, which includes the thermodynamic glass transition temperature (Tg ˜320 K) of the system. A change from Ohmic conduction to space charge limited current conduction at higher (⩾1.2 V) applied bias voltages above  ⩾200 K is observed from J-V characteristics. From capacitance-voltage (C-V) measurement at room temperature, the occurrence of a peak near the built-in voltage is observed below the dielectric relaxation frequency, originating from the competition between drift and diffusion driven motions of charges. Carrier concentration (N) is calculated from C-V measurements taken at different temperatures. Room temperature mobility values at various applied bias voltages are in accordance with that obtained from transient charge extraction by linearly increasing voltage measurement. Sample impedance is measured over five decades of frequency across temperature range by using lock-in detection. This data is used to extract temperature dependence of carrier mobility (μ), and dc conductivity (σ_dc ) which is low frequency extrapolation of ac conductivity. An activation energy of  ˜126 meV for the carrier hopping process at the metal-semiconductor interface is estimated from temperature dependence of σ_dc . Above T g, μ levels off to a constant value, whereas σ_dc starts to decrease after a transition knee at T g that can be seen as a combined effect of changes in μ and N. All these observed changes across T g can be correlated to enhanced polymer motion above the glass transition.

A wideband photonic microwave phase shifter with 360-degree phase tunable range based on a DP-QPSK modulator

NASA Astrophysics Data System (ADS)

Chen, Yang

2018-03-01

A novel wideband photonic microwave phase shifter with 360-degree phase tunable range is proposed based on a single dual-polarization quadrature phase shift-keying (DP-QPSK) modulator. The two dual-parallel Mach-Zehnder modulators (DP-MZMs) in the DP-QPSK modulator are properly biased to serve as a carrier-suppressed single-sideband (CS-SSB) modulator and an optical phase shifter (OPS), respectively. The microwave signal is applied to the CS-SSB modulator, while a control direct-current (DC) voltage is applied to the OPS. The first-order optical sideband generated from the CS-SSB modulator and the phase tunable optical carrier from the OPS are combined and then detected in a photodetector, where a microwave signal is generated with its phase controlled by the DC voltage applied to the OPS. The proposed technique is theoretically analyzed and experimentally demonstrated. Microwave signals with a carrier frequency from 10 to 23 GHz are continuously phase shifted over 360-degree phase range. The proposed technique features very compact configuration, easy phase tuning and wide operation bandwidth.

Inhibition of Crystal Growth during Plasma Enhanced Atomic Layer Deposition by Applying BIAS

PubMed Central

Ratzsch, Stephan; Kley, Ernst-Bernhard; Tünnermann, Andreas; Szeghalmi, Adriana

2015-01-01

In this study, the influence of direct current (DC) biasing on the growth of titanium dioxide (TiO2) layers and their nucleation behavior has been investigated. Titania films were prepared by plasma enhanced atomic layer deposition (PEALD) using Ti(OiPr)4 as metal organic precursor. Oxygen plasma, provided by remote inductively coupled plasma, was used as an oxygen source. The TiO2 films were deposited with and without DC biasing. A strong dependence of the applied voltage on the formation of crystallites in the TiO2 layer is shown. These crystallites form spherical hillocks on the surface which causes high surface roughness. By applying a higher voltage than the plasma potential no hillock appears on the surface. Based on these results, it seems likely, that ions are responsible for the nucleation and hillock growth. Hence, the hillock formation can be controlled by controlling the ion energy and ion flux. The growth per cycle remains unchanged, whereas the refractive index slightly decreases in the absence of energetic oxygen ions. PMID:28793679

Ion funnel device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ibrahim, Yehia M.; Chen, Tsung-Chi; Harrer, Marques B.

2017-11-21

An ion funnel device is disclosed. A first pair of electrodes is positioned in a first direction. A second pair of electrodes is positioned in a second direction. The device includes an RF voltage source and a DC voltage source. A RF voltage with a superimposed DC voltage gradient is applied to the first pair of electrodes, and a DC voltage gradient is applied to the second pair of electrodes.

Digital Signal Processing and Generation for a DC Current Transformer for Particle Accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zorzetti, Silvia

2013-01-01

The thesis topic, digital signal processing and generation for a DC current transformer, focuses on the most fundamental beam diagnostics in the field of particle accelerators, the measurement of the beam intensity, or beam current. The technology of a DC current transformer (DCCT) is well known, and used in many areas, including particle accelerator beam instrumentation, as non-invasive (shunt-free) method to monitor the DC current in a conducting wire, or in our case, the current of charged particles travelling inside an evacuated metal pipe. So far, custom and commercial DCCTs are entirely based on analog technologies and signal processing, whichmore » makes them inflexible, sensitive to component aging, and difficult to maintain and calibrate.« less

Analysis of Electric Vehicle DC High Current Conversion Technology

NASA Astrophysics Data System (ADS)

Yang, Jing; Bai, Jing-fen; Lin, Fan-tao; Lu, Da

2017-05-01

Based on the background of electric vehicles, it is elaborated the necessity about electric energy accurate metering of electric vehicle power batteries, and it is analyzed about the charging and discharging characteristics of power batteries. It is needed a DC large current converter to realize accurate calibration of power batteries electric energy metering. Several kinds of measuring methods are analyzed based on shunts and magnetic induction principle in detail. It is put forward power batteries charge and discharge calibration system principle, and it is simulated and analyzed ripple waves containing rate and harmonic waves containing rate of power batteries AC side and DC side. It is put forward suitable DC large current measurement methods of power batteries by comparing different measurement principles and it is looked forward the DC large current measurement techniques.

Photovoltaic system with improved DC connections and method of making same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cioffi, Philip Michael; Todorovic, Maja Harfman; Herzog, Michael Scott

A micro-inverter assembly includes a housing having an opening formed in a bottom surface thereof, and a direct current (DC)-to-alternating current (AC) micro-inverter disposed within the housing at a position adjacent to the opening. The micro-inverter assembly further includes a micro-inverter DC connector electrically coupled to the DC-to-AC micro-inverter and positioned within the opening of the housing, the micro-inverter DC connector having a plurality of exposed electrical contacts.

Auxiliary resonant DC tank converter

DOEpatents

Peng, Fang Z.

2000-01-01

An auxiliary resonant dc tank (ARDCT) converter is provided for achieving soft-switching in a power converter. An ARDCT circuit is coupled directly across a dc bus to the inverter to generate a resonant dc bus voltage, including upper and lower resonant capacitors connected in series as a resonant leg, first and second dc tank capacitors connected in series as a tank leg, and an auxiliary resonant circuit comprising a series combination of a resonant inductor and a pair of auxiliary switching devices. The ARDCT circuit further includes first clamping means for holding the resonant dc bus voltage to the dc tank voltage of the tank leg, and second clamping means for clamping the resonant dc bus voltage to zero during a resonant period. The ARDCT circuit resonantly brings the dc bus voltage to zero in order to provide a zero-voltage switching opportunity for the inverter, then quickly rebounds the dc bus voltage back to the dc tank voltage after the inverter changes state. The auxiliary switching devices are turned on and off under zero-current conditions. The ARDCT circuit only absorbs ripples of the inverter dc bus current, thus having less current stress. In addition, since the ARDCT circuit is coupled in parallel with the dc power supply and the inverter for merely assisting soft-switching of the inverter without participating in real dc power transmission and power conversion, malfunction and failure of the tank circuit will not affect the functional operation of the inverter; thus a highly reliable converter system is expected.

Human perception of electric fields and ion currents associated with high-voltage DC transmission lines.

PubMed

Blondin, J P; Nguyen, D H; Sbeghen, J; Goulet, D; Cardinal, C; Maruvada, P S; Plante, M; Bailey, W H

1996-01-01

The objective of this study was to assess the ability of humans to detect the presence of DC electric field and ion currents. An exposure chamber simulating conditions present in the vicinity of high-voltage DC (HVDC) lines was designed and built for this purpose. In these experiments, the facility was used to expose observers to DC electric fields up to 50 kV/m and ion current densities up to 120 nA/m2. Forty-eight volunteers (25 women and 23 men) between the ages of 18 and 57 years served as observers. Perception of DC fields was examined by using two psychophysical methods: an adaptive staircase procedure and a rating method derived from signal-detection theory. Subjects completed three different series of observations by using each of these methods; one was conducted without ion currents, and the other two involved various combinations of electric fields and ion currents. Overall, subjects were significantly more likely to detect DC fields as the intensity increased. Observers were able to detect the presence of DC fields alone, but only at high intensities; the average threshold was 45 kV/m. Except in the most sensitive individuals, ion current densities up to 60 nA/m2 did not significantly facilitate the detection of DC fields. However, higher ion current densities were associated with a substantial lowering of sensory thresholds in a large majority of observers. Data analysis also revealed large variations in perceptual thresholds among observers. Normative data indicating DC field and ion current intensities that can be detected by 50% of all observers are provided. In addition, for the most sensitive observers, several other detection proportions were derived from the distribution of individual detection capabilities. These data can form the basis for environmental guidelines relating to the design of HVDC lines.

Performance of 22.4-kW nonlaminated-frame dc series motor with chopper controller. [a dc to dc voltage converter

NASA Technical Reports Server (NTRS)

Schwab, J. R.

1979-01-01

Performance data obtained through experimental testing of a 22.4 kW traction motor using two types of excitation are presented. Ripple free dc from a motor-generator set for baseline data and pulse width modulated dc as supplied by a battery pack and chopper controller were used for excitation. For the same average values of input voltage and current, the motor power output was independent of the type of excitation. However, at the same speeds, the motor efficiency at low power output (corresponding to low duty cycle of the controller) was 5 to 10 percentage points lower on chopped dc than on ripple free dc. The chopped dc locked-rotor torque was approximately 1 to 3 percent greater than the ripple free dc torque for the same average current.

An Optimal Current Observer for Predictive Current Controlled Buck DC-DC Converters

PubMed Central

Min, Run; Chen, Chen; Zhang, Xiaodong; Zou, Xuecheng; Tong, Qiaoling; Zhang, Qiao

2014-01-01

In digital current mode controlled DC-DC converters, conventional current sensors might not provide isolation at a minimized price, power loss and size. Therefore, a current observer which can be realized based on the digital circuit itself, is a possible substitute. However, the observed current may diverge due to the parasitic resistors and the forward conduction voltage of the diode. Moreover, the divergence of the observed current will cause steady state errors in the output voltage. In this paper, an optimal current observer is proposed. It achieves the highest observation accuracy by compensating for all the known parasitic parameters. By employing the optimal current observer-based predictive current controller, a buck converter is implemented. The converter has a convergently and accurately observed inductor current, and shows preferable transient response than the conventional voltage mode controlled converter. Besides, costs, power loss and size are minimized since the strategy requires no additional hardware for current sensing. The effectiveness of the proposed optimal current observer is demonstrated experimentally. PMID:24854061

Leakage current evaluation for pn junctions formed in DC and RF MeV ion implanted wells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yanagisawa, Yasunobu; Honda, Mitsuharu; Ogasawara, Makota

1996-12-31

The leakage current of pn junctions formed in DC and RF MeV implanted wells have been evaluated. There is no substantial difference in the leakage current levels between the continuous and pulsive beam implantations. However, the leakage current, so called diffusion current, for RF implanted wells is slightly higher than that for DC implanted wells on some condition. This suggests a possibility that relatively higher density of residual defects remains in the case of RIF implant.

Effects of combined electrical stimulation of the dorsal column and dorsal roots on wide-dynamic range neuronal activity in nerve-injured rats

PubMed Central

Yang, Fei; Zhang, Tong; Tiwari, Vinod; Shu, Bin; Zhang, Chen; Wang, Yun; Vera-Portocarrero, Louis P.; Raja, Srinivasa N.; Guan, Yun

2015-01-01

Objectives Electrical stimulation at the dorsal column (DC) and dorsal root (DR) may inhibit spinal wide-dynamic-range (WDR) neuronal activity in nerve-injured rats. The objective of this study was to determine if applying electrical conditioning stimulation (CS) at both sites provides additive or synergistic benefits. Materials and Methods By conducting in vivo extracellular recordings of WDR neurons in rats that had undergone L5 spinal nerve ligation, we tested whether combining 50 Hz CS at the two sites in either a concurrent (2.5 minutes) or alternate (5 minutes) pattern inhibits WDR neuronal activity better than CS at DC alone (5 minutes). The intensities of CS were determined by recording antidromic compound action potentials to graded stimulation at the DC and DR. We measured the current thresholds that resulted in the first detectable Aα/β waveform (Ab0) and the peak Aα/β waveform (Ab1) to select CS intensity at each site. The same number of electrical pulses and amount of current were delivered in different patterns to allow comparison. Results At a moderate intensity of 50%(Ab0+Ab1), different patterns of CS all attenuated the C-component of WDR neurons in response to graded intracutaneous electrical stimuli (0.1-10 mA, 2 ms), and inhibited windup in response to repetitive noxious stimuli (0.5 Hz). However, the inhibitory effects did not differ significantly between different patterns. At the lower intensity (Ab0), no CS inhibited WDR neurons. Conclusions These findings suggest that combined stimulation of DC and DR may not be superior to DC stimulation alone for inhibition of WDR neurons. PMID:26307526

Electrowetting of liquid polymer on petal-mimetic microbowl-array surfaces for formation of microlens array with varying focus on a single substrate

NASA Astrophysics Data System (ADS)

Li, Xiangmeng; Shao, Jinyou; Li, Xiangming; Tian, Hongmiao

2015-03-01

In this paper, microlens array with varying focal lengths were fabricated on a single microbowl-array textured substrate. The solid microbowl-arrayed NOA61 (kind of polyurethane-based polymer with UV curablity) surface was resulted from nanoimprinting by polydimethylsiloxane (PDMS) mold. The PDMS mold was replicated from an SU-8 master which was generated by electron beam lithography. Such microbowl-arrayed surfaces demonstrate petal-mimetic highly adhesive hydrophobic wetting properties, which can promote an irreversible electrowetting (EW) effect and a dereased contact angle of water droplets as well as other liquid droplets by applying direct current (DC) voltage. To fabricate a microlens array with varying focal-lengths, liquid NOA61 was supplied from a syringe on the solid NOA61 microtextured film and DC voltage was applied succesively. After removing the DC voltage, these liquid NOA61 microdrops deposited on the solid microtextured NOA61 surface on tin-indium-oxide coated substrate could be solidified via UV irradiation, thus leading to microlens array with uneven numerical apertures on a single substrate. Numerical simulation was also done to verify the EW effect. Finally, optical imaging characterization was performed to confirm the varied focus of the NOA61 microdrops.

High voltage dc--dc converter with dynamic voltage regulation and decoupling during load-generated arcs

DOEpatents

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.

High voltage dc-dc converter with dynamic voltage regulation and decoupling during load-generated arcs

DOEpatents

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.

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

DOEpatents

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

2017-08-29

A high-voltage direct-current (HVDC) transmission system includes an alternating current (AC) electrical source and a power converter channel that includes an AC-DC converter electrically coupled to the electrical source and a DC-AC inverter electrically coupled to the AC-DC converter. The AC-DC converter and the DC-AC inverter each include a plurality of legs that includes at least one switching device. The power converter channel further includes a commutating circuit communicatively coupled to one or more switching devices. The commutating circuit is configured to "switch on" one of the switching devices during a first portion of a cycle of the H-bridge switching circuits and "switch off" the switching device during a second portion of the cycle of the first and second H-bridge switching circuits.

77 FR 36950 - Airworthiness Directives; Dassault Aviation Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-20

... time between overhauls, and required an initial overhaul, of the direct current (DC) generator... overhauls, and required an initial overhaul, of the DC generator (bearings). That NPRM resulted from... condition as: Time between overhaul (TBO) of DC [direct current] generator bearings is set at 1,000 flight...

Multiple high voltage output DC-to-DC power converter

NASA Technical Reports Server (NTRS)

Cronin, Donald L. (Inventor); Farber, Bertrand F. (Inventor); Gehm, Hartmut K. (Inventor); Goldin, Daniel S. (Inventor)

1977-01-01

Disclosed is a multiple output DC-to-DC converter. The DC input power is filtered and passed through a chopper preregulator. The chopper output is then passed through a current source inverter controlled by a squarewave generator. The resultant AC is passed through the primary winding of a transformer, with high voltages induced in a plurality of secondary windings. The high voltage secondary outputs are each solid-state rectified for passage to individual output loads. Multiple feedback loops control the operation of the chopper preregulator, one being responsive to the current through the primary winding and another responsive to the DC voltage level at a selected output.

Modified Perfect Harmonics Cancellation Control of a Grid Interfaced SPV Power Generation

NASA Astrophysics Data System (ADS)

Singh, B.; Shahani, D. T.; Verma, A. K.

2015-03-01

This paper deals with a grid interfaced solar photo voltaic (SPV) power generating system with modified perfect harmonic cancellation (MPHC) control for power quality improvement in terms of mitigation of the current harmonics, power factor correction, control of point of common coupling (PCC) voltage with reactive power compensation and load balancing in a three phase distribution system. The proposed grid interfaced SPV system consists of a SPV array, a dc-dc boost converter and a voltage source converter (VSC) used for the compensation of other connected linear and nonlinear loads at PCC. The reference grid currents are estimated using MPHC method and control signals are derived by using pulse width modulation (PWM) current controller of VSC. The SPV power is fed to the common dc bus of VSC and dc-dc boost converter using maximum power point tracking (MPPT). The dc link voltage of VSC is regulated by using dc voltage proportional integral (PI) controller. The analysis of the proposed SPV power generating system is carried out under dc/ac short circuit and severe SPV-SX and SPV-TX intrusion.

FAST TRACK COMMUNICATION: Plasma agents in bio-decontamination by dc discharges in atmospheric air

NASA Astrophysics Data System (ADS)

Machala, Zdenko; Chládeková, Lenka; Pelach, Michal

2010-06-01

Bio-decontamination of water and surfaces contaminated by bacteria (Salmonella typhimurium) was investigated in two types of positive dc discharges in atmospheric pressure air, in needle-to-plane geometry: the streamer corona and its transition to a novel regime called transient spark with short high current pulses of limited energy. Both generate a cold non-equilibrium plasma. Electro-spraying of treated water through a needle electrode was applied for the first time and resulted in fast bio-decontamination. Experiments providing separation of various biocidal plasma agents, along with the emission spectra and coupled with oxidation stress measurements in the cell membranes helped to better understand the mechanisms of microbial inactivation. The indirect exposure of contaminated surfaces to neutral active species was almost as efficient as the direct exposure to the plasma, whereas applying only UV radiation from the plasma had no biocidal effects. Radicals and reactive oxygen species were identified as dominant biocidal agents.

Applying PWM to control overcurrents at unbalanced faults of force-commutated VSCs used as static var compensators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Y.; Ekstroem, A.

1997-01-01

This study is devoted to investigating the possibility of controlling the overcurrent of a forced-commutated voltage source converter (VSC) by PWM when the ac system is undergoing large unbalanced disturbance. The converter is supposed to be used as a static var compensator at a high power level. A novel control strategy is proposed for controlling the reactive current and the dc side voltage independently. Digital simulation results are presented and compared with the results by using just the reactive current control with fundamental switching frequency.

An Advanced Photovoltaic Array Regulator Module

NASA Technical Reports Server (NTRS)

Button, Robert M.

1996-01-01

Current trends in satellite design are focused on developing small, reliable, and inexpensive spacecraft. To that end, a modular power management and distribution system is proposed which will help transition the aerospace industry towards an assembly line approach to building spacecraft. The modular system is based on an innovative DC voltage boost converter called the Series Connected Boost Unit (SCBU). The SCBU uses any isolating DC-DC converter and adds a unique series connection. This simple modification provides the SCBU topology with many advantages over existing boost converters. Efficiencies of 94-98%, power densities above 1,000 W/kg, and inherent fault tolerance are just a few of the characteristics presented. Limitations of the SCBU technology are presented, and it is shown that the SCBU makes an ideal photovoltaic an-ay regulator. A set of photovoltaic power system requirements are presented that can be applied to almost any low Earth orbit satellite. Finally, a modular design based on the series connected boost unit is outlined and functional descriptions of the components are given.

Interface layer to tailor the texture and surface morphology of Al-doped ZnO polycrystalline films on glass substrates

NASA Astrophysics Data System (ADS)

Nomoto, Junichi; Inaba, Katsuhiko; Kobayashi, Shintaro; Makino, Hisao; Yamamoto, Tetsuya

2017-06-01

A 10-nm-thick radio frequency magnetron-sputtered aluminum-doped zinc oxide (AZO) showing a texture with a preferential (0001) orientation on amorphous glass substrates was used as an interface layer for tailoring the orientation of 490-nm-thick polycrystalline AZO films subsequently deposited by direct current (DC) magnetron sputtering at a substrate temperature of 200 °C. Wide-angle X-ray diffraction pole figure analysis showed that the resulting 500-nm-thick AZO films showed a texture with a highly preferential c-axis orientation. This showed that DC-magnetron-sputtered AZO films grew along with the orientation matching that of the interface layer, whereas 500-nm-thick AZO films deposited on bare glass substrates by DC magnetron sputtering exhibited a mixed orientation of the c-plane and other planes. The surface morphology was also improved while retaining the lateral grain size by applying the interface layer as revealed by atomic force microscopy.

Superconducting dc Current Limiting Vacuum Circuit Breaker

NASA Astrophysics Data System (ADS)

Alferov, D. F.; Akhmetgareev, M. R.; Budovskii, A. I.; Bunin, R. A.; Voloshin, I. F.; Degtyarenko, P. N.; Yevsin, D. V.; Ivanov, V. P.; Sidorov, V. A.; Fisher, L. M.; Tshai, E. V.

Acircuitofadc superconductingfault current limiter witha direct current circuit-breaker fora nominal current 300A is proposed. It includes the 2G high temperature superconducting (HTS) tapes and the high-speed dc vacuum circuit breaker.Thetestresultsof current-limitingcapacityandrecoverytimeof superconductivityafter currentfaultatvoltage upto3 kV are presented.

Unity power factor converter

NASA Technical Reports Server (NTRS)

Wester, Gene W. (Inventor)

1980-01-01

A unity power factor converter capable of effecting either inversion (dc-to-dc) or rectification (ac-to-dc), and capable of providing bilateral power control from a DC source (or load) through an AC transmission line to a DC load (or source) for power flow in either direction, is comprised of comparators for comparing the AC current i with an AC signal i.sub.ref (or its phase inversion) derived from the AC ports to generate control signals to operate a switch control circuit for high speed switching to shape the AC current waveform to a sine waveform, and synchronize it in phase and frequency with the AC voltage at the AC ports, by selectively switching the connections to a series inductor as required to increase or decrease the current i.

Single Phase Passive Rectification Versus Active Rectification Applied to High Power Stirling Engines

NASA Technical Reports Server (NTRS)

Santiago, Walter; Birchenough, Arthur G.

2006-01-01

Stirling engine converters are being considered as potential candidates for high power energy conversion systems required by future NASA explorations missions. These types of engines typically contain two major moving parts, the displacer and the piston, in which a linear alternator is attached to the piston to produce a single phase sinusoidal waveform at a specific electric frequency. Since all Stirling engines perform at low electrical frequencies (less or equal to 100 Hz), space explorations missions that will employ these engines will be required to use DC power management and distribution (PMAD) system instead of an AC PMAD system to save on space and weight. Therefore, to supply such DC power an AC to DC converter is connected to the Stirling engine. There are two types of AC to DC converters that can be employed, a passive full bridge diode rectifier and an active switching full bridge rectifier. Due to the inherent line inductance of the Stirling Engine-Linear Alternator (SE-LA), their sinusoidal voltage and current will be phase shifted producing a power factor below 1. In order to keep power the factor close to unity, both AC to DC converters topologies will implement power factor correction. This paper discusses these power factor correction methods as well as their impact on overall mass for exploration applications. Simulation results on both AC to DC converters topologies with power factor correction as a function of output power and SE-LA line inductance impedance are presented and compared.

Light-weight DC to very high voltage DC converter

DOEpatents

Druce, Robert L.; Kirbie, Hugh C.; Newton, Mark A.

1998-01-01

A DC-DC converter capable of generating outputs of 100 KV without a transformer comprises a silicon opening switch (SOS) diode connected to allow a charging current from a capacitor to flow into an inductor. When a specified amount of charge has flowed through the SOS diode, it opens up abruptly; and the consequential collapsing field of the inductor causes a voltage and current reversal that is steered into a load capacitor by an output diode. A switch across the series combination of the capacitor, inductor, and SOS diode closes to periodically reset the SOS diode by inducing a forward-biased current.

Effects of DC bias on magnetic performance of high grades grain-oriented silicon steels

NASA Astrophysics Data System (ADS)

Ma, Guang; Cheng, Ling; Lu, Licheng; Yang, Fuyao; Chen, Xin; Zhu, Chengzhi

2017-03-01

When high voltage direct current (HVDC) transmission adopting mono-polar ground return operation mode or unbalanced bipolar operation mode, the invasion of DC current into neutral point of alternating current (AC) transformer will cause core saturation, temperature increasing, and vibration acceleration. Based on the MPG-200D soft magnetic measurement system, the influence of DC bias on magnetic performance of 0.23 mm and 0.27 mm series (P1.7=0.70-1.05 W/kg, B8>1.89 T) grain-oriented (GO) silicon steels under condition of AC / DC hybrid excitation were systematically realized in this paper. For the high magnetic induction GO steels (core losses are the same), greater thickness can lead to stronger ability of resisting DC bias, and the reasons for it were analyzed. Finally, the magnetostriction and A-weighted magnetostriction velocity level of GO steel under DC biased magnetization were researched.

A robust low quiescent current power receiver for inductive power transmission in bio implants

NASA Astrophysics Data System (ADS)

Helalian, Hamid; Pasandi, Ghasem; Jafarabadi Ashtiani, Shahin

2017-05-01

In this paper, a robust low quiescent current complementary metal-oxide semiconductor (CMOS) power receiver for wireless power transmission is presented. This power receiver consists of three main parts including rectifier, switch capacitor DC-DC converter and low-dropout regulator (LDO) without output capacitor. The switch capacitor DC-DC converter has variable conversion ratios and synchronous controller that lets the DC-DC converter to switch among five different conversion ratios to prevent output voltage drop and LDO regulator efficiency reduction. For all ranges of output current (0-10 mA), the voltage regulator is compensated and is stable. Voltage regulator stabilisation does not need the off-chip capacitor. In addition, a novel adaptive biasing frequency compensation method for low dropout voltage regulator is proposed in this paper. This method provides essential minimum current for compensation and reduces the quiescent current more effectively. The power receiver was designed in a 180-nm industrial CMOS technology, and the voltage range of the input is from 0.8 to 2 V, while the voltage range of the output is from 1.2 to 1.75 V, with a maximum load current of 10 mA, the unregulated efficiency of 79.2%, and the regulated efficiency of 64.4%.

Integrating Nano-patterned Ferromagnetic and Ferroelectric Thin Films for Electrically Tunable RF Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Tengxing; Peng, Yujia; Jiang, Wei

Tunable radio frequency (RF) components are pivotal elements in frequency-agile and multifunctional systems. However, there is a technical barrier to achieve miniaturized fully electrically tunable RF components. This paper provides and demonstrates the efficacy of a first unique design methodology in developing fully electrically tunable RF components by integrating ferromagnetic (e.g., Permalloy) and ferroelectric (e.g., Lead Zirconate Titanate: PZT) thin films patterns. Permalloy thin film has been patterned in nanometer scale to improve its ferromagnetic resonance frequency (FMR) for RF applications. Tunable inductors are developed with the utilization of different thickness of Permalloy thin film, which show over 50% incrementmore » in inductance and over 4% in tunability with DC current. More tunability can be achieved with multiple layers of Permalloy thin film and optimized thickness. A fully electrically tunable slow wave RF transmission line with simultaneously variable inductance and capacitance density has been implemented and thoroughly investigated for the first time. Measured results show that a fixed phase shift of 90° can be achieved from 1.5 GHz to 1.85 GHz continuously by applying external DC current from 0 to 200 mA and external DC voltage from 0 to 15 Volts, respectively.« less

Novel design of high voltage pulse source for efficient dielectric barrier discharge generation by using silicon diodes for alternating current.

PubMed

Truong, Hoa Thi; Hayashi, Misaki; Uesugi, Yoshihiko; Tanaka, Yasunori; Ishijima, Tatsuo

2017-06-01

This work focuses on design, construction, and optimization of configuration of a novel high voltage pulse power source for large-scale dielectric barrier discharge (DBD) generation. The pulses were generated by using the high-speed switching characteristic of an inexpensive device called silicon diodes for alternating current and the self-terminated characteristic of DBD. The operation started to be powered by a primary DC low voltage power supply flexibly equipped with a commercial DC power supply, or a battery, or DC output of an independent photovoltaic system without transformer employment. This flexible connection to different types of primary power supply could provide a promising solution for the application of DBD, especially in the area without power grid connection. The simple modular structure, non-control requirement, transformer elimination, and a minimum number of levels in voltage conversion could lead to a reduction in size, weight, simple maintenance, low cost of installation, and high scalability of a DBD generator. The performance of this pulse source has been validated by a load of resistor. A good agreement between theoretically estimated and experimentally measured responses has been achieved. The pulse source has also been successfully applied for an efficient DBD plasma generation.

Novel design of high voltage pulse source for efficient dielectric barrier discharge generation by using silicon diodes for alternating current

NASA Astrophysics Data System (ADS)

Truong, Hoa Thi; Hayashi, Misaki; Uesugi, Yoshihiko; Tanaka, Yasunori; Ishijima, Tatsuo

2017-06-01

This work focuses on design, construction, and optimization of configuration of a novel high voltage pulse power source for large-scale dielectric barrier discharge (DBD) generation. The pulses were generated by using the high-speed switching characteristic of an inexpensive device called silicon diodes for alternating current and the self-terminated characteristic of DBD. The operation started to be powered by a primary DC low voltage power supply flexibly equipped with a commercial DC power supply, or a battery, or DC output of an independent photovoltaic system without transformer employment. This flexible connection to different types of primary power supply could provide a promising solution for the application of DBD, especially in the area without power grid connection. The simple modular structure, non-control requirement, transformer elimination, and a minimum number of levels in voltage conversion could lead to a reduction in size, weight, simple maintenance, low cost of installation, and high scalability of a DBD generator. The performance of this pulse source has been validated by a load of resistor. A good agreement between theoretically estimated and experimentally measured responses has been achieved. The pulse source has also been successfully applied for an efficient DBD plasma generation.

Perpendicular momentum input of lower hybrid waves and its influence on driving plasma rotation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guan, Xiaoyin

The mechanism of perpendicular momentum input of lower hybrid waves and its influence on plasma rotation are studied. Discussion for parallel momentum input of lower hybrid waves is presented for comparison. It is found out that both toroidal and poloidal projections of perpendicular momentum input of lower hybrid waves are stronger than those of parallel momentum input. The perpendicular momentum input of lower hybrid waves therefore plays a dominant role in forcing the changes of rotation velocity observed during lower hybrid current drive. Lower hybrid waves convert perpendicular momentum carried by the waves into the momentum of dc electromagnetic fieldmore » by inducing a resonant-electron flow across flux surfaces therefore charge separation and a radial dc electric field. The dc field releases its momentum into plasma through the Lorentz force acting on the radial return current driven by the radial electric field. Plasma is spun up by the Lorentz force. An improved quasilinear theory with gyro-phase dependent distribution function is developed to calculate the radial flux of resonant electrons. Rotations are determined by a set of fluid equations for bulk electrons and ions, which are solved numerically by applying a finite-difference method. Analytical expressions for toroidal and poloidal rotations are derived using the same hydrodynamic model.« less

Integrating Nano-patterned Ferromagnetic and Ferroelectric Thin Films for Electrically Tunable RF Applications

DOE PAGES

Wang, Tengxing; Peng, Yujia; Jiang, Wei; ...

2016-10-31

Tunable radio frequency (RF) components are pivotal elements in frequency-agile and multifunctional systems. However, there is a technical barrier to achieve miniaturized fully electrically tunable RF components. This paper provides and demonstrates the efficacy of a first unique design methodology in developing fully electrically tunable RF components by integrating ferromagnetic (e.g., Permalloy) and ferroelectric (e.g., Lead Zirconate Titanate: PZT) thin films patterns. Permalloy thin film has been patterned in nanometer scale to improve its ferromagnetic resonance frequency (FMR) for RF applications. Tunable inductors are developed with the utilization of different thickness of Permalloy thin film, which show over 50% incrementmore » in inductance and over 4% in tunability with DC current. More tunability can be achieved with multiple layers of Permalloy thin film and optimized thickness. A fully electrically tunable slow wave RF transmission line with simultaneously variable inductance and capacitance density has been implemented and thoroughly investigated for the first time. Measured results show that a fixed phase shift of 90° can be achieved from 1.5 GHz to 1.85 GHz continuously by applying external DC current from 0 to 200 mA and external DC voltage from 0 to 15 Volts, respectively.« less

Patterned Ferroelectric Films for Tunable Microwave Devices

NASA Technical Reports Server (NTRS)

Miranda, Felix A.; Mueller, Carl H.

2008-01-01

Tunable microwave devices based on metal terminals connected by thin ferroelectric films can be made to perform better by patterning the films to include suitably dimensioned, positioned, and oriented constrictions. The patterns can be formed during fabrication by means of selective etching processes. If the width of the ferroelectric film in such a device is reduced at one or more locations, then both the microwave field and any applied DC bias (tuning) electric field become concentrated at those locations. The magnitudes of both the permittivity and the dielectric loss of a ferroelectric material are reduced by application of a DC field. Because the concentration of the DC field in the constriction(s) magnifies the permittivity- and loss-reducing effects of the applied DC voltage, the permittivity and dielectric loss in the constriction(s) are smaller in the constriction(s) than they are in the wider parts of the ferroelectric film. Furthermore, inasmuch as displacement current must flow through either the constriction(s) or the low-loss dielectric substrate, the net effect of the constriction(s) is equivalent to that of incorporating one or more low-loss, low-permittivity region(s) in series with the high-loss, high-permittivity regions. In a series circuit, the properties of the low-capacitance series element (in this case, the constriction) dominate the overall performance. Concomitantly, the capacitance between the metal terminals is reduced. By making the capacitance between the metal terminals small but tunable, a constriction increases the upper limit of the frequency range amenable to ferroelectric tuning. The present patterning concept is expected to be most advantageous for devices and circuits that must operate at frequencies from about 4 to about 60 GHz. A constriction can be designed such that the magnitude of the microwave electric field and the effective width of the region occupied by the microwave electric field become functions of the applied DC electric field, so that tunability is enhanced. It should even be possible to design the constriction to obtain a specific tuning-versus-voltage profile.

Direct Current as an Integrating Platform for ZNE Buildings with EVs and Storage: DC Direct Systems – A Bridge to a Low Carbon Future?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Karl; Vossos, Vagelis; Kloss, Margarita

2016-09-01

Cost effective zero net energy (ZNE) schemes exist for many types of residential and commercial buildings. Yet, today’s alternating current (AC) based ZNE designs may be as much as 10% to 20% less efficient, more costly, and more complicated than a design based on direct current (DC) technologies. An increasing number of research organizations and manufacturers are just starting the process of developing products and conducting research and development (R&D) efforts. These early R&D efforts indicate that the use of DC technologies may deliver many energy and non-energy benefits relative to AC-based typologies. DC ZNE schemes may provide for anmore » ideal integrating platform for natively DC-based onsite generation, storage, electric vehicle (EV) charging and end-use loads. Emerging empirical data suggest that DC end-use appliances are more efficient, simpler, more durable, and lower cost. DC technologies appear to provide ratepayers a lower cost pathway to achieve resilient ZNE buildings, and simultaneously yield a plethora of benefits. This paper draws from the current research effort entitled "Direct Current as an Integrating and Enabling Platform," co-led by the Lawrence Berkeley National Laboratory (LBNL), the California Institute for Energy and the Environment (CIEE), the Electric Power Research Institute (EPRI) and funded under the California Energy Commission’s Energy Program Investment Charge (CEC EPIC). The first phase of this EPIC research is focused on assembling and summarizing known global performance information on DC and DC-AC hybrid end-use appliances and power systems. This paper summarizes the information and insights gained from this research effort.« less

Androgen Ablation Augments Prostate Cancer Vaccine Immunogenicity Only When Applied After Immunization

PubMed Central

Koh, Yi T.; Gray, Andrew; Higgins, Sean A.; Hubby, Bolyn; Kast, W. Martin

2009-01-01

Background Androgen ablation (AA) causes apoptosis of normal and neoplastic prostate cells. It is a standard treatment for advanced prostate cancer. Androgen ablation-mediated immunological effects include bone marrow hyperplasia, thymic regeneration, T and B cell lymphopoeisis and restoration of age-related peripheral T cell dysfunction. Androgens also regulate the transcription of several cytokines. Dendritic cells (DC) are the most potent antigen presenting cells that can activate antigen-specific naïve T cells. Despite myriad clinical trials involving DC-based prostate cancer immunotherapies, the effects of AA on DC function remain largely uncharacterized. Therefore, we investigated the effects of AA on DC and whether it could improve the efficacy of prostate cancer immunotherapy. Methods Cytokine expression changes due to AA were quantified by multiplex ELISA. Flow cytometry was used to assess AA-mediated effects on DC maturation and expression of costimulatory markers. Mixed leukocyte reactions and cell-mediated lysis assays elucidated the role of androgens in DC function. The effect of AA on the efficacy of vaccination against a prostate tumor-associated antigen was tested using Elispot assays. Results Androgen ablation increased dendritic cell maturation and costimulatory marker expression, but had no effect on DC costimulatory function. However, DC isolated from castrated mice increased the expression of key cytokines by antigen-experienced T cells while decreasing their expression in naïve cells. Finally, androgen ablation improved immune responses to vaccination only when applied after immunization. Conclusion Androgen ablation causes differential effects of DC on primary and secondary T cell responses, thus augmenting vaccine immunogenicity only when applied after immunization. PMID:19143030

Power conversion apparatus and method

DOEpatents

Su, Gui-Jia [Knoxville, TN

2012-02-07

A power conversion apparatus includes an interfacing circuit that enables a current source inverter to operate from a voltage energy storage device (voltage source), such as a battery, ultracapacitor or fuel cell. The interfacing circuit, also referred to as a voltage-to-current converter, transforms the voltage source into a current source that feeds a DC current to a current source inverter. The voltage-to-current converter also provides means for controlling and maintaining a constant DC bus current that supplies the current source inverter. The voltage-to-current converter also enables the current source inverter to charge the voltage energy storage device, such as during dynamic braking of a hybrid electric vehicle, without the need of reversing the direction of the DC bus current.

The dc power circuits: A compilation

NASA Technical Reports Server (NTRS)

1972-01-01

A compilation of reports concerning power circuits is presented for the dissemination of aerospace information to the general public as part of the NASA Technology Utilization Program. The descriptions for the electronic circuits are grouped as follows: dc power supplies, power converters, current-voltage power supply regulators, overload protection circuits, and dc constant current power supplies.

Quantum efficiency and dark current evaluation of a backside illuminated CMOS image sensor

NASA Astrophysics Data System (ADS)

Vereecke, Bart; Cavaco, Celso; De Munck, Koen; Haspeslagh, Luc; Minoglou, Kyriaki; Moore, George; Sabuncuoglu, Deniz; Tack, Klaas; Wu, Bob; Osman, Haris

2015-04-01

We report on the development and characterization of monolithic backside illuminated (BSI) imagers at imec. Different surface passivation, anti-reflective coatings (ARCs), and anneal conditions were implemented and their effect on dark current (DC) and quantum efficiency (QE) are analyzed. Two different single layer ARC materials were developed for visible light and near UV applications, respectively. QE above 75% over the entire visible spectrum range from 400 to 700 nm is measured. In the spectral range from 260 to 400 nm wavelength, QE values above 50% over the entire range are achieved. A new technique, high pressure hydrogen anneal at 20 atm, was applied on photodiodes and improvement in DC of 30% for the BSI imager with HfO2 as ARC as well as for the front side imager was observed. The entire BSI process was developed 200 mm wafers and evaluated on test diode structures. The knowhow is then transferred to real imager sensors arrays.

A Modular PV System Using Chain-Link-Type Multilevel Converter

NASA Astrophysics Data System (ADS)

Hatano, Nobuhiko; Ise, Toshifumi

This paper presents a modular photovoltaic system (MPVS) that uses a chain-link-type multilevel converter (CLMC). In large-scale PV generating systems, the DC power supply is generally composed of a large number of PV panels. Hence, losses are caused by differences in the maximum power point at each PV panel. An MPVS has been proposed to address the above mentioned problem. It helps improve the photoelectric conversion efficiency by applying maximum power point tracking (MPPT) control to each group of PV panels. In addition, if a CLMC is used in an MPVS, a high voltage can be output from the AC side and transmission losses can be decreased. However, with this circuit configuration, the current output from the AC side may be unbalanced. Therefore, we propose a method to output balanced current from the AC side, even if the output of the DC power supply is unbalanced. The validity of the proposed method is examined by digital simulation.

Radiofrequency generation by coherently moving fluxons

NASA Astrophysics Data System (ADS)

Dobrovolskiy, O. V.; Sachser, R.; Huth, M.; Shklovskij, V. A.; Vovk, R. V.; Bevz, V. M.; Tsindlekht, M. I.

2018-04-01

A lattice of Abrikosov vortices in type II superconductors is characterized by a periodic modulation of the magnetic induction perpendicular to the applied magnetic field. For a coherent vortex motion under the action of a transport current, the magnetic induction at a given point of the sample varies in time with a washboard frequency fWB = v/d, where v is the vortex velocity and d is the distance between the vortices in the direction of motion. Here, by using a spectrum analyzer connected to a 50 nm-wide Au nanowire meander near the surface of a superconducting Nb film, we detect an ac voltage induced by coherently moving fluxons. The voltage is peaked at the washboard frequency, fWB, and its subharmonics, fTOF = fWB/5, determined by the antenna width. By sweeping the dc current value, we reveal that fWB can be tuned from 100 MHz to 1.5 GHz, thereby demonstrating that patterned normal metal/superconductor nanostructures can be used as dc-tunable generators operating in the radiofrequency range.

Determination of efficiencies, loss mechanisms, and performance degradation factors in chopper controlled dc vehical motors. Section 2: The time dependent finite element modeling of the electromagnetic field in electrical machines: Methods and applications. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Hamilton, H. B.; Strangas, E.

1980-01-01

The time dependent solution of the magnetic field is introduced as a method for accounting for the variation, in time, of the machine parameters in predicting and analyzing the performance of the electrical machines. The method of time dependent finite element was used in combination with an also time dependent construction of a grid for the air gap region. The Maxwell stress tensor was used to calculate the airgap torque from the magnetic vector potential distribution. Incremental inductances were defined and calculated as functions of time, depending on eddy currents and saturation. The currents in all the machine circuits were calculated in the time domain based on these inductances, which were continuously updated. The method was applied to a chopper controlled DC series motor used for electric vehicle drive, and to a salient pole sychronous motor with damper bars. Simulation results were compared to experimentally obtained ones.

Driving and detecting ferromagnetic resonance in insulators with the spin Hall effect

DOE PAGES

Sklenar, Joseph; Zhang, Wei; Jungfleisch, Matthias B.; ...

2015-11-06

We demonstrate the generation and detection of spin-torque ferromagnetic resonance in Pt/Y 3Fe 5O 12 (YIG) bilayers. A unique attribute of this system is that the spin Hall effect lies at the heart of both the generation and detection processes and no charge current is passing through the insulating magnetic layer. When the YIG undergoes resonance, a dc voltage is detected longitudinally along the Pt that can be described by two components. One is the mixing of the spin Hall magnetoresistance with the microwave current. The other results from spin pumping into the Pt being converted to a dc currentmore » through the inverse spin Hall effect. The voltage is measured with applied magnetic field directions that range in-plane to nearly perpendicular. In conclusion, we find that for magnetic fields that are mostly out-of-plane, an imaginary component of the spin mixing conductance is required to model our data.« less

Simultaneous distribution of AC and DC power

DOEpatents

Polese, Luigi Gentile

2015-09-15

A system and method for the transport and distribution of both AC (alternating current) power and DC (direct current) power over wiring infrastructure normally used for distributing AC power only, for example, residential and/or commercial buildings' electrical wires is disclosed and taught. The system and method permits the combining of AC and DC power sources and the simultaneous distribution of the resulting power over the same wiring. At the utilization site a complementary device permits the separation of the DC power from the AC power and their reconstruction, for use in conventional AC-only and DC-only devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dürrenfeld, P., E-mail: philipp.durrenfeld@physics.gu.se; Ranjbar, M.; Gerhard, F.

We investigate the influence of a spin current generated from a platinum layer on the ferromagnetic resonance (FMR) properties of an adjacent ferromagnetic layer composed of the halfmetallic half-Heusler material NiMnSb. Spin Hall nano-oscillator devices are fabricated, and the technique of spin torque FMR is used to locally study the magnetic properties as in-plane anisotropies and resonance fields. A change in the FMR linewidth, in accordance with the additional spin torque produced by the spin Hall effect, is present for an applied dc current. For sufficiently large currents, this should yield auto-oscillations, which however are not achievable in the presentmore » device geometry.« less

Push-pull switching power amplifier

NASA Technical Reports Server (NTRS)

Cuk, Slobodan M. (Inventor)

1980-01-01

A true push-pull switching power amplifier is disclosed utilizing two dc-to-dc converters. Each converter is comprised of two inductances, one inductance in series with a DC source and the other inductor in series with the output load, and an electrical energy transferring device with storage capability, namely storage capacitance, with suitable switching means between the inductances to obtain DC level conversion, where the switching means allows bidirectional current (and power) flow, and the switching means of one dc-to-dc converter is driven by the complement of a square-wave switching signal for the other dc-to-dc converter for true push-pull operation. For reduction of current ripple, the inductances in each of the two converters may be coupled, and with proper design of the coupling, the ripple can be reduced to zero at either the input or the output, but preferably the output.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, T.; Yang, Z.; Dong, P.

The cold-cathode Penning ion gauge (PIG) type ion source has been used for generation of negative hydrogen (H{sup -}) ions as the internal ion source of a compact cyclotron. A novel method called electrical shielding box dc beam measurement is described in this paper, and the beam intensity was measured under dc extraction inside an electrical shielding box. The results of the trajectory simulation and dc H{sup -} beam extraction measurement were presented. The effect of gas flow rate, magnetic field strength, arc current, and extraction voltage were also discussed. In conclusion, the dc H{sup -} beam current of aboutmore » 4 mA from the PIG ion source with the puller voltage of 40 kV and arc current of 1.31 A was extrapolated from the measurement at low extraction dc voltages.« less

The modelling of an SF6 arc in a supersonic nozzle: II. Current zero behaviour of the nozzle arc

NASA Astrophysics Data System (ADS)

Zhang, Q.; Liu, J.; Yan, J. D.; Fang, M. T. C.

2016-08-01

The present work (part II) forms the second part of an investigation into the behaviour of SF6 nozzle arc. It is concerned with the aerodynamic and electrical behaviour of a transient nozzle arc under a current ramp specified by a rate of current decay (di/dt) before current zero and a voltage ramp (dV/dt) after current zero. The five flow models used in part I [1] for cold gas flow and DC nozzle arcs have been applied to study the transient arc at three stagnation pressures (P 0) and two values of di/dt for the current ramp, representing a wide range of arcing conditions. An analysis of the physical mechanisms encompassed in each flow model is given with an emphasis on the adequacy of a particular model in describing the rapidly varying arc around current zero. The critical rate of rise of recovery voltage (RRRV) is found computationally and compared with test results of Benenson et al [2]. For transient nozzle arcs, the RRRV is proportional to the square of P 0, rather than to the square root of P 0 for DC nozzle arcs. The physical mechanisms responsible for the strong dependence of RRRV on P 0 have been investigated. The relative merits of the flow models employed are discussed.

Frequency-dependent failure mechanisms of nanocrystalline gold interconnect lines under general alternating current

NASA Astrophysics Data System (ADS)

Luo, X. M.; Zhang, B.; Zhang, G. P.

2014-09-01

Thermal fatigue failure of metallization interconnect lines subjected to alternating currents (AC) is becoming a severe threat to the long-term reliability of micro/nanodevices with increasing electrical current density/power. Here, thermal fatigue failure behaviors and damage mechanisms of nanocrystalline Au interconnect lines on the silicon glass substrate have been investigated by applying general alternating currents (the pure alternating current coupled with a direct current (DC) component) with different frequencies ranging from 0.05 Hz to 5 kHz. We observed both thermal fatigue damages caused by Joule heating-induced cyclic strain/stress and electromigration (EM) damages caused by the DC component. Besides, the damage formation showed a strong electrically-thermally-mechanically coupled effect and frequency dependence. At lower frequencies, thermal fatigue damages were dominant and the main damage forms were grain coarsening with grain boundary (GB) cracking/voiding and grain thinning. At higher frequencies, EM damages took over and the main damage forms were GB cracking/voiding of smaller grains and hillocks. Furthermore, the healing effect of the reversing current was considered to elucidate damage mechanisms of the nanocrystalline Au lines generated by the general AC. Lastly, a modified model was proposed to predict the lifetime of the nanocrystalline metal interconnect lines, i.e., that was a competing drift velocity-based approach based on the threshold time required for reverse diffusion/healing to occur.

Modeling and real time simulation of an HVDC inverter feeding a weak AC system based on commutation failure study.

PubMed

Mankour, Mohamed; Khiat, Mounir; Ghomri, Leila; Chaker, Abdelkader; Bessalah, Mourad

2018-06-01

This paper presents modeling and study of 12-pulse HVDC (High Voltage Direct Current) based on real time simulation where the HVDC inverter is connected to a weak AC system. In goal to study the dynamic performance of the HVDC link, two serious kind of disturbance are applied at HVDC converters where the first one is the single phase to ground AC fault and the second one is the DC link to ground fault. The study is based on two different mode of analysis, which the first is to test the performance of the DC control and the second is focalized to study the effect of the protection function on the system behavior. This real time simulation considers the strength of the AC system to witch is connected and his relativity with the capacity of the DC link. The results obtained are validated by means of RT-lab platform using digital Real time simulator Hypersim (OP-5600), the results carried out show the effect of the DC control and the influence of the protection function to reduce the probability of commutation failures and also for helping inverter to take out from commutation failure even while the DC control fails to eliminate them. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

Cochlear transducer operating point adaptation.

PubMed

Zou, Yuan; Zheng, Jiefu; Ren, Tianying; Nuttall, Alfred

2006-04-01

The operating point (OP) of outer hair cell (OHC) mechanotransduction can be defined as any shift away from the center position on the transduction function. It is a dc offset that can be described by percentage of the maximum transduction current or as an equivalent dc pressure in the ear canal. The change of OP can be determined from the changes of the second and third harmonics of the cochlear microphonic (CM) following a calibration of its initial value. We found that the initial OP was dependent on sound level and cochlear sensitivity. From CM generated by a lower sound level at 74 dB SPL to avoid saturation and suppression of basal turn cochlear amplification, the OHC OP was at constant 57% of the maximum transduction current (an ear canal pressure of -0.1 Pa). To perturb the OP, a constant force was applied to the bony shell of the cochlea at the 18 kHz best frequency location using a blunt probe. The force applied over the scala tympani induced an OP change as if the organ of Corti moved toward the scala vestibuli (SV) direction. During an application of the constant force, the second harmonic of the CM partially recovered toward the initial level, which could be described by two time constants. Removing the force induced recovery of the second harmonic to its normal level described by a single time constant. The force applied over the SV caused an opposite result. These data indicate an active mechanism for OHC transduction OP.

Selective accumulation of langerhans-type dendritic cells in small airways of patients with COPD

PubMed Central

2010-01-01

Background Dendritic cells (DC) linking innate and adaptive immune responses are present in human lungs, but the characterization of different subsets and their role in COPD pathogenesis remain to be elucidated. The aim of this study is to characterize and quantify pulmonary myeloid DC subsets in small airways of current and ex-smokers with or without COPD. Methods Myeloid DC were characterized using flowcytometry on single cell suspensions of digested human lung tissue. Immunohistochemical staining for langerin, BDCA-1, CD1a and DC-SIGN was performed on surgical resection specimens from 85 patients. Expression of factors inducing Langerhans-type DC (LDC) differentiation was evaluated by RT-PCR on total lung RNA. Results Two segregated subsets of tissue resident pulmonary myeloid DC were identified in single cell suspensions by flowcytometry: the langerin+ LDC and the DC-SIGN+ interstitial-type DC (intDC). LDC partially expressed the markers CD1a and BDCA-1, which are also present on their known blood precursors. In contrast, intDC did not express langerin, CD1a or BDCA-1, but were more closely related to monocytes. Quantification of DC in the small airways by immunohistochemistry revealed a higher number of LDC in current smokers without COPD and in COPD patients compared to never smokers and ex-smokers without COPD. Importantly, there was no difference in the number of LDC between current and ex-smoking COPD patients. In contrast, the number of intDC did not differ between study groups. Interestingly, the number of BDCA-1+ DC was significantly lower in COPD patients compared to never smokers and further decreased with the severity of the disease. In addition, the accumulation of LDC in the small airways significantly correlated with the expression of the LDC inducing differentiation factor activin-A. Conclusions Myeloid DC differentiation is altered in small airways of current smokers and COPD patients resulting in a selective accumulation of the LDC subset which correlates with the pulmonary expression of the LDC-inducing differentiation factor activin-A. This study identified the LDC subset as an interesting focus for future research in COPD pathogenesis. PMID:20307269

Cycle life improvement of alkaline batteries via optimization of pulse current deposition of manganese dioxide under low bath temperatures

NASA Astrophysics Data System (ADS)

Adelkhani, H.; Ghaemi, M.; Jafari, S. M.

Pulse current electrodeposition (PCD) method has been applied to the preparation of novel electrolytic manganese dioxide (EMD) in order to enhance the cycle life of rechargeable alkaline MnO 2-Zn batteries (RAM). The investigation was carried out under atmospheric pressure through a systematic variation of pulse current parameters using additive free sulfuric acid-MnSO 4 electrolyte solutions. On time (t on) was varied from 0.1 to 98.5 ms, off time (t off) from 0.25 to 19.5 ms, pulse frequencies (f) from 10 to 1000 Hz and duty cycles (θ) from 0.02 to 0.985. A constant pulse current density (I p) of 0.8 A dm -2 and average current densities (I a) in the range of 0.08-0.8 A dm -2 were applied in all experiments. Resultant materials were characterized by analyzing their chemical compositions, X-ray diffractions (XRD) and scanning electron microscopy (SEM). Electrochemical characterizations carried out by charge/discharge cycling of samples in laboratory designed RAM batteries and cyclic voltammetric experiments (CV). It has been proved that specific selection of duty cycle, in the order of 0.25, and a pulse frequency of 500 Hz, results in the production of pulse deposited samples (pcMDs) with more uniform distribution of particles and more compact structure than those obtained by direct current techniques (dcMDs). Results of the test batteries demonstrated that, in spite of reduction of bath temperature in the order of 40 °C, the cycle life of batteries made of pcMDs (bath temperature: 60 °C) was rather higher than those made of conventional dcMDs (boiling electrolyte solution). Under the same conditions of EMD synthesis temperature of 80 °C and battery testing, the maximum obtainable cycle life of optimized pcMD was nearly 230 cycles with approximately 30 mAh g -1 MnO 2, compared to that of dcMD, which did not exceed 20 cycles. In accordance to these results, CV has confirmed that the pulse duty cycle is the most influential parameter on the cycle life than the pulse frequency. Because of operating at lower bath temperatures, the presented synthetic mode could improve its competitiveness in economical aspects.

A CMOS power-efficient low-noise current-mode front-end amplifier for neural signal recording.

PubMed

Wu, Chung-Yu; Chen, Wei-Ming; Kuo, Liang-Ting

2013-04-01

In this paper, a new current-mode front-end amplifier (CMFEA) for neural signal recording systems is proposed. In the proposed CMFEA, a current-mode preamplifier with an active feedback loop operated at very low frequency is designed as the first gain stage to bypass any dc offset current generated by the electrode-tissue interface and to achieve a low high-pass cutoff frequency below 0.5 Hz. No reset signal or ultra-large pseudo resistor is required. The current-mode preamplifier has low dc operation current to enhance low-noise performance and decrease power consumption. A programmable current gain stage is adopted to provide adjustable gain for adaptive signal scaling. A following current-mode filter is designed to adjust the low-pass cutoff frequency for different neural signals. The proposed CMFEA is designed and fabricated in 0.18-μm CMOS technology and the area of the core circuit is 0.076 mm(2). The measured high-pass cutoff frequency is as low as 0.3 Hz and the low-pass cutoff frequency is adjustable from 1 kHz to 10 kHz. The measured maximum current gain is 55.9 dB. The measured input-referred current noise density is 153 fA /√Hz , and the power consumption is 13 μW at 1-V power supply. The fabricated CMFEA has been successfully applied to the animal test for recording the seizure ECoG of Long-Evan rats.

Light-weight DC to very high voltage DC converter

DOEpatents

Druce, R.L.; Kirbie, H.C.; Newton, M.A.

1998-06-30

A DC-DC converter capable of generating outputs of 100 KV without a transformer comprises a silicon opening switch (SOS) diode connected to allow a charging current from a capacitor to flow into an inductor. When a specified amount of charge has flowed through the SOS diode, it opens up abruptly; and the consequential collapsing field of the inductor causes a voltage and current reversal that is steered into a load capacitor by an output diode. A switch across the series combination of the capacitor, inductor, and SOS diode closes to periodically reset the SOS diode by inducing a forward-biased current. 1 fig.

DC current distribution mapping system of the solar panels using a HTS-SQUID gradiometer

NASA Astrophysics Data System (ADS)

Miyazaki, Shingo; Kasuya, Syohei; Mawardi Saari, Mohd; Sakai, Kenji; Kiwa, Toshihiko; Tsukamoto, Akira; Adachi, Seiji; Tanabe, Keiichi; Tsukada, Keiji

2014-05-01

Solar panels are expected to play a major role as a source of sustainable energy. In order to evaluate solar panels, non-destructive tests, such as defect inspections and response property evaluations, are necessary. We developed a DC current distribution mapping system of the solar panels using a High Critical Temperature Superconductor Superconducting Quantum Interference Device (HTS-SQUID) gradiometer with ramp edge type Josephson junctions. Two independent components of the magnetic fields perpendicular to the panel surface (∂Bz/∂x, ∂Bz/∂y) were detected. The direct current of the solar panel is visualized by calculating the composition of the two signal components, the phase angle, and mapping the DC current vector. The developed system can evaluate the uniformity of DC current distributions precisely and may be applicable for defect detection of solar panels.

Optical Properties of Blow-Off Particulates.

DTIC Science & Technology

1984-02-29

examination of the SEM data in Sec- tion 3, for the particulates vary greatly in size, structure and melting points . Table 4. Refractive indices of minerals...of the balance. With no dc field applied the particle oscillates about a point below the midplane of the balance. When a dc field is applied to offset...electric field near the null point (midplane) of the balance is given by V dc Edc,z x- (11) where C is a geometrical constant which takes into account the

Comparison of direct current and 50 Hz alternating current microscopic corona characteristics on conductors

NASA Astrophysics Data System (ADS)

Zhang, Shuai; Zhang, Bo; He, Jinliang

2014-06-01

Corona discharge is one of the major design factors for extra-high voltage and ultra-high voltage DC/AC transmission lines. Under different voltages, corona discharge reveals different characteristics. This paper aims at investigating DC and AC coronas on the microscopic scale. To obtain the specific characteristics of DC and AC coronas, a new measurement approach that utilizes a coaxial wire-cylinder corona cage is designed in this paper, and wires of different diameters are used in the experiment. Based on the measurements, the respective microscopic characteristics of DC and AC coronas are analyzed and compared. With differences in characteristics between DC and AC coronas proposed, this study provides useful insights into DC/AC corona discharges on transmission line applications.

Onboard power line conditioning system for an electric or hybrid vehicle

DOEpatents

Kajouke, Lateef A.; Perisic, Milun

2016-06-14

A power line quality conditioning system for a vehicle includes an onboard rechargeable direct current (DC) energy storage system and an onboard electrical system coupled to the energy storage system. The energy storage system provides DC energy to drive an electric traction motor of the vehicle. The electrical system operates in a charging mode such that alternating current (AC) energy from a power grid external to the vehicle is converted to DC energy to charge the DC energy storage system. The electrical system also operates in a vehicle-to-grid power conditioning mode such that DC energy from the DC energy storage system is converted to AC energy to condition an AC voltage of the power grid.

75 FR 47199 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-9-10 Series Airplanes, DC-9-30...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-05

... Airplanes, DC-9-81 (MD-81) Airplanes, DC-9-82 (MD-82) Airplanes, DC-9-83 (MD-83) Airplanes, DC-9- 87 (MD-87...) airplanes, DC-9-87 (MD-87) airplanes, MD-88 airplanes, and MD-90-30 airplanes. That AD currently requires... INFORMATION: Discussion On June 18, 2010, we issued AD 2009-15-16, Amendment 39-16345 (75 FR 38017, July 1...

The a.c. Josephson effect without superconductivity

PubMed Central

Gaury, Benoit; Weston, Joseph; Waintal, Xavier

2015-01-01

Superconductivity derives its most salient features from the coherence of the associated macroscopic wave function. The related physical phenomena have now moved from exotic subjects to fundamental building blocks for quantum circuits such as qubits or single photonic modes. Here we predict that the a.c. Josephson effect—which transforms a d.c. voltage Vb into an oscillating signal cos (2eVbt/ħ)—has a mesoscopic counterpart in normal conductors. We show that when a d.c. voltage Vb is applied to an electronic interferometer, there exists a universal transient regime where the current oscillates at frequency eVb/h. This effect is not limited by a superconducting gap and could, in principle, be used to produce tunable a.c. signals in the elusive 0.1–10-THz ‘terahertz gap’. PMID:25765929

A No-Arc DC Circuit Breaker Based on Zero-Current Interruption

NASA Astrophysics Data System (ADS)

Xiang, Xuewei; Chai, Jianyun; Sun, Xudong

2017-05-01

A dc system has no natural current zero-crossing point, so a dc arc is more difficult to extinguish than an ac arc. In order to effectively solve the problem of the dc arc, this paper proposes a dc circuit breaker (DCCB) capable of implementing a no-arc interruption. The proposed DCCB includes a main branch consisting of a mechanical switch, a diode and a current-limiting inductor, a semi-period resonance circuit consisting of a diode, an inductor and a capacitor, and a buffer branch consisting of a capacitor, a thyristor and a resistor. The mechanical switch is opened in a zero-current state, and the overvoltage caused by the counter electromotive force of the inductor does not exist. Meanwhile, the capacitor has a buffering effect on the voltage. The rising of the voltage of the mechanical switch is slower than the rising of the insulating strength of a contact gap of the mechanical switch, resulting in the contact gap not able to be broken down. Thus, the arc cannot be generated. The simulation results show that the proposed DCCB does not generate the arc in the interruption process, the rise rate of the short circuit current can be effectively limited, and the short circuit fault point can be rapidly isolated from the dc power supply.

DC to DC power converters and methods of controlling the same

DOEpatents

Steigerwald, Robert Louis; Elasser, Ahmed; Sabate, Juan Antonio; Todorovic, Maja Harfman; Agamy, Mohammed

2012-12-11

A power generation system configured to provide direct current (DC) power to a DC link is described. The system includes a first power generation unit configured to output DC power. The system also includes a first DC to DC converter comprising an input section and an output section. The output section of the first DC to DC converter is coupled in series with the first power generation unit. The first DC to DC converter is configured to process a first portion of the DC power output by the first power generation unit and to provide an unprocessed second portion of the DC power output of the first power generation unit to the output section.

Analysis and Design of Bridgeless Switched Mode Power Supply for Computers

NASA Astrophysics Data System (ADS)

Singh, S.; Bhuvaneswari, G.; Singh, B.

2014-09-01

Switched mode power supplies (SMPSs) used in computers need multiple isolated and stiffly regulated output dc voltages with different current ratings. These isolated multiple output dc voltages are obtained by using a multi-winding high frequency transformer (HFT). A half-bridge dc-dc converter is used here for obtaining different isolated and well regulated dc voltages. In the front end, non-isolated Single Ended Primary Inductance Converters (SEPICs) are added to improve the power quality in terms of low input current harmonics and high power factor (PF). Two non-isolated SEPICs are connected in a way to completely eliminate the need of single-phase diode-bridge rectifier at the front end. Output dc voltages at both the non-isolated and isolated stages are controlled and regulated separately for power quality improvement. A voltage mode control approach is used in the non-isolated SEPIC stage for simple and effective control whereas average current control is used in the second isolated stage.

Strong mechanically induced effects in DC current-biased suspended Josephson junctions

NASA Astrophysics Data System (ADS)

McDermott, Thomas; Deng, Hai-Yao; Isacsson, Andreas; Mariani, Eros

2018-01-01

Superconductivity is a result of quantum coherence at macroscopic scales. Two superconductors separated by a metallic or insulating weak link exhibit the AC Josephson effect: the conversion of a DC voltage bias into an AC supercurrent. This current may be used to activate mechanical oscillations in a suspended weak link. As the DC-voltage bias condition is remarkably difficult to achieve in experiments, here we analyze theoretically how the Josephson effect can be exploited to activate and detect mechanical oscillations in the experimentally relevant condition with purely DC current bias. We unveil how changing the strength of the electromechanical coupling results in two qualitatively different regimes showing dramatic effects of the oscillations on the DC-voltage characteristic of the device. These include the appearance of Shapiro-type plateaus for weak coupling and a sudden mechanically induced retrapping for strong coupling. Our predictions, measurable in state-of-the-art experimental setups, allow the determination of the frequency and quality factor of the resonator using DC only techniques.

Temperature-dependent performance of all-NbN DC-SQUID magnetometers

NASA Astrophysics Data System (ADS)

Liu, Quansheng; Wang, Huiwu; Zhang, Qiyu; Wang, Hai; Peng, Wei; Wang, Zhen

2017-05-01

Integrated NbN direct current superconducting quantum interference device (DC-SQUID) magnetometers were developed based on high-quality epitaxial NbN/AlN/NbN Josephson junctions for SQUID applications operating at high temperatures. We report the current-voltage and voltage-flux characteristics and the noise performance of the NbN DC-SQUIDs for temperatures ranging from 4.2 to 9 K. The critical current and voltage swing of the DC-SQUIDs decreased by 15% and 25%, respectively, as the temperature was increased from 4.2 to 9 K. The white flux noise of the DC-SQUID magnetometer at 1 kHz increased from 3.9 μΦ0/Hz1/2 at 4.2 K to 4.8 μΦ0/Hz1/2 at 9 K with 23% increase, corresponding to the magnetic field noise of 6.6 and 8.1 fT/Hz1/2, respectively. The results show that NbN DC-SQUIDs improve the tolerance of the operating temperatures and temperature fluctuations in SQUID applications.

Electrical shielding box measurement of the negative hydrogen beam from Penning ion gauge ion source.

PubMed

Wang, T; Yang, Z; Dong, P; long, J D; He, X Z; Wang, X; Zhang, K Z; Zhang, L W

2012-06-01

The cold-cathode Penning ion gauge (PIG) type ion source has been used for generation of negative hydrogen (H(-)) ions as the internal ion source of a compact cyclotron. A novel method called electrical shielding box dc beam measurement is described in this paper, and the beam intensity was measured under dc extraction inside an electrical shielding box. The results of the trajectory simulation and dc H(-) beam extraction measurement were presented. The effect of gas flow rate, magnetic field strength, arc current, and extraction voltage were also discussed. In conclusion, the dc H(-) beam current of about 4 mA from the PIG ion source with the puller voltage of 40 kV and arc current of 1.31 A was extrapolated from the measurement at low extraction dc voltages.

Frequency analysis of DC tolerant current transformers

NASA Astrophysics Data System (ADS)

Mlejnek, P.; Kaspar, P.

2013-09-01

This article deals with wide frequency range behaviour of DC tolerant current transformers that are usually used in modern static energy meters. In this application current transformers must comply with European and International Standards in their accuracy and DC tolerance. Therefore, the linear DC tolerant current transformers and double core current transformers are used in this field. More details about the problems of these particular types of transformers can be found in our previous works. Although these transformers are designed mainly for power distribution network frequency (50/60 Hz), it can be interesting to understand their behaviour in wider frequency range. Based on this knowledge the new generations of energy meters with measuring quality of electric energy will be produced. This solution brings better measurement of consumption of nonlinear loads or measurement of non-sinusoidal voltage and current sources such as solar cells or fuel cells. The determination of actual power consumption in such energy meters is done using particular harmonics component of current and voltage. We measured the phase and ratio errors that are the most important parameters of current transformers, to characterize several samples of current transformers of both types.

Correlation of anomalous write error rates and ferromagnetic resonance spectrum in spin-transfer-torque-magnetic-random-access-memory devices containing in-plane free layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evarts, Eric R.; Rippard, William H.; Pufall, Matthew R.

In a small fraction of magnetic-tunnel-junction-based magnetic random-access memory devices with in-plane free layers, the write-error rates (WERs) are higher than expected on the basis of the macrospin or quasi-uniform magnetization reversal models. In devices with increased WERs, the product of effective resistance and area, tunneling magnetoresistance, and coercivity do not deviate from typical device properties. However, the field-swept, spin-torque, ferromagnetic resonance (FS-ST-FMR) spectra with an applied DC bias current deviate significantly for such devices. With a DC bias of 300 mV (producing 9.9 × 10{sup 6} A/cm{sup 2}) or greater, these anomalous devices show an increase in the fraction of the power presentmore » in FS-ST-FMR modes corresponding to higher-order excitations of the free-layer magnetization. As much as 70% of the power is contained in higher-order modes compared to ≈20% in typical devices. Additionally, a shift in the uniform-mode resonant field that is correlated with the magnitude of the WER anomaly is detected at DC biases greater than 300 mV. These differences in the anomalous devices indicate a change in the micromagnetic resonant mode structure at high applied bias.« less

Removal of virus and toxin using heatable multi-walled carbon nanotube web filters

NASA Astrophysics Data System (ADS)

Jang, Hoon-Sik; Jeon, Sang Koo; Ryu, Kwon-Sang; Nahm, Seung Hoon

2016-02-01

Many studies have used a carbon nanotube (CNT) filter for pathogen removal and/or inactivation by means of electrochemical or electrochlorination. The large surface area, fine pore size and high electrical and thermal conductivity of CNTs make them suitable and distinct to use for the filtering and removal of pathogens. Here, we grew spin-capable multi-walled CNTs (MWCNTs) and manufactured a web filter using the spun MWCNTs. Botulinum toxin type E light chain (BoT/E-LC) and vaccinia virus (VV) were filtered using the MWCNT web filters and were evaporated and removed by applying direct current (DC) voltage to both sides of the MWCNT webs, excluding electrochemical or electrochlorination. The filtering and removal of BoT/E-LC and VV were performed after seven layers of the MWCNT sheets were coated onto a silicon oxide porous plate. The electrical resistance of the webs in the seven layer sheet was 293 Ω. The temperature of MWCNTs webs was linearly increased to ˜300 °C at 210 V of DC voltage. This temperature was enough to remove BoT/E-LC and VV. From the SEM and XPS results, we confirmed that BoT/E-LC and VV on the MWCNT webs were almost removed by applying a DC voltage and that some element (N, Na, Cl, etc.) as residues on the MWCNT webs remained.

Feasibility analysis of a novel hybrid-type superconducting circuit breaker in multi-terminal HVDC networks

NASA Astrophysics Data System (ADS)

Khan, Umer Amir; Lee, Jong-Geon; Seo, In-Jin; Amir, Faisal; Lee, Bang-Wook

2015-11-01

Voltage source converter-based HVDC systems (VSC-HVDC) are a better alternative than conventional thyristor-based HVDC systems, especially for developing multi-terminal HVDC systems (MTDC). However, one of the key obstacles in developing MTDC is the absence of an adequate protection system that can quickly detect faults, locate the faulty line and trip the HVDC circuit breakers (DCCBs) to interrupt the DC fault current. In this paper, a novel hybrid-type superconducting circuit breaker (SDCCB) is proposed and feasibility analyses of its application in MTDC are presented. The SDCCB has a superconducting fault current limiter (SFCL) located in the main current path to limit fault currents until the final trip signal is received. After the trip signal the IGBT located in the main line commutates the current into a parallel line where DC current is forced to zero by the combination of IGBTs and surge arresters. Fault simulations for three-, four- and five-terminal MTDC were performed and SDCCB performance was evaluated in these MTDC. Passive current limitation by SFCL caused a significant reduction of fault current interruption stress in the SDCCB. It was observed that the DC current could change direction in MTDC after a fault and the SDCCB was modified to break the DC current in both the forward and reverse directions. The simulation results suggest that the proposed SDCCB could successfully suppress the DC fault current, cause a timely interruption, and isolate the faulty HVDC line in MTDC.

Analysis of asymmetric property with DC bias current on thin-film magnetoimpedance element

NASA Astrophysics Data System (ADS)

Kikuchi, Hiroaki; Sumida, Chihiro

2018-05-01

We theoretically analyzed the magnetoimpedance profile of a thin-film element with a DC bias current using the bias susceptibility theory and Maxwell's equations. Although the analysis model predicts that an element with a rectangular cross section shows symmetric impedance property with respect to the Z-axis with DC bias current, the experimental results showed asymmetric properties. Taking the shape imbalance and trapezoidal cross section of the element into account, we explained the asymmetric impedance properties qualitatively.

B-periodic oscillations in the Hall-resistance induced by a dc-current-bias under combined microwave-excitation and dc-current bias in the GaAs/AlGaAs 2D system.

PubMed

Liu, Han-Chun; Reichl, C; Wegscheider, W; Mani, R G

2018-05-18

We report the observation of dc-current-bias-induced B-periodic Hall resistance oscillations and Hall plateaus in the GaAs/AlGaAs 2D system under combined microwave radiation- and dc bias excitation at liquid helium temperatures. The Hall resistance oscillations and plateaus appear together with concomitant oscillations also in the diagonal magnetoresistance. The periods of Hall and diagonal resistance oscillations are nearly identical, and source power (P) dependent measurements demonstrate sub-linear relationship of the oscillation amplitude with P over the span 0 < P ≤ 20 mW.

Unexpected resonant response in [Fe(001)/Cr(001)]10/MgO(001) multilayers in a magnetic field.

PubMed

Aliev, F G; Pryadun, V V; Snoeck, E

2009-01-23

We observed unexpected resonant response in [Fe/Cr]10 multilayers epitaxially grown on MgO(100) substrates which exists only when both ac current and dc magnetic field are simultaneously applied. The magnitude of the resonances is determined by the multilayer magnetization proving their intrinsic character. The reduction of interface epitaxy leads to nonlinear dependence of the magnitude of resonances on the alternating current density. We speculate that the existence of the interface transition zone could facilitate the subatomic vibrations in thin metallic films and multilayers grown on bulk insulating substrates.

77 FR 55693 - D&C Red No. 6 and D&C Red No. 7; Change in Specification; Confirmation of Effective Date

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-11

... DEPARTMENT OF HEALTH AND HUMAN SERVICES Food and Drug Administration 21 CFR Part 74 [Docket No. FDA-2011-C-0050] D&C Red No. 6 and D&C Red No. 7; Change in Specification; Confirmation of Effective... the requirements for D&C Red No. 6 and D&C Red No. 7 by replacing the current specification for...

A Cryogenic Dc-Dc Power Converter for a 100 kW Synchronous HTS Generator at Liquid Nitrogen Temperatures

NASA Astrophysics Data System (ADS)

Bailey, Wendell; Wen, Hauming; Yang, Yifeng; Forsyth, Andrew; Jia, Chungjiang

A dc-dc converter has been developed for retrofitting inside the vacuum space of the HTS rotor of a synchronous generator. The heavy copper sections of the current leads used for energising the HTS field winding were replaced by cryogenic power electronics; consisting of the converter and a rotor control unit. The converter board was designed using an H-bridge configuration with two 5A rated wires connecting the cryogenic boards to the stator control board located on the outside of the generator and drawing power from a (5A, 50 V) dc power source. The robustness of converter board was well demonstrated when it was powered up from a cold start at 82K. When charging the field winding with moderate currents (30A), the heat in-leak to the 'cold' rotor core was only 2W. It continued to function down to 74K, surviving several quenches. However, the quench protection function failed when injecting 75A into the field winding, resulting in the burn out of one of the DC-link capacitors. The magnitudes of the critical currents measured with the original current leads were compared to the quench currents, which was defined as the current which triggered quench protection protocol. The difference between the two currents was rather large, (∼20A). However, additional measurements using a single HTS coil in liquid nitrogen found that this reduction should not be so dramatic and in the region of 4A. Our conclusions identified the converter's switching voltage and its operating frequency as two parameters, which could have contributed to lowering the quench current. Magnetic fields and eddy currents are expected to be more prominent the field winding and its impact on the converter also need further investigation.

Global Noise Studies for CMS Tracker Upgrade

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arteche, F.; /Zaragoza, ITA; Esteban, C.

The characterization of the noise emissions of DC-DC converters at system level is critical to optimize the design of the detector and define rules for the integration strategy. This paper presents the impedance effects on the noise emissions of DC-DC converters at system level. Conducted and radiated noise emissions at the input and at the output from DC-DC converters have been simulated for different types of power network and FEE impedances. System aspects as granularity, stray capacitances of the system and different working conditions of the DC-DC converters are presented too. This study has been carried out using simulation modelsmore » of noise emissions of DC-DC converters in the real scenario. The results of these studies show important recommendations and criteria to be applied to integrate the DC-DC converters and decrease the system noise level.« less

Comparison of direct current and 50 Hz alternating current microscopic corona characteristics on conductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Shuai, E-mail: zhangshuai94@gmail.com; Zhang, Bo, E-mail: shizbcn@mail.tsinghua.edu.cn; He, Jinliang, E-mail: hejl@tsinghua.edu.cn

Corona discharge is one of the major design factors for extra-high voltage and ultra-high voltage DC/AC transmission lines. Under different voltages, corona discharge reveals different characteristics. This paper aims at investigating DC and AC coronas on the microscopic scale. To obtain the specific characteristics of DC and AC coronas, a new measurement approach that utilizes a coaxial wire-cylinder corona cage is designed in this paper, and wires of different diameters are used in the experiment. Based on the measurements, the respective microscopic characteristics of DC and AC coronas are analyzed and compared. With differences in characteristics between DC and ACmore » coronas proposed, this study provides useful insights into DC/AC corona discharges on transmission line applications.« less

Evaluation of constant current alternating current iontophoresis for transdermal drug delivery.

PubMed

Yan, Guang; Li, S Kevin; Higuchi, William I

2005-12-10

Previous studies in our laboratory have demonstrated that alternating current (AC) iontophoresis can significantly decrease skin electric resistance and enhance the transport of charged permeants across skin. Flux variability of neutral permeants during AC iontophoresis was also found to be less than that of conventional direct current (DC) iontophoresis. The objectives of the present study were to evaluate flux enhancement of constant current AC transdermal iontophoresis and compare the AC flux with that of constant current DC iontophoresis. Iontophoresis studies of AC amplitude of 1, 2, and 5 mA were conducted in side-by-side diffusion cells with donor solution of 0.015, 0.15, and 1.0 M tetraethylammonium (TEA) chloride and receiver solution of phosphate buffered saline (PBS) using human epidermal membrane (HEM). Conventional constant current DC iontophoresis of 0.2 mA was also performed under similar conditions. TEA and mannitol were the model permeants. The following are the major findings in the present study. The flux of TEA increased proportionally with the AC current for all three TEA chloride concentrations and at the AC frequency used in the present study. When the permeant and its counter ion were the only ionic species in the donor chamber, the fluxes during DC iontophoresis were weakly dependent of its donor concentration. The fluxes of TEA during constant current AC iontophoresis were moderately related to the donor concentration with the highest TEA flux observed under the 1.0 M TEA chloride condition although the relationship between flux and donor concentration was not linear. A trend of decreasing electroosmotic transport with increasing donor TEA chloride concentration was observed with significant sample-to-sample variability during DC iontophoresis. Mannitol permeability was also observed to decrease with increasing TEA chloride concentration in the donor under the AC conditions, but data variability under AC was significantly smaller than that under DC. The results in the present study indicate that constant current AC iontophoresis under conditions tolerable to human (2 and 5 mA) can provide predictable fluxes that were lower than but of comparable magnitude as those of conventional constant current DC iontophoresis (0.2 mA).

On the wide-range bias dependence of transistor d.c. and small-signal current gain factors.

NASA Technical Reports Server (NTRS)

Schmidt, P.; Das, M. B.

1972-01-01

Critical reappraisal of the bias dependence of the dc and small-signal ac current gain factors of planar bipolar transistors over a wide range of currents. This is based on a straightforward consideration of the three basic components of the dc base current arising due to emitter-to-base injected minority carrier transport, base-to-emitter carrier injection, and emitter-base surface depletion layer recombination effects. Experimental results on representative n-p-n and p-n-p silicon devices are given which support most of the analytical findings.

Cyclotron resonance of the magnetic ratchet effect and second harmonic generation in bilayer graphene

NASA Astrophysics Data System (ADS)

Kheirabadi, Narjes; McCann, Edward; Fal'ko, Vladimir I.

2018-02-01

We model the magnetic ratchet effect in bilayer graphene in which a dc electric current is produced by an ac electric field of frequency ω in the presence of a steady in-plane magnetic field and inversion-symmetry breaking. In bilayer graphene, the ratchet effect is tunable by an external metallic gate which breaks inversion symmetry. For zero in-plane magnetic field, we show that trigonal warping and inversion-symmetry breaking are able to produce a large dc valley current, but not a nonzero total dc charge current. For the magnetic ratchet in a tilted magnetic field, the perpendicular field component induces cyclotron motion with frequency ωc and we find that the dc current displays cyclotron resonance at ωc=ω , although this peak in the current is actually smaller than its value at ωc=0 . Second harmonic generation, however, is greatly enhanced by resonances at ωc=ω and ωc=2 ω for which the current is generally much larger than at ωc=0 .

Ion trap device

DOEpatents

Ibrahim, Yehia M.; Smith, Richard D.

2016-01-26

An ion trap device is disclosed. The device includes a series of electrodes that define an ion flow path. A radio frequency (RF) field is applied to the series of electrodes such that each electrode is phase shifted approximately 180 degrees from an adjacent electrode. A DC voltage is superimposed with the RF field to create a DC gradient to drive ions in the direction of the gradient. A second RF field or DC voltage is applied to selectively trap and release the ions from the device. Further, the device may be gridless and utilized at high pressure.

Application of drive circuit based on L298N in direct current motor speed control system

NASA Astrophysics Data System (ADS)

Yin, Liuliu; Wang, Fang; Han, Sen; Li, Yuchen; Sun, Hao; Lu, Qingjie; Yang, Cheng; Wang, Quanzhao

2016-10-01

In the experiment of researching the nanometer laser interferometer, our design of laser interferometer circuit system is up to the wireless communication technique of the 802.15.4 IEEE standard, and we use the RF TI provided by Basic to receive the data on speed control system software. The system's hardware is connected with control module and the DC motor. However, in the experiment, we found that single chip microcomputer control module is very difficult to drive the DC motor directly. The reason is that the DC motor's starting and braking current is larger than the causing current of the single chip microcomputer control module. In order to solve this problem, we add a driving module that control board can transmit PWM wave signal through I/O port to drive the DC motor, the driving circuit board can come true the function of the DC motor's positive and reversal rotation and speed adjustment. In many various driving module, the L298N module's integrated level is higher compared with other driver module. The L298N model is easy to control, it not only can control the DC motor, but also achieve motor speed control by modulating PWM wave that the control panel output. It also has the over-current protection function, when the motor lock, the L298N model can protect circuit and motor. So we use the driver module based on L298N to drive the DC motor. It is concluded that the L298N driver circuit module plays a very important role in the process of driving the DC motor in the DC motor speed control system.

UDE-based control of variable-speed wind turbine systems

NASA Astrophysics Data System (ADS)

Ren, Beibei; Wang, Yeqin; Zhong, Qing-Chang

2017-01-01

In this paper, the control of a PMSG (permanent magnet synchronous generator)-based variable-speed wind turbine system with a back-to-back converter is considered. The uncertainty and disturbance estimator (UDE)-based control approach is applied to the regulation of the DC-link voltage and the control of the RSC (rotor-side converter) and the GSC (grid-side converter). For the rotor-side controller, the UDE-based vector control is developed for the RSC with PMSG control to facilitate the application of the MPPT (maximum power point tracking) algorithm for the maximum wind energy capture. For the grid-side controller, the UDE-based vector control is developed to control the GSC with the power reference generated by a UDE-based DC-link voltage controller. Compared with the conventional vector control, the UDE-based vector control can achieve reliable current decoupling control with fast response. Moreover, the UDE-based DC-link voltage regulation can achieve stable DC-link voltage under model uncertainties and external disturbances, e.g. wind speed variations. The effectiveness of the proposed UDE-based control approach is demonstrated through extensive simulation studies in the presence of coupled dynamics, model uncertainties and external disturbances under varying wind speeds. The UDE-based control is able to generate more energy, e.g. by 5% for the wind profile tested.

The power of power: electrokinetic control of PAH interactions with exfoliated graphite.

PubMed

Qin, Jinyi; Moustafa, Ahmed; Harms, Hauke; El-Din, Mohamed Gamal; Wick, Lukas Y

2015-05-15

Exfoliated graphite (EG) exhibits exceptional sorption capacity for petroleum and dissolved hydrocarbons owing to its highly hydrophobic surface and wide pore size distribution. The high price of preparing EG, however, restricts its application. Methods which increase the rate or extent of sorption to EG even further are thus longed for. Here, we assess the effects of weak direct current (DC) fields on the sorption of the polycyclic aromatic hydrocarbon phenanthrene (PHE) to EG. DC applied to an ionic solution in a solid matrix invokes electroosmotic flow (EOF), i.e., the surface charge-induced movement of the solution. EG was exposed to weak DC fields in the presence of dissolved PHE to test if EOF increases transport of PHE to poorly accessible sorption sites. DC fields increased PHE sorption rates in EG sevenfold and reduced the desorption rate of sorbed PHE by >99%. EOF thus appeared to be highly effective in translocating PHE into pores, which contribute most of the sorption sites, but are difficult to access in the absence of EOF by molecular diffusion only. The observed 'power of power' may be used to kinetically regulate the interaction of sorbates with EG or other porous sorbents in environmental (bio-) technology. Copyright © 2015 Elsevier B.V. All rights reserved.

[Preparation of electrodeposited Cr-La coating and its spectral properties].

PubMed

Liu, Xiao-zhen; Wang, Gang; Song, Ling-ling; Li, Xin; Zhu, Xu-qiang

2011-07-01

Cr-La coating (dc) and Cr-La coating (pulse) were prepared by electrodeposition method of direct current and pulsating current respectively. The Cr-La coating (dc) and Cr-La coating (pulse) were characterized with ICP-AES, EDAX, XRD and SEM techniques, respectively. Cr-La coating(dc) was amorphous. There were crystalline La and CrC in Cr-La coating (pulse). The microhardness of the Cr-La coating(dc) and Cr-La coating (pulse) were as high as 860.3 and 930.2 HV respectively, which were higher 11.15% and 20.18% higher than that of the Cr coating (774.0 HV). The wear weight losses of Cr-La coating(dc) and Cr-La coating(pulse) were 1.29 and 2.25 times lower than that of Cr coating, respectively. The friction coefficient of Cr coating, Cr-La coating(dc) and Cr-La coating(pulse) were 0. 884, 0. 640 and 0. 648 respectively. The properties of wear weight loss and microhardness of coatings were improved with pulsating current. The wear weight loss and microhardness of Cr-La coating(pulse) were lower 1.75 time lower and higher 8.13% higher than that of the Cr-La coating(dc), respectively.

The effect of humidity on ionic wind velocity in ambient air

NASA Astrophysics Data System (ADS)

Chen, She; Nobelen, J. C. P. Y.; Nijdam, S.

2016-09-01

Due to the evolution of portable electronics and LED lightning system, advances in air cooling technologies must also keep pace. Active cooling by ionic wind, which is usually generated by corona discharge, can greatly reduce the noise and lifetime issues compared to the mechanical fans. The wind is induced when a gas discharge is formed, and neutral molecules gain their energy by the momentum transfer of ion-neutral collisions. However, there is few discussion about the effect of gas composition such as humidity on the wind generation and the physical mechanism is not clear. In the experiment, a positive 5-20 kV DC voltage is applied to the needle-cylinder electrodes with separation of 20 mm. The ionic wind velocity is measured by hot wire anemometry. As the relative humidity (RH) in the ambient air increases, the velocity is found to be severely inhibited. The current is also measured between the cylinder electrode and earth. The results show that the DC component of corona current decreases when RH increases. Since both the discharge current and the ion mobility are reduced when RH increases, their combined effects determine the ionic wind velocity. This work is supported by STW project 13651.

Influence of the magnetic field profile on ITER conductor testing

NASA Astrophysics Data System (ADS)

Nijhuis, A.; Ilyin, Y.; ten Kate, H. H. J.

2006-08-01

We performed simulations with the numerical CUDI-CICC code on a typical short ITER (International Thermonuclear Experimental Reactor) conductor test sample of dual leg configuration, as usually tested in the SULTAN test facility, and made a comparison with the new EFDA-Dipole test facility offering a larger applied DC field region. The new EFDA-Dipole test facility, designed for short sample testing of conductors for ITER, has a homogeneous high field region of 1.2 m, while in the SULTAN facility this region is three times shorter. The inevitable non-uniformity of the current distribution in the cable, introduced by the joints at both ends, has a degrading effect on voltage-current (VI) and voltage-temperature (VT) characteristics, particularly for these short samples. This can easily result in an underestimation or overestimation of the actual conductor performance. A longer applied DC high field region along a conductor suppresses the current non-uniformity by increasing the overall longitudinal cable electric field when reaching the current sharing mode. The numerical interpretation study presented here gives a quantitative analysis for a relevant practical case of a test of a short sample poloidal field coil insert (PFCI) conductor in SULTAN. The simulation includes the results of current distribution analysis from self-field measurements with Hall sensor arrays, current sharing measurements and inter-petal resistance measurements. The outcome of the simulations confirms that the current uniformity improves with a longer high field region but the 'measured' VI transition is barely affected, though the local peak voltages become somewhat suppressed. It appears that the location of the high field region and voltage taps has practically no influence on the VI curve as long as the transverse voltage components are adequately cancelled. In particular, for a thin conduit wall, the voltage taps should be connected to the conduit in the form of an (open) azimuthally soldered wire, averaging the transverse conduit surface potentials initiated in the joints.

Filtering and Control of High Speed Motor Current in a Flywheel Energy Storage System

NASA Technical Reports Server (NTRS)

Kenny, Barbara H.; Santiago, Walter

2004-01-01

The NASA Glenn Research Center has been developing technology to enable the use of high speed flywheel energy storage units in future spacecraft for the last several years. An integral part of the flywheel unit is the three phase motor/generator that is used to accelerate and decelerate the flywheel. The motor/generator voltage is supplied from a pulse width modulated (PWM) inverter operating from a fixed DC voltage supply. The motor current is regulated through a closed loop current control that commands the necessary voltage from the inverter to achieve the desired current. The current regulation loop is the innermost control loop of the overall flywheel system and, as a result, must be fast and accurate over the entire operating speed range (20,000 to 60,000 rpm) of the flywheel. The voltage applied to the motor is a high frequency PWM version of the DC bus voltage that results in the commanded fundamental value plus higher order harmonics. Most of the harmonic content is at the switching frequency and above. The higher order harmonics cause a rapid change in voltage to be applied to the motor that can result in large voltage stresses across the motor windings. In addition, the high frequency content in the motor causes sensor noise in the magnetic bearings that leads to disturbances for the bearing control. To alleviate these problems, a filter is used to present a more sinusoidal voltage to the motor/generator. However, the filter adds additional dynamics and phase lag to the motor system that can interfere with the performance of the current regulator. This paper will discuss the tuning methodology and results for the motor/generator current regulator and the impact of the filter on the control. Results at speeds up to 50,000 rpm are presented.

Electrical overstress in AlGaN/GaN HEMTs: study of degradation processes

NASA Astrophysics Data System (ADS)

Kuzmík, J.; Pogany, D.; Gornik, E.; Javorka, P.; Kordoš, P.

2004-02-01

We study degradation mechanisms in 50 μm gate width/0.45 μm length AlGaN/GaN HEMTs after electrical overstresses. One hundred nanosecond long rectangular current pulses are applied on the drain contact keeping either both of the source and gate grounded or the source grounded and gate floating. Source-drain pulsed I- V characteristics show similar shape for both connections. After the HEMT undergoes the source-drain breakdown, a negative differential resistance region transits into a low voltage/high current region. Changes in the Schottky contact dc I- V characteristics and in the source and drain ohmic contacts are investigated as a function of the current stress level and are related to the HEMT dc performance. Catastrophic HEMT degradation was observed after Istress=1.65 A in case of the 'gate floating' connection due to ohmic contacts burnout. In case of the 'gate grounded' connection, Istress=0.45 A was sufficient for the gate failure showing a high gate susceptibility to overstress. Backside transient interferometric mapping technique experiment reveals a current filament formation under both HEMT stress connections. Infrared camera observations lead to conclusion that the filament formation together with a consequent high-density electron flow is responsible for a dark spot formation and gradual ohmic contact degradation.

Statistical analysis of the effect of temperature and inlet humidities on the parameters of a semiempirical model of the internal resistance of a polymer electrolyte membrane fuel cell

NASA Astrophysics Data System (ADS)

Giner-Sanz, J. J.; Ortega, E. M.; Pérez-Herranz, V.

2018-03-01

The internal resistance of a PEM fuel cell depends on the operation conditions and on the current delivered by the cell. This work's goal is to obtain a semiempirical model able to reproduce the effect of the operation current on the internal resistance of an individual cell of a commercial PEM fuel cell stack; and to perform a statistical analysis in order to study the effect of the operation temperature and the inlet humidities on the parameters of the model. First, the internal resistance of the individual fuel cell operating in different operation conditions was experimentally measured for different DC currents, using the high frequency intercept of the impedance spectra. Then, a semiempirical model based on Springer and co-workers' model was proposed. This model is able to successfully reproduce the experimental trends. Subsequently, the curves of resistance versus DC current obtained for different operation conditions were fitted to the semiempirical model, and an analysis of variance (ANOVA) was performed in order to determine which factors have a statistically significant effect on each model parameter. Finally, a response surface method was applied in order to obtain a regression model.

Impacts on the Voltage Profile of DC Distribution Network with DG Access

NASA Astrophysics Data System (ADS)

Tu, J. J.; Yin, Z. D.

2017-07-01

With the development of electronic, more and more distributed generations (DGs) access into grid and cause the research fever of direct current (DC) distribution network. Considering distributed generation (DG) location and capacity have great impacts on voltage profile, so use IEEE9 and IEEE33 typical circuit as examples, with DGs access in centralized and decentralized mode, to compare voltage profile in alternating and direct current (AC/DC) distribution network. Introducing the voltage change ratio as an evaluation index, so gets the general results on voltage profile of DC distributed network with DG access. Simulation shows that, in the premise of reasonable location and capacity, DC distribution network is more suitable for DG access.

Pulse-Width-Modulating Driver for Brushless dc Motor

NASA Technical Reports Server (NTRS)

Salomon, Phil M.

1991-01-01

High-current pulse-width-modulating driver for brushless dc motor features optical coupling of timing signals from low-current control circuitry to high-current motor-driving circuitry. Provides high electrical isolation of motor-power supply, helping to prevent fast, high-current motor-driving pulses from being coupled through power supplies into control circuitry, where they interfere with low-current control signals.

Numerical modelling of dynamic resistance in high-temperature superconducting coated-conductor wires

NASA Astrophysics Data System (ADS)

Ainslie, Mark D.; Bumby, Chris W.; Jiang, Zhenan; Toyomoto, Ryuki; Amemiya, Naoyuki

2018-07-01

The use of superconducting wire within AC power systems is complicated by the dissipative interactions that occur when a superconductor is exposed to an alternating current and/or magnetic field, giving rise to a superconducting AC loss caused by the motion of vortices within the superconducting material. When a superconductor is exposed to an alternating field whilst carrying a constant DC transport current, a DC electrical resistance can be observed, commonly referred to as ‘dynamic resistance.’ Dynamic resistance is relevant to many potential high-temperature superconducting (HTS) applications and has been identified as critical to understanding the operating mechanism of HTS flux pump devices. In this paper, a 2D numerical model based on the finite-element method and implementing the H -formulation is used to calculate the dynamic resistance and total AC loss in a coated-conductor HTS wire carrying an arbitrary DC transport current and exposed to background AC magnetic fields up to 100 mT. The measured angular dependence of the superconducting properties of the wire are used as input data, and the model is validated using experimental data for magnetic fields perpendicular to the plane of the wire, as well as at angles of 30° and 60° to this axis. The model is used to obtain insights into the characteristics of such dynamic resistance, including its relationship with the applied current and field, the wire’s superconducting properties, the threshold field above which dynamic resistance is generated and the flux-flow resistance that arises when the total driven transport current exceeds the field-dependent critical current, I c( B ), of the wire. It is shown that the dynamic resistance can be mostly determined by the perpendicular field component with subtle differences determined by the angular dependence of the superconducting properties of the wire. The dynamic resistance in parallel fields is essentially negligible until J c is exceeded and flux-flow resistance occurs.

21 CFR 74.2711 - D&C Yellow No. 11.

Code of Federal Regulations, 2010 CFR

2010-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2711 D&C Yellow No. 11. (a) Identity and specifications. The color additive D&C Yellow No. 11 shall conform in identity and specifications to the... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2260 - D&C Orange No. 10.

Code of Federal Regulations, 2010 CFR

2010-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2260 D&C Orange No. 10. (a) Identity and specifications. The color additive D&C Orange No. 10 shall conform in identity and specifications to the... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2206 - D&C Green No. 6.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2206 D&C Green No. 6. (a) Identity and specifications. The color additive D&C Green No. 6 shall conform in identity and specifications to the requirements of § 74... applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling requirements. The...

21 CFR 74.2261 - D&C Orange No. 11.

Code of Federal Regulations, 2010 CFR

2010-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2261 D&C Orange No. 11. (a) Identity and specifications. The color additive D&C Orange No. 11 shall conform in identity and specifications to the... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2254 - D&C Orange No. 4.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2254 D&C Orange No. 4. (a) Identity and specifications. The color additive D&C Orange No. 4 shall conform in identity and specifications to the requirements... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2708 - D&C Yellow No. 8.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2708 D&C Yellow No. 8. (a) Identity and specifications. The color additive D&C Yellow No. 8 shall conform in identity and specifications to the requirements... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2707 - D&C Yellow No. 7.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2707 D&C Yellow No. 7. (a) Identity and specifications. The color additive D&C Yellow No. 7 shall conform in identity and specifications to the requirements... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2254 - D&C Orange No. 4.

Code of Federal Regulations, 2012 CFR

2012-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2254 D&C Orange No. 4. (a) Identity and specifications. The color additive D&C Orange No. 4 shall conform in identity and specifications to the requirements... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2206 - D&C Green No. 6.

Code of Federal Regulations, 2012 CFR

2012-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2206 D&C Green No. 6. (a) Identity and specifications. The color additive D&C Green No. 6 shall conform in identity and specifications to the requirements of § 74... applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling requirements. The...

21 CFR 74.2707 - D&C Yellow No. 7.

Code of Federal Regulations, 2013 CFR

2013-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2707 D&C Yellow No. 7. (a) Identity and specifications. The color additive D&C Yellow No. 7 shall conform in identity and specifications to the requirements... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2707 - D&C Yellow No. 7.

Code of Federal Regulations, 2014 CFR

2014-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2707 D&C Yellow No. 7. (a) Identity and specifications. The color additive D&C Yellow No. 7 shall conform in identity and specifications to the requirements... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2260 - D&C Orange No. 10.

Code of Federal Regulations, 2013 CFR

2013-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2260 D&C Orange No. 10. (a) Identity and specifications. The color additive D&C Orange No. 10 shall conform in identity and specifications to the... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2711 - D&C Yellow No. 11.

Code of Federal Regulations, 2013 CFR

2013-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2711 D&C Yellow No. 11. (a) Identity and specifications. The color additive D&C Yellow No. 11 shall conform in identity and specifications to the... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2260 - D&C Orange No. 10.

Code of Federal Regulations, 2012 CFR

2012-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2260 D&C Orange No. 10. (a) Identity and specifications. The color additive D&C Orange No. 10 shall conform in identity and specifications to the... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2711 - D&C Yellow No. 11.

Code of Federal Regulations, 2011 CFR

2011-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2711 D&C Yellow No. 11. (a) Identity and specifications. The color additive D&C Yellow No. 11 shall conform in identity and specifications to the... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2708 - D&C Yellow No. 8.

Code of Federal Regulations, 2011 CFR

2011-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2708 D&C Yellow No. 8. (a) Identity and specifications. The color additive D&C Yellow No. 8 shall conform in identity and specifications to the requirements... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2707 - D&C Yellow No. 7.

Code of Federal Regulations, 2012 CFR

2012-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2707 D&C Yellow No. 7. (a) Identity and specifications. The color additive D&C Yellow No. 7 shall conform in identity and specifications to the requirements... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2261 - D&C Orange No. 11.

Code of Federal Regulations, 2014 CFR

2014-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2261 D&C Orange No. 11. (a) Identity and specifications. The color additive D&C Orange No. 11 shall conform in identity and specifications to the... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2708 - D&C Yellow No. 8.

Code of Federal Regulations, 2012 CFR

2012-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2708 D&C Yellow No. 8. (a) Identity and specifications. The color additive D&C Yellow No. 8 shall conform in identity and specifications to the requirements... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2206 - D&C Green No. 6.

Code of Federal Regulations, 2013 CFR

2013-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2206 D&C Green No. 6. (a) Identity and specifications. The color additive D&C Green No. 6 shall conform in identity and specifications to the requirements of § 74... applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling requirements. The...

21 CFR 74.2261 - D&C Orange No. 11.

Code of Federal Regulations, 2013 CFR

2013-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2261 D&C Orange No. 11. (a) Identity and specifications. The color additive D&C Orange No. 11 shall conform in identity and specifications to the... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2206 - D&C Green No. 6.

Code of Federal Regulations, 2014 CFR

2014-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2206 D&C Green No. 6. (a) Identity and specifications. The color additive D&C Green No. 6 shall conform in identity and specifications to the requirements of § 74... applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling requirements. The...

21 CFR 74.2708 - D&C Yellow No. 8.

Code of Federal Regulations, 2013 CFR

2013-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2708 D&C Yellow No. 8. (a) Identity and specifications. The color additive D&C Yellow No. 8 shall conform in identity and specifications to the requirements... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2254 - D&C Orange No. 4.

Code of Federal Regulations, 2013 CFR

2013-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2254 D&C Orange No. 4. (a) Identity and specifications. The color additive D&C Orange No. 4 shall conform in identity and specifications to the requirements... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2260 - D&C Orange No. 10.

Code of Federal Regulations, 2014 CFR

2014-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2260 D&C Orange No. 10. (a) Identity and specifications. The color additive D&C Orange No. 10 shall conform in identity and specifications to the... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2711 - D&C Yellow No. 11.

Code of Federal Regulations, 2012 CFR

2012-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2711 D&C Yellow No. 11. (a) Identity and specifications. The color additive D&C Yellow No. 11 shall conform in identity and specifications to the... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2261 - D&C Orange No. 11.

Code of Federal Regulations, 2012 CFR

2012-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2261 D&C Orange No. 11. (a) Identity and specifications. The color additive D&C Orange No. 11 shall conform in identity and specifications to the... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2254 - D&C Orange No. 4.

Code of Federal Regulations, 2014 CFR

2014-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2254 D&C Orange No. 4. (a) Identity and specifications. The color additive D&C Orange No. 4 shall conform in identity and specifications to the requirements... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2708 - D&C Yellow No. 8.

Code of Federal Regulations, 2014 CFR

2014-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2708 D&C Yellow No. 8. (a) Identity and specifications. The color additive D&C Yellow No. 8 shall conform in identity and specifications to the requirements... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

21 CFR 74.2711 - D&C Yellow No. 11.

Code of Federal Regulations, 2014 CFR

2014-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2711 D&C Yellow No. 11. (a) Identity and specifications. The color additive D&C Yellow No. 11 shall conform in identity and specifications to the... coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling...

Efficiency enhancement using voltage biasing for ferroelectric polarization in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Kim, Sangmo; Song, Myoung Geun; Bark, Chung Wung

2018-01-01

Dye-sensitized solar cells (DSSCs) are one of the most promising third generation solar cells that have been extensively researched over the past decade as alternative to silicon-based solar cells, due to their low production cost and high energy-conversion efficiency. In general, a DSSC consists of a transparent electrode, a counter electrode, and an electrolyte such as dye. To achieve high power-conversion efficiency in cells, many research groups have focused their efforts on developing efficient dyes for liquid electrolytes. In this work, we report on the photovoltaic properties of DSSCs fabricated using a mixture of TiO2 with nanosized Fe-doped bismuth lanthanum titanate (nFe-BLT) powder). Firstly, nFe-BLT powders were prepared using a high-energy ball milling process and then, TiO2 and nFe-BLT powders were stoichiometrically blended. Direct current (DC) bias of 20 MV/m was applied to lab-made DSSCs. With the optimal concentration of nFe-BLT doped in the electrode, their light-to-electricity conversion efficiency could be improved by ∼64% compared with DSSCs where no DC bias was applied.

Increased Energy Delivery for Parallel Battery Packs with No Regulated Bus

NASA Astrophysics Data System (ADS)

Hsu, Chung-Ti

In this dissertation, a new approach to paralleling different battery types is presented. A method for controlling charging/discharging of different battery packs by using low-cost bi-directional switches instead of DC-DC converters is proposed. The proposed system architecture, algorithms, and control techniques allow batteries with different chemistry, voltage, and SOC to be properly charged and discharged in parallel without causing safety problems. The physical design and cost for the energy management system is substantially reduced. Additionally, specific types of failures in the maximum power point tracking (MPPT) in a photovoltaic (PV) system when tracking only the load current of a DC-DC converter are analyzed. The periodic nonlinear load current will lead MPPT realized by the conventional perturb and observe (P&O) algorithm to be problematic. A modified MPPT algorithm is proposed and it still only requires typically measured signals, yet is suitable for both linear and periodic nonlinear loads. Moreover, for a modular DC-DC converter using several converters in parallel, the input power from PV panels is processed and distributed at the module level. Methods for properly implementing distributed MPPT are studied. A new approach to efficient MPPT under partial shading conditions is presented. The power stage architecture achieves fast input current change rate by combining a current-adjustable converter with a few converters operating at a constant current.

Cytotoxicity, Bactericidal, and Antioxidant Activity of Sodium Alginate Hydrosols Treated with Direct Electric Current

PubMed Central

Król, Żaneta; Marycz, Krzysztof; Kulig, Dominika; Marędziak, Monika; Jarmoluk, Andrzej

2017-01-01

The aim of the study was to investigate the effect of using direct electric current (DC) of 0, 200, and 400 mA for five minutes on the physiochemical properties, cytotoxicity, antibacterial, and antioxidant activity of sodium alginate hydrosols with different sodium chloride concentrations. The pH, oxidation-reduction potential (ORP), electrical conductivity (EC), and available chlorine concentration (ACC) were measured. The effect of sodium alginate hydrosols treated with DC on Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Micrococcus luteus, Escherichia coli, Salmonella enteritidis, Yersinia enterocolitica, Pseudomonas fluorescence, and RAW 264.7 and L929 cells was investigated. Subsequently, the antioxidant properties of hydrosols were evaluated by determining the scavenging ability of 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH) and ferric reducing antioxidant power (FRAP). The results have shown that after applying 400 mA in hydrosol samples with 0.1% and 0.2% NaCl all tested bacteria were inactivated. The ACC concentration of C400 samples with NaCl was equal to 13.95 and 19.71 mg/L, respectively. The cytotoxicity analysis revealed that optimized electric field conditions and the addition of sodium chloride allow for the avoidance of toxicity effects on normal cells without disturbing the antibacterial effects. Due to the presence of oxidizing substances, the DPPH of variants treated with DC was lower than the DPPH of control samples. PMID:28327520

Cytotoxicity, Bactericidal, and Antioxidant Activity of Sodium Alginate Hydrosols Treated with Direct Electric Current.

PubMed

Król, Żaneta; Marycz, Krzysztof; Kulig, Dominika; Marędziak, Monika; Jarmoluk, Andrzej

2017-03-22

The aim of the study was to investigate the effect of using direct electric current (DC) of 0, 200, and 400 mA for five minutes on the physiochemical properties, cytotoxicity, antibacterial, and antioxidant activity of sodium alginate hydrosols with different sodium chloride concentrations. The pH, oxidation-reduction potential (ORP), electrical conductivity (EC), and available chlorine concentration (ACC) were measured. The effect of sodium alginate hydrosols treated with DC on Staphylococcus aureus , Listeria monocytogenes , Bacillus cereus , Micrococcus luteus , Escherichia coli , Salmonella enteritidis , Yersinia enterocolitica , Pseudomonas fluorescence , and RAW 264.7 and L929 cells was investigated. Subsequently, the antioxidant properties of hydrosols were evaluated by determining the scavenging ability of 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH) and ferric reducing antioxidant power (FRAP). The results have shown that after applying 400 mA in hydrosol samples with 0.1% and 0.2% NaCl all tested bacteria were inactivated. The ACC concentration of C400 samples with NaCl was equal to 13.95 and 19.71 mg/L, respectively. The cytotoxicity analysis revealed that optimized electric field conditions and the addition of sodium chloride allow for the avoidance of toxicity effects on normal cells without disturbing the antibacterial effects. Due to the presence of oxidizing substances, the DPPH of variants treated with DC was lower than the DPPH of control samples.

Heat current through an artificial Kondo impurity beyond linear response

NASA Astrophysics Data System (ADS)

Sierra, Miguel A.; Sánchez, David

2018-03-01

We investigate the heat current of a strongly interacting quantum dot in the presence of a voltage bias in the Kondo regime. Using the slave-boson mean-field theory, we discuss the behavior of the energy flow and the Joule heating. We find that both contributions to the heat current display interesting symmetry properties under reversal of the applied dc bias. We show that the symmetries arise from the behavior of the dot transmission function. Importantly, the transmission probability is a function of both energy and voltage. This allows us to analyze the heat current in the nonlinear regime of transport. We observe that nonlinearities appear already for voltages smaller than the Kondo temperature. Finally, we suggest to use the contact and electric symmetry coefficients as a way to measure pure energy currents.

Enhancing Earth Science And IT Literacy Through Environmental Science Information Technology Activities

NASA Astrophysics Data System (ADS)

Cuff, K. E.; Molinaro, M.

2004-12-01

The Environmental Science Information Technology Activities (ESITA) program provides grades 9 and 10 students with under-represented minority backgrounds in the East San Francisco Bay Area with real-world opportunities to learn about and apply information technologies through a series of project-based activities related to environmental science. Supported by the NSF Information Technology Experiences for Students and Teachers (ITEST) program, ESITA activities engage students in the use of newly acquired information technology (IT) skills and understandings while performing air and water quality research investigations. One project that ESITA students have become involved in relates to the currently relevant issue of elevated levels of lead found in drinking waters in Washington, D.C. Students based in the Bay Area have initiated and maintained E-mail correspondence with children who attend elementary schools in the D.C. area. After receiving a thorough explanation of required sampling procedures devised by the Bay Area students, the elementary school children have sent 500 ml water samples from their homes and schools to Berkeley along with information about the locations from which the water samples were collected. These samples were then prepared for lead analysis at Lawrence Hall of Science by ESITA students, who used resulting data to perform a preliminary assessment of the geospatial distribution of lead trouble spots throughout Washington, DC. Later, ESITA student scientists will work with students from the UC Berkeley School of Public Health to develop surveys and questionnaires that generate high quality information useful with regard to assessing the impact of the current lead crisis on younger children in the Washington, D.C. area. Through the application of new understandings to current, real-world environmental problems and issues such as that related to lead, positive changes in students' attitudes towards IT and science have occurred, which accompany increases in their content learning and skills acquisition abilities.

Single Event Burnout in DC-DC Converters for the LHC Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Claudio H. Rivetta et al.

High voltage transistors in DC-DC converters are prone to catastrophic Single Event Burnout in the LHC radiation environment. This paper presents a systematic methodology to analyze single event effects sensitivity in converters and proposes solutions based on de-rating input voltage and output current or voltage.

Method and device for ion mobility separations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ibrahim, Yehia M.; Garimella, Sandilya V. B.; Smith, Richard D.

2017-07-11

Methods and devices for ion separations or manipulations in gas phase are disclosed. The device includes a single non-planar surface. Arrays of electrodes are coupled to the surface. A combination of RF and DC voltages are applied to the arrays of electrodes to create confining and driving fields that move ions through the device. The DC voltages are static DC voltages or time-dependent DC potentials or waveforms.

Automatic generation and analysis of solar cell IV curves

DOEpatents

Kraft, Steven M.; Jones, Jason C.

2014-06-03

A photovoltaic system includes multiple strings of solar panels and a device presenting a DC load to the strings of solar panels. Output currents of the strings of solar panels may be sensed and provided to a computer that generates current-voltage (IV) curves of the strings of solar panels. Output voltages of the string of solar panels may be sensed at the string or at the device presenting the DC load. The DC load may be varied. Output currents of the strings of solar panels responsive to the variation of the DC load are sensed to generate IV curves of the strings of solar panels. IV curves may be compared and analyzed to evaluate performance of and detect problems with a string of solar panels.

Large amplitude Fourier transformed ac voltammetry at a rotating disc electrode: a versatile technique for covering Levich and flow rate insensitive regimes in a single experiment.

PubMed

Bano, Kiran; Kennedy, Gareth F; Zhang, Jie; Bond, Alan M

2012-04-14

The theory for large amplitude Fourier transformed ac voltammetry at a rotating disc electrode is described. Resolution of time domain data into dc and ac harmonic components reveals that the mass transport for the dc component is controlled by convective-diffusion, while the background free higher order harmonic components are flow rate insensitive and mainly governed by linear diffusion. Thus, remarkable versatility is available; Levich behaviour of the dc component limiting current provides diffusion coefficient values and access to higher harmonics allows fast electrode kinetics to be probed. Two series of experiments (dc and ac voltammetry) have been required to extract these parameters; here large amplitude ac voltammetry with RDE methodology is used to demonstrate that kinetics and diffusion coefficient information can be extracted from a single experiment. To demonstrate the power of this approach, theoretical and experimental comparisons of data obtained for the reversible [Ru(NH(3))(6)](3+/2+) and quasi-reversible [Fe(CN)(6)](3-/4-) electron transfer processes are presented over a wide range of electrode rotation rates and with different concentrations and electrode materials. Excellent agreement of experimental and simulated data is achieved, which allows parameters such as electron transfer rate, diffusion coefficient, uncompensated resistance and others to be determined using a strategically applied approach that takes into account the different levels of sensitivity of each parameter to the dc or the ac harmonic.

Influence of dust particles on the neon spectral line intensities at the uniform positive column of dc discharge at the space apparatus “Plasma Kristall-4”

NASA Astrophysics Data System (ADS)

Usachev, A. D.; Zobnin, A. V.; Shonenkov, A. V.; Lipaev, A. M.; Molotkov, V. I.; Petrov, O. F.; Fortov, V. E.; Pustyl'nik, M. Y.; Fink, M. A.; Thoma, M. A.; Thomas, H. M.; Padalka, G. I.

2018-01-01

Influence of the elongated dust cloud on the intensities of different neon spectral lines in visible and near ir spectral ranges in the uniform positive column has been experimentally investigated using the Russian-European space apparatus “Plasma Kristall-4” (SA PK-4) on board of the International Space Station (ISS). The investigation was performed in the low pressure (0.5 mbar) direct current (dc, 1 mA) gas discharge in neon. Microgravity allowed us to perform experiments with a large dust cloud in the steady-state regime. To avoid the dust cloud drift in the dc electric field a switching dc polarity discharge mode has been applied. During the experiment a dust cloud of 9 mm in diameter in the discharge tube of 30 mm in diameter with the length of about 100 mm has been observed in the steady-state regime. In this regard, the intensities of neon spectral lines corresponding to 3p → 3s electronic transitions have increased by a factor of 1.4 times, while the intensities of neon spectral lines corresponding to 3d → 3p electronic transitions have increased by a factor of 1.6 times. The observed phenomenon is explained on the basis of the Schottky approach by a self-consistent rising dc electric field in the dusty plasma cloud resulting in an increase of the electron temperature.

Controllable Bidirectional dc Power Sources For Large Loads

NASA Technical Reports Server (NTRS)

Tripp, John S.; Daniels, Taumi S.

1995-01-01

System redesigned for greater efficiency, durability, and controllability. Modern electronically controlled dc power sources proposed to supply currents to six electromagnets used to position aerodynamic test model in wind tunnel. Six-phase bridge rectifier supplies load with large current at voltage of commanded magnitude and polarity. Current-feedback circuit includes current-limiting feature giving some protection against overload.

Analysis of transient state in HTS tapes under ripple DC load current

NASA Astrophysics Data System (ADS)

Stepien, M.; Grzesik, B.

2014-05-01

The paper concerns the analysis of transient state (quench transition) in HTS tapes loaded with the current having DC component together with a ripple component. Two shapes of the ripple were taken into account: sinusoidal and triangular. Very often HTS tape connected to a power electronic current supply (i.e. superconducting coil for SMES) that delivers DC current with ripples and it needs to be examined under such conditions. Additionally, measurements of electrical (and thermal) parameters under such ripple excitation is useful to tape characterization in broad range of load currents. The results presented in the paper were obtained using test bench which contains programmable DC supply and National Instruments data acquisition system. Voltage drops and load currents were measured vs. time. Analysis of measured parameters as a function of the current was used to tape description with quench dynamics taken into account. Results of measurements were also used to comparison with the results of numerical modelling based on FEM. Presented provisional results show possibility to use results of measurements in transient state to prepare inverse models of superconductors and their detailed numerical modelling.

Small, efficient power supply for xenon lamps

NASA Technical Reports Server (NTRS)

Goodwin, J. E.

1970-01-01

Device, which operates from 28 V dc, has four sections, a preregulator, a dc-to-dc converter, a current regulator, and a high voltage starter. The unique characteristics of the individual sections are described.

Fuzzy logic, PSO based fuzzy logic algorithm and current controls comparative for grid-connected hybrid system

NASA Astrophysics Data System (ADS)

Borni, A.; Abdelkrim, T.; Zaghba, L.; Bouchakour, A.; Lakhdari, A.; Zarour, L.

2017-02-01

In this paper the model of a grid connected hybrid system is presented. The hybrid system includes a variable speed wind turbine controlled by aFuzzy MPPT control, and a photovoltaic generator controlled with PSO Fuzzy MPPT control to compensate the power fluctuations caused by the wind in a short and long term, the inverter currents injected to the grid is controlled by a decoupled PI current control. In the first phase, we start by modeling of the conversion system components; the wind system is consisted of a turbine coupled to a gearless permanent magnet generator (PMG), the AC/DC and DC-DC (Boost) converter are responsible to feed the electric energy produced by the PMG to the DC-link. The solar system consists of a photovoltaic generator (GPV) connected to a DC/DC boost converter controlled by a PSO fuzzy MPPT control to extract at any moment the maximum available power at the GPV terminals, the system is based on maximum utilization of both of sources because of their complementary. At the end. The active power reached to the DC-link is injected to the grid through a DC/AC inverter, this function is achieved by controlling the DC bus voltage to keep it constant and close to its reference value, The simulation studies have been performed using Matlab/Simulink. It can be concluded that a good control system performance can be achieved.

DC bias effect on alternating current electrical conductivity of poly(ethylene terephthalate)/alumina nanocomposites

NASA Astrophysics Data System (ADS)

Nikam, Pravin N.; Deshpande, Vineeta D.

2016-05-01

Polymer nanocomposites based on metal oxide (ceramic) nanoparticles are a new class of materials with unique properties and designed for various applications such as electronic device packaging, insulation, fabrication and automotive industries. Poly(ethylene terephthalate) (PET)/alumina (Al2O3) nanocomposites with filler content between 1 wt% and 5 wt% were prepared by melt compounding method using co-rotating twin screw extruder and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and precision LCR meter techniques. The results revealed that proper uniform dispersion at lower content up to 2 wt% of nano-alumina observed by using TEM. Aggregation of nanoparticles was observed at higher content of alumina examined by using SEM and TEM. The frequency dependences of the alternating current (AC) conductivity (σAC) of PET/alumina nanocomposites on the filler content and DC bias were investigated in the frequency range of 20Hz - 1MHz. The results showed that the AC and direct current (DC) conductivity increases with increasing DC bias and nano-alumina content upto 3 wt%. It follows the Jonscher's universal power law of solids. It revealed that σAC of PET/alumina nanocomposites can be well characterized by the DC conductivity (σDC), critical frequency (ωc), critical exponent of the power law (s). Roll of DC bias potential led to an increase of DC conductivity (σDC) due to the creation of additional conducting paths with the polymer nanocomposites and percolation behavior achieved through co-continuous morphology.

Connection between plasma response and resonant magnetic perturbation (RMP) edge localized mode (ELM) suppression in DIII-D [Connection between plasma response and RMP ELM suppression in DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wingen, Andreas; Ferraro, Nathaniel M.; Shafer, Morgan W.

Calculations of the plasma response to applied non-axisymmetric fields in several DIII-D discharges show that predicted displacements depend strongly on the edge current density. This result is found using both a linear two-fluid-MHD model (M3D-C1) and a nonlinear ideal-MHD model (VMEC). Furthermore, it is observed that the probability of a discharge being edge localized mode (ELM)-suppressed is most closely related to the edge current density, as opposed to the pressure gradient. It is found that discharges with a stronger kink response are closer to the peeling–ballooning stability limit in ELITE simulations and eventually cross into the unstable region, causing ELMsmore » to reappear. Thus for effective ELM suppression, the RMP has to prevent the plasma from generating a large kink response, associated with ELM instability. Experimental observations are in agreement with the finding; discharges which have a strong kink response in the MHD simulations show ELMs or ELM mitigation during the RMP phase of the experiment, while discharges with a small kink response in the MHD simulations are fully ELM suppressed in the experiment by the applied resonant magnetic perturbation. The results are cross-checked against modeled 3D ideal MHD equilibria using the VMEC code. The procedure of constructing optimal 3D equilibria for diverted H-mode discharges using VMEC is presented. As a result, kink displacements in VMEC are found to scale with the edge current density, similar to M3D-C1, but the displacements are smaller. A direct correlation in the flux surface displacements to the bootstrap current is shown.« less

Connection between plasma response and resonant magnetic perturbation (RMP) edge localized mode (ELM) suppression in DIII-D [Connection between plasma response and RMP ELM suppression in DIII-D

DOE PAGES

Wingen, Andreas; Ferraro, Nathaniel M.; Shafer, Morgan W.; ...

2015-09-03

Calculations of the plasma response to applied non-axisymmetric fields in several DIII-D discharges show that predicted displacements depend strongly on the edge current density. This result is found using both a linear two-fluid-MHD model (M3D-C1) and a nonlinear ideal-MHD model (VMEC). Furthermore, it is observed that the probability of a discharge being edge localized mode (ELM)-suppressed is most closely related to the edge current density, as opposed to the pressure gradient. It is found that discharges with a stronger kink response are closer to the peeling–ballooning stability limit in ELITE simulations and eventually cross into the unstable region, causing ELMsmore » to reappear. Thus for effective ELM suppression, the RMP has to prevent the plasma from generating a large kink response, associated with ELM instability. Experimental observations are in agreement with the finding; discharges which have a strong kink response in the MHD simulations show ELMs or ELM mitigation during the RMP phase of the experiment, while discharges with a small kink response in the MHD simulations are fully ELM suppressed in the experiment by the applied resonant magnetic perturbation. The results are cross-checked against modeled 3D ideal MHD equilibria using the VMEC code. The procedure of constructing optimal 3D equilibria for diverted H-mode discharges using VMEC is presented. As a result, kink displacements in VMEC are found to scale with the edge current density, similar to M3D-C1, but the displacements are smaller. A direct correlation in the flux surface displacements to the bootstrap current is shown.« less

Method and apparatus to provide power conversion with high power factor

DOEpatents

Perreault, David J.; Lim, Seungbum; Otten, David M.

2017-05-23

A power converter circuit rectifies a line voltage and applies the rectified voltage to a stack of capacitors. Voltages on the capacitors are coupled to a plurality of regulating converters to be converted to regulated output signals. The regulated output signals are combined and converted to a desired DC output voltage of the power converter. Input currents of the regulating converters are modulated in a manner that enhances the power factor of the power converter.

Electromechanical actuator with controllable motion, fast response rate, and high-frequency resonance based on graphene and polydiacetylene.

PubMed

Liang, Jiajie; Huang, Lu; Li, Na; Huang, Yi; Wu, Yingpeng; Fang, Shaoli; Oh, Jiyoung; Kozlov, Mikhail; Ma, Yanfeng; Li, Feifei; Baughman, Ray; Chen, Yongsheng

2012-05-22

Although widely investigated, novel electromechanical actuators with high overall actuation performance are still in urgent need for various practical and scientific applications, such as robots, prosthetic devices, sensor switches, and sonar projectors. In this work, combining the properties of unique environmental perturbations-actuated deformational isomerization of polydiacetylene (PDA) and the outstanding intrinsic features of graphene together for the first time, we design and fabricate an electromechanical bimorph actuator composed of a layer of PDA crystal and a layer of flexible graphene paper through a simple yet versatile solution approach. Under low applied direct current (dc), the graphene-PDA bimorph actuator with strong mechanical strength can generate large actuation motion (curvature is about 0.37 cm(-1) under a current density of 0.74 A/mm(2)) and produce high actuation stress (more than 160 MPa/g under an applied dc of only 0.29 A/mm(2)). When applying alternating current (ac), this actuator can display reversible swing behavior with long cycle life under high frequencies even up to 200 Hz; significantly, while the frequency and the value of applied ac and the state of the actuators reach an appropriate value, the graphene-PDA actuator can produce a strong resonance and the swing amplitude will jump to a peak value. Moreover, this stable graphene-PDA actuator also demonstrates rapidly and partially reversible electrochromatic phenomenon when applying an ac. Two mechanisms-the dominant one, electric-induced deformation, and a secondary one, thermal-induced expansion of PDA-are proposed to contribute to these interesting actuation performances of the graphene-PDA actuators. On the basis of these results, a mini-robot with controllable direction of motion based on the graphene-PDA actuator is designed to illustrate the great potential of our discoveries for practical use. Combining the unique actuation mechanism and many outstanding properties of graphene and PDA, this novel kind of graphene-PDA actuator exhibits compelling advantages to traditional electromechanical actuation technology and may provide a new avenue for actuation applications.

Using LDR as Sensing Element for an External Fuzzy Controller Applied in Photovoltaic Pumping Systems with Variable-Speed Drives.

PubMed

Maranhão, Geraldo Neves De A; Brito, Alaan Ubaiara; Leal, Anderson Marques; Fonseca, Jéssica Kelly Silva; Macêdo, Wilson Negrão

2015-09-22

In the present paper, a fuzzy controller applied to a Variable-Speed Drive (VSD) for use in Photovoltaic Pumping Systems (PVPS) is proposed. The fuzzy logic system (FLS) used is embedded in a microcontroller and corresponds to a proportional-derivative controller. A Light-Dependent Resistor (LDR) is used to measure, approximately, the irradiance incident on the PV array. Experimental tests are executed using an Arduino board. The experimental results show that the fuzzy controller is capable of operating the system continuously throughout the day and controlling the direct current (DC) voltage level in the VSD with a good performance.

Variable frequency inverter for ac induction motors with torque, speed and braking control

NASA Technical Reports Server (NTRS)

Nola, F. J. (Inventor)

1975-01-01

A variable frequency inverter was designed for driving an ac induction motor which varies the frequency and voltage to the motor windings in response to varying torque requirements for the motor so that the applied voltage amplitude and frequency are of optimal value for any motor load and speed requirement. The slip frequency of the motor is caused to vary proportionally to the torque and feedback is provided so that the most efficient operating voltage is applied to the motor. Winding current surge is limited and a controlled negative slip causes motor braking and return of load energy to a dc power source.

Changes in behavioral responses of Lygus lineolaris (Hemiptera: Miridae) from various applied signal voltages during EPG recordings

USDA-ARS?s Scientific Manuscript database

A 3rd-generation AC-DC electrical penetration graph (EPG) monitor was used to study feeding behaviors of pre-reproductive adult Lygus lineolaris (Hemiptera: Miridae) on pinhead (<3mm) cotton squares, applying different signal voltages at several input impedances. The AC-DC monitor allows a user to s...

Effect of DC bias on dielectric properties of nanocrystalline CuAlO2

NASA Astrophysics Data System (ADS)

Prakash, T.; Ramasamy, S.; Murty, B. S.

2013-03-01

Grain boundary effect on the room temperature dielectric behavior in mechanically alloyed nanocrystalline CuAlO2 has been investigated using impedance spectroscopy under the applied DC bias voltages 0 V to 4.8 V in a periodic interval of 0.2 V. Analysis of impedance data confirms the existence of double Schottky potential barrier heights ( Φ b ) between two adjacent grains (left and right side) with grain boundary and its influences in dielectric relaxation time ( τ), dielectric constant ( ɛ') and dielectric loss (tan δ) factor. Also, clear evidence on the suppression of Φ b was demonstrated in the higher applied bias voltages with the parameter τ. At equilibrium state, τ is 0.63 ms and it was reduced to 0.13 ms after the 3.2 V applied DC bias. These observed DC bias voltage effects are obeying `brick layer model' and also elucidates Φ b is playing a crucial role in controlling dielectric properties of nanomaterials.

Forecasting of high voltage insulation performance: Testing of recommended potting materials and of capacitors

NASA Technical Reports Server (NTRS)

Bever, R. S.

1984-01-01

Nondestructive high voltage test techniques (mostly electrical methods) are studied to prevent total or catastrophic breakdown of insulation systems under applied high voltage in space. Emphasis is on the phenomenon of partial breakdown or partial discharge (P.D.) as a symptom of insulation quality, notably partial discharge testing under D.C. applied voltage. Many of the electronic parts and high voltage instruments in space experience D.C. applied stress in service, and application of A.C. voltage to any portion thereof would be prohibited. Suggestions include: investigation of the ramp test method for D.C. partial discharge measurements; testing of actual flight-type insulation specimen; perfect plotting resin samples with controlled defects for test; several types of plotting resins and recommendations of the better ones from the electrical characteristics; thermal and elastic properties are also considered; testing of commercial capaciters; and approximate acceptance/rejection/rerating criteria for sample test elements for space use, based on D.C. partial discharge.

LOW-LEVEL DIRECT CURRENT AMPLIFIER

DOEpatents

Kerns, Q.A.

1959-05-01

A d-c amplifier is described. Modulation is provided between a d-c signal and an alternating current to give an output signal proportional to the d- c signal. The circuit has high sensitivity and accuracy. (T.R.H.)

Performance of a 14.9-kW laminated-frame dc series motor with chopper controller

NASA Technical Reports Server (NTRS)

Schwab, J. R.

1979-01-01

Traction motor using two types of excitation: ripple free dc from a motor generator set for baseline data and chopped dc as supplied by a battery and chopper controller was tested. For the same average values of input voltage and current, the power output was independent of the type of excitation. At the same speeds, motor efficiency at low power output (corresponding to low duty cycle of the controller) was 5 to 10 percentage points less on chopped dc than on ripple-free dc. This illustrates that for chopped waveforms, it is incorrect to calculate input power as the product of average voltage and average current. Locked-rotor torque, no load losses, and magnetic saturation data were so determined.

21 CFR 74.2317 - D&C Red No. 17.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2317 D&C Red No. 17. (a) Identity and specifications. The color additive D&C Red No. 17 shall conform in identity and specifications to the requirements of § 74... externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling. The label...

21 CFR 74.2331 - D&C Red No. 31.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2331 D&C Red No. 31. (a) Identity and specifications. The color additive D&C Red No. 31 shall conform in identity and specifications to the requirements of § 74... externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling. The label...

21 CFR 74.2707a - Ext. D&C Yellow No. 7.

Code of Federal Regulations, 2010 CFR

2010-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2707a Ext. D&C Yellow No. 7. (a) Identity and specifications. The color additive Ext. D&C Yellow No. 7 shall conform in identity and specifications to the... for coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c...

21 CFR 74.2334 - D&C Red No. 34.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2334 D&C Red No. 34. (a) Identity and specifications. The color additive D&C Red No. 34 shall conform in identity and specifications to the requirements of § 74... externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling. The label...

21 CFR 74.2104 - D&C Blue No. 4.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2104 D&C Blue No. 4. (a) Identity and specifications. The color additive D&C Blue No. 4 shall conform in identity and specifications to the requirements of § 74... externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling. The label...

21 CFR 74.2317 - D&C Red No. 17.

Code of Federal Regulations, 2014 CFR

2014-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2317 D&C Red No. 17. (a) Identity and specifications. The color additive D&C Red No. 17 shall conform in identity and specifications to the requirements of § 74... externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling. The label...

21 CFR 74.2707a - Ext. D&C Yellow No. 7.

Code of Federal Regulations, 2012 CFR

2012-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2707a Ext. D&C Yellow No. 7. (a) Identity and specifications. The color additive Ext. D&C Yellow No. 7 shall conform in identity and specifications to the... for coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c...

21 CFR 74.2334 - D&C Red No. 34.

Code of Federal Regulations, 2012 CFR

2012-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2334 D&C Red No. 34. (a) Identity and specifications. The color additive D&C Red No. 34 shall conform in identity and specifications to the requirements of § 74... externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling. The label...

21 CFR 74.2317 - D&C Red No. 17.

Code of Federal Regulations, 2012 CFR

2012-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2317 D&C Red No. 17. (a) Identity and specifications. The color additive D&C Red No. 17 shall conform in identity and specifications to the requirements of § 74... externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling. The label...

21 CFR 74.2334 - D&C Red No. 34.

Code of Federal Regulations, 2013 CFR

2013-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2334 D&C Red No. 34. (a) Identity and specifications. The color additive D&C Red No. 34 shall conform in identity and specifications to the requirements of § 74... externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling. The label...

21 CFR 74.2707a - Ext. D&C Yellow No. 7.

Code of Federal Regulations, 2014 CFR

2014-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2707a Ext. D&C Yellow No. 7. (a) Identity and specifications. The color additive Ext. D&C Yellow No. 7 shall conform in identity and specifications to the... for coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c...

21 CFR 74.2331 - D&C Red No. 31.

Code of Federal Regulations, 2012 CFR

2012-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2331 D&C Red No. 31. (a) Identity and specifications. The color additive D&C Red No. 31 shall conform in identity and specifications to the requirements of § 74... externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling. The label...

21 CFR 74.2331 - D&C Red No. 31.

Code of Federal Regulations, 2013 CFR

2013-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2331 D&C Red No. 31. (a) Identity and specifications. The color additive D&C Red No. 31 shall conform in identity and specifications to the requirements of § 74... externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling. The label...

21 CFR 74.2331 - D&C Red No. 31.

Code of Federal Regulations, 2014 CFR

2014-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2331 D&C Red No. 31. (a) Identity and specifications. The color additive D&C Red No. 31 shall conform in identity and specifications to the requirements of § 74... externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling. The label...

21 CFR 74.2317 - D&C Red No. 17.

Code of Federal Regulations, 2013 CFR

2013-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2317 D&C Red No. 17. (a) Identity and specifications. The color additive D&C Red No. 17 shall conform in identity and specifications to the requirements of § 74... externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling. The label...

21 CFR 74.2707a - Ext. D&C Yellow No. 7.

Code of Federal Regulations, 2013 CFR

2013-04-01

... COLOR ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2707a Ext. D&C Yellow No. 7. (a) Identity and specifications. The color additive Ext. D&C Yellow No. 7 shall conform in identity and specifications to the... for coloring externally applied cosmetics in amounts consistent with good manufacturing practice. (c...

21 CFR 74.2334 - D&C Red No. 34.

Code of Federal Regulations, 2014 CFR

2014-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2334 D&C Red No. 34. (a) Identity and specifications. The color additive D&C Red No. 34 shall conform in identity and specifications to the requirements of § 74... externally applied cosmetics in amounts consistent with good manufacturing practice. (c) Labeling. The label...

A Comparison of Alternating Current and Direct Current Electrospray Ionization for Mass Spectrometry

PubMed Central

Sarver, Scott A.; Gartner, Carlos A.; Chetwani, Nishant; Go, David B.; Dovichi, Norman J.

2014-01-01

A series of studies comparing the performance of alternating current electrospray ionization (AC ESI) mass spectrometry (MS) and direct current electrospray ionization (DC ESI) MS has been conducted, exploring the absolute signal intensity and signal-to-background ratios produced by both methods using caffeine and a model peptide as targets. Because the high-voltage AC signal was more susceptible to generating gas discharges, the operating voltage range of AC ESI was significantly smaller than that for DC ESI, such that the absolute signal intensities produced by DC ESI at peak voltages were 1 - 2 orders of magnitude greater than those for AC ESI. Using an electronegative nebulizing gas, sulfur hexafluoride (SF6), instead of nitrogen (N2) increased the operating range of AC ESI by ~50%, but did not appreciably improve signal intensities. While DC ESI generated far greater signal intensities, both ionization methods produced comparable signal-to-background noise, with AC ESI spectra appearing qualitatively cleaner. A quantitative calibration analysis was performed for two analytes, caffeine and the peptide MRFA. AC ESI utilizing SF6 outperforms all other techniques for the detection of MRFA, producing chromatographic limits of detection nearly one order of magnitude lower than that of DC ESI utilizing N2, and one half that of DC ESI utilizing SF6. However, DC ESI outperforms AC ESI for the analysis of caffeine, indicating improvements in spectral quality may benefit certain compounds, or classes of compounds, on an individual basis. PMID:24464359

The BepiColombo Laser Altimeter (BeLA) power converter module (PCM): Concept and characterisation.

PubMed

Rodrigo, J; Gasquet, E; Castro, J-M; Herranz, M; Lara, L-M; Muñoz, M; Simon, A; Behnke, T; Thomas, N

2017-03-01

This paper presents the principal considerations when designing DC-DC converters for space instruments, in particular for the power converter module as part of the first European space laser altimeter: "BepiColombo Laser Altimeter" on board the European Space Agency-Japan Aerospace Exploration Agency (JAXA) mission BepiColombo. The main factors which determine the design of the DC-DC modules in space applications are printed circuit board occupation, mass, DC-DC converter efficiency, and environmental-survivability constraints. Topics included in the appropriated DC-DC converter design flow are hereby described. The topology and technology for the primary and secondary stages, input filters, transformer design, and peripheral components are discussed. Component selection and design trade-offs are described. Grounding, load and line regulation, and secondary protection circuitry (under-voltage, over-voltage, and over-current) are then introduced. Lastly, test results and characterization of the final flight design are also presented. Testing of the inrush current, the regulated output start-up, and the switching function of the power supply indicate that these performances are fully compliant with the requirements.

A simulation-based efficiency comparison of AC and DC power distribution networks in commercial buildings

DOE PAGES

Gerber, Daniel L.; Vossos, Vagelis; Feng, Wei; ...

2017-06-12

Direct current (DC) power distribution has recently gained traction in buildings research due to the proliferation of on-site electricity generation and battery storage, and an increasing prevalence of internal DC loads. The research discussed in this paper uses Modelica-based simulation to compare the efficiency of DC building power distribution with an equivalent alternating current (AC) distribution. The buildings are all modeled with solar generation, battery storage, and loads that are representative of the most efficient building technology. A variety of paramet ric simulations determine how and when DC distribution proves advantageous. These simulations also validate previous studies that use simplermore » approaches and arithmetic efficiency models. This work shows that using DC distribution can be considerably more efficient: a medium sized office building using DC distribution has an expected baseline of 12% savings, but may also save up to 18%. In these results, the baseline simulation parameters are for a zero net energy (ZNE) building that can island as a microgrid. DC is most advantageous in buildings with large solar capacity, large battery capacity, and high voltage distribution.« less

A simulation-based efficiency comparison of AC and DC power distribution networks in commercial buildings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerber, Daniel L.; Vossos, Vagelis; Feng, Wei

Direct current (DC) power distribution has recently gained traction in buildings research due to the proliferation of on-site electricity generation and battery storage, and an increasing prevalence of internal DC loads. The research discussed in this paper uses Modelica-based simulation to compare the efficiency of DC building power distribution with an equivalent alternating current (AC) distribution. The buildings are all modeled with solar generation, battery storage, and loads that are representative of the most efficient building technology. A variety of paramet ric simulations determine how and when DC distribution proves advantageous. These simulations also validate previous studies that use simplermore » approaches and arithmetic efficiency models. This work shows that using DC distribution can be considerably more efficient: a medium sized office building using DC distribution has an expected baseline of 12% savings, but may also save up to 18%. In these results, the baseline simulation parameters are for a zero net energy (ZNE) building that can island as a microgrid. DC is most advantageous in buildings with large solar capacity, large battery capacity, and high voltage distribution.« less

Dilution-triggered SMM behavior under zero field in a luminescent Zn2Dy2 tetranuclear complex incorporating carbonato-bridging ligands derived from atmospheric CO2 fixation.

PubMed

Titos-Padilla, Silvia; Ruiz, José; Herrera, Juan Manuel; Brechin, Euan K; Wersndorfer, Wolfgang; Lloret, Francesc; Colacio, Enrique

2013-08-19

The synthesis, structure, magnetic, and luminescence properties of the Zn2Dy2 tetranuclear complex of formula {(μ3-CO3)2[Zn(μ-L)Dy(NO3)]2}·4CH3OH (1), where H2L is the compartmental ligand N,N',N″-trimethyl-N,N″-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine, are reported. The carbonate anions that bridge two Zn(μ-L)Dy units come from the atmospheric CO2 fixation in a basic medium. Fast quantum tunneling relaxation of the magnetization (QTM) is very effective in this compound, so that single-molecule magnet (SMM) behavior is only observed in the presence of an applied dc field of 1000 Oe, which is able to partly suppress the QTM relaxation process. At variance, a 1:10 Dy:Y magnetic diluted sample, namely, 1', exhibits SMM behavior at zero applied direct-current (dc) field with about 3 times higher thermal energy barrier than that in 1 (U(eff) = 68 K), thus demonstrating the important role of intermolecular dipolar interactions in favoring the fast QTM relaxation process. When a dc field of 1000 Oe is applied to 1', the QTM is almost fully suppressed, the reversal of the magnetization slightly slows, and U(eff) increases to 78 K. The dilution results combined with micro-SQUID magnetization measurements clearly indicate that the SMM behavior comes from single-ion relaxation of the Dy(3+) ions. Analysis of the relaxation data points out that a Raman relaxation process could significantly affect the Orbach relaxation process, reducing the thermal energy barrier U(eff) for slow relaxation of the magnetization.

Broad-beam high-current dc ion source based on a two-stage glow discharge plasma.

PubMed

Vizir, A V; Oks, E M; Yushkov, G Yu

2010-02-01

We have designed, made, and demonstrated a broad-beam, dc, ion source based on a two-stage, hollow-cathode, and glow discharges plasma. The first-stage discharge (auxiliary discharge) produces electrons that are injected into the cathode cavity of a second-stage discharge (main discharge). The electron injection causes a decrease in the required operating pressure of the main discharge down to 0.05 mTorr and a decrease in required operating voltage down to about 50 V. The decrease in operating voltage of the main discharge leads to a decrease in the fraction of impurity ions in the ion beam extracted from the main gas discharge plasma to less than 0.2%. Another feature of the source is a single-grid accelerating system in which the ion accelerating voltage is applied between the plasma itself and the grid electrode. The source has produced steady-state Ar, O, and N ion beams of about 14 cm diameter and current of more than 2 A at an accelerating voltage of up to 2 kV.

Sputter crater formation in the case of microsecond pulsed glow discharge in a Grimm-type source. Comparison of direct current and radio frequency modes

NASA Astrophysics Data System (ADS)

Efimova, Varvara; Hoffmann, Volker; Eckert, Jürgen

2012-10-01

Depth profiling with pulsed glow discharge is a promising technique. The application of pulsed voltage for sputtering reduces the sputtering rate and thermal stress and hereby improves the analysis of thin layered and thermally fragile samples. However pulsed glow discharge is not well studied and this limits its practical use. The current work deals with the questions which usually arise when the pulsed mode is applied: Which duty cycle, frequency and pulse length must be chosen to get the optimal sputtering rate and crater shape? Are the well-known sputtering effects of the continuous mode valid also for the pulsed regime? Is there any difference between dc and rf pulsing in terms of sputtering? It is found that the pulse length is a crucial parameter for the crater shape and thermal effects. Sputtering with pulsed dc and rf modes is found to be similar. The observed sputtering effects at various pulsing parameters helped to interpret and optimize the depth resolution of GD OES depth profiles.

Changes of hydrogen peroxide and radical-scavenging activity of raspberry during osmotic, convective, and freeze-drying.

PubMed

Novaković, Miroslav M; Stevanović, Snežana M; Gorjanović, Stanislava Ž; Jovanovic, Predrag M; Tešević, Vele V; Janković, Miodrag A; Sužnjević, Desanka Ž

2011-05-01

This study was conducted to investigate the influence of different drying treatments on antioxidant (AO) activity and phenolic content of raspberry (Rubus idaeus), cultivar Willamette. Whole raspberry fruits were dried convectively (air-drying), osmotically, and freeze-dried. Acetone-water extracts of fresh and dried raspberries were assessed for total phenolic content by standard Folin-Ciocalteau method. Two AO assays were applied, a recently developed direct current (DC) polarographic assay based on decrease of anodic oxidation current of hydrogen peroxide and widely used radical scavenge against the 1,1-diphenyl-2-picrylhydrazyl (DPPH). Strong correlation has been obtained between both AO assays and total phenolic content. In addition, some individual phenolic compounds present in raspberry have been assessed using DPPH and DC polarographic assay. Comparison and evaluation of drying methods has been based on preservation of AO activity and total phenolic content. Obtained results confirmed superiority of freeze-drying; convective drying caused slight changes while osmotic dehydration showed a significant decrease of phenolic compounds and AO activity. © 2011 Institute of Food Technologists®

Two-dimensional hybrid Monte Carlo–fluid modelling of dc glow discharges: Comparison with fluid models, reliability, and accuracy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eylenceoğlu, E.; Rafatov, I., E-mail: rafatov@metu.edu.tr; Kudryavtsev, A. A.

2015-01-15

Two-dimensional hybrid Monte Carlo–fluid numerical code is developed and applied to model the dc glow discharge. The model is based on the separation of electrons into two parts: the low energetic (slow) and high energetic (fast) electron groups. Ions and slow electrons are described within the fluid model using the drift-diffusion approximation for particle fluxes. Fast electrons, represented by suitable number of super particles emitted from the cathode, are responsible for ionization processes in the discharge volume, which are simulated by the Monte Carlo collision method. Electrostatic field is obtained from the solution of Poisson equation. The test calculations weremore » carried out for an argon plasma. Main properties of the glow discharge are considered. Current-voltage curves, electric field reversal phenomenon, and the vortex current formation are developed and discussed. The results are compared to those obtained from the simple and extended fluid models. Contrary to reports in the literature, the analysis does not reveal significant advantages of existing hybrid methods over the extended fluid model.« less

Effect of phase advance on the brushless dc motor torque speed respond

NASA Astrophysics Data System (ADS)

Mohd, M. S.; Karsiti, M. N.; Mohd, M. S.

2015-12-01

Brushless direct current (BLDC) motor is widely used in small and medium sized electric vehicles as it exhibit highest specific power and thermal efficiency as compared to the induction motor. Permanent magnets BLDC rotor create a constant magnetic flux, which limit the motor top speed. As the back electromotive force (EMF) voltage increases proportionally with motor rotational speed and it approaches the amplitude of the input voltage, the phase current amplitude will reach zero. By advancing the phase current, it is possible to extend the maximum speed of the BLDC motor beyond the rated top speed. This will allow smaller BLDC motor to be used in small electric vehicles (EV) and in larger applications will allow the use of BLDC motor without the use of multispeed transmission unit for high speed operation. However, increasing the speed of BLDC will affect the torque speed response. The torque output will decrease as speed increases. Adjusting the phase angle will affect the speed of the motor as each coil is energized earlier than the corresponding rise in the back emf of the coil. This paper discusses the phase advance strategy of Brushless DC motor by phase angle manipulation approaches using external hall sensors. Tests have been performed at different phase advance angles in advance and retard positions for different voltage levels applied. The objective is to create the external hall sensor system to commutate the BLDC motor, to establish the phase advance of the BLDC by varying the phase angle through external hall sensor manipulation, observe the respond of the motor while applying the phase advance by hall sensor adjustment.

Analysis of payload bay magnetic fields due to dc power multipoint and single point ground configurations

NASA Technical Reports Server (NTRS)

Lawton, R. M.

1976-01-01

An analysis of magnetic fields in the Orbiter Payload Bay resulting from the present grounding configuration (structure return) was presented and the amount of improvement that would result from installing wire returns for the three dc power buses was determined. Ac and dc magnetic fields at five points in a cross-section of the bay are calculated for both grounding configurations. Y and Z components of the field at each point are derived in terms of a constant coefficient and the current amplitude of each bus. The dc loads assumed are 100 Amperes for each bus. The ac noise current used is a spectrum 6 db higher than the Orbiter equipment limit for narrowband conducted emissions. It was concluded that installing return wiring to provide a single point ground for the dc Buses in the Payload Bay would reduce the ac and dc magnetic field intensity by approximately 30 db.

R Dump Converter without DC Link Capacitor for an 8/6 SRM: Experimental Investigation

PubMed Central

Kavitha, Pasumalaithevan; Umamaheswari, Bhaskaran

2015-01-01

The objective of this paper is to investigate the performance of 8/6 switched reluctance motor (SRM) when excited with sinusoidal voltage. The conventional R dump converter provides DC excitation with the help of capacitor. In this paper the converter used is the modified R dump converter without DC link capacitor providing AC or sinusoidal excitation. Torque ripple and speed ripple are investigated based on hysteresis current control. Constant and sinusoidal current references are considered for comparison in both DC and AC excitation. Extensive theoretical and experimental investigations are made to bring out the merits and demerits of AC versus DC excitation. It is shown that the constructionally simple SRM can be favorably controlled with simple R dump converter with direct AC excitation without need for DC link capacitor. A 4-phase 8/6 0.5 kW SRM is used for experimentation. PMID:25642452

R dump converter without DC link capacitor for an 8/6 SRM: experimental investigation.

PubMed

Kavitha, Pasumalaithevan; Umamaheswari, Bhaskaran

2015-01-01

The objective of this paper is to investigate the performance of 8/6 switched reluctance motor (SRM) when excited with sinusoidal voltage. The conventional R dump converter provides DC excitation with the help of capacitor. In this paper the converter used is the modified R dump converter without DC link capacitor providing AC or sinusoidal excitation. Torque ripple and speed ripple are investigated based on hysteresis current control. Constant and sinusoidal current references are considered for comparison in both DC and AC excitation. Extensive theoretical and experimental investigations are made to bring out the merits and demerits of AC versus DC excitation. It is shown that the constructionally simple SRM can be favorably controlled with simple R dump converter with direct AC excitation without need for DC link capacitor. A 4-phase 8/6 0.5 kW SRM is used for experimentation.

The negative hydrogen Penning ion gauge ion source for KIRAMS-13 cyclotron

DOE Office of Scientific and Technical Information (OSTI.GOV)

An, D. H.; Jung, I. S.; Kang, J.

2008-02-15

The cold-cathode-type Penning ion gauge (PIG) ion source for the internal ion source of KIRAMS-13 cyclotron has been used for generation of negative hydrogen ions. The dc H-beam current of 650 {mu}A from the PIG ion source with the Dee voltage of 40 kV and arc current of 1.0 A is extrapolated from the measured dc extraction beam currents at the low extraction dc voltages. The output optimization of PIG ion source in the cyclotron has been carried out by using various chimneys with different sizes of the expansion gap between the plasma boundary and the chimney wall. This papermore » presents the results of the dc H-extraction measurement and the expansion gap experiment.« less

Analysis, Simulation, and Fabrication of Current Mode Controlled DC-DC Power Converters

DTIC Science & Technology

1999-12-01

susceptibility), vou/ vin . 3 . The output impedance including the load. 22 The crossover frequency, coc, appears in all poles and is defined as: oo... VIN - 3 0 VIN - 3 V Delay to Outputs (TJ=25*C, (Note 2) 200 500 200 500 ns ( Current Limit Adjust Section Current Limit Offset

Bidirectional dc-to-dc Power Converter

NASA Technical Reports Server (NTRS)

Griesbach, C. R.

1986-01-01

Solid-state, series-resonant converter uses high-voltage thyristors. Converter used either to convert high-voltage, low-current dc power to lowvoltage, high current power or reverse. Taking advantage of newly-available high-voltage thyristors to provide better reliability and efficiency than traditional converters that use vacuum tubes as power switches. New converter essentially maintenance free and provides greatly increased mean time between failures. Attractive in industrial applications whether or not bidirectional capability is required.

Load flows and faults considering dc current injections

NASA Technical Reports Server (NTRS)

Kusic, G. L.; Beach, R. F.

1991-01-01

The authors present novel methods for incorporating current injection sources into dc power flow computations and determining network fault currents when electronic devices limit fault currents. Combinations of current and voltage sources into a single network are considered in a general formulation. An example of relay coordination is presented. The present study is pertinent to the development of the Space Station Freedom electrical generation, transmission, and distribution system.

Series-Connected Buck Boost Regulators

NASA Technical Reports Server (NTRS)

Birchenough, Arthur G.

2005-01-01

A series-connected buck boost regulator (SCBBR) is an electronic circuit that bucks a power-supply voltage to a lower regulated value or boosts it to a higher regulated value. The concept of the SCBBR is a generalization of the concept of the SCBR, which was reported in "Series-Connected Boost Regulators" (LEW-15918), NASA Tech Briefs, Vol. 23, No. 7 (July 1997), page 42. Relative to prior DC-voltage-regulator concepts, the SCBBR concept can yield significant reductions in weight and increases in power-conversion efficiency in many applications in which input/output voltage ratios are relatively small and isolation is not required, as solar-array regulation or battery charging with DC-bus regulation. Usually, a DC voltage regulator is designed to include a DC-to-DC converter to reduce its power loss, size, and weight. Advances in components, increases in operating frequencies, and improved circuit topologies have led to continual increases in efficiency and/or decreases in the sizes and weights of DC voltage regulators. The primary source of inefficiency in the DC-to-DC converter portion of a voltage regulator is the conduction loss and, especially at high frequencies, the switching loss. Although improved components and topology can reduce the switching loss, the reduction is limited by the fact that the converter generally switches all the power being regulated. Like the SCBR concept, the SCBBR concept involves a circuit configuration in which only a fraction of the power is switched, so that the switching loss is reduced by an amount that is largely independent of the specific components and circuit topology used. In an SCBBR, the amount of power switched by the DC-to-DC converter is only the amount needed to make up the difference between the input and output bus voltage. The remaining majority of the power passes through the converter without being switched. The weight and power loss of a DC-to-DC converter are determined primarily by the amount of power processed. In the SCBBR, the unswitched majority of the power is passed through with very little power loss, and little if any increase in the sizes of the converter components is needed to enable the components to handle the unswitched power. As a result, the power-conversion efficiency of the regulator can be very high, as shown in the example of Figure 1. A basic SCBBR includes a DC-to-DC converter (see Figure 2). The switches and primary winding of a transformer in the converter is connected across the input bus, while the secondary winding and switches are connected in series with the output bus, so that the output voltage is the sum of the input voltage and the secondary voltage of the converter. In the breadboard SCBBR, the input voltage applied to the primary winding is switched by use of metal oxide/semiconductor field-effect transistors (MOSFETs) in a full bridge circuit; the secondary winding is center-tapped, with two MOSFET switches and diode rectifiers connected in opposed series in each leg. The sets of opposed switches and rectifiers are what enable operation in either a boost or a buck mode. In the boost mode, input voltage and current, and the output voltage and current are all positive; that is, the secondary voltage is added to the input voltage and the net output voltage can be regulated at a value equal or greater than the input voltage. In the buck mode, input voltage is still positive and the current still flows in the same direction in the secondary, but the switches are controlled such that some power flows from the secondary to the primary. The voltage across the secondary and the current into the primary are reversed. The result is that the output voltage is lower than the input voltage, and some power is recirculated from the converter secondary back to the input. Quantitatively, the advantage of an SCBBR is a direct function of the regulation range required. If, for example, a regulation range of 20 percent is required for a 500-W supply, th it suffices to design the DC-to-DC converter in the SCBBR for a power rating of only 100 W. The switching loss and size are much smaller than those of a conventional regulator that must be rated for switching of all 500 W. The reduction in size and the increase in efficiency are not directly proportional to switched-power ratio of 5:1 because the additional switches contribute some conduction loss and the input and output filters must be larger than those typically required for a 100-W converter. Nevertheless, the power loss and the size can be much smaller than those of a 500-W converter.

DC bias effect on alternating current electrical conductivity of poly(ethylene terephthalate)/alumina nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nikam, Pravin N., E-mail: pravinya26@gmail.com; Deshpande, Vineeta D., E-mail: drdeshpandevd@gmail.com

Polymer nanocomposites based on metal oxide (ceramic) nanoparticles are a new class of materials with unique properties and designed for various applications such as electronic device packaging, insulation, fabrication and automotive industries. Poly(ethylene terephthalate) (PET)/alumina (Al{sub 2}O{sub 3}) nanocomposites with filler content between 1 wt% and 5 wt% were prepared by melt compounding method using co-rotating twin screw extruder and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and precision LCR meter techniques. The results revealed that proper uniform dispersion at lower content up to 2 wt% of nano-alumina observed by using TEM. Aggregation of nanoparticles was observedmore » at higher content of alumina examined by using SEM and TEM. The frequency dependences of the alternating current (AC) conductivity (σ{sub AC}) of PET/alumina nanocomposites on the filler content and DC bias were investigated in the frequency range of 20Hz - 1MHz. The results showed that the AC and direct current (DC) conductivity increases with increasing DC bias and nano-alumina content upto 3 wt%. It follows the Jonscher’s universal power law of solids. It revealed that σ{sub AC} of PET/alumina nanocomposites can be well characterized by the DC conductivity (σ{sub DC}), critical frequency (ω{sub c}), critical exponent of the power law (s). Roll of DC bias potential led to an increase of DC conductivity (σ{sub DC}) due to the creation of additional conducting paths with the polymer nanocomposites and percolation behavior achieved through co-continuous morphology.« less

Bidirectional DC/DC Converter

NASA Astrophysics Data System (ADS)

Pedersen, F.

2008-09-01

The presented bidirectional DC/DC converter design concept is a further development of an already existing converter used for low battery voltage operation.For low battery voltage operation a high efficient low parts count DC/DC converter was developed, and used in a satellite for the battery charge and battery discharge function.The converter consists in a bidirectional, non regulating DC/DC converter connected to a discharge regulating Buck converter and a charge regulating Buck converter.The Bidirectional non regulating DC/DC converter performs with relatively high efficiency even at relatively high currents, which here means up to 35Amps.This performance was obtained through the use of power MOSFET's with on- resistances of only a few mille Ohms connected to a special transformer allowing paralleling several transistor stages on the low voltage side of the transformer. The design is patent protected. Synchronous rectification leads to high efficiency at the low battery voltages considered, which was in the range 2,7- 4,3 Volt DC.The converter performs with low switching losses as zero voltage zero current switching is implemented in all switching positions of the converter.Now, the drive power needed, to switch a relatively large number of low Ohm , hence high drive capacitance, power MOSFET's using conventional drive techniques would limit the overall conversion efficiency.Therefore a resonant drive consuming considerable less power than a conventional drive circuit was implemented in the converter.To the originally built and patent protected bidirectional non regulating DC/DC converter, is added the functionality of regulation.Hereby the need for additional converter stages in form of a Charge Buck regulator and a Discharge Buck regulator is eliminated.The bidirectional DC/DC converter can be used in connection with batteries, motors, etc, where the bidirectional feature, simple design and high performance may be useful.

77 FR 31341 - Application To Export Electric Energy; DC Energy, LLC

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-25

... energy from the United States to Canada as a power marketer for a five-year term. The current export... DC Energy. The application also indicates that DC Energy is a power marketer authorized by the...

Pump-Probe Noise Spectroscopy of Molecular Junctions.

PubMed

Ochoa, Maicol A; Selzer, Yoram; Peskin, Uri; Galperin, Michael

2015-02-05

The slow response of electronic components in junctions limits the direct applicability of pump-probe type spectroscopy in assessing the intramolecular dynamics. Recently the possibility of getting information on a sub-picosecond time scale from dc current measurements was proposed. We revisit the idea of picosecond resolution by pump-probe spectroscopy from dc measurements and show that any intramolecular dynamics not directly related to charge transfer in the current direction is missed by current measurements. We propose a pump-probe dc shot noise spectroscopy as a suitable alternative. Numerical examples of time-dependent and average responses of junctions are presented for generic models.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yalong; Jones, Edward A.; Wang, Fred

Arm inductor in a modular multilevel converter (MMC) is used to limit the circulating current and dc short circuit fault current. The circulating current in MMC is dominated by second-order harmonic, which can be largely reduced with circulating current suppressing control. By analyzing the mechanism of the circulating current suppressing control, it is found that the circulating current at switching frequency becomes the main harmonic when suppression control is implemented. Unlike the second-order harmonic that circulates only within the three phases, switching frequency harmonic also flows through the dc side and may further cause high-frequency dc voltage harmonic. This articlemore » develops the theoretical relationship between the arm inductance and switching frequency circulating current, which can be used to guide the arm inductance selection. The experimental results with a downscaled MMC prototype verify the existence of the switching frequency circulating current and its relationship with arm inductance.« less

21 CFR 82.1255 - D&C Orange No. 5.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 1 2010-04-01 2010-04-01 false D&C Orange No. 5. 82.1255 Section 82.1255 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF CERTIFIED...) The color additive D&C Orange No. 5. may be safely used for coloring externally applied drugs in...

21 CFR 82.1255 - D&C Orange No. 5.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 1 2011-04-01 2011-04-01 false D&C Orange No. 5. 82.1255 Section 82.1255 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF CERTIFIED...) The color additive D&C Orange No. 5. may be safely used for coloring externally applied drugs in...

DC Potentials Applied to an End-cap Electrode of a 3-D Ion Trap for Enhanced MSn Functionality

PubMed Central

Prentice, Boone M.; Xu, Wei; Ouyang, Zheng; McLuckey, Scott A.

2010-01-01

The effects of the application of various DC magnitudes and polarities to an end-cap of a 3-D quadrupole ion trap throughout a mass spectrometry experiment were investigated. Application of a monopolar DC field was achieved by applying a DC potential to the exit end-cap electrode, while maintaining the entrance end-cap electrode at ground potential. Control over the monopolar DC magnitude and polarity during time periods associated with ion accumulation, mass analysis, ion isolation, ion/ion reaction, and ion activation can have various desirable effects. Included amongst these are increased ion capture efficiency, increased ion ejection efficiency during mass analysis, effective isolation of ions using lower AC resonance ejection amplitudes, improved temporal control of the overlap of oppositely charged ion populations, and the performance of “broad-band” collision induced dissociation (CID). These results suggest general means to improve the performance of the 3-D ion trap in a variety of mass spectrometry and tandem mass spectrometry experiments. PMID:21927573

Experimental Investigation of DC-Bias Related Core Losses in a Boost Inductor (Postprint)

DTIC Science & Technology

2014-08-01

dc bias-flux conditions. These dc bias conditions result in distorted hysteresis loops , increased core losses, and have been shown to be independent...These dc bias conditions result in dis- torted hysteresis loops , increased core losses, and have been shown to be independent of core material. The...controllable converter load currents, this topology is ideal to study dc-related losses. Inductor core hysteresis loop characterization was accomplished

A complete dc characterization of a constant-frequency, clamped-mode, series-resonant converter

NASA Technical Reports Server (NTRS)

Tsai, Fu-Sheng; Lee, Fred C.

1988-01-01

The dc behavior of a clamped-mode series-resonant converter is characterized systematically. Given a circuit operating condition, the converter's mode of operation is determined and various circuit parameters are calculated, such as average inductor current (load current), rms inductor current, peak capacitor voltage, rms switch currents, average diode currents, switch turn-on currents, and switch turn-off currents. Regions of operation are defined, and various circuit characteristics are derived to facilitate the converter design.

The Rated Voltage Determination of DC Building Power Supply System Considering Human Beings Safety

NASA Astrophysics Data System (ADS)

Wang, Zhicheng; Yu, Kansheng; Xie, Guoqiang; Zou, Jin

2018-01-01

Generally two-level voltages are adopted for DC building power supply system. From the point of view of human beings safety, only the lower level voltage which may be contacted barehanded is discussed in this paper based on the related safety thresholds of human beings current effect. For several voltage levels below 100V recommended by IEC, the body current and current density of human electric shock under device normal work condition, as well as effect of unidirectional single impulse currents of short durations are calculated and analyzed respectively. Finally, DC 60V is recommended as the lower level rating voltage through the comprehensive consideration of technical condition and cost of safety criteria.

Influence of TiN coating and hydrogen glow discharge treatments on the conditioning of a direct current separator made of aluminum alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Momose, T.; Ishimaru, H.

1986-03-01

The effects of hydrogen glow discharges and TiN coatings on the condit ng of a dc separator for the TRISTAN electron-positron collider were studi ed. In order to determine if high-voltage operation is possible, we teste d whether the conditioning time could be shortened if the TiN coating was applied to the separator cathode or if the entire assembly were treated in a hydrogen glow discharge. (AIP)

Modeling and analysis of fractional order DC-DC converter.

PubMed

Radwan, Ahmed G; Emira, Ahmed A; AbdelAty, Amr M; Azar, Ahmad Taher

2017-07-11

Due to the non-idealities of commercial inductors, the demand for a better model that accurately describe their dynamic response is elevated. So, the fractional order models of Buck, Boost and Buck-Boost DC-DC converters are presented in this paper. The detailed analysis is made for the two most common modes of converter operation: Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM). Closed form time domain expressions are derived for inductor currents, voltage gain, average current, conduction time and power efficiency where the effect of the fractional order inductor is found to be strongly present. For example, the peak inductor current at steady state increases with decreasing the inductor order. Advanced Design Systems (ADS) circuit simulations are used to verify the derived formulas, where the fractional order inductor is simulated using Valsa Constant Phase Element (CPE) approximation and Generalized Impedance Converter (GIC). Different simulation results are introduced with good matching to the theoretical formulas for the three DC-DC converter topologies under different fractional orders. A comprehensive comparison with the recently published literature is presented to show the advantages and disadvantages of each approach. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Review of the development of multi-terminal HVDC and DC power grid

NASA Astrophysics Data System (ADS)

Chen, Y. X.

2017-11-01

Traditional power equipment, power-grid structures, and operation technology are becoming increasingly powerless with the large-scale renewable energy access to the grid. Thus, we must adopt new technologies, new equipment, and new grid structure to satisfy future requirements in energy patterns. Accordingly, the multiterminal direct current (MTDC) transmission system is receiving increasing attention. This paper starts with a brief description of current developments in MTDC worldwide. The MTDC project, which has been placed into practical operation, is introduced by the Italian-Corsica-Sardinian three-terminal high-voltage DC (HVDC) project. We then describe the basic characteristics and regulations of multiterminal DC transmission. The current mainstream of several control methods are described. In the third chapter, the key to the development of MTDC system or hardware and software technology that restricts the development of multiterminal DC transmission is discussed. This chapter focuses on the comparison of double-ended HVDC and multiterminal HVDC in most aspects and subsequently elaborates the key and difficult point of MTDC development. Finally, this paper summarizes the prospect of a DC power grid. In a few decades, China can build a strong cross-strait AC-DC hybrid power grid.

DEFINED CONTRIBUTION PLANS, DEFINED BENEFIT PLANS, AND THE ACCUMULATION OF RETIREMENT WEALTH

PubMed Central

Poterba, James; Rauh, Joshua; Venti, Steven; Wise, David

2010-01-01

The private pension structure in the United States, once dominated by defined benefit (DB) plans, is currently divided between defined contribution (DC) and DB plans. Wealth accumulation in DC plans depends on the participant's contribution behavior and on financial market returns, while accumulation in DB plans is sensitive to a participant's labor market experience and to plan parameters. This paper simulates the distribution of retirement wealth under representative DB and DC plans. It uses data from the Health and Retirement Study (HRS) to explore how asset returns, earnings histories, and retirement plan characteristics contribute to the variation in retirement wealth outcomes. We simulate DC plan accumulation by randomly assigning individuals a share of wages that they and their employer contribute to the plan. We consider several possible asset allocation strategies, with asset returns drawn from the historical return distribution. Our DB plan simulations draw earnings histories from the HRS, and randomly assign each individual a pension plan drawn from a sample of large private and public defined benefit plans. The simulations yield distributions of both DC and DB wealth at retirement. Average retirement wealth accruals under current DC plans exceed average accruals under private sector DB plans, although DC plans are also more likely to generate very low retirement wealth outcomes. The comparison of current DC plans with more generous public sector DB plans is less definitive, because public sector DB plans are more generous on average than their private sector counterparts. PMID:21057597

Construction and evaluation of photovoltaic power generation and power storage system using SiC field-effect transistor inverter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oku, Takeo, E-mail: oku@mat.usp.ac.jp; Matsumoto, Taisuke; Ohishi, Yuya

A power storage system using spherical silicon (Si) solar cells, maximum power point tracking charge controller, lithium-ion battery and a direct current-alternating current (DC-AC) inverter was constructed. Performance evaluation of the DC-AC inverter was carried out, and the DC-AC conversion efficiencies of the SiC field-effect transistor (FET) inverter was improved compared with those of the ordinary Si-FET based inverter.

Alternating current long range alpha particle detector

DOEpatents

MacArthur, Duncan W.; McAtee, James L.

1993-01-01

An alpha particle detector, utilizing alternating currents, whcih is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

Alternating current long range alpha particle detector

DOEpatents

MacArthur, D.W.; McAtee, J.L.

1993-02-16

An alpha particle detector, utilizing alternating currents, which is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

Design of conduction cooling system for a high current HTS DC reactor

NASA Astrophysics Data System (ADS)

Dao, Van Quan; Kim, Taekue; Le Tat, Thang; Sung, Haejin; Choi, Jongho; Kim, Kwangmin; Hwang, Chul-Sang; Park, Minwon; Yu, In-Keun

2017-07-01

A DC reactor using a high temperature superconducting (HTS) magnet reduces the reactor’s size, weight, flux leakage, and electrical losses. An HTS magnet needs cryogenic cooling to achieve and maintain its superconducting state. There are two methods for doing this: one is pool boiling and the other is conduction cooling. The conduction cooling method is more effective than the pool boiling method in terms of smaller size and lighter weight. This paper discusses a design of conduction cooling system for a high current, high temperature superconducting DC reactor. Dimensions of the conduction cooling system parts including HTS magnets, bobbin structures, current leads, support bars, and thermal exchangers were calculated and drawn using a 3D CAD program. A finite element method model was built for determining the optimal design parameters and analyzing the thermo-mechanical characteristics. The operating current and inductance of the reactor magnet were 1,500 A, 400 mH, respectively. The thermal load of the HTS DC reactor was analyzed for determining the cooling capacity of the cryo-cooler. The study results can be effectively utilized for the design and fabrication of a commercial HTS DC reactor.

Distinguishing between deep trapping transients of electrons and holes in TiO2 nanotube arrays using planar microwave resonator sensor.

PubMed

Zarifi, Mohammad H; Wiltshire, Benjamin Daniel; Mahdi, Najia; Shankar, Karthik; Daneshmand, Mojgan

2018-05-16

A large signal DC bias and a small signal microwave bias were simultaneously applied to TiO2 nanotube membranes mounted on a planar microwave resonator. The DC bias modulated the electron concentration in the TiO2 nanotubes, and was varied between 0 and 120 V in this study. Transients immediately following the application and removal of DC bias were measured by monitoring the S-parameters of the resonator as a function of time. The DC bias stimulated Poole-Frenkel type trap-mediated electrical injection of excess carriers into TiO2 nanotubes which resulted in a near constant resonant frequency but a pronounced decrease in the microwave amplitude due to free electron absorption. When ultraviolet illumination and DC bias were both present and then step-wise removed, the resonant frequency shifted due to trapping -mediated change in the dielectric constant of the nanotube membranes. Characteristic lifetimes of 60-80 s, 300-800 s and ~3000 s were present regardless of whether light or bias was applied and are also observed in the presence of a hole scavenger, which we attribute to oxygen adsorption and deep electron traps while another characteristic lifetime > 9000 s was only present when illumination was applied, and is attributed to the presence of hole traps.

Research on design feasibility of high-power light-weight dc-to-dc converters for space power applications

NASA Technical Reports Server (NTRS)

Wilson, T. G.

1981-01-01

Utilizing knowledge gained from past experience with experimental current-or-voltage step-up dc-to-dc converter power stages operating at output powers up to and in excess of 2 kW, a new experimental current-or-voltage step-up power stage using paralleled bipolar junction transistors (BJTs) as the controlled power switch, was constructed during the current reporting period. The major motivation behind the construction of this new experimental power stage was to improve the circuit layout so as to reduce the effects of stray circuit parasitic inductances resulting from excess circuit lead lengths and circuit loops, and to take advantage of the layout improvements which could be made when some recently-available power components, particularly power diodes and polypropylene filter capacitors, were incorporated into the design.

DC Rocks! Using Place-Based Learning to Introduce Washington DC's K-12 Students to the Geosciences

NASA Astrophysics Data System (ADS)

Mayberry, G. C.; Mattietti, G. K.

2017-12-01

The Washington DC area has interesting geology and a multitude of agencies that deal with the geosciences, yet K-12 public school students in DC, most of whom are minorities, have limited exposure to the geosciences. Geoscience agencies in the DC area have a unique opportunity to address this by introducing the geosciences to local students who otherwise may not have such an opportunity, by highlighting the geology in the students' "backyard," and by leveraging partnerships among DC-based geoscience-related agencies. The USGS and George Mason University are developing a project called DC Rocks, which will give DC's students an exciting introduction into the world of geoscience with place-based learning opportunities that will make geoscience relevant to their lives and their futures. Both the need in DC and the potential for lasting impact are great; the geosciences have the lowest racial diversity of all the science, technology, engineering, and math (STEM) fields, 89% of students in DC public schools are minorities, and there is no dedicated geoscience curriculum in DC. DC Rocks aims to give these students early exposure to the earth sciences, and encourage them to consider careers in the profession. DC Rocks will work with partner agencies to apply several methods that are recommended by researchers to increase the participation of minority students in the geosciences, including providing profoundly positive experiences that spark interest in the geosciences (Levine et al., 2007); increasing students' sense of belonging in the geosciences (Huntoon, et al, 2016); and place-based teaching practices that emphasize the study of local sites (Semken, 2005), such as DC's Rock Creek Park. DC Rocks will apply these methods by coordinating local geoscientists and resources to provide real-world examples of the geosciences' impact on students' lives. Through the DC Rocks website, educators will be able to request geoscience-related resources such as class presentations by local scientists and curricula, and students will be able to access information about geoscience-related opportunities in DC such as field trips. DC Rocks has the potential to encourage minority students to consider higher education in the geosciences by exposing them to the field early on and ultimately these students may pursue geoscience careers.

A Study of 4-level DC-DC Boost Inverter with Passive Component Reduction Consideration

NASA Astrophysics Data System (ADS)

Kasiran, A. N.; Ponniran, A.; Harimon, M. A.; Hamzah, H. H.

2018-04-01

This study is to analyze design principles of boost inductor and capacitor used in the 4-level DC-DC boost converter to realize size reduction of passive component referring to their attributes. The important feature of this circuit is that most of the boost-up energy is transferred from the capacitor-clamped to the output side which the small inductance can be used at the input side. The inductance of the boost inductor is designed by referring the inductor current ripple. On the other hand, the capacitance of the capacitor-clamped is designed by considering voltage stress on semiconductor devices and also the used switching frequency. Besides that, according to the design specifications, the required inductance in 4-level DC-DC boost converter is decreased compared to a conventional conventional DC-DC boost converter. Meanwhile, voltage stress on semiconductor device is depending on the maximum voltage ripple of the capacitor-clamped. A 50 W 4-level DC-DC boost converter prototype has been constructed. The results show that the inductor current ripple was 1.15 A when the inductors, 1 mH and 0.11 mH were used in the conventional and 4-level DC-DC boost converters, respectively. Thus, based on the experimental results, it shows that the reduction of passive components by referring to their attributes in 4-level DC-DC boost converter is achieved. Moreover, the decreasing of voltage stress on the semiconductor devices is an advantage for the selection of low ON-resistance of the devices which will contribute to the reduction of the semiconductor conduction loss. The integration result of boost converter and H-bridge inverter is also shown.

Spontaneous Analogy by Piggybacking on a Perceptual System

DTIC Science & Technology

2013-08-01

1992). High-level Perception, Representation, and Analogy: A Critique of Artificial Intelligence Methodology. J. Exp. Theor. Artif . Intell., 4(3...nrl.navy.mil David W. Aha Navy Center for Applied Research in Artificial Intelligence Naval Research Laboratory (Code 5510); Washington, DC 20375 david.aha...Research Laboratory,Center for Applied Research in Artificial Intelligence (Code 5510),4555 Overlook Ave., SW,Washington,DC,20375 8. PERFORMING ORGANIZATION

Informational model verification of ZVS Buck quasi-resonant DC-DC converter

NASA Astrophysics Data System (ADS)

Vakovsky, Dimiter; Hinov, Nikolay

2016-12-01

The aim of the paper is to create a polymorphic informational model of a ZVS Buck quasi-resonant DC-DC converter for the modeling purposes of the object. For the creation of the model is applied flexible open standards for setting, storing, publishing and exchange of data in distributed information environment. The created model is useful for creation of many and different by type variants with different configuration of the composing elements and different inner model of the examined object.

Amplification of Genomic DNA for Decoy Receptor 3 Predicts Post-Resection Disease Recurrence in Breast Cancer Patients.

PubMed

Kanbayashi, Chizuko; Koyama, Yu; Ichikawa, Hiroshi; Sakata, Eiko; Hasegawa, Miki; Toshikawa, Chie; Manba, Naoko; Ikarashi, Mayuko; Kobayashi, Takashi; Minagawa, Masahiro; Kosugi, Shin-Ichi; Wakai, Toshifumi

2014-02-01

Decoy receptor 3 (DcR3), a member of the tumor necrosis factor receptor (TNFR) superfamily, shows inhibitory effects on Fas-mediated apoptosis. Currently, data are lacking on the correlation between DcR3 and the recurrence of breast cancer. The authors examined DcR3 mRNA expression and genomic amplification in breast cancer, and investigated the effect of DcR3 gene amplification on prognosis of patients. A total of 95 patients formed the basis of the current retrospective study. DcR3 mRNA expression in breast cancer tissues was examined by RNase protection assay and in situ hybridization. DcR3 gene amplification was examined by quantitative polymerase chain reaction. The correlation between DcR3 gene amplification status and clinicopathological factors was examined and also the relationship between DcR3-Amp and relapse and survival. The relative copy numbers of DcR3 genomic DNA correlated significantly with the levels of DcR3 mRNA expression (ρ = 0.755, P = 0.0067). In addition, lymphatic invasion correlated significantly with DcR3 gene amplification (P = 0.012). However, there was no correlation between the remaining clinicopathological factors and DcR3 gene amplification. In the univariate analysis, the recurrence-free survival (RFS) rate of patients who were positive for DcR3 gene amplification was significantly lower than that of patients who were negative for DcR3 gene amplification (P = 0.0271). Multivariate analysis showed that DcR3 gene amplification (P = 0.028) and disease stage (P < 0.001) remained significant independent predictors of RFS. DcR3 gene amplification was significantly correlated with lymphatic invasion, and also DcR3 gene amplification predicts recurrence after resection, which may be an important prognostic factor in breast cancer patients.

Apparatuses and method for converting electromagnetic radiation to direct current

DOEpatents

Kotter, Dale K; Novack, Steven D

2014-09-30

An energy conversion device may include a first antenna and a second antenna configured to generate an AC current responsive to incident radiation, at least one stripline, and a rectifier coupled with the at least one stripline along a length of the at least one stripline. An energy conversion device may also include an array of nanoantennas configured to generate an AC current in response to receiving incident radiation. Each nanoantenna of the array includes a pair of resonant elements, and a shared rectifier operably coupled to the pair of resonant elements, the shared rectifier configured to convert the AC current to a DC current. The energy conversion device may further include a bus structure operably coupled with the array of nanoantennas and configured to receive the DC current from the array of nanoantennas and transmit the DC current away from the array of nanoantennas.

Dendritic cells for active immunotherapy: optimizing design and manufacture in order to develop commercially and clinically viable products.

PubMed

Nicolette, C A; Healey, D; Tcherepanova, I; Whelton, P; Monesmith, T; Coombs, L; Finke, L H; Whiteside, T; Miesowicz, F

2007-09-27

Dendritic cell (DC) active immunotherapy is potentially efficacious in a broad array of malignant disease settings. However, challenges remain in optimizing DC-based therapy for maximum clinical efficacy within manufacturing processes that permit quality control and scale-up of consistent products. In this review we discuss the critical issues that must be addressed in order to optimize DC-based product design and manufacture, and highlight the DC based platforms currently addressing these issues. Variables in DC-based product design include the type of antigenic payload used, DC maturation steps and activation processes, and functional assays. Issues to consider in development include: (a) minimizing the invasiveness of patient biological material collection; (b) minimizing handling and manipulations of tissue at the clinical site; (c) centralized product manufacturing and standardized processing and capacity for commercial-scale production; (d) rapid product release turnaround time; (e) the ability to manufacture sufficient product from limited starting material; and (f) standardized release criteria for DC phenotype and function. Improvements in the design and manufacture of DC products have resulted in a handful of promising leads currently in clinical development.

Electronics and Software Engineer for Robotics Project Intern

NASA Technical Reports Server (NTRS)

Teijeiro, Antonio

2017-01-01

I was assigned to mentor high school students for the 2017 First Robotics Competition. Using a team based approach, I worked with the students to program the robot and applied my electrical background to build the robot from start to finish. I worked with students who had an interest in electrical engineering to teach them about voltage, current, pulse width modulation, solenoids, electromagnets, relays, DC motors, DC motor controllers, crimping and soldering electrical components, Java programming, and robotic simulation. For the simulation, we worked together to generate graphics files, write simulator description format code, operate Linux, and operate SOLIDWORKS. Upon completion of the FRC season, I transitioned over to providing full time support for the LCS hardware team. During this phase of my internship I helped my co-intern write test steps for two networking hardware DVTs , as well as run cables and update cable running lists.

The vacuum ultraviolet spectrum of krypton and xenon excimers excited in a cooled dc discharge

NASA Astrophysics Data System (ADS)

Gerasimov, G.; Krylov, B.; Loginov, A.; Zvereva, G.; Hallin, R.; Arnesen, A.; Heijkenskjöld, F.

1998-01-01

We present results of an experimental and theoretical study of the VUV spectra of krypton and xenon excimers excited by a dc discharge in a capillary tube cooled by liquid nitrogen. The studied spectral regions of 115-170 nm and 140-195 nm for krypton and xenon respectively correspond to transitions between the lowest excited dimer states 1u, 0u+ and the weakly bound ground state 0g+. A semiempirical method was suggested and applied to describe the experimental spectra and to estimate the temperature of the radiating plasma volume. Electron impact, transferring dimers from the ground state to the excited states, is shown to be an efficient excitation mechanism in the 100-850 hPa and the 10-50 mA pressure and discharge current ranges. The spectra obtained as well as the results of calculations corroborate the high rate of this mechanism.

Power Strategy in DC/DC Converters to Increase Efficiency of Electrical Stimulators.

PubMed

Aqueveque, Pablo; Acuña, Vicente; Saavedra, Francisco; Debelle, Adrien; Lonys, Laurent; Julémont, Nicolas; Huberland, François; Godfraind, Carmen; Nonclercq, Antoine

2016-06-13

Power efficiency is critical for electrical stimulators. Battery life of wearable stimulators and wireless power transmission in implanted systems are common limiting factors. Boost DC/DC converters are typically needed to increase the supply voltage of the output stage. Traditionally, boost DC/DC converters are used with fast control to regulate the supply voltage of the output. However, since stimulators are acting as current sources, such voltage regulation is not needed. Banking on this, this paper presents a DC/DC conversion strategy aiming to increase power efficiency. It compares, in terms of efficiency, the traditional use of boost converters to two alternatives that could be implemented in future hardware designs.

Cirrus Dopant Nano-Composite Coatings

DTIC Science & Technology

2014-11-01

100 200 300 400 500 600 HARDNESS (HV) MICROHARDNESS - ELECTROPLATED NICKEL STANDARD DC PLATED DOPED DC PLATED DOPED PULSE PLATED ↑48% 10...STANDARD COATING HARDNESS (HV) DOPED COATING MICROHARDNESS - ELECTROPLATED ZN NI ↑32% DC ZnNi Cirrus ZnNi Current Test Applications cirrus nano

Electromigration failures under bidirectional current stress

NASA Astrophysics Data System (ADS)

Tao, Jiang; Cheung, Nathan W.; Hu, Chenming

1998-01-01

Electromigration failure under DC stress has been studied for more than 30 years, and the methodologies for accelerated DC testing and design rules have been well established in the IC industry. However, the electromigration behavior and design rules under time-varying current stress are still unclear. In CMOS circuits, as many interconnects carry pulsed-DC (local VCC and VSS lines) and bidirectional AC current (clock and signal lines), it is essential to assess the reliability of metallization systems under these conditions. Failure mechanisms of different metallization systems (Al-Si, Al-Cu, Cu, TiN/Al-alloy/TiN, etc.) and different metallization structures (via, plug and interconnect) under AC current stress in a wide frequency range (from mHz to 500 MHz) has been study in this paper. Based on these experimental results, a damage healing model is developed, and electromigration design rules are proposed. It shows that in the circuit operating frequency range, the "design-rule current" is the time-average current. The pure AC component of the current only contributes to self-heating, while the average (DC component) current contributes to electromigration. To ensure longer thermal-migration lifetime under high frequency AC stress, an additional design rule is proposed to limit the temperature rise due to self-joule heating.

DC currents collected by a RF biased electrode quasi-parallel to the magnetic field

NASA Astrophysics Data System (ADS)

Faudot, E.; Devaux, S.; Moritz, J.; Bobkov, V.; Heuraux, S.

2017-10-01

Local plasma biasings due to RF sheaths close to ICRF antennas result mainly in a negative DC current collection on the antenna structure. In some specific cases, we may observe positive currents when the ion mobility (seen from the collecting surface) overcomes the electron one or/and when the collecting surface on the antenna side becomes larger than the other end of the flux tube connected to the wall. The typical configuration is when the antenna surface is almost parallel to the magnetic field lines and the other side perpendicular. To test the optimal case where the magnetic field is quasi-parallel to the electrode surface, one needs a linear magnetic configuration as our magnetized RF discharge experiment called Aline. The magnetic field angle is in our case lower than 1 relative to the RF biased surface. The DC current flowing through the discharge has been measured as a function of the magnetic field strength, neutral gas (He) pressure and RF power. The main result is the reversal of the DC current depending on the magnetic field, collision frequency and RF power level.

High sensitivity measurement system for the direct-current, capacitance-voltage, and gate-drain low frequency noise characterization of field effect transistors.

PubMed

Giusi, G; Giordano, O; Scandurra, G; Rapisarda, M; Calvi, S; Ciofi, C

2016-04-01

Measurements of current fluctuations originating in electron devices have been largely used to understand the electrical properties of materials and ultimate device performances. In this work, we propose a high-sensitivity measurement setup topology suitable for the automatic and programmable Direct-Current (DC), Capacitance-Voltage (CV), and gate-drain low frequency noise characterization of field effect transistors at wafer level. Automatic and programmable operation is particularly useful when the device characteristics relax or degrade with time due to optical, bias, or temperature stress. The noise sensitivity of the proposed topology is in the order of fA/Hz(1/2), while DC performances are limited only by the source and measurement units used to bias the device under test. DC, CV, and NOISE measurements, down to 1 pA of DC gate and drain bias currents, in organic thin film transistors are reported to demonstrate system operation and performances.

Input current shaped ac-to-dc converters

NASA Technical Reports Server (NTRS)

1985-01-01

Input current shaping techniques for ac-to-dc converters were investigated. Input frequencies much higher than normal, up to 20 kHz were emphasized. Several methods of shaping the input current waveform in ac-to-dc converters were reviewed. The simplest method is the LC filter following the rectifier. The next simplest method is the resistor emulation approach in which the inductor size is determined by the converter switching frequency and not by the line input frequency. Other methods require complicated switch drive algorithms to construct the input current waveshape. For a high-frequency line input, on the order of 20 kHz, the simple LC cannot be discarded so peremptorily, since the inductor size can be compared with that for the resistor emulation method. In fact, since a dc regulator will normally be required after the filter anyway, the total component count is almost the same as for the resistor emulation method, in which the filter is effectively incorporated into the regulator.

DC current induced metal-insulator transition in epitaxial Sm{sub 0.6}Nd{sub 0.4}NiO{sub 3}/LaAlO{sub 3} thin film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Haoliang; CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026; Luo, Zhenlin, E-mail: zlluo@ustc.edu.cn

2014-05-15

The metal-insulator transition (MIT) in strong correlated electron materials can be induced by external perturbation in forms of thermal, electrical, optical, or magnetic fields. We report on the DC current induced MIT in epitaxial Sm{sub 0.6}Nd{sub 0.4}NiO{sub 3} (SNNO) thin film deposited by pulsed laser deposition on (001)-LaAlO{sub 3} substrate. It was found that the MIT in SNNO film not only can be triggered by thermal, but also can be induced by DC current. The T{sub MI} of SNNO film decreases from 282 K to 200 K with the DC current density increasing from 0.003 × 10{sup 9} A•m{sup −2}more » to 4.9 × 10{sup 9} A•m{sup −2}. Based on the resistivity curves measured at different temperatures, the MIT phase diagram has been successfully constructed.« less

High sensitivity measurement system for the direct-current, capacitance-voltage, and gate-drain low frequency noise characterization of field effect transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giusi, G.; Giordano, O.; Scandurra, G.

Measurements of current fluctuations originating in electron devices have been largely used to understand the electrical properties of materials and ultimate device performances. In this work, we propose a high-sensitivity measurement setup topology suitable for the automatic and programmable Direct-Current (DC), Capacitance-Voltage (CV), and gate-drain low frequency noise characterization of field effect transistors at wafer level. Automatic and programmable operation is particularly useful when the device characteristics relax or degrade with time due to optical, bias, or temperature stress. The noise sensitivity of the proposed topology is in the order of fA/Hz{sup 1/2}, while DC performances are limited only bymore » the source and measurement units used to bias the device under test. DC, CV, and NOISE measurements, down to 1 pA of DC gate and drain bias currents, in organic thin film transistors are reported to demonstrate system operation and performances.« less

Simulation of Space Charge Dynamic in Polyethylene Under DC Continuous Electrical Stress

NASA Astrophysics Data System (ADS)

Boukhari, Hamed; Rogti, Fatiha

2016-10-01

The space charge dynamic plays a very important role in the aging and breakdown of polymeric insulation materials under high voltage. This is due to the intensification of the local electric field and the attendant chemical-mechanical effects in the vicinity around the trapped charge. In this paper, we have investigated the space charge dynamic in low-density polyethylene under high direct-current voltage, which is evaluated by experimental conditions. The evaluation is on the basis of simulation using a bipolar charge transport model consisting of charge injection, transports, trapping, detrapping, and recombination phenomena. The theoretical formulation of the physical problem is based on the Poisson, the continuity, and the transport equations. Numerical results provide temporal and local distributions of the electric field, the space charge density for the different kinds of charges (net charge density, mobile and trapped of electron density, mobile hole density), conduction and displacement current densities, and the external current. The result shows the appearance of the negative packet-like space charge with a large amount of the bulk under the dc electric field of 100 kV/mm, and the induced distortion of the electric field is largely near to the anode, about 39% higher than the initial electric field applied.

Using LDR as Sensing Element for an External Fuzzy Controller Applied in Photovoltaic Pumping Systems with Variable-Speed Drives

PubMed Central

Maranhão, Geraldo Neves De A.; Brito, Alaan Ubaiara; Leal, Anderson Marques; Fonseca, Jéssica Kelly Silva; Macêdo, Wilson Negrão

2015-01-01

In the present paper, a fuzzy controller applied to a Variable-Speed Drive (VSD) for use in Photovoltaic Pumping Systems (PVPS) is proposed. The fuzzy logic system (FLS) used is embedded in a microcontroller and corresponds to a proportional-derivative controller. A Light-Dependent Resistor (LDR) is used to measure, approximately, the irradiance incident on the PV array. Experimental tests are executed using an Arduino board. The experimental results show that the fuzzy controller is capable of operating the system continuously throughout the day and controlling the direct current (DC) voltage level in the VSD with a good performance. PMID:26402688

Direct Current Contamination of Kilohertz Frequency Alternating Current Waveforms

PubMed Central

Franke, Manfred; Bhadra, Niloy; Bhadra, Narendra; Kilgore, Kevin

2014-01-01

Kilohertz Frequency Alternating Current (KHFAC) waveforms are being evaluated in a variety of physiological settings because of their potential to modulate neural activity uniquely when compared to frequencies in the sub-kilohertz range. However, the use of waveforms in this frequency range presents some unique challenges regarding the generator output. In this study we explored the possibility of undesirable contamination of the KHFAC waveforms by direct current (DC). We evaluated current- and voltage-controlled KHFAC waveform generators in configurations that included a capacitive coupling between generator and electrode, a resistive coupling and combinations of capacitive with inductive coupling. Our results demonstrate that both voltage- and current-controlled signal generators can unintentionally add DC-contamination to a KHFAC signal, and that capacitive coupling is not always sufficient to eliminate this contamination. We furthermore demonstrated that high value inductors, placed in parallel with the electrode, can be effective in eliminating DC-contamination irrespective of the type of stimulator, reducing the DC contamination to less than 1 μA. This study highlights the importance of carefully designing the electronic setup used in KHFAC studies and suggests specific testing that should be performed and reported in all studies that assess the neural response to KHFAC waveforms. PMID:24820914

Circulating Current Suppressing Control’s Impact on Arm Inductance Selection for Modular Multilevel Converter

DOE PAGES

Li, Yalong; Jones, Edward A.; Wang, Fred

2016-10-13

Arm inductor in a modular multilevel converter (MMC) is used to limit the circulating current and dc short circuit fault current. The circulating current in MMC is dominated by second-order harmonic, which can be largely reduced with circulating current suppressing control. By analyzing the mechanism of the circulating current suppressing control, it is found that the circulating current at switching frequency becomes the main harmonic when suppression control is implemented. Unlike the second-order harmonic that circulates only within the three phases, switching frequency harmonic also flows through the dc side and may further cause high-frequency dc voltage harmonic. This articlemore » develops the theoretical relationship between the arm inductance and switching frequency circulating current, which can be used to guide the arm inductance selection. The experimental results with a downscaled MMC prototype verify the existence of the switching frequency circulating current and its relationship with arm inductance.« less

Modeling resistive wall modes and disruptive instabilities with M3D-C1

NASA Astrophysics Data System (ADS)

Ferraro, Nm; Jardin, Sc; Pfefferle, D.

2016-10-01

Disruptive instabilities pose a significant challenge to the tokamak approach to magnetic fusion energy, and must be reliably avoided in a successful reactor. These instabilities generally involve rapid, global changes to the magnetic field, and electromagnetic interaction with surrounding conducting structures. Here we apply the extended-MHD code M3D-C1 to calculate the stability and evolution of disruptive modes, including their interaction with external conducting structures. The M3D-C1 model includes the effects of resistivity, equilibrium rotation, and resistive walls of arbitrary thickness, each of which may play important roles in the stability and evolution of disruptive modes. The strong stabilizing effect of rotation on resistive wall modes is explored and compared with analytic theory. The nonlinear evolution of vertical displacement events is also considered, including the evolution of non-axisymmetric instabilities that may arise during the current-quench phase of the disruption. It is found that the non-axisymmetric stability of the plasma during a VDE depends strongly on the thermal history of the plasma. This work is supported by US DOE Grant DE-AC02-09CH11466 and the SciDAC Center for Extended MHD Modeling.

Design and application of electromechanical actuators for deep space missions

NASA Technical Reports Server (NTRS)

Haskew, Tim A.; Wander, John

1993-01-01

The annual report Design and Application of Electromechanical Actuators for Deep Space Missions is presented. The reporting period is 16 Aug. 1992 to 15 Aug. 1993. However, the primary focus will be work performed since submission of our semi-annual progress report in Feb. 1993. Substantial progress was made. We currently feel confident in providing guidelines for motor and control strategy selection in electromechanical actuators to be used in thrust vector control (TVC) applications. A small portion was presented in the semi-annual report. At this point, we have implemented highly detailed simulations of various motor/drive systems. The primary motor candidates were the brushless dc machine, permanent magnet synchronous machine, and the induction machine. The primary control implementations were pulse width modulation and hysteresis current control. Each of the two control strategies were applied to each of the three motor choices. With either pulse width modulation or hysteresis current control, the induction machine was always vector controlled. A standard test position command sequence for system performance evaluation is defined. Currently, we are gathering all of the necessary data for formal presentation of the results. Briefly stated for TVC application, we feel that the brushless dc machine operating under PWM current control is the best option. Substantial details on the topic, with supporting simulation results, will be provided later, in the form of a technical paper prepared for submission and also in the next progress report with more detail than allowed for paper publication.

Development, Integration and Testing of Automated Triggering Circuit for Hybrid DC Circuit Breaker

NASA Astrophysics Data System (ADS)

Kanabar, Deven; Roy, Swati; Dodiya, Chiragkumar; Pradhan, Subrata

2017-04-01

A novel concept of Hybrid DC circuit breaker having combination of mechanical switch and static switch provides arc-less current commutation into the dump resistor during quench in superconducting magnet operation. The triggering of mechanical and static switches in Hybrid DC breaker can be automatized which can effectively reduce the overall current commutation time of hybrid DC circuit breaker and make the operation independent of opening time of mechanical switch. With this view, a dedicated control circuit (auto-triggering circuit) has been developed which can decide the timing and pulse duration for mechanical switch as well as static switch from the operating parameters. This circuit has been tested with dummy parameters and thereafter integrated with the actual test set up of hybrid DC circuit breaker. This paper deals with the conceptual design of the auto-triggering circuit, its control logic and operation. The test results of Hybrid DC circuit breaker using this circuit have also been discussed.

Inactivation of Crotalus atrox venom hemorrhagic activity by direct current exposure using hens' egg assay.

PubMed

Calzia, Daniela; Ravera, Silvia; Aluigi, Maria Grazia; Falugi, Carla; Morelli, Alessandro; Panfoli, Isabella

2011-01-01

The hemotoxic venoms of Viperidae and Crotalidae are responsible for most of the evenomations in the United States, West Africa, India, South-East Asia, New Guinea, and Latin America. We previously reported that a short exposure of Crotalus atrox venom to direct electric current (dc) from a low-voltage generator, in solution, causes consistent and irreversible inactivation of venom phospholipase A(2) and metalloproteases. Here we report by in vivo assay on chicken embryos at stage 18 of development according to Hamburger and Hamilton that the hemorrhagic activity of C. atrox venom is lost after exposure to dc (from low voltage). Venom was exposed to dc ranging between 0 and 1 mA. dc values above 0.7 mA abolished hemorrhage. Such in vivo data, showing that dc neutralizes C. atrox venom hemorrhagic activity suggest that a deeper knowledge is needed to understand the relationship among dc and biological matter. Copyright © 2011 Wiley Periodicals, Inc.

[Electrophysiological markers of middle cerebral artery blood flow velocity in healthy subjects].

PubMed

Fokin, V F; Ponomareva, N V; Kuntsevich, G I

2013-01-01

to determine electrophysiological markers of middle cerebral artery blood flow velocity (BFV). transcranial Doppler registration of middle cerebral artery BFV and direct current (DC) potentials recording from surface of head were performed in 30 healthy volunteers. Analysis of correlation between the BFV and DC potentials was used. significant correlation between BFV and DC potential characteristics was observed. The highest correlation was found between BFV in middle cerebral artery and the difference of DC potentials between central and temporal areas of head (r = 0,55; p = 0,003). These areas coincide with the location of middle cerebral artery and the correlation observed may be connected with streaming potential generated by the blood flow in middle cerebral artery. If electrode placement did not coincide with blood current, DC potentials and BFV were not correlated. it is assumed that electrical field created BFV in middle cerebral artery may contribute to the generation of DC potentials registered from the head.

Differences between direct current and alternating current capacitance nonlinearities in high-k dielectrics and their relation to hopping conduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khaldi, O.; Kassmi, M.; El Manar University, LMOP, 2092 Tunis

2014-08-28

Capacitance nonlinearities were studied in atomic layer deposited HfO{sub 2} films using two types of signals: a pure ac voltage of large magnitude (ac nonlinearities) and a small ac voltage superimposed to a large dc voltage (dc nonlinearities). In theory, ac and dc nonlinearities should be of the same order of magnitude. However, in practice, ac nonlinearities are found to be an order of magnitude higher than dc nonlinearities. Besides capacitance nonlinearities, hopping conduction is studied using low-frequency impedance measurements and is discussed through the correlated barrier hopping model. The link between hopping and nonlinearity is established. The ac nonlinearitiesmore » are ascribed to the polarization of isolated defect pairs, while dc nonlinearities are attributed to electrode polarization which originates from defect percolation paths. Both the ac and dc capacitance nonlinearities display an exponential variation with voltage, which results from field-induced lowering of the hopping barrier energy.« less

Transient analysis of an HTS DC power cable with an HVDC system

NASA Astrophysics Data System (ADS)

Dinh, Minh-Chau; Ju, Chang-Hyeon; Kim, Jin-Geun; Park, Minwon; Yu, In-Keun; Yang, Byeongmo

2013-11-01

The operational characteristics of a superconducting DC power cable connected to a highvoltage direct current (HVDC) system are mainly concerned with the HVDC control and protection system. To confirm how the cable operates with the HVDC system, verifications using simulation tools are needed. This paper presents a transient analysis of a high temperature superconducting (HTS) DC power cable in connection with an HVDC system. The study was conducted via the simulation of the HVDC system and a developed model of the HTS DC power cable using a real time digital simulator (RTDS). The simulation was performed with some cases of short circuits that may have caused system damage. The simulation results show that during the faults, the quench did not happen with the HTS DC power cable because the HVDC controller reduced some degree of the fault current. These results could provide useful data for the protection design of a practical HVDC and HTS DC power cable system.

On Application of Model Predictive Control to Power Converter with Switching

NASA Astrophysics Data System (ADS)

Zanma, Tadanao; Fukuta, Junichi; Doki, Shinji; Ishida, Muneaki; Okuma, Shigeru; Matsumoto, Takashi; Nishimori, Eiji

This paper concerns a DC-DC converter control. In DC-DC converters, there exist both continuous components such as inductance, conductance and resistance and discrete ones, IGBT and MOSFET as semiconductor switching elements. Such a system can be regarded as a hybrid dynamical system. Thus, this paper presents a dc-dc control technique based on the model predictive control. Specifically, a case in which the load of the dc-dc converter changes from active to sleep is considered. In the case, a control method which makes the output voltage follow to the reference quickly in transition, and the switching frequency be constant in steady state. In addition, in applying the model predictive control to power electronics circuits, the switching characteristic of the device and the restriction condition for protection are also considered. The effectiveness of the proposed method is illustrated by comparing a conventional method through some simulation results.

Design and manufacture of a D-shape coil-based toroid-type HTS DC reactor using 2nd generation HTS wire

NASA Astrophysics Data System (ADS)

Kim, Kwangmin; Go, Byeong-Soo; Sung, Hae-Jin; Park, Hea-chul; Kim, Seokho; Lee, Sangjin; Jin, Yoon-Su; Oh, Yunsang; Park, Minwon; Yu, In-Keun

2014-09-01

This paper describes the design specifications and performance of a real toroid-type high temperature superconducting (HTS) DC reactor. The HTS DC reactor was designed using 2G HTS wires. The HTS coils of the toroid-type DC reactor magnet were made in the form of a D-shape. The target inductance of the HTS DC reactor was 400 mH. The expected operating temperature was under 20 K. The electromagnetic performance of the toroid-type HTS DC reactor magnet was analyzed using the finite element method program. A conduction cooling method was adopted for reactor magnet cooling. Performances of the toroid-type HTS DC reactor were analyzed through experiments conducted under the steady-state and charge conditions. The fundamental design specifications and the data obtained from this research will be applied to the design of a commercial-type HTS DC reactor.

Detection of High-impedance Arcing Faults in Radial Distribution DC Systems

NASA Technical Reports Server (NTRS)

Gonzalez, Marcelo C.; Button, Robert M.

2003-01-01

High voltage, low current arcing faults in DC power systems have been researched at the NASA Glenn Research Center in order to develop a method for detecting these 'hidden faults', in-situ, before damage to cables and components from localized heating can occur. A simple arc generator was built and high-speed and low-speed monitoring of the voltage and current waveforms, respectively, has shown that these high impedance faults produce a significant increase in high frequency content in the DC bus voltage and low frequency content in the DC system current. Based on these observations, an algorithm was developed using a high-speed data acquisition system that was able to accurately detect high impedance arcing events induced in a single-line system based on the frequency content of the DC bus voltage or the system current. Next, a multi-line, radial distribution system was researched to see if the arc location could be determined through the voltage information when multiple 'detectors' are present in the system. It was shown that a small, passive LC filter was sufficient to reliably isolate the fault to a single line in a multi-line distribution system. Of course, no modification is necessary if only the current information is used to locate the arc. However, data shows that it might be necessary to monitor both the system current and bus voltage to improve the chances of detecting and locating high impedance arcing faults

On the modelling of linear-assisted DC-DC voltage regulators for photovoltaic solar energy systems

NASA Astrophysics Data System (ADS)

Martínez-García, Herminio; García-Vílchez, Encarna

2017-11-01

This paper shows the modelling of linear-assisted or hybrid (linear & switching) DC/DC voltage regulators. In this kind of regulators, an auxiliary linear regulator is used, which objective is to cancel the ripple at the output voltage and provide fast responses for load variations. On the other hand, a switching DC/DC converter, connected in parallel with the linear regulator, allows to supply almost the whole output current demanded by the load. The objective of this topology is to take advantage of the suitable regulation characteristics that series linear voltage regulators have, but almost achieving the high efficiency that switching DC/DC converters provide. Linear-assisted DC/DC regulators are feedback systems with potential instability. Therefore, their modelling is mandatory in order to obtain design guidelines and assure stability of the implemented power supply system.

A 10 kW dc-dc converter using IGBTs with active snubbers. [Insulated Gate Bipolar Transistor

NASA Technical Reports Server (NTRS)

Masserant, Brian J.; Shriver, Jeffrey L.; Stuart, Thomas A.

1993-01-01

This full bridge dc-dc converter employs zero voltage switching (ZVS) on one leg and zero current switching (ZCS) on the other. This technique produces exceptionally low IGBT switching losses through the use of an active snubber that recycles energy back to the source. Experimental results are presented for a 10 kW, 20 kHz converter.

Electro-optically Induced and Manipulated Terahertz Waves from Fe-doped InGaAs Surfaces

NASA Astrophysics Data System (ADS)

Hatem, O.

2018-03-01

We demonstrate the presence of dual simultaneous nonlinear mechanisms: field-induced optical rectification (FIOR) and field-induced surge current (FISC) for the generation of terahertz (THz) pulses from p-type and n-type Fe:In0.53Ga0.47As surfaces upon excitation with femtosecond laser pulses centered at 800 nm wavelength. Experimental investigations of the dependence of the generated THz waves on the incident angular optical polarization, optical irradiance, and the direction and magnitude of applied electric DC fields give confirming results to the proposed THz generation mechanisms. Applying external DC electric fields in the plane of the incident optical field shows efficient capability in manipulating the direction and phase of the generated THz waves, and controlling the refractive index of Fe:In0.53Ga0.47As material in the THz range, in addition to enhancing the emitted THz power up to two orders of magnitude. The fast and reliable response of Fe:In0.53Ga0.47As to the changes in the direction and magnitude of the optical and electrical fields suggests its use in amplitude and phase modulators, and ultrafast optoelectronic systems.

ICRF antenna-plasma interactions and its influence on W sputtering in ASDEX upgrade

NASA Astrophysics Data System (ADS)

ASDEX Upgrade Team Bobkov, Vl.; Braun, F.; Colas, L.; Dux, R.; Faugel, H.; Giannone, L.; Herrmann, A.; Kallenbach, A.; Müller, H. W.; Neu, R.; Noterdaeme, J.-M.; Pütterich, Th.; Siegl, G.; Wolfrum, E.

2011-08-01

Analysis of the W concentration during ICRF over AUG experimental campaigns confirms the critical role of W antenna limiters for the W content in plasma, though other structures connected to antennas along magnetic field lines cannot be neglected as W sources.Abrupt changes of spectroscopically measured W sputtering patterns are observed which correlate with step-wise changes of connection lengths at antenna limiters. Analysis of discharges with the reversed direction of toroidal magnetic field shows less W release compared to identical discharges with the normal direction. The lower W release is accompanied by lower intensity of fluctuations of reflected ICRF power in the 1-60 kHz range. The observations suggest that local magnetic geometry and density convection at the antennas are at least as important for the W sputtering as the distribution of RF near-fields at the antenna.Measurements of DC currents flowing through the antenna limiters show that the limiters at the active antenna collect predominantly negative DC currents whereas those distant from the active antenna collect predominantly positive DC currents. The latter decrease and become more negative when the intensity of the RF pickup measured at the limiters increases. The mutual compensation between the positive and negative currents can lead to lower values of the DC current than those expected from simplified theoretical models of the RF/DC circuit.

ICRF antenna-plasma interactions and its influence on W sputtering in ASDEX upgrade

NASA Astrophysics Data System (ADS)

Bobkov, Vl.; Braun, F.; Colas, L.; Dux, R.; Faugel, H.; Giannone, L.; Herrmann, A.; Kallenbach, A.; Müller, H. W.; Neu, R.; Noterdaeme, J.-M.; Pütterich, Th.; Siegl, G.; Wolfrum, E.; ASDEX Upgrade Team

2011-08-01

Analysis of the W concentration during ICRF over AUG experimental campaigns confirms the critical role of W antenna limiters for the W content in plasma, though other structures connected to antennas along magnetic field lines cannot be neglected as W sources. Abrupt changes of spectroscopically measured W sputtering patterns are observed which correlate with step-wise changes of connection lengths at antenna limiters. Analysis of discharges with the reversed direction of toroidal magnetic field shows less W release compared to identical discharges with the normal direction. The lower W release is accompanied by lower intensity of fluctuations of reflected ICRF power in the 1-60 kHz range. The observations suggest that local magnetic geometry and density convection at the antennas are at least as important for the W sputtering as the distribution of RF near-fields at the antenna. Measurements of DC currents flowing through the antenna limiters show that the limiters at the active antenna collect predominantly negative DC currents whereas those distant from the active antenna collect predominantly positive DC currents. The latter decrease and become more negative when the intensity of the RF pickup measured at the limiters increases. The mutual compensation between the positive and negative currents can lead to lower values of the DC current than those expected from simplified theoretical models of the RF/DC circuit.

Application of Direct Current Atmospheric Pressure Glow Microdischarge Generated in Contact with a Flowing Liquid Solution for Synthesis of Au-Ag Core-Shell Nanoparticles.

PubMed

Dzimitrowicz, Anna; Jamroz, Piotr; Nyk, Marcin; Pohl, Pawel

2016-04-06

A direct current atmospheric pressure glow microdischarge (dc-μAPGD) generated between an Ar nozzle microjet and a flowing liquid was applied to produce Au-Ag core-shell nanoparticles (Au@AgCSNPs) in a continuous flow system. Firstly, operating dc-μAPGD with the flowing solution of the Au(III) ions as the cathode, the Au nanoparticles (AuNPs) core was produced. Next, to produce the core-shell nanostructures, the collected AuNPs solution was immediately mixed with an AgNO₃ solution and passed through the system with the reversed polarity to fabricate the Ag nanoshell on the AuNPs core. The formation of Au@AgCSNPs was confirmed using ultraviolet-visible (UV-Vis) absorbance spectrophotometry, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Three localized surface plasmon resonance absorption bands with wavelengths centered at 372, 546, and 675 nm were observed in the UV-Vis spectrum of Au@AgCSNPs, confirming the reduction of both the Au(III) and Ag(I) ions. The right configuration of metals in Au@AgCSNPs was evidenced by TEM. The Au core diameter was 10.2 ± 2.0 nm, while the thickness of the Ag nanoshell was 5.8 ± 1.8 nm. The elemental composition of the bimetallic nanoparticles was also confirmed by EDS. It is possible to obtain 90 mL of a solution containing Au@AgCSNPs per hour using the applied microdischarge system.

Piezoelectric two-dimensional nanosheets/anionic layer heterojunction for efficient direct current power generation.

PubMed

Kim, Kwon-Ho; Kumar, Brijesh; Lee, Keun Young; Park, Hyun-Kyu; Lee, Ju-Hyuck; Lee, Hyun Hwi; Jun, Hoin; Lee, Dongyun; Kim, Sang-Woo

2013-01-01

Direct current (DC) piezoelectric power generator is promising for the miniaturization of a power package and self-powering of nanorobots and body-implanted devices. Hence, we report the first use of two-dimensional (2D) zinc oxide (ZnO) nanostructure and an anionic nanoclay layer to generate piezoelectric DC output power. The device, made from 2D nanosheets and an anionic nanoclay layer heterojunction, has potential to be the smallest size power package, and could be used to charge wireless nano/micro scale systems without the use of rectifier circuits to convert alternating current into DC to store the generated power. The combined effect of buckling behaviour of the ZnO nanosheets, a self-formed anionic nanoclay layer, and coupled semiconducting and piezoelectric properties of ZnO nanosheets contributes to efficient DC power generation. The networked ZnO nanosheets proved to be structurally stable under huge external mechanical loads.

Periodic direct current does not promote wound closure in an in vitro dynamic model of cell migration.

PubMed

Godbout, Charles; Frenette, Jérôme

2006-01-01

A prevailing paradigm is that electrical fields can promote cell migration and tissue healing. To further validate this paradigm, we tested the hypothesis that periodic direct current (DC) can enhance wound closure using an in vitro dynamic model of cell migration. Layers of primary fibroblasts were wounded and treated with DC under various voltages. Repair area, cell velocity, and directionality as well as lamellipodium area were evaluated at different times. Direct current had no beneficial effect on cell migration. Moreover, prolonged stimulation under the highest voltage led to significant reduction in wound closure and cell velocity. The reduction of membrane protusions in stimulated cells may be associated with the deleterious effect of DC. Contrary to the authors' expectations, they found that periodic DC did not promote wound closure, a finding that emphasizes the need to clarify the complex effects of electrical fields on migrating cells.

Immediate adhesive properties to dentin and enamel of a universal adhesive associated with a hydrophobic resin coat.

PubMed

Perdigão, J; Muñoz, M A; Sezinando, A; Luque-Martinez, I V; Staichak, R; Reis, A; Loguercio, A D

2014-01-01

To evaluate the effect of acid etching and application of a hydrophobic resin coat on the enamel/dentin bond strengths and degree of conversion (DC) within the hybrid layer of a universal adhesive system (G-Bond Plus [GB]). A total of 60 extracted third molars were divided into four groups for bond-strength testing, according to the adhesive strategy: GB applied as a one-step self-etch adhesive (1-stepSE); GB applied as in 1-stepSE followed by one coat of the hydrophobic resin Heliobond (2-stepSE); GB applied as a two-step etch-and-rinse adhesive (2-stepER); GB applied as in 2-stepER followed by one coat of the hydrophobic resin Heliobond (3-stepER). There were 40 teeth used for enamel microshear bond strength (μSBS) and DC; and 20 teeth used for dentin microtensile bond strength (μTBS) and DC. After restorations were constructed, specimens were stored in water (37°C/24 h) and then tested at 0.5 mm/min (μTBS) or 1.0 mm/min (μSBS). Enamel-resin and dentin-resin interfaces from each group were evaluated for DC using micro-Raman spectroscopy. Data were analyzed with two-way analysis of variance for each substrate and the Tukey test (α=0.05). For enamel, the use of a hydrophobic resin coat resulted in statistically significant higher mean enamel μSBS only for the ER strategy (3-stepER vs 2-stepER, p<0.0002). DC was significantly improved for the SE strategy (p<0.00002). For dentin, the use of a hydrophobic resin coat resulted in significantly higher dentin mean μTBS only for the SE strategy (2-stepSE vs 1-stepSE, p<0.0007). DC was significantly improved in groups 2-stepSE and 3-stepER when compared with 1-stepSE and 2-stepER, respectively (p<0.0009). The use of a hydrophobic resin coat may be beneficial for the selective enamel etching technique, because it improves bond strengths to enamel when applied with the ER strategy and to dentin when used with the SE adhesion strategy. The application of a hydrophobic resin coat may improve DC in resin-dentin interfaces formed with either the SE or the ER strategy. On enamel, DC may benefit from the application of a hydrophobic resin coat over 1-stepSE adhesives.

Radiofrequency amplifier based on a dc superconducting quantum interference device

DOEpatents

Hilbert, C.; Martinis, J.M.; Clarke, J.

1984-04-27

A low noise radiofrequency amplifer, using a dc SQUID (superconducting quantum interference device) as the input amplifying element. The dc SQUID and an input coil are maintained at superconductivity temperatures in a superconducting shield, with the input coil inductively coupled to the superconducting ring of the dc SQUID. A radiofrequency signal from outside the shield is applied to the input coil, and an amplified radiofrequency signal is developed across the dc SQUID ring and transmitted to exteriorly of the shield. A power gain of 19.5 +- 0.5 dB has been achieved with a noise temperature of 1.0 +- 0.4 K at a frequency of 100 MHz.

Efficiencies from Applying a Rotational Equipping Strategy

DTIC Science & Technology

2011-01-01

Washington, D.C.: United States Government Accountability Office, 2007. NOTES: BFV = Bradley Fighting Vehicle, HEMTT = heavy expanded mobility tactical...of Its Equipment Reset Strategy, Washington, D.C.: United States Government Accountability Office, 2007. NOTES: BFV = Bradley Fighting Vehicle

An Intelligent Control for the Distributed Flexible Network Photovoltaic System using Autonomous Control and Agent

NASA Astrophysics Data System (ADS)

Park, Sangsoo; Miura, Yushi; Ise, Toshifumi

This paper proposes an intelligent control for the distributed flexible network photovoltaic system using autonomous control and agent. The distributed flexible network photovoltaic system is composed of a secondary battery bank and a number of subsystems which have a solar array, a dc/dc converter and a load. The control mode of dc/dc converter can be selected based on local information by autonomous control. However, if only autonomous control using local information is applied, there are some problems associated with several cases such as voltage drop on long power lines. To overcome these problems, the authors propose introducing agents to improve control characteristics. The autonomous control with agents is called as intelligent control in this paper. The intelligent control scheme that employs the communication between agents is applied for the model system and proved with simulation using PSCAD/EMTDC.

2D modeling of DC potential structures induced by RF sheaths with transverse currents in front of ICRF antenna

NASA Astrophysics Data System (ADS)

Faudot, E.; Heuraux, S.; Colas, L.

2005-09-01

Understanding DC potential generation in front of ICRF antennas is crucial for long pulse high RF power systems. DC potentials are produced by sheath rectification of these RF potentials. To reach this goal, near RF parallel electric fields have to be computed in 3D and integrated along open magnetic field lines to yield a 2D RF potential map in a transverse plane. DC potentials are produced by sheath rectification of these RF potentials. As RF potentials are spatially inhomogeneous, transverse polarization currents are created, modifying RF and DC maps. Such modifications are quantified on a `test map' having initially a Gaussian shape and assuming that the map remains Gaussian near its summit,the time behavior of the peak can be estimated analytically in presence of polarization current as a function of its width r0 and amplitude φ0 (normalized to a characteristic length for transverse transport and to the local temperature). A `peaking factor' is built from the DC peak potential normalized to φ0, and validated with a 2D fluid code and a 2D PIC code (XOOPIC). In an unexpected way transverse currents can increase this factor. Realistic situations of a Tore Supra antenna are also studied, with self-consistent near fields provided by ICANT code. Basic processes will be detailed and an evaluation of the `peaking factor' for ITER will be presented for a given configuration.

2D modeling of DC potential structures induced by RF sheaths with transverse currents in front of ICRF antenna

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faudot, E.; Heuraux, S.; Colas, L.

2005-09-26

Understanding DC potential generation in front of ICRF antennas is crucial for long pulse high RF power systems. DC potentials are produced by sheath rectification of these RF potentials. To reach this goal, near RF parallel electric fields have to be computed in 3D and integrated along open magnetic field lines to yield a 2D RF potential map in a transverse plane. DC potentials are produced by sheath rectification of these RF potentials. As RF potentials are spatially inhomogeneous, transverse polarization currents are created, modifying RF and DC maps. Such modifications are quantified on a 'test map' having initially amore » Gaussian shape and assuming that the map remains Gaussian near its summit,the time behavior of the peak can be estimated analytically in presence of polarization current as a function of its width r0 and amplitude {phi}0 (normalized to a characteristic length for transverse transport and to the local temperature). A 'peaking factor' is built from the DC peak potential normalized to {phi}0, and validated with a 2D fluid code and a 2D PIC code (XOOPIC). In an unexpected way transverse currents can increase this factor. Realistic situations of a Tore Supra antenna are also studied, with self-consistent near fields provided by ICANT code. Basic processes will be detailed and an evaluation of the 'peaking factor' for ITER will be presented for a given configuration.« less

Silicon Carbide Diodes Characterization at High Temperature and Comparison With Silicon Devices

NASA Technical Reports Server (NTRS)

Lebron-Velilla, Ramon C.; Schwarze, Gene E.; Gardner, Brent G.; Adams, Jerry D., Jr.

2004-01-01

Commercially available silicon carbide (SiC) Schottky diodes from different manufacturers rated at 200, 300, 600, and 1200 V, were electrically tested and characterized as a function of temperature up to 300 C. Electrical tests included both steady state and dynamic tests. Steady state tests produced forward and reverse I-V characteristic curves. Transient tests evaluated the switching performance of the diodes in either a hard-switched DC to DC buck converter or a half-bridge boost converter. For evaluation and comparison purposes, the same tests were performed with current state-of-the-art ultra fast silicon (Si) pn-junction diodes of similar ratings and also a Si Schottky diode. The comparisons made were forward voltage drop at rated current, reverse current at rated voltage, and turn-off peak reverse recovery current and reverse recovery time. In addition, efficiency measurements were taken for the buck DC to DC converter using both the SiC Schottky diodes and the Si pn-junction diodes at different temperatures and frequencies. The test results showed that at high temperature, the forward voltage drop for SiC Schottky diodes is higher than the forward drop of the ultra fast Si pn-junction diodes. As the temperature increased, the forward voltage drop of the SiC Schottky increased while for the ultra fast Si pn-junction diodes, the forward voltage drop decreased as temperature increased. For the elevated temperature steady state reverse voltage tests, the SiC Schottky diodes showed low leakage current at their rated voltage. Likewise, for the transient tests, the SiC Schottky diodes displayed low reverse recovery currents over the range of temperatures tested. Conversely, the Si pn-junction diodes showed increasing peak reverse current values and reverse recovery times with increasing temperature. Efficiency measurements in the DC to DC buck converter showed the advantage of the SiC Schottky diodes over the ultra fast Si pn-junction diodes, especially at the higher temperatures and higher frequencies.

Logarithmic circuit with wide dynamic range

NASA Technical Reports Server (NTRS)

Wiley, P. H.; Manus, E. A. (Inventor)

1978-01-01

A circuit deriving an output voltage that is proportional to the logarithm of a dc input voltage susceptible to wide variations in amplitude includes a constant current source which forward biases a diode so that the diode operates in the exponential portion of its voltage versus current characteristic, above its saturation current. The constant current source includes first and second, cascaded feedback, dc operational amplifiers connected in negative feedback circuit. An input terminal of the first amplifier is responsive to the input voltage. A circuit shunting the first amplifier output terminal includes a resistor in series with the diode. The voltage across the resistor is sensed at the input of the second dc operational feedback amplifier. The current flowing through the resistor is proportional to the input voltage over the wide range of variations in amplitude of the input voltage.

Direct current ballast circuit for metal halide lamp

NASA Technical Reports Server (NTRS)

Lutus, P. (Inventor)

1981-01-01

A direct current ballast circuit for a two electrode metal halide lamp is described. Said direct current ballast circuit includes a low voltage DC input and a high frequency power amplifier and power transformer for developing a high voltage output. The output voltage is rectified by diodes and filtered by inductor and capacitor to provide a regulated DC output through commutating diodes to one terminal of the lamp at the output terminal. A feedback path from the output of the filter capacitor through the bias resistor to power the high frequency circuit which includes the power amplifier and the power transformer for sustaining circuit operations during low voltage transients on the input DC supply is described. A current sensor connected to the output of the lamp through terminal for stabilizing lamp current following breakdown of the lamp is described.

On the radiated EMI current extraction of dc transmission line based on corona current statistical measurements

NASA Astrophysics Data System (ADS)

Yi, Yong; Chen, Zhengying; Wang, Liming

2018-05-01

Corona-originated discharge of DC transmission lines is the main reason for the radiated electromagnetic interference (EMI) field in the vicinity of transmission lines. A joint time-frequency analysis technique was proposed to extract the radiated EMI current (excitation current) of DC corona based on corona current statistical measurements. A reduced-scale experimental platform was setup to measure the statistical distributions of current waveform parameters of aluminum conductor steel reinforced. Based on the measured results, the peak value, root-mean-square value and average value with 9 kHz and 200 Hz band-with of 0.5 MHz radiated EMI current were calculated by the technique proposed and validated with conventional excitation function method. Radio interference (RI) was calculated based on the radiated EMI current and a wire-to-plate platform was built for the validity of the RI computation results. The reason for the certain deviation between the computations and measurements was detailed analyzed.

Laser beam apparatus and method for analyzing solar cells

DOEpatents

Staebler, David L.

1980-01-01

A laser beam apparatus and method for analyzing, inter alia, the current versus voltage curve at the point of illumination on a solar cell and the open circuit voltage of a solar cell. The apparatus incorporates a lock-in amplifier, and a laser beam light chopper which permits the measurement of the AC current of the solar cell at an applied DC voltage at the position on the solar cell where the cell is illuminated and a feedback scheme which permits the direct scanning measurements of the open circuit voltage. The accuracy of the measurement is a function of the intensity and wavelength of the laser light with respect to the intensity and wavelength distribution of sunlight and the percentage the dark current is at the open circuit voltage to the short circuit current of the solar cell.

Shapiro spikes and negative mobility for skyrmion motion on quasi-one-dimensional periodic substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reichhardt, Charles; Olson Reichhardt, Cynthia Jane

2017-01-12

Using a simple numerical model of skyrmions in a two-dimensional system interacting with a quasi-one-dimensional periodic substrate under combined dc and ac drives where the dc drive is applied perpendicular to the substrate periodicity, we show that a rich variety of novel phase-locking dynamics can occur due to the influence of the Magnus term on the skyrmion dynamics. Instead of Shapiro steps, the velocity response in the direction of the dc drive exhibits a series of spikes, including extended dc drive intervals over which the skyrmions move in the direction opposite to the dc drive, producing negative mobility. Also, theremore » are specific dc drive values at which the skyrmions move exactly perpendicular to the dc drive direction, giving a condition of absolute transverse mobility.« less

Forback DC-to-DC converter

NASA Technical Reports Server (NTRS)

Lukemire, Alan T. (Inventor)

1995-01-01

A pulse-width modulated DC-to-DC power converter including a first inductor, i.e. a transformer or an equivalent fixed inductor equal to the inductance of the secondary winding of the transformer, coupled across a source of DC input voltage via a transistor switch which is rendered alternately conductive (ON) and nonconductive (OFF) in accordance with a signal from a feedback control circuit is described. A first capacitor capacitively couples one side of the first inductor to a second inductor which is connected to a second capacitor which is coupled to the other side of the first inductor. A circuit load shunts the second capacitor. A semiconductor diode is additionally coupled from a common circuit connection between the first capacitor and the second inductor to the other side of the first inductor. A current sense transformer generating a current feedback signal for the switch control circuit is directly coupled in series with the other side of the first inductor so that the first capacitor, the second inductor and the current sense transformer are connected in series through the first inductor. The inductance values of the first and second inductors, moreover, are made identical. Such a converter topology results in a simultaneous voltsecond balance in the first inductance and ampere-second balance in the current sense transformer.

75 FR 35611 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, and MD-10-10F...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-23

... one-time high frequency eddy current inspection of fastener holes for cracks at the left and right... frequency eddy current inspection of fastener holes for cracks at the left and right side wing rear spar... frequency eddy current inspection for cracking of fastener holes at the left and right side wing rear spar...

75 FR 2831 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, and MD-10-10F...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-19

... proposed AD would require a one-time high frequency eddy current inspection of fastener holes for cracks at... high frequency eddy current inspection of fastener holes for cracking at the left and right side wing... of this AD, do a one-time high frequency eddy current inspection for cracking of fastener holes at...

Five years of full-scale utility demonstration of pulsed energization of electric precipitators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schultz, S.A.; Jacobus, P.L.; Casey, P.J.

1996-11-01

In a conventional electrostatic precipitator (ESP) the applied dc voltage fulfills three functions: (1) generation of negative ions, (2) charging of particles, and (3) transport of the charged particles to the collecting plates. In the case of high resistivity fly-ash (often associated with the burning of low sulfur coal) the dc voltage is limited by repeated electrical discharges and in extreme cases by back-corona. Lowering the applied dc voltage reduces sparking and back-corona, but also reduces the field on the discharge wires and leads to poorly distributed ion generation as well as reduced charging and particle transport forces. Pulsed energization,more » which consists of superimposing high voltage pulses of short duration onto the existing base dc voltage, offers an attractive way to improve the collection efficiency of ESPs suffering from poor energization. The superimposed pulses become responsible for uniform ion generation while the underlying dc field continues to fulfill the function of particle charging and transport. This paper describes the five-year test of the ESP at Madison Gas and Electric`s Blount Station.« less

Equilibrium evolution in oscillating-field current-drive experiments

NASA Astrophysics Data System (ADS)

McCollam, K. J.; Anderson, J. K.; Blair, A. P.; Craig, D.; Den Hartog, D. J.; Ebrahimi, F.; O'Connell, R.; Reusch, J. A.; Sarff, J. S.; Stephens, H. D.; Stone, D. R.; Brower, D. L.; Deng, B. H.; Ding, W. X.

2010-08-01

Oscillating-field current drive (OFCD) is a proposed method of steady-state toroidal plasma sustainment in which ac poloidal and toroidal loop voltages are applied to produce a dc plasma current. OFCD is added to standard, inductively sustained reversed-field pinch plasmas in the Madison Symmetric Torus [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)]. Equilibrium profiles and fluctuations during a single cycle are measured and analyzed for different relative phases between the two OFCD voltages and for OFCD off. For OFCD phases leading to the most added plasma current, the measured energy confinement is slightly better than that for OFCD off. By contrast, the phase of the maximum OFCD helicity-injection rate also has the maximum decay rate, which is ascribed to transport losses during discrete magnetic-fluctuation events induced by OFCD. Resistive-magnetohydrodynamic simulations of the experiments reproduce the observed phase dependence of the added current.

Combining parallel detection of proton echo planar spectroscopic imaging (PEPSI) measurements with a data-consistency constraint improves SNR.

PubMed

Tsai, Shang-Yueh; Hsu, Yi-Cheng; Chu, Ying-Hua; Kuo, Wen-Jui; Lin, Fa-Hsuan

2015-12-01

One major challenge of MRSI is the poor signal-to-noise ratio (SNR), which can be improved by using a surface coil array. Here we propose to exploit the spatial sensitivity of different channels of a coil array to enforce the k-space data consistency (DC) in order to suppress noise and consequently to improve MRSI SNR. MRSI data were collected using a proton echo planar spectroscopic imaging (PEPSI) sequence at 3 T using a 32-channel coil array and were averaged with one, two and eight measurements (avg-1, avg-2 and avg-8). The DC constraint was applied using a regularization parameter λ of 1, 2, 3, 5 or 10. Metabolite concentrations were quantified using LCModel. Our results show that the suppression of noise by applying the DC constraint to PEPSI reconstruction yields up to 32% and 27% SNR gain for avg-1 and avg-2 data with λ = 5, respectively. According to the reported Cramer-Rao lower bounds, the improvement in metabolic fitting was significant (p < 0.01) when the DC constraint was applied with λ ≥ 2. Using the DC constraint with λ = 3 or 5 can minimize both root-mean-square errors and spatial variation for all subjects using the avg-8 data set as reference values. Our results suggest that MRSI reconstructed with a DC constraint can save around 70% of scanning time to obtain images and spectra with similar SNRs using λ = 5. Copyright © 2015 John Wiley & Sons, Ltd.

Microstructural Evolution in Intensively Melt Sheared Direct Chill Cast Al-Alloys

NASA Astrophysics Data System (ADS)

Jones, S.; Rao, A. K. Prasada; Patel, J. B.; Scamans, G. M.; Fan, Z.

The work presented here introduces the novel melt conditioned direct chill casting (MC-DC) technology, where intensive melt shearing is applied to the conventional direct-chill casting process. MC-DC casting can successfully produce high quality Al-alloy billets. The results obtained from 80 mm diameter billets cast at speed of 200 mm/min show that MC-DC casting of Al-alloys, substantially refines the microstructure and reduces macro-segregation. In this paper, we present the preliminary results and discuss microstructural evolution during MC-DC casting of Al-alloys.

DC magnetic fields from the human body generally: a historical overview.

PubMed

Cohen, D

2004-11-30

A review is presented of the earliest dc magnetic field (dcMF) measurements, made between 1969 and 1983, due to natural currents in the body. The measurements were essentially a mapping over the whole body, except for the brain (dcMEG), which was omitted because of interfering non-neural sources in the head. This mapping can be useful today in interpreting new measurements over the body, especially dcMEG data, where the new authors assume only a neural source in the head; our mapping suggests that this assumption may be in error. Briefly, in our mapping, dcMFs were found over almost the entire body; they were larger over the limbs and head than over the torso proper except over the abdomen, where it was usually the largest in the body Some of the sources were: 1. A strong and complicated reflex in the abdomen due to drinking cold water, suggesting that other dcMF reflexes might be common in the body. 2. Long muscle fibers in the limbs, suggesting sources also in scalp muscles. 3. Hair follicles due to touching the scalp; these sources could also exist, unrecognized, in recent dcMEG whole-head measurements. 4. Injury currents from the ischemic human heart, suggesting dcMFs could arise from injured muscle in the body generally. One major mechanism for producing dcMFs appeared to be a change in the potassium ion concentration in the vicinity of long excitable fibers. Overall, we concluded that the dcMFs were complicated, and it may be difficult to identify each source, especially in the head.

Dark Chocolate: Opportunity for an Alliance between Medical Science and the Food Industry?

PubMed Central

Petyaev, Ivan M.; Bashmakov, Yuriy K.

2017-01-01

Dark chocolate (DC) was originally introduced in human nutrition as a medicinal product consumable in a liquid form. Century-long efforts of food industry transformed this hardly appealing product into a valuable modern culinary delight with clear predominance of confectionery brands of DC on the market. However, current epidemiological data as well as multiple experimental and clinical observations reveal that DC consumption may have a profound effect on cardiovascular, central nervous systems, hemostasis, and lipid metabolism. However, despite of growing body of modern scientific evidence revealing medicinal properties of cocoa-based products, DC remains more gourmet culinary item than medicinal food product. Even today there are no clear dietary recommendations on consumption of cocoa flavonoids (flavanols) for health purpose. Clinical trials with DC rarely include monitoring of plasma flavanol concentration in volunteers. Moreover, there is no standardized assay or any quantitative requirements for flavanol content in the commercial brands of DC. High flavanol content is often sacrificed during manufacturing for a better taste of DC due to bitterness of cocoa flavonoids. All these problems including subsequently arising ethical issues need to be addressed by joint efforts of food industry and medical science. Moreover, application of microencapsulation technology in DC manufacturing, as well as molecular selection of best flavanol producers may drastically change bioavailability of DC bioactive ingredients and DC production technology. Nevertheless, only strict causative approach, linking possible health effect of DC to its bioactive ingredients considered as nutraceuticals, may change the current landscape in nutritional research related to cocoa-based products and create a trustworthy path for their medicinal use. PMID:29034240

Dark Chocolate: Opportunity for an Alliance between Medical Science and the Food Industry?

PubMed

Petyaev, Ivan M; Bashmakov, Yuriy K

2017-01-01

Dark chocolate (DC) was originally introduced in human nutrition as a medicinal product consumable in a liquid form. Century-long efforts of food industry transformed this hardly appealing product into a valuable modern culinary delight with clear predominance of confectionery brands of DC on the market. However, current epidemiological data as well as multiple experimental and clinical observations reveal that DC consumption may have a profound effect on cardiovascular, central nervous systems, hemostasis, and lipid metabolism. However, despite of growing body of modern scientific evidence revealing medicinal properties of cocoa-based products, DC remains more gourmet culinary item than medicinal food product. Even today there are no clear dietary recommendations on consumption of cocoa flavonoids (flavanols) for health purpose. Clinical trials with DC rarely include monitoring of plasma flavanol concentration in volunteers. Moreover, there is no standardized assay or any quantitative requirements for flavanol content in the commercial brands of DC. High flavanol content is often sacrificed during manufacturing for a better taste of DC due to bitterness of cocoa flavonoids. All these problems including subsequently arising ethical issues need to be addressed by joint efforts of food industry and medical science. Moreover, application of microencapsulation technology in DC manufacturing, as well as molecular selection of best flavanol producers may drastically change bioavailability of DC bioactive ingredients and DC production technology. Nevertheless, only strict causative approach, linking possible health effect of DC to its bioactive ingredients considered as nutraceuticals, may change the current landscape in nutritional research related to cocoa-based products and create a trustworthy path for their medicinal use.

Comparative Study of DC and AC Microgrids in Commercial Buildings Across Different Climates and Operating Profiles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fregosi, Daniel; Ravula, Sharmila; Brhlik, Dusan

2015-06-07

Bosch has developed and demonstrated a novel direct current (DC) microgrid system that maximizes the efficiency of locally generated photovoltaic energy while offering high reliability, safety, redundancy, and reduced cost compared to equivalent alternating current (AC) systems. Several demonstration projects validating the system feasibility and expected efficiency gains have been completed and additional ones are in progress. This paper gives an overview of the Bosch DC microgrid system and presents key results from a large simulation study done to estimate the energy savings of the Bosch DC microgrid over conventional AC systems. The study examined the system performance in locationsmore » across the United States for several commercial building types and operating profiles. It found that the Bosch DC microgrid uses generated PV energy 6%-8% more efficiently than traditional AC systems.« less

Mutual influence between current-induced giant magnetoresistance and radiation-induced magnetoresistance oscillations in the GaAs/AlGaAs 2DES

DOE PAGES

Samaraweera, R. L.; Liu, H. -C.; Wang, Z.; ...

2017-07-11

Radiation-induced magnetoresistance oscillations are examined in the GaAs/AlGaAs 2D system in the regime where an observed concurrent giant magnetoresistance is systematically varied with a supplementary dc-current, I dc . The I dc tuned giant magnetoresistance is subsequently separated from the photo-excited oscillatory resistance using a multi-conduction model in order to examine the interplay between the two effects. The results show that the invoked multiconduction model describes the observed giant magnetoresistance effect even in the presence of radiation-induced magnetoresistance oscillations, the magnetoresistance oscillations do not modify the giant magnetoresistance, and the magnetoresistance oscillatory extrema, i.e., maxima and minima, disappear rather asymmetricallymore » with increasing I dc. Lastly, the results suggest the interpretation that the I dc serves to suppress scattering between states near the Fermi level in a strong magnetic field limit.« less

Influence of DC-biasing on the performance of graphene spin valve

NASA Astrophysics Data System (ADS)

Iqbal, Muhammad Zahir; Hussain, Ghulam; Siddique, Salma; Hussain, Tassadaq; Iqbal, Muhammad Javaid

2018-04-01

Generating and controlling the spin valve signal are key factors in 'spintronics', which aims to utilize the spin degree of electrons. For this purpose, spintronic devices are constructed that can detect the spin signal. Here we investigate the effect of direct current (DC) on the magnetoresistance (MR) of graphene spin valve. The DC input not only decreases the magnitude of MR but also distorts the spin valve signal at higher DC inputs. Also, low temperature measurements revealed higher MR for the device, while the magnitude is noticed to decrease at higher temperatures. Furthermore, the spin polarization associated with NiFe electrodes is continuously increased at low DC bias and low temperatures. We also demonstrate the ohmic behavior of graphene spin valve by showing linear current-voltage (I-V) characteristics of the junction. Our findings may contribute significantly in modulating and controlling the spin transport properties of vertical spin valve structures.

Golgi polarization plays a role in the directional migration of neonatal dermal fibroblasts induced by the direct current electric fields.

PubMed

Kim, Min Sung; Lee, Mi Hee; Kwon, Byeong-Ju; Koo, Min-Ah; Seon, Gyeung Mi; Park, Jong-Chul

2015-05-01

Directional cell migration requires cell polarization. The reorganization of the Golgi apparatus is an important phenomenon in the polarization and migration of many types of cells. Direct current electric fields (dc (EF) induced directional cell migration in a wide variety of cells. Here nHDFs migrated toward cathode under 1 V/cm dc EF, however 1 μM of brefeldin A (BFA) inhibited the dc EF induced directional migration. BFA (1 μM) did not cause the complete Golgi dispersal for 2 h. When the Golgi polarization maintained their direction of polarity, the direction of cell migration also kept toward the same direction of the Golgi polarization even though the dc EF was reversed. In this study, the importance of the Golgi polarization in the directional migration of nHDf under dc EF was identified. Copyright © 2015 Elsevier Inc. All rights reserved.

Modeling and Dynamic Analysis of Paralleled dc/dc Converters With Master-Slave Current Sharing Control

NASA Technical Reports Server (NTRS)

Rajagopalan, J.; Xing, K.; Guo, Y.; Lee, F. C.; Manners, Bruce

1996-01-01

A simple, application-oriented, transfer function model of paralleled converters employing Master-Slave Current-sharing (MSC) control is developed. Dynamically, the Master converter retains its original design characteristics; all the Slave converters are forced to depart significantly from their original design characteristics into current-controlled current sources. Five distinct loop gains to assess system stability and performance are identified and their physical significance is described. A design methodology for the current share compensator is presented. The effect of this current sharing scheme on 'system output impedance' is analyzed.

Modular high voltage power supply for chemical analysis

DOEpatents

Stamps, James F [Livermore, CA; Yee, Daniel D [Dublin, CA

2007-01-09

A high voltage power supply for use in a system such as a microfluidics system, uses a DC--DC converter in parallel with a voltage-controlled resistor. A feedback circuit provides a control signal for the DC--DC converter and voltage-controlled resistor so as to regulate the output voltage of the high voltage power supply, as well as, to sink or source current from the high voltage supply.

Modular high voltage power supply for chemical analysis

DOEpatents

Stamps, James F [Livermore, CA; Yee, Daniel D [Dublin, CA

2010-05-04

A high voltage power supply for use in a system such as a microfluidics system, uses a DC-DC converter in parallel with a voltage-controlled resistor. A feedback circuit provides a control signal for the DC-DC converter and voltage-controlled resistor so as to regulate the output voltage of the high voltage power supply, as well as, to sink or source current from the high voltage supply.

Modular high voltage power supply for chemical analysis

DOEpatents

Stamps, James F [Livermore, CA; Yee, Daniel D [Dublin, CA

2008-07-15

A high voltage power supply for use in a system such as a microfluidics system, uses a DC-DC converter in parallel with a voltage-controlled resistor. A feedback circuit provides a control signal for the DC-DC converter and voltage-controlled resistor so as to regulate the output voltage of the high voltage power supply, as well as, to sink or source current from the high voltage supply.

A Bidirectional High-Power-Quality Grid Interface With a Novel Bidirectional Noninverted Buck Boost Converter for PHEVs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onar, Omer C

2012-01-01

Plug-in hybrid electric vehicles (PHEVs) will play a vital role in future sustainable transportation systems due to their potential in terms of energy security, decreased environmental impact, improved fuel economy, and better performance. Moreover, new regulations have been established to improve the collective gas mileage, cut greenhouse gas emissions, and reduce dependence on foreign oil. This paper primarily focuses on two major thrust areas of PHEVs. First, it introduces a grid-friendly bidirectional alternating current/direct current ac/dc dc/ac rectifier/inverter for facilitating vehicle-to-grid (V2G) integration of PHEVs. Second, it presents an integrated bidirectional noninverted buck boost converter that interfaces the energy storagemore » device of the PHEV to the dc link in both grid-connected and driving modes. The proposed bidirectional converter has minimal grid-level disruptions in terms of power factor and total harmonic distortion, with less switching noise. The integrated bidirectional dc/dc converter assists the grid interface converter to track the charge/discharge power of the PHEV battery. In addition, while driving, the dc/dc converter provides a regulated dc link voltage to the motor drive and captures the braking energy during regenerative braking.« less

21 CFR 74.2328 - D&C Red No. 28.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2328 D&C Red No. 28. (a) Identity and specifications. The color additive D&C Red No. 28 shall conform in identity and specifications to the requirements of § 74... cosmetics generally in amounts consistent with current good manufacturing practice. (c) Labeling...

21 CFR 74.2330 - D&C Red No. 30.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2330 D&C Red No. 30. (a) Identity and specifications. The color additive D&C Red No. 30 shall conform in identity and specifications to the requirements of § 74... cosmetics generally in amounts consistent with current good manufacturing practice. (c) Labeling...

21 CFR 74.2327 - D&C Red No. 27.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2327 D&C Red No. 27. (a) Identity and specifications. The color additive D&C Red No. 27 shall conform in identity and specifications to the requirements of § 74... cosmetics generally in amounts consistent with current good manufacturing practice. (c) Labeling...

77 FR 37827 - Airworthiness Directives; The Cessna Aircraft Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-25

...) generator control unit (GCU). We are proposing this AD to prevent DC generator overvoltage events, which... proposed AD. Discussion We have received reports of direct current (DC) generator overvoltage events. The... generator and the left and right engine DC generators, and corrective actions if necessary. That AD also...

78 FR 25310 - Biweekly Notice; Applications and Amendments to Facility Operating Licenses and Combined Licenses...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-30

.../diminished. There are no design changes associated with this TS amendment. The DC power system/batteries will... changes restructure the Technical Specifications (TS) for the direct current (DC) electrical power system... battery and battery charger operability requirements. The DC electrical power system, including associated...

21 CFR 74.2328 - D&C Red No. 28.

Code of Federal Regulations, 2014 CFR

2014-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2328 D&C Red No. 28. (a) Identity and specifications. The color additive D&C Red No. 28 shall conform in identity and specifications to the requirements of § 74... cosmetics generally in amounts consistent with current good manufacturing practice. (c) Labeling...

21 CFR 74.2328 - D&C Red No. 28.

Code of Federal Regulations, 2012 CFR

2012-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2328 D&C Red No. 28. (a) Identity and specifications. The color additive D&C Red No. 28 shall conform in identity and specifications to the requirements of § 74... cosmetics generally in amounts consistent with current good manufacturing practice. (c) Labeling...

21 CFR 74.2330 - D&C Red No. 30.

Code of Federal Regulations, 2012 CFR

2012-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2330 D&C Red No. 30. (a) Identity and specifications. The color additive D&C Red No. 30 shall conform in identity and specifications to the requirements of § 74... cosmetics generally in amounts consistent with current good manufacturing practice. (c) Labeling...

21 CFR 74.2330 - D&C Red No. 30.

Code of Federal Regulations, 2014 CFR

2014-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2330 D&C Red No. 30. (a) Identity and specifications. The color additive D&C Red No. 30 shall conform in identity and specifications to the requirements of § 74... cosmetics generally in amounts consistent with current good manufacturing practice. (c) Labeling...

21 CFR 74.2327 - D&C Red No. 27.

Code of Federal Regulations, 2013 CFR

2013-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2327 D&C Red No. 27. (a) Identity and specifications. The color additive D&C Red No. 27 shall conform in identity and specifications to the requirements of § 74... cosmetics generally in amounts consistent with current good manufacturing practice. (c) Labeling...

21 CFR 74.2330 - D&C Red No. 30.

Code of Federal Regulations, 2013 CFR

2013-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2330 D&C Red No. 30. (a) Identity and specifications. The color additive D&C Red No. 30 shall conform in identity and specifications to the requirements of § 74... cosmetics generally in amounts consistent with current good manufacturing practice. (c) Labeling...

21 CFR 74.2327 - D&C Red No. 27.

Code of Federal Regulations, 2014 CFR

2014-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2327 D&C Red No. 27. (a) Identity and specifications. The color additive D&C Red No. 27 shall conform in identity and specifications to the requirements of § 74... cosmetics generally in amounts consistent with current good manufacturing practice. (c) Labeling...

21 CFR 74.2327 - D&C Red No. 27.

Code of Federal Regulations, 2012 CFR

2012-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2327 D&C Red No. 27. (a) Identity and specifications. The color additive D&C Red No. 27 shall conform in identity and specifications to the requirements of § 74... cosmetics generally in amounts consistent with current good manufacturing practice. (c) Labeling...

21 CFR 74.2328 - D&C Red No. 28.

Code of Federal Regulations, 2013 CFR

2013-04-01

... ADDITIVES SUBJECT TO CERTIFICATION Cosmetics § 74.2328 D&C Red No. 28. (a) Identity and specifications. The color additive D&C Red No. 28 shall conform in identity and specifications to the requirements of § 74... cosmetics generally in amounts consistent with current good manufacturing practice. (c) Labeling...

Brushless DC motor control system responsive to control signals generated by a computer or the like

NASA Technical Reports Server (NTRS)

Packard, D. T. (Inventor)

1985-01-01

A control system for a brushless DC motor responsive to digital control signals is disclosed. The motor includes a multiphase wound stator and a permanent magnet rotor. The motor is arranged so that each phase winding, when energized from a DC source, will drive the rotor through a predetermined angular position or step. A commutation signal generator responsive to the shaft position provides a commutation signal for each winding. A programmable control signal generator such as a computer or microprocessor produces individual digital control signals for each phase winding. The control signals and commutation signals associated with each winding are applied to an AND gate for that phase winding. Each gate controls a switch connected in series with the associated phase winding and the DC source so that each phase winding is energized only when the commutation signal and the control signal associated with that phase winding are present. The motor shaft may be advanced one step at a time to a desired position by applying a predetermined number of control signals in the proper sequence to the AND gates and the torque generated by the motor be regulated by applying a separate control signal and each AND gate which is pulse width modulated to control the total time that each switch connects its associated winding to the DC source during each commutation period.

Brushless DC motor control system responsive to control signals generated by a computer or the like

NASA Technical Reports Server (NTRS)

Packard, Douglas T. (Inventor); Schmitt, Donald E. (Inventor)

1987-01-01

A control system for a brushless DC motor responsive to digital control signals is disclosed. The motor includes a multiphase wound stator and a permanent magnet rotor. The rotor is arranged so that each phase winding, when energized from a DC source, will drive the rotor through a predetermined angular position or step. A commutation signal generator responsive to the shaft position provides a commutation signal for each winding. A programmable control signal generator such as a computer or microprocessor produces individual digital control signals for each phase winding. The control signals and commutation signals associated with each winding are applied to an AND gate for that phase winding. Each gate controls a switch connected in series with the associated phase winding and the DC source so that each phase winding is energized only when the commutation signal and the control signal associated with that phase winding are present. The motor shaft may be advanced one step at a time to a desired position by applying a predetermined number of control signals in the proper sequence to the AND gates and the torque generated by the motor may be regulated by applying a separate control signal to each AND gate which is pulse width modulated to control the total time that each switch connects its associated winding to the DC source during each commutation period.

Using bioimpedance spectroscopy parameters as real-time feedback during tDCS.

PubMed

Nejadgholi, Isar; Caytak, Herschel; Bolic, Miodrag

2016-08-01

An exploratory analysis is carried out to investigate the feasibility of using BioImpedance Spectroscopy (BIS) parameters, measured on scalp, as real-time feedback during Transcranial Direct Current Stimulation (tDCS). TDCS is shown to be a potential treatment for neurological disorders. However, this technique is not considered as a reliable clinical treatment, due to the lack of a measurable indicator of treatment efficacy. Although the voltage that is applied on the head is very simple to measure during a tDCS session, changes of voltage are difficult to interpret in terms of variables that affect clinical outcome. BIS parameters are considered as potential feedback parameters, because: 1) they are shown to be associated with the DC voltage applied on the head, 2) they are interpretable in terms of conductive and capacitive properties of head tissues, 3) physical interpretation of BIS measurements makes them prone to be adjusted by clinically controllable variables, 4) BIS parameters are measurable in a cost-effective and safe way and do not interfere with DC stimulation. This research indicates that a quadratic regression model can predict the DC voltage between anode and cathode based on parameters extracted from BIS measurements. These parameters are extracted by fitting the measured BIS spectra to an equivalent electrical circuit model. The effect of clinical tDCS variables on BIS parameters needs to be investigated in future works. This work suggests that BIS is a potential method to be used for monitoring a tDCS session in order to adjust, tailor, or personalize tDCS treatment protocols.

E-beam high voltage switching power supply

DOEpatents

Shimer, D.W.; Lange, A.C.

1996-10-15

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.

E-beam high voltage switching power supply

DOEpatents

Shimer, Daniel W.; Lange, Arnold C.

1996-01-01

A high-power power supply produces a controllable, constant high voltage put 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.

Nerve lesioning with direct current

NASA Astrophysics Data System (ADS)

Ravid, E. Natalie; Shi Gan, Liu; Todd, Kathryn; Prochazka, Arthur

2011-02-01

Spastic hypertonus (muscle over-activity due to exaggerated stretch reflexes) often develops in people with stroke, cerebral palsy, multiple sclerosis and spinal cord injury. Lesioning of nerves, e.g. with phenol or botulinum toxin is widely performed to reduce spastic hypertonus. We have explored the use of direct electrical current (DC) to lesion peripheral nerves. In a series of animal experiments, DC reduced muscle force by controlled amounts and the reduction could last several months. We conclude that in some cases controlled DC lesioning may provide an effective alternative to the less controllable molecular treatments available today.

Development of a solar charged laboratory bench power supply

NASA Astrophysics Data System (ADS)

Ayara, W. A.; Omotosho, T. V.; Usikalu, M. R.; Singh, M. S. J.; Suparta, W.

2017-05-01

This product is an improvement on available DC laboratory bench power supply. It is capable of delivering low voltage Alternating Current (AC) and Direct Current (DC) to carry out basic laboratory experiment for both secondary schools and also at higher education institutions. The power supply is capable of delivering fixed DC voltages of 5V, 9V, 12V, variable voltage of between 1.25-30V and a 12V AC voltage. Also Incorporated is a USB port that allows for charging cell phones and other mobile devices, and a dedicated 12V DC output to power 5-7 Watt LED bulb to provide illumination in the laboratory for the instructor who may need to work at night in the absence of utility power.

Gas tube-switched high voltage DC power converter

DOEpatents

She, Xu; Bray, James William; Sommerer, Timothy John; Chokhawala, Rahul

2018-05-15

A direct current (DC)-DC converter includes a transformer and a gas tube-switched inverter circuit. The transformer includes a primary winding and a secondary winding. The gas tube-switched inverter circuit includes first and second inverter load terminals and first and second inverter input terminals. The first and second inverter load terminals are coupled to the primary winding. The first and second inverter input terminals are couplable to a DC node. The gas tube-switched inverter circuit further includes a plurality of gas tube switches respectively coupled between the first and second inverter load terminals and the first and second inverter input terminals. The plurality of gas tube switches is configured to operate to generate an alternating current (AC) voltage at the primary winding.

Modeling and simulation, and their validation of three-phase transformers with three legs under DC bias

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fuchs, E.F.; You, Y.; Roesler, D.J.

This paper proposes a new model for three-phase transformers with three legs with and without tank under DC bias based on electric and magnetic circuit theory. For the calculation of the nonsinusoidal no-load currents, a combination of time and frequency domains is used. The analysis shows that (1) asymmetric three-phase transformers with three legs generate magnetizing currents with triplen harmonics not being of the zero-sequence type. (2) The wave shapes of the three magnetizing currents of (asymmetric) transformers are dependent on the phase sequence. (3) The magnetic history of transformer magnetization -- due to residual magnetization and hysteresis of themore » tank -- cannot be ignored if a DC bias is present and the magnetic influence of the tank is relatively strong, e.g., for oil-cooled transformers. (4) Symmetric three-phase transformers with three legs generate no-load currents without triplen harmonics. (5) The effects of DC bias currents (e.g., reactive power demand, harmonic distortion) can be suppressed employing symmetric three-phase transformers with three legs including tank. Measurements corroborate computational results; thus this nonlinear model is valid and accurate.« less

Silicon Carbide Diodes Performance Characterization and Comparison With Silicon Devices

NASA Technical Reports Server (NTRS)

Lebron-Velilla, Ramon C.; Schwarze, Gene E.; Trapp, Scott

2003-01-01

Commercially available silicon carbide (SiC) Schottky diodes from different manufacturers were electrically tested and characterized at room temperature. Performed electrical tests include steady state forward and reverse I-V curves, as well as switching transient tests performed with the diodes operating in a hard switch dc-to-dc buck converter. The same tests were performed in current state of the art silicon (Si) and gallium arsenide (GaAs) Schottky and pn junction devices for evaluation and comparison purposes. The SiC devices tested have a voltage rating of 200, 300, and 600 V. The comparison parameters are forward voltage drop at rated current, reverse current at rated voltage and peak reverse recovery currents in the dc to dc converter. Test results show that steady state characteristics of the tested SiC devices are not superior to the best available Si Schottky and ultra fast pn junction devices. Transient tests reveal that the tested SiC Schottky devices exhibit superior transient behavior. This is more evident at the 300 and 600 V rating where SiC Schottky devices showed drastically lower reverse recovery currents than Si ultra fast pn diodes of similar rating.

DC to DC Converter Testing for Space Applications: Use of EMI Filters and Thermal Range of Operation

NASA Technical Reports Server (NTRS)

Leon, Rosa

2008-01-01

Several tests were performed on Interpoint and International Rectifier (IR) direct current (DC) to DC converters to evaluate potential performance and reliability issues in space use of DC to DC converters and to determine if the use of electromagnetic interference (EMI) filters mitigates concerns observed during previous tests. Test findings reported here include those done up until September - October 2008. Tests performed include efficiency, regulation, cross-regulation, power consumption with inhibit on, load transient response, synchronization, and turn-on tests. Some of the test results presented here span the thermal range -55 C to 125 C. Lower range was extended to -120 C in some tested converters. Determination of failure root cause in DC/DC converters that failed at thermal extremes is also included.

Trade Electricity. Motors & Controls--Level 3. Standardized Curriculum.

ERIC Educational Resources Information Center

New York City Board of Education, Brooklyn, NY. Office of Occupational and Career Education.

This curriculum guide consists of seven modules on motors and controls, one of the three divisions of the standardized trade electricity curriculum in high schools in New York City. The seven modules cover the following subjects: energy conservation wiring, direct current (DC) motor repair and rewinding, DC motor controls, alternating current (AC)…

12 CFR 261a.5 - Request for access to record.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Reserve System, 20th and Constitution Avenue NW., Washington, DC 20551. (2) A request by a current Board... Constitution Avenue NW., Washington, DC 20551. (3) A request by a current Board employee for information other... Information Office, Board of Governors of the Federal Reserve System, 20th and Constitution Avenue NW...

Direct current contamination of kilohertz frequency alternating current waveforms.

PubMed

Franke, Manfred; Bhadra, Niloy; Bhadra, Narendra; Kilgore, Kevin

2014-07-30

Kilohertz frequency alternating current (KHFAC) waveforms are being evaluated in a variety of physiological settings because of their potential to modulate neural activity uniquely when compared to frequencies in the sub-kilohertz range. However, the use of waveforms in this frequency range presents some unique challenges regarding the generator output. In this study we explored the possibility of undesirable contamination of the KHFAC waveforms by direct current (DC). We evaluated current- and voltage-controlled KHFAC waveform generators in configurations that included a capacitive coupling between generator and electrode, a resistive coupling and combinations of capacitive with inductive coupling. Our results demonstrate that both voltage- and current-controlled signal generators can unintentionally add DC-contamination to a KHFAC signal, and that capacitive coupling is not always sufficient to eliminate this contamination. We furthermore demonstrated that high value inductors, placed in parallel with the electrode, can be effective in eliminating DC-contamination irrespective of the type of stimulator, reducing the DC contamination to less than 1 μA. This study highlights the importance of carefully designing the electronic setup used in KHFAC studies and suggests specific testing that should be performed and reported in all studies that assess the neural response to KHFAC waveforms. Published by Elsevier B.V.

Electrochromic and optical properties of tungsten oxide films deposited with DC sputtering by introducing hydrogen.

PubMed

Chen, Hsi-Chao; Jan, Der-Jun; Luo, Yu-Siang; Huang, Kuo-Ting

2014-02-01

Research was undertaken to investigate the electrochromic and optical properties of tungsten oxide (WO3) films deposited by introducing hydrogen with a direct current (DC) and pulsed DC sputtering. The results show that WO3 films have optimum electrochromic properties at a hydrogen flow of 4 and 3 sccm for DC and pulsed DC, respectively. In the Raman spectra, the peak intensity increased with the increase of hydrogen flow at both 770  cm1 and 950  cm(-1) peaks, which resulted in bonds of W(6+)-O and W(6+)=O, respectively. Simultaneously, the transmittance (ΔT550  nm) variations were 65.6% and 64.4%, and the average transmittance (ΔT400-500  nm) variations were 56.7% and 56.4% for DC and pulsed DC, respectively. The bleached/colored ability of the cyclic voltammograms (CVs) was DC>pulsed DC, and the resistances of AC impedance were pulsed DC>DC.

Nonlinear control of voltage source converters in AC-DC power system.

PubMed

Dash, P K; Nayak, N

2014-07-01

This paper presents the design of a robust nonlinear controller for a parallel AC-DC power system using a Lyapunov function-based sliding mode control (LYPSMC) strategy. The inputs for the proposed control scheme are the DC voltage and reactive power errors at the converter station and the active and reactive power errors at the inverter station of the voltage-source converter-based high voltage direct current transmission (VSC-HVDC) link. The stability and robust tracking of the system parameters are ensured by applying the Lyapunov direct method. Also the gains of the sliding mode control (SMC) are made adaptive using the stability conditions of the Lyapunov function. The proposed control strategy offers invariant stability to a class of systems having modeling uncertainties due to parameter changes and exogenous inputs. Comprehensive computer simulations are carried out to verify the proposed control scheme under several system disturbances like changes in short-circuit ratio, converter parametric changes, and faults on the converter and inverter buses for single generating system connected to the power grid in a single machine infinite-bus AC-DC network and also for a 3-machine two-area power system. Furthermore, a second order super twisting sliding mode control scheme has been presented in this paper that provides a higher degree of nonlinearity than the LYPSMC and damps faster the converter and inverter voltage and power oscillations. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Influence of direct and alternating current electric fields on efficiency promotion and leaching risk alleviation of chelator assisted phytoremediation.

PubMed

Luo, Jie; Cai, Limei; Qi, Shihua; Wu, Jian; Sophie Gu, Xiaowen

2018-03-01

Direct and alternating current electric fields with various voltages were used to improve the decontamination efficiency of chelator assisted phytoremediation for multi-metal polluted soil. The alleviation effect of electric field on leaching risk caused by chelator application during phytoremediation process was also evaluated. Biomass yield, pollutant uptake and metal leaching retardation under alternating current (AC) and direct current (DC) electric fields were compared. The biomass yield of Eucalyptus globulus under AC fields with various voltages (2, 4 and 10 V) were 3.91, 4.16 and 3.67kg, respectively, significantly higher than the chelator treatment without electric field (2.71kg). Besides growth stimulation, AC fields increased the metal concentrations of plant tissues especially in aerial parts manifested by the raised translocation factor of different metals. Direct current electric fields with low and moderate voltages increased the biomass production of the species to 3.45 and 3.12kg, respectively, while high voltage on the contrary suppressed the growth of the plants (2.66kg). Under DC fields, metal concentrations elevated obviously with increasing voltages and the metal translocation factors were similar under all voltages. Metal extraction per plant achieved the maximum value under moderate voltage due to the greatest biomass production. DC field with high voltage (10V) decreased the volume of leachate from the chelator treatment without electric field from 1224 to 56mL, while the leachate gathered from AC field treatments raised from 512 to 670mL. DC field can retard the downward movement of metals caused by chelator application more effectively relative to AC field due to the constant water flow and electroosmosis direction. Alternating current field had more promotive effect on chelator assisted phytoremediation efficiency than DC field illustrated by more metal accumulation in the species. However, with the consideration of leaching risk, DC field with moderate voltage was the optimal supplementary technique for phytoremediation. Copyright © 2017 Elsevier Inc. All rights reserved.

75 FR 68731 - Airworthiness Directives; The Cessna Aircraft Company Model 750 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-09

... auxiliary power unit (APU) generator and the left and right engine direct current (DC) generators, and... manual. This proposed AD results from a report of a DC generator overvoltage event which caused smoke in... associated with the engine and APU DC generators. Relevant Service Information We have reviewed Cessna...

77 FR 57994 - Airworthiness Directives; The Cessna Aircraft Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-19

... unit (GCU). We are issuing this AD to prevent DC generator overvoltage events, which could result in... AD was prompted by reports of direct current (DC) generator overvoltage events. We are issuing this AD to prevent DC generator overvoltage events, which could result in smoke in the cockpit and loss of...

A Solid-State Fault Current Limiting Device for VSC-HVDC Systems

NASA Astrophysics Data System (ADS)

Larruskain, D. Marene; Zamora, Inmaculada; Abarrategui, , Oihane; Iturregi, Araitz

2013-08-01

Faults in the DC circuit constitute one of the main limitations of voltage source converter VSC-HVDC systems, as the high fault currents can damage seriously the converters. In this article, a new design for a fault current limiter (FCL) is proposed, which is capable of limiting the fault current as well as interrupting it, isolating the DC grid. The operation of the proposed FCL is analysed and verified with the most usual faults that can occur in overhead lines.

Life Balancing -- A Better Way to Balance Large Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, R. Dyche; Zane, Regan; Plett, Gregory

2017-03-28

A new cell balancing technology was developed under a Department of Energy contract which merges the DC/DC converter function into cell balancing. Instead of conventional passive cell balancing technology which bypasses current through a resistor, or active cell balancing which moves current from one cell to another, with significant cost and additional inefficiencies, this concept takes variable amount of current from each cell or small group of cells and converts it to current for the low voltage system.

Ultrananocrystalline Diamond Cantilever Wide Dynamic Range Acceleration/Vibration /Pressure Sensor

DOEpatents

Krauss, Alan R.; Gruen, Dieter M.; Pellin, Michael J.; Auciello, Orlando

2003-09-02

An ultrananocrystalline diamond (UNCD) element formed in a cantilever configuration is used in a highly sensitive, ultra-small sensor for measuring acceleration, shock, vibration and static pressure over a wide dynamic range. The cantilever UNCD element may be used in combination with a single anode, with measurements made either optically or by capacitance. In another embodiment, the cantilever UNCD element is disposed between two anodes, with DC voltages applied to the two anodes. With a small AC modulated voltage applied to the UNCD cantilever element and because of the symmetry of the applied voltage and the anode-cathode gap distance in the Fowler-Nordheim equation, any change in the anode voltage ratio V1/V2 required to maintain a specified current ratio precisely matches any displacement of the UNCD cantilever element from equilibrium. By measuring changes in the anode voltage ratio required to maintain a specified current ratio, the deflection of the UNCD cantilever can be precisely determined. By appropriately modulating the voltages applied between the UNCD cantilever and the two anodes, or limit electrodes, precise independent measurements of pressure, uniaxial acceleration, vibration and shock can be made. This invention also contemplates a method for fabricating the cantilever UNCD structure for the sensor.

Ultrananocrystalline diamond cantilever wide dynamic range acceleration/vibration/pressure sensor

DOEpatents

Krauss, Alan R [Naperville, IL; Gruen, Dieter M [Downers Grove, IL; Pellin, Michael J [Naperville, IL; Auciello, Orlando [Bolingbrook, IL

2002-07-23

An ultrananocrystalline diamond (UNCD) element formed in a cantilever configuration is used in a highly sensitive, ultra-small sensor for measuring acceleration, shock, vibration and static pressure over a wide dynamic range. The cantilever UNCD element may be used in combination with a single anode, with measurements made either optically or by capacitance. In another embodiment, the cantilever UNCD element is disposed between two anodes, with DC voltages applied to the two anodes. With a small AC modulated voltage applied to the UNCD cantilever element and because of the symmetry of the applied voltage and the anode-cathode gap distance in the Fowler-Nordheim equation, any change in the anode voltage ratio V1/N2 required to maintain a specified current ratio precisely matches any displacement of the UNCD cantilever element from equilibrium. By measuring changes in the anode voltage ratio required to maintain a specified current ratio, the deflection of the UNCD cantilever can be precisely determined. By appropriately modulating the voltages applied between the UNCD cantilever and the two anodes, or limit electrodes, precise independent measurements of pressure, uniaxial acceleration, vibration and shock can be made. This invention also contemplates a method for fabricating the cantilever UNCD structure for the sensor.

Chromophore Poling in Thin Films of Organic Glasses. 2. Two-Electrode Corona Discharge Setup

NASA Astrophysics Data System (ADS)

Vilitis, O.; Muzikante, I.; Rutkis, M.; Vembris, A.

2012-01-01

In Part 1 of the article we provided description of the corona discharge physics and overview of the methods used for corona poling in thin organic films. Subsequent sections describe comparatively simple technical methods for poling the organic nonlinear optical polymers using a two-electrode (point-to-plate or wire-to-plate) technique. The polarization build-up was studied by the DC positive corona method for poling the nonlinear optical (NLO) polymers. The experimental setup provides the corona discharge current from 0.5 μA up to 3 μA by applying 3 kV - 12 kV voltage to the corona electrode and makes possible selection among the types of corona electrodes (needle, multi-needle, wire, etc.). The results of experimental testing of the poling setup show that at fixed optimal operational parameters of poling - the sample orientation temperature and the discharge current - the corona charging of polymeric materials can successfully be performed applying the two-electrode technique. To study the dynamics of both poling and charge transport processes the three-electrode charging system - a corona triode - should be applied.

Electrohydrodynamic Flows in Electrochemical Systems

NASA Technical Reports Server (NTRS)

Saville, D. A.

2005-01-01

Recent studies have established a new class of assembly processes with colloidal suspensions. Particles are driven together to form large crystalline structures in both dc and ac fields. The current work centers on this new class of flows in ac fields. In the research carried out under the current award, it was established that: (i) Small colloidal particles crystallize near an electrode due to electrohydrodynamic flows induced by an sinusoidally varying applied potential. (ii) These flows originate due to disturbances in the electrode polarization layer arising from the presence of the particles. Inasmuch as the charge and the field strength both scale on the applied field, the flows are proportional to the square of the applied voltage. (iii) Suspensions of two different sorts of particles can be crystallized and will form well-ordered binary crystals. (iv) At high frequencies the EHD flows die out. Thus, with a homogeneous system the particles become widely spaced due to dipolar repulsion. With a binary suspension, however, the particles may become attractive due to dipolar attraction arising from differences in electrokinetic dipoles. Consequently binary crystals form at both high and low frequencies.

A High Voltage Ratio and Low Ripple Interleaved DC-DC Converter for Fuel Cell Applications

PubMed Central

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. PMID:23365536

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

PubMed

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.

Structure of physical crystalline membranes within the self-consistent screening approximation.

PubMed

Gazit, Doron

2009-10-01

The anomalous exponents governing the long-wavelength behavior of the flat phase of physical crystalline membranes are calculated within a self-consistent screening approximation (SCSA) applied to second order expansion in 1/dC ( dC is the codimension), extending the seminal work of Le Doussal and Radzihovsky [Phys. Rev. Lett. 69, 1209 (1992)]. In particular, the bending rigidity is found to harden algebraically in the long-wavelength limit with an exponent eta=0.789... , which is used to extract the elasticity softening exponent eta(u)=0.422... , and the roughness exponent zeta=0.605... . The scaling relation eta(u)=2-2eta is proven to hold to all orders in SCSA. Further, applying the SCSA to an expansion in 1/dC , is found to be essential, as no solution to the self-consistent equations is found in a two-bubble level, which is the naive second-order expansion. Surprisingly, even though the expansion parameter for physical membrane is 1/dC=1 , the SCSA applied to second-order expansion deviates only slightly from the first order, increasing zeta by mere 0.016. This supports the high quality of the SCSA for physical crystalline membranes, as well as improves the comparison to experiments and numerical simulations of these systems. The prediction of SCSA applied to first order expansion for the Poisson ratio is shown to be exact to all orders.

Degradation and recovery of iron doped barium titanate single crystals via modulus spectroscopy and thermally stimulated depolarization current

NASA Astrophysics Data System (ADS)

Carter, J. J.; Bayer, T. J. M.; Randall, C. A.

2017-04-01

Understanding resistance degradation during the application of DC bias and recovery after removing the DC bias provides insight into failure mechanisms and defects in dielectric materials. In this experiment, modulus spectroscopy and thermally stimulated depolarization current (TSDC) techniques were used to characterize the degradation and recovery of iron-doped barium titanate single crystals. Modulus spectroscopy is a very powerful analytical tool applied during degradation and recovery to observe changes in the local conductivity distribution. During degradation, oxygen vacancies migrate to the cathode region, and a counter flow of oxygen anions migrates towards the anode. With increasing time during degradation, the distribution of conductivity broadens only slightly exhibiting crucial differences to iron doped strontium titanate. After removing the DC bias, the recovery shows that a second previously unobserved and distinct conductivity maximum arises in the modulus data. This characteristic with two maxima related to different conductivities in the anode and cathode region is what can be expected from the published defect chemistry. It will be concluded that only the absence of an external electric field during recovery measurements permits the observation of local conductivity measurements without the presence of non-equilibrium conditions such as charge injection. Equilibrium conductivity as a function of oxygen vacancy concentration is described schematically. Oxygen vacancy migration during degradation and recovery is verified by TSDC analysis. We establish a self-consistent rationale of the transient changes in the modulus and TSDC for the iron doped barium titanate single crystal system including electron, hole and oxygen vacancy conductivity. During degradation, the sample fractured.

Modeling and Dynamic Analysis of Paralleled of dc/dc Converters with Master-Slave Current Sharing Control

NASA Technical Reports Server (NTRS)

Rajagopalan, J.; Xing, K.; Guo, Y.; Lee, F. C.; Manners, Bruce

1996-01-01

A simple, application-oriented, transfer function model of paralleled converters employing Master-Slave Current-sharing (MSC) control is developed. Dynamically, the Master converter retains its original design characteristics; all the Slave converters are forced to depart significantly from their original design characteristics into current-controlled current sources. Five distinct loop gains to assess system stability and performance are identified and their physical significance is described. A design methodology for the current share compensator is presented. The effect of this current sharing scheme on 'system output impedance' is analyzed.

Dacarbazine (DTIC) versus vaccination with autologous peptide-pulsed dendritic cells (DC) in first-line treatment of patients with metastatic melanoma: a randomized phase III trial of the DC study group of the DeCOG.

PubMed

Schadendorf, D; Ugurel, S; Schuler-Thurner, B; Nestle, F O; Enk, A; Bröcker, E-B; Grabbe, S; Rittgen, W; Edler, L; Sucker, A; Zimpfer-Rechner, C; Berger, T; Kamarashev, J; Burg, G; Jonuleit, H; Tüttenberg, A; Becker, J C; Keikavoussi, P; Kämpgen, E; Schuler, G

2006-04-01

This randomized phase III trial was designed to demonstrate the superiority of autologous peptide-loaded dendritic cell (DC) vaccination over standard dacarbazine (DTIC) chemotherapy in stage IV melanoma patients. DTIC 850 mg/m2 intravenously was applied in 4-week intervals. DC vaccines loaded with MHC class I and II-restricted peptides were applied subcutaneously at 2-week intervals for the first five vaccinations and every 4 weeks thereafter. The primary study end point was objective response (OR); secondary end points were toxicity, overall (OS) and progression-free survival (PFS). At the time of the first interim analysis 55 patients had been enrolled into the DTIC and 53 into the DC-arm (ITT). OR was low (DTIC: 5.5%, DC: 3.8%), but not significantly different in the two arms. The Data Safety & Monitoring Board recommended closure of the study. Unscheduled subset analyses revealed that patients with normal serum LDH and/or stage M1a/b survived longer in both arms than those with elevated serum LDH and/or stage M1c. Only in the DC-arm did those patients with (i) an initial unimpaired general health status (Karnofsky = 100) or (ii) an HLA-A2+/HLA-B44- haplotype survive significantly longer than patients with a Karnofsky index <100 (P = 0.007 versus P = 0.057 in the DTIC-arm) or other HLA haplotypes (P = 0.04 versus P = 0.57 in DTIC-treated patients). DC vaccination could not be demonstrated to be more effective than DTIC chemotherapy in stage IV melanoma patients. The observed association of overall performance status and HLA haplotype with overall survival for patients treated by DC vaccination should be tested in future trials employing DC vaccines.

Two-stage energy storage equalization system for lithium-ion battery pack

NASA Astrophysics Data System (ADS)

Chen, W.; Yang, Z. X.; Dong, G. Q.; Li, Y. B.; He, Q. Y.

2017-11-01

How to raise the efficiency of energy storage and maximize storage capacity is a core problem in current energy storage management. For that, two-stage energy storage equalization system which contains two-stage equalization topology and control strategy based on a symmetric multi-winding transformer and DC-DC (direct current-direct current) converter is proposed with bidirectional active equalization theory, in order to realize the objectives of consistent lithium-ion battery packs voltages and cells voltages inside packs by using a method of the Range. Modeling analysis demonstrates that the voltage dispersion of lithium-ion battery packs and cells inside packs can be kept within 2 percent during charging and discharging. Equalization time was 0.5 ms, which shortened equalization time of 33.3 percent compared with DC-DC converter. Therefore, the proposed two-stage lithium-ion battery equalization system can achieve maximum storage capacity between lithium-ion battery packs and cells inside packs, meanwhile efficiency of energy storage is significantly improved.

Performance analyses of Z-source and quasi Z-source inverter for photovoltaic applications

NASA Astrophysics Data System (ADS)

Himabind, S.; Priya, T. Hari; Manjeera, Ch.

2018-04-01

This paper presents the comparative analysis of Z-source and Quasi Z-source converter for renewable energy applications. Due to the dependency of renewable energy sources on external weather conditions the output voltage, current changes accordingly which effects the performance of traditional voltage source and current source inverters connected across it. To overcome the drawbacks of VSI and CSI, Z-source and Quasi Z-source inverter (QZSI) are used, which can perform multiple tasks like ac-to-dc, dc-to-ac, ac-to-ac, dc-to-dc conversion. They can be used for both buck and boost operations, by utilizing the shoot-through zero state. The QZSI is derived from the ZSI topology, with a slight change in the impedance network and it overcomes the drawbacks of ZSI. The QZSI draws a constant current from the source when compared to ZSI. A comparative analysis is performed between Z-source and Quasi Z-source inverter, simulation is performed in MATLAB/Simulink environment.

Highly efficient maximum power point tracking using DC-DC coupled inductor single-ended primary inductance converter for photovoltaic power systems

NASA Astrophysics Data System (ADS)

Quamruzzaman, M.; Mohammad, Nur; Matin, M. A.; Alam, M. R.

2016-10-01

Solar photovoltaics (PVs) have nonlinear voltage-current characteristics, with a distinct maximum power point (MPP) depending on factors such as solar irradiance and operating temperature. To extract maximum power from the PV array at any environmental condition, DC-DC converters are usually used as MPP trackers. This paper presents the performance analysis of a coupled inductor single-ended primary inductance converter for maximum power point tracking (MPPT) in a PV system. A detailed model of the system has been designed and developed in MATLAB/Simulink. The performance evaluation has been conducted on the basis of stability, current ripple reduction and efficiency at different operating conditions. Simulation results show considerable ripple reduction in the input and output currents of the converter. Both the MPPT and converter efficiencies are significantly improved. The obtained simulation results validate the effectiveness and suitability of the converter model in MPPT and show reasonable agreement with the theoretical analysis.

50% duty cycle may be inappropriate to achieve a sufficient chest compression depth when cardiopulmonary resuscitation is performed by female or light rescuers.

PubMed

Lee, Chang Jae; Chung, Tae Nyoung; Bae, Jinkun; Kim, Eui Chung; Choi, Sung Wook; Kim, Ok Jun

2015-03-01

Current guidelines for cardiopulmonary resuscitation recommend chest compressions (CC) during 50% of the duty cycle (DC) in part because of the ease with which individuals may learn to achieve it with practice. However, no consideration has been given to a possible interaction between DC and depth of CC, which has been the subject of recent study. Our aim was to determine if 50% DC is inappropriate to achieve sufficient chest compression depth for female and light rescuers. Previously collected CC data, performed by senior medical students guided by metronome sounds with various down-stroke patterns and rates, were included in the analysis. Multiple linear regression analysis was performed to determine the association between average compression depth (ACD) with average compression rate (ACR), DC, and physical characteristics of the performers. Expected ACD was calculated for various settings. DC, ACR, body weight, male sex, and self-assessed physical strength were significantly associated with ACD in multivariate analysis. Based on our calculations, with 50% of DC, only men with ACR of 140/min or faster or body weight over 74 kg with ACR of 120/min can achieve sufficient ACD. A shorter DC is independently correlated with deeper CC during simulated cardiopulmonary resuscitation. The optimal DC recommended in current guidelines may be inappropriate for achieving sufficient CD, especially for female or lighter-weight rescuers.

Numerical simulation of dynamics of brushless dc motors for aerospace and other applications. Volume 1: Model development and applications, part B

NASA Technical Reports Server (NTRS)

Demerdash, N. A. O.; Nehl, T. W.

1979-01-01

A mathematical model was developed and computerized simulations were obtained for a brushless dc motor. Experimentally obtained oscillograms of the machine phase currents are presented and the corresponding current and voltage waveforms for various modes of operation of the motor are presented and discussed.

Operation of AC Adapters Visualized Using Light-Emitting Diodes

ERIC Educational Resources Information Center

Regester, Jeffrey

2016-01-01

A bridge rectifier is a diamond-shaped configuration of diodes that serves to convert alternating current(AC) into direct current (DC). In our world of AC outlets and DC electronics, they are ubiquitous. Of course, most bridge rectifiers are built with regular diodes, not the light-emitting variety, because LEDs have a number of disadvantages. For…

Plasma characteristics of direct current enhanced cylindrical inductively coupled plasma source

NASA Astrophysics Data System (ADS)

Yue, HUA; Jian, SONG; Zeyu, HAO; Chunsheng, REN

2018-06-01

Experimental results of a direct current enhanced inductively coupled plasma (DCE-ICP) source which consists of a typical cylindrical ICP source and a plate-to-grid DC electrode are reported. With the use of this new source, the plasma characteristic parameters, namely, electron density, electron temperature and plasma uniformity, are measured by Langmuir floating double probe. It is found that DC discharge enhances the electron density and decreases the electron temperature, dramatically. Moreover, the plasma uniformity is obviously improved with the operation of DC and radio frequency (RF) hybrid discharge. Furthermore, the nonlinear enhancement effect of electron density with DC + RF hybrid discharge is confirmed. The presented observation indicates that the DCE-ICP source provides an effective method to obtain high-density uniform plasma, which is desirable for practical industrial applications.

Fabrication and Modification of Nanoporous Silicon Particles

NASA Technical Reports Server (NTRS)

Ferrari, Mauro; Liu, Xuewu

2010-01-01

Silicon-based nanoporous particles as biodegradable drug carriers are advantageous in permeation, controlled release, and targeting. The use of biodegradable nanoporous silicon and silicon dioxide, with proper surface treatments, allows sustained drug release within the target site over a period of days, or even weeks, due to selective surface coating. A variety of surface treatment protocols are available for silicon-based particles to be stabilized, functionalized, or modified as required. Coated polyethylene glycol (PEG) chains showed the effective depression of both plasma protein adsorption and cell attachment to the modified surfaces, as well as the advantage of long circulating. Porous silicon particles are micromachined by lithography. Compared to the synthesis route of the nanomaterials, the advantages include: (1) the capability to make different shapes, not only spherical particles but also square, rectangular, or ellipse cross sections, etc.; (2) the capability for very precise dimension control; (3) the capacity for porosity and pore profile control; and (4) allowance of complex surface modification. The particle patterns as small as 60 nm can be fabricated using the state-of-the-art photolithography. The pores in silicon can be fabricated by exposing the silicon in an HF/ethanol solution and then subjecting the pores to an electrical current. The size and shape of the pores inside silicon can be adjusted by the doping of the silicon, electrical current application, the composition of the electrolyte solution, and etching time. The surface of the silicon particles can be modified by many means to provide targeted delivery and on-site permanence for extended release. Multiple active agents can be co-loaded into the particles. Because the surface modification of particles can be done on wafers before the mechanical release, asymmetrical surface modification is feasible. Starting from silicon wafers, a treatment, such as KOH dipping or reactive ion etching (RIE), may be applied to make the surface rough. This helps remove the nucleation layer. A protective layer is then deposited on the wafer. The protective layer, such as silicon nitride film or photoresist film, protects the wafer from electrochemical etching in an HF-based solution. A lithography technique is applied to pattern the particles onto the protective film. The undesired area of the protective film is removed, and the protective film on the back side of the wafer is also removed. Then the pattern is exposed to HF/surfactant solution, and a larger DC electrical current is applied to the wafers for a selected time. This step removes the nucleation layer. Then a DC current is applied to generate the nanopores. Next, a large electrical current is applied to generate a release layer. The particles are mechanically suspended in the solvent and collected by filtration or centrifuge.

Center conductor diagnostic for multipactor detection in inaccessible geometries

NASA Astrophysics Data System (ADS)

Chaplin, Vernon H.; Hubble, Aimee A.; Clements, Kathryn A.; Graves, Timothy P.

2017-01-01

Electron collecting current probes are the most reliable diagnostic of multipactor and radiofrequency (RF) ionization breakdown; however, stand-alone probes can only be used in test setups where the breakdown region is physically accessible. This paper describes techniques for measuring multipactor current directly on the center conductor of a coaxial RF device (or more generally, on the signal line in any two-conductor RF system) enabling global multipactor detection with improved sensitivity compared to other common diagnostics such as phase null, third harmonic, and reflected power. The center conductor diagnostic may be AC coupled for use in systems with a low DC impedance between the center conductor and ground. The effect of DC bias on the breakdown threshold was studied: in coaxial geometry, the change in threshold was <1 dB for positive biases satisfying VD C/VR F 0 <0.8 , where VRF0 is the RF voltage amplitude at the unperturbed breakdown threshold. In parallel plate geometry, setting VD C/VR F 0 <0.2 was necessary to avoid altering the threshold by more than 1 dB. In most cases, the center conductor diagnostic functions effectively with no bias at all—this is the preferred implementation, but biases in the range VD C=0 -10 V may be applied if necessary. The polarity of the detected current signal may be positive or negative depending on whether there is net electron collection or emission globally.

Hot electrons injection in carbon nanotubes under the influence of quasi-static ac-field

NASA Astrophysics Data System (ADS)

Amekpewu, M.; Mensah, S. Y.; Musah, R.; Mensah, N. G.; Abukari, S. S.; Dompreh, K. A.

2016-07-01

The theory of hot electrons injection in carbon nanotubes (CNTs) where both dc electric field (Ez), and a quasi-static ac field exist simultaneously (i.e. when the frequency ω of ac field is much less than the scattering frequency v (ω ⪡ v or ωτ ⪡ 1, v =τ-1) where τ is relaxation time) is studied. The investigation is done theoretically by solving semi-classical Boltzmann transport equation with and without the presence of the hot electrons source to derive the current densities. Plots of the normalized current density versus dc field (Ez) applied along the axis of the CNTs in the presence and absence of hot electrons reveal ohmic conductivity initially and finally negative differential conductivity (NDC) provided ωτ ⪡ 1 (i.e. quasi- static case). With strong enough axial injection of the hot electrons, there is a switch from NDC to positive differential conductivity (PDC) about Ez ≥ 75 kV / cm and Ez ≥ 140 kV / cm for a zigzag CNT and an armchair CNT respectively. Thus, the most important tough problem for NDC region which is the space charge instabilities can be suppressed due to the switch from the NDC behaviour to the PDC behaviour predicting a potential generation of terahertz radiations whose applications are relevance in current-day technology, industry, and research.