Impact of multiple-dose versus single-dose inhaler devices on COPD patients’ persistence with long-acting β2-agonists: a dispensing database analysis

PubMed Central

van Boven, Job FM; van Raaij, Joost J; van der Galiën, Ruben; Postma, Maarten J; van der Molen, Thys; Dekhuijzen, PN Richard; Vegter, Stefan

2014-01-01

Background: With a growing availability of different devices and types of medication, additional evidence is required to assist clinicians in prescribing the optimal medication in relation to chronic obstructive pulmonary disease (COPD) patients’ persistence with long-acting β2-agonists (LABAs). Aims: To assess the impact of the type of inhaler device (multiple-dose versus single-dose inhalers) on 1-year persistence and switching patterns with LABAs. Methods: A retrospective observational cohort study was performed comparing a cohort of patients initiating multiple-dose inhalers and a cohort initiating single-dose inhalers. The study population consisted of long-acting bronchodilator naive COPD patients, initiating inhalation therapy with mono-LABAs (formoterol, indacaterol or salmeterol). Analyses were performed using pharmacy dispensing data from 1994 to 2012, obtained from the IADB.nl database. Study outcomes were 1-year persistence and switching patterns. Results were adjusted for initial prescriber, initial medication, dosing regimen and relevant comorbidities. Results: In all, 575 patients initiating LABAs were included in the final study cohort. Among them, 475 (83%) initiated a multiple-dose inhaler and 100 (17%) a single-dose inhaler. Further, 269 (47%) initiated formoterol, 9 (2%) indacaterol and 297 (52%) salmeterol. There was no significant difference in persistence between users of multiple-dose or single-dose inhalers (hazard ratio: 0.98, 95% confidence interval: 0.76–1.26, P=0.99). Over 80% re-started or switched medication. Conclusions: There seems no impact of inhaler device (multiple-dose versus single-dose inhalers) on COPD patients’ persistence with LABAs. Over 80% of patients who initially seemed to discontinue LABAs, re-started their initial medication or switched inhalers or medication within 1 year. PMID:25274453

Persistence and ergodicity of a stochastic single species model with Allee effect under regime switching

NASA Astrophysics Data System (ADS)

Yu, Xingwang; Yuan, Sanling; Zhang, Tonghua

2018-06-01

Allee effect can interact with environment stochasticity and is active when population numbers are small. Our goal of this paper is to investigate such effect on population dynamics. More precisely, we develop and investigate a stochastic single species model with Allee effect under regime switching. We first prove the existence of global positive solution of the model. Then, we perform the survival analysis to seek sufficient conditions for the extinction, non-persistence in mean, persistence in mean and stochastic permanence. By constructing a suitable Lyapunov function, we show that the model is positive recurrent and ergodic. Our results indicate that the regime switching can suppress the extinction of the species. Finally, numerical simulations are carried out to illustrate the obtained theoretical results, where a real-life example is also discussed showing the inclusion of Allee effect in the model provides a better match to the data.

Persistent random walk of cells involving anomalous effects and random death

NASA Astrophysics Data System (ADS)

Fedotov, Sergei; Tan, Abby; Zubarev, Andrey

2015-04-01

The purpose of this paper is to implement a random death process into a persistent random walk model which produces sub-ballistic superdiffusion (Lévy walk). We develop a stochastic two-velocity jump model of cell motility for which the switching rate depends upon the time which the cell has spent moving in one direction. It is assumed that the switching rate is a decreasing function of residence (running) time. This assumption leads to the power law for the velocity switching time distribution. This describes the anomalous persistence of cell motility: the longer the cell moves in one direction, the smaller the switching probability to another direction becomes. We derive master equations for the cell densities with the generalized switching terms involving the tempered fractional material derivatives. We show that the random death of cells has an important implication for the transport process through tempering of the superdiffusive process. In the long-time limit we write stationary master equations in terms of exponentially truncated fractional derivatives in which the rate of death plays the role of tempering of a Lévy jump distribution. We find the upper and lower bounds for the stationary profiles corresponding to the ballistic transport and diffusion with the death-rate-dependent diffusion coefficient. Monte Carlo simulations confirm these bounds.

Persistent circular currents of exciton-polaritons in cylindrical pillar microcavities

NASA Astrophysics Data System (ADS)

Lukoshkin, V. A.; Kalevich, V. K.; Afanasiev, M. M.; Kavokin, K. V.; Hatzopoulos, Z.; Savvidis, P. G.; Sedov, E. S.; Kavokin, A. V.

2018-05-01

We have experimentally observed an eddy current of exciton polaritons arising in a cylindrical GaAs/AlGaAs pillar microcavity under the nonresonant optical pumping. The polariton current manifests itself in a Mach-Zehnder interferometry image as a characteristic spiral that occurs due to the interference of the light emitted by an exciton-polariton condensate with a reference spherical wave. We have experimentally observed the condensates with the topological charges m =+1 ,m =-1 , and m =-2 . The interference pattern corresponding to the m =-2 current represents the twin spiral emerging from the center of the micropillar. The switching between the current modes with different topological charges is achieved by a weak displacement of the pump spot.

Persistence of community college engineering science students: The impact of selected cognitive and noncognitive characteristics

NASA Astrophysics Data System (ADS)

Chatman, Lawrence M., Jr.

If the United States is to remain technologically competitive, persistence in engineering programs must improve. This study on student persistence employed a mixed-method design to identify the cognitive and noncognitive factors which contribute to students remaining in an engineering science curriculum or switching from an engineering curriculum at a community college in the northeast United States. Records from 372 students were evaluated to determine the characteristics of two groups: those students that persisted with the engineering curriculum and those that switched from engineering; also, the dropout phenomenon was evaluated. The quantitative portion of the study used a logistic regression analyses on 22 independent variables, while the qualitative portion of the study used group interviews to investigate the noncognitive factors that influenced persisting or switching. The qualitative portion of the study added depth and credibility to the results from the quantitative portion. The study revealed that (1) high grades in first year calculus, physics and chemistry courses, (2) fewer number of semesters enrolled, (3) attendance with full time status, and (4) not participating in an English as a Second Language (ESL) program were significant variables used to predict student persistence. The group interviews confirmed several of these contributing factors. Students that dropped out of college began with (1) the lowest levels of remediation, (2) the lowest grade point averages, and (3) the fewest credits earned.

Sequences of emotions in patients with borderline personality disorder.

PubMed

Reisch, T; Ebner-Priemer, U W; Tschacher, W; Bohus, M; Linehan, M M

2008-07-01

To investigate sequences of emotions (temporal dependence of emotions) to identify specific patterns of borderline personality disorder (BPD). The perceived emotions of 50 BPD patients and 50 healthy controls (HC) were monitored by using a hand-held computer system for a 24-h period in a daily life setting. Participants were prompted four times per hour to assess their current perceived emotions. Differences between BPD patients and HC in terms of activation, persistence and down-regulation of emotions were analyzed. Healthy controls in contrast to BPD patients more often activated joy and interest. BPD patients more often experienced persistence of anxiety and sadness. BPD patients more frequently switched from anxiety to sadness, from anxiety to anger and from sadness to anxiety. Anger was predominantly preceded by anxiety. Persistence of sadness and anxiety, as well as emotional oscillating between anxiety, sadness and anger are important aspects of the emotional dysregulation in BPD patients.

Exploring individual differences in task switching: Persistence and other personality traits related to anterior cingulate cortex function.

PubMed

Umemoto, A; Holroyd, C B

2016-01-01

Anterior cingulate cortex (ACC) is involved in cognitive control and decision-making but its precise function is still highly debated. Based on evidence from lesion, neurophysiological, and neuroimaging studies, we have recently proposed a critical role for ACC in motivating extended behaviors according to learned task values (Holroyd and Yeung, 2012). Computational simulations based on this theory suggest a hierarchical mechanism in which a caudal division of ACC selects and applies control over task execution, and a rostral division of ACC facilitates switches between tasks according to a higher task strategy (Holroyd and McClure, 2015). This theoretical framework suggests that ACC may contribute to personality traits related to persistence and reward sensitivity (Holroyd and Umemoto, 2016). To explore this possibility, we carried out a voluntary task switching experiment in which on each trial participants freely chose one of two tasks to perform, under the condition that they try to select the tasks "at random" and equally often. The participants also completed several questionnaires that assessed personality trait related to persistence, apathy, anhedonia, and rumination, in addition to the Big 5 personality inventory. Among other findings, we observed greater compliance with task instructions by persistent individuals, as manifested by a greater facility with switching between tasks, which is suggestive of increased engagement of rostral ACC. © 2016 Elsevier B.V. All rights reserved.

Switching long acting antipsychotic medications to aripiprazole long acting once-a-month: expert consensus by a panel of Italian and Spanish psychiatrists.

PubMed

Fagiolini, Andrea; Alfonsi, Emilia; Amodeo, Giovanni; Cenci, Mario; Di Lella, Michele; Farinella, Francesco; Ferraiuolo, Fabrizio; Fraguas, David; Loparco, Natale; Gutierrez-Rojas, Luis; Mignone, Maria Laura; Pataracchia, Giuseppe; Pillai, Gianluca; Russo, Felicia; Sanchez-Gistau, Vanessa; Spinogatti, Franco; Toscano, Marco; Villari, Vincenzo; De Filippis, Sergio

2016-01-01

Aripiprazole long acting once-monthly (AOM) is a long acting atypical antipsychotic with proven efficacy in schizophrenia and with a pharmacological and a side effect profile that is different from other antipsychotics. These and other characteristics make AOM a possible alternative in patients requiring a change in long acting antipsychotic treatment due to issues such as lack of efficacy or persistent side effects. Both clinical and pharmacological factors should be considered when switching antipsychotics, and specific guidelines for long acting antipsychotic switching that address all these factors are needed. A panel of Italian and Spanish experts in psychiatry met to discuss the strategies for the switch to AOM in patients with schizophrenia. Real life clinical experiences were shared and the clinical strategies to improve the likelihood of success were discussed. Due to its specific pharmacological and tolerability profile, AOM represents a suitable alternative for patients with schizophrenia requiring a switch to a new LAI treatment because of lack of efficacy or persistent side effects from another LAI. Possible strategies for the switch to AOM are presented in this expert consensus paper in an attempt to provide guidance throughout the entire switching process.

Dynamics of an HBV/HCV infection model with intracellular delay and cell proliferation

NASA Astrophysics Data System (ADS)

Zhang, Fengqin; Li, Jianquan; Zheng, Chongwu; Wang, Lin

2017-01-01

A new mathematical model of hepatitis B/C virus (HBV/HCV) infection which incorporates the proliferation of healthy hepatocyte cells and the latent period of infected hepatocyte cells is proposed and studied. The dynamics is analyzed via Pontryagin's method and a newly proposed alternative geometric stability switch criterion. Sharp conditions ensuring stability of the infection persistent equilibrium are derived by applying Pontryagin's method. Using the intracellular delay as the bifurcation parameter and applying an alternative geometric stability switch criterion, we show that the HBV/HCV infection model undergoes stability switches. Furthermore, numerical simulations illustrate that the intracellular delay can induce complex dynamics such as persistence bubbles and chaos.

Switching Phenomena in a System with No Switches

NASA Astrophysics Data System (ADS)

Preis, Tobias; Stanley, H. Eugene

2010-02-01

It is widely believed that switching phenomena require switches, but this is actually not true. For an intriguing variety of switching phenomena in nature, the underlying complex system abruptly changes from one state to another in a highly discontinuous fashion. For example, financial market fluctuations are characterized by many abrupt switchings creating increasing trends ("bubble formation") and decreasing trends ("financial collapse"). Such switching occurs on time scales ranging from macroscopic bubbles persisting for hundreds of days to microscopic bubbles persisting only for a few seconds. We analyze a database containing 13,991,275 German DAX Future transactions recorded with a time resolution of 10 msec. For comparison, a database providing 2,592,531 of all S&P500 daily closing prices is used. We ask whether these ubiquitous switching phenomena have quantifiable features independent of the time horizon studied. We find striking scale-free behavior of the volatility after each switching occurs. We interpret our findings as being consistent with time-dependent collective behavior of financial market participants. We test the possible universality of our result by performing a parallel analysis of fluctuations in transaction volume and time intervals between trades. We show that these financial market switching processes have properties similar to those of phase transitions. We suggest that the well-known catastrophic bubbles that occur on large time scales—such as the most recent financial crisis—are no outliers but single dramatic representatives caused by the switching between upward and downward trends on time scales varying over nine orders of magnitude from very large (≈102 days) down to very small (≈10 ms).

Investigation of the Genes Involved in Antigenic Switching at the vlsE Locus in Borrelia burgdorferi: An Essential Role for the RuvAB Branch Migrase

PubMed Central

Dresser, Ashley R.; Hardy, Pierre-Olivier; Chaconas, George

2009-01-01

Persistent infection by pathogenic organisms requires effective strategies for the defense of these organisms against the host immune response. A common strategy employed by many pathogens to escape immune recognition and clearance is to continually vary surface epitopes through recombinational shuffling of genetic information. Borrelia burgdorferi, a causative agent of Lyme borreliosis, encodes a surface-bound lipoprotein, VlsE. This protein is encoded by the vlsE locus carried at the right end of the linear plasmid lp28-1. Adjacent to the expression locus are 15 silent cassettes carrying information that is moved into the vlsE locus through segmental gene conversion events. The protein players and molecular mechanism of recombinational switching at vlsE have not been characterized. In this study, we analyzed the effect of the independent disruption of 17 genes that encode factors involved in DNA recombination, repair or replication on recombinational switching at the vlsE locus during murine infection. In Neisseria gonorrhoeae, 10 such genes have been implicated in recombinational switching at the pilE locus. Eight of these genes, including recA, are either absent from B. burgdorferi, or do not show an obvious requirement for switching at vlsE. The only genes that are required in both organisms are ruvA and ruvB, which encode subunits of a Holliday junction branch migrase. Disruption of these genes results in a dramatic decrease in vlsE recombination with a phenotype similar to that observed for lp28-1 or vls-minus spirochetes: productive infection at week 1 with clearance by day 21. In SCID mice, the persistence defect observed with ruvA and ruvB mutants was fully rescued as previously observed for vlsE-deficient B. burgdorferi. We report the requirement of the RuvAB branch migrase in recombinational switching at vlsE, the first essential factor to be identified in this process. These findings are supported by the independent work of Lin et al. in the accompanying article, who also found a requirement for the RuvAB branch migrase. Our results also indicate that the mechanism of switching at vlsE in B. burgdorferi is distinct from switching at pilE in N. gonorrhoeae, which is the only other organism analyzed genetically in detail. Finally, our findings suggest a unique mechanism for switching at vlsE and a role for currently unidentified B. burgdorferi proteins in this process. PMID:19997508

Adherence to iron chelation therapy in patients who switched from deferasirox dispersible tablets to deferasirox film-coated tablets.

PubMed

Cheng, Wendy Y; Said, Qayyim; Hao, Yanni; Xiao, Yongling; Vekeman, Francis; Bobbili, Priyanka; Duh, Mei Sheng; Nandal, Savita; Blinder, Morey

2018-06-04

To compare real-world adherence to and persistence with deferasirox film-coated tablets (DFX-FCT) and deferasirox dispersible tablets (DFX-DT) among patients who switched from DFX-DT to DFX-FCT, overall and by disease type (sickle cell disease [SCD], thalassemia, and myelodysplastic syndrome [MDS]). Patients were ≥2 years old and had ≥2 DFX-FCT claims over the study period and ≥2 DFX-DT claims before the index date (first DFX-FCT claim). The DFX-DT period was defined from the first DFX-DT claim to the index date; the DFX-FCT period was defined from the index date to the end of the study period. Adherence was measured as medication possession ratio (MPR) and proportion of days covered (PDC). Persistence was defined as continuous medication use without a gap ≥30 or 60 days between refills. Comparisons were conducted using paired-sample Wilcoxon sign-rank and McNemar's tests. In total, 606 patients were selected (SCD: 348; thalassemia: 107; MDS: 106; other: 45). Adherence and persistence in the DFX-FCT vs DFX-DT period was significantly higher across all measures: mean MPR was 0.80 vs 0.76 (p < .001); 60.9% vs 54.3% of patients had MPR ≥ 0.8 (p = .009); mean 3-month PDC was 0.83 vs 0.71 (p < .001); 64.2% vs 45.4% of patients had 3-month PDC ≥ 0.8 (p < .001); 87.2% vs 63.4% of patients had 3-month persistence with no gap ≥30 days and 96.1% vs 79.9% with no gap ≥60 days (p < .001). Adherence and persistence improved after switching across all diseases, particularly MDS. Adherence and persistence improved significantly after switching from DFX-DT to DFX-FCT for all diseases, but especially MDS.

Adherence, persistence, and medication discontinuation in patients with attention-deficit/hyperactivity disorder – a systematic literature review

PubMed Central

Gajria, Kavita; Lu, Mei; Sikirica, Vanja; Greven, Peter; Zhong, Yichen; Qin, Paige; Xie, Jipan

2014-01-01

Untreated attention-deficit/hyperactivity disorder (ADHD) can lead to substantial adverse social, economic, and emotional outcomes for patients. The effectiveness of current pharmacologic treatments is often reduced, due to low treatment adherence and medication discontinuation. This current systematic literature review analyzes the current state of knowledge surrounding ADHD medication discontinuation, focusing on: 1) the extent of patient persistence; 2) adherence; and 3) the underlying reasons for patients’ treatment discontinuation and how discontinuation rates and reasons vary across patient subgroups. We selected 91 original studies (67 with persistence/discontinuation results, 26 with adherence results, and 41 with reasons for discontinuation, switching, or nonadherence) and 36 expert opinion reviews on ADHD medication discontinuation, published from 1990 to 2013. Treatment persistence on stimulants, measured by treatment duration during the 12-month follow-up periods, averaged 136 days for children and adolescents and 230 days for adults. Owing to substantial study heterogeneity, comparisons across age or medication type subgroups were generally inconclusive; however, long-acting formulations and amphetamines were associated with longer treatment duration than short-acting formulations and methylphenidates. The medication possession ratio, used to measure adherence, was <0.7 for all age groups and medication classes during a 12-month period. Adverse effects were the most commonly cited reason for discontinuation in all studies. Original research studies reported the lack of symptom control as a common discontinuation reason, followed by dosing inconvenience, social stigma associated with ADHD medication, and the patient’s attitude. In summary, although there was a lack of consistency in the measurement of adherence and persistence, these findings indicate that drug adherence and persistence are generally poor among patients with ADHD. Clinicians may be able to help improve adherence and persistence to ADHD treatment by educating caregivers and patients on treatment goals, administering long-acting medications, and following-up with patients to verify if medication is still effective and well-tolerated. PMID:25187718

Adherence to Positive Airway Therapy After Switching From CPAP to ASV: A Big Data Analysis.

PubMed

Pépin, Jean-Louis D; Woehrle, Holger; Liu, Dongquan; Shao, Shiyun; Armitstead, Jeff P; Cistulli, Peter A; Benjafield, Adam V; Malhotra, Atul

2018-01-15

There is a lack of data regarding adherence trajectories when switching from continuous positive airway pressure (CPAP) to adaptive servoventilation (ASV) in the context of persistent or treatment-emergent central sleep apnea (CSA). This study investigated 90-day adherence rates in patients with sleep apnea based on the type of positive airway pressure (PAP) device used and any switching of PAP modality over time. Telemonitoring data were obtained from a United States PAP database. Eligible patients were a 30% random sample who started PAP, plus all who started ASV, from January 1, 2015 to October 2, 2015. All received PAP and had at least one session with usage of 1 hour or more. Adherence and device usage were determined in three groups: started on CPAP and stayed on CPAP (CPAP only); started on ASV and stayed on ASV (ASV only); started on CPAP, switched to ASV (Switch). The United States Medicare definition of adherence was used. The study included 198,890 patients; 189,724 (CPAP only), 8,957 (ASV only) and 209 (Switch). In the Switch group, average apnea-hypopnea index decreased significantly on ASV versus CPAP. At 90 days, adherence rates were 73.8% and 73.2% in the CPAP only and ASV only groups. In the Switch group, CPAP adherence was 62.7%, improving to 76.6% after the switch to ASV. Mean device usage at 90 days was 5.27, 5.31, and 5.73 h/d in the CPAP only, ASV only, and Switch groups, respectively. Treatment-emergent or persistent CSA during CPAP reduced therapy adherence, but adherence improved early after switching from CPAP to ASV. © 2018 American Academy of Sleep Medicine

Anti-osteoporotic treatments in France: initiation, persistence and switches over 6 years of follow-up.

PubMed

Belhassen, M; Confavreux, C B; Cortet, B; Lamezec, L; Ginoux, M; Van Ganse, E

2017-03-01

Limited information is available on anti-osteoporotic treatment initiation patterns in France. In 2006-2013, the most frequently prescribed first-line treatment class for osteoporosis was represented by bisphosphonates (alendronic acid and risedronic acid), followed by strontium ranelate. Persistence with anti-osteoporotic treatment was low, with high proportions of treatment discontinuations and switches. This epidemiological, longitudinal study described first-line treatment initiation, persistence, switches to second-line treatment, and medical care consumption in osteoporotic patients in France during the 2007-2013 period. Patients aged ≥50 years, who were recorded in a French claims database and did not die during the observation period, were included if they met ≥1 inclusion criteria for osteoporosis in 2007 (≥1 reimbursement for anti-osteoporotic treatment, hospitalisation for osteoporotic fracture (spine, hip, femur, forearm bones, humerus, wrist), or ≥1 reimbursement for long-term osteoporosis-associated status). We collected data on consumption of anti-osteoporotic treatment (alendronic acid, ibandronic acid, risedronic acid, zoledronic acid, raloxifene, strontium ranelate, teriparatide) and of osteoporosis-related medical care after the date of first reimbursement for anti-osteoporotic treatment. We obtained 2219 patients with a 6-year follow-up and 1387 who initiated an anti-osteoporotic treatment in 2007 and who can be selected for the treatment regimen analysis. The most frequently used first-line treatments were alendronic acid (32.7 %), risedronic acid (22.4 %), strontium ranelate (19.3 %), ibandronic acid (13.1 %) and raloxifene (12.2 %). Among patients who received these treatments, the highest persistence after 6 years was observed for raloxifene (37.3 %), alendronic acid (35.1 %) and risedronic acid (32.3 %). Treatment discontinuations were reported for 35.5 % (raloxifene) to 53.4 % (strontium ranelate) and treatment switches for 27.4 % (alendronic acid) to 56.6 % (ibandronic acid) of these patients. This study showed that persistence with anti-osteoporotic treatment was relatively low in France, with high proportions of treatment discontinuations and switches, and that patients with osteoporosis were insufficiently monitored by bone specialists.

Patterns of Persistence in Intended College Major with a Focus on STEM Majors

ERIC Educational Resources Information Center

Shaw, Emily J.; Barbuti, Sandra

2010-01-01

In this study, we examined patterns of persisting in and switching from an intended college major (chosen in high school) in the third year of college. We focused on science, technology, engineering, and math (STEM) major persistence because of the national effort to increase those entering STEM careers. Results showed differences in persistence…

Monitoring Coastal Marshes for Persistent Flooding and Salinity Stress

NASA Technical Reports Server (NTRS)

Kalcic, Maria

2010-01-01

Our objective is to provide NASA remote sensing products that provide inundation and salinity information on an ecosystem level to support habitat switching models. Project born out of need by the Coastal Restoration Monitoring System (CRMS), joint effort by Louisiana Department of Natural Resources and the U.S. Geological Survey, for information on persistence of flooding by storm surge and other flood waters. The results of the this work support the habitat-switching modules in the Coastal Louisiana Ecosystem Assessment and Restoration (CLEAR) model, which provides scientific evaluation for restoration management. CLEAR is a collaborative effort between the Louisiana Board of Regents, the Louisiana Department of Natural Resources (LDNR), the U.S. Geological Survey (USGS), and the U.S. Army Corps of Engineers (USACE). Anticipated results will use: a) Resolution enhanced time series data combining spatial resolution of Landsat with temporal resolution of MODIS for inundation estimates. b) Potential salinity products from radar and multispectral modeling. c) Combined inundation and salinity inputs to habitat switching module to produce habitat switching maps (shown at left)

Better Bet-Hedging with coupled positive and negative feedback loops

NASA Astrophysics Data System (ADS)

Narula, Jatin; Igoshin, Oleg

2011-03-01

Bacteria use the phenotypic heterogeneity associated with bistable switches to distribute the risk of activating stress response strategies like sporulation and persistence. However bistable switches offer little control over the timing of phenotype switching and first passage times (FPT) for individual cells are found to be exponentially distributed. We show that a genetic circuit consisting of interlinked positive and negative feedback loops allows cells to control the timing of phenotypic switching. Using a mathematical model we find that in this system a stable high expression state and stable low expression limit cycle coexist and the FPT distribution for stochastic transitions between them shows multiple peaks at regular intervals. A multimodal FPT distribution allows cells to detect the persistence of stress and control the rate of phenotype transition of the population. We further show that extracellular signals from cell-cell communication that change the strength of the feedback loops can modulate the FPT distribution and allow cells even greater control in a bet-hedging strategy.

Comparative efficacy of switching to natalizumab in active multiple sclerosis

PubMed Central

Spelman, Timothy; Kalincik, Tomas; Zhang, Annie; Pellegrini, Fabio; Wiendl, Heinz; Kappos, Ludwig; Tsvetkova, Larisa; Belachew, Shibeshih; Hyde, Robert; Verheul, Freek; Grand-Maison, Francois; Izquierdo, Guillermo; Grammond, Pierre; Duquette, Pierre; Lugaresi, Alessandra; Lechner-Scott, Jeannette; Oreja-Guevara, Celia; Hupperts, Raymond; Petersen, Thor; Barnett, Michael; Trojano, Maria; Butzkueven, Helmut

2015-01-01

Objective To compare treatment efficacy and persistence in patients who switched to natalizumab versus those who switched between glatiramer acetate (GA) and interferon-beta (IFNβ) after an on-treatment relapse on IFNβ or GA using propensity score matched real-world datasets. Methods Patients included were registered in MSBase or the TYSABRI Observational Program (TOP), had relapsed on IFNβ or GA within 12 months prior to switching to another therapy, and had initiated natalizumab or IFNβ/GA treatment ≤6 months after discontinuing prior therapy. Covariates were balanced across post switch treatment groups by propensity score matching at treatment initiation. Relapse, persistence, and disability measures were compared between matched treatment arms in the total population (n = 869/group) and in subgroups defined by prior treatment history (IFNβ only [n = 578/group], GA only [n = 165/group], or both IFNβ and GA [n = 176/group]). Results Compared to switching between IFNβ and GA, switching to natalizumab reduced annualized relapse rate in year one by 65–75%, the risk of first relapse by 53–82% (mean follow-up 1.7–2.2 years) and treatment discontinuation events by 48–65% (all P ≤ 0.001). In the total population, switching to natalizumab reduced the risk of confirmed disability progression by 26% (P = 0.036) and decreased the total disability burden by 1.54 EDSS-years (P < 0.0001) over the first 24 months post switch. Interpretation Using large, real-world, propensity-matched datasets we demonstrate that after a relapse on IFNβ or GA, switching to natalizumab (rather than between IFNβ and GA) led to superior outcomes for patients in all measures assessed. Results were consistent regardless of the prior treatment identity. PMID:25909083

Nanoscale memory elements based on the superconductor-ferromagnet proximity effect and spin-transfer torque magnetization switching

NASA Astrophysics Data System (ADS)

Baek, Burm

Superconducting-ferromagnetic hybrid devices have potential for a practical memory technology compatible with superconducting logic circuits and may help realize energy-efficient, high-performance superconducting computers. We have developed Josephson junction devices with pseudo-spin-valve barriers. We observed changes in Josephson critical current depending on the magnetization state of the barrier (parallel or anti-parallel) through the superconductor-ferromagnet proximity effect. This effect persists to nanoscale devices in contrast to the remanent field effect. In nanopillar devices, the magnetization states of the pseudo-spin-valve barriers could also be switched with applied bias currents at 4 K, which is consistent with the spin-transfer torque effect in analogous room-temperature spin valve devices. These results demonstrate devices that combine major superconducting and spintronic effects for scalable read and write of memory states, respectively. Further challenges and proposals towards practical devices will also be discussed.In collaboration with: William Rippard, NIST - Boulder, Matthew Pufall, NIST - Boulder, Stephen Russek, NIST-Boulder, Michael Schneider, NIST - Boulder, Samuel Benz, NIST - Boulder, Horst Rogalla, NIST-Boulder, Paul Dresselhaus, NIST - Boulder

Undergraduate Women's Persistence in the Sciences

ERIC Educational Resources Information Center

George-Jackson, Casey E.

2014-01-01

This study uses longitudinal data of undergraduate students from five public land-grant universities to better understand undergraduate students' persistence in and switching of majors, with particular attention given to women's participation in science, technology, engineering, and mathematics (STEM) fields. Specifically, the study examines…

Phenotypic switching in bacteria

NASA Astrophysics Data System (ADS)

Merrin, Jack

Living matter is a non-equilibrium system in which many components work in parallel to perpetuate themselves through a fluctuating environment. Physiological states or functionalities revealed by a particular environment are called phenotypes. Transitions between phenotypes may occur either spontaneously or via interaction with the environment. Even in the same environment, genetically identical bacteria can exhibit different phenotypes of a continuous or discrete nature. In this thesis, we pursued three lines of investigation into discrete phenotypic heterogeneity in bacterial populations: the quantitative characterization of the so-called bacterial persistence, a theoretical model of phenotypic switching based on those measurements, and the design of artificial genetic networks which implement this model. Persistence is the phenotype of a subpopulation of bacteria with a reduced sensitivity to antibiotics. We developed a microfluidic apparatus, which allowed us to monitor the growth rates of individual cells while applying repeated cycles of antibiotic treatments. We were able to identify distinct phenotypes (normal and persistent) and characterize the stochastic transitions between them. We also found that phenotypic heterogeneity was present prior to any environmental cue such as antibiotic exposure. Motivated by the experiments with persisters, we formulated a theoretical model describing the dynamic behavior of several discrete phenotypes in a periodically varying environment. This theoretical framework allowed us to quantitatively predict the fitness of dynamic populations and to compare survival strategies according to environmental time-symmetries. These calculations suggested that persistence is a strategy used by bacterial populations to adapt to fluctuating environments. Knowledge of the phenotypic transition rates for persistence may provide statistical information about the typical environments of bacteria. We also describe a design of artificial genetic networks that would implement a more general theoretical model of phenotypic switching. We will use a new cloning strategy in order to systematically assemble a large number of genetic features, such as site-specific recombination components from the R64 plasmid, which invert several coexisting DNA segments. The inversion of these segments would lead to discrete phenotypic transitions inside a living cell. These artificial phenotypic switches can be controlled precisely in experiments and may serve as a benchmark for their natural counterparts.

Effects of dietary history on energy metabolism and physiological parameters in C57BL/6J mice.

PubMed

Hoevenaars, Femke P M; Keijer, Jaap; Swarts, Hans J; Snaas-Alders, Sophie; Bekkenkamp-Grovenstein, Melissa; van Schothorst, Evert M

2013-05-01

Understanding body weight regulation is essential to fight obesity. Mouse studies, using different types of diets, showed conflicting results in terms of body weight persistence after changing from an ad libitum high-fat diet to an ad libitum low-fat diet. In this study, we questioned specifically whether the energy content of the diet has a lasting effect on energy balance and body weight, using multiple switches and two purified diets with a different fat-to-sugar ratio, but otherwise identical ingredients. Young-adult obesity-prone male C57BL/6J mice were fed single or double switches of semi-purified diets with either 10 energy % (en%) fat (LF) or 40en% fat (HF), with starch replaced by fat, while protein content remained equal. After none, one or two dietary changes, energy metabolism was assessed at 5, 14 and 19 weeks. We observed no systematic continuous compensation in diet and energy intake when returning to LF after HF consumption. Body weight, white adipose tissue mass and histology, serum metabolic parameters, energy expenditure and substrate usage all significantly reflected the current diet intake, independent of dietary changes. This contrasts with studies that used diets with different ingredients and showed persistent effects of dietary history on body weight, suggesting diet-dependent metabolic set points. We conclude that body weight and metabolic parameters 'settle', based on current energetic input and output. This study also highlights the importance of considering the choice of diet in physiological and metabolic intervention studies.

Construction and Operation of an Internal Coil Device, RT-1, with a High-Temperature Superconductor

NASA Astrophysics Data System (ADS)

Ogawa, Yuichi; Yoshida, Zensho; Morikawa, Junji; Saito, Haruhiko; Watanabe, Sho; Yano, Yoshihisa; Mizumaki, Shoichi; Tosaka, Taizo

An internal coil device called Ring Trap-1 (RT-1) has been constructed to explore an innovative concept for a high-beta plasma based on a new relaxation theory. A high-temperature superconductor (HTS) Bi-2223 tape is employed for the internal coil of RT-1. The coil is cooled to 20 K with helium gas supplied by G-M refrigerators, and charged to a magnetomotive force of 250 kA using an external power supply. For these cooling and charging methods, we have developed several innovative techniques such as a demountable transfer tube system, persistent current switch, detachable electrode, and others. In addition, we have paid much attention to the deterioration of the HTS tape during the fabrication of the internal coil. As a result, we have demonstrated that the decay of the persistent current of the internal coil is ˜1% during 8 h. The internal coil is lifted with a levitation coil located at the upper region of the vacuum vessel. The coil position monitored with laser sensors is feedback controlled through the regulation of the levitation coil current. Stable levitation for a few hours has been demonstrated for various plasma experiments.

Magneto-optical quantum interferences in a system of spinor excitons

NASA Astrophysics Data System (ADS)

Kuan, Wen-Hsuan; Gudmundsson, Vidar

2018-04-01

In this work we investigate magneto-optical properties of two-dimensional semiconductor quantum-ring excitons with Rashba and Dresselhaus spin-orbit interactions threaded by a magnetic flux perpendicular to the plane of the ring. By calculating the excitonic Aharonov-Bohm spectrum, we study the Coulomb and spin-orbit effects on the Aharonov-Bohm features. From the light-matter interactions of the excitons, we find that for scalar excitons, there are open channels for spontaneous recombination resulting in a bright photoluminescence spectrum, whereas the forbidden recombination of dipolar excitons results in a dark photoluminescence spectrum. We investigate the generation of persistent charge and spin currents. The exploration of spin orientations manifests that by adjusting the strength of the spin-orbit interactions, the exciton can be constructed as a squeezed complex with specific spin polarization. Moreover, a coherently moving dipolar exciton acquires a nontrivial dual Aharonov-Casher phase, creating the possibility to generate persistent dipole currents and spin dipole currents. Our study reveals that in the presence of certain spin-orbit generated fields, the manipulation of the magnetic field provides a potential application for quantum-ring spinor excitons to be utilized in nano-scaled magneto-optical switches.

Motivation of Students Who Switch from Engineering to Engineering Technology

ERIC Educational Resources Information Center

Ramirez, Nichole

2017-01-01

A set of studies is reported describing the demographics, outcomes, and motivations of students who start in engineering and switch their major to engineering technology. There has been extensive research in engineering persistence, but little focus has been given to the "T" in STEM. Most research combines technology with other science…

Multi-line triggering and interdigitated electrode structure for photoconductive semiconductor switches

DOEpatents

Mar, Alan [Albuquerque, NM; Zutavern, Fred J [Albuquerque, NM; Loubriel, Guillermo [Albuquerque, NM

2007-02-06

An improved photoconductive semiconductor switch comprises multiple-line optical triggering of multiple, high-current parallel filaments between the switch electrodes. The switch can also have a multi-gap, interdigitated electrode for the generation of additional parallel filaments. Multi-line triggering can increase the switch lifetime at high currents by increasing the number of current filaments and reducing the current density at the contact electrodes in a controlled manner. Furthermore, the improved switch can mitigate the degradation of switching conditions with increased number of firings of the switch.

Adult age differences in information foraging in an interactive reading environment.

PubMed

Liu, Xiaomei; Chin, Jessie; Payne, Brennan R; Fu, Wai-Tat; Morrow, Daniel G; Stine-Morrow, Elizabeth A L

2016-05-01

When learning about a single topic in natural reading environments, readers are confronted with multiple sources varying in the type and amount of information. In this situation, readers are free to adaptively respond to the constraints of the environment (e.g., through selection of resources and time allocation for study), but there may be costs of exploring and switching between sources (e.g., disruption of attention, opportunity costs for study). From an ecological perspective, such properties of the environment are expected to influence learning strategies. In the current study, we used a novel reading paradigm to investigate age differences in the effects of information richness (i.e., sentence elaboration) and costs of switching between texts (i.e., time delay) on selection of sources and study time allocation. Consistent with the ecological view, participants progressed from less informative to more informative texts. Furthermore, increased switch cost led to a tendency to allocate more effort to easier materials and to greater persistence in reading, which in turn, led to better memory in both immediate and delayed recall. Older adults showed larger effects of switch cost, such that the age difference in delayed recall was eliminated in the high switch cost condition. Based on an ecological paradigm of reading that affords choice and self-regulation, our study provided evidence for preservation with age in the ability to adapt to changing learning environments so as to improve performance. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Attention Difficulties and Mood-Related Ruminative Response Style in Adolescents with Unipolar Depression

ERIC Educational Resources Information Center

Wilkinson, Paul O.; Goodyer, Ian M.

2006-01-01

Background: Depressed adults may show impairment in switching attention from one task to another. Rumination on negative thoughts is associated with the onset and persistence of depressive episodes. It is unclear if such mood-related ruminations are specifically associated with slowed ability in switching attention from one task to another.…

Maintaining persistence and adherence with subcutaneous growth-hormone therapy in children: comparing jet-delivery and needle-based devices.

PubMed

Spoudeas, Helen A; Bajaj, Priti; Sommerford, Nathan

2014-01-01

Persistence and adherence with subcutaneous growth hormone (GH; somatropin) therapy in children is widely acknowledged to be suboptimal. This study aimed to investigate how the use of a jet-delivery device, ZomaJet(®), impacts on medication-taking behaviors compared to needle-based devices. A retrospective cohort study of children aged ≤18 years was conducted using a UK-based, nationwide database of GH home-delivery schedules. Data were evaluated for the period between January 2010 and December 2012 for 6,061 children receiving either Zomacton(®) (somatropin) via the ZomaJet jet-delivery device or one of six brands of GH all administered via needle-based devices. Persistence was analyzed for patients with appropriate data, measured as the time interval between first and last home deliveries. An analysis of adherence was conducted only for patients using ZomaJet who had appropriate data, measured by proportion of days covered. Brand switches were identified for all patients. Persistence with GH therapy was significantly longer in patients using ZomaJet compared to needle-based devices (599 days versus 535 days, respectively, n=4,093; P<0.001); this association was observed in both sexes and across age subgroups (≤10 and 11-16 years). The majority (58%) of patients using ZomaJet were classed as adherent (n=728). Only 297 patients (5%) switched GH brand (n=6,061), and patients tended to use ZomaJet for longer than other devices before switching. It appears important that the choice of a jet-delivery device is offered to children prescribed daily GH therapy. These devices may represent a much-needed effective strategy for maintaining persistence with subcutaneous GH administration in children, potentially offering better clinical outcomes and greater cost-efficiency.

Survival of Pseudomonas aeruginosa exposed to sunlight resembles the phenom of persistence.

PubMed

Forte Giacobone, Ana F; Oppezzo, Oscar J

2015-01-01

During exposure of Pseudomonas aeruginosa stationary phase cells to natural solar radiation, a reduction in the rate of loss of bacterial viability was observed when survival fractions were lower than 1/10,000. This reduction was independent of the growth medium used and of the initial bacterial concentration, and was also observed when irradiation was performed with artificial UVA radiation (365nm, 47Wm(-2)). These results indicate the presence of a small bacterial subpopulation with increased tolerance to radiation. Such a tolerance is non-heritable, since survival curves comparable to those of the parental strain were obtained from survivors to long-term exposure to radiation. The radiation response described here resembles the phenomenon called persistence, which consists of the presence of a small subpopulation of slow-growing cells which are able to survive antibiotic treatment within a susceptible bacterial population. The condition of persister cells is acquired via a reversible switch and involves active defense systems towards oxidative stress. Persistence is probably responsible for biphasic responses of bacteria to several stress conditions, one of which may be exposure to sunlight. The models currently used to analyze the lethal action of sunlight overestimate the effect of high-dose irradiation. These models could be improved by including the potential formation of persister cells. Copyright © 2014 Elsevier B.V. All rights reserved.

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.

Gate drive latching circuit for an auxiliary resonant commutation circuit

NASA Technical Reports Server (NTRS)

Delgado, Eladio Clemente (Inventor); Kheraluwala, Mustansir Hussainy (Inventor)

1999-01-01

A gate drive latching circuit for an auxiliary resonant commutation circuit for a power switching inverter includes a current monitor circuit providing a current signal to a pair of analog comparators to implement latching of one of a pair of auxiliary switching devices which are used to provide commutation current for commutating switching inverters in the circuit. Each of the pair of comparators feeds a latching circuit which responds to an active one of the comparators for latching the associated gate drive circuit for one of the pair of auxiliary commutating switches. An initial firing signal is applied to each of the commutating switches to gate each into conduction and the resulting current is monitored to determine current direction and therefore the one of the switches which is carrying current. The comparator provides a latching signal to the one of the auxiliary power switches which is actually conducting current and latches that particular power switch into an on state for the duration of current through the device. The latching circuit is so designed that the only time one of the auxiliary switching devices can be latched on is during the duration of an initial firing command signal.

Fast and efficient STT switching in MTJ using additional transient pulse current

NASA Astrophysics Data System (ADS)

Pathak, Sachin; Cha, Jongin; Jo, Kangwook; Yoon, Hongil; Hong, Jongill

2017-06-01

We propose a profile of write pulse current-density to switch magnetization in a perpendicular magnetic tunnel junction to reduce switching time and write energy as well. Our simulated results show that an overshoot transient pulse current-density (current spike) imposed to conventional rectangular-shaped pulse current-density (main pulse) significantly improves switching speed that yields the reduction in write energy accordingly. For example, we could dramatically reduce the switching time by 80% and thereby reduce the write energy over 9% in comparison to the switching without current spike. The current spike affects the spin dynamics of the free layer and reduces the switching time mainly due to spin torque induced. On the other hand, the large Oersted field induced causes changes in spin texture. We believe our proposed write scheme can make a breakthrough in magnetic random access memory technology seeking both high speed operation and low energy consumption.

Hybrid switch for resonant power converters

DOEpatents

Lai, Jih-Sheng; Yu, Wensong

2014-09-09

A hybrid switch comprising two semiconductor switches connected in parallel but having different voltage drop characteristics as a function of current facilitates attainment of zero voltage switching and reduces conduction losses to complement reduction of switching losses achieved through zero voltage switching in power converters such as high-current inverters.

Women, Strategic Identity Management, and Persistence in College Engineering

ERIC Educational Resources Information Center

Naphan, Dara Elizabeth

2016-01-01

In this dissertation, I researched factors that predicted women's likelihood of persistence in college engineering. Women are less likely to study engineering in college than men, and when they do, they are more likely to switch out to another major. As a male-dominated field, micro-aggressions and other forms of discrimination from males are not…

High accuracy switched-current circuits using an improved dynamic mirror

NASA Technical Reports Server (NTRS)

Zweigle, G.; Fiez, T.

1991-01-01

The switched-current technique, a recently developed circuit approach to analog signal processing, has emerged as an alternative/compliment to the well established switched-capacitor circuit technique. High speed switched-current circuits offer potential cost and power savings over slower switched-capacitor circuits. Accuracy improvements are a primary concern at this stage in the development of the switched-current technique. Use of the dynamic current mirror has produced circuits that are insensitive to transistor matching errors. The dynamic current mirror has been limited by other sources of error including clock-feedthrough and voltage transient errors. In this paper we present an improved switched-current building block using the dynamic current mirror. Utilizing current feedback the errors due to current imbalance in the dynamic current mirror are reduced. Simulations indicate that this feedback can reduce total harmonic distortion by as much as 9 dB. Additionally, we have developed a clock-feedthrough reduction scheme for which simulations reveal a potential 10 dB total harmonic distortion improvement. The clock-feedthrough reduction scheme also significantly reduces offset errors and allows for cancellation with a constant current source. Experimental results confirm the simulated improvements.

Coherent quantum dynamics of a superconducting flux qubit.

PubMed

Chiorescu, I; Nakamura, Y; Harmans, C J P M; Mooij, J E

2003-03-21

We have observed coherent time evolution between two quantum states of a superconducting flux qubit comprising three Josephson junctions in a loop. The superposition of the two states carrying opposite macroscopic persistent currents is manipulated by resonant microwave pulses. Readout by means of switching-event measurement with an attached superconducting quantum interference device revealed quantum-state oscillations with high fidelity. Under strong microwave driving, it was possible to induce hundreds of coherent oscillations. Pulsed operations on this first sample yielded a relaxation time of 900 nanoseconds and a free-induction dephasing time of 20 nanoseconds. These results are promising for future solid-state quantum computing.

Patterns of medical management of overactive bladder (OAB) and benign prostatic hyperplasia (BPH) in the United States.

PubMed

Anger, Jennifer T; Goldman, Howard B; Luo, Xuemei; Carlsson, Martin O; Chapman, Douglass; Zou, Kelly H; Russell, David; Ntanios, Fady; Esinduy, Canan B; Clemens, J Quentin

2018-01-01

Overactive bladder (OAB) and benign prostatic hyperplasia (BPH) are highly prevalent conditions that place a large burden on the United States (US) health care system. We sought to analyze patterns of prescription medication usage for incident OAB in men and women, and for incident BPH in men using US health insurance claims data. This study used Truven Health MarketScan® Commercial and Medicare Supplemental Research databases. The data were pooled from diverse points of care. BPH subjects included men age 18+ with the first and last two diagnoses of BPH ≥30 days apart and no BPH diagnosis for 1 year prior. OAB subjects included men and women age 18+, who were diagnosed similarly with incident OAB. The type of medication, medication continuation (persistence), and switching to a different medication were analyzed through September 30, 2013. Medication persistence was much higher overall for BPH than OAB (56% vs 34%, respectively, P < 0.0001), and was highest among men with BPH age 65+ (62%). Patients age 18-64 were less likely to continue medication than older adults (age 65+) for both BPH and OAB. A 9.4% of patients in the OAB cohort and 6.9% of men with BPH switched from one medication to another. Persistence was higher with BPH than OAB medications overall, whereas switching rates were higher in the OAB group. The lower persistence of OAB medication may be due to less efficacy or tolerability. The possibility of under treatment of OAB also warrants future investigations. © 2017 Wiley Periodicals, Inc.

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

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

Focia, Ronald Jeffrey

2017-08-22

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

Trend Switching Processes in Financial Markets

NASA Astrophysics Data System (ADS)

Preis, Tobias; Stanley, H. Eugene

For an intriguing variety of switching processes in nature, the underlying complex system abruptly changes at a specific point from one state to another in a highly discontinuous fashion. Financial market fluctuations are characterized by many abrupt switchings creating increasing trends ("bubble formation") and decreasing trends ("bubble collapse"), on time scales ranging from macroscopic bubbles persisting for hundreds of days to microscopic bubbles persisting only for very short time scales. Our analysis is based on a German DAX Future data base containing 13,991,275 transactions recorded with a time resolution of 10- 2 s. For a parallel analysis, we use a data base of all S&P500 stocks providing 2,592,531 daily closing prices. We ask whether these ubiquitous switching processes have quantifiable features independent of the time horizon studied. We find striking scale-free behavior of the volatility after each switching occurs. We interpret our findings as being consistent with time-dependent collective behavior of financial market participants. We test the possible universality of our result by performing a parallel analysis of fluctuations in transaction volume and time intervals between trades. We show that these financial market switching processes have features similar to those present in phase transitions. We find that the well-known catastrophic bubbles that occur on large time scales - such as the most recent financial crisis - are no outliers but in fact single dramatic representatives caused by the formation of upward and downward trends on time scales varying over nine orders of magnitude from the very large down to the very small.

Diabetic macular edema treated with ranibizumab following bevacizumab failure in Israel (DERBI study).

PubMed

Ehrlich, Rita; Pokroy, Russell; Segal, Ori; Goldstein, Michaella; Pollack, Ayala; Hanhart, Joel; Barak, Yoreh; Kehat, Rinat; Shulman, Shiri; Vidne, Orit; Abu Ahmad, Wiessam; Chowers, Itay

2018-06-01

To evaluate the outcome of second-line intravitreal ranibizumab treatment in eyes with diabetic macular edema having persistent edema following initial therapy with intravitreal bevacizumab. Diabetic macular edema treated with ranibizumab following bevacizumab failure in Israel was a retrospective, multi-center study. Consecutive eyes with persistent diabetic macular edema following at least three previous intravitreal bevacizumab injections prior to intravitreal ranibizumab, at least three-monthly intravitreal ranibizumab injections and at least 12 months of follow-up were included. Data collected included demographics, ocular findings, diabetes control, details of intravitreal bevacizumab and ranibizumab injections, and visual and anatomical measurements before and after intravitreal ranibizumab treatment. In total, 202 eyes of 162 patients treated at 11 medical centers across Israel were included. Patients received a mean (±standard deviation) of 8.8 ± 4.9 intravitreal bevacizumab injections prior to the switch to intravitreal ranibizumab. A mean of 7.0 ± 2.7 intravitreal ranibizumab injections were given during the 12 months following the switch to intravitreal ranibizumab. The median central subfield retinal thickness (±interquartile range) by spectral-domain optical coherence tomography decreased from 436 ± 162 µm at baseline to 319 ± 113 µm at month 12 (p < 0.001). Median logMAR visual acuity (±interquartile range) improved from 0.40 ± 0.48 at baseline to 0.38 ± 0.40 at month 12 (p = 0.001). Linear regression suggested that higher number of intravitreal ranibizumab injections and higher pre-switch central subfield retinal thickness were associated with favorable visual outcome. Higher number of intravitreal bevacizumab injections and the presence of intraretinal fluid before the switch lessened the odds of favorable outcome. Switching from bevacizumab to ranibizumab in persistent diabetic macular edema was associated with anatomical improvement in the majority of eyes and ⩾2 lines of vision improvement in 22% of eyes.

Persistence and extinction of a stochastic single-specie model under regime switching in a polluted environment.

PubMed

Liu, Meng; Wang, Ke

2010-06-07

A new single-species model disturbed by both white noise and colored noise in a polluted environment is developed and analyzed. Sufficient criteria for extinction, stochastic nonpersistence in the mean, stochastic weak persistence in the mean, stochastic strong persistence in the mean and stochastic permanence of the species are established. The threshold between stochastic weak persistence in the mean and extinction is obtained. The results show that both white and colored environmental noises have sufficient effect to the survival results. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

DC switching regulated power supply for driving an inductive load

DOEpatents

Dyer, George R.

1986-01-01

A power supply for driving an inductive load current from a dc power supply hrough a regulator circuit including a bridge arrangement of diodes and switching transistors controlled by a servo controller which regulates switching in response to the load current to maintain a selected load current. First and second opposite legs of the bridge are formed by first and second parallel-connected transistor arrays, respectively, while the third and fourth legs of the bridge are formed by appropriately connected first and second parallel connected diode arrays, respectively. The regulator may be operated in three "stages" or modes: (1) For current runup in the load, both first and second transistor switch arrays are turned "on" and current is supplied to the load through both transistor arrays. (2) When load current reaches the desired level, the first switch is turned "off", and load current "flywheels" through the second switch array and the fourth leg diode array connecting the second switch array in series with the load. Current is maintained by alternating between modes 1 and 2 at a suitable duty cycle and switching rate set by the controller. (3) Rapid current rundown is accomplished by turning both switch arrays "off", allowing load current to be dumped back into the source through the third and fourth diode arrays connecting the source in series opposition with the load to recover energy from the inductive load. The three operating states are controlled automatically by the controller.

Stochastic switching in biology: from genotype to phenotype

NASA Astrophysics Data System (ADS)

Bressloff, Paul C.

2017-03-01

There has been a resurgence of interest in non-equilibrium stochastic processes in recent years, driven in part by the observation that the number of molecules (genes, mRNA, proteins) involved in gene expression are often of order 1-1000. This means that deterministic mass-action kinetics tends to break down, and one needs to take into account the discrete, stochastic nature of biochemical reactions. One of the major consequences of molecular noise is the occurrence of stochastic biological switching at both the genotypic and phenotypic levels. For example, individual gene regulatory networks can switch between graded and binary responses, exhibit translational/transcriptional bursting, and support metastability (noise-induced switching between states that are stable in the deterministic limit). If random switching persists at the phenotypic level then this can confer certain advantages to cell populations growing in a changing environment, as exemplified by bacterial persistence in response to antibiotics. Gene expression at the single-cell level can also be regulated by changes in cell density at the population level, a process known as quorum sensing. In contrast to noise-driven phenotypic switching, the switching mechanism in quorum sensing is stimulus-driven and thus noise tends to have a detrimental effect. A common approach to modeling stochastic gene expression is to assume a large but finite system and to approximate the discrete processes by continuous processes using a system-size expansion. However, there is a growing need to have some familiarity with the theory of stochastic processes that goes beyond the standard topics of chemical master equations, the system-size expansion, Langevin equations and the Fokker-Planck equation. Examples include stochastic hybrid systems (piecewise deterministic Markov processes), large deviations and the Wentzel-Kramers-Brillouin (WKB) method, adiabatic reductions, and queuing/renewal theory. The major aim of this review is to provide a self-contained survey of these mathematical methods, mainly within the context of biological switching processes at both the genotypic and phenotypic levels. However, applications to other examples of biological switching are also discussed, including stochastic ion channels, diffusion in randomly switching environments, bacterial chemotaxis, and stochastic neural networks.

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.

Evolution of households’ responses to the groundwater arsenic crisis in Bangladesh: information on environmental health risks can have increasing behavioral impact over time

PubMed Central

Balasubramanya, Soumya; Pfaff, Alexander; Bennear, Lori; Tarozzi, Alessandro; Ahmed, Kazi Matin; Schoenfeld, Amy; van Geen, Alexander

2014-01-01

A national campaign of well testing through 2003 enabled households in rural Bangladesh to switch, at least for drinking, from high-arsenic wells to neighboring lower-arsenic wells. We study the well-switching dynamics over time by re-interviewing, in 2008, a randomly selected subset of households in the Araihazar region who had been interviewed in 2005. Contrary to concerns that the impact of arsenic information on switching behavior would erode over time, we find that not only was 2003–2005 switching highly persistent but also new switching by 2008 doubled the share of households at unsafe wells who had switched. The passage of time also had a cost: 22% of households did not recall test results by 2008. The loss of arsenic knowledge led to staying at unsafe wells and switching from safe wells. Our results support ongoing well testing for arsenic to reinforce this beneficial information. PMID:25383015

Design notes for the next generation persistent object manager for CAP

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

Isely, M.; Fischler, M.; Galli, M.

1995-05-01

The CAP query system software at Fermilab has several major components, including SQS (for managing the query), the retrieval system (for fetching auxiliary data), and the query software itself. The central query software in particular is essentially a modified version of the `ptool` product created at UIC (University of Illinois at Chicago) as part of the PASS project under Bob Grossman. The original UIC version was designed for use in a single-user non-distributed Unix environment. The Fermi modifications were an attempt to permit multi-user access to a data set distributed over a set of storage nodes. (The hardware is anmore » IBM SP-x system - a cluster of AIX POWER2 nodes with an IBM-proprietary high speed switch interconnect). Since the implementation work of the Fermi-ized ptool, the CAP members have learned quite a bit about the nature of queries and where the current performance bottlenecks exist. This has lead them to design a persistent object manager that will overcome these problems. For backwards compatibility with ptool, the ptool persistent object API will largely be retained, but the implementation will be entirely different.« less

Should We Still Be Talking about Leaving? A Comparative Examination of Social Inequality in Undergraduate Patterns of Switching Majors. WCER Working Paper No. 2014-5

ERIC Educational Resources Information Center

Ferrare, Joseph J.; Lee, You-Geon

2014-01-01

Despite extensive efforts to increase the number of undergraduates majoring and persisting in science, math, engineering, and technology (STEM) fields, there is surprisingly little understanding of recent patterns of switching from these majors to those in other fields of study. In addition, little is known about whether the racial, class, and…

Persistency of use of COX-2-specific inhibitors and non-specific non-steroidal anti-inflammatory drugs (NSAIDs) in Quebec.

PubMed

Moride, Y; Ducruet, T; Rochon, S; Lavoie, F

2003-11-01

The effectiveness of pharmacological therapies is dependent in part on patient persistency with the prescribed therapeutic regimen. In the case of non-specific non-steroidal anti-inflammatory drugs (NSAIDs), effectiveness is often compromised by undesirable side-effects, poor compliance or discontinuation of therapy. While patterns of utilization of non-specific NSAIDs have been investigated, few data are available on the patterns of persistency for cyclooxygenase (COX)-2-specific inhibitors. This study used a provincial health-care system database in Quebec, Canada, to determine the duration of treatment in new users of COX-2-specific inhibitors and non-specific NSAIDs over the first 3 months of treatment, and to characterize the factors associated with treatment persistency. Results demonstrate that the median duration of treatment was longer among patients initially prescribed COX-2-specific inhibitors (30 days and 23 days for celecoxib and rofecoxib respectively) than in those prescribed non-selective NSAIDs (10 days). Although the percentage of patients remaining on COX-2-specific drugs declined over the course of treatment, few patients on either celecoxib or rofecoxib switched drugs, either to the other COX-2-specific inhibitor or to non-specific NSAIDs. Factors associated with persistent drug use were: COX-2-specific inhibitors, age, and the use of gastroprotective agents either at treatment initiation or during follow-up. Dosage, chronic disease score and prescriber's specialty were only marginally associated with persistency. Prior use of gastroprotective agents was associated with lower persistency. Although the limitations of this study, which included lack of information on the indication for the prescription and the reason for switch or discontinuation, preclude definite conclusions regarding patterns of use of these drugs, the data suggest that the use of COX-2-specific inhibitors may result in increased persistency with treatment.

The role of satisfaction and switching costs in Medicare Part D choices.

PubMed

Han, Jayoung; Ko, Dong Woo; Urmie, Julie M

2014-01-01

Most U.S. states had over 50 Medicare Prescription Drug Plans (PDPs) in 2007. Medicare beneficiaries are expected to switch Part D plans based on their health and financial needs; however, the switching rate has been low. Such consumer inertia potentially has negative effects on both beneficiaries and the insurance market, resulting in a critical need to investigate its cause. To 1) describe how Medicare beneficiaries who were satisfied with their current Part D plan differed from those who were not satisfied; 2) examine the effect of switching costs on consideration of switching among Medicare beneficiaries who were dissatisfied with their current Part D plan. Data from the 2007 Prescription Drug Study supplement to the Health and Retirement Study (HRS) survey were used in this study. The satisfied and dissatisfied groups were compared in terms of cost variables, switching costs, and perception of Part D complexity. Structural equation modeling was used to examine relationships among switching costs, Part D complexity, cost variables, and consideration of switching for beneficiaries who were dissatisfied with their current Part D coverage. Out of 467 participants, a total of 255 (54.6%) were satisfied with their current Part D plan. The satisfied group paid lower out-of-pocket costs ($50.63 vs. $114.60) and premiums ($30.88 vs. $40.77) than the dissatisfied group. They also had lower switching costs. Only 11.3% of the dissatisfied beneficiaries switched plans. Among respondents who were dissatisfied with their current plan, those who perceived Part D as complex had high switching costs and were less likely to consider switching plans. Out-of-pocket cost did not have a statistically significant association with consideration of switching. Medicare beneficiaries who were satisfied with their current Part D plans had lower out-of-pocket costs and premiums as well as higher switching costs. Among beneficiaries who were dissatisfied with their current Part D plan, those who had higher switching costs were less likely to consider switching Part D plans. Copyright © 2014 Elsevier Inc. All rights reserved.

Persistent Diet-Induced Obesity in Male C57BL/6 Mice Resulting from Temporary Obesigenic Diets

PubMed Central

Guo, Juen; Jou, William; Gavrilova, Oksana; Hall, Kevin D.

2009-01-01

Background Does diet-induced obesity persist after an obesigenic diet is removed? We investigated this question by providing male C57BL/6 mice with free access to two different obesigenic diets followed by a switch to chow to determine if obesity was reversible. Methodology/Principal Findings Male C57BL/6 mice were randomly assigned to five weight-matched groups: 1) C group that continuously received a chow diet; 2) HF group on a 60% high fat diet; 3) EN group on the high fat diet plus liquid Ensure®; 4) HF-C group switched from high fat to chow after 7 weeks; 5) EN-C group switched from high fat plus Ensure® to chow after 7 weeks. All food intake was ad libitum. Body weight was increased after 7 weeks on both obesigenic diets (44.6±0.65, 39.8±0.63, and 28.6±0.63 g for EN, HF, and C groups, respectively) and resulted in elevated concentrations of serum insulin, glucose, and leptin and lower serum triglycerides. Development of obesity in HF and EN mice was caused by increased energy intake and a relative decrease of average energy output along with decreased ambulatory activity. After the switch to chow, the HF-C and EN-C groups lost weight but subsequently maintained a state of persistent obesity in comparison to the C group (34.8±1.2, 34.1±1.2 vs. 30.8±0.8 g respectively; P<0.05) with a 40–50% increase of body fat. All serum hormones and metabolites returned to control levels with the exception of a trend for increased leptin. The HF-C and EN-C groups had an average energy output in line with the C group and the persistent obesity was maintained despite a non-significant increase of energy intake of less than 1 kcal/d at the end of the study. Conclusion Our results illustrate the importance of considering the history of energy imbalance in determining body weight and that a persistent elevation of body weight after removal of obesigenic diets can result from very small increases of energy intake. PMID:19401758

Switching stable patients with schizophrenia from their oral antipsychotics to aripiprazole lauroxil: a post hoc safety analysis of the initial 12-week crossover period.

PubMed

Weiden, Peter J; Du, Yangchun; Liu, Chih-Chin; Stanford, Arielle D

2018-06-26

Switching antipsychotic medications is common in patients with schizophrenia who are experiencing persistent symptoms or tolerability issues associated with their current drug regimen. This analysis assessed the safety of switching from an oral antipsychotic to the long-acting injectable antipsychotic aripiprazole lauroxil (AL). This was a post hoc analysis of outpatients with schizophrenia who were prescribed an oral antipsychotic and who enrolled in an international, open-label, long-term (52-week) safety study of AL. The analysis focused on the first 3 injections of AL 882 mg over 12 weeks, divided into the immediate 4-week crossover period between the first and second AL injections (initiation phase) and the subsequent 8 weeks (stabilization phase). Patients were grouped by preswitch oral antipsychotic medication, and safety and clinical symptoms were assessed. In total, 190 patients had switched from one of the following oral antipsychotic medications: aripiprazole, conventional antipsychotics, risperidone/paliperidone, olanzapine, or quetiapine. The 12-week completion rate was high (92.1%) and similar across the different preswitch oral antipsychotic groups. Overall, adverse event (AE) rates experienced over 12 weeks were modest; no AEs were considered serious. The most common AEs in the initiation phase were injection site pain (5.8%), insomnia (5.8%), and akathisia (3.2%). No apparent relationship was observed between preswitch medication and early-onset AEs. Mean Positive and Negative Syndrome Scale total scores remained stable during this period across preswitch antipsychotic groups. Switching from an oral antipsychotic to AL was feasible in an outpatient setting for patients with schizophrenia, and the 12-week retention rate was favorable.

Maintaining persistence and adherence with subcutaneous growth-hormone therapy in children: comparing jet-delivery and needle-based devices

PubMed Central

Spoudeas, Helen A; Bajaj, Priti; Sommerford, Nathan

2014-01-01

Purpose Persistence and adherence with subcutaneous growth hormone (GH; somatropin) therapy in children is widely acknowledged to be suboptimal. This study aimed to investigate how the use of a jet-delivery device, ZomaJet®, impacts on medication-taking behaviors compared to needle-based devices. Materials and methods A retrospective cohort study of children aged ≤18 years was conducted using a UK-based, nationwide database of GH home-delivery schedules. Data were evaluated for the period between January 2010 and December 2012 for 6,061 children receiving either Zomacton® (somatropin) via the ZomaJet jet-delivery device or one of six brands of GH all administered via needle-based devices. Persistence was analyzed for patients with appropriate data, measured as the time interval between first and last home deliveries. An analysis of adherence was conducted only for patients using ZomaJet who had appropriate data, measured by proportion of days covered. Brand switches were identified for all patients. Results Persistence with GH therapy was significantly longer in patients using ZomaJet compared to needle-based devices (599 days versus 535 days, respectively, n=4,093; P<0.001); this association was observed in both sexes and across age subgroups (≤10 and 11–16 years). The majority (58%) of patients using ZomaJet were classed as adherent (n=728). Only 297 patients (5%) switched GH brand (n=6,061), and patients tended to use ZomaJet for longer than other devices before switching. Conclusion It appears important that the choice of a jet-delivery device is offered to children prescribed daily GH therapy. These devices may represent a much-needed effective strategy for maintaining persistence with subcutaneous GH administration in children, potentially offering better clinical outcomes and greater cost-efficiency. PMID:25258519

DC switching regulated power supply for driving an inductive load

DOEpatents

Dyer, G.R.

1983-11-29

A dc switching regulated power supply for driving an inductive load is provided. The regulator basic circuit is a bridge arrangement of diodes and transistors. First and second opposite legs of the bridge are formed by first and second parallel-connected transistor arrays, respectively, while the third and fourth legs of the bridge are formed by appropriately connected first and second parallel connected diode arrays, respectively. A dc power supply is connected to the input of the bridge and the output is connected to the load. A servo controller is provided to control the switching rate of the transistors to maintain a desired current to the load. The regulator may be operated in three stages or modes: (1) for current runup in the load, both first and second transistor switch arrays are turned on and current is supplied to the load through both transistor arrays. (2) When load current reaches the desired level, the first switch is turned off, and load current flywheels through the second switch array and the fourth leg diode array connecting the second switch array in series with the load. Current is maintained by alternating between modes 1 and 2 at a suitable duty cycle and switching rate set by the controller. (3) Rapid current rundown is accomplished by turning both switch arrays off, allowing load current to be dumped back into the source through the third and fourth diode arrays connecting the source in series opposition with the load to recover energy from the inductive load.

Simulation study of a new inverse-pinch high Coulomb transfer switch

NASA Technical Reports Server (NTRS)

Choi, S. H.

1984-01-01

A simulation study of a simplified model of a high coulomb transfer switch is performed. The switch operates in an inverse pinch geometry formed by an all metal chamber, which greatly reduces hot spot formations on the electrode surfaces. Advantages of the switch over the conventional switches are longer useful life, higher current capability and lower inductance, which improves the characteristics required for a high repetition rate switch. The simulation determines the design parameters by analytical computations and comparison with the experimentally measured risetime, current handling capability, electrode damage, and hold-off voltages. The parameters of initial switch design can be determined for the anticipated switch performance. Results are in agreement with the experiment results. Although the model is simplified, the switch characteristics such as risetime, current handling capability, electrode damages, and hold-off voltages are accurately determined.

Novel zero voltage transition pulse width modulation flyback converter

NASA Astrophysics Data System (ADS)

Adib, Ehsan; Farzanehfard, Hosein

2010-09-01

In this article, a new zero voltage (ZV) transition flyback converter is introduced which uses a simple auxiliary circuit. In this converter, ZV switching condition is achieved for the converter switch while zero current switching condition is attained for the auxiliary switch. There is no additional voltage and current stress on the main switch. Main diode, auxiliary circuit voltage and current ratings are low. The proposed converter is analysed and design procedure is discussed. The presented experimental results of a prototype converter justify the theoretical analysis.

Oculomotor Cognitive Control Abnormalities in Australian Rules Football Players with a History of Concussion.

PubMed

Clough, Meaghan; Mutimer, Steven; Wright, David K; Tsang, Adrian; Costello, Daniel M; Gardner, Andrew J; Stanwell, Peter; Mychasiuk, Richelle; Sun, Mujun; Brady, Rhys D; McDonald, Stuart J; Webster, Kyria M; Johnstone, Maddison R; Semple, Bridgette D; Agoston, Denes V; White, Owen B; Frayne, Richard; Fielding, Joanne; O'Brien, Terence J; Shultz, Sandy R

2018-03-01

This study used oculomotor, cognitive, and multi-modal magnetic resonance imaging (MRI) measures to assess for neurological abnormalities in current asymptomatic amateur Australian rules footballers (i.e., Australia's most participated collision sport) with a history of sports-related concussion (SRC). Participants were 15 male amateur Australian rules football players with a history of SRC greater than 6 months previously, and 15 sex-, age-, and education-matched athlete control subjects that had no history of neurotrauma or participation in collision sports. Participants completed a clinical interview, neuropsychological measures, and oculomotor measures of cognitive control. MRI investigation involved structural imaging, as well as diffusion tensor imaging and resting-state functional MRI sequences. Despite no group differences on conventional neuropsychological tests and multi-modal MRI measures, Australian rules football players with a history of SRC performed significantly worse on an oculomotor switch task: a measure of cognitive control that interleaves the response of looking towards a target (i.e., a prosaccade) with the response of looking away from a target (i.e., an antisaccade). Specifically, Australian footballers performed significantly shorter latency prosaccades and found changing from an antisaccade trial to a prosaccade trial (switch cost) significantly more difficult than control subjects. Poorer switch cost was related to poorer performance on a number of neuropsychological measures of inhibitory control. Further, when comparing performance on the cognitively more demanding switch task with performance on simpler, antisaccade/prosaccades tasks which require a single response, Australian footballers demonstrated a susceptibility to increased cognitive load, compared to the control group who were unaffected. These initial results suggest that current asymptomatic amateur Australian rules football players with a history of SRC may have persisting, subtle, cognitive changes, which are demonstrable on oculomotor cognitive measures. Future studies are required in order to further elucidate the full nature and clinical relevance of these findings.

Current interruption in inductive storage systems with inertial current source

NASA Astrophysics Data System (ADS)

Vitkovitsky, I. M.; Conte, D.; Ford, R. D.; Lupton, W. H.

1980-03-01

Utilization of inertial current source inductive storage with high power output requires a switch with short opening time. This switch must operate as a circuit breaker, i.e., be capable to carry the current for a time period characteristic of inertial systems, such as homopolar generators. For reasonable efficiency, its opening time must be fast to minimize the energy dissipated in downstream fuse stages required for any additional pulse compression. A switch that satisfies these criteria, as well as other requirements such as that for high voltage operation associated with high power output, is an explosively driven switch consisting of large number of gaps arranged in series. The performance of this switch in limiting and/or interrupting currents produced by large generators has been studied. Single switch modules were designed and tested for limiting the commutating current output of 1 MW, 60 Hz, generator and 500 KJ capacitor banks. Current limiting and commutation were evaluated, using these sources, for currents ranging up to 0.4 MA. The explosive opening of the switch was found to provide an effective first stage for further pulse compression. It opens in tens of microseconds, commutates current at high efficiency ( = 905) recovers very rapidly over a wide range of operating conditions.

Current Source Logic Gate

NASA Technical Reports Server (NTRS)

Krasowski, Michael J. (Inventor); Prokop, Norman F. (Inventor)

2017-01-01

A current source logic gate with depletion mode field effect transistor ("FET") transistors and resistors may include a current source, a current steering switch input stage, and a resistor divider level shifting output stage. The current source may include a transistor and a current source resistor. The current steering switch input stage may include a transistor to steer current to set an output stage bias point depending on an input logic signal state. The resistor divider level shifting output stage may include a first resistor and a second resistor to set the output stage point and produce valid output logic signal states. The transistor of the current steering switch input stage may function as a switch to provide at least two operating points.

A wearable fabric-based speech-generating device: system design and case demonstration.

PubMed

Fleury, Amanda; Wu, Gloria; Chau, Tom

2018-05-26

Existing speech generating devices (SGD) often require caregiver intervention for setup and positioning, and thus limit opportunities for spontaneous social interaction. The advent of conductive fabrics presents an opportunity to render SGDs wearable, thus persistently available. Our goal was to design and test a wearable SGD incorporating resistive textile-based switches for a nonverbal pediatric participant with vision impairment. Quad-key fabric keypads were designed using two conductive fabrics in combination with felt and mesh insulators. The keypad with the most repeatable low force activations and the least cross-talk among keys was chosen for implementation in a wrist-worn, four-message textile SGD. The fabric-based SGD was used by a nonverbal pediatric participant for two one-week analysis periods, alternating with the user's current device for usage reference. Data were derived from usage logs, parent questionnaires and an end-of-study participant interview. The best performing keypad consisted of two layers of woven conductive fabrics and one layer of insulating felt with 10 mm apertures. Communicative interactions were higher with the fabric-based SGD, particularly at school. Unprompted initiation of communication was observed only with the fabric-based SGD. The persistent availability of the textile solution, along with esthetic appeal likely contributed to its utilization. While the participant preferred the fabric-based SGD, the parent opted for the iPod alternative, citing enhanced message intelligibility. Fabric-based SGDs are a new alternative to conventional SGD designs using rigid electronics. As such, tactile differentiability of keys, device wearability and esthetic personalization may be promising advantages for pediatric users. Implications for rehabilitation Fabric-based switches may be a promising alternative to conventional electro-mechanical switches for the control of speech-generating devices, offering functional (e.g., comfort and tactile differentiability), expressive (e.g., non-stigmatizing textile integration) and esthetic (e.g., colors and textures) appeal. The material combination of two layers of woven conductive material and one insulating layer of felt with 10 mm diameter apertures seems to provide a fabric-based keypad suitable for pediatric use, requiring low-force activation and minimal cross-talk among buttons. Fabric-based devices offer advantages of tactile differentiability and thus may be particularly suited to individuals with vision impairments. Wearable textile SGDs can be persistently available and may thus increase opportunities for communication.

Time and spatial evolution of spin-orbit torque-induced magnetization switching in W/CoFeB/MgO structures with various sizes

NASA Astrophysics Data System (ADS)

Zhang, Chaoliang; Fukami, Shunsuke; DuttaGupta, Samik; Sato, Hideo; Ohno, Hideo

2018-04-01

We study spin-orbit torque (SOT) switching in W/CoFeB/MgO structures with various dot sizes (120-3500 nm) using pulsed current of various widths τ (800 ps-100 ms) to examine the time and spatial evolution of magnetization switching. We show that the switching behavior and the resultant threshold switching current density J th strongly depend on device size and pulse width. The switching mode in a 3500 nm dot device changes from probabilistic switching to reproducible partial switching as τ decreases. At τ = 800 ps, J th becomes more than 3 times larger than that in the long-pulse regime. A decrease in dot size to 700 nm does not significantly change the switching characteristics, suggesting that domain-wall propagation among the nucleated multiple domains governs switching. In contrast, devices with further reduced size (120 nm) show normal full switching with increasing probability with current and insignificant dependence of J th on τ, indicating that nucleation governs switching.

Power-Switching Circuit

NASA Technical Reports Server (NTRS)

Praver, Gerald A.; Theisinger, Peter C.; Genofsky, John

1987-01-01

Functions of circuit breakers, meters, and switches combined. Circuit that includes power field-effect transistors (PFET's) provides on/off switching, soft starting, current monitoring, current tripping, and protection against overcurrent for 30-Vdc power supply at normal load currents up to 2 A. Has no moving parts.

Analysis of reliable sub-ns spin-torque switching under transverse bias magnetic fields

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

D'Aquino, M., E-mail: daquino@uniparthenope.it; Perna, S.; Serpico, C.

2015-05-07

The switching process of a magnetic spin-valve nanosystem subject to spin-polarized current pulses is considered. The dependence of the switching probability on the current pulse duration is investigated. The further application of a transverse field along the intermediate anisotropy axis of the particle is used to control the quasi-random relaxation of magnetization to the reversed magnetization state. The critical current amplitudes to realize the switching are determined by studying the phase portrait of the Landau-Lifshtz-Slonczewski dynamics. Macrospin numerical simulations are in good agreement with the theoretical prediction and demonstrate reliable switching even for very short (below 100 ps) current pulses.

Persistence border collisions in a vibrating system excited by an unbalanced motor with a relay control

NASA Astrophysics Data System (ADS)

Zhusubaliyev, Zhanybai T.; Avrutin, Viktor; Rubanov, Vasily G.; Bushuev, Dmitry A.; Titov, Dmitry V.; Yanochkina, Olga O.

2018-05-01

The paper describes a new scenario for the transition to complex dynamics in a vibrating system with an unbalanced rotor and a relay feedback control. We show that the transition from a regular dynamics without switching events in the relay element to an irregular dynamics which takes place completely in the hysteresis region occurs via a cascade of persistence border collisions.

Outcomes of tumor necrosis factor inhibitor cycling versus switching to a disease-modifying anti-rheumatic drug with a new mechanism of action among patients with rheumatoid arthritis.

PubMed

Chastek, Benjamin; Becker, Laura K; Chen, Chieh-I; Mahajan, Puneet; Curtis, Jeffrey R

2017-05-01

To examine treatment patterns, treatment effectiveness, and treatment costs for 1 year after patients with rheumatoid arthritis switched from a tumor necrosis factor inhibitor (TNFi) (adalimumab, certolizumab pegol, etanercept, golimumab, or infliximab), either cycling to another TNFi ("TNFi cyclers") or switching to a new mechanism of action (abatacept, tocilizumab, or tofacitinib) ("new MOA switchers"). This retrospective cohort study used administrative claims data for a national insurer. Treatment persistence (without switching again, restarting, or discontinuing), treatment effectiveness (defined below), and costs were assessed for the 12-month post-switch period. Patients were "effectively treated" if they satisfied all six criteria for a treatment effectiveness algorithm (high adherence, no dose increase, no new conventional synthetic disease-modifying anti-rheumatic drug, no subsequent switch in therapy, no new/increased oral glucocorticoids, and <2 glucocorticoid injections). Multivariable logistic models were used to adjust for baseline factors. The database included 581 new MOA switchers and 935 TNFi cyclers. New MOA switchers were 39% more likely than TNFi cyclers to persist after the switch (odds ratio [OR] = 1.39; 95% confidence interval [CI] = 1.12-1.74; p = .003) and 36% less likely to switch therapy again (OR = 0.64; 95% CI = 0.51-0.81; p < .001). New MOA switchers were 43% more likely than TNFi cyclers to be effectively treated (OR = 1.43; 95% CI = 1.11-1.85; p = .006). New MOA switchers had 16% lower drug costs than TNFi cyclers (cost ratio = 0.84; 95% CI = 0.79-0.88; p < .001) and 11% lower total costs of rheumatoid arthritis-related medical care (cost ratio = 0.89; 95% CI = 0.84-0.94; p < .001). Claims payments may not reflect rebates or other cost offsets. Medical and pharmacy claims do not include clinical end-points or reasons that lead to new MOA switching vs TNFi cycling. These results support switching to a new MOA after a patient fails treatment with a TNFi, which is consistent with recent guidelines for the pharmacologic management of established rheumatoid arthritis.

A fault-tolerant strategy based on SMC for current-controlled converters

NASA Astrophysics Data System (ADS)

Azer, Peter M.; Marei, Mostafa I.; Sattar, Ahmed A.

2018-05-01

The sliding mode control (SMC) is used to control variable structure systems such as power electronics converters. This paper presents a fault-tolerant strategy based on the SMC for current-controlled AC-DC converters. The proposed SMC is based on three sliding surfaces for the three legs of the AC-DC converter. Two sliding surfaces are assigned to control the phase currents since the input three-phase currents are balanced. Hence, the third sliding surface is considered as an extra degree of freedom which is utilised to control the neutral voltage. This action is utilised to enhance the performance of the converter during open-switch faults. The proposed fault-tolerant strategy is based on allocating the sliding surface of the faulty leg to control the neutral voltage. Consequently, the current waveform is improved. The behaviour of the current-controlled converter during different types of open-switch faults is analysed. Double switch faults include three cases: two upper switch fault; upper and lower switch fault at different legs; and two switches of the same leg. The dynamic performance of the proposed system is evaluated during healthy and open-switch fault operations. Simulation results exhibit the various merits of the proposed SMC-based fault-tolerant strategy.

Understanding Statin Use in America and Gaps in Patient Education (USAGE): an internet-based survey of 10,138 current and former statin users.

PubMed

Cohen, Jerome D; Brinton, Eliot A; Ito, Matthew K; Jacobson, Terry A

2012-01-01

Statins substantially reduce the risk of cardiovascular disease and are generally well-tolerated. Despite this, many patients discontinue therapy. A better understanding of the characteristics of current and former statin users may be helpful for formulating strategies to improve long-term adherence. The Understanding Statin Use in America and Gaps in Education (USAGE) survey assessed the attitudes, beliefs, practices, and behavior of current and former statin users. Individuals 18 years or older who reported a history of high cholesterol and current or former statin use were identified within a registered consumer panel cohort in the United States and invited to participate in an Internet survey. Of the 10,138 respondents, 8918 (88%) were current statin users and 1220 (12%) were former users. Participants (mean age 61 years) were predominantly white (92%), female (61%), of middle income (median $44,504/yr), and had health insurance (93%). Among current users, 95% took a statin alone, and 70% had not missed a dose in the past month. Although ∼70% reported that their physicians had explained the importance of cholesterol levels for their heart health former users were less satisfied with the discussions (65% vs. 83%, P < .05). Muscle-related side effects were reported by 60% and 25% of former and current users, respectively (P < .05). Nearly half of all respondents switched statins at least once. The primary reason for switching by current users was cost (32%) and the primary reason for discontinuation was side effects (62%). This survey provides important insights into behavior and attitudes among current and former statin users and the results suggest that more effective dialogue between healthcare providers and patients may increase persistence of statin use, particularly when the patient has concerns about side effects and drug costs. Copyright © 2012 National Lipid Association. Published by Elsevier Inc. All rights reserved.

Formation and disruption of current paths of anodic porous alumina films by conducting atomic force microscopy

NASA Astrophysics Data System (ADS)

Oyoshi, K.; Nigo, S.; Inoue, J.; Sakai, O.; Kitazawa, H.; Kido, G.

2010-11-01

Anodic porous alumina (APA) films have a honeycomb cell structure of pores and a voltage-induced bi-stable switching effect. We have applied conducting atomic force microscopy (CAFM) as a method to form and to disrupt current paths in the APA films. A bi-polar switching operation was confirmed. We have firstly observed terminals of current paths as spots or areas typically on the center of the triangle formed by three pores. In addition, though a part of the current path showed repetitive switching, most of them were not observed again at the same position after one cycle of switching operations in the present experiments. This suggests that a part of alumina structure and/or composition along the current paths is modified during the switching operations.

Strong Orientation-Dependent Spin-Orbit Torque in Thin Films of the Antiferromagnet Mn2Au

NASA Astrophysics Data System (ADS)

Zhou, X. F.; Zhang, J.; Li, F.; Chen, X. Z.; Shi, G. Y.; Tan, Y. Z.; Gu, Y. D.; Saleem, M. S.; Wu, H. Q.; Pan, F.; Song, C.

2018-05-01

Antiferromagnets with zero net magnetic moment, strong anti-interference, and ultrafast switching speed are potentially competitive in high-density information storage. The body-centered tetragonal antiferromagnet Mn2Au with opposite-spin sublattices is a unique metallic material for Néel-order spin-orbit-torque (SOT) switching. We investigate the SOT switching in quasiepitaxial (103), (101) and (204) Mn2Au films prepared by a simple magnetron sputtering method. We demonstrate current-induced antiferromagnetic moment switching in all of the prepared Mn2Au films by using a short current pulse at room temperature, whereas differently oriented films exhibit distinguished switching characters. A direction-independent reversible switching is attained in Mn2Au (103) films due to negligible magnetocrystalline anisotropy energy, while for Mn2Au (101) and (204) films, the switching is invertible with the current applied along the in-plane easy axis and its vertical axis, but it becomes attenuated seriously during initial switching circles when the current is applied along the hard axis because of the existence of magnetocrystalline anisotropy energy. Besides the fundamental significance, the strong orientation-dependent SOT switching, which is not realized, irrespective of ferromagnet and antiferromagnet, provides versatility for spintronics.

Investigation of the environmental implications of the CNT switch through its life cycle

NASA Astrophysics Data System (ADS)

Dahlben, Lindsay Johanna

Carbon nanotubes (CNTs) are unique allotropes of carbon that have high tensile strength, a high Young's modulus, good thermal conductivity, and depending on the CNT chirality can be metallic or semiconducting. These mechanical, thermal, and electrical properties make CNTs an attractive element in electronic applications such as conductive films, photovoltaics, non-volatile memory devices, batteries, sensors, and displays. Although commercialization of CNT-enabled products is increasing, there remains a significant lack of information regarding the health effects and environmental impacts of CNTs. Some studies have even shown that the behavior, toxicity, and persistence of CNTs may differ from bulk heterogeneous carbon. Given these uncertainties, it is prudent to assess the environmental attributes of CNT products and processes now to discover and potentially prevent adverse effects. This study investigates the environmental implications of a non-volatile bi-stable electromechanical CNT switch through its life cycle. Life cycle assessment (LCA) methodology is used to track the environmental impacts of the CNT switch through its fabrication and expected use and end-of-life (EOL) stages. Process parameters, energy consumption, input materials, output emissions, and yield efficiencies are determined for the laboratory and full-scale manufacture environments. The Ecoinvent(TM) inventory database and Eco-indicator 1999(TM) method are utilized for the impact assessment. Results for the fabrication stage are reported for highest contributions to environmental impact such as airborne inorganics, land use, and fossil fuels due to Au refining processes and electricity consumption. Extension of the LCA scope is evaluated for the potential replacement of CNT switches to current field-effect transistors (FETs) in flash memory for a cellular phone application. First-order predictions are made for the functionality and performance of the CNT switch during the use stage through an environmental perspective. Existing cellular phone EOL management options including recycling and direct disposal to landfill and incineration are evaluated for potential limitations, concerns, and environmental releases that may occur from the assimilation of CNT switch-enabled phones into the waste stream. In this manner, potential environmental effects of the CNT switch throughout its life cycle stages can be addressed alongside its technological development to ensure safe, sustainable, and successful CNT products.

Arc-Free High-Power dc Switch

NASA Technical Reports Server (NTRS)

Miller, W. N.; Gray, O. E.

1982-01-01

Hybrid switch allows high-power direct current to be turned on and off without arcing or erosion. Switch consists of bank of transistors in parallel with mechanical contacts. Transistor bank makes and breaks switched circuit; contacts carry current only during steady-state "on" condition. Designed for Space Shuttle orbiter, hybrid switch can be used also in high-power control circuits in aircraft, electric autos, industrial furnaces, and solar-cell arrays.

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.

Interplay between Switching Driven by the Tunneling Current and Atomic Force of a Bistable Four-Atom Si Quantum Dot.

PubMed

Yamazaki, Shiro; Maeda, Keisuke; Sugimoto, Yoshiaki; Abe, Masayuki; Zobač, Vladimír; Pou, Pablo; Rodrigo, Lucia; Mutombo, Pingo; Pérez, Ruben; Jelínek, Pavel; Morita, Seizo

2015-07-08

We assemble bistable silicon quantum dots consisting of four buckled atoms (Si4-QD) using atom manipulation. We demonstrate two competing atom switching mechanisms, downward switching induced by tunneling current of scanning tunneling microscopy (STM) and opposite upward switching induced by atomic force of atomic force microscopy (AFM). Simultaneous application of competing current and force allows us to tune switching direction continuously. Assembly of the few-atom Si-QDs and controlling their states using versatile combined AFM/STM will contribute to further miniaturization of nanodevices.

High-frequency high-voltage high-power DC-to-DC converters

NASA Astrophysics Data System (ADS)

Wilson, T. G.; Owen, H. A., Jr.; Wilson, P. M.

1981-07-01

The current and voltage waveshapes associated with the power transitor and the power diode in an example current-or-voltage step-up (buck-boost) converter were analyzed to highlight the problems and possible tradeoffs involved in the design of high voltage high power converters operating at switching frequencies in the range of 100 Khz. Although the fast switching speeds of currently available power diodes and transistors permit converter operation at high switching frequencies, the resulting time rates of changes of current coupled with parasitic inductances in series with the semiconductor switches, produce large repetitive voltage transients across the semiconductor switches, potentially far in excess of the device voltage ratings. The need is established for semiconductor switch protection circuitry to control the peak voltages appearing across the semiconductor switches, as well as to provide the waveshaping action require for a given semiconductor device. The possible tradeoffs, as well as the factors affecting the tradeoffs that must be considered in order to maximize the efficiency of the converters are enumerated.

High-frequency high-voltage high-power DC-to-DC converters

NASA Technical Reports Server (NTRS)

Wilson, T. G.; Owen, H. A., Jr.; Wilson, P. M.

1981-01-01

The current and voltage waveshapes associated with the power transitor and the power diode in an example current-or-voltage step-up (buck-boost) converter were analyzed to highlight the problems and possible tradeoffs involved in the design of high voltage high power converters operating at switching frequencies in the range of 100 Khz. Although the fast switching speeds of currently available power diodes and transistors permit converter operation at high switching frequencies, the resulting time rates of changes of current coupled with parasitic inductances in series with the semiconductor switches, produce large repetitive voltage transients across the semiconductor switches, potentially far in excess of the device voltage ratings. The need is established for semiconductor switch protection circuitry to control the peak voltages appearing across the semiconductor switches, as well as to provide the waveshaping action require for a given semiconductor device. The possible tradeoffs, as well as the factors affecting the tradeoffs that must be considered in order to maximize the efficiency of the converters are enumerated.

Circuit with a Switch for Charging a Battery in a Battery Capacitor Circuit

NASA Technical Reports Server (NTRS)

Stuart, Thomas A. (Inventor); Ashtiani, Cyrus N. (Inventor)

2008-01-01

A circuit for charging a battery combined with a capacitor includes a power supply adapted to be connected to the capacitor, and the battery. The circuit includes an electronic switch connected to the power supply. The electronic switch is responsive to switch between a conducting state to allow current and a non-conducting state to prevent current flow. The circuit includes a control device connected to the switch and is operable to generate a control signal to continuously switch the electronic switch between the conducting and non-conducting states to charge the battery.

Suppression of TFT leakage current effect on active matrix displays by employing a new circular switch

NASA Astrophysics Data System (ADS)

Lee, Jae-Hoon; Park, Hyun-Sang; Jeon, Jae-Hong; Han, Min-Koo

2008-03-01

We have proposed a new poly-Si TFT pixel, which can suppress TFT leakage current effect on active matrix organic diode (AMOLED) displays, by employing a new circular switching TFT and additional signal line for compensating the leakage current. When the leakage current of switching TFT is increased, the VGS of the current driving TFT in the proposed pixel is not altered by the variable data voltages due to the circular switching TFT. Our simulation results show that OLED current variation of the proposed pixel can be suppressed less than 3%, while that of conventional pixel exceeds 30%. The proposed pixel may be suitable to suppress the leakage current effect on AMOLED display.

Studies of current-perpendicular-to-plane magnetoresistance (CPP-MR) and current-induced magnetization switching (CIMS)

NASA Astrophysics Data System (ADS)

Kurt, Huseyin

2005-08-01

We present two CPP-MR studies of spin-valves based upon ferromagnetic/nonmagnetic/ferromagnetic (F/N/F) trilayers. We measure the spin-diffusion lengths of N = Pd, Pt, and Au at 4.2K, and both the specific resistances (sample area A times resistance R) and spin-memory-loss of N/Cu interfaces. Pd, Pt and Au are of special device interest because they give perpendicular anisotropy when sandwiching very thin Co layers. Comparing our spin-memory-loss data at Pd/Cu and Pt/Cu interfaces with older data for Nb/Cu and W/Cu gives insight into the importance of spin-orbit coupling in producing such loss. We reproduce and extend prior studies by Eid of 'magnetic activity' at the interface of Co and N-metals (or combinations of N-metals), when the other side of the N-metal contacts a superconductor (S). Our data suggest that magnetic activity may require strong spin-flipping at the N/S interface. We present five studies of a new phenomenon, CIMS, in F1/N/F2 trilayers, with F1 a thick 'polarizing' layer and F2 a thin 'switching' layer. In all prior studies of CIMS, positive current caused the magnetization of F2 to switch from parallel (P) to anti-parallel (AP) to that of F1- 'normal' switching. By judicious addition of impurities to F-metals, we are able to controllably produce both 'normal' and 'inverse' switching- where positive current switches the magnetization of F2 from AP to P to that of F1. In the samples studied, whether the switching is normal or inverse is set by the 'net polarization' produced by F1 and is independent of the properties of F2. As scattering in the bulk of F1 and F2 is essential to producing our results, these results cannot be described by ballistic models, which allow scattering only at interfaces. Most CIMS experiments use Cu as the N-layer due to its low resistivity and long spin-diffusion length. We show that Ag and Au have low enough resistivities and long enough spin-diffusion lengths to be useful alternatives to Cu for some devices. While most technical applications of CIMS require low switching currents, some, like read-heads, require high switching currents. We show that use of a synthetic antiferromagnet can increase the switching current. Manschot et al. recently predicted that the positive critical current for switching from P to AP could be reduced by up to a factor of five by using asymmetric current leads. In magnetically uncoupled samples, we find that highly asymmetric current leads do not significantly reduce the switching current. A CIMS equation given by Katine et al. predicts that lowering the demagnetization field should reduce the switching current. To test this prediction, we compare switching currents for Co/Au/Co(t)/Au nanopillars with t = 1 to 4 nm (where the easy axis should be normal to the layer planes at least for t = 1 and 2 nm) with those for Co/Cu/Co(t)/Au nanopillars (where the easy axis should be in the layer planes). We do not find significant differences in switching currents for the two systems.

AlGaN/GaN-on-Si monolithic power-switching device with integrated gate current booster

NASA Astrophysics Data System (ADS)

Han, Sang-Woo; Jo, Min-Gi; Kim, Hyungtak; Cho, Chun-Hyung; Cha, Ho-Young

2017-08-01

This study investigates the effects of a monolithic gate current booster integrated with an AlGaN/GaN-on-Si power-switching device. The integrated gate current booster was implemented by a single-stage inverter topology consisting of a recessed normally-off AlGaN/GaN MOS-HFET and a mesa resistor. The monolithically integrated gate current booster in a switching FET eliminated the parasitic elements caused by external interconnection and enabled fast switching operation. The gate charging and discharging currents were boosted by the integrated inverter, which significantly reduced both rise and fall times: the rise time was reduced from 626 to 41.26 ns, while the fall time was reduced from 554 to 42.19 ns by the single-stage inverter. When the packaged monolithic power chip was tested under 1 MHz hard-switching operation with VDD = 200 V, the switching loss was found to have been drastically reduced, from 5.27 to 0.55 W.

Spin-orbit torque-induced switching in ferrimagnetic alloys: Experiments and modeling

NASA Astrophysics Data System (ADS)

Je, Soong-Geun; Rojas-Sánchez, Juan-Carlos; Pham, Thai Ha; Vallobra, Pierre; Malinowski, Gregory; Lacour, Daniel; Fache, Thibaud; Cyrille, Marie-Claire; Kim, Dae-Yun; Choe, Sug-Bong; Belmeguenai, Mohamed; Hehn, Michel; Mangin, Stéphane; Gaudin, Gilles; Boulle, Olivier

2018-02-01

We investigate spin-orbit torque (SOT)-induced switching in rare-earth-transition metal ferrimagnetic alloys using W/CoTb bilayers. The switching current is found to vary continuously with the alloy concentration, and no reduction in the switching current is observed at the magnetic compensation point despite a very large SOT efficiency. A model based on coupled Landau-Lifschitz-Gilbert (LLG) equations shows that the switching current density scales with the effective perpendicular anisotropy which does not exhibit strong reduction at the magnetic compensation, explaining the behavior of the switching current density. This model also suggests that conventional SOT effective field measurements do not allow one to conclude whether the spins are transferred to one sublattice or just simply to the net magnetization. The effective spin Hall angle measurement shows an enhancement of the spin Hall angle with the Tb concentration which suggests an additional SOT contribution from the rare earth Tb atoms.

Switched-capacitor isolated LED driver

DOEpatents

Sanders, Seth R.; Kline, Mitchell

2016-03-22

A switched-capacitor voltage converter which is particularly well-suited for receiving a line voltage from which to drive current through a series of light emitting diodes (LEDs). Input voltage is rectified in a multi-level rectifier network having switched capacitors in an ascending-bank configuration for passing voltages in uniform steps between zero volts up to full received voltage V.sub.DC. A regulator section, operating on V.sub.DC, comprises switched-capacitor stages of H-bridge switching and flying capacitors. A current controlled oscillator drives the states of the switched-capacitor stages and changes its frequency to maintain a constant current to the load. Embodiments are described for isolating the load from the mains, utilizing an LC tank circuit or a multi-primary-winding transformer.

Alternating between pro- and antisaccades: switch-costs manifest via decoupling the spatial relations between stimulus and response.

PubMed

Heath, Matthew; Gillen, Caitlin; Samani, Ashna

2016-03-01

Antisaccades are a nonstandard task requiring a response mirror-symmetrical to the location of a target. The completion of an antisaccade has been shown to delay the reaction time (RT) of a subsequent prosaccade, whereas the converse switch elicits a null RT cost (i.e., the unidirectional prosaccade switch-cost). The present study sought to determine whether the prosaccade switch-cost arises from low-level interference specific to the sensory features of a target (i.e., modality-dependent) or manifests via the high-level demands of dissociating the spatial relations between stimulus and response (i.e., modality-independent). Participants alternated between pro- and antisaccades wherein the target associated with the response alternated between visual and auditory modalities. Thus, the present design involved task-switch (i.e., switching from a pro- to antisaccade and vice versa) and modality-switch (i.e., switching from a visual to auditory target and vice versa) trials as well as their task- and modality-repetition counterparts. RTs were longer for modality-switch than modality-repetition trials. Notably, however, modality-switch trials did not nullify or lessen the unidirectional prosaccade switch-cost; that is, the magnitude of the RT cost for task-switch prosaccades was equivalent across modality-switch and modality-repetition trials. Thus, competitive interference within a sensory modality does not contribute to the unidirectional prosaccade switch-cost. Instead, the modality-independent findings evince that dissociating the spatial relations between stimulus and response instantiates a high-level and inertially persistent nonstandard task-set that impedes the planning of a subsequent prosaccade.

Characteristics of switching plasma in an inverse-pinch switch

NASA Technical Reports Server (NTRS)

Lee, Ja H.; Choi, Sang H.; Venable, Demetrius D.; Han, Kwang S.; Nam, Sang H.

1993-01-01

Characteristics of the plasma that switches on tens of giga volt-ampere in an inverse-pinch plasma switch (INPIStron) have been made. Through optical and spectroscopic diagnostics of the current carrying plasma, the current density, the motion of current paths, dominant ionic species have been determined in order to access their effects on circuit parameters and material erosion. Also the optimum operational condition of the plasma-puff triggering method required for azimuthally uniform conduction in the INPIStron has been determined.

Robust random telegraph conductivity noise in single crystals of the ferromagnetic insulating manganite La0.86Ca0.14MnO3

NASA Astrophysics Data System (ADS)

Przybytek, J.; Fink-Finowicki, J.; Puźniak, R.; Shames, A.; Markovich, V.; Mogilyansky, D.; Jung, G.

2017-03-01

Robust random telegraph conductivity fluctuations have been observed in La0.86Ca0.14MnO3 manganite single crystals. At room temperatures, the spectra of conductivity fluctuations are featureless and follow a 1 /f shape in the entire experimental frequency and bias range. Upon lowering the temperature, clear Lorentzian bias-dependent excess noise appears on the 1 /f background and eventually dominates the spectral behavior. In the time domain, fully developed Lorentzian noise appears as pronounced two-level random telegraph noise with a thermally activated switching rate, which does not depend on bias current and applied magnetic field. The telegraph noise is very robust and persists in the exceptionally wide temperature range of more than 50 K. The amplitude of the telegraph noise decreases exponentially with increasing bias current in exactly the same manner as the sample resistance increases with the current, pointing out the dynamic current redistribution between percolation paths dominated by phase-separated clusters with different conductivity as a possible origin of two-level conductivity fluctuations.

Presynaptic learning and memory with a persistent firing neuron and a habituating synapse: a model of short term persistent habituation.

PubMed

Ramanathan, Kiruthika; Ning, Ning; Dhanasekar, Dhiviya; Li, Guoqi; Shi, Luping; Vadakkepat, Prahlad

2012-08-01

Our paper explores the interaction of persistent firing axonal and presynaptic processes in the generation of short term memory for habituation. We first propose a model of a sensory neuron whose axon is able to switch between passive conduction and persistent firing states, thereby triggering short term retention to the stimulus. Then we propose a model of a habituating synapse and explore all nine of the behavioral characteristics of short term habituation in a two neuron circuit. We couple the persistent firing neuron to the habituation synapse and investigate the behavior of short term retention of habituating response. Simulations show that, depending on the amount of synaptic resources, persistent firing either results in continued habituation or maintains the response, both leading to longer recovery times. The effectiveness of the model as an element in a bio-inspired memory system is discussed.

SEPP-ZVS High Frequency Inverter Incorporating Auxiliary Switch

NASA Astrophysics Data System (ADS)

Ogiwara, Hiroyuki; Itoi, Misao; Nakaoka, Mutsuo

This paper presents a novel circuit topology to attain ZVS operation of a high frequency inverter over a wide range output power regulation using a PWM control technique by connecting an auxiliary switch to the conventional single ended push-pull (SEPP) ZVS high frequency inverter. A switching current is injected into the main switches via the auxiliary switch only during the short period between its turn-on and off times to supply a current required for its ZVS operation.

Etanercept and adalimumab treatment patterns in psoriatic arthritis patients enrolled in a commercial health plan.

PubMed

Chastek, Benjamin; Fox, Kathleen M; Watson, Crystal; Gandra, Shravanthi R

2012-08-01

Treatment patterns, including persistence, gaps in therapy, switching, and discontinuation, were examined in patients with psoriatic arthritis (PsA) who received the tumor necrosis factor (TNF)-blockers etanercept or adalimumab. This retrospective study utilized administrative claims data from a United States commercial health plan. Adults (age 18-64 years) with PsA who started therapy with etanercept or adalimumab as index therapy between January 1, 2006 and December 31, 2008 were included in the analysis. Patients were continuously enrolled in the health plan for at least 6 months before and at least 12 months after the start of index therapy. Initial TNF-blocker dose and rates of therapy persistence (continuous use of index medication without a gap of at least 60 days), therapy gaps, and discontinuation (gap in therapy of at least 60 days) were estimated. Those who discontinued were further classified as: (1) discontinued all biologic therapy, (2) restarted index medication, (3) switched to another biologic therapy, or (4) other. A total of 346 patients with PsA (202 etanercept, 144 adalimumab) were eligible. Most (90.6% etanercept; 88.9% adalimumab) started index therapy at the labeled dose. Persistence with index therapy for 12 months was observed in 50% of patients on etanercept and 45% of patients on adalimumab (P = 0.37). Patients on etanercept had a longer duration of persistence (434 vs. 353 days; P = 0.02), more pauses of at least 7 days (4.7 vs. 3.5; P = 0.004), and a longer mean pause length (48.6 vs. 29.3 days; P = 0.01) than patients on adalimumab. Of patients who discontinued (24.8% etanercept; 35.1% adalimumab), 46.4% and 41.5% restarted etanercept and adalimumab, respectively; 24.8% and 35.1% discontinued all TNF-blockers; 20.0% and 19.2% switched to another biologic; and 8.8% and 4.3% had other therapy changes. Approximately half of PsA patients were persistent on their index TNF-blocker for 12 months. Pauses in therapy and therapy discontinuation were common, but more than 40% of patients restarted their index TNF-blocker after discontinuation.

Optically triggered high voltage switch network and method for switching a high voltage

DOEpatents

El-Sharkawi, Mohamed A.; Andexler, George; Silberkleit, Lee I.

1993-01-19

An optically triggered solid state switch and method for switching a high voltage electrical current. A plurality of solid state switches (350) are connected in series for controlling electrical current flow between a compensation capacitor (112) and ground in a reactive power compensator (50, 50') that monitors the voltage and current flowing through each of three distribution lines (52a, 52b and 52c), which are supplying three-phase power to one or more inductive loads. An optical transmitter (100) controlled by the reactive power compensation system produces light pulses that are conveyed over optical fibers (102) to a switch driver (110') that includes a plurality of series connected optical triger circuits (288). Each of the optical trigger circuits controls a pair of the solid state switches and includes a plurality of series connected resistors (294, 326, 330, and 334) that equalize or balance the potential across the plurality of trigger circuits. The trigger circuits are connected to one of the distribution lines through a trigger capacitor (340). In each switch driver, the light signals activate a phototransistor (300) so that an electrical current flows from one of the energy reservoir capacitors through a pulse transformer (306) in the trigger circuit, producing gate signals that turn on the pair of serially connected solid state switches (350).

Tests of a low-pressure switch protected by a saturating inductor

NASA Astrophysics Data System (ADS)

Lauer, E. J.; Birx, D. L.

Low pressure switches and magnetic switches were tested as possible replacements for the high pressure switches currently used on Experimental Test Accelerator and Advanced Test Accelerator. When the low pressure switch is used with a low impedance transmission line, runaway electrons form a pinched electron beam which damages the anode. The use of the low pressure switch as the first switch in the pulsed power chain was tested; i.e., the switch would be used to connect a charged capacitor across the primary winding of a step up transformer. An inductor with a saturating core is connected in series so that, initially, there is a large inductive voltage drop. As a result, there is small voltage across the switch. By the time the inductor core saturates, the switch has developed sufficient ionization so that the switch voltage remains small, even with peak current, and an electron beam is not produced.

Persistence factors among engineering students at the Polytechnic University of Puerto Rico: Student perceptions and curricular implications

NASA Astrophysics Data System (ADS)

Gonzalez Juarbe, Juan M.

Various persistence studies demonstrate that there is a direct correlation between college or university academic program completion and the amount of students' involvement in the college or university on a social, academic, and institutional level. These studies suggest that, over the course of time, the greater the level of involvement the greater the probability of increased persistence towards program completion. Student persistence among Hispanic engineering students was researched at the Polytechnic University of Puerto Rico during the period of January 2002 to April 2003. Persistence factors lead students to either one of the following behaviors: (1) to re-enroll, (2) to switch to another educational program, or (3) to depart from the institution. Increased student persistence is the result of recurring decisions to re-enroll each trimester. Decreased student persistence is the outcome associated with a decision to either depart or switch to another educational vocation. Early departure at the institution is linked to perceptions formed day-to-day as the student experiences the educational environment. These perceptions inspire behavioral outcomes to either persist or depart the education process. Desirable behavioral outcomes are closely related with educational commitments leading to increased persistence. Likewise, undesirable behavioral outcomes are those resulting in decreased persistence. Satisfactory student experiences in successfully achieving social, academic, and institutional responsibilities set the course towards increased persistence. In the research undertaken, student and faculty educational experiences were analyzed and documented. This was accomplished by the use of a combined quantitative and qualitative research methodology. The volunteer participants in this study included: six full time professors, eight part time professors, eighty-one students at a job fair, and seven individual student participants. Personal data on the participants was kept confidential. A questionnaire based on persistence variable indicators was developed and used as a data collection instrument for a statistical quantitative analysis. Eighty-one students responded to questionnaire items using a Likert scale ranging from one representing disagreement to five representing agreement. This was followed by a qualitative analysis to increase the scope and depth of the quantitative phase. The qualitative analysis involved discussions with full time professors, part time professors, students, and student graduates. Persistence indicators were then classified into social, academic, and institutional classifications to develop a graphic model of student persistence and a persistence interaction formula indicator. Student persistence levels are proportionally correlated to student contentment with educational outcomes.

A single promoter inversion switches Photorhabdus between pathogenic and mutualistic states.

PubMed

Somvanshi, Vishal S; Sloup, Rudolph E; Crawford, Jason M; Martin, Alexander R; Heidt, Anthony J; Kim, Kwi-suk; Clardy, Jon; Ciche, Todd A

2012-07-06

Microbial populations stochastically generate variants with strikingly different properties, such as virulence or avirulence and antibiotic tolerance or sensitivity. Photorhabdus luminescens bacteria have a variable life history in which they alternate between pathogens to a wide variety of insects and mutualists to their specific host nematodes. Here, we show that the P. luminescens pathogenic variant (P form) switches to a smaller-cell variant (M form) to initiate mutualism in host nematode intestines. A stochastic promoter inversion causes the switch between the two distinct forms. M-form cells are much smaller (one-seventh the volume), slower growing, and less bioluminescent than P-form cells; they are also avirulent and produce fewer secondary metabolites. Observations of form switching by individual cells in nematodes revealed that the M form persisted in maternal nematode intestines, were the first cells to colonize infective juvenile (IJ) offspring, and then switched to P form in the IJ intestine, which armed these nematodes for the next cycle of insect infection.

Analysis and development of fourth order LCLC resonant based capacitor charging power supply for pulse power applications.

PubMed

Naresh, P; Hitesh, C; Patel, A; Kolge, T; Sharma, Archana; Mittal, K C

2013-08-01

A fourth order (LCLC) resonant converter based capacitor charging power supply (CCPS) is designed and developed for pulse power applications. Resonant converters are preferred t utilize soft switching techniques such as zero current switching (ZCS) and zero voltage switching (ZVS). An attempt has been made to overcome the disadvantages in 2nd and 3rd resonant converter topologies; hence a fourth order resonant topology is used in this paper for CCPS application. In this paper a novel fourth order LCLC based resonant converter has been explored and mathematical analysis carried out to calculate load independent constant current. This topology provides load independent constant current at switching frequency (fs) equal to resonant frequency (fr). By changing switching condition (on time and dead time) this topology has both soft switching techniques such as ZCS and ZVS for better switching action to improve the converter efficiency. This novel technique has special features such as low peak current through switches, DC blocking for transformer, utilizing transformer leakage inductance as resonant component. A prototype has been developed and tested successfully to charge a 100 μF capacitor to 200 V.

Coexistence of diode-like volatile and multilevel nonvolatile resistive switching in a ZrO2/TiO2 stack structure.

PubMed

Li, Yingtao; Yuan, Peng; Fu, Liping; Li, Rongrong; Gao, Xiaoping; Tao, Chunlan

2015-10-02

Diode-like volatile resistive switching as well as nonvolatile resistive switching behaviors in a Cu/ZrO₂/TiO₂/Ti stack are investigated. Depending on the current compliance during the electroforming process, either volatile resistive switching or nonvolatile resistive switching is observed. With a lower current compliance (<10 μA), the Cu/ZrO₂/TiO₂/Ti device exhibits diode-like volatile resistive switching with a rectifying ratio over 10(6). The permanent transition from volatile to nonvolatile resistive switching can be obtained by applying a higher current compliance of 100 μA. Furthermore, by using different reset voltages, the Cu/ZrO₂/TiO₂/Ti device exhibits multilevel memory characteristics with high uniformity. The coexistence of nonvolatile multilevel memory and diode-like volatile resistive switching behaviors in the same Cu/ZrO₂/TiO₂/Ti device opens areas of applications in high-density storage, logic circuits, neural networks, and passive crossbar memory selectors.

A coaxial radial opening switch for a distributed-energy-store rail launcher

NASA Astrophysics Data System (ADS)

Upshaw, J. L.; Zowarka, R. C.

1984-03-01

The design, fabrication, and initial testing results for a coaxial radial opening switch for a distributed-energy-store rail launcher are presented. In this nonarcing switch, the voltage needed to transfer current to the rail launcher is generated in a fixed resistor sized to absorb the energy required to accomplish the switching. The coaxial geometry consisting of concentric rings allowed flexibility in defining the conductive and resistive portions of the switch, and also provided tight coupling by minimizing the inductance of the current path between the charging path and the load path to minimize the energy absorption requirements. The resistive portion of the switch is composed of a series of stacked circular steel ring laminations. Switching is completed in three intervals through radial actuation. The switch parts were machined from ETP 110 electrical tough pitch copper plate, 2000 series aluminum plate, and close-tolerance standed GFR epoxy. Current may be transferred at levels less than 20 kA.

Non-volatile, solid state bistable electrical switch

NASA Technical Reports Server (NTRS)

Williams, Roger M. (Inventor)

1994-01-01

A bistable switching element is made of a material whose electrical resistance reversibly decreases in response to intercalation by positive ions. Flow of positive ions between the bistable switching element and a positive ion source is controlled by means of an electrical potential applied across a thermal switching element. The material of the thermal switching element generates heat in response to electrical current flow therethrough, which in turn causes the material to undergo a thermal phase transition from a high electrical resistance state to a low electrical resistance state as the temperature increases above a predetermined value. Application of the electrical potential in one direction renders the thermal switching element conductive to pass electron current out of the ion source. This causes positive ions to flow from the source into the bistable switching element and intercalate the same to produce a non-volatile, low resistance logic state. Application of the electrical potential in the opposite direction causes reverse current flow which de-intercalates the bistable logic switching element and produces a high resistance logic state.

A Switch Is Not a Switch: Syntactically-Driven Bilingual Language Control

ERIC Educational Resources Information Center

Gollan, Tamar H.; Goldrick, Matthew

2018-01-01

The current study investigated the possibility that language switches could be relatively automatically triggered by context. "Single-word switches," in which bilinguals switched languages on a single word in midsentence and then immediately switched back, were contrasted with more complete "whole-language switches," in which…

Current-driven thermo-magnetic switching in magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Kravets, A. F.; Polishchuk, D. M.; Pashchenko, V. A.; Tovstolytkin, A. I.; Korenivski, V.

2017-12-01

We investigate switching of magnetic tunnel junctions (MTJs) driven by the thermal effect of the transport current through the junctions. The switching occurs in a specially designed composite free layer, which acts as one of the MTJ electrodes, and is due to a current-driven ferro-to-paramagnetic Curie transition with the associated exchange decoupling within the free layer leading to magnetic reversal. We simulate the current and heat propagation through the device and show how heat focusing can be used to improve the power efficiency. The Curie-switch MTJ demonstrated in this work has the advantage of being highly tunable in terms of its operating temperature range, conveniently to or just above room temperature, which can be of technological significance and competitive with the known switching methods using spin-transfer torques.

Rates of initial acceptance of PAP masks and outcomes of mask switching.

PubMed

Bachour, Adel; Vitikainen, Pirjo; Maasilta, Paula

2016-05-01

Recently, we noticed a considerable development in alleviating problems related to positive airway pressure (PAP) masks. In this study, we report on the initial PAP mask acceptance rates and the effects of mask switching on mask-related symptoms. We prospectively collected all cases of mask switching in our sleep unit for a period of 14 months. At the time of the study, we used ResMed™ CPAP devices and masks. Mask switching was defined as replacing a mask used for at least 1 day with another type of mask. Changing to a different size but keeping the same type of mask did not count as mask switching. Switching outcomes were considered failed if the initial problem persisted or reappeared during the year that followed switching. Our patient pool was 2768. We recorded 343 cases of mask switching among 267 patients. Of the 566 patients who began new PAP therapy, 108 (39 women) had switched masks, yielding an initial mask acceptance rate of 81 %. The reason for switching was poor-fit/uncomfortable mask in 39 %, leak-related in 30 %, outdated model in 25 %, and nasal stuffiness in 6 % of cases; mask switching resolved these problems in 61 %. Mask switching occurred significantly (p = 0.037) more often in women and in new PAP users. The odds ratio for abandoning PAP therapy within 1 year after mask switching was 7.2 times higher (interval 4.7-11.1) than not switching masks. The initial PAP mask acceptance rate was high. Patients who switched their masks are at greater risk for abandoning PAP therapy.

Persistent photocurrent and deep level traps in PLD-grown In-Ga-Zn-O thin films studied by thermally stimulated current spectroscopy

NASA Astrophysics Data System (ADS)

Wang, Buguo; Anders, Jason; Leedy, Kevin; Schuette, Michael; Look, David

2018-02-01

InGaZnO (IGZO) is a promising semiconductor material for thin-film transistors (TFTs) used in DC and RF switching applications, especially since it can be grown at low temperatures on a wide variety of substrates. Enhancement-mode TFTs based on IGZO thin films grown by pulsed laser deposition (PLD) have been recently fabricated and these transistors show excellent performance; however, compositional variations and defects can adversely affect film quality, especially in regard to electrical properties. In this study, we use thermally stimulated current (TSC) spectroscopy to characterize the electrical properties and the deep traps in PLD-grown IGZO thin films. It was found that the as-grown sample has a DC activation energy of 0.62 eV, and two major traps with activation energies at 0.16-0.26 eV and at 0.90 eV. However, a strong persistent photocurrent (PPC) sometimes exists in the as-grown sample, so we carry out post-growth annealing in an attempt to mitigate the effect. It was found that annealing in argon increases the conduction, produces more PPC and also makes more traps observable. Annealing in air makes the film more resistive, and removes PPC and all traps but one. This work demonstrates that current-based trap emission, such as that associated with the TSC, can effectively reveal electronic defects in highlyresistive semiconductor materials, especially those are not amenable to capacitance-based techniques, such as deeplevel transient spectroscopy (DLTS).

Alpha3, a transposable element that promotes host sexual reproduction.

PubMed

Barsoum, Emad; Martinez, Paula; Aström, Stefan U

2010-01-01

Theoretical models predict that selfish DNA elements require host sex to persist in a population. Therefore, a transposon that induces sex would strongly favor its own spread. We demonstrate that a protein homologous to transposases, called alpha3, was essential for mating type switch in Kluyveromyces lactis. Mutational analysis showed that amino acids conserved among transposases were essential for its function. During switching, sequences in the 5' and 3' flanking regions of the alpha3 gene were joined, forming a DNA circle, showing that alpha3 mobilized from the genome. The sequences encompassing the alpha3 gene circle junctions in the mating type alpha (MATalpha) locus were essential for switching from MATalpha to MATa, suggesting that alpha3 mobilization was a coupled event. Switching also required a DNA-binding protein, Mating type switch 1 (Mts1), whose binding sites in MATalpha were important. Expression of Mts1 was repressed in MATa/MATalpha diploids and by nutrients, limiting switching to haploids in low-nutrient conditions. A hairpin-capped DNA double-strand break (DSB) was observed in the MATa locus in mre11 mutant strains, indicating that mating type switch was induced by MAT-specific DSBs. This study provides empirical evidence for selfish DNA promoting host sexual reproduction by mediating mating type switch.

Hybrid high direct current circuit interrupter

DOEpatents

Rockot, Joseph H.; Mikesell, Harvey E.; Jha, Kamal N.

1998-01-01

A device and a method for interrupting very high direct currents (greater than 100,000 amperes) and simultaneously blocking high voltages (greater than 600 volts). The device utilizes a mechanical switch to carry very high currents continuously with low loss and a silicon controlled rectifier (SCR) to bypass the current around the mechanical switch while its contacts are separating. A commutation circuit, connected in parallel with the SCR, turns off the SCR by utilizing a resonant circuit to divert the SCR current after the switch opens.

Allergic inflammation induces a persistent mechanistic switch in thromboxane-mediated airway constriction in the mouse

PubMed Central

Cyphert, Jaime M.; Allen, Irving C.; Church, Rachel J.; Latour, Anne M.; Snouwaert, John N.; Coffman, Thomas M.

2012-01-01

Actions of thromboxane (TXA2) to alter airway resistance were first identified over 25 years ago. However, the mechanism underlying this physiological response has remained largely undefined. Here we address this question using a novel panel of mice in which expression of the thromboxane receptor (TP) has been genetically manipulated. We show that the response of the airways to TXA2 is complex: it depends on expression of other G protein-coupled receptors but also on the physiological context of the signal. In the healthy airway, TXA2-mediated airway constriction depends on expression of TP receptors by smooth muscle cells. In contrast, in the inflamed lung, the direct actions of TXA2 on smooth muscle cell TP receptors no longer contribute to bronchoconstriction. Instead, in allergic lung disease, TXA2-mediated airway constriction depends on neuronal TP receptors. Furthermore, this mechanistic switch persists long after resolution of pulmonary inflammation. Our findings demonstrate the powerful ability of lung inflammation to modify pathways leading to airway constriction, resulting in persistent changes in mechanisms of airway reactivity to key bronchoconstrictors. Such alterations are likely to shape the pathogenesis of asthmatic lung disease. PMID:21984570

Fast switching and signature of efficient domain wall motion driven by spin-orbit torques in a perpendicular anisotropy magnetic insulator/Pt bilayer

NASA Astrophysics Data System (ADS)

Avci, Can Onur; Rosenberg, Ethan; Baumgartner, Manuel; Beran, Lukáš; Quindeau, Andy; Gambardella, Pietro; Ross, Caroline A.; Beach, Geoffrey S. D.

2017-08-01

We report fast and efficient current-induced switching of a perpendicular anisotropy magnetic insulator thulium iron garnet by using spin-orbit torques (SOT) from the Pt overlayer. We first show that, with quasi-DC (10 ms) current pulses, SOT-induced switching can be achieved with an external field as low as 2 Oe, making TmIG an outstanding candidate to realize efficient switching in heterostructures that produce moderate stray fields without requiring an external field. We then demonstrate deterministic switching with fast current pulses (≤20 ns) with an amplitude of ˜1012 A/m2, similar to all-metallic structures. We reveal that, in the presence of an initially nucleated domain, the critical switching current is reduced by up to a factor of five with respect to the fully saturated initial state, implying efficient current-driven domain wall motion in this system. Based on measurements with 2 ns-long pulses, we estimate the domain wall velocity of the order of ˜400 m/s per j = 1012 A/m2.

Current induced magnetization switching in Co/Cu/Ni-Fe nanopillar with orange peel coupling

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

Aravinthan, D.; Daniel, M.; Sabareesan, P.

The impact of orange peel coupling on spin current induced magnetization switching in a Co/Cu/Ni-Fe nanopillar device is investigated by solving the switching dynamics of magnetization of the free layer governed by the Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation. The value of the critical current required to initiate the magnetization switching is calculated analytically by solving the LLGS equation and verified the same through numerical analysis. Results of numerical simulation of the LLGS equation using Runge-Kutta fourth order procedure shows that the presence of orange peel coupling between the spacer and the ferromagnetic layers reduces the switching time of the nanopillar device frommore » 67 ps to 48 ps for an applied current density of 4 × 10{sup 12}Am{sup −2}. Also, the presence of orange peel coupling reduces the critical current required to initiate switching, and in this case, from 1.65 × 10{sup 12}Am{sup −2} to 1.39 × 10{sup 12}Am{sup −2}.« less

High Current, Multi-Filament Photoconductive Semiconductor Switching

DTIC Science & Technology

2011-06-01

linear PCSS triggered with a 100 fs laser pulse . Figure 1. A generic photoconductive semiconductor switch rapidly discharges a charged capacitor...switching is the most critical challenge remaining for photoconductive semiconductor switch (PCSS) applications in Pulsed Power. Many authors have...isolation and control, pulsed or DC charging, and long device lifetime, provided the current per filament is limited to 20-30A for short pulse (10

Effect of biquadratic coupling on current induced magnetization switching in Co/Cu/Ni-Fe nanopillar

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

Aravinthan, D.; Daniel, M., E-mail: danielcnld@gmail.com; Sabareesan, P.

2016-05-23

The effect of biquadratic coupling on spin current induced magnetization switching in a Co/Cu/Ni-Fe nanopillar device is investigated by solving the free layer magnetization switching dynamics governed by the Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation. The LLGS equation is numerically solved by using Runge-Kutta fourth order procedure for an applied current density of 5 × 10{sup 12} Am{sup -2}. Presence of biquadratic coupling in the ferromagnetic layers reduces the magnetization switching time of the nanopillar device from 61 ps to 49 ps.

HOLLOTRON switch for megawatt lightweight space inverters

NASA Technical Reports Server (NTRS)

Poeschel, R. L.; Goebel, D. M.; Schumacher, R. W.

1991-01-01

The feasibility of satisfying the switching requirements for a megawatt ultralight inverter system using HOLLOTRON switch technology was determined. The existing experimental switch hardware was modified to investigate a coaxial HOLLOTRON switch configuration and the results were compared with those obtained for a modified linear HOLLOTRON configuration. It was concluded that scaling the HOLLOTRON switch to the current and voltage specifications required for a megawatt converter system is indeed feasible using a modified linear configuration. The experimental HOLLOTRON switch operated at parameters comparable to the scaled coaxial HOLLOTRON. However, the linear HOLLOTRON data verified the capability for meeting all the design objectives simultaneously including current density (greater than 2 A/sq cm), voltage (5 kV), switching frequency (20 kHz), switching time (300 ns), and forward voltage drop (less than or equal to 20 V). Scaling relations were determined and a preliminary design was completed for an engineering model linear HOLLOTRON switch to meet the megawatt converter system specifications.

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

Synchrony in Metapopulations with Sporadic Dispersal

NASA Astrophysics Data System (ADS)

Jeter, Russell; Belykh, Igor

2015-06-01

We study synchronization in ecological networks under the realistic assumption that the coupling among the patches is sporadic/stochastic and due to rare and short-term meteorological conditions. Each patch is described by a tritrophic food chain model, representing the producer, consumer, and predator. If all three species can migrate, we rigorously prove that the network can synchronize as long as the migration occurs frequently, i.e. fast compared to the period of the ecological cycle, even though the network is disconnected most of the time. In the case where only the top trophic level (i.e. the predator) can migrate, we reveal an unexpected range of intermediate switching frequencies where synchronization becomes stable in a network which switches between two nonsynchronous dynamics. As spatial synchrony increases the danger of extinction, this counterintuitive effect of synchrony emerging from slower switching dispersal can be destructive for overall metapopulation persistence, presumably expected from switching between two dynamics which are unfavorable to extinction.

Characterisation of the current switch mechanism in two-stage wire array Z-pinches

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

Burdiak, G. C.; Lebedev, S. V.; Harvey-Thompson, A. J.

2015-11-15

In this paper, we describe the operation of a two-stage wire array z-pinch driven by the 1.4 MA, 240 ns rise-time Magpie pulsed-power device at Imperial College London. In this setup, an inverse wire array acts as a fast current switch, delivering a current pre-pulse into a cylindrical load wire array, before rapidly switching the majority of the generator current into the load after a 100–150 ns dwell time. A detailed analysis of the evolution of the load array during the pre-pulse is presented. Measurements of the load resistivity and energy deposition suggest significant bulk heating of the array mass occurs. Themore » ∼5 kA pre-pulse delivers ∼0.8 J of energy to the load, leaving it in a mixed, predominantly liquid-vapour state. The main current switch occurs as the inverse array begins to explode and plasma expands into the load region. Electrical and imaging diagnostics indicate that the main current switch may evolve in part as a plasma flow switch, driven by the expansion of a magnetic cavity and plasma bubble along the length of the load array. Analysis of implosion trajectories suggests that approximately 1 MA switches into the load in 100 ns, corresponding to a doubling of the generator dI/dt. Potential scaling of the device to higher current machines is discussed.« less

Prognostic health monitoring in switch-mode power supplies with voltage regulation

NASA Technical Reports Server (NTRS)

Hofmeister, James P (Inventor); Judkins, Justin B (Inventor)

2009-01-01

The system includes a current injection device in electrical communication with the switch mode power supply. The current injection device is positioned to alter the initial, non-zero load current when activated. A prognostic control is in communication with the current injection device, controlling activation of the current injection device. A frequency detector is positioned to receive an output signal from the switch mode power supply and is able to count cycles in a sinusoidal wave within the output signal. An output device is in communication with the frequency detector. The output device outputs a result of the counted cycles, which are indicative of damage to an a remaining useful life of the switch mode power supply.

Nonlinear Magnetic Dynamics and The Switching Phase Diagrams in Spintronic Devices

NASA Astrophysics Data System (ADS)

Yan, Shu

Spin-transfer torque induced magnetic switching, by which the spin-polarized current transfers its magnetic moment to the ferromagnetic layer and changes its magnetization, holds great promise towards faster and smaller magnetic bits in data-storage applications due to the lower power consumption and better scalability. We propose an analytic approach which can be used to calculate the switching phase diagram of a nanomagnetic system in the presence of both magnetic field and spin-transfer torque in an exact fashion. This method is applied to the study of switching conditions for the uniaxial, single domain magnetic layers in different spin-transfer devices. In a spin valve with spin polarization collinear with the easy axis, we get a modified Stoner-Wohlfarth astroid which represents many of the features that have been found in experiment. It also shows a self-crossing boundary and demonstrates a region with three stable equilibria. We demonstrate that the region of stable equilibria with energy near the maximum can be reached only through a narrow bottleneck in the field space, which sets a stringent requirement for magnetic field alignment in the experiments. Switching diagrams are then calculated for the setups with magnetic field not perfectly aligned with the easy axis. In a ferromagnet-heavy-metal bilayer device with strong spin Hall effect, the in plane current becomes spin-polarized and transfers its magnetic moment to the ferromagnetic layer by diffusion. The three-dimensional asymmetric phase diagram is calculated. In the case that the external field is confined in the vertical plane defined by the direction of the current and the easy axis, the spin-transfer torque shifts the conventional in-plane (IP) equilibria within the same plane, and also creates two out-of-plane (OOP) equilibria, one of which can be stable. The threshold switching currents for IP switching and OOP switching are discussed. We also address the magnetic switching processes. Damping switching and precessional switching are two different switching types that are typically considered in recent studies. In the damping mode the switching is slow and heavily depends on the initial deviation, while in the precessional mode the accurate manipulation of the field or current pulse is required. We propose a switching scenario for a fast and reliable switching by taking advantage of the out-of-plane stable equilibrium in the SHE induced magnetic switching. The magnetization is first driven by a pulse of field and current towards the OOP equilibrium without precession. Since it is in the lower half of the unit sphere, no backwards pulse is required for a complete switching. This indicates a potentially feasible method of reliable ultra-fast magnetic control.

Reversible Control of Interfacial Magnetism through Ionic-Liquid-Assisted Polarization Switching

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

Herklotz, Andreas; Guo, Er-Jia; Wong, Anthony T.

The ability to control magnetism of materials via electric field enables a myriad of technological innovations in information storage, sensing, and computing. In this paper, we use ionic-liquid-assisted ferroelectric switching to demonstrate reversible modulation of interfacial magnetism in a multiferroic heterostructure composed of ferromagnetic (FM) La 0.8Sr 0.2MnO 3 and ferroelectric (FE) PbZr 0.2Ti 0.8O 3. It is shown that ionic liquids can be used to persistently and reversibly switch a large area of a FE film. Finally, this is a prerequisite for polarized neutron reflectometry (PNR) studies that are conducted to directly probe magnetoelectric coupling of the FE polarizationmore » to the interfacial magnetization.« less

Reversible Control of Interfacial Magnetism through Ionic-Liquid-Assisted Polarization Switching

DOE PAGES

Herklotz, Andreas; Guo, Er-Jia; Wong, Anthony T.; ...

2017-02-06

The ability to control magnetism of materials via electric field enables a myriad of technological innovations in information storage, sensing, and computing. In this paper, we use ionic-liquid-assisted ferroelectric switching to demonstrate reversible modulation of interfacial magnetism in a multiferroic heterostructure composed of ferromagnetic (FM) La 0.8Sr 0.2MnO 3 and ferroelectric (FE) PbZr 0.2Ti 0.8O 3. It is shown that ionic liquids can be used to persistently and reversibly switch a large area of a FE film. Finally, this is a prerequisite for polarized neutron reflectometry (PNR) studies that are conducted to directly probe magnetoelectric coupling of the FE polarizationmore » to the interfacial magnetization.« less

49 CFR 229.87 - Hand-operated switches.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 4 2013-10-01 2013-10-01 false Hand-operated switches. 229.87 Section 229.87....87 Hand-operated switches. All hand-operated switches carrying currents with a potential of more than... outside of the cover. Means shall be provided to show whether the switches are open or closed. Switches...

49 CFR 229.87 - Hand-operated switches.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 4 2012-10-01 2012-10-01 false Hand-operated switches. 229.87 Section 229.87....87 Hand-operated switches. All hand-operated switches carrying currents with a potential of more than... outside of the cover. Means shall be provided to show whether the switches are open or closed. Switches...

49 CFR 229.87 - Hand-operated switches.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 4 2011-10-01 2011-10-01 false Hand-operated switches. 229.87 Section 229.87....87 Hand-operated switches. All hand-operated switches carrying currents with a potential of more than... outside of the cover. Means shall be provided to show whether the switches are open or closed. Switches...

49 CFR 229.87 - Hand-operated switches.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 4 2014-10-01 2014-10-01 false Hand-operated switches. 229.87 Section 229.87....87 Hand-operated switches. All hand-operated switches carrying currents with a potential of more than... outside of the cover. Means shall be provided to show whether the switches are open or closed. Switches...

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

Yoshizumi, K.; Sasaki, A.; Kohda, M.

We demonstrate gate-controlled switching between persistent spin helix (PSH) state and inverse PSH state, which are detected by quantum interference effect on magneto-conductance. These special symmetric spin states showing weak localization effect give rise to a long spin coherence when the strength of Rashba spin-orbit interaction (SOI) is close to that of Dresselhaus SOI. Furthermore, in the middle of two persistent spin helix states, where the Rashba SOI can be negligible, the bulk Dresselhaus SOI parameter in a modulation doped InGaAs/InAlAs quantum well is determined.

Ultrafast Power Processor for Smart Grid Power Module Development

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

MAITRA, ARINDAM; LITWIN, RAY; lai, Jason

This project’s goal was to increase the switching speed and decrease the losses of the power semiconductor devices and power switch modules necessary to enable Smart Grid energy flow and control equipment such as the Ultra-Fast Power Processor. The primary focus of this project involves exploiting the new silicon-based Super-GTO (SGTO) technology and build on prototype modules already being developed. The prototype super gate-turn-off thyristor (SGTO) has been tested fully under continuously conducting and double-pulse hard-switching conditions for conduction and switching characteristics evaluation. The conduction voltage drop measurement results indicate that SGTO has excellent conduction characteristics despite inconsistency among somemore » prototype devices. Tests were conducted with two conditions: (1) fixed gate voltage and varying anode current condition, and (2) fixed anode current and varying gate voltage condition. The conduction voltage drop is relatively a constant under different gate voltage condition. In terms of voltage drop as a function of the load current, there is a fixed voltage drop about 0.5V under zero current condition, and then the voltage drop is linearly increased with the current. For a 5-kV voltage blocking device that may operate under 2.5-kV condition, the projected voltage drop is less than 2.5 V under 50-A condition, or 0.1%. If the device is adopted in a converter operating under soft-switching condition, then the converter can achieve an ultrahigh efficiency, typically above 99%. The two-pulse switching test results indicate that SGTO switching speed is very fast. The switching loss is relatively low as compared to that of the insulated-gate-bipolar-transistors (IGBTs). A special phenomenon needs to be noted is such a fast switching speed for the high-voltage switching tends to create an unexpected Cdv/dt current, which reduces the turn-on loss because the dv/dt is negative and increases the turn-off loss because the dv/dt is positive. As a result, the turn-on loss at low current is quite low, and the turn-off loss at low current is relatively high. The phenomenon was verified with junction capacitance measurement along with the dv/dt calculation. Under 2-kV test condition, the turn-on and turn-off losses at 25-A is about 3 and 9 mJ, respectively. As compared to a 4.5-kV, 60-A rated IGBT, which has turn-on and turn-off losses about 25 and 20 mJ under similar test condition, the SGTO shows significant switching loss reduction. The switching loss depends on the switching frequency, but under hard-switching condition, the SGTO is favored to the IGBT device. The only concern is during low current turn-on condition, there is a voltage bump that can translate to significant power loss and associated heat. The reason for such a current bump is not known from this study. It is necessary that the device manufacturer perform though test and provide the answer so the user can properly apply SGTO in pulse-width-modulated (PWM) converter and inverter applications.« less

Hybrid high direct current circuit interrupter

DOEpatents

Rockot, J.H.; Mikesell, H.E.; Jha, K.N.

1998-08-11

A device and a method are disclosed for interrupting very high direct currents (greater than 100,000 amperes) and simultaneously blocking high voltages (greater than 600 volts). The device utilizes a mechanical switch to carry very high currents continuously with low loss and a silicon controlled rectifier (SCR) to bypass the current around the mechanical switch while its contacts are separating. A commutation circuit, connected in parallel with the SCR, turns off the SCR by utilizing a resonant circuit to divert the SCR current after the switch opens. 7 figs.

Current limiter circuit system

DOEpatents

Witcher, Joseph Brandon; Bredemann, Michael V.

2017-09-05

An apparatus comprising a steady state sensing circuit, a switching circuit, and a detection circuit. The steady state sensing circuit is connected to a first, a second and a third node. The first node is connected to a first device, the second node is connected to a second device, and the steady state sensing circuit causes a scaled current to flow at the third node. The scaled current is proportional to a voltage difference between the first and second node. The switching circuit limits an amount of current that flows between the first and second device. The detection circuit is connected to the third node and the switching circuit. The detection circuit monitors the scaled current at the third node and controls the switching circuit to limit the amount of the current that flows between the first and second device when the scaled current is greater than a desired level.

MOSFET Switching Circuit Protects Shape Memory Alloy Actuators

NASA Technical Reports Server (NTRS)

Gummin, Mark A.

2011-01-01

A small-footprint, full surface-mount-component printed circuit board employs MOSFET (metal-oxide-semiconductor field-effect transistor) power switches to switch high currents from any input power supply from 3 to 30 V. High-force shape memory alloy (SMA) actuators generally require high current (up to 9 A at 28 V) to actuate. SMA wires (the driving element of the actuators) can be quickly overheated if power is not removed at the end of stroke, which can damage the wires. The new analog driver prevents overheating of the SMA wires in an actuator by momentarily removing power when the end limit switch is closed, thereby allowing complex control schemes to be adopted without concern for overheating. Either an integral pushbutton or microprocessor-controlled gate or control line inputs switch current to the actuator until the end switch line goes from logic high to logic low state. Power is then momentarily removed (switched off by the MOSFET). The analog driver is suited to use with nearly any SMA actuator.

Organic Bistable Memory Switching Phenomena in Squarylium-Dye Langmuir-Blodgett Films

NASA Astrophysics Data System (ADS)

Kushida, Masahito; Inomata, Hisao; Miyata, Hiroshi; Harada, Kieko; Saito, Kyoichi; Sugita, Kazuyuki

2003-06-01

We have investigated the relationship between the switching phenomena and H-like aggregates in squarylium-dye Langmuir-Blodgett (SQ LB) films. The current-voltage characteristics of SQ LB films sandwiched between the top gold electrode and the bottom aluminum electrode indicated conductance switching phenomena below the temperature of 100°C but not at 140°C. Current densities suddenly increased at switching voltages between 2 and 4 V. The switching voltage increased as the temperature increased between room temperature and 100°C. Current densities were 50-100 μA/cm2 in a low-impedance state (ON state). A high-impedance state (OFF state) can be recovered by applying a reverse bias, and therefore, these bistable devices are ideal for memory applications. The dependence of conductance switching phenomena and ultraviolet-visible absorption spectra on annealing temperatures was studied. The results revealed that conductance switching phenomena were caused by the presence of H-like aggregates in the SQ LB films.

Research of an electromagnetically actuated spark gap switch

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

Zhang, Tianyang; Chen, Dongqun, E-mail: csycdq@163.com; Liu, Jinliang

2013-11-15

As an important part of pulsed power systems, high-voltage and high-current triggered spark gap switch and its trigger system are expected to achieve a compact structure. In this paper, a high-voltage, high-current, and compact electromagnetically actuated spark gap switch is put forward, and it can be applied as a part of an intense electron-beam accelerator (IEBA). A 24 V DC power supply is used to trigger the switch. The characteristics of the switch were measured for N{sub 2} when the gas pressure is 0.10–0.30 MPa. The experimental results showed that the voltage/pressure (V/p) curve of the switch was linear relationship.more » The operating ranges of the switch were 21%–96%, 21%–95%, 21%–95%, 19%–95%, 17%–95%, and 16%–96% of the switch's self-breakdown voltage when the gas pressures were 0.10, 0.14, 0.18, 0.22, 0.26, and 0.30 MPa, respectively. The switch and its trigger system worked steadily and reliably with a peak voltage of 30 kV, a peak current of 60 kA in the IEBA when the pressure of N{sub 2} in the switch was 0.30 MPa.« less

Megavolt, Multigigawatt Pulsed Plasma Switch

NASA Technical Reports Server (NTRS)

Lee, Ja H.; Choi, Sang H.; Song, Kyo D.

1996-01-01

Plasma switch proposed for use in high-voltage, high-current pulse power system. Designed not only to out-perform conventional spark-gap switch but also relatively compact and lightweight. Features inverse-pinch configuration to prevent constriction of current sheets into filaments, plus multiple-ring-electrode structure to resist high-voltage breakdown.

62. VIEW LOOKING NORTHWEST AT THE OIL FILLED CIRCUIT BREAKER ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

62. VIEW LOOKING NORTHWEST AT THE OIL FILLED CIRCUIT BREAKER FOR GENERATOR NUMBER 1. CIRCUIT BREAKERS ARE AUTOMATED SWITCHES WHICH DISCONNECT THE GENERATORS FROM THE LINE WHEN SHORT CIRCUITS OCCUR. WHEN CIRCUITS INVOLVING HIGH CURRENTS AND VOLTAGES ARE BROKEN, THE AIR SURROUNDING MECHANICAL PARTS OF THE SWITCH BECOMES IONIZED AND CONTINUES TO CONDUCT ELECTRIC POWER ACROSS ANY GAP IN THE SWITCH CONTACTS. TO PREVENT THIS AND INSURE A POSITIVE INTERRUPTION OF CURRENT, THE SWITCH CONTACTS ARE IMMERSED IN A CONTAINER OF OIL. THE OIL DOES NOT SUPPORT THE FORMATION OF AN ARC AND EFFECTIVELY CUTS OFF THE CURRENT WHEN THE SWITCH CONTACTS ARE OPENED. - New York, New Haven & Hartford Railroad, Cos Cob Power Plant, Sound Shore Drive, Greenwich, Fairfield County, CT

Apparatus for producing voltage and current pulses

DOEpatents

Kirbie, Hugh; Dale, Gregory E.

2010-12-21

An apparatus having one or more modular stages for producing voltage and current pulses. Each module includes a diode charging means to charge a capacitive means that stores energy. One or more charging impedance means are connected to the diode charging means to provide a return current pathway. A solid-state switch discharge means, with current interruption capability, is connected to the capacitive means to discharge stored energy. Finally, a control means is provided to command the switching action of the solid-state switch discharge means.

Low-current-density spin-transfer switching in Gd{sub 22}Fe{sub 78}-MgO magnetic tunnel junction

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

Kinjo, Hidekazu, E-mail: kinjou.h-lk@nhk.or.jp; Machida, Kenji; Aoshima, Ken-ichi

2014-05-28

Magnetization switching of a relatively thick (9 nm) Gd-Fe free layer was achieved with a low spin injection current density of 1.0 × 10{sup 6} A/cm{sup 2} using MgO based magnetic tunnel junction devices, fabricated for light modulators. At about 560 × 560 nm{sup 2} in size, the devices exhibited a tunneling magnetoresistance ratio of 7%. This low-current switching is mainly attributed to thermally assisted spin-transfer switching in consequence of its thermal magnetic behavior arising from Joule heating.

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

The influence of preferred orientation and poling temperature on the polarization switching current in PZT thin films

NASA Astrophysics Data System (ADS)

Xiao, Mi; Zhang, Weikang; Zhang, Zebin; Zhang, Ping; Lan, Kuibo

2017-07-01

In this paper, Pb(Zr0.52Ti0.48)O3 (PZT) thin films with different preferred orientation were prepared on platinized silicon substrates by a modified sol-gel method. Our results indicate that the polarization switching current in PZT thin films is dependent on preferred orientation and poling temperature. In our measurements, (111)-oriented PZT has a larger polarization switching current than randomly oriented PZT, and with the increase of the degree of (111) preferred orientation and the poling temperature, the polarization switching current gradually increase. Considering the contact of PZT thin film with electrodes, the space-charged limited conduction (SCLC) combined with domain switching mechanism may be responsible for such phenomena. By analyzing the conduction data, we found the interface-limited Schottky emission (ES) and bulk-limited Poole-Frenkel hopping (PF) are not suitable for our samples.

Transient current interruption mechanism in a magnetically delayed vacuum switch

NASA Technical Reports Server (NTRS)

Morris, Gibson, Jr.; Dougal, Roger A.

1993-01-01

The capacity of a magnetically delayed vacuum switch to conduct current depends on the density of plasma injected into the switch. Exceeding the current capacity results in the switch entering a lossy mode of operation characterized by a transient interruption of the main current (opening behavior) and a rapid increase of voltage across the vacuum gap. Streak and framing photographs of the discharge indicate that a decrease of luminosity near the middle of the gap preceeds the transition to the opening phase. The zone of low luminosity propagates toward the cathode. This evidence suggests that the mechanism causing the opening phase is erosion of the background plasma in a manner similar to that in a plasma-opening switch. The resulting ion depletion forces a space-charge-limited conduction mode. The switch inductance maintains a high discharge current even during the space-charge-limited conduction phase, thus producing high internal fields. The high accelerating voltage, in turn, produces electron and ion beams that heat the electrode surfaces. As a result of the heating, jets of electrode vapor issue from the electrodes, either cathode or anode, depending on the selection of electrode materials.

On-line Monitoring Device for High-voltage Switch Cabinet Partial Discharge Based on Pulse Current Method

NASA Astrophysics Data System (ADS)

Y Tao, S.; Zhang, X. Z.; Cai, H. W.; Li, P.; Feng, Y.; Zhang, T. C.; Li, J.; Wang, W. S.; Zhang, X. K.

2017-12-01

The pulse current method for partial discharge detection is generally applied in type testing and other off-line tests of electrical equipment at delivery. After intensive analysis of the present situation and existing problems of partial discharge detection in switch cabinets, this paper designed the circuit principle and signal extraction method for partial discharge on-line detection based on a high-voltage presence indicating systems (VPIS), established a high voltage switch cabinet partial discharge on-line detection circuit based on the pulse current method, developed background software integrated with real-time monitoring, judging and analyzing functions, carried out a real discharge simulation test on a real-type partial discharge defect simulation platform of a 10KV switch cabinet, and verified the sensitivity and validity of the high-voltage switch cabinet partial discharge on-line monitoring device based on the pulse current method. The study presented in this paper is of great significance for switch cabinet maintenance and theoretical study on pulse current method on-line detection, and has provided a good implementation method for partial discharge on-line monitoring devices for 10KV distribution network equipment.

Explaining pathological changes in axonal excitability through dynamical analysis of conductance-based models

NASA Astrophysics Data System (ADS)

Coggan, Jay S.; Ocker, Gabriel K.; Sejnowski, Terrence J.; Prescott, Steven A.

2011-10-01

Neurons rely on action potentials, or spikes, to relay information. Pathological changes in spike generation likely contribute to certain enigmatic features of neurological disease, like paroxysmal attacks of pain and muscle spasm. Paroxysmal symptoms are characterized by abrupt onset and short duration, and are associated with abnormal spiking although the exact pathophysiology remains unclear. To help decipher the biophysical basis for 'paroxysmal' spiking, we replicated afterdischarge (i.e. continued spiking after a brief stimulus) in a minimal conductance-based axon model. We then applied nonlinear dynamical analysis to explain the dynamical basis for initiation and termination of afterdischarge. A perturbation could abruptly switch the system between two (quasi-)stable attractor states: rest and repetitive spiking. This bistability was a consequence of slow positive feedback mediated by persistent inward current. Initiation of afterdischarge was explained by activation of the persistent inward current forcing the system to cross a saddle point that separates the basins of attraction associated with each attractor. Termination of afterdischarge was explained by the attractor associated with repetitive spiking being destroyed. This occurred when ultra-slow negative feedback, such as intracellular sodium accumulation, caused the saddle point and stable limit cycle to collide; in that regard, the active attractor is not truly stable when the slowest dynamics are taken into account. The model also explains other features of paroxysmal symptoms, including temporal summation and refractoriness.

Switching a Perpendicular Ferromagnetic Layer by Competing Spin Currents

NASA Astrophysics Data System (ADS)

Ma, Qinli; Li, Yufan; Gopman, D. B.; Kabanov, Yu. P.; Shull, R. D.; Chien, C. L.

2018-03-01

An ultimate goal of spintronics is to control magnetism via electrical means. One promising way is to utilize a current-induced spin-orbit torque (SOT) originating from the strong spin-orbit coupling in heavy metals and their interfaces to switch a single perpendicularly magnetized ferromagnetic layer at room temperature. However, experimental realization of SOT switching to date requires an additional in-plane magnetic field, or other more complex measures, thus severely limiting its prospects. Here we present a novel structure consisting of two heavy metals that delivers competing spin currents of opposite spin indices. Instead of just canceling the pure spin current and the associated SOTs as one expects and corroborated by the widely accepted SOTs, such devices manifest the ability to switch the perpendicular CoFeB magnetization solely with an in-plane current without any magnetic field. Magnetic domain imaging reveals selective asymmetrical domain wall motion under a current. Our discovery not only paves the way for the application of SOT in nonvolatile technologies, but also poses questions on the underlying mechanism of the commonly believed SOT-induced switching phenomenon.

Persistent Flagellate Hyperpigmentation

DTIC Science & Technology

2017-04-28

hydroquinone), laser modalities such as Q-switched 755/1064 nm lasers , and ablative C02 resurfacing lasers . In addition, patients should be counseled on...the importance of UV protection. The patient was treated with each of these treatment modal ities with minimal improvement. Resources: 1. Lee HY

A Global Perspective on Hantavirus Ecology, Epidemiology, and Disease

PubMed Central

Jonsson, Colleen B.; Figueiredo, Luiz Tadeu Moraes; Vapalahti, Olli

2010-01-01

Summary: Hantaviruses are enzootic viruses that maintain persistent infections in their rodent hosts without apparent disease symptoms. The spillover of these viruses to humans can lead to one of two serious illnesses, hantavirus pulmonary syndrome and hemorrhagic fever with renal syndrome. In recent years, there has been an improved understanding of the epidemiology, pathogenesis, and natural history of these viruses following an increase in the number of outbreaks in the Americas. In this review, current concepts regarding the ecology of and disease associated with these serious human pathogens are presented. Priorities for future research suggest an integration of the ecology and evolution of these and other host-virus ecosystems through modeling and hypothesis-driven research with the risk of emergence, host switching/spillover, and disease transmission to humans. PMID:20375360

5.8kV SiC PiN Diode for Switching of High-Efficiency Inductive Pulsed Plasma Thruster Circuits

NASA Technical Reports Server (NTRS)

Toftul, Alexandra; Polzin, Kurt A.; Hudgins, Jerry L.

2014-01-01

Inductive Pulsed Plasma Thruster (IPPT) pulse circuits, such as those needed to operate the Pulsed Inductive Thruster (PIT), are required to quickly switch capacitor banks operating at a period of µs while conducting current at levels on the order of at least 10 kA. [1,2] For all iterations of the PIT to date, spark gaps have been used to discharge the capacitor bank through an inductive coil. Recent availability of fast, high-power solid state switching devices makes it possible to consider the use of semiconductor switches in modern IPPTs. In addition, novel pre-ionization schemes have led to a reduction in discharge energy per pulse for electric thrusters of this type, relaxing the switching requirements for these thrusters. [3,4] Solid state switches offer the advantage of greater controllability and reliability, as well as decreased drive circuit dimensions and mass relative to spark gap switches. The use of solid state devices such as Integrated Gate Bipolar Transistors (IGBTs), Gate Turn-off Thyristors (GTOs) and Silicon-Controlled Rectifiers (SCRs) often involves the use of power diodes. These semiconductor devices may be connected antiparallel to the switch for protection from reverse current, or used to reduce power loss in a circuit by clamping off current ringing. In each case, higher circuit efficiency may be achieved by using a diode that is able to transition, or 'switch,' from the forward conducting state ('on' state) to the reverse blocking state ('off' state) in the shortest amount of time, thereby minimizing current ringing and switching losses. Silicon Carbide (SiC) PiN diodes offer significant advantages to conventional fast-switching Silicon (Si) diodes for high power and fast switching applications. A wider band gap results in a breakdown voltage 10 times that of Si, so that a SiC device may have a thinner drift region for a given blocking voltage. [5] This leads to smaller, lighter devices for high voltage applications, as well as reduced forward conduction losses, faster reverse recovery time (faster turn-off), and lower-magnitude reverse recovery current. In addition, SiC devices have lower leakage current as compared to their Si counterparts, and a high thermal conductivity, potentially allowing the former to operate at higher temperatures with a smaller, lighter heatsink (or no heatsink at all).

High-power microstrip switch

NASA Technical Reports Server (NTRS)

Choi, S. D.

1974-01-01

Switch, which uses only two p-i-n diodes on microstrip substrate, has been developed for application in spacecraft radio systems. Switch features improved power drain, weight, volume, magnetic cleanliness, and reliability, over currently-used circulator and electromechanical switches.

Treatment duration (persistence) of basal insulin supported oral therapy (BOT) in Type-2 diabetic patients: comparison of insulin glargine with NPH insulin.

PubMed

Quinzler, Renate; Ude, Miriam; Franzmann, Alexandra; Feldt, Sandra; Schüssel, Katrin; Leuner, Kristina; Müller, Walter E; Dippel, Franz-Werner; Schulz, Martin

2012-01-01

To compare the persistence (treatment duration) of basal insulin supported oral therapy (BOT) using insulin glargine (GLA) or NPH insulin (NPH) in Type-2 diabetic patients. This retrospective cohort study reports results from an analysis of claims data from prescriptions for ambulatory patients within the German Statutory Health Insurance scheme. The study is based on claims data from more than 80% of German community pharmacies. Treatment duration until switching to a basal bolus treatment regimen (intensified conventional insulin therapy: ICT) was determined in insulin-naïve patients who began treatment with BOT using GLA or NPH between 01/2003 and 12/2006. A total of 97,998 patients (61,070 GLA and 36,928 NPH) were included. Within the observation period, 23.5% of GLA patients and 28.0% of NPH patients switched from BOT to ICT. The upper quartile of probability of continuation of therapy (the 75th percentile) was reached after 769 days in GLA patients and after 517 days in NPH patients. Therefore, the risk of switching to ICT was significantly higher with NPH compared to GLA: hazard ratios were 1.34 (99% CI: 1.29-1.38; unadjusted) and 1.22 (99% CI: 1.18-1.27) after adjustment for predefined covariates. Various sensitivity analyses using modified inclusion criteria and endpoint definitions were applied and these confirmed the initial results. Type-2 diabetic patients under BOT with GLA stayed significantly longer on the initial therapy before switching to ICT than patients on BOT using NPH.

Integral Battery Power Limiting Circuit for Intrinsically Safe Applications

NASA Technical Reports Server (NTRS)

Burns, Bradley M.; Blalock, Norman N.

2010-01-01

A circuit topology has been designed to guarantee the output of intrinsically safe power for the operation of electrical devices in a hazardous environment. This design uses a MOSFET (metal oxide semiconductor field-effect transistor) as a switch to connect and disconnect power to a load. A test current is provided through a separate path to the load for monitoring by a comparator against a preset threshold level. The circuit is configured so that the test current will detect a fault in the load and open the switch before the main current can respond. The main current passes through the switch and then an inductor. When a fault occurs in the load, the current through the inductor cannot change immediately, but the voltage drops immediately to safe levels. The comparator detects this drop and opens the switch before the current in the inductor has a chance to respond. This circuit protects both the current and voltage from exceeding safe levels. Typically, this type of protection is accomplished by a fuse or a circuit breaker, but in order for a fuse or a circuit breaker to blow or trip, the current must exceed the safe levels momentarily, which may be just enough time to ignite anything in a hazardous environment. To prevent this from happening, a fuse is typically current-limited by the addition of the resistor to keep the current within safe levels while the fuse reacts. The use of a resistor is acceptable for non-battery applications where the wasted energy and voltage drop across the resistor can be tolerated. The use of the switch and inductor minimizes the wasted energy. For example, a circuit runs from a 3.6-V battery that must be current-limited to 200 mA. If the circuit normally draws 10 mA, then an 18-ohm resistor would drop 180 mV during normal operation, while a typical switch (0.02 ohm) and inductor (0.97 ohm) would only drop 9.9 mV. From a power standpoint, the current-limiting resistor protection circuit wastes about 18 times more power than the switch and the inductor configuration. In the fault condition, both the resistor and the inductor react immediately. The resistor reacts by allowing more current to flow and dropping the voltage. Initially, the inductor reacts by dropping the voltage, and then by not allowing the current to change. When the comparator detects the drop in voltage, it opens the switch, thus preventing any further current flow. The inductor alone is not sufficient protection, because after the voltage drop has settled, the inductor would then allow the current to change, in this example, the current would be 3.7 A. In the fault condition, the resistor is flowing 200 mA until the fuse blows (anywhere from 1 ms to 100 s), while the switch and inductor combination is flowing about 2 A test current while monitoring for the fault to be corrected. Finally, as an additional safety feature, the circuit can be configured to hold the switch opened until both the load and source are disconnected.

Tests of a low-pressure switch protected by a saturating inductor

NASA Astrophysics Data System (ADS)

Lauer, E. J.; Birx, D. L.

1981-10-01

A triggered low-pressure switch was tested switching a charged capacitor across a damping resistor simulating a transformer. A series saturating inductor protected the switch from electron beam anode damage. The capacitor was 15 micro F and charge voltages up to 50 kV were used. The time to current maximum was 5 to 8 micro S. The current terminated at about 50 micro S and voltage could be reapplied at about 100 micro S.

Optically Driven Q-Switches For Lasers

NASA Technical Reports Server (NTRS)

Hemmati, Hamid

1994-01-01

Optically driven Q-switches for pulsed lasers proposed, taking place of acousto-optical, magneto-optical, and electro-optical switches. Optical switching beams of proposed Q-switching most likely generated in pulsed diode lasers or light-emitting diodes, outputs of which are amplitude-modulated easily by direct modulation of relatively small input currents. Energy efficiencies exceed those of electrically driven Q-switches.

Switching gains and health plan price elasticities: 20 years of managed competition reforms in The Netherlands.

PubMed

Douven, Rudy; Katona, Katalin; T Schut, Frederik; Shestalova, Victoria

2017-11-01

In this paper we estimate health plan price elasticities and financial switching gains for consumers over a 20-year period in which managed competition was introduced in the Dutch health insurance market. The period is characterized by a major health insurance reform in 2006 to provide health insurers with more incentives and tools to compete, and to provide consumers with a more differentiated choice of products. Prior to the reform, in the period 1995-2005, we find a low number of switchers, between 2 and 4% a year, modest average total switching gains of 2 million euros per year and short-term health plan price elasticities ranging from -0.1 to -0.4. The major reform in 2006 resulted in an all-time high switching rate of 18%, total switching gains of 130 million euros, and a high short-term price elasticity of -5.7. During 2007-2015 switching rates returned to lower levels, between 4 and 8% per year, with total switching gains in the order of 40 million euros per year on average. Total switching gains could have been 10 times higher if all consumers had switched to one of the cheapest plans. We find short-term price elasticities ranging between -0.9 and -2.2. Our estimations suggest substantial consumer inertia throughout the entire period, as we find degrees of choice persistence ranging from about 0.8 to 0.9.

Evaluation of resistive switching properties of Si-rich oxide embedded with Ti nanodots by applying constant voltage and current

NASA Astrophysics Data System (ADS)

Ohta, Akio; Kato, Yusuke; Ikeda, Mitsuhisa; Makihara, Katsunori; Miyazaki, Seiichi

2018-06-01

We have studied the resistive switching behaviors of electron beam (EB) evaporated Si-rich oxide (SiO x ) sandwiched between Ni electrodes by applying a constant voltage and current. Additionally, the impact of Ti nanodots (NDs) embedded into SiO x on resistive switching behaviors was investigated because it is expected that NDs can trigger the formation of a conductive filament path in SiO x . The resistive switching behaviors of SiO x show that the response time during resistance switching was decreased by increasing the applied constant current or constant voltage. It was found that Ti-NDs in SiO x enhance the conductive filament path formation owing to electric field concentration by Ti-NDs.

Stochastic predation events and population persistence in bighorn sheep

PubMed Central

Festa-Bianchet, Marco; Coulson, Tim; Gaillard, Jean-Michel; Hogg, John T; Pelletier, Fanie

2006-01-01

Many studies have reported temporal changes in the relative importance of density-dependence and environmental stochasticity in affecting population growth rates, but they typically assume that the predominant factor limiting growth remains constant over long periods of time. Stochastic switches in limiting factors that persist for multiple time-steps have received little attention, but most wild populations may periodically experience such switches. Here, we consider the dynamics of three populations of individually marked bighorn sheep (Ovis canadensis) monitored for 24–28 years. Each population experienced one or two distinct cougar (Puma concolor) predation events leading to population declines. The onset and duration of predation events were stochastic and consistent with predation by specialist individuals. A realistic Markov chain model confirms that predation by specialist cougars can cause extinction of isolated populations. We suggest that such processes may be common. In such cases, predator–prey equilibria may only occur at large geographical and temporal scales, and are unlikely with increasing habitat fragmentation. PMID:16777749

A soft switching with reduced voltage stress ZVT-PWM full-bridge converter

NASA Astrophysics Data System (ADS)

Sahin, Yakup; Ting, Naim Suleyman; Acar, Fatih

2018-04-01

This paper introduces a novel active snubber cell for soft switching pulse width modulation DC-DC converters. In the proposed converter, the main switch is turned on under zero voltage transition and turned off under zero voltage switching (ZVS). The auxiliary switch is turned on under zero current switching (ZCS) and turned off under zero current transition. The main diode is turned on under ZVS and turned off under ZCS. All of the other semiconductors in the converter are turned on and off with soft switching. There is no extra voltage stress on the semiconductor devices. Besides, the proposed converter has simple structure and ease of control due to common ground. The detailed theoretical analysis of the proposed converter is presented and also verified with both simulation and experimental study at 100 kHz switching frequency and 600 W output power. Furthermore, the efficiency of the proposed converter is 95.7% at nominal power.

Base drive circuit for a four-terminal power Darlington

DOEpatents

Lee, Fred C.; Carter, Roy A.

1983-01-01

A high power switching circuit which utilizes a four-terminal Darlington transistor block to improve switching speed, particularly in rapid turn-off. Two independent reverse drive currents are utilized during turn off in order to expel the minority carriers of the Darlington pair at their own charge sweep-out rate. The reverse drive current may be provided by a current transformer, the secondary of which is tapped to the base terminal of the power stage of the Darlington block. In one application, the switching circuit is used in each power switching element in a chopper-inverter drive of an electric vehicle propulsion system.

An Annual Cycle Of Currents Around Tsushima Island And Resulting Inflow Conditions In The Sea Of Japan

NASA Astrophysics Data System (ADS)

Perkins, H.; Teague, W. J.; Chang, K.-I.; Suk, M.-S.; Lee, J.-C.; Book, J. W.; Jacobs, G. A.

A ten-month long time series of current measurements has been made on two sections across Korea/Tsushima Strait, thus revealing most of an annual cycle of the Tsushima Current that flows into the Japan/East Sea. One section is southwest, the other north- east, of Tsushima Island, giving respectively conditions upstream and downstream of the Island. Along the bathymetric slope upstream of the Island, the current consists of a single, broad stream concentrated in mid-channel. Downstream, this single core is found to have separated into two branches, one on each of the Strait. Between these two near-coastal streams, in the apparent wake of the Island, currents are variable and lack a well-defined mean. This separation persisted during all seasons despite vari- ation in total transport by a factor of two, from 3.5 Sv in October 1999 to 1.7 Sv in January 2000, and despite changes from maximum to minimum stratification. Both branches of the divided current were stronger during high transport and weaker during low transport, but since each branch was measured by only one or two moorings, trans- port estimates for the separate branches are not available. Strongest currents occurred at the surface close to the Korean coast near Ulsan in early fall with low-pass surface currents reaching 90 cm/s during October and November. Farther downstream, outside the measurement area, the two branches define the inflow to the Japan/East Sea. The branch along the Japanese coast remains close to the coast. It undergoes strong annual variability but is steady on shorter time scales. The Korean branch of the current also undergoes strong annual changes but experiences very strong variability, especially in winter. This branch is thought to switch between two paths. The first parallels the Ko- rean coast; the second follows bathymetric contours that lead it back to the Japanese coast. A mechanism for switching between these paths is provided by vorticity asso- ciated with bottom intrusions of cold water in the area. Seasonal variations of flow into the Japan Sea thus depend on the interplay between seasonal variations around Tsushima Island and intrusions of cold bottom water.

Hardware Model of a Shipboard Zonal Electrical Distribution System (ZEDS): Alternating Current/Direct Current (AC/DC)

DTIC Science & Technology

2010-06-01

perfect example on how to lead, manage and strive for excellence in every aspect of your life. Your leadership is essential to fostering the loyalty ...share my success, I could not have ever achieved the level of satisfaction and enjoyment that I have. You will never understand how helpful the...A typical wall mounted light switch is a single pole single throw switch. A common industrial motor start switch is a three pole single throw switch

Riociguat in patients with chronic thromboembolic pulmonary hypertension: results from an early access study.

PubMed

McLaughlin, Vallerie V; Jansa, Pavel; Nielsen-Kudsk, Jens E; Halank, Michael; Simonneau, Gérald; Grünig, Ekkehard; Ulrich, Silvia; Rosenkranz, Stephan; Gómez Sánchez, Miguel A; Pulido, Tomás; Pepke-Zaba, Joanna; Barberá, Joan Albert; Hoeper, Marius M; Vachiéry, Jean-Luc; Lang, Irene; Carvalho, Francine; Meier, Christian; Mueller, Katharina; Nikkho, Sylvia; D'Armini, Andrea M

2017-12-28

Following positive results from the Phase III CHEST-1 study in patients with inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH), the Phase IIIb CTEPH early access study (EAS) was designed to assess the safety and tolerability of riociguat in real-world clinical practice, as well as to provide patients with early access to riociguat before launch. Riociguat is approved for the treatment of inoperable and persistent/recurrent CTEPH. We performed an open-label, uncontrolled, single-arm, early access study in which 300 adult patients with inoperable or persistent/recurrent CTEPH received riociguat adjusted from 1 mg three times daily (tid) to a maximum of 2.5 mg tid. Patients switching from unsatisfactory prior pulmonary arterial hypertension (PAH)-targeted therapy (n = 84) underwent a washout period of at least 3 days before initiating riociguat. The primary aim was to assess the safety and tolerability of riociguat, with World Health Organization functional class and 6-min walking distance (6MWD) as exploratory efficacy endpoints. In total, 262 patients (87%) completed study treatment and entered the safety follow-up (median treatment duration 47 weeks). Adverse events were reported in 273 patients (91%). The most frequently reported serious adverse events were syncope (6%), right ventricular failure (3%), and pneumonia (2%). There were five deaths, none of which was considered related to study medication. The safety and tolerability of riociguat was similar in patients switched from other PAH-targeted therapies and those who were treatment naïve. In patients with data available, mean ± standard deviation 6MWD had increased by 33 ± 42 m at Week 12 with no clinically relevant differences between the switched and treatment-naïve subgroups. Riociguat was well tolerated in patients with CTEPH who were treatment naïve, and in those who were switched from other PAH-targeted therapies. No new safety signals were observed. ClinicalTrials.org NCT01784562 . Registered February 4, 2013.

Technical Note: MR-visualization of interventional devices using transient field alterations and balanced steady-state free precession imaging.

PubMed

Eibofner, Frank; Martirosian, Petros; Würslin, Christian; Graf, Hansjörg; Syha, Roland; Clasen, Stephan

2015-11-01

In interventional magnetic resonance imaging, instruments can be equipped with conducting wires for visualization by current application. The potential of sequence triggered application of transient direct currents in balanced steady-state free precession (bSSFP) imaging is demonstrated. A conductor and a modified catheter were examined in water phantoms and in an ex vivo porcine liver. The current was switched by a trigger pulse in the bSSFP sequence in an interval between radiofrequency pulse and signal acquisition. Magnitude and phase images were recorded. Regions with transient field alterations were evaluated by a postprocessing algorithm. A phase mask was computed and overlaid with the magnitude image. Transient field alterations caused continuous phase shifts, which were separated by the postprocessing algorithm from phase jumps due to persistent field alterations. The overlaid images revealed the position of the conductor. The modified catheter generated visible phase offset in all orientations toward the static magnetic field and could be unambiguously localized in the ex vivo porcine liver. The application of a sequence triggered, direct current in combination with phase imaging allows conspicuous localization of interventional devices with a bSSFP sequence.

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.

FAST ACTING CURRENT SWITCH

DOEpatents

Batzer, T.H.; Cummings, D.B.; Ryan, J.F.

1962-05-22

A high-current, fast-acting switch is designed for utilization as a crowbar switch in a high-current circuit such as used to generate the magnetic confinement field of a plasma-confining and heat device, e.g., Pyrotron. The device particularly comprises a cylindrical housing containing two stationary, cylindrical contacts between which a movable contact is bridged to close the switch. The movable contact is actuated by a differential-pressure, airdriven piston assembly also within the housing. To absorb the acceleration (and the shock imparted to the device by the rapidly driven, movable contact), an adjustable air buffer assembly is provided, integrally connected to the movable contact and piston assembly. Various safety locks and circuit-synchronizing means are also provided to permit proper cooperation of the invention and the high-current circuit in which it is installed. (AEC)

Method and apparatus for clockless analog-to-digital conversion and peak detection

DOEpatents

DeGeronimo, Gianluigi

2007-03-06

An apparatus and method for analog-to-digital conversion and peak detection includes at least one stage, which includes a first switch, second switch, current source or capacitor, and discriminator. The discriminator changes state in response to a current or charge associated with the input signal exceeding a threshold, thereby indicating whether the current or charge associated with the input signal is greater than the threshold. The input signal includes a peak or a charge, and the converter includes a peak or charge detect mode in which a state of the switch is retained in response to a decrease in the current or charge associated with the input signal. The state of the switch represents at least a portion of a value of the peak or of the charge.

A β-Ta system for current induced magnetic switching in the absence of external magnetic field

NASA Astrophysics Data System (ADS)

Chen, Wenzhe; Qian, Lijuan; Xiao, Gang

2018-05-01

Magnetic switching via Giant Spin Hall Effect (GSHE) has received great interest for its role in developing future spintronics logic or memory devices. In this work, a new material system (i.e. a transition metal sandwiched between two ferromagnetic layers) with interlayer exchange coupling is introduced to realize the deterministic field-free perpendicular magnetic switching. This system uses β-Ta, as the GSHE agent to generate a spin current and as the interlayer exchange coupling medium to generate an internal field. The critical switching current density at zero field is on the order of 106 A/cm2 due to the large spin Hall angle of β-Ta. The internal field, along with switching efficiency, depends strongly on the orthogonal magnetization states of two ferromagnetic coupling layers in this system.

Restraining for switching effects in an AC driving pixel circuit of the OLED-on-silicon

NASA Astrophysics Data System (ADS)

Liu, Yan-Yan; Geng, Wei-Dong; Dai, Yong-Ping

2010-03-01

The AC driving scheme for OLEDs, which uses the pixel circuit with two transistors and one capacitor (2T1C), can extend the lifetime of the active matrix organic light-emitting diode (AMOLED) on silicon, but there are switching effects during the switch of AC signals, which result in the voltage variation on the storage capacitor and cause the current glitch in OLED. That would decrease the gray scale of the OLED. This paper proposes a novel pixel circuit consisting of three transistors and one capacitor to realize AC driving for the OLED-on-silicon while restraining the switching effects. Simulation results indicate that the proposed circuit is less sensitive to switching effects. Also, another pixel circuit is proposed to further reduce the driving current to meet the current constraints for the OLED-on-silicon.

Repetitive switching for an electromagnetic rail gun

NASA Astrophysics Data System (ADS)

Gruden, J. M.

1983-12-01

Previous testing on a repetitive opening switch for inductive energy storage has proved the feasibility of the rotary switch concept. The concept consists of a rotating copper disk (rotor) with a pie-shaped insulator section and brushes which slide along each of the rotor surfaces. While on top of the copper surface, the brushes and rotor conduct current allowing the energy storage inductor to charge. When the brushes slide onto the insulator section, the current cannot pass through the rotor and is diverted into the load. This study investigates two new brush designs and a rotor modification designed to improve the current commutating capabilities of the switch. One brush design (fringe fiber) employs carbon fibers on the leading and trailing edge of the brush to increase the resistive commutating action as the switch opens and closes. The other brush design uses fingers to conduct current to the rotor surface, effectively increasing the number of brush contact points. The rotor modification was the placement of tungsten inserts at the copper-insulator interfaces.

Digital switched hydraulics

NASA Astrophysics Data System (ADS)

Pan, Min; Plummer, Andrew

2018-06-01

This paper reviews recent developments in digital switched hydraulics particularly the switched inertance hydraulic systems (SIHSs). The performance of SIHSs is presented in brief with a discussion of several possible configurations and control strategies. The soft switching technology and high-speed switching valve design techniques are discussed. Challenges and recommendations are given based on the current research achievements.

Thermionic gas switch

DOEpatents

Hatch, G.L.; Brummond, W.A.; Barrus, D.M.

1984-04-05

The present invention is directed to an improved temperature responsive thermionic gas switch utilizing a hollow cathode and a folded emitter surface area. The folded emitter surface area of the thermionic switch substantially increases the on/off ratio by changing the conduction surface area involved in the two modes thereof. The improved switch of this invention provides an on/off ratio of 450:1 compared to the 10:1 ratio of the prior known thermionic switch, while providing for adjusting the on current. In the improved switch of this invention the conduction area is made small in the off mode, while in the on mode the conduction area is made large. This is achieved by utilizing a folded hollow cathode configuration and utilizing a folded emitter surface area, and by making the dimensions of the folds small enough so that a space charge will develop in the convolutions of the folds and suppress unignited current, thus limiting the current carrying surface in the off mode.

Monitoring Coastal Marshes for Persistent Saltwater Intrusion

NASA Technical Reports Server (NTRS)

Kalcic, Maria; Hall, Callie; Fletcher, Rose; Russell, Jeff

2009-01-01

Primary goal: Provide resource managers with remote sensing products that support ecosystem forecasting models requiring salinity and inundation data. Work supports the habitat-switching modules in the Coastal Louisiana Ecosystem Assessment and Restoration (CLEAR) model, which provides scientific evaluation for restoration management (Visser et al., 2008). Ongoing work to validate flooding with radar (NWRC/USGS) and enhance persistence estimates through "fusion" of MODIS and Landsat time series (ROSES A.28 Gulf of Mexico). Additional work will also investigate relationship between saltwater dielectric constant and radar returns (Radarsat) (ROSES A.28 Gulf of Mexico).

Protection relay of phase-shifting device with thyristor switch for high voltage power transmission lines

NASA Astrophysics Data System (ADS)

Lachugin, V. F.; Panfilov, D. I.; Akhmetov, I. M.; Astashev, M. G.; Shevelev, A. V.

2014-12-01

Problems of functioning of differential current protection systems of phase shifting devices (PSD) with mechanically changed coefficient of transformation of shunt transformer are analyzed. Requirements for devices of protection of PSD with thyristor switch are formulated. Based on use of nonlinear models of series-wound and shunt transformers of PSD modes of operation of major protection during PSD, switching to zero load operation and to operation under load and during short circuit operation were studied for testing PSD with failures. Use of the principle of duplicating by devices of differential current protection (with realization of functions of breaking) of failures of separate pares of PSD with thyristor switch was substantiated. To ensure protection sensitivity to the shunt transformer winding short circuit, in particular, to a short circuit that is not implemented in the current differential protection for PSD with mechanical switch, the differential current protection reacting to the amount of primary ampere-turns of high-voltage and low-voltage winding of this transformer was designed. Studies have shown that the use of differential current cutoff instead of overcurrent protection for the shunt transformer wndings allows one to provide the sensitivity during thyristor failure with the formation of a short circuit. The results of simulation mode for the PSD with switch thyristor designed to be installed as switching point of Voskhod-Tatarskaya-Barabinsk 220 kV transmission line point out the efficiency of the developed solutions that ensure reliable functioning of the PSD.

Sigma Factor SigB Is Crucial to Mediate Staphylococcus aureus Adaptation during Chronic Infections.

PubMed

Tuchscherr, Lorena; Bischoff, Markus; Lattar, Santiago M; Noto Llana, Mariangeles; Pförtner, Henrike; Niemann, Silke; Geraci, Jennifer; Van de Vyver, Hélène; Fraunholz, Martin J; Cheung, Ambrose L; Herrmann, Mathias; Völker, Uwe; Sordelli, Daniel O; Peters, Georg; Löffler, Bettina

2015-04-01

Staphylococcus aureus is a major human pathogen that causes a range of infections from acute invasive to chronic and difficult-to-treat. Infection strategies associated with persisting S. aureus infections are bacterial host cell invasion and the bacterial ability to dynamically change phenotypes from the aggressive wild-type to small colony variants (SCVs), which are adapted for intracellular long-term persistence. The underlying mechanisms of the bacterial switching and adaptation mechanisms appear to be very dynamic, but are largely unknown. Here, we analyzed the role and the crosstalk of the global S. aureus regulators agr, sarA and SigB by generating single, double and triple mutants, and testing them with proteome analysis and in different in vitro and in vivo infection models. We were able to demonstrate that SigB is the crucial factor for adaptation in chronic infections. During acute infection, the bacteria require the simultaneous action of the agr and sarA loci to defend against invading immune cells by causing inflammation and cytotoxicity and to escape from phagosomes in their host cells that enable them to settle an infection at high bacterial density. To persist intracellularly the bacteria subsequently need to silence agr and sarA. Indeed agr and sarA deletion mutants expressed a much lower number of virulence factors and could persist at high numbers intracellularly. SigB plays a crucial function to promote bacterial intracellular persistence. In fact, ΔsigB-mutants did not generate SCVs and were completely cleared by the host cells within a few days. In this study we identified SigB as an essential factor that enables the bacteria to switch from the highly aggressive phenotype that settles an acute infection to a silent SCV-phenotype that allows for long-term intracellular persistence. Consequently, the SigB-operon represents a possible target to develop preventive and therapeutic strategies against chronic and therapy-refractory infections.

Strategies for addressing adherence problems in patients with serious and persistent mental illness: recommendations from the expert consensus guidelines.

PubMed

Velligan, Dawn I; Weiden, Peter J; Sajatovic, Martha; Scott, Jan; Carpenter, Daniel; Ross, Ruth; Docherty, John P

2010-09-01

Poor adherence to medication can have devastating consequences for patients with serious mental illness. The literature review and recommendations in this article are reprinted from The Expert Consensus Guideline Series: Adherence Problems in Patients with Serious and Persistent Mental Illness, published in 2009. The expert consensus survey (39 questions, 521 options) on adherence problems in schizophrenia and bipolar disorder was completed by 41 experts in 2008. This article first reviews the literature on interventions aimed at improving adherence. It then presents the experts' recommendations for targeting factors that can contribute to nonadherence and relates them to the literature. The following psychosocial/programmatic and pharmacologic interventions were rated first line for specific problems that can lead to nonadherence: ongoing symptom/ side-effect monitoring for persistent symptoms or side effects; services targeting logistic problems; medication monitoring/environmental supports (e.g., Cognitive Adaptation Training, assertive community treatment) for lack of routines or cognitive deficits; and adjusting the dose or switching to a different oral antipsychotic for persistent side effects (also high second-line for persistent symptoms). Among pharmacologic interventions, the experts gave high second-line ratings to switching to a long-acting antipsychotic when lack of insight, substance use, persistent symptoms, logistic problems, lack of routines, or lack of family/ social support interfere with adherence and to simplifying the treatment regimen when logistic problems, lack of routines, cognitive deficits, or lack of family/social support interfere with adherence. Psychosocial/programmatic interventions that received high second-line ratings in a number of situations included medication monitoring/environmental supports, patient psychoeducation, more frequent and/or longer visits if possible, cognitive behavioral therapy (CBT), family-focused therapy, and services targeting logistic problems. It is important to identify specific factors that may be contributing to a patient's adherence problems in order to customize interventions and to consider using a multifaceted approach since multiple problems may be involved.

Food Restriction Increases Acquisition, Persistence and Drug Prime-Induced Expression of a Cocaine-Conditioned Place Preference in Rats

PubMed Central

Zheng, Danielle; de Vaca, Soledad Cabeza; Carr, Kenneth D.

2011-01-01

Cocaine conditioned place preference (CPP) is more persistent in food-restricted than ad libitum fed rats. This study assessed whether food restriction acts during conditioning and/or expression to increase persistence. In Experiment 1, rats were food-restricted during conditioning with a 7.0 mg/kg (i.p.) dose of cocaine. After the first CPP test, half of the rats were switched to ad libitum feeding for three weeks, half remained on food restriction, and this was followed by CPP testing. Rats tested under the ad libitum feeding condition displayed extinction by the fifth test. Their CPP did not reinstate in response to overnight food deprivation or a cocaine prime. Rats maintained on food restriction displayed a persistent CPP. In Experiment 2, rats were ad libitum fed during conditioning with the 7.0 mg/kg dose. In the first test only a trend toward CPP was displayed. Rats maintained under the ad libitum feeding condition did not display a CPP during subsequent testing and did not respond to a cocaine prime. Rats tested under food-restriction also did not display a CPP, but expressed a CPP following a cocaine prime. In Experiment 3, rats were ad libitum fed during conditioning with a 12.0 mg/kg dose. After the first test, half of the rats were switched to food restriction for three weeks. Rats that were maintained under the ad libitum condition displayed extinction by the fourth test. Their CPP was not reinstated by a cocaine prime. Rats tested under food-restriction displayed a persistent CPP. These results indicate that food restriction lowers the threshold dose for cocaine CPP and interacts with a previously acquired CPP to increase its persistence. In so far as CPP models Pavlovian conditioning that contributes to addiction, these results suggest the importance of diet and the physiology of energy balance as modulatory factors. PMID:22074687

Food restriction increases acquisition, persistence and drug prime-induced expression of a cocaine-conditioned place preference in rats.

PubMed

Zheng, Danielle; Cabeza de Vaca, Soledad; Carr, Kenneth D

2012-01-01

Cocaine conditioned place preference (CPP) is more persistent in food-restricted than ad libitum fed rats. This study assessed whether food restriction acts during conditioning and/or expression to increase persistence. In Experiment 1, rats were food-restricted during conditioning with a 7.0 mg/kg (i.p.) dose of cocaine. After the first CPP test, half of the rats were switched to ad libitum feeding for three weeks, half remained on food restriction, and this was followed by CPP testing. Rats tested under the ad libitum feeding condition displayed extinction by the fifth test. Their CPP did not reinstate in response to overnight food deprivation or a cocaine prime. Rats maintained on food restriction displayed a persistent CPP. In Experiment 2, rats were ad libitum fed during conditioning with the 7.0 mg/kg dose. In the first test only a trend toward CPP was displayed. Rats maintained under the ad libitum feeding condition did not display a CPP during subsequent testing and did not respond to a cocaine prime. Rats tested under food-restriction also did not display a CPP, but expressed a CPP following a cocaine prime. In Experiment 3, rats were ad libitum fed during conditioning with a 12.0 mg/kg dose. After the first test, half of the rats were switched to food restriction for three weeks. Rats that were maintained under the ad libitum condition displayed extinction by the fourth test. Their CPP was not reinstated by a cocaine prime. Rats tested under food-restriction displayed a persistent CPP. These results indicate that food restriction lowers the threshold dose for cocaine CPP and interacts with a previously acquired CPP to increase its persistence. In so far as CPP models Pavlovian conditioning that contributes to addiction, these results suggest the importance of diet and the physiology of energy balance as modulatory factors. Copyright © 2011 Elsevier Inc. All rights reserved.

Caltech campus executive LDRD.

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

Shepodd, Timothy J.; Knudsen, Tamara

2013-01-01

The environment most brain systems of humans and other animals are almost constantly confronted with is complex and continuously changing, with each time step updating a potentially bewildering set of opportunities and demands for action. Far from the controlled, discrete trials used in most neuro- and psychological investigations, behavior outside the lab at Caltech is a seamless and continuous process of monitoring (and error correction) of ongoing action, and of evaluating persistence in the current activity with respect to opportunities to switch tasks as alternatives become available. Prior work on frontopolar and prefrontal task switching, use tasks within the samemore » modality (View a stream of symbols on a screen and perform certain response mappings depending on task rules). However, in these task switches the effector is constant: only the mapping of visual symbols to the specific button changes. In this task, the subjects are choosing what kinds of future action decisions they want to perform, where they can control either which body part will act, or which direction they will orient an instructed body action. An effector choice task presents a single target and the subject selects which effector to use to reach the target (eye or hand). While the techniques available for humans can be less spatially resolved compared to non-human primate neural data, they do allow for experimentation on multiple brain areas with relative ease. Thus, we address a broader network of areas involved in motor decisions. We aim to resolve a current dispute regarding the specific functional roles of brain areas that are often co-activated in studies of decision tasks, dorsal premotor cortex(PMd) and posterior parietal cortex(PPC). In one model, the PPC distinctly drives intentions for action selection, whereas PMd stimulation results in complex multi-joint movements without any awareness of, nor subjective feeling of, willing the elicited movement, thus seems to merely help execute the chosen action.« less

Antidamping-Torque-Induced Switching in Biaxial Antiferromagnetic Insulators

NASA Astrophysics Data System (ADS)

Chen, X. Z.; Zarzuela, R.; Zhang, J.; Song, C.; Zhou, X. F.; Shi, G. Y.; Li, F.; Zhou, H. A.; Jiang, W. J.; Pan, F.; Tserkovnyak, Y.

2018-05-01

We investigate the current-induced switching of the Néel order in NiO (001 )/Pt heterostructures, which is manifested electrically via the spin Hall magnetoresistance. Significant reversible changes in the longitudinal and transverse resistances are found at room temperature for a current threshold lying in the range of 1 07 A /cm2 . The order-parameter switching is ascribed to the antiferromagnetic dynamics triggered by the (current-induced) antidamping torque, which orients the Néel order towards the direction of the writing current. This is in stark contrast to the case of antiferromagnets such as Mn2Au and CuMnAs, where fieldlike torques induced by the Edelstein effect drive the Néel switching, therefore resulting in an orthogonal alignment between the Néel order and the writing current. Our findings can be readily generalized to other biaxial antiferromagnets, providing broad opportunities for all-electrical writing and readout in antiferromagnetic spintronics.

Radio frequency-assisted fast superconducting switch

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

Solovyov, Vyacheslav; Li, Qiang

A radio frequency-assisted fast superconducting switch is described. A superconductor is closely coupled to a radio frequency (RF) coil. To turn the switch "off," i.e., to induce a transition to the normal, resistive state in the superconductor, a voltage burst is applied to the RF coil. This voltage burst is sufficient to induce a current in the coupled superconductor. The combination of the induced current with any other direct current flowing through the superconductor is sufficient to exceed the critical current of the superconductor at the operating temperature, inducing a transition to the normal, resistive state. A by-pass MOSFET maymore » be configured in parallel with the superconductor to act as a current shunt, allowing the voltage across the superconductor to drop below a certain value, at which time the superconductor undergoes a transition to the superconducting state and the switch is reset.« less

A long-term epigenetic memory switch controls bacterial virulence bimodality

PubMed Central

Ronin, Irine; Katsowich, Naama; Rosenshine, Ilan; Balaban, Nathalie Q

2017-01-01

When pathogens enter the host, sensing of environmental cues activates the expression of virulence genes. Opposite transition of pathogens from activating to non-activating conditions is poorly understood. Interestingly, variability in the expression of virulence genes upon infection enhances colonization. In order to systematically detect the role of phenotypic variability in enteropathogenic E. coli (EPEC), an important human pathogen, both in virulence activating and non-activating conditions, we employed the ScanLag methodology. The analysis revealed a bimodal growth rate. Mathematical modeling combined with experimental analysis showed that this bimodality is mediated by a hysteretic memory-switch that results in the stable co-existence of non-virulent and hyper-virulent subpopulations, even after many generations of growth in non-activating conditions. We identified the per operon as the key component of the hysteretic switch. This unique hysteretic memory switch may result in persistent infection and enhanced host-to-host spreading. DOI: http://dx.doi.org/10.7554/eLife.19599.001 PMID:28178445

Understanding Host-Switching by Ecological Fitting

PubMed Central

Araujo, Sabrina B. L.; Braga, Mariana Pires; Brooks, Daniel R.; Agosta, Salvatore J.; Hoberg, Eric P.; von Hartenthal, Francisco W.; Boeger, Walter A.

2015-01-01

Despite the fact that parasites are highly specialized with respect to their hosts, empirical evidence demonstrates that host switching rather than co-speciation is the dominant factor influencing the diversification of host-parasite associations. Ecological fitting in sloppy fitness space has been proposed as a mechanism allowing ecological specialists to host-switch readily. That proposal is tested herein using an individual-based model of host switching. The model considers a parasite species exposed to multiple host resources. Through time host range expansion can occur readily without the prior evolution of novel genetic capacities. It also produces non-linear variation in the size of the fitness space. The capacity for host colonization is strongly influenced by propagule pressure early in the process and by the size of the fitness space later. The simulations suggest that co-adaptation may be initiated by the temporary loss of less fit phenotypes. Further, parasites can persist for extended periods in sub-optimal hosts, and thus may colonize distantly related hosts by a "stepping-stone" process. PMID:26431199

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.

Parallel, staged opening switch power conditioning techniques for flux compression generator applications

NASA Astrophysics Data System (ADS)

Reinovsky, R. E.; Levi, P. S.; Bueck, J. C.; Goforth, J. H.

The Air Force Weapons Laboratory, working jointly with Los Alamos National Laboratory, has conducted a series of experiments directed at exploring composite, or staged, switching techniques for use in opening switches in applications which require the conduction of very high currents (or current densities) with very low losses for relatively long times (several tens of microseconds), and the interruption of these currents in much shorter times (ultimately a few hundred nanoseconds). The results of those experiments are reported.

MOSFET Power Controller

NASA Technical Reports Server (NTRS)

Mitchell, J.; Jones, K.

1986-01-01

High current and voltage controlled remotely. Remote Power Conroller includes two series-connected banks of parallel-connected MOSFET's to withstand high current and voltage. Voltage sharing between switch banks, low-impedance, gate-drive circuits used. Provided controlled range for turn on. Individually trimmable to insure simultaneous switching within few nanoseconds during both turn on and turn off. Control circuit for each switch bank and over-current trip circuit float independently and supplied power via transformer T1 from inverter. Control of floating stages by optocouplers.

20 kA PFN capacitor bank with solid-state switching. [pulse forming network for plasma studies

NASA Technical Reports Server (NTRS)

Posta, S. J.; Michels, C. J.

1973-01-01

A compact high-current pulse-forming network capacitor bank using paralleled silicon controlled rectifiers as switches is described. The maximum charging voltage of the bank is 1kV and maximum load current is 20 kA. The necessary switch equalization criteria and performance with dummy load and an arc plasma generator are described.

Measurement of resistance switching dynamics in copper sulfide memristor structures

NASA Astrophysics Data System (ADS)

McCreery, Kaitlin; Olson, Matthew; Teitsworth, Stephen

Resistance switching materials are the subject of current research in large part for their potential to enable novel computing devices and architectures such as resistance random access memories and neuromorphic chips. A common feature of memristive structures is the hysteretic switching between high and low resistance states which is induced by the application of a sufficiently large electric field. Here, we describe a relatively simple wet chemistry process to fabricate Cu2 S / Cu memristive structures with Cu2 S film thickness ranging up to 150 micron. In this case, resistance switching is believed to be mediated by electromigration of Cu ions from the Cu substrate into the Cu2 S film. Hysteretic current-voltage curves are measured and reveal switching voltages of about 0.8 Volts with a relatively large variance and independent of film thickness. In order to gain insight into the dynamics and variability of the switching process, we have measured the time-dependent current response to voltage pulses of varying height and duration with a time resolution of 1 ns. The transient response consists of a deterministic RC component as well as stochastically varying abrupt current steps that occur within a few microseconds of the pulse application.

Switching Dynamics of an Underdamped Josephson Junction Coupled to a Microwave Cavity

NASA Astrophysics Data System (ADS)

Oelsner, G.; Il'ichev, E.

2018-05-01

Current-biased Josephson junctions are promising candidates for the detection of single photons in the microwave frequency domain. With modern fabrication technologies, the switching properties of the junction can be adjusted to achieve quantum limited sensitivity. Namely, the width of the switching current distribution can be reduced well below the current amplitude produced by a single photon trapped inside a superconducting cavity. However, for an effective detection a strong junction cavity coupling is required, providing nonlinear system dynamics. We compare experimental findings for our prototype device with a theoretical analysis aimed to describe the switching dynamics of junctions under microwave irradiation. Measurements are found in qualitative agreement with our simulations.

Compensation of voltage drops in solid-state switches used with thermoelectric generators

NASA Technical Reports Server (NTRS)

Shimada, K.

1972-01-01

Seebeck effect solid state switch was developed eliminating thermoelectric generator switch voltage drops. Semiconductor switches were fabricated from materials with large Seebeck coefficients, arranged such that Seebeck potential is generated with such polarity that current flow is aided.

PHz current switching in calcium fluoride single crystal

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

Kwon, Ojoon; Kim, D., E-mail: kimd@postech.ac.kr; Max Planck Center for Attosecond Science, Max Planck POSTECH/Korea Res. Init., Pohang 37673

2016-05-09

We demonstrate that a current can be induced and switched in a sub-femtosecond time-scale in an insulating calcium fluoride single crystal by an intense optical field. This measurement indicates that a sizable current can be generated and also controlled by an optical field in a dielectric medium, implying the capability of rapid current switching at a rate of optical frequency, PHz (10{sup 15} Hz), which is a couple of orders of magnitude higher than that of contemporary electronic signal processing. This demonstration may serve to facilitate the development of ultrafast devices in PHz frequency.

Zener diode controls switching of large direct currents

NASA Technical Reports Server (NTRS)

1965-01-01

High-current zener diode is connected in series with the positive input terminal of a dc supply to block the flow of direct current until a high-frequency control signal is applied across the zener diode. This circuit controls the switching of large dc signals.

Current polarity-dependent manipulation of antiferromagnetic domains

NASA Astrophysics Data System (ADS)

Wadley, Peter; Reimers, Sonka; Grzybowski, Michal J.; Andrews, Carl; Wang, Mu; Chauhan, Jasbinder S.; Gallagher, Bryan L.; Campion, Richard P.; Edmonds, Kevin W.; Dhesi, Sarnjeet S.; Maccherozzi, Francesco; Novak, Vit; Wunderlich, Joerg; Jungwirth, Tomas

2018-05-01

Antiferromagnets have several favourable properties as active elements in spintronic devices, including ultra-fast dynamics, zero stray fields and insensitivity to external magnetic fields1. Tetragonal CuMnAs is a testbed system in which the antiferromagnetic order parameter can be switched reversibly at ambient conditions using electrical currents2. In previous experiments, orthogonal in-plane current pulses were used to induce 90° rotations of antiferromagnetic domains and demonstrate the operation of all-electrical memory bits in a multi-terminal geometry3. Here, we demonstrate that antiferromagnetic domain walls can be manipulated to realize stable and reproducible domain changes using only two electrical contacts. This is achieved by using the polarity of the current to switch the sign of the current-induced effective field acting on the antiferromagnetic sublattices. The resulting reversible domain and domain wall reconfigurations are imaged using X-ray magnetic linear dichroism microscopy, and can also be detected electrically. Switching by domain-wall motion can occur at much lower current densities than those needed for coherent domain switching.

Electrically controlled optical latch and switch requires less current

NASA Technical Reports Server (NTRS)

Pieczonka, W. A.; Roy, M. M.; Yeh, T. H.

1966-01-01

Electrically controlled optical latch consists of a sensitive phototransistor and a solid-state light source. This design requires less current to activate an optically activated switch than in prior art.

The Minimum Requirements of Language Control: Evidence from Sequential Predictability Effects in Language Switching

ERIC Educational Resources Information Center

Declerck, Mathieu; Koch, Iring; Philipp, Andrea M.

2015-01-01

The current study systematically examined the influence of sequential predictability of languages and concepts on language switching. To this end, 2 language switching paradigms were combined. To measure language switching with a random sequence of languages and/or concepts, we used a language switching paradigm that implements visual cues and…

Correction to: Real-World Switching to Riociguat: Management and Practicalities in Patients with PAH and CTEPH.

PubMed

Gall, Henning; Vachiéry, Jean-Luc; Tanabe, Nobuhiro; Halank, Michael; Orozco-Levi, Mauricio; Mielniczuk, Lisa; Chang, MiKyung; Vogtländer, Kai; Grünig, Ekkehard

2018-06-01

The original version of this article unfortunately contained a mistake. In the "Results" section, the percentage of patients with inoperable or persistent/recurrent CTEPH included in the study was reported as 85%. This has been corrected to 68% with this erratum.

100-kA vacuum current breaker of a modular design

NASA Astrophysics Data System (ADS)

Ivanov, V. P.; Vozdvijenskii, V. A.; Jagnov, V. A.; Solodovnikov, S. G.; Mazulin, A. V.; Ryjkov, V. M.

1994-05-01

Direct current breaker of a modular design is developed for the strong field tokamak power supply system. The power supply system comprises four 800 MW alternative current generators with 4 GJ flywheels, thyristor rectifiers providing inductive stores pumping by a current up to 100 kA for 1 - 4 sec. To form current pulses of various shapes in the tokamak windings current breakers are used with either pneumatic or explosive drive, at a current switching synchronously of not worse than 100 mks. Current breakers of these types require that the current conducting elements be replaced after each shot. For recent years vacuum arc quenching chambers with an axial magnetic field are successfully employed as repetitive performance current breakers, basically for currents up to 40 kA. In the report some results of researches of a vacuum switch modular are presented which we used as prototype switch for currents of the order of 100 kA.

Superconducting coil system and methods of assembling the same

DOEpatents

Rajput-Ghoshal, Renuka; Rochford, James H.; Ghoshal, Probir K.

2016-01-19

A superconducting magnet apparatus is provided. The superconducting magnet apparatus includes a power source configured to generate a current; a first switch coupled in parallel to the power source; a second switch coupled in series to the power source; a coil coupled in parallel to the first switch and the second switch; and a passive quench protection device coupled to the coil and configured to by-pass the current around the coil and to decouple the coil from the power source when the coil experiences a quench.

Impact of electrically formed interfacial layer and improved memory characteristics of IrOx/high-κx/W structures containing AlOx, GdOx, HfOx, and TaOx switching materials.

PubMed

Prakash, Amit; Maikap, Siddheswar; Banerjee, Writam; Jana, Debanjan; Lai, Chao-Sung

2013-09-06

Improved switching characteristics were obtained from high-κ oxides AlOx, GdOx, HfOx, and TaOx in IrOx/high-κx/W structures because of a layer that formed at the IrOx/high-κx interface under external positive bias. The surface roughness and morphology of the bottom electrode in these devices were observed by atomic force microscopy. Device size was investigated using high-resolution transmission electron microscopy. More than 100 repeatable consecutive switching cycles were observed for positive-formatted memory devices compared with that of the negative-formatted devices (only five unstable cycles) because it contained an electrically formed interfacial layer that controlled 'SET/RESET' current overshoot. This phenomenon was independent of the switching material in the device. The electrically formed oxygen-rich interfacial layer at the IrOx/high-κx interface improved switching in both via-hole and cross-point structures. The switching mechanism was attributed to filamentary conduction and oxygen ion migration. Using the positive-formatted design approach, cross-point memory in an IrOx/AlOx/W structure was fabricated. This cross-point memory exhibited forming-free, uniform switching for >1,000 consecutive dc cycles with a small voltage/current operation of ±2 V/200 μA and high yield of >95% switchable with a large resistance ratio of >100. These properties make this cross-point memory particularly promising for high-density applications. Furthermore, this memory device also showed multilevel capability with a switching current as low as 10 μA and a RESET current of 137 μA, good pulse read endurance of each level (>105 cycles), and data retention of >104 s at a low current compliance of 50 μA at 85°C. Our improvement of the switching characteristics of this resistive memory device will aid in the design of memory stacks for practical applications.

Non-oxidized porous silicon-based power AC switch peripheries.

PubMed

Menard, Samuel; Fèvre, Angélique; Valente, Damien; Billoué, Jérôme; Gautier, Gaël

2012-10-11

We present in this paper a novel application of porous silicon (PS) for low-power alternating current (AC) switches such as triode alternating current devices (TRIACs) frequently used to control small appliances (fridge, vacuum cleaner, washing machine, coffee makers, etc.). More precisely, it seems possible to benefit from the PS electrical insulation properties to ensure the OFF state of the device. Based on the technological aspects of the most commonly used AC switch peripheries physically responsible of the TRIAC blocking performances (leakage current and breakdown voltage), we suggest to isolate upper and lower junctions through the addition of a PS layer anodically etched from existing AC switch diffusion profiles. Then, we comment the voltage capability of practical samples emanating from the proposed architecture. Thanks to the characterization results of simple Al-PS-Si(P) structures, the experimental observations are interpreted, thus opening new outlooks in the field of AC switch peripheries.

Spacecraft solid state power distribution switch

NASA Technical Reports Server (NTRS)

Praver, G. A.; Theisinger, P. C.

1986-01-01

As a spacecraft performs its mission, various loads are connected to the spacecraft power bus in response to commands from an on board computer, a function called power distribution. For the Mariner Mark II set of planetary missions, the power bus is 30 volts dc and when loads are connected or disconnected, both the bus and power return side must be switched. In addition, the power distribution function must be immune to single point failures and, when power is first applied, all switches must be in a known state. Traditionally, these requirements have been met by electromechanical latching relays. This paper describes a solid state switch which not only satisfies the requirements but incorporates several additional features including soft turn on, programmable current trip point with noise immunity, instantaneous current limiting, and direct telemetry of load currents and switch status. A breadboard of the design has been constructed and some initial test results are included.

An integrated circuit switch

NASA Technical Reports Server (NTRS)

Bonin, E. L.

1969-01-01

Multi-chip integrated circuit switch consists of a GaAs photon-emitting diode in close proximity with S1 phototransistor. A high current gain is obtained when the transistor has a high forward common-emitter current gain.

Hybrid zero-voltage switching (ZVS) control for power inverters

DOEpatents

Amirahmadi, Ahmadreza; Hu, Haibing; Batarseh, Issa

2016-11-01

A power inverter combination includes a half-bridge power inverter including first and second semiconductor power switches receiving input power having an intermediate node therebetween providing an inductor current through an inductor. A controller includes input comparison circuitry receiving the inductor current having outputs coupled to first inputs of pulse width modulation (PWM) generation circuitry, and a predictive control block having an output coupled to second inputs of the PWM generation circuitry. The predictive control block is coupled to receive a measure of Vin and an output voltage at a grid connection point. A memory stores a current control algorithm configured for resetting a PWM period for a switching signal applied to control nodes of the first and second power switch whenever the inductor current reaches a predetermined upper limit or a predetermined lower limit.

Decay of the de Sitter vacuum

NASA Astrophysics Data System (ADS)

Anderson, Paul R.; Mottola, Emil; Sanders, Dillon H.

2018-03-01

The decay rate of the Bunch-Davies state of a massive scalar field in the expanding flat spatial sections of de Sitter space is determined by an analysis of the particle pair creation process in real time. The Feynman definition of particle and antiparticle Fourier mode solutions of the scalar wave equation and their adiabatic phase analytically continued to the complexified time domain show conclusively that the Bunch-Davies state is not the vacuum state at late times. The closely analogous creation of charged particle pairs in a uniform electric field is reviewed and Schwinger's result for the vacuum decay rate is recovered by this same real time analysis. The vacuum decay rate in each case is also calculated by switching the background field on adiabatically, allowing it to act for a very long time, and then adiabatically switching it off again. In both the uniform electric field and de Sitter cases, the particles created while the field is switched on are verified to be real, in the sense that they persist in the final asymptotic flat zero-field region. In the de Sitter case, there is an interesting residual dependence of the rate on how the de Sitter phase is ended, indicating a greater sensitivity to spatial boundary conditions. The electric current of the created particles in the E -field case and their energy density and pressure in the de Sitter case are also computed, and the magnitude of their backreaction effects on the background field estimated. Possible consequences of the Hubble scale instability of the de Sitter vacuum for cosmology, vacuum dark energy, and the cosmological "constant" problem are discussed.

Development and simulation study of a new inverse-pinch high Coulomb transfer switch

NASA Technical Reports Server (NTRS)

Choi, Sang H.

1989-01-01

The inverse-pinch plasma switch was studied using a computer simulation code. The code was based on a 2-D, 2-temperature magnetohydrodynamic (MHD) model. The application of this code was limited to the disk-type inverse-pinch plasma switch. The results of the computer analysis appear to be in agreement with the experimental results when the same parameters are used. An inverse-pinch plasma switch for closing has been designed and tested for high-power switching requirements. An azimuthally uniform initiation of breakdown is a key factor in achieving an inverse-pinch current path in the switch. Thus, various types of triggers, such as trigger pins, wire-brush, ring trigger, and hypocycloidal-pinch (HCP) devices have been tested for uniform breakdown. Recently, triggering was achieved by injection of a plasma-ring (plasma puff) that is produced separately with hypocycloidal-pinch electrodes placed under the cathode of the main gap. The current paths at switch closing, initiated by the injection of a plasma-ring from the HCP trigger are azimuthally uniform, and the local current density is significantly reduced, so that damage to the electrodes and the insulator surfaces is minimized. The test results indicate that electron bombardment on the electrodes and the insulator surfaces is minimized. The test results indicate that electron bombardment on the electrodes is four orders of magnitude less than that of a spark-gap switch for the same switching power. Indeed, a few thousand shots with peak current exceeding a mega-ampere and with hold-off voltage up to 20 kV have been conducted without showing measurable damage to the electrodes and insulators.

Digital optical signal processing with polarization-bistable semiconductor lasers

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

Jai-Ming Liu,; Ying-Chin Chen,

1985-04-01

The operations of a complete set of optical AND, NAND, OR, and NOR gates and clocked optical S-R, D, J-K, and T flip-flops are demonstrated, based on direct polarization switching and polarization bistability, which we have recently observed in InGaAsP/InP semiconductor lasers. By operating the laser in the direct-polarizationswitchable mode, the output of the laser can be directly switched between the TM00 and TE00 modes with high extinction ratios by changing the injection-current level, and optical logic gates are constructed with two optoelectronic switches or photodetectors. In the polarization-bistable mode, the laser exhibits controllable hysteresis loops in the polarization-resolved powermore » versus current characteristics. When the laser is biased in the middle of the hysteresis loop, the light output can be switched between the two polarization states by injection of short electrical or optical pulses, and clocked optical flip-flops are constructed with a few optoelectronic switches and/or photodetectors. The 1 and 0 states of these devices are defined through polarization changes of the laser and direct complement functions are obtainable from the TE and TM output signals from the same laser. Switching of the polarization-bistable lasers with fast-rising current pulses has an instrument-limited mode-switching time on the order of 1 ns. With fast optoelectronic switches and/or fast photodetectors, the overall switching speed of the logic gates and flip-flops is limited by the polarizationbistable laser to <1 ns. We have demonstrated the operations of these devices using optical signals generated by semiconductor lasers. The proposed schemes of our devices are compatible with monolithic integration based on current fabrication technology and are applicable to other types of bistable semiconductor lasers.« less

Methodology for Wide Band-Gap Device Dynamic Characterization

DOE PAGES

Zhang, Zheyu; Guo, Ben; Wang, Fei Fred; ...

2017-01-19

Here, the double pulse test (DPT) is a widely accepted method to evaluate the dynamic behavior of power devices. Considering the high switching-speed capability of wide band-gap devices, the test results are very sensitive to the alignment of voltage and current (V-I) measurements. Also, because of the shoot-through current induced by Cdv/dt (i.e., cross-talk), the switching losses of the nonoperating switch device in a phase-leg must be considered in addition to the operating device. This paper summarizes the key issues of the DPT, including components and layout design, measurement considerations, grounding effects, and data processing. Additionally, a practical method ismore » proposed for phase-leg switching loss evaluation by calculating the difference between the input energy supplied by a dc capacitor and the output energy stored in a load inductor. Based on a phase-leg power module built with 1200-V/50-A SiC MOSFETs, the test results show that this method can accurately evaluate the switching loss of both the upper and lower switches by detecting only one switching current and voltage, and it is immune to V-I timing misalignment errors.« less

High PRF high current switch

DOEpatents

Moran, Stuart L.; Hutcherson, R. Kenneth

1990-03-27

A triggerable, high voltage, high current, spark gap switch for use in pu power systems. The device comprises a pair of electrodes in a high pressure hydrogen environment that is triggered by introducing an arc between one electrode and a trigger pin. Unusually high repetition rates may be obtained by undervolting the switch, i.e., operating the trigger at voltages much below the self-breakdown voltage of the device.

Predictors of switch from depression to mania in bipolar disorder.

PubMed

Niitsu, Tomihisa; Fabbri, Chiara; Serretti, Alessandro

2015-01-01

Manic switch is a relevant issue when treating bipolar depression. Some risk factors have been suggested, but unequivocal findings are lacking. We therefore investigated predictors of switch from depression to mania in the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD) sample. Manic switch was defined as a depressive episode followed by a (hypo)manic or mixed episode within the following 12 weeks. We assessed possible predictors of switch using generalized linear mixed models (GLMM). 8403 episodes without switch and 512 episodes with switch (1720 subjects) were included in the analysis. Several baseline variables were associated with a higher risk of switch. They were younger age, previous history of: rapid cycling, severe manic symptoms, suicide attempts, amphetamine use and some pharmacological and psychotherapeutic treatments. During the current depressive episode, the identified risk factors were: any possible mood elevation, multiple mania-associated symptoms with at least moderate severity, and comorbid panic attacks. In conclusion, our study suggests that both characteristics of the disease history and clinical features of the current depressive episode may be risk factors for manic switch. Copyright © 2015 Elsevier Ltd. All rights reserved.

Trajectories of suicidal ideation in depressed older adults undergoing antidepressant treatment.

PubMed

Kasckow, John; Youk, Ada; Anderson, Stewart J; Dew, Mary Amanda; Butters, Meryl A; Marron, Megan M; Begley, Amy E; Szanto, Katalin; Dombrovski, Alexander Y; Mulsant, Benoit H; Lenze, Eric J; Reynolds, Charles F

2016-02-01

Suicide is a public health concern in older adults. Recent cross sectional studies suggest that impairments in executive functioning, memory and attention are associated with suicidal ideation in older adults. It is unknown whether these neuropsychological features predict persistent suicidal ideation. We analyzed data from 468 individuals ≥ age 60 with major depression who received venlafaxine XR monotherapy for up to 16 weeks. We used latent class growth modeling to classify groups of individuals based on trajectories of suicidal ideation. We also examined whether cognitive dysfunction predicted suicidal ideation while controlling for time-dependent variables including depression severity, and age and education. The optimal model using a zero inflated Poisson link classified individuals into four groups, each with a distinct temporal trajectory of suicidal ideation: those with 'minimal suicidal ideation' across time points; those with 'low suicidal ideation'; those with 'rapidly decreasing suicidal ideation'; and those with 'high and persistent suicidal ideation'. Participants in the 'high and persistent suicidal ideation' group had worse scores relative to those in the "rapidly decreasing suicidal ideation" group on the Color-Word 'inhibition/switching' subtest from the Delis-Kaplan Executive Function Scale, worse attention index scores on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and worse total RBANS index scores. These findings suggest that individuals with poorer ability to switch between inhibitory and non-inhibitory responses as well as worse attention and worse overall cognitive status are more likely to have persistently higher levels of suicidal ideation. CLINICALTRIAL. NCT00892047. Published by Elsevier Ltd.

Development of compact rapid charging power supply for capacitive energy storage in pulsed power drivers.

PubMed

Sharma, Surender Kumar; Shyam, Anurag

2015-02-01

High energy capacitor bank is used for primary electrical energy storage in pulsed power drivers. The capacitors used in these pulsed power drivers have low inductance, low internal resistance, and less dc life, so it has to be charged rapidly and immediately discharged into the load. A series resonant converter based 45 kV compact power supply is designed and developed for rapid charging of the capacitor bank with constant charging current up to 150 mA. It is short circuit proof, and zero current switching technique is used to commute the semiconductor switch. A high frequency resonant inverter switching at 10 kHz makes the overall size small and reduces the switching losses. The output current of the power supply is limited by constant on-time and variable frequency switching control technique. The power supply is tested by charging the 45 kV/1.67 μF and 15 kV/356 μF capacitor banks. It has charged the capacitor bank up to rated voltage with maximum charging current of 150 mA and the average charging rate of 3.4 kJ/s. The output current of the power supply is limited by reducing the switching frequency at 5 kHz, 3.3 kHz, and 1.7 kHz and tested with 45 kV/1.67 μF capacitor bank. The protection circuit is included in the power supply for over current, under voltage, and over temperature. The design details and the experimental testing results of the power supply for resonant current, output current, and voltage traces of the power supply with capacitive, resistive, and short circuited load are presented and discussed.

High-efficiency thermal switch based on topological Josephson junctions

NASA Astrophysics Data System (ADS)

Sothmann, Björn; Giazotto, Francesco; Hankiewicz, Ewelina M.

2017-02-01

We propose theoretically a thermal switch operating by the magnetic-flux controlled diffraction of phase-coherent heat currents in a thermally biased Josephson junction based on a two-dimensional topological insulator. For short junctions, the system shows a sharp switching behavior while for long junctions the switching is smooth. Physically, the switching arises from the Doppler shift of the superconducting condensate due to screening currents induced by a magnetic flux. We suggest a possible experimental realization that exhibits a relative temperature change of 40% between the on and off state for realistic parameters. This is a factor of two larger than in recently realized thermal modulators based on conventional superconducting tunnel junctions.

Wide Bandgap Extrinsic Photoconductive Switches

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

Sullivan, James S.

2012-01-20

Photoconductive semiconductor switches (PCSS) have been investigated since the late 1970s. Some devices have been developed that withstand tens of kilovolts and others that switch hundreds of amperes. However, no single device has been developed that can reliably withstand both high voltage and switch high current. Yet, photoconductive switches still hold the promise of reliable high voltage and high current operation with subnanosecond risetimes. Particularly since good quality, bulk, single crystal, wide bandgap semiconductor materials have recently become available. In this chapter we will review the basic operation of PCSS devices, status of PCSS devices and properties of the widemore » bandgap semiconductors 4H-SiC, 6H-SiC and 2H-GaN.« less

Design and fabrication of GaAs OMIST photodetector

NASA Astrophysics Data System (ADS)

Kang, Xuejun; Lin, ShiMing; Liao, Qiwei; Gao, Junhua; Liu, Shi'an; Cheng, Peng; Wang, Hongjie; Zhang, Chunhui; Wang, Qiming

1998-08-01

We designed and fabricated GaAs OMIST (Optical-controlled Metal-Insulator-Semiconductor Thyristor) device. Using oxidation of AlAs layer that is grown by MBE forms the Ultra- Thin semi-Insulating layer (UTI) of the GAAS OMIST. The accurate control and formation of high quality semi-insulating layer (AlxOy) are the key processes for fabricating GaAs OMIST. The device exhibits a current-controlled negative resistance region in its I-V characteristics. When illuminated, the major effect of optical excitation is the reduction of the switching voltage. If the GaAs OMIST device is biased at a voltage below its dark switching voltage Vs, sufficient incident light can switch OMIST from high impedance low current 'off' state to low impedance high current 'on' state. The absorbing material of OMIST is GaAS, so if the wavelength of incident light within 600 to approximately 850 nm can be detected effectively. It is suitable to be used as photodetector for digital optical data process. The other attractive features of GaAs OMIST device include suitable conducted current, switching voltage and power levels for OEIC, high switch speed and high sensitivity to light or current injection.

Compact high voltage solid state switch

DOEpatents

Glidden, Steven C.

2003-09-23

A compact, solid state, high voltage switch capable of high conduction current with a high rate of current risetime (high di/dt) that can be used to replace thyratrons in existing and new applications. The switch has multiple thyristors packaged in a single enclosure. Each thyristor has its own gate drive circuit that circuit obtains its energy from the energy that is being switched in the main circuit. The gate drives are triggered with a low voltage, low current pulse isolated by a small inexpensive transformer. The gate circuits can also be triggered with an optical signal, eliminating the trigger transformer altogether. This approach makes it easier to connect many thyristors in series to obtain the hold off voltages of greater than 80 kV.

Remote switch actuator

DOEpatents

Haas, Edwin Gerard; Beauman, Ronald; Palo, Jr., Stefan

2013-01-29

The invention provides a device and method for actuating electrical switches remotely. The device is removably attached to the switch and is actuated through the transfer of a user's force. The user is able to remain physically removed from the switch site obviating need for protective equipment. The device and method allow rapid, safe actuation of high-voltage or high-current carrying electrical switches or circuit breakers.

Experimental Results from a Laser-Triggered, Gas-Insulated, Spark-Gap Switch

NASA Astrophysics Data System (ADS)

Camacho, J. F.; Ruden, E. L.; Domonkos, M. T.

2017-10-01

We are performing experiments on a laser-triggered spark-gap switch with the goal of studying the transition from photoionization to current conduction. The discharge of current through the switch is triggered by a focused 532-nm wavelength beam from a Q-switched Nd:YAG laser with a pulse duration of about 10 ns. The trigger pulse is delivered along the longitudinal axis of the switch, and the focal spot can be placed anywhere along the axis of the 5-mm, gas-insulated gap between the switch electrodes. The switch test bed is designed to support a variety of working gases (e.g., Ar, N2) over a range of pressures. Electrical and optical diagnostics are used to measure switch performance as a function of parameters such as charge voltage, trigger pulse energy, insulating gas pressure, and gas species. A Mach-Zehnder imaging interferometer system operating at 532 nm is being used to obtain interferograms of the discharge plasma in the switch. We are also developing a 1064-nm interferometry diagnostic in an attempt to measure plasma free electron and neutral gas density profiles simultaneously within the switch gap. Results from our most recent experiments will be presented.

Thermionic gas switch

DOEpatents

Hatch, George L.; Brummond, William A.; Barrus, Donald M.

1986-01-01

A temperature responsive thermionic gas switch having folded electron emitting surfaces. An ionizable gas is located between the emitter and an interior surface of a collector, coaxial with the emitter. In response to the temperature exceeding a predetermined level, sufficient electrons are derived from the emitter to cause the gas in the gap between the emitter and collector to become ionized, whereby a very large increase in current in the gap occurs. Due to the folded emitter surface area of the switch, increasing the "on/off" current ratio and adjusting the "on" current capacity is accomplished.

Electrical motor/generator drive apparatus and method

DOEpatents

Su, Gui Jia

2013-02-12

The present disclosure includes electrical motor/generator drive systems and methods that significantly reduce inverter direct-current (DC) bus ripple currents and thus the volume and cost of a capacitor. The drive methodology is based on a segmented drive system that does not add switches or passive components but involves reconfiguring inverter switches and motor stator winding connections in a way that allows the formation of multiple, independent drive units and the use of simple alternated switching and optimized Pulse Width Modulation (PWM) schemes to eliminate or significantly reduce the capacitor ripple current.

Reversing-counterpulse repetitive-pulse inductive storage circuit

DOEpatents

Honig, Emanuel M.

1987-01-01

A high-power reversing-counterpulse repetitive-pulse inductive storage and transfer circuit includes an opening switch, a main energy storage coil, a counterpulse capacitor and a small inductor. After counterpulsing the opening switch off, the counterpulse capacitor is recharged by the main energy storage coil before the load pulse is initiated. This gives the counterpulse capacitor sufficient energy for the next counterpulse operation, although the polarity of the capacitor's voltage must be reversed before that can occur. By using a current-zero switch as the counterpulse start switch, the capacitor is disconnected from the circuit (with a full charge) when the load pulse is initiated, preventing the capacitor from depleting its energy store by discharging through the load. After the load pulse is terminated by reclosing the main opening switch, the polarity of the counterpulse capacitor voltage is reversed by discharging the capacitor through a small inductor and interrupting the discharge current oscillation at zero current and peak reversed voltage. The circuit enables high-power, high-repetition-rate operation with reusable switches and features total control (pulse-to-pulse) over output pulse initiation, duration, repetition rate, and, to some extent, risetime.

Reversing-counterpulse repetitive-pulse inductive storage circuit

DOEpatents

Honig, E.M.

1984-06-05

A high power reversing-counterpulse repetitive-pulse inductive storage and transfer circuit includes an opening switch, a main energy storage coil, a counterpulse capacitor and a small inductor. After counterpulsing the opening switch off, the counterpulse capacitor is recharged by the main energy storage coil before the load pulse is initiated. This gives the counterpulse capacitor sufficient energy for the next counterpulse operation, although the polarity of the capacitor's voltage must be reversed before that can occur. By using a current-zero switch as the counterpulse start switch, the capacitor is disconnected from the circuit (with a full charge) when the load pulse is initiated, preventing the capacitor from depleting its energy store by discharging through the load. After the load pulse is terminated by reclosing the main opening switch, the polarity of the counterpulse capacitor voltage is reversed by discharging the capacitor through a small inductor and interrupting the discharge current oscillation at zero current and peak reversed voltage. The circuit enables high-power, high-repetition-rate operation with reusable switches and features total control (pulse-to-pulse) over output pulse initiation, duration, repetition rate, and, to some extent, risetime.

Peroxide induced volatile and non-volatile switching behavior in ZnO-based electrochemical metallization memory cell

NASA Astrophysics Data System (ADS)

Mangasa Simanjuntak, Firman; Chandrasekaran, Sridhar; Pattanayak, Bhaskar; Lin, Chun-Chieh; Tseng, Tseung-Yuen

2017-09-01

We explore the use of cubic-zinc peroxide (ZnO2) as a switching material for electrochemical metallization memory (ECM) cell. The ZnO2 was synthesized with a simple peroxide surface treatment. Devices made without surface treatment exhibits a high leakage current due to the self-doped nature of the hexagonal-ZnO material. Thus, its switching behavior can only be observed when a very high current compliance is employed. The synthetic ZnO2 layer provides a sufficient resistivity to the Cu/ZnO2/ZnO/ITO devices. The high resistivity of ZnO2 encourages the formation of a conducting bridge to activate the switching behavior at a lower operation current. Volatile and non-volatile switching behaviors with sufficient endurance and an adequate memory window are observed in the surface-treated devices. The room temperature retention of more than 104 s confirms the non-volatility behavior of the devices. In addition, our proposed device structure is able to work at a lower operation current among other reported ZnO-based ECM cells.

An Energy Saving Green Plug Device for Nonlinear Loads

NASA Astrophysics Data System (ADS)

Bloul, Albe; Sharaf, Adel; El-Hawary, Mohamed

2018-03-01

The paper presents a low cost a FACTS Based flexible fuzzy logic based modulated/switched tuned arm filter and Green Plug compensation (SFC-GP) scheme for single-phase nonlinear loads ensuring both voltage stabilization and efficient energy utilization. The new Green Plug-Switched filter compensator SFC modulated LC-Filter PWM Switched Capacitive Compensation Devices is controlled using a fuzzy logic regulator to enhance power quality, improve power factor at the source and reduce switching transients and inrush current conditions as well harmonic contents in source current. The FACTS based SFC-GP Device is a member of family of Green Plug/Filters/Compensation Schemes used for efficient energy utilization, power quality enhancement and voltage/inrush current/soft starting control using a dynamic error driven fuzzy logic controller (FLC). The device with fuzzy logic controller is validated using the Matlab / Simulink Software Environment for enhanced power quality (PQ), improved power factor and reduced inrush currents. This is achieved using modulated PWM Switching of the Filter-Capacitive compensation scheme to cope with dynamic type nonlinear and inrush cyclical loads..

Invasive Congeners Differ in Successional Impacts across Space and Time

PubMed Central

David, Aaron S.; Zarnetske, Phoebe L.; Hacker, Sally D.; Ruggiero, Peter; Biel, Reuben G.; Seabloom, Eric W.

2015-01-01

Invasive species can alter the succession of ecological communities because they are often adapted to the disturbed conditions that initiate succession. The extent to which this occurs may depend on how widely they are distributed across environmental gradients and how long they persist over the course of succession. We focus on plant communities of the USA Pacific Northwest coastal dunes, where disturbance is characterized by changes in sediment supply, and the plant community is dominated by two introduced grasses – the long-established Ammophila arenaria and the currently invading A. breviligulata. Previous studies showed that A. breviligulata has replaced A. arenaria and reduced community diversity. We hypothesize that this is largely due to A. breviligulata occupying a wider distribution across spatial environmental gradients and persisting in later-successional habitat than A. arenaria. We used multi-decadal chronosequences and a resurvey study spanning 2 decades to characterize distributions of both species across space and time, and investigated how these distributions were associated with changes in the plant community. The invading A. breviligulata persisted longer and occupied a wider spatial distribution across the dune, and this corresponded with a reduction in plant species richness and native cover. Furthermore, backdunes previously dominated by A. arenaria switched to being dominated by A. breviligulata, forest, or developed land over a 23-yr period. Ammophila breviligulata likely invades by displacing A. arenaria, and reduces plant diversity by maintaining its dominance into later successional backdunes. Our results suggest distinct roles in succession, with A. arenaria playing a more classically facilitative role and A. breviligulata a more inhibitory role. Differential abilities of closely-related invasive species to persist through time and occupy heterogeneous environments allows for distinct impacts on communities during succession. PMID:25658824

14 CFR 27.1367 - Switches.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Switches. 27.1367 Section 27.1367... STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Electrical Systems and Equipment § 27.1367 Switches. Each switch must be— (a) Able to carry its rated current; (b) Accessible to the crew; and (c) Labeled as to...

14 CFR 27.1367 - Switches.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Switches. 27.1367 Section 27.1367... STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Electrical Systems and Equipment § 27.1367 Switches. Each switch must be— (a) Able to carry its rated current; (b) Accessible to the crew; and (c) Labeled as to...

14 CFR 27.1367 - Switches.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Switches. 27.1367 Section 27.1367... STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Electrical Systems and Equipment § 27.1367 Switches. Each switch must be— (a) Able to carry its rated current; (b) Accessible to the crew; and (c) Labeled as to...

14 CFR 27.1367 - Switches.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Switches. 27.1367 Section 27.1367... STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Electrical Systems and Equipment § 27.1367 Switches. Each switch must be— (a) Able to carry its rated current; (b) Accessible to the crew; and (c) Labeled as to...

14 CFR 27.1367 - Switches.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Switches. 27.1367 Section 27.1367... STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment Electrical Systems and Equipment § 27.1367 Switches. Each switch must be— (a) Able to carry its rated current; (b) Accessible to the crew; and (c) Labeled as to...

Learning Switching Control: A Tank Level-Control Exercise

ERIC Educational Resources Information Center

Pasamontes, M.; Alvarez, J. D.; Guzman, J. L.; Berenguel, M.

2012-01-01

A key topic in multicontroller strategies is the mechanism for switching between controllers, depending on the current operating point. The objective of the switching mechanism is to keep the control action coherent. To help students understand the switching strategy involved in multicontroller schema and the relationship between the system…

Sub-100 fJ and sub-nanosecond thermally driven threshold switching in niobium oxide crosspoint nanodevices.

PubMed

Pickett, Matthew D; Williams, R Stanley

2012-06-01

We built and measured the dynamical current versus time behavior of nanoscale niobium oxide crosspoint devices which exhibited threshold switching (current-controlled negative differential resistance). The switching speeds of 110 × 110 nm(2) devices were found to be Δt(ON) = 700 ps and Δt(OFF) = 2:3 ns while the switching energies were of the order of 100 fJ. We derived a new dynamical model based on the Joule heating rate of a thermally driven insulator-to-metal phase transition that accurately reproduced the experimental results, and employed the model to estimate the switching time and energy scaling behavior of such devices down to the 10 nm scale. These results indicate that threshold switches could be of practical interest in hybrid CMOS nanoelectronic circuits.

Tunneling Nanoelectromechanical Switches Based on Compressible Molecular Thin Films.

PubMed

Niroui, Farnaz; Wang, Annie I; Sletten, Ellen M; Song, Yi; Kong, Jing; Yablonovitch, Eli; Swager, Timothy M; Lang, Jeffrey H; Bulović, Vladimir

2015-08-25

Abrupt switching behavior and near-zero leakage current of nanoelectromechanical (NEM) switches are advantageous properties through which NEMs can outperform conventional semiconductor electrical switches. To date, however, typical NEMs structures require high actuation voltages and can prematurely fail through permanent adhesion (defined as stiction) of device components. To overcome these challenges, in the present work we propose a NEM switch, termed a "squitch," which is designed to electromechanically modulate the tunneling current through a nanometer-scale gap defined by an organic molecular film sandwiched between two electrodes. When voltage is applied across the electrodes, the generated electrostatic force compresses the sandwiched molecular layer, thereby reducing the tunneling gap and causing an exponential increase in the current through the device. The presence of the molecular layer avoids direct contact of the electrodes during the switching process. Furthermore, as the layer is compressed, the increasing surface adhesion forces are balanced by the elastic restoring force of the deformed molecules which can promote zero net stiction and recoverable switching. Through numerical analysis, we demonstrate the potential of optimizing squitch design to enable large on-off ratios beyond 6 orders of magnitude with operation in the sub-1 V regime and with nanoseconds switching times. Our preliminary experimental results based on metal-molecule-graphene devices suggest the feasibility of the proposed tunneling switching mechanism. With optimization of device design and material engineering, squitches can give rise to a broad range of low-power electronic applications.

Study of switching transients in high frequency converters

NASA Technical Reports Server (NTRS)

Zinger, Donald S.; Elbuluk, Malik E.; Lee, Tony

1993-01-01

As the semiconductor technologies progress rapidly, the power densities and switching frequencies of many power devices are improved. With the existing technology, high frequency power systems become possible. Use of such a system is advantageous in many aspects. A high frequency ac source is used as the direct input to an ac/ac pulse-density-modulation (PDM) converter. This converter is a new concept which employs zero voltage switching techniques. However, the development of this converter is still in its infancy stage. There are problems associated with this converter such as a high on-voltage drop, switching transients, and zero-crossing detecting. Considering these problems, the switching speed and power handling capabilities of the MOS-Controlled Thyristor (MCT) makes the device the most promising candidate for this application. A complete insight of component considerations for building an ac/ac PDM converter for a high frequency power system is addressed. A power device review is first presented. The ac/ac PDM converter requires switches that can conduct bi-directional current and block bi-directional voltage. These bi-directional switches can be constructed using existing power devices. Different bi-directional switches for the converter are investigated. Detailed experimental studies of the characteristics of the MCT under hard switching and zero-voltage switching are also presented. One disadvantage of an ac/ac converter is that turn-on and turn-off of the switches has to be completed instantaneously when the ac source is at zero voltage. Otherwise shoot-through current or voltage spikes can occur which can be hazardous to the devices. In order for the devices to switch softly in the safe operating area even under non-ideal cases, a unique snubber circuit is used in each bi-directional switch. Detailed theory and experimental results for circuits using these snubbers are presented. A current regulated ac/ac PDM converter built using MCT's and IGBT's is evaluated.

Hierarchically Self-Assembled Block Copolymer Blends for Templating Hollow Phase-Change Nanostructures with an Extremely Low Switching Current

DOE PAGES

Park, Woon Ik; Kim, Jong Min; Jeong, Jae Won; ...

2015-03-17

Phase change memory (PCM) is one of the most promising candidates for next-generation nonvolatile memory devices because of its high speed, excellent reliability, and outstanding scalability. But, the high switching current of PCM devices has been a critical hurdle to realize low-power operation. Although one solution is to reduce the switching volume of the memory, the resolution limit of photolithography hinders further miniaturization of device dimensions. Here, we employed unconventional self-assembly geometries obtained from blends of block copolymers (BCPs) to form ring-shaped hollow PCM nanostructures with an ultrasmall contact area between a phase-change material (Ge 2Sb 2Te 5) and amore » heater (TiN) electrode. The high-density (approximately 0.1 terabits per square inch) PCM nanoring arrays showed extremely small switching current of 2-3 mu A. Furthermore, the relatively small reset current of the ring-shaped PCM compared to the pillar-shaped devices is attributed to smaller switching volume, which is well supported by electro-thermal simulation results. Our approach may also be extended to other nonvolatile memory device applications such as resistive switching memory and magnetic storage devices, where the control of nanoscale geometry can significantly affect device performances.« less

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

PubMed

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

2010-12-01

Vanadium dioxide is an intensively studied material that undergoes a temperature-induced metal-insulator phase transition accompanied by a large change in electrical resistivity. Electrical switches based on this material show promising properties in terms of speed and broadband operation. The exploration of the failure behavior and reliability of such devices is very important in view of their integration in practical electronic circuits. We performed systematic lifetime investigations of two-terminal switches based on the electrical activation of the metal-insulator transition in VO 2 thin films. The devices were integrated in coplanar microwave waveguides (CPWs) in series configuration. We detected the evolution of a 10 GHz microwave signal transmitted through the CPW, modulated by the activation of the VO 2 switches in both voltage- and current-controlled modes. We demonstrated enhanced lifetime operation of current-controlled VO 2 -based switching (more than 260 million cycles without failure) compared with the voltage-activated mode (breakdown at around 16 million activation cycles). The evolution of the electrical self-oscillations of a VO 2 -based switch induced in the current-operated mode is a subtle indicator of the material properties modification and can be used to monitor its behavior under various external stresses in sensor applications.

View of the current distribution "bus" atop switching cabinets within ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View of the current distribution "bus" atop switching cabinets within the former transformer building. Looking northwest - Childs-Irving Hydroelectric Project, Childs System, Childs Powerhouse, Forest Service Road 708/502, Camp Verde, Yavapai County, AZ

Switching Magnetism and Superconductivity with Spin-Polarized Current in Iron-Based Superconductor.

PubMed

Choi, Seokhwan; Choi, Hyoung Joon; Ok, Jong Mok; Lee, Yeonghoon; Jang, Won-Jun; Lee, Alex Taekyung; Kuk, Young; Lee, SungBin; Heinrich, Andreas J; Cheong, Sang-Wook; Bang, Yunkyu; Johnston, Steven; Kim, Jun Sung; Lee, Jhinhwan

2017-12-01

We explore a new mechanism for switching magnetism and superconductivity in a magnetically frustrated iron-based superconductor using spin-polarized scanning tunneling microscopy (SPSTM). Our SPSTM study on single-crystal Sr_{2}VO_{3}FeAs shows that a spin-polarized tunneling current can switch the Fe-layer magnetism into a nontrivial C_{4} (2×2) order, which cannot be achieved by thermal excitation with an unpolarized current. Our tunneling spectroscopy study shows that the induced C_{4} (2×2) order has characteristics of plaquette antiferromagnetic order in the Fe layer and strongly suppresses superconductivity. Also, thermal agitation beyond the bulk Fe spin ordering temperature erases the C_{4} state. These results suggest a new possibility of switching local superconductivity by changing the symmetry of magnetic order with spin-polarized and unpolarized tunneling currents in iron-based superconductors.

Switching Magnetism and Superconductivity with Spin-Polarized Current in Iron-Based Superconductor

NASA Astrophysics Data System (ADS)

Choi, Seokhwan; Choi, Hyoung Joon; Ok, Jong Mok; Lee, Yeonghoon; Jang, Won-Jun; Lee, Alex Taekyung; Kuk, Young; Lee, SungBin; Heinrich, Andreas J.; Cheong, Sang-Wook; Bang, Yunkyu; Johnston, Steven; Kim, Jun Sung; Lee, Jhinhwan

2017-12-01

We explore a new mechanism for switching magnetism and superconductivity in a magnetically frustrated iron-based superconductor using spin-polarized scanning tunneling microscopy (SPSTM). Our SPSTM study on single-crystal Sr2VO3FeAs shows that a spin-polarized tunneling current can switch the Fe-layer magnetism into a nontrivial C4 (2 ×2 ) order, which cannot be achieved by thermal excitation with an unpolarized current. Our tunneling spectroscopy study shows that the induced C4 (2 ×2 ) order has characteristics of plaquette antiferromagnetic order in the Fe layer and strongly suppresses superconductivity. Also, thermal agitation beyond the bulk Fe spin ordering temperature erases the C4 state. These results suggest a new possibility of switching local superconductivity by changing the symmetry of magnetic order with spin-polarized and unpolarized tunneling currents in iron-based superconductors.

Variable temperature performance of a fully screen printed transistor switch

NASA Astrophysics Data System (ADS)

Zambou, Serges; Magunje, Batsirai; Rhyme, Setshedi; Walton, Stanley D.; Idowu, M. Florence; Unuigbe, David; Britton, David T.; Härting, Margit

2016-12-01

This article reports on the variable temperature performance of a flexible printed transistor which works as a current driven switch. In this work, electronic ink is formulated from nanostructured silicon produced by milling polycrystalline silicon. The study of the silicon active layer shows that its conductivity is based on thermal activation of carriers, and could be used as active layers in active devices. We further report on the transistors switching operation and their electrical performance under variable temperature. The reliability of the transistors at constant current bias was also investigated. Analysis of the electrical transfer characteristics from 340 to 10 K showed that the printed devices' current ON/OFF ratio increases as temperature decreases making it a better switch at lower temperatures. A constant current bias on a terminal for up to six hours shows extraordinary stability in electrical performance of the device.

Method and apparatus for controlling current in inductive loads such as large diameter coils

DOEpatents

Riveros, Carlos A.

1981-01-01

A method and apparatus for controlling electric current in loads that are essentially inductive, such that sparking and "ringing" current problems are reduced or eliminated. The circuit apparatus employs a pair of solid state switches (each of which switch may be an array of connected or parallel solid state switching devices such as transistors) and means for controlling those switches such that a power supply supplying two d.c. voltages (e.g. positive 150 volts d.c. and negative 150 volts d.c.) at low resistance may be connected across an essentially inductive load (e.g. a 6 gauge wire loop one hundred meters in diameter) alternatively and such that the first solid state switch is turned off and the second is turned on such that both are not on at the same time but the first turned on and the other on in less time than the inductive time constant (L/R) so that the load is essentially always presented with a low resistance path across its input. In this manner a steady AC current may be delivered to the load at a frequency desired. Shut-off problems are avoided by gradually shortening the period of switching to less than the time constant so that the maximum energy contained in the inductive load is reduced to approximately zero and dissipated in the inherent resistance. The invention circuit may be employed by adjusting the timing of switching to deliver a desired waveform (such as sinusoidal) to the load.

Current-induced switching of magnetic molecules on topological insulator surfaces

NASA Astrophysics Data System (ADS)

Locane, Elina; Brouwer, Piet W.

2017-03-01

Electrical currents at the surface or edge of a topological insulator are intrinsically spin polarized. We show that such surface or edge currents can be used to switch the orientation of a molecular magnet weakly coupled to the surface or edge of a topological insulator. For the edge of a two-dimensional topological insulator as well as for the surface of a three-dimensional topological insulator the application of a well-chosen surface or edge current can lead to a complete polarization of the molecule if the molecule's magnetic anisotropy axis is appropriately aligned with the current direction. For a generic orientation of the molecule a nonzero but incomplete polarization is obtained. We calculate the probability distribution of the magnetic states and the switching rates as a function of the applied current.

A CW Gunn Diode Switching Element.

ERIC Educational Resources Information Center

Hurtado, Marco; Rosenbaum, Fred J.

As part of a study of the application of communication satellites to educational development, certain technical aspects of such a system were examined. A current controlled bistable switching element using a CW Gunn diode is reported on here. With modest circuits switching rates of the order of 10 MHz have been obtained. Switching is initiated by…

Role of nanorods insertion layer in ZnO-based electrochemical metallization memory cell

NASA Astrophysics Data System (ADS)

Mangasa Simanjuntak, Firman; Singh, Pragya; Chandrasekaran, Sridhar; Juanda Lumbantoruan, Franky; Yang, Chih-Chieh; Huang, Chu-Jie; Lin, Chun-Chieh; Tseng, Tseung-Yuen

2017-12-01

An engineering nanorod array in a ZnO-based electrochemical metallization device for nonvolatile memory applications was investigated. A hydrothermally synthesized nanorod layer was inserted into a Cu/ZnO/ITO device structure. Another device was fabricated without nanorods for comparison, and this device demonstrated a diode-like behavior with no switching behavior at a low current compliance (CC). The switching became clear only when the CC was increased to 75 mA. The insertion of a nanorods layer induced switching characteristics at a low operation current and improve the endurance and retention performances. The morphology of the nanorods may control the switching characteristics. A forming-free electrochemical metallization memory device having long switching cycles (>104 cycles) with a sufficient memory window (103 times) for data storage application, good switching stability and sufficient retention was successfully fabricated by adjusting the morphology and defect concentration of the inserted nanorod layer. The nanorod layer not only contributed to inducing resistive switching characteristics but also acted as both a switching layer and a cation diffusion control layer.

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

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

She, Xu; Chokhawala, Rahul Shantilal; Zhou, Rui

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

Partial spin absorption induced magnetization switching and its voltage-assisted improvement in an asymmetrical all spin logic device at the mesoscopic scale

NASA Astrophysics Data System (ADS)

Zhang, Yue; Zhang, Zhizhong; Wang, Lezhi; Nan, Jiang; Zheng, Zhenyi; Li, Xiang; Wong, Kin; Wang, Yu; Klein, Jacques-Olivier; Khalili Amiri, Pedram; Zhang, Youguang; Wang, Kang L.; Zhao, Weisheng

2017-07-01

Beyond memory and storage, future logic applications put forward higher requirements for electronic devices. All spin logic devices (ASLDs) have drawn exceptional interest as they utilize pure spin current instead of charge current, which could promise ultra-low power consumption. However, relatively low efficiencies of spin injection, transport, and detection actually impede high-speed magnetization switching and challenge perspectives of ASLD. In this work, we study partial spin absorption induced magnetization switching in asymmetrical ASLD at the mesoscopic scale, in which the injector and detector have the nano-fabrication compatible device size (>100 nm) and their contact areas are different. The enlarged contact area of the detector is conducive to the spin current absorption, and the contact resistance difference between the injector and the detector can decrease the spin current backflow. Rigorous spin circuit modeling and micromagnetic simulations have been carried out to analyze the electrical and magnetic features. The results show that, at the fabrication-oriented technology scale, the ferromagnetic layer can hardly be switched by geometrically partial spin current absorption. The voltage-controlled magnetic anisotropy (VCMA) effect has been applied on the detector to accelerate the magnetization switching by modulating magnetic anisotropy of the ferromagnetic layer. With a relatively high VCMA coefficient measured experimentally, a voltage of 1.68 V can assist the whole magnetization switching within 2.8 ns. This analysis and improving approach will be of significance for future low-power, high-speed logic applications.

Temporally Shaped Current Pulses on a Two-Cavity Linear Transformer Driver System

DTIC Science & Technology

2011-06-01

essentially at a fraction of the total switch voltage. Non-uniform corona current characteristics of the different corona needles could cause imperfect...withstand twice the capacitor voltage. A pulse applied to the switch trigger electrodes initiate closure of each switch. We have arranged triggering in...internal cavity potential to ground, allows the trigger electrode of the spark gaps to be at ground potential during charging, and eliminates a

Neonatal maternal separation delays the GABA excitatory-to-inhibitory functional switch by inhibiting KCC2 expression.

PubMed

Furukawa, Minami; Tsukahara, Takao; Tomita, Kazuo; Iwai, Haruki; Sonomura, Takahiro; Miyawaki, Shouichi; Sato, Tomoaki

2017-11-25

The excitatory-to-inhibitory functional switch of γ-aminobutyric acid (GABA; GABA switch), which normally occurs in the first to the second postnatal week in the hippocampus, is necessary for the development of appropriate central nervous system function. A deficit in GABAergic inhibitory function could cause excitatory/inhibitory (E/I) neuron imbalance that is found in many neurodegenerative disorders. In the present study, we examined whether neonatal stress can affect the timing of the GABA functional switch and cause disorders during adolescence. Neonatal stress was induced in C57BL/6J male mouse pups by maternal separation (MS) on postnatal days (PND) 1-21. Histological quantification of K + -Cl - co-transporter (KCC2) and Ca 2+ imaging were performed to examine the timing of the GABA switch during the MS period. To evaluate the influence of neonatal MS on adolescent hippocampal function, we quantified KCC2 expression and evaluated hippocampal-related behavioral tasks at PND35-38. We showed that MS delayed the timing of the GABA switch in the hippocampus and inhibited the increase in membrane KCC2 expression, with KCC2 expression inhibition persisting until adolescence. Behavioral tests showed impaired cognition, declined attention, hyperlocomotion, and aggressive character in maternally separated mice. Taken together, our results show that neonatal stress delayed the timing of the GABA switch, which could change the E/I balance and cause neurodegenerative disorders in later life. Copyright © 2017 Elsevier Inc. All rights reserved.

Design Method of Digital Optimal Control Scheme and Multiple Paralleled Bridge Type Current Amplifier for Generating Gradient Magnetic Fields in MRI Systems

NASA Astrophysics Data System (ADS)

Watanabe, Shuji; Takano, Hiroshi; Fukuda, Hiroya; Hiraki, Eiji; Nakaoka, Mutsuo

This paper deals with a digital control scheme of multiple paralleled high frequency switching current amplifier with four-quadrant chopper for generating gradient magnetic fields in MRI (Magnetic Resonance Imaging) systems. In order to track high precise current pattern in Gradient Coils (GC), the proposal current amplifier cancels the switching current ripples in GC with each other and designed optimum switching gate pulse patterns without influences of the large filter current ripple amplitude. The optimal control implementation and the linear control theory in GC current amplifiers have affinity to each other with excellent characteristics. The digital control system can be realized easily through the digital control implementation, DSPs or microprocessors. Multiple-parallel operational microprocessors realize two or higher paralleled GC current pattern tracking amplifier with optimal control design and excellent results are given for improving the image quality of MRI systems.

Hidden dynamics in models of discontinuity and switching

NASA Astrophysics Data System (ADS)

Jeffrey, Mike R.

2014-04-01

Sharp switches in behaviour, like impacts, stick-slip motion, or electrical relays, can be modelled by differential equations with discontinuities. A discontinuity approximates fine details of a switching process that lie beyond a bulk empirical model. The theory of piecewise-smooth dynamics describes what happens assuming we can solve the system of equations across its discontinuity. What this typically neglects is that effects which are vanishingly small outside the discontinuity can have an arbitrarily large effect at the discontinuity itself. Here we show that such behaviour can be incorporated within the standard theory through nonlinear terms, and these introduce multiple sliding modes. We show that the nonlinear terms persist in more precise models, for example when the discontinuity is smoothed out. The nonlinear sliding can be eliminated, however, if the model contains an irremovable level of unknown error, which provides a criterion for systems to obey the standard Filippov laws for sliding dynamics at a discontinuity.

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.

Medicare Part D Beneficiaries' Plan Switching Decisions and Information Processing.

PubMed

Han, Jayoung; Urmie, Julie

2017-03-01

Medicare Part D beneficiaries tend not to switch plans despite the government's efforts to engage beneficiaries in the plan switching process. Understanding current and alternative plan features is a necessary step to make informed plan switching decisions. This study explored beneficiaries' plan switching using a mixed-methods approach, with a focus on the concept of information processing. We found large variation in beneficiary comprehension of plan information among both switchers and nonswitchers. Knowledge about alternative plans was especially poor, with only about half of switchers and 2 in 10 nonswitchers being well informed about plans other than their current plan. We also found that helpers had a prominent role in plan decision making-nearly twice as many switchers as nonswitchers worked with helpers for their plan selection. Our study suggests that easier access to helpers as well as helpers' extensive involvement in the decision-making process promote informed plan switching decisions.

Suspended few-layer graphene beam electromechanical switch with abrupt on-off characteristics and minimal leakage current

NASA Astrophysics Data System (ADS)

Kim, Sung Min; Song, Emil B.; Lee, Sejoon; Seo, Sunae; Seo, David H.; Hwang, Yongha; Candler, R.; Wang, Kang L.

2011-07-01

Suspended few-layer graphene beam electro-mechanical switches (SGSs) with 0.15 μm air-gap are fabricated and electrically characterized. The SGS shows an abrupt on/off current characteristics with minimal off current. In conjunction with the narrow air-gap, the outstanding mechanical properties of graphene enable the mechanical switch to operate at a very low pull-in voltage (VPI) of 1.85 V, which is compatible with conventional complimentary metal-oxide-semiconductor (CMOS) circuit requirements. In addition, we show that the pull-in voltage exhibits an inverse dependence on the beam length.

Low-dose thiopurine with allopurinol co-therapy overcomes thiopurine intolerance and allows thiopurine continuation in inflammatory bowel disease.

PubMed

Vasudevan, Abhinav; Beswick, Lauren; Friedman, Antony B; Moltzen, Alicia; Haridy, James; Raghunath, Ajay; Sparrow, Miles; van Langenberg, Daniel

2018-02-10

To assess the utility and tolerability of thiopurine-allopurinol co-therapy in inflammatory bowel disease (IBD) patients with intolerance to thiopurine monotherapy. A retrospective observational study assessed cases of thiopurine intolerance then switched to thiopurine allopurinol co-therapy between 2011 and 2015 at two centres. Indications for switch, dosing and subsequent clinical outcomes (including thiopurine persistence) were recorded. Of 767 patients on thiopurines for IBD, 89 (12%) were switched to co-therapy for intolerance. 64/89 (72%) had Crohn's disease, 38 (43%) were males, median age at switch was 40y (range 17-78), median IBD duration 6y (0-29). Median follow-up was 1.9y (0-5). Reasons for switching to co-therapy included fatigue (37%), hepatotoxicity (23%), nausea (23%), arthralgia (10%), headache (12%) and hypersensitivity reaction (4%). Overall, 66 (74%) patients remained on co-therapy until most recent review and achieved a clinical response. High rates of overcoming intolerance (62-100%) occurred with co-therapy for all reasons above, although fatigue was less amenable to switching than non-fatigue indications (62% vs 91%, p = <0.001). Of 34 patients not escalated to biologics with endoscopic data, 15 were in remission (44%) at most recent review. Low-dose thiopurine combined with allopurinol appears safe and effective in overcoming intolerances to thiopurine monotherapy in many cases. Copyright © 2018. Published by Elsevier Ltd.

Switch Detection in Preschoolers' Cognitive Flexibility

ERIC Educational Resources Information Center

Chevalier, Nicolas; Wiebe, Sandra A.; Huber, Kristina L.; Espy, Kimberly Andrews

2011-01-01

The current study addressed the role of switch detection in cognitive flexibility by testing the effect of transition cues (i.e., cues that directly signal the need to switch or maintain a given task goal) in a cued set-shifting paradigm at 5 years of age. Children performed better, especially on switch trials, when transition cues were combined…

Triggered plasma opening switch

DOEpatents

Mendel, Clifford W.

1988-01-01

A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductors and a magnetic field for breaking the plasma conduction path and magnetically insulating the electrons when it is desired to open the switch.

Fault-tolerant power distribution system

NASA Technical Reports Server (NTRS)

Volp, Jeffrey A. (Inventor)

1987-01-01

A fault-tolerant power distribution system which includes a plurality of power sources and a plurality of nodes responsive thereto for supplying power to one or more loads associated with each node. Each node includes a plurality of switching circuits, each of which preferably uses a power field effect transistor which provides a diode operation when power is first applied to the nodes and which thereafter provides bi-directional current flow through the switching circuit in a manner such that a low voltage drop is produced in each direction. Each switching circuit includes circuitry for disabling the power field effect transistor when the current in the switching circuit exceeds a preselected value.

Development of a switched integrator amplifier for high-accuracy optical measurements.

PubMed

Mountford, John; Porrovecchio, Geiland; Smid, Marek; Smid, Radislav

2008-11-01

In the field of low flux optical measurements, the development and use of large area silicon detectors is becoming more frequent. The current/voltage conversion of their photocurrent presents a set of problems for traditional transimpedance amplifiers. The switched integration principle overcomes these limitations. We describe the development of a fully characterized current-voltage amplifier using the switched integrator technique. Two distinct systems have been developed in parallel at the United Kingdom's National Physical Laboratory (NPL) and Czech Metrology Institute (CMI) laboratories. We present the circuit theory and best practice in the design and construction of switched integrators. In conclusion the results achieved and future developments are discussed.

Low-power embedded read-only memory using atom switch and silicon-on-thin-buried-oxide transistor

NASA Astrophysics Data System (ADS)

Sakamoto, Toshitsugu; Tada, Munehiro; Tsuji, Yukihide; Makiyama, Hideki; Hasegawa, Takumi; Yamamoto, Yoshiki; Okanishi, Shinobu; Banno, Naoki; Miyamura, Makoto; Okamoto, Koichiro; Iguchi, Noriyuki; Ogasahara, Yasuhiro; Oda, Hidekazu; Kamohara, Shiro; Yamagata, Yasushi; Sugii, Nobuyuki; Hada, Hiromitsu

2015-04-01

We developed an atom-switch read-only memory (ROM) fabricated on silicon-on-thin-buried-oxide (SOTB) for use in a low-power microcontroller for the first time. An atom switch with a low programming voltage and large ON/OFF conductance ratio is suitable for low-power nonvolatile memory. The atom-switch ROM using an SOTB transistor uses a 0.34-1.2 V operating voltage and 12 µA/MHz active current (or 4.5 µW/MHz active power). Furthermore, the sleep current is as low as 0.4 µA when a body bias voltage is applied to the SOTB.

Current-induced switching in CoGa/L10 MnGa/(CoGa)/Pt structure with different thicknesses

NASA Astrophysics Data System (ADS)

Ranjbar, R.; Suzuki, K. Z.; Mizukami, S.

2018-06-01

In this paper, we present the results of our study into current-induced spin-orbit torque (SOT) switching in perpendicularly magnetized CoGa/MnGa/Pt trilayers with different thicknesses of MnGa and Pt. The SOT switching was observed for all films that undergo Joule heating. We also investigate SOT switching in the bottom (CoGa)/MnGa/top(CoGa/Pt) films with different top layers. Although both the bottom and top layers contribute to the SOT, the relative magnitudes of the switching current densities JC in the top and bottom layers indicate that the SOT is dominant in the top layer. The JC as a function of thickness is discussed in terms of the magnetic properties and resistivity. Experimental data suggested that the MnGa thickness dependence of JC may originate from the perpendicular magnetic anisotropy thickness product Kueff t value. On the other hand, JC as a function of the Pt thickness shows weak dependence. This may be attributed to the slight change of spin-Hall angle θSH value with different thicknesses of Pt, when we assumed that the SOT switching is primarily due to the spin-Hall effect.

Reversing-counterpulse repetitive-pulse inductive storage circuit

DOEpatents

Honig, E.M.

1987-02-10

A high-power reversing-counterpulse repetitive-pulse inductive storage and transfer circuit includes an opening switch, a main energy storage coil, a counterpulse capacitor and a small inductor. After counterpulsing the opening switch off, the counterpulse capacitor is recharged by the main energy storage coil before the load pulse is initiated. This gives the counterpulse capacitor sufficient energy for the next counterpulse operation, although the polarity of the capacitor's voltage must be reversed before that can occur. By using a current-zero switch as the counterpulse start switch, the capacitor is disconnected from the circuit (with a full charge) when the load pulse is initiated, preventing the capacitor from depleting its energy store by discharging through the load. After the load pulse is terminated by reclosing the main opening switch, the polarity of the counterpulse capacitor voltage is reversed by discharging the capacitor through a small inductor and interrupting the discharge current oscillation at zero current and peak reversed voltage. The circuit enables high-power, high-repetition-rate operation with reusable switches and features total control (pulse-to-pulse) over output pulse initiation, duration, repetition rate, and, to some extent, risetime. 10 figs.

Shuttle-promoted nano-mechanical current switch

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

Song, Taegeun, E-mail: tsong@ictp.it; Kiselev, Mikhail N.; Gorelik, Leonid Y.

2015-09-21

We investigate electron shuttling in three-terminal nanoelectromechanical device built on a movable metallic rod oscillating between two drains. The device shows a double-well shaped electromechanical potential tunable by a source-drain bias voltage. Four stationary regimes controllable by the bias are found for this device: (i) single stable fixed point, (ii) two stable fixed points, (iii) two limit cycles, and (iv) single limit cycle. In the presence of perpendicular magnetic field, the Lorentz force makes possible switching from one electromechanical state to another. The mechanism of tunable transitions between various stable regimes based on the interplay between voltage controlled electromechanical instabilitymore » and magnetically controlled switching is suggested. The switching phenomenon is implemented for achieving both a reliable active current switch and sensoring of small variations of magnetic field.« less

High-Voltage, High-Power Gaseous Electronics Switch For Electric Grid Power Conversion

NASA Astrophysics Data System (ADS)

Sommerer, Timothy J.

2014-05-01

We are developing a high-voltage, high-power gas switch for use in low-cost power conversion terminals on the electric power grid. Direct-current (dc) power transmission has many advantages over alternating current (ac) transmission, but at present the high cost of ac-dc power interconversion limits the use of dc. The gas switch we are developing conducts current through a magnetized cold cathode plasma in hydrogen or helium to reach practical current densities > 1 A/cm2. Thermal and sputter damage of the cathode by the incident ion flux is a major technical risk, and is being addressed through use of a ``self-healing'' liquid metal cathode (eg, gallium). Plasma conditions and cathode sputtering loss are estimated by analyzing plasma spectral emission. A particle-in-cell plasma model is used to understand various aspects of switch operation, including the conduction phase (where plasma densities can exceed 1013 cm-3), the switch-open phase (where the high-voltage must be held against gas breakdown on the left side of Paschen's curve), and the switching transitions (especially the opening process, which is initiated by forming an ion-matrix sheath adjacent to a control grid). The information, data, or work presented herein was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000298.

In-operando hard X-ray photoelectron spectroscopy study on the impact of current compliance and switching cycles on oxygen and carbon defects in resistive switching Ti/HfO{sub 2}/TiN cells

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

Sowinska, Malgorzata, E-mail: sowinska@ihp-microelectronics.com; Bertaud, Thomas; Walczyk, Damian

2014-05-28

In this study, direct experimental materials science evidence of the important theoretical prediction for resistive random access memory (RRAM) technologies that a critical amount of oxygen vacancies is needed to establish stable resistive switching in metal-oxide-metal samples is presented. In detail, a novel in-operando hard X-ray photoelectron spectroscopy technique is applied to non-destructively investigates the influence of the current compliance and direct current voltage sweep cycles on the Ti/HfO{sub 2} interface chemistry and physics of resistive switching Ti/HfO{sub 2}/TiN cells. These studies indeed confirm that current compliance is a critical parameter to control the amount of oxygen vacancies in themore » conducting filaments in the oxide layer during the RRAM cell operation to achieve stable switching. Furthermore, clear carbon segregation towards the Ti/HfO{sub 2} interface under electrical stress is visible. Since carbon impurities impact the oxygen vacancy defect population under resistive switching, this dynamic carbon segregation to the Ti/HfO{sub 2} interface is suspected to negatively influence RRAM device endurance. Therefore, these results indicate that the RRAM materials engineering needs to include all impurities in the dielectric layer in order to achieve reliable device performance.« less

Nondissipative optimum charge regulator

NASA Technical Reports Server (NTRS)

Rosen, R.; Vitebsky, J. N.

1970-01-01

Optimum charge regulator provides constant level charge/discharge control of storage batteries. Basic power transfer and control is performed by solar panel coupled to battery through power switching circuit. Optimum controller senses battery current and modifies duty cycle of switching circuit to maximize current available to battery.

Fundamental studies on initiation and evolution of multi-channel discharges and their application to next generation pulsed power machines.

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

Schwarz, Jens; Savage, Mark E.; Lucero, Diego Jose

Future pulsed power systems may rely on linear transformer driver (LTD) technology. The LTD's will be the building blocks for a driver that can deliver higher current than the Z-Machine. The LTD's would require tens of thousands of low inductance ( %3C 85nH), high voltage (200 kV DC) switches with high reliability and long lifetime ( 10 4 shots). Sandia's Z-Machine employs 36 megavolt class switches that are laser triggered by a single channel discharge. This is feasible for tens of switches but the high inductance and short switch life- time associated with the single channel discharge are undesirable formore » future machines. Thus the fundamental problem is how to lower inductance and losses while increasing switch life- time and reliability. These goals can be achieved by increasing the number of current-carrying channels. The rail gap switch is ideal for this purpose. Although those switches have been extensively studied during the past decades, each effort has only characterized a particular switch. There is no comprehensive understanding of the underlying physics that would allow predictive capability for arbitrary switch geometry. We have studied rail gap switches via an extensive suite of advanced diagnostics in synergy with theoretical physics and advanced modeling capability. Design and topology of multichannel switches as they relate to discharge dynamics are investigated. This involves electrically and optically triggered rail gaps, as well as discrete multi-site switch concepts.« less

Multivariate assessment of subjective and objective measures of social and family satisfaction in Veterans with history of traumatic brain injury.

PubMed

Orff, Henry J; Hays, Chelsea C; Twamley, Elizabeth W

2016-01-01

Approximately 20% of current-era Veterans have sustained a traumatic brain injury (TBI), which can result in persistent postconcussive symptoms. These symptoms may disrupt family and social functioning. We explored psychiatric, postconcussive, and cognitive factors as correlates of objective functioning and subjective satisfaction in family and social relationships. At entry into a supported employment study, 50 unemployed Veterans with a history of mild to moderate TBI and current cognitive impairment were administered baseline assessments. Multivariate stepwise regressions determined that higher levels of depressive symptomatology were strongly associated with less frequent social contact, as well as lower subjective satisfaction with family and social relationships. Worse verbal fluency predicted less frequent social contact, whereas worse processing speed and switching predicted higher levels of subjective satisfaction with family relationships. The pattern of results remained similar when examining those Veterans with only mild TBI. Depressive symptoms and cognitive functioning may impact Veterans' social contact and satisfaction with family and social relationships. Evidence-based interventions addressing depression and cognition may therefore aid in improving community reintegration and satisfaction with social and family relationships.

Valley magnetoelectricity in single-layer MoS2

NASA Astrophysics Data System (ADS)

Lee, Jieun; Wang, Zefang; Xie, Hongchao; Mak, Kin Fai; Shan, Jie

2017-09-01

The magnetoelectric (ME) effect, the phenomenon of inducing magnetization by application of an electric field or vice versa, holds great promise for magnetic sensing and switching applications. Studies of the ME effect have so far focused on the control of the electron spin degree of freedom (DOF) in materials such as multiferroics and conventional semiconductors. Here, we report a new form of the ME effect based on the valley DOF in two-dimensional Dirac materials. By breaking the three-fold rotational symmetry in single-layer MoS 2 via a uniaxial stress, we have demonstrated the pure electrical generation of valley magnetization in this material, and its direct imaging by Kerr rotation microscopy. The observed out-of-plane magnetization is independent of in-plane magnetic field, linearly proportional to the in-plane current density, and optimized when the current is orthogonal to the strain-induced piezoelectric field. These results are fully consistent with a theoretical model of valley magnetoelectricity driven by Berry curvature effects. Furthermore, the effect persists at room temperature, opening possibilities for practical valleytronic devices.

Valley magnetoelectricity in single-layer MoS2.

PubMed

Lee, Jieun; Wang, Zefang; Xie, Hongchao; Mak, Kin Fai; Shan, Jie

2017-09-01

The magnetoelectric (ME) effect, the phenomenon of inducing magnetization by application of an electric field or vice versa, holds great promise for magnetic sensing and switching applications. Studies of the ME effect have so far focused on the control of the electron spin degree of freedom (DOF) in materials such as multiferroics and conventional semiconductors. Here, we report a new form of the ME effect based on the valley DOF in two-dimensional Dirac materials. By breaking the three-fold rotational symmetry in single-layer MoS 2 via a uniaxial stress, we have demonstrated the pure electrical generation of valley magnetization in this material, and its direct imaging by Kerr rotation microscopy. The observed out-of-plane magnetization is independent of in-plane magnetic field, linearly proportional to the in-plane current density, and optimized when the current is orthogonal to the strain-induced piezoelectric field. These results are fully consistent with a theoretical model of valley magnetoelectricity driven by Berry curvature effects. Furthermore, the effect persists at room temperature, opening possibilities for practical valleytronic devices.

Remote two-wire data entry method and device

DOEpatents

Kronberg, James W.

1995-01-01

A device for detecting switch closure such as in a keypad for entering data comprising a matrix of conductor pairs and switches, each pair of conductors shorted by the pressing of a particular switch, and current-regulating devices on each conductor for limiting current in one direction and passing it without limit in the other direction. The device is driven by alternating current. The ends of the conductors in a conductor pair limit current of opposing polarities with respect to each other so that the signal on a shorted pair is an alternating current signal with a unique combination of a positive and a negative peak, which, when analyzed, allows the determination of which key was pressed. The binary identification of the pressed key is passed to the input port of a host device.

Method and apparatus for current-output peak detection

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

De Geronimo, Gianluigi

2017-01-24

A method and apparatus for a current-output peak detector. A current-output peak detector circuit is disclosed and works in two phases. The peak detector circuit includes switches to switch the peak detector circuit from the first phase to the second phase upon detection of the peak voltage of an input voltage signal. The peak detector generates a current output with a high degree of accuracy in the second phase.

Study of Electromagnetic Repulsion Switch to High Speed Reclosing and Recover Time Characteristics of Superconductor

NASA Astrophysics Data System (ADS)

Koyama, Tomonori; Kaiho, Katsuyuki; Yamaguchi, Iwao; Yanabu, Satoru

Using a high-temperature superconductor, we constructed and tested a model superconducting fault current limiter (SFCL). The superconductor and vacuum interrupter as the commutation switch were connected in parallel using a bypass coil. When the fault current flows in this equipment, the superconductor is quenched and the current is then transferred to the parallel coil due to the voltage drop in the superconductor. This large current in the parallel coil actuates the magnetic repulsion mechanism of the vacuum interrupter and the current in the superconductor is broken. Using this equipment, the current flow time in the superconductor can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of the parallel coil. This system has many merits. So, we introduced to electromagnetic repulsion switch. There is duty of high speed re-closing after interrupting fault current in the electrical power system. So the SFCL should be recovered to superconducting state before high speed re-closing. But, superconductor generated heat at the time of quench. It takes time to recover superconducting state. Therefore it is a matter of recovery time. In this paper, we studied recovery time of superconductor. Also, we proposed electromagnetic repulsion switch with reclosing system.

Comparing functional responses in predator-infected eco-epidemics models.

PubMed

Haque, Mainul; Rahman, Md Sabiar; Venturino, Ezio

2013-11-01

The current paper deals with the mathematical models of predator-prey system where a transmissible disease spreads among the predator species only. Four mathematical models are proposed and analysed with several popular predator functional responses in order to show the influence of functional response on eco-epidemic models. The existence, boundedness, uniqueness of solutions of all the models are established. Mathematical analysis including stability and bifurcation are observed. Comparison among the results of these models allows the general conclusion that relevant behaviour of the eco-epidemic predator-prey system, including switching of stability, extinction, persistence and oscillations for any species depends on four important parameters viz. the rate of infection, predator interspecies competition and the attack rate on susceptible predator. The paper ends with a discussion of the biological implications of the analytical and numerical results. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Vpma phase variation is important for survival and persistence of Mycoplasma agalactiae in the immunocompetent host

PubMed Central

Zimmermann, Martina; Citti, Christine

2017-01-01

Despite very small genomes, mycoplasmas retain large multigene families encoding variable antigens whose exact role in pathogenesis needs to be proven. To understand their in vivo significance, we used Mycoplasma agalactiae as a model exhibiting high-frequency variations of a family of immunodominant Vpma lipoproteins via Xer1-mediated site-specific recombinations. Phase-Locked Mutants (PLMs) expressing single stable Vpma products served as first breakthrough tools in mycoplasmology to study the role of such sophisticated antigenic variation systems. Comparing the general clinical features of sheep infected with a mixture of phase-invariable PLMs (PLMU and PLMY) and the wild type strain, it was earlier concluded that Vpma phase variation is not necessary for infection. Conversely, the current study demonstrates the in vivo indispensability of Vpma switching as inferred from the Vpma phenotypic and genotypic analyses of reisolates obtained during sheep infection and necropsy. PLMY and PLMU stably expressing VpmaY and VpmaU, respectively, for numerous in vitro generations, switched to new Vpma phenotypes inside the sheep. Molecular genetic analysis of selected ‘switchover’ clones confirmed xer1 disruption and revealed complex new rearrangements like chimeras, deletions and duplications in the vpma loci that were previously unknown in type strain PG2. Another novel finding is the differential infection potential of Vpma variants, as local infection sites demonstrated an almost complete dominance of PLMY over PLMU especially during early stages of both conjunctival and intramammary co-challenge infections, indicating a comparatively better in vivo fitness of VpmaY expressors. The data suggest that Vpma antigenic variation is imperative for survival and persistence inside the immunocompetent host, and although Xer1 is necessary for causing Vpma variation in vitro, it is not a virulence factor because alternative Xer1-independent mechanisms operate in vivo, likely under the selection pressure of the host-induced immune response. This singular study highlights exciting new aspects of mycoplasma antigenic variation systems, including the regulation of expression by host factors. PMID:28957426

Comparative simulation of switching regimes of magnetic explosion generators by copper and aluminum magnetodynamic current breakers taking into account elastoplastic properties of materials

NASA Astrophysics Data System (ADS)

Bazanov, A. A.; Ivanovskii, A. V.; Panov, A. I.; Samodolov, A. V.; Sokolov, S. S.; Shaidullin, V. Sh.

2017-06-01

We report on the results of the computer simulation of the operation of magnetodynamic break switches used as the second stage of current pulse formation in magnetic explosion generators. The simulation was carried out under the conditions when the magnetic field energy density on the surface of the switching conductor as a function of the current through it was close to but still did not exceed the critical value typical of the beginning of electric explosion. In the computational model, we used the parameters of experimentally tested sample of a coil magnetic explosion generator that can store energy of up to 2.7 MJ in the inductive storage circuit and equipped with a primary explosion stage of the current pulse formation. It has been shown that the choice of the switching conductor material, as well as its elastoplastic properties, considerably affects the breaker speed. Comparative results of computer simulation for copper and aluminum have been considered.

Fast repetition rate (FRR) flasher

DOEpatents

Kolber, Zbigniew; Falkowski, Paul

1997-02-11

A fast repetition rate (FRR) flasher suitable for high flash photolysis including kinetic chemical and biological analysis. The flasher includes a power supply, a discharge capacitor operably connected to be charged by the power supply, and a flash lamp for producing a series of flashes in response to discharge of the discharge capacitor. A triggering circuit operably connected to the flash lamp initially ionizes the flash lamp. A current switch is operably connected between the flash lamp and the discharge capacitor. The current switch has at least one insulated gate bipolar transistor for switching current that is operable to initiate a controllable discharge of the discharge capacitor through the flash lamp. Control means connected to the current switch for controlling the rate of discharge of the discharge capacitor thereby to effectively keep the flash lamp in an ionized state between Successive discharges of the discharge capacitor. Advantageously, the control means is operable to discharge the discharge capacitor at a rate greater than 10,000 Hz and even up to a rate greater than about 250,000 Hz.

Student Attraction, Persistence and Retention in STEM Programs: Successes and Continuing Challenges

ERIC Educational Resources Information Center

Sithole, Alec; Chiyaka, Edward T.; McCarthy, Peter; Mupinga, Davison M.; Bucklein, Brian K.; Kibirige, Joachim

2017-01-01

Low student enrollment and high attrition rates in Science, Technology, Engineering, and Mathematics (STEM) education are major challenges in higher education. Many STEM entrants end-up switching their majors to non-STEM fields, perform poorly relative to their peers in other programs, and/or drop out of college without earning any academic…

Deterministic switching of hierarchy during wrinkling in quasi-planar bilayers

DOE PAGES

Saha, Sourabh K.; Culpepper, Martin L.

2016-04-25

Emergence of hierarchy during compression of quasi-planar bilayers is preceded by a mode-locked state during which the quasi-planar form persists. Transition to hierarchy is determined entirely by geometrically observable parameters. This results in a universal transition phase diagram that enables one to deterministically tune hierarchy even with limited knowledge about material properties.

Tight coupling between nucleus and cell migration through the perinuclear actin cap

PubMed Central

Kim, Dong-Hwee; Cho, Sangkyun; Wirtz, Denis

2014-01-01

ABSTRACT Although eukaryotic cells are known to alternate between ‘advancing’ episodes of fast and persistent movement and ‘hesitation’ episodes of low speed and low persistence, the molecular mechanism that controls the dynamic changes in morphology, speed and persistence of eukaryotic migratory cells remains unclear. Here, we show that the movement of the interphase nucleus during random cell migration switches intermittently between two distinct modes – rotation and translocation – that follow with high fidelity the sequential rounded and elongated morphologies of the nucleus and cell body, respectively. Nuclear rotation and translocation mediate the stop-and-go motion of the cell through the dynamic formation and dissolution, respectively, of the contractile perinuclear actin cap, which is dynamically coupled to the nuclear lamina and the nuclear envelope through LINC complexes. A persistent cell movement and nuclear translocation driven by the actin cap are halted following the disruption of the actin cap, which in turn allows the cell to repolarize for its next persistent move owing to nuclear rotation mediated by cytoplasmic dynein light intermediate chain 2. PMID:24639463

Spin-Orbit Torque-Assisted Switching in Magnetic Insulator Thin Films with Perpendicular Magnetic Anisotropy

NASA Astrophysics Data System (ADS)

Wu, Mingzhong

As an in-plane charge current flows in a heavy metal film with spin-orbit coupling, it produces a torque that can induce magnetization switching in a neighboring ferromagnetic metal film. Such spin-orbit torque (SOT)-induced switching has been studied extensively in recent years and has shown higher efficiency than switching using conventional spin-transfer torque. This presentation reports the SOT-assisted switching in heavy metal/magnetic insulator systems.1 The experiments made use of Pt/BaFe12O19 bi-layered structures. Thanks to its strong spin-orbit coupling, Pt has been widely used to produce pure spin currents in previous studies. BaFe12O19 is an M-type barium hexagonal ferrite and is often referred as BaM. It is one of the few magnetic insulators with strong magneto-crystalline anisotropy and shows an effective uniaxial anisotropy field of about 17 kOe. It's found that the switching response in the BaM film strongly depends on the charge current applied to the Pt film. When a constant magnetic field is applied in the film plane, the charge current in the Pt film can switch the normal component of the magnetization (M⊥) in the BaM film between the up and down states. The current also dictates the up and down states of the remnant magnetization when the in-plane field is reduced to zero. When M⊥ is measured by sweeping an in-plane field, the response manifests itself as a hysteresis loop, which evolves in a completely opposite manner if the sign of the charge current is flipped. When the coercivity is measured by sweeping an out-of-plane field, its value can be reduced or increased by as much as about 500 Oe if an appropriate charge current is applied. 1. P. Li, T. Liu, H. Chang, A. Kalitsov, W. Zhang, G. Csaba, W. Li, D. Richardson, A. Demann, G. Rimal, H. Dey, J. S. Jiang, W. Porod, S. Field, J. Tang, M. C. Marconi, A. Hoffmann, O. Mryasov, and M. Wu, Nature Commun. 7:12688 doi: 10.1038/ncomms12688 (2016).

Humoral Immune Reconstitution Kinetics after Allogeneic Hematopoietic Stem Cell Transplantation in Children: A Maturation Block of IgM Memory B Cells May Lead to Impaired Antibody Immune Reconstitution.

PubMed

Abdel-Azim, Hisham; Elshoury, Amro; Mahadeo, Kris M; Parkman, Robertson; Kapoor, Neena

2017-09-01

Although T cell immune reconstitution after allogeneic hematopoietic stem cell transplantation (allo-HSCT) has been well studied, long-term B cell immune reconstitution remains less characterized. We evaluated humoral immune reconstitution among 71 pediatric allo-HSCT recipients. Although tetanus toxoid antibody levels were normal at 1 year after allo-HSCT, antipolysaccharide carbohydrate antibodies remained persistently low for up to 5 years. While naive B cell counts normalized by 6 months, IgM memory B cell deficiency persisted for up to 2 years (P = .01); switched memory B cell deficiency normalized by 1 year after allo-HSCT. CD4 + T cell immune reconstitution correlated with that of switched memory B cells as early as 6 months after allo-HSCT (r = .55, P = .002) but did not correlate with IgM memory B cells at any time point after allo-HSCT. Taken together, this suggests that allo-HSCT recipients have impaired antibody immune reconstitution, mainly due to IgM memory B cell maturation block, compared with more prompt T cell-dependent switched memory cell immune reconstitution. We further explored other factors that might affect humoral immune reconstitution. The use of total body irradiation was associated with lower naive B cells counts at 6 months after HSCT (P = .04) and lower IgM (P = .008) and switched (P = .003) memory B cells up to 2 years. Allo-HSCT recipients with extensive chronic graft-versus-host disease had lower IgM memory B cell counts (P = .03) up to 2 years after allo-HSCT. The use of cord blood was associated with better naive (P = .01), IgM (P = .0005), and switched memory (P = .006) B cells immune reconstitution. These findings may inform future prophylaxis and treatment strategies regarding risk of overwhelming infection, graft-versus-host disease, and post-allogeneic HSCT revaccination. Copyright © 2017 The American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.

Power- and Low-Resistance-State-Dependent, Bipolar Reset-Switching Transitions in SiN-Based Resistive Random-Access Memory

NASA Astrophysics Data System (ADS)

Kim, Sungjun; Park, Byung-Gook

2016-08-01

A study on the bipolar-resistive switching of an Ni/SiN/Si-based resistive random-access memory (RRAM) device shows that the influences of the reset power and the resistance value of the low-resistance state (LRS) on the reset-switching transitions are strong. For a low LRS with a large conducting path, the sharp reset switching, which requires a high reset power (>7 mW), was observed, whereas for a high LRS with small multiple-conducting paths, the step-by-step reset switching with a low reset power (<7 mW) was observed. The attainment of higher nonlinear current-voltage ( I-V) characteristics in terms of the step-by-step reset switching is due to the steep current-increased region of the trap-controlled space charge-limited current (SCLC) model. A multilevel cell (MLC) operation, for which the reset stop voltage ( V STOP) is used in the DC sweep mode and an incremental amplitude is used in the pulse mode for the step-by-step reset switching, is demonstrated here. The results of the present study suggest that well-controlled conducting paths in a SiN-based RRAM device, which are not too strong and not too weak, offer considerable potential for the realization of low-power and high-density crossbar-array applications.

Concepts, characterization, and modeling of MEMS microswitches with gold contacts in MUMPs

NASA Astrophysics Data System (ADS)

Lafontan, Xavier; Dufaza, Christian; Robert, Michel; Pressecq, Francis; Perez, Guy

2001-04-01

This paper demonstrates that RF MEMS micro-switches can be realized with a low cost MEMS technology such as MUMPs. Two different switches are proposed, namely the hinged beam switch and the gold overflowing switch. Their concepts, design and characterization are described in details. On-resistance as low as 5 - 6 (Omega) for the gold overflowing switch and 2 - 3 (Omega) for the hinged beam switch have been measured. Finally, experimental measurements showed that force and electrical current had strong influences on the overall electrical contact.

Switching antipsychotic medications.

PubMed

Weiden, P J; Aquila, R; Dalheim, L; Standard, J M

1997-01-01

Compared with conventional antipsychotics, the so-called "atypical" antipsychotics promise improved side effect profiles and better control of the symptoms of schizophrenia. Therefore, most patients currently taking conventional antipsychotics could potentially benefit from a switch to an atypical antipsychotic. Often, the key issue in deciding whether to switch is the presence of countervailing factors that mitigate against the change. This paper discusses the indications and contraindications for switching antipsychotics, plus issues that require consideration before a switch is made. Also, the advantages and disadvantages of various switching techniques are discussed, with a particular focus on the newer antipsychotic olanzapine.

Fast infrared response of YBCO thin films

NASA Technical Reports Server (NTRS)

Ballentine, P. H.; Kadin, A. M.; Donaldson, W. R.; Scofield, J. H.; Bajuk, L.

1990-01-01

The response to short infrared pulses of some epitaxial YBCO films prepared by sputter deposition and by electron-beam evaporation is reported. The response is found to be essentially bolometric on the ns timescale, with some indirect hints of nonequilibrium electron transport on the ps scale. Fast switching could be obtained either by biasing the switch close to the critical current or by cooling the film below about 20 K. These results are encouraging for potential application to a high-current optically-triggered opening switch.

Hardware Model Of A Shipboard Zonal Electrical Distribution System (ZEDS): Alternating Current/Direct Current (AC/DC)

DTIC Science & Technology

2010-06-01

essential to fostering the loyalty , dedication and pride that enables the diverse student population within your department to be the very best systems...that I have enjoyed in my short time with you. Without you in my life, to share my success, I could not have ever achieved the level of satisfaction ...used. A typical wall mounted light switch is a single pole single throw switch. A common industrial motor start switch is a three pole single throw

Evidence for thermally assisted threshold switching behavior in nanoscale phase-change memory cells

NASA Astrophysics Data System (ADS)

Le Gallo, Manuel; Athmanathan, Aravinthan; Krebs, Daniel; Sebastian, Abu

2016-01-01

In spite of decades of research, the details of electrical transport in phase-change materials are still debated. In particular, the so-called threshold switching phenomenon that allows the current density to increase steeply when a sufficiently high voltage is applied is still not well understood, even though there is wide consensus that threshold switching is solely of electronic origin. However, the high thermal efficiency and fast thermal dynamics associated with nanoscale phase-change memory (PCM) devices motivate us to reassess a thermally assisted threshold switching mechanism, at least in these devices. The time/temperature dependence of the threshold switching voltage and current in doped Ge2Sb2Te5 nanoscale PCM cells was measured over 6 decades in time at temperatures ranging from 40 °C to 160 °C. We observe a nearly constant threshold switching power across this wide range of operating conditions. We also measured the transient dynamics associated with threshold switching as a function of the applied voltage. By using a field- and temperature-dependent description of the electrical transport combined with a thermal feedback, quantitative agreement with experimental data of the threshold switching dynamics was obtained using realistic physical parameters.

A three-level support method for smooth switching of the micro-grid operation model

NASA Astrophysics Data System (ADS)

Zong, Yuanyang; Gong, Dongliang; Zhang, Jianzhou; Liu, Bin; Wang, Yun

2018-01-01

Smooth switching of micro-grid between the grid-connected operation mode and off-grid operation mode is one of the key technologies to ensure it runs flexible and efficiently. The basic control strategy and the switching principle of micro-grid are analyzed in this paper. The reasons for the fluctuations of the voltage and the frequency in the switching process are analyzed from views of power balance and control strategy, and the operation mode switching strategy has been improved targeted. From the three aspects of controller’s current inner loop reference signal, voltage outer loop control strategy optimization and micro-grid energy balance management, a three-level security strategy for smooth switching of micro-grid operation mode is proposed. From the three aspects of controller’s current inner loop reference signal tracking, voltage outer loop control strategy optimization and micro-grid energy balance management, a three-level strategy for smooth switching of micro-grid operation mode is proposed. At last, it is proved by simulation that the proposed control strategy can make the switching process smooth and stable, the fluctuation problem of the voltage and frequency has been effectively improved.

Redefining the Speed Limit of Phase Change Memory Revealed by Time-resolved Steep Threshold-Switching Dynamics of AgInSbTe Devices

NASA Astrophysics Data System (ADS)

Shukla, Krishna Dayal; Saxena, Nishant; Durai, Suresh; Manivannan, Anbarasu

2016-11-01

Although phase-change memory (PCM) offers promising features for a ‘universal memory’ owing to high-speed and non-volatility, achieving fast electrical switching remains a key challenge. In this work, a correlation between the rate of applied voltage and the dynamics of threshold-switching is investigated at picosecond-timescale. A distinct characteristic feature of enabling a rapid threshold-switching at a critical voltage known as the threshold voltage as validated by an instantaneous response of steep current rise from an amorphous off to on state is achieved within 250 picoseconds and this is followed by a slower current rise leading to crystallization. Also, we demonstrate that the extraordinary nature of threshold-switching dynamics in AgInSbTe cells is independent to the rate of applied voltage unlike other chalcogenide-based phase change materials exhibiting the voltage dependent transient switching characteristics. Furthermore, numerical solutions of time-dependent conduction process validate the experimental results, which reveal the electronic nature of threshold-switching. These findings of steep threshold-switching of ‘sub-50 ps delay time’, opens up a new way for achieving high-speed non-volatile memory for mainstream computing.

Selection by current compliance of negative and positive bipolar resistive switching behaviour in ZrO2-x /ZrO2 bilayer memory

NASA Astrophysics Data System (ADS)

Huang, Ruomeng; Yan, Xingzhao; Morgan, Katrina A.; Charlton, Martin D. B.; (Kees de Groot, C. H.

2017-05-01

We report here a ZrO2-x /ZrO2-based bilayer resistive switching memory with unique properties that enables the selection of the switching mode by applying different electroforming current compliances. Two opposite polarity modes, positive bipolar and negative bipolar, correspond to the switching in the ZrO2 and ZrO2-x layer, respectively. The ZrO2 layer is proved to be responsible for the negative bipolar mode which is also observed in a ZrO2 single layer device. The oxygen deficient ZrO2-x layer plays the dominant role in the positive bipolar mode, which is exclusive to the bilayer memory. A systematic investigation of the ZrO2-x composition in the bilayer memory suggests that ZrO1.8 layer demonstrates optimum switching performance with low switching voltage, narrow switching voltage distribution and good cycling endurance. An excess of oxygen vacancies, beyond this composition, leads to a deterioration of switching properties. The formation and dissolution of the oxygen vacancy filament model has been proposed to explain both polarity switching behaviours and the improved properties in the bilayer positive bipolar mode are attributed to the confined oxygen vacancy filament size within the ZrO2-x layer.

The Implementation Of Solid State Switches In A Parallel Configuration To Gain Output Current Capacity In A High Current Capacitive Discharge Unit (CDU).

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

Chaves, Mario Paul

2017-07-01

For my project I have selected to research and design a high current pulse system, which will be externally triggered from a 5V pulse. The research will be conducted in the region of paralleling the solid state switches for a higher current output, as well as to see if there will be any other advantages in doing so. The end use of the paralleled solid state switches will be used on a Capacitive Discharge Unit (CDU). For the first part of my project, I have set my focus on the design of the circuit, selection of components, and simulation ofmore » the circuit.« less

High-explosive driven crowbar switch

DOEpatents

Dike, Robert S.; Kewish, Jr., Ralph W.

1976-01-13

The disclosure relates to a compact explosive driven switch for use as a low resistance, low inductance crowbar switch. A high-explosive charge extrudes a deformable conductive metallic plate through a polyethylene insulating layer to achieve a hard current contact with a supportive annular conductor.

A 0.2 V Micro-Electromechanical Switch Enabled by a Phase Transition.

PubMed

Dong, Kaichen; Choe, Hwan Sung; Wang, Xi; Liu, Huili; Saha, Bivas; Ko, Changhyun; Deng, Yang; Tom, Kyle B; Lou, Shuai; Wang, Letian; Grigoropoulos, Costas P; You, Zheng; Yao, Jie; Wu, Junqiao

2018-04-01

Micro-electromechanical (MEM) switches, with advantages such as quasi-zero leakage current, emerge as attractive candidates for overcoming the physical limits of complementary metal-oxide semiconductor (CMOS) devices. To practically integrate MEM switches into CMOS circuits, two major challenges must be addressed: sub 1 V operating voltage to match the voltage levels in current circuit systems and being able to deliver at least millions of operating cycles. However, existing sub 1 V mechanical switches are mostly subject to significant body bias and/or limited lifetimes, thus failing to meet both limitations simultaneously. Here 0.2 V MEM switching devices with ≳10 6 safe operating cycles in ambient air are reported, which achieve the lowest operating voltage in mechanical switches without body bias reported to date. The ultralow operating voltage is mainly enabled by the abrupt phase transition of nanolayered vanadium dioxide (VO 2 ) slightly above room temperature. The phase-transition MEM switches open possibilities for sub 1 V hybrid integrated devices/circuits/systems, as well as ultralow power consumption sensors for Internet of Things applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spin–orbit torque-assisted switching in magnetic insulator thin films with perpendicular magnetic anisotropy

DOE PAGES

Li, Peng; Liu, Tao; Chang, Houchen; ...

2016-09-01

As an in-plane charge current flows in a heavy metal film with spin-orbit coupling, it produces a torque on and thereby switches the magnetization in a neighbouring ferromagnetic metal film. Such spin-orbit torque (SOT)-induced switching has been studied extensively in recent years and has shown higher efficiency than switching using conventional spin-transfer torque. Here we report the SOT-assisted switching in heavy metal/magnetic insulator systems. The experiments used a Pt/BaFe 12O 19 bilayer where the BaFe 12O 19 layer exhibits perpendicular magnetic anisotropy. As a charge current is passed through the Pt film, it produces a SOT that can control themore » up and down states of the remnant magnetization in the BaFe 12O 19 film when the film is magnetized by an in-plane magnetic field. Furthermore, it can reduce or increase the switching field of the BaFe 12O 19 film by as much as about 500 Oe when the film is switched with an out-of-plane field.« less

Spin-orbit torque-assisted switching in magnetic insulator thin films with perpendicular magnetic anisotropy

NASA Astrophysics Data System (ADS)

Li, Peng; Liu, Tao; Chang, Houchen; Kalitsov, Alan; Zhang, Wei; Csaba, Gyorgy; Li, Wei; Richardson, Daniel; Demann, August; Rimal, Gaurab; Dey, Himadri; Jiang, J. S.; Porod, Wolfgang; Field, Stuart B.; Tang, Jinke; Marconi, Mario C.; Hoffmann, Axel; Mryasov, Oleg; Wu, Mingzhong

2016-09-01

As an in-plane charge current flows in a heavy metal film with spin-orbit coupling, it produces a torque on and thereby switches the magnetization in a neighbouring ferromagnetic metal film. Such spin-orbit torque (SOT)-induced switching has been studied extensively in recent years and has shown higher efficiency than switching using conventional spin-transfer torque. Here we report the SOT-assisted switching in heavy metal/magnetic insulator systems. The experiments used a Pt/BaFe12O19 bilayer where the BaFe12O19 layer exhibits perpendicular magnetic anisotropy. As a charge current is passed through the Pt film, it produces a SOT that can control the up and down states of the remnant magnetization in the BaFe12O19 film when the film is magnetized by an in-plane magnetic field. It can reduce or increase the switching field of the BaFe12O19 film by as much as about 500 Oe when the film is switched with an out-of-plane field.

Multistate storage nonvolatile memory device based on ferroelectricity and resistive switching effects of SrBi2Ta2O9 films

NASA Astrophysics Data System (ADS)

Song, Zhiwei; Li, Gang; Xiong, Ying; Cheng, Chuanpin; Zhang, Wanli; Tang, Minghua; Li, Zheng; He, Jiangheng

2018-05-01

A memory device with a Pt/SrBi2Ta2O9(SBT)/Pt(111) structure was shown to have excellent combined ferroelectricity and resistive switching properties, leading to higher multistate storage memory capacity in contrast to ferroelectric memory devices. In this device, SBT polycrystalline thin films with significant (115) orientation were fabricated on Pt(111)/Ti/SiO2/Si(100) substrates using CVD (chemical vapor deposition) method. Measurement results of the electric properties exhibit reproducible and reliable ferroelectricity switching behavior and bipolar resistive switching effects (BRS) without an electroforming process. The ON/OFF ratio of the resistive switching was found to be about 103. Switching mechanisms for the low resistance state (LRS) and high resistance state (HRS) currents are likely attributed to the Ohmic and space charge-limited current (SCLC) behavior, respectively. Moreover, the ferroelectricity and resistive switching effects were found to be mutually independent, and the four logic states were obtained by controlling the periodic sweeping voltage. This work holds great promise for nonvolatile multistate memory devices with high capacity and low cost.

Micro optical fiber display switch based on the magnetohydrodynamic (MHD) principle

NASA Astrophysics Data System (ADS)

Lian, Kun; Heng, Khee-Hang

2001-09-01

This paper reports on a research effort to design, microfabricate and test an optical fiber display switch based on magneto hydrodynamic (MHD) principal. The switch is driven by the Lorentz force and can be used to turn on/off the light. The SU-8 photoresist and UV light source were used for prototype fabrication in order to lower the cost. With a magnetic field supplied by an external permanent magnet, and a plus electrical current supplied across the two inert sidewall electrodes, the distributed body force generated will produce a pressure difference on the fluid mercury in the switch chamber. By change the direction of current flow, the mercury can turn on or cut off the light pass in less than 10 ms. The major advantages of a MHD-based micro-switch are that it does not contain any solid moving parts and power consumption is much smaller comparing to the relay type switches. This switch can be manufactured by molding gin batch production and may have potential applications in extremely bright traffic control,, high intensity advertising display, and communication.

The Roles of Relative Linguistic Proficiency and Modality Switching in Language Switch Cost: Evidence from Chinese Visual Unimodal and Bimodal Bilinguals.

PubMed

Lu, Aitao; Wang, Lu; Guo, Yuyang; Zeng, Jiahong; Zheng, Dongping; Wang, Xiaolu; Shao, Yulan; Wang, Ruiming

2017-09-01

The current study investigated the mechanism of language switching in unbalanced visual unimodal bilinguals as well as balanced and unbalanced bimodal bilinguals during a picture naming task. All three groups exhibited significant switch costs across two languages, with symmetrical switch cost in balanced bimodal bilinguals and asymmetrical switch cost in unbalanced unimodal bilinguals and bimodal bilinguals. Moreover, the relative proficiency of the two languages but not their absolute proficiency had an effect on language switch cost. For the bimodal bilinguals the language switch cost also arose from modality switching. These findings suggest that the language switch cost might originate from multiple sources from both outside (e.g., modality switching) and inside (e.g., the relative proficiency of the two languages) the linguistic lexicon.

Surviving bacterial sibling rivalry: inducible and reversible phenotypic switching in Paenibacillus dendritiformis.

PubMed

Be'er, Avraham; Florin, E-L; Fisher, Carolyn R; Swinney, Harry L; Payne, Shelley M

2011-01-01

Natural habitats vary in available nutrients and room for bacteria to grow, but successful colonization can lead to overcrowding and stress. Here we show that competing sibling colonies of Paenibacillus dendritiformis bacteria survive overcrowding by switching between two distinct vegetative phenotypes, motile rods and immotile cocci. Growing colonies of the rod-shaped bacteria produce a toxic protein, Slf, which kills cells of encroaching sibling colonies. However, sublethal concentrations of Slf induce some of the rods to switch to Slf-resistant cocci, which have distinct metabolic and resistance profiles, including resistance to cell wall antibiotics. Unlike dormant spores of P. dendritiformis, the cocci replicate. If cocci encounter conditions that favor rods, they secrete a signaling molecule that induces a switch to rods. Thus, in contrast to persister cells, P. dendritiformis bacteria adapt to changing environmental conditions by inducible and reversible phenotypic switching. In favorable environments, species may face space and nutrient limits due to overcrowding. Bacteria provide an excellent model for analyzing principles underlying overcrowding and regulation of density in nature, since their population dynamics can be easily and accurately assessed under controlled conditions. We describe a newly discovered mechanism for survival of a bacterial population during overcrowding. When competing with sibling colonies, Paenibacillus dendritiformis produces a lethal protein (Slf) that kills cells at the interface of encroaching colonies. Slf also induces a small proportion of the cells to switch from motile, rod-shaped cells to nonmotile, Slf-resistant, vegetative cocci. When crowding is reduced and nutrients are no longer limiting, the bacteria produce a signal that induces cocci to switch back to motile rods, allowing the population to spread. Genes encoding components of this phenotypic switching pathway are widespread among bacterial species, suggesting that this survival mechanism is not unique to P. dendritiformis.

30 CFR 7.64 - Technical requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... produce the required firing current is attained. (d) Firing switch. The switch used to initiate the... current is available to the blasting circuit. (e) Firing line terminals. The terminals used to connect the blasting circuit to the blasting unit shall— (1) Provide a secure, low-resistance connection to the...

30 CFR 7.64 - Technical requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... produce the required firing current is attained. (d) Firing switch. The switch used to initiate the... current is available to the blasting circuit. (e) Firing line terminals. The terminals used to connect the blasting circuit to the blasting unit shall— (1) Provide a secure, low-resistance connection to the...

High power operation of a nitrogen doped, vanadium compensated, 6H-SiC extrinsic photoconductive switch

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

Sullivan, J. S.

2014-04-28

We report the high power operation of nitrogen doped, vanadium compensated, 6H-SiC, extrinsic photoconductive switches with improved vanadium and nitrogen dopant density. Photoconductive switching tests are performed on 1 mm thick, m-plane, switch substrates at switch voltage and currents up to 17 kV and 1.5 kA, respectively. Sub-ohm minimum switch on resistance is achieved for peak optical intensities ≥35 MW/cm{sup 2} at 532 nm applied to the switch facet. A reduction of greater than nine orders of magnitude is observed in switch material resistivity between dark and illuminated states.

Plasma opening switch

DOEpatents

Savage, Mark E.; Mendel, Jr., Clifford W.

2001-01-01

A command triggered plasma opening switch assembly using an amplification stage. The assembly surrounds a coaxial transmission line and has a main plasma opening switch (POS) close to the load and a trigger POS upstream from the main POS. The trigger POS establishes two different current pathways through the assembly depended on whether it has received a trigger current pulse. The initial pathway has both POS's with plasma between their anodes and cathodes to form a short across the transmission line and isolating the load. The final current pathway is formed when the trigger POS receives a trigger current pulse which energizes its fast coil to push the conductive plasma out from between its anode and cathode, allowing the main transmission line current to pass to the fast coil of the main POS, thus pushing its plasma out the way so as to establish a direct current pathway to the load.

TaOx-based resistive switching memories: prospective and challenges

PubMed Central

2013-01-01

Resistive switching memories (RRAMs) are attractive for replacement of conventional flash in the future. Although different switching materials have been reported; however, low-current operated devices (<100 μA) are necessary for productive RRAM applications. Therefore, TaOx is one of the prospective switching materials because of two stable phases of TaO2 and Ta2O5, which can also control the stable low- and high-resistance states. Long program/erase endurance and data retention at high temperature under low-current operation are also reported in published literature. So far, bilayered TaOx with inert electrodes (Pt and/or Ir) or single layer TaOx with semi-reactive electrodes (W and Ti/W or Ta/Pt) is proposed for real RRAM applications. It is found that the memory characteristics at current compliance (CC) of 80 μA is acceptable for real application; however, data are becoming worst at CC of 10 μA. Therefore, it is very challenging to reduce the operation current (few microampere) of the RRAM devices. This study investigates the switching mode, mechanism, and performance of low-current operated TaOx-based devices as compared to other RRAM devices. This topical review will not only help for application of TaOx-based nanoscale RRAM devices but also encourage researcher to overcome the challenges in the future production. PMID:24107610

Status report on Project Hercules

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

Loree, D.; Giesselmann, M.; Kristiansen, M.

1993-01-01

Project Hercules is a project to improve ignitron switches which will then be used on the upgrade of Lawrence Livermore's Nova Laser for their ICF program. The goals of Hercules, which stands for High Energy Research Concerning the Ultimate Lifetime of Experimental Switches, are to lifetime test (up to 10,000 shots) prototype ignitrons or other switches with the required Nova current and coulomb parameters (300 kA, 200 C), recommend design changes, and retest the second generation switches. This report describes the design and construction of the test circuit and necessary diagnostics. The details of the design and construction of themore » test circuit and necessary diagnostics. The details of the design and construction of a 0.5 MJ electrolytic capacitor bank and a semi-automatic diagnostic/control system are described. The required test run data include peak current and corresponding tube voltage for every shot, entire current and voltage waveforms every few shots, and ignitor resistance values every few shots. Additionally, the conversion of a 120 kW, 12 kV constant voltage supply to an 8 A constant current supply with the use of six SCRs and a commercial control board will be described. The final results of this project will be lifetime data at high current and high coulomb for and improvements on some of the best of the new generation of pulsed power switches.« less

Signal persistence and amplification in cancer development and possible, related opportunities for novel therapies.

PubMed

Ford, Shea A; Blanck, George

2015-01-01

Research in cancer biology has been largely driven by experimental approaches whereby discreet inputs are used to assess discreet outputs, for example, gene-knockouts to assess cancer occurrence. However, cancer hallmarks are only rarely, if ever, exclusively dependent on discreet regulatory processes. Rather, cancer-related regulatory factors affect multiple cancer hallmarks. Thus, novel approaches and paradigms are needed for further advances. Signal pathway persistence and amplification, rather than signal pathway activation resulting from an on/off switch, represent emerging paradigms for cancer research, closely related to developmental regulatory paradigms. In this review, we address both mechanisms and effects of signal pathway persistence and amplification in cancer settings; and address the possibility that hyper-activation of pro-proliferative signal pathways in certain cancer settings could be exploited for therapy. Copyright © 2014. Published by Elsevier B.V.

Quantum switching of π-electron rotations in a nonplanar chiral molecule by using linearly polarized UV laser pulses.

PubMed

Mineo, Hirobumi; Yamaki, Masahiro; Teranishi, Yoshiaki; Hayashi, Michitoshi; Lin, Sheng Hsien; Fujimura, Yuichi

2012-09-05

Nonplanar chiral aromatic molecules are candidates for use as building blocks of multidimensional switching devices because the π electrons can generate ring currents with a variety of directions. We employed (P)-2,2'-biphenol because four patterns of π-electron rotations along the two phenol rings are possible and theoretically determine how quantum switching of the π-electron rotations can be realized. We found that each rotational pattern can be driven by a coherent excitation of two electronic states under two conditions: one is the symmetry of the electronic states and the other is their relative phase. On the basis of the results of quantum dynamics simulations, we propose a quantum control method for sequential switching among the four rotational patterns that can be performed by using ultrashort overlapped pump and dump pulses with properly selected relative phases and photon polarization directions. The results serve as a theoretical basis for the design of confined ultrafast switching of ring currents of nonplanar molecules and further current-induced magnetic fluxes of more sophisticated systems.

Giant thermal spin torque assisted magnetic tunnel junction switching

NASA Astrophysics Data System (ADS)

Pushp, Aakash

Spin-polarized charge-currents induce magnetic tunnel junction (MTJ) switching by virtue of spin-transfer-torque (STT). Recently, by taking advantage of the spin-dependent thermoelectric properties of magnetic materials, novel means of generating spin-currents from temperature gradients, and their associated thermal-spin-torques (TSTs) have been proposed, but so far these TSTs have not been large enough to influence MTJ switching. Here we demonstrate significant TSTs in MTJs by generating large temperature gradients across ultrathin MgO tunnel barriers that considerably affect the switching fields of the MTJ. We attribute the origin of the TST to an asymmetry of the tunneling conductance across the zero-bias voltage of the MTJ. Remarkably, we estimate through magneto-Seebeck voltage measurements that the charge-currents that would be generated due to the temperature gradient would give rise to STT that is a thousand times too small to account for the changes in switching fields that we observe. Reference: A. Pushp*, T. Phung*, C. Rettner, B. P. Hughes, S.-H. Yang, S. S. P. Parkin, 112, 6585-6590 (2015).

Double-injection, deep-impurity switch development

NASA Technical Reports Server (NTRS)

Whitson, D. W.

1985-01-01

The overall objective of this program was the development of device design and process techniques for the fabrication of a double-injection, deep-impurity (DI) sup 2 silicon switch that operates in the 2-10 kV range with conduction current values of 5 A at 2 kV and 1 A at 10 kV. Other major specifications include a holding voltage of 10 V with no gate current, 10 microsec switching time, and power dissipation of 50 W at 75 C. It was decided to concentrate on the lateral circular devices in order to optimize the gold diffusion. This resulted in devices that are much better switches (approx.1 micro sec switching time), and in a gold diffusion process that is much more controllable than those previously developed. Some results with injection-gated devices were also obtained. The current conduction for V less than VT was analyzed and seen to agree, for the most part, with Lampert's theory. Various sections of this report describe the device designs, wafer-processing techniques, and various measurements which include ac and dc characteristics and four-point probe.

Remote two-wire data entry method and device

DOEpatents

Kronberg, J.W.

1991-01-01

This invention is comprised of a device for detecting switch closure such as in a keypad for entering data comprising a matrix of conductor pairs and switches, each pair of conductors shorted by the pressing of a particular switch, and current-regulating devices on each conductor for limiting current in one direction and passing it without limit in the other direction. The device is driven by alternating current. The ends of the conductors in a conductor pair limit current of opposing polarities with respect to each other so that the signal on a shorted pair is an alternating current signal with a unique combination of a positive and a negative peak, which, when analyzed, allows the determination of which key was pressed. The binary identification of the pressed key is passed to the input port of a host device.

Listeria monocytogenes switches from dissemination to persistence by adopting a vacuolar lifestyle in epithelial cells.

PubMed

Kortebi, Mounia; Milohanic, Eliane; Mitchell, Gabriel; Péchoux, Christine; Prevost, Marie-Christine; Cossart, Pascale; Bierne, Hélène

2017-11-01

Listeria monocytogenes causes listeriosis, a foodborne disease that poses serious risks to fetuses, newborns and immunocompromised adults. This intracellular bacterial pathogen proliferates in the host cytosol and exploits the host actin polymerization machinery to spread from cell-to-cell and disseminate in the host. Here, we report that during several days of infection in human hepatocytes or trophoblast cells, L. monocytogenes switches from this active motile lifestyle to a stage of persistence in vacuoles. Upon intercellular spread, bacteria gradually stopped producing the actin-nucleating protein ActA and became trapped in lysosome-like vacuoles termed Listeria-Containing Vacuoles (LisCVs). Subpopulations of bacteria resisted degradation in LisCVs and entered a slow/non-replicative state. During the subculture of host cells harboring LisCVs, bacteria showed a capacity to cycle between the vacuolar and the actin-based motility stages. When ActA was absent, such as in ΔactA mutants, vacuolar bacteria parasitized host cells in the so-called "viable but non-culturable" state (VBNC), preventing their detection by conventional colony counting methods. The exposure of infected cells to high doses of gentamicin did not trigger the formation of LisCVs, but selected for vacuolar and VBNC bacteria. Together, these results reveal the ability of L. monocytogenes to enter a persistent state in a subset of epithelial cells, which may favor the asymptomatic carriage of this pathogen, lengthen the incubation period of listeriosis, and promote bacterial survival during antibiotic therapy.

Listeria monocytogenes switches from dissemination to persistence by adopting a vacuolar lifestyle in epithelial cells

PubMed Central

Mitchell, Gabriel

2017-01-01

Listeria monocytogenes causes listeriosis, a foodborne disease that poses serious risks to fetuses, newborns and immunocompromised adults. This intracellular bacterial pathogen proliferates in the host cytosol and exploits the host actin polymerization machinery to spread from cell-to-cell and disseminate in the host. Here, we report that during several days of infection in human hepatocytes or trophoblast cells, L. monocytogenes switches from this active motile lifestyle to a stage of persistence in vacuoles. Upon intercellular spread, bacteria gradually stopped producing the actin-nucleating protein ActA and became trapped in lysosome-like vacuoles termed Listeria-Containing Vacuoles (LisCVs). Subpopulations of bacteria resisted degradation in LisCVs and entered a slow/non-replicative state. During the subculture of host cells harboring LisCVs, bacteria showed a capacity to cycle between the vacuolar and the actin-based motility stages. When ActA was absent, such as in ΔactA mutants, vacuolar bacteria parasitized host cells in the so-called “viable but non-culturable” state (VBNC), preventing their detection by conventional colony counting methods. The exposure of infected cells to high doses of gentamicin did not trigger the formation of LisCVs, but selected for vacuolar and VBNC bacteria. Together, these results reveal the ability of L. monocytogenes to enter a persistent state in a subset of epithelial cells, which may favor the asymptomatic carriage of this pathogen, lengthen the incubation period of listeriosis, and promote bacterial survival during antibiotic therapy. PMID:29190284

Overload protection for switching regulators

NASA Technical Reports Server (NTRS)

Lachochi, E.

1980-01-01

Circuit protects all output lines of switching regulator against overloads without requiring current sensors on every line. If overload is sensed, device short circuits bias on switching transistor so that power is rapidly cut off from loads. Circuit also includes delay network to inhibit erroneous operation during startup.

Load insensitive electrical device. [power converters for supplying direct current at one voltage from a source at another voltage

NASA Technical Reports Server (NTRS)

Schwarz, F. C. (Inventor)

1974-01-01

A class of power converters is described for supplying direct current at one voltage from a source at another voltage. It includes a simple passive circuit arrangement of solid-state switches, inductors, and capacitors by which the output voltage of the converter tends to remain constant in spite of changes in load. The switches are sensitive to the current flowing in the circuit and are employed to permit the charging of capacitance devices in accordance with the load requirements. Because solid-state switches (such as SCR's) may be used with relatively high voltage and because of the inherent efficiency of the invention that permits relatively high switching frequencies, power supplies built in accordance with the invention, together with their associated cabling, can be substantially lighter in weight for a given output power level and efficiency of operation than systems of the prior art.

Optimization of the Switch Mechanism in a Circuit Breaker Using MBD Based Simulation

PubMed Central

Jang, Jin-Seok; Yoon, Chang-Gyu; Ryu, Chi-Young; Kim, Hyun-Woo; Bae, Byung-Tae; Yoo, Wan-Suk

2015-01-01

A circuit breaker is widely used to protect electric power system from fault currents or system errors; in particular, the opening mechanism in a circuit breaker is important to protect current overflow in the electric system. In this paper, multibody dynamic model of a circuit breaker including switch mechanism was developed including the electromagnetic actuator system. Since the opening mechanism operates sequentially, optimization of the switch mechanism was carried out to improve the current breaking time. In the optimization process, design parameters were selected from length and shape of each latch, which changes pivot points of bearings to shorten the breaking time. To validate optimization results, computational results were compared to physical tests with a high speed camera. Opening time of the optimized mechanism was decreased by 2.3 ms, which was proved by experiments. Switch mechanism design process can be improved including contact-latch system by using this process. PMID:25918740

Using a small hybrid pulse power transformer unit as component of a high-current opening switch for a railgun

NASA Astrophysics Data System (ADS)

Leung, E. M. W.; Bailey, R. E.; Michels, P. H.

1989-03-01

The hybrid pulse power transformer (HPPT) is a unique concept utilizing the ultrafast superconducting-to-normal transition process of a superconductor. When used in the form of a hybrid transformer current-zero switch (HTCS), this creates an approach in which the large, high-power, high-current opening switch in a conventional railgun system can be eliminated. This represents an innovative application of superconductivity to pulsed power conditioning required for the Strategic Defense Initiative (SDI). The authors explain the working principles of a 100-KJ unit capable of switching up to 500 kA at a frequency of 0.5 Hz and with a system efficiency of greater than 90 percent. Circuit analysis using a computer code called SPICE PLUS was used to verify the HTCS concept. This concept can be scaled up to applications in the several mega-ampere levels.

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.

Inverting Quasi-Resonant Switched-Capacitor Bidirectional Converter and Its Application to Battery Equalization

NASA Astrophysics Data System (ADS)

Lee, Yuang-Shung; Chiu, Yin-Yuan; Cheng, Ming-Wang; Ko, Yi-Pin; Hsiao, Sung-Hsin

The proposed quasi-resonant (QR) zero current switching (ZCS) switched-capacitor (SC) converter is a new type of bidirectional power flow control conversion scheme. The proposed converter is able to provide voltage conversion ratios from -3/-{1 \\over 3} (triple-mode/trisection-mode) to -n/-{1 \\over n} (-n-mode/-{1 \\over n}-mode) by adding a different number of switched-capacitors and power MOSFET switches with a small series connected resonant inductor for forward and reverse power flow control schemes. It possesses the advantages of low switching losses and current stress in this QR ZCS SC converter. The principle of operation, theoretical analysis of the proposed triple-mode/trisection-mode bidirectional power conversion scheme is described in detail with circuit model analysis. Simulation and experimental studies are carried out to verify the performance of the proposed inverting type ZCS SC QR bidirectional converter. The proposed converters can be applied to battery equalization for battery management system (BMS).

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

Li, Peng; Liu, Tao; Chang, Houchen

As an in-plane charge current flows in a heavy metal film with spin-orbit coupling, it produces a torque on and thereby switches the magnetization in a neighbouring ferromagnetic metal film. Such spin-orbit torque (SOT)-induced switching has been studied extensively in recent years and has shown higher efficiency than switching using conventional spin-transfer torque. Here we report the SOT-assisted switching in heavy metal/magnetic insulator systems. The experiments used a Pt/BaFe 12O 19 bilayer where the BaFe 12O 19 layer exhibits perpendicular magnetic anisotropy. As a charge current is passed through the Pt film, it produces a SOT that can control themore » up and down states of the remnant magnetization in the BaFe 12O 19 film when the film is magnetized by an in-plane magnetic field. Furthermore, it can reduce or increase the switching field of the BaFe 12O 19 film by as much as about 500 Oe when the film is switched with an out-of-plane field.« less

Testing Single Phase IGBT H-Bridge Switch Plates for the High Voltage Converter Modulator at the Spallation Neutron Source

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

Peplov, Vladimir V; Anderson, David E; Solley, Dennis J

2014-01-01

Three IGBT H-bridge switching networks are used in each High Voltage Converter Modulator (HVCM) system at the Spallation Neutron Source (SNS) to generate drive currents to three boost transformer primaries switching between positive and negative bus voltages at 20 kHz. Every switch plate assembly is tested before installing it into an operational HVCM. A Single Phase Test Stand has been built for this purpose, and it is used for adjustment, measurement and testing of different configurations of switch plates. This paper will present a description of the Test Stand configuration and discuss the results of testing switch plates with twomore » different types of IGBT gate drivers currently in use on the HVCM systems. Comparison of timing characteristics of the original and new drivers and the resulting performance reinforces the necessity to replace the original H-bridge network drivers with the upgraded units.« less

System for automatically switching transformer coupled lines

NASA Technical Reports Server (NTRS)

Dwinell, W. S. (Inventor)

1979-01-01

A system is presented for automatically controlling transformer coupled alternating current electric lines. The secondary winding of each transformer is provided with a center tap. A switching circuit is connected to the center taps of a pair of secondary windings and includes a switch controller. An impedance is connected between the center taps of the opposite pair of secondary windings. The switching circuit has continuity when the AC lines are continuous and discontinuity with any disconnect of the AC lines. Normally open switching means are provided in at least one AC line. The switch controller automatically opens the switching means when the AC lines become separated.

Resonant snubber inverter

DOEpatents

Lai, Jih-Sheng; Young, Sr., Robert W.; Chen, Daoshen; Scudiere, Matthew B.; Ott, Jr., George W.; White, Clifford P.; McKeever, John W.

1997-01-01

A resonant, snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the main inverter switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter.

Resonant snubber inverter

DOEpatents

Lai, J.S.; Young, R.W. Sr.; Chen, D.; Scudiere, M.B.; Ott, G.W. Jr.; White, C.P.; McKeever, J.W.

1997-06-24

A resonant, snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the main inverter switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter. 14 figs.

Reducing Ripple In A Switching Voltage Regulator

NASA Technical Reports Server (NTRS)

Paulkovich, John; Rodriguez, G. Ernest

1994-01-01

Ripple voltage in output of switching voltage regulator reduced substantially by simple additional circuitry adding little to overall weight and size of regulator. Heretofore, additional filtering circuitry needed to obtain comparable reductions in ripple typically as large and heavy as original regulator. Current opposing ripple current injected into filter capacitor.

Theoretical Modeling of the Plasma Erosion Opening Switch for Inductive Storage Applications.

DTIC Science & Technology

1983-10-27

instantaneous and depends on the switch and load characteristics. In general T is finite and T >T >0. Thus energy will be lost to switch heatings s op - as...Top, then the switch opening time is the dominant factor and T T Clearly T must be small compared with the decay time of the load S op 5 current, T_

Multi-megavolt low jitter multistage switch

DOEpatents

Humphreys, D.R.; Penn, K.J. Jr.

1985-06-19

It is one object of the present invention to provide a multistage switch capable of holding off numerous megavolts, until triggered, from a particle beam accelerator of the type used for inertial confinement fusion. The invention provides a multistage switch having low timing jitter and capable of producing multiple spark channels for spreading current over a wider area to reduce electrode damage and increase switch lifetime. The switch has fairly uniform electric fields and a short spark gap for laser triggering and is engineered to prevent insulator breakdowns.

Multi-gap high impedance plasma opening switch

DOEpatents

Mason, Rodney J.

1996-01-01

A high impedance plasma opening switch having an anode and a cathode and at least one additional electrode placed between the anode and cathode. The presence of the additional electrodes leads to the creation of additional plasma gaps which are in series, increasing the net impedance of the switch. An equivalent effect can be obtained by using two or more conventional plasma switches with their plasma gaps wired in series. Higher impedance switches can provide high current and voltage to higher impedance loads such as plasma radiation sources.

Silicon controlled rectifier polyphase bridge inverter commutated with gate-turn-off thyristor

NASA Technical Reports Server (NTRS)

Edwards, Dean B. (Inventor); Rippel, Wally E. (Inventor)

1986-01-01

A polyphase SCR inverter (10) having N switching poles, each comprised of two SCR switches (1A, 1B; 2A, 2B . . . NA, NB) and two diodes (D1B; D1B; D2A, D2B . . . DNA, DNB) in series opposition with saturable reactors (L1A, L1B; L2A, L2B . . . LNA, LNB) connecting the junctions between the SCR switches and diodes to an output terminal (1, 2 . . . 3) is commutated with only one GTO thyristor (16) connected between the common negative terminal of a dc source and a tap of a series inductor (14) connected to the positive terminal of the dc source. A clamp winding (22) and diode (24) are provided, as is a snubber (18) which may have its capacitance (c) sized for maximum load current divided into a plurality of capacitors (C.sub.1, C.sub.2 . . . C.sub.N), each in series with an SCR switch S.sub.1, S.sub.2 . . . S.sub.N). The total capacitance may be selected by activating selected switches as a function of load current. A resistor 28 and SCR switch 26 shunt reverse current when the load acts as a generator, such as a motor while braking.

When should irrigators invest in more water-efficient technologies as an adaptation to climate change?

NASA Astrophysics Data System (ADS)

Malek, K.; Adam, J. C.; Stockle, C.; Brady, M.; Yoder, J.

2015-12-01

The western US is expected to experience more frequent droughts with higher magnitudes and persistence due to the climate change, with potentially large impacts on agricultural productivity and the economy. Irrigated farmers have many options for minimizing drought impacts including changing crops, engaging in water markets, and switching irrigation technologies. Switching to more efficient irrigation technologies, which increase water availability in the crop root zone through reduction of irrigation losses, receives significant attention because of the promise of maintaining current production with less. However, more efficient irrigation systems are almost always more capital-intensive adaptation strategy particularly compared to changing crops or trading water. A farmer's decision to switch will depend on how much money they project to save from reducing drought damages. The objective of this study is to explore when (and under what climate change scenarios) it makes sense economically for farmers to invest in a new irrigation system. This study was performed over the Yakima River Basin (YRB) in Washington State, although the tools and information gained from this study are transferable to other watersheds in the western US. We used VIC-CropSyst, a large-scale grid-based modeling framework that simulates hydrological processes while mechanistically capturing crop water use, growth and development. The water flows simulated by VIC-CropSyst were used to run the RiverWare river system and water management model (YAK-RW), which simulates river processes and calculates regional water availability for agricultural use each day (i.e., the prorationing ratio). An automated computational platform has been developed and programed to perform the economic analysis for each grid cell, crop types and future climate projections separately, which allows us to explore whether or not implementing a new irrigation system is economically viable. Results of this study indicate that climate change could justify the investment in new irrigation systems during this century, but the timing of a farmer's response is likely to depend on a variety of factors, including changes in the frequency and magnitude of drought events, current irrigation systems, climatological characteristics within the basin, and crop type.

Delta connected resonant snubber circuit

DOEpatents

Lai, J.S.; Peng, F.Z.; Young, R.W. Sr.; Ott, G.W. Jr.

1998-01-20

A delta connected, resonant snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the dc supply voltage through the main inverter switches and the auxiliary switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter. 36 figs.

Delta connected resonant snubber circuit

DOEpatents

Lai, Jih-Sheng; Peng, Fang Zheng; Young, Sr., Robert W.; Ott, Jr., George W.

1998-01-01

A delta connected, resonant snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the dc supply voltage through the main inverter switches and the auxiliary switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter.

AC motor controller with 180 degree conductive switches

NASA Technical Reports Server (NTRS)

Oximberg, Carol A. (Inventor)

1995-01-01

An ac motor controller is operated by a modified time-switching scheme where the switches of the inverter are on for electrical-phase-and-rotation intervals of 180.degree. as opposed to the conventional 120.degree.. The motor is provided with three-phase drive windings, a power inverter for power supplied from a dc power source consisting of six switches, and a motor controller which controls the current controlled switches in voltage-fed mode. During full power, each switch is gated continuously for three successive intervals of 60.degree. and modulated for only one of said intervals. Thus, during each 60.degree. interval, the two switches with like signs are on continuously and the switch with the opposite sign is modulated.

A Time Hazard Analysis of Student Persistence: A US University Undergraduate Mathematics Major Experience

ERIC Educational Resources Information Center

Bahi, Saïd; Higgins, Devin; Staley, Patrick

2015-01-01

Individual level data for the entire cohort of undergraduate mathematics students of a relatively small US public university was used to estimate the risk that a student will switch major to another one before degree completion. The data set covers the period from 1999 to 2006. Survival tables and logistic models were estimated and used to discuss…

Enhancing the x-ray output of a single-wire explosion with a gas-puff based plasma opening switch

NASA Astrophysics Data System (ADS)

Engelbrecht, Joseph T.; Ouart, Nicholas D.; Qi, Niansheng; de Grouchy, Philip W.; Shelkovenko, Tatiana A.; Pikuz, Sergey A.; Banasek, Jacob T.; Potter, William M.; Rocco, Sophia V.; Hammer, David A.; Kusse, Bruce R.; Giuliani, John L.

2018-02-01

We present experiments performed on the 1 MA COBRA generator using a low density, annular, gas-puff z-pinch implosion as an opening switch to rapidly transfer a current pulse into a single metal wire on axis. This gas-puff on axial wire configuration was studied for its promise as an opening switch and as a means of enhancing the x-ray output of the wire. We demonstrate that current can be switched from the gas-puff plasma into the wire, and that the timing of the switch can be controlled by the gas-puff plenum backing pressure. X-ray detector measurements indicate that for low plenum pressure Kr or Xe shots with a copper wire, this configuration can offer a significant enhancement in the peak intensity and temporal distribution of radiation in the 1-10 keV range.

High-voltage, high-power, solid-state remote power controllers for aerospace applications

NASA Technical Reports Server (NTRS)

Sturman, J. C.

1985-01-01

Two general types of remote power controller (RPC) that combine the functions of a circuit breaker and a switch were developed for use in direct-current (dc) aerospace systems. Power-switching devices used in these designs are the relatively new gate-turnoff thyristor (GTO) and poweer metal-oxide-semiconductor field-effect transistors (MOSFET). The various RPC's can switch dc voltages to 1200 V and currents to 100 A. Seven different units were constructed and subjected to comprehensive laboratory and thermal vacuum testing. Two of these were dual units that switch both positive and negative voltages simultaneously. The RPC's using MOSFET's have slow turnon and turnoff times to limit voltage spiking from high di/dt. The GTO's have much faster transition times. All RPC's have programmable overload tripout and microsecond tripout for large overloads. The basic circuits developed can be used to build switchgear limited only by the ratings of the switching device used.

Rapid mapping of polarization switching through complete information acquisition

NASA Astrophysics Data System (ADS)

Somnath, Suhas; Belianinov, Alex; Kalinin, Sergei V.; Jesse, Stephen

2016-12-01

Polarization switching in ferroelectric and multiferroic materials underpins a broad range of current and emergent applications, ranging from random access memories to field-effect transistors, and tunnelling devices. Switching in these materials is exquisitely sensitive to local defects and microstructure on the nanometre scale, necessitating spatially resolved high-resolution studies of these phenomena. Classical piezoresponse force microscopy and spectroscopy, although providing necessary spatial resolution, are fundamentally limited in data acquisition rates and energy resolution. This limitation stems from their two-tiered measurement protocol that combines slow (~1 s) switching and fast (~10 kHz-1 MHz) detection waveforms. Here we develop an approach for rapid probing of ferroelectric switching using direct strain detection of material response to probe bias. This approach, facilitated by high-sensitivity electronics and adaptive filtering, enables spectroscopic imaging at a rate 3,504 times faster the current state of the art, achieving high-veracity imaging of polarization dynamics in complex microstructures.

Control strategy based on SPWM switching patterns for grid connected photovoltaic inverter

NASA Astrophysics Data System (ADS)

Hassaine, L.; Mraoui, A.

2017-02-01

Generally, for lower installation of photovoltaic systems connected to the grid, pulse width modulation (PWM) is a widely used technique for controlling the voltage source inverters injects currents into the grid. The current injected must be sinusoidal with reduced harmonic distortion. In this paper, a digital implementation of a control strategy based on PWM switching patterns for an inverter for photovoltaic system connected to the grid is presented. This strategy synchronize a sinusoidal inverter output current with a grid voltage The digital implementation of the proposed PWM switching pattern when is compared with the conventional one exhibit the advantage: Simplicity, reduction of the memory requirements and power calculation for the control

Technical Study on Improvement of Endurance Capability of Limit Short-circuit Current of Charge Control SMART Meter

NASA Astrophysics Data System (ADS)

Li, W. W.; Du, Z. Z.; Yuan, R. m.; Xiong, D. Z.; Shi, E. W.; Lu, G. N.; Dai, Z. Y.; Chen, X. Q.; Jiang, Z. Y.; Lv, Y. G.

2017-10-01

Smart meter represents the development direction of energy-saving smart grid in the future. The load switch, one of the core parts of smart meter, should be of high reliability, safety and endurance capability of limit short-circuit current. For this reason, this paper discusses the quick simulation of relationship between attraction and counterforce of load switch without iteration, establishes dual response surface model of attraction and counterforce and optimizes the design scheme of load switch for charge control smart meter, thus increasing electromagnetic attraction and spring counterforce. In this way, this paper puts forward a method to improve the withstand capacity of limit short-circuit current.

Electrical studies of Ge4Sb1Te5 devices for memory applications

NASA Astrophysics Data System (ADS)

Sangeetha, B. G.; Shylashree, N.

2018-05-01

In this paper, the Ge4Sb1Te5 thin film device preparation and electrical studies for memory devices were carried out. The device was deposited using vapor-evaporation technique. RESET to SET state switching was shown using current-voltage characterization. The current-voltage characterization shows the switching between SET to RESET state and it was found that it requires a low energy for transition. Switching between amorphous to crystalline nature was studied using resistance-voltage characteristics. The endurance showed the effective use of this composition for memory device.

Field-current phase diagrams of in-plane spin transfer torque memory cells with low effective magnetization storage layers

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

San Emeterio Alvarez, L.; Lacoste, B.; Rodmacq, B.

2014-05-07

Field-current phase diagrams were measured on in-plane anisotropy Co{sub 60}Fe{sub 20}B{sub 20} magnetic tunnel junctions to obtain the spin transfer torque (STT) field-current switching window. These measurements were used to characterise junctions with varying free layer thicknesses from 2.5 down to 1.1 nm having a reduced effective demagnetizing field due to the perpendicular magnetic anisotropy at CoFeB/MgO interface. Diagrams were obtained with 100 ns current pulses, of either same or alternating polarity. When consecutive pulses have the same polarity, it is possible to realize the STT switching even for conditions having a low switching probability. This was evidenced in diagrams with consecutivemore » pulses of alternating polarity, with 100% switching obtained at 4.7 MA/cm{sup 2}, compared to the lower 3.4 MA/cm{sup 2} value for same polarity pulses. Although the low level of the current density window is higher in alternating polarity diagrams, the field window in both diagrams is the same and therefore independent of the pulse polarity sequence.« less

Bypass apparatus and method for series connected energy storage devices

DOEpatents

Rouillard, Jean; Comte, Christophe; Daigle, Dominik

2000-01-01

A bypass apparatus and method for series connected energy storage devices. Each of the energy storage devices coupled to a common series connection has an associated bypass unit connected thereto in parallel. A current bypass unit includes a sensor which is coupled in parallel with an associated energy storage device or cell and senses an energy parameter indicative of an energy state of the cell, such as cell voltage. A bypass switch is coupled in parallel with the energy storage cell and operable between a non-activated state and an activated state. The bypass switch, when in the non-activated state, is substantially non-conductive with respect to current passing through the energy storage cell and, when in the activated state, provides a bypass current path for passing current to the series connection so as to bypass the associated cell. A controller controls activation of the bypass switch in response to the voltage of the cell deviating from a pre-established voltage setpoint. The controller may be included within the bypass unit or be disposed on a control platform external to the bypass unit. The bypass switch may, when activated, establish a permanent or a temporary bypass current path.

The Effect of Hierarchical Task Representations on Task Selection in Voluntary Task Switching

ERIC Educational Resources Information Center

Weaver, Starla M.; Arrington, Catherine M.

2013-01-01

The current study explored the potential for hierarchical representations to influence action selection during voluntary task switching. Participants switched between 4 individual task elements. In Experiment 1, participants were encouraged to represent the task elements as grouped within a hierarchy based on experimental manipulations of varying…

Control and Interference in Task Switching--A Review

ERIC Educational Resources Information Center

Kiesel, Andrea; Steinhauser, Marco; Wendt, Mike; Falkenstein, Michael; Jost, Kerstin; Philipp, Andrea M.; Koch, Iring

2010-01-01

The task-switching paradigm offers enormous possibilities to study cognitive control as well as task interference. The current review provides an overview of recent research on both topics. First, we review different experimental approaches to task switching, such as comparing mixed-task blocks with single-task blocks, predictable task-switching…

Particle in cell simulation of peaking switch for breakdown evaluation

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

Umbarkar, Sachin B.; Bindu, S.; Mangalvedekar, H.A.

2014-07-01

Marx generator connected to peaking capacitor and peaking switch can generate Ultra-Wideband (UWB) radiation. A new peaking switch is designed for converting the existing nanosecond Marx generator to a UWB source. The paper explains the particle in cell (PIC) simulation for this peaking switch, using MAGIC 3D software. This peaking switch electrode is made up of copper tungsten material and is fixed inside the hermitically sealed derlin material. The switch can withstand a gas pressure up to 13.5 kg/cm{sup 2}. The lower electrode of the switch is connected to the last stage of the Marx generator. Initially Marx generator (withoutmore » peaking stage) in air; gives the output pulse with peak amplitude of 113.75 kV and pulse rise time of 25 ns. Thus, we design a new peaking switch to improve the rise time of output pulse and to pressurize this peaking switch separately (i.e. Marx and peaking switch is at different pressure). The PIC simulation gives the particle charge density, current density, E counter plot, emitted electron current, and particle energy along the axis of gap between electrodes. The charge injection and electric field dependence on ionic dissociation phenomenon are briefly analyzed using this simulation. The model is simulated with different gases (N{sub 2}, H{sub 2}, and Air) under different pressure (2 kg/cm{sup 2}, 5 kg/cm{sup 2}, 10 kg/cm{sup 2}). (author)« less

Electron-Impact-Ionization and Electron-Attachment Cross Sections of Radicals Important in Transient Gaseous Discharges.

DTIC Science & Technology

1988-02-05

for understanding the microscopic processes of electrical discharges and for designing gaseous discharge switches. High power gaseous discharge switches...half-maximum) energy resolution. The electron gun and ion extraction were of the same design of Srivastava at the Jet Propulsion Laboratory. Ions...photons. - The observed current switching can be applied to the design of discharge switches. Elec- tron transport parameters are needed for the

Evidence for thermally assisted threshold switching behavior in nanoscale phase-change memory cells

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

Le Gallo, Manuel; Athmanathan, Aravinthan; Krebs, Daniel

2016-01-14

In spite of decades of research, the details of electrical transport in phase-change materials are still debated. In particular, the so-called threshold switching phenomenon that allows the current density to increase steeply when a sufficiently high voltage is applied is still not well understood, even though there is wide consensus that threshold switching is solely of electronic origin. However, the high thermal efficiency and fast thermal dynamics associated with nanoscale phase-change memory (PCM) devices motivate us to reassess a thermally assisted threshold switching mechanism, at least in these devices. The time/temperature dependence of the threshold switching voltage and current inmore » doped Ge{sub 2}Sb{sub 2}Te{sub 5} nanoscale PCM cells was measured over 6 decades in time at temperatures ranging from 40 °C to 160 °C. We observe a nearly constant threshold switching power across this wide range of operating conditions. We also measured the transient dynamics associated with threshold switching as a function of the applied voltage. By using a field- and temperature-dependent description of the electrical transport combined with a thermal feedback, quantitative agreement with experimental data of the threshold switching dynamics was obtained using realistic physical parameters.« less

Liquid Nitrogen as Fast High Voltage Switching Medium

NASA Astrophysics Data System (ADS)

Dickens, J.; Neuber, A.; Haustein, M.; Krile, J.; Krompholz, H.

2002-12-01

Compact pulsed power systems require new switching technologies. For high voltages, liquid nitrogen seems to be a suitable switching medium, with high hold-off voltage, low dielectric constant, and no need for pressurized systems as in high pressure gas switches. The discharge behavior in liquid nitrogen, such as breakdown voltages, formative times, current rise as function of voltage, recovery, etc. are virtually unknown, however. The phenomenology of breakdown in liquid nitrogen is investigated with high speed (temporal resolution < 1 ns) electrical and optical diagnostics, in a coaxial system with 50-Ohm impedance. Discharge current and voltage are determined with transmission line type current sensors and capacitive voltage dividers. The discharge luminosity is measured with photomultiplier tubes. Preliminary results of self-breakdown investigations (gap 1 mm, breakdown voltage 44 kV, non-boiling supercooled nitrogen) show a fast (2 ns) transition from an unknown current level to several mA, a long-duration (100 ns) phase with constant current superimposed by ns-spikes, and a final fast transition to the impedance limited current during several nanoseconds. The optical measurements will be expanded toward spectroscopy and high speed photography with the aim of clarifying the overall breakdown mechanisms, including electronic initiation, bubble formation, bubble dynamics, and their role in breakdown, for different electrode geometries (different macroscopic field enhancements).

Video signal processing system uses gated current mode switches to perform high speed multiplication and digital-to-analog conversion

NASA Technical Reports Server (NTRS)

Gilliland, M. G.; Rougelot, R. S.; Schumaker, R. A.

1966-01-01

Video signal processor uses special-purpose integrated circuits with nonsaturating current mode switching to accept texture and color information from a digital computer in a visual spaceflight simulator and to combine these, for display on color CRT with analog information concerning fading.

Switching power supply

DOEpatents

Mihalka, A.M.

1984-06-05

The invention is a repratable capacitor charging, switching power supply. A ferrite transformer steps up a dc input. The transformer primary is in a full bridge configuration utilizing power MOSFETs as the bridge switches. The transformer secondary is fed into a high voltage, full wave rectifier whose output is connected directly to the energy storage capacitor. The transformer is designed to provide adequate leakage inductance to limit capacitor current. The MOSFETs are switched to the variable frequency from 20 to 50 kHz to charge a capacitor from 0.6 kV. The peak current in a transformer primary and secondary is controlled by increasing the pulse width as the capacitor charges. A digital ripple counter counts pulses and after a preselected desired number is reached an up-counter is clocked.

Fast repetition rate (FRR) flasher

DOEpatents

Kolber, Z.; Falkowski, P.

1997-02-11

A fast repetition rate (FRR) flasher is described suitable for high flash photolysis including kinetic chemical and biological analysis. The flasher includes a power supply, a discharge capacitor operably connected to be charged by the power supply, and a flash lamp for producing a series of flashes in response to discharge of the discharge capacitor. A triggering circuit operably connected to the flash lamp initially ionizes the flash lamp. A current switch is operably connected between the flash lamp and the discharge capacitor. The current switch has at least one insulated gate bipolar transistor for switching current that is operable to initiate a controllable discharge of the discharge capacitor through the flash lamp. Control means connected to the current switch for controlling the rate of discharge of the discharge capacitor thereby to effectively keep the flash lamp in an ionized state between successive discharges of the discharge capacitor. Advantageously, the control means is operable to discharge the discharge capacitor at a rate greater than 10,000 Hz and even up to a rate greater than about 250,000 Hz. 14 figs.

Characterization and snubbing of a bidirectional MCT in a resonant ac link converter

NASA Technical Reports Server (NTRS)

Lee, Tony; Elbuluk, Malik E.; Zinger, Donald S.

1993-01-01

The MOS-Controlled Thyristor (MCT) is emerging as a powerful switch that combines the better characteristics of existing power devices. A study of switching stresses on an MCT switch under zero voltage resonant switching is presented. The MCT is used as a bidirectional switch in an ac/ac pulse density modulated inverter for induction motor drive. Current and voltage spikes are observed and analyzed with variations in the timing of the switching. Different snubber circuit configurations are under investigation to minimize the effect of these transients. The results will be extended to study and test the MCT switching in a medium power (5 hp) induction motor drive.

Reactive power compensator

DOEpatents

El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.; Chen, Mingliang; Andexler, George; Huang, Tony

1992-01-01

A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation.

Reactive Power Compensator.

DOEpatents

El-Sharkawi, M.A.; Venkata, S.S.; Chen, M.; Andexler, G.; Huang, T.

1992-07-28

A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation. 26 figs.

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

NASA Astrophysics Data System (ADS)

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

2016-10-01

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

Power inverter with optical isolation

DOEpatents

Duncan, Paul G.; Schroeder, John Alan

2005-12-06

An optically isolated power electronic power conversion circuit that includes an input electrical power source, a heat pipe, a power electronic switch or plurality of interconnected power electronic switches, a mechanism for connecting the switch to the input power source, a mechanism for connecting comprising an interconnecting cable and/or bus bar or plurality of interconnecting cables and/or input bus bars, an optically isolated drive circuit connected to the switch, a heat sink assembly upon which the power electronic switch or switches is mounted, an output load, a mechanism for connecting the switch to the output load, the mechanism for connecting including an interconnecting cable and/or bus bar or plurality of interconnecting cables and/or output bus bars, at least one a fiber optic temperature sensor mounted on the heat sink assembly, at least one fiber optic current sensor mounted on the load interconnection cable and/or output bus bar, at least one fiber optic voltage sensor mounted on the load interconnection cable and/or output bus bar, at least one fiber optic current sensor mounted on the input power interconnection cable and/or input bus bar, and at least one fiber optic voltage sensor mounted on the input power interconnection cable and/or input bus bar.

Light-Gated Memristor with Integrated Logic and Memory Functions.

PubMed

Tan, Hongwei; Liu, Gang; Yang, Huali; Yi, Xiaohui; Pan, Liang; Shang, Jie; Long, Shibing; Liu, Ming; Wu, Yihong; Li, Run-Wei

2017-11-28

Memristive devices are able to store and process information, which offers several key advantages over the transistor-based architectures. However, most of the two-terminal memristive devices have fixed functions once made and cannot be reconfigured for other situations. Here, we propose and demonstrate a memristive device "memlogic" (memory logic) as a nonvolatile switch of logic operations integrated with memory function in a single light-gated memristor. Based on nonvolatile light-modulated memristive switching behavior, a single memlogic cell is able to achieve optical and electrical mixed basic Boolean logic of reconfigurable "AND", "OR", and "NOT" operations. Furthermore, the single memlogic cell is also capable of functioning as an optical adder and digital-to-analog converter. All the memlogic outputs are memristive for in situ data storage due to the nonvolatile resistive switching and persistent photoconductivity effects. Thus, as a memdevice, the memlogic has potential for not only simplifying the programmable logic circuits but also building memristive multifunctional optoelectronics.

Crude oil price dynamics: A study on effects of market expectation and strategic supply on price movements

NASA Astrophysics Data System (ADS)

Jin, Xin

Recent years have seen dramatic fluctuations in crude oil prices. This dissertation attempts to better understand price behavior. The first chapter studies the behavior of crude oil spot and futures prices. Oil prices, particularly spot and short-term futures prices, appear to have switched from I(0) to I(1) in early 2000s. To better understand this apparent change in persistence, a factor model of oil prices is proposed, where the prices are decomposed into long-term and short-term components. The change in the persistence behavior can be explained by changes in the relative volatility of the underlying components. Fitting the model to weekly data on WTI prices, the volatility of the persistent shocks increased substantially relative to other shocks. In addition, the risk premiums in futures prices have changed their signs and become more volatile. The estimated net marginal convenience yield using the model also shows changes in its behavior. These observations suggest that a dramatic fundamental change occurred in the period from 2002 to 2004 in the dynamics of the crude oil market. The second chapter explores the short-run price-inventory dynamics in the presence of different shocks. Classical competitive storage model states that inventory decision considers both current and future market condition, and thus interacts with spot and expected future spot prices. We study competitive storage holding in an equilibrium framework, focusing on the dynamic response of price and inventory to different shocks. We show that news shock generates response profile different from traditional contemporaneous shocks in price and inventory. The model is applied to world crude oil market, where the market expectation is estimated to experience a sharp change in early 2000s, together with a persisting constrained supply relative to demand. The expectation change has limited effect on crude oil spot price though. The world oil market structure has been studied extensively but no consensus has been reached on OPEC strategic behavior. In the third chapter, we are interested in the effects of supply-side market power on oil price dynamics in face of different demand shocks, and model the oil market as composed of a strategic dominant firm and several competitive fringe producers. In each period, the dominant firm makes decision while taking fringe's response into consideration. We consider two alternative pricing strategies for the dominant firm. Our results show that this dynamic strategic model improves the potential of dominant firm-competitive fringe model in fitting and explaining real world data. A regime switch after a permanent demand increase generates a time path for price that looks like the price movements in the recent years.

A graphite based STT-RAM cell with reduction in switching current

NASA Astrophysics Data System (ADS)

Varghani, Ali; Peiravi, Ali

2015-10-01

Spin Transfer Torque Random Access Memory (STT-RAM) is a serious candidate for "universal memory" because of its non-volatility, fast access time, high density, good scalability, high endurance and relatively low power dissipation. However, problems with low write speed and large write current are important existing challenges in STT-RAM design and there is a tradeoff between them and data retention time. In this study, a novel STT-RAM cell structure which uses perfect graphite based Magnetic Tunnel Junction (MTJ) is proposed. First, the cross-section of the structure is selected to be an ellipse of 45 nm and 180 nm dimensions and a six-layer graphite is used as tunnel barrier. By passing a lateral current with a short pulse width (before applying STT current and independent of it) through four middle graphene layers of the tunnel barrier, a 27% reduction in the amplitude of the switching current (for fast switching time of 2 ns) or a 58% reduction in its pulse width is achieved without any reduction in data retention time. Finally, the effect of downscaling of technology on the proposed structure is evaluated. A reduction of 31.6% and 9% in switching current is achieved for 90 and 22 nm cell width respectively by passing sufficient current (100 μA with 0.1 ns pulse width) through the tunnel barrier. Simulations are done using Object Oriented Micro Magnetic Framework (OOMMF).

Novel control system of the high-voltage IGBT-switch

NASA Astrophysics Data System (ADS)

Ponomarev, A. V.; Mamontov, Y. I.; Gusev, A. I.; Pedos, M. S.

2017-05-01

HV solid-state switch control circuit was developed and tested. The switch was made with series connection IGBT-transistors. The distinctive feature of the circuit is an ability to fine-tune the switching time of every transistor. Simultaneous switching provides balancing of the dynamic voltage at all switch elements. A separate control board switches on and off every transistor. On and off signals from the main conductor are sent to the board by current pulses of different polarity. A positive pulse provides the transistor switch-on, while a negative pulse provides their switch-off. The time interval between pulses defines the time when the switch is turned on. The minimum time when the switch is turned on equals to a few microseconds, while the maximum time is not limited. This paper shows the test results of 4 kV switch prototype. The switch was used to produce rectangular pulses of a microsecond range under resistive load. The possibility to generate the damped harmonic oscillations was also tested. On the basis of this approach, positive testing results open up a possibility to design switches under an operating voltage of tens kilovolts.

Low-temperature DC-contact piezoelectric switch operable in high magnetic fields

NASA Astrophysics Data System (ADS)

Kaltenbacher, Thomas; Caspers, Fritz; Doser, Michael; Kellerbauer, Alban; Pribyl, Wolfgang

2013-11-01

A piezoelectric single-pole single-throw (SPST) switch has been developed, since there is no satisfying commercial low-resistance, high current DC-contact RF switch available which is operable at 4.2 K and in a high magnetic field of at least 0.5 T. This piezoelectric switch shows very low insertion loss of less than -0.1 dB within a bandwidth of 100 MHz when operated at 4.2 K. The switch could also be used to mechanically disconnect and connect electrodes or electrical circuits from one another.

Multi-gap high impedance plasma opening switch

DOEpatents

Mason, R.J.

1996-10-22

A high impedance plasma opening switch having an anode and a cathode and at least one additional electrode placed between the anode and cathode is disclosed. The presence of the additional electrodes leads to the creation of additional plasma gaps which are in series, increasing the net impedance of the switch. An equivalent effect can be obtained by using two or more conventional plasma switches with their plasma gaps wired in series. Higher impedance switches can provide high current and voltage to higher impedance loads such as plasma radiation sources. 12 figs.

A novel high temperature superconducting magnetic flux pump for MRI magnets

NASA Astrophysics Data System (ADS)

Bai, Zhiming; Yan, Guo; Wu, Chunli; Ding, Shufang; Chen, Chuan

2010-10-01

This paper presents a kind of minitype magnetic flux pump made of high temperature superconductor. This kind of novel high temperature superconducting (HTS) flux pump has not any mechanical revolving parts or thermal switches. The excitation current of copper coils in magnetic pole system is controlled by a singlechip. The structure design and operational principle have been described. The operating performance of the new model magnetic flux pump has been preliminarily tested. The experiments show that the maximum pumping current is approximately 200 A for Bi2223 flux pump and 80 A for MgB 2 flux pump operating at 20 K. By comparison, it is discovered that the operating temperature range is wider, the ripple is smaller and the pumping frequency is higher in Bi2223 flux pump than those in MgB 2 flux pump. These results indicate that the newly developed Bi2223 magnetic flux pump may efficiently compensate the magnetic field decay in HTS magnet and make the magnet operate in persistent current mode, this point is significant to the magnetic resonance imaging (MRI) magnets. This new flux pump is under construction presently. It is expected that the Bi2223 flux pump would be applied to the superconducting MRI magnets by further optimizing structure and improving working process.

Pulsed Power Supply Based on Magnetic Energy Storage for Non-Destructive High Field Magnets

NASA Astrophysics Data System (ADS)

Aubert, G.; Defoug, S.; Joss, W.; Sala, P.; Dubois, M.; Kuchinsk, V.

2004-11-01

The first test results of a recently built pulsed power supply based on magnetic energy storage will be described. The system consists of the 16 kV shock alternator with a short-circuit power of 3600 MVA of the VOLTA Testing Center of the Schneider Electric SA company, a step-down transformer with a ratio of 1/24, a three-phase diode bridge designed for a current rising exponentially to 120 kA, and a big, 10 ton, heavy, 10 mH aluminum storage coil. The system is designed to store 72 MJ, normal operation will be at 50 MJ, and will work with voltages up to 20 kV. A transfer of 20% of the stored energy into the high field coil should be possible. Special making switches and interrupters have been developed to switch the high currents in a very short time. For safety and redundancy two independent monitoring systems control the energy transfer. A sequencing control system operates the switches on the ac side and protective switches on the dc side, a specially developed real-time control-monitoring system checks several currents and voltages and commands the dc circuit breakers and making switches.

Combined EEG-fNIRS decoding of motor attempt and imagery for brain switch control: an offline study in patients with tetraplegia.

PubMed

Blokland, Yvonne; Spyrou, Loukianos; Thijssen, Dick; Eijsvogels, Thijs; Colier, Willy; Floor-Westerdijk, Marianne; Vlek, Rutger; Bruhn, Jorgen; Farquhar, Jason

2014-03-01

Combining electrophysiological and hemodynamic features is a novel approach for improving current performance of brain switches based on sensorimotor rhythms (SMR). This study was conducted with a dual purpose: to test the feasibility of using a combined electroencephalogram/functional near-infrared spectroscopy (EEG-fNIRS) SMR-based brain switch in patients with tetraplegia, and to examine the performance difference between motor imagery and motor attempt for this user group. A general improvement was found when using both EEG and fNIRS features for classification as compared to using the single-modality EEG classifier, with average classification rates of 79% for attempted movement and 70% for imagined movement. For the control group, rates of 87% and 79% were obtained, respectively, where the "attempted movement" condition was replaced with "actual movement." A combined EEG-fNIRS system might be especially beneficial for users who lack sufficient control of current EEG-based brain switches. The average classification performance in the patient group for attempted movement was significantly higher than for imagined movement using the EEG-only as well as the combined classifier, arguing for the case of a paradigm shift in current brain switch research.

Integrated Joule switches for the control of current dynamics in parallel superconducting strips

NASA Astrophysics Data System (ADS)

Casaburi, A.; Heath, R. M.; Cristiano, R.; Ejrnaes, M.; Zen, N.; Ohkubo, M.; Hadfield, R. H.

2018-06-01

Understanding and harnessing the physics of the dynamic current distribution in parallel superconducting strips holds the key to creating next generation sensors for single molecule and single photon detection. Non-uniformity in the current distribution in parallel superconducting strips leads to low detection efficiency and unstable operation, preventing the scale up to large area sensors. Recent studies indicate that non-uniform current distributions occurring in parallel strips can be understood and modeled in the framework of the generalized London model. Here we build on this important physical insight, investigating an innovative design with integrated superconducting-to-resistive Joule switches to break the superconducting loops between the strips and thus control the current dynamics. Employing precision low temperature nano-optical techniques, we map the uniformity of the current distribution before- and after the resistive strip switching event, confirming the effectiveness of our design. These results provide important insights for the development of next generation large area superconducting strip-based sensors.

Ames Lab 101: Ultrafast Magnetic Switching

ScienceCinema

Wang; Jigang

2018-01-01

Ames Laboratory physicists have found a new way to switch magnetism that is at least 1000 times faster than currently used in magnetic memory technologies. Magnetic switching is used to encode information in hard drives, magnetic random access memory and other computing devices. The discovery potentially opens the door to terahertz and faster memory speeds.

Cognitive Flexibility in ASD; Task Switching with Emotional Faces

ERIC Educational Resources Information Center

de Vries, Marieke; Geurts, Hilde M.

2012-01-01

Children with autism spectrum disorders (ASDs) show daily cognitive flexibility deficits, but laboratory data are unconvincing. The current study aimed to bridge this gap. Thirty-one children with ASD (8-12 years) and 31 age- and IQ-matched typically developing children performed a gender emotion switch task. Unannounced switches and complex…

Cognates Facilitate Switches and Then Confusion: Contrasting Effects of Cascade versus Feedback on Language Selection

ERIC Educational Resources Information Center

Li, Chuchu; Gollan, Tamar H.

2018-01-01

The current study investigated the hypothesis that cognates (i.e., translation equivalents that overlap in form, e.g., "lemon" is "limón" in Spanish) facilitate language switches. Spanish-English bilinguals were cued to switch languages while repeatedly naming pictures with cognate versus noncognate names in separate…

Neuropsychiatric adverse events after switching from an antiretroviral regimen containing efavirenz without tenofovir to an efavirenz regimen containing tenofovir: a report of nine cases.

PubMed

Allavena, Clotilde; Le Moal, Gwenael; Michau, Christophe; Chiffoleau, Anne; Raffi, François

2006-01-01

The combination of tenofovir (TDF) and efavirenz (EFV) has not been associated with any pharmakokinetic interaction or with enhancement of neuropsychiatric disturbances. We report nine cases of neuropsychiatric intolerance occurring early after a switch from an antiretroviral regimen without TDF to an EFV and TDF-containing regimen. Nine HIV-1-infected patients were treated with an EFV-containing regimen for a median duration of 31 months without any EFV-related central nervous system (CNS) effects. They were switched to an EFV-TDF-containing regimen because of lipodystrophy (n=2) and/or the wish to simplify to a once-daily regimen (n=9). Moderate to severe neuropsychiatric events occurred immediately (<48 hours) after TDF initiation in five patients and 2 weeks to 24 months after the switch in the remaining four patients. Treatment modifications occurred in six patients (switch to EFV-nevirapine [n=3], TDF-zidovudine [n=2] or treatment discontinuation [n=1]), leading to a marked improvement of CNS intolerance. Treatment remained unchanged in three patients; two patients experienced chronic persistent sleeping disorders and one patient underwent a spontaneous improvement of symptoms within 2 weeks. EFV plasma concentrations, which were available in two patients before the switch and in four patients after the switch, remained in the therapeutic range. Although the exact mechanism of these symptoms remains hypothetical, neuropsychiatric disorders could be either a consequence of an unexplained interaction between EFV and TDF or an infrequent TDF-related side effect. The incidence of these side effects needs to be evaluated in large databases or pharmacokinetic studies.

Overnight switching from oxcarbazepine to eslicarbazepine acetate: an observational study.

PubMed

Schmid, E; Kuchukhidze, G; Kirschner, M; Leitinger, M; Höfler, J; Rohracher, A; Kalss, G; Wendling, A-S; Steinhoff, B J; Trinka, E

2017-04-01

There are clinical situations where it might be appropriate to switch patients from immediate-release oxcarbazepine (OXC) to eslicarbazepine acetate (ESL). We investigated the effects of transitioning patients overnight from OXC to ESL. A retrospective, single-center study was conducted in which patients with drug-resistant focal epilepsy on a stable dose of immediate-release OXC for at least 4 weeks were switched overnight to ESL. Patients were switched because they experienced persistent seizures with OXC but were unable to tolerate increased OXC dosing due to adverse events. Tolerability was assessed using the Adverse Events Profile (AEP), quality of life was assessed using the Quality of Life in Epilepsy Inventory 10 (QOLIE-10), and alertness was assessed as reaction time using a subtest of the Test Battery for Attention Performance version 2.3. Assessments were performed immediately prior to and 5 days after switching from OXC to ESL (days 0 and 5, respectively). The analysis included 21 patients (12 women, 9 men; mean age 36 years). After switching from OXC to ESL, there were significant improvements in mean scores for AEP (P<.001), QOLIE-10 (P=.001), and alertness (P<.05). Adverse Events Profile total scores improved for 21/21 (100.0%) patients, QOLIE-10 total scores improved for 17/21 (81.0%) patients, and alertness scores improved for 16/21 (76.2%) patients. In this short-term, single-center study, an overnight switch from twice-daily OXC to once-daily ESL in patients with drug-resistant focal epilepsies resulted in improvements in side effects, quality of life, and alertness. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Experimental Study on Short Circuit Phenomena in Air Switch of Distribution Line due to Sparkover between Different Poles on Which One Surge Arrester of the Three Ones is Omitted

NASA Astrophysics Data System (ADS)

Sato, Tomoyuki; Uemura, Satoshi; Asakawa, Akira; Yokoyama, Shigeru; Honda, Hideki; Horikoshi, Kazuhiro

In this study, we experimentally examined the possibility of the internal short circuit of an air switch due to the sparkover between different poles under the condition that no surge arrester exists in neighboring poles and one of three surge arresters is omitted at the pole with an air switch. Experiments at Shiobara Testing Yard and Akagi Testing Center of CRIEPI clarified the following. Fault current may flow via the grounding point of a pole with an air switch and that of the next pole on a different phase from grounded phase of the pole with an air switch. If the low-voltage wire, overhead ground wire or communication wire forms a short circuit between them, ultimately the air switch may burn out. Moreover Fault current continues even if the length of the short-circuit between different poles is increased. Although the increase of the short-circuit length results in the increase of wire impedance, the amount of increase is still small compared with source impedance.

A high-current rail-type gas switch with preionization by an additional corona discharge

NASA Astrophysics Data System (ADS)

Antipov, E. I.; Belozerov, O. S.; Krastelev, E. G.

2016-12-01

The characteristics of a high-current rail-type gas switch with preionization of the gas (air) in a spark gap by an additional corona discharge are investigated. The experiments were performed in a voltage range of 10-45 kV using a two-electrode switch consisting of two cylindrical electrodes with a diameter of 22 mm and a length of 100 mm and a set of laterally located corona-discharge needles. The requirements for the position and size of the needles are defined for which a corona discharge is ignited before a breakdown of the main gap and does not change to a sparking form, and the entire length of the rail electrodes is efficiently used. The fulfillment of these requirements ensures stable operation of the switch with a small variation of the pulse breakdown voltage, which is not more than 1% for a fixed voltage-pulse rise time in the range from 150 ns to 3.5 μs. A short delay time of the switch breakdown makes it possible to control the two-electrode switch by an overvoltage pulse of nanosecond duration.

Circulating current battery heater

DOEpatents

Ashtiani, Cyrus N.; Stuart, Thomas A.

2001-01-01

A circuit for heating energy storage devices such as batteries is provided. The circuit includes a pair of switches connected in a half-bridge configuration. Unidirectional current conduction devices are connected in parallel with each switch. A series resonant element for storing energy is connected from the energy storage device to the pair of switches. An energy storage device for intermediate storage of energy is connected in a loop with the series resonant element and one of the switches. The energy storage device which is being heated is connected in a loop with the series resonant element and the other switch. Energy from the heated energy storage device is transferred to the switched network and then recirculated back to the battery. The flow of energy through the battery causes internal power dissipation due to electrical to chemical conversion inefficiencies. The dissipated power causes the internal temperature of the battery to increase. Higher internal temperatures expand the cold temperature operating range and energy capacity utilization of the battery. As disclosed, either fixed frequency or variable frequency modulation schemes may be used to control the network.

A Current Source Method For t(sub q) Measurement of Fast Switching Thyristors

NASA Technical Reports Server (NTRS)

Niedra, Janis M.

2006-01-01

A current source driven circuit has been constructed to measure the turn-off time (t(sub q)) of fast-switching SiC thyristors. This circuit operates from a single power supply and a dual channel pulse generator to provide adjustment of forward current, magnitude and duration of reverse applied voltage, and rate of rise of reapplied forward voltage. Values of t(sub q) down to 100 ns can be resolved.

Electric field-triggered metal-insulator transition resistive switching of bilayered multiphasic VOx

NASA Astrophysics Data System (ADS)

Won, Seokjae; Lee, Sang Yeon; Hwang, Jungyeon; Park, Jucheol; Seo, Hyungtak

2018-01-01

Electric field-triggered Mott transition of VO2 for next-generation memory devices with sharp and fast resistance-switching response is considered to be ideal but the formation of single-phase VO2 by common deposition techniques is very challenging. Here, VOx films with a VO2-dominant phase for a Mott transition-based metal-insulator transition (MIT) switching device were successfully fabricated by the combined process of RF magnetron sputtering of V metal and subsequent O2 annealing to form. By performing various material characterizations, including scanning transmission electron microscopy-electron energy loss spectroscopy, the film is determined to have a bilayer structure consisting of a VO2-rich bottom layer acting as the Mott transition switching layer and a V2O5/V2O3 mixed top layer acting as a control layer that suppresses any stray leakage current and improves cyclic performance. This bilayer structure enables excellent electric field-triggered Mott transition-based resistive switching of Pt-VOx-Pt metal-insulator-metal devices with a set/reset current ratio reaching 200, set/reset voltage of less than 2.5 V, and very stable DC cyclic switching upto 120 cycles with a great set/reset current and voltage distribution less than 5% of standard deviation at room temperature, which are specifications applicable for neuromorphic or memory device applications. [Figure not available: see fulltext.

[Indicators of statin use as a model for qualitative evaluation of chronic disease management in the Local Health Unit Roma B].

PubMed

Ciaralli, Fabrizio; Summaria, Francesco; Mustilli, Marina; Vasselli, Loredana; D'Urso, Antonio; Degrassi, Flori

2010-01-01

In chronic diseases the adherence and persistence to therapeutic treatments are often lower than guidelines said. This leads to a worse therapeutic effect of the treatments and to a misuse in healthcare costs. Our study evaluates the impact of a pharmacoutilization analysis model, derived from the administrative database of the Local Health Unit Roma B. In particularly we calculate some indicators of adherence, persistence, occasional treatment and switch in patients on statins secondary prevention treatment (patients discharged from Hospital with Acute Myocardial Infarction diagnosis). The model that we developed would be successfully used in the cost-effective analysis of other drugs.

High Field Side MHD Activity During Local Helicity Injection

NASA Astrophysics Data System (ADS)

Pachicano, J. L.; Bongard, M. W.; Fonck, R. J.; Perry, J. M.; Reusch, J. A.; Richner, N. J.

2017-10-01

MHD is an essential part of understanding the mechanism for local helicity injection (LHI) current drive. The new high field side (HFS) LHI system on the Pegasus ST permits new tests of recent NIMROD simulations. In that model, LHI current streams in the plasma edge undergo large-scale reconnection events, leading to current drive. This produces bursty n = 1 activity around 30 kHz on low field side (LFS) Mirnov coils, consistent with experiment. The simulations also feature coherent injector streams winding down the center column. Improvements to the core high-resolution poloidal Mirnov array with Cat7A Ethernet cabling and differentially driven signal processing eliminated EMI-driven switching noise, enabling detailed spectral analysis. Preliminary results from the recovered HFS poloidal Mirnov coils suggest n = 1 activity is present at the top of the vessel core, but does not persist down the centerstack. HFS LHI experiments can exhibit an operating regime where the high amplitude MHD is abruptly reduced by more than an order of magnitude on LFS Mirnov coils, leading to higher plasma current and improved particle confinement. This reduction is not observed on the HFS midplane magnetics. Instead, they show broadband turbulence-like magnetic features with near consistent amplitude in a frequency range of 90-200 kHz. Work supported by US DOE Grant DE-FG02-96ER54375.

Is an epigenetic switch the key to persistent extinction?

PubMed Central

Stafford, James M.; Lattal, K. Matthew

2011-01-01

Many studies of learning have demonstrated that conditioned behavior can be eliminated when previously established relations between stimuli are severed. This extinction process has been extremely important for the development of learning theories and, more recently, for delineating the neurobiological mechanisms that underlie memory. A key finding from behavioral studies of extinction is that extinction eliminates behavior without eliminating the original memory; extinguished behavior often returns with time or with a return to the context in which the original learning occurred. This persistence of the original memory after extinction creates a challenge for clinical applications that use extinction as part of a treatment intervention. Consequently, a goal of recent neurobiological research on extinction is to identify potential pharmacological targets that may result in persistent extinction. Drugs that promote epigenetic changes are particularly promising because they can result in a long-term molecular signal that, combined with the appropriate behavioral treatment, can cause persistent changes in behavior induced by extinction. We will review evidence demonstrating extinction enhancements by drugs that target epigenetic mechanisms and will describe some of the challenges that epigenetic approaches face in promoting persistent suppression of memories. PMID:21536141

Cycling firing method for bypass operation of bridge converters

DOEpatents

Zabar, Zivan

1982-01-01

The bridge converter comprises a number of switching elements and an electronic logic system which regulated the electric power levels by controlling the firing, i.e., the initiation of the conduction period of the switching elements. Cyclic firing of said elements allows the direct current to bypass the alternating current system with high power factor and negligible losses.

Application Study of a High Temperature Superconducting Fault Current Limiter for Electric Power System

NASA Astrophysics Data System (ADS)

Naito, Yuji; Shimizu, Iwao; Yamaguchi, Iwao; Kaiho, Katsuyuki; Yanabu, Satoru

Using high temperature superconductor, a Superconducting Fault Current Limiter (SFCL) was made and tested. Superconductor and vacuum interrupter as commutation switch are connected in parallel with bypass coil. When a fault occurs and the excessive current flows, superconductor is first quenched and the current is transferred to bypass coil because on voltage drop of superconductor. At the same time, since magnetic field is generated by current which flows in bypass coil, commutation switch is immediately driven by electromagnetic repulsion plate connected to driving rod of vacuum interrupter, and superconductor is separated from this circuit. Using the testing model, we could separate the superconductor from a circuit due to movement of vacuum interrupter within half-cycle current and transfer all current to bypass coil. Since operation of a commutation switch is included in current limiting operation of this testing model, it is one of helpful circuit of development of SFCL in the future. Moreover, since it can make the consumed energy of superconductor small during fault state due to realization of high-speed switch with simple composition, the burden of superconductor is reduced compared with conventional resistive type SFCL and it is considered that the flexibility of a SFCL design increases. Cooperation with a circuit breaker was also considered, the trial calculation of a parameter and energy of operation is conducted and discussion in the case of installing the SFCL to electric power system is made.

Capacitance measuring device

DOEpatents

Andrews, W.H. Jr.

1984-08-01

A capacitance measuring circuit is provided in which an unknown capacitance is measured by comparing the charge stored in the unknown capacitor with that stored in a known capacitance. Equal and opposite voltages are repetitively simultaneously switched onto the capacitors through an electronic switch driven by a pulse generator to charge the capacitors during the ''on'' portion of the cycle. The stored charge is compared by summing discharge currents flowing through matched resistors at the input of a current sensor during the ''off'' portion of the switching cycle. The net current measured is thus proportional to the difference in value of the two capacitances. The circuit is capable of providing much needed accuracy and stability to a great variety of capacitance-based measurement devices at a relatively low cost.

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.

Modulated spin orbit torque in a Pt/Co/Pt/YIG multilayer by nonequilibrium proximity effect

NASA Astrophysics Data System (ADS)

Liu, Q. B.; Meng, K. K.; Cai, Y. Z.; Qian, X. H.; Wu, Y. C.; Zheng, S. Q.; Jiang, Y.

2018-01-01

We have compared the spin orbit torque (SOT) induced magnetization switching in Pt/Co/Pt/Y3Fe5O12 (YIG) and Pt/Co/Pt/SiO2 multilayers. The critical switching current in Pt/Co/Pt/YIG is almost half of that in Pt/Co/Pt/SiO2. Through harmonic measurements, we demonstrated the enhancement of the effective spin Hall angle in Pt/Co/Pt/YIG. The increased efficiency of SOT is ascribed to the nonequilibrium proximity effect at the Pt/YIG interface, which suppresses the spin current reflection and enhances the effective spin accumulation at the Co/Pt interface. Our method can effectively reduce the switching current density and provide another way to modulate SOT.

Zinc-chlorine battery plant system and method

DOEpatents

Whittlesey, Curtis C.; Mashikian, Matthew S.

1981-01-01

A zinc-chlorine battery plant system and method of redirecting the electrical current around a failed battery module. The battery plant includes a power conditioning unit, a plurality of battery modules connected electrically in series to form battery strings, a plurality of battery strings electrically connected in parallel to the power conditioning unit, and a bypass switch for each battery module in the battery plant. The bypass switch includes a normally open main contact across the power terminals of the battery module, and a set of normally closed auxiliary contacts for controlling the supply of reactants electrochemically transformed in the cells of the battery module. Upon the determination of a failure condition, the bypass switch for the failed battery module is energized to close the main contact and open the auxiliary contacts. Within a short time, the electrical current through the battery module will substantially decrease due to the cutoff of the supply of reactants, and the electrical current flow through the battery string will be redirected through the main contact of the bypass switch.

An Improved Model Predictive Current Controller of Switched Reluctance Machines Using Time-Multiplexed Current Sensor

PubMed Central

Li, Bingchu; Ling, Xiao; Huang, Yixiang; Gong, Liang; Liu, Chengliang

2017-01-01

This paper presents a fixed-switching-frequency model predictive current controller using multiplexed current sensor for switched reluctance machine (SRM) drives. The converter was modified to distinguish currents from simultaneously excited phases during the sampling period. The only current sensor installed in the converter was time division multiplexing for phase current sampling. During the commutation stage, the control steps of adjacent phases were shifted so that sampling time was staggered. The maximum and minimum duty ratio of pulse width modulation (PWM) was limited to keep enough sampling time for analog-to-digital (A/D) conversion. Current sensor multiplexing was realized without complex adjustment of either driver circuit nor control algorithms, while it helps to reduce the cost and errors introduced in current sampling due to inconsistency between sensors. The proposed controller is validated by both simulation and experimental results with a 1.5 kW three-phase 12/8 SRM. Satisfied current sampling is received with little difference compared with independent phase current sensors for each phase. The proposed controller tracks the reference current profile as accurately as the model predictive current controller with independent phase current sensors, while having minor tracking errors compared with a hysteresis current controller. PMID:28513554

Comparison of patients undergoing switching versus augmentation of antipsychotic medications during treatment for schizophrenia.

PubMed

Ascher-Svanum, Haya; Brnabic, Alan Jm; Lawson, Anthony H; Kinon, Bruce J; Stauffer, Virginia L; Feldman, Peter D; Kelin, Katarina

2012-01-01

It is often difficult to determine whether a patient may best benefit by augmenting their current medication or switching them to another. This post-hoc analysis compares patients' clinical and functional profiles at the time their antipsychotic medications were either switched or augmented. Adult outpatients receiving oral antipsychotic treatment for schizophrenia were assessed during a 12-month international observational study. Clinical and functional measures were assessed at the time of first treatment switch/augmentation (0-14 days prior) and compared between Switched and Augmented patient groups. Due to low numbers of patients providing such data, interpretations are based on effect sizes. Data at the time of change were available for 87 patients: 53 Switched and 34 Augmented. Inadequate response was the primary reason for treatment change in both groups, whereas lack of adherence was more prevalent in the Switched group (26.4% vs 8.8%). Changes in clinical severity from study initiation to medication change were similar, as indicated by Clinical Global Impressions-Severity scores. However, physical and mental component scores of the 12-item Short-Form Health Survey improved in the Augmented group, but worsened in the Switched group. These findings suggest that the patient's worsening or lack of meaningful improvement prompts clinicians to switch antipsychotic medications, whereas when patients show some improvement, clinicians may be more likely to try bolstering the improvements through augmentation. Current findings are consistent with physicians' stated reasons for switching versus augmenting antipsychotics in the treatment of schizophrenia. Confirmation of these findings requires further research.

Evidence for phase change memory behavior in In2(SexTe1-x)3 thin films

NASA Astrophysics Data System (ADS)

Matheswaran, P.; Sathyamoorthy, R.; Asokan, K.

2012-08-01

Crystalline In2(Se0.5Te0.5)3 thin films are prepared by thermal evaporation and subsequently annealed at 300°C in Ar atmosphere. SEM image of the crystalline sample shows spherical nature of constituents, distributed uniformly throughout the surface. Island structure of the surface is clearly visible after switching. Elemental composition of the sample remains unchanged even after switching. Temperature dependent I-V analysis shows stoichiometric phase change at 80°C [from In2(Se0.5Te0.5)3 to In2Te3 and In2Se3 phase], where current switches three orders of magnitude higher than that in lower temperature. Further rise in temperature results increase in current only after switching, where threshold voltage remains constant.

Electrically-controlled nonlinear switching and multi-level storage characteristics in WOx film-based memory cells

NASA Astrophysics Data System (ADS)

Duan, W. J.; Wang, J. B.; Zhong, X. L.

2018-05-01

Resistive switching random access memory (RRAM) is considered as a promising candidate for the next generation memory due to its scalability, high integration density and non-volatile storage characteristics. Here, the multiple electrical characteristics in Pt/WOx/Pt cells are investigated. Both of the nonlinear switching and multi-level storage can be achieved by setting different compliance current in the same cell. The correlations among the current, time and temperature are analyzed by using contours and 3D surfaces. The switching mechanism is explained in terms of the formation and rupture of conductive filament which is related to oxygen vacancies. The experimental results show that the non-stoichiometric WOx film-based device offers a feasible way for the applications of oxide-based RRAMs.

Enhanced bipolar resistive switching behavior in polar Cr-doped barium titanate thin films without electro-forming process

NASA Astrophysics Data System (ADS)

Thakre, Atul; Kumar, Ashok

2017-12-01

An enhanced, repeatable and robust resistive switching phenomenon was observed in Cr substituted BaTiO3 polar ferroelectric thin films; fabricated and deposited by the sol-gel approach and spin coating technique, respectively. An enhanced bistable bipolar resistive switching (BRS) phenomenon without electro-forming process, low switching voltage (˜ 2 V) and moderate retention characteristics of 104 s along with a high Roff/Ron resistance ratio ˜103 was achieved. The current conduction analysis showed that the space charge limited conduction (SCLC) and Schottky emission conduction dominate in the high voltage range, while thermally active charge carriers (ohmic) in the lower voltage range. The impedance spectroscopy study indicates the formation of current conducting path and rupturing of oxygen vacancies during SET and RESET process.

Schottky Emission Distance and Barrier Height Properties of Bipolar Switching Gd:SiOx RRAM Devices under Different Oxygen Concentration Environments

PubMed Central

Chen, Kai-Huang; Tsai, Tsung-Ming; Cheng, Chien-Min; Huang, Shou-Jen; Chang, Kuan-Chang; Liang, Shu-Ping; Young, Tai-Fa

2017-01-01

In this study, the hopping conduction distance and bipolar switching properties of the Gd:SiOx thin film by (radio frequency, rf) rf sputtering technology for applications in RRAM devices were calculated and investigated. To discuss and verify the electrical switching mechanism in various different constant compliance currents, the typical current versus applied voltage (I-V) characteristics of gadolinium oxide RRAM devices was transferred and fitted. Finally, the transmission electrons’ switching behavior between the TiN bottom electrode and Pt top electrode in the initial metallic filament forming process of the gadolinium oxide thin film RRAM devices for low resistance state (LRS)/high resistance state (HRS) was described and explained in a simulated physical diagram model. PMID:29283368

Conductance Switching Phenomena and H-Like Aggregates in Squarylium-Dye Langmuir-Blodgett Films

NASA Astrophysics Data System (ADS)

Kushida, Masahito; Inomata, Hisao; Tanaka, Yuichiro; Harada, Kieko; Saito, Kyoichi; Sugita, Kazuyuki

2002-03-01

The current-voltage characteristics of sandwich devices with the structure of top gold electrode/squarylium-dye Langmuir-Blodgett (SQ LB) films/bottom aluminum electrode indicated four kinds of conductivity depending on the evaporation conditions of the top gold electrode. The current densities of two, which showed conductance switching, of the four samples were 30-40 μA/cm2 and 20-30 mA/cm2 in the ON state. In the former case, the dependence of conductance switching voltage on the number of SQ LB films and ultraviolet-visible absorption spectra were studied. The results revealed that conductance switching phenomena were induced at the interface between the top gold electrode and SQ LB films, and caused by the presence of H-like aggregates in SQ LB films.

Design of high-voltage, high-power, solid state remote power controllers for aerospace applications

NASA Technical Reports Server (NTRS)

Sturman, J. C.

1985-01-01

Two general types of remote power controllers (RPC's), which combine the functions of a circuit breaker and a switch, were developed for use in dc aerospace systems. Power-switching devices used in the designs are the gate-turnoff thyristor (GTO) and MOSFET. The RPC's can switch dc voltages to 1200 V and currents to 1000 A. Seven different units were constructed and subjected to laboratory and thermal vacuum testing. Two of these were dual units that switch both positive and negative voltages simultaneously. The RPC's using MOSFET's have slow turnon and turnoff times which limit surge currents and voltage spiking from high di/dt. The GTO's have much faster transition times. All RPC's have programmable overload tripout proportional to I sq T and microsecond tripout for large overloads.

Design of high-voltage, high-power, solid state remote power controllers for aerospace applications

NASA Astrophysics Data System (ADS)

Sturman, J. C.

1985-05-01

Two general types of remote power controllers (RPC's), which combine the functions of a circuit breaker and a switch, were developed for use in dc aerospace systems. Power-switching devices used in the designs are the gate-turnoff thyristor (GTO) and MOSFET. The RPC's can switch dc voltages to 1200 V and currents to 1000 A. Seven different units were constructed and subjected to laboratory and thermal vacuum testing. Two of these were dual units that switch both positive and negative voltages simultaneously. The RPC's using MOSFET's have slow turnon and turnoff times which limit surge currents and voltage spiking from high di/dt. The GTO's have much faster transition times. All RPC's have programmable overload tripout proportional to I sq T and microsecond tripout for large overloads.

Task Inhibition and Response Inhibition in Older vs. Younger Adults: A Diffusion Model Analysis

PubMed Central

Schuch, Stefanie

2016-01-01

Differences in inhibitory ability between older (64–79 years, N = 24) and younger adults (18–26 years, N = 24) were investigated using a diffusion model analysis. Participants performed a task-switching paradigm that allows assessing n−2 task repetition costs, reflecting inhibitory control on the level of tasks, as well as n−1 response-repetition costs, reflecting inhibitory control on the level of responses. N−2 task repetition costs were of similar size in both age groups. Diffusion model analysis revealed that for both younger and older adults, drift rate parameters were smaller in the inhibition condition relative to the control condition, consistent with the idea that persisting task inhibition slows down response selection. Moreover, there was preliminary evidence for task inhibition effects in threshold separation and non-decision time in the older, but not the younger adults, suggesting that older adults might apply different strategies when dealing with persisting task inhibition. N−1 response-repetition costs in mean RT were larger in older than younger adults, but in mean error rates tended to be larger in younger than older adults. Diffusion-model analysis revealed longer non-decision times in response repetitions than response switches in both age groups, consistent with the idea that motor processes take longer in response repetitions than response switches due to persisting response inhibition of a previously executed response. The data also revealed age-related differences in overall performance: Older adults responded more slowly and more accurately than young adults, which was reflected by a higher threshold separation parameter in diffusion model analysis. Moreover, older adults showed larger non-decision times and higher variability in non-decision time than young adults, possibly reflecting slower and more variable motor processes. In contrast, overall drift rate did not differ between older and younger adults. Taken together, diffusion model analysis revealed differences in overall performance between the age groups, as well as preliminary evidence for age differences in dealing with task inhibition, but no evidence for an inhibitory deficit in older age. PMID:27895599

Quantum coherent π-electron rotations in a non-planar chiral molecule induced by using a linearly polarized UV laser pulse

NASA Astrophysics Data System (ADS)

Mineo, Hirobumi; Fujimura, Yuichi

2015-06-01

We propose an ultrafast quantum switching method of π-electron rotations, which are switched among four rotational patterns in a nonplanar chiral aromatic molecule (P)-2,2’- biphenol and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses. Coherent π-electron dynamics are generated by applying the linearly polarized UV pulse laser to create a pair of coherent quasidegenerated excited states. We also plot the time-dependent π-electron ring current, and discussed ring current transfer between two aromatic rings.

Explosive-driven, high speed, arcless switch

DOEpatents

Skogmo, P.J.; Tucker, T.J.

1986-05-02

An explosive-actuated, fast-acting arcless switch contains a highly conductive foil to carry high currents positioned adjacent a dielectric surface within a casing. At one side of the foil opposite the dielectric surface is an explosive which, when detonated, drives the conductive foil against the dielectric surface. A pattern of grooves in the dielectric surface ruptures the foil to establish a rupture path having a pattern corresponding to the pattern of the grooves. The impedance of the ruptured foil is greater than that of the original foil to divert high current to a load. Planar and cylindrical embodiments of the switch are disclosed.

Fractal model of polarization switching kinetics in ferroelectrics under nonequilibrium conditions of electron irradiation

NASA Astrophysics Data System (ADS)

Maslovskaya, A. G.; Barabash, T. K.

2018-03-01

The paper presents the results of the fractal and multifractal analysis of polarization switching current in ferroelectrics under electron irradiation, which allows statistical memory effects to be estimated at dynamics of domain structure. The mathematical model of formation of electron beam-induced polarization current in ferroelectrics was suggested taking into account the fractal nature of domain structure dynamics. In order to realize the model the computational scheme was constructed using the numerical solution approximation of fractional differential equation. Evidences of electron beam-induced polarization switching process in ferroelectrics were specified at a variation of control model parameters.

Explosive-driven, high speed, arcless switch

DOEpatents

Skogmo, Phillip J.; Tucker, Tillman J.

1987-01-01

An explosive-actuated, fast-acting arcless switch contains a highly conductive foil to carry high currents positioned adjacent a dielectric surface within a casing. At one side of the foil opposite the dielectric surface is an explosive which, when detonated, drives the conductive foil against the dielectric surface. A pattern of grooves in the dielectric surface ruptures the foil to establish a rupture path having a pattern corresponding to the pattern of the grooves. The impedance of the ruptured foil is greater than that of the original foil to divert high current to a load. Planar and cylindrical embodiments of the switch are disclosed.

A solid-state dielectric elastomer switch for soft logic

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

Chau, Nixon; Slipher, Geoffrey A., E-mail: geoffrey.a.slipher.civ@mail.mil; Mrozek, Randy A.

In this paper, we describe a stretchable solid-state electronic switching material that operates at high voltage potentials, as well as a switch material benchmarking technique that utilizes a modular dielectric elastomer (artificial muscle) ring oscillator. The solid-state switching material was integrated into our oscillator, which self-started after 16 s and performed 5 oscillations at a frequency of 1.05 Hz with 3.25 kV DC input. Our materials-by-design approach for the nickel filled polydimethylsiloxane based switch has resulted in significant improvements over previous carbon grease-based switches in four key areas, namely, sharpness of switching behavior upon applied stretch, magnitude of electrical resistance change, ease ofmore » manufacture, and production rate. Switch lifetime was demonstrated to be in the range of tens to hundreds of cycles with the current process. An interesting and potentially useful strain-based switching hysteresis behavior is also presented.« less

Enhancement of resistive switching properties in Al2O3 bilayer-based atomic switches: multilevel resistive switching

NASA Astrophysics Data System (ADS)

Vishwanath, Sujaya Kumar; Woo, Hyunsuk; Jeon, Sanghun

2018-06-01

Atomic switches are considered to be building blocks for future non-volatile data storage and internet of things. However, obtaining device structures capable of ultrahigh density data storage, high endurance, and long data retention, and more importantly, understanding the switching mechanisms are still a challenge for atomic switches. Here, we achieved improved resistive switching performance in a bilayer structure containing aluminum oxide, with an oxygen-deficient oxide as the top switching layer and stoichiometric oxide as the bottom switching layer, using atomic layer deposition. This bilayer device showed a high on/off ratio (105) with better endurance (∼2000 cycles) and longer data retention (104 s) than single-oxide layers. In addition, depending on the compliance current, the bilayer device could be operated in four different resistance states. Furthermore, the depth profiles of the hourglass-shaped conductive filament of the bilayer device was observed by conductive atomic force microscopy.

A single-stage optical load-balanced switch for data centers.

PubMed

Huang, Qirui; Yeo, Yong-Kee; Zhou, Luying

2012-10-22

Load balancing is an attractive technique to achieve maximum throughput and optimal resource utilization in large-scale switching systems. However current electronic load-balanced switches suffer from severe problems in implementation cost, power consumption and scaling. To overcome these problems, in this paper we propose a single-stage optical load-balanced switch architecture based on an arrayed waveguide grating router (AWGR) in conjunction with fast tunable lasers. By reuse of the fast tunable lasers, the switch achieves both functions of load balancing and switching through the AWGR. With this architecture, proof-of-concept experiments have been conducted to investigate the feasibility of the optical load-balanced switch and to examine its physical performance. Compared to three-stage load-balanced switches, the reported switch needs only half of optical devices such as tunable lasers and AWGRs, which can provide a cost-effective solution for future data centers.

Correlates of Neuropsychological Impairment in Older Adult Pain Clinic Patients

PubMed Central

Karp, Jordan F.; Reynolds, Charles F.; Butters, Meryl; Dew, Mary Amanda; Mazumdar, Sati; Begley, Amy E.; Lenze, Eric; Weiner, Debra K.

2010-01-01

Objective Persistent pain and cognitive impairment are common in older adults. Memory and mental flexibility are cognitive domains which may be vulnerable in the aging brain. We were interested in examining the effects of persistent pain and opioid use on cognition in community dwelling, non-demented older adults. Setting Older Adult Pain Management Program. Design 57 new patients (mean age 76.1) were recruited to describe 1) rates of persistent pain conditions and pain intensity, 2) cognition (memory and mental flexibility), 3) rates and severity of depression, and 4) sleep quality. All patients had non-malignant pain for at least 3 months. Pain intensity was measured with the McGill Pain Questionnaire. Diagnosis of depression was via the Patient Health Questionnaire and depression severity assessed with the Hamilton Rating Scale for Depression. Cognition was assessed with: 1) Mini Mental State Examination, 2) number-letter-switching and motor speed trail-making subtests, 3) Digit Symbol Subtest of the WAIS-R, and 4) free and paired recall of the WAIS-R. To determine which variables predicted poorer outcomes on mental flexibility tests, these variables were entered into a multiple regression. Results Pain severity was associated with impaired number-letter switching (r = −0.42, p = 0.002). Multiple regression showed pain severity was associated with impaired mental flexibility (parameter estimate = −0.29 (t = −2.00), p = 0.05). Patients taking opioids had worse memory (t = 2.17, df = 39, p = 0.04). Conclusions In community-dwelling older adults, pain severity is associated with impaired mental flexibility. In addition, opioids may increase memory problems. PMID:17014605

Sporadic on/off switching of HTLV-1 Tax expression is crucial to maintain the whole population of virus-induced leukemic cells

PubMed Central

Mahgoub, Mohamed; Iwami, Shingo; Nakaoka, Shinji; Koizumi, Yoshiki; Shimura, Kazuya; Matsuoka, Masao

2018-01-01

Viruses causing chronic infection artfully manipulate infected cells to enable viral persistence in vivo under the pressure of immunity. Human T-cell leukemia virus type 1 (HTLV-1) establishes persistent infection mainly in CD4+ T cells in vivo and induces leukemia in this subset. HTLV-1–encoded Tax is a critical transactivator of viral replication and a potent oncoprotein, but its significance in pathogenesis remains obscure due to its very low level of expression in vivo. Here, we show that Tax is expressed in a minor fraction of leukemic cells at any given time, and importantly, its expression spontaneously switches between on and off states. Live cell imaging revealed that the average duration of one episode of Tax expression is ∼19 hours. Knockdown of Tax rapidly induced apoptosis in most cells, indicating that Tax is critical for maintaining the population, even if its short-term expression is limited to a small subpopulation. Single-cell analysis and computational simulation suggest that transient Tax expression triggers antiapoptotic machinery, and this effect continues even after Tax expression is diminished; this activation of the antiapoptotic machinery is the critical event for maintaining the population. In addition, Tax is induced by various cytotoxic stresses and also promotes HTLV-1 replication. Thus, it seems that Tax protects infected cells from apoptosis and increases the chance of viral transmission at a critical moment. Keeping the expression of Tax minimal but inducible on demand is, therefore, a fundamental strategy of HTLV-1 to promote persistent infection and leukemogenesis. PMID:29358408

Current-level triggered plasma-opening switch

DOEpatents

Mendel, C.W.

1987-06-29

An opening switch for very high power electrical pulses uses a slow magnetic field to confine a plasma across a gap between two electrodes. The plasma conducts the electric pulse across the gap while the switch is closed. A magnetic field generated by the pulse repels the slow magnetic field from the negative electrode to push the plasma from the electrode, opening the switch. A plurality of radial vanes may be used to enhance the slow magnetic field. 5 figs.

STE/ICE (Simplified Test Equipment/Internal Combustion Engines) Design Guide for Vehicle Diagnostic Connector Assemblies

DTIC Science & Technology

1982-08-01

19 3.2 Diesel Engine Speed Transducer 20 3.3 Pressure Transducer 20 3.4 Temperature Transducer 22 3.5 Differential Pressure Switch 22 3.6 Differential... Pressure Switch , Multi-Point 22 3.7 Current Measurement Transducer 23 - 3.8 Electrolyte Level Probes 23 3.9 Diagnostic Connector 24 3.10 Harness...12258933 Differential Pressure Switch - Multi-point 12258934 K -. Differential Pressure Switch 12258938 Electrolyte Level Sensor 12258935 Shunt 1000

Current-level triggered plasma-opening switch

DOEpatents

Mendel, Clifford W.

1989-01-01

An opening switch for very high power electrical pulses uses a slow magnetic field to confine a plasma across a gap between two electrodes. The plasma conducts the electric pulse across the gap while the switch is closed. A magnetic field generated by the pulse repels the slow magnetic field from the negative electrode to push the plasma from the electrode, opening the switch. A plurality of radial vanes may be used to enhance the slow magnetic field.

Contact effects in light activated GaAs switches

NASA Astrophysics Data System (ADS)

Durkin, P. S.

1985-05-01

The purpose of this work was to examine the effects of various types of contacts on the switching behavior of a light-triggered power switch. The switch was constructed from a homogeneous wafer of chromium-doped gallium arsenide; the contacts were either ohmic, non-ohmic, or Schottky barriers. These were formed on the wafer in two geometries; both contacts on one side, and one contact spacings were used to permit the effects of the location of the existing laser pulse to be studied. A high voltage power supply (zero to 20 kV) was employed as the bias supply. A Nd:YAG laser, in the pulsed mode, was used to trigger the switch, which was mounted on a cold finger cooled to near liquid nitrogen temperature. Cooling reduced the dark current to manageable values (less than 1 micro A), and also reduced the avalanche breakdown voltage. The results of the measurements indicate that ohmic contacts produced more reliable switching than the non-ohmic or Schottky contacts, in as much as the shape of the output current pulse was better, and the number of pulses which the switches could sustain before the pulse shape deteriorated was greater, for the ohmic contacts. Surface discharge between the one-sided contacts obscured any differences in switching characteristics which might have depended on the location of the pulsed light excitation, so that no correlation between position and behavior could be obtained.

Poly-4-vinylphenol (PVP) and Poly(melamine-co-formaldehyde) (PMF)-Based Atomic Switching Device and Its Application to Logic Gate Circuits with Low Operating Voltage.

PubMed

Kang, Dong-Ho; Choi, Woo-Young; Woo, Hyunsuk; Jang, Sungkyu; Park, Hyung-Youl; Shim, Jaewoo; Choi, Jae-Woong; Kim, Sungho; Jeon, Sanghun; Lee, Sungjoo; Park, Jin-Hong

2017-08-16

In this study, we demonstrate a high-performance solid polymer electrolyte (SPE) atomic switching device with low SET/RESET voltages (0.25 and -0.5 V, respectively), high on/off-current ratio (10 5 ), excellent cyclic endurance (>10 3 ), and long retention time (>10 4 s), where poly-4-vinylphenol (PVP)/poly(melamine-co-formaldehyde) (PMF) is used as an SPE layer. To accomplish these excellent device performance parameters, we reduce the off-current level of the PVP/PMF atomic switching device by improving the electrical insulating property of the PVP/PMF electrolyte through adjustment of the number of cross-linked chains. We then apply a titanium buffer layer to the PVP/PMF switching device for further improvement of bipolar switching behavior and device stability. In addition, we first implement SPE atomic switch-based logic AND and OR circuits with low operating voltages below 2 V by integrating 5 × 5 arrays of PVP/PMF switching devices on the flexible substrate. In particular, this low operating voltage of our logic circuits was much lower than that (>5 V) of the circuits configured by polymer resistive random access memory. This research successfully presents the feasibility of PVP/PMF atomic switches for flexible integrated circuits for next-generation electronic applications.

Treatment adherence and persistence with long-acting somatostatin analog therapy for the treatment of acromegaly: a retrospective analysis.

PubMed

Gurel, Michelle H; Han, Yi; Stevens, Andrea L; Furtado, Aaron; Cox, David

2017-04-04

Many patients with acromegaly require medical treatment that includes somatostatin analogs (SSAs). Long-acting SSA formulations are widely used, due in part to increased patient convenience and increased treatment adherence vs daily medications. Although medication compliance can be poor in patients with chronic conditions, adherence and persistence with these SSAs in patients with acromegaly has not been evaluated. This analysis utilized claims data to estimate treatment adherence and persistence for lanreotide depot and long-acting octreotide in this population. This retrospective analysis used the MarketScan® database (~100 payors, 500 million claims in the US), which was searched between January 2007 and June 2012 to identify patients with acromegaly taking either lanreotide depot or long-acting octreotide. Patients switching treatments were excluded. Treatment adherence was assessed using medication possession ratio (MPR; number of doses dispensed in relation to dispensing period; ≥80% is considered adherent), injection count, and treatment time. Persistence was estimated by Kaplan-Meier analyses and Cox proportional hazards modeling. A washout period, defined as no acromegaly-related prescription activity 180 days prior to the index date, was employed to minimize effects of prior therapy and focus on patients more likely to be treatment-naïve. Altogether 1308 patients with acromegaly receiving a single SSA for treatment (1127 octreotide, 181 lanreotide) who had not switched treatments were identified. Mean MPR in patients with a 180-day washout (n = 663) was 89% for those receiving octreotide (n = 545) and 87% for those receiving lanreotide (n = 118). Median number of days on therapy was 169 (95% CI 135-232) for octreotide patients and 400 (95% CI 232-532) for lanreotide patients. The point estimate of the Cox proportional hazard ratio for stopping treatment was 1.385 for octreotide vs lanreotide (95% CI 1.079-1.777), suggesting a 38.5% increased risk for stopping octreotide before lanreotide. Treatment adherence was similarly good for both injectable SSA treatments studied, at 87% or greater. Persistence was greater with lanreotide than octreotide and the risk of discontinuing therapy was lower with lanreotide than octreotide. Further studies to determine factors leading to these differences in persistence or to predict discontinuation of therapy may aid in clinical management of these patients.

Electronic States and Persistent Currents in Nanowire Quantum Ring

NASA Astrophysics Data System (ADS)

Kokurin, I. A.

2018-04-01

The new model of a quantum ring (QR) defined inside a nanowire (NW) is proposed. The one-particle Hamiltonian for electron in [111]-oriented NW QR is constructed taking into account both Rashba and Dresselhaus spin-orbit coupling (SOC). The energy levels as a function of magnetic field are found using the exact numerical diagonalization. The persistent currents (both charge and spin) are calculated. The specificity of SOC and arising anticrossings in energy spectrum lead to unusual features in persistent current behavior. The variation of magnetic field or carrier concentration by means of gate can lead to pure spin persistent current with the charge current being zero.

A retrospective 15-year review: survival advantage after switching to sirolimus in hepatitis C virus infected liver graft recipients.

PubMed

Shah, M; Shankar, A; Gee, I; Nash, K; Hoare, M; Gibbs, P; Davies, S; Alexander, G J M

2015-02-01

The use of sirolimus-based immune suppression in liver transplantation, particularly in hepatitis C virus (HCV)-infected recipients, remains contentious. There is some evidence that sirolimus retards hepatic fibrosis, is renal sparing and may be of benefit in preventing hepatocellular carcinoma (HCC) recurrence. Sirolimus has not been adopted by many transplant centres because of persistent concerns regarding an increased risk of hepatic artery thrombosis, graft loss and death with de novo sirolimus. To review the impact of switching to sirolimus monotherapy in HCV-infected liver recipients with respect to survival, graft loss and hepatic fibrosis. A retrospective review of 190 patients from a single centre undergoing first liver transplantation for HCV over 15 years. 113 patients were switched from calcineurin inhibitor (CNI)-based therapy to low-dose sirolimus monotherapy at a median of 15 months after transplantation for HCV-related fibrosis (72%), renal impairment (14%) or high-risk HCC (5%). Patients switched to sirolimus had improved survival (P < 0.001) and slower progression to cirrhosis (P = 0.001). In patients with HCC (n = 91), sirolimus duration rather than strategy was an independent predictor of survival (P = 0.001) and extended time to HCC recurrence (33 vs. 16 months). Patients switched for renal dysfunction showed improvement in serum creatinine (140-108 μmol/L, P = 0.001). Those remaining on CNI-therapy were more likely to develop post-transplant diabetes (P = 0.03). These data suggest selective switching to low-dose sirolimus monotherapy in HCV-positive liver recipients improves clinical outcome. © 2014 John Wiley & Sons Ltd.

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.

Load-Dependent Soft-Switching Method of Half-Bridge Current Doubler for High-Voltage Point-of-Load Converter in Data Center Power Supplies

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

Cui, Yutian; Yang, Fei; Tolbert, Leon M.

With the increased cloud computing and digital information storage, the energy requirement of data centers keeps increasing. A high-voltage point of load (HV POL) with an input series output parallel structure is proposed to convert 400 to 1 VDC within a single stage to increase the power conversion efficiency. The symmetrical controlled half-bridge current doubler is selected as the converter topology in the HV POL. A load-dependent soft-switching method has been proposed with an auxiliary circuit that includes inductor, diode, and MOSFETs so that the hard-switching issue of typical symmetrical controlled half-bridge converters is resolved. The operation principles of themore » proposed soft-switching half-bridge current doubler have been analyzed in detail. Then, the necessity of adjusting the timing with the loading in the proposed method is analyzed based on losses, and a controller is designed to realize the load-dependent operation. A lossless RCD current sensing method is used to sense the output inductor current value in the proposed load-dependent operation. In conclusion, experimental efficiency of a hardware prototype is provided to show that the proposed method can increase the converter's efficiency in both heavy- and light-load conditions.« less

Load-Dependent Soft-Switching Method of Half-Bridge Current Doubler for High-Voltage Point-of-Load Converter in Data Center Power Supplies

DOE PAGES

Cui, Yutian; Yang, Fei; Tolbert, Leon M.; ...

2016-06-14

With the increased cloud computing and digital information storage, the energy requirement of data centers keeps increasing. A high-voltage point of load (HV POL) with an input series output parallel structure is proposed to convert 400 to 1 VDC within a single stage to increase the power conversion efficiency. The symmetrical controlled half-bridge current doubler is selected as the converter topology in the HV POL. A load-dependent soft-switching method has been proposed with an auxiliary circuit that includes inductor, diode, and MOSFETs so that the hard-switching issue of typical symmetrical controlled half-bridge converters is resolved. The operation principles of themore » proposed soft-switching half-bridge current doubler have been analyzed in detail. Then, the necessity of adjusting the timing with the loading in the proposed method is analyzed based on losses, and a controller is designed to realize the load-dependent operation. A lossless RCD current sensing method is used to sense the output inductor current value in the proposed load-dependent operation. In conclusion, experimental efficiency of a hardware prototype is provided to show that the proposed method can increase the converter's efficiency in both heavy- and light-load conditions.« less

A Pt/TiO(2)/Ti Schottky-type selection diode for alleviating the sneak current in resistance switching memory arrays.

PubMed

Park, Woo Young; Kim, Gun Hwan; Seok, Jun Yeong; Kim, Kyung Min; Song, Seul Ji; Lee, Min Hwan; Hwang, Cheol Seong

2010-05-14

This study examined the properties of Schottky-type diodes composed of Pt/TiO(2)/Ti, where the Pt/TiO(2) and TiO(2)/Ti junctions correspond to the blocking and ohmic contacts, respectively, as the selection device for a resistive switching cross-bar array. An extremely high forward-to-reverse current ratio of approximately 10(9) was achieved at 1 V when the TiO(2) film thickness was 19 nm. TiO(2) film was grown by atomic layer deposition at a substrate temperature of 250 degrees C. Conductive atomic force microscopy revealed that the forward current flew locally, which limits the maximum forward current density to < 10 A cm(-2) for a large electrode (an area of approximately 60 000 microm(2)). However, the local current measurement showed a local forward current density as high as approximately 10(5) A cm(-2). Therefore, it is expected that this type of Schottky diode effectively suppresses the sneak current without adverse interference effects in a nano-scale resistive switching cross-bar array with high block density.

Investigation of regime switching from mode locking to Q-switching in a 2 µm InGaSb/AlGaAsSb quantum well laser.

PubMed

Li, Xiang; Wang, Hong; Qiao, Zhongliang; Guo, Xin; Wang, Wanjun; Ng, Geok Ing; Zhang, Yu; Xu, Yingqiang; Niu, Zhichuan; Tong, Cunzhu; Liu, Chongyang

2018-04-02

A two-section InGaSb/AlGaAsSb single quantum well (SQW) laser emitting at 2 μm is presented. By varying the absorber bias voltage with a fixed gain current at 130 mA, passive mode locking at ~18.40 GHz, Q-switched mode locking, and passive Q-switching are observed in this laser. In the Q-switched mode locking regimes, the Q-switched RF signal and mode locked RF signal coexist, and the Q-switched lasing and mode-locked lasing happen at different wavelengths. This is the first observation of these three pulsed working regimes in a GaSb-based diode laser. An analysis of the regime switching mechanism is given based on the interplay between the gain saturation and the saturable absorption.

Electrical switching in cadmium boracite single crystals

NASA Technical Reports Server (NTRS)

Takahashi, T.; Yamada, O.

1981-01-01

Cadmium boracite single crystals at high temperatures ( 300 C) were found to exhibit a reversible electric field-induced transition between a highly insulative and a conductive state. The switching threshold is smaller than a few volts for an electrode spacing of a few tenth of a millimeter corresponding to an electric field of 100 to 1000 V/cm. This is much smaller than the dielectric break-down field for an insulator such as boracite. The insulative state reappears after voltage removal. A pulse technique revealed two different types of switching. Unstable switching occurs when the pulse voltage slightly exceeds the switching threshold and is characterized by a pre-switching delay and also a residual current after voltage pulse removal. A stable type of switching occurs when the voltage becomes sufficiently high. Possible device applications of this switching phenomenon are discussed.

High precision triangular waveform generator

DOEpatents

Mueller, Theodore R.

1983-01-01

An ultra-linear ramp generator having separately programmable ascending and descending ramp rates and voltages is provided. Two constant current sources provide the ramp through an integrator. Switching of the current at current source inputs rather than at the integrator input eliminates switching transients and contributes to the waveform precision. The triangular waveforms produced by the waveform generator are characterized by accurate reproduction and low drift over periods of several hours. The ascending and descending slopes are independently selectable.

High-precision triangular-waveform generator

DOEpatents

Mueller, T.R.

1981-11-14

An ultra-linear ramp generator having separately programmable ascending and decending ramp rates and voltages is provided. Two constant current sources provide the ramp through an integrator. Switching of the current at current source inputs rather than at the integrator input eliminates switching transients and contributes to the waveform precision. The triangular waveforms produced by the waveform generator are characterized by accurate reproduction and low drift over periods of several hours. The ascending and descending slopes are independently selectable.

A 13.56 MHz CMOS Active Rectifier With Switched-Offset and Compensated Biasing for Biomedical Wireless Power Transfer Systems.

PubMed

Yan Lu; Wing-Hung Ki

2014-06-01

A full-wave active rectifier switching at 13.56 MHz with compensated bias current for a wide input range for wirelessly powered high-current biomedical implants is presented. The four diodes of a conventional passive rectifier are replaced by two cross-coupled PMOS transistors and two comparator- controlled NMOS switches to eliminate diode voltage drops such that high voltage conversion ratio and power conversion efficiency could be achieved even at low AC input amplitude |VAC|. The comparators are implemented with switched-offset biasing to compensate for the delays of active diodes and to eliminate multiple pulsing and reverse current. The proposed rectifier uses a modified CMOS peaking current source with bias current that is quasi-inversely proportional to the supply voltage to better control the reverse current over a wide AC input range (1.5 to 4 V). The rectifier was fabricated in a standard 0.35 μm CMOS N-well process with active area of 0.0651 mm(2). For the proposed rectifier measured at |VAC| = 3.0 V, the voltage conversion ratios are 0.89 and 0.93 for RL=500 Ω and 5 kΩ, respectively, and the measured power conversion efficiencies are 82.2% to 90.1% with |VAC| ranges from 1.5 to 4 V for RL=500 Ω.

Modality and Task Switching Interactions using Bi-Modal and Bivalent Stimuli

ERIC Educational Resources Information Center

Sandhu, Rajwant; Dyson, Benjamin J.

2013-01-01

Investigations of concurrent task and modality switching effects have to date been studied under conditions of uni-modal stimulus presentation. As such, it is difficult to directly compare resultant task and modality switching effects, as the stimuli afford both tasks on each trial, but only one modality. The current study investigated task and…

Packet Switching Networks: An Introduction with Some Attention to Selected Vendors.

ERIC Educational Resources Information Center

Sanchez, James Joseph

The purpose of this paper is to provide an overview of the history, development, and services of the packet switching network services that currently exist in the United States. The character of packet switching, a computerized method of transmitting data, is used as the basis for tracing the development of the industry itself. Contending that the…

Current-induced spin-orbit torque switching of perpendicularly magnetized Hf|CoFeB|MgO and Hf|CoFeB|TaO{sub x} structures

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

Akyol, Mustafa; Department of Physics, University of Çukurova, Adana 01330; Yu, Guoqiang

2015-04-20

We study the effect of the oxide layer on current-induced perpendicular magnetization switching properties in Hf|CoFeB|MgO and Hf|CoFeB|TaO{sub x} tri-layers. The studied structures exhibit broken in-plane inversion symmetry due to a wedged CoFeB layer, resulting in a field-like spin-orbit torque (SOT), which can be quantified by a perpendicular (out-of-plane) effective magnetic field. A clear difference in the magnitude of this effective magnetic field (H{sub z}{sup FL}) was observed between these two structures. In particular, while the current-driven deterministic perpendicular magnetic switching was observed at zero magnetic bias field in Hf|CoFeB|MgO, an external magnetic field is necessary to switch the CoFeBmore » layer deterministically in Hf|CoFeB|TaO{sub x}. Based on the experimental results, the SOT magnitude (H{sub z}{sup FL} per current density) in Hf|CoFeB|MgO (−14.12 Oe/10{sup 7} A cm{sup −2}) was found to be almost 13× larger than that in Hf|CoFeB|TaO{sub x} (−1.05 Oe/10{sup 7} A cm{sup −2}). The CoFeB thickness dependence of the magnetic switching behavior, and the resulting  H{sub z}{sup FL} generated by in-plane currents are also investigated in this work.« less

Emerging memories: resistive switching mechanisms and current status

NASA Astrophysics Data System (ADS)

Jeong, Doo Seok; Thomas, Reji; Katiyar, R. S.; Scott, J. F.; Kohlstedt, H.; Petraru, A.; Hwang, Cheol Seong

2012-07-01

The resistance switching behaviour of several materials has recently attracted considerable attention for its application in non-volatile memory (NVM) devices, popularly described as resistive random access memories (RRAMs). RRAM is a type of NVM that uses a material(s) that changes the resistance when a voltage is applied. Resistive switching phenomena have been observed in many oxides: (i) binary transition metal oxides (TMOs), e.g. TiO2, Cr2O3, FeOx and NiO; (ii) perovskite-type complex TMOs that are variously functional, paraelectric, ferroelectric, multiferroic and magnetic, e.g. (Ba,Sr)TiO3, Pb(Zrx Ti1-x)O3, BiFeO3 and PrxCa1-xMnO3 (iii) large band gap high-k dielectrics, e.g. Al2O3 and Gd2O3; (iv) graphene oxides. In the non-oxide category, higher chalcogenides are front runners, e.g. In2Se3 and In2Te3. Hence, the number of materials showing this technologically interesting behaviour for information storage is enormous. Resistive switching in these materials can form the basis for the next generation of NVM, i.e. RRAM, when current semiconductor memory technology reaches its limit in terms of density. RRAMs may be the high-density and low-cost NVMs of the future. A review on this topic is of importance to focus concentration on the most promising materials to accelerate application into the semiconductor industry. This review is a small effort to realize the ambitious goal of RRAMs. Its basic focus is on resistive switching in various materials with particular emphasis on binary TMOs. It also addresses the current understanding of resistive switching behaviour. Moreover, a brief comparison between RRAMs and memristors is included. The review ends with the current status of RRAMs in terms of stability, scalability and switching speed, which are three important aspects of integration onto semiconductors.

Electrode erosion properties of gas spark switches for fast linear transformer drivers

NASA Astrophysics Data System (ADS)

Li, Xiaoang; Pei, Zhehao; Zhang, Yuzhao; Liu, Xuandong; Li, Yongdong; Zhang, Qiaogen

2017-12-01

Fast linear transformer drivers (FLTDs) are a popular and potential route for high-power devices employing multiple "bricks" in series and parallel, but they put extremely stringent demands on gas switches. Electrode erosion of FLTD gas switches is a restrictive and unavoidable factor that degrades performance and limits stability. In this paper, we systematically investigated the electrode erosion characteristics of a three-electrode field distortion gas switch under the typical working conditions of FLTD switches, and the discharge current was 7-46 kA with 46-300 ns rise time. A high speed frame camera and a spectrograph were used to capture the expansion process and the spectral emission of the spark channel was used to estimate the current density and the spark temperature, and then the energy fluxes and the external forces on the electrode surface were calculated. A tens of kilo-ampere nanosecond pulse could generate a 1011 W/m2 energy flux injection and 1.3-3.5 MPa external pressure on the electrode surface, resulting in a millimeter-sized erosion crater with the maximum peak height Rz reaching 100 μm magnitude. According to the morphological images by a laser scanning confocal microscope, the erosion crater of a FLTD switch contained three kinds of local morphologies, namely a center boiling region, an overflow region and a sputtering region. In addition, the crater size, the surface roughness, and the mass loss were highly dependent on the current amplitude and the transferred charge. We also observed Morphology Type I and Type II, respectively, with different pulse parameters, which had an obvious influence on surface roughness and mass loss. Finally, the quantitative relationship between the electrode mass loss and the pulse parameter was clarified. The transferred charge and the current amplitude were proved to be the main factors determining the electrode mass loss of a FLTD switch, and a least squares fitting expression for mass loss was also obtained.

Rapid mapping of polarization switching through complete information acquisition

DOE PAGES

Somnath, Suhas; Belianinov, Alex; Kalinin, Sergei V.; ...

2016-12-02

Polarization switching in ferroelectric and multiferroic materials underpins a broad range of current and emergent applications, ranging from random access memories to field-effect transistors, and tunnelling devices. Switching in these materials is exquisitely sensitive to local defects and microstructure on the nanometre scale, necessitating spatially resolved high-resolution studies of these phenomena. Classical piezoresponse force microscopy and spectroscopy, although providing necessary spatial resolution, are fundamentally limited in data acquisition rates and energy resolution. This limitation stems from their two-tiered measurement protocol that combines slow (~1 s) switching and fast (~10 kHz–1 MHz) detection waveforms. Here we develop an approach for rapidmore » probing of ferroelectric switching using direct strain detection of material response to probe bias. This approach, facilitated by high-sensitivity electronics and adaptive filtering, enables spectroscopic imaging at a rate 3,504 times faster the current state of the art, achieving high-veracity imaging of polarization dynamics in complex microstructures.« less

Rapid mapping of polarization switching through complete information acquisition

PubMed Central

Somnath, Suhas; Belianinov, Alex; Kalinin, Sergei V.; Jesse, Stephen

2016-01-01

Polarization switching in ferroelectric and multiferroic materials underpins a broad range of current and emergent applications, ranging from random access memories to field-effect transistors, and tunnelling devices. Switching in these materials is exquisitely sensitive to local defects and microstructure on the nanometre scale, necessitating spatially resolved high-resolution studies of these phenomena. Classical piezoresponse force microscopy and spectroscopy, although providing necessary spatial resolution, are fundamentally limited in data acquisition rates and energy resolution. This limitation stems from their two-tiered measurement protocol that combines slow (∼1 s) switching and fast (∼10 kHz–1 MHz) detection waveforms. Here we develop an approach for rapid probing of ferroelectric switching using direct strain detection of material response to probe bias. This approach, facilitated by high-sensitivity electronics and adaptive filtering, enables spectroscopic imaging at a rate 3,504 times faster the current state of the art, achieving high-veracity imaging of polarization dynamics in complex microstructures. PMID:27910941

Modelling switching-time effects in high-frequency power conditioning networks

NASA Technical Reports Server (NTRS)

Owen, H. A.; Sloane, T. H.; Rimer, B. H.; Wilson, T. G.

1979-01-01

Power transistor networks which switch large currents in highly inductive environments are beginning to find application in the hundred kilohertz switching frequency range. Recent developments in the fabrication of metal-oxide-semiconductor field-effect transistors in the power device category have enhanced the movement toward higher switching frequencies. Models for switching devices and of the circuits in which they are imbedded are required to properly characterize the mechanisms responsible for turning on and turning off effects. Easily interpreted results in the form of oscilloscope-like plots assist in understanding the effects of parametric studies using topology oriented computer-aided analysis methods.

Note: Cryogenic heat switch with stepper motor actuator

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

Melcher, B. S., E-mail: bsmelche@syr.edu; Timbie, P. T., E-mail: pttimbie@wisc.edu

2015-12-15

A mechanical cryogenic heat switch has been developed using a commercially available stepper motor and control electronics. The motor requires 4 leads, each carrying a maximum, pulsed current of 0.5 A. With slight modifications of the stepper motor, the switch functions reliably in vacuum at temperatures between 300 K and 4 K. The switch generates a clamping force of 262 N at room temperature. At 4 K it achieves an “on state” thermal conductance of 5.04 mW/K and no conductance in the “off state.” The switch is optimized for cycling an adiabatic demagnetization refrigerator.

High-voltage, low-inductance gas switch

DOEpatents

Gruner, Frederick R.; Stygar, William A.

2016-03-22

A low-inductance, air-insulated gas switch uses a de-enhanced annular trigger ring disposed between two opposing high voltage electrodes. The switch is DC chargeable to 200 kilovolts or more, triggerable, has low jitter (5 ns or less), has pre-fire and no-fire rates of no more than one in 10,000 shots, and has a lifetime of greater than 100,000 shots. Importantly, the switch also has a low inductance (less than 60 nH) and the ability to conduct currents with less than 100 ns rise times. The switch can be used with linear transformer drives or other pulsed-power systems.

GAS DISCHARGE SWITCH EVALUATION FOR RHIC BEAM ABORT KICKER APPLICATION.

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

ZHANG,W.; SANDBERG,J.; SHELDRAKE,R.

2002-06-30

A gas discharge switch EEV HX3002 is being evaluated at Brookhaven National Laboratory as a possible candidate of RHIC Beam Abort Kicker modulator main switch. At higher beam energy and higher beam intensity, the switch stability becomes very crucial. The hollow anode thyratron used in the existing system is not rated for long reverse current conduction. The reverse voltage arcing caused thyratron hold-off voltage de-rating has been the main limitation of the system operation. To improve the system reliability, a new type of gas discharge switch has been suggested by Marconi Applied Technology for its reverse conducting capability.

Analytical design equations for self-tuned Class-E power amplifier.

PubMed

Hu, Zhe; Troyk, Philip

2011-01-01

For many emerging neural prosthesis designs that are powered by inductive coupling, their small physical size requires large current in the extracorporeal transmitter coil, and the Class-E power amplifier topology is often used for the transmitter design. Tuning of Class-E circuits for efficient operation is difficult and a self-tuned circuit can facilitate the tuning. The coil current is sensed and used to tune the switching of the transistor switch in the Class-E circuit in order to maintain its high-efficiency operation. Although mathematically complex, the analysis and design procedure for the self-tuned Class-E circuit can be simplified due to the current feedback control, which makes the phase angle between the switching pulse and the coil current predetermined. In this paper explicit analytical design equations are derived and a detailed design procedure is presented and compared with the conventional Class-E design approaches.

Design and Development of a Series Switch for High Voltage in RF Heating

NASA Astrophysics Data System (ADS)

Patel, Himanshu K.; Shah, Deep; Thacker, Mauli; Shah, Atman

2013-02-01

Plasma is the fourth state of matter. To sustain plasma in its ionic form very high temperature is essential. RF heating systems are used to provide the required temperature. Arching phenomenon in these systems can cause enormous damage to the RF tube. Heavy current flows across the anode-cathode junction, which need to be suppressed in minimal time for its protection. Fast-switching circuit breakers are used to cut-off the load from the supply in cases of arching. The crowbar interrupts the connection between the high voltage power supply (HVPS) and the RF tube for a temporary period between which the series switch has to open. The crowbar shunts the current across the load but in the process leads to short circuiting the HVPS. Thus, to protect the load as well as the HVPS a series switch is necessary. This paper presents the design and development of high voltage Series Switch for the high power switching applications. Fiber optic based Optimum triggering scheme is designed and tested to restrict the time delay well within the stipulated limits. The design is well supported with the experimental results for the whole set-up along with the series switch at various voltage level before its approval for operation at 5.2 kV.

Analysis of optical route in a micro high-speed magneto-optic switch

NASA Astrophysics Data System (ADS)

Weng, Zihua; Yang, Guoguang; Huang, Yuanqing; Chen, Zhimin; Zhu, Yun; Wu, Jinming; Lin, Shufen; Mo, Weiping

2005-02-01

A novel micro high-speed 2x2 magneto-optic switch and its optical route, which is used in high-speed all-optical communication network, is designed and analyzed in this paper. The study of micro high-speed magneto-optic switch mainly involves the optical route and high-speed control technique design. The optical route design covers optical route design of polarization in optical switch, the performance analysis and material selection of magneto-optic crystal and magnetic path design in Faraday rotator. The research of high-speed control technique involves the study of nanosecond pulse generator, high-speed magnetic field and its control technique etc. High-speed current transients from nanosecond pulse generator are used to switch the magnetization of the magneto-optic crystal, which propagates a 1550nm optical beam. The optical route design schemes and electronic circuits of high-speed control technique are both simulated on computer and test by the experiments respectively. The experiment results state that the nanosecond pulse generator can output the pulse with rising edge time 3~35ns, voltage amplitude 10~90V and pulse width 10~100ns. Under the control of CPU singlechip, the optical beam can be stably switched and the switching time is less than 1μs currently.

Enhancement of macroscopic quantum tunneling in the higher-order phase switches of Bi2212 intrinsic Josephson junctions

NASA Astrophysics Data System (ADS)

Kitano, Haruhisa; Yamaguchi, Ayami; Takahashi, Yusaku; Umegai, Shunpei; Watabe, Yuji; Ohnuma, Haruka; Hosaka, Kazutaka; Kakehi, Daiki

2018-03-01

The macroscopic quantum tunneling (MQT) in the current-biased intrinsic Josephson junctions (IJJs) of high-T c cuprates has attracted much attention for decades. Although the MQT for the phase switches from the zero to the first voltage state (1st SW) in the multiple-branched I-V curves is well explained by the conventional theory, the occurrence of MQT for the higher order switches such as the switch from the 1st to 2nd voltage state (2nd SW) has been still debated. Here, we present an experimental study on the phase switches of small IJJs fabricated from underdoped Bi2Sr2(Ca,Y)Cu2Oy. We observed the single photon transition between quantized energy levels in the 3rd phase switches at 59.15 GHz and 2 K. The comparison with the previous studies on the nearly optimal-doped Bi2Sr2CaCu2Oy clearly suggests a possibility that the MQT rate for the higher-order phase switches is commonly enhanced by the effective suppression of the energy barrier for the higher-order phase escape due to the phase-running state after the 1st SW, in spite of the large difference in a critical current density and T c.

Bi-stable dendrite in constant electric field: a model analysis.

PubMed

Baginskas, A; Gutman, A; Svirskis, G

1993-03-01

Some neurons possess dendritic persistent inward current, which is activated during depolarization. Dendrites can be stably depolarized, i.e. they are bi-stable if the net current is inward. A proper method to show the existence of dendritic bi-stability is putting the neuron into the electric field to induce transmembrane potential changes along the dendrites. Here we present analytical and computer simulation of the bi-stable dendrite in the d.c. field. A prominent jump to a depolarization plateau can be seen in the soma upon initial hyperpolarization of its membrane. If a considerable portion of dendrites are parallel to the field it is impossible to switch off the depolarization plateau by changing the direction and the strength of the electric field. There is nothing similar in neurons with ohmic dendrites. The results of the simulation conform to the experimental observations in turtle motoneurons [Hounsgaard J. and Kiehn O. (1993) J. Physiol., Lond. (in press)]; comparison of the theoretical and the experimental results makes semi-quantitative estimation of some electrical parameters of dendrites possible. We propose modifications of the experiment which enable one to measure dendritic length constants and other parameters of stained neurons.

Research on multi-switch synchronization based on single trigger generator

NASA Astrophysics Data System (ADS)

Geng, Jiuyuan; Cheng, Xinbing; Yang, Jianhua; Yang, Xiao; Chen, Rong

2018-05-01

Multi-switch synchronous operation is an effective approach to provide high-voltage high-current for a high-power device. In this paper, we present a synchronization system with a corona stabilized triggered switch (CSTS) as main switch and an all-solid modularized quasi-square pulse forming system. In addition, this paper provides explanations of low jitter and accurate triggering of CSTS based on streamer theory. Different switches of the module are triggered by an electrical pulse created by a trigger generator, a quasi-square pulse can be created on the load. The experimental results show that it is able to switch voltages in excess of 40kV with nanosecond system jitter for three-module synchronous operation.

High Efficiency Single Output ZVS-ZCS Voltage Doubled Flyback Converter

NASA Astrophysics Data System (ADS)

Kaliyaperumal, Deepa; Saju, Hridya Merin; Kumar, M. Vijaya

2016-06-01

A switch operating at high switching frequency increases the switching losses of the converter resulting in lesser efficiency. Hence this paper proposes a new topology which has resonant switches [zero voltage switching (ZVS)] in the primary circuit to eliminate the above said disadvantages, and voltage doubler zero current switching (ZCS) circuit in the secondary to double the output voltage, and hence the output power, power density and efficiency. The design aspects of the proposed topology for a single output of 5 V at 50 kHz, its simulation and hardware results are discussed in detail. The analysis of the results obtained from a 2.5 W converter reveals the superiority of the proposed converter.

Validation of Finite-Element Models of Persistent-Current Effects in Nb 3Sn Accelerator Magnets

DOE PAGES

Wang, X.; Ambrosio, G.; Chlachidze, G.; ...

2015-01-06

Persistent magnetization currents are induced in superconducting filaments during the current ramping in magnets. The resulting perturbation to the design magnetic field leads to field quality degradation, in particular at low field where the effect is stronger relative to the main field. The effects observed in NbTi accelerator magnets were reproduced well with the critical-state model. However, this approach becomes less accurate for the calculation of the persistent-current effects observed in Nb 3Sn accelerator magnets. Here a finite-element method based on the measured strand magnetization is validated against three state-of-art Nb3Sn accelerator magnets featuring different subelement diameters, critical currents, magnetmore » designs and measurement temperatures. The temperature dependence of the persistent-current effects is reproduced. Based on the validated model, the impact of conductor design on the persistent current effects is discussed. The performance, limitations and possible improvements of the approach are also discussed.« less

Improved Thermal-Switch Disks Protect Batteries

NASA Technical Reports Server (NTRS)

Darcy, Eric; Bragg, Bobby

1990-01-01

Improved thermal-switch disks help protect electrical batteries against high currents like those due to short circuits or high demands for power in circuits supplied by batteries. Protects batteries against excessive temperatures. Centered by insulating fiberglass washer. Contains conductive polymer that undergoes abrupt increase in electrical resistance when excessive current raises its temperature above specific point. After cooling, polymer reverts to low resistance. Disks reusable.

Plasma density evolution in plasma opening switch obtained by a time-resolved sensitive He-Ne interferometer

NASA Astrophysics Data System (ADS)

Chen, Lin; Ren, Jing; Guo, Fan; Zhou, LiangJi; Li, Ye; He, An; Jiang, Wei

2014-03-01

To understand the formation process of vacuum gap in coaxial microsecond conduction time plasma opening switch (POS), we have made measurements of the line-integrated plasma density during switch operation using a time-resolved sensitive He-Ne interferometer. The conduction current and conduction time in experiments are about 120 kA and 1 μs, respectively. As a result, more than 85% of conduction current has been transferred to an inductive load with rise time of 130 ns. The radial dependence of the density is measured by changing the radial location of the line-of-sight for shots with the same nominal POS parameters. During the conduction phase, the line-integrated plasma density in POS increases at all radial locations over the gun-only case by further ionization of material injected from the guns. The current conduction is observed to cause a radial redistribution of the switch plasma. A vacuum gap forms rapidly in the plasma at 5.5 mm from the center conductor, which is consistent with the location where magnetic pressure is the largest, allowing current to be transferred from the POS to the load.

Automatic Locker Key With Barcode Based Microcontroller Atmega 8535

NASA Astrophysics Data System (ADS)

Fahmi, M. Irfan; Efendi Hutagalung, Jhonson

2017-12-01

MCB (miniature circuit breaker) is an electromagnetic device that embodies complete enclosure in a molded insulating material. The main function of an MCB is to switch the circuit, i.e., to open the circuit (which has been connected to it) automatically when the current passing through it (MCB) exceeds the value for which it is set. Unlike fuse, an MCB can be easily reset and thus offers improved operational safety and greater convenience without incurring large operating cost.The principal of operation is simple. In simple terms MCB is a switch which automatically turns off when the current flowing through it passes the maximum allowable limit. Generally MCB are designed to protect against over current and over temperature faults (over heating). Sometimes the overload the current through the bimetal causes to raise the temperature of it. The heat generated within the bimetal itself enough to cause deflection due to thermal expansion of metals. This solution is used by LDR, and LM 35 as the sencor to control center. Therefore it is very important because it is related about local control switches, isolating switches against faults and overload protection devices for installations or specific equipments or appliances

Using of explosive technologies for development of a compact current-limiting device for operation on 110 kV class systems

NASA Astrophysics Data System (ADS)

Shurupov, A. V.; Shurupov, M. A.; Kozlov, A. A.; Kotov, A. V.

2016-11-01

This paper considers the possibility of creating on new physical principles a highspeed current-limiting device (CLD) for the networks with voltage of 110 kV, namely, on the basis of the explosive switching elements. The device is designed to limit the steady short-circuit current to acceptable values for the time does not exceed 3 ms at electric power facilities. The paper presents an analysis of the electrical circuit of CLD. The main features of the scheme are: a new high-speed switching element with high regenerating voltage; fusible switching element that enables to limit the overvoltage after sudden breakage of network of the explosive switch; non-inductive resistor with a high heat capacity and a special reactor with operating time less than 1 s. We analyzed the work of the CLD with help of special software PSPICE, which is based on the equivalent circuit of single-phase short circuit to ground in 110 kV network. Analysis of the equivalent circuit operation CLD shows its efficiency and determines the CLD as a perspective direction of the current-limiting devices of new generation.

Atomically Thin Femtojoule Memristive Device

DOE PAGES

Zhao, Huan; Dong, Zhipeng; Tian, He; ...

2017-10-25

The morphology and dimension of the conductive filament formed in a memristive device are strongly influenced by the thickness of its switching medium layer. Aggressive scaling of this active layer thickness is critical toward reducing the operating current, voltage, and energy consumption in filamentary-type memristors. Previously, the thickness of this filament layer has been limited to above a few nanometers due to processing constraints, making it challenging to further suppress the on-state current and the switching voltage. In this paper, the formation of conductive filaments in a material medium with sub-nanometer thickness formed through the oxidation of atomically thin two-dimensionalmore » boron nitride is studied. The resulting memristive device exhibits sub-nanometer filamentary switching with sub-pA operation current and femtojoule per bit energy consumption. Furthermore, by confining the filament to the atomic scale, current switching characteristics are observed that are distinct from that in thicker medium due to the profoundly different atomic kinetics. The filament morphology in such an aggressively scaled memristive device is also theoretically explored. Finally, these ultralow energy devices are promising for realizing femtojoule and sub-femtojoule electronic computation, which can be attractive for applications in a wide range of electronics systems that desire ultralow power operation.« less

Breakover mechanism of GaAs photoconductive switch triggering spark gap for high power applications

NASA Astrophysics Data System (ADS)

Tian, Liqiang; Shi, Wei; Feng, Qingqing

2011-11-01

A spark gap (SG) triggered by a semi-insulating GaAs photoconductive semiconductor switch (PCSS) is presented. Currents as high as 5.6 kA have been generated using the combined switch, which is excited by a laser pulse with energy of 1.8 mJ and under a bias of 4 kV. Based on the transferred-electron effect and gas streamer theory, the breakover characteristics of the combined switch are analyzed. The photoexcited carrier density in the PCSS is calculated. The calculation and analysis indicate that the PCSS breakover is caused by nucleation of the photoactivated avalanching charge domain. It is shown that the high output current is generated by the discharge of a high-energy gas streamer induced by the strong local electric field distortion or by overvoltage of the SG resulting from quenching of the avalanching domain, and periodic oscillation of the current is caused by interaction between the gas streamer and the charge domain. The cycle of the current oscillation is determined by the rise time of the triggering electric pulse generated by the PCSS, the pulse transmission time between the PCSS and the SG, and the streamer transit time in the SG.

Clinical and economic impact of mirabegron compared with antimuscarinics for the treatment of overactive bladder in Canada.

PubMed

Hakimi, Zalmai; Nazir, Jameel; McCrea, Charles; Berling, Malin; Fatoye, Francis; Ramos, Barbara; Wagg, Adrian

2017-06-01

The β 3 -adrenoceptor agonist, mirabegron, and antimuscarinic agents provide similar efficacy for the treatment of overactive bladder (OAB), but mirabegron appears to be associated with better persistence, perhaps due to an absence of anticholinergic side-effects. This study estimated the expected costs associated with the management of OAB in Canada from a societal perspective by utilizing real-world evidence. An economic model with monthly cycles and a 1-year time horizon was developed to depict a treatment pathway for a hypothetical cohort of 100 patients with OAB. At model entry, patients receive mirabegron or an antimuscarinic. Patients who do not persist may switch treatment, undergo a minimally invasive procedure, or remain symptomatic (uncontrolled). The model includes direct costs (e.g. physician visits) and indirect costs (e.g. lost productivity). A one-way univariate sensitivity analysis assessed a ±20% variation in each of the key model inputs. At 1 year, a greater proportion of patients persisted on treatment with mirabegron compared with antimuscarinics (33% vs 15-23%), and a smaller proportion switched treatment (17% vs 20-22%). The number of healthcare visits (292 vs 299-304), pads used (74,098 vs 77,878-81,669), and work hours lost (4,497 vs 5,372-6,249) were all lower for mirabegron vs antimuscarinics. The estimated total annual cost of treatment per patient with mirabegron was $2,127.46 Canadian dollars (CAD) ($5.82 CAD/day) compared with $2,150.20-$2,496.69 CAD ($5.89-$6.84 CAD/day) for antimuscarinics. The one-way sensitivity analysis indicated the results are robust. Improved persistence observed in routine clinical practice with mirabegron appears to translate into benefits of reduced healthcare resource use, and lower direct and indirect costs of treatment compared with antimuscarinics. Overall, these data suggest that mirabegron may offer clinical and economic benefits for the management of patients with OAB in Canada.

Adaptation of superconducting fault current limiter to high-speed reclosing

NASA Astrophysics Data System (ADS)

Koyama, T.; Yanabu, S.

2009-10-01

Using a high temperature superconductor, we constructed and tested a model superconducting fault current limiter (SFCL). The superconductor might break in some cases because of its excessive generation of heat. Therefore, it is desirable to interrupt early the current that flows to superconductor. So, we proposed the SFCL using an electromagnetic repulsion switch which is composed of a superconductor, a vacuum interrupter and a by-pass coil, and its structure is simple. Duration that the current flow in the superconductor can be easily minimized to the level of less than 0.5 cycle using this equipment. On the other hand, the fault current is also easily limited by large reactance of the parallel coil. There is duty of high-speed reclosing after interrupting fault current in the electric power system. After the fault current is interrupted, the back-up breaker is re-closed within 350 ms. So, the electromagnetic repulsion switch should return to former state and the superconductor should be recovered to superconducting state before high-speed reclosing. Then, we proposed the SFCL using an electromagnetic repulsion switch which employs our new reclosing function. We also studied recovery time of the superconductor, because superconductor should be recovered to superconducting state within 350 ms. In this paper, the recovery time characteristics of the superconducting wire were investigated. Also, we combined the superconductor with the electromagnetic repulsion switch, and we did performance test. As a result, a high-speed reclosing within 350 ms was proven to be possible.

OpT2mise: a randomized controlled trial to compare insulin pump therapy with multiple daily injections in the treatment of type 2 diabetes-research design and methods.

PubMed

Aronson, Ronnie; Cohen, Ohad; Conget, Ignacio; Runzis, Sarah; Castaneda, Javier; de Portu, Simona; Lee, Scott; Reznik, Yves

2014-07-01

In insulin-requiring type 2 diabetes patients, current insulin therapy approaches such as basal-alone or basal-bolus multiple daily injections (MDI) have not consistently provided achievement of optimal glycemic control. Previous studies have suggested a potential benefit of continuous subcutaneous insulin infusion (CSII) in these patients. The OpT2mise study is a multicenter, randomized, trial comparing CSII with MDI in a large cohort of subjects with evidence of persistent hyperglycemia despite previous MDI therapy. Subjects were enrolled into a run-in period for optimization of their MDI insulin regimen. Subjects showing persistent hyperglycemia (glycated hemoglobin [HbA1c] ≥8% and ≤12%) were then randomly assigned to CSII or continuing an MDI regimen for a 6-month phase followed by a single crossover of the MDI arm, switching to CSII. The primary end point is the between-group difference in mean change in HbA1c from baseline to 6 months. Secondary end points include change in mean 24-h glucose values, area under the curve and time spent in hypoglycemia and hyperglycemia, measures of glycemic excursions, change in postprandial hyperglycemia, and evaluation of treatment satisfaction. Safety end points include hypoglycemia, hospital admissions, and emergency room visits. When subject enrollment was completed in May 2013, 495 subjects had been enrolled in the study. The study completion for the primary end point is expected in January 2014. OpT2mise will represent the largest studied homogeneous cohort of type 2 diabetes patients with persistent hyperglycemia despite optimized MDI therapy. OpT2mise will help define the role of CSII in insulin intensification and define its safety, rate of hypoglycemia, patient adherence, and patient satisfaction.

Magnetic thin-film split-domain current sensor-recorder

DOEpatents

Hsieh, Edmund J.

1979-01-01

A sensor-recorder for recording a representation of the direction and peak amplitude of a transient current. A magnetic thin film is coated on a glass substrate under the influence of a magnetic field so that the finished film is magnetically uniaxial and anisotropic. The film is split into two oppositely magnetized contiguous domains with a central boundary by subjecting adjacent portions of the film simultaneously to magnetic fields that are opposed 180.degree.. With the split-domain sensor-recorder placed with the film plane and domain boundary either perpendicular or parallel to the expected conductive path of a transient current, the occurrence of the transient causes switching of a portion of one domain to the direction of the other domain. The amount of the switched domain portion is indicative of the amplitude of the peak current of the transient, while the particular domain that is switched is indicative of the direction of the current. The resulting domain patterns may be read with a passive magnetic tape viewer.

Multiscale modeling of current-induced switching in magnetic tunnel junctions using ab initio spin-transfer torques

NASA Astrophysics Data System (ADS)

Ellis, Matthew O. A.; Stamenova, Maria; Sanvito, Stefano

2017-12-01

There exists a significant challenge in developing efficient magnetic tunnel junctions with low write currents for nonvolatile memory devices. With the aim of analyzing potential materials for efficient current-operated magnetic junctions, we have developed a multi-scale methodology combining ab initio calculations of spin-transfer torque with large-scale time-dependent simulations using atomistic spin dynamics. In this work we introduce our multiscale approach, including a discussion on a number of possible schemes for mapping the ab initio spin torques into the spin dynamics. We demonstrate this methodology on a prototype Co/MgO/Co/Cu tunnel junction showing that the spin torques are primarily acting at the interface between the Co free layer and MgO. Using spin dynamics we then calculate the reversal switching times for the free layer and the critical voltages and currents required for such switching. Our work provides an efficient, accurate, and versatile framework for designing novel current-operated magnetic devices, where all the materials details are taken into account.

Magnetization switching in ferromagnets by adsorbed chiral molecules without current or external magnetic field.

PubMed

Ben Dor, Oren; Yochelis, Shira; Radko, Anna; Vankayala, Kiran; Capua, Eyal; Capua, Amir; Yang, See-Hun; Baczewski, Lech Tomasz; Parkin, Stuart Stephen Papworth; Naaman, Ron; Paltiel, Yossi

2017-02-23

Ferromagnets are commonly magnetized by either external magnetic fields or spin polarized currents. The manipulation of magnetization by spin-current occurs through the spin-transfer-torque effect, which is applied, for example, in modern magnetoresistive random access memory. However, the current density required for the spin-transfer torque is of the order of 1 × 10 6  A·cm -2 , or about 1 × 10 25 electrons s -1 cm -2 . This relatively high current density significantly affects the devices' structure and performance. Here we demonstrate magnetization switching of ferromagnetic thin layers that is induced solely by adsorption of chiral molecules. In this case, about 10 13 electrons per cm 2 are sufficient to induce magnetization reversal. The direction of the magnetization depends on the handedness of the adsorbed chiral molecules. Local magnetization switching is achieved by adsorbing a chiral self-assembled molecular monolayer on a gold-coated ferromagnetic layer with perpendicular magnetic anisotropy. These results present a simple low-power magnetization mechanism when operating at ambient conditions.

Magnetization switching in ferromagnets by adsorbed chiral molecules without current or external magnetic field

PubMed Central

Ben Dor, Oren; Yochelis, Shira; Radko, Anna; Vankayala, Kiran; Capua, Eyal; Capua, Amir; Yang, See-Hun; Baczewski, Lech Tomasz; Parkin, Stuart Stephen Papworth; Naaman, Ron; Paltiel, Yossi

2017-01-01

Ferromagnets are commonly magnetized by either external magnetic fields or spin polarized currents. The manipulation of magnetization by spin-current occurs through the spin-transfer-torque effect, which is applied, for example, in modern magnetoresistive random access memory. However, the current density required for the spin-transfer torque is of the order of 1 × 106 A·cm−2, or about 1 × 1025 electrons s−1 cm−2. This relatively high current density significantly affects the devices' structure and performance. Here we demonstrate magnetization switching of ferromagnetic thin layers that is induced solely by adsorption of chiral molecules. In this case, about 1013 electrons per cm2 are sufficient to induce magnetization reversal. The direction of the magnetization depends on the handedness of the adsorbed chiral molecules. Local magnetization switching is achieved by adsorbing a chiral self-assembled molecular monolayer on a gold-coated ferromagnetic layer with perpendicular magnetic anisotropy. These results present a simple low-power magnetization mechanism when operating at ambient conditions. PMID:28230054

Simple Multiplexing Hand-Held Control Unit

NASA Technical Reports Server (NTRS)

Hannaford, Blake

1989-01-01

Multiplexer consists of series of resistors, each shunted by single-pole, single-throw switch. User operates switches by pressing buttons or squeezing triggers. Prototype includes three switches operated successfully in over 200 hours of system operations. Number of switches accommodated determined by signal-to-noise ratio of current source, noise induced in control unit and cable, and number of bits in output of analog-to-digital converter. Because many computer-contolled robots have extra analog-to-digital channels, such multiplexer added at little extra cost.

High-speed and low-energy nitride memristors

DOE PAGES

Choi, Byung Joon; Torrezan, Antonio C.; Strachan, John Paul; ...

2016-05-24

High-performance memristors based on AlN films have been demonstrated, which exhibit ultrafast ON/OFF switching times (≈85 ps for microdevices with waveguide) and relatively low switching current (≈15 μA for 50 nm devices). Physical characterizations are carried out to understand the device switching mechanism, and rationalize speed and energy performance. The formation of an Al-rich conduction channel through the AlN layer is revealed. Here, the motion of positively charged nitrogen vacancies is likely responsible for the observed switching.

Restrike Particle Beam Experiments on a Dense Plasma Focus. Opening Switch Research on a Dense Plasma Focus.

DTIC Science & Technology

1985-06-01

Research on this grant has focused on plasma focus experiments in the areas of particle beam generation and as a potential repetitive opening switch...as were scaling laws for the increase of electron energy and current with input energy. The potential of the plasma focus as an opening switch was...delay line technique. The observed frequencies were most consistent with the lower hybrid frequency. Keywords include: Dense Plasma Focus , Particle Beam Generation, Opening Switch, Load Experiments, Pulsed Power.

Using Benchmarking To Strengthen the Assessment of Persistence.

PubMed

McLachlan, Michael S; Zou, Hongyan; Gouin, Todd

2017-01-03

Chemical persistence is a key property for assessing chemical risk and chemical hazard. Current methods for evaluating persistence are based on laboratory tests. The relationship between the laboratory based estimates and persistence in the environment is often unclear, in which case the current methods for evaluating persistence can be questioned. Chemical benchmarking opens new possibilities to measure persistence in the field. In this paper we explore how the benchmarking approach can be applied in both the laboratory and the field to deepen our understanding of chemical persistence in the environment and create a firmer scientific basis for laboratory to field extrapolation of persistence test results.

Driver circuit for solid state light sources

DOEpatents

Palmer, Fred; Denvir, Kerry; Allen, Steven

2016-02-16

A driver circuit for a light source including one or more solid state light sources, a luminaire including the same, and a method of so driving the solid state light sources are provided. The driver circuit includes a rectifier circuit that receives an alternating current (AC) input voltage and provides a rectified AC voltage. The driver circuit also includes a switching converter circuit coupled to the light source. The switching converter circuit provides a direct current (DC) output to the light source in response to the rectified AC voltage. The driver circuit also includes a mixing circuit, coupled to the light source, to switch current through at least one solid state light source of the light source in response to each of a plurality of consecutive half-waves of the rectified AC voltage.

Method and apparatus for low power analog-to-digital conversion

DOEpatents

De Geronimo, Gianluigi; Nambiar, Neena

2013-10-01

A method and apparatus for analog-to-digital conversion. An Analog-to-Digital Converter (ADC) includes M ADC.sub.j, j=1, 2, . . . , M. Each ADC.sub.j comprises a number of cells each of which comprises a first switch, a second switch, a current sink and an inverter. An inverter of a cell in an ADC.sub.j changes state in response to a current associate with an input signal of the ADC.sub.j exceeding a threshold, thus switching on the next cell. Each ADC.sub.j is enabled to perform analog-to-digital conversion on a residual current of a previous ADC.sub.j-1 after the previous ADC.sub.j-1 has completed its analog-to-digital conversion and has been disabled.

Neurosteroid dehydroepiandrosterone sulphate inhibits persistent sodium currents in rat medial prefrontal cortex via activation of sigma-1 receptors.

PubMed

Cheng, Zheng-Xiang; Lan, Dan-Mei; Wu, Pei-Ying; Zhu, Yan-Hua; Dong, Yi; Ma, Lan; Zheng, Ping

2008-03-01

Dehydroepiandrosterone sulphate is one of the most important neurosteroids. In the present paper, we studied the effect of dehydroepiandrosterone sulphate on persistent sodium currents and its mechanism and functional consequence with whole-cell patch clamp recording method combined with a pharmacological approach in the rat medial prefrontal cortex slices. The results showed that dehydroepiandrosterone sulphate inhibited the amplitude of persistent sodium currents and the inhibitory effect was significant at 0.1 microM, reached maximum at 1 microM and decreased with the increase in the concentrations of above 1 microM. The effect of dehydroepiandrosterone sulphate on persistent sodium currents was canceled by the Gi protein inhibitor and the protein kinase C inhibitor, but not by the protein kinase A inhibitor. The effect of dehydroepiandrosterone sulphate on persistent sodium currents was also canceled by the sigma-1 receptor blockers and the sigma-1 receptor agonist could mimic the effect of dehydroepiandrosterone sulphate. Dehydroepiandrosterone sulphate had no significant influence on neuronal excitability but could significantly inhibit chemical inhibition of mitochondria-evoked increase in persistent sodium currents. These results suggest that dehydroepiandrosterone sulphate inhibits persistent sodium currents via the activation of sigma-1 receptors-Gi protein-protein kinase C-coupled signaling pathway, and the main functional consequence of this effect of DHEAS is presumably to protect neurons under ischemia.

Does pen help? A real-world outcomes study of switching from vial to disposable pen among insulin glargine-treated patients with type 2 diabetes mellitus.

PubMed

Xie, Lin; Zhou, Steve; Wei, Wenhui; Gill, Jasvinder; Pan, Chunshen; Baser, Onur

2013-03-01

The study was designed to evaluate real-world data on clinical and economic outcome differences between patients with type 2 diabetes mellitus (T2DM) who use insulin glargine with vial-and-syringe delivery and those who switch to pen administration. This retrospective study analyzed medical and pharmacy claims information from the national managed-care IMPACT(®) database (Ingenix Inc., Salt Lake City, UT). Adults with T2DM treated with insulin glargine were evaluated. Clinical and economic outcomes over 1 year were compared between individuals who had converted from administering glargine via vial-and-syringe to the SoloSTAR(®) (sanofi-aventis U.S., Bridgewater, NJ) pen (Switchers) and patients who continued to use vial-and-syringe administration (Continuers). Patients from each cohort were matched using propensity score matching for a comparison sample. In total, 3,893 eligible patients were identified (665 Switchers and 3,228 Continuers), with a matched cohort with 603 patients in each group. Baseline characteristics were similar between groups. One-year treatment persistence was significantly higher with Switchers versus Continuers (65.3% vs. 49.8%; P<0.0001). Medication possession ratio was also significantly higher among Switchers (0.79 vs. 0.76; P=0.0173). Insulin use and glycemic control were similar between groups. Healthcare utilization and total costs were also similar between groups. Higher prescription costs among Switchers were offset by lower overall and diabetes-related outpatient and inpatient costs. Switching from insulin glargine vial-and-syringe administration to pen delivery resulted in improved treatment adherence and persistence, with comparable clinical and economic outcomes.

Comparing Biologic Cost Per Treated Patient Across Indications Among Adult US Managed Care Patients: A Retrospective Cohort Study.

PubMed

Gu, Tao; Shah, Neel; Deshpande, Gaurav; Tang, Derek H; Eisenberg, Debra F

2016-12-01

The relative cost of biologics in the treatment of autoimmune disorders, including rheumatoid arthritis, psoriatic arthritis, psoriasis, and ankylosing spondylitis, is a key consideration for managed care payers. Our objective was to estimate biologic costs and treatment patterns in US managed care patients with rheumatoid arthritis, psoriatic arthritis, psoriasis, and/or ankylosing spondylitis. This retrospective study used administrative claims data from the HealthCore Integrated Research Database (HIRD SM ) for adults with rheumatoid arthritis, psoriatic arthritis, psoriasis, and/or ankylosing spondylitis who received abatacept, adalimumab, certolizumab, etanercept, golimumab, infliximab, rituximab, tocilizumab, or ustekinumab between 1 July 2009 and 31 January 2013. Biologic costs (based on drug utilization) and treatment patterns (discontinued, restarted after a >45-day gap, switched to another biologic, or persisted without switching or stopping) were analyzed for the first year post-index. Most of the 24,460 patients received etanercept (48 %), adalimumab (29 %), or infliximab (12 %) as the index biologic. On the index date, 44 % were new to biologic therapy and 56 % were continuing biologic therapy. Biologic cost per treated patient for 1 year was as follows: etanercept $US24,859, adalimumab $US26,537, and infliximab $US26,468. Treatment patterns across indications for etanercept, adalimumab, and infliximab were as follows: persistent (52, 49, 67 %), restarted (23, 21, 12 %), switched (12, 13, 11 %), and discontinued (14, 18, 10 %). These findings from a large health benefits organization in the USA are similar to those of several previous cost analyses assessing different populations, which demonstrates the external validity of the results from the previous studies, both over time and across large populations.

Short-Term Attentional Perseveration Associated with Real-Life Creative Achievement

PubMed Central

Zabelina, Darya L.; Beeman, Mark

2013-01-01

There are at least two competing hypotheses of how attention interacts with creative cognition, although they are not mutually exclusive. The first hypothesis is that highly creative people are particularly flexible at switching their attention – that is, they adaptively shift focus among different attentional levels using cognitive control. The second, less common, view is that creative people exhibit attentional persistence, or an ability for sustained attention. We suggest these two views need not be competing, as they may both operate, but on different time scales or on different components of creativity. In the present study we examined the role of attention in real-world creative achievement and in divergent thinking. In Experiment 1 participants with high and low real-world creative achievements identified whether the stimulus contained letters S or H within hierarchically constructed letters (e.g., large S made of small Es – global level; large E made up of small Ss – local level), which were presented in blocks of eight trials per level. In Experiment 2 participants with high, medium, and low creative achievements identified the same stimulus letters, but in blocks of five, seven, and nine trials per level. Results from both experiments indicated that people with high creative achievements made significantly more errors on trials in which they had to switch the level of attention, even after controlling for general intelligence. In Experiment 2, divergent thinking was also assessed, but it was not related to switching cost. Results from both experiments demonstrate that real-world creative acts relate to increased levels of attentional persistence, even if it comes with the cost of perseveration in certain circumstances. PMID:23630508

Switching-type regulator circuit has increased efficiency

NASA Technical Reports Server (NTRS)

Clapp, W. M.

1967-01-01

Switching series regulator circuit uses an inductive network to feed most of the current applied to the control circuit to the load. This circuit eliminates resistive losses and the need for heat sinks.

Power-MOSFET Voltage Regulator

NASA Technical Reports Server (NTRS)

Miller, W. N.; Gray, O. E.

1982-01-01

Ninety-six parallel MOSFET devices with two-stage feedback circuit form a high-current dc voltage regulator that also acts as fully-on solid-state switch when fuel-cell out-put falls below regulated voltage. Ripple voltage is less than 20 mV, transient recovery time is less than 50 ms. Parallel MOSFET's act as high-current dc regulator and switch. Regulator can be used wherever large direct currents must be controlled. Can be applied to inverters, industrial furnaces photovoltaic solar generators, dc motors, and electric autos.

Study of Ag/RGO/ITO sandwich structure for resistive switching behavior deposited on plastic substrate

NASA Astrophysics Data System (ADS)

Vartak, Rajdeep; Rag, Adarsh; De, Shounak; Bhat, Somashekhara

2018-05-01

We report here the use of facile and environmentally benign way synthesized reduced graphene oxide (RGO) for low-voltage non-volatile memory device as charge storing element. The RGO solutions have been synthesized using electrochemical exfoliation of battery electrode. The solution processed based RGO solution is suitable for large area and low-cost processing on plastic substrate. Room-temperature current-voltage characterisation has been carried out in Ag/RGO/ITO PET sandwich configuration to study the type of trap distribution. It is observed that in the low-voltage sweep, ohmic current is the main mechanism of current flow and trap filled/assisted conduction is observed at high-sweep voltage region. The Ag/RGO/ITO PET sandwich structure showed bipolar resistive switching behavior. These mechanisms can be analyzed based on oxygen availability and vacancies in the RGO giving rise to continuous least resistive path (conductive) and high resistance path along the structure. An Ag/RGO/ITO arrangement demonstrates long retention time with low operating voltage, low set/reset voltage, good ON/OFF ratio of 103 (switching transition between lower resistance state and higher resistance state and decent switching performance. The RGO memory showed decent results with an almost negligible degradation in switching properties which can be used for low-voltage and low-cost advanced flexible electronics.

Dynamics of a gain-switched distributed feedback ridge waveguide laser in nanoseconds time scale under very high current injection conditions.

PubMed

Klehr, A; Wenzel, H; Brox, O; Schwertfeger, S; Staske, R; Erbert, G

2013-02-11

We present detailed experimental investigations of the temporal, spectral and spatial behavior of a gain-switched distributed feedback (DFB) laser emitting at a wavelength of 1064 nm. Gain-switching is achieved by injecting nearly rectangular shaped current pulses having a length of 50 ns and a very high amplitude up to 2.5 A. The repetition frequency is 200 kHz. The laser has a ridge waveguide (RW) for lateral waveguiding with a ridge width of 3 µm and a cavity length of 1.5 mm. Time resolved investigations show, depending on the amplitude of the current pulses, that the optical power exhibits different types of oscillatory behavior during the pulses, accompanied by changes in the lateral near field intensity profiles and optical spectra. Three different types of instabilities can be distinguished: mode beating with frequencies between 25 GHz and 30 GHz, switching between different lateral intensity profiles with a frequency of 0.4 GHz and self-sustained oscillations with a frequency of 4 GHz. The investigations are of great relevance for the utilization of gain-switched DFB-RW lasers as seed lasers for fiber laser systems and in other applications, which require a high optical power.

Superconducting Switch for Fast On-Chip Routing of Quantum Microwave Fields

NASA Astrophysics Data System (ADS)

Pechal, M.; Besse, J.-C.; Mondal, M.; Oppliger, M.; Gasparinetti, S.; Wallraff, A.

2016-08-01

A switch capable of routing microwave signals at cryogenic temperatures is a desirable component for state-of-the-art experiments in many fields of applied physics, including but not limited to quantum-information processing, communication, and basic research in engineered quantum systems. Conventional mechanical switches provide low insertion loss but disturb operation of dilution cryostats and the associated experiments by heat dissipation. Switches based on semiconductors or microelectromechanical systems have a lower thermal budget but are not readily integrated with current superconducting circuits. Here we design and test an on-chip switch built by combining tunable transmission-line resonators with microwave beam splitters. The device is superconducting and as such dissipates a negligible amount of heat. It is compatible with current superconducting circuit fabrication techniques, operates with a bandwidth exceeding 100 MHz, is capable of handling photon fluxes on the order of 1 05 μ s-1 , equivalent to powers exceeding -90 dBm , and can be switched within approximately 6-8 ns. We successfully demonstrate operation of the device in the quantum regime by integrating it on a chip with a single-photon source and using it to route nonclassical itinerant microwave fields at the single-photon level.

A high-current rail-type gas switch with preionization by an additional corona discharge

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

Antipov, E. I.; Belozerov, O. S.; Krastelev, E. G., E-mail: ekrastelev@yandex.ru

The characteristics of a high-current rail-type gas switch with preionization of the gas (air) in a spark gap by an additional corona discharge are investigated. The experiments were performed in a voltage range of 10–45 kV using a two-electrode switch consisting of two cylindrical electrodes with a diameter of 22 mm and a length of 100 mm and a set of laterally located corona-discharge needles. The requirements for the position and size of the needles are defined for which a corona discharge is ignited before a breakdown of the main gap and does not change to a sparking form, andmore » the entire length of the rail electrodes is efficiently used. The fulfillment of these requirements ensures stable operation of the switch with a small variation of the pulse breakdown voltage, which is not more than 1% for a fixed voltage-pulse rise time in the range from 150 ns to 3.5 μs. A short delay time of the switch breakdown makes it possible to control the two-electrode switch by an overvoltage pulse of nanosecond duration.« less

Conceptual design of a high-speed electromagnetic switch for a modified flux-coupling-type SFCL and its application in renewable energy system.

PubMed

Chen, Lei; Chen, Hongkun; Yang, Jun; Shu, Zhengyu; He, Huiwen; Shu, Xin

2016-01-01

The modified flux-coupling-type superconducting fault current (SFCL) is a high-efficient electrical auxiliary device, whose basic function is to suppress the short-circuit current by controlling the magnetic path through a high-speed switch. In this paper, the high-speed switch is based on electromagnetic repulsion mechanism, and its conceptual design is carried out to promote the application of the modified SFCL. Regarding that the switch which is consisting of a mobile copper disc, two fixed opening and closing coils, the computational method for the electromagnetic force is discussed, and also the dynamic mathematical model including circuit equation, magnetic field equation as well as mechanical motion equation is theoretically deduced. According to the mathematical modeling and calculation of characteristic parameters, a feasible design scheme is presented, and the high-speed switch's response time can be less than 0.5 ms. For that the modified SFCL is equipped with this high-speed switch, the SFCL's application in a 10 kV micro-grid system with multiple renewable energy sources are assessed in the MATLAB software. The simulations are well able to affirm the SFCL's performance behaviors.

The extent of cigarette brand and company switching: results from the Adult Use-of-Tobacco Survey.

PubMed

Siegel, M; Nelson, D E; Peddicord, J P; Merritt, R K; Giovino, G A; Eriksen, M P

1996-01-01

To evaluate the effects of cigarette advertising on brand switching, an accurate estimate of the extent of cigarette brand and company switching among current smokers is needed. Data from the 1986 Adult Use-of-Tobacco Survey were analyzed to estimate the percentage of adult smokers who switched cigarette brands and companies in the previous year. Approximately 9.2% of adult smokers (4.2 million) switched cigarette brands in 1986, and 6.7% (3.1 million) switched cigarette companies. The aggregate profitability of brand switching in 1986 was approximately $362 million. Based on this analysis, brand switching alone justifies only a small percentage of a cigarette company's advertising and promotion expenditures, suggesting that future research should address other potential effects of advertising, including maintenance of brand loyalty and expanding the cigarette market. Medical Subject Headings (MeSH): addictive behavior, advertising, smoking, tobacco.

An energy-consistent fracture model for ferroelectrics

NASA Astrophysics Data System (ADS)

Miao, Hongchen; Li, Faxin

2017-02-01

The fracture behavior of ferroelectrics has been intensively studied in recent decades, though currently a widely accepted fracture mechanism is still lacking. In this work, enlightened by previous experimental observations that crack propagation in ferroelectrics is always accompanied by domain switching, we propose a micromechanical model in which both crack propagation and domain switching are controlled by energy-based criteria. Both electric energy and mechanical energy can induce domain switching, while only mechanical energy can drive crack propagation. Furthermore, constrained domain switching is considered in this model, leading to the gradient domain switching zone near the crack tip. Analysis results show that stress-induced ferroelastic switching always has a toughening effect as the mechanical energy release rate serves as the driving force for both fracture and domain switching. In comparison, the electric-field-induced switching may have either a toughening or detoughening effect. The proposed model can qualitatively agree with the existing experimental results.

Aircraft Loss-of-Control Accident Prevention: Switching Control of the GTM Aircraft with Elevator Jam Failures

NASA Technical Reports Server (NTRS)

Chang, Bor-Chin; Kwatny, Harry G.; Belcastro, Christine; Belcastro, Celeste

2008-01-01

Switching control, servomechanism, and H2 control theory are used to provide a practical and easy-to-implement solution for the actuator jam problem. A jammed actuator not only causes a reduction of control authority, but also creates a persistent disturbance with uncertain amplitude. The longitudinal dynamics model of the NASA GTM UAV is employed to demonstrate that a single fixed reconfigured controller design based on the proposed approach is capable of accommodating an elevator jam failure with arbitrary jam position as long as the thrust control has enough control authority. This paper is a first step towards solving a more comprehensive in-flight loss-of-control accident prevention problem that involves multiple actuator failures, structure damages, unanticipated faults, and nonlinear upset regime recovery, etc.

Systems and methods for reducing transient voltage spikes in matrix converters

DOEpatents

Kajouke, Lateef A.; Perisic, Milun; Ransom, Ray M.

2013-06-11

Systems and methods are provided for delivering energy using an energy conversion module that includes one or more switching elements. An exemplary electrical system comprises a DC interface, an AC interface, an isolation module, a first conversion module between the DC interface and the isolation module, and a second conversion module between the AC interface and the isolation module. A control module is configured to operate the first conversion module to provide an injection current to the second conversion module to reduce a magnitude of a current through a switching element of the second conversion module before opening the switching element.

Explosive-driven, high speed, arcless switch

DOEpatents

Skogmo, P.J.; Tucker, T.J.

1987-07-14

An explosive-actuated, fast-acting arcless switch contains a highly conductive foil to carry high currents positioned adjacent a dielectric surface within a casing. At one side of the foil opposite the dielectric surface is an explosive which, when detonated, drives the conductive foil against the dielectric surface. A pattern of grooves in the dielectric surface ruptures the foil to establish a rupture path having a pattern corresponding to the pattern of the grooves. The impedance of the ruptured foil is greater than that of the original foil to divert high current to a load. Planar and cylindrical embodiments of the switch are disclosed. 7 figs.

Linear beam raster magnet driver based on H-bridge technique

DOEpatents

Sinkine, Nikolai I.; Yan, Chen; Apeldoorn, Cornelis; Dail, Jeffrey Glenn; Wojcik, Randolph Frank; Gunning, William

2006-06-06

An improved raster magnet driver for a linear particle beam is based on an H-bridge technique. Four branches of power HEXFETs form a two-by-two switch. Switching the HEXFETs in a predetermined order and at the right frequency produces a triangular current waveform. An H-bridge controller controls switching sequence and timing. The magnetic field of the coil follows the shape of the waveform and thus steers the beam using a triangular rather than a sinusoidal waveform. The system produces a raster pattern having a highly uniform raster density distribution, eliminates target heating from non-uniform raster density distributions, and produces higher levels of beam current.

Analysis of the threshold switching mechanism of a Te-SbO selector device for crosspoint nonvolatile memory applications

NASA Astrophysics Data System (ADS)

Kim, Young Seok; Park, Ji Woon; Lee, Jong Ho; Choi, In Ah; Heo, Jaeyeong; Kim, Hyeong Joon

2017-10-01

The threshold switching mechanism of Te-SbO thin films with a unique microstructure in which a Te nanocluster is present in the SbO matrix is analyzed. During the electro-forming process, amorphous Te filaments are formed in the Te nanocluster. However, unlike conventional Ovonic threshold switching (TS) selector devices, it has been demonstrated that the off-current flows along the filament. Numerical calculations show that the off-current is due to the trap present in the filament. We also observed changes in TS parameters through controls in the strength or volume of the filaments.

S(+)amphetamine induces a persistent leak in the human dopamine transporter: molecular stent hypothesis

PubMed Central

Rodriguez-Menchaca, Aldo A; Solis Jr, Ernesto; Cameron, Krasnodara; De Felice, Louis J

2012-01-01

BACKGROUND AND PURPOSE Wherever they are located, dopamine transporters (DATs) clear dopamine (DA) from the extracellular milieu to help regulate dopaminergic signalling. Exposure to amphetamine (AMPH) increases extracellular DA in the synaptic cleft, which has been ascribed to DAT reverse transport. Increased extracellular DA prolongs postsynaptic activity and reinforces abuse and hedonic behaviour. EXPERIMENTAL APPROACH Xenopus laevis oocytes expressing human (h) DAT were voltage-clamped and exposed to DA, R(-)AMPH, or S(+)AMPH. KEY RESULTS At -60mV, near neuronal resting potentials, S(+)AMPH induced a depolarizing current through hDAT, which after removing the drug, persisted for more than 30 min. This persistent leak in the absence of S(+)AMPH was in contrast to the currents induced by R(-)AMPH and DA, which returned to baseline immediately after their removal. Our data suggest that S(+)AMPH and Na+ carry the initial S(+)AMPH-induced current, whereas Na+ and Cl- carry the persistent leak current. We propose that the persistent current results from the internal action of S(+)AMPH on hDAT because the temporal effect was consistent with S(+)AMPH influx, and intracellular S(+)AMPH activated the effect. The persistent current was dependent on Na+ and was blocked by cocaine. Intracellular injection of S(+)AMPH also activated a DA-induced persistent leak current. CONCLUSIONS AND IMPLICATIONS We report a hitherto unknown action of S(+)AMPH on hDAT that potentially affects AMPH-induced DA release. We propose that internal S(+)AMPH acts as a molecular stent that holds the transporter open even after external S(+)AMPH is removed. Amphetamine-induced persistent leak currents are likely to influence dopaminergic signalling, DA release mechanisms, and amphetamine abuse. PMID:22014068

Coordinating DNA polymerase traffic during high and low fidelity synthesis.

PubMed

Sutton, Mark D

2010-05-01

With the discovery that organisms possess multiple DNA polymerases (Pols) displaying different fidelities, processivities, and activities came the realization that mechanisms must exist to manage the actions of these diverse enzymes to prevent gratuitous mutations. Although many of the Pols encoded by most organisms are largely accurate, and participate in DNA replication and DNA repair, a sizeable fraction display a reduced fidelity, and act to catalyze potentially error-prone translesion DNA synthesis (TLS) past lesions that persist in the DNA. Striking the proper balance between use of these different enzymes during DNA replication, DNA repair, and TLS is essential for ensuring accurate duplication of the cell's genome. This review highlights mechanisms that organisms utilize to manage the actions of their different Pols. A particular emphasis is placed on discussion of current models for how different Pols switch places with each other at the replication fork during high fidelity replication and potentially error-pone TLS. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Frontal Lobe Contusion in Mice Chronically Impairs Prefrontal-Dependent Behavior

PubMed Central

Rosi, Susanna

2016-01-01

Traumatic brain injury (TBI) is a major cause of chronic disability in the world. Moderate to severe TBI often results in damage to the frontal lobe region and leads to cognitive, emotional, and social behavioral sequelae that negatively affect quality of life. More specifically, TBI patients often develop persistent deficits in social behavior, anxiety, and executive functions such as attention, mental flexibility, and task switching. These deficits are intrinsically associated with prefrontal cortex (PFC) functionality. Currently, there is a lack of analogous, behaviorally characterized TBI models for investigating frontal lobe injuries despite the prevalence of focal contusions to the frontal lobe in TBI patients. We used the controlled cortical impact (CCI) model in mice to generate a frontal lobe contusion and studied behavioral changes associated with PFC function. We found that unilateral frontal lobe contusion in mice produced long-term impairments to social recognition and reversal learning while having only a minor effect on anxiety and completely sparing rule shifting and hippocampal-dependent behavior. PMID:26964036

A Double-Pole High Voltage High Current Switch

DTIC Science & Technology

2005-12-01

NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited A DOUBLE- POLE HIGH...December 2005 3. REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE: A Double- Pole High Voltage High Current Switch 6. AUTHOR(S...to divert heavy charged particles, e.g. Cu+. 15. NUMBER OF PAGES 68 14. SUBJECT TERMS Double- Pole , Pulse Forming Inductive Network, PFIN

The effect of episodic retrieval on inhibition in task switching.

PubMed

Grange, James A; Kowalczyk, Agnieszka W; O'Loughlin, Rory

2017-08-01

Inhibition in task switching is inferred from n-2 repetition costs: the observation that ABA task switching sequences are responded to slower than CBA sequences. This is thought to reflect the persisting inhibition of Task A, which slows reactivation attempts. Mayr (2002) reported an experiment testing a critical noninhibitory account of this effect, namely episodic retrieval: If the trial parameters for Task A match across an ABA sequence, responses should be facilitated because of priming from episodic retrieval; a cost would occur if trial parameters mismatch. In a rule-switching paradigm, Mayr reported no significant difference in n-2 repetition cost when the trial parameters repeated or switched across an ABA sequence, in clear contrast to the episodic retrieval account. What remains unclear is whether successful episodic retrieval modulates the n-2 repetition cost. Across 3 experiments-including a close replication of Mayr-we find clear evidence of reduced n-2 task repetition costs when episodic retrieval is controlled. We find that the effect of episodic retrieval on the n-2 task repetition cost is increased when the cue-task relationship is made more abstract, suggesting the effect is because of interference in establishing the relevant attentional set. We also demonstrate that the episodic retrieval effect is not influenced by retrieval of low-level, perceptual, elements. Together, the data suggest the n-2 task repetition cost-typically attributable to an inhibitory mechanism-also reflects episodic retrieval effects. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Effectiveness, safety and cost of drug substitution in hypertension

PubMed Central

Johnston, Atholl; Stafylas, Panagiotis; Stergiou, George S

2010-01-01

Cost-containment measures in healthcare provision include the implementation of therapeutic and generic drug substitution strategies in patients whose condition is already well controlled with pharmacotherapy. Treatment for hypertension is frequently targeted for such measures. However, drug acquisition costs are only part of the cost-effectiveness equation, and a variety of other factors need to be taken into account when assessing the impact of switching antihypertensives. From the clinical perspective, considerations include maintenance of an appropriate medication dose during the switching process; drug equivalence in terms of clinical effectiveness; and safety issues, including the diverse adverse-event profiles of available alternative drugs, differences in the ‘inactive’ components of drug formulations and the quality of generic formulations. Patients' adherence to and persistence with therapy may be negatively influenced by switching, which will also impact on treatment effectiveness. From the economic perspective, the costs that are likely to be incurred by switching antihypertensives include those for additional clinic visits and laboratory tests, and for hospitalization if required to address problems arising from adverse events or poorly controlled hypertension. Indirect costs and the impact on patients' quality of life also require assessment. Substitution strategies for antihypertensives have not been tested in large outcome trials and there is little available clinical or economic evidence on which to base decisions to switch drugs. Although the cost of treatment should always be considered, careful assessment of the human and economic costs and benefits of antihypertensive drug substitution is required before this practice is recommended. PMID:20716230

Effectiveness, safety and cost of drug substitution in hypertension.

PubMed

Johnston, Atholl; Stafylas, Panagiotis; Stergiou, George S

2010-09-01

Cost-containment measures in healthcare provision include the implementation of therapeutic and generic drug substitution strategies in patients whose condition is already well controlled with pharmacotherapy. Treatment for hypertension is frequently targeted for such measures. However, drug acquisition costs are only part of the cost-effectiveness equation, and a variety of other factors need to be taken into account when assessing the impact of switching antihypertensives. From the clinical perspective, considerations include maintenance of an appropriate medication dose during the switching process; drug equivalence in terms of clinical effectiveness; and safety issues, including the diverse adverse-event profiles of available alternative drugs, differences in the 'inactive' components of drug formulations and the quality of generic formulations. Patients' adherence to and persistence with therapy may be negatively influenced by switching, which will also impact on treatment effectiveness. From the economic perspective, the costs that are likely to be incurred by switching antihypertensives include those for additional clinic visits and laboratory tests, and for hospitalization if required to address problems arising from adverse events or poorly controlled hypertension. Indirect costs and the impact on patients' quality of life also require assessment. Substitution strategies for antihypertensives have not been tested in large outcome trials and there is little available clinical or economic evidence on which to base decisions to switch drugs. Although the cost of treatment should always be considered, careful assessment of the human and economic costs and benefits of antihypertensive drug substitution is required before this practice is recommended.

Fault tolerant onboard packet switch architecture for communication satellites: Shared memory per beam approach

NASA Technical Reports Server (NTRS)

Shalkhauser, Mary JO; Quintana, Jorge A.; Soni, Nitin J.

1994-01-01

The NASA Lewis Research Center is developing a multichannel communication signal processing satellite (MCSPS) system which will provide low data rate, direct to user, commercial communications services. The focus of current space segment developments is a flexible, high-throughput, fault tolerant onboard information switching processor. This information switching processor (ISP) is a destination-directed packet switch which performs both space and time switching to route user information among numerous user ground terminals. Through both industry study contracts and in-house investigations, several packet switching architectures were examined. A contention-free approach, the shared memory per beam architecture, was selected for implementation. The shared memory per beam architecture, fault tolerance insertion, implementation, and demonstration plans are described.

PWM Switching Frequency Effects on Eddy Current Sensors for Magnetically Suspended Flywheel Systems

NASA Technical Reports Server (NTRS)

Jansen, Ralph; Lebron, Ramon; Dever, Timothy P.; Birchenough, Arthur G.

2003-01-01

A flywheel magnetic bearing (MB) pulse width modulated power amplifier (PWM) configuration is selected to minimize noise generated by the PWMs in the flywheel position sensor system. Two types of noise are addressed: beat frequency noise caused by variations in PWM switching frequencies, and demodulation noise caused by demodulation of high order harmonics of the switching voltage into the MB control band. Beat frequency noise is eliminated by synchronizing the PWM switch frequencies, and demodulation noise is minimized by selection of a switching frequency which does not have harmonics at the carrier frequency of the sensor. The recommended MB PWM system has five synchronized PWMs switching at a non-integer harmonic of the sensor carrier.

Measuring bi-directional current through a field-effect transistor by virtue of drain-to-source voltage measurement

DOEpatents

Turner, Steven Richard

2006-12-26

A method and apparatus for measuring current, and particularly bi-directional current, in a field-effect transistor (FET) using drain-to-source voltage measurements. The drain-to-source voltage of the FET is measured and amplified. This signal is then compensated for variations in the temperature of the FET, which affects the impedance of the FET when it is switched on. The output is a signal representative of the direction of the flow of current through the field-effect transistor and the level of the current through the field-effect transistor. Preferably, the measurement only occurs when the FET is switched on.

Electrical Conductance Tuning and Bistable Switching in Poly(N-vinylcarbazole)-Carbon Nanotube Composite Films.

PubMed

Liu, Gang; Ling, Qi-Dan; Teo, Eric Yeow Hwee; Zhu, Chun-Xiang; Chan, D Siu-Hung; Neoh, Koon-Gee; Kang, En-Tang

2009-07-28

By varying the carbon nanotube (CNT) content in poly(N-vinylcarbazole) (PVK) composite thin films, the electrical conductance behavior of an indium-tin oxide/PVK-CNT/aluminum (ITO/PVK-CNT/Al) sandwich structure can be tuned in a controlled manner. Distinctly different electrical conductance behaviors, such as (i) insulator behavior, (ii) bistable electrical conductance switching effects (write-once read-many-times (WORM) memory effect and rewritable memory effect), and (iii) conductor behavior, are discernible from the current density-voltage characteristics of the composite films. The turn-on voltage of the two bistable conductance switching devices decreases and the ON/OFF state current ratio of the WORM device increases with the increase in CNT content of the composite film. Both the WORM and rewritable devices are stable under a constant voltage stress or a continuous pulse voltage stress, with an ON/OFF state current ratio in excess of 10(3). The conductance switching effects of the composite films have been attributed to electron trapping in the CNTs of the electron-donating/hole-transporting PVK matrix.

Design and development of repetitive capacitor charging power supply based on series-parallel resonant converter topology.

PubMed

Patel, Ankur; Nagesh, K V; Kolge, Tanmay; Chakravarthy, D P

2011-04-01

LCL resonant converter based repetitive capacitor charging power supply (CCPS) is designed and developed in the division. The LCL converter acts as a constant current source when switching frequency is equal to the resonant frequency. When both resonant inductors' values of LCL converter are same, it results in inherent zero current switching (ZCS) in switches. In this paper, ac analysis with fundamental frequency approximation of LCL resonant tank circuit, frequency dependent of current gain converter followed by design, development, simulation, and practical result is described. Effect of change in switching frequency and resonant frequency and change in resonant inductors ratio on CCPS will be discussed. An efficient CCPS of average output power of 1.2 kJ/s, output voltage 3 kV, and 300 Hz repetition rate is developed in the division. The performance of this CCPS has been evaluated in the laboratory by charging several values of load capacitance at various repetition rates. These results indicate that this design is very feasible for use in capacitor-charging applications. © 2011 American Institute of Physics

On the role of verbalization during task set selection: switching or serial order control?

PubMed

Bryck, Richard L; Mayr, Ulrich

2005-06-01

Recent task-switching work in which paper-and-pencil administered single-task lists were compared with task-alternation lists has demonstrated large increases in task-switch costs with concurrent articulatory suppression (AS), implicating a crucial role for verbalization during switching (Baddeley, Chincotta, & Adlam, 2001; Emerson & Miyake, 2003). Experiment 1 replicated this result, using computerized assessment, albeit with much smaller effect sizes than in the original reports. In Experiment 2, AS interference was reduced when a sequential cue (spatial location) that indicated the current position in the sequence of task alternations was given. Finally, in Experiment 3, switch trials and no-switch trials were compared within a block of alternating runs of two tasks. Again, AS interference was obtained mainly when the endogenous sequencing demand was high, and it was comparable for no-switch and switch trials. These results suggest that verbalization may be critical for endogenous maintenance and updating of a sequential plan, rather than exclusively for the actual switching process.

Enhancement of resistive switching properties in Al2O3 bilayer-based atomic switches: multilevel resistive switching.

PubMed

Vishwanath, Sujaya Kumar; Woo, Hyunsuk; Jeon, Sanghun

2018-06-08

Atomic switches are considered to be building blocks for future non-volatile data storage and internet of things. However, obtaining device structures capable of ultrahigh density data storage, high endurance, and long data retention, and more importantly, understanding the switching mechanisms are still a challenge for atomic switches. Here, we achieved improved resistive switching performance in a bilayer structure containing aluminum oxide, with an oxygen-deficient oxide as the top switching layer and stoichiometric oxide as the bottom switching layer, using atomic layer deposition. This bilayer device showed a high on/off ratio (10 5 ) with better endurance (∼2000 cycles) and longer data retention (10 4 s) than single-oxide layers. In addition, depending on the compliance current, the bilayer device could be operated in four different resistance states. Furthermore, the depth profiles of the hourglass-shaped conductive filament of the bilayer device was observed by conductive atomic force microscopy.

Time-dependent quantum transport and power-law decay of the transient current in a nano-relay and nano-oscillator

NASA Astrophysics Data System (ADS)

Cuansing, Eduardo C.; Liang, Gengchiau

2011-10-01

Time-dependent nonequilibrium Green's functions are used to study electron transport properties in a device consisting of two linear chain leads and a time-dependent interlead coupling that is switched on non-adiabatically. We derive a numerically exact expression for the particle current and examine its characteristics as it evolves in time from the transient regime to the long-time steady-state regime. We find that just after switch-on, the current initially overshoots the expected long-time steady-state value, oscillates and decays as a power law, and eventually settles to a steady-state value consistent with the value calculated using the Landauer formula. The power-law parameters depend on the values of the applied bias voltage, the strength of the couplings, and the speed of the switch-on. In particular, the oscillating transient current decays away longer for lower bias voltages. Furthermore, the power-law decay nature of the current suggests an equivalent series resistor-inductor-capacitor circuit wherein all of the components have time-dependent properties. Such dynamical resistive, inductive, and capacitive influences are generic in nano-circuits where dynamical switches are incorporated. We also examine the characteristics of the dynamical current in a nano-oscillator modeled by introducing a sinusoidally modulated interlead coupling between the two leads. We find that the current does not strictly follow the sinusoidal form of the coupling. In particular, the maximum current does not occur during times when the leads are exactly aligned. Instead, the times when the maximum current occurs depend on the values of the bias potential, nearest-neighbor coupling, and the interlead coupling.

Persistent fluctuations in stride intervals under fractal auditory stimulation.

PubMed

Marmelat, Vivien; Torre, Kjerstin; Beek, Peter J; Daffertshofer, Andreas

2014-01-01

Stride sequences of healthy gait are characterized by persistent long-range correlations, which become anti-persistent in the presence of an isochronous metronome. The latter phenomenon is of particular interest because auditory cueing is generally considered to reduce stride variability and may hence be beneficial for stabilizing gait. Complex systems tend to match their correlation structure when synchronizing. In gait training, can one capitalize on this tendency by using a fractal metronome rather than an isochronous one? We examined whether auditory cues with fractal variations in inter-beat intervals yield similar fractal inter-stride interval variability as isochronous auditory cueing in two complementary experiments. In Experiment 1, participants walked on a treadmill while being paced by either an isochronous or a fractal metronome with different variation strengths between beats in order to test whether participants managed to synchronize with a fractal metronome and to determine the necessary amount of variability for participants to switch from anti-persistent to persistent inter-stride intervals. Participants did synchronize with the metronome despite its fractal randomness. The corresponding coefficient of variation of inter-beat intervals was fixed in Experiment 2, in which participants walked on a treadmill while being paced by non-isochronous metronomes with different scaling exponents. As expected, inter-stride intervals showed persistent correlations similar to self-paced walking only when cueing contained persistent correlations. Our results open up a new window to optimize rhythmic auditory cueing for gait stabilization by integrating fractal fluctuations in the inter-beat intervals.