Mitigation of voltage dip and power system oscillations damping using dual STATCOM for grid connected DFIG

OpenAIRE

D.V.N. Ananth; G.V. Nagesh Kumar

2017-01-01

During grid fault, transmission lines reach its thermal limit and lose its capability to transfer. If this fault current enters generator terminals, it will lead to dip in stator voltage and consequently produces torque and real power oscillations. This further affects in the form of internal heat in rotor windings and finally damages the generator. A new control strategy is proposed to limit fault current using dual STATCOM, which will damp power oscillations and mitigate the voltage dip due...

Method to minimize the low-frequency neutral-point voltage oscillations with time-offset injection for neutral-point-clamped inverters

DEFF Research Database (Denmark)

Choi, Uimin; Lee, Kyo-Beum; Blaabjerg, Frede

2013-01-01

This paper proposes a method to reduce the low-frequency neutral-point voltage oscillations. The neutral-point voltage oscillations are considerably reduced by adding a time-offset to the three phase turn-on times. The proper time-offset is simply calculated considering the phase currents and dwell...

Noise-Induced Transition in a Voltage-Controlled Oscillator Neuron Model

International Nuclear Information System (INIS)

Xie Huizhang; Liu Xuemei; Li Zhibing; Ai Baoquan; Liu Lianggang

2008-01-01

In the presence of Gaussian white noise, we study the properties of voltage-controlled oscillator neuron model and discuss the effects of the additive and multiplicative noise. It is found that the additive noise can accelerate and counterwork the firing of neuron, which depends on the value of central frequency of neuron itself, while multiplicative noise can induce the continuous change or mutation of membrane potential

Spontaneous oscillations of cell voltage, power density, and anode exit CO concentration in a PEM fuel cell.

Science.gov (United States)

Lu, Hui; Rihko-Struckmann, Liisa; Sundmacher, Kai

2011-10-28

The spontaneous oscillations of the cell voltage and output power density of a PEMFC (with PtRu/C anode) using CO-containing H(2) streams as anodic fuels have been observed during galvanostatic operating. It is ascribed to the dynamic coupling of the CO adsorption (poisoning) and the electrochemical CO oxidation (reactivating) processes in the anode chamber of the single PEMFC. Accompanying the cell voltage and power density oscillations, the discrete CO concentration oscillations at the anode outlet of the PEMFC were also detected, which directly confirms the electrochemical CO oxidation taking place in the anode chamber during galvanostatic operating. This journal is © the Owner Societies 2011

Microwave-Induced Magneto-Oscillations and Signatures of Zero-Resistance States in Phonon-Drag Voltage in Two-Dimensional Electron Systems.

Science.gov (United States)

Levin, A D; Momtaz, Z S; Gusev, G M; Raichev, O E; Bakarov, A K

2015-11-13

We observe the phonon-drag voltage oscillations correlating with the resistance oscillations under microwave irradiation in a two-dimensional electron gas in perpendicular magnetic field. This phenomenon is explained by the influence of dissipative resistivity modified by microwaves on the phonon-drag voltage perpendicular to the phonon flux. When the lowest-order resistance minima evolve into zero-resistance states, the phonon-drag voltage demonstrates sharp features suggesting that current domains associated with these states can exist in the absence of external dc driving.

Slow voltage oscillations in Ag-doped superconducting Y-Ba-Cu-O

International Nuclear Information System (INIS)

Altinkok, A.; Yetis, H.; Kilic, K.; Kilic, A.; Olutas, M.

2008-01-01

The time effects in Ag-doped YBa 2 Cu 3 O 7-x sample (YBCO/Ag) were examined by means of transport relaxation measurements (V-t curves). At well-defined values of transport current (I), temperature (T) and external magnetic field (H), an abrupt rise in sample voltage was observed at the early stage of the relaxation process. After reducing the initial current to a finite value, the sample voltage levels off within a very short time. The rapid voltage drops seen in V-t curves were attributed to the rapid dynamic reorganization of flux lines traversing the sample edges. These observations were also interpreted as an indication of doping of YBCO with Ag and easy suppression of superconducting order parameter due to the presence of Ag. In addition, we investigated the influence of bidirectional square wave (BSW) current on the evolution of V-t curves at different temperatures and external magnetic fields. It was observed that a nonlinear response seen in V-t curves to BSW current with sufficiently short periods or sufficiently low amplitude reflects itself as regular sinusoidal- type voltage oscillations, which were discussed mainly in terms of the dynamic competition between pinning and depinning

Influence of voltage rise time on microwave generation in relativistic backward wave oscillator

International Nuclear Information System (INIS)

Wu, Ping; Deng, Yuqun; Sun, Jun; Teng, Yan; Shi, Yanchao; Chen, Changhua

2015-01-01

In relativistic backward wave oscillators (RBWOs), although the slow wave structure (SWS) and electron beam determine the main characteristics of beam-wave interaction, many other factors can also significantly affect the microwave generation process. This paper investigates the influence of voltage rise time on beam-wave interaction in RBWOs. Preliminary analysis and PIC simulations demonstrate if the voltage rise time is moderately long, the microwave frequency will gradually increase during the startup process until the voltage reaches its amplitude, which can be explained by the dispersion relation. However, if the voltage rise time is long enough, the longitudinal resonance of the finitely-long SWS will force the RBWO to work with unwanted longitudinal modes for a while and then gradually hop to the wanted longitudinal mode, and this will lead to an impure microwave frequency spectrum. Besides, a longer voltage rise time will delay the startup process and thus lead to a longer microwave saturation time. And if unwanted longitudinal modes are excited due to long voltage rise time, the microwave saturation time will be further lengthened. Therefore, the voltage rise time of accelerators adopted in high power microwave technology should not be too long in case unwanted longitudinal modes are excited

Slow voltage oscillations in Ag-doped superconducting Y-Ba-Cu-O

Energy Technology Data Exchange (ETDEWEB)

Altinkok, A. [Abant Izzet Baysal University, Department of Physics, Turgut Gulez Research Laboratory, 14280 Bolu (Turkey)], E-mail: altinkok_a@ibu.edu.tr; Yetis, H.; Kilic, K.; Kilic, A.; Olutas, M. [Abant Izzet Baysal University, Department of Physics, Turgut Gulez Research Laboratory, 14280 Bolu (Turkey)

2008-09-15

The time effects in Ag-doped YBa{sub 2}Cu{sub 3}O{sub 7-x} sample (YBCO/Ag) were examined by means of transport relaxation measurements (V-t curves). At well-defined values of transport current (I), temperature (T) and external magnetic field (H), an abrupt rise in sample voltage was observed at the early stage of the relaxation process. After reducing the initial current to a finite value, the sample voltage levels off within a very short time. The rapid voltage drops seen in V-t curves were attributed to the rapid dynamic reorganization of flux lines traversing the sample edges. These observations were also interpreted as an indication of doping of YBCO with Ag and easy suppression of superconducting order parameter due to the presence of Ag. In addition, we investigated the influence of bidirectional square wave (BSW) current on the evolution of V-t curves at different temperatures and external magnetic fields. It was observed that a nonlinear response seen in V-t curves to BSW current with sufficiently short periods or sufficiently low amplitude reflects itself as regular sinusoidal- type voltage oscillations, which were discussed mainly in terms of the dynamic competition between pinning and depinning.

Voltage Oscillations in a Polymer Electrolyte Membrane Fuel Cell with Pd-Pt/C and Pd/C Anodes.

Science.gov (United States)

Nogueira, Jéssica Alves; Varela, Hamilton

2017-10-01

Polymer electrolyte membrane fuel cells (PEMFC) fed with H 2 contaminated with CO may exhibit oscillatory behavior when operated galvanostatically. The self-organization of the anodic overpotential is interesting because it can be accompanied by an increase in the average performance. Herein we report experimental studies of voltage oscillations that emerge in a PEMFC equipped with a Pd/C or PdPt/C anode and fed with H 2 contaminated with CO (100 ppm). We used on-line mass spectrometry to investigate how the mass fragments associated with CO 2 and CO ( m / z 44 and 28, respectively) varied with the voltage oscillations. Overall, we observed that oscillations in the anodic overpotential are in phase with that of the CO and CO 2 signals. This fact is consistent with an autonomous adsorption-oxidation cyclic process. For both anodes, it has been observed that, in general, an increase in current density implies an increase in oscillatory frequency. By using CO stripping, we also discuss how the onset of CO oxidation is related to the maximum overpotential reached during a cycle, whereas the minimum overpotential can be associated with the catalytic activity of the electrode for H 2 oxidation.

Voltage-driven quantum oscillations in graphene

International Nuclear Information System (INIS)

Yampol'skii, V A; Savel'ev, S; Nori, Franco

2008-01-01

We predict unusual (for non-relativistic quantum mechanics) electron states in graphene, which are localized within a finite-width potential barrier. The density of localized states in the sufficiently high and/or wide graphene barrier exhibits a number of singularities at certain values of the energy. Such singularities provide quantum oscillations of both the transport (e.g. conductivity) and thermodynamic properties of graphene-when increasing the barrier height and/or width, similarly to the well-known Shubnikov-de-Haas (SdH) oscillations of conductivity in pure metals. However, here the SdH-like oscillations are driven by an electric field instead of the usual magnetically driven SdH-oscillations

Realisations of single-resistance-controlled quadrature oscillators using a generalised current follower transconductance amplifier and a unity-gain voltage-follower

OpenAIRE

Herencsár, Norbert; Vrba, Kamil; Koton, Jaroslav; Lahiri, Abhirup

2010-01-01

This article presents realisations of single-resistance-controlled-oscillators (SRCOs) using the recently proposed modern active building block (ABB), namely the generalised current follower transconductance amplifier (GCFTA) and unity-gain voltage-follower (UGVF). The SRCO is made using reduced number of components: one GCFTA and one UGVF as the ABBs, two resistors and two grounded capacitors. The circuit offers the advantage of non-interactive control of condition of oscillation and frequen...

An optimized low-power voltage controlled oscillator

Science.gov (United States)

Shah, Kriyang; Le, Hai Phuong; Singh, Jugdutt

2007-01-01

This paper presents an optimised low-power low-phase-noise Voltage Controlled Oscillator (VCO) for Bluetooth wireless applications. The system level design issues and tradeoffs related to Direct Conversion Receiver (DCR) and Low Intermediate Frequency (IF) architecture for Bluetooth are discussed. Subsequently, for a low IF architecture, the critical VCO performance parameters are derived from system specifications. The VCO presented in the paper is optimised by implementing a novel biasing circuit that employs two current mirrors, one at the top and the other one at the bottom of the cross-coupled complementary VCO, to give the exact replica of the current in both the arms of current mirror circuit. This approach, therefore, significantly reduces the system power consumption as well as improves the system performance. Results show that, the VCO consumes only 281μW of power at 2V supply. Its phase noise performance are -115dBc/Hz, -130dBc/Hz and -141dBc/Hz at the offset frequency of 1MHz, 3MHz and 5MHz respectively. Results indicate that 31% reduction in power consumption is achieved as compared to the traditional VCO design. These characteristics make the designed VCO a better candidate for Bluetooth wireless application where power consumption is the major issue.

A voltage-controlled ring oscillator using InP full enhancement-mode HEMT logic

Energy Technology Data Exchange (ETDEWEB)

Du Rui; Dai Yang; Chen Yanling; Yang Fuhua, E-mail: ddrr@semi.ac.c [Research Center of Semiconductor Integration, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

2009-03-15

A voltage-controlled ring oscillator (VCO) based on a full enhancement-mode InAlAs/InGaAs/InP high electron mobility transistor (HEMT) logic is proposed. An enhancement-mode HEMT (E-HEMT) is fabricated, whose threshold is demonstrated to be 10 mV. The model of the E-HEMT is established and used in the SPICE simulation of the VCO. The result proves that the full E-HEMT logic technology can be applied to the VCO. And compared with the HEMT DCFL technology, the complexity of our fabrication process is reduced and the reliability is improved.

The Study of a Nonlinear Duffing – Type Oscillator Driven by Two Voltage Sources

Directory of Open Access Journals (Sweden)

J. O. Maaita

2013-10-01

Full Text Available In the present work, a detailed study of a nonlinear electrical oscillator with damping and external excitation is presented. The system under study consists of a Duffing-type circuit driven by two sinusoidal voltage sources having different frequencies. The dynamical behavior of the proposed system is investigated numerically, by solving the system of state equations and simulating its behavior as a circuit using MultiSim. The tools of the theoretical approach are the bifurcation diagrams, the Poincaré sections, the phase portraits, and the maximum Lyapunov exponent. The numerical investigation showed that the system has rich complex dynamics including phenomena such as quasiperiodicity, 3-tori, and chaos.

Observation of Sinusoidal Voltage Behaviour in Silver Doped YBCO

Science.gov (United States)

Altinkok, Atilgan; Olutas, Murat; Kilic, Kivilcim; Kilic, Atilla

The influence of bi-directional square wave (BSW) current was investigated on the evolution of the V - t curves at different periods (P) , temperatures and external magnetic fields. It was observed that slow transport relaxation measurements result in regular sinusoidal voltage oscillations which were discussed mainly in terms of the dynamic competition between pinning and depinning.The symmetry in the voltage oscillations was attributed to the elastic coupling between the flux lines and the pinning centers along grain boundaries and partly inside the grains. This case was also correlated to the equality between flux entry and exit along the YBCO/Ag sample during regular oscillations. It was shown that the voltage oscillations can be described well by an empirical expression V (t) sin(wt + φ) . We found that the phase angle φgenerally takes different values for the repetitive oscillations. Fast Fourier Transform analysis of the V - t oscillations showed that the oscillation period is comparable to that (PI) of the BSW current. This finding suggests a physical mechanism associated with charge density waves (CDWs), and, indeed, the weakly pinned flux line system in YBCO/Ag resembles the general behavior of CDWs. At certain values of PI, amplitude of BSW current, H and T, the YBCO/Ag sample behaves like a double-integrator, since it converts the BSW current to sinusoidal voltage oscillations in time.

Self-oscillating resonant power converter

DEFF Research Database (Denmark)

2014-01-01

The present invention relates to resonant power converters and inverters comprising a self-oscillating feedback loop coupled from a switch output to a control input of a switching network comprising one or more semiconductor switches. The self-oscillating feedback loop sets a switching frequency...... of the power converter and comprises a first intrinsic switch capacitance coupled between a switch output and a control input of the switching network and a first inductor. The first inductor is coupled in-between a first bias voltage source and the control input of the switching network and has...... a substantially fixed inductance. The first bias voltage source is configured to generate an adjustable bias voltage applied to the first inductor. The output voltage of the power converter is controlled in a flexible and rapid manner by controlling the adjustable bias voltage....

Evidence of Gate Voltage Oscillations during Short Circuit of Commercial 1.7 kV/ 1 kA IGBT Power Modules

DEFF Research Database (Denmark)

Reigosa, Paula Diaz; Wu, Rui; Iannuzzo, Francesco

2015-01-01

This paper analyzes the evidence of critical gate voltage oscillations in 1.7 kV/1 kA Insulated-Gate Bipolar Transistor (IGBT) power modules under short circuit conditions. A 6 kA/1.1 kV Non-Destructive Test (NDT) set up for repeatable short circuit tests has been built with a 40 nH stray inducta...

The Coefficient of the Voltage Induced Frequency Shift Measurement on a Quartz Tuning Fork

Directory of Open Access Journals (Sweden)

Yubin Hou

2014-11-01

Full Text Available We have measured the coefficient of the voltage induced frequency shift (VIFS of a 32.768 KHz quartz tuning fork. Three vibration modes were studied: one prong oscillating, two prongs oscillating in the same direction, and two prongs oscillating in opposite directions. They all showed a parabolic dependence of the eigen-frequency shift on the bias voltage applied across the fork, due to the voltage-induced internal stress, which varies as the fork oscillates. The average coefficient of the VIFS effect is as low as several hundred nano-Hz per millivolt, implying that fast-response voltage-controlled oscillators and phase-locked loops with nano-Hz resolution can be built.

Constant Switching Frequency Self-Oscillating Controlled Class-D Amplifiers

DEFF Research Database (Denmark)

Nguyen-Duy, Khiem; Knott, Arnold; Andersen, Michael A. E.

2014-01-01

The self-oscillating control approach has been used extensively in class-D amplifiers. It has several advantages such as high bandwidth and high audio performance. However, one of the primary disadvantages in a self-oscillating controlled system is that the switching frequency of the amplifier...... varies with the ratio of the output voltage to the input rail voltage. In other words, the switching frequency varies with the duty cycle of the output. The drop in the frequency results in lower control bandwidth and higher output voltage ripple, which are undesirable. This paper proposes a new self-oscillating...... control scheme that maintains a constant switching frequency over the full range of output voltage. The frequency difference is processed by a compensator whose output adjusts the total loop gain of the control system. It has been proven by simulation that a con-stant switching frequency self-oscillating...

Phase diagrams and switching of voltage and magnetic field in dilute magnetic semiconductor nanostructures

Energy Technology Data Exchange (ETDEWEB)

Escobedo, R. [Departamento de Matematica Aplicada y Ciencias de la Computacion, Universidad de Cantabria, 39005 Santander (Spain); Carretero, M.; Bonilla, L.L. [G. Millan Institute, Fluid Dynamics, Nanoscience and Industrial Maths., Universidad Carlos III de Madrid, 28911 Leganes (Spain); Unidad Asociada al Instituto de Ciencia de Materiales, CSIC, 28049 Cantoblanco, Madrid (Spain); Platero, G. [Instituto de Ciencia de Materiales, CSIC, 28049 Cantoblanco, Madrid (Spain)

2010-04-15

The response of an n-doped dc voltage biased II-VI multi-quantum well dilute magnetic semiconductor nanostructure having its first well doped with magnetic (Mn) impurities is analyzed by sweeping wide ranges of both the voltage and the Zeeman level splitting induced by an external magnetic field. The level splitting versus voltage phase diagram shows regions of stable self-sustained current oscillations immersed in a region of stable stationary states. Transitions between stationary states and self-sustained current oscillations are systematically analyzed by both voltage and level splitting abrupt switching. Sudden voltage or/and magnetic field changes may switch on current oscillations from an initial stationary state, and reciprocally, current oscillations may disappear after sudden changes of voltage or/and magnetic field changes into the stable stationary states region. The results show how to design such a device to operate as a spin injector and a spin oscillator by tuning the Zeeman splitting (through the applied external magnetic field), the applied voltage and the sample configuration parameters (doping density, barrier and well widths, etc.) to select the desired stationary or oscillatory behavior. Phase diagram of Zeeman level splitting {delta} vs. dimensionless applied voltage {phi} for N = 10 QWs. White region: stable stationary states; black: stable self-sustained current oscillations. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Intrinsic current oscillations in an asymmetric triple-barrier resonant tunnelling diode

International Nuclear Information System (INIS)

Wójcik, P; Spisak, B J; Wołoszyn, M; Adamowski, J

2010-01-01

The electronic transport characteristics of an asymmetric triple-barrier resonant tunnelling diode are calculated by the time-dependent Wigner–Poisson method. The intrinsic current oscillations are found in two separate bias voltage ranges. The first one is located below the resonant current peak, and the second lies in the negative differential resistance region. We provide the explanation of the current density oscillations in these two separate bias voltage ranges based on the analysis of the self-consistent potential profiles and changes of electron density. We have shown that two different formation mechanisms are responsible for the current density oscillations in these two bias voltage ranges. In the bias voltage range below the resonant current peak in the current–voltage characteristics, the current density oscillations are caused by the coupling between quasi-bound states in the left and right quantum wells. On the other hand, the current density oscillations in the negative differential resistance region result from the coupling between quasi-bound states in the left quantum well and the quantum well formed in the region of the left contact

Possibility of persistent voltage observation in a system of asymmetric superconducting rings

International Nuclear Information System (INIS)

Burlakov, A.A.; Gurtovoi, V.L.; Ilin, A.I.; Nikulov, A.V.; Tulin, V.A.

2012-01-01

The possibility of observing persistent voltage in superconducting rings of different arm widths is experimentally investigated. It was previously found that switching of the arms between superconducting and normal states by an AC current induces DC voltage oscillation in the magnetic field with a period corresponding to the flux quantum inside the ring. We used systems with a large number of asymmetric rings connected in series to investigate the possibility of observing this quantum phenomenon near the superconducting transition, where thermal fluctuations lead to switching of ring segments without an external influence and the persistent current is much smaller than in the superconducting state. -- Highlights: ► A possibility to observe the persistent voltage is investigated experimentally. ► The persistent voltage is a DC voltage observed at thermodynamic equilibrium. ► It oscillates in magnetic field like the persistent current in superconducting ring. ► The period of the oscillations corresponds to the flux quantum inside the ring. ► The quantum oscillations of the DC voltage were observed on asymmetric rings.

Integrated circuit manufacture and tuning of subassemblies of a statistical analyzer of voltage oscillations (AKON). Izgotovleniye na integral'nykh skhemakh i nastroyka uzlov statisticheskogo analizatora kolebaniy napryazheniya (AKON)

Energy Technology Data Exchange (ETDEWEB)

Yermakov, V.F.; Oleynik, V.I.; Sambarov, Yu.M.

1982-01-01

The basic circuits and instructions for tuning subassemblies of a statistical analyzer of voltage oscillation are described. The device is intended for monitoring quality of voltage in electric networks in accordance with GOST13109-67. The component base of the device includes integrated circuits of the series 140, 155, 218 and 228.

Electronically tunable RC sinusoidal oscillators

International Nuclear Information System (INIS)

Florescu, Valeriu

2008-01-01

This paper presents two types of active configurations for realizing electronically tunable RC sinusoidal oscillators. The type-1 network employs two grounded scaled resistances KR 1 and KR 2 , where K is scaling factor. The frequency of oscillation W 0 is controlled conveniently by adjusting K, since W 0 appears in the form W 0 =1/K √ R 1 C 1 R 2 C 2 . For realizing the scaled resistances, an active configuration is proposed, which realizes KR 1 =R 1 /(1+f(V B )), where f(V B ) denotes a function of a controlling voltage V B . Thus the frequency tuning can be effected by controlling a voltage V B . The type-2 oscillator uses two periodically switched conductances. It is shown that the tuning of oscillation frequency can be done by varying the pulse width-to-period ratio (t/T) of the periodically switched conductances. (author)

A Class-F CMOS Oscillator

NARCIS (Netherlands)

Babaie, M.; Staszewski, R.B.

2013-01-01

An oscillator topology demonstrating an improved phase noise performance is proposed in this paper. It exploits the time-variant phase noise model with insights into the phase noise conversion mechanisms. The proposed oscillator is based on enforcing a pseudo-square voltage waveform around the LC

Design and Implementation of a High-Voltage Generator with Output Voltage Control for Vehicle ER Shock-Absorber Applications

Directory of Open Access Journals (Sweden)

Chih-Lung Shen

2013-01-01

Full Text Available A self-oscillating high-voltage generator is proposed to supply voltage for a suspension system in order to control the damping force of an electrorheological (ER fluid shock absorber. By controlling the output voltage level of the generator, the damping force in the ER fluid shock absorber can be adjusted immediately. The shock absorber is part of the suspension system. The high-voltage generator drives a power transistor based on self-excited oscillation, which converts dc to ac. A high-frequency transformer with high turns ratio is used to increase the voltage. In addition, the system uses the car battery as dc power supply. By regulating the duty cycle of the main switch in the buck converter, the output voltage of the buck converter can be linearly adjusted so as to obtain a specific high voltage for ER. The driving system is self-excited; that is, no additional external driving circuit is required. Thus, it reduces cost and simplifies system structure. A prototype version of the actual product is studied to measure and evaluate the key waveforms. The feasibility of the proposed system is verified based on experimental results.

Recent Progress in Silicon Mems Oscillators

Science.gov (United States)

2008-12-01

MEMS oscillator. As shown, a MEMS resonator is connected to an IC. The reference oscillator, which is basically a transimpedance amplifier ...small size), and (3) DC bias voltage required to operate the resonators. As a result, instead of Colpitts or Pierce architecture, a transimpedence ... amplifier is typically used for sustain the oscillation. The frequency of the resonators is determined by both material properties and geometry of

Control Strategy for Microgrid Inverter under Unbalanced Grid Voltage Conditions

DEFF Research Database (Denmark)

Guo, Xiaoqiang; Liu, Wenzhao; Zhang, X.

2014-01-01

This paper presents the theoretical analysis of the inherent reason of current harmonic and power oscillation phenomena in case of operating the microgrid inverter under unbalanced grid voltage conditions. In order to flexibly control the current harmonic and power oscillation, a new stationary...... inverter. Finally, the performance evaluation tests are carried out under unbalanced grid voltage conditions. Results verify the effectiveness of the propose method....

Voltage Control System of A DC Generator Using PLC

OpenAIRE

Subrata CHATTOPADHYAY; Sagarika PAL

2008-01-01

The voltage control system of a DC generator may suffer from high frequency oscillations without offset or low frequency oscillation with offset. A PID controller can eliminate both these errors. In the present paper, the voltage control system of a DC generator using a PLC based PID controller has been designed. Operation of PLC as a continuous controller has been described and the load characteristic of DC generator with and without controller have been determined experimentally and reporte...

Border-Collision Bifurcations and Chaotic Oscillations in a Piecewise-Smooth Dynamical System

DEFF Research Database (Denmark)

Zhusubaliyev, Z.T.; Soukhoterin, E.A.; Mosekilde, Erik

2002-01-01

Many problems of engineering and applied science result in the consideration of piecewise-smooth dynamical systems. Examples are relay and pulse-width control systems, impact oscillators, power converters, and various electronic circuits with piecewise-smooth characteristics. The subject...... of investigation in the present paper is the dynamical model of a constant voltage converter which represents a three-dimensional piecewise-smooth system of nonautonomous differential equations. A specific type of phenomena that arise in the dynamics of piecewise-smooth systems are the so-called border......-collision bifurcations. The paper contains a detailed analysis of this type of bifurcational transition in the dynamics of the voltage converter, in particular, the merging and subsequent disappearance of cycles of different types, change of solution type, and period-doubling, -tripling, -quadrupling and -quintupling...

Development of copper bromide laser master oscillator power ...

Indian Academy of Sciences (India)

2014-02-09

Feb 9, 2014 ... Development of master oscillator power amplifier (MOPA) system of copper bromide laser (CBL) operating at ... The spectral distribution of power at .... It is evident from the voltage waveforms that the breakdown voltage drops.

Frequency-dependent transient response of an oscillating electrically actuated droplet

International Nuclear Information System (INIS)

Dash, S; Kumari, N; Garimella, S V

2012-01-01

The transient response of a millimeter-sized sessile droplet under electrical actuation is experimentally investigated. Under dc actuation, the droplet spreading rate increases as the applied voltage is increased due to the higher electrical forces induced. At sufficiently high dc voltages, competition between the electrical actuation force, droplet inertia, the retarding surface tension force and contact line friction leads to droplet oscillation. The timescale for the droplet to attain its maximum wetted diameter during step actuation is analyzed. Systematic experiments are conducted over a frequency range of 5–200 Hz and actuation voltages of 40–80 V rms to determine the dependence of droplet oscillation on these parameters. The response of the droplet to different actuation frequencies and voltages is determined in terms of its contact angle and contact radius variation. The frequency of the driving force (equal to twice the frequency of the applied electrical signal) determines the mode of oscillation of the droplet which, together with its resonance characteristics, governs whether the droplet contact angle and contact radius vary in phase or out of phase with each other. In addition to the primary frequency response at the electrical forcing frequency, the droplet oscillation exhibits sub-harmonic oscillation at half of the forcing frequency that is attributed to the parametric nature of the electrical force acting on the triple contact line of the droplet. (paper)

The current-voltage characteristic and potential oscillations of a double layer in a triple plasma device

International Nuclear Information System (INIS)

Carpenter, R.T.; Torven, S.

1986-07-01

The properties of a strong double layer in a current circuit with a capacitance and an inductance are investigated in a triple plasma device. The double layer gives rise to a region of negative differential resistance in the current-voltage characteristic of the device, and this gives non-linear oscillations in the current and the potential drop over the double layer (PhiDL). For a sufficiently large circuit inductance PhiDL reaches an amplitude given by the induced voltage (-LdI/dt) which is much larger than the circuit EMF due to the rapid current decrease when PhiDL increases. A variable potential minimum exists in the plasma on the low potential side of the double layer, and the depth of the minimum increases when PhiDL increases. An increasing fraction of the electrons incident at the double layer are then reflected, and this is found to be the main process giving rise to the negative differential resistance. A qualitative model for the variation of the minimum potential with PhiDL is also proposed. It is based on the condition that the minimum potential must adjust itself self-consistentely so that quasi-neutrality is maintained in the plasma region where the minimum is assumed. (authors)

Discharge Oscillations in a Permanent Magnet Cylindrical Hall-Effect Thruster

Science.gov (United States)

Polzin, K. A.; Sooby, E. S.; Raitses, Y.; Merino, E.; Fisch, N. J.

2009-01-01

Measurements of the discharge current in a cylindrical Hall thruster are presented to quantify plasma oscillations and instabilities without introducing an intrusive probe into the plasma. The time-varying component of the discharge current is measured using a current monitor that possesses a wide frequency bandwidth and the signal is Fourier transformed to yield the frequency spectra present, allowing for the identification of plasma oscillations. The data show that the discharge current oscillations become generally greater in amplitude and complexity as the voltage is increased, and are reduced in severity with increasing flow rate. The breathing mode ionization instability is identified, with frequency as a function of discharge voltage not increasing with discharge voltage as has been observed in some traditional Hall thruster geometries, but instead following a scaling similar to a large-amplitude, nonlinear oscillation mode recently predicted in for annular Hall thrusters. A transition from lower amplitude oscillations to large relative fluctuations in the oscillating discharge current is observed at low flow rates and is suppressed as the mass flow rate is increased. A second set of peaks in the frequency spectra are observed at the highest propellant flow rate tested. Possible mechanisms that might give rise to these peaks include ionization instabilities and interactions between various oscillatory modes.

Voltage Control System of A DC Generator Using PLC

Directory of Open Access Journals (Sweden)

Subrata CHATTOPADHYAY

2008-06-01

Full Text Available The voltage control system of a DC generator may suffer from high frequency oscillations without offset or low frequency oscillation with offset. A PID controller can eliminate both these errors. In the present paper, the voltage control system of a DC generator using a PLC based PID controller has been designed. Operation of PLC as a continuous controller has been described and the load characteristic of DC generator with and without controller have been determined experimentally and reported in this paper.

Electronically Tunable Quadrature Sinusoidal Oscillator with Equal Output Amplitudes during Frequency Tuning Process

Directory of Open Access Journals (Sweden)

Den Satipar

2017-01-01

Full Text Available A new configuration of voltage-mode quadrature sinusoidal oscillator is proposed. The proposed oscillator employs two voltage differencing current conveyors (VDCCs, two resistors, and two grounded capacitors. In this design, the use of multiple/dual output terminal active building block is not required. The tuning of frequency of oscillation (FO can be done electronically by adjusting the bias current of active device without affecting condition of oscillation (CO. The electronic tuning can be done by controlling the bias current using a digital circuit. The amplitude of two sinusoidal outputs is equal when the frequency of oscillation is tuned. This makes the sinusoidal output voltages meet good total harmonic distortions (THD. Moreover, the proposed circuit can provide the sinusoidal output current with high impedance which is connected to external load or to another circuit without the use of buffer device. To confirm that the oscillator can generate the quadrature sinusoidal output signal, the experimental results using VDCC constructed from commercially available ICs are also included. The experimental results agree well with theoretical anticipation.

Constant Switching Frequency Self-Oscillating Controlled Class-D Amplifiers

OpenAIRE

Nguyen-Duy, Khiem; Knott, Arnold; Andersen, Michael A. E.

2014-01-01

The self-oscillating control approach has been used extensively in class-D amplifiers. It has several advantages such as high bandwidth and high audio performance. However, one of the primary disadvantages in a self-oscillating controlled system is that the switching frequency of the amplifier varies with the ratio of the output voltage to the input rail voltage. In other words, the switching frequency varies with the duty cycle of the output. The drop in the frequency results in lower contro...

Branching in current-voltage characteristics of intrinsic Josephson junctions

International Nuclear Information System (INIS)

Shukrinov, Yu M; Mahfouzi, F

2007-01-01

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

TCAD analysis of short-circuit oscillations in IGBTs

DEFF Research Database (Denmark)

Reigosa, Paula Diaz; Iannuzzo, Francesco; Rahimo, Munaf

2017-01-01

Insulated-Gate Bipolar Transistors (IGBTs) exhibit a gate-voltage oscillation phenomenon during short-circuit, which can result in a gate-oxide breakdown. The oscillations have been investigated through device simulations and experimental investigations of a 3.3-kV IGBT. It has been found...... during short circuit....

The Mechanical Transient Process at Asynchronous Motor Oscillating Mode

Science.gov (United States)

Antonovičs, Uldis; Bražis, Viesturs; Greivulis, Jānis

2009-01-01

The research object is squirrel-cage asynchronous motor connected to single-phase sinusoidal. There are shown, that by connecting to the stator windings a certain sequence of half-period positive and negative voltage, a motor rotor is rotated, but three times slower than in the three-phase mode. Changing the connecting sequence of positive and negative half-period voltage to stator windings, motor can work in various oscillating modes. It is tested experimentally. The mechanical transient processes had been researched in rotation and oscillating modes.

Bias voltage dependence of a flux-sensitive Al/GaAs/Al (SNS) interferometer

DEFF Research Database (Denmark)

Kutchinsky, Jonatan; Taboryski, Rafael Jozef; Hansen, Jørn Bindslev

1999-01-01

bias voltage the fabricated interferometers typically exhibit 3% sinusoidal modulation of the conductance as a function of a magnetic field applied perpendicular to the loop. The conductance modulation is caused by resonant Andreev states in the normal GaAs region of the device. With increasing bias...... voltage of the order of a few microvolts the device is driven out of resonance and the conductance oscillations are extinguished. However, at higher bias voltage corresponding to the superconducting energy gap of Al (178 mu V) the conductance oscillations reappear but with reduced amplitude...

Oscillating plasma bubbles. IV. Grids, geometry, and gradients

Energy Technology Data Exchange (ETDEWEB)

Stenzel, R. L. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States); Urrutia, J. M. [Urrutia Scientific, Van Nuys, California 91406 (United States)

2012-08-15

Plasma bubbles are created in an ambient plasma. The bubble is formed inside a cavity bounded by a negatively biased grid. Ions are injected through the grid and neutralized by electrons from either the background plasma or an internal electron emitter. The external electron supply is controlled by the grid bias relative to the external plasma potential. When the electron flux is restricted to the ion flux, the sheath of the bubble becomes unstable and causes the plasma potential to oscillate near the ion plasma frequency. The exact frequency depends on the net space charge density in the bubble sheath. The frequency increases with density and grid voltage, provided the grid forms a parallel equipotential surface. The present investigation shows that when the Debye length becomes smaller than the grid openings the electron flux cannot be controlled by the grid voltage. The frequency dependence on grid voltage and density is modified creating frequency and amplitude jumps. Low frequency sheath oscillations modulate the high frequency normal oscillations. Harmonics and subharmonics are excited by electrons in an ion-rich sheath. When the plasma parameters vary over the bubble surface, the sheath may oscillate at different frequencies. A cavity with two isolated grids has been used to investigate anisotropies of the energetic electron flux in a discharge plasma. The frequency dependence on grid voltage is entirely different when the grid controls the energetic electrons or the bulk electrons. These observations are important to several fields of basic plasma physics, such as sheaths, sheath instabilities, diagnostic probes, current, and space charge neutralization of ion beams.

Design and Control of a Dynamic Voltage Restorer

DEFF Research Database (Denmark)

Nielsen, John Godsk

voltage until the energy storage is completely drained or the voltages have returned to normal voltage levels. The control of the HV-DVR is a combined feedforward and feedback control to have a fast response time and load independent voltages. The control is implemented in a rotating dq-reference frame...... electric consumers against voltage dips and surges in the medium and low voltage distribution grid. The thesis first gives an introduction to relevant power quality issues for a DVR and power electronic controllers for voltage dip mitigation. Thereafter the operation and the elements in a DVR are described...... of symmetrical and non-symmetrical voltage dips. In most cases the DVR is capable of restoring the load voltages within 2 ms. During the transition phases load voltage oscillations can be generated and during the return of the supply voltages short time over-voltages can be generated by the DVR. Both...

Low-frequency oscillations at high density in JFT-2

International Nuclear Information System (INIS)

Maeno, Masaki; Katagiri, Masaki; Suzuki, Norio; Fujisawa, Noboru

1977-12-01

Low-frequency oscillations in a plasma were measured with magnetic probes and Si surface-barrier detectors, and behaviour of the high density plasmas was studied. The plasma current profile in the phase of decreasing density after the interruption of gas input is more peaked than during gas input. The introduction of hydrogen during a discharge results in a reduction of the impurities flux. The increase of density by fast gas input is limited with a negative voltage spike. Immediately before a negative voltage spike, oscillations of m=1,2 grow, leading to the spike. (auth.)

Partial discharge characteristics and mechanism in voids at impulse voltages

International Nuclear Information System (INIS)

Zhao, X F; Guo, Z F; Wang, Y Y; Li, J H; Li, Y M; Yao, X

2011-01-01

Partial discharge (PD) characteristics and mechanism in artificial cavities in an epoxy plate have been investigated for different void dimensions and impulse voltage waveforms. A differential measurement system was developed in order to detect PD current pulses effectively. Experimental results showed that the 50% probability PD inception voltage (PDIV 50 ) increases initially as the cavity diameter decreases at constant depth for double exponential impulses as well as oscillating impulses, but after aging, it becomes independent of the cavity diameter. Moreover, some distinctive characteristics of PD (e.g. main discharge and reverse discharge during the rise and fall phases of the applied voltage) were also investigated. The differences of the PD propagation and the mechanism between double exponential impulses and oscillating impulse were discussed

Reactor oscillator - I - III, Part III - Electronic device; Reaktorski oscilator - I-III, III Deo - Elektronski uredjaj

Energy Technology Data Exchange (ETDEWEB)

Lolic, B; Jovanovic, S [Institute of Nuclear Sciences Boris Kidric, Laboratorija za fiziku reaktora, Vinca, Beograd (Serbia and Montenegro)

1961-12-15

This report describes functioning of the reactor oscillator electronic system. Two methods of oscillator operation were discussed. The first method is so called method of amplitude modulation of the reactor power, and the second newer method is phase method. Both methods are planned for the present reactor oscillator.

Simulations of signal amplification and oscillations using a SNS junction

International Nuclear Information System (INIS)

Luiz, A.M.; Soares, V.; Nicolsky, R.

1998-01-01

A superconducting - normal metal - superconducting junction (SNS junction) may exhibit a low voltage negative differential resistance (LVNDR) effect over part of its current voltage characteristic (CVC). As the LVNDR effect is stable against a bias voltage at this CVC range, it should be possible to combine a SNS junction with conventional electronic circuits to obtain electronic devices such as mixers, amplifiers and oscillators. Making use of this remarkable effect, we show that an amplifier may be feasible by assembling a simple voltage divider made up of a SNS junction in series with a resistor. The amplifier circuit includes an adjustable DC voltage supply (the bias voltage) and an AC signal source with a given voltage. The SNS junction is connected in series with a resistor R. Choosing values of the load resistance R approximately equal to the module of the negative differential resistance (dV/dI), at the bias voltage, we may obtain large gains in this amplifier device. In order to get an oscillator, the SNS junction should be connected to a RLC tank circuit with a bias voltage adjusted in the range of the LVNDR region of its CVC. A power output of the order of one microwatt may be easily obtained. (orig.)

Oscillations of disks

CERN Document Server

Kato, Shoji

2016-01-01

This book presents the current state of research on disk oscillation theory, focusing on relativistic disks and tidally deformed disks. Since the launch of the Rossi X-ray Timing Explorer (RXTE) in 1996, many high-frequency quasiperiodic oscillations (HFQPOs) have been observed in X-ray binaries. Subsequently, similar quasi-periodic oscillations have been found in such relativistic objects as microquasars, ultra-luminous X-ray sources, and galactic nuclei. One of the most promising explanations of their origin is based on oscillations in relativistic disks, and a new field called discoseismology is currently developing. After reviewing observational aspects, the book presents the basic characteristics of disk oscillations, especially focusing on those in relativistic disks. Relativistic disks are essentially different from Newtonian disks in terms of several basic characteristics of their disk oscillations, including the radial distributions of epicyclic frequencies. In order to understand the basic processes...

Magnetically insulated transmission line oscillator

Science.gov (United States)

Bacon, L.D.; Ballard, W.P.; Clark, M.C.; Marder, B.M.

1987-05-19

A magnetically insulated transmission line oscillator employs self-generated magnetic fields to generate microwave energy. An anode of the oscillator includes slow-wave structures which are formed of a plurality of thin conductive vanes defining cavities therebetween, and a gap is formed between the anode and a cathode of the oscillator. In response to a pulsed voltage applied to the anode and cathode, self-generated magnetic fields are produced in a cross-field orientation with respect to the orientation of the electric field between the anode and the cathode. The cross-field magnetic fields insulate the flow of electrons in the gap and confine the flow of electrons within the gap. 11 figs.

Voltage measurements at the vacuum post-hole convolute of the Z pulsed-power accelerator

Directory of Open Access Journals (Sweden)

E. M. Waisman

2014-12-01

Full Text Available Presented are voltage measurements taken near the load region on the Z pulsed-power accelerator using an inductive voltage monitor (IVM. Specifically, the IVM was connected to, and thus monitored the voltage at, the bottom level of the accelerator’s vacuum double post-hole convolute. Additional voltage and current measurements were taken at the accelerator’s vacuum-insulator stack (at a radius of 1.6 m by using standard D-dot and B-dot probes, respectively. During postprocessing, the measurements taken at the stack were translated to the location of the IVM measurements by using a lossless propagation model of the Z accelerator’s magnetically insulated transmission lines (MITLs and a lumped inductor model of the vacuum post-hole convolute. Across a wide variety of experiments conducted on the Z accelerator, the voltage histories obtained from the IVM and the lossless propagation technique agree well in overall shape and magnitude. However, large-amplitude, high-frequency oscillations are more pronounced in the IVM records. It is unclear whether these larger oscillations represent true voltage oscillations at the convolute or if they are due to noise pickup and/or transit-time effects and other resonant modes in the IVM. Results using a transit-time-correction technique and Fourier analysis support the latter. Regardless of which interpretation is correct, both true voltage oscillations and the excitement of resonant modes could be the result of transient electrical breakdowns in the post-hole convolute, though more information is required to determine definitively if such breakdowns occurred. Despite the larger oscillations in the IVM records, the general agreement found between the lossless propagation results and the results of the IVM shows that large voltages are transmitted efficiently through the MITLs on Z. These results are complementary to previous studies [R. D. McBride et al., Phys. Rev. ST Accel. Beams 13, 120401 (2010

New Realizations of Single OTRA-Based Sinusoidal Oscillators

Directory of Open Access Journals (Sweden)

Hung-Chun Chien

2014-01-01

Full Text Available This study proposes three new sinusoidal oscillators based on an operational transresistance amplifier (OTRA. Each of the proposed oscillator circuits consists of one OTRA combined with a few passive components. The first circuit is an OTRA-based minimum RC oscillator. The second circuit is capable of providing independent control on the condition of oscillation without affecting the oscillation frequency. The third circuit exhibits independent control of oscillation frequency through a capacitor. This study first introduces the OTRA and the related formulations of the proposed oscillator circuits, and then discusses the nonideal effects, sensitivity analyses, and frequency stability of the presented circuits. The proposed oscillators exhibit low sensitivities and good frequency stability. Because the presented circuits feature low impedance output, they can be connected directly to the next stage without cascading additional voltage buffers. HSPICE simulations and experimental results confirm the feasibility of the new oscillator circuits.

Exploration of genetically encoded voltage indicators based on a chimeric voltage sensing domain

Directory of Open Access Journals (Sweden)

Yukiko eMishina

2014-09-01

Full Text Available Deciphering how the brain generates cognitive function from patterns of electrical signals is one of the ultimate challenges in neuroscience. To this end, it would be highly desirable to monitor the activities of very large numbers of neurons while an animal engages in complex behaviours. Optical imaging of electrical activity using genetically encoded voltage indicators (GEVIs has the potential to meet this challenge. Currently prevalent GEVIs are based on the voltage-sensitive fluorescent protein (VSFP prototypical design or on the voltage dependent state transitions of microbial opsins.We recently introduced a new VSFP design in which the voltage-sensing domain (VSD is sandwiched between a FRET pair of fluorescent proteins (termed VSFP-Butterflies and also demonstrated a series of chimeric VSD in which portions of the VSD of Ciona intestinalis voltage-sensitive phosphatase (Ci-VSP are substituted by homologous portions of a voltage-gated potassium channel subunit. These chimeric VSD had faster sensing kinetics than that of the native Ci-VSD. Here, we describe a new set of VSFPs that combine chimeric VSD with the Butterfly structure. We show that these chimeric VSFP-Butterflies can report membrane voltage oscillations of up to 200 Hz in cultured cells and report sensory evoked cortical population responses in living mice. This class of GEVIs may be suitable for imaging of brain rhythms in behaving mammalians.

Exploration of genetically encoded voltage indicators based on a chimeric voltage sensing domain.

Science.gov (United States)

Mishina, Yukiko; Mutoh, Hiroki; Song, Chenchen; Knöpfel, Thomas

2014-01-01

Deciphering how the brain generates cognitive function from patterns of electrical signals is one of the ultimate challenges in neuroscience. To this end, it would be highly desirable to monitor the activities of very large numbers of neurons while an animal engages in complex behaviors. Optical imaging of electrical activity using genetically encoded voltage indicators (GEVIs) has the potential to meet this challenge. Currently prevalent GEVIs are based on the voltage-sensitive fluorescent protein (VSFP) prototypical design or on the voltage-dependent state transitions of microbial opsins. We recently introduced a new VSFP design in which the voltage-sensing domain (VSD) is sandwiched between a fluorescence resonance energy transfer pair of fluorescent proteins (termed VSFP-Butterflies) and also demonstrated a series of chimeric VSD in which portions of the VSD of Ciona intestinalis voltage-sensitive phosphatase are substituted by homologous portions of a voltage-gated potassium channel subunit. These chimeric VSD had faster sensing kinetics than that of the native Ci-VSD. Here, we describe a new set of VSFPs that combine chimeric VSD with the Butterfly structure. We show that these chimeric VSFP-Butterflies can report membrane voltage oscillations of up to 200 Hz in cultured cells and report sensory evoked cortical population responses in living mice. This class of GEVIs may be suitable for imaging of brain rhythms in behaving mammalians.

Density-wave oscillations

International Nuclear Information System (INIS)

Belblidia, L.A.; Bratianu, C.

1979-01-01

Boiling flow in a steam generator, a water-cooled reactor, and other multiphase processes can be subject to instabilities. It appears that the most predominant instabilities are the so-called density-wave oscillations. They can cause difficulties for three main reasons; they may induce burnout; they may cause mechanical vibrations of components; and they create system control problems. A comprehensive review is presented of experimental and theoretical studies concerning density-wave oscillations. (author)

Control Of Stepper Motor Movement By DC Voltage

International Nuclear Information System (INIS)

Gayani, Didi; Margono; Indasah, Iin; Sugito

2000-01-01

Instrumentation for controlling the power of reactor of TRIGA Mark II uses the stepper motor to move the control rod of neutron absorbers. The direction and speed of control rod movement are determined by the polarity and the amplitude of DC voltage as an error signal that is the difference of set point of power and the power of being measured on the control system. The unit of stepper motor controller of reactor instrumentation of TRIGA Mark II uses patent module of trade Mark of Vexta, USA. In this chance, the electronic circuit is made to function as the control of stepper motor movement by using the DC voltage to anticipate the problem may be faced in case of repair and maintenance of reactor instrumentation. As a result of experiment, it is stated that the control of motor movement by using DC voltage is performed into 2 stages. First, by making the oscillator that is proportional to the positive DC voltage. Secondly, by making the translator to translate the oscillator signal to be a logic pattern for controlling the movement of stepper motor. Translator and motor driver are made by using the L297 and L298 as a pair of stepper motor controller of SGS T HOMSON

A Low-Voltage Ride-Through Control Strategy for Three-Phase Grid-Connected PV Systems

DEFF Research Database (Denmark)

Afshari, Ehsan; Farhangi, Babak; Yang, Yongheng

2017-01-01

similar variations in the dc-link voltage of conventional two-stage PV inverters. In such systems with an electrolytic capacitor in the dc-link, the oscillations of the dc-link voltage with DGF can deteriorate the capacitor lifetime, and thus the entire system. The proposed Low-Voltage Ride-Through (LVRT...

Breathing oscillations in enlarged cylindrical-anode-layer Hall plasma accelerator

Energy Technology Data Exchange (ETDEWEB)

Geng, S. F.; Wang, C. X. [Southwestern Institute of Physics, Chengdu 610041 (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Tang, D. L.; Qiu, X. M. [Southwestern Institute of Physics, Chengdu 610041 (China); Fu, R. K. Y. [Plasma Technology Limited, Festival Walk Tower, Tat Chee Avenue, Kowloon, Hong Kong (China); Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)

2013-05-28

Breathing oscillations in the discharge of an enlarged cylindrical-anode-layer Hall plasma accelerator are investigated by three-dimensional particle-in-cell (PIC) simulation. Different from the traditional breathing mode in a circular Hall plasma accelerator, the bulk plasma oscillation here is trigged by the potential barrier generated by the concentrated ion beam and substantial enough to compete with the anode voltage. The electric field near the anode is suppressed by the potential barrier thereby decreasing the electron density by {approx}36%. The discharge is restored to the normal level after the concentrated beam explodes and then it completes one cycle of electro-driven breathing oscillation. The breathing mode identified by the PIC simulation has a frequency range of {approx}156 kHz-{approx}250 kHz and does not vary monotonically with the discharge voltage.

Improved impedance transformation between microwave oscillator and Josephson junction series array

International Nuclear Information System (INIS)

Gutmann, P.; Vollmer, E.; Niemeyer, J.

1993-01-01

Superconducting microwave monolithic integrated circuits (S-MMIC), based on Josephson tunnel junctions, are a well-established tool to reproduce the volt at the highest level of accuracy. An external oscillator of a fixed frequency f supplies microwave energy through a waveguide to the S-MMIC. The wave changes its mode at a waveguide-antipodal finline-stripline taper before entering a series array stripline of up to 30 000 Josephson tunnel junctions and is dissipated as heat in a lossy stripline. Both striplines have a characteristic impedance Z of 2 to 5 Ω. An equivalent circuit is shown in figure 1. The oscillator is matched to the waveguide with a source resistance R G Z(waveguide) ∼ 550 Ω. The most critical part is the taper, which should work as a lossless impedance matching network at the frequency of the oscillator. Microwave energy is fed into the tunnel junctions by the surface current I HF of the travelling wave in the series array stripline producing an rf voltage amplitude U JHF across the capacitance C of each junction. The Josephson tunnel junctions work as self-oscillating parametric mixers producing steps of constant voltage V in the current-voltage characteristic whenever (nf - 2eV/h) = 0, with n denoting an integer and e and h denoting the elementary charge and Planck's constant, respectively. The equivalent circuit of a Josephson tunnel element used in a voltage standard for 1 V working at a frequency of f = 70 GHz is given by a lumped parallel resonant circuit with a nonlinear inductance on the order of L = φ 0 /2πI 0 ∼ 1 pH, flux quantum φ 0 = h/2e and a linear capacitance of C ∼ 40 pF. These tunnel junctions have a maximum zero voltage current of approximately I 0 ∼ 350 μA. (orig.)

Robustness of MW-Level IGBT modules against gate oscillations under short circuit events

DEFF Research Database (Denmark)

Reigosa, Paula Diaz; Wu, Rui; Iannuzzo, Francesco

2015-01-01

The susceptibility of MW-level IGBT power modules to critical gate voltage oscillations during short circuit events has been evidenced experimentally. This paper proposes a sensitivity analysis method to better understand the oscillating behavior dependence on different operating conditions (i...... the oscillation phenomenon, as well as to further improve the device performance during short circuit....

Summary of transient high-voltage calculations for the FRX-C experiment

International Nuclear Information System (INIS)

Kewish, R.W. Jr.; Rej, D.J.

1982-06-01

Calculations of the electrical circuit equations are performed over a wide range of parameters corresponding to the FRX-C field-reversed THETA-pinch experiment at Los Alamos. Without any plasma or external damping, serious voltage doubling and quadrupling of the main capacitor bank charge voltage are observed. These oscillating high voltages are found to be adequately suppressed by the strategic placement of external snubber circuitry. On the other hand, no doubling of the THETA-pinch preionization bank charge voltage is found. Calculations of the equations for the z-pinch preionization circuit are also performed

Characterization of chaotic electroconvection near flat electrodes under oscillatory voltages

Science.gov (United States)

Kim, Jeonglae; Davidson, Scott; Mani, Ali

2017-11-01

Onset of hydrodynamic instability and chaotic electroconvection in aqueous systems are studied by directly solving the two-dimensional coupled Poisson-Nernst-Planck and Navier-Stokes equations. An aqueous binary electrolyte is bounded by two planar electrodes where time-harmonic voltage is applied at a constant oscillation frequency. The governing equations are solved using a fully-conservative second-order-accurate finite volume discretization and a second-order implicit Euler time advancement. At a sufficiently high amplitude of applied voltage, the system exhibits chaotic behaviors involving strong hydrodynamic mixing and enhanced electroconvection. The system responses are characterized as a function of oscillation frequency, voltage magnitude, and the ratio of diffusivities of two ion species. Our results indicate that electroconvection is most enhanced for frequencies on the order of inverse system RC time scale. We will discuss the dependence of this optimal frequency on the asymmetry of the diffusion coefficients of ionic species. Supported by the Stanford's Precourt Institute.

Simply Adjustable Sinusoidal Oscillator Based on Negative Three-Port Current Conveyors

Directory of Open Access Journals (Sweden)

R. Sotner

2010-09-01

Full Text Available The paper deals with sinusoidal oscillator employing two controlled second-generation negative-current conveyors and two capacitors. The proposed oscillator has a simple circuit configuration. Electronic (voltage adjusting of the oscillation frequency and condition of oscillation are possible. The presented circuit is verified in PSpice utilizing macro models of commercially available negative current conveyors. The circuit is also verified by experimental measurements. Important characteristics and drawbacks of the proposed circuit and influences of real active elements in the designed circuit are discussed in detail.

Activity patterns in networks stabilized by background oscillations.

Science.gov (United States)

Hoppensteadt, Frank

2009-07-01

The brain operates in a highly oscillatory environment. We investigate here how such an oscillating background can create stable organized behavior in an array of neuro-oscillators that is not observable in the absence of oscillation, much like oscillating the support point of an inverted pendulum can stabilize its up position, which is unstable without the oscillation. We test this idea in an array of electronic circuits coming from neuroengineering: we show how the frequencies of the background oscillation create a partition of the state space into distinct basins of attraction. Thus, background signals can stabilize persistent activity that is otherwise not observable. This suggests that an image, represented as a stable firing pattern which is triggered by a voltage pulse and is sustained in synchrony or resonance with the background oscillation, can persist as a stable behavior long after the initial stimulus is removed. The background oscillations provide energy for organized behavior in the array, and these behaviors are categorized by the basins of attraction determined by the oscillation frequencies.

Reactor oscillator - I - III, Part III - Electronic device

International Nuclear Information System (INIS)

Lolic, B.; Jovanovic, S.

1961-12-01

This report describes functioning of the reactor oscillator electronic system. Two methods of oscillator operation were discussed. The first method is so called method of amplitude modulation of the reactor power, and the second newer method is phase method. Both methods are planned for the present reactor oscillator

A cascaded three-phase symmetrical multistage voltage multiplier

International Nuclear Information System (INIS)

Iqbal, Shahid; Singh, G K; Besar, R; Muhammad, G

2006-01-01

A cascaded three-phase symmetrical multistage Cockcroft-Walton voltage multiplier (CW-VM) is proposed in this report. It consists of three single-phase symmetrical voltage multipliers, which are connected in series at their smoothing columns like string of batteries and are driven by three-phase ac power source. The smoothing column of each voltage multiplier is charged twice every cycle independently by respective oscillating columns and discharged in series through load. The charging discharging process completes six times a cycle and therefore the output voltage ripple's frequency is of sixth order of the drive signal frequency. Thus the proposed approach eliminates the first five harmonic components of load generated voltage ripples and sixth harmonic is the major ripple component. The proposed cascaded three-phase symmetrical voltage multiplier has less than half the voltage ripple, and three times larger output voltage and output power than the conventional single-phase symmetrical CW-VM. Experimental and simulation results of the laboratory prototype are given to show the feasibility of proposed cascaded three-phase symmetrical CW-VM

On the (Frequency) Modulation of Coupled Oscillator Arrays in Phased Array Beam Control

Science.gov (United States)

Pogorzelski, R.; Acorn, J.; Zawadzki, M.

2000-01-01

It has been shown that arrays of voltage controlled oscillators coupled to nearest neighbors can be used to produce useful aperture phase distributions for phased array antennas. However, placing information of the transmitted signal requires that the oscillations be modulated.

Fast switching thyristor applied in nanosecond-pulse high-voltage generator with closed transformer core.

Science.gov (United States)

Li, Lee; Bao, Chaobing; Feng, Xibo; Liu, Yunlong; Fochan, Lin

2013-02-01

For a compact and reliable nanosecond-pulse high-voltage generator (NPHVG), the specification parameter selection and potential usage of fast controllable state-solid switches have an important bearing on the optimal design. The NPHVG with closed transformer core and fast switching thyristor (FST) was studied in this paper. According to the analysis of T-type circuit, the expressions for the voltages and currents of the primary and secondary windings on the transformer core of NPHVG were deduced, and the theoretical maximum analysis was performed. For NPHVG, the rise-rate of turn-on current (di/dt) across a FST may exceed its transient rating. Both mean and maximum values of di/dt were determined by the leakage inductances of the transformer, and the difference is 1.57 times. The optimum winding ratio is helpful to getting higher voltage output with lower specification FST, especially when the primary and secondary capacitances have been established. The oscillation period analysis can be effectively used to estimate the equivalent leakage inductance. When the core saturation effect was considered, the maximum di/dt estimated from the oscillating period of the primary current is more accurate than one from the oscillating period of the secondary voltage. Although increasing the leakage inductance of NPHVG can decrease di/dt across FST, it may reduce the output peak voltage of the NPHVG.

Self oscillating PWM modulators, a topological comparison

DEFF Research Database (Denmark)

Poulsen, Søren; Andersen, Michael Andreas E.

2004-01-01

or fs/ð range respectively, where fs is the switching frequency of the converter. For some applications this will require unacceptable high switching frequency to achieve enough control loop bandwidth for the desired dynamic performance. With self oscillating modulators, the open loop bandwidth is equal...... to fs which makes this type of modulators an excellent choice for a wide range of applications. Self oscillating PWM modulators can be made in a number of ways, either as voltage or current mode modulators, and the self oscillating behavior can be achieved either by using hysteresis control...... or by shaping the open loop function of the modulator so its gain and phase response causes a closed loop natural oscillation. The two main types of self oscillating modulators have many similarities, but differences in dynamic performance and linearity are present. The work presented is related to the author...

Excitation of RF oscillations in a discharge with negative differential conductivity

International Nuclear Information System (INIS)

Antonov, A.N.; Kovpik, O.F.; Kornilov, E.A.

2001-01-01

The excitation of oscillations in a discharge with negative differential conductivity is studied experimentally. The possibility is demonstrated of amplifying oscillations in the cathode dark space at frequencies close to the electron plasma frequency of the positive-column plasma. The phase velocities of waves at these frequencies are determined. When the waves pass from the cathode dark space to the discharge positive column, their phase velocities decrease; the closer the frequency is to the electron plasma frequency, the more pronounced the decrease in the phase velocity. As the intensity of oscillations increases, the discharge becomes non-steady-state. This is confirmed by the time evolution of the current-voltage characteristic. The shape of the current-voltage characteristic, its splitting, and the rate at which it varies depend on the input RF power. The decrease in the cathode dark space indicates that the ionization processes in the discharge are strongly influenced by electron plasma oscillations excited due to the collective interaction of the electron beam formed at the cathode with the discharge plasma. It is these processes that determine the maximum values of both the frequency of the excited oscillations and the power that can be withdrawn from the discharge

Effect of boundary on controlled memristor-based oscillator

KAUST Repository

Fouda, Mohamed E.

2012-10-01

Recently, the applications of memristors have spread into many fields and especially in the circuit theory. Many models have been proposed for the HP-memristor based on the window functions. In this paper, we introduce a complete mathematical analysis of the controlled reactance-less oscillator for two different window functions of Joglekar\\'s model (linear and nonlinear dopant drift) to discuss the effect of changing the window function on the oscillator\\'s behavior. The generalized necessary and sufficient conditions based on the circuit elements and control voltages for both the linear and nonlinear models are introduced. Moreover, closed form expressions for the oscillation frequency and duty cycle are derived for these models and verified using PSPICE simulations showing an excellent matching. Finally a comparison between the linear and nonlinear models which shows their effect on the oscillation frequency and conditions of oscillation is introduced. © 2012 IEEE.

Dynamics and Collapse in a Power System Model with Voltage Variation: The Damping Effect.

Science.gov (United States)

Ma, Jinpeng; Sun, Yong; Yuan, Xiaoming; Kurths, Jürgen; Zhan, Meng

2016-01-01

Complex nonlinear phenomena are investigated in a basic power system model of the single-machine-infinite-bus (SMIB) with a synchronous generator modeled by a classical third-order differential equation including both angle dynamics and voltage dynamics, the so-called flux decay equation. In contrast, for the second-order differential equation considering the angle dynamics only, it is the classical swing equation. Similarities and differences of the dynamics generated between the third-order model and the second-order one are studied. We mainly find that, for positive damping, these two models show quite similar behavior, namely, stable fixed point, stable limit cycle, and their coexistence for different parameters. However, for negative damping, the second-order system can only collapse, whereas for the third-order model, more complicated behavior may happen, such as stable fixed point, limit cycle, quasi-periodicity, and chaos. Interesting partial collapse phenomena for angle instability only and not for voltage instability are also found here, including collapse from quasi-periodicity and from chaos etc. These findings not only provide a basic physical picture for power system dynamics in the third-order model incorporating voltage dynamics, but also enable us a deeper understanding of the complex dynamical behavior and even leading to a design of oscillation damping in electric power systems.

Magnetically driven oscillator and resonance: a teaching tool

Science.gov (United States)

Erol, M.; Çolak, İ. Ö.

2018-05-01

This paper reports a simple magnetically driven oscillator, designed and resolved in order to achieve a better student understanding and to overcome certain instructional difficulties. The apparatus is mainly comprised of an ordinary spring pendulum with a neodymium magnet attached to the bottom, a coil placed in the same vertical direction, an ordinary function generator, an oscilloscope and a smartphone. Driven oscillation and resonance is basically managed by applying a sinusoidal voltage to the coil and tuning the driving frequency to the natural frequency of the pendulum. The resultant oscillation is recorded by a smartphone video application and analyzed via a video analysis programme. The designed apparatus can easily be employed in basic physics laboratories to achieve an enhanced and deeper understanding of driven oscillation and resonance.

Oscillator representations for self-adjoint Calogero Hamiltonians

Energy Technology Data Exchange (ETDEWEB)

Gitman, D M [Institute of Physics, University of Sao Paulo (Brazil); Tyutin, I V; Voronov, B L, E-mail: gitman@dfn.if.usp.br, E-mail: tyutin@lpi.ru, E-mail: voronov@lpi.ru [Lebedev Physical Institute, Moscow (Russian Federation)

2011-10-21

In Gitman et al (2010 J. Phys. A: Math. Theor. 43 145205), we presented a mathematically rigorous quantum-mechanical treatment of a one-dimensional motion of a particle in the Calogero potential V(x) = {alpha}x{sup -2}. We described all possible self-adjoint (s.a.) operators (s.a. Hamiltonians) associated with the differential operation H=-d{sub x}{sup 2}+{alpha}x{sup -2} for the Calogero Hamiltonian. Here, we discuss a new aspect of the problem, the so-called oscillator representations for the Calogero Hamiltonians. As is known, operators of the form N-hat = a-hat{sup +} a-hat and A-hat = a-hat a-hat{sup +} are called operators of oscillator type. Oscillator-type operators possess a number of useful properties in the case when the elementary operators a-hat are closed. It turns out that some s.a. Calogero Hamiltonians allow oscillator-type representations. We describe such Hamiltonians and find the corresponding mutually adjoint elementary operators a-hat and a-hat{sup +}. An oscillator-type representation for a given Hamiltonian is generally not unique. (paper)

Oscillator representations for self-adjoint Calogero Hamiltonians

International Nuclear Information System (INIS)

Gitman, D M; Tyutin, I V; Voronov, B L

2011-01-01

In Gitman et al (2010 J. Phys. A: Math. Theor. 43 145205), we presented a mathematically rigorous quantum-mechanical treatment of a one-dimensional motion of a particle in the Calogero potential V(x) = αx -2 . We described all possible self-adjoint (s.a.) operators (s.a. Hamiltonians) associated with the differential operation H=-d x 2 +αx -2 for the Calogero Hamiltonian. Here, we discuss a new aspect of the problem, the so-called oscillator representations for the Calogero Hamiltonians. As is known, operators of the form N-hat = a-hat + a-hat and A-hat = a-hat a-hat + are called operators of oscillator type. Oscillator-type operators possess a number of useful properties in the case when the elementary operators a-hat are closed. It turns out that some s.a. Calogero Hamiltonians allow oscillator-type representations. We describe such Hamiltonians and find the corresponding mutually adjoint elementary operators a-hat and a-hat + . An oscillator-type representation for a given Hamiltonian is generally not unique. (paper)

Control, synchronization, and enhanced reliability of aperiodic oscillations in the Mercury Beating Heart system

Science.gov (United States)

Kumar, Pawan; Parmananda, P.

2018-04-01

Experiments involving the Mercury Beating Heart (MBH) oscillator, exhibiting irregular (aperiodic) dynamics, are performed. In the first set of experiments, control over irregular dynamics of the MBH oscillator was obtained via a superimposed periodic voltage signal. These irregular (aperiodic) dynamics were recovered once the control was switched off. Subsequently, two MBH oscillators were coupled to attain synchronization of their aperiodic oscillations. Finally, two uncoupled MBH oscillators were subjected, repeatedly, to a common stochastic forcing, resulting in an enhancement of their mutual phase correlation.

Sigma-Delta Voltage to Frequency Converter With Phase Modulation Possibility

OpenAIRE

STORK, Milan

2014-01-01

Voltage to frequency converter (VFC) is an oscillator whose frequency is linearly proportional to control voltage. There are two common VFC architectures: the current steering multivibrator and the charge-balance VFC. For higher linearity, the charge-balancing method is preferred. The charge balanced VFC may be made in asynchronous or synchronous (clocked) forms. The synchronous charge balanced VFC or "sigma delta" (S-D) VFC is used when output pulses are synchroni...

Hybrid AC-High Voltage DC Grid Stability and Controls

Science.gov (United States)

Yu, Jicheng

The growth of energy demands in recent years has been increasing faster than the expansion of transmission facility construction. This tendency cooperating with the continuous investing on the renewable energy resources drives the research, development, and construction of HVDC projects to create a more reliable, affordable, and environmentally friendly power grid. Constructing the hybrid AC-HVDC grid is a significant move in the development of the HVDC techniques; the form of dc system is evolving from the point-to-point stand-alone dc links to the embedded HVDC system and the multi-terminal HVDC (MTDC) system. The MTDC is a solution for the renewable energy interconnections, and the MTDC grids can improve the power system reliability, flexibility in economic dispatches, and converter/cable utilizing efficiencies. The dissertation reviews the HVDC technologies, discusses the stability issues regarding the ac and HVDC connections, proposes a novel power oscillation control strategy to improve system stability, and develops a nonlinear voltage droop control strategy for the MTDC grid. To verify the effectiveness the proposed power oscillation control strategy, a long distance paralleled AC-HVDC transmission test system is employed. Based on the PSCAD/EMTDC platform simulation results, the proposed power oscillation control strategy can improve the system dynamic performance and attenuate the power oscillations effectively. To validate the nonlinear voltage droop control strategy, three droop controls schemes are designed according to the proposed nonlinear voltage droop control design procedures. These control schemes are tested in a hybrid AC-MTDC system. The hybrid AC-MTDC system, which is first proposed in this dissertation, consists of two ac grids, two wind farms and a five-terminal HVDC grid connecting them. Simulation studies are performed in the PSCAD/EMTDC platform. According to the simulation results, all the three design schemes have their unique salient

Artifactual voltage response recorded from hair cells with patch-clamp amplifiers.

Science.gov (United States)

Masetto, S; Weng, T; Valli, P; Correia, M J

1999-06-23

Patch-clamp amplifiers (PCAs) are commonly used to characterize voltage- and current-clamp responses in the same cell. However, the cell membrane voltage response can be severely distorted by PCAs working in the current-clamp mode. Here we compare the voltage response of pigeon semicircular canal hair cells in situ, recorded with two different PCAs, and with a classic microelectrode bridge amplifier (BA). We found that the voltage response of hair cells recorded with PCAs differed significantly from that recorded with the BA. The true hair cell membrane voltage response to positive current steps was characterized by a strongly damped oscillation, whose frequency and duration depended on hair cell location in the sensory crista ampullaris.

Flexible operation of parallel grid-connecting converters under unbalanced grid voltage

DEFF Research Database (Denmark)

Lu, Jinghang; Savaghebi, Mehdi; Guerrero, Josep M.

2017-01-01

-link voltage ripple, and overloading. Moreover, under grid voltage unbalance, the active power delivery ability is decreased due to the converter's current rating limitation. In this paper, a thorough study on the current limitation of the grid-connecting converter under grid voltage unbalance is conducted....... In addition, based on the principle that total output active power should be oscillation free, a coordinated control strategy is proposed for the parallel grid-connecting converters. The case study has been conducted to demonstrate the effectiveness of this proposed control strategy....

Voltage-assisted polymer wafer bonding

International Nuclear Information System (INIS)

Varsanik, J S; Bernstein, J J

2012-01-01

Polymer wafer bonding is a widely used process for fabrication of microfluidic devices. However, best practices for polymer bonds do not achieve sufficient bond strength for many applications. By applying a voltage to a polymer bond in a process called voltage-assisted bonding, bond strength is shown to improve dramatically for two polymers (Cytop™ and poly(methyl methacrylate)). Several experiments were performed to provide a starting point for further exploration of this technique. An optimal voltage range is experimentally observed with a reduction in bonding strength at higher voltages. Additionally, voltage-assisted bonding is shown to reduce void diameter due to bond defects. An electrostatic force model is proposed to explain the improved bond characteristics. This process can be used to improve bond strength for most polymers. (paper)

Modeling Bloch oscillations in nanoscale Josephson junctions

Science.gov (United States)

Vora, Heli; Kautz, R. L.; Nam, S. W.; Aumentado, J.

2018-01-01

Bloch oscillations in nanoscale Josephson junctions with a Coulomb charging energy comparable to the Josephson coupling energy are explored within the context of a model previously considered by Geigenmüller and Schön that includes Zener tunneling and treats quasiparticle tunneling as an explicit shot-noise process. The dynamics of the junction quasicharge are investigated numerically using both Monte Carlo and ensemble approaches to calculate voltage-current characteristics in the presence of microwaves. We examine in detail the origin of harmonic and subharmonic Bloch steps at dc biases I = (n/m)2ef induced by microwaves of frequency f and consider the optimum parameters for the observation of harmonic (m = 1) steps. We also demonstrate that the GS model allows a detailed semiquantitative fit to experimental voltage-current characteristics previously obtained at the Chalmers University of Technology, confirming and strengthening the interpretation of the observed microwave-induced steps in terms of Bloch oscillations. PMID:29577106

The pulse-driven AC Josephson voltage normal

International Nuclear Information System (INIS)

Kieler, Oliver

2016-01-01

In this contribution quantum precise alternating-voltage sources are presented, which make the generation of arbitrary wave forms with highest spectral purity with a high bandwidth from DC up to the MHz range possible. Heartpiece of these Josephson voltage normals is a serial circuit of many thousand Josephson contacts, which make by irradiation with high-frequency radiation (microwaves) the generation of highly precise voltage values possible. Thereby in the current-voltage characteristics stages of constant voltage, so called Shapiro stages, occur. Illustratively these stages can be described by the transfer of a certain number of flux quanta through the Josephson contacts.

Quantum resonances in a single plaquette of Josephson junctions: excitations of Rabi oscillations

Science.gov (United States)

Fistul, M. V.

2002-03-01

We present a theoretical study of a quantum regime of the resistive (whirling) state of dc driven anisotropic single plaquette containing small Josephson junctions. The current-voltage characteristics of such systems display resonant steps that are due to the resonant interaction between the time dependent Josephson current and the excited electromagnetic oscillations (EOs). The voltage positions of the resonances are determined by the quantum interband transitions of EOs. We show that in the quantum regime as the system is driven on the resonance, coherent Rabi oscillations between the quantum levels of EOs occur. At variance with the classical regime the magnitude and the width of resonances are determined by the frequency of Rabi oscillations that in turn, depends in a peculiar manner on an externally applied magnetic field and the parameters of the system.

OSCILLATING FILAMENTS. I. OSCILLATION AND GEOMETRICAL FRAGMENTATION

Energy Technology Data Exchange (ETDEWEB)

Gritschneder, Matthias; Heigl, Stefan; Burkert, Andreas, E-mail: gritschm@usm.uni-muenchen.de [University Observatory Munich, LMU Munich, Scheinerstrasse 1, D-81679 Munich (Germany)

2017-01-10

We study the stability of filaments in equilibrium between gravity and internal as well as external pressure using the grid-based AMR code RAMSES. A homogeneous, straight cylinder below a critical line mass is marginally stable. However, if the cylinder is bent, such as with a slight sinusoidal perturbation, an otherwise stable configuration starts to oscillate, is triggered into fragmentation, and collapses. This previously unstudied behavior allows a filament to fragment at any given scale, as long as it has slight bends. We call this process “geometrical fragmentation.” In our realization, the spacing between the cores matches the wavelength of the sinusoidal perturbation, whereas up to now, filaments were thought to be only fragmenting on the characteristic scale set by the mass-to-line ratio. Using first principles, we derive the oscillation period as well as the collapse timescale analytically. To enable a direct comparison with observations, we study the line-of-sight velocity for different inclinations. We show that the overall oscillation pattern can hide the infall signature of cores.

Determination of the cathode fall voltage in fluorescent lamps by measurement of the operating voltage

International Nuclear Information System (INIS)

Hilscher, A.

2002-01-01

A new method for the determination of the cathode fall voltage of fluorescent lamps is shown. The cathode fall voltage can be determined by measurement of the lamp operating voltage at constant lamp wall temperature, constant discharge current and variation of the electrode heating current. Commercial lamps, which do not need to be specially prepared, can be used for the measurement. The results show good correlation to other measurements of the cathode fall voltage at various discharge currents by means of capacitive coupling. The measured values of the cathode fall voltage are used for determining the minimum, target and maximum setting of the sum of the squares of the pin currents of one electrode (the so-called SOS value) as a function of the discharge current in fluorescent lamp dimming. (author)

The Wigner distribution function for the one-dimensional parabose oscillator

International Nuclear Information System (INIS)

Jafarov, E; Lievens, S; Jeugt, J Van der

2008-01-01

In the beginning of the 1950s, Wigner introduced a fundamental deformation from the canonical quantum mechanical harmonic oscillator, which is nowadays sometimes called a Wigner quantum oscillator or a parabose oscillator. Also, in quantum mechanics the so-called Wigner distribution is considered to be the closest quantum analogue of the classical probability distribution over the phase space. In this paper, we consider which definition for such a distribution function could be used in the case of non-canonical quantum mechanics. We then explicitly compute two different expressions for this distribution function for the case of the parabose oscillator. Both expressions turn out to be multiple sums involving (generalized) Laguerre polynomials. Plots then show that the Wigner distribution function for the ground state of the parabose oscillator is similar in behaviour to the Wigner distribution function of the first excited state of the canonical quantum oscillator

Genetically encoded fluorescent voltage sensors using the voltage-sensing domain of Nematostella and Danio phosphatases exhibit fast kinetics.

Science.gov (United States)

Baker, Bradley J; Jin, Lei; Han, Zhou; Cohen, Lawrence B; Popovic, Marko; Platisa, Jelena; Pieribone, Vincent

2012-07-15

A substantial increase in the speed of the optical response of genetically encoded fluorescent protein voltage sensors (FP voltage sensors) was achieved by using the voltage-sensing phosphatase genes of Nematostella vectensis and Danio rerio. A potential N. vectensis voltage-sensing phosphatase was identified in silico. The voltage-sensing domain (S1-S4) of the N. vectensis homolog was used to create an FP voltage sensor called Nema. By replacing the phosphatase with a cerulean/citrine FRET pair, a new FP voltage sensor was synthesized with fast off kinetics (Tau(off)voltage-sensing phosphatase homolog, designated Zahra and Zahra 2, exhibited fast on and off kinetics within 2ms of the time constants observed with the organic voltage-sensitive dye, di4-ANEPPS. Mutagenesis of the S4 region of the Danio FP voltage sensor shifted the voltage dependence to more negative potentials but did not noticeably affect the kinetics of the optical signal. Copyright © 2012 Elsevier B.V. All rights reserved.

Genetically-encoded fluorescent voltage sensors using the voltage-sensing domain of Nematostella and Danio phosphatases exhibit fast kinetics

Science.gov (United States)

Baker, Bradley J.; Jin, Lei; Han, Zhou; Cohen, Lawrence B.; Popovic, Marko; Platisa, Jelena; Pieribone, Vincent

2012-01-01

A substantial increase in the speed of the optical response of genetically-encoded Fluorescent Protein voltage sensors (FP voltage sensors) was achieved by using the voltage-sensing phosphatase genes of Nematostella vectensis and Danio rerio. A potential N. vectensis voltage-sensing phosphatase was identified in silico. The voltage-sensing domain (S1–S4) of the N. vectensis homolog was used to create an FP voltage sensor called Nema. By replacing the phosphatase with a cerulean/citrine FRET pair, a new FP voltage sensor was synthesized with fast off kinetics (Tauoff voltage-sensing phosphatase homolog, designated Zahra and Zahra 2, exhibited fast on and off kinetics within 2 msec of the time constants observed with the organic voltage-sensitive dye, di4-ANEPPS. Mutagenesis of the S4 region of the Danio FP voltage sensor shifted the voltage dependence to more negative potentials but did not noticeably affect the kinetics of the optical signal. PMID:22634212

The effect of voltage droop on the output of an electrostatic accelerator free electron laser

International Nuclear Information System (INIS)

Wright, C.C.; Al-Shamma'a, A.I.; Lucas, J.; Stuart, R.A.

2000-01-01

Electrostatic accelerator FEL oscillators when operated with energy recovery offer the prospect of long pulse, single-mode operation with very narrow linewidth at high-power levels. However, special care with wiggler construction, electron beam steering, and collector design is necessary to reduce the fraction of the electron beam lost before depressed collection to a sufficiently small value to stop the output hopping from one longitudinal mode of the cavity to another due to the droop of the terminal accelerating voltage. We are investigating what minimum recovery fraction is required both experimentally and theoretically. We have constructed a pulsed microwave FEM oscillator having an accelerating voltage of 65 kV supplied by a source, which is a capacitor, charged by a low-current, high-voltage supply. By changing the capacitor value, it is easily possible to achieve a range of voltage droop rates. Furthermore, because the gain bandwidth of the FEM is small, only 1 or 2 longitudinal modes are capable of being amplified at any voltage which eases the problem of analysing mode hopping behaviour. A simple model of mode switching is outlined

Simple Moving Voltage Average Incremental Conductance MPPT Technique with Direct Control Method under Nonuniform Solar Irradiance Conditions

Directory of Open Access Journals (Sweden)

Amjad Ali

2015-01-01

Full Text Available A new simple moving voltage average (SMVA technique with fixed step direct control incremental conductance method is introduced to reduce solar photovoltaic voltage (VPV oscillation under nonuniform solar irradiation conditions. To evaluate and validate the performance of the proposed SMVA method in comparison with the conventional fixed step direct control incremental conductance method under extreme conditions, different scenarios were simulated. Simulation results show that in most cases SMVA gives better results with more stability as compared to traditional fixed step direct control INC with faster tracking system along with reduction in sustained oscillations and possesses fast steady state response and robustness. The steady state oscillations are almost eliminated because of extremely small dP/dV around maximum power (MP, which verify that the proposed method is suitable for standalone PV system under extreme weather conditions not only in terms of bus voltage stability but also in overall system efficiency.

The effect of voltage droop on the output of an electrostatic accelerator free electron laser

CERN Document Server

Wright, C C; Lucas, J; Stuart, R A

2000-01-01

Electrostatic accelerator FEL oscillators when operated with energy recovery offer the prospect of long pulse, single-mode operation with very narrow linewidth at high-power levels. However, special care with wiggler construction, electron beam steering, and collector design is necessary to reduce the fraction of the electron beam lost before depressed collection to a sufficiently small value to stop the output hopping from one longitudinal mode of the cavity to another due to the droop of the terminal accelerating voltage. We are investigating what minimum recovery fraction is required both experimentally and theoretically. We have constructed a pulsed microwave FEM oscillator having an accelerating voltage of 65 kV supplied by a source, which is a capacitor, charged by a low-current, high-voltage supply. By changing the capacitor value, it is easily possible to achieve a range of voltage droop rates. Furthermore, because the gain bandwidth of the FEM is small, only 1 or 2 longitudinal modes are capable of b...

State reference design and saturated control of doubly-fed induction generators under voltage dips

Science.gov (United States)

Tilli, Andrea; Conficoni, Christian; Hashemi, Ahmad

2017-04-01

In this paper, the stator/rotor currents control problem of doubly-fed induction generator under faulty line voltage is carried out. Common grid faults cause a steep decline in the line voltage profile, commonly denoted as voltage dip. This point is critical for such kind of machines, having their stator windings directly connected to the grid. In this respect, solid methodological nonlinear control theory arguments are exploited and applied to design a novel controller, whose main goal is to improve the system behaviour during voltage dips, endowing it with low voltage ride through capability, a fundamental feature required by modern Grid Codes. The proposed solution exploits both feedforward and feedback actions. The feedforward part relies on suitable reference trajectories for the system internal dynamics, which are designed to prevent large oscillations in the rotor currents and command voltages, excited by line perturbations. The feedback part uses state measurements and is designed according to Linear Matrix Inequalities (LMI) based saturated control techniques to further reduce oscillations, while explicitly accounting for the system constraints. Numerical simulations verify the benefits of the internal dynamics trajectory planning, and the saturated state feedback action, in crucially improving the Doubly-Fed Induction Machine response under severe grid faults.

Low Voltage, High-Q SOI MEMS Varactors for RF Applications

DEFF Research Database (Denmark)

Yalcinkaya, Arda Deniz; Jensen, Søren; Hansen, Ole

2003-01-01

A micro electromechanical tunable capacitor with a low control voltage, a wide tuning range and high electrical quality factor is presented with detailed characterizations. A 50μm thick single-crystalline silicon layer was etched using deep reactive ion etching (DRIE) for obtaining high-aspect ra...... is a suitable passive component to be used in band-pass filtering, voltage controlled oscillator or impedance matching applications on the very high frequency(VHF) and ultra high frequency (UHF) bands....

A revisit to self-excited push pull vacuum tube radio frequency oscillator for ion sources and power measurements

International Nuclear Information System (INIS)

Hlondo, L. R.; Lalremruata, B.; Punte, L. R. M.; Rebecca, L.; Lalnunthari, J.; Thanga, H. H.

2016-01-01

Self-excited push-pull vacuum tube oscillator is one of the most commonly used oscillators in radio frequency (RF)-ion plasma sources for generation of ions using radio frequency. However, in spite of its fundamental role in the process of plasma formation, the working and operational characteristics are the most frequently skip part in the descriptions of RF ion sources in literatures. A more detailed treatment is given in the present work on the RF oscillator alone using twin beam power tetrodes 829B and GI30. The circuit operates at 102 MHz, and the oscillation conditions, stability in frequency, and RF output power are studied and analyzed. A modified form of photometric method and RF peak voltage detection method are employed to study the variation of the oscillator output power with plate voltage. The power curves obtained from these measurements are quadratic in nature and increase with increase in plate voltage. However, the RF output power as measured by photometric methods is always less than the value calculated from peak voltage measurements. This difference is due to the fact that the filament coil of the ordinary light bulb used as load/detector in photometric method is not a perfect inductor. The effect of inductive reactance on power transfer to load was further investigated and a technique is developed to estimate the amount of power correction needed in the photometric measurement result.

Design and operational experience and testing of 50 kW/120 kHz oscillator for 3 MeV, 30 kW DC accelerator

International Nuclear Information System (INIS)

Srivastava, S.K.; Bakhtsingh, R.I.; Saroj, P.C.

2011-01-01

A 3 MeV, 30 kW dc industrial electron beam Accelerator is being developed at EBC, Kharghar, Navi Mumbai. The 3 MV dc is generated by parallel coupled voltage multiplier operating at 120 kHz. This requires an input voltage of 150 kV-0-150 kV at 120 kHz. This is achieved by 50 kW/120 kHz power oscillator in conjunction with a tuned air-core step-up transformer. Input primary voltage of 6 kV-0-6 kV at 120 kHz is generated by an oscillator using BW1121J2 water cooled triodes in push-pull Colpitts configuration. The tank circuit for the oscillator is formed by the secondary winding inductance of the step-up transformer and capacitance formed by RF feeder electrodes of the voltage multiplier column. Grid feedback for the oscillator is derived by arranging a set of electrodes in the feeder assembly in a capacitive divider configuration. The oscillator is operated in class-C mode with grid leak bias for better efficiency which also has the advantages of self-adjustment with varying load conditions. High power test has been conducted in a simulated test set-up on dummy load up to 30kW. Subsequently, the power oscillator has been tested with HV multiplier at 1MeV level satisfactorily. This paper describes the design, test results and operational experiences of the oscillator. (author)

Voltage Dependence of Supercapacitor Capacitance

Directory of Open Access Journals (Sweden)

Szewczyk Arkadiusz

2016-09-01

Full Text Available Electronic Double-Layer Capacitors (EDLC, called Supercapacitors (SC, are electronic devices that are capable to store a relatively high amount of energy in a small volume comparing to other types of capacitors. They are composed of an activated carbon layer and electrolyte solution. The charge is stored on electrodes, forming the Helmholtz layer, and in electrolyte. The capacitance of supercapacitor is voltage- dependent. We propose an experimental method, based on monitoring of charging and discharging a supercapacitor, which enables to evaluate the charge in an SC structure as well as the Capacitance-Voltage (C-V dependence. The measurement setup, method and experimental results of charging/discharging commercially available supercapacitors in various voltage and current conditions are presented. The total charge stored in an SC structure is proportional to the square of voltage at SC electrodes while the charge on electrodes increases linearly with the voltage on SC electrodes. The Helmholtz capacitance increases linearly with the voltage bias while a sublinear increase of total capacitance was found. The voltage on SC increases after the discharge of electrodes due to diffusion of charges from the electrolyte to the electrodes. We have found that the recovery voltage value is linearly proportional to the initial bias voltage value.

Oscilaciones de Potencia, Tensión y Corriente en Unidades de Generación Distribuida; Power, Voltage and Current Oscillations in Distributed Generation Units

Directory of Open Access Journals (Sweden)

Marcos Alberto de Armas Teyra

2013-06-01

Full Text Available En las plantas de generación distribuidas accionadas por motores reciprocantes es necesario conocer las fluctuaciones de tensión, corriente y potencia para evaluar la calidad de la energía que entregan estos grupos electrógenos y como criterio de diagnóstico técnico. Las causas de estas fluctuaciones son diversas. La fundamental se debe a la presencia de oscilaciones forzadas producidas por el momento irregular de los motores primarios. Otras razones se encuentran en las excentricidades constructivas, el desbalance de corriente, los armónicos espaciales y de tiempo, la variación de la configuración del sistema, etc. En este trabajo fueron evaluadas satisfactoriamente las oscilaciones de una máquina conectada a la red mediante la instalación de un analizador de redes de 32 cortes por ciclo a la salida del generador de una de estas unidades. Se expone como caso de estudio las oscilaciones observadas en un generador de 425 kVA480 V accionado por un motor Diesel de seis cilindros y cuatro tiempos en la Provincia de Cienfuegos, Cuba.  In distributed and standby power plants driven by reciprocating motors, is important to know the voltage, current and power oscillation as a delivery power quality and diagnostic criteria. There are several oscillation causes. The fundamental is due to the irregular torque of primary motors. Other causes are due to constructive eccentricities, current unbalance, time and spatial harmonics, changes in systems configuration, etc. In this paper the fundamental oscillations of a grid connected machine were evaluated with a power analyzer installed in one generating power plant. As a case there are shown the observed oscillations in 425 kVA generator driven by a four times, six cylinders Diesel motor in Cienfuegos Province of Cuba.

Oscilaciones de Potencia, Tensión y Corriente en Unidades de Generación Distribuida: Power, Voltage and Current Oscillations in Distributed Generation Units

Directory of Open Access Journals (Sweden)

Marcos Alberto de Armas Teyra

2013-06-01

Full Text Available En las plantas de generación distribuidas accionadas por motores reciprocantes es necesario conocer las fluctuaciones de tensión, corriente y potencia para evaluar la calidad de la energía que entregan estos grupos electrógenos y como criterio de diagnóstico técnico. Las causas de estas fluctuaciones son diversas. La fundamental se debe a la presencia de oscilaciones forzadas producidas por el momento irregular de los motores primarios. Otras razones se encuentran en las excentricidades constructivas, el desbalance de corriente, los armónicos espaciales y de tiempo, la variación de la configuración del sistema, etc. En este trabajo fueron evaluadas satisfactoriamente las oscilaciones de una máquina conectada a la red mediante la instalación de un analizador de redes de 32 cortes por ciclo a la salida del generador de una de estas unidades. Se expone como caso de estudio las oscilaciones observadas en un generador de 425 kVA480 V accionado por un motor Diesel de seis cilindros y cuatro tiempos en la Provincia de Cienfuegos, Cuba.In distributed and standby power plants driven by reciprocating motors, is important to know the voltage, current and power oscillation as a delivery power quality and diagnostic criteria. There are several oscillation causes. The fundamental is due to the irregular torque of primary motors. Other causes are due to constructive eccentricities, current unbalance, time and spatial harmonics, changes in systems configuration, etc. In this paper the fundamental oscillations of a grid connected machine were evaluated with a power analyzer installed in one generating power plant. As a case there are shown the observed oscillations in 425 kVA generator driven by a four times, six cylinders Diesel motor in Cienfuegos Province of Cuba.

On-chip high-voltage generator design design methodology for charge pumps

CERN Document Server

Tanzawa, Toru

2016-01-01

This book provides various design techniques for switched-capacitor on-chip high-voltage generators, including charge pump circuits, regulators, level shifters, references, and oscillators.  Readers will see these techniques applied to system design in order to address the challenge of how the on-chip high-voltage generator is designed for Flash memories, LCD drivers, and other semiconductor devices to optimize the entire circuit area and power efficiency with a low voltage supply, while minimizing the cost.  This new edition includes a variety of useful updates, including coverage of power efficiency and comprehensive optimization methodologies for DC-DC voltage multipliers, modeling of extremely low voltage Dickson charge pumps, and modeling and optimum design of AC-DC switched-capacitor multipliers for energy harvesting and power transfer for RFID.

Low-Voltage, Low-Power, and Wide-Tuning-Range Ring-VCO for Frequency ΔΣ Modulator

DEFF Research Database (Denmark)

Tuan Vu, Cao; Wisland, Dag T.; Lande, Tor Sverre

A low-voltage, low-power, and wide-tuning-range VCO which converts an analog input voltage to phase information for a frequency ΔΣ modulator is proposed in this paper. The VCO is based on a differential ring oscillator, which is improved with modified symmetric load and a positive feedback...

Digital power and performance analysis of inkjet printed ring oscillators based on electrolyte-gated oxide electronics

Science.gov (United States)

Cadilha Marques, Gabriel; Garlapati, Suresh Kumar; Dehm, Simone; Dasgupta, Subho; Hahn, Horst; Tahoori, Mehdi; Aghassi-Hagmann, Jasmin

2017-09-01

Printed electronic components offer certain technological advantages over their silicon based counterparts, like mechanical flexibility, low process temperatures, maskless and additive manufacturing possibilities. However, to be compatible to the fields of smart sensors, Internet of Things, and wearables, it is essential that devices operate at small supply voltages. In printed electronics, mostly silicon dioxide or organic dielectrics with low dielectric constants have been used as gate isolators, which in turn have resulted in high power transistors operable only at tens of volts. Here, we present inkjet printed circuits which are able to operate at supply voltages as low as ≤2 V. Our transistor technology is based on lithographically patterned drive electrodes, the dimensions of which are carefully kept well within the printing resolutions; the oxide semiconductor, the electrolytic insulator and the top-gate electrodes have been inkjet printed. Our inverters show a gain of ˜4 and 2.3 ms propagation delay time at 1 V supply voltage. Subsequently built 3-stage ring oscillators start to oscillate at a supply voltage of only 0.6 V with a frequency of ˜255 Hz and can reach frequencies up to ˜350 Hz at 2 V supply voltage. Furthermore, we have introduced a systematic methodology for characterizing ring oscillators in the printed electronics domain, which has been largely missing. Benefiting from this procedure, we are now able to predict the switching capacitance and driver capability at each stage, as well as the power consumption of our inkjet printed ring oscillators. These achievements will be essential for analyzing the performance and power characteristics of future inkjet printed digital circuits.

CMOS-based active RC sinusoidal oscillator with four-phase quadrature outputs and single-resistance-controlled (SRC) tuning laws

OpenAIRE

Lahiri, Abhirup; Herencsár, Norbert

2012-01-01

This paper proposes a very compact CMOS realization of active RC sinusoidal oscillator capable of generating four quadrature voltage outputs. The oscillator is based on the cascade of lossless and lossy integrators in loop. The governing laws for the condition of oscillation (CO) and the frequency of oscillation (FO) are single-resistance-controlled (SRC) and which allow independent FO tuning. Unlike previously reported SRC-based sinusoidal oscillators based on the active building block (ABB)...

Voltage-Driven Magnetization Switching and Spin Pumping in Weyl Semimetals

Science.gov (United States)

Kurebayashi, Daichi; Nomura, Kentaro

2016-10-01

We demonstrate electrical magnetization switching and spin pumping in magnetically doped Weyl semimetals. The Weyl semimetal is a three-dimensional gapless topological material, known to have nontrivial coupling between the charge and the magnetization due to the chiral anomaly. By solving the Landau-Lifshitz-Gilbert equation for a multilayer structure of a Weyl semimetal, an insulator and a metal while taking the charge-magnetization coupling into account, magnetization dynamics is analyzed. It is shown that the magnetization dynamics can be driven by the electric voltage. Consequently, switching of the magnetization with a pulsed electric voltage can be achieved, as well as precession motion with an applied oscillating electric voltage. The effect requires only a short voltage pulse and may therefore be energetically favorable for us in spintronics devices compared to conventional spin-transfer torque switching.

Self-oscillating loop based piezoelectric power converter

DEFF Research Database (Denmark)

2013-01-01

The present invention relates to a piezoelectric power converter comprising an input driver electrically coupled directly to an input or primary electrode of the piezoelectric transformer without any intervening series or parallel inductor. A feedback loop is operatively coupled between an output......- oscillation loop within a zero-voltage-switching (ZVS) operation range of the piezoelectric transformer....

Anharmonic potential in the oscillator representation

International Nuclear Information System (INIS)

Dineykhan, M.; Efimov, G.V.

1994-01-01

In the non relativistic and relativized Schroedinger equation the Wick ordering method called the oscillator representation is proposed to calculate the energy spectrum for a wide class of potentials allowing the existence of a bound state. The oscillator representation method gives a unique regular way to describe and calculate the energy levels of ground as well as orbital and radial excitation states for a wide class of potentials. The results of the zeroth approximation oscillator representation are in good agreement with the exact values for the anharmonic potentials. The oscillator representation method was applied to the relativized Schroedinger equation too. The perturbation series converges fairly fast, i.e., the highest perturbation corrections over the interaction Hamiltonian are small enough. 29 refs.; 4 tabs. (author)

Influence of surface losses and the self-pumping effect on current-voltage characteristics of a long Josephson junction

DEFF Research Database (Denmark)

Pankratov, A.L.; Sobolev, A.S.; Koshelets, V.P.

2007-01-01

We have numerically investigated the dynamics of a long linear Josephson tunnel junction with overlap geometry. Biased by a direct current (dc) and an applied dc magnetic field, the junction has important applications as tunable high frequency oscillator [flux-flow oscillator (FFO......) placed at both ends of the FFO. In our model, the damping parameter depends both on the spatial coordinate and on the amplitude of the ac voltage. In order to find the dc current-voltage curves, the damping parameter has to be calculated self-consistently by successive approximations and time integration...

Voltage distribution in tapered winding of tesla-transformer during discharge process of PFL

International Nuclear Information System (INIS)

Xin Jiaqi; Chang Anbi; Li Mingjia; Kang Qiang

2007-01-01

The operation principle of integral construction of Tesla transformer and PFL was investigated in Tesla-transformer-type accelerator. Experiment was carried out on Tesla transformer's secondary winding to study the impulse voltage distribution while PFL was discharging. The regularities of turn-ground voltage distribution and interturn voltage distribution were summarized. Voltage distribution within PFL was calculated and it was compared with the experimental result. Structural winding of parallel coils in the head, parallel coils in the end and shading ring were used to improve voltage distribution and that was testified by experiment. The results indicate that taper winding doesn't effect electric field within PFL, the turn-ground voltage appears linearly, the interturn voltage fluctuates seriously and it is the biggest in head of winding. The three optimized methods help to depress oscillation, the structural winding of parallel coils in the head decreases the interturn voltage in head of winding remark-ably and the parallel coils in the end decrease the interturn voltage in the end. (authors)

LIMIT SOLUTIONS OF EQUATIONS OF A DC HIGH-VOLTAGE CASCADE GENERATOR

Directory of Open Access Journals (Sweden)

V. O. Brzhezitsky

2015-04-01

Full Text Available In the paper the issue of calculating the high voltage cascade mode oscillator with a nonlinear load using the analytical method under different conditions of selection values of its components is presented. The peculiarity of the method of the study is that during multivariate calculations output parameters load generator remain unchanged. For high-voltage cascade direct current power found conditions under which can be significantly reduced high capacity capacitors cascade generator. The calculations show that acceptable for practical applications of high-voltage characteristics of cascade generators can be achieved with substantial reduction of the volume of their constituents, and thus substantial decline in their value.

Evidence of Mixed-mode oscillations and Farey arithmetic in double plasma system in presence of fireball

Science.gov (United States)

Mitra, Vramori; Sarma, Bornali; Sarma, Arun

2017-10-01

Plasma fireballs are luminous glowing region formed around a positively biased electrode. The present work reports the observation of mix mode oscillation (MMO) in the dynamics of plasma oscillations that are excited in the presence of fireball in a double plasma device. Source voltage and applied electrode voltage are considered as the controlling parameters for the experiment. Many sequences of distinct multi peaked periodic states reflects the presence of MMO with the variation of control parameter. The sequences of states with two patterns are characterized well by Farey arithmetic, which provides rational approximations of irrational numbers. These states can be characterized by a firing number, the ratio of the number of small amplitude oscillations to the total number of oscillations per period. The dynamical transition in plasma fireball is also demonstrated by spectral analysis, recurrence quantification analysis (RQA) and by statistical measures viz., skewness and kurtosis. The mix mode phenomenon observed in the experiment is consistent with a model that describes the dynamics of ionization instabilities.

Very High Frequency Interleaved Self-Oscillating Resonant SEPIC Converter

DEFF Research Database (Denmark)

Kovacevic, Milovan; Knott, Arnold; Andersen, Michael A. E.

2013-01-01

interconnection network between the switches which provides self-oscillating and interleaved operation. A design approach to ensure zero voltage switching (ZVS) condition of the MOSFET devices is provided. To verify the proposed method, an 11 W, 50 MHz prototype was built using low-cost VDMOS devices...

Laminar phase flow for an exponentially tapered Josephson oscillator

DEFF Research Database (Denmark)

Benabdallah, A.; Caputo, J. G.; Scott, Alwyn C.

2000-01-01

Exponential tapering and inhomogeneous current feed were recently proposed as means to improve the performance of a Josephson flux flow oscillator. Extensive numerical results backed up by analysis are presented here that support this claim and demonstrate that exponential tapering reduces...... the small current instability region and leads to a laminar flow regime where the voltage wave form is periodic giving the oscillator minimal spectral width. Tapering also leads to an increased output power. Since exponential tapering is not expected to increase the difficulty of fabricating a flux flow...

Digitized self-oscillating loop for piezoelectric transformer-based power converters

DEFF Research Database (Denmark)

Ekhtiari, Marzieh; Andersen, Thomas; Zhang, Zhe

2016-01-01

A new method is implemented in designing of self-oscillating loop for driving piezoelectric transformers. The implemented method is based on combining both analog and digital control systems. Digitized delay, or digitized phase shift through the self-oscillating loop results in a very precise...... frequency control and ensures an optimum operation of the piezoelectric transformer in terms of voltage gain and efficiency. In this work, additional time delay is implemented digitally for the first time through 16 bit digital-to-analog converter to the self-oscillating loop. Delay control setpoints...... updates at a rate of 417 kHz. This allows the control loop to dynamically follow frequency changes of the transformer in each resonant cycle. The operation principle behind self-oscillating is discussed in this paper. Moreover, experimental results are reported....

Liquid Metal Oscillation and Arc Behaviour during Welding

NARCIS (Netherlands)

Yudodibroto, B.Y.B.

2010-01-01

The purpose of this research is to obtain insight into the oscillation behaviour of the liquid metal and the arc behaviour during GMA welding. Observations of the weld pool and the arc were undertaken by visual means using a high-speed video and by analysis of the voltage. To deal with the complex

CDBA-Based Universal Biquad Filter and Quadrature Oscillator

Directory of Open Access Journals (Sweden)

Worapong Tangsrirat

2008-01-01

Full Text Available The voltage-mode universal biquadratic filter and sinusoidal quadrature oscillator based on the use of current differencing buffered amplifiers (CDBAs as active components have been proposed in this paper. All the proposed configurations employ only two CDBAs and six passive components. The first proposed CDBA-based biquad configuration can realize all the standard types of the biquadratic functions, that is, lowpass, bandpass, highpass, bandstop, and allpass, from the same topology, and can also provide orthogonal tuning of the natural angular frequency (ωo and the bandwidth (BW through separate virtually grounded passive components. By slight modification of the first proposed configuration, the new CDBA-based sinusoidal quadrature oscillator is easily obtained. The oscillation condition and the oscillation frequency are independently adjustable by different virtually grounded resistors. The sensitivity analysis of all proposed circuit configurations is shown to be low. PSPICE simulations and experimental results based upon commercially available AD844-type CFAs are included, which confirm the workability of the proposed circuits.

Pulsed voltage electrospray ion source and method for preventing analyte electrolysis

Science.gov (United States)

Kertesz, Vilmos [Knoxville, TN; Van Berkel, Gary [Clinton, TN

2011-12-27

An electrospray ion source and method of operation includes the application of pulsed voltage to prevent electrolysis of analytes with a low electrochemical potential. The electrospray ion source can include an emitter, a counter electrode, and a power supply. The emitter can include a liquid conduit, a primary working electrode having a liquid contacting surface, and a spray tip, where the liquid conduit and the working electrode are in liquid communication. The counter electrode can be proximate to, but separated from, the spray tip. The power system can supply voltage to the working electrode in the form of a pulse wave, where the pulse wave oscillates between at least an energized voltage and a relaxation voltage. The relaxation duration of the relaxation voltage can range from 1 millisecond to 35 milliseconds. The pulse duration of the energized voltage can be less than 1 millisecond and the frequency of the pulse wave can range from 30 to 800 Hz.

Dual radiofrequency drive quantum voltage standard with nanovolt resolution based on a closed-loop refrigeration cycle

International Nuclear Information System (INIS)

Georgakopoulos, D; Budovsky, I; Hagen, T; Sasaki, H; Yamamori, H

2012-01-01

We have developed a programmable Josephson voltage standard that can produce voltages up to 20 V with a resolution of better than 0.1 µV over the whole voltage range and better than 1 nV for voltages up to 10 mV. The standard has two superconductor–normal metal–superconductor junction arrays connected in series and driven by two radiofrequency oscillators. The cryogenic part of the standard is based on a cryocooler. The new standard agrees with the primary quantum voltage standard maintained at the National Measurement Institute, Australia, within 10 nV and forms the basis of an automated calibration system for digital multimeters and voltage references. (paper)

Measurements of temperature characteristics and estimation of terahertz negative differential conductance in resonant-tunneling-diode oscillators

Directory of Open Access Journals (Sweden)

M. Asada

2017-11-01

Full Text Available The temperature dependences of output power, oscillation frequency, and current-voltage curve are measured for resonant-tunneling-diode terahertz (THz oscillators. The output power largely changes with temperature owing to the change in Ohmic loss. In contrast to the output power, the oscillation frequency and current-voltage curve are almost insensitive to temperature. The measured temperature dependence of output power is compared with the theoretical calculation including the negative differential conductance (NDC as a fitting parameter assumed to be independent of temperature. Very good agreement was obtained between the measurement and calculation, and the NDC in the THz frequency region is estimated. The results show that the absolute values of NDC in the THz region significantly decrease relative to that at DC, and increases with increasing frequency in the measured frequency range.

Development of a fast voltage control method for electrostatic accelerators

International Nuclear Information System (INIS)

Lobanov, Nikolai R.; Linardakis, Peter; Tsifakis, Dimitrios

2014-01-01

The concept of a novel fast voltage control loop for tandem electrostatic accelerators is described. This control loop utilises high-frequency components of the ion beam current intercepted by the image slits to generate a correction voltage that is applied to the first few gaps of the low- and high-energy acceleration tubes adjoining the high voltage terminal. New techniques for the direct measurement of the transfer function of an ultra-high impedance structure, such as an electrostatic accelerator, have been developed. For the first time, the transfer function for the fast feedback loop has been measured directly. Slow voltage variations are stabilised with common corona control loop and the relationship between transfer functions for the slow and new fast control loops required for optimum operation is discussed. The main source of terminal voltage instabilities, which are due to variation of the charging current caused by mechanical oscillations of charging chains, has been analysed

A time-domain digitally controlled oscillator composed of a free running ring oscillator and flying-adder

International Nuclear Information System (INIS)

Liu Wei; Zhang Shengdong; Wang Yangyuan; Li Wei; Ren Peng; Lin Qinglong

2009-01-01

A time-domain digitally controlled oscillator (DCO) is proposed. The DCO is composed of a free-running ring oscillator (FRO) and a two lap-selectors integrated flying-adder (FA). With a coiled cell array which allows uniform loading capacitances of the delay cells, the FRO produces 32 outputs with consistent tap spacing for the FA as reference clocks. The FA uses the outputs from the FRO to generate the output of the DCO according to the control number, resulting in a linear dependence of the output period, instead of the frequency on the digital controlling word input. Thus the proposed DCO ensures a good conversion linearity in a time-domain, and is suitable for time-domain all-digital phase locked loop applications. The DCO was implemented in a standard 0.13 μm digital logic CMOS process. The measurement results show that the DCO has a linear and monotonic tuning curve with gain variation of less than 10%, and a very low root mean square period jitter of 9.3 ps in the output clocks. The DCO works well at supply voltages ranging from 0.6 to 1.2 V, and consumes 4 mW of power with 500 MHz frequency output at 1.2 V supply voltage.

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

OpenAIRE

Cheremisin, M. V.

2003-01-01

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

Effect of the change in the load resistance on the high voltage pulse transformer of the intense electron-beam accelerators.

Science.gov (United States)

Cheng, Xin-bing; Liu, Jin-liang; Qian, Bao-liang; Zhang, Yu; Zhang, Hong-bo

2009-11-01

A high voltage pulse transformer (HVPT) is usually used as a charging device for the pulse forming line (PFL) of intense electron-beam accelerators (IEBAs). Insulation of the HVPT is one of the important factors that restrict the development of the HVPT. Until now, considerable effort has been focused on minimizing high field regions to avoid insulation breakdown between windings. Characteristics of the HVPT have been widely discussed to achieve these goals, but the effects of the PFL and load resistance on HVPT are usually neglected. In this paper, a HVPT is used as a charging device for the PFL of an IEBA and the effect of the change in the load resistance on the HVPT of the IEBA is presented. When the load resistance does not match the wave impedance of the PFL, a high-frequency bipolar oscillating voltage will occur, and the amplitude of the oscillating voltage will increase with the decrease in the load resistance. The load resistance approximates to zero and the amplitude of the oscillating voltage is much higher. This makes it easier for surface flashover along the insulation materials to form and decrease the lifetime of the HVPT.

Temperature and magnetic field effect on oscillations observed in GaInNAs/GaAs multiple quantum wells structures

International Nuclear Information System (INIS)

Khalil, H.M.; Mazzucato, S.; Ardali, S.; Celik, O.; Mutlu, S.; Royall, B.; Tiras, E.; Balkan, N.; Puustinen, J.; Korpijärvi, V.-M.; Guina, M.

2012-01-01

Highlights: ► We studied p-i-n GaInNAs MQW devices as function of temperature and magnetic field. ► Observed oscillations in the sample current–voltage curves at low temperature. ► Shift in oscillation position with magnetic field described by Landau level split. ► Resonant tunnelling and thermionic emission used to describe oscillations. - Abstract: The photoconductivity of p-i-n GaInNAs/GaAs multiple quantum well (MQW) mesa structures is investigated. When illuminated with photons at energy greater than the GaAs bandgap, a number of oscillations are observed in the current–voltage I–V characteristics. The amplitude and position of the oscillations is shown to depend upon the temperature, as well as upon the exciting wavelength and intensity. Due to the absence of the oscillations in the dark I–V and at temperatures above T = 200 K, we explain them in terms of photogenerated electrons escaping from quantum wells via tunnelling or thermionic emission. Magnetic fields up to B = 11 T were applied parallel to the planes of the QWs. A small voltage shift in the position of the oscillations was observed, proportional to the magnetic field intensity and dependent upon the temperature. Calculation of the Landau level energy separation (16 meV) agrees with the observed experimental data. Magneto-tunnelling spectroscopy probes in detail the nature of band- or impurity-like states responsible for resonances in first and second subbands, observing the I–V plot in dark condition and under illumination. The field-dependence of the amplitude of the oscillation peaks in I–V has the characteristic form of a quantum mechanical admixing effect. This enhancement is also probably due to the hole recombination with majority electrons tunnelling in the N-related states of the quantum wells.

Temperature and magnetic field effect on oscillations observed in GaInNAs/GaAs multiple quantum wells structures

Energy Technology Data Exchange (ETDEWEB)

Khalil, H.M., E-mail: hkhalia@essex.ac.uk [School of Computer Science and Electronic Engineering, University of Essex, CO4 3SQ, Colchester (United Kingdom); Mazzucato, S. [School of Computer Science and Electronic Engineering, University of Essex, CO4 3SQ, Colchester (United Kingdom); Ardali, S.; Celik, O.; Mutlu, S. [Anadolu University, Faculty of Science, Department of Physics, Yunus Emre Campus 26470, Eskisehir (Turkey); Royall, B. [School of Computer Science and Electronic Engineering, University of Essex, CO4 3SQ, Colchester (United Kingdom); Tiras, E. [Anadolu University, Faculty of Science, Department of Physics, Yunus Emre Campus 26470, Eskisehir (Turkey); Balkan, N. [School of Computer Science and Electronic Engineering, University of Essex, CO4 3SQ, Colchester (United Kingdom); Puustinen, J.; Korpijaervi, V.-M.; Guina, M. [Optoelectronics Research Centre, Tampere University of Technology, Korkeakoulunkatu 10, FI-33720 Tampere (Finland)

2012-06-05

Highlights: Black-Right-Pointing-Pointer We studied p-i-n GaInNAs MQW devices as function of temperature and magnetic field. Black-Right-Pointing-Pointer Observed oscillations in the sample current-voltage curves at low temperature. Black-Right-Pointing-Pointer Shift in oscillation position with magnetic field described by Landau level split. Black-Right-Pointing-Pointer Resonant tunnelling and thermionic emission used to describe oscillations. - Abstract: The photoconductivity of p-i-n GaInNAs/GaAs multiple quantum well (MQW) mesa structures is investigated. When illuminated with photons at energy greater than the GaAs bandgap, a number of oscillations are observed in the current-voltage I-V characteristics. The amplitude and position of the oscillations is shown to depend upon the temperature, as well as upon the exciting wavelength and intensity. Due to the absence of the oscillations in the dark I-V and at temperatures above T = 200 K, we explain them in terms of photogenerated electrons escaping from quantum wells via tunnelling or thermionic emission. Magnetic fields up to B = 11 T were applied parallel to the planes of the QWs. A small voltage shift in the position of the oscillations was observed, proportional to the magnetic field intensity and dependent upon the temperature. Calculation of the Landau level energy separation (16 meV) agrees with the observed experimental data. Magneto-tunnelling spectroscopy probes in detail the nature of band- or impurity-like states responsible for resonances in first and second subbands, observing the I-V plot in dark condition and under illumination. The field-dependence of the amplitude of the oscillation peaks in I-V has the characteristic form of a quantum mechanical admixing effect. This enhancement is also probably due to the hole recombination with majority electrons tunnelling in the N-related states of the quantum wells.

Coherent charge fluctuations in Josephson junctions and the oscillations of the effective capacitance

International Nuclear Information System (INIS)

Krive, I.V.; Rozhavsky, A.S.

1990-07-01

We predict novel voltage oscillations of the effective capacitance of small Josephson junctions. This macroscopic effect involves coherent charge fluctuations with charge 2e, leading to a period of oscillations, V c = 2e/C, where C is the junction capacitance. The amplitude of the effect decreases with temperature as exp(-π 2 T/ε c ), where ε c = (2e) 2 /C. (author). 6 refs

Stability Boundaries for Offshore Wind Park Distributed Voltage Control

DEFF Research Database (Denmark)

Gryning, Mikkel P.S.; Wu, Qiuwei; Kocewiak, Lukasz

2017-01-01

pilot control. Using data from the actual wind power plant, all stabilizing subsystem voltage proportional-integral controller parameters are first characterized based on their Hurwitz signature. Inner loop current control is then designed using Internal Mode Control principles, and guidelines for feed......In order to identify mechanisms causing slow reactive power oscillations observed in an existing offshore wind power plant, and be able to avoid similar events in the future, voltage control is studied in this paper for a plant with a static synchronous compensator, type-4 wind turbines and a park...... forward filter design are given to obtain required disturbance rejection properties. The paper contributes by providing analytical relations between power plant control, droop, sampling time, electrical parameters and voltage control characteristics, and by assessing frequencies and damping of reactive...

Assessment of effect of SSSC stabilizer in different control channels on damping inter-area oscillations

Energy Technology Data Exchange (ETDEWEB)

Shakarami, M.R., E-mail: shakarami@iust.ac.i [Centre of Excellence for Power System Automation and Operation, Department of Electrical Engineering, Iran University of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of); Kazemi, A. [Centre of Excellence for Power System Automation and Operation, Department of Electrical Engineering, Iran University of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of)

2011-03-15

A static synchronous series compensator (SSSC) is one of the series flexible ac transmission system (FACTS) devices that injects a balanced three-phase voltage in quadrature with the transmission line current. There are two channels for controlling of phase and magnitude of the voltage. When the SSSC is used for damping of inter-area oscillations, a SSSC-based stabilizer can be included in both channels. In this paper, the best location and suitable input control signal for SSSC in order to enhance the damping of inter-area oscillations are selected by residue analysis. A method by quadratic mathematic programming has been presented to the design of the stabilizer. By this method, the effect of the stabilizer in both control channels of the SSSC on damping of inter-area oscillations has been assessed. By considering the gain of stabilizer as a criterion, obtained results from studying on a small and a large multi-machine power system show that the stabilizer in the phase control channel is more effective for damping inter-are oscillations.

Speed Control of Matrix Converter-Fed Five-Phase Permanent Magnet Synchronous Motors under Unbalanced Voltages

Directory of Open Access Journals (Sweden)

Borzou Yousefi

2017-09-01

Full Text Available Five-phase permanent magnet synchronous motors (PMSM have special applications in which highly accurate speed and torque control of the motor are a strong requirement. Direct Torque Control (DTC is a suitable method for the driver structure of these motors. If in this method, instead of using a common five-phase voltage source inverter, a three-phase to five-phase matrix converter is used, the low-frequency current harmonics and the high torque ripple are limited, and an improved input power factor is obtained. Because the input voltages of such converters are directly supplied by input three-phase supply voltages, an imbalance in the voltages will cause problems such as unbalanced stator currents and electromagnetic torque fluctuations. In this paper, a new method is introduced to remove speed and torque oscillator factors. For this purpose, motor torque equations were developed and the oscillation components created by the unbalanced source voltage, determined. Then, using the active and reactive power reference generator, the controller power reference was adjusted in such a way that the electromagnetic torque of the motor did not change. By this means, a number of features including speed, torque, and flux of the motor were improved in terms of the above-mentioned conditions. Simulations were analyzed using Matlab/Simulink software.

Low-sensitivity, low-bounce, high-linearity current-controlled oscillator suitable for single-supply mixed-mode instrumentation system.

Science.gov (United States)

Hwang, Yuh-Shyan; Kung, Che-Min; Lin, Ho-Cheng; Chen, Jiann-Jong

2009-02-01

A low-sensitivity, low-bounce, high-linearity current-controlled oscillator (CCO) suitable for a single-supply mixed-mode instrumentation system is designed and proposed in this paper. The designed CCO can be operated at low voltage (2 V). The power bounce and ground bounce generated by this CCO is less than 7 mVpp when the power-line parasitic inductance is increased to 100 nH to demonstrate the effect of power bounce and ground bounce. The power supply noise caused by the proposed CCO is less than 0.35% in reference to the 2 V supply voltage. The average conversion ratio KCCO is equal to 123.5 GHz/A. The linearity of conversion ratio is high and its tolerance is within +/-1.2%. The sensitivity of the proposed CCO is nearly independent of the power supply voltage, which is less than a conventional current-starved oscillator. The performance of the proposed CCO has been compared with the current-starved oscillator. It is shown that the proposed CCO is suitable for single-supply mixed-mode instrumentation systems.

Mikheyev-smirnov-wolfenstein effects in vacuum oscillations

Science.gov (United States)

Friedland

2000-07-31

We point out that for solar neutrino oscillations with the mass-squared difference of Deltam(2) approximately 10(-10)-10(-9) eV(2), i.e., in the so-called vacuum oscillation range, the solar matter effects are non-negligible, particularly for the low energy pp neutrinos. One consequence of this is that the values of the mixing angle straight theta and pi/2-straight theta are not equivalent, making it necessary to consider the entire physical range of the mixing angle 0oscillation parameters.

Mikheyev-Smirnov-Wolfenstein Effects in Vacuum Oscillations

International Nuclear Information System (INIS)

Friedland, Alexander

2000-01-01

We point out that for solar neutrino oscillations with the mass-squared difference of Δm 2 ∼10 -10 - 10 -9 eV 2 , i.e., in the so-called vacuum oscillation range, the solar matter effects are non-negligible, particularly for the low energy pp neutrinos. One consequence of this is that the values of the mixing angle θ and π/2-θ are not equivalent, making it necessary to consider the entire physical range of the mixing angle 0≤θ≤π/2 when determining the allowed values of the neutrino oscillation parameters. (c) 2000 The American Physical Society

Resonant Spin-Transfer-Torque Nano-Oscillators

Science.gov (United States)

Sharma, Abhishek; Tulapurkar, Ashwin A.; Muralidharan, Bhaskaran

2017-12-01

Spin-transfer-torque nano-oscillators are potential candidates for replacing the traditional inductor-based voltage-controlled oscillators in modern communication devices. Typical oscillator designs are based on trilayer magnetic tunnel junctions, which have the disadvantages of low power outputs and poor conversion efficiencies. We theoretically propose using resonant spin filtering in pentalayer magnetic tunnel junctions as a possible route to alleviate these issues and present viable device designs geared toward a high microwave output power and an efficient conversion of the dc input power. We attribute these robust qualities to the resulting nontrivial spin-current profiles and the ultrahigh tunnel magnetoresistance, both of which arise from resonant spin filtering. The device designs are based on the nonequilibrium Green's-function spin-transport formalism self-consistently coupled with the stochastic Landau-Lifshitz-Gilbert-Slonczewski equation and Poisson's equation. We demonstrate that the proposed structures facilitate oscillator designs featuring a large enhancement in microwave power of around 1150% and an efficiency enhancement of over 1100% compared to typical trilayer designs. We rationalize the optimum operating regions via an analysis of the dynamic and static device resistances. We also demonstrate the robustness of our structures against device design fluctuations and elastic dephasing. This work sets the stage for pentalyer spin-transfer-torque nano-oscillator device designs that ameliorate major issues associated with typical trilayer designs.

Unbalanced voltage faults: the impact on structural loads of doubly fed asynchronous generator wind turbines

DEFF Research Database (Denmark)

Barahona Garzón, Braulio; Cutululis, Nicolaos Antonio; Hansen, Anca Daniela

2014-01-01

This paper investigates the impact that unbalanced voltage faults have on wind turbine structural loads. In such cases, electromagnetic torque oscillations occur at two times the supply voltage frequency. The objectives of this work are to quantify wind turbine structural loads induced...... by unbalanced voltage faults relative to those during normal operation; and to evaluate the potential for reducing structural loads with the control of the generator. The method applied is integrated dynamic analysis. Namely, dynamic analysis with models that consider the most important aeroelastic, electrical...

Current oscillations in avalanche particle detectors with PNIPN-structure

International Nuclear Information System (INIS)

Lukin, K.A.

1995-08-01

The model of an avalanche high energy particle detector consisting of two pn-junctions, connected through an intrinsic semiconductor with a reverse biased voltage applied. This detector is able to generate the oscillatory response on the single particle passage through the structure. The possibility of oscillations leading to chaotic behaviour is pointed out

Modulation of low-frequency oscillations in GaAs MESFETs' channel current by sidegating bias

Institute of Scientific and Technical Information of China (English)

DING Yong; LU Shengli; ZHAO Fuchuan

2005-01-01

Low-frequency oscillations in channel current are usually observed when measuring the GaAs MESFET's output characteristics. This paper studies the oscillations by testing the MESFET's output characteristics under different sidegate bias conditions. It is shown that the low-frequency oscillations of channel current are directly related to the sidegate bias. In other words, the sidegate bias can modulate the oscillations. Whether the sidegate bias varies positively or negatively, there will inevitably be a threshold voltage after which the low-frequency oscillations disappear. The observation is strongly dependent upon the peculiarities of channel-substrate (C-S) junction and impact ionization of traps-EL2 under high field. This conclusion is of particular pertinence to the design of low-noise GaAs IC's.

Spherical ion oscillations in a positive polarity gridded inertial-electrostatic confinement device

Energy Technology Data Exchange (ETDEWEB)

Bandara, R.; Khachan, J. [Plasma Physics, School of Physics, University of Sydney, Camperdown, New South Wales 2006 (Australia)

2013-07-15

A pulsed, positive polarity gridded inertial electrostatic confinement device has been investigated experimentally, using a differential emissive probe and potential traces as primary diagnostics. Large amplitude oscillations in the plasma current and plasma potential were observed within a microsecond of the discharge onset, which are indicative of coherent ion oscillations about a temporarily confined excess of recirculating electron space charge. The magnitude of the depth of the potential well in the established virtual cathode was determined using a differential emissive Langmuir probe, which correlated well to the potential well inferred from the ion oscillation frequency for both hydrogen and argon experiments. It was found that the timescale for ion oscillation dispersion is strongly dependent on the neutral gas density, and weakly dependent on the peak anode voltage. The cessation of the oscillations was found to be due to charge exchange processes converting ions to high velocity neutrals, causing the abrupt de-coherence of the oscillations through an avalanche dispersion in phase space.

Spherical ion oscillations in a positive polarity gridded inertial-electrostatic confinement device

Science.gov (United States)

Bandara, R.; Khachan, J.

2013-07-01

A pulsed, positive polarity gridded inertial electrostatic confinement device has been investigated experimentally, using a differential emissive probe and potential traces as primary diagnostics. Large amplitude oscillations in the plasma current and plasma potential were observed within a microsecond of the discharge onset, which are indicative of coherent ion oscillations about a temporarily confined excess of recirculating electron space charge. The magnitude of the depth of the potential well in the established virtual cathode was determined using a differential emissive Langmuir probe, which correlated well to the potential well inferred from the ion oscillation frequency for both hydrogen and argon experiments. It was found that the timescale for ion oscillation dispersion is strongly dependent on the neutral gas density, and weakly dependent on the peak anode voltage. The cessation of the oscillations was found to be due to charge exchange processes converting ions to high velocity neutrals, causing the abrupt de-coherence of the oscillations through an avalanche dispersion in phase space.

Golden quantum oscillator and Binet–Fibonacci calculus

International Nuclear Information System (INIS)

Pashaev, Oktay K; Nalci, Sengul

2012-01-01

The Binet formula for Fibonacci numbers is treated as a q-number and a q-operator with Golden ratio bases q = φ and Q = −1/φ, and the corresponding Fibonacci or Golden calculus is developed. A quantum harmonic oscillator for this Golden calculus is derived so that its spectrum is given only by Fibonacci numbers. The ratio of successive energy levels is found to be the Golden sequence, and for asymptotic states in the limit n → ∞ it appears as the Golden ratio. We call this oscillator the Golden oscillator. Using double Golden bosons, the Golden angular momentum and its representation in terms of Fibonacci numbers and the Golden ratio are derived. Relations of Fibonacci calculus with a q-deformed fermion oscillator and entangled N-qubit states are indicated. (paper)

Golden quantum oscillator and Binet-Fibonacci calculus

Energy Technology Data Exchange (ETDEWEB)

Pashaev, Oktay K; Nalci, Sengul, E-mail: oktaypashaev@iyte.edu.tr [Department of Mathematics, Izmir Institute of Technology, Urla-Izmir 35430 (Turkey)

2012-01-13

The Binet formula for Fibonacci numbers is treated as a q-number and a q-operator with Golden ratio bases q = {phi} and Q = -1/{phi}, and the corresponding Fibonacci or Golden calculus is developed. A quantum harmonic oscillator for this Golden calculus is derived so that its spectrum is given only by Fibonacci numbers. The ratio of successive energy levels is found to be the Golden sequence, and for asymptotic states in the limit n {yields} {infinity} it appears as the Golden ratio. We call this oscillator the Golden oscillator. Using double Golden bosons, the Golden angular momentum and its representation in terms of Fibonacci numbers and the Golden ratio are derived. Relations of Fibonacci calculus with a q-deformed fermion oscillator and entangled N-qubit states are indicated. (paper)

Power Oscillation Damping from VSC-HVDC Connected Offshore Wind Power Plants

DEFF Research Database (Denmark)

Zeni, Lorenzo; Eriksson, Robert; Goumalatsos, Spyridon

2016-01-01

The implementation of power oscillation damping service on offshore wind power plants connected to onshore grids by voltage-source-converter-based high voltage direct current transmission is discussed. Novel design guidelines for damping controllers on voltage-source converters and wind power plant...... regarding real wind power plants are discussed: 1) robustness against control/communication delays; 2) limitations due to mechanical resonances in wind turbine generators; 3) actual capability of wind power plants to provide damping without curtailing production; and 4) power-ramp rate limiters....... controllers are derived, using phasor diagrams and a test network model and are then verified on a generic power system model. The effect of voltage regulators is analyzed, which is important for selecting the most robust damping strategy. Furthermore, other often disregarded practical implementation aspects...

Quantum damped oscillator I: Dissipation and resonances

International Nuclear Information System (INIS)

Chruscinski, Dariusz; Jurkowski, Jacek

2006-01-01

Quantization of a damped harmonic oscillator leads to so called Bateman's dual system. The corresponding Bateman's Hamiltonian, being a self-adjoint operator, displays the discrete family of complex eigenvalues. We show that they correspond to the poles of energy eigenvectors and the corresponding resolvent operator when continued to the complex energy plane. Therefore, the corresponding generalized eigenvectors may be interpreted as resonant states which are responsible for the irreversible quantum dynamics of a damped harmonic oscillator

Responsive demand to mitigate slow recovery voltage sags

DEFF Research Database (Denmark)

Garcia-Valle, Rodrigo; da Silva, Luiz Carlos Pereira; Xu, Zhao

2012-01-01

, and reactive power reserve for peak load management through price responsive methods and also as energy providers through embedded generation technologies. This article introduces a new technology, called demand as voltagecontrolled reserve, which can help mitigation of momentary voltage sags. The technology...... faults. This article presents detailed models, discussion, and simulation tests to demonstrate the technical viability and effectiveness of the demand as voltage-controlled reserve technology for mitigating voltage sags....... can be provided by thermostatically controlled loads as well as other types of load. This technology has proven to be effective in distribution systems with a large composition of induction motors, when voltage sags present slow recovery characteristics because of the deceleration of the motors during...

Adaptive Voltage Control Strategy for Variable-Speed Wind Turbine Connected to a Weak Network

DEFF Research Database (Denmark)

Abulanwar, Elsayed; Hu, Weihao; Chen, Zhe

2016-01-01

and smoothness at the point of connection (POC) in order to maximise the wind power penetration into such networks. Intensive simulation case studies under different network topology and wind speed ranges reveal the effectiveness of the AVC scheme to effectively suppress the POC voltage variations particularly......Significant voltage fluctuations and power quality issues pose considerable constraints on the efficient integration of remotely located wind turbines into weak networks. Besides, 3p oscillations arising from the wind shear and tower shadow effects induce further voltage perturbations during...... continuous operation. This study investigates and analyses the repercussions raised by integrating a doubly-fed induction generator wind turbine into an ac network of different parameters and very weak conditions. An adaptive voltage control (AVC) strategy is proposed to retain voltage constancy...

Quantum resonances in a single plaquette of Josephson junctions: excitations of Rabi oscillations

OpenAIRE

Fistul, M. V.

2001-01-01

We present a theoretical study of a quantum regime of the resistive (whirling) state of dc driven anisotropic single plaquette containing three small Josephson junctions. The current-voltage characteristics of such a system display resonant steps that are due to the resonant interaction between the time dependent Josephson current and the excited electromagnetic oscillations (EOs). The voltage positions of the resonances are determined by the quantum interband transitions of EOs. We show that...

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

DEFF Research Database (Denmark)

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

2012-01-01

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

Influence of voltage on magnetization of ferromagnetic semiconductors with colossal magnetoresistance

International Nuclear Information System (INIS)

Povzner, A.A.; Volkov, A.G.

2017-01-01

Graphical abstract: We investigate nonequilibrium states of strongly correlated electron subsystem of lanthanum manganite, resulting in an external electric field. It is shown that the Joule heat leads to localization of electrons. As result, electric resistance, magnetization and other characteristics of the electronic system are depending on the applied voltage. This leads to the formation of the bistable state of the electronic system in the vicinity of the Curie point in an external electric field. This manifests itself in non-linear current-voltage characteristics of these substances, and should lead to oscillations of the magnetization and current. - Abstract: The nonequilibrium processes of “self-heating” arising during the flow of electric current are studied for ferromagnetic semiconductors with colossal magnetoresistance near the Curie temperature. These processes lead to the emergence of “hot” paramagnons and the destruction of ferromagnetic order. The solution to the heat balance equation takes into account the temperature dependence of the electrical conductivity caused by Anderson localization of electrons due to their scattering on magnetic inhomogeneities. Description of delocalized electrons subsystem takes into account the spin-flip processes leading to the double exchange. At that, the value of the Anderson percolation threshold and the double exchange depends on the amplitude of spin fluctuations. It was found that N-shaped current-voltage characteristics and hysteresis dependencies of magnetization on the voltage arise in a steady state due to the emergence of “hot” (by internal sample temperature) semiconductor paramagnetic phase. It is shown that the occurrence of self-oscillations of current and magnetization there may be.

Influence of voltage on magnetization of ferromagnetic semiconductors with colossal magnetoresistance

Energy Technology Data Exchange (ETDEWEB)

Povzner, A.A., E-mail: a.a.povzner@urfu.ru; Volkov, A.G., E-mail: agvolkov@yandex.ru

2017-06-15

Graphical abstract: We investigate nonequilibrium states of strongly correlated electron subsystem of lanthanum manganite, resulting in an external electric field. It is shown that the Joule heat leads to localization of electrons. As result, electric resistance, magnetization and other characteristics of the electronic system are depending on the applied voltage. This leads to the formation of the bistable state of the electronic system in the vicinity of the Curie point in an external electric field. This manifests itself in non-linear current-voltage characteristics of these substances, and should lead to oscillations of the magnetization and current. - Abstract: The nonequilibrium processes of “self-heating” arising during the flow of electric current are studied for ferromagnetic semiconductors with colossal magnetoresistance near the Curie temperature. These processes lead to the emergence of “hot” paramagnons and the destruction of ferromagnetic order. The solution to the heat balance equation takes into account the temperature dependence of the electrical conductivity caused by Anderson localization of electrons due to their scattering on magnetic inhomogeneities. Description of delocalized electrons subsystem takes into account the spin-flip processes leading to the double exchange. At that, the value of the Anderson percolation threshold and the double exchange depends on the amplitude of spin fluctuations. It was found that N-shaped current-voltage characteristics and hysteresis dependencies of magnetization on the voltage arise in a steady state due to the emergence of “hot” (by internal sample temperature) semiconductor paramagnetic phase. It is shown that the occurrence of self-oscillations of current and magnetization there may be.

Power Oscillations Damping in DC Microgrids

OpenAIRE

Hamzeh, Mohsen; Ghafouri, Mohsen; Karimi, Houshang; Sheshyekani, Keyhan; Guerrero, Josep M.

2016-01-01

This paper proposes a new control strategy for damping of power oscillations in a multi-source dc microgrid. A parallel combination of a fuel cell (FC), a photovoltaic (PV) system and a supercapacitor (SC) are used as a hybrid power conversion system (HPCS). The SC compensates for the slow transient response of the FC stack. The HPCS controller comprises a multi-loop voltage controller and a virtual impedance loop for power management. The virtual impedance loop uses a dynamic droop gain to a...

Voltage-gated proton channel is expressed on phagosomes

International Nuclear Information System (INIS)

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

2009-01-01

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

A low-cost, Nist-traceable, high performance dielectric resonator Master Oscillator

International Nuclear Information System (INIS)

Doolittle, L.R.; Hovater, C.; Merminga, L.; Musson, J.; Wiseman, W.

1999-01-01

The current CEBAF Master Oscillator (MO) uses a quartz-based 10 MHz reference to synthesize 70 MHz and 499 MHz, which are then distributed to each of the klystron galleries on site. Due to the specialized nature of CEBAF's MO requirements, it has been determined that an in-house design and fabrication would provide a cost-effective alternative to purchasing or modifying vendor equipment. A Global Positioning System (GPS) disciplined, Direct Digital Synthesis (DDS) based MO is proposed which incorporates low-cost consumer RF components, designed for cellular communications. A 499 MHz Dielectric Resonant Oscillator (DRO) Voltage Controlled Oscillator (VCO) is phase-locked to a GPS-disciplined 10 MHz reference, and micro-tuned via a DDS, in an effort to achieve the lowest phase noise possible

MOSFET-based high voltage short pulse generator for ultrasonic transducer excitation

Science.gov (United States)

Hidayat, Darmawan; Setianto, Syafei, Nendi Suhendi; Wibawa, Bambang Mukti

2018-02-01

This paper presents the generation of a high-voltage short pulse for the excitation of high frequency ultrasonic transducers. This is highly required in the purpose of various ultrasonic-based evaluations, particularly when high resolution measurement is necessary. A high voltage (+760 V) DC voltage source was pulsated by an ultrafast switching MOSFET which was driven by a pulse generator circuit consisting of an astable multivibrator, a one-shot multivibrator with Schmitt trigger input and a high current MOSFET driver. The generated pulses excited a 200-kHz and a 1-MHz ultrasonic transducers and tested in the transmission mode propagation to evaluate the performances of the generated pulse. The test results showed the generator were able to produce negative spike pulses up to -760 V voltage with the shortest time-width of 107.1 nanosecond. The transmission-received ultrasonic waves show frequency oscillation at 200 and 961 kHz and their amplitudes varied with the voltage of excitation pulse. These results conclude that the developed pulse generator is applicable to excite transducer for the generation of high frequency ultrasonic waves.

Chimera states in mechanical oscillator networks

DEFF Research Database (Denmark)

Martens, Erik Andreas; Thutupalli, Shashi; Fourrière, Antoine

2013-01-01

of identical oscillators, numerous theoretical studies in recent years have revealed the intriguing possibility of "chimera states," in which the symmetry of the oscillator population is broken into a synchronous part and an asynchronous part. However, a striking lack of empirical evidence raises the question...... of whether chimeras are indeed characteristic of natural systems. This calls for a palpable realization of chimera states without any fine-tuning, from which physical mechanisms underlying their emergence can be uncovered. Here, we devise a simple experiment with mechanical oscillators coupled...... in a hierarchical network to show that chimeras emerge naturally from a competition between two antagonistic synchronization patterns. We identify a wide spectrum of complex states, encompassing and extending the set of previously described chimeras. Our mathematical model shows that the self-organization observed...

Detecting Power Voltage Dips using Tracking Filters - A Comparison against Kalman

Directory of Open Access Journals (Sweden)

STANCIU, I.-R.

2012-11-01

Full Text Available Due of its significant economical impact, Power-Quality (PQ analysis is an important domain today. Severe voltage distortions affect the consumers and disturb their activity. They may be caused by short circuits (in this case the voltage drops significantly or by varying loads (with a smaller drop. These two types are the PQ currently issues. Monitoring these phenomena (called dips or sags require powerful techniques. Digital Signal Processing (DSP algorithms are currently employed to fulfill this task. Discrete Wavelet Transforms, (and variants, Kalman filters, and S-Transform are currently proposed by researchers to detect voltage dips. This paper introduces and examines a new tool to detect voltage dips: the so-called tracking filters. Discovered and tested during the cold war, they can estimate a parameter of interest one-step-ahead based on the previously observed values. Two filters are implemented. Their performance is assessed by comparison against the Kalman filter?s results.

Observation of multi-scale oscillation of laminar lifted flames with low-frequency AC electric fields

KAUST Repository

Ryu, Seol

2010-01-01

The oscillation behavior of laminar lifted flames under the influence of low-frequency AC has been investigated experimentally in coflow jets. Various oscillation modes were existed depending on jet velocity and the voltage and frequency of AC, especially when the AC frequency was typically smaller than 30 Hz. Three different oscillation modes were observed: (1) large-scale oscillation with the oscillation frequency of about 0.1 Hz, which was independent of the applied AC frequency, (2) small-scale oscillation synchronized to the applied AC frequency, and (3) doubly-periodic oscillation with small-scale oscillation embedded in large-scale oscillation. As the AC frequency decreased from 30 Hz, the oscillation modes were in the order of the large-scale oscillation, doubly-periodic oscillation, and small-scale oscillation. The onset of the oscillation for the AC frequency smaller than 30 Hz was in close agreement with the delay time scale for the ionic wind effect to occur, that is, the collision response time. Frequency-doubling behavior for the small-scale oscillation has also been observed. Possible mechanisms for the large-scale oscillation and the frequency-doubling behavior have been discussed, although the detailed understanding of the underlying mechanisms will be a future study. © 2009 The Combustion Institute.

Automatic oscillator frequency control system

Science.gov (United States)

Smith, S. F. (Inventor)

1985-01-01

A frequency control system makes an initial correction of the frequency of its own timing circuit after comparison against a frequency of known accuracy and then sequentially checks and corrects the frequencies of several voltage controlled local oscillator circuits. The timing circuit initiates the machine cycles of a central processing unit which applies a frequency index to an input register in a modulo-sum frequency divider stage and enables a multiplexer to clock an accumulator register in the divider stage with a cyclical signal derived from the oscillator circuit being checked. Upon expiration of the interval, the processing unit compares the remainder held as the contents of the accumulator against a stored zero error constant and applies an appropriate correction word to a correction stage to shift the frequency of the oscillator being checked. A signal from the accumulator register may be used to drive a phase plane ROM and, with periodic shifts in the applied frequency index, to provide frequency shift keying of the resultant output signal. Interposition of a phase adder between the accumulator register and phase plane ROM permits phase shift keying of the output signal by periodic variation in the value of a phase index applied to one input of the phase adder.

Electron beam modification of vanadium dioxide oscillators

Energy Technology Data Exchange (ETDEWEB)

Belyaev, Maksim; Velichko, Andrey; Putrolaynen, Vadim; Perminov, Valentin; Pergament, Alexander [Petrozavodsk State University, Petrozavodsk (Russian Federation)

2017-03-15

The paper presents the results of a study of electron-beam modification (EBM) of VO{sub 2}-switch I-V curve threshold parameters and the self-oscillation frequency of a circuit containing such a switching device. EBM in vacuum is reversible and the parameters are restored when exposed to air at pressure of 150 Pa. At EBM with a dose of 3 C cm{sup -2}, the voltages of switching-on (V{sub th}) and off (V{sub h}), as well as the OFF-state resistance R{sub off}, decrease down to 50% of the initial values, and the oscillation frequency increases by 30% at a dose of 0.7 C cm{sup -2}. Features of physics of EBM of an oscillator are outlined considering the contribution of the metal and semiconductor phases of the switching channel. Controlled modification allows EBM forming of switches with preset parameters. Also, it might be used in artificial oscillatory neural networks for pattern recognition based on frequency shift keying. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Solution Hamilton-Jacobi equation for oscillator Caldirola-Kanai

Directory of Open Access Journals (Sweden)

LEONARDO PASTRANA ARTEAGA

2016-12-01

Full Text Available The method allows Hamilton-Jacobi explicitly determine the generating function from which is possible to derive a transformation that makes soluble Hamilton's equations. Using the separation of variables the partial differential equation of the first order called Hamilton-Jacobi equation is solved; as a particular case consider the oscillator Caldirola-Kanai (CK, which is characterized in that the mass presents a temporal evolution exponentially  . We demonstrate that the oscillator CK position presents an exponential decay in time similar to that obtained in the damped sub-critical oscillator, which reflects the dissipation of total mechanical energy. We found that in the limit that the damping factor  is small, the behavior is the same as an oscillator with simple harmonic motion, where the effects of energy dissipation is negligible.

Patterns of interval correlations in neural oscillators with adaptation

Directory of Open Access Journals (Sweden)

Tilo eSchwalger

2013-11-01

Full Text Available Neural firing is often subject to negative feedback by adaptationcurrents. These currents can induce strong correlations among the timeintervals between spikes. Here we study analytically the intervalcorrelations of a broad class of noisy neural oscillators withspike-triggered adaptation of arbitrary strength and time scale. Ourweak-noise theory provides a general relation between the correlationsand the phase-response curve (PRC of the oscillator, provesanti-correlations between neighboring intervals for adapting neuronswith type I PRC and identifies a single order parameter thatdetermines the qualitative pattern of correlations. Monotonicallydecaying or oscillating correlation structures can be related toqualitatively different voltage traces after spiking, which can beexplained by the phase plane geometry. At high firing rates, thelong-term variability of the spike train associated with thecumulative interval correlations becomes small, independent of modeldetails. Our results are verified by comparison with stochasticsimulations of the exponential, leaky, and generalizedintegrate-and-fire models with adaptation.

Dynamic electrical characteristics of low-power ring oscillators constructed with inorganic nanoparticles on flexible plastics.

Science.gov (United States)

Yun, Junggwon; Cho, Kyoungah; Kim, Sangsig

2012-11-01

In this study, we demonstrate for the first time the low-power and stable performance of a ring oscillator constructed on a flexible plastic with solution-processable inorganic nanoparticles (NPs). Our flexible ring oscillator is composed of three inverters based on n- and p-type inorganic NP thin-film transistors. Each of the component inverters exhibits a gain of ∼80 at a voltage of 5 V. For the ring oscillator, the sine waves are generated with a frequency of up to 12 kHz. The waveforms are undistorted under strained conditions and maintained even after 5000 bending cycles. The frequency and waveform of the output waves obtained from our flexible ring oscillator are analyzed and discussed in detail.

Self-excitation of microwave oscillations in plasma-assisted slow-wave oscillators by an electron beam with a movable focus

Science.gov (United States)

Bliokh, Yu. P.; Nusinovich, G. S.; Shkvarunets, A. G.; Carmel, Y.

2004-10-01

Plasma-assisted slow-wave oscillators (pasotrons) operate without external magnetic fields, which makes these devices quite compact and lightweight. Beam focusing in pasotrons is provided by ions, which appear in the device due to the impact ionization of a neutral gas by beam electrons. Typically, the ionization time is on the order of the rise time of the beam current. This means that, during the rise of the current, beam focusing by ions becomes stronger. Correspondingly, a beam of electrons, which was initially diverging radially due to the self-electric field, starts to be focused by ions, and this focus moves towards the gun as the ion density increases. This feature makes the self-excitation of electromagnetic (em) oscillations in pasotrons quite different from practically all other microwave sources where em oscillations are excited by a stationary electron beam. The process of self-excitation of em oscillations has been studied both theoretically and experimentally. It is shown that in pasotrons, during the beam current rise the amount of current entering the interaction space and the beam coupling to the em field vary. As a result, the self-excitation can proceed faster than in conventional microwave sources with similar operating parameters such as the operating frequency, cavity quality-factor and the beam current and voltage.

Self Oscillating Mixer with Dielectric Resonator for Low Noise Block Application

Directory of Open Access Journals (Sweden)

Endon Bharata

2011-08-01

Full Text Available In this paper, the development of a self oscillating mixer (SOM as part of a low noise block (LNB for a satellite television receiver is investigated numerically and experimentally. In contrast to other mixers, the developed SOM requires no separate local oscillator as it generates own local oscillator signal. The SOM is developed using a monolithic microwave integrated circuit (MMIC comprised of two bipolar transistors coupled as a Darlington pair and a dielectric resonator to establish a local oscillator signal. The SOM is designed to oscillate at 3.62GHz driven from 50W signal generator. The prototype of SOM is fabricated on a dielectric substrate of glass-reinforced hydrocarbon/ceramic lamination (RO4350B board which has a thickness of 0.762mm and relative permittivity of 3.66. The prototype is then characterized experimentally and exhibits a conversion gain of 8dB with the input and output voltage standing wave ratio (VSWR less than 2 across the 2520MHz to 2670MHz operating frequency band.

Self-excited nonlinear plasma series resonance oscillations in geometrically symmetric capacitively coupled radio frequency discharges

International Nuclear Information System (INIS)

Donko, Z.; Schulze, J.; Czarnetzki, U.; Luggenhoelscher, D.

2009-01-01

At low pressures, nonlinear self-excited plasma series resonance (PSR) oscillations are known to drastically enhance electron heating in geometrically asymmetric capacitively coupled radio frequency discharges by nonlinear electron resonance heating (NERH). Here we demonstrate via particle-in-cell simulations that high-frequency PSR oscillations can also be excited in geometrically symmetric discharges if the driving voltage waveform makes the discharge electrically asymmetric. This can be achieved by a dual-frequency (f+2f) excitation, when PSR oscillations and NERH are turned on and off depending on the electrical discharge asymmetry, controlled by the phase difference of the driving frequencies

The algebra of two dimensional generalized Chebyshev-Koornwinder oscillator

International Nuclear Information System (INIS)

Borzov, V. V.; Damaskinsky, E. V.

2014-01-01

In the previous works of Borzov and Damaskinsky [“Chebyshev-Koornwinder oscillator,” Theor. Math. Phys. 175(3), 765–772 (2013)] and [“Ladder operators for Chebyshev-Koornwinder oscillator,” in Proceedings of the Days on Diffraction, 2013], the authors have defined the oscillator-like system that is associated with the two variable Chebyshev-Koornwinder polynomials. We call this system the generalized Chebyshev-Koornwinder oscillator. In this paper, we study the properties of infinite-dimensional Lie algebra that is analogous to the Heisenberg algebra for the Chebyshev-Koornwinder oscillator. We construct the exact irreducible representation of this algebra in a Hilbert space H of functions that are defined on a region which is bounded by the Steiner hypocycloid. The functions are square-integrable with respect to the orthogonality measure for the Chebyshev-Koornwinder polynomials and these polynomials form an orthonormalized basis in the space H. The generalized oscillator which is studied in the work can be considered as the simplest nontrivial example of multiboson quantum system that is composed of three interacting oscillators

Design of Self-Oscillating Gels and Application to Biomimetic Actuators

Directory of Open Access Journals (Sweden)

Ryo Yoshida

2010-03-01

Full Text Available As a novel biomimetic polymer, we have developed polymer gels with an autonomous self-oscillating function. This was achieved by utilizing oscillating chemical reactions, called the Belousov-Zhabotinsky (BZ reaction, which is recognized as a chemical model for understanding several autonomous phenomena in biological systems. Under the coexistence of the reactants, the polymer gel undergoes spontaneous swelling-deswelling changes without any on-off switching by external stimuli. In this review, our recent studies on the self-oscillating polymer gels and application to biomimetic actuators are summarized.

The pulse-driven AC Josephson voltage normal; Das pulsgetriebene AC-Josephson-Spannungsnormal

Energy Technology Data Exchange (ETDEWEB)

Kieler, Oliver [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany). Arbeitsgruppe 2.43 ' ' Josephson-Schaltungen' '

2016-09-15

In this contribution quantum precise alternating-voltage sources are presented, which make the generation of arbitrary wave forms with highest spectral purity with a high bandwidth from DC up to the MHz range possible. Heartpiece of these Josephson voltage normals is a serial circuit of many thousand Josephson contacts, which make by irradiation with high-frequency radiation (microwaves) the generation of highly precise voltage values possible. Thereby in the current-voltage characteristics stages of constant voltage, so called Shapiro stages, occur. Illustratively these stages can be described by the transfer of a certain number of flux quanta through the Josephson contacts.

Developing Antimatter Containment Technology: Modeling Charged Particle Oscillations in a Penning-Malmberg Trap

Science.gov (United States)

Chakrabarti, S.; Martin, J. J.; Pearson, J. B.; Lewis, R. A.

2003-01-01

The NASA MSFC Propulsion Research Center (PRC) is conducting a research activity examining the storage of low energy antiprotons. The High Performance Antiproton Trap (HiPAT) is an electromagnetic system (Penning-Malmberg design) consisting of a 4 Tesla superconductor, a high voltage confinement electrode system, and an ultra high vacuum test section; designed with an ultimate goal of maintaining charged particles with a half-life of 18 days. Currently, this system is being experimentally evaluated using normal matter ions which are cheap to produce and relatively easy to handle and provide a good indication of overall trap behavior, with the exception of assessing annihilation losses. Computational particle-in-cell plasma modeling using the XOOPIC code is supplementing the experiments. Differing electrode voltage configurations are employed to contain charged particles, typically using flat, modified flat and harmonic potential wells. Ion cloud oscillation frequencies are obtained experimentally by amplification of signals induced on the electrodes by the particle motions. XOOPIC simulations show that for given electrode voltage configurations, the calculated charged particle oscillation frequencies are close to experimental measurements. As a two-dimensional axisymmetric code, XOOPIC cannot model azimuthal plasma variations, such as those induced by radio-frequency (RF) modulation of the central quadrupole electrode in experiments designed to enhance ion cloud containment. However, XOOPIC can model analytically varying electric potential boundary conditions and particle velocity initial conditions. Application of these conditions produces ion cloud axial and radial oscillation frequency modes of interest in achieving the goal of optimizing HiPAT for reliable containment of antiprotons.

Comparison of Virtual Oscillator and Droop Control

Energy Technology Data Exchange (ETDEWEB)

Johnson, Brian B [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rodriguez, Miguel [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sinha, Mohit [University of Minnesota; Dhople, Sairaj [University of Minnesota

2017-08-21

Virtual oscillator control (VOC) and droop control are distinct methods to ensure synchronization and power sharing of parallel inverters in islanded systems. VOC is a control strategy where the dynamics of a nonlinear oscillator are used to derive control states to modulate the switch terminals of an inverter. Since VOC is a time-domain controller that reacts to instantaneous measurements with no additional filters or computations, it provides a rapid response during transients and stabilizes volatile dynamics. In contrast, droop control regulates the inverter voltage in response to the measured average real and reactive power output. Given that real and reactive power are phasor quantities that are not well-defined in real time, droop controllers typically use multiplicative operations in conjunction with low-pass filters on the current and voltage measurements to calculate such quantities. Since these filters must suppress low frequency ac harmonics, they typically have low cutoff frequencies that ultimately impede droop controller bandwidth. Although VOC and droop control can be engineered to produce similar steady-state characteristics, their dynamic performance can differ markedly. This paper presents an analytical framework to characterize and compare the dynamic response of VOC and droop control. The analysis is experimentally validated with three 120 V inverters rated at 1kW, demonstrating that for the same design specifications VOC is roughly 8 times faster and presents almost no overshoot after a transient.

Improvement the Capacity of Cockcroft-Walton High Voltage Source from 300 kV/20 mA to 500 kV/20 mA for Accelerating Voltage of Electron Beam Machine

International Nuclear Information System (INIS)

Suprapto; Djasiman

2002-01-01

The improvement capacity of Cockcroft-Walton high voltage source from 300 kV/20 mA to 500 kV/mA has been carrying out. To improve the capacity of high voltage source was done by means of increasing the stage number of voltage multiplier from 11 to 18 and its output voltage measuring resistance. Each stage of voltage multiplier consists of 2 capacitors and 2 circuits of high voltage diode. This voltage multiplier is constructed using main components of high voltage capacitor and high voltage diode each of 0.22 μF/50 kV and UF 5408 respectively. To avoid stray discharge and corona it was provided with high voltage electrode and corona ring. The test result indicated that the output voltage obtained from 16 stages was 350 kV according to operating condition of 25 MΩ resistive load and first stage voltage of 28.5 kV with oscillator frequency of 24 Hz. That condition requires anode voltage and current of 5.5 kV and 2.5 A respectively. The no load test for 16 stages indicates 400 kV of output voltage and 28.5 kV first stage voltage. Efficiency of high voltage source was 48 % at 6.75 kW of output power. The expected test of 500 kV with 18 stages of voltage multiplier can not be carried out because of some restrictive of loading system. From the test result can be predicted that the output voltage of 500 kV with 18 stages of voltage multiplier requires 31.2 kV of first stage voltage. Then the expected high voltage source of Cockcroft-Walton is capable as accelerating voltage source for Electron Beam Machine with energy of 500 kV. (author)

Real-time combustion control and diagnostics sensor-pressure oscillation monitor

Science.gov (United States)

Chorpening, Benjamin T [Morgantown, WV; Thornton, Jimmy [Morgantown, WV; Huckaby, E David [Morgantown, WV; Richards, George A [Morgantown, WV

2009-07-14

An apparatus and method for monitoring and controlling the combustion process in a combustion system to determine the amplitude and/or frequencies of dynamic pressure oscillations during combustion. An electrode in communication with the combustion system senses hydrocarbon ions and/or electrons produced by the combustion process and calibration apparatus calibrates the relationship between the standard deviation of the current in the electrode and the amplitudes of the dynamic pressure oscillations by applying a substantially constant voltage between the electrode and ground resulting in a current in the electrode and by varying one or more of (1) the flow rate of the fuel, (2) the flow rate of the oxidant, (3) the equivalence ratio, (4) the acoustic tuning of the combustion system, and (5) the fuel distribution in the combustion chamber such that the amplitudes of the dynamic pressure oscillations in the combustion chamber are calculated as a function of the standard deviation of the electrode current. Thereafter, the supply of fuel and/or oxidant is varied to modify the dynamic pressure oscillations.

Theory of terahertz electric oscillations by supercooled superconductors

Energy Technology Data Exchange (ETDEWEB)

Mishonov, Todor M; Mishonov, Mihail T [Department of Theoretical Physics, Faculty of Physics, University of Sofia St Kliment Ohridski, 5 J Bourchier Boulevard, 1164 Sofia (Bulgaria); Laboratorium voor Vaste-Stoffysica en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200 D B-3001 Leuven (Belgium)

2005-11-15

We predict that below T{sub c} a regime of negative differential conductivity (NDC) can be reached. The superconductor should be supercooled to Tvoltage. In such a nonequilibrium situation the NDC of the superconductor is created by the excess conductivity of the fluctuation Cooper pairs. We propose NDC of supercooled superconductors to be used as an active medium for generation of electric oscillations. Such generators can be used in the superconducting electronics as a new type THz source of radiation. Oscillations can be modulated by the change of the bias voltage, electrostatic doping by a gate electrode when the superconductor is the channel of a field effect transistor, or by light. When small amplitude oscillations are stabilized near the critical temperature T{sub c} the generator can be used as a bolometer. NDC, which is essential for the applications, is predicted on the basis of analysis of known results for fluctuation conductivity, obtained in previous papers by solving the Boltzmann kinetic equation for the Cooper pairs metastable in the normal phase. The Boltzmann equation for fluctuation Cooper pairs is a result of state-of-the-art application of the microscopic theory of superconductivity. Our theoretical conclusions are based on some approximations like time dependent Ginzburg-Landau theory initially derived for gapless superconductors, but nevertheless can reliably predict the appearance of NDC. NDC is the main ingredient of the proposed technical applications. The maximal frequency at which superconductors can operate as generators is determined by the critical temperature {Dirac_h}/2{pi}{omega}{sub max} {approx} k{sub B}T{sub c}. For high-T{sub c} superconductors this maximal frequency falls well inside the terahertz range. Technical conditions to avoid nucleation of the superconducting phase are briefly discussed. We suggest that nanostructured high-T{sub c} superconductors patterned in a single chip can

Analysis of the Degradation of MOSFETs in Switching Mode Power Supply by Characterizing Source Oscillator Signals

Directory of Open Access Journals (Sweden)

Xueyan Zheng

2013-01-01

Full Text Available Switching Mode Power Supply (SMPS has been widely applied in aeronautics, nuclear power, high-speed railways, and other areas related to national strategy and security. The degradation of MOSFET occupies a dominant position in the key factors affecting the reliability of SMPS. MOSFETs are used as low-voltage switches to regulate the DC voltage in SMPS. The studies have shown that die-attach degradation leads to an increase in on-state resistance due to its dependence on junction temperature. On-state resistance is the key indicator of the health of MOSFETs. In this paper, an online real-time method is presented for predicting the degradation of MOSFETs. First, the relationship between an oscillator signal of source and on-state resistance is introduced. Because oscillator signals change when they age, a feature is proposed to capture these changes and use them as indicators of the state of health of MOSFETs. A platform for testing characterizations is then established to monitor oscillator signals of source. Changes in oscillator signal measurement were observed with aged on-state resistance as a result of die-attach degradation. The experimental results demonstrate that the method is efficient. This study will enable a method to predict the failure of MOSFETs to be developed.

Module Seven: Combination Circuits and Voltage Dividers; Basic Electricity and Electronics Individualized Learning System.

Science.gov (United States)

Bureau of Naval Personnel, Washington, DC.

In this module the student will learn to apply the rules previously learned for series and parallel circuits to more complex circuits called series-parallel circuits, discover the utility of a common reference when making reference to voltage values, and learn how to obtain a required voltage from a voltage divider network. The module is divided…

Pacemaker neuron and network oscillations depend on a neuromodulator-regulated linear current

Directory of Open Access Journals (Sweden)

Shunbing Zhao

2010-05-01

Full Text Available Linear leak currents have been implicated in the regulation of neuronal excitability, generation of neuronal and network oscillations, and network state transitions. Yet, few studies have directly tested the dependence of network oscillations on leak currents or explored the role of leak currents on network activity. In the oscillatory pyloric network of decapod crustaceans neuromodulatory inputs are necessary for pacemaker activity. A large subset of neuromodulators is known to activate a single voltage-gated inward current IMI, which has been shown to regulate the rhythmic activity of the network and its pacemaker neurons. Using the dynamic clamp technique, we show that the crucial component of IMI for the generation of oscillatory activity is only a close-to-linear portion of the current-voltage relationship. The nature of this conductance is such that the presence or the absence of neuromodulators effectively regulates the amount of leak current and the input resistance in the pacemaker neurons. When deprived of neuromodulatory inputs, pyloric oscillations are disrupted; yet, a linear reduction of the total conductance in a single neuron within the pacemaker group recovers not only the pacemaker activity in that neuron, but also leads to a recovery of oscillations in the entire pyloric network. The recovered activity produces proper frequency and phasing that is similar to that induced by neuromodulators. These results show that the passive properties of pacemaker neurons can significantly affect their capacity to generate and regulate the oscillatory activity of an entire network, and that this feature is exploited by neuromodulatory inputs.

Oscillations in quasineutral plasmas

International Nuclear Information System (INIS)

Grenier, E.

1996-01-01

The purpose of this article is to describe the limit, as the vacuum electric permittivity goes to zero, of a plasma physics system, deduced from the Vlasov-Poisson system for special initial data (distribution functions which are analytic in the space variable, with compact support in velocity), a limit also called open-quotes quasineutral regimeclose quotes of the plasma, and the related oscillations of the electric field, with high frequency in time. 20 refs

Design and Simulation Test of an Open D-Dot Voltage Sensor

Directory of Open Access Journals (Sweden)

Yunjie Bai

2015-09-01

Full Text Available Nowadays, sensor development focuses on miniaturization and non-contact measurement. According to the D-dot principle, a D-dot voltage sensor with a new structure was designed based on the differential D-dot sensor with a symmetrical structure, called an asymmetric open D-dot voltage sensor. It is easier to install. The electric field distribution of the sensor was analyzed through Ansoft Maxwell and an open D-dot voltage sensor was designed. This open D-voltage sensor is characteristic of accessible insulating strength and small electric field distortion. The steady and transient performance test under 10 kV-voltage reported satisfying performances of the designed open D-dot voltage sensor. It conforms to requirements for a smart grid measuring sensor in intelligence, miniaturization and facilitation.

Oscillating field current drive for reversed field pinch discharges

International Nuclear Information System (INIS)

Schoenberg, K.F.; Gribble, R.F.; Baker, D.A.

1984-06-01

Oscillating Field Current Drive (OFCD), also known as F-THETA pumping, is a steady-state current-drive technique proposed for the Reversed Field Pinch (RFP). Unlike other current-drive techniques, which employ high-technology, invasive, and power intensive schemes using radio frequency or neutral particle injection, F-THETA pumping entails driving the toroidal and poloidal magnetic field circuits with low-frequency (audio) oscillating voltage sources. Current drive by this technique is a consequence of the strong nonlinear plasma coupling in the RFP. Because of its low frequency and efficient plasma coupling, F-THETA pumping shows excellent promise as a reactor-relevant current-drive technique. A conceptual and computational study of this concept, including its experimental and reactor relevance, is explored in this paper

Demasking biological oscillators : Properties and principles of entrainment exemplified by the Neurospora circadian clock

NARCIS (Netherlands)

Roenneberg, T; Dragovic, Z; Merrow, M; Takahashi, Joseph S.

2005-01-01

Oscillations are found throughout the physical and biological worlds. Their interactions can result in a systematic process of synchronization called entrainment, which is distinct from a simple stimulus-response pattern. Oscillators respond to stimuli at some times in their cycle and may not

Experimental dynamical characterization of five autonomous chaotic oscillators with tunable series resistance

Energy Technology Data Exchange (ETDEWEB)

Minati, Ludovico, E-mail: lminati@ieee.org, E-mail: ludovico.minati@unitn.it [MR-Lab, Center for Mind/Brain Science, University of Trento, Trento, Italy and Scientific Department, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan (Italy)

2014-09-01

In this paper, an experimental characterization of the dynamical properties of five autonomous chaotic oscillators, based on bipolar-junction transistors and obtained de-novo through a genetic algorithm in a previous study, is presented. In these circuits, a variable resistor connected in series to the DC voltage source acts as control parameter, for a range of which the largest Lyapunov exponent, correlation dimension, approximate entropy, and amplitude variance asymmetry are calculated, alongside bifurcation diagrams and spectrograms. Numerical simulations are compared to experimental measurements. The oscillators can generate a considerable variety of regular and chaotic sine-like and spike-like signals.

Self-sustained spin-polarized current oscillations in multiquantum well structures

Energy Technology Data Exchange (ETDEWEB)

Escobedo, Ramon [Departamento de Matematica Aplicada y Ciencias de la Computacion, Universidad de Cantabria, 39005 Santander (Spain); Carretero, Manuel; Bonilla, Luis L [G. Millan Institute, Fluid Dynamics, Nanoscience and Industrial Mathematics, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Platero, Gloria [Instituto de Ciencia de Materiales, CSIC, 28049 Cantoblanco (Spain)], E-mail: escobedo@unican.es, E-mail: manuel.carretero@uc3m.es, E-mail: bonilla@ing.uc3m.es, E-mail: gplatero@icmm.csic.es

2009-01-15

Nonlinear transport through diluted magnetic semiconductor nanostructures is investigated. We have considered a II-VI multiquantum well nanostructure whose wells are selectively doped with Mn. The response to a dc voltage bias may be either a stationary or an oscillatory current. We have studied the transition from stationary to time-dependent current as a function of the doping density and the number of quantum wells. Analysis and numerical solution of a nonlinear spin transport model shows that the current in a structure without magnetic impurities is stationary, whereas current oscillations may appear if at least one well contains magnetic impurities. For long structures having two wells with magnetic impurities, a detailed analysis of nucleation of charge dipole domains shows that self-sustained current oscillations are caused by repeated triggering of dipole domains at the magnetic wells and motion towards the collector. Depending on the location of the magnetic wells and the voltage, dipole domains may be triggered at both wells or at only one. In the latter case, the well closer to the collector may inhibit domain motion between the first and the second well inside the structure. Our study could allow design of oscillatory spin-polarized current injectors.

A Comparative Study of Analog Voltage-mode Control Methods for Ultra-Fast Tracking Power Supplies

DEFF Research Database (Denmark)

Høyerby, Mikkel Christian Wendelboe; Andersen, Michael Andreas E.

2007-01-01

This paper presents a theoretical and experimental comparison of the standard PWM/PID voltage-mode control method for single-phase buck converters with two highperformance self-oscillating (a.k.a. sliding mode) control methods. The application considered is ultra-fast tracking power supplies...... (UFTPSs) for RF power amplifiers, where the switching converter needs to track a varying reference voltage precisely and quickly while maintaining low output impedance. The small-signal analyses performed on the different controllers show that the hysteretic-type controller can achieve the highest loop...

Search for νμ → νe oscillations

International Nuclear Information System (INIS)

Godley, A.R.

1998-01-01

Full text: Neutrino oscillations, the changing of neutrino flavour state from one of τ, μ or e, to another, are proof of massive neutrinos, in turn pointing to Physics beyond the Standard Model, and so are of great current interest. Solar and atmospheric neutrino results suggested evidence for neutrino oscillations. Further, a tau neutrino mass of ∼ 10 eV could supply the missing mass needed to close the Universe. To satisfy the increasing interest, CERN's Neutrino Physics Program commissioned two concurrent experiments to investigate the possibility of neutrino oscillations, one of which is NOMAD, Neutrino Oscillation Magnetic Detector. NOMAD was designed to verify or deny the earlier positive neutrino oscillations results by searching for muon to tauon neutrino oscillations in accelerator neutrinos. The LSND experiment later provided evidence for muon to electron neutrino oscillations, but due to the multi-purpose design of NOMAD, it was also possible to investigate this channel. Moreover, the area of phase space being uncovered, (related to neutrino energy and oscillation length), overlaps considerably with that of LSND. An electron neutrino oscillation search involves looking for electron neutrinos in what is primarily a muon neutrino beam, with just a small contamination of electron neutrinos. It is surmised that the excess of electron neutrinos come from oscillated muon neutrinos. This type of search is called an appearance search. The principles of such a search will be detailed herein. These include a breakdown of the CERN Neutrino Beam and a method for detecting and collating different neutrino flavours at NOMAD

Geomagnetically induced pipe-to-soil voltages in the Czech oil pipelines during October-November 2003

Directory of Open Access Journals (Sweden)

P. Hejda

2005-11-01

Full Text Available Whereas geomagnetically induced currents are a source of problems for technological systems mainly at high geomagnetic latitudes, strong geomagnetic disturbances can have quite strong effects even at mid-latitudes. This paper deals with the analysis of the pipe-to-soil (P/S voltage measured in oil pipelines in the Czech Republic during the Halloween magnetic storms in 2003. It is shown that the simplest - plane wave and uniform Earth-model of the electric field corresponds well to the measured P/S voltage. Although the largest amplitudes of the geomagnetic field were reached on the onset of the geomagnetic storm, large voltages were also induced in the main and recovery phases due to Pc5 oscillations.

Review of the Dynamics of Coalescence and Demulsification by High-Voltage Pulsed Electric Fields

Directory of Open Access Journals (Sweden)

Ye Peng

2016-01-01

Full Text Available The coalescence of droplets in oil can be implemented rapidly by high-voltage pulse electric field, which is an effective demulsification dehydration technological method. At present, it is widely believed that the main reason of pulse electric field promoting droplets coalescence is the dipole coalescence and oscillation coalescence in pulse electric field, and the optimal coalescence pulse electric field parameters exist. Around the above content, the dynamics of high-voltage pulse electric field promoting the coalescence of emulsified droplets is studied by researchers domestically and abroad. By review, the progress of high-voltage pulse electric field demulsification technology can get a better understanding, which has an effect of throwing a sprat to catch a whale on promoting the industrial application.

Modeling microtubule oscillations

DEFF Research Database (Denmark)

Jobs, E.; Wolf, D.E.; Flyvbjerg, H.

1997-01-01

Synchronization of molecular reactions in a macroscopic volume may cause the volume's physical properties to change dynamically and thus reveal much about the reactions. As an example, experimental time series for so-called microtubule oscillations are analyzed in terms of a minimal model...... for this complex polymerization-depolymerization cycle. The model reproduces well the qualitatively different time series that result from different experimental conditions, and illuminates the role and importance of individual processes in the cycle. Simple experiments are suggested that can further test...... and define the model and the polymer's reaction cycle....

Temperature- and supply voltage-independent time references for wireless sensor networks

CERN Document Server

De Smedt, Valentijn; Dehaene, Wim

2015-01-01

This book investigates the possible circuit solutions to overcome the temperature- and supply voltage-sensitivity of fully-integrated time references for ultra-low-power communication in wireless sensor networks. The authors provide an elaborate theoretical introduction and literature study to enable full understanding of the design challenges and shortcomings of current oscillator implementations.  Furthermore, a closer look to the short-term as well as the long-term frequency stability of integrated oscillators is taken. Next, a design strategy is developed and applied to 5 different oscillator topologies and 1 sensor interface.All 6 implementations are subject to an elaborate study of frequency stability, phase noise, and power consumption. In the final chapter all blocks are compared to the state of the art. The main goals of this book are: • to provide a comprehensive overview of timing issues and solutions in wireless sensor networks; • to gain understanding of all underlying mechanisms by starti...

Moderately nonlinear diffuse-charge dynamics under an ac voltage.

Science.gov (United States)

Stout, Robert F; Khair, Aditya S

2015-09-01

The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of V_{o}/(k_{B}T/e), where V_{o} is the amplitude of the driving voltage and k_{B}T/e is the thermal voltage with k_{B} as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D/λ_{D}L, where D is the ion diffusivity, λ_{D} is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O(V_{o}^{3}) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in V_{o}. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing V_{o}. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.

Moderately nonlinear diffuse-charge dynamics under an ac voltage

Science.gov (United States)

Stout, Robert F.; Khair, Aditya S.

2015-09-01

The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of Vo/(kBT /e ) , where Vo is the amplitude of the driving voltage and kBT /e is the thermal voltage with kB as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D /λDL , where D is the ion diffusivity, λD is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O (Vo3) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in Vo. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing Vo. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.

Smart control application in the oscillations using FACTS (STATCOM and SVC

Directory of Open Access Journals (Sweden)

Alfonso James Alzate Gomez

2017-07-01

Full Text Available Context: Reducing the oscillations of the electrical power systems is an important task in order to maintain their stability. This paper presents a methodology for adjusting the parameters of a fuzzy oscillations controller with a Static Var Compensator (SVC and a Static Synchronous Compensator (STATCOM. Methodology: The methodology consists of tuning a fuzzy controller to dampen oscillations in an electrical power system, with different optimization techniques such as: Genetic Algorithms (GA, Particle Swarm Optimization (PSO, and Chaotic Optimization Algorithm (COA. Results: The voltage and speed oscillations of a system composed of a synchronous machine connected to an infinite bus bar (SMIB are obtained through simulations. There is data before and after connecting a SVC and a STATCOM, installed independently and in different operating conditions. The results obtained show that using a technique for adjusting parameters in the fuzzy controller is better than the adjustment of trial and error. Conclusion: With the obtained results, it is possible to verify the effectiveness of the fuzzy controller using Flexible AC Transmissions Systems (FACTS.

Investigation on multi-frequency oscillations in InGaAs planar Gunn diode with multiple anode-cathode spacings

Science.gov (United States)

Li, B.; Alimi, Y.; Ma, G. L.

2016-12-01

Current oscillations in an AlGaAs/InGaAs/AlGaAs-based two-dimensional electron gas (2DEG)-based hetero-structure have been investigated by means of semiconductor device simulation software SILVACO, with an interest on the charge domain formation at large biases. Single-frequency oscillations are generated in planar Gunn diodes with uniform anode and cathode contacts. The oscillation frequency reduces as the applied bias voltage increases. We show that it is possible to create multiple, independent charge domains in a novel Gunn diode structure with designed multiple anode-cathode spacings. This enables simultaneous generation of multiple frequency oscillations in a single planar device, in contrast to traditional vertical Gunn diodes where only single-frequency oscillations can be achieved. More interestingly, frequency mixing in multiple-channel configured Gunn diodes appeared. This proof-of-concept opens up the possibility for realizing compact self-oscillating mixer at millimeter-wave applications.

MPPT algorithm for voltage controlled PV inverters

DEFF Research Database (Denmark)

Kerekes, Tamas; Teodorescu, Remus; Liserre, Marco

2008-01-01

This paper presents a novel concept for an MPPT that can be used in case of a voltage controlled grid connected PV inverters. In case of single-phase systems, the 100 Hz ripple in the AC power is also present on the DC side. Depending on the DC link capacitor, this power fluctuation can be used t...... to track the MPP of the PV array, using the information that at MPP the power oscillations are very small. In this way the algorithm can detect the fact that the current working point is at the MPP, for the current atmospheric conditions....

Comparison of Virtual Oscillator and Droop Control: Preprint

Energy Technology Data Exchange (ETDEWEB)

Johnson, Brian B [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rodriguez, Miguel [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Dhople, Sairaj [University of Minessota; Sinha, Mohit [University of Minessota

2017-09-01

Virtual oscillator control and droop control are two techniques that can be used to ensure synchronization and power sharing of parallel inverters in islanded operation. VOC relies on the implementation of non-linear Van der Pol oscillator equations in the control system of the inverter, acting upon the time-domain instantaneous inverter current and terminal voltage. On the other hand, DC explicitly computes active and reactive power produced by the inverter and relies on limited bandwidth low-pass filters. Even though both methods can be engineered to produce the same steady-state characteristics, their dynamic performances are significantly different. This paper presents analytical and experimental results that aim to compare both methods. It is shown that VOC is inherently faster and enables minimizing the circulating currents. The results are verified using three 120V, 1kW inverters.

High performance ring oscillators from 10-nm wide silicon nanowire field-effect transistors

KAUST Repository

Huang, Ruo-Gu; Tham, Douglas; Wang, Dunwei; Heath, James R.

2011-01-01

We explore 10-nm wide Si nanowire (SiNW) field-effect transistors (FETs) for logic applications, via the fabrication and testing of SiNW-based ring oscillators. We report on SiNW surface treatments and dielectric annealing, for producing SiNW FETs that exhibit high performance in terms of large on/off-state current ratio (~108), low drain-induced barrier lowering (~30 mV) and low subthreshold swing (~80 mV/decade). The performance of inverter and ring-oscillator circuits fabricated from these nanowire FETs are also explored. The inverter demonstrates the highest voltage gain (~148) reported for a SiNW-based NOT gate, and the ring oscillator exhibits near rail-to-rail oscillation centered at 13.4 MHz. The static and dynamic characteristics of these NW devices indicate that these SiNW-based FET circuits are excellent candidates for various high-performance nanoelectronic applications. © 2011 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

High performance ring oscillators from 10-nm wide silicon nanowire field-effect transistors

KAUST Repository

Huang, Ruo-Gu

2011-06-24

We explore 10-nm wide Si nanowire (SiNW) field-effect transistors (FETs) for logic applications, via the fabrication and testing of SiNW-based ring oscillators. We report on SiNW surface treatments and dielectric annealing, for producing SiNW FETs that exhibit high performance in terms of large on/off-state current ratio (~108), low drain-induced barrier lowering (~30 mV) and low subthreshold swing (~80 mV/decade). The performance of inverter and ring-oscillator circuits fabricated from these nanowire FETs are also explored. The inverter demonstrates the highest voltage gain (~148) reported for a SiNW-based NOT gate, and the ring oscillator exhibits near rail-to-rail oscillation centered at 13.4 MHz. The static and dynamic characteristics of these NW devices indicate that these SiNW-based FET circuits are excellent candidates for various high-performance nanoelectronic applications. © 2011 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

Predicting chaos in memristive oscillator via harmonic balance method.

Science.gov (United States)

Wang, Xin; Li, Chuandong; Huang, Tingwen; Duan, Shukai

2012-12-01

This paper studies the possible chaotic behaviors in a memristive oscillator with cubic nonlinearities via harmonic balance method which is also called the method of describing function. This method was proposed to detect chaos in classical Chua's circuit. We first transform the considered memristive oscillator system into Lur'e model and present the prediction of the existence of chaotic behaviors. To ensure the prediction result is correct, the distortion index is also measured. Numerical simulations are presented to show the effectiveness of theoretical results.

Low-pressure glow discharges with oscillating electrons in different electrode systems

International Nuclear Information System (INIS)

Bersenev, V.V.; Gavriolv, N.V.; Nikulin, S.P.

1995-01-01

One of the main applications of low - pressure glow discharges is the development on their basis of charged - particle beam sources. The use of glow discharges with oscillating electrons, which can operate stably in the voltage and pressure range to the left of the left branch of Pashen's curve, shows promise, because the decrease in critical pressure p 0 , below which the discharge operation becomes impossible, in the discharge system of a source promotes an increase in the electrical strength of its accelerating system. This, in its turn, makes possible the expansion of the operation range of accelerating voltages. This experimental investigation of glow discharges in such well - known systems with oscillating electrons, as Hollow Cathode (HC), Penning's System (PS) and Inverse Magnetron (IM), is aimed at revealing the system operating at the lowest pressure. Besides, both common features and peculiarities of discharge operation in these systems are discussed. Though there is an extensive amount of published information covering all the specified discharges, the carrying out of such investigation is justified, since a comparative analysis of results obtained by different authors is hampered by various conditions of their experiments

Influence of Wind Plant Ancillary Voltage Control on System Small Signal Stability

DEFF Research Database (Denmark)

Su, Chi; Chen, Zhe

2012-01-01

As a common tendency, large-scale wind farms are increasingly connected to the transmission system of modern power grids. This introduces some new challenges to the connected power systems, and the transmission system operators (TSOs) have to put some new requirements as part of the grid codes...... on the integration of wind farms. One common requirement to wind farms is the function of system voltage control which can be implemented in the grid-side convertor controller of a variable speed wind turbine. This ancillary voltage control provided by wind farms could have some influence on the system small signal...... stability. This paper implements an ancillary voltage control strategy on a direct-drive-full-convertor-based wind farm and studies its influence on the damping ratio values of the dominant oscillation mode within the connected power system. All the calculations and simulations are conducted in DIg...

Potential role of the glycolytic oscillator in acute hypoxia in tumors

International Nuclear Information System (INIS)

Fru, Leonard Che; Adamson, Erin B; Campos, David D; Fain, Sean B; Song, Chihwa; Kissick, Michael W; Jacques, Steven L; Van der Kogel, Albert J; Nickel, Kwang P; Kimple, Randall J

2015-01-01

Tumor acute hypoxia has a dynamic component that is also, at least partially, coherent. Using blood oxygen level dependent magnetic resonance imaging, we observed coherent oscillations in hemoglobin saturation dynamics in cell line xenograft models of head and neck squamous cell carcinoma. We posit a well-established biochemical nonlinear oscillatory mechanism called the glycolytic oscillator as a potential cause of the coherent oscillations in tumors. These data suggest that metabolic changes within individual tumor cells may affect the local tumor microenvironment including oxygen availability and therefore radiosensitivity. These individual cells can synchronize the oscillations in patches of similar intermediate glucose levels. These alterations have potentially important implications for radiation therapy and are a potential target for optimizing the cancer response to radiation. (paper)

Optical, UV, and EUV Oscillations of SS Cygni in Outburst

Science.gov (United States)

Mauche, Christopher W.

2004-07-01

I provide a review of observations in the optical, UV (HST), and EUV (EUVE and Chandra LETG) of the rapid periodic oscillations of nonmagnetic, disk-accreting, high mass-accretion rate cataclysmic variables (CVs), with particular emphasis on the dwarf nova SS Cyg in outburst. In addition, I drawn attention to a correlation, valid over nearly six orders of magnitude in frequency, between the frequencies of the quasi-periodic oscillations (QPOs) of white dwarf, neutron star, and black hole binaries. This correlation identifies the high frequency quasi-coherent oscillations (so-called ``dwarf nova oscillations'') of CVs with the kilohertz QPOs of low mass X-ray binaries (LMXBs), and the low frequency and low coherence QPOs of CVs with the horizontal branch oscillations (or the broad noise component identified as such) of LMXBs. Assuming that the same mechanisms produce the QPOs of white dwarf, neutron star, and black hole binaries, this correlation has important implications for QPO models.

Oscillator representation and generalized van der Waals Hamiltonians

International Nuclear Information System (INIS)

Dinejkhan, M.

1996-01-01

The method called the oscillator representation is extended to calculate the energy spectrum of bound state described by axially symmetrical potentials in the parabolic system coordinates. In particular, the method is applied to calculate the energy of the ground and excited states of the hydrogen atom in the uniform electric field and van der Waals field. The method gives the perturbation formulas for the analytic spectrum of the hydrogen atom in the generalized van der Waals field and defined oscillator strengths for transitions from the ground state to the perturbed manifold n=10, m=0. 14 refs., 1 fig

Serially-Connected Compensator for Eliminating the Unbalanced Three-Phase Voltage Impact on Wind Turbine Generators: Preprint

Energy Technology Data Exchange (ETDEWEB)

Wu, Z.; Hsu, P.; Muljadi, E.; Gao, W.

2015-04-06

Untransposed transmission lines, unbalanced tap changer operations, and unbalanced loading in weak distribution lines can cause unbalanced-voltage conditions. The resulting unbalanced voltage at the point of interconnection affects proper gird integration and reduces the lifetime of wind turbines due to power oscillations, torque pulsations, mechanical stresses, energy losses, and uneven and overheating of the generator stator winding. This work investigates the dynamic impact of unbalanced voltage on the mechanical and electrical components of integrated Fatigue, Aerodynamics, Structures, and Turbulence (FAST) wind turbine generation systems (WTGs) of Type 1 (squirrel-cage induction generator) and Type 3 (doubly-fed induction generator). To alleviate this impact, a serially-connected compensator for a three-phase power line is proposed to balance the wind turbine-side voltage. Dynamic simulation studies are conducted in MATLAB/Simulink to compare the responses of these two types of wind turbine models under normal and unbalanced-voltage operation conditions and demonstrate the effectiveness of the proposed compensator.

Modeling Bloch oscillations in ultra-small Josephson junctions

Science.gov (United States)

Vora, Heli; Kautz, Richard; Nam, Sae Woo; Aumentado, Jose

In a seminal paper, Likharev et al. developed a theory for ultra-small Josephson junctions with Josephson coupling energy (Ej) less than the charging energy (Ec) and showed that such junctions demonstrate Bloch oscillations which could be used to make a fundamental current standard that is a dual of the Josephson volt standard. Here, based on the model of Geigenmüller and Schön, we numerically calculate the current-voltage relationship of such an ultra-small junction which includes various error processes present in a nanoscale Josephson junction such as random quasiparticle tunneling events and Zener tunneling between bands. This model allows us to explore the parameter space to see the effect of each process on the width and height of the Bloch step and serves as a guide to determine whether it is possible to build a quantum current standard of a metrological precision using Bloch oscillations.

Information cloning of harmonic oscillator coherent states

Indian Academy of Sciences (India)

We show that in the case of unknown harmonic oscillator coherent statesit is possible to achieve what we call perfect information cloning. By this we mean that it is still possible to make arbitrary number of copies of a state which has exactly the same information content as the original unknown coherent state. By making use ...

Preliminary design and optimization of a G-band extended interaction oscillator based on a pseudospark-sourced electron beam

Energy Technology Data Exchange (ETDEWEB)

Yin, Y., E-mail: yong.yin@strath.ac.uk, E-mail: yinyong@uestc.edu.cn [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Department of Physics, Scottish Universities Physics Alliance, University of Strathclyde, Glasgow G4 0NG (United Kingdom); He, W.; Zhang, L.; Yin, H.; Cross, A. W. [Department of Physics, Scottish Universities Physics Alliance, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

2015-07-15

The design and simulation of a G-band extended interaction oscillator (EIO) driven by a pseudospark-sourced electron beam is presented. The characteristic of the EIO and the pseudospark-based electron beam were studied to enhance the performance of the newly proposed device. The beam-wave interaction of the EIO can be optimized by choosing a suitable pseudospark discharging voltage and by widening the operating voltage region of the EIO circuit. Simulation results show that a peak power of over 240 W can be achieved at G-band using a pseudospark discharge voltage of 41 kV.

Phase and Amplitude Drift Research of Millimeter Wave Band Local Oscillator System

Directory of Open Access Journals (Sweden)

Changhoon Lee

2010-06-01

Full Text Available In this paper, we developed a local oscillator (LO system of millimeter wave band receiver for radio astronomy observation. We measured the phase and amplitude drift stability of this LO system. The voltage control oscillator (VCO of this LO system use the 3 mm band Gunn oscillator. We developed the digital phase locked loop (DPLL module for the LO PLL function that can be computer-controlled. To verify the performance, we measured the output frequency/power and the phase/amplitude drift stability of the developed module and the commercial PLL module, respectively. We show the good performance of the LO system based on the developed PLL module from the measured data analysis. The test results and discussion will be useful tutorial reference to design the LO system for very long baseline interferometry (VLBI receiver and single dish radio astronomy receiver at the 3 mm frequency band.

The Detection of Subsynchronous Oscillation in HVDC Based on the Stochastic Subspace Identification Method

Directory of Open Access Journals (Sweden)

Chen Shi

2014-01-01

Full Text Available Subsynchronous oscillation (SSO usually caused by series compensation, power system stabilizer (PSS, high voltage direct current transmission (HVDC and other power electronic equipment, which will affect the safe operation of generator shafting even the system. It is very important to identify the modal parameters of SSO to take effective control strategies as well. Since the identification accuracy of traditional methods are not high enough, the stochastic subspace identification (SSI method is proposed to improve the identification accuracy of subsynchronous oscillation modal. The stochastic subspace identification method was compared with the other two methods on subsynchronous oscillation IEEE benchmark model and Xiang-Shang HVDC system model, the simulation results show that the stochastic subspace identification method has the advantages of high identification precision, high operation efficiency and strong ability of anti-noise.

Design and Analysis of a Slope Voltage Control for a DFIG Wind Power Plant

DEFF Research Database (Denmark)

Martínez, J.; Kjær, P. C.; Rodriguez, Pedro

2012-01-01

This paper addresses a detailed design of a wind power plant and turbine slope voltage control in the presence of communication delays for a wide short-circuit ratio range operation. The implemented voltage control scheme is based upon the secondary voltage control concept, which offers fast...... of connection with the grid. The performance has been tested using PSCAD/EMTDC program. The plant layout used in the simulations is based on an installed wind power plant, composed of 23 doubly fed generator wind turbines. The resulting performance is evaluated using a compilation of grid code voltage control...... response to grid disturbances, despite the communication delays, i.e., this concept is based on a primary voltage control, located in the wind turbine, which follows an external voltage reference sent by a central controller, called secondary voltage control, which is controlling the voltage at the point...

Heat-pump performance: voltage dip/sag, under-voltage and over-voltage

Directory of Open Access Journals (Sweden)

William J.B. Heffernan

2014-12-01

Full Text Available Reverse cycle air-source heat-pumps are an increasingly significant load in New Zealand and in many other countries. This has raised concern over the impact wide-spread use of heat-pumps may have on the grid. The characteristics of the loads connected to the power system are changing because of heat-pumps. Their performance during under-voltage events such as voltage dips has the potential to compound the event and possibly cause voltage collapse. In this study, results from testing six heat-pumps are presented to assess their performance at various voltages and hence their impact on voltage stability.

A memristor-based third-order oscillator: beyond oscillation

KAUST Repository

Talukdar, Abdul Hafiz Ibne

2012-10-06

This paper demonstrates the first third-order autonomous linear time variant circuit realization that enhances parametric oscillation through the usage of memristor in conventional oscillators. Although the output has sustained oscillation, the linear features of the conventional oscillators become time dependent. The poles oscillate in nonlinear behavior due to the oscillation of memristor resistance. The mathematical formulas as well as SPICE simulations are introduced for the memristor-based phase shift oscillator showing a great matching.

A memristor-based third-order oscillator: beyond oscillation

KAUST Repository

Talukdar, Abdul Hafiz Ibne; Radwan, Ahmed G.; Salama, Khaled N.

2012-01-01

This paper demonstrates the first third-order autonomous linear time variant circuit realization that enhances parametric oscillation through the usage of memristor in conventional oscillators. Although the output has sustained oscillation, the linear features of the conventional oscillators become time dependent. The poles oscillate in nonlinear behavior due to the oscillation of memristor resistance. The mathematical formulas as well as SPICE simulations are introduced for the memristor-based phase shift oscillator showing a great matching.

Axonal voltage-gated ion channels as pharmacological targets for pain

DEFF Research Database (Denmark)

Moldovan, Mihai; Alvarez, Susana; Romer Rosberg, Mette

2013-01-01

Upon peripheral nerve injury (caused by trauma or disease process) axons of the dorsal root ganglion (DRG) somatosensory neurons have the ability to sprout and regrow/remyelinate to reinnervate distant target tissue or form a tangled scar mass called a neuroma. This regenerative response can become...... maladaptive leading to a persistent and debilitating pain state referred to as chronic pain corresponding to the clinical description of neuropathic/chronic inflammatory pain. There is little agreement to what causes peripheral chronic pain other than hyperactivity of the nociceptive DRG neurons which...... ultimately depends on the function of voltage-gated ion channels. This review focuses on the pharmacological modulators of voltage-gated ion channels known to be present on axonal membrane which represents by far the largest surface of DRG neurons. Blockers of voltage-gated Na(+) channels, openers of voltage...

An inductor-based converter with EMI reduction for low-voltage thermoelectric energy harvesting

Science.gov (United States)

Wang, Chuang; Zhao, Kai; Li, Zunchao

2017-07-01

This paper presents a self-powered inductor-based converter which harvests thermoelectric energy and boosts extremely low voltage to a typical voltage level for supplying body sensor nodes. Electromagnetic interference (EMI) of the converter is reduced by spreading spectrum of fundamental frequency and harmonics via pseudo-random modulation, which is obtained via combining the linear feedback shift register and digitally controlled oscillator. Besides, the methods, namely extracting energy near MPP and reducing the power dissipation, are employed to improve the power efficiency. The presented inductor-based converter is designed and verified in CSMC CMOS 0.18-µm 1P6M process. The results reveal that it achieves the high efficiency and EMI reduction at the same time.

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

Directory of Open Access Journals (Sweden)

Md Shafiul Alam

2017-11-01

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

Mitigation of Unbalanced Voltage Sags and Voltage Unbalance in CIGRE Low Voltage Distribution Network

DEFF Research Database (Denmark)

Mustafa, Ghullam; Bak-Jensen, Birgitte; Mahat, Pukar

2013-01-01

Any problem with voltage in a power network is undesirable as it aggravates the quality of the power. Power electronic devices such as Voltage Source Converter (VSC) based Static Synchronous Compensator (STATCOM) etc. can be used to mitigate the voltage problems in the distribution system...... to unbalanced faults. The compensation of unbalanced voltage sags and voltage unbalance in the CIGRE distribution network is done by using the four STATCOM compensators already existing in the test grid. The simulations are carried out in DIgSILENT power factory software version 15.0........ The voltage problems dealt with in this paper are to show how to mitigate unbalanced voltage sags and voltage unbalance in the CIGRE Low Voltage (LV) test network and net-works like this. The voltage unbalances, for the tested cases in the CIGRE LV test network are mainly due to single phase loads and due...

Oscillation-based test in mixed-signal circuits

CERN Document Server

Sánchez, Gloria Huertas; Rueda, Adoración Rueda

2007-01-01

This book presents the development and experimental validation of the structural test strategy called Oscillation-Based Test - OBT in short. The results presented here assert, not only from a theoretical point of view, but also based on a wide experimental support, that OBT is an efficient defect-oriented test solution, complementing the existing functional test techniques for mixed-signal circuits.

Enhancement of the output power of terahertz folded waveguide oscillator by two parallel electron beams

International Nuclear Information System (INIS)

Li, Ke; Cao, Miaomiao; Liu, Wenxin; Wang, Yong; Liao, Suying

2015-01-01

A novel two-beam folded waveguide (FW) oscillator is presented for the purpose of gaining higher power with a small-size circuit compared with the normal FW oscillator. The high-frequency characteristics of the two-beam FW, including dispersion and interaction impedance, were investigated by the numerical simulation and compared with the one-beam FW. The radio-frequency loss of the two-beam FW was also analyzed. A 3-D particle-in-cell code CHIPIC was applied to analyze and optimize the performance of a G-band two-beam FW oscillator. The influences of the distance between the two beam tunnels, beam voltage, the number of periods, magnetic field, radius of beam tunnel, and the packing ratio on the circuit performance are investigated in detail. Compared with a one-beam circuit, a larger output power of the two-beam circuit with the same beam power was observed by the simulation. Moreover, the start-oscillation current of two-beam circuit is much lower than the one-beam circuit with better performance. It will favor the miniaturized design of the high-power terahertz oscillator

Enhancement of the output power of terahertz folded waveguide oscillator by two parallel electron beams

Energy Technology Data Exchange (ETDEWEB)

Li, Ke, E-mail: like.3714@163.com; Cao, Miaomiao, E-mail: mona486@yeah.net [Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100190 (China); Liu, Wenxin, E-mail: lwenxin@mail.ie.ac.cn; Wang, Yong, E-mail: wangyong3845@sina.com [Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China); Liao, Suying, E-mail: suying-liao@163.com [Air Force Airborne Academy, Guilin, Guangxi 541003 (China)

2015-11-15

A novel two-beam folded waveguide (FW) oscillator is presented for the purpose of gaining higher power with a small-size circuit compared with the normal FW oscillator. The high-frequency characteristics of the two-beam FW, including dispersion and interaction impedance, were investigated by the numerical simulation and compared with the one-beam FW. The radio-frequency loss of the two-beam FW was also analyzed. A 3-D particle-in-cell code CHIPIC was applied to analyze and optimize the performance of a G-band two-beam FW oscillator. The influences of the distance between the two beam tunnels, beam voltage, the number of periods, magnetic field, radius of beam tunnel, and the packing ratio on the circuit performance are investigated in detail. Compared with a one-beam circuit, a larger output power of the two-beam circuit with the same beam power was observed by the simulation. Moreover, the start-oscillation current of two-beam circuit is much lower than the one-beam circuit with better performance. It will favor the miniaturized design of the high-power terahertz oscillator.

Oscillators that sync and swarm.

Science.gov (United States)

O'Keeffe, Kevin P; Hong, Hyunsuk; Strogatz, Steven H

2017-11-15

Synchronization occurs in many natural and technological systems, from cardiac pacemaker cells to coupled lasers. In the synchronized state, the individual cells or lasers coordinate the timing of their oscillations, but they do not move through space. A complementary form of self-organization occurs among swarming insects, flocking birds, or schooling fish; now the individuals move through space, but without conspicuously altering their internal states. Here we explore systems in which both synchronization and swarming occur together. Specifically, we consider oscillators whose phase dynamics and spatial dynamics are coupled. We call them swarmalators, to highlight their dual character. A case study of a generalized Kuramoto model predicts five collective states as possible long-term modes of organization. These states may be observable in groups of sperm, Japanese tree frogs, colloidal suspensions of magnetic particles, and other biological and physical systems in which self-assembly and synchronization interact.

Calculation of Onset Voltage of Sliding Discharge over a Dielectric Barrier

Directory of Open Access Journals (Sweden)

Abdel-Salam Mazen

2016-01-01

Full Text Available This paper is aimed at calculating the onset voltage of a sliding discharge established between two electrodes at the upper and bottom surfaces of a dielectric barrier plate; named sliding dielectric barrier discharge (SDBD driven by AC voltage during negative half cycle. The onset voltage is based on the condition of self-sustenance of avalanche growth in the vicinity of the stressed electrode. This calls at first for calculation of the electric field in the vicinity of stressed electrode. The dependency of onset voltage on the thickness and permittivity of the dielectric barrier as well as the thickness of the stressed electrode and the inter-electrode spacing between the stressed and ground electrodes is investigated. The obtained results are discussed in the light of gas discharge physics.

Pure odd-order oscillators with constant excitation

Science.gov (United States)

Cveticanin, L.

2011-02-01

In this paper the excited vibrations of a truly nonlinear oscillator are analyzed. The excitation is assumed to be constant and the nonlinearity is pure (without a linear term). The mathematical model is a second-order nonhomogeneous differential equation with strong nonlinear term. Using the first integral, the exact value of period of vibration i.e., angular frequency of oscillator described with a pure nonlinear differential equation with constant excitation is analytically obtained. The closed form solution has the form of gamma function. The period of vibration depends on the value of excitation and of the order and coefficient of the nonlinear term. For the case of pure odd-order-oscillators the approximate solution of differential equation is obtained in the form of trigonometric function. The solution is based on the exact value of period of vibration. For the case when additional small perturbation of the pure oscillator acts, the so called 'Cveticanin's averaging method' for a truly nonlinear oscillator is applied. Two special cases are considered: one, when the additional term is a function of distance, and the second, when damping acts. To prove the correctness of the method the obtained results are compared with those for the linear oscillator. Example of pure cubic oscillator with constant excitation and linear damping is widely discussed. Comparing the analytically obtained results with exact numerical ones it is concluded that they are in a good agreement. The investigations reported in the paper are of special interest for those who are dealing with the problem of vibration reduction in the oscillator with constant excitation and pure nonlinear restoring force the examples of which can be found in various scientific and engineering systems. For example, such mechanical systems are seats in vehicles, supports for machines, cutting machines with periodical motion of the cutting tools, presses, etc. The examples can be find in electronics

Comparative analysis of gyrotron backward-wave oscillators operating at different cyclotron harmonics

International Nuclear Information System (INIS)

Yeh, Y.S.; Chang, T.H.; Wu, T.S.

2004-01-01

A comparative analysis between the fundamental and second cyclotron harmonics of gyrotron backward-wave oscillators (gyro-BWOs) is presented. The simulation results reveal that nonlinear field contraction is a common feature for both harmonic interactions. Besides, the electron transit angle, used to characterize the axial modes of the fundamental harmonic TE 11 mode at the start-oscillation conditions, is found to be applicable even for the second harmonic TE 21 mode. Each axial mode of either the fundamental harmonic TE 11 or the second harmonic TE 21 modes is maintained at a constant value of the electron transit angle while changing the operating parameters, such as magnetic field and beam voltage. Extensive numerical calculations are conducted for the start-oscillation currents and tuning properties. Moreover, single-mode operating regimes are suggested where the second harmonic TE 21 gyro-BWO could generate a considerable output power, comparing with the fundamental harmonic TE 11 gyro-BWO

Study of current oscillations and hard x-ray emissions in pre-cursor phase of major disruptions in Damavand tokamak

International Nuclear Information System (INIS)

Amrollahi, R.

2002-01-01

We notice that the hard x-ray activity before disruption consists of a series of spikes, uniformly distributed in time domain forming an orderly periodic series of oscillations at a frequency of 6.0 kHz. Disruption starts with an initial fast rise followed by decay. Current decay occurs in two regimes: the first corresponds to slow decay, in which the current is oscillating and reducing down to ∼70% its max value, and the second corresponds to fast decay, in which it totally vanishes abruptly in about 0.2 ms. In the first regime, the loop voltage also oscillates with considerable amplitude. The frequency of oscillations in the first regime is measured to be also about 6.0 kHz. As well, they follow the oscillation phase of hard x-rays. Thus the micro-instabilities driven by runaway electrons, being responsible for the production of hard x-rays bursts and small current oscillations, play a significant role in the disruption. (author)

Chimera states in mechanical oscillator networks.

Science.gov (United States)

Martens, Erik Andreas; Thutupalli, Shashi; Fourrière, Antoine; Hallatschek, Oskar

2013-06-25

The synchronization of coupled oscillators is a fascinating manifestation of self-organization that nature uses to orchestrate essential processes of life, such as the beating of the heart. Although it was long thought that synchrony and disorder were mutually exclusive steady states for a network of identical oscillators, numerous theoretical studies in recent years have revealed the intriguing possibility of "chimera states," in which the symmetry of the oscillator population is broken into a synchronous part and an asynchronous part. However, a striking lack of empirical evidence raises the question of whether chimeras are indeed characteristic of natural systems. This calls for a palpable realization of chimera states without any fine-tuning, from which physical mechanisms underlying their emergence can be uncovered. Here, we devise a simple experiment with mechanical oscillators coupled in a hierarchical network to show that chimeras emerge naturally from a competition between two antagonistic synchronization patterns. We identify a wide spectrum of complex states, encompassing and extending the set of previously described chimeras. Our mathematical model shows that the self-organization observed in our experiments is controlled by elementary dynamical equations from mechanics that are ubiquitous in many natural and technological systems. The symmetry-breaking mechanism revealed by our experiments may thus be prevalent in systems exhibiting collective behavior, such as power grids, optomechanical crystals, or cells communicating via quorum sensing in microbial populations.

Oscillation Performance and Wide‐area Coordination Control of Power System with Large‐scale Wind Farms

DEFF Research Database (Denmark)

Su, Chi

and residue identification. Simulation results show the effectiveness of this damping controller under different operating conditions of the SSSC. Influence of a direct‐drive‐full‐convertor based wind farm ancillary frequency control and voltage control on power system oscillation performance is investigated...... oscillation mode damping ratio, respectively. The former controller is implemented in individual wind turbines; the latter controller is implemented in the wind farm level as a supplementary damping controller. Finally, the coordinating selection and parameter design strategy for PSS is extended for all types...... to this problem need to be implemented in the power systems. On the other hand, wind power especially largescale wind farms are increasingly integrated into modern power systems and bring new challenges to power system operation and control. The influence of wind power integration on system oscillation...

Design of an electronically tunable millimeter wave Gyrotron Backward Wave Oscillator

International Nuclear Information System (INIS)

Caplan, M.

1987-01-01

A non-linear self-consistent computer simulation code is used to analyze the saturated output of the Gyrotron Backward Wave Oscillator (Gyro BWO) which can be used as a tunable driver for a 250 GHz FEL amplifier. Simulations show that the Gyrotron BWO using a Pierce/Wiggler gun configuration can produce at least 10 kW of microwave power over the range 249 GHz to 265 GHz by varying beam voltage alone

Electron heating of voltage-driven and matched dual frequency discharges

International Nuclear Information System (INIS)

Lieberman, M A; Lichtenberg, A J

2010-01-01

In a dual frequency capacitive sheath, a high frequency uniform sheath motion is coupled with a low frequency Child law sheath motion. For current-driven high and low frequency sheaths, the high frequency sheath motion generates most of the ohmic and stochastic heating of the discharge electrons. The low frequency motion, in addition to its primary purpose of establishing the ion bombarding energy, also increases the heating by widening the sheath width and transporting the oscillating electrons to regions of lower plasma density, and hence higher sheath velocity. In this work, we show that for voltage-driven high and low frequency sheaths, increasing the low frequency voltage reduces the heating, due to the reduced high frequency current that flows through the sheath under voltage-driven conditions. We determine the dependence of the heating on various parameters and compare the results with the current-driven case. Particle-in-cell simulations are used to confirm this result. Discharges generally employ a matching network to maximize the power transmitted to the plasma. We obtain analytic expressions for the effect of the low frequency source under matched conditions and, again, find that the low frequency source reduces the heating.

Modernization of the Light generators voltage regulation systems and evaluation of the necessity of stabilizers

Energy Technology Data Exchange (ETDEWEB)

Barros, Paulo R.G.M. de; Oliveira Aires, Joao C. de; Nascimento, Anselmo R; Almeida, Antonio J.B. de [Light Servicos de Eletricidade SA, Rio de Janeiro, RJ (Brazil); Souza Pedroso, Alquindar de [Centro de Pesquisas de Energia Eletrica, Rio de Janeiro, RJ (Brazil)

1988-12-31

This paper presents the studies and solutions adopted by Light to mitigate the problems relative to the lack of power and voltage oscillation damping in the Rio de Janeiro area (Southeast Brazil) for the contingencies of South/Southeast interconnection loss and 500 kV transmission line loss. The characteristics of Light generating system, comprised of the Fontes Velha, Fontes Nova, Ilha dos Pombos, Nilo Pecanha, and Pereira Passos hydroelectric plants are shown. Excitation/Voltage regulation alternatives are also presented. The performance of proposed equipment is discussed based on some simulation analysis. Finally, some alternatives for improvement of Rio de Janeiro area dynamic performance are suggested. 4 refs., 3 tabs., 5 figs.

Factorization method and new potentials from the inverted oscillator

International Nuclear Information System (INIS)

Bermudez, David; Fernández C, David J.

2013-01-01

In this article we will apply the first- and second-order supersymmetric quantum mechanics to obtain new exactly-solvable real potentials departing from the inverted oscillator potential. This system has some special properties; in particular, only very specific second-order transformations produce non-singular real potentials. It will be shown that these transformations turn out to be the so-called complex ones. Moreover, we will study the factorization method applied to the inverted oscillator and the algebraic structure of the new Hamiltonians. -- Highlights: •We apply supersymmetric quantum mechanics to the inverted oscillator potential. •The complex second-order transformations allow us to build new non-singular potentials. •The algebraic structure of the initial and final potentials is analyzed. •The initial potential is described by a complex-deformed Heisenberg–Weyl algebra. •The final potentials are described by polynomial Heisenberg algebras

Neuropharmacology of altered brain oscillations in schizophrenia.

Science.gov (United States)

Koch, Michael; Schmiedt-Fehr, Christina; Mathes, Birgit

2016-05-01

Impairments in spatial and temporal integration of brain network activity are a core feature of schizophrenia. Neural network oscillatory activity is considered to be fundamentally important in coordinating neural activity throughout the brain. Hence, exploration of brain oscillations has become an indispensible tool to study the neural basis of mental illnesses. However, most of the studies in schizophrenia include medicated patients. This implicates the question to what extent are changes in the electrophysiological parameters genuine illness effects, genuine drug effects or a mixture of both. We here provide a short overview of the neuropharmacology of brain oscillations with respect to schizophrenia. The core assumption of the so-called "pharmaco-EEG" approach is that drug effects on mental and cognitive functions are reflected in changes in quantitative EEG parameters. Hence, clinical efficacy of drugs might be predicted on the basis of the neuropharmacology of electrophysiological measures, such as brain oscillations. Vice versa, knowledge of drug effects on brain oscillations can be of essence in understanding schizophrenia. However, the current literature lacks systematic findings, because of at least two problems. First, the pharmacology of most antipsychotic drugs is complex including interactions with several transmitter receptors. Second, the neuropathology of schizophrenia still has no pathognomonic signature. Even though it is presently not possible to clearly dissociate drug- and illness effects in neural oscillations, this review emphasizes future studies to foster the understanding of this relationship in schizophrenia and other neuropsychiatric diseases. Copyright © 2015 Elsevier B.V. All rights reserved.

Analytical Solutions to Nonlinear Conservative Oscillator with Fifth-Order Nonlinearity

DEFF Research Database (Denmark)

Sfahania, M. G.; Ganji, S. S.; Barari, Amin

2010-01-01

This paper describes analytical and numerical methods to analyze the steady state periodic response of an oscillator with symmetric elastic and inertia nonlinearity. A new implementation of the homotopy perturbation method (HPM) and an ancient Chinese method called the max-min approach are presen...

Different types of bursting calcium oscillations in non-excitable cells

International Nuclear Information System (INIS)

Perc, Matjaz; Marhl, Marko

2003-01-01

In the paper different types of bursting Ca 2+ oscillations are presented. We analyse bursting behaviour in four recent mathematical models for Ca 2+ oscillations in non-excitable cells. Separately, regular, quasi-periodic, and chaotic bursting Ca 2+ oscillations are classified into several subtypes. The classification is based on the dynamics of separated fast and slow subsystems, the so-called fast-slow burster analysis. For regular bursting Ca 2+ oscillations two types of bursting are specified: Point-Point and Point-Cycle bursting. In particular, the slow passage effect, important for the Hopf-Hopf and SubHopf-SubHopf bursting subtypes, is explained by local divergence calculated for the fast subsystem. Quasi-periodic bursting Ca 2+ oscillations can be found in only one of the four studied mathematical models and appear via a homoclinic bifurcation with a homoclinic torus structure. For chaotic bursting Ca 2+ oscillations, we found that bursting patterns resulting from the period doubling root to chaos considerably differ from those appearing via intermittency and have to be treated separately. The analysis and classification of different types of bursting Ca 2+ oscillations provides better insight into mechanisms of complex intra- and intercellular Ca 2+ signalling. This improves our understanding of several important biological phenomena in cellular signalling like complex frequency-amplitude signal encoding and synchronisation of intercellular signal transduction between coupled cells in tissue

Diagonal ordering operation technique applied to Morse oscillator

Energy Technology Data Exchange (ETDEWEB)

Popov, Dušan, E-mail: dusan_popov@yahoo.co.uk [Politehnica University Timisoara, Department of Physical Foundations of Engineering, Bd. V. Parvan No. 2, 300223 Timisoara (Romania); Dong, Shi-Hai [CIDETEC, Instituto Politecnico Nacional, Unidad Profesional Adolfo Lopez Mateos, Mexico D.F. 07700 (Mexico); Popov, Miodrag [Politehnica University Timisoara, Department of Steel Structures and Building Mechanics, Traian Lalescu Street, No. 2/A, 300223 Timisoara (Romania)

2015-11-15

We generalize the technique called as the integration within a normally ordered product (IWOP) of operators referring to the creation and annihilation operators of the harmonic oscillator coherent states to a new operatorial approach, i.e. the diagonal ordering operation technique (DOOT) about the calculations connected with the normally ordered product of generalized creation and annihilation operators that generate the generalized hypergeometric coherent states. We apply this technique to the coherent states of the Morse oscillator including the mixed (thermal) state case and get the well-known results achieved by other methods in the corresponding coherent state representation. Also, in the last section we construct the coherent states for the continuous dynamics of the Morse oscillator by using two new methods: the discrete–continuous limit, respectively by solving a finite difference equation. Finally, we construct the coherent states corresponding to the whole Morse spectrum (discrete plus continuous) and demonstrate their properties according the Klauder’s prescriptions.

A study of kinetic friction: The Timoshenko oscillator

Science.gov (United States)

Henaff, Robin; Le Doudic, Gabriel; Pilette, Bertrand; Even, Catherine; Fischbach, Jean-Marie; Bouquet, Frédéric; Bobroff, Julien; Monteverde, Miguel; Marrache-Kikuchi, Claire A.

2018-03-01

Friction is a complex phenomenon that is of paramount importance in everyday life. We present an easy-to-build and inexpensive experiment illustrating Coulomb's law of kinetic friction. The so-called friction, or Timoshenko, oscillator consists of a plate set into periodic motion through the competition between gravity and friction on its rotating supports. The period of such an oscillator gives a measurement of the coefficient of kinetic friction μk between the plate and the supports. Our prototype is mainly composed of a motor, LEGO blocks, and a low-cost microcontroller, but despite its simplicity, the results obtained are in good agreement with values of μk found in the literature (enhanced online).

Domain wall oscillation in magnetic nanowire with a geometrically confined region

Science.gov (United States)

Sbiaa, R.; Bahri, M. Al; Piramanayagam, S. N.

2018-06-01

In conventional magnetic devices such as magnetic tunnel junctions, a steady oscillation of a soft layer magnetization could find its application in various electronic systems. However, these devices suffer from their low output signal and large spectral linewidth. A more elegant scheme based on domain wall oscillation could be a solution to these issues if DW dynamics could be controlled precisely in space and time. In fact, in DW devices, the magnetic configuration of domain wall and its position are strongly dependent on the device geometry and material properties. Here we show that in a constricted device with judiciously adjusted dimensions, a DW can be trapped within the central part and keep oscillating with a single frequency f. For 200 nm by 40 nm nanowire, f was found to vary from 2 GHz to 3 GHz for a current density between 4.8 × 1012 A/m2 and 5.6 × 1012 A/m2. More interestingly, the device fabrication is simply based on two long nanowires connected by adjusting the offset in both x and y directions. This new type of devices enables the conversion of dc-current to an ac-voltage in a controllable manner opening thus the possibility of a new nano-oscillators with better performance.

Carrier Distortion in Hysteretic Self-Oscillating Class-D Audio Power

DEFF Research Database (Denmark)

Høyerby, Mikkel Christian Kofod; Andersen, Michael A. E.

2009-01-01

An important distortion mechanism in hysteretic self-oscillating (SO) class-D (switch mode) power amplifiers-–carrier distortion-–is analyzed and an optimization method is proposed. This mechanism is an issue in any power amplifier application where a high degree of proportionality between input...... and output is required, such as in audio power amplifiers or xDSL drivers. From an average-mode point of view, carrier distortion is shown to be caused by nonlinear variation of the hysteretic comparator input average voltage with the output average voltage. This easily causes total harmonic distortion...... figures in excess of 0.1–0.2%, inadequate for high-quality audio applications. Carrier distortion is shown to be minimized when the feedback system is designed to provide a triangular carrier (sliding) signal at the input of a hysteretic comparator. The proposed optimization method is experimentally...

Experimental research on Ku-band magnetically insulated transmission line oscillator

Energy Technology Data Exchange (ETDEWEB)

Jiang, Tao; Zhang, Jiande; He, Juntao; Li, Zhiqiang; Ling, Junpu [College of Optoelectric Science and Engineering, National University of Defense Technology, Hunan 410073 (China)

2015-10-15

An improved Ku-band magnetically insulated transmission line oscillator is proposed and investigated experimentally. In the particle-in-cell simulation, the Ku-band MILO generates the microwave with a power of 1.62 GW and a frequency of 13 GHz at the input voltage of 474 kV. The device is fabricated based on the simulation results, and an experiment system is designed. In the preliminary experiments, output microwave with frequency of 13.02 GHz, power of 150 MW, and pulse width of 17 ns is generated, under the diode voltage of 450 kV. Analysis on the experiment results shows that plasma produced due to the large current hitting to the outside of the collection tank is the essential cause for the low amplitude of the microwave power and short pulse width.

A multiple-pass ring oscillator based dual-loop phase-locked loop

International Nuclear Information System (INIS)

Chen Danfeng; Ren Junyan; Deng Jingjing; Li Wei; Li Ning

2009-01-01

A dual-loop phase-locked loop (PLL) for wideband operation is proposed. The dual-loop architecture combines a coarse-tuning loop with a fine-tuning one, enabling a wide tuning range and low voltage-controlled oscillator (VCO) gain without poisoning phase noise and reference spur suppression performance. An analysis of the phase noise and reference spur of the dual-loop PLL is emphasized. A novel multiple-pass ring VCO is designed for the dual-loop application. It utilizes both voltage-control and current-control simultaneously in the delay cell. The PLL is fabricated in Jazz 0.18-μm RF CMOS technology. The measured tuning range is from 4.2 to 5.9 GHz. It achieves a low phase noise of -99 dBc/Hz - 1 MHz offset from a 5.5 GHz carrier.

A multiple-pass ring oscillator based dual-loop phase-locked loop

Energy Technology Data Exchange (ETDEWEB)

Chen Danfeng; Ren Junyan; Deng Jingjing; Li Wei; Li Ning, E-mail: dfchen@fudan.edu.c [State Key Laboratory of ASIC and System, Fudan University, Shanghai 201203 (China)

2009-10-15

A dual-loop phase-locked loop (PLL) for wideband operation is proposed. The dual-loop architecture combines a coarse-tuning loop with a fine-tuning one, enabling a wide tuning range and low voltage-controlled oscillator (VCO) gain without poisoning phase noise and reference spur suppression performance. An analysis of the phase noise and reference spur of the dual-loop PLL is emphasized. A novel multiple-pass ring VCO is designed for the dual-loop application. It utilizes both voltage-control and current-control simultaneously in the delay cell. The PLL is fabricated in Jazz 0.18-{mu}m RF CMOS technology. The measured tuning range is from 4.2 to 5.9 GHz. It achieves a low phase noise of -99 dBc/Hz - 1 MHz offset from a 5.5 GHz carrier.

An impact analysis of the fault impedance on voltage sags

Energy Technology Data Exchange (ETDEWEB)

Ramos, Alessandro Candido Lopes [CELG - Companhia Energetica de Goias, Goiania, GO (Brazil). Generation and Transmission. System' s Operation Center], E-mail: alessandro.clr@celg.com.br; Batista, Adalberto Jose [Federal University of Goias (UFG), Goiania, GO (Brazil)], E-mail: batista@eee.ufg.br; Leborgne, Roberto Chouhy [Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil)], E-mail: rcl@ece.ufrgs.br; Emiliano, Pedro Henrique Mota, E-mail: ph@phph.com.br

2009-07-01

This paper presents an impact analysis of the fault impedance, in terms of its module and angle, on voltage sags caused by faults. Symmetrical and asymmetrical faults are simulated, at transmission and distribution lines, by using a frequency-domain fault simulation software called ANAFAS. Voltage sags are monitored at buses where sensitive end-users are connected. In order to overcome some intrinsic limitations of this software concerning its automatic execution for several cases, a computational tool was developed in Java programming language. This solution allows the automatic simulation of cases including the effect of the fault position, the fault type, and the proper fault impedance. The main conclusion is that the module and angle of the fault impedance can have a significant influence on voltage sag depending on the fault characteristics. (author)

Multipurpose Compensation Scheme for Voltage Sag/Swell and Selective Harmonics Elimination in Distribution Systems

Directory of Open Access Journals (Sweden)

Mustafa Inci

2018-01-01

Full Text Available Voltage harmonics, sag, and swell are the most harmful disturbances in distribution systems. This paper introduces a novel effective controller method for simultaneous compensation of both voltage sag/swell and voltage harmonics by using multifunctional dynamic voltage restorer. In proposed controller method called FFT with integrated ISRF, ISRF detects the magnitudes of voltage sag/swell quickly and precisely, and FFT extracts the selective components of voltage harmonics very effectively. The proposed method integrates the superior properties of ISRF and FFT methods. FFT integrated ISRF is applied for the first time to provide the compensation of both sag/swell and selective harmonics together. The proposed system has ability to compensate symmetrical/asymmetrical sag/swell and symmetrical/asymmetrical selective harmonics which are 5th, 7th, 11th and 13th. The controlled system is modelled in PSCAD/EMDTC and compared with conventional methods. The performance results verify that the proposed method compensates voltage disturbances effectively in the system.

Nonlinear oscillation system of mass with serial linear and nonlinear springs

DEFF Research Database (Denmark)

Seyedalizadeh Ganji,, S.R; Barari, Amin; Karimpour, S

2013-01-01

In this paper, two powerful methods called Max–Min and parameter expansion have been applied for the determination of the periodic solutions of the nonlinear free vibration of a conservative oscillator with inertia and static type cubic nonlinearities. It is found that these methods introduce two...... alternatives to overcome the difficulty of capturing the periodic behavior of the solution, as the most evident characteristic of oscillators. It can be clearly observed that approximate frequencies and periodic solutions are in excellent agreement with the exact ones. First approximation leads to high...

Coordinated Voltage Control of Distributed PV Inverters for Voltage Regulation in Low Voltage Distribution Networks

DEFF Research Database (Denmark)

Nainar, Karthikeyan; Pokhrel, Basanta Raj; Pillai, Jayakrishnan Radhakrishna

2017-01-01

This paper reviews and analyzes the existing voltage control methods of distributed solar PV inverters to improve the voltage regulation and thereby the hosting capacity of a low-voltage distribution network. A novel coordinated voltage control method is proposed based on voltage sensitivity...... optimization. The proposed method is used to calculate the voltage bands and droop settings of PV inverters at each node by the supervisory controller. The local controller of each PV inverter implements the volt/var control and if necessary, the active power curtailment as per the received settings and based...... on measured local voltages. The advantage of the proposed method is that the calculated reactive power and active power droop settings enable fair contribution of the PV inverters at each node to the voltage regulation. Simulation studies are conducted using DigSilent Power factory software on a simplified...

Coupled-oscillator theory of dispersion and Casimir-Polder interactions

Energy Technology Data Exchange (ETDEWEB)

Berman, P. R.; Ford, G. W. [Physics Department, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040 (United States); Milonni, P. W. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States)

2014-10-28

We address the question of the applicability of the argument theorem (of complex variable theory) to the calculation of two distinct energies: (i) the first-order dispersion interaction energy of two separated oscillators, when one of the oscillators is excited initially and (ii) the Casimir-Polder interaction of a ground-state quantum oscillator near a perfectly conducting plane. We show that the argument theorem can be used to obtain the generally accepted equation for the first-order dispersion interaction energy, which is oscillatory and varies as the inverse power of the separation r of the oscillators for separations much greater than an optical wavelength. However, for such separations, the interaction energy cannot be transformed into an integral over the positive imaginary axis. If the argument theorem is used incorrectly to relate the interaction energy to an integral over the positive imaginary axis, the interaction energy is non-oscillatory and varies as r{sup −4}, a result found by several authors. Rather remarkably, this incorrect expression for the dispersion energy actually corresponds to the nonperturbative Casimir-Polder energy for a ground-state quantum oscillator near a perfectly conducting wall, as we show using the so-called “remarkable formula” for the free energy of an oscillator coupled to a heat bath [G. W. Ford, J. T. Lewis, and R. F. O’Connell, Phys. Rev. Lett. 55, 2273 (1985)]. A derivation of that formula from basic results of statistical mechanics and the independent oscillator model of a heat bath is presented.

Coupled-oscillator theory of dispersion and Casimir-Polder interactions

International Nuclear Information System (INIS)

Berman, P. R.; Ford, G. W.; Milonni, P. W.

2014-01-01

We address the question of the applicability of the argument theorem (of complex variable theory) to the calculation of two distinct energies: (i) the first-order dispersion interaction energy of two separated oscillators, when one of the oscillators is excited initially and (ii) the Casimir-Polder interaction of a ground-state quantum oscillator near a perfectly conducting plane. We show that the argument theorem can be used to obtain the generally accepted equation for the first-order dispersion interaction energy, which is oscillatory and varies as the inverse power of the separation r of the oscillators for separations much greater than an optical wavelength. However, for such separations, the interaction energy cannot be transformed into an integral over the positive imaginary axis. If the argument theorem is used incorrectly to relate the interaction energy to an integral over the positive imaginary axis, the interaction energy is non-oscillatory and varies as r −4 , a result found by several authors. Rather remarkably, this incorrect expression for the dispersion energy actually corresponds to the nonperturbative Casimir-Polder energy for a ground-state quantum oscillator near a perfectly conducting wall, as we show using the so-called “remarkable formula” for the free energy of an oscillator coupled to a heat bath [G. W. Ford, J. T. Lewis, and R. F. O’Connell, Phys. Rev. Lett. 55, 2273 (1985)]. A derivation of that formula from basic results of statistical mechanics and the independent oscillator model of a heat bath is presented

Model Based Optimization of Integrated Low Voltage DC-DC Converter for Energy Harvesting Applications

Science.gov (United States)

Jayaweera, H. M. P. C.; Muhtaroğlu, Ali

2016-11-01

A novel model based methodology is presented to determine optimal device parameters for the fully integrated ultra low voltage DC-DC converter for energy harvesting applications. The proposed model feasibly contributes to determine the maximum efficient number of charge pump stages to fulfill the voltage requirement of the energy harvester application. The proposed DC-DC converter based power consumption model enables the analytical derivation of the charge pump efficiency when utilized simultaneously with the known LC tank oscillator behavior under resonant conditions, and voltage step up characteristics of the cross-coupled charge pump topology. The verification of the model has been done using a circuit simulator. The optimized system through the established model achieves more than 40% maximum efficiency yielding 0.45 V output with single stage, 0.75 V output with two stages, and 0.9 V with three stages for 2.5 kΩ, 3.5 kΩ and 5 kΩ loads respectively using 0.2 V input.

Performance Analysis of Phase Controlled Unidirectional and Bidirectional AC Voltage Controllers

Directory of Open Access Journals (Sweden)

Abdul Sattar Larik

2011-01-01

Full Text Available AC voltage controllers are used to vary the output ac voltage from a fixed ac input source. They are also commonly called ac voltage regulators or ac choppers. The output voltage is either controlled by PAC (Phase Angle Control method or on-off control method. Due to various advantages of ac voltage controllers, such as high efficiency, simplicity, low cost and ability to control large amount of power they efficiently control the speed of ac motors, light dimming and industrial heating, etc. These converters are variable structure systems and generate harmonics during the operation which will affect the power quality when connected to system network. During the last couple of years, a number of new semiconductor devices and various power electronic converters has been introduced. Accordingly the subject of harmonics and its problems are of great concern to power industry and customers. In this research work, initially the simulation models of single phase unidirectional and bidirectional ac voltage controllers were developed by using MATLAB software. The harmonics of these models are investigated by simulation. In the end, the harmonics were also analyzed experimentally. The simulated as well as experimental results are presented.

Observations of electric discharge streamer propagation and capillary oscillations on the surface of air bubbles in water

Energy Technology Data Exchange (ETDEWEB)

Sommers, B S; Foster, J E [Department of Nuclear Engineering and Radiological Science, University of Michigan, Ann Arbor, MI, 48109 (United States); Babaeva, N Yu; Kushner, Mark J [Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, 48109 (United States)

2011-03-02

The propagation of electric discharge streamers inside bubbles in liquids is of interest for the remediation of toxins in water and plasma-based surgical instruments. The manner of streamer propagation has an important influence on the production of reactive species that are critical to these applications. Streamer propagation along the surface of electrode-attached bubbles of air in water, previously predicted by numerical simulations, has been experimentally imaged using a fast frame-rate camera. The successive pulsing of the streamer discharge inside the bubbles produced oscillations along the air-water interface. Subsequent streamers were observed to closely follow surface distortions induced by such oscillations. The oscillations likely arise from the non-uniform perturbation of the bubble driven by the electric field of the streamer and were found to be consistent with Kelvin's equation for capillary oscillations. For a narrow range of applied voltage pulse frequencies, the oscillation amplitude increased over several pulse periods indicating, potentially, resonant behaviour. We also observed coupling between bubbles wherein oscillations in a second bubble without an internal discharge were induced by the presence of a streamer in a fixed bubble. (fast track communication)

Impact of excitation waveform on the frequency stability of electrostatically-actuated micro-electromechanical oscillators

Science.gov (United States)

Juillard, J.; Brenes, A.

2018-05-01

In this paper, the frequency stability of high-Q electrostatically-actuated MEMS oscillators with cubic restoring forces, and its relation with the amplitude, the phase and the shape of the excitation waveform, is studied. The influence on close-to-the carrier frequency noise of additive processes (such as thermomechanical noise) or parametric processes (bias voltage fluctuations, feedback phase fluctuations, feedback level fluctuations) is taken into account. It is shown that the optimal operating conditions of electrostatically-actuated MEMS oscillators are highly waveform-dependent, a factor that is largely overlooked in the existing literature. This simulation-based study covers the cases of harmonic and pulsed excitation of a parallel-plate capacitive MEMS resonator.

Frequency pulling in a low-voltage medium-power gyrotron

Science.gov (United States)

Luo, Li; Du, Chao-Hai; Huang, Ming-Guang; Liu, Pu-Kun

2018-04-01

Many recent biomedical applications use medium-power frequency-tunable terahertz (THz) sources, such as sensitivity-enhanced nuclear magnetic resonance, THz imaging, and biomedical treatment. As a promising candidate, a low-voltage gyrotron can generate watt-level, continuous THz-wave radiation. In particular, the frequency-pulling effect in a gyrotron, namely, the effect of the electron beam parameters on the oscillation frequency, can be used to tune the operating frequency. Most previous investigations used complicated and time-consuming gyrotron nonlinear theory to study the influence of many beam parameters on the interaction performance. While gyrotron linear theory investigation demonstrates the advantages of rapidly and clearly revealing the physical influence of individual key beam parameters on the overall system performance, this paper demonstrates systematically the use of gyrotron linear theory to study the frequency-pulling effect in a low-voltage gyrotron with either a Gaussian or a sinusoidal axial-field profile. Furthermore, simulations of a gyrotron operating in the first axial mode are carried out in the framework of nonlinear theory as a contrast. Close agreement is achieved between the two theories. Besides, some interesting results are obtained. In a low-current sinusoidal-profile cavity, the ranges of frequency variation for different axial modes are isolated from each other, and the frequency tuning bandwidth for each axial mode increases by increasing either the beam voltage or pitch factor. Lowering the voltage, the total tuning ranges are squeezed and become concentrated. However, the isolated frequency regions of each axial mode cannot be linked up unless the beam current is increased, meaning that higher current operation is the key to achieving a wider and continuous tuning frequency range. The results presented in this paper can provide a reference for designing a broadband low-voltage gyrotron.

IGZO TFT-based circuit with tunable threshold voltage by laser annealing

Science.gov (United States)

Huang, Xiaoming; Yu, Guang; Wu, Chenfei

2017-11-01

In this work, a high-performance inverter based on amorphous indium-gallium-zinc oxide thin-film transistors (TFTs) has been fabricated, which consists of a driver TFT and a load TFT. The threshold voltage (Vth) of the load TFT can be tuned by applying an area-selective laser annealing. The transfer curve of the load TFT shows a parallel shift into the negative bias direction upon laser annealing. Based on x-ray photoelectron spectroscopy analyses, the negative Vth shift can be attributed to the increase of oxygen vacancy concentration within the device channel upon laser irradiation. Compared to the untreated inverter, the laser annealed inverter shows much improved switching characteristics, including a large output swing range which is close to full swing, as well as an enhanced output voltage gain. Furthermore, the dynamic performance of ring oscillator based on the laser-annealed inverter is improved.

Dynamics of the resistive state of a narrow superconducting channel in the ac voltage-driven regime

International Nuclear Information System (INIS)

Yerin, Yu.S.; Fenchenko, V.N.

2013-01-01

Within the time-dependent Ginzburg-Landau equations the dynamics of the order parameter in superconducting narrow channels of different lengths is investigated in the ac voltage-driven regime. The resistive state of the system at low frequencies of the applied voltage is characterized by the formation of periodic-in-time groups of oscillating phase-slip centers (PSC). An increase in frequency reduces the duration of the existence of these periodic groups. Depending on the length of the channel the ac voltage either tends to revert the channel to the state with one central PSC in periodic groups or minimizes the number of forming PSCs and orders their pattern in the system. A further increase in frequency for rather short channels leads to suppression of the order parameter without any creation of PSCs. For systems, whose length exceeds the specified limit, the formation of PSC occurs after a certain time which increases rapidly with frequency. The current-voltage characteristics of rather short channels at different applied voltage frequencies are calculated too. It is found that the current-voltage characteristics have a step-like structure, and the height of the first step is determined by the quadruple value of the Josephson frequency.

Baryon acoustic oscillation intensity mapping of dark energy.

Science.gov (United States)

Chang, Tzu-Ching; Pen, Ue-Li; Peterson, Jeffrey B; McDonald, Patrick

2008-03-07

The expansion of the Universe appears to be accelerating, and the mysterious antigravity agent of this acceleration has been called "dark energy." To measure the dynamics of dark energy, baryon acoustic oscillations (BAO) can be used. Previous discussions of the BAO dark energy test have focused on direct measurements of redshifts of as many as 10(9) individual galaxies, by observing the 21 cm line or by detecting optical emission. Here we show how the study of acoustic oscillation in the 21 cm brightness can be accomplished by economical three-dimensional intensity mapping. If our estimates gain acceptance they may be the starting point for a new class of dark energy experiments dedicated to large angular scale mapping of the radio sky, shedding light on dark energy.

Subpanel on accelerator-based neutrino oscillation experiments

International Nuclear Information System (INIS)

1995-09-01

Neutrinos are among nature's fundamental constituents, and they are also the ones about which we know least. Their role in the universe is widespread, ranging from the radioactive decay of a single atom to the explosions of supernovae and the formation of ordinary matter. Neutrinos might exhibit a striking property that has not yet been observed. Like the back-and-forth swing of a pendulum, neutrinos can oscillate to-and-from among their three types (or flavors) if nature provides certain conditions. These conditions include neutrinos having mass and a property called open-quotes mixing.close quotes The phenomenon is referred to as neutrino oscillations. The questions of the origin of neutrino mass and mixing among the neutrino flavors are unsolved problems for which the Standard Model of particle physics holds few clues. It is likely that the next critical step in answering these questions will result from the experimental observation of neutrino oscillations. The High Energy Physics Advisory Panel (HEPAP) Subpanel on Accelerator-Based Neutrino Oscillation Experiments was charged to review the status and discovery potential of ongoing and proposed accelerator experiments on neutrino oscillations, to evaluate the opportunities for the U.S. in this area of physics, and to recommend a cost-effective plan for pursuing this physics, as appropriate. The complete charge is provided in Appendix A. The Subpanel studied these issues over several months and reviewed all the relevant and available information on the subject. In particular, the Subpanel reviewed the two proposed neutrino oscillation programs at Fermi National Accelerator Laboratory (Fermilab) and at Brookhaven National Laboratory (BNL). The conclusions of this review are enumerated in detail in Chapter 7 of this report. The recommendations given in Chapter 7 are also reproduced in this summary

High voltage K/sub a/-band gyrotron oscillator experiment

International Nuclear Information System (INIS)

Gold, S.H.; Fliflet, A.W.; Manheimer, W.M.; Black, W.M.; Granatstein, V.L.; Kinkead, A.K.; Hardesty, D.L.; Sucy, M.

1986-01-01

Future applications of millimeter-waves may require significantly higher powers (>100 MW) than are available from the long-pulse thermionic gyrotrons that are presently available or under development. Scaling studies suggest that these power levels should be accessible to gyrotrons employing relativistic (0.5-1 MeV), multi-kA electron beams, such as can be generated for short pulse lengths (≤100 nsec) using pulseline accelerators with plasma-induced field-emission cathodes. To explore this potential, the authors have assembled a new gyrotron experiment based on a compact Febetron pulser. Initial experiments using a 350keV, 700A electron beam with a ratio of transverse to longitudinal velocity of ≅0.75 have produced ≅20MW at 35GHz at 8.5% efficiency in a TE/sub 62/ mode, in good agreement with the predictions of theory for the experimental parameters. Substantially higher powers and efficiencies are predicted for a new experimental configuration, which will operate at a higher voltage with improved beam parameters. In this new experiment, a 600 keV, multi-kA electron beam will be produced with low initial transverse energy. Transverse kinetic energy will then be added to the beam either by resonant pumping, via a magnetic wiggler, or by transit through a nonadiabatic magnetic ''bump.'' Finally, the beam will be adiabatically compressed to the desired radius in the gyrotron cavity with a final α≅1. The authors plan to report on the latest results from this new experimental configuration

Voltage protection scheme for MG sets used to drive inductive energy storage systems

International Nuclear Information System (INIS)

Campen, G.L.; Easter, R.B.

1977-01-01

A recent tokamak proposal at ORNL called for MG (motor-generator) sets to drive the ohmic heating (OH] coil, which was to be subjected to 20 kV immediately after coil charge-up to initiate the experiment. Since most rotating machinery is inherently low voltage, including the machines available at ORNL, a mechanism was necessary to isolate the generators from the high voltage portions of the circuit before the appearance of this voltage. It is not the expected 20 kV at the coil that causes difficulty, because the main interrupting switch handles this. The voltage induced in the armature due to di/dt and the possibility of faults are the greatest causes for concern and are responsible for the complexity of the voltage protection scheme, which must accommodate any possible combination of fault time and location. Such a protection scheme is presented in this paper

Mitigation of Voltage Sags in CIGRE Low Voltage Distribution Network

DEFF Research Database (Denmark)

Mustafa, Ghullam; Bak-Jensen, Birgitte; Mahat, Pukar

2013-01-01

Any problem in voltage in a power network is undesirable as it aggravates the quality of the power. Power electronic devices such as Voltage Source Converter (VSC) based Static Synchronous Compensator (STATCOM), Dynamic Voltage Restorer (DVR) etc. are commonly used for the mitigation of voltage p....... The compensation of voltage sags in the different parts of CIGRE distribution network is done by using the four STATCOM compensators already existing in the test grid. The simulations are carried out in DIgSILENT power factory software version 15.0.......Any problem in voltage in a power network is undesirable as it aggravates the quality of the power. Power electronic devices such as Voltage Source Converter (VSC) based Static Synchronous Compensator (STATCOM), Dynamic Voltage Restorer (DVR) etc. are commonly used for the mitigation of voltage...... problems in the distribution system. The voltage problems dealt with in this paper are to show how to mitigate voltage sags in the CIGRE Low Voltage (LV) test network and networks like this. The voltage sags, for the tested cases in the CIGRE LV test network are mainly due to three phase faults...

David Shoenberg and the beauty of quantum oscillations

Science.gov (United States)

Pudalov, V. M.

2011-01-01

The quantum oscillation effect was discovered in Leiden in 1930, by W. J. de Haas and P. M. van Alphen when measuring magnetization, and by L. W. Shubnikov and de Haas when measuring magnetoresistance. Studying single crystals of bismuth, they observed oscillatory variations in the magnetization and magnetoresistance with magnetic field. Shoenberg, whose first research in Cambridge had been on bismuth, found that much stronger oscillations are observed when a bismuth sample is cooled to liquid helium temperature rather than liquid hydrogen, which had been used by de Haas. In 1938 Shoenberg went from Cambridge to Moscow to study these oscillations at Kapitza's Institute where liquid helium was available at that time. In 1947, J. Marcus observed similar oscillations in zinc and that persuaded Schoenberg to return to this research. After that, the dHvA effect became one of his main research topics. In particular, he developed techniques for quantitative measurement of this effect in many metals. A theoretical explanation of quantum oscillations was given by L. Onsager in 1952, and an analytical quantitative theory by I. M. Lifshitz and A. M. Kosevich in 1955. These theoretical advances seemed to provide a comprehensive description of the effect. Since then, quantum oscillations have been widely used as a tool for measuring Fermi surface extremal cross-sections and all-angle electron scattering times. In his pioneering experiments of the 1960's, Shoenberg revealed the richness and deep essence of the quantum oscillation effect and showed how the beauty of the effect is disclosed under nonlinear conditions imposed by interactions in the system under study. It was quite surprising that "magnetic interaction" conditions could cause the apparently weak quantum oscillation effect to have such strong consequences as breaking the sample into magnetic (now called "Shoenberg") domains and forming an inhomogeneous magnetic state. With his contributions to the field of quantum

David Schoenberg and the beauty of quantum oscillations

International Nuclear Information System (INIS)

Pudalov, V.M.

2012-01-01

The quantum oscillation effect was discovered in Leiden, in 1930, by W.J. de Haas and P.M. van Alphen in magnetization measurement, and by L.W. Shubnikov and de Haas - in magnetoresistance. Studying single crystals of bismuth, they observed oscillatory variations of magnetization and magnetoresistance with magnetic field. Shoenberg, whose first research in Cambridge had been on bismuth, found that much stronger oscillations are observed when a bismuth sample is cooled to liquid helium rather than to liquid hydrogen, which had been used by de Haas. In 1938 Shoenberg came from Cambridge to Moscow to study these oscillations at Kapitza Institute where liquid helium was available at that time. In 1947, J. Marcus observed similar oscillations in zinc, that persuaded Shoenberg to return to this research, and, since then, the dHvA effect had been one of his main research topic. In particular, he developed techniques for quantitative measurements of the effect in many metals. Theoretical explanation of quantum oscillations was given by L. Onsager in 1952, and the analytical quantitative theory by I.M. Lifshitz and A.M. Kosevich in 1955. These theoretical advancements seemed to provide a comprehensive description of the effect. Since then, quantum oscillations were commonly considered as a tool for measuring Fermi surface extremal cross-sections and all-angle electron scattering times. However, in his pioneering experiments in 1960s, Shoenberg revealed the richness and deep essence of the quantum oscillation effect and showed how the beauty of the effect is disclosed under nonlinear conditions imposed by interactions in the system under study. It was quite unexpected, that under 'magnetic interaction' conditions, the apparently weak effect of quantum oscillations may lead to such strong consequences as breaking the sample into magnetic (now called 'Shoenberg') domains and the formation of an inhomogeneous magnetic state. Owing to his contribution to the field of quantum

Oscillator representation method in the theory of a hydrogen atom in an external field

International Nuclear Information System (INIS)

Dinejkhan, M.

1996-01-01

The Wick-ordering method called the Oscillator representation in the non-relativistic Schroedinger equation is proposed to calculate the energy spectrum for spherically symmetric and axially symmetric potentials allowing the existence of a bound state. In particular, the method is applied to calculate the energy spectrum of (2s)-states of a hydrogen atom in a uniform magnetic field of an arbitrary strength. In the perturbation (external field) approximation, the energy spectrum of the so-called quadratic and spherical quadratic Zeeman problem and the problem of a hydrogen atom in a generalized van der Waals potential is calculated analytically. The results of the zeroth approximation of oscillator representation are in good agreement with the exact values. 31 refs., 3 tabs

Fluctuation characteristics of arc voltage and jet flow in a non-transferred dc plasma generated at reduced pressure

International Nuclear Information System (INIS)

Pan, W X; Guo, Z Y; Meng, X; Huang, H J; Wu, C K

2009-01-01

A torch with a set of inter-electrode inserts between the cathode and the anode/nozzle with a wide nozzle exit was designed to generate plasma jets at chamber pressures of 500-10 000 Pa. The variation of the arc voltage was examined with the change in working parameters such as gas flow rate and chamber pressure. The fluctuation in the arc voltage was recorded with an oscilloscope, and the plasma jet fluctuation near the torch exit was observed with a high-speed video camera and detected with a double-electrostatic probe. Results show that the 300 Hz wave originated from the tri-phase rectified power supply was always detected under all generating conditions. Helmholtz oscillations over 3000 Hz was detected superposed on the 300 Hz wave at gas flow rates higher than 8.8 slm with a peak to valley amplitude lower than 5% of the average voltage value. No appreciable voltage fluctuation caused by the irregular arc root movement is detected, and mechanisms for the arc voltage and jet flow fluctuations are discussed.

Coulomb oscillations in three-layer graphene nanostructures

International Nuclear Information System (INIS)

Guettinger, J; Stampfer, C; Molitor, F; Graf, D; Ihn, T; Ensslin, K

2008-01-01

We present transport measurements on a tunable three-layer graphene single electron transistor (SET). The device consists of an etched three-layer graphene flake with two narrow constrictions separating the island from source and drain contacts. Three lateral graphene gates are used to electrostatically tune the device. An individual three-layer graphene constriction has been investigated separately showing a transport gap near the charge neutrality point. The graphene tunneling barriers show a strongly nonmonotonic coupling as a function of gate voltage indicating the presence of localized states in the constrictions. We show Coulomb oscillations and Coulomb diamond measurements proving the functionality of the graphene SET. A charging energy of ∼0.6 meV is extracted.

Development of a New Cascade Voltage-Doubler for Voltage Multiplication

OpenAIRE

Toudeshki, Arash; Mariun, Norman; Hizam, Hashim; Abdul Wahab, Noor Izzri

2014-01-01

For more than eight decades, cascade voltage-doubler circuits are used as a method to produce DC output voltage higher than the input voltage. In this paper, the topological developments of cascade voltage-doublers are reviewed. A new circuit configuration for cascade voltage-doubler is presented. This circuit can produce a higher value of the DC output voltage and better output quality compared to the conventional cascade voltage-doubler circuits, with the same number of stages.

Phase locking of an S-band wide-gap klystron amplifier with high power injection driven by a relativistic backward wave oscillator

Energy Technology Data Exchange (ETDEWEB)

Bai Xianchen; Zhang Jiande; Yang Jianhua; Jin Zhenxing [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

2012-12-15

Theoretical analyses and preliminary experiments on the phase-locking characteristics of an inductively loaded 2-cavity wide-gap klystron amplifier (WKA) with high power injection driven by a GW-class relativistic backward wave oscillator (RBWO) are presented. Electric power of the amplifier and oscillator is supplied by a single accelerator being capable of producing dual electron beams. The well phase-locking effect of the RBWO-WKA system requires the oscillator have good frequency reproducibility and stability from pulse to pulse. Thus, the main switch of the accelerator is externally triggered to stabilize the diode voltage and then the working frequency. In the experiment, frequency of the WKA is linearly locked by the RBWO. With a diode voltage of 530 kV and an input power of {approx}22 MW, an output power of {approx}230 MW with the power gain of {approx}10.2 dB is obtained from the WKA. As the main switch is triggered, the relative phase difference between the RBWO and the WKA is less than {+-}15 Degree-Sign in a single shot, and phase jitter of {+-}11 Degree-Sign is obtained within a series of shots with duration of about 40 ns.

Phase locking of an S-band wide-gap klystron amplifier with high power injection driven by a relativistic backward wave oscillator

Science.gov (United States)

Bai, Xianchen; Zhang, Jiande; Yang, Jianhua; Jin, Zhenxing

2012-12-01

Theoretical analyses and preliminary experiments on the phase-locking characteristics of an inductively loaded 2-cavity wide-gap klystron amplifier (WKA) with high power injection driven by a GW-class relativistic backward wave oscillator (RBWO) are presented. Electric power of the amplifier and oscillator is supplied by a single accelerator being capable of producing dual electron beams. The well phase-locking effect of the RBWO-WKA system requires the oscillator have good frequency reproducibility and stability from pulse to pulse. Thus, the main switch of the accelerator is externally triggered to stabilize the diode voltage and then the working frequency. In the experiment, frequency of the WKA is linearly locked by the RBWO. With a diode voltage of 530 kV and an input power of ˜22 MW, an output power of ˜230 MW with the power gain of ˜10.2 dB is obtained from the WKA. As the main switch is triggered, the relative phase difference between the RBWO and the WKA is less than ±15° in a single shot, and phase jitter of ±11° is obtained within a series of shots with duration of about 40 ns.

Voltage-carrying states in superconducting microstrips

International Nuclear Information System (INIS)

Stuivinga, M.E.C.

1983-01-01

When the critical current is exceeded in a superconducting microstrip, voltage-carrying states with a resistance significantly below the normal state resistance can occur. Phase-slip centers (PSC) appear at about the critical temperature. These are successive local voltage units which manifest themselves as strip-like increments in voltage in the I-V characteristic. For temperatures off the critical temperature the PSC regime degenerates into a region of normal material, a so-called hot spot. These two phenomena, PSC and hot spots, form the subject of this thesis. To gain a better understanding of the phase-slip center process, an experiment was designed to measure local values of the quasi-particle and pair potential. The results of local potential and gap measurements at a PSC in aluminium are presented and discussed. Special attention is paid to pair-breaking interactions which can shorten the relaxation time. A non-linear differential equation is derived which describes the development of a PSC into a normal hot spot under the influence of Joule heating. It incorporates the temperature rise due to the dissipative processes occurring in the charge imbalance tails. Numerical solutions are presented for a set of parameters, including those for aluminium and tin. Subsequently, they are compared with experiments. (Auth.)

Numerical simulation of a split cavity oscillator and rf conversion

International Nuclear Information System (INIS)

Lemke, R.W.

1991-07-01

We have conducted an extensive investigation of the split cavity oscillator (SCO) using particle-in-cell simulation. The goal of this work is to test and optimize an inverse diode rf convertor for use with a cylindrical SCO, while simultaneously determining factors that control rf extraction efficiency. We present results from simulations of several configurations including the SCO with inverse diode extractor, the SCO in conjunction with post-acceleration and inverse diode extraction, and the SCO, using electron beams with a variety of currents, voltages, and radii. 7 refs., 8 figs

Unconventional strain-dependent conductance oscillations in pristine phosphorene.

Science.gov (United States)

Ray, S J; Kamalakar, M Venkata

2018-05-16

Phosphorene is a single elemental, two-dimensional semiconductor that has quickly emerged as a high mobility material for transistors and optoelectronic devices. In addition, being a 2D material it can sustain high levels of strain, enabling sensitive modification of its electronic properties. In this paper, we investigate the strain dependent electronic properties of phosphorene nanocrystals. By performing extensive calculations we determine the electrical conductance as a function of uniaxial, as well as biaxial strain stimuli and uncover a unique zone phase diagram. This enables us to uncover conductance oscillations in pristine phosphorene for the first time, by the simple application of strain. We show that such unconventional current-voltage behaviour is tuneable by the nature of strain, and that an additional gate voltage can modulate the amplitude (peak to valley ratio) of the observed phenomena and its switching efficiency. Furthermore, we show that the switching is highly robust against doping and defects. Our detailed results present new leads for innovation in strain based gauging and high-frequency nanoelectronic switches of phosphorene.

Voltage-probe-position dependence and magnetic-flux contribution to the measured voltage in ac transport measurements: which measuring circuit determines the real losses?

International Nuclear Information System (INIS)

Pe, T.; McDonald, J.; Clem, J.R.

1995-01-01

The voltage V ab measured between two voltage taps a and b during magnetic flux transport in a type-II superconductor carrying current I is the sum of two contributions, the line integral from a to b of the electric field along an arbitrary path C s through the superconductor and a term proportional to the time rate of change of magnetic flux through the area bounded by the path C s and the measuring circuit leads. When the current I(t) is oscillating with time t, the apparent ac loss (the time average of the product IV ab ) depends upon the measuring circuit used. Only when the measuring-circuit leads are brought out far from the surface does the apparent power dissipation approach the real (or true) ac loss associated with the length of sample probed. Calculations showing comparisons between the apparent and real ac losses in a flat strip of rectangular cross section will be presented, showing the behavior as a function of the measuring-circuit dimensions. Corresponding calculations also are presented for a sample of elliptical cross section

Suppressing voltage transients in high voltage power supplies

International Nuclear Information System (INIS)

Lickel, K.F.; Stonebank, R.

1979-01-01

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

Oscillations During Thermonuclear X-ray Bursts: A New Probe of Neutron Stars

Science.gov (United States)

Strohmayer, Tod E.; White, Nicholas E. (Technical Monitor)

2002-01-01

Observations of thermonuclear (also called Type 1) X-ray bursts from neutron stars in low mass X-ray binaries (LMXB) with the Rossi X-ray Timing Explorer (RXTE) have revealed large amplitude, high coherence X-ray brightness oscillations with frequencies in the 300 - 600 Hz range. Substantial spectral and timing evidence point to rotational modulation of the X-ray burst flux as the cause of these oscillations, and it is likely that they reveal the spin frequencies of neutron stars in LMXB from which they are detected. Here we review the status of our knowledge of these oscillations and describe how they can be used to constrain the masses and radii of neutron stars as well as the physics of thermonuclear burning on accreting neutron stars.

Trapped Ion Oscillation Frequencies as Sensors for Spectroscopy

Directory of Open Access Journals (Sweden)

Wilfried Nörtershäuser

2010-03-01

Full Text Available The oscillation frequencies of charged particles in a Penning trap can serve as sensors for spectroscopy when additional field components are introduced to the magnetic and electric fields used for confinement. The presence of so-called “magnetic bottles” and specific electric anharmonicities creates calculable energy-dependences of the oscillation frequencies in the radiofrequency domain which may be used to detect the absorption or emission of photons both in the microwave and optical frequency domains. The precise electronic measurement of these oscillation frequencies therefore represents an optical sensor for spectroscopy. We discuss possible applications for precision laser and microwave spectroscopy and their role in the determination of magnetic moments and excited state lifetimes. Also, the trap-assisted measurement of radiative nuclear de-excitations in the X-ray domain is discussed. This way, the different applications range over more than 12 orders of magnitude in the detectable photon energies, from below μeV in the microwave domain to beyond MeV in the X-ray domain.

On the Quantum Potential and Pulsating Wave Packet in the Harmonic Oscillator

International Nuclear Information System (INIS)

Dubois, Daniel M.

2008-01-01

A fundamental mathematical formalism related to the Quantum Potential factor, Q, is presented in this paper. The Schroedinger equation can be transformed to two equations depending on a group velocity and a density of presence of the particle. A factor, in these equations, was called ''Quantum Potential'' by D. Bohm and B. Hiley. In 1999, I demonstrated that this Quantum Potential, Q, can be split in two Quantum Potentials, Q 1 , and Q 2 , for which the relation, Q=Q 1 +Q 2 , holds. These two Quantum Potentials depend on a fundamental new variable, what I called a phase velocity, u, directly related to the probability density of presence of the wave-particle, given by the modulus of the wave function. This paper gives some further developments for explaining the Quantum Potential for oscillating and pulsating Gaussian wave packets in the Harmonic Oscillator. It is shown that the two Quantum Potentials play a central role in the interpretation of quantum mechanics. A breakthrough in the formalism of the Quantum Mechanics could be provoked by the physical properties of these Quantum Potentials. The probability density of presence of the oscillating and pulsating Gaussian wave packets in the Harmonic Oscillator is directly depending on the ratio Q 2 /Q 1 of the two Quantum Potentials. In the general case, the energy of these Gaussian wave packets is not constant, but is oscillating. The energy is given by the sum of the kinetic energy, T, the potential energy, V, and the two Quantum Potentials: E=T+V+Q 1 +Q 2 . For some conditions, given in the paper, the energy can be a constant. The first remarkable result is the fact that the first Quantum Potential, Q 1 , is related to the ground state energy, E 0 , of the Quantum Harmonic Oscillator: Q 1 =h-bar ω/2=E 0 . The second result is related to the property of the second Quantum Potential, Q 2 , which plays the role of an anti-potential, Q 2 =-V(x), where V is the harmonic oscillator potential. This Quantum Potential

Quenching oscillating behaviors in fractional coupled Stuart-Landau oscillators

Science.gov (United States)

Sun, Zhongkui; Xiao, Rui; Yang, Xiaoli; Xu, Wei

2018-03-01

Oscillation quenching has been widely studied during the past several decades in fields ranging from natural sciences to engineering, but investigations have so far been restricted to oscillators with an integer-order derivative. Here, we report the first study of amplitude death (AD) in fractional coupled Stuart-Landau oscillators with partial and/or complete conjugate couplings to explore oscillation quenching patterns and dynamics. It has been found that the fractional-order derivative impacts the AD state crucially. The area of the AD state increases along with the decrease of the fractional-order derivative. Furthermore, by introducing and adjusting a limiting feedback factor in coupling links, the AD state can be well tamed in fractional coupled oscillators. Hence, it provides one an effective approach to analyze and control the oscillating behaviors in fractional coupled oscillators.

Control of chaotic oscillators via a class of model free active controller: Suppresion and synchronization

Energy Technology Data Exchange (ETDEWEB)

Aguilar-Lopez, Ricardo [Division de Ciencias Basicas e Ingenieria, Universidad Autonoma Metropolitana, Av. San Pablo No. 180, Reynosa-Tamaulipas, 02200, Azcapotzalco, Mexico D.F. (Mexico)], E-mail: raguilar@correo.azc.uam.mx; Martinez-Guerra, Rafael [Departamento de Control Automatico, CINVESTAV-IPN, Apartado Postal 14-740, 07360 Mexico D.F. (Mexico)], E-mail: rguerra@ctrl.cinvestav.mx

2008-10-15

The goal of this work is related with the control of chaotic oscillators for chaos suppression and synchronization purposes. The proposed methodology is related with a class of robust active control (RAC) law, where the stabilizing part of the control structure is related with an integral high order sliding-mode and proportional form of the so-called control error. The proposed controller is applied to chaos suppression, synchronization and anti-synchronization tasks for nonlinear oscillators with different order and structure. Numerical experiments illustrate the satisfactory performance of the proposed methodology, when it is applied to Duffing and Chen oscillators.

Control of chaotic oscillators via a class of model free active controller: Suppresion and synchronization

International Nuclear Information System (INIS)

Aguilar-Lopez, Ricardo; Martinez-Guerra, Rafael

2008-01-01

The goal of this work is related with the control of chaotic oscillators for chaos suppression and synchronization purposes. The proposed methodology is related with a class of robust active control (RAC) law, where the stabilizing part of the control structure is related with an integral high order sliding-mode and proportional form of the so-called control error. The proposed controller is applied to chaos suppression, synchronization and anti-synchronization tasks for nonlinear oscillators with different order and structure. Numerical experiments illustrate the satisfactory performance of the proposed methodology, when it is applied to Duffing and Chen oscillators

Preliminary Planck constant measurements via UME oscillating magnet Kibble balance

Science.gov (United States)

Ahmedov, H.; Babayiğit Aşkın, N.; Korutlu, B.; Orhan, R.

2018-06-01

The UME Kibble balance project was initiated in the second half of 2014. During this period we have studied the theoretical aspects of Kibble balances, in which an oscillating magnet generates AC Faraday’s voltage in a stationary coil, and constructed a trial version to implement this idea. The remarkable feature of this approach is that it can establish the link between the Planck constant and a macroscopic mass by one single experiment in the most natural way. Weak dependences on variations of environmental and experimental conditions, small size, and other useful features offered by this novel approach reduce the complexity of the experimental set-up. This paper describes the principles of the oscillating magnet Kibble balance and gives details of the preliminary Planck constant measurements. The value of the Planck constant determined with our apparatus is \\boldsymbol{h}/{{\\boldsymbol{h}}\\boldsymbol 90}={1}{.000} {004}~ , with a relative standard uncertainty of 6 ppm.

Reduction of ripple voltage in a dynamitron

International Nuclear Information System (INIS)

Langsdorf, A. Jr.

1982-01-01

We determined that a precise neutralization of the RF ripple voltage on the high-voltage terminal of a Dynamitron has previously been prevented by a nonegligible phase shift of RF currents in the two halves of the approx. 100-kHz class C oscillator tank circuit, which is actually constituted of two slightly unequal high-Q coupled circuits because it has two ground points: the inescapable center-tap-ground in the capacitive legs and a center-tap-ground lead to the induction coil. The latter is needed to prevent damage by flashover transients; equivalent to its removal was the adjusting of RF ground return current to a null by aid of a current transformer on this lead and the suitable adjusting of trimmer capacitance. While the phase shift was thus held to a null, the actual ripple amplitude on the hv terminal was minimized by adjusting additional trimmer capacitances installed in the terminal of the machine. Then p/p 100-kHz ripple at 2-MV dc output was reduced to about 50V and RMS resolution by (p,#betta#) resonance threshold data near 1 MV was about 250 V. The limit to resolution has various causes including mechanical vibrations and unbalanced harmonics of the RF

The energy spectrum of the 'runaway' electrons from a high voltage pulsed discharge

International Nuclear Information System (INIS)

Ruset, C.

1985-01-01

Some experimental results are presented on the influence of the pressure upon the energy spectrum of the runaway electrons generated into a pulsed high voltage argon discharge. These electrons enter a state of continuous acceleration between two collisions with rapidly increasing free path. The applied discharge current varies from 10 to 300 A, the pulse time is about 800 ns. Relativistic effects are taken into consideration. Theoretical explanation is based on the pnenomenon of electron spreading on plasma oscillations. (D.Gy.)

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

Directory of Open Access Journals (Sweden)

Harley T Kurata

2010-02-01

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

Transient voltage sharing in series-coupled high voltage switches

Directory of Open Access Journals (Sweden)

Editorial Office

1992-07-01

Full Text Available For switching voltages in excess of the maximum blocking voltage of a switching element (for example, thyristor, MOSFET or bipolar transistor such elements are often coupled in series - and additional circuitry has to be provided to ensure equal voltage sharing. Between each such series element and system ground there is a certain parasitic capacitance that may draw a significant current during high-speed voltage transients. The "open" switch is modelled as a ladder network. Analy­sis reveals an exponential progression in the distribution of the applied voltage across the elements. Overstressing thus oc­curs in some of the elements at levels of the total voltage that are significantly below the design value. This difficulty is overcome by grading the voltage sharing circuitry, coupled in parallel with each element, in a prescribed manner, as set out here.

Oscillators and Eigenvalues

DEFF Research Database (Denmark)

Lindberg, Erik

1997-01-01

In order to obtain insight in the nature of nonlinear oscillators the eigenvalues of the linearized Jacobian of the differential equations describing the oscillator are found and displayed as functions of time. A number of oscillators are studied including Dewey's oscillator (piecewise linear wit...... with negative resistance), Kennedy's Colpitts-oscillator (with and without chaos) and a new 4'th order oscillator with hyper-chaos....

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

International Nuclear Information System (INIS)

Matra, K; Furuta, H; Hatta, A

2013-01-01

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

Nonlinear control of voltage source converters in AC-DC power system.

Science.gov (United States)

Dash, P K; Nayak, N

2014-07-01

This paper presents the design of a robust nonlinear controller for a parallel AC-DC power system using a Lyapunov function-based sliding mode control (LYPSMC) strategy. The inputs for the proposed control scheme are the DC voltage and reactive power errors at the converter station and the active and reactive power errors at the inverter station of the voltage-source converter-based high voltage direct current transmission (VSC-HVDC) link. The stability and robust tracking of the system parameters are ensured by applying the Lyapunov direct method. Also the gains of the sliding mode control (SMC) are made adaptive using the stability conditions of the Lyapunov function. The proposed control strategy offers invariant stability to a class of systems having modeling uncertainties due to parameter changes and exogenous inputs. Comprehensive computer simulations are carried out to verify the proposed control scheme under several system disturbances like changes in short-circuit ratio, converter parametric changes, and faults on the converter and inverter buses for single generating system connected to the power grid in a single machine infinite-bus AC-DC network and also for a 3-machine two-area power system. Furthermore, a second order super twisting sliding mode control scheme has been presented in this paper that provides a higher degree of nonlinearity than the LYPSMC and damps faster the converter and inverter voltage and power oscillations. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

To Stabilize Power Systems from Various Kind of Oscillations using a State Feedback Controller

International Nuclear Information System (INIS)

Afridi, M. A.

2012-01-01

Damping of electromechanical oscillations in power systems is one of the major concerns in the operation of power system since many years. These oscillations cause improper of the power system incorporating losses. This thesis work presents the coordinated AVR+PSS structure, called the Desensitized four loops Regulator, designed to damp these oscillations in the power system. It is shown here that it is possible to transform the structure of this controller into any standard IEEE AVR+PSS structure. The AVR+PSS structure obtained through this structure is efficient to damp out many types of oscillations present in the Power system. These models are to be incorporated with the generator models to get a power system model with state feedback control. On simulating the system in Simulink with the controllers we have obtained the power system model with state feedback control and observed that how these controllers are helpful in damping the oscillations. (author)

Power conditioning using dynamic voltage restorers under different voltage sag types.

Science.gov (United States)

Saeed, Ahmed M; Abdel Aleem, Shady H E; Ibrahim, Ahmed M; Balci, Murat E; El-Zahab, Essam E A

2016-01-01

Voltage sags can be symmetrical or unsymmetrical depending on the causes of the sag. At the present time, one of the most common procedures for mitigating voltage sags is by the use of dynamic voltage restorers (DVRs). By definition, a DVR is a controlled voltage source inserted between the network and a sensitive load through a booster transformer injecting voltage into the network in order to correct any disturbance affecting a sensitive load voltage. In this paper, modelling of DVR for voltage correction using MatLab software is presented. The performance of the device under different voltage sag types is described, where the voltage sag types are introduced using the different types of short-circuit faults included in the environment of the MatLab/Simulink package. The robustness of the proposed device is evaluated using the common voltage sag indices, while taking into account voltage and current unbalance percentages, where maintaining the total harmonic distortion percentage of the load voltage within a specified range is desired. Finally, several simulation results are shown in order to highlight that the DVR is capable of effective correction of the voltage sag while minimizing the grid voltage unbalance and distortion, regardless of the fault type.

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

Directory of Open Access Journals (Sweden)

Martin Janecek

2012-12-01

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

Calculating Asteroseismic Diagrams for Solar-Like Oscillations

DEFF Research Database (Denmark)

White, T.R.; Bedding, T.R.; Stello, D.

2011-01-01

With the success of the Kepler and CoRoT missions, the number of stars with detected solar-like oscillations has increased by several orders of magnitude; for the first time we are able to perform large-scale ensemble asteroseismology of these stars. In preparation for this golden age of asterose......With the success of the Kepler and CoRoT missions, the number of stars with detected solar-like oscillations has increased by several orders of magnitude; for the first time we are able to perform large-scale ensemble asteroseismology of these stars. In preparation for this golden age...... of these stars. We investigate the scaling relation between the large frequency separation, Δν, and mean stellar density. Furthermore we present model evolutionary tracks for several asteroseismic diagrams. We have extended the so-called C-D diagram beyond the main sequence to the subgiants and the red giant...

Modeling of dielectric elastomer oscillators for soft biomimetic applications.

Science.gov (United States)

Henke, E-F M; Wilson, Katherine E; Anderson, I A

2018-06-26

Biomimetic, entirely soft robots with animal-like behavior and integrated artificial nervous systems will open up totally new perspectives and applications. However, until now, most presented studies on soft robots were limited to only partly soft designs, since all solutions at least needed conventional, stiff electronics to sense, process signals and activate actuators. We present a novel approach for a set up and the experimental validation of an artificial pace maker that is able to drive basic robotic structures and act as artificial central pattern generator. The structure is based on multi-functional dielectric elastomers (DEs). DE actuators, DE switches and DE resistors are combined to create complex DE oscillators (DEOs). Supplied with only one external DC voltage, the DEO autonomously generates oscillating signals that can be used to clock a robotic structure, control the cyclic motion of artificial muscles in bionic robots or make a whole robotic structure move. We present the basic functionality, derive a mathematical model for predicting the generated signal waveform and verify the model experimentally.

Mitigation of voltage sags in the distribution system with dynamic voltage restorer

International Nuclear Information System (INIS)

Viglas, D.; Belan, A.

2012-01-01

Dynamic voltage restorer is a custom power device that is used to improve voltage sags or swells in electrical distribution system. The components of the Dynamic Voltage Restorer consist of injection transformers, voltage source inverter, passive filters and energy storage. The main function of the Dynamic voltage restorer is used to inject three phase voltage in series and in synchronism with the grid voltages in order to compensate voltage disturbances. This article deals with mitigation of voltage sags caused by three-phase short circuit. Dynamic voltage restorer is modelled in MATLAB/Simulink. (Authors)

Twin peak high-frequency quasi-periodic oscillations as a spectral imprint of dual oscillation modes of accretion tori

Science.gov (United States)

Bakala, P.; Goluchová, K.; Török, G.; Šrámková, E.; Abramowicz, M. A.; Vincent, F. H.; Mazur, G. P.

2015-09-01

Context. High-frequency (millisecond) quasi-periodic oscillations (HF QPOs) are observed in the X-ray power-density spectra of several microquasars and low-mass X-ray binaries. Two distinct QPO peaks, so-called twin peak QPOs, are often detected simultaneously exhibiting their frequency ratio close or equal to 3:2. A widely discussed class of proposed QPOs models is based on oscillations of accretion toroidal structures orbiting in the close vicinity of black holes or neutron stars. Aims: Following the analytic theory and previous studies of observable spectral signatures, we aim to model the twin peak QPOs as a spectral imprint of specific dual oscillation regime defined by a combination of the lowest radial and vertical oscillation mode of slender tori. We consider the model of an optically thick slender accretion torus with constant specific angular momentum. We examined power spectra and fluorescent Kα iron line profiles for two different simulation setups with the mode frequency relations corresponding to the epicyclic resonance HF QPOs model and modified relativistic precession QPOs model. Methods: We used relativistic ray-tracing implemented in the parallel simulation code LSDplus. In the background of the Kerr spacetime geometry, we analyzed the influence of the distant observer inclination and the spin of the central compact object. Relativistic optical projection of the oscillating slender torus is illustrated by images in false colours related to the frequency shift. Results: We show that performed simulations yield power spectra with the pair of dominant peaks that correspond to the frequencies of radial and vertical oscillation modes and with the peak frequency ratio equal to the proper value 3:2 on a wide range of inclinations and spin values. We also discuss exceptional cases of a very low and very high inclination, as well as unstable high spin relativistic precession-like configurations that predict a constant frequency ratio equal to 1:2. We

Maximum covariance analysis to identify intraseasonal oscillations over tropical Brazil

Science.gov (United States)

Barreto, Naurinete J. C.; Mesquita, Michel d. S.; Mendes, David; Spyrides, Maria H. C.; Pedra, George U.; Lucio, Paulo S.

2017-09-01

A reliable prognosis of extreme precipitation events in the tropics is arguably challenging to obtain due to the interaction of meteorological systems at various time scales. A pivotal component of the global climate variability is the so-called intraseasonal oscillations, phenomena that occur between 20 and 100 days. The Madden-Julian Oscillation (MJO), which is directly related to the modulation of convective precipitation in the equatorial belt, is considered the primary oscillation in the tropical region. The aim of this study is to diagnose the connection between the MJO signal and the regional intraseasonal rainfall variability over tropical Brazil. This is achieved through the development of an index called Multivariate Intraseasonal Index for Tropical Brazil (MITB). This index is based on Maximum Covariance Analysis (MCA) applied to the filtered daily anomalies of rainfall data over tropical Brazil against a group of covariates consisting of: outgoing longwave radiation and the zonal component u of the wind at 850 and 200 hPa. The first two MCA modes, which were used to create the { MITB}_1 and { MITB}_2 indices, represent 65 and 16 % of the explained variance, respectively. The combined multivariate index was able to satisfactorily represent the pattern of intraseasonal variability over tropical Brazil, showing that there are periods of activation and inhibition of precipitation connected with the pattern of MJO propagation. The MITB index could potentially be used as a diagnostic tool for intraseasonal forecasting.

Discreteness-induced resonances and ac voltage amplitudes in long one-dimensional Josephson junction arrays

International Nuclear Information System (INIS)

Duwel, A.E.; Watanabe, S.; Trias, E.; Orlando, T.P.; van der Zant, H.S.; Strogatz, S.H.

1997-01-01

New resonance steps are found in the experimental current-voltage characteristics of long, discrete, one-dimensional Josephson junction arrays with open boundaries and in an external magnetic field. The junctions are underdamped, connected in parallel, and dc biased. Numerical simulations based on the discrete sine-Gordon model are carried out, and show that the solutions on the steps are periodic trains of fluxons, phase locked by a finite amplitude radiation. Power spectra of the voltages consist of a small number of harmonic peaks, which may be exploited for possible oscillator applications. The steps form a family that can be numbered by the harmonic content of the radiation, the first member corresponding to the Eck step. Discreteness of the arrays is shown to be essential for appearance of the higher order steps. We use a multimode extension of the harmonic balance analysis, and estimate the resonance frequencies, the ac voltage amplitudes, and the theoretical limit on the output power on the first two steps. copyright 1997 American Institute of Physics

Fractional dynamics of globally slow transcription and its impact on deterministic genetic oscillation.

Directory of Open Access Journals (Sweden)

Kun Wei

Full Text Available In dynamical systems theory, a system which can be described by differential equations is called a continuous dynamical system. In studies on genetic oscillation, most deterministic models at early stage are usually built on ordinary differential equations (ODE. Therefore, gene transcription which is a vital part in genetic oscillation is presupposed to be a continuous dynamical system by default. However, recent studies argued that discontinuous transcription might be more common than continuous transcription. In this paper, by appending the inserted silent interval lying between two neighboring transcriptional events to the end of the preceding event, we established that the running time for an intact transcriptional event increases and gene transcription thus shows slow dynamics. By globally replacing the original time increment for each state increment by a larger one, we introduced fractional differential equations (FDE to describe such globally slow transcription. The impact of fractionization on genetic oscillation was then studied in two early stage models--the Goodwin oscillator and the Rössler oscillator. By constructing a "dual memory" oscillator--the fractional delay Goodwin oscillator, we suggested that four general requirements for generating genetic oscillation should be revised to be negative feedback, sufficient nonlinearity, sufficient memory and proper balancing of timescale. The numerical study of the fractional Rössler oscillator implied that the globally slow transcription tends to lower the chance of a coupled or more complex nonlinear genetic oscillatory system behaving chaotically.

Fractional dynamics of globally slow transcription and its impact on deterministic genetic oscillation.

Science.gov (United States)

Wei, Kun; Gao, Shilong; Zhong, Suchuan; Ma, Hong

2012-01-01

In dynamical systems theory, a system which can be described by differential equations is called a continuous dynamical system. In studies on genetic oscillation, most deterministic models at early stage are usually built on ordinary differential equations (ODE). Therefore, gene transcription which is a vital part in genetic oscillation is presupposed to be a continuous dynamical system by default. However, recent studies argued that discontinuous transcription might be more common than continuous transcription. In this paper, by appending the inserted silent interval lying between two neighboring transcriptional events to the end of the preceding event, we established that the running time for an intact transcriptional event increases and gene transcription thus shows slow dynamics. By globally replacing the original time increment for each state increment by a larger one, we introduced fractional differential equations (FDE) to describe such globally slow transcription. The impact of fractionization on genetic oscillation was then studied in two early stage models--the Goodwin oscillator and the Rössler oscillator. By constructing a "dual memory" oscillator--the fractional delay Goodwin oscillator, we suggested that four general requirements for generating genetic oscillation should be revised to be negative feedback, sufficient nonlinearity, sufficient memory and proper balancing of timescale. The numerical study of the fractional Rössler oscillator implied that the globally slow transcription tends to lower the chance of a coupled or more complex nonlinear genetic oscillatory system behaving chaotically.

Parameter study of global and cluster synchronization in arrays of dry friction oscillators

Energy Technology Data Exchange (ETDEWEB)

Marszal, Michał, E-mail: michal.marszal@p.lodz.pl; Stefański, Andrzej

2017-04-18

Highlights: • Synchronization properties in arrays of coupled dry friction oscillators are investigated. • Master stability function in form of two-oscillator probe is used for predicting synchronization thresholds. • Two network topologies are checked: open and closed nearest neighbor coupling. • Regions of complete and cluster synchronization are found in parameter space. - Abstract: We investigate synchronization thresholds in arrays of identical classic stick-slip dry friction oscillators connected in a nearest neighbor fashion in closed and open ring network. Friction force is modeled by smoothened Stribeck model. Arrays of different length are checked in two parameter space (i.e., coupling coefficient vs. excitation frequency) for complete synchronization as well as cluster synchronization. Synchronization thresholds obtained by brute force numerical integration are compared with possible synchronization regions using the concept called master stability function in the form of two-oscillator reference probe. The results show existence of both complete synchronization and cluster synchronization regions in the investigated systems and confirm that two-oscillator probe can be applied for prediction of synchronization thresholds in systems with stick-slip phenomenon.

Voltage regulating circuit

NARCIS (Netherlands)

2005-01-01

A voltage regulating circuit comprising a rectifier (2) for receiving an AC voltage (Vmains) and for generating a rectified AC voltage (vrec), and a capacitor (3) connected in parallel with said rectified AC voltage for providing a DC voltage (VDC) over a load (5), characterized by a unidirectional

Oscillation and non-oscillation criterion for Riemann–Weber type half-linear differential equations

Directory of Open Access Journals (Sweden)

Petr Hasil

2016-08-01

Full Text Available By the combination of the modified half-linear Prüfer method and the Riccati technique, we study oscillatory properties of half-linear differential equations. Taking into account the transformation theory of half-linear equations and using some known results, we show that the analysed equations in the Riemann–Weber form with perturbations in both terms are conditionally oscillatory. Within the process, we identify the critical oscillation values of their coefficients and, consequently, we decide when the considered equations are oscillatory and when they are non-oscillatory. As a direct corollary of our main result, we solve the so-called critical case for a certain type of half-linear non-perturbed equations.

Voltage-Mode Four-Phase Sinusoidal Generator and Its Useful Extensions

Directory of Open Access Journals (Sweden)

Sudhanshu Maheshwari

2013-01-01

Full Text Available This paper introduces a new voltage-mode second-order sinusoidal generator circuit with four active elements and six passive elements, including grounded capacitors. The frequency and condition of oscillation can be independently controlled. The effect of active element’s nonidealities and parasitic effects is also studied; the proposed topology is good in absorbing several parasitic elements involved with the active elements. The circuit is advantageous for generating high frequency signals which is demonstrated for 25 MHz outputs. Several circuit extensions are also given which makes the new proposal useful for real circuit adoption. The proposed theory is validated through simulation results.

Nanopore Current Oscillations: Nonlinear Dynamics on the Nanoscale.

Science.gov (United States)

Hyland, Brittany; Siwy, Zuzanna S; Martens, Craig C

2015-05-21

In this Letter, we describe theoretical modeling of an experimentally realized nanoscale system that exhibits the general universal behavior of a nonlinear dynamical system. In particular, we consider the description of voltage-induced current fluctuations through a single nanopore from the perspective of nonlinear dynamics. We briefly review the experimental system and its behavior observed and then present a simple phenomenological nonlinear model that reproduces the qualitative behavior of the experimental data. The model consists of a two-dimensional deterministic nonlinear bistable oscillator experiencing both dissipation and random noise. The multidimensionality of the model and the interplay between deterministic and stochastic forces are both required to obtain a qualitatively accurate description of the physical system.

On One Means of Hard Excitation of Oscillations in Nonlinear Flutter Systems

Directory of Open Access Journals (Sweden)

S. D. Glyzin

2014-01-01

Full Text Available Considered are so-called finite-dimensional flutter systems, i.e. systems of ordinary differential equations, arising from Galerkin approximations of certain boundary value problems of aeroelasticity theory as well as from a number of radiophysics applications. We study small oscillations of these equations in case of 1 : 3 resonance. By combining analytical and numerical methods, it is concluded that the mentioned resonance can cause a hard excitation of oscillations. Namely, for flutter systems shown is the possibility of coexistence, along with the stable zero state, of stable invariant tori of arbitrary finite dimension as well as chaotic attractors.

Synchronization and chaos in spin-transfer-torque nano-oscillators coupled via a high-speed operational amplifier

International Nuclear Information System (INIS)

Sanid, C; Murugesh, S

2014-01-01

We propose a system of two coupled spin-torque nano-oscillators (STNOs), one driver and another response, and demonstrate using numerical studies the synchronization of the response system to the frequency of the driver system. To this end we use a high-speed operational amplifier in the form of a voltage follower, which essentially isolates the drive system from the response system. We find the occurrence of 1 : 1 as well as 2 : 1 synchronization in the system, wherein the oscillators show limit cycle dynamics. An increase in power output is noticed when the two oscillators are locked in 1 : 1 synchronization. Moreover in the crossover region between these two synchronization dynamics we show the existence of chaotic dynamics in the slave system. The coupled dynamics under periodic forcing, using a small ac input current in addition to that of the dc part, is also studied. The slave oscillator is seen to retain its qualitative identity in the parameter space in spite of being fed in, at times, a chaotic signal. Such electrically coupled STNOs will be highly useful in fabricating commercial spin-valve oscillators with high power output, when integrated with other spintronic devices. (paper)

Store-operated calcium entry is required for sustained contraction and Ca2+ oscillations of airway smooth muscle.

Science.gov (United States)

Chen, Jun; Sanderson, Michael J

2017-05-15

Airway hyper-responsiveness in asthma is driven by excessive contraction of airway smooth muscle cells (ASMCs). Agonist-induced Ca 2+ oscillations underlie this contraction of ASMCs and the magnitude of this contraction is proportional to the Ca 2+ oscillation frequency. Sustained contraction and Ca 2+ oscillations require an influx of extracellular Ca 2+ , although the mechanisms and pathways mediating this Ca 2+ influx during agonist-induced ASMC contraction are not well defined. By inhibiting store-operated calcium entry (SOCE) or voltage-gated Ca 2+ channels (VGCCs), we show that SOCE, rather than Ca 2+ influx via VGCCs, provides the major Ca 2+ entry pathway into ASMCs to sustain ASMCs contraction and Ca 2+ oscillations. SOCE may therefore serve as a potential target for new bronchodilators to reduce airway hyper-responsiveness in asthma. Asthma is characterized by airway hyper-responsiveness: the excessive contraction of airway smooth muscle. The extent of this airway contraction is proportional to the frequency of Ca 2+ oscillations within airway smooth muscle cells (ASMCs). Sustained Ca 2+ oscillations require a Ca 2+ influx to replenish Ca 2+ losses across the plasma membrane. Our previous studies implied store-operated calcium entry (SOCE) as the major pathway for this Ca 2+ influx. In the present study, we explore this hypothesis, by examining the effects of SOCE inhibitors (GSK7975A and GSK5498A) as well as L-type voltage-gated Ca 2+ channel inhibitors (nifedipine and nimodipine) on airway contraction and Ca 2+ oscillations and SOCE-mediated Ca 2+ influx in ASMCs within mouse precision-cut lung slices. We found that both GSK7975A and GSK5498A were able to fully relax methacholine-induced airway contraction by abolishing the Ca 2+ oscillations, in a manner similar to that observed in zero extracellular Ca 2+ ([Ca 2+ ] e ). In addition, GSK7975A and GSK5498A inhibited increases in intracellular Ca 2+ ([Ca 2+ ] i ) in ASMCs with depleted Ca 2+ -stores in

Spectrum of resonant plasma oscillations in long Josephson junctions

International Nuclear Information System (INIS)

Holst, T.

1996-01-01

An analysis is presented for the amplitude of the plasma oscillations in the zero-voltage state of a long and narrow Josephson tunnel junction. The calculation is valid for arbitrary normalized junction length and arbitrary bias current. The spectrum of the plasma resonance is found numerically as solutions to an analytical equation. The low-frequency part of the spectrum contains a single resonance, which is known to exist also in the limit of a short and narrow junction. Above a certain cutoff frequency, a series of high-frequency standing wave plasma resonances is excited, a special feature of long Josephson junctions. copyright 1996 The American Physical Society

The slow oscillation in cortical and thalamic networks: mechanisms and functions

Directory of Open Access Journals (Sweden)

Garrett T. Neske

2016-01-01

Full Text Available During even the most quiescent behavioral periods, the cortex and thalamus express rich spontaneous activity in the form of slow (<1 Hz, synchronous network state transitions. Throughout this so-called slow oscillation, cortical and thalamic neurons fluctuate between periods of intense synaptic activity (Up states and almost complete silence (Down states. The two decades since the original characterization of the slow oscillation in the cortex and thalamus have seen considerable advances in deciphering the cellular and network mechanisms associated with this pervasive phenomenon. There are, nevertheless, many questions regarding the slow oscillation that await more thorough illumination, particularly the mechanisms by which Up states initiate and terminate, the functional role of the rhythmic activity cycles in unconscious or minimally conscious states, and the precise relation between Up states and the activated states associated with waking behavior. Given the substantial advances in multineuronal recording and imaging methods in both in vivo and in vitro preparations, the time is ripe to take stock of our current understanding of the slow oscillation and pave the way for future investigations of its mechanisms and functions. My aim in this Review is to provide a comprehensive account of the mechanisms and functions of the slow oscillation, and to suggest avenues for further exploration.

Realization of Current Mode Universal Filter and a Dual-Mode Single Resistance Controlled Quadrature Oscillator Employing VDCC and Only Grounded Passive Elements

Directory of Open Access Journals (Sweden)

Manish Gupta

2017-01-01

Full Text Available The manuscript presents a circuit that can act as a universal filter as well as a single resistence controlled oscillator by unpretentiously changing the switch positions. The circuit employs only two active devices and all grounded passive elements. The utilization of only grounded passive components makes this circuit a better choice for integrated circuit implementation. The current mode biquadratic filter offers all the five basic responses along with independent tunability of its quality factor. The dual-mode quadrature sinusoidal oscillator offers explicit current outputs along with voltage outputs. The circuit also offers a simple and uncoupled condition of oscillation and frequency of oscillation. The typical analysis such as non-ideal, sensitivity and parasitic analysis along with the regular simulation results as well as experimental results are exposed here, to strengthen the design idea.

Time domain oscillating poles: Stability redefined in Memristor based Wien-oscillators

KAUST Repository

Talukdar, Abdul Hafiz Ibne

2012-07-28

Traditionally, the necessary and sufficient condition for any system to be oscillating is that its poles are located on the imaginary (jω) axis. In this paper, for the first time, we have shown that systems can oscillate with time-domain oscillating poles. The idea is verified using a Memristor based Wien oscillator. Sustained oscillations are observed without having the poles of the system fixed on the imaginary axis and the oscillating behavior of the system poles is reported. The oscillating resistance and triangular shape of FFT are also demonstrated with mathematical reasoning and simulation results to support the unusual and surprising characteristics. © 2009 IEEE.

Soft Dielectric Elastomer Oscillators Driving Bioinspired Robots.

Science.gov (United States)

Henke, E-F Markus; Schlatter, Samuel; Anderson, Iain A

2017-12-01

Entirely soft robots with animal-like behavior and integrated artificial nervous systems will open up totally new perspectives and applications. To produce them, we must integrate control and actuation in the same soft structure. Soft actuators (e.g., pneumatic and hydraulic) exist but electronics are hard and stiff and remotely located. We present novel soft, electronics-free dielectric elastomer oscillators, which are able to drive bioinspired robots. As a demonstrator, we present a robot that mimics the crawling motion of the caterpillar, with an integrated artificial nervous system, soft actuators and without any conventional stiff electronic parts. Supplied with an external DC voltage, the robot autonomously generates all signals that are necessary to drive its dielectric elastomer actuators, and it translates an in-plane electromechanical oscillation into a crawling locomotion movement. Therefore, all functional and supporting parts are made of polymer materials and carbon. Besides the basic design of this first electronic-free, biomimetic robot, we present prospects to control the general behavior of such robots. The absence of conventional stiff electronics and the exclusive use of polymeric materials will provide a large step toward real animal-like robots, compliant human machine interfaces, and a new class of distributed, neuron-like internal control for robotic systems.

Controlled X-ray pumping in a wide range of piezo-electric oscillation frequencies

CERN Document Server

Navasardyan, M A; Galoyan, K G

1986-01-01

In case of Laue diffraction the transmitted X-ray reflection in shown to be effectively controllable in the perfect quartz single crystal when it generates ultrasonic oscillations at the resonance frequency or in its vicinity. The maximum effective amplitude of applied sinusoidal oscillations is equal to 70 V. The pumping degree depends on the voltage amplitude. In this work monochromatic K subalpha sub 1 and K subalpha sub 2 molybdenum lines satisfying the thin crystal condition, mu t<=1, are used (mu is the linear absorption coefficient of the sample for the given wavelength and t is its thickness). The radiation was reflected from different planes such as (1011), (1011), (2022) etc. The complete pumping strongly restricts the structural factor possibilities in estimating the intensity of diffracted X-rays in case of considerable deformations in the bulk of perfect single crystal.

Nature's Autonomous Oscillators

Science.gov (United States)

Mayr, H. G.; Yee, J.-H.; Mayr, M.; Schnetzler, R.

2012-01-01

Nonlinearity is required to produce autonomous oscillations without external time dependent source, and an example is the pendulum clock. The escapement mechanism of the clock imparts an impulse for each swing direction, which keeps the pendulum oscillating at the resonance frequency. Among nature's observed autonomous oscillators, examples are the quasi-biennial oscillation and bimonthly oscillation of the Earth atmosphere, and the 22-year solar oscillation. The oscillations have been simulated in numerical models without external time dependent source, and in Section 2 we summarize the results. Specifically, we shall discuss the nonlinearities that are involved in generating the oscillations, and the processes that produce the periodicities. In biology, insects have flight muscles, which function autonomously with wing frequencies that far exceed the animals' neural capacity; Stretch-activation of muscle contraction is the mechanism that produces the high frequency oscillation of insect flight, discussed in Section 3. The same mechanism is also invoked to explain the functioning of the cardiac muscle. In Section 4, we present a tutorial review of the cardio-vascular system, heart anatomy, and muscle cell physiology, leading up to Starling's Law of the Heart, which supports our notion that the human heart is also a nonlinear oscillator. In Section 5, we offer a broad perspective of the tenuous links between the fluid dynamical oscillators and the human heart physiology.

Oscillating heat pipes

CERN Document Server

Ma, Hongbin

2015-01-01

This book presents the fundamental fluid flow and heat transfer principles occurring in oscillating heat pipes and also provides updated developments and recent innovations in research and applications of heat pipes. Starting with fundamental presentation of heat pipes, the focus is on oscillating motions and its heat transfer enhancement in a two-phase heat transfer system. The book covers thermodynamic analysis, interfacial phenomenon, thin film evaporation,  theoretical models of oscillating motion and heat transfer of single phase and two-phase flows, primary  factors affecting oscillating motions and heat transfer,  neutron imaging study of oscillating motions in an oscillating heat pipes, and nanofluid’s effect on the heat transfer performance in oscillating heat pipes.  The importance of thermally-excited oscillating motion combined with phase change heat transfer to a wide variety of applications is emphasized. This book is an essential resource and learning tool for senior undergraduate, gradua...

Power Quality Improvement Using an Enhanced Network-Side-Shunt-Connected Dynamic Voltage Restorer

Science.gov (United States)

Fereidouni, Alireza; Masoum, Mohammad A. S.; Moghbel, Moayed

2015-10-01

Among the four basic dynamic voltage restorer (DVR) topologies, the network-side shunt-connected DVR (NSSC-DVR) has a relatively poor performance and is investigated in this paper. A new configuration is proposed and implemented for NSSC-DVR to enhance its performance in compensating (un)symmetrical deep and long voltage sags and mitigate voltage harmonics. The enhanced NSSC-DVR model includes a three-phase half-bridge semi-controlled network-side-shunt-connected rectifier and a three-phase full-bridge series-connected inverter implemented with a back-to-back configuration through a bidirectional buck-boost converter. The network-side-shunt-connected rectifier is employed to inject/draw the required energy by NSSC-DVR to restore the load voltage to its pre-fault value under sag/swell conditions. The buck-boost converter is responsible for maintaining the DC-link voltage of the series-connected inverter at its designated value in order to improve the NSSC-DVR capability in compensating deep and long voltage sags/swells. The full-bridge series-connected inverter permits to compensate unbalance voltage sags containing zero-sequence component. The harmonic compensation of the load voltage is achieved by extracting harmonics from the distorted network voltage using an artificial neural network (ANN) method called adaptive linear neuron (Adaline) strategy. Detailed simulations are performed by SIMULINK/MATLAB software for six case studies to verify the highly robustness of the proposed NSSC-DVR model under various conditions.

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

Science.gov (United States)

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

2018-04-18

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

Time domain oscillating poles: Stability redefined in Memristor based Wien-oscillators

KAUST Repository

Talukdar, Abdul Hafiz Ibne; Radwan, Ahmed G.; Salama, Khaled N.

2012-01-01

poles. The idea is verified using a Memristor based Wien oscillator. Sustained oscillations are observed without having the poles of the system fixed on the imaginary axis and the oscillating behavior of the system poles is reported. The oscillating

Convective-core Overshoot and Suppression of Oscillations: Constraints from Red Giants in NGC 6811

Energy Technology Data Exchange (ETDEWEB)

Arentoft, T.; Brogaard, K.; Jessen-Hansen, J.; Silva Aguirre, V.; Kjeldsen, H.; Mosumgaard, J. R. [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Sandquist, E. L., E-mail: toar@phys.au.dk [San Diego State University, Department of Astronomy, San Diego, CA 92182 (United States)

2017-04-01

Using data from the NASA spacecraft Kepler , we study solar-like oscillations in red giant stars in the open cluster NGC 6811. We determine oscillation frequencies, frequency separations, period spacings of mixed modes, and mode visibilities for eight cluster giants. The oscillation parameters show that these stars are helium-core-burning red giants. The eight stars form two groups with very different oscillation power spectra; the four stars with the lowest Δ ν values display rich sets of mixed l = 1 modes, while this is not the case for the four stars with higher Δ ν . For the four stars with lowest Δ ν , we determine the asymptotic period spacing of the mixed modes, Δ P , which together with the masses we derive for all eight stars suggest that they belong to the so-called secondary clump. Based on the global oscillation parameters, we present initial theoretical stellar modeling that indicates that we can constrain convective-core overshoot on the main sequence and in the helium-burning phase for these ∼2 M {sub ⊙} stars. Finally, our results indicate less mode suppression than predicted by recent theories for magnetic suppression of certain oscillation modes in red giants.

Stray voltage mitigation

Energy Technology Data Exchange (ETDEWEB)

Jamali, B.; Piercy, R.; Dick, P. [Kinetrics Inc., Toronto, ON (Canada). Transmission and Distribution Technologies

2008-04-09

This report discussed issues related to farm stray voltage and evaluated mitigation strategies and costs for limiting voltage to farms. A 3-phase, 3-wire system with no neutral ground was used throughout North America before the 1930s. Transformers were connected phase to phase without any electrical connection between the primary and secondary sides of the transformers. Distribution voltage levels were then increased and multi-grounded neutral wires were added. The earth now forms a parallel return path for the neutral current that allows part of the neutral current to flow continuously through the earth. The arrangement is responsible for causing stray voltage. Stray voltage causes uneven milk production, increased incidences of mastitis, and can create a reluctance to drink water amongst cows when stray voltages are present. Off-farm sources of stray voltage include phase unbalances, undersized neutral wire, and high resistance splices on the neutral wire. Mitigation strategies for reducing stray voltage include phase balancing; conversion from single to 3-phase; increasing distribution voltage levels, and changing pole configurations. 22 refs., 5 tabs., 13 figs.

One dimension harmonic oscillator

International Nuclear Information System (INIS)

Cohen-Tannoudji, Claude; Diu, Bernard; Laloe, Franck.

1977-01-01

The importance of harmonic oscillator in classical and quantum physics, eigenvalues and eigenstates of hamiltonian operator are discussed. In complement are presented: study of some physical examples of harmonic oscillators; study of stationnary states in the /x> representation; Hermite polynomials; resolution of eigenvalue equation of harmonic oscillator by polynomial method; isotope harmonic oscillator with three dimensions; charged harmonic oscillator in uniform electric field; quasi classical coherent states of harmonic oscillator; eigenmodes of vibration of two coupled harmonic oscillators; vibration modus of a continuous physical system (application to radiation: photons); vibration modus of indefinite linear chain of coupled harmonic oscillators (phonons); one-dimensional harmonic oscillator in thermodynamic equilibrium at temperature T [fr

Regular and irregular patterns of self-localized excitation in arrays of coupled phase oscillators

Energy Technology Data Exchange (ETDEWEB)

Wolfrum, Matthias; Omel' chenko, Oleh E. [Weierstrass Institute, Mohrenstrasse 39, Berlin 10117 (Germany); Sieber, Jan [College of Engineering, Mathematics and Physical Sciences, University of Exeter, North Park Road, Exeter EX4 4QF (United Kingdom)

2015-05-15

We study a system of phase oscillators with nonlocal coupling in a ring that supports self-organized patterns of coherence and incoherence, called chimera states. Introducing a global feedback loop, connecting the phase lag to the order parameter, we can observe chimera states also for systems with a small number of oscillators. Numerical simulations show a huge variety of regular and irregular patterns composed of localized phase slipping events of single oscillators. Using methods of classical finite dimensional chaos and bifurcation theory, we can identify the emergence of chaotic chimera states as a result of transitions to chaos via period doubling cascades, torus breakup, and intermittency. We can explain the observed phenomena by a mechanism of self-modulated excitability in a discrete excitable medium.

Reactor oscillator - I - III, Part I; Reaktorski oscilator - I-III, I Deo

Energy Technology Data Exchange (ETDEWEB)

Lolic, B [Institute of Nuclear Sciences Boris Kidric, Laboratorija za fiziku reaktora, Vinca, Beograd (Serbia and Montenegro)

1961-12-15

Project 'Reactor oscillator' covers the following activities: designing reactor oscillators for reactors RA and RB with detailed engineering drawings; constructing and mounting of the oscillator; designing and constructing the appropriate electronic equipment for the oscillator; measurements at the RA and RB reactors needed for completing the oscillator construction.

Heartbeat of the Southern Oscillation explains ENSO climatic resonances

Science.gov (United States)

Bruun, John T.; Allen, J. Icarus; Smyth, Timothy J.

2017-08-01

records in combination with theoretical models of ENSO. This fundamental result that shows the ENSO phenomenon has a stable tropical Pacific attractor with El Niño and La Niña phases, tropical and extratropical coupling and an intermittency or longer-term form of chaos. We call this attractor the Heartbeat of the Southern Oscillation as the phenomenon is measurable in the Southern Oscillation. We predict future ENSO states based on a stable hysteresis scenario of short-term and long-term ENSO oscillations over the next century.

Stochastic process of pragmatic information for 2D spiral wave turbulence in globally and locally coupled Alief-Panfilov oscillators

Science.gov (United States)

Kuwahara, Jun; Miyata, Hajime; Konno, Hidetoshi

2017-09-01

Recently, complex dynamics of globally coupled oscillators have been attracting many researcher's attentions. In spite of their numerous studies, their features of nonlinear oscillator systems with global and local couplings in two-dimension (2D) are not understood fully. The paper focuses on 2D states of coherent, clustered and chaotic oscillation especially under the effect of negative global coupling (NGC) in 2D Alief-Panfilov model. It is found that the tuning NGC can cause various new coupling-parameter dependency on the features of oscillations. Then quantitative characterization of various states of oscillations (so called spiral wave turbulence) is examined by using the pragmatic information (PI) which have been utilized in analyzing multimode laser, solar activity and neuronal systems. It is demonstrated that the dynamics of the PI for various oscillations can be characterized successfully by the Hyper-Gamma stochastic process.

Krypton excimer laser oscillation by discharge pumping

International Nuclear Information System (INIS)

Shirai, Takahiro; Tabe, Yoshitaka; Kubodera, Shoichi; Sasaki, Wataru; Kawanaka, Junji

2001-01-01

We have demonstrated vacuum ultraviolet (VUV) laser oscillation of the krypton excimer (Kr 2 *) excited by a compact self-sustained discharge device. We have observed a spectral narrowing of the Kr 2 * emission centered at 147.8 nm. A deconvoluted spectral width is 0.5 nm (FWHM), which reveals a contrast to a 13 nm spectral width of the spontaneous emission. The Kr 2 * intensity has increased one order of magnitude when a charging voltage was increased larger than 29 kV. The success of the lasing in the VUV spectral region has been attributed to the success of a stable glow discharge of Kr at 10 atm. The pulse width of the VUV laser radiation is 400 ns (FWHM). The maximum output energy measured is as large as 150 μJ. (author)

Quantum simulations and experiments on Rabi oscillations of spin qubits : Intrinsic vs extrinsic damping

NARCIS (Netherlands)

De Raedt, Hans; Barbara, Bernard; Miyashita, Seiji; Michielsen, Kristel; Bertaina, Sylvain; Gambarelli, Serge

2012-01-01

Electron paramagnetic resonance experiments show that the decay of Rabi oscillations of ensembles of spin qubits depends noticeably on the microwave power, and more precisely on the Rabi frequency, an effect recently called "driven decoherence." By direct numerical solution of the time-dependent

Beta Beams: an accelerator based facility to explore Neutrino oscillation physics

CERN Document Server

Wildner, E; Hansen, C; De Melo Mendonca, T; Stora, T; Payet, J; Chance, A; Zorin, V; Izotov, I; Rasin, S; Sidorov, A; Skalyga, V; De Angelis, G; Prete, G; Cinausero, M; Kravchuk, VL; Gramegna, F; Marchi, T; Collazuol, G; De Rosa, G; Delbar, T; Loiselet, M; Keutgen, T; Mitrofanov, S; Lamy, T; Latrasse, L; Marie-Jeanne, M; Sortais, P; Thuillier, T; Debray, F; Trophime, C; Hass, M; Hirsh, T; Berkovits, D; Stahl, A

2011-01-01

The discovery that the neutrino changes flavor as it travels through space has implications for the Standard Model of particle physics (SM)[1]. To know the contribution of neutrinos to the SM, needs precise measurements of the parameters governing the neutrino oscillations. This will require a high intensity beam-based neutrino oscillation facility. The EURONu Design Study will review three currently accepted methods of realizing this facility (the so-called Super-Beams, Beta Beams and Neutrino Factories) and perform a cost assessment that, coupled with the physics performance, will give means to the European research authorities to make a decision on the layout and construction of the future European neutrino oscillation facility. ”Beta Beams” produce collimated pure electron neutrino and antineutrino beams by accelerating beta active ions to high energies and letting them decay in a race-track shaped storage ring. EURONu Beta Beams are based on CERNs infrastructure and the fact that some of the already ...

Coupled slow and fast surface dynamics in an electrocatalytic oscillator: Model and simulations

International Nuclear Information System (INIS)

Nascimento, Melke A.; Nagao, Raphael; Eiswirth, Markus; Varela, Hamilton

2014-01-01

The co-existence of disparate time scales is pervasive in many systems. In particular for surface reactions, it has been shown that the long-term evolution of the core oscillator is decisively influenced by slow surface changes, such as progressing deactivation. Here we present an in-depth numerical investigation of the coupled slow and fast surface dynamics in an electrocatalytic oscillator. The model consists of four nonlinear coupled ordinary differential equations, investigated over a wide parameter range. Besides the conventional bifurcation analysis, the system was studied by means of high-resolution period and Lyapunov diagrams. It was observed that the bifurcation diagram changes considerably as the irreversible surface poisoning evolves, and the oscillatory region shrinks. The qualitative dynamics changes accordingly and the chaotic oscillations are dramatically suppressed. Nevertheless, periodic cascades are preserved in a confined region of the resistance vs. voltage diagram. Numerical results are compared to experiments published earlier and the latter reinterpreted. Finally, the comprehensive description of the time-evolution in the period and Lyapunov diagrams suggests further experimental studies correlating the evolution of the system's dynamics with changes of the catalyst structure

Reliability of supply of switchgear for auxiliary low voltage in substations extra high voltage to high voltage

Directory of Open Access Journals (Sweden)

Perić Dragoslav M.

2015-01-01

Full Text Available Switchgear for auxiliary low voltage in substations (SS of extra high voltages (EHV to high voltage (HV - SS EHV/HV kV/kV is of special interest for the functioning of these important SS, as it provides a supply for system of protection and other vital functions of SS. The article addresses several characteristic examples involving MV lines with varying degrees of independence of their supply, and the possible application of direct transformation EHV/LV through special voltage transformers. Auxiliary sources such as inverters and diesel generators, which have limited power and expensive energy, are also used for the supply of switchgear for auxiliary low voltage. Corresponding reliability indices are calculated for all examples including mean expected annual engagement of diesel generators. The applicability of certain solutions of switchgear for auxiliary low voltage SS EHV/HV, taking into account their reliability, feasibility and cost-effectiveness is analyzed too. In particular, the analysis of applications of direct transformation EHV/LV for supply of switchgear for auxiliary low voltage, for both new and existing SS EHV/HV.

Charge-pump voltage converter

Science.gov (United States)

Brainard, John P [Albuquerque, NM; Christenson, Todd R [Albuquerque, NM

2009-11-03

A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

Oscillator monitor

International Nuclear Information System (INIS)

McNeill, G.A.

1981-01-01

Present high-speed data acquisition systems in nuclear diagnostics use high-frequency oscillators to provide timing references for signals recorded on fast, traveling-wave oscilloscopes. An oscillator's sinusoidal wave shape is superimposed on the recorded signal with each cycle representing a fixed time increment. During data analysis the sinusoid is stripped from the signal, leaving a clean signal shape with known timing. Since all signal/time relationships are totally dependant upon working oscillators, these critical devices must have remote verification of proper operation. This manual presents the newly-developed oscillator monitor which will provide the required verification

Zeta functions for the spectrum of the non-commutative harmonic oscillators

CERN Document Server

Ichinose, T

2004-01-01

This paper investigates the spectral zeta function of the non-commutative harmonic oscillator studied in \\cite{PW1, 2}. It is shown, as one of the basic analytic properties, that the spectral zeta function is extended to a meromorphic function in the whole complex plane with a simple pole at $s=1$, and further that it has a zero at all non-positive even integers, i.e. at $s=0$ and at those negative even integers where the Riemann zeta function has the so-called trivial zeros. As a by-product of the study, both the upper and the lower bounds are also given for the first eigenvalue of the non-commutative harmonic oscillator.

High voltage systems

International Nuclear Information System (INIS)

Martin, M.

1991-01-01

Industrial processes usually require electrical power. This power is used to drive motors, to heat materials, or in electrochemical processes. Often the power requirements of a plant require the electric power to be delivered at high voltage. In this paper high voltage is considered any voltage over 600 V. This voltage could be as high as 138,000 V for some very large facilities. The characteristics of this voltage and the enormous amounts of power being transmitted necessitate special safety considerations. Safety must be considered during the four activities associated with a high voltage electrical system. These activities are: Design; Installation; Operation; and Maintenance

Piezoelectric transformers for low-voltage generation of gas discharges and ionic winds in atmospheric air

Energy Technology Data Exchange (ETDEWEB)

Johnson, Michael J. [Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indianapolis 46556 (United States); Go, David B., E-mail: dgo@nd.edu [Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indianapolis 46556 (United States); Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indianapolis 46556 (United States)

2015-12-28

To generate a gas discharge (plasma) in atmospheric air requires an electric field that exceeds the breakdown threshold of ∼30 kV/cm. Because of safety, size, or cost constraints, the large applied voltages required to generate such fields are often prohibitive for portable applications. In this work, piezoelectric transformers are used to amplify a low input applied voltage (<30 V) to generate breakdown in air without the need for conventional high-voltage electrical equipment. Piezoelectric transformers (PTs) use their inherent electromechanical resonance to produce a voltage amplification, such that the surface of the piezoelectric exhibits a large surface voltage that can generate corona-like discharges on its corners or on adjacent electrodes. In the proper configuration, these discharges can be used to generate a bulk air flow called an ionic wind. In this work, PT-driven discharges are characterized by measuring the discharge current and the velocity of the induced ionic wind with ionic winds generated using input voltages as low as 7 V. The characteristics of the discharge change as the input voltage increases; this modifies the resonance of the system and subsequent required operating parameters.

Random-phase approximation and its extension for the O(2) anharmonic oscillator

International Nuclear Information System (INIS)

Aouissat, Z.; Martin, C.

2004-01-01

We apply the random-phase approximation (RPA) and its extension called renormalized RPA to the quantum anharmonic oscillator with an O(2) symmetry. We first obtain the equation for the RPA frequencies in the standard and in the renormalized RPAs using the equation-of-motion method. In the case where the ground state has a broken symmetry, we check the existence of a zero frequency in the standard and in the renormalized RPAs. Then we use a time-dependent approach where the standard-RPA frequencies are obtained as small oscillations around the static solution in the time-dependent Hartree-Bogolyubov equation. We draw the parallel between the two approaches. (orig.)

Random-phase approximation and its extension for the O(2) anharmonic oscillator

Energy Technology Data Exchange (ETDEWEB)

Aouissat, Z. [Institut fuer Kernphysik, Technische Hochschule Darmstadt, Schlossgarten 9, D-64289, Darmstadt (Germany); Martin, C. [Groupe de Physique Theorique, Institut de Physique Nucleaire, F-91406, Orsay Cedex (France)

2004-02-01

We apply the random-phase approximation (RPA) and its extension called renormalized RPA to the quantum anharmonic oscillator with an O(2) symmetry. We first obtain the equation for the RPA frequencies in the standard and in the renormalized RPAs using the equation-of-motion method. In the case where the ground state has a broken symmetry, we check the existence of a zero frequency in the standard and in the renormalized RPAs. Then we use a time-dependent approach where the standard-RPA frequencies are obtained as small oscillations around the static solution in the time-dependent Hartree-Bogolyubov equation. We draw the parallel between the two approaches. (orig.)

Power oscillation damping controller

DEFF Research Database (Denmark)

2012-01-01

A power oscillation damping controller is provided for a power generation device such as a wind turbine device. The power oscillation damping controller receives an oscillation indicating signal indicative of a power oscillation in an electricity network and provides an oscillation damping control...

Simulation Model solves exact the Enigma named Generating high Voltages and high Frequencies by Tesla Coil

OpenAIRE

Simo Janjanin

2016-01-01

Simulation model of Tesla coil has been successfully completed, and has been verified the procedure and functioning. The literature and documentation for the model were taken from the rich sources, especially the copies of Tesla patents. The oscillating system‟s electrical scheme consists of the voltage supply 220/50 Hz, Fe transformer, capacitor and belonging chosen electrical components, the air gap in the primary Tesla coil (air transformer) and spark gap in the exit of the coil. The inves...

Quantum oscillations and the electronic transport properties in multichain nanorings

International Nuclear Information System (INIS)

Racolta, D.

2009-01-01

We consider a system of multichain nanorings in static electric and magnetic field. The magnetic field induces characteristic phase changes. These phase shifts produce interference phenomena in the case of nanosystems for which the coherence length is larger than the sample dimension. We obtain energy solutions that are dependent on the number of sites N α characterizing a chain, of phase on the phase φ α and on the applied voltage. We found rich oscillations structures exhibited by the magnetic flux and we established the transmission probability. This proceeds by applying Landauer conductance formulae which opens the way to study electronic transport properties. (authors)

Oscillators - a simple introduction

DEFF Research Database (Denmark)

Lindberg, Erik

2013-01-01

Oscillators are kernel components of electrical and electronic circuits. Discussion of history, mechanisms and design based on Barkhausens observation. Discussion of a Wien Bridge oscillator based on the question: Why does this circuit oscillate ?......Oscillators are kernel components of electrical and electronic circuits. Discussion of history, mechanisms and design based on Barkhausens observation. Discussion of a Wien Bridge oscillator based on the question: Why does this circuit oscillate ?...

Low-Energy Real-Time OS Using Voltage Scheduling Algorithm for Variable Voltage Processors

OpenAIRE

Okuma, Takanori; Yasuura, Hiroto

2001-01-01

This paper presents a real-time OS based on $ mu $ITRON using proposed voltage scheduling algorithm for variable voltage processors which can vary supply voltage dynamically. The proposed voltage scheduling algorithms assign voltage level for each task dynamically in order to minimize energy consumption under timing constraints. Using the presented real-time OS, running tasks with low supply voltage leads to drastic energy reduction. In addition, the presented voltage scheduling algorithm is ...

Calculation of xenon-oscillations in the HPLWR

International Nuclear Information System (INIS)

Reiss, T.; Feher, S.; Czifrus, Sz.

2009-01-01

The European version of the Supercritical Water Cooled Reactor (SCWR) is being developed under the name High Performance Light Water Reactor (HPLWR). In the most recent design, a three-pass core is foreseen with a heat-up of the coolant (supercritical pressure water) from 280degC to 500degC. Due to the operating pressure of 25 MPa, there is no phase change in the core but the density drop of the coolant can be as high as one order of magnitude. This results in a system which is sensitive to local temperature, power and density oscillations. This attribute is enhanced by the pseudocritical transformation of supercritical pressure water. Due to the relatively large dimensions of the core, xenon-oscillations are probable. The characteristic time of this process is several hours, thus a coupled quasi-stationary neutronics-thermohydraulics (CQNT) code completed with the xenon poisoning differential equations (XPDE) can predict the extent of xenon-oscillations. A program system is being developed at the Budapest University of Technology which is capable to perform full core CQNT calculations including the XPDE. The program system is designed to calculate one-pass (which was the first core proposal for HPLWRs, today called PWR-SC) and three-pass cores. The CQNT code is made up of an MCNP part (neutronics part) and of a thermohydraulics part developed at our Institute. Since full core MCNP calculations are very time consuming, upon symmetry considerations only one eighth of the core is modelled. On the other hand, this approach of modelling momentarily limits the phenomena which can be studied to axial oscillations. (author)

Call Forecasting for Inbound Call Center

Directory of Open Access Journals (Sweden)

Peter Vinje

2009-01-01

Full Text Available In a scenario of inbound call center customer service, the ability to forecast calls is a key element and advantage. By forecasting the correct number of calls a company can predict staffing needs, meet service level requirements, improve customer satisfaction, and benefit from many other optimizations. This project will show how elementary statistics can be used to predict calls for a specific company, forecast the rate at which calls are increasing/decreasing, and determine if the calls may stop at some point.

Method and split cavity oscillator/modulator to generate pulsed particle beams and electromagnetic fields

Science.gov (United States)

Clark, M. Collins; Coleman, P. Dale; Marder, Barry M.

1993-01-01

A compact device called the split cavity modulator whose self-generated oscillating electromagnetic field converts a steady particle beam into a modulated particle beam. The particle beam experiences both signs of the oscillating electric field during the transit through the split cavity modulator. The modulated particle beam can then be used to generate microwaves at that frequency and through the use of extractors, high efficiency extraction of microwave power is enabled. The modulated beam and the microwave frequency can be varied by the placement of resistive wires at nodes of oscillation within the cavity. The short beam travel length through the cavity permit higher currents because both space charge and pinching limitations are reduced. The need for an applied magnetic field to control the beam has been eliminated.

A New Control Structure for Multi-Terminal dc Grids to Damp Inter-Area Oscillations

DEFF Research Database (Denmark)

Eriksson, Robert

2014-01-01

This article analyzes the control structure of the multi-terminal dc (MTDC) system to damp ac system interarea oscillations through active power modulation. A new control structure is presented that maximizes the relative controllability without the need for communication among the dc terminals....... In point-to-point high voltage dc (HVDC) transmission, the active power modulation of the two terminals occurs in opposite directions. In this case the control direction is given and only needs to be phase compensated to align for maximal damping. In the case of MTDC systems the control direction...... interrelates with the active power modulation share of the dc terminals and the relative controllability depends on this. The new control structure eliminates the need of communication between the dc terminals by performing dc voltage feedback loop shaping. This makes it possible to modulate the power in one...

Study of λφ4 theory in the coupled independent double-oscillator approximation

International Nuclear Information System (INIS)

Bray, H.; Stevenson, P.M.

1992-01-01

A scalar field can be viewed as an infinite set of coupled oscillators, one at each lattice point in space, as the lattice spacing goes to zero. Λφ 4 theory considers the case when each oscillator is given a potential of the form V(φ) = 1/2m 2 φ 2 + λφ 4 . The question the authors wish to investigate is whether or not such a potential can cause spontaneous symmetry breaking. They approach this problem by defining an open-quotes effective potentialclose quotes which takes into account the quantum effects of the oscillators. This is useful because a double well effective potential would imply spontaneous symmetry breaking. They consider a variational calculation with a trial wavefunctional that is a product of independent double-oscillator wavefunctions. Each double-oscillator wavefunction is defined to be the sum of two Gaussians with the same widths, centered around φ o . They then define the effective potential at φ o to be the energy density resulting from this variational calculation, where the separation and the width of the Gaussians are the parameters which are allowed to vary. They call this the open-quotes Coupled Independent Double-Oscillator Approximation.close quotes The goal of this research is to compute this effective potential, renormalize the variables, and to gain additional insight into whether or not spontaneous symmetry breaking occurs

A voltage biased superconducting quantum interference device bootstrap circuit

International Nuclear Information System (INIS)

Xie Xiaoming; Wang Huiwu; Wang Yongliang; Dong Hui; Jiang Mianheng; Zhang Yi; Krause, Hans-Joachim; Braginski, Alex I; Offenhaeusser, Andreas; Mueck, Michael

2010-01-01

We present a dc superconducting quantum interference device (SQUID) readout circuit operating in the voltage bias mode and called a SQUID bootstrap circuit (SBC). The SBC is an alternative implementation of two existing methods for suppression of room-temperature amplifier noise: additional voltage feedback and current feedback. Two circuit branches are connected in parallel. In the dc SQUID branch, an inductively coupled coil connected in series provides the bias current feedback for enhancing the flux-to-current coefficient. The circuit branch parallel to the dc SQUID branch contains an inductively coupled voltage feedback coil with a shunt resistor in series for suppressing the preamplifier noise current by increasing the dynamic resistance. We show that the SBC effectively reduces the preamplifier noise to below the SQUID intrinsic noise. For a helium-cooled planar SQUID magnetometer with a SQUID inductance of 350 pH, a flux noise of about 3 μΦ 0 Hz -1/2 and a magnetic field resolution of less than 3 fT Hz -1/2 were obtained. The SBC leads to a convenient direct readout electronics for a dc SQUID with a wider adjustment tolerance than other feedback schemes.

Restoration of oscillation in network of oscillators in presence of direct and indirect interactions

Energy Technology Data Exchange (ETDEWEB)

Majhi, Soumen; Bera, Bidesh K. [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata-700108 (India); Bhowmick, Sourav K. [Department of Electronics, Asutosh College, Kolkata-700026 (India); Ghosh, Dibakar, E-mail: diba.ghosh@gmail.com [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata-700108 (India)

2016-10-23

The suppression of oscillations in coupled systems may lead to several unwanted situations, which requires a suitable treatment to overcome the suppression. In this paper, we show that the environmental coupling in the presence of direct interaction, which can suppress oscillation even in a network of identical oscillators, can be modified by introducing a feedback factor in the coupling scheme in order to restore the oscillation. We inspect how the introduction of the feedback factor helps to resurrect oscillation from various kinds of death states. We numerically verify the resurrection of oscillations for two paradigmatic limit cycle systems, namely Landau–Stuart and Van der Pol oscillators and also in generic chaotic Lorenz oscillator. We also study the effect of parameter mismatch in the process of restoring oscillation for coupled oscillators. - Highlights: • Amplitude death is observed using direct and indirect coupling. • Revival of oscillation using feedback parameter is discussed. • Restoration of oscillation is observed in limit cycle and chaotic systems.

Proportional-Resonant Control of Doubly-Fed Induction Generator Wind Turbines for Low-Voltage Ride-Through Enhancement

Directory of Open Access Journals (Sweden)

Zhan-Feng Song

2012-11-01

Full Text Available A novel control strategy is proposed in this paper for the rotor side converter (RSC of doubly-fed induction generator (DFIG-based wind power generation systems. It is supposed to enhance the low-voltage ride-through (LVRT capability of DFIGs during great-level grid voltage dips. The strategy consists of a proportional-resonant (PR controller and auxiliary PR controllers. The auxiliary controllers compensate the output voltage of the RSC in case of grid faults, thus limiting the rotor inrush current of DFIG and meeting the requirements of LVRT. Sequential-component decompositions of current are not required in the control system to improve the response of system. Since the resonant compensator is a double-side integrator, the auxiliary controllers can be simplified through coordinate transformation. The feasibility of the control strategy is validated by simulation on a 1.5 MW wind-turbine driven DFIG system. The impact of the RSC converter voltage rating on the LVRT capability of DFIG is investigated. Meanwhile, the influence of angular frequency detection and control parameters are also discussed. Compared with traditional vector control schemes based on PI current controllers, the presented control strategy effectively suppress rotor current and reduce oscillations of DFIG power and torque under grid faults.

Spectrum analysis of a voltage source converter due to semiconductor voltage drops

DEFF Research Database (Denmark)

Rasmussen, Tonny Wederberg; Eltouki, Mustafa

2017-01-01

It is known that power electronic voltage source converters are non-ideal. This paper presents a state-of-the-art review on the effect of semiconductor voltage drop on the output voltage spectrum, using single-phase H-bridge two-level converter topology with natural sampled pulse width modulation....... The paper describes the analysis of output voltage spectrum, when the semiconductor voltage drop is added. The results of the analysis of the spectral contribution including and excluding semiconductor voltage drop reveal a good agreement between the theoretical results, simulations and laboratory...

Voltage Regulation Using a Permanent Magnet Synchronous Generator with a Series Compensator: Preprint

Energy Technology Data Exchange (ETDEWEB)

Hsu, Ping; Wu, Ziping; Muljadi, Eduard; Gao, Wenzhong

2015-08-24

A wind power plant (WPP) is often operated at unity power factor, and the utility host where the WPP connects prefers to regulate the voltage. Although this may not be an issue in a stiff grid, the connection to a weak grid can be a problematic. This paper explores the advantages of having voltage regulation capability via reactive power control. Another issue in wind power generation is that not all turbines are able to control their reactive power due to technical reasons or contractual obligations. A synchronous condenser (SC) using a permanent magnet synchronous generator (PMSG) is proposed to provide necessary reactive power for regulating voltage at a weak grid connection. A PMSG has the advantage of higher efficiency and reliability. Because of its lack of a field winding, a PMSG is typically controlled by a full-power converter, which can be costly. In the proposed system, the reactive power of the SC is controlled by a serially connected compensator operating in a closed-loop configuration. The compensator also damps the PMSG’s tendency to oscillate. The compensator’s VA rating is only a fraction of the rating of the SC and the PMSG. In this initial investigation, the proposed scheme is shown to be effective by computer simulations.

Study of protection devices against the effects of electric discharges inside a very high voltage generator: the Vivitron accelerator

International Nuclear Information System (INIS)

Nolot, E.

1996-01-01

The Vivitron tandem is a large electrostatic accelerator comprising a Van de Graaff generator designed to reach terminal voltages of around 30 MV. The machine is limited at rather lower nominal voltages (about 20 MV) due to the sensitivity of the insulating column structure to transient overvoltages. These are induced by electrical discharges in compressed SF 6 . This thesis first aims at analysing the fundamental reasons of electrical discharges in order to limit the probability of their occurrence. Then we simulate the transient overvoltages induced and present some improvements which may lead to a stable behaviour of the Vivitron at nominal voltages higher than 20 MV. Initially we deduce discharge onset voltages and actual breakdown field limitations in the different gap geometries from analysis of possible breakdown mechanisms in compressed SF 6 . In a second part, some electrical characteristics of the insulating column structure are measured at high voltage. Fast rising oscillating waves induced by sparking in the Vivitron, along with the associated energies,are determined in the third part. The last part deals with new surge protections of the insulating column structure. Spark gaps with precise onset voltage and optimized shielding electrodes are discussed. ZnO-based varistors designed for operation at very high fields have also been developed in order to reduce transient overvoltage values. (author)

Oscillations of void lattices

International Nuclear Information System (INIS)

Akhiezer, A.I.; Davydov, L.N.; Spol'nik, Z.A.

1976-01-01

Oscillations of a nonideal crystal are studied, in which macroscopic defects (pores) form a hyperlattice. It is shown that alongside with acoustic and optical phonons (relative to the hyperlattice), in such a crystal oscillations of the third type are possible which are a hydridization of sound oscillations of atoms and surface oscillations of a pore. Oscillation spectra of all three types were obtained

Prediction of femtosecond oscillations in the transient current of a quantum dot in the Kondo regime

KAUST Repository

Goker, A.

2010-10-11

We invoke the time-dependent noncrossing approximation in order to study the effects of the density of states of gold contacts on the instantaneous conductance of a single electron transistor which is abruptly moved into the Kondo regime by means of a gate voltage. For an asymmetrically coupled system, we observe that the instantaneous conductance in the Kondo time scale exhibits beating with distinct frequencies, which are proportional to the separation between the Fermi level and the sharp features in the density of states of gold. Increasing the ambient temperature or bias quenches the amplitude of the oscillations. We attribute the oscillations to interference between the emerging Kondo resonance and van-Hove singularities in the density of state. In addition, we propose an experimental realization of this model.

Fundamental characteristics of heat conduction enhancement in oscillating viscous flow-dream pipe

International Nuclear Information System (INIS)

Katsuta, M.; Nagata, K.; Maruyama, Y.; Tsujimori, A.

1991-01-01

This paper reports that to confirm the heat conduction augmentation technique via sinusoidal oscillation experimentally and to establish a fundamental data base of this device, systematic measurements using almost identically scaled with Kurzweg's apparatus for demonstration were conducted. In this heat exchanger, the fluid occupied a capillary tube or its bundle that connected two reservoirs at different temperature; a special constructed oscillation driving unit generated a pulsed motion of working fluid. Operation took place at various tube diameters, oscillated frequency and stroke using pure water and ethanol as working liquid. As a result, a new factor so-called heat transport coefficient which indicates the heat transfer rate multiplying temperature gradient between hot and cold reservoir was introduced. This factor increased with increasing oscillated frequency and stroke, however, beyond a critical frequency, this trend disappeared. Using modified Reynolds number and stroke ratio, a new empirical formula which correlated the data regardless of the difference of working liquid was proposed. A discussion of tube bundle was also made using this correlation. Finally, an attempt was performed to correlate the data using effective thermal diffusivity predicted by simple lumped capacitance analysis and characteristic period

Nonlinear Analysis of Ring Oscillator and Cross-Coupled Oscillator Circuits

KAUST Repository

Ge, Xiaoqing

2010-12-01

Hassan Khalil’s research results and beautifully written textbook on nonlinear systems have influenced generations of researchers, including the authors of this paper. Using nonlinear systems techniques, this paper analyzes ring oscillator and cross-coupled oscillator circuits, which are essential building blocks in digital systems. The paper first investigates local and global stability properties of an n-stage ring oscillator by making use of its cyclic structure. It next studies global stability properties of a class of cross-coupled oscillators which admit the representation of a dynamic system in feedback with a static nonlinearity, and presents su cient conditions for almost global convergence of the solutions to a limit cycle when the feedback gain is in the vicinity of a bifurcation point. The result are also extended to the synchronization of interconnected identical oscillator circuits.

Nonlinear Analysis of Ring Oscillator and Cross-Coupled Oscillator Circuits

KAUST Repository

Ge, Xiaoqing; Arcak, Murat; Salama, Khaled N.

2010-01-01

Hassan Khalil’s research results and beautifully written textbook on nonlinear systems have influenced generations of researchers, including the authors of this paper. Using nonlinear systems techniques, this paper analyzes ring oscillator and cross-coupled oscillator circuits, which are essential building blocks in digital systems. The paper first investigates local and global stability properties of an n-stage ring oscillator by making use of its cyclic structure. It next studies global stability properties of a class of cross-coupled oscillators which admit the representation of a dynamic system in feedback with a static nonlinearity, and presents su cient conditions for almost global convergence of the solutions to a limit cycle when the feedback gain is in the vicinity of a bifurcation point. The result are also extended to the synchronization of interconnected identical oscillator circuits.

The effect of external visible light on the breakdown voltage of a long discharge tube

Science.gov (United States)

Shishpanov, A. I.; Ionikh, Yu. Z.; Meshchanov, A. V.

2016-06-01

The breakdown characteristics of a discharge tube with a configuration typical of gas-discharge light sources and electric-discharge lasers (a so-called "long discharge tube") filled with argon or helium at a pressure of 1 Torr have been investigated. A breakdown has been implemented using positive and negative voltage pulses with a linear leading edge having a slope dU/ dt ~ 10-107 V/s. Visible light from an external source (halogen incandescent lamp) is found to affect the breakdown characteristics. The dependences of the dynamic breakdown voltage of the tube on dU/ dt and on the incident light intensity are measured. The breakdown voltage is found to decrease under irradiation of the high-voltage anode of the tube in a wide range of dU/ dt. A dependence of the effect magnitude on the light intensity and spectrum is obtained. Possible physical mechanisms of this phenomenon are discussed.

Sticky orbits in a kicked-oscillator model

CERN Document Server

Lowenstein, J H; Vivaldi, F

2005-01-01

We study a 4-fold symmetric kicked-oscillator map with sawtooth kick function. For the values of the kick amplitude $\\lambda=2\\cos(2\\pi p/q)$ with rational $p/q$, the dynamics is known to be pseudochaotic, with no stochastic web of non-zero Lebesgue measure. We show that this system can be represented as a piecewise affine map of the unit square ---the so-called local map--- driving a lattice map. We develop a framework for the study of long-time behaviour of the orbits, in the case in which the local map features exact scaling. We apply this method to several quadratic irrational values of $\\lambda$, for which the local map possesses a full Legesgue measure of periodic orbits; these are promoted to either periodic orbits or accelerator modes of the kicked-oscillator map. By constrast, the aperiodic orbits of the local map can generate various asymptotic behaviours. For some parameter values the orbits remain bounded, while others have excursions which grow logarithmically or as a power of the time. In the po...

Optimizing of verification photographs by using the so-called tangential field technique

International Nuclear Information System (INIS)

Proske, H.; Merte, H.; Kratz, H.

1991-01-01

When irradiating under high voltage condition, verification photographs prove to be difficult to take if the Gantry position is not aligned to 0deg respectively 180deg, since the patient is being irradiated diagonally. Under these conditions it is extremely difficult to align the X-ray-cartridge vertically to the central beam of the therapeutic radiation. This results in, amongst others, misprojections, so that definite dimensions of portrayed organ structures become practical impossible to determine. This paper describes how we have solved these problems on our high voltage units (tele-gamma cobalt unit and linear-accelerator). By using simple accessories, determination of dimensions of organ structures, as shown on the verification photographs, are made possible. We illustrate our method by using the so-called tangential fields technique when irradiating mamma carcinoma. (orig.) [de

Self-oscillation in spin torque oscillator stabilized by field-like torque

International Nuclear Information System (INIS)

Taniguchi, Tomohiro; Tsunegi, Sumito; Kubota, Hitoshi; Imamura, Hiroshi

2014-01-01

The effect of the field-like torque on the self-oscillation of the magnetization in spin torque oscillator with a perpendicularly magnetized free layer was studied theoretically. A stable self-oscillation at zero field is excited for negative β while the magnetization dynamics stops for β = 0 or β > 0, where β is the ratio between the spin torque and the field-like torque. The reason why only the negative β induces the self-oscillation was explained from the view point of the energy balance between the spin torque and the damping. The oscillation power and frequency for various β were also studied by numerical simulation

Conservative Chaos Generators with CCII+ Based on Mathematical Model of Nonlinear Oscillator

Directory of Open Access Journals (Sweden)

J. Slezak

2008-09-01

Full Text Available In this detailed paper, several novel oscillator's configurations which consist only of five positive second generation current conveyors (CCII+ are presented and experimentally verified. Each network is able to generate the conservative chaotic attractors with the certain degree of the structural stability. It represents a class of the autonomous deterministic dynamical systems with two-segment piecewise linear (PWL vector fields suitable also for the theoretical analysis. Route to chaos can be traced and observed by a simple change of the external dc voltage. Advantages and other possible improvements are briefly discussed in the text.

Voltage surges induced in transformer secondaries with loads characterized by sensitive electronic equipment

Energy Technology Data Exchange (ETDEWEB)

Cogo, Joao Roberto [GSI Engenharia e Consultoria Ltda., Taubate, SP (Brazil)], Email: gsi@gsiconsultoria.com.br; Dommel, Hermann Wilhelm [University of British Columbia, Vancouver (Canada)], Email: hermannd@ece.ubc.ca

2007-07-01

The grounding of sensitive electronic equipment such as computers, programmable logic controllers (PLC), process control systems, and other electronic equipment is one of the most important considerations towards obtaining an efficient operation of such systems. Such equipment, which for the purposes of this work is called 'Sensitive Electronic Equipment - SEE' is very sensitive to faults and low intensity random voltages which have no effect upon the electrical power equipment and upon human beings. In this work, the grounding problem is evaluated, to guide the user on the proper installation of SEEs, so as to prevent them from being damaged. The following items will be discussed: voltages which SEEs are subject to during incidence of atmospheric surges in the distribution overhead lines to which they are connected; sustained voltage that the high voltage supply of SEEs must be able to withstand during line-to-ground faults that originate from atmospheric surges that reach the transmission lines which are connected to the electrical power self producers (or electrical power independent producers). (author)

Combustion-Driven Oscillation in Process Heaters

Energy Technology Data Exchange (ETDEWEB)

Seebold, J.G. [Chevron Corporation (Retired), 198 James Avenue, Atherton, CA 94027 (United States)

2005-10-15

At this moment in thousands of process heaters all over the world there are, to borrow a phrase from the late Carl Sagan, 'billions and billions' of Btu/hr beneficially being released entirely free of pulsation. On those few occasions, perhaps a dozen and a half in my career, when I would get the inevitable 'Why me?' call, I have generally responsed with something like, 'Consider yourself lucky, you have a rare scientific curiosity on your hands'. Reflecting on the solutions ultimately found, I'm reminded that many years ago my friend Abbott Putnam shared with me an early AGA (American Gas Association) field-service bulletin that included a prescription for eliminating combustion-driven oscillations in home heating units; viz., 'Drill a hole; if that doesn't work, drill another hole' or words to that effect. Many times have I wished that I still had a copy of that bulletin and in this paper we will have occasion, once again, to reflect upon the value of that advice. In this paper we will discuss an instance that arose in a pioneering installation of a breakthrough development of 'extremely', to distinguish it from 'ultra', low-NOx lean premix burner technology. We will illustrate how, when and under what circumstances combustion-driven oscillation can arise; we will touch on the many alternatives for its elimination that were considered and investigated; and we will discuss three practical alternatives for eliminating combustion-driven oscillations.

Oscillations of non-isothermal N/S boundary with a high frequency and large amplitude

International Nuclear Information System (INIS)

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

2016-01-01

Within the framework of the phenomenological approach based on the heat balance equation and the dependence of the critical temperature of the superconductor on the current value theoretically investigated the impact of high-frequency current of high amplitude and arbitrary shape on the non-isothermal balance of the oscillating N/S interface in a long superconductor. We introduce a self-consistent average temperature field of rapidly oscillating non-isothermal N/S boundary (heat kink), which allows to go beyond the well-known concept of mean-square heating and consider the impact of current waveform. With regard to experiments on the effects of microwave high-power radiation on the current-voltage characteristics (CVC) of superconducting films, we give the classification of the families of the CVC for inhomogeneous superconductors which carry a current containing a high frequency component of large amplitude. Several characteristics have hysteresis of thermal nature.

Multifunction Voltage-Mode Filter Using Single Voltage Differencing Differential Difference Amplifier

Directory of Open Access Journals (Sweden)

Chaichana Amornchai

2017-01-01

Full Text Available In this paper, a voltage mode multifunction filter based on single voltage differencing differential difference amplifier (VDDDA is presented. The proposed filter with three input voltages and single output voltage is constructed with single VDDDA, two capacitors and two resistors. Its quality factor can be adjusted without affecting natural frequency. Also, the natural frequency can be electronically tuned via adjusting of bias current. The filter can offer five output responses, high-pas (HP, band-pass (BP, band-reject (BR, low-pass (LP and all-ass (AP functions in the same circuit topology. The output response can be selected by choosing the suitable input voltage without the component matching condition and the requirement of additional double gain voltage amplifier. PSpice simulation results to confirm an operation of the proposed filter correspond to the theory.

Modeling of the CIGRE Low Voltage Test Distribution Network and the Development of Appropriate Controllers

DEFF Research Database (Denmark)

Mustafa, Ghullam; Bak-Jensen, Birgitte; Mahat, Pukar

2013-01-01

The fluctuating nature of some of the Distributed Generation (DG) sources can cause power quality related problems like power frequency oscillations, voltage fluctuations etc. In future, the DG penetration is expected to increase and hence this requires some control actions to deal with the power...... controller. The control system is tested in the distribution test network set up by CIGRE. The new approach of the PV controller is done in such a way that it can control AC and DC voltage of the PV converter during dynamic conditions. The battery controller is also developed in such a way that it can...... quality issues. The main focus of this paper is on development of controllers for a distribution system with different DG’s and especially development of a Photovoltaic (PV) controller using a Static Compensator (STATCOM) controller and on modeling of a Battery Storage System (BSS) also based on a STATCOM...

Instability and electrical response of small laminar coflow diffusion flames under AC electric fields: Toroidal vortex formation and oscillating and spinning flames

KAUST Repository

Xiong, Yuan; Chung, Suk-Ho; Cha, Min

2016-01-01

Dynamical and electrical responses of a small coflow diffusion flame were investigated by applying a high-voltage alternating current (AC), to a fuel jet nozzle. High-speed imaging and electrical diagnostics were adopted to capture flame dynamics and electrical signals, such as voltage (V ), frequency (f ) and current (I ). In the V -f domain of 0-5kV and 0-5kHz, AC-driven instabilities, resulting in various flame modes such as an oscillation, pinch-off and spinning of flames were identified. Characteristic frequency of each mode was determined and a visualization of near-nozzle flow structures suggested a close causality of initial counter-rotating vortices (inner and outer toroidal vortices - ITV and OTV), to the other observed flame. An axisymmetric ITV shedding was identified within oscillating and pinch-off modes, while asymmetric ITV shedding was identified with the spinning mode. Integrated electric power over several AC periods correlated well with variation in the flame surface area for these instabilities, demonstrating that measured electric power is a potential indicator of combustion instabilities in electric-field-assisted combustion.

Instability and electrical response of small laminar coflow diffusion flames under AC electric fields: Toroidal vortex formation and oscillating and spinning flames

KAUST Repository

Xiong, Yuan

2016-06-24

Dynamical and electrical responses of a small coflow diffusion flame were investigated by applying a high-voltage alternating current (AC), to a fuel jet nozzle. High-speed imaging and electrical diagnostics were adopted to capture flame dynamics and electrical signals, such as voltage (V ), frequency (f ) and current (I ). In the V -f domain of 0-5kV and 0-5kHz, AC-driven instabilities, resulting in various flame modes such as an oscillation, pinch-off and spinning of flames were identified. Characteristic frequency of each mode was determined and a visualization of near-nozzle flow structures suggested a close causality of initial counter-rotating vortices (inner and outer toroidal vortices - ITV and OTV), to the other observed flame. An axisymmetric ITV shedding was identified within oscillating and pinch-off modes, while asymmetric ITV shedding was identified with the spinning mode. Integrated electric power over several AC periods correlated well with variation in the flame surface area for these instabilities, demonstrating that measured electric power is a potential indicator of combustion instabilities in electric-field-assisted combustion.

Dielectric oil-based polymer actuator for improved thickness strain and breakdown voltage

International Nuclear Information System (INIS)

Cho, Min Sung; Yamamoto, Akio

2016-01-01

Dielectric elastomer actuators (DEAs) have been increasingly investigated as alternative actuators to conventional ones. However, DEAs suffer from high rates of premature failure. Therefore, this study proposes a dielectric oil-based polymer actuator, also called a Dielectric liquid actuator (DLA), to compensate for the drawbacks of DEAs. DLA was experimentally compared with conventional DEAs. Results showed that DLA successfully prevented thermal runaway at defects in the electrode and excessive thinning of the film, resulting in increased breakdown voltage. Consequently, premature failure was inhibited, and the performance was improved. The breakdown voltages of DLA and DEA were 6000 and 2000 V, respectively, and their maximum thickness strains were 49.5% and 37.5%, respectively

Dielectric oil-based polymer actuator for improved thickness strain and breakdown voltage

Energy Technology Data Exchange (ETDEWEB)

Cho, Min Sung; Yamamoto, Akio [Dept. of Precision Engineering, School of Engineering, The University of Tokyo, Tokyo (Japan)

2016-09-15

Dielectric elastomer actuators (DEAs) have been increasingly investigated as alternative actuators to conventional ones. However, DEAs suffer from high rates of premature failure. Therefore, this study proposes a dielectric oil-based polymer actuator, also called a Dielectric liquid actuator (DLA), to compensate for the drawbacks of DEAs. DLA was experimentally compared with conventional DEAs. Results showed that DLA successfully prevented thermal runaway at defects in the electrode and excessive thinning of the film, resulting in increased breakdown voltage. Consequently, premature failure was inhibited, and the performance was improved. The breakdown voltages of DLA and DEA were 6000 and 2000 V, respectively, and their maximum thickness strains were 49.5% and 37.5%, respectively.

Temporary over voltages in the high voltage networks

International Nuclear Information System (INIS)

Vukelja, Petar; Naumov, Radomir; Mrvic, Jovan; Minovski, Risto

2001-01-01

The paper treats the temporary over voltages that may arise in the high voltage networks as a result of: ground faults, loss of load, loss of one or two phases and switching operation. Based on the analysis, the measures for their limitation are proposed. (Original)

Voltage regulator for generator

Energy Technology Data Exchange (ETDEWEB)

Naoi, K

1989-01-17

It is an object of this invention to provide a voltage regulator for a generator charging a battery, wherein even if the ambient temperature at the voltage regulator rises abnormally high, possible thermal breakage of the semiconductor elements constituting the voltage regulator can be avoided. A feature of this invention is that the semiconductor elements can be protected from thermal breakage, even at an abnormal ambient temperature rise at the voltage regulator for the battery charging generator, by controlling a maximum conduction ratio of a power transistor in the voltage regulator in accordance with the temperature at the voltage regulator. This is achieved through a switching device connected in series to the field coil of the generator and adapted to be controlled in accordance with an output voltage of the generator and the ambient temperature at the voltage regulator. 6 figs.

Synchronization of pairwise-coupled, identical, relaxation oscillators based on metal-insulator phase transition devices: A model study

Science.gov (United States)

Parihar, Abhinav; Shukla, Nikhil; Datta, Suman; Raychowdhury, Arijit

2015-02-01

Computing with networks of synchronous oscillators has attracted wide-spread attention as novel materials and device topologies have enabled realization of compact, scalable and low-power coupled oscillatory systems. Of particular interest are compact and low-power relaxation oscillators that have been recently demonstrated using MIT (metal-insulator-transition) devices using properties of correlated oxides. Further the computational capability of pairwise coupled relaxation oscillators has also been shown to outperform traditional Boolean digital logic circuits. This paper presents an analysis of the dynamics and synchronization of a system of two such identical coupled relaxation oscillators implemented with MIT devices. We focus on two implementations of the oscillator: (a) a D-D configuration where complementary MIT devices (D) are connected in series to provide oscillations and (b) a D-R configuration where it is composed of a resistor (R) in series with a voltage-triggered state changing MIT device (D). The MIT device acts like a hysteresis resistor with different resistances in the two different states. The synchronization dynamics of such a system has been analyzed with purely charge based coupling using a resistive (RC) and a capacitive (CC) element in parallel. It is shown that in a D-D configuration symmetric, identical and capacitively coupled relaxation oscillator system synchronizes to an anti-phase locking state, whereas when coupled resistively the system locks in phase. Further, we demonstrate that for certain range of values of RC and CC, a bistable system is possible which can have potential applications in associative computing. In D-R configuration, we demonstrate the existence of rich dynamics including non-monotonic flows and complex phase relationship governed by the ratios of the coupling impedance. Finally, the developed theoretical formulations have been shown to explain experimentally measured waveforms of such pairwise coupled

Determining the Lyapunov Spectrum of Continuous-Time 1D and 2D Multiscroll Chaotic Oscillators via the Solution of m-PWL Variational Equations

Directory of Open Access Journals (Sweden)

Jesus Manuel Munoz-Pacheco

2013-01-01

Full Text Available An algorithm to compute the Lyapunov exponents of piecewise linear function-based multidirectional multiscroll chaotic oscillators is reported. Based on the m regions in the piecewise linear functions, the suggested algorithm determines the individual expansion rate of Lyapunov exponents from m-piecewise linear variational equations and their associated m-Jacobian matrices whose entries remain constant during all computation cycles. Additionally, by considering OpAmp-based chaotic oscillators, we study the impact of two analog design procedures on the magnitude of Lyapunov exponents. We focus on analyzing variations of both frequency bandwidth and voltage/current dynamic range of the chaotic signals at electronic system level. As a function of the design parameters, a renormalization factor is proposed to estimate correctly the Lyapunov spectrum. Numerical simulation results in a double-scroll type chaotic oscillator and complex chaotic oscillators generating multidirectional multiscroll chaotic attractors on phase space confirm the usefulness of the reported algorithm.

[Geomagnetic storm decreases coherence of electric oscillations of human brain while working at the computer].

Science.gov (United States)

Novik, O B; Smirnov, F A

2013-01-01

The effect of geomagnetic storms at the latitude of Moscow on the electric oscillations of the human brain cerebral cortex was studied. In course of electroencephalogram measurements it was shown that when the voluntary persons at the age of 18-23 years old were performing tasks using a computer during moderate magnetic storm or no later than 24 hrs after it, the value of the coherence function of electric oscillations of the human brain in the frontal and occipital areas in a range of 4.0-7.9 Hz (so-called the theta rhythm oscillations of the human brain) decreased by a factor of two or more, sometimes reaching zero, although arterial blood pressure, respiratory rate and the electrocardiogram registered during electroencephalogram measurements remained within the standard values.

Suppression and revival of oscillation in indirectly coupled limit cycle oscillators

International Nuclear Information System (INIS)

Sharma, P.R.; Kamal, N.K.; Verma, U.K.; Suresh, K.; Thamilmaran, K.; Shrimali, M.D.

2016-01-01

Highlights: • The phenomena of suppression and revival of oscillations are studied in indirectly coupled nonlinear oscillators. • The decay parameter and a feedback factor play a crucial role in emergent dynamical behavior of oscillators. • The critical curves for different dynamical regions are obtained analytically using linear stability analysis. • Electronic circuit experiments demonstrate these emergent dynamical states. - Abstract: We study the phenomena of suppression and revival of oscillations in a system of limit cycle oscillators coupled indirectly via a dynamic local environment. The dynamics of the environment is assumed to decay exponentially with time. We show that for appropriate coupling strength, the decay parameter of the environment plays a crucial role in the emergent dynamics such as amplitude death (AD) and oscillation death (OD). We also show that introducing a feedback factor in the diffusion term revives the oscillations in this system. The critical curves for the regions of different emergent states as a function of coupling strength, decay parameter of the environment and feedback factor in the coupling are obtained analytically using linear stability analysis. These results are found to be consistent with the numerics and are also observed experimentally.

Integral Plus Resonant Sliding Mode Direct Power Control for VSC-HVDC Systems under Unbalanced Grid Voltage Conditions

Directory of Open Access Journals (Sweden)

Weipeng Yang

2017-10-01

Full Text Available An integral plus resonant sliding mode direct power control (IRSMC DPC strategy for voltage source converter high voltage direct current (VSC-HVDC systems under unbalanced grid voltage conditions is proposed in this paper. Through detailed instantaneous power flow analysis, a generalized power compensation method, by which the ratio between the amplitude of active and reactive power ripples can be controlled continuously, is obtained. This enables the system to provide flexible power control, so that the desired performance of the system on both the ac and dc sides can be attained under different operating conditions. When the grid voltage is unbalanced, one or both of the active and reactive power terms contain ripples, oscillating at twice the grid frequency, to obtain non-distorted ac current. A power controller consisting of the proportional, integral and resonant control laws is designed using the sliding mode control approach, to achieve accurate power control objective. Simulation studies on a two-terminal VSC-HVDC system using MATLAB/SIMULINK (R2013b, Mathworks, Natick, MA, USA are conducted to verify the effectiveness of the IRSMC DPC strategy. The results show that this strategy ensures satisfactory performance of the system over a wide range of operating conditions.

Prediction of breakdown voltages in novel gases for high voltage insulation

International Nuclear Information System (INIS)

Koch, M.

2015-01-01

This thesis submitted to the Swiss Federal Institute of Technology ETH in Zurich examines the use of sulphur hexafluoride (SF_6) and similar gases as important insulation media for high voltage equipment. Due to its superior insulation properties, SF_6 is widely used in gas-insulated switchgear. However, the gas also has a very high global warming potential and the content of SF_6 in the atmosphere is constantly increasing. The search for new insulation gases using classical breakdown experiments is discussed. A model for SF_6 based on the stepped leader model is described. This calculates the breakdown voltages in arbitrary electrode configurations and under standard voltage waveforms. Thus, the thesis provides a method for the prediction of breakdown voltages of arbitrary field configurations under standard voltage waveforms for gases with electron-attaching properties. With this, further gases can be characterized for usage as high voltage insulation media

A novel Ka-band coaxial transit-time oscillator with a four-gap buncher

Energy Technology Data Exchange (ETDEWEB)

Song, Lili; He, Juntao; Ling, Junpu [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

2015-05-15

A novel Ka-band coaxial transit-time oscillator (TTO) with a four-gap buncher is proposed and investigated. Simulation results show that an output power of 1.27 GW and a frequency of 26.18 GHz can be achieved with a diode voltage of 447 kV and a beam current of 7.4 kA. The corresponding power efficiency is 38.5%, and the guiding magnetic field is 0.6 T. Studies and analysis indicate that a buncher with four gaps can modulate the electron beam better than the three-gap buncher in such a Ka-band TTO. Moreover, power efficiency increases with the coupling coefficient between the buncher and the extractor. Further simulation demonstrates that power efficiency can reach higher than 30% with a guiding magnetic field of above 0.5 T. Besides, the power efficiency exceeds 30% in a relatively large range of diode voltage from 375 kV to 495 kV.

On-site voltage measurement with capacitive sensors on high voltage systems

NARCIS (Netherlands)

Wu, L.; Wouters, P.A.A.F.; Heesch, van E.J.M.; Steennis, E.F.

2011-01-01

In Extra/High-Voltage (EHV/HV) power systems, over-voltages occur e.g. due to transients or resonances. At places where no conventional voltage measurement devices can be installed, on-site measurement of these occurrences requires preferably non intrusive sensors, which can be installed with little

Prediction of breakdown voltages in novel gases for high voltage insulation

Energy Technology Data Exchange (ETDEWEB)

Koch, M.

2015-07-01

This thesis submitted to the Swiss Federal Institute of Technology ETH in Zurich examines the use of sulphur hexafluoride (SF{sub 6}) and similar gases as important insulation media for high voltage equipment. Due to its superior insulation properties, SF{sub 6} is widely used in gas-insulated switchgear. However, the gas also has a very high global warming potential and the content of SF{sub 6} in the atmosphere is constantly increasing. The search for new insulation gases using classical breakdown experiments is discussed. A model for SF{sub 6} based on the stepped leader model is described. This calculates the breakdown voltages in arbitrary electrode configurations and under standard voltage waveforms. Thus, the thesis provides a method for the prediction of breakdown voltages of arbitrary field configurations under standard voltage waveforms for gases with electron-attaching properties. With this, further gases can be characterized for usage as high voltage insulation media.

Gyromagnetic nonlinear transmission line generator of high voltage pulses modulated at 4 GHz frequency with 1000 Hz pulse repetition rate

International Nuclear Information System (INIS)

Ulmasculov, M R; Sharypov, K A; Shunailov, S A; Shpak, V G; Yalandin, M I; Pedos, M S; Rukin, S N

2017-01-01

Results of testing of a generator based on a solid-state drive and the parallel gyromagnetic nonlinear transmission lines with external bias are presented. Stable rf-modulated high-voltage nanosecond pulses were shaped in each of the four channels in 1 s packets with 1000 Hz repetition frequencies. Pulse amplitude reaches -175 kV, at a modulation depth of rf-oscillations to 50 % and the effective frequency ∼4 GHz. (paper)

High voltage engineering

CERN Document Server

Rizk, Farouk AM

2014-01-01

Inspired by a new revival of worldwide interest in extra-high-voltage (EHV) and ultra-high-voltage (UHV) transmission, High Voltage Engineering merges the latest research with the extensive experience of the best in the field to deliver a comprehensive treatment of electrical insulation systems for the next generation of utility engineers and electric power professionals. The book offers extensive coverage of the physical basis of high-voltage engineering, from insulation stress and strength to lightning attachment and protection and beyond. Presenting information critical to the design, selec

Device for monitoring cell voltage

Science.gov (United States)

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

2012-08-21

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

The Oscillator Principle of Nature

DEFF Research Database (Denmark)

Lindberg, Erik

2012-01-01

Oscillators are found on all levels in Nature. The general oscillator concept is defined and investigated. Oscillators may synchronize into fractal patterns. Apparently oscillators are the basic principle in Nature. The concepts of zero and infinite are discussed. Electronic manmade oscillators...

Two new types of solvability of the one-dimensional anharmonic oscillators

International Nuclear Information System (INIS)

Znojil, M.

1989-01-01

In the Schroedinger picture, we propose a new modification of the so-called Hill-determinant technique. It is shown to guarantee a proper matching of the two underlying power series Ψ(x) at x=0. In the Heisenberg picture, an evolution of the same one-dimensional polynomially anharmonic oscillator is considered. A modified Peano-Baker method is applied and shown to define the explicit solutions by recurrences. 11 refs

Atypical transistor-based chaotic oscillators: Design, realization, and diversity

Science.gov (United States)

Minati, Ludovico; Frasca, Mattia; OświÈ©cimka, Paweł; Faes, Luca; DroŻdŻ, Stanisław

2017-07-01

In this paper, we show that novel autonomous chaotic oscillators based on one or two bipolar junction transistors and a limited number of passive components can be obtained via random search with suitable heuristics. Chaos is a pervasive occurrence in these circuits, particularly after manual adjustment of a variable resistor placed in series with the supply voltage source. Following this approach, 49 unique circuits generating chaotic signals when physically realized were designed, representing the largest collection of circuits of this kind to date. These circuits are atypical as they do not trivially map onto known topologies or variations thereof. They feature diverse spectra and predominantly anti-persistent monofractal dynamics. Notably, we recurrently found a circuit comprising one resistor, one transistor, two inductors, and one capacitor, which generates a range of attractors depending on the parameter values. We also found a circuit yielding an irregular quantized spike-train resembling some aspects of neural discharge and another one generating a double-scroll attractor, which represent the smallest known transistor-based embodiments of these behaviors. Through three representative examples, we additionally show that diffusive coupling of heterogeneous oscillators of this kind may give rise to complex entrainment, such as lag synchronization with directed information transfer and generalized synchronization. The replicability and reproducibility of the experimental findings are good.

Preliminary oscillating fluxes current drive experiment in DIII-D tokamak

International Nuclear Information System (INIS)

Yamaguchi, S.; Schaffer, M.; Kondoh, Y.

1995-01-01

A preliminary oscillating flux helicity injection experiment was done on DIII-D tokamak. The toroidal flux was modulated by programming the plasma elongation. Instead of programming the surface voltage directly, the plasma current was programmed with a periodic modulation at some phase shift. The theoretical basis of this modulation is discussed in terms of the helicity injection and also introduced by cross-field motion of the modulated plasma. Because the primary winding is well coupled with the plasma current and the power supply is strong, the plasma current behaves as programmed. However, as the plasma shape is not coupled strongly with the shaping and equilibrium coils, the elongation amplitude and phase are affected by the change of plasma current and do not behave as programmed. Because of this, the voltage induced by the helicity injection is low, and the experiment did not test the principle of helicity injection. The injection powers of helicity and energy, and the electric field intensity of the helicity injection model and the cross-field motion of plasma are compared with each other experimentally. The improvement necessary to do the experiment is also proposed. ((orig.))

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

Directory of Open Access Journals (Sweden)

Parol Mirosław

2016-03-01

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

Self-excited current oscillations in a resonant tunneling diode described by a model based on the Caldeira–Leggett Hamiltonian

International Nuclear Information System (INIS)

Sakurai, Atsunori; Tanimura, Yoshitaka

2014-01-01

The quantum dissipative dynamics of a tunneling process through double barrier structures is investigated on the basis of non-perturbative and non-Markovian treatment. We employ a Caldeira–Leggett Hamiltonian with an effective potential calculated self-consistently, accounting for the electron distribution. With this Hamiltonian, we use the reduced hierarchy equations of motion in the Wigner space representation to study non-Markovian and non-perturbative thermal effects at finite temperature in a rigorous manner. We study current variation in time and the current–voltage (I–V ) relation of the resonant tunneling diode for several widths of the contact region, which consists of doped GaAs. Hysteresis and both single and double plateau-like behavior are observed in the negative differential resistance (NDR) region. While all of the current oscillations decay in time in the NDR region in the case of a strong system–bath coupling, there exist self-excited high-frequency current oscillations in some parts of the plateau in the NDR region in the case of weak coupling. We find that the effective potential in the oscillating case possesses a basin-like form on the emitter side (emitter basin) and that the current oscillation results from tunneling between the emitter basin and the quantum well in the barriers. We find two distinct types of current oscillations, with large and small oscillation amplitudes, respectively. These two types of oscillation appear differently in the Wigner space, with one exhibiting tornado-like motion and the other exhibiting a two piston engine-like motion. (paper)

76 FR 70721 - Voltage Coordination on High Voltage Grids; Notice of Staff Workshop

Science.gov (United States)

2011-11-15

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. AD12-5-000] Voltage Coordination on High Voltage Grids; Notice of Staff Workshop Take notice that the Federal Energy Regulatory Commission will hold a Workshop on Voltage Coordination on High Voltage Grids on Thursday, December 1, 2011...

Co-ordinated Control Strategy for Hybrid Wind Farms with PMSG and FSIG under Unbalanced Grid Voltage Condition

DEFF Research Database (Denmark)

Zeng, Xin; Yao, Jun; Chen, Zhiqian

2016-01-01

-sequence current from the PMSG-based wind farm by the modified negative-sequence voltage and current double closed-loop control system is then developed. Finally, the correctness of theoretical analysis and the effectiveness of the proposed control strategy are validated by the experimental results....... to inject negative-sequence current for decreasing voltage unbalance factor (VUF) at point of common coupling (PCC), the double grid frequency oscillations in electromagnetic torque, active and reactive power output from the FSIG-based wind farm can be suppressed. In this paper, the maximum amplitude...... of the negative-sequence current provided by the PMSG-based wind farm under different average active power output and different VUF conditions is deduced, and the impacts of its phase angle on the VUF mitigation control effect are further studied. The improved control strategy of injecting negative...

Are the North Atlantic oscillation and the southern oscillation related in any time-scale?

Energy Technology Data Exchange (ETDEWEB)

Garcia, R.; Ribera, P.; Hernandez, E. [Universidad Complutense de Madrid (Spain). Facultad de Ciencias Fisicas; Gimenoo, L. [Fac. Ciencias, Univ. Vigo, Ourense (Spain)

2000-02-01

The north Atlantic oscillation (NAO) and the southern oscillation (SO) are compared from the standpoint of a possible common temporal scale of oscillation. To do this a cross-spectrum of the temporal series of NAO and SO indices was determined, finding a significant common oscillation of 6-8 years. To assure this finding, both series were decomposed in their main oscillations using singular spectrum analysis (SSA). Resulting reconstructed series of 6-8 years' oscillation were then cross-correlated without and with pre-whitened, the latter being significant. The main conclusion is a possible relationship between a common oscillation of 6-8 years that represents about 20% of the SO variance and about 25% of the NAO variance. (orig.)

Automatic Oscillating Turret.

Science.gov (United States)

1981-03-01

Final Report: February 1978 ZAUTOMATIC OSCILLATING TURRET SYSTEM September 1980 * 6. PERFORMING 01G. REPORT NUMBER .J7. AUTHOR(S) S. CONTRACT OR GRANT...o....e.... *24 APPENDIX P-4 OSCILLATING BUMPER TURRET ...................... 25 A. DESCRIPTION 1. Turret Controls ...Other criteria requirements were: 1. Turret controls inside cab. 2. Automatic oscillation with fixed elevation to range from 20* below the horizontal to

Voltage splay modes and enhanced phase locking in a modified linear Josephson array

Science.gov (United States)

Harris, E. B.; Garland, J. C.

1997-02-01

We analyze a modified linear Josephson-junction array in which additional unbiased junctions are used to greatly enhance phase locking. This geometry exhibits strong correlated behavior, with an external magnetic field tuning the voltage splay angle between adjacent Josephson oscillators. The array displays a coherent in-phase mode for f=, where f is the magnetic frustration, while for 0tolerant of critical current disorder approaching 100%. The stability of the array has also been studied by computing Floquet exponents. These exponents are found to be negative for all array lengths, with a 1/N2 dependence, N being the number of series-connected junctions.

Inverted oscillator

Energy Technology Data Exchange (ETDEWEB)

Yuce, C [Physics Department, Anadolu University, Eskisehir (Turkey); Kilic, A [Physics Department, Anadolu University, Eskisehir (Turkey); Coruh, A [Physics Department, Sakarya University, Sakarya (Turkey)

2006-07-15

The inverted harmonic oscillator problem is investigated quantum mechanically. The exact wavefunction for the confined inverted oscillator is obtained and it is shown that the associated energy eigenvalues are discrete, and the energy is given as a linear function of the quantum number n.

Ion Concentration- and Voltage-Dependent Push and Pull Mechanisms of Potassium Channel Ion Conduction.

Directory of Open Access Journals (Sweden)

Kota Kasahara

Full Text Available The mechanism of ion conduction by potassium channels is one of the central issues in physiology. In particular, it is still unclear how the ion concentration and the membrane voltage drive ion conduction. We have investigated the dynamics of the ion conduction processes in the Kv1.2 pore domain, by molecular dynamics (MD simulations with several different voltages and ion concentrations. By focusing on the detailed ion movements through the pore including selectivity filter (SF and cavity, we found two major conduction mechanisms, called the III-IV-III and III-II-III mechanisms, and the balance between the ion concentration and the voltage determines the mechanism preference. In the III-IV-III mechanism, the outermost ion in the pore is pushed out by a new ion coming from the intracellular fluid, and four-ion states were transiently observed. In the III-II-III mechanism, the outermost ion is pulled out first, without pushing by incoming ions. Increases in the ion concentration and voltage accelerated ion conductions, but their mechanisms were different. The increase in the ion concentrations facilitated the III-IV-III conductions, while the higher voltages increased the III-II-III conductions, indicating that the pore domain of potassium channels permeates ions by using two different driving forces: a push by intracellular ions and a pull by voltage.

Sodium-calcium exchanger and R-type Ca2+ channels mediate spontaneous [Ca2+](i) oscillations in magnocellular neurones of the rat supraoptic nucleus

Czech Academy of Sciences Publication Activity Database

Kortus, Štěpán; Srinivasan, Ch.; Forostyak, O.; Zápotocký, Martin; Ueta, Y.; Syková, E.; Chvátal, A.; Verkhratsky, A.; Dayanithi, G.

2016-01-01

Roč. 59, č. 6 (2016), s. 289-298 ISSN 0143-4160 R&D Projects: GA ČR(CZ) GBP304/12/G069 Institutional support: RVO:67985823 Keywords : magnocellular neurosecretory cells * voltage-gated Ca2+ channels * intracellular Ca2+ stores * Ca2+ imaging * Ca2+ oscillations Subject RIV: FH - Neurology Impact factor: 3.707, year: 2016

Reactor oscillator - Proposal of the organisation for oscillator operation; Reaktorski oscilator - Predlog organizacije rada na oscilatoru

Energy Technology Data Exchange (ETDEWEB)

Lolic, B; Loloc, B [Institute of Nuclear Sciences Boris Kidric, Laboratorija za fiziku reaktora, Vinca, Beograd (Serbia and Montenegro)

1961-12-15

The organizational structure for operating the reactor with the reactor oscillator describes the duties of the reactor operators; staff responsible for operating the oscillator who are responsible for measurements, preparation of the samples and further treatment of the obtained results.

Experimental demonstration of revival of oscillations from death in coupled nonlinear oscillators

Energy Technology Data Exchange (ETDEWEB)

Senthilkumar, D. V., E-mail: skumarusnld@gmail.com [School of Physics, Indian Institute of Science Education and Research, Thiruvananthapuram 695016 (India); Centre for Nonlinear Science and Engineering, School of Electrical and Electronics Engineering, SASTRA University, Thanjavur 613 401 (India); Suresh, K. [Department of Physics, Anjalai Ammal-Engineering College, Kovilvenni 614 403, Tamilnadu (India); Centre for Nonlinear Dynamics, Bharathidasan University, Trichy 620024, Tamilnadu (India); Chandrasekar, V. K. [Centre for Nonlinear Science and Engineering, School of Electrical and Electronics Engineering, SASTRA University, Thanjavur 613 401 (India); Zou, Wei [School of Mathematics and Statistics, Huazhong University of Science and Technology, Wuhan 430074 (China); Centre for Mathematical Sciences, Huazhong University of Science and Technology, Wuhan 430074 (China); Dana, Syamal K. [CSIR-Indian Institute of Chemical Biology, Kolkata 700032 (India); Kathamuthu, Thamilmaran [Centre for Nonlinear Dynamics, Bharathidasan University, Trichy 620024, Tamilnadu (India); Kurths, Jürgen [Potsdam Institute for Climate Impact Research, Telegrafenberg, Potsdam D-14415 (Germany); Institute of Physics, Humboldt University Berlin, Berlin D-12489 (Germany); Institute for Complex Systems and Mathematical Biology, University of Aberdeen, Aberdeen AB24 3FX (United Kingdom); Department of Control Theory, Nizhny Novgorod State University, Gagarin Avenue 23, 606950 Nizhny Novgorod (Russian Federation)

2016-04-15

We experimentally demonstrate that a processing delay, a finite response time, in the coupling can revoke the stability of the stable steady states, thereby facilitating the revival of oscillations in the same parameter space where the coupled oscillators suffered the quenching of oscillation. This phenomenon of reviving of oscillations is demonstrated using two different prototype electronic circuits. Further, the analytical critical curves corroborate that the spread of the parameter space with stable steady state is diminished continuously by increasing the processing delay. Finally, the death state is completely wiped off above a threshold value by switching the stability of the stable steady state to retrieve sustained oscillations in the same parameter space. The underlying dynamical mechanism responsible for the decrease in the spread of the stable steady states and the eventual reviving of oscillation as a function of the processing delay is explained using analytical results.

Influence of the voltage waveform during nanocomposite layer deposition by aerosol-assisted atmospheric pressure Townsend discharge

Energy Technology Data Exchange (ETDEWEB)

Profili, J. [LAPLACE, Université de Toulouse, CNRS, INPT, UPS, Toulouse (France); Département de Physique, Université de Montréal, Montréal, Québec H3C 3J7 (Canada); Levasseur, O.; Stafford, L. [Département de Physique, Université de Montréal, Montréal, Québec H3C 3J7 (Canada); Naudé, N.; Gherardi, N., E-mail: nicolas.gherardi@laplace.univ-tlse.fr [LAPLACE, Université de Toulouse, CNRS, INPT, UPS, Toulouse (France); Chaneac, C. [Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Collège de France, Laboratoire de Chimie de la Matière Condensée de Paris (CMCP), 4 place Jussieu, F-75005 Paris (France)

2016-08-07

This work examines the growth dynamics of TiO{sub 2}-SiO{sub 2} nanocomposite coatings in plane-to-plane Dielectric Barrier Discharges (DBDs) at atmospheric pressure operated in a Townsend regime using nebulized TiO{sub 2} colloidal suspension in hexamethyldisiloxane as the growth precursors. For low-frequency (LF) sinusoidal voltages applied to the DBD cell, with voltage amplitudes lower than the one required for discharge breakdown, Scanning Electron Microscopy of silicon substrates placed on the bottom DBD electrode reveals significant deposition of TiO{sub 2} nanoparticles (NPs) close to the discharge entrance. On the other hand, at higher frequencies (HF), the number of TiO{sub 2} NPs deposited strongly decreases due to their “trapping” in the oscillating voltage and their transport along the gas flow lines. Based on these findings, a combined LF-HF voltage waveform is proposed and used to achieve significant and spatially uniform deposition of TiO{sub 2} NPs across the whole substrate surface. For higher voltage amplitudes, in the presence of hexamethyldisiloxane and nitrous oxide for plasma-enhanced chemical vapor deposition of inorganic layers, it is found that TiO{sub 2} NPs become fully embedded into a silica-like matrix. Similar Raman spectra are obtained for as-prepared TiO{sub 2} NPs and for nanocomposite TiO{sub 2}-SiO{sub 2} coating, suggesting that plasma exposure does not significantly alter the crystalline structure of the TiO{sub 2} NPs injected into the discharge.

Current regulators for I/SUP 2/L circuits to be operated from low-voltage power supplies

DEFF Research Database (Denmark)

Bruun, Erik; Hansen, Ole

1980-01-01

A new bandgap current reference is described which can be used to control the injector current of I/SUP 2/L circuits for supply voltages down to about 1 V. For small currents the total injector current is obtained as a mirror of the reference current. For large injector currents the current control......, but well controlled temperature coefficient is desired. It is shown how a temperature stable ring oscillator with I/SUP 2/L gates can be constructed by tailoring the temperature dependence of the supply current appropriately....

Universal Voltage Conveyor and its Novel Dual-Output Fully-Cascadable VM APF Application

Directory of Open Access Journals (Sweden)

Norbert Herencsar

2017-03-01

Full Text Available This letter presents a novel realization of a voltage-mode (VM first-order all-pass filter (APF with attractive features. The proposed circuit employs a single readily available six-terminal active device called as universal voltage conveyor (UVC and only grounded passive components, which predict its easy monolithic integration with desired circuit simplicity. The auxiliary voltage input (W and output (ZP, ZN terminals of the device fully ensure easy cascadability of VM APF, since the input and output terminal impedances are theoretically infinitely high and zero, respectively. Moreover, thanks to mutually inverse outputs of the UVC, the proposed filter simultaneously provides both inverting and non-inverting outputs from the same configuration. All of these features make the UVC a unique active device currently available in the literature. The behavior of the filter was experimentally measured using the readily available UVC-N1C 0520 chip, which was produced in cooperation with ON Semiconductor Czech Republic, Ltd.

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

DEFF Research Database (Denmark)

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

2013-01-01

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

Variation, differential reproduction and oscillation: the evolution of nucleic acid hybridization.

Science.gov (United States)

Suárez-Díaz, Edna

2013-01-01

This paper builds upon Hans-Jörg Rheinberger ideas on the oscillation and intercalation of epistemic things and technical objects in experimental systems, to give a fine-grained analysis of what here is called the problems of "adaptation" between our material and cognitive tools and the phenomena of the material world. To do so, it relies on the case-study of the evolution of nucleic acid hybridization and the stabilization of satellite DNA.

Mapping of Residues Forming the Voltage Sensor of the Voltage-Dependent Anion-Selective Channel

Science.gov (United States)

Thomas, Lorie; Blachly-Dyson, Elizabeth; Colombini, Marco; Forte, Michael

1993-06-01

Voltage-gated ion-channel proteins contain "voltage-sensing" domains that drive the conformational transitions between open and closed states in response to changes in transmembrane voltage. We have used site-directed mutagenesis to identify residues affecting the voltage sensitivity of a mitochondrial channel, the voltage-dependent anion-selective channel (VDAC). Although charge changes at many sites had no effect, at other sites substitutions that increased positive charge also increased the steepness of voltage dependance and substitutions that decreased positive charge decreased voltage dependance by an appropriate amount. In contrast to the plasma membrane K^+ and Na^+ channels, these residues are distributed over large parts of the VDAC protein. These results have been used to define the conformational transitions that accompany voltage gating of an ion channel. This gating mechanism requires the movement of large portions of the VDAC protein through the membrane.

Molecular mechanism of voltage sensing in voltage-gated proton channels

Science.gov (United States)

Rebolledo, Santiago; Perez, Marta E.

2013-01-01

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

Chromospheric oscillations

NARCIS (Netherlands)

Lites, B.W.; Rutten, R.J.; Thomas, J.H.

1995-01-01

We show results from SO/Sacramento Peak data to discuss three issues: (i)--the spatial occurrence of chromospheric 3--min oscillations; (ii)--the validity of Ca II H&K line-center Doppler Shift measurements; (iii)--the signi ?cance of oscillation power and phase at frequencies above 10 mHz.

Vivitron 1995, transient voltage simulation, high voltage insulator tests, electric field calculation

International Nuclear Information System (INIS)

Frick, G.; Osswald, F.; Heusch, B.

1996-01-01

Preliminary investigations showed clearly that, because of the discrete electrode structure of the Vivitron, important overvoltage leading to insulator damage can appear in case of a spark. The first high voltage tests showed damage connected with such events. This fact leads to a severe voltage limitation. This work describes, at first, studies made to understand the effects of transients and the associated over-voltage appearing in the Vivitron. Then we present the high voltage tests made with full size Vivitron components using the CN 6 MV machine as a pilot machine. Extensive field calculations were made. These involve simulations of static stresses and transient overvoltages, on insulating boards and electrodes. This work gave us the solutions for arrangements and modifications in the machine. After application, the Vivitron runs now without any sparks and damage at 20 MV. In the same manner, we tested column insulators of a new design and so we will find out how to get to higher voltages. Electric field calculation around the tie bars connecting the discrete electrodes together showed field enhancements when the voltages applied on the discrete electrodes are not equally distributed. This fact is one of the sources of discharges and voltage limitations. A scenario of a spark event is described and indications are given how to proceed towards higher voltages, in the 30 MV range. (orig.)

Nonstationary oscillation of gyrotron backward wave oscillators with cylindrical interaction structure

International Nuclear Information System (INIS)

Chen, Shih-Hung; Chen, Liu

2013-01-01

The nonstationary oscillation of the gyrotron backward wave oscillator (gyro-BWO) with cylindrical interaction structure was studied utilizing both steady-state analyses and time-dependent simulations. Comparisons of the numerical results reveal that the gyro-BWO becomes nonstationary when the trailing field structure completely forms due to the dephasing energetic electrons. The backward propagation of radiated waves with a lower resonant frequency from the trailing field structure interferes with the main internal feedback loop, thereby inducing the nonstationary oscillation of the gyro-BWO. The nonstationary gyro-BWO exhibits the same spectral pattern of modulated oscillations with a constant frequency separation between the central frequency and sidebands throughout the whole system. The frequency separation is found to be scaled with the square root of the maximum field amplitude, thus further demonstrating that the nonstationary oscillation of the gyro-BWO is associated with the beam-wave resonance detuning

Investigation of power oscillation mechanisms based on noise analysis at Forsmark-1 BWR

International Nuclear Information System (INIS)

Oguma, Ritsuo

1996-01-01

Noise analysis has been performed for stability test data collected during reactor start-up in January 1989 at the boiling water reactor (BWR) Forsmark unit 1. A unique instrumentation to measure local coolant flow in this reactor allowed investigation of dynamic interactions between neutron flux and coolant flow noise signals at different radial positions in the core. The causal relationship for these signals was evaluated based on a method called signal transmission path (STP) analysis with the aim of identifying the principal mechanism of power oscillations in this reactor. The results of the present study indicated that large amplitude power oscillations were induced by two instability mechanisms concurrent in the core. The first is the global void reactivity feedback effect which played the most significant role to power oscillations at a resonant frequency of about 0.53 Hz. The second is the thermal-hydraulics coupling with neutron kinetics, inducing resonant oscillations at about 0.45 Hz. The latter was found to be active only in a certain core region. A peculiar phenomenon of amplitude modulations observed in some local power range monitor (LPRM) signals was also examined. It was interpreted to occur as the consequence of these two resonant power oscillations, the frequencies of which lie close to each other. The noise analysis technique applied in the present study is expected to be useful to get a deeper understanding of the power oscillation mechanism which is active in the reactor under evaluation. The technique may be applicable to BWRs with instruments to measure local channel flow together with in-core neutron detectors. (Author)

Oscillation Baselining and Analysis Tool

Energy Technology Data Exchange (ETDEWEB)

2017-03-27

PNNL developed a new tool for oscillation analysis and baselining. This tool has been developed under a new DOE Grid Modernization Laboratory Consortium (GMLC) Project (GM0072 - “Suite of open-source applications and models for advanced synchrophasor analysis”) and it is based on the open platform for PMU analysis. The Oscillation Baselining and Analysis Tool (OBAT) performs the oscillation analysis and identifies modes of oscillations (frequency, damping, energy, and shape). The tool also does oscillation event baselining (fining correlation between oscillations characteristics and system operating conditions).

Technological Aspects: High Voltage

CERN Document Server

Faircloth, D.C.

2013-12-16

This paper covers the theory and technological aspects of high-voltage design for ion sources. Electric field strengths are critical to understanding high-voltage breakdown. The equations governing electric fields and the techniques to solve them are discussed. The fundamental physics of high-voltage breakdown and electrical discharges are outlined. Different types of electrical discharges are catalogued and their behaviour in environments ranging from air to vacuum are detailed. The importance of surfaces is discussed. The principles of designing electrodes and insulators are introduced. The use of high-voltage platforms and their relation to system design are discussed. The use of commercially available high-voltage technology such as connectors, feedthroughs and cables are considered. Different power supply technologies and their procurement are briefly outlined. High-voltage safety, electric shocks and system design rules are covered.

Capacitor Voltages Measurement and Balancing in Flying Capacitor Multilevel Converters Utilizing a Single Voltage Sensor

DEFF Research Database (Denmark)

Farivar, Glen; Ghias, Amer M. Y. M.; Hredzak, Branislav

2017-01-01

This paper proposes a new method for measuring capacitor voltages in multilevel flying capacitor (FC) converters that requires only one voltage sensor per phase leg. Multiple dc voltage sensors traditionally used to measure the capacitor voltages are replaced with a single voltage sensor at the ac...... side of the phase leg. The proposed method is subsequently used to balance the capacitor voltages using only the measured ac voltage. The operation of the proposed measurement and balancing method is independent of the number of the converter levels. Experimental results presented for a five-level FC...

Improvement in the Design of Metal-Ceramic High Voltage Feedthroughs for use in High Energy Particle Accelerators

CERN Document Server

Weterings, W

1999-01-01

Large high-voltage devices operate in particle accelerators to steer charged particles in the desired direction. Solid and hollow rods of sintered alumina are used as insulating supports and high-voltage feedthroughs to power the electrodes of these electrostatic systems. The performance of the systems is often limited by voltage breakdown along the surface of the ceramic insulator (so-called surface flashover) or discharge between feedthrough and vacuum tank, which can lead to significant disruptions in terms of overall machine efficiency. Available results on the influence of the mechanical preparation, thermal history and particular cleaning techniques on commercially obtainable alumina samples have been studied in order to investigate possibilities for better preparation methodology of the insulating supports. Also the influence of the relative position of the feedthrough inside the vacuum tank on the high-voltage breakdown behaviour has been studied. This paper describes the theoretical and practical bac...

Control and Testing of a Dynamic Voltage Restorer (DVR) at Medium Voltage Level

DEFF Research Database (Denmark)

Nielsen, John Godsk; Newman, Michael; Nielsen, Hans Ove

2004-01-01

power sensitive loads from voltage sags. This paper reports practical test results obtained on a medium voltage (10 kV) level using a DVR at a Distribution test facility in Kyndby, Denmark. The DVR was designed to protect a 400-kVA load from a 0.5-p.u. maximum voltage sag. The reported DVR verifies......The dynamic voltage restorer (DVR) has become popular as a cost effective solution for the protection of sensitive loads from voltage sags. Implementations of the DVR have been proposed at both a low voltage (LV) level, as well as a medium voltage (MV) level; and give an opportunity to protect high...... the use of a feed-forward and feed-back technique of the controller and it obtains both good transient and steady state responses. The effect of the DVR on the system is experimentally investigated under both faulted and non-faulted system states, for a variety of linear and non-linear loads. Variable...

Flexible and low-voltage integrated circuits constructed from high-performance nanocrystal transistors.

Science.gov (United States)

Kim, David K; Lai, Yuming; Diroll, Benjamin T; Murray, Christopher B; Kagan, Cherie R

2012-01-01

Colloidal semiconductor nanocrystals are emerging as a new class of solution-processable materials for low-cost, flexible, thin-film electronics. Although these colloidal inks have been shown to form single, thin-film field-effect transistors with impressive characteristics, the use of multiple high-performance nanocrystal field-effect transistors in large-area integrated circuits has not been shown. This is needed to understand and demonstrate the applicability of these discrete nanocrystal field-effect transistors for advanced electronic technologies. Here we report solution-deposited nanocrystal integrated circuits, showing nanocrystal integrated circuit inverters, amplifiers and ring oscillators, constructed from high-performance, low-voltage, low-hysteresis CdSe nanocrystal field-effect transistors with electron mobilities of up to 22 cm(2) V(-1) s(-1), current modulation >10(6) and subthreshold swing of 0.28 V dec(-1). We fabricated the nanocrystal field-effect transistors and nanocrystal integrated circuits from colloidal inks on flexible plastic substrates and scaled the devices to operate at low voltages. We demonstrate that colloidal nanocrystal field-effect transistors can be used as building blocks to construct complex integrated circuits, promising a viable material for low-cost, flexible, large-area electronics.

Engineering of a genetically encodable fluorescent voltage sensor exploiting fast Ci-VSP voltage-sensing movements.

Science.gov (United States)

Lundby, Alicia; Mutoh, Hiroki; Dimitrov, Dimitar; Akemann, Walther; Knöpfel, Thomas

2008-06-25

Ci-VSP contains a voltage-sensing domain (VSD) homologous to that of voltage-gated potassium channels. Using charge displacement ('gating' current) measurements we show that voltage-sensing movements of this VSD can occur within 1 ms in mammalian membranes. Our analysis lead to development of a genetically encodable fluorescent protein voltage sensor (VSFP) in which the fast, voltage-dependent conformational changes of the Ci-VSP voltage sensor are transduced to similarly fast fluorescence read-outs.

Neutrino oscillations in matter

International Nuclear Information System (INIS)

Mikheyev, S.P.; Smirnov, A.Yu.

1986-01-01

In this paper we describe united formalism of ν-oscillations for different regimes, which is immediate generalization of vacuum oscillations theory. Adequate graphical representation of this formalism is given. We summarize main properties of ν-oscillations for different density distributions. (orig./BBOE)

Technological Aspects: High Voltage

International Nuclear Information System (INIS)

Faircloth, D C

2013-01-01

This paper covers the theory and technological aspects of high-voltage design for ion sources. Electric field strengths are critical to understanding high-voltage breakdown. The equations governing electric fields and the techniques to solve them are discussed. The fundamental physics of high-voltage breakdown and electrical discharges are outlined. Different types of electrical discharges are catalogued and their behaviour in environments ranging from air to vacuum are detailed. The importance of surfaces is discussed. The principles of designing electrodes and insulators are introduced. The use of high-voltage platforms and their relation to system design are discussed. The use of commercially available high-voltage technology such as connectors, feedthroughs and cables are considered. Different power supply technologies and their procurement are briefly outlined. High-voltage safety, electric shocks and system design rules are covered. (author)

Two integrator loop quadrature oscillators: A review

Directory of Open Access Journals (Sweden)

Ahmed M. Soliman

2013-01-01

Full Text Available A review of the two integrator loop oscillator circuits providing two quadrature sinusoidal output voltages is given. All the circuits considered employ the minimum number of capacitors namely two except one circuit which uses three capacitors. The circuits considered are classified to four different classes. The first class includes floating capacitors and floating resistors and the active building blocks realizing these circuits are the Op Amp or the OTRA. The second class employs grounded capacitors and includes floating resistors and the active building blocks realizing these circuits are the DCVC or the unity gain cells or the CFOA. The third class employs grounded capacitors and grounded resistors and the active building blocks realizing these circuits are the CCII. The fourth class employs grounded capacitors and no resistors and the active building blocks realizing these circuits are the TA. Transformation methods showing the generation of different classes from each other is given in details and this is one of the main objectives of this paper.

Robust synchronization of coupled neural oscillators using the derivative-free nonlinear Kalman Filter.

Science.gov (United States)

Rigatos, Gerasimos

2014-12-01

A synchronizing control scheme for coupled neural oscillators of the FitzHugh-Nagumo type is proposed. Using differential flatness theory the dynamical model of two coupled neural oscillators is transformed into an equivalent model in the linear canonical (Brunovsky) form. A similar linearized description is succeeded using differential geometry methods and the computation of Lie derivatives. For such a model it becomes possible to design a state feedback controller that assures the synchronization of the membrane's voltage variations for the two neurons. To compensate for disturbances that affect the neurons' model as well as for parametric uncertainties and variations a disturbance observer is designed based on Kalman Filtering. This consists of implementation of the standard Kalman Filter recursion on the linearized equivalent model of the coupled neurons and computation of state and disturbance estimates using the diffeomorphism (relations about state variables transformation) provided by differential flatness theory. After estimating the disturbance terms in the neurons' model their compensation becomes possible. The performance of the synchronization control loop is tested through simulation experiments.

Voltage Management in Unbalanced Low Voltage Networks Using a Decoupled Phase-Tap-Changer Transformer

DEFF Research Database (Denmark)

Coppo, Massimiliano; Turri, Roberto; Marinelli, Mattia

2014-01-01

The paper studies a medium voltage-low voltage transformer with a decoupled on load tap changer capability on each phase. The overall objective is the evaluation of the potential benefits on a low voltage network of such possibility. A realistic Danish low voltage network is used for the analysis...

Automatic voltage imbalance detector

Science.gov (United States)

Bobbett, Ronald E.; McCormick, J. Byron; Kerwin, William J.

1984-01-01

A device for indicating and preventing damage to voltage cells such as galvanic cells and fuel cells connected in series by detecting sequential voltages and comparing these voltages to adjacent voltage cells. The device is implemented by using operational amplifiers and switching circuitry is provided by transistors. The device can be utilized in battery powered electric vehicles to prevent galvanic cell damage and also in series connected fuel cells to prevent fuel cell damage.

Engineering of a genetically encodable fluorescent voltage sensor exploiting fast Ci-VSP voltage-sensing movements.

Directory of Open Access Journals (Sweden)

Alicia Lundby

2008-06-01

Full Text Available Ci-VSP contains a voltage-sensing domain (VSD homologous to that of voltage-gated potassium channels. Using charge displacement ('gating' current measurements we show that voltage-sensing movements of this VSD can occur within 1 ms in mammalian membranes. Our analysis lead to development of a genetically encodable fluorescent protein voltage sensor (VSFP in which the fast, voltage-dependent conformational changes of the Ci-VSP voltage sensor are transduced to similarly fast fluorescence read-outs.

Analysis of Switched-Rigid Floating Oscillator

Directory of Open Access Journals (Sweden)

Prabhakar R. Marur

2009-01-01

Full Text Available In explicit finite element simulations, a technique called deformable-to-rigid (D2R switching is used routinely to reduce the computation time. Using the D2R option, the deformable parts in the model can be switched to rigid and reverted back to deformable when needed during the analysis. The time of activation of D2R however influences the overall dynamics of the system being analyzed. In this paper, a theoretical basis for the selection of time of rigid switching based on system energy is established. A floating oscillator problem is investigated for this purpose and closed-form analytical expressions are derived for different phases in rigid switching. The analytical expressions are validated by comparing the theoretical results with numerical computations.

The colpitts oscillator family

DEFF Research Database (Denmark)

Lindberg, Erik; Murali, K.; Tamasevicius, A.

A tutorial study of the Colpitts oscillator family defined as all oscillators based on a nonlinear amplifier and a three- terminal linear resonance circuit with one coil and two capacitors. The original patents are investigated. The eigenvalues of the linearized Jacobian for oscillators based...

Electrocardiogram voltage discordance: Interpretation of low QRS voltage only in the precordial leads.

Science.gov (United States)

Kim, Diana H; Verdino, Ralph J

To define clinical correlates of low voltage isolated to precordial leads on the surface electrocardiogram (ECG). Low voltage (V) on the ECG is defined as QRS Vvoltage isolated to the precordial leads with normal limb lead voltages is unclear. Twelve-lead ECGs with QRS V>5mm in one or more limb leads and voltage was found in 256 of 150,000 ECGs (~0.2%). 50.4% of patients had discordant ECGs that correlated with classic etiologies, with a higher incidence of LV dilation in those with classic etiologies than those without. Low precordial voltage is associated with classic etiologies and LV dilation. Copyright © 2017 Elsevier Inc. All rights reserved.

Bounded-oscillation Pushdown Automata

Directory of Open Access Journals (Sweden)

Pierre Ganty

2016-09-01

Full Text Available We present an underapproximation for context-free languages by filtering out runs of the underlying pushdown automaton depending on how the stack height evolves over time. In particular, we assign to each run a number quantifying the oscillating behavior of the stack along the run. We study languages accepted by pushdown automata restricted to k-oscillating runs. We relate oscillation on pushdown automata with a counterpart restriction on context-free grammars. We also provide a way to filter all but the k-oscillating runs from a given PDA by annotating stack symbols with information about the oscillation. Finally, we study closure properties of the defined class of languages and the complexity of the k-emptiness problem asking, given a pushdown automaton P and k >= 0, whether P has a k-oscillating run. We show that, when k is not part of the input, the k-emptiness problem is NLOGSPACE-complete.

Analytical Evaluation of the Nonlinear Vibration of Coupled Oscillator Systems

DEFF Research Database (Denmark)

Bayat, M.; Shahidi, M.; Barari, Amin

2011-01-01

approximations to the achieved nonlinear differential oscillation equations where the displacement of the two-mass system can be obtained directly from the linear second-order differential equation using the first order of the current approach. Compared with exact solutions, just one iteration leads us to high......We consider periodic solutions for nonlinear free vibration of conservative, coupled mass-spring systems with linear and nonlinear stiffnesses. Two practical cases of these systems are explained and introduced. An analytical technique called energy balance method (EBM) was applied to calculate...

Magnetically Coupled Magnet-Spring Oscillators

Science.gov (United States)

Donoso, G.; Ladera, C. L.; Martin, P.

2010-01-01

A system of two magnets hung from two vertical springs and oscillating in the hollows of a pair of coils connected in series is a new, interesting and useful example of coupled oscillators. The electromagnetically coupled oscillations of these oscillators are experimentally and theoretically studied. Its coupling is electromagnetic instead of…

Observation of a Pomeau-Manneville intermittent route to chaos in a nonlinear oscillator

International Nuclear Information System (INIS)

Jeffries, C.; Perez, J.

1982-01-01

For a driven nonlinear semiconductor oscillator which shows a period-doubling pitchfork bifurcation route to chaos, we report an additional route to chaos: the Pomeau-Manneville intermittency route, characterized by a periodic (laminar) phase interrupted by bursts of aperiodic behavior. This occurs near a tangent bifurcation as the system driving parameter is reduced by epsilon from the threshold value for a periodic window. Data are presented for the dependence of the average laminar length on epsilon, and also on additive random noise voltage. The results are in reasonable agreement with the intermittency theory of Hirsch, Huberman, and Scalapino. The distribution P(l) is also reported

Coupled opto electronic oscillator with a passively mode locked extended cavity diode laser

International Nuclear Information System (INIS)

Lee, Jeongmin; Jang, Gwang Hoon; Yoon, Duseong; Song, Minsoo; Yoon, Tai Hyun

2008-01-01

An opto electronic oscillator(OEO)has very unique properties compared to the conventional quartz based microwave oscillators in that its oscillation frequency is determined by the beat note frequency of a phase coherent optical frequency comb generated as a side bands to an optical single mode carrier by using an electro optic modulator (EOM)or a direct current modulation of a semiconductor laser. Recently, a different type of OEO called a COEO has been demonstrated, where the optical carrier in the OEO system has been replaced by a mode locked laser so that an EOM or a direct current modulation are no longer necessary, but has potentially a much lower phase noise thanks to the high Q value of the optical frequency comb due to the mode locking mechanism. In this paper, we propose and demonstrate a COEO based on a passively mode locked ECDL at 852nm in which the fourth harmonic of the repetition frequency of the ECDL matched exactly the ground state hyperfine splitting frequency of the Cs atoms

Coupled opto electronic oscillator with a passively mode locked extended cavity diode laser

Energy Technology Data Exchange (ETDEWEB)

Lee, Jeongmin; Jang, Gwang Hoon; Yoon, Duseong; Song, Minsoo; Yoon, Tai Hyun [Korea Univ., Seoul (Korea, Republic of)

2008-11-15

An opto electronic oscillator(OEO)has very unique properties compared to the conventional quartz based microwave oscillators in that its oscillation frequency is determined by the beat note frequency of a phase coherent optical frequency comb generated as a side bands to an optical single mode carrier by using an electro optic modulator (EOM)or a direct current modulation of a semiconductor laser. Recently, a different type of OEO called a COEO has been demonstrated, where the optical carrier in the OEO system has been replaced by a mode locked laser so that an EOM or a direct current modulation are no longer necessary, but has potentially a much lower phase noise thanks to the high Q value of the optical frequency comb due to the mode locking mechanism. In this paper, we propose and demonstrate a COEO based on a passively mode locked ECDL at 852nm in which the fourth harmonic of the repetition frequency of the ECDL matched exactly the ground state hyperfine splitting frequency of the Cs atoms.

Low-Voltage Consumption Coordination for Loss Minimization and Voltage Control

DEFF Research Database (Denmark)

Juelsgaard, Morten; Sloth, Christoffer; Wisniewski, Rafal

2014-01-01

This work presents a strategy for minimizing active power losses in low-voltage grids, by coordinating the consumption of electric vehicles and power generation from solar panels. We show that minimizing losses, also reduces voltage variations, and illustrate how this may be employed for increasing...

DC-link Voltage Control to Compensate Voltage Deviation for PV–BESSs Integrated System in Low-Voltage (LV Networks

Directory of Open Access Journals (Sweden)

Lee Gyu-sub

2016-01-01

Full Text Available The exhaustion of fossil fuel and the greenhouse gas emission are one of the most significant energy and environmental issues, respectively. Photovoltaic (PV generators and battery energy storage systems (BESSs have been significantly increased for recent years. The BESSs are mainly used for smoothing active power fluctuation of the PV. In this paper, PV–BESSs integration of two DC/DC converters and one AC/DC converter is investigated and DC-link voltage control to compensate the AC voltage deviation is proposed for the PV‒BESS system in low-voltage (LV networks.

A VHF Class E DC-DC Converter with Self-Oscillating Gate Driver

DEFF Research Database (Denmark)

Andersen, Toke Meyer; Christensen, Søren K.; Knott, Arnold

2011-01-01

, is inherently resonant, and switching losses are greatly reduced by ensuring Zero Voltage Switching (ZVS) of the power semiconductor devices. A design method to ensure ZVS operation when combining the inverter, rectifier, and gate driver is provided. Several parasitic effects and their influence on converter......This paper describes the analysis and design of a DC-DC converter topology which is operational at frequencies in the Very High Frequency (VHF) band ranging from 30 MHz − 300 MHz. The presented topology, which consists of a class E inverter, class E rectifier, and self-oscillating gate driver...... operation are discussed, and measurement results of a 100 MHz prototype converter are presented and evaluated. The designed prototype converter verifies the described topology....

Memristor-based reactance-less oscillator

KAUST Repository

Zidan, Mohammed A.; Omran, Hesham; Radwan, Ahmed G.; Salama, Khaled N.

2012-01-01

The first reactance-less oscillator is introduced. By using a memristor, the oscillator can be fully implemented on-chip without the need for any capacitors or inductors, which results in an area-efficient fully integrated solution. The concept of operation of the proposed oscillator is explained and detailed mathematical analysis is introduced. Closed-form expressions for the oscillation frequency and oscillation conditions are derived. Finally, the derived equations are verified with circuit simulations showing excellent agreement. © 2011 The Institution of Engineering and Technology.

Memristor-based reactance-less oscillator

KAUST Repository

Zidan, Mohammed A.

2012-10-02

The first reactance-less oscillator is introduced. By using a memristor, the oscillator can be fully implemented on-chip without the need for any capacitors or inductors, which results in an area-efficient fully integrated solution. The concept of operation of the proposed oscillator is explained and detailed mathematical analysis is introduced. Closed-form expressions for the oscillation frequency and oscillation conditions are derived. Finally, the derived equations are verified with circuit simulations showing excellent agreement. © 2011 The Institution of Engineering and Technology.

Three-Input Single-Output Voltage-Mode Multifunction Filter with Electronic Controllability Based on Single Commercially Available IC

Directory of Open Access Journals (Sweden)

Supachai Klungtong

2017-01-01

Full Text Available This paper presents a second-order voltage-mode filter with three inputs and single-output voltage using single commercially available IC, one resistor, and two capacitors. The used commercially available IC, called LT1228, is manufactured by Linear Technology Corporation. The proposed filter is based on parallel RLC circuit. The filter provides five output filter responses, namely, band-pass (BP, band-reject (BR, low-pass (LP, high-pass (HP, and all-pass (AP functions. The selection of each filter response can be done without the requirement of active and passive component matching condition. Furthermore, the natural frequency and quality factor are electronically controlled. Besides, the nonideal case is also investigated. The output voltage node exhibits low impedance. The experimental results can validate the theoretical analyses.

Field angle dependence of voltage-induced ferromagnetic resonance under DC bias voltage

International Nuclear Information System (INIS)

Shiota, Yoichi; Miwa, Shinji; Tamaru, Shingo; Nozaki, Takayuki; Kubota, Hitoshi; Fukushima, Akio; Suzuki, Yoshishige; Yuasa, Shinji

2016-01-01

We studied the rectification function of microwaves in CoFeB/MgO-based magnetic tunnel junctions using voltage-induced ferromagnetic resonance (FMR). Our findings reveal that the shape of the structure of the spectrum depends on the rotation angle of the external magnetic field, providing clear evidence that FMR dynamics are excited by voltage-induced magnetic anisotropy changes. Further, enhancement of the rectified voltage was demonstrated under a DC bias voltage. In our experiments, the highest microwave detection sensitivity obtained was 350 mV/mW, at an RF frequency of 1.0 GHz and field angle of θ_H=80°, ϕ_H=0°. The experimental results correlated with those obtained via simulation, and the calculated results revealed the magnetization dynamics at the resonance state. - Highlights: • Examined voltage-induced ferromagnetic resonance (FMR) under various field angles. • FMR dynamics are excited by voltage-induced magnetic anisotropy changes. • Microwave detection sensitivity depends on input RF and elevation angle. • Microwave detection sensitivity=350 mV/mW at RF=1.0 GHz, θ_H=80°, ϕ_H=0°.

High voltage test techniques

CERN Document Server

Kind, Dieter

2001-01-01

The second edition of High Voltage Test Techniques has been completely revised. The present revision takes into account the latest international developments in High Voltage and Measurement technology, making it an essential reference for engineers in the testing field.High Voltage Technology belongs to the traditional area of Electrical Engineering. However, this is not to say that the area has stood still. New insulating materials, computing methods and voltage levels repeatedly pose new problems or open up methods of solution; electromagnetic compatibility (EMC) or components and systems al

Pulse-voltage fast generator